US20020123244A1 - Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof - Google Patents
Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof Download PDFInfo
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- US20020123244A1 US20020123244A1 US10/015,665 US1566501A US2002123244A1 US 20020123244 A1 US20020123244 A1 US 20020123244A1 US 1566501 A US1566501 A US 1566501A US 2002123244 A1 US2002123244 A1 US 2002123244A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76224—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials
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- the present invention relates to a semiconductor device, and more particularly to a layer for precluding segregation of impurity ions which prevents impurity ion permeation between a device isolation region and a semiconductor substrate, a fabrication method thereof, an isolation structure for a semiconductor device using the segregation precluding layer and a fabrication method thereof.
- a LOCOS (local oxidation of silicon) structure using a LOCOS method has been often used as an isolation structure of a conventional semiconductor device, but there is limit to improvement of integration of the semiconductor device due to generation of a bird's beaks thereof.
- STI shallow trench isolation
- PGI profiled groove isolation
- FIG. 1 is a plan diagram illustrating a cell array unit of a semiconductor device, particularly, a DRAM (dynamic random access memory).
- a semiconductor substrate 100 is divided into an active region 101 and a non-active region 102 which covers the active region 101 , the non-active region 102 being called a device isolation region.
- the active region is a part where a semiconductor device, that is, a transistor is formed and in which impurity ions are implanted, thus a source 101 a and a drain 101 b are provided.
- the device isolation region 102 electrically isolates the semiconductor device and has the STI or PGI structure.
- a gate electrode 104 is formed on the active region 101 .
- a channel of the transistor is formed in a portion of the semiconductor substrate where the active region 101 and the gate electrode 104 are overlapped.
- FIG. 2A is a cross-sectional vertical view taken along the line lla-lla of FIG. 1, the line horizontally crossing the active region 101 in a center point of a channel width of the transistor.
- the active region 101 of the semiconductor substrate 100 is covered by the device isolation region 102 .
- the device isolation region 102 is etched to a predetermined depth (for example, about 0.5-0.8 mm), thereby forming a trench 102 a and an insulator 102 b is filled therein.
- the source 101 a and the drain 101 b as shown in FIG. 1, are provided in the semiconductor substrate 100 having a predetermined distance and a gate insulating film 103 and a gate electrode 104 are formed on the semiconductor substrate 100 .
- FIG. 2B is a cross-sectional vertical view taken along the line llb-llb of FIG. 1, the line being perpendicular to the line lla-lla of FIG. 1.
- the trench or groove 102 a is formed in the semiconductor substrate 100 and the insulator 102 b is filled in the trench or groove 102 a .
- the part 102 in which the insulator is filled corresponds to the device isolation region.
- the gate insulating film 103 is formed on the semiconductor substrate 100 and a gate electrode 104 is formed thereon, the gate electrode 104 being formed in the active region 101 and extended to the upper surface of the device isolation region 102 .
- 101 c is a part where impurity ions in the semiconductor substrate segregate to the device isolation region and thus density thereof is considerably low.
- 101 d is a center part of the channel region of the transistor.
- the conventional semiconductor device having the STI or PGI structure particularly the semiconductor which is an N-channel transistor has problems as follows.
- the N-channel transistor is generally formed in a p-type semiconductor substrate or in a p-type well.
- Impurity ions in particular, boron ions in the p-type semiconductor substrate or the p-type wall have a tendency to easily segregate to the device isolation region and accordingly the density of the impurity ions of a portion adjacent to the device isolation region, that is, a portion 101 c of the semiconductor substrate adjacent to a sidewall of the trench 102 a becomes decreased. Accordingly, an impurity depletion layer is formed in the semiconductor substrate along the sidewall of the trench.
- the channel of the transistor is normally formed above a threshold voltage in accordance with a voltage applied to the gate electrode, but in the channel region adjacent to the device isolation region a channel is easily formed below the threshold voltage, so that the threshold voltage decreases.
- an electrical characteristic of the semiconductor device is unstable that, for example, a subthreshold current increases and a subthreshold current curve has a hump, which results in the deterioration of the semiconductor device.
- the present invention is directed to an impurity ion segregation precluding layer, a fabrication method thereof, an isolation structure for semiconductor device using the impurity ion segregation precluding layer and a fabricating method thereof which obviate the problems and disadvantages in the conventional art.
- An object of the present invention is to provide an impurity ion segregation precluding layer and a fabrication method thereof that prevent impurity ions in a semiconductor substrate from permeating into a device isolation region thereof.
- an object of the present invention is to provide an isolation structure of a semiconductor device and a fabrication method thereof that stabilize electric characteristics of a semiconductor device using the above impurity ion segregation precluding layer and thereby improve reliability thereof.
- an impurity ion segregation precluding layer having a thickness of 1-10A by placing a semiconductor substrate formed of silicon in a high-temperature furnace and annealing the semiconductor substrate while flowing a nitride gas thereinto at at least 20l/min.
- an isolation structure of a semiconductor device which includes a semiconductor substrate, a trench formed in a predetermined portion of the semiconductor substrate, an impurity ion segregation precluding layer formed on a surface of the trench, and an insulator filled in the trench, the impurity ion segregation precluding layer being obtained by placing the semiconductor substrate into a furnace at a high temperature and annealing the semiconductor substrate flowing a nitride gas into the furnace at about 20 l/min.
