WO2003017738A1

WO2003017738A1 - Large-area plasma antenna(lapa) and plasma source for making uniform plasma

Info

Publication number: WO2003017738A1
Application number: PCT/KR2002/001364
Authority: WO
Inventors: Gon-Ho Kim
Original assignee: Sem Technology Co., Ltd.
Priority date: 2001-07-20
Filing date: 2002-07-20
Publication date: 2003-02-27
Also published as: KR100476902B1; KR20030008856A

Abstract

A large area plasma antenna to generate inductively coupled uniform plasma in a large area reactor is disclosed. The antenna is composed of an inner and an outer coils. The feature of the antenna is: One end of the inner coil is connected to one end of the outer coil and the connection is not on the same plane containing those coils. The other end of the inner coil or the outer coil is connected to the terminal of power source or to the ground, respectively, or vise versa. The position between the coils and the power source or the ground is placed oppositely to the connection between the coils on the antenna. The antenna is able to regulate the strength of the induced electric field inside of the reactor so that it can control the diffusion of the plasma inside of the reactor properly and produce the large area plasma uniformly in the reactor.

Description

LARGE-AREA PLASMA ANTENNA (LAPA) AND PLASMA SOURCE FOR MAKING UNIFORM PLASMA

TECHNICAL FIELD OF THE INVENTION The present invention relates to an antenna for inductively coupled , large-area plasma and a plasma source including the antenna.

BACKGROUND OF THE INVENTION

As a plasma source, a capacitively coupled plasma source, an inductively coupled plasma source, a helicon wave plasma source, and a microwave plasma source were suggested. Among them, - the most widely used one is the inductively coupled plasma source that can form a high density plasma at a low operating pressure .

FIG. 1 shows a cross-sectional view of a representative example of the inductively coupled plasma source. As shown in FIG. 1, the inductively coupled plasma source 1 comprises a chamber 101 inside which plasma 106 is generated, a gas inlet 102 through which a reacting gas (or a processing gas) is supplied into the chamber 101, and a vacuum pump 103 which evacuate the chamber 101 by exhausting the effluent gas -from the chamber 101, produced after the treatment of the substrate with the plasma has been completed. Further, A substrate holder 105 to load the substrate 104 (for example, a wafer) to be processed is installed inside the chamber 101, and an antenna 107 connected to the RF power source 109 is installed above the chamber 101. When the electric power from a RF power source 109 through an impedance matching unit 108 is applied to the antenn . 107, RF power, i.e., a RF electric potential and a current, is imposed to the antenna 107. The imposed RF potential forms a time-dependent electric field, perpendicularly to a dielectric window 110 located below the antenna 107. The imposed RF current forms a magnetic field inside the inner space 111 of the chamber 101, and the magnetic field induces an inductive electric field. The reacting gas introduced into the chamber 101 gains a sufficient energy to be ionized from the imposed electromagnetic field and produces the plasma 106. The plasma 106 thus obtained is delivered to and processes the substrate 104 located on the substrate holder 105 to which a direct current (DC) bias voltage by other RF power source 112 is applied.

Meanwhile, the density of the plasma 106 formed inside the chamber 101 is getting higher by the inductive electric field induced from the magnetic field. This plasma is called as an inductively coupled plasma and this kind of apparatus is called as an inductively coupled plasma source (or an inductively coupled plasma generating apparatus) . This inductively coupled plasma source has a merit to produce high density plasma at a low operating pressure.

FIG. 2 shows the conventional planar spiral antenna used in the inductively coupled plasma source. When RF power is imposed to the planar spiral antenna, an electromagnetic field is formed largely at the center of the planar spiral antenna. Therefore, the density distribution of the inductively coupled plasma generated from the reacting gas is not uniform. That is, the density of the plasma is very high at the center, but it is decreased as it goes to the edge. It is well known that to process a large area substrate longer than 300mm, uniform plasma distribution should be formed at least within the substrate area. Consequently, the planar spiral antenna suffers from the disadvantage that uniform plasma cannot be obtained such that large area substrates cannot be processed.

