CN100587934C - Improved system and method for optical key dimension measurement accuracy - Google Patents
Improved system and method for optical key dimension measurement accuracy Download PDFInfo
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Abstract
A method for improving accuracy of optical critical dimension measurement of a substrate is provided. The method comprises: finding a technique parameter; finding process parameter that influences therefractive index and extinction coefficient of a thin film in the substrate; while the regression simulation, using the technique parameter to adjust the refractive index and extinction coefficient across a plurality of wavelengths as a function; during the regression modeling of the optical critical dimension measurement, the refractive index and extinction coefficient across the plurality of wavelengths is adjusted through the function via the technique parameter; the system comprises a way for finding process parameter that influences the refractive index and extinction coefficient of a thin film in the substrate; and a way for finding the function; a way for using the technique parameter to adjust the refractive index and extinction coefficient across a plurality of wavelengths as a function; and a way for completing the optical critical dimension measurement for the key size. The invention adjusts the refractive index/ extinction coefficient (n/k) on the film by the technique parameter to reduce the error of the key size measurement.
Description
Technical field
The present invention relates to a kind of technology about integrated circuit technology, particularly a kind of about improving critical size (critical dimension, CD) method and system of accuracy of measurement in the integrated circuit technology.Or rather, the present invention is a kind of about carrying out " scattering art formula optical key dimension mensuration " (scatterometry-based optical critical dimension metrology, during the simulation of OCD) Regression Model, by adjustable refractive index/extinction coefficient (n/k) that the film on the substrate is provided to improve the method and system of key dimension measurement accuracy.
Background technology
In the manufacture process of integrated circuit, generally speaking earlier photoresist (resist) is coated on the crystal column surface.Seeing through a photomask (photomask or reticle) then exposes to photoresist.Then carry out postexposure bake (post-exposure bake).For eurymeric chemistry double type photoetching jelly (positive-tone chemically amplified resist); this will cause protective reaction (deprotection reaction); make developer solution be easier to dissolve the photoresist of exposure region; thereby can be in follow-up developing process the photoresist of exposure region be removed, and produced the photoresist pattern.Detect after back extended meeting is then developed (after-development inspection, ADI).The back of developing is detected and is comprised that (scanning electron microscope SEM) measures the critical size of photoresist pattern, and is whether up to specification to judge it with the scanning type electron microscope.If up to specification, then carry out etch process to shift the photoresist pattern to wafer.And after removing photoresist, carry out detecting after the etching (after-etching inspection, AEI).
Yet, because argon fluoride photoresist (ArF resist) damages because of the irradiation that is subjected to electron beam (e-beam) easily, with and the reason of the line edge roughness (line edgeroughness) of photoresist pattern itself, make the detection mode of using SEM traditionally become the bottleneck of the key dimension measurement that provides accurate and repeatable.So, propose to replace SEM at this and detect with OCD.OCD mainly is to use the light of wavelength in visible-range to carry out the measurement of critical size, and is therefore atomic for the photoresist pattern influence that is measured.In addition, owing to only measure the pattern of the large-scale grating of tool (gratings) (for example, the length of side is 50 microns a square grating), and only collect the light that scatters to special angle, so OCD can avoid the interference of line edge roughness.Moreover OCD does not detect the critical size of photoresist pattern only, and (profile in the application of OCD, usually with Sidewall angles (Side-Wall Angle SWA) describes), more can detect the thickness of each film on wafer substrate to also have its section profile.So OCD can provide about photoresist pattern information widely than SEM.
Yet different with SEM is, OCD (that is, fully via simulated mode) indirectly obtains the measuring value of photoresist pattern.Therefore, the accuracy of resulting critical size and Sidewall angles depends on the correctness of simulation fully.In order to reduce the burden in the calculating, many OCD softwares are that refractive index/extinction coefficient (n/k) homogeneous of each layer film on the hypothesis substrate is a fixed value when simulating.For instance, when carrying out the Regression Model simulation, refractive index/the extinction coefficient of the film on the substrate (n/k) is assumed to be fixed value, film on the substrate for example is organic bottom antireflective layer (organicbottom anti-reflection coating, organic BARC), this is a well hypothesis.
But for other forms of film, for example inorganic bottom anti-reflection layer (inorganic BARC), the technology controlling and process when its uniformity with a variable refractive index/extinction coefficient (n/k) depends on deposit film, this is to reach perfect.Therefore need a kind of method and system, can be when returning simulation, the refractive index variable/extinction coefficient (n/k) that floats when measuring critical size to improve on, changes the error in measurement that is produced because of refractive index/extinction coefficient (n/k).
This shows that above-mentioned existing optical key dimension measurement obviously still has inconvenience and defective, and demands urgently further being improved in method and use.In order to solve the problem of above-mentioned existence, relevant manufacturer there's no one who doesn't or isn't seeks solution painstakingly, but do not see always that for a long time suitable design finished by development, and common product and method do not have appropriate structure and method to address the above problem, and this obviously is the problem that the anxious desire of relevant dealer solves.Therefore how to found a kind of improvement system and method thereof of new optical key dimension measurement accuracy, real one of the current important research and development problem that belongs to, also becoming the current industry utmost point needs improved target.