- a method for fabricating an isolation structure of a semiconductor device which includes forming a trench in a portion of a semiconductor substrate formed of silicon corresponding to a device isolation region, placing the semiconductor substrate into a furnace at a high temperature and annealing the semiconductor substrate flowing a nitride gas into the furnace at about 20 l/min, and filling an insulator in the trench.
- FIG. 1 is a plan diagram of a conventional DRAM cell array unit
- FIG. 2A is a cross-sectional vertical view taken along the line lla-lla of FIG. 1;
- FIG. 2B is a cross-sectional vertical view taken along the line llb-llb of FIG. 1;
- FIG. 3 is a cross-sectional vertical view of an isolation structure of a semiconductor device according to the present invention.
- FIGS. 4A through 4E are cross-sectional vertical views illustrating a fabrication method of an isolation structure of a semiconductor device according to the present invention.
- FIG. 3 is a cross-sectional vertical view illustrating an isolation structure of a semiconductor device using an insulating film according to the present invention.
- a trench 301 is formed in a device isolation region in a semiconductor substrate 300 and an impurity ion segregation precluding layer 302 is formed on a surface of the semiconductor substrate 300 along a sidewall and a bottom of the trench 301 , the impurity ion segregation precluding layer 302 having a thickness of about 1-9A.
- An insulator 303 which is a silicon oxide SiO 2 or silicon nitride Si 3 N 4 is filled in the trench 301 .
- the impurity ion segregation precluding layer 302 at the thickness of 1-9A formed along the sidewall and bottom of the trench 301 prevents the impurity ions in the semiconductor substrate 300 from permeating through the insulator 303 in the trench 301 , thus preventing decrease in the impurity density of the semiconductor substrate. Accordingly, decrease in the threshold voltage in which a channel is formed below the threshold voltage is prevented and thus the reliability of the semiconductor device can improve.
- the impurity ion segregation precluding layer 302 is obtained by putting the semiconductor substrate 300 having trench 301 in a high-temperature furnace (a furnace that is generally used in a semiconductor mass-production line) at about 800 ⁇ C and annealing the semiconductor substrate 300 while flowing nitride gas into the furnace at over 20 l/min. Since the semiconductor substrate 300 is silicon and the annealing process is applied with flowing the nitride gas, the impurity ion segregation precluding layer 302 formed on the bottom and sidewall of the trench 301 of the semiconductor substrate 300 is a silicon nitride which includes silicon and nitride atoms, respectively.
- a high-temperature furnace a furnace that is generally used in a semiconductor mass-production line
- the silicon nitride it is considered that a combination ratio of silicon to nitride is under 0.75 because of the large inflow of the nitride gas. That is, the silicon nitride has the most stable condition when three (3) silicon atoms are combined with four (4) nitride atoms such as Si 3 N 4 .
- the combination ratio of the silicon to the nitride is not 3:4, but the ratio of the nitride atom is higher than the silicon. Accordingly, the silicon nitride according to the present invention will be referred to a nitrogen-rich silicon nitride.
- such a nitrogen-rich silicon nitride can be Si 3 N 4.1 , Si 3 N 4.2 , Si 3 N 4.3 , Si 3 N 4.4 . . . , or Si 2.9 N 4 , Si 2.8 N 4 , Si 2.7 N 4 , Si 2.6 N 4 , that is, when the silicon atom is 3, the nitride atom is at least 4, or when the nitride atom is 4, the silicon atom is less than 3.
- the impurity ion segregation precluding layer is considerably thin, of which a thickness is less than 10A. Since the thickness of the insulating film is less than 10A, the insulating film is a single nitride atom layer. However, it has been observed through the experiment that the impurity ion segregation effect of this thin layer is excellent.
- the thickness of the impurity ion segregation precluding layer according to the present invention is not a measured value but an estimated one, because “Telcor” of Telcor which the inventor used for measuring the film can only measure a film which has a thickness of at least 10A. As a result of measuring the thickness of the impurity ion segregation precluding layer, it indicated 10A, which is the lowest value that the instrument could measure. Thus, it is estimated that the thickness of the film is 10A or less.
- the impurity permeation preventing film is a silicon nitride.
- the amount of the employed nitride gas is considerably larger than the nitride gas (6 l/min at its maximum), which is used for the annealing process in the semiconductor device fabrication process, it is considered to be the nitrogen-rich silicon nitride.
- the inventor additionally carried out the following experiment to evaluate the existence of the impurity ion segregation precluding layer and the characteristics thereof.
- Table 1 illustrates results of the experiment that measured a thickness of an oxide formed on the semiconductor substrate when the semiconductor substrate was placed in the furnace at a temperature of at least about 800 ⁇ C and annealed in an oxygen atmosphere while flowing the nitride gas at 12 l/min and 20 l/min, respectively, thereinto.
- the thickness of the oxide formed on the silicon substrate which was obtained under the same conditions in the oxygen atmosphere was 70A.
- the thickness of each oxide formed on the semiconductor substrate was less than 70A.