To process large area substrates, various types- of antennae are suggested. For instance, Korean Patent Application No. 7010807/2000 discloses a parallel antenna coupled to a transformer shown in FIG. 3, in which planar antennae are situated in parallel. Korean Patent Application No. 14578/1998 discloses spinning-type large area planar antennae shown in FIGs . 4a and 4b. Korean Patent Application No. 35702/1999 discloses parallel-type antennae shown in FIGs. 5a and 5b. Nevertheless, they are also suffered from the above-mentioned problem. Further, the problems caused on applying this kinds of antennas are : difficulty on match the antenna with the electric power input, the electromagnetic field disturbance built up between the pieced antennae, difficulties on manufacturing process, and the safety problem caused during the long term operation because characteristics of some antennae are independently changed and uncontrollable. In case of the parallel antenna, since it is composed of various antenna coils, an inductor or a capacitor is required to be installed on each parallel antenna line independently to adjust the potential of the input electric current flowing on the each parallel antenna line from the input terminal to the output terminal of antenna structurally. This additional requirement also restricts the operating range of the reactor.

An antenna which has one input terminal and one output terminal is most ideal and the antenna should produce uniformly- distributed plasma by controlling the electromagnetic field formed, which avoids higher density at the center of the conventional planar spiral antenna.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an antenna that enables to control plasma density, so that the problem caused by the conventional planar spiral antenna, higher density at the center of the reactor, can be avoid. More specifically, the antenna according to the present invention solves uneven plasma distribution caused by the conventional planar spiral antenna that gives higher plasma density at the center and the rapidly decreased density at the edge .

Another object of the present invention is to provide a plasma source comprising the antenna referred above.

These objects and other objects which will be described in the detailed description of the present invention can be achieved by providing an antenna in which inductive electromagnetic field distribution in the plasma generating apparatus is managed by changing the antenna shape so that the direction of the current, which is flowing in the antenna, is controlled, a plasma with uniform distribution is generated in the plasma source, and stable operating is possible.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a representative example of the inductively coupled plasma source. FIG. 2 shows the conventional planar spiral antenna used in the inductively coupled plasma source.

FIG. 3 shows a^' parallel antenna coupled to a transformer according to Korean Patent Application No. 7010807/2000. FIGs. 4a and 4b show spinning-type large area planar antennae according to Patent Application No. 14578/1998.

FIGs. 5a and 5b show parallel-type antennae according to Korean Patent Application No. 35702/1999.

FIGs. 6 to 10 show preferred embodiments of the antennas for the large area inductively coupled plasma according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION To achieve the objects referred above, the antenna for large area inductively coupled plasma according to the present invention includes an inner coil, and an outer coil. One end of the inner coil is connected to one end of the outer coil at out of a plane containing the inner coil as well as a plane containing the outer coil . The other ends of the inner coil and the outer coil are connected to a terminal of a power source and to a ground, respectively, or vice versa. The position on which the connection between the inner coil and the outer coil is made is located in an opposite side to the position on which the connection between the coils and the power source is made. More specifically, the antenna according to the present invention includes an inner coil, an outer coil, two connection auxiliary coils and a connection coil. One end of the inner coil is connected to one end of the outer coil each other through the connection auxiliary coils and the connection coil at a different plane from the planes containing the inner coil and the outer coil, and the other ends of the inner coil and the outer coil are connected to a terminal of a power source and to a ground, respectively, or vice versa. Also, the connecting part (the connection auxiliary coils and the connection coil) and the terminal of the power source are located in an opposite side to each other.

The antenna for the large area inductively coupled plasma having the structure as discussed above could regulate the electromagnetic field induced into the reactor of the plasma source and control the diffusion of the plasma generated inside the reactor such that the plasma could be uniformly produced inside the reactor. That is, the antenna for the large area inductively coupled plasma according to the present invention has been configured to flow the current on the inner coil in an opposite direction with that of the outer coil. Therefore, the overlaps of the electromagnetic fields from the inner coil and the outer coil at the center of the reactor could be prevented, which enables to form uniform electromagnetic field and to generate evenly distributed plasma inside the reactor of the plasma source. Further, the inner and outer coils of the antenna for the large area inductively coupled plasma are connected as an integrated form in the present invention so that the antenna has a simple structure to make the refrigerant flow smooth.

The antenna for the large area inductively coupled plasma according to the present invention could be one of various shapes including circle, quadrangle (including rectangle and square) and oval. For instance, both the inner and outer coils could be formed circle, oval or quadrangle, or the inner coil could be circle or oval and the outer coil could be quadrangle, or vice versa. It is preferable that the inner coil and the outer coil are situated on the same plane, but not limited thereto. They could be located on different planes. This will be more fully illustrated, referring to accompanying figures.