Because the defective that above-mentioned existing optical key dimension measurement exists, the inventor is based on being engaged in this type of product design manufacturing abundant for many years practical experience and professional knowledge, and the utilization of cooperation scientific principle, actively studied innovation, in the hope of founding a kind of improvement system and method thereof of new optical key dimension measurement accuracy, can improve general existing optical key dimension measurement, make it have more practicality.Through constantly research, design, and after studying sample and improvement repeatedly, create the present invention who has practical value finally.
Summary of the invention
The objective of the invention is to, overcome the defective that existing optical key dimension measurement exists, and provide a kind of improvement system of novel optical key dimension measurement accuracy, technical problem to be solved is that it is improved when carrying out the Regression Model of optical key dimension measurement, because of the refractive index/extinction coefficient (n/k) of each layer film on the hypothesis wafer substrate is a fixed value, the error in measurement of the critical size that is caused is very suitable for practicality.
Another object of the present invention is to, overcome the defective that existing optical key dimension measurement exists, and provide a kind of improvement method of new optical key dimension measurement accuracy, technical problem to be solved is that it is improved when carrying out the Regression Model of optical key dimension measurement, because of the refractive index/extinction coefficient (n/k) of each layer film on the hypothesis wafer substrate is a fixed value, the error in measurement of the critical size that is caused, thus be suitable for practicality more.
The object of the invention to solve the technical problems realizes by the following technical solutions.For achieving the above object, according to the improvement method of optical key dimension measurement accuracy of the present invention, it comprises: find out a technological parameter, the refractive index (n) of this effects of process parameters film on a base material and extinction coefficient (k); Find out under the used a plurality of wavelength of optical key dimension measurement, refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter; In recurrence when simulation of carrying out optical key dimension measurement, utilize and adjust this technological parameter and via the refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength; And by an optimum value that obtains this technological parameter, finish this optical key dimension measurement, wherein this optimum value minimization the difference between experimental spectrum and its theoretical prediction.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein this technological parameter is the flow rate of a specific gas.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein find out under the used a plurality of wavelength of optical key dimension measurement, the step that refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter comprises: use the set point of a plurality of flow rates of this specific gas, respectively this film of deposition on a plurality of base materials; To each described set point and to each described wavelength, measure on a plurality of positions in the base material of correspondence refractive index of this film (n) and extinction coefficient (k) respectively; And refractive index (n) and the extinction coefficient (k) of will be in each described position measuring this film corresponding to following of each described wavelength do on average, is the function of this specific gas flow rate with refractive index (n) and the extinction coefficient (k) that obtains this film.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein this film is an inorganic bottom anti-reflective film.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein the refractive index (n) of this inorganic bottom anti-reflective film and extinction coefficient (k) are adjustable.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein to the used wavelength of each optical key dimension measurement, the refractive index of this film (n) is the function of this specific gas flow rate, comprises: n (x)=a0+a1*x+a2*x
2, wherein, x represents the flow rate of this specific gas, a0, a1 and a2 are constant, employed board and technology during according to this film of deposition.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein to the used wavelength of each optical key dimension measurement, the extinction coefficient of this film (k) is the function of this specific gas flow rate, comprises: k (x)=b0+b1*x+b2*x
2, wherein, x represents the flow rate of specific gas, b0, b1 and b2 are constant, employed board and technology during according to this film of deposition.
The improvement method of aforesaid optical key dimension measurement accuracy, wherein when the recurrence simulation of carrying out optical key dimension measurement, utilize to adjust this technological parameter via described function with the refractive index (n) that is adjusted at this film under the described wavelength and the step of extinction coefficient (k), more comprise: the refractive index (n) and the extinction coefficient (k) that are adjusted at this film under the described wavelength via the flow rate of this specific gas via described function.
The improvement method of aforesaid optical key dimension measurement accuracy, the difference between experimental spectrum and its theoretical prediction wherein, (goodness of fit GOF) represents, wherein this goodness of fit is in order to quantize the quality of optical key dimension measurement with a goodness of fit.
The object of the invention to solve the technical problems also adopts following technical scheme to realize.For achieving the above object, improvement system according to optical key dimension measurement accuracy of the present invention, it comprises: one first finds out means, in order to find out a technological parameter, the refractive index (n) of this effects of process parameters film on a base material and extinction coefficient (k); One second finds out means, and in order to find out under the used a plurality of wavelength of optical key dimension measurement, refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter; One first adjustment means in order to when the recurrence of carrying out optical key dimension measurement is simulated, utilize this technological parameter via refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength; And one finish means, in order to by an optimum value that obtains this technological parameter, finishes this optical key dimension measurement, wherein this optimum value minimization the difference between experimental spectrum and its theoretical prediction.