- the oxide formed on the silicon semiconductor substrate had a thickness of 66.8A on average through experiments of three times, which had nearly the same result as the oxide formed on the semiconductor substrate without the nitride gas inflow into the furnace.
- the oxide formed on the silicon semiconductor substrate had a thickness of 36.6A on average through experiments of three times, which has about half the thickness of the oxide formed on the semiconductor substrate without the nitride gas inflow into the furnace. Accordingly, it can be seen that when the nitride gas was flowed at least at 20 l/min during the annealing process, there is formed a film that prevents oxidization of a surface of the silicon semiconductor substrate.
- Si 3 N 4 which is a stable silicon nitride.
- the oxide grows, but the growth speed of the oxide was controlled while growing.
- the silicon nitride has an unstable combination of a compound, not a stable one, and thus the inventor referred to the silicon nitride as the nitrogen-rich silicon nitride.
- the nitrogen-rich silicon nitride is not sufficiently formed on the semiconductor substrate, but when the annealing process is performed with the inflow of the nitride gas into the furnace at at least 20 l/min, there is formed on the surface of the trench the nitrogen-rich silicon nitride that has a desirable effect of precluding the impurity ion segregation.
- a trench 401 is formed in a part of a semiconductor substrate 400 corresponding to a device isolation region.
- the trench 401 is formed by the following process.
- a pad oxide 411 is formed over the semiconductor substrate 400 .
- the pad oxide 411 can be formed by oxidizing a silicon substrate by a thermal oxidization method or deposited by a chemical vapor deposition method.
- a silicon nitride 412 is deposited on the pad oxide 411 , and a photoresist film (not shown) is applied on the silicon nitride 412 and a photolithography process is performed, so that the photoresist film remains on the silicon nitride 412 , which corresponds to an active region, which becomes a photoresist film pattern (not shown).
- the photoresist film pattern as a mask, the silicon nitride 412 and the pad oxide 411 are etched by a reactive ion etching method and then the semiconductor substrate 400 formed under the etched pad oxide 411 is etched to a predetermined depth, thereby forming the trench 401 .
- the semiconductor substrate is annealed at 1050 ⁇ C in an O 2 atmosphere, so that there is formed a thermal oxide 402 at a thickness of about 50-200A on the semiconductor substrate 400 in the trench 401 .
- the thermal oxide 402 is removed using an HF solution.
- the semiconductor substrate of FIG. 4 b is placed in a furnace at a temperature of at least 800 ⁇ C and annealed while flowing a nitride gas N 2 into the furnace at 20-50 l/min, thereby forming an impurity ion segregation precluding layer 403 at a thickness of 1-10A on the semiconductor substrate 400 along an inner wall and a bottom of the trench 401 .
- the impurity ion segregation precluding layer 403 is the nitrogen-rich silicon nitride which has been above described.
- ia nitride ion implantation method can be performed as a method for forming the nitrogen-rich silicon nitride on the semiconductor substrate, however since such an ion implantation method damages the surface of the semiconductor substrate it is not recommendable. Specifically, when a portion of the semiconductor substrate adjacent to the device isolation region is damaged, a leakage current may be generated, thus it is more desirable to perform the annealing process in the nitride atmosphere, rather than the ion implantation method.
- an insulator 404 is formed on an entire surface of the resultant structure of FIG. 4C including the trench 401 and an annealing process is performed to the resultant structure.
- the insulator is preferably a silicon oxide or silicon nitride. Then, a chemical mechanical polishing process is performed to the insulator 404 for thereby removing a portion of the insulator formed on the silicon nitride 412 , so that a surface level of the resultant semiconductor substrate 400 becomes planarized.
- the silicon nitride 412 and the pad oxide 411 are sequentially removed, thereby completing the fabrication of the isolation structure of the semiconductor device.
- the thin impurity ion segregation precluding layer that is, the nitrogen-rich silicon nitride at a thickness of several A is formed on the surface of the part of the semiconductor substrate corresponding to the device isolation region, thereby preventing the inter-permeation of the impurity ions between the device isolation reclion and the semiconductor substrate, which has an effect of improving the reliability of semiconductor device by stabilizing the electric characteristics of the device.
Abstract
The present invention relates to the impurity ion segregation precluding layer, the fabrication method thereof, the isolation structure for the semiconductor device using the segregation precluding layer and the fabrication method thereof, which are provided to prevent impurity ions from segregating into a device isolation region in a semiconductor substrate and eventually restrain decrease in a threshold voltage due to the segregation of impurity ion, particularly, boron ions in the semiconductor substrate. The isolation structure of the semiconductor device is fabricated by forming a trench in a portion of the semiconductor substrate; placing the semiconductor substrate into a high-temperature furnace; annealing the semiconductor substrate flowing a nitride gas at about 20 l/min into the furnace; and filling an insulator in the trench. Thus, an impurity ion segregation precluding film is formed on a surface of the trench at a thickness of 1-10A in the annealing process using the nitride gas, so that the decrease in the threshold voltage of the semiconductor device is restrained and thus the semiconductor device can stably operate.