FIG. 6 shows one exemplary preferred embodiment of the antenna for the large area inductively coupled plasma according to the present invention. This antenna 2 is composed of an inner coil 201 and an outer coil 202, which are not closed. One end of each coil 201 and 202 is derived by two connection auxiliary coils 203 out of the planes containing the coils 201 and 202, and is connected to each other through a connection coil 204. As a result, the connecting part, the two connection auxiliary coils 203 and the connection coil 204, is not on the same plane containing the inner coil 201 as well as the plane containing the outer coil 202. The other end 205 of the inner coil 201 is connected to a terminal of a power source (or a ground) and the other end 206 of the outer coil 202 is connected to a ground (or a power source) , respectively, and the two ends 205 and 206 of the coils 201 and 202 are located in an opposite side along the y-axis to the other ends of the coils 201 and 202 through which the connection of the two coils are made. Therefore, the electric current (i_in) at the inner coil 201 and the electric current (i_ex) at the outer coil 202 flow in an opposite direction with each other, which forms an uniform electromagnetic field inside the reactor. The power supply is, preferably, connected to the end 205 of the inner coil 201 through the dotted line 208, which has the same height with that of the connection coil 204 and pass above the end 206 of the outer coil 202 or the dotted line 207 through which the outer coil 202 is closed. Further, the end 206 of the outer coil 202 is connected to the ground at the outside of the antenna area formed by the outer coil 202 through the dotted line 209 having at least the same height with the connection coil 204. The inner coil 201, the outer coil 202, the connection auxiliary coils 203, and the connection coil 204 are made of an electrically conductive material. Although the inner coil 201 and the outer coil 202 are assembled with a regular interval, the interval can be suitably chosen such that uniform distribution of the plasma generated inside chamber by the antenna can be obtained. In addition, the refrigerant could flow smoothly through the end 205 of the inner coil 202 and the end 206 of the outer coil 202.

Meanwhile, each of the centers of the inner coil 201 and the outer coil 202 can be located in a different position with each other. Such an example is shown in Fig. 7. As shown in FIG. 7, FIGs. 7(a) and 7(b) show that the center of the inner coil is located at a different position from that of the outer coil. FIG 7(c) shows that the plane containing the inner coil is located above the plane containing the outer coil and FIG. 7(d) shows that the plane containing the inner coil is located below the plane containing the outer coil .

FIG. 8 shows another preferred embodiment of the antenna for the large area inductively coupled plasma according to the present invention, in which quadrangle coils are used. The antenna 3 is composed of an inner coil 301 and an outer coil 302, which are not closed. Both the inner coil 301 and the outer coil 302 are located on one plane, but they are connected to each other at out of the plane containing the coils 301 and 302, through two connection auxiliary coils 303 and a connection coil 304. The inner coil 301 and the outer coil 302 could have the square shape or rectangle shape. The other end 305 of the inner coil 301 is connected to the input terminal (or output terminal) and the other end 306 of the outer coil 302 is connected to the output terminal (or input terminal) . Therefore, the electric current (i_in) flowing through the inner coil 301 and the electric current (i_ex) flowing through the outer coil 302 flow in an opposite direction with each other, which forms an uniform electromagnetic field inside the reactor. The power supply is, preferably, connected to the end 305 of the inner coil 301 through the dotted line 308, which has the same height with that of the connection coil 304 and pass above the end 306 of the outer coil 302 or the dotted line 307 through which the outer coil 302 is closed. Further, the end 306 of the outer coil 302 is connected to the ground at the outside of the antenna area formed by the outer coil 302 through the dotted line 309 having at least the same height with the connection coil 304. The inner coil 301, the outer coil 302, the connection auxiliary coils 303, and the connection coil 304 are made of an electrically conductive material. Although the inner coil 301 and the outer coil 302 are assembled with the regular interval, the interval can be suitably chosen such that uniform distribution of the plasma generated inside chamber by the antenna can be obtained. In addition, the refrigerant could flow smoothly over the end 305 of the inner coil 302 and the end 306 of the outer coil 302.