The improvement system of aforesaid optical key dimension measurement accuracy, wherein this second finds out means, more comprises: deposition means, in order to deposition one film on a plurality of base materials respectively, this film uses a plurality of set points of this technological parameter; One measurement means, in order to measure on a plurality of positions in this base material respectively, corresponding to each described set point and to each described wavelength, refractive index of this film (n) and extinction coefficient (k); And average means, in order to average refractive index (n) and the extinction coefficient (k) of measuring this film in each described position corresponding to following of each described wavelength, be the function of this specific gas flow rate with refractive index (n) and the extinction coefficient (k) that obtains this film.
The improvement system of aforesaid optical key dimension measurement accuracy, wherein these first adjustment means are in order to when the recurrence of carrying out optical key dimension measurement is simulated, utilize and adjust this technological parameter via the refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength, more comprise: one second adjustment means, in order in recurrence when simulation of carrying out optical key dimension measurement, utilize the flow rate of a specific gas to be adjusted at the refractive index (n) and the extinction coefficient (k) of this film under the described wavelength via described function.
The improvement system of aforesaid optical key dimension measurement accuracy, wherein this film is an inorganic bottom anti-reflective film, this inorganic bottom anti-reflective film comprises silicon oxynitride.
The improvement system of aforesaid optical key dimension measurement accuracy, wherein this refractive index (n) and extinction coefficient (k) only limit to this film.
The improvement system of aforesaid optical key dimension measurement accuracy, wherein refractive index of this inorganic bottom anti-reflection layer (n) and extinction coefficient (k) are adjustable.
The present invention compared with prior art has tangible advantage and beneficial effect.By technique scheme, the improvement system and the method thereof of optical key dimension measurement accuracy of the present invention have following advantage and beneficial effect at least:
Improvement method and system thereof according to a kind of optical key dimension measurement accuracy proposed by the invention: by a technological parameter is provided, make when the recurrence simulation of carrying out the optical key dimension measurement method, can adjust refractive index/extinction coefficient (n/k) value of wafer substrate upper film.To reduce error because of refractive index/extinction coefficient (n/k) value key dimension measurement that variation was caused of diverse location in wafer.For example: the measurement of critical size can quantize the error in measurement of optical key dimension measurement method when fixing and refractive index/extinction coefficient (n/k) was unsteady via refractive index/extinction coefficient (n/k) relatively.Learn from a real example, uniformity (the within-wafer CD uniformity of critical size in wafer when refractive index/extinction coefficient (n/k) is fixed and refractive index/extinction coefficient (n/k) floats, represent with 3 σ) difference be 0.5nm, approximately be to account for inhomogeneity 30% of critical size in total wafer.
Above-mentioned explanation only is the general introduction of technical solution of the present invention, for can clearer understanding technological means of the present invention, and can be implemented according to the content of specification, and for above-mentioned and other purposes, feature and advantage of the present invention can be become apparent, below especially exemplified by preferred embodiment, and conjunction with figs., be described in detail as follows.
Description of drawings
Fig. 1 illustrates a kind of photoetching process system schematic into a preferred embodiment of the present invention.
Fig. 2 illustrates to measure the schematic diagram of the critical size of wafer with OCD.
Fig. 3 a illustrates and is critical size image in the wafer that is measured with use optical key dimension measurement method after the specific photomask exposure.
Fig. 3 b illustrates and is the wafer madial wall angular image to use the optical key dimension measurement method to be measured after the specific photomask exposure.
Fig. 3 c illustrate be one correspond to Fig. 3 a and Fig. 3 b at the pairing goodness of fit image of each measuring point.
It is the recurrence simulation of an employing optical key dimension measurement method that Fig. 3 d illustrates, in each wafer, use the optical key dimension measurement method to measure inorganic bottom anti-reflection layer refractive index/extinction coefficient that the position measured, critical size image in the wafer that is measured.
It is the recurrence simulation of an employing optical key dimension measurement method that Fig. 3 e illustrates, in each wafer, to use the optical key dimension measurement method to measure inorganic bottom anti-reflection layer refractive index/extinction coefficient that the position was measured, the wafer madial wall angular image that measures.
Fig. 3 f illustrate be one correspond to Fig. 3 d and Fig. 3 e at the pairing goodness of fit image of each measuring point.
Fig. 4 illustrates the flow chart into the improvement method of a kind of optical key dimension measurement accuracy of a preferred embodiment of the present invention.
Fig. 5 illustrates and is the exemplary flow process among Fig. 4, finds out under the employed wavelength of arbitrary OCD, and the refractive index/extinction coefficient of film (n/k) is the flow chart of the function of technological parameter.
Fig. 6 illustrates and how to verify a single technological parameter for explanation among Fig. 4 and can be used to be described in simultaneously the refractive index of inorganic bottom anti-reflection layer on the wafer substrate (n) and dissipation coefficient (k) flow chart along with wavelength change.
Fig. 7 a illustrates the measuring value curve chart of the refractive index (n) that is an inorganic bottom anti-reflective film.