Description
- 1. Field of the Invention
- The present invention relates to a semiconductor device, and more particularly to a layer for precluding segregation of impurity ions which prevents impurity ion permeation between a device isolation region and a semiconductor substrate, a fabrication method thereof, an isolation structure for a semiconductor device using the segregation precluding layer and a fabrication method thereof.
- 2. Description of the Conventional Art
- A LOCOS (local oxidation of silicon) structure using a LOCOS method has been often used as an isolation structure of a conventional semiconductor device, but there is limit to improvement of integration of the semiconductor device due to generation of a bird's beaks thereof. Thus, there is a tendency to adopt an STI (shallow trench isolation) or PGI (profiled groove isolation) structure in which a trench or a groove is formed in a semiconductor substrate as a device isolation structure and then an insulator is filled therein.
- FIG. 1 is a plan diagram illustrating a cell array unit of a semiconductor device, particularly, a DRAM (dynamic random access memory). A
semiconductor substrate 100 is divided into anactive region 101 and anon-active region 102 which covers theactive region 101, thenon-active region 102 being called a device isolation region. The active region is a part where a semiconductor device, that is, a transistor is formed and in which impurity ions are implanted, thus asource 101 a and adrain 101 b are provided. Thedevice isolation region 102 electrically isolates the semiconductor device and has the STI or PGI structure. Agate electrode 104 is formed on theactive region 101. A channel of the transistor is formed in a portion of the semiconductor substrate where theactive region 101 and thegate electrode 104 are overlapped. - FIG. 2A is a cross-sectional vertical view taken along the line lla-lla of FIG. 1, the line horizontally crossing the
active region 101 in a center point of a channel width of the transistor. As shown therein, theactive region 101 of thesemiconductor substrate 100 is covered by thedevice isolation region 102. Thedevice isolation region 102 is etched to a predetermined depth (for example, about 0.5-0.8 mm), thereby forming atrench 102 a and aninsulator 102 b is filled therein. Thesource 101 a and thedrain 101 b, as shown in FIG. 1, are provided in thesemiconductor substrate 100 having a predetermined distance and a gateinsulating film 103 and agate electrode 104 are formed on thesemiconductor substrate 100. - While, FIG. 2B is a cross-sectional vertical view taken along the line llb-llb of FIG. 1, the line being perpendicular to the line lla-lla of FIG. 1. As shown therein, the trench or
groove 102 a is formed in thesemiconductor substrate 100 and theinsulator 102 b is filled in the trench orgroove 102 a. Here, thepart 102 in which the insulator is filled corresponds to the device isolation region. Thegate insulating film 103 is formed on thesemiconductor substrate 100 and agate electrode 104 is formed thereon, thegate electrode 104 being formed in theactive region 101 and extended to the upper surface of thedevice isolation region 102. 101 c is a part where impurity ions in the semiconductor substrate segregate to the device isolation region and thus density thereof is considerably low. Also, 101 d is a center part of the channel region of the transistor. - However, the conventional semiconductor device having the STI or PGI structure, particularly the semiconductor which is an N-channel transistor has problems as follows.
- The N-channel transistor is generally formed in a p-type semiconductor substrate or in a p-type well. Impurity ions, in particular, boron ions in the p-type semiconductor substrate or the p-type wall have a tendency to easily segregate to the device isolation region and accordingly the density of the impurity ions of a portion adjacent to the device isolation region, that is, a
portion 101 c of the semiconductor substrate adjacent to a sidewall of thetrench 102 a becomes decreased. Accordingly, an impurity depletion layer is formed in the semiconductor substrate along the sidewall of the trench. As a result, in thecenter part 101 d of the channel region the channel of the transistor is normally formed above a threshold voltage in accordance with a voltage applied to the gate electrode, but in the channel region adjacent to the device isolation region a channel is easily formed below the threshold voltage, so that the threshold voltage decreases. In addition, an electrical characteristic of the semiconductor device is unstable that, for example, a subthreshold current increases and a subthreshold current curve has a hump, which results in the deterioration of the semiconductor device. - Accordingly, the present invention is directed to an impurity ion segregation precluding layer, a fabrication method thereof, an isolation structure for semiconductor device using the impurity ion segregation precluding layer and a fabricating method thereof which obviate the problems and disadvantages in the conventional art.
- An object of the present invention is to provide an impurity ion segregation precluding layer and a fabrication method thereof that prevent impurity ions in a semiconductor substrate from permeating into a device isolation region thereof.
- Also, an object of the present invention is to provide an isolation structure of a semiconductor device and a fabrication method thereof that stabilize electric characteristics of a semiconductor device using the above impurity ion segregation precluding layer and thereby improve reliability thereof.
- To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an impurity ion segregation precluding layer having a thickness of 1-10A by placing a semiconductor substrate formed of silicon in a high-temperature furnace and annealing the semiconductor substrate while flowing a nitride gas thereinto at at least 20l/min.
- Also, to achieve the above objects of the present invention, there is provided an isolation structure of a semiconductor device, which includes a semiconductor substrate, a trench formed in a predetermined portion of the semiconductor substrate, an impurity ion segregation precluding layer formed on a surface of the trench, and an insulator filled in the trench, the impurity ion segregation precluding layer being obtained by placing the semiconductor substrate into a furnace at a high temperature and annealing the semiconductor substrate flowing a nitride gas into the furnace at about 20 l/min.
- Also, to achieve the above objects of the present invention, there is provided a method for fabricating an isolation structure of a semiconductor device, which includes forming a trench in a portion of a semiconductor substrate formed of silicon corresponding to a device isolation region, placing the semiconductor substrate into a furnace at a high temperature and annealing the semiconductor substrate flowing a nitride gas into the furnace at about 20 l/min, and filling an insulator in the trench.
- The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
- In the drawings:
- FIG. 1 is a plan diagram of a conventional DRAM cell array unit;
- FIG. 2A is a cross-sectional vertical view taken along the line lla-lla of FIG. 1;
- FIG. 2B is a cross-sectional vertical view taken along the line llb-llb of FIG. 1;
- FIG. 3 is a cross-sectional vertical view of an isolation structure of a semiconductor device according to the present invention; and
- FIGS. 4A through 4E are cross-sectional vertical views illustrating a fabrication method of an isolation structure of a semiconductor device according to the present invention.
- Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
- FIG. 3 is a cross-sectional vertical view illustrating an isolation structure of a semiconductor device using an insulating film according to the present invention.
- As shown therein, a
trench 301 is formed in a device isolation region in asemiconductor substrate 300 and an impurity ionsegregation precluding layer 302 is formed on a surface of thesemiconductor substrate 300 along a sidewall and a bottom of thetrench 301, the impurity ionsegregation precluding layer 302 having a thickness of about 1-9A. Aninsulator 303 which is a silicon oxide SiO2 or silicon nitride Si3N4 is filled in thetrench 301. The impurity ionsegregation precluding layer 302 at the thickness of 1-9A formed along the sidewall and bottom of thetrench 301 prevents the impurity ions in thesemiconductor substrate 300 from permeating through theinsulator 303 in thetrench 301, thus preventing decrease in the impurity density of the semiconductor substrate. Accordingly, decrease in the threshold voltage in which a channel is formed below the threshold voltage is prevented and thus the reliability of the semiconductor device can improve. - The impurity ion
segregation precluding layer 302 is obtained by putting thesemiconductor substrate 300 havingtrench 301 in a high-temperature furnace (a furnace that is generally used in a semiconductor mass-production line) at about 800□C and annealing thesemiconductor substrate 300 while flowing nitride gas into the furnace at over 20 l/min. Since thesemiconductor substrate 300 is silicon and the annealing process is applied with flowing the nitride gas, the impurity ionsegregation precluding layer 302 formed on the bottom and sidewall of thetrench 301 of thesemiconductor substrate 300 is a silicon nitride which includes silicon and nitride atoms, respectively. In the silicon nitride, it is considered that a combination ratio of silicon to nitride is under 0.75 because of the large inflow of the nitride gas. That is, the silicon nitride has the most stable condition when three (3) silicon atoms are combined with four (4) nitride atoms such as Si3N4. However, according to the present invention, it is considered that the combination ratio of the silicon to the nitride is not 3:4, but the ratio of the nitride atom is higher than the silicon. Accordingly, the silicon nitride according to the present invention will be referred to a nitrogen-rich silicon nitride. However, such a nitrogen-rich silicon nitride can be Si3N4.1, Si3N4.2, Si3N4.3, Si3N4.4 . . . , or Si2.9N4, Si2.8N4, Si2.7N4, Si2.6N4, that is, when the silicon atom is 3, the nitride atom is at least 4, or when the nitride atom is 4, the silicon atom is less than 3. Also, the impurity ion segregation precluding layer is considerably thin, of which a thickness is less than 10A. Since the thickness of the insulating film is less than 10A, the insulating film is a single nitride atom layer. However, it has been observed through the experiment that the impurity ion segregation effect of this thin layer is excellent. - The thickness of the impurity ion segregation precluding layer according to the present invention is not a measured value but an estimated one, because “Telcor” of Telcor which the inventor used for measuring the film can only measure a film which has a thickness of at least 10A. As a result of measuring the thickness of the impurity ion segregation precluding layer, it indicated 10A, which is the lowest value that the instrument could measure. Thus, it is estimated that the thickness of the film is 10A or less.
- The reason that it is considered that the film exists, although the thickness of the film was not accurately measured by the instrument is as follows.
- First, as described above, when forming the device isolation region by filling the insulator in the trench and then forming the transistor on the semiconductor substrate, after annealing the semiconductor substrate with the inflow the nitride gas at at least 20 l/min, decrease in the threshold voltage due to the impurity ion segregation of the semiconductor substrate was not shown. Accordingly, it can be assumed that there exists in the device isolation region a film that prevents the impurity permeation between the insulator and the semiconductor substrate.
- Further, the following explains the reason why it is assumed that the impurity permeation preventing film is a silicon nitride.
- After performing the annealing using the nitride gas, the inventor etched the semiconductor substrate with a BOE (buffered oxide etchant=buffered hydrofluorine), formed the device isolation region by filling the insulator in the trench and fabricated a transistor using the semiconductor substrate. Then, such a transistor had the same result as the semiconductor substrate before performing the BOE etching. Accordingly, it is estimated that the impurity permeation preventing film is not the silicon oxide, but there is provided a material of which nitride and silicon are combined, that is, the silicon nitride, since the silicon substrate was annealed using the nitride gas. Further, since the amount of the employed nitride gas is considerably larger than the nitride gas (6 l/min at its maximum), which is used for the annealing process in the semiconductor device fabrication process, it is considered to be the nitrogen-rich silicon nitride.