Fig. 7 b illustrates the measuring value curve chart of the extinction coefficient (k) that is an inorganic bottom anti-reflective film.
Fig. 8 a illustrate for the explanation how to use interpolation method (interpolation) to obtain refractive index (n) value of inorganic bottom anti-reflective film under any specific gas flow rate.
Fig. 8 b illustrate for the explanation how to use interpolation method to obtain dissipation coefficient (k) value of inorganic bottom anti-reflective film under any specific gas flow rate.
[main element symbol description]
100: photoetching process system 102: the wafer feeding mechanism
104: photoresist coating station 106: soft baking station
108: exposure station 110: the postexposure bake station
112: the station 114 of developing: hard baking station
116: controller 118: the optical detection station
200: wafer 202: ground floor
204: the second layer 206: polysilicon layer
208: anti-reflecting layer 210: photoresist layer
212: incident light 214: scattered light
402～406: step 400: flow process
602～606: step 502～506: step
702: refractive index 700: curve chart
706～714: represent different flow rates 704: wavelength
722: dissipation coefficient 720: curve chart
726～734: represent different flow rates 724: wavelength
820: curve chart 800: curve chart
Embodiment
Reach technological means and the effect that predetermined goal of the invention is taked for further setting forth the present invention, below in conjunction with accompanying drawing and preferred embodiment, improvement system and its embodiment of method, structure, method, step, feature and the effect thereof of the optical key dimension measurement accuracy that foundation the present invention is proposed, describe in detail as after.
Relevant aforementioned and other technology contents, characteristics and effect of the present invention can clearly present in the following detailed description that cooperates with reference to graphic preferred embodiment.For convenience of description, in following embodiment, components identical is represented with identical numbering.
Please refer to Fig. 1, it illustrates a kind of photoetching process system schematic according to a preferred embodiment of the present invention.Photoetching process system 100 comprises a wafer feeding mechanism 102, a photoresist coating station 104, one soft baking station 106, an exposure station 108, a postexposure bake station 110,114 and one optical detection station 118,112, one hard baking station, a development station.By the running of above-mentioned each unit of a controller 116 controls, with this photoetching process system 100 of automation.
At first, the wafer in the technology is delivered to photoresist coating station 104 via wafer feeding mechanism 102, on the surface of wafer, to be coated with photoresist.Wafer carries out soft baking at soft baking station 106 then, the wafer after the soft baking is delivered to exposure station 108 expose, and the wafer after the exposure is delivered to postexposure bake station 110 carry out postexposure bake, and the wafer after finishing is sent to the station 112 of developing and develops.After development was finished, wafer toasted firmly at hard baking station 114, at last wafer is delivered to optical detection station 118 and detects.Wherein optical detection station 118 comprises a spectrometer (spectrometer), and spectrometer can be collected from the scattered light of photoresist pattern.Controller 116 is analyzed the spectrum of the collected scattered light of spectrometer.
Please refer to Fig. 2, it illustrates to (Optical critical dimension OCD) measures the schematic diagram of the critical size of wafer with optical key dimension.Wafer 200 comprises a ground floor 202 and a second layer 204.Ground floor 202 can comprise one by the made substrate of silicon (silicon).It is an optical density (OD) layer (Optical Density Layer, OD layer) that ground floor 202 is also referred to as.The second layer 204 can comprise a polysilicon (polysilicon) layer 206, one anti-reflecting layer 208 and a photoresist layer 210.Polysilicon layer 206 can comprise silicon dioxide (silicon dioxide), silication nitrogen (siliconnitride) etc.Anti-reflecting layer 208 can be an organic bottom antireflective layer or is an inorganic bottom anti-reflection layer, and wherein inorganic bottom anti-reflection layer can be inorganic material, as silicon oxynitride (siliconoxynitride, SiON) etc.
The probe source of spectrometer produces the detecting area that an incident light 212 incides photoresist layer 210, and its incidence angle θ is to spend to 90 degree between 0 with respect to photoresist layer 210 surfaces.Incident light 212 experiences multipath reflection/transmission in each film after, can come out and form a scattered light 214 from the surface scattering of photoresist layer 210 or anti-reflecting layer 208.Can collect the scattered light 214 of different wave length as PDAD (diode array detector) by existing detector.Can carry out diffraction analysis (diffraction analysis) to scattered light 214 subsequently, and then obtain three dimensional informations and other extra information of photoresist layer 210.Diffraction analysis can be carried out by a controller (for example controller among Fig. 1 116).
When carrying out diffraction analysis, can simulate the section profile of photoresist by the mode that returns, the critical size that is measured to obtain.In order to alleviate the computation burden of doing to return simulation, usually have only that the thickness of each layer film on the thickness of the critical size of the critical size at photoresist top, photoresist bottom, photoresist and the wafer substrate is used as is free parameter, and the refractive index/extinction coefficient (n/k) of each layer film on the wafer substrate is supposed to fix.For the organic bottom antireflective layer, this is an available hypothesis.Yet, for the inorganic bottom anti-reflection layer of the adjustable variation of refractive index/extinction coefficient (n/k), the technology controlling and process the when uniformity of its refractive index/extinction coefficient (n/k) depends on thin film deposition, this is to reach perfect.Therefore, aforementioned refractive index/extinction coefficient (n/k) is the not realistic situation of hypothesis of fixed value.