- While, the inventor additionally carried out the following experiment to evaluate the existence of the impurity ion segregation precluding layer and the characteristics thereof.
- Table 1 illustrates results of the experiment that measured a thickness of an oxide formed on the semiconductor substrate when the semiconductor substrate was placed in the furnace at a temperature of at least about 800□C and annealed in an oxygen atmosphere while flowing the nitride gas at 12 l/min and 20 l/min, respectively, thereinto. When the nitride gas was not flowed thereinto, the thickness of the oxide formed on the silicon substrate which was obtained under the same conditions in the oxygen atmosphere was 70A. However, when the nitride gas was flowed into the furnace at 12 l/min and 20 l/min, respectively, and annealed in the oxygen atmosphere, the thickness of each oxide formed on the semiconductor substrate was less than 70A. In other words, when the annealing process was performed in the oxygen atmosphere with the inflow of the nitride gas into the furnace at 12 l/min, the oxide formed on the silicon semiconductor substrate had a thickness of 66.8A on average through experiments of three times, which had nearly the same result as the oxide formed on the semiconductor substrate without the nitride gas inflow into the furnace. Further, when the annealing process was performed in the oxygen atmosphere with the inflow of the nitride gas into the furnace at 20 l/min, the oxide formed on the silicon semiconductor substrate had a thickness of 36.6A on average through experiments of three times, which has about half the thickness of the oxide formed on the semiconductor substrate without the nitride gas inflow into the furnace. Accordingly, it can be seen that when the nitride gas was flowed at least at 20 l/min during the annealing process, there is formed a film that prevents oxidization of a surface of the silicon semiconductor substrate.
- Generally, it is known that an oxide is hardly formed on Si3N4, which is a stable silicon nitride. Thus, it can be assumed that growth of the oxide was restrained because there was formed the silicon nitride of which the nitride and the silicon were combined. In particular, the oxide grows, but the growth speed of the oxide was controlled while growing. Thus, it is considered that the silicon nitride has an unstable combination of a compound, not a stable one, and thus the inventor referred to the silicon nitride as the nitrogen-rich silicon nitride.
- Further, as a result of the experiments, the oxide, formed on the semiconductor substrate when the nitride gas was flowed into the furnace at 12 l/min, has the thickness similar to the oxide which was formed without flowing the nitride gas into the furnace. Thus, it can be assumed that when the nitride gas is flowed at 12 l/min, the nitrogen-rich silicon nitride is not sufficiently formed on the semiconductor substrate, but when the annealing process is performed with the inflow of the nitride gas into the furnace at at least 20 l/min, there is formed on the surface of the trench the nitrogen-rich silicon nitride that has a desirable effect of precluding the impurity ion segregation. However, considering the fabrication cost, it is preferred to perform the annealing process with the inflow of the nitride gas into the furnace at 20 to 50 l/min.
TABLE 1 Experiment (time) 1 2 3 average Nitride 12 thickness of 66.9 66.5 67.0 66.8 (l) 20 oxide(A) 39.3 31.2 39.3 36.6 - Next, a fabrication method of the semiconductor device isolation structure of FIG. 3 according to the present invention will be described with the reference to FIGS. 4A to4E.
- First, as shown in FIG. 4A, a
trench 401 is formed in a part of asemiconductor substrate 400 corresponding to a device isolation region. Thetrench 401 is formed by the following process. First, apad oxide 411 is formed over thesemiconductor substrate 400. Thepad oxide 411 can be formed by oxidizing a silicon substrate by a thermal oxidization method or deposited by a chemical vapor deposition method. Asilicon nitride 412 is deposited on thepad oxide 411, and a photoresist film (not shown) is applied on thesilicon nitride 412 and a photolithography process is performed, so that the photoresist film remains on thesilicon nitride 412, which corresponds to an active region, which becomes a photoresist film pattern (not shown). Using the photoresist film pattern as a mask, thesilicon nitride 412 and thepad oxide 411 are etched by a reactive ion etching method and then thesemiconductor substrate 400 formed under the etchedpad oxide 411 is etched to a predetermined depth, thereby forming thetrench 401. Further, to recover a surface of thesemiconductor substrate 400 which has been damaged in the etching process to form thetrench 401, the semiconductor substrate is annealed at 1050□C in an O2 atmosphere, so that there is formed athermal oxide 402 at a thickness of about 50-200A on thesemiconductor substrate 400 in thetrench 401. - As shown in FIG. 4B, the
thermal oxide 402 is removed using an HF solution. - Next, as shown in FIG. 4C, the semiconductor substrate of FIG. 4b is placed in a furnace at a temperature of at least 800□C and annealed while flowing a nitride gas N2 into the furnace at 20-50 l/min, thereby forming an impurity ion
segregation precluding layer 403 at a thickness of 1-10A on thesemiconductor substrate 400 along an inner wall and a bottom of thetrench 401. Here, the impurity ionsegregation precluding layer 403 is the nitrogen-rich silicon nitride which has been above described. Also, ia nitride ion implantation method can be performed as a method for forming the nitrogen-rich silicon nitride on the semiconductor substrate, however since such an ion implantation method damages the surface of the semiconductor substrate it is not recommendable. Specifically, when a portion of the semiconductor substrate adjacent to the device isolation region is damaged, a leakage current may be generated, thus it is more desirable to perform the annealing process in the nitride atmosphere, rather than the ion implantation method. - As shown in FIG. 4D, an
insulator 404 is formed on an entire surface of the resultant structure of FIG. 4C including thetrench 401 and an annealing process is performed to the resultant structure. Here, the insulator is preferably a silicon oxide or silicon nitride. Then, a chemical mechanical polishing process is performed to theinsulator 404 for thereby removing a portion of the insulator formed on thesilicon nitride 412, so that a surface level of theresultant semiconductor substrate 400 becomes planarized. - Next, as shown in FIG. 4E, the
silicon nitride 412 and thepad oxide 411 are sequentially removed, thereby completing the fabrication of the isolation structure of the semiconductor device. - As described above, the thin impurity ion segregation precluding layer, that is, the nitrogen-rich silicon nitride at a thickness of several A is formed on the surface of the part of the semiconductor substrate corresponding to the device isolation region, thereby preventing the inter-permeation of the impurity ions between the device isolation reclion and the semiconductor substrate, which has an effect of improving the reliability of semiconductor device by stabilizing the electric characteristics of the device.