In order to ensure the quality of resulting critical size data, (Goodness ofFit GOF) quantizes to return the quality of simulation can to adopt the goodness of fit.The definition of the goodness of fit is as the formula (1):
R wherein
M(λ) and P
S(λ) be respectively when wavelength is λ, measure and simulate resulting scattered light signal, and
That is the goodness of fit has been described the scattering spectrum that measured and the difference between its theoretical prediction.
Wafer for the film that contains adjustable variable refractivity/extinction coefficient (n/k) (as inorganic bottom anti-reflection layer), result after measuring with the optical key dimension measurement method shows that near the goodness of fit crystal circle center is to be lower than in other regional goodnesses of fit of wafer.Resulting critical dimension measurements may be inaccurate than what come in other regional resulting critical dimension measurements of wafer near this was illustrated in crystal circle center.It is generally acknowledged, cause the inaccurate main cause of critical dimension measurements, is when carrying out the Regression Model of optical key dimension, the refractive index/extinction coefficient (n/k) of each layer film on the wafer substrate is assumed to be fixed value causes.
In order to prove above-mentioned inference, in photoetching process (lithography process) before, measure refractive index/extinction coefficient (n/k) value of inorganic bottom anti-reflection layer on the wafer substrate earlier, carry out photoetching process again.Photoetching process comprises with a specific photomask exposes to a plurality of positions in the wafer.After photoetching process, use the optical key dimension measurement method that each is measured through the formed photoresist pattern that exposes.Measure resulting critical size and Sidewall angles shown in Fig. 3 a and Fig. 3 b, then be shown in Fig. 3 c in the pairing goodness of fit of each measuring point.Learn that by figure near the goodness of fit crystal circle center is to be lower than in other regional goodnesses of fit of wafer.Therefore, near the measuring value crystal circle center may be inaccurate than what come at other regional measuring values of wafer.Yet, if when the recurrence simulation of carrying out the optical key dimension measurement method, each indivedual position is used refractive index/extinction coefficient (n/k) value that its corresponding amount measures respectively on wafer, and then the distribution map of interior critical size of wafer and Sidewall angles is shown in Fig. 3 d and Fig. 3 e.And corresponding to the distribution map of the goodness of fit of Fig. 3 d and Fig. 3 e, then shown in Fig. 3 f.Can observe out near the goodness of fit of crystal circle center is enhanced.
Yet, on the production line of semiconductor factory, will be before photoetching process, measure refractive index/extinction coefficient (n/k) value of the film of each sample position in each sampling wafer, so that after photoetching process, provide and do the required refractive index/extinction coefficient of optical key dimension measurement (n/k) value, on carrying out, its difficulty is arranged.On the other hand, because when the recurrence simulation of carrying out the optical key dimension measurement method, it is not refractive index/extinction coefficient (n/k) value of only using a specific wavelength, but use refractive index/extinction coefficient (n/k) value of the wave-length coverage that whole OCD uses, therefore, when returning simulation, be free parameter if refractive index/extinction coefficient (n/k) value of all wavelengths all is used as, be impossible in one rational period, finish the work that returns simulation.
According to one embodiment of the invention, a kind of method and system is provided, can be via finding out a single parameter (this single parameter can be described on the wafer substrate film along with refractive index/extinction coefficient (n/k) value of wavelength change), make after the recurrence simulation of finishing OCD, can automatically determine on wafer substrate, about this film refractive index/extinction coefficient (n/k) value more accurately on each sampling point, so that obtain about critical size measuring value more accurately.With inorganic bottom anti-reflection layer is example, can change its refractive index/extinction coefficient (n/k) value by the flow rate (flow rate) of the specific gas in the technology that is adjusted at its deposition.Simultaneously, in the wave-length coverage that the flow rate of this specific gas also can be used to be described in all OCD simultaneously and used, the variation of refractive index (n) and extinction coefficient (k) value.
Please refer to Fig. 4, it illustrates the flow chart according to the improvement method of a kind of optical key dimension measurement accuracy of a preferred embodiment of the present invention.This flow process 400 is begun by step 402.Step 402 among the parameter that can influence this film refractive index/extinction coefficient (n/k) value, is selected a technological parameter when deposit film.In the present embodiment, this technological parameter is a flow rate in order to the specific gas that deposits this film.Because in the technology of this film of deposition, can obtain refractive index/extinction coefficient (n/k) value of the film wanted by the flow rate of adjusting this specific gas.