- It will be apparent to those skilled in the art that various modifications and variations can be made in the impurity ion segregation precluding layer, the fabrication method thereof, the isolation structure for the semiconductor device using the segregation precluding layer and the fabrication method thereof of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Claims (19)
1. An impurity ion segregation precluding layer formed on a silicon substrate and having a thickness of 10A or less, said segregation precluding layer being obtained by placing the silicon substrate in a high-temperature furnace and annealing the silicon substrate while flowing a nitride gas at at least 20 l/min thereinto.
2. The impurity ion segregation precluding layer according to claim 1 , wherein the impurity ion segregation precluding layer is a nitrogen-rich silicon nitride.
3. The impurity ion segregation precluding layer according to claim 1 , wherein the annealing process is performed in the furnace at about 800□C.
4. The impurity ion segregation precluding layer according to claim 1 , wherein the impurity ion segregation precluding layer restrains oxidization of the silicon substrate.
5. The impurity ion segregation precluding layer according to claim 1 , wherein the impurity ion segregation precluding layer is not etched by a buffered oxide etchant (BOE).
6. A method for fabricating an impurity ion segregation precluding layer, comprising the steps of:
preparing a silicon substrate and
placing the silicon substrate into a furnace at a high temperature and annealing the silicon substrate flowing a nitride gas at about 20 l/min into the furnace.
7. The method according to claim 6 , wherein the annealing process is performed in the furnace at about 800□C.
8. The method according to claim 6 , wherein the annealing process is performed to form a nitrogen-rich silicon nitride having a thickness of 10 A or less.
9. An isolation structure of a semiconductor device, comprising:
a semiconductor substrate;
a trench formed in a predetermined portion of the semiconductor substrate;
an impurity ion segregation precluding layer formed on a surface of the trench; and
an insulator filled in the trench, the impurity ion segregation precluding layer being obtained by placing the semiconductor substrate into a furnace at a high temperature and annealing the semiconductor substrate flowing a nitride gas at about 20 l/min into the furnace.
10. The isolation structure according to claim 9 , wherein the impurity ion segregation precluding layer has a thickness of 10A or less.
11. The isolation structure according to claim 9 , wherein the insulator is a silicon oxide or a silicon nitride.
12. The isolation structure according to claim 9 , wherein the impurity ion segregation precluding layer is a nitrogen-rich silicon nitride.
13. A method of fabricating an isolation structure of a semiconductor device, comprising the steps of:
preparing a semiconductor substrate;
forming a trench in a portion of the semiconductor substrate corresponding to a device isolation region;
forming a nitrogen-rich silicon nitride having a thickness of 10A or less on a surface of the trench; and
filling an insulator in the trench.
14. A method of fabricating an isolation structure of a semiconductor device, comprising the steps of:
preparing a semiconductor substrate;
forming a trench in a portion of the semiconductor substrate corresponding to a device isolation region;
placing the semiconductor substrate into a furnace at a high temperature;
annealing the semiconductor substrate flowing a nitride gas at about 20 l/min into the furnace; and
filling an insulator in the trench.
15. The method according to claim 14 , wherein the annealing process is performed to form an impurity ion segregation precluding layer having a thickness of 10A or less on a sidewall and a bottom surface of the trench of the semiconductor substrate.
16. The method according to claim 15 , wherein the impurity ion segregation precluding layer is a nitrogen-rich silicon nitride.
17. The method according to claim 14 , further comprising the steps of:
after forming the trench, annealing the semiconductor substrate at a temperature of 1000-1050□C in an oxygen atmosphere, for thereby forming a thermal oxide on the surface of the trench, the thermal oxide having a thickness of 50-200A; and
removing the thermal oxide with an HF solution.