After technological parameter was selected, flow process 400 continued step 404, finds out in the employed all wavelengths of each OCD, and the refractive index/extinction coefficient of this film (n/k) is respectively the function of input value with this technological parameter.About being specified in the explanation with further reference to Fig. 5 of step 404.Flow process 400 continues step 406, when the recurrence simulation of carrying out optical key dimension measurement, by adjusting this technological parameter, change refractive index/extinction coefficient (n/k) value of this film in the employed wave-length coverage of all OCD, to obtain a theoretical modeling spectrum that coincide the most with experimental spectrum.
Please refer to Fig. 5, it illustrates according to the exemplary flow process among Fig. 4, finds out under the employed wavelength of arbitrary OCD, and the refractive index/extinction coefficient of film (n/k) is the flow chart of the function of this technological parameter.In the present embodiment, define the flow rate that this technological parameter is a specific gas.Yet under the situation of spirit that does not break away from present embodiment and scope, other technological parameters also can be used to be described in all wavelengths excursion, the variation of refractive index/extinction coefficient (n/k) value.
Flow process 404 uses the set point of the different flow rates of a specific gas to deposit this film on a plurality of wafers respectively by step 502 beginning.In the present embodiment, if this film is silicon oxynitride (SiOxNy), then specific gas is for using silane (SiH4).Flow process 404 continues steps 504 then, under the set point of each flow rate of specific gas, measures on all sampling points in wafer corresponding in the wave-length coverage that each OCD used the refractive index/extinction coefficient of this film (n/k) value.Flow process 404 continues step 506 then, use the wafer of the different flow rates settings of specific gas for each sheet, in the employed wavelength of each OCD, refractive index/extinction coefficient (n/k) value to the sampling point of all wafer upper films is done on average, is the function of specific gas flow rate with the refractive index/extinction coefficient (n/k) that obtains film.For example: in the employed wavelength of each OCD, it is the function (being input value with the specific gas flow rate promptly) of this specific gas flow rate that refractive index (n) is considered as, and represents suc as formula (2) with a second order polynomial
n(x)＝a0+a1*x+a2*x2 (2)
Wherein, x represents the flow rate of this specific gas, and a0, a1 and a2 are constant, depends on deposition employed technology of this film and board.
Similarly, at the employed wavelength of each OCD, it is the function of this specific gas flow rate that extinction coefficient (k) is considered as, and represents suc as formula (3) with a second order polynomial
k(x)＝b?0+b1*x+b2*x2 (3)
Wherein, x represents the flow rate of this specific gas, and b0, b1 and b2 are constant, depends on deposition employed technology of this film and board.
In case the flow rate of given this specific gas then at the employed wavelength of each OCD, by formula (2) and formula (3), can obtain refractive index/extinction coefficient (n/k) value of this film.
Please refer to Fig. 6, illustrate how to verify that a single technological parameter can be used to be described in simultaneously the refractive index of inorganic bottom anti-reflection layer on the wafer substrate (n) and extinction coefficient (k) flow chart along with wavelength change.Flow process 406 is from step 602, and for a certain specific wavelength, refractive index (n) value that can measure according to a certain ad-hoc location on wafer determines the flow rate of this specific gas via formula (2).Flow process 406 continues step 604, according to the flow rate of this specific gas that is determined, calculates corresponding extinction coefficient (k) value via formula (3).Can find that extinction coefficient (k) value of calculating is in close proximity to measurement resulting extinction coefficient (k) value.Flow process 406 continues step 606, for the employed wavelength of each OCD, and the position repeating step 604 of each sampling in wafer.Can verify out that under the employed wavelength of all OCD the refractive index/extinction coefficient of a film (n/k) value on the wafer substrate can be by a single technological parameter, that is, be the function input value as the flow rate of specific gas, give parametrization.
Please refer to Fig. 7 a, illustrate the measuring value of the refractive index (n) of inorganic bottom anti-reflective film.In the present embodiment, inorganic bottom anti-reflective film is silicon oxynitride (SiOxNy), and corresponding specific gas is silane (SiH4).Curve chart 700 illustrates at each of specific gas and sets under flow rate, measurement refractive index (n) (702) of (704) in the employed wave-length coverage of all OCD.When flow rate was 280,340,380,420 and 500, measurement refractive index (n) (702) of (704) in the employed wave-length coverage of all OCD was represented by curve 706,708,710,712 and 714 respectively.
Please refer to Fig. 7 b, illustrate the measuring value of the extinction coefficient (k) of inorganic bottom anti-reflective film.In the present embodiment, inorganic bottom anti-reflective film is silicon oxynitride (SiOxNy), and corresponding specific gas is silane (SiH4).Curve chart 720 illustrates under each flow rate of specific gas is set, measurement extinction coefficient (k) (722) of (724) in the employed wave-length coverage of all OCD.When flow rate was 280,340,380,420 and 500, measurement extinction coefficient (k) (722) of (724) in the employed wave-length coverage of all OCD was represented by curve 726,728,730,732 and 734 respectively.