18. The method according to claim 14 , wherein the step of filling the insulator in the trench includes:
forming an insulating film over an entire surface of the semiconductor substrate which is obtained from the annealing process; and
planarizing the insulating film by a chemical mechanical polishing method, so that the insulating film only remains in the trench.
19. The method according to claim 14 , wherein the step of forming the trench includes:
forming a pad oxide on the semiconductor substrate;
forming a silicon nitride on the pad oxide;
forming a photoresist pattern on a portion of the silicon nitride corresponding to an active region; and
removing the silicon nitride and the pad oxide by using the photoresist pattern as a mask and etching the semiconductor substrate formed under the removed pad oxide to a predetermined depth.
Priority Applications (1)
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US10/015,665 US20020123244A1 (en) | 1999-05-10 | 2001-12-17 | Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof |
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KR1019990016624A KR100319620B1 (en) | 1999-05-10 | 1999-05-10 | Isolation structure for semiconductor device and fabricating method thereof |
KR16624/1999 | 1999-05-10 | ||
US09/441,206 US6337256B1 (en) | 1999-05-10 | 1999-11-16 | Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof |
US10/015,665 US20020123244A1 (en) | 1999-05-10 | 2001-12-17 | Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof |
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US10/015,665 Abandoned US20020123244A1 (en) | 1999-05-10 | 2001-12-17 | Impurity ion segregation precluding layer, fabrication method thereof, isolation structure for semiconductor device using the impurity ion segregation precluding layer and fabricating method thereof |
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Cited By (1)
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CN102543760A (en) * | 2012-02-28 | 2012-07-04 | 上海华力微电子有限公司 | Method for increasing shallow trench isolating compressive stress and improving NMOS electron mobility |
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JP2003297915A (en) * | 2002-04-05 | 2003-10-17 | Nec Electronics Corp | Manufacturing method of semiconductor device |
US20070212850A1 (en) * | 2002-09-19 | 2007-09-13 | Applied Materials, Inc. | Gap-fill depositions in the formation of silicon containing dielectric materials |
US7335609B2 (en) * | 2004-08-27 | 2008-02-26 | Applied Materials, Inc. | Gap-fill depositions introducing hydroxyl-containing precursors in the formation of silicon containing dielectric materials |
US7141483B2 (en) * | 2002-09-19 | 2006-11-28 | Applied Materials, Inc. | Nitrous oxide anneal of TEOS/ozone CVD for improved gapfill |
US7456116B2 (en) * | 2002-09-19 | 2008-11-25 | Applied Materials, Inc. | Gap-fill depositions in the formation of silicon containing dielectric materials |
US7431967B2 (en) | 2002-09-19 | 2008-10-07 | Applied Materials, Inc. | Limited thermal budget formation of PMD layers |
US6713385B1 (en) * | 2002-10-31 | 2004-03-30 | Intel Corporation | Implanting ions in shallow trench isolation structures |
US7642171B2 (en) * | 2004-08-04 | 2010-01-05 | Applied Materials, Inc. | Multi-step anneal of thin films for film densification and improved gap-fill |
US20070212847A1 (en) * | 2004-08-04 | 2007-09-13 | Applied Materials, Inc. | Multi-step anneal of thin films for film densification and improved gap-fill |
KR101942504B1 (en) * | 2012-08-31 | 2019-01-28 | 에스케이하이닉스 주식회사 | Semiconductor device having buried gate, module and system having the device and manufacturing method of the device |
US9018108B2 (en) | 2013-01-25 | 2015-04-28 | Applied Materials, Inc. | Low shrinkage dielectric films |
KR102246280B1 (en) * | 2014-03-26 | 2021-04-29 | 에스케이하이닉스 주식회사 | Semiconductor device and method for fabricating the same |
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US4571819A (en) * | 1984-11-01 | 1986-02-25 | Ncr Corporation | Method for forming trench isolation structures |
US5447884A (en) * | 1994-06-29 | 1995-09-05 | International Business Machines Corporation | Shallow trench isolation with thin nitride liner |
US5985735A (en) * | 1995-09-29 | 1999-11-16 | Intel Corporation | Trench isolation process using nitrogen preconditioning to reduce crystal defects |
US5780346A (en) * | 1996-12-31 | 1998-07-14 | Intel Corporation | N2 O nitrided-oxide trench sidewalls and method of making isolation structure |
US6051478A (en) * | 1997-12-18 | 2000-04-18 | Advanced Micro Devices, Inc. | Method of enhancing trench edge oxide quality |
KR100292616B1 (en) * | 1998-10-09 | 2001-07-12 | 윤종용 | Manufacturing method of trench isolation |
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US5458820A (en) * | 1991-09-23 | 1995-10-17 | Essilor International Cie Generale D'optique | Method of making a thermoplastic lens coated with a thermosetting protective layer |
US5376317A (en) * | 1992-12-08 | 1994-12-27 | Galic Maus Ventures | Precision surface-replicating thermoplastic injection molding method and apparatus, using a heating phase and a cooling phase in each molding cycle |
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KR100319620B1 (en) | 2002-01-05 |
US6337256B1 (en) | 2002-01-08 |
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