Please refer to Fig. 8 a, illustrate how to use interpolation method (interpolation) to obtain refractive index (n) value of inorganic bottom anti-reflective film under any specific gas flow rate.Curve chart 800 is that the curve chart 700 from Fig. 7 a derives out.Point in curve chart 800 is represented respectively when the flow rate of specific gas is 280,340,380,420 and 500, and inorganic bottom anti-reflective film is refractive index (n) value under the 673nm at wavelength.Second order polynomial shown in the line expression (2) in curve chart 800, this second order polynomial can be by above-mentioned each λ of match (fitting) and refractive index (n) several to (λ n) obtains.Fig. 8 a also can find out simultaneously, when the refractive index/extinction coefficient (n/k) of the inorganic bottom of checking anti-reflective film is worth the variation of diverse location in wafer, in the time of can giving parametrization by the flow rate of specific gas, how via the flow rate of formula (2) to the pairing specific gas of refractive index (n) value calculating that some positions measured in the wafer.
Please refer to Fig. 8 b, illustrate how to use interpolation method to obtain extinction coefficient (k) value of inorganic bottom anti-reflective film under any specific gas flow rate.Curve chart 820 is that the curve chart 720 from Fig. 7 b derives out.Point in curve chart 820 is represented respectively when the flow rate of specific gas is 280,340,380,420 and 500, and inorganic bottom anti-reflective film is extinction coefficient (k) value under the 320nm at wavelength.Second order polynomial shown in the line expression (3) in curve chart 820.This second order polynomial can be by above-mentioned each λ of match and extinction coefficient (k) several to (λ k) obtains.Fig. 8 b also can find out simultaneously, when the variation of refractive index/extinction coefficient (n/k) value diverse location in wafer of checking inorganic bottom anti-reflective film can give parametrization by the flow rate of specific gas, how via flow rate calculation pairing extinction coefficient (k) value of formula (3) to the specific gas that in Fig. 8 a, calculated.Can find to calculate resulting extinction coefficient (k) value and approach very much extinction coefficient (k) value that on the position that measures refractive index (n) place, measured.For the position of taking a sample in the employed wavelength of each OCD and each wafer, repeat the program that Fig. 8 a and Fig. 8 b are illustrated, the variation that can prove refractive index/extinction coefficient (n/k) diverse location in wafer of inorganic bottom anti-reflective film can be by a single parameter, that is, the flow rate of specific gas gives parametrization.
The above, it only is preferred embodiment of the present invention, be not that the present invention is done any pro forma restriction, though the present invention discloses as above with preferred embodiment, yet be not in order to limit the present invention, any those skilled in the art, in not breaking away from the technical solution of the present invention scope, when the method that can utilize above-mentioned announcement and technology contents are made a little change or be modified to the equivalent embodiment of equivalent variations, in every case be the content that does not break away from technical solution of the present invention, according to technical spirit of the present invention to any simple modification that above embodiment did, equivalent variations and modification all still belong in the scope of technical solution of the present invention.
Claims (15)
1, a kind of improvement method of optical key dimension measurement accuracy is characterized in that: comprise:
Find out a technological parameter, the refractive index (n) of this effects of process parameters film on a base material and extinction coefficient (k);
Find out under the used a plurality of wavelength of optical key dimension measurement, refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter;
In recurrence when simulation of carrying out optical key dimension measurement, utilize and adjust this technological parameter and via the refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength; And
By an optimum value that obtains this technological parameter, finish this optical key dimension measurement, wherein this optimum value minimization the difference between experimental spectrum and its theoretical prediction.
2, the improvement method of optical key dimension measurement accuracy according to claim 1 is characterized in that wherein this technological parameter is the flow rate of a specific gas.
3, the improvement method of optical key dimension measurement accuracy according to claim 2, it is characterized in that wherein finding out under the used a plurality of wavelength of optical key dimension measurement, the step that refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter comprises:
Use the set point of a plurality of flow rates of this specific gas, respectively this film of deposition on a plurality of base materials;
To each described set point and to each described wavelength, measure on a plurality of positions in the base material of correspondence refractive index of this film (n) and extinction coefficient (k) respectively; And
Refractive index (n) and the extinction coefficient (k) of will be in each described position measuring this film corresponding to following of each described wavelength are done on average, are the function of this specific gas flow rate with refractive index (n) and the extinction coefficient (k) that obtains this film.
4. the improvement method of optical key dimension measurement accuracy according to claim 3 is characterized in that wherein this film is an inorganic bottom anti-reflective film.
5. the improvement method of optical key dimension measurement accuracy according to claim 4 is characterized in that wherein the refractive index (n) and the extinction coefficient (k) of this inorganic bottom anti-reflective film are adjustable.
6. the improvement method of optical key dimension measurement accuracy according to claim 3 is characterized in that wherein to the used wavelength of each optical key dimension measurement, the refractive index of this film (n) is the function of this specific gas flow rate, comprises:
n(x)＝a0+a1*x+a2*x
2
Wherein, x represents the flow rate of this specific gas, and a0, a1 and a2 are constant, employed board and technology during according to this film of deposition.
7. the improvement method of optical key dimension measurement accuracy according to claim 3 is characterized in that wherein to the used wavelength of each optical key dimension measurement, the extinction coefficient of this film (k) is the function of this specific gas flow rate, comprises:
k(x)＝b0+b1*x+b2*x
2
Wherein, x represents the flow rate of specific gas, and b0, b1 and b2 are constant, employed board and technology during according to this film of deposition.
8. the improvement method of optical key dimension measurement accuracy according to claim 1, it is characterized in that wherein when the recurrence simulation of carrying out optical key dimension measurement, utilize to adjust this technological parameter via described function with the refractive index (n) that is adjusted at this film under the described wavelength and the step of extinction coefficient (k), more comprise:
Utilize the flow rate of this specific gas to be adjusted at the refractive index (n) and the extinction coefficient (k) of this film under the described wavelength via described function.
9. the improvement method of optical key dimension measurement accuracy according to claim 1, it is characterized in that the wherein difference between the experimental spectrum and its theoretical prediction, represent that with a goodness of fit wherein this goodness of fit is in order to quantize the quality of optical key dimension measurement.
10. the improvement system of an optical key dimension measurement accuracy is characterized in that, comprises:
One first finds out means, in order to find out a technological parameter, the refractive index (n) of this effects of process parameters film on a base material and extinction coefficient (k);
One second finds out means, and in order to find out under the used a plurality of wavelength of optical key dimension measurement, refractive index of this film (n) and extinction coefficient (k) are respectively the function of this technological parameter;
One first adjustment means in order to when the recurrence of carrying out optical key dimension measurement is simulated, utilize this technological parameter via refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength; And
One finishes means, in order to by an optimum value that obtains this technological parameter, finishes this optical key dimension measurement, wherein this optimum value minimization the difference between experimental spectrum and its theoretical prediction.
11. the improvement system of optical key dimension measurement accuracy according to claim 10 is characterized in that wherein this second finds out means, more comprises:
One deposition means, in order to deposit a film respectively on a plurality of base materials, this film uses a plurality of set points of this technological parameter;
One measurement means, in order to measure on a plurality of positions in this base material respectively, corresponding to each described set point and to each described wavelength, refractive index of this film (n) and extinction coefficient (k); And
One average means in order to average refractive index (n) and the extinction coefficient (k) of measuring this film in each described position corresponding to following of each described wavelength, are the function of this specific gas flow rate with refractive index (n) and the extinction coefficient (k) that obtains this film.
12. the improvement system of optical key dimension measurement accuracy according to claim 10, it is characterized in that wherein these first adjustment means are in order to when the recurrence of carrying out optical key dimension measurement is simulated, utilize and adjust this technological parameter, more comprise via the refractive index (n) and the extinction coefficient (k) of described function to be adjusted at this film under the described wavelength:
One second adjustment means in order in recurrence when simulation of carrying out optical key dimension measurement, utilize the flow rate of a specific gas to be adjusted at the refractive index (n) and the extinction coefficient (k) of this film under the described wavelength via described function.
13. the improvement system of optical key dimension measurement accuracy according to claim 11 is characterized in that wherein this film is an inorganic bottom anti-reflective film, this inorganic bottom anti-reflective film comprises silicon oxynitride.
14. the improvement system of optical key dimension measurement accuracy according to claim 11 is characterized in that wherein this refractive index (n) and extinction coefficient (k) only limit to this film.
15. the improvement system of optical key dimension measurement accuracy according to claim 13 is characterized in that wherein refractive index of this inorganic bottom anti-reflection layer (n) and extinction coefficient (k) are for adjustable.
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| CN102566321B (en) * | 2012-02-28 | 2014-11-05 | 上海华力微电子有限公司 | Method for monitoring offset of focal length of lithography machine |
| US20160217240A1 (en) * | 2015-01-28 | 2016-07-28 | Dmo Systems Limited | Methodology Of Incorporating Wafer Physical Measurement With Digital Simulation For Improving Semiconductor Device Fabrication |
| CN106289095B (en) * | 2015-06-12 | 2019-02-19 | 睿励科学仪器（上海）有限公司 | Critical size measurement method and equipment based on preceding value |
| CN110823089B (en) * | 2018-08-10 | 2021-06-04 | 睿励科学仪器（上海）有限公司 | Method and apparatus for measuring optical critical dimension of semiconductor device |
| CN109212637B (en) * | 2018-11-02 | 2020-06-19 | 天津津航技术物理研究所 | Optical characteristic obtaining method of spherical optical multilayer film element |
| CN110348071B (en) * | 2019-06-19 | 2023-01-10 | Tcl华星光电技术有限公司 | Drying film forming process optimization method and device and electronic equipment |
| CN112729108B (en) * | 2020-12-18 | 2022-12-06 | 长江存储科技有限责任公司 | Calibration method of optical critical dimension OCD measuring equipment |
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