FIG. 9 shows other preferred embodiment of the antenna for the large area inductively coupled plasma according to the present invention. The antenna 4 is comprised of the inner coil 401 and the outer coil 402, which are closed. Both the inner coil 401 and the outer coil 402 are located on one plane, but they are connected each other at out of the plane containing the coils 401 and 402, through two connection auxiliary coils 403 and a connection coil 404. The other end 405 of the inner coil 401 is connected to a terminal of a power source, and the other end of the outer coil 402 is connected to a ground, but the two ends 405 and 406 are point-symmetric along the center of the coils 401 and 402 with the other ends of the coils 401 and 402 through which the connection of the coils 401 and 402 are made. It is preferable that the power supply is connected to the end 405 of the inner coil 401 with the same height with that of the connection coil 404 and pass above the end 406 of the outer coil 402, and the end 406 of the outer coil 402 is connected to the ground at the outside of the region formed by the outer coil 402 with at least the same height with the connection coil 404. The electric current (i_in) flowing through the inner coil 401 and the electric current (i_ex) flowing through the outer coil 402 flow in an opposite direction with each other, which forms an uniform electromagnetic field inside the reactor. In addition, the refrigerant could flow smoothly through the end 405 of the inner coil 402 and the end 406 of the outer coil 402. Although the antenna for the large area inductively coupled plasma 4 referred above has a circular coils, it could be changed to a different shape. For instance, the inner oil 401 could have an oval shape with the longer width radii than the length radii, or vice versa. Also, the outer coil 402 could be an oval. In addition, the inner coil 401 and the outer coil 402 could be located on the different planes each other.

FIG. 10 shows further another preferred embodiment of the square antenna for the large area inductively coupled plasma. This square antenna for the large area inductively coupled plasma 5 is composed of the inner coil 501 and the outer coil 502, which are closed. Both the inner coil 501 and the outer coil 502 are located on one plane, but they are connected each other at out of the plane containing the coils 501 and 502, and is connected through two connection auxiliary coils 503 and a connection coil 504. The other end 505 of the inner coil 501 is connected to a terminal of a power source, and the other end of the outer coil 502 is connected to a ground, but the two ends 505 and 506 are point-symmetric along the center of the coils 501 and 502 with the other ends of the coils 501 and 502 through which the connection of the coils 501 and 502 are made. It is preferable that the power supply is connected to the end 505 of the inner coil 501 with the same height with that of the connection coil 504 and pass above the end 506 of the outer coil 502, and the end 506 of the outer coil 502 is connected to the ground at the outside of the region formed by the outer coil 502 with at least the same height with the connection coil 504. The electric current (i_in) flowing through the inner coil 501 and the electric current (i_ex) flowing through the outer coil 502 flow in an opposite direction with each other, which forms an uniform electromagnetic field inside the reactor. In addition, the refrigerant could flow smoothly through the end 505 of the inner coil 502 and the end 506 of the outer coil 502. In addition, the inner coil 501 and the outer coil 502 could be located on the different planes each other. The antenna for the large area inductively coupled plasma according to the present invention could be used in various plasma sources including the plasma source shown in FIG. 1. Specifically, the antenna according to the present invention can be used for various plasma sources, which comprises a chamber inside which a plasma is generated, a gas inlet through which a reacting gas is introduced into the chamber, a vacuum pump which evacuate the chamber by exhausting the effluent gas produced after the treatment with the plasma has been completed, a substrate holder to load a substrate to be processed, and a dielectric window to which an antenna is placed proximate. When an electromagnetic energy from a RF power source, which is impedance matched, is imposed to the antenna, an induced electric fields caused by the currents flowing along the inner coil and the outer coil is not overlap at the center of the coils. To the contrary, the induced electrical field caused by the current on the inner coil is diminished to a certain degree by the induced electric field caused by the current at the outer coil, and uniform electromagnetic field can be formed inside the chamber of the plasma source. As thus, the plasma with the uniform distribution is generated and is delivered to the substrate holder, whereto the negative DC voltage is biased by other RF power source and makes it possible to process the surface of the substrate in a uniform manner. If required, the antenna could be located inside the plasma source. Further, they can be connected in parallel.

More specifically, the antenna for the large area inductively coupled large area plasma is composed of the inner coil and the outer coil, in which the flow of the current on the inner coil is opposite to that of the outer coil such that the reinforcement of the electromagnetic field, which is generated from the inner coil .and the outer coil, at the center of the reactor can be avoided. For this reason, uniform plasma could be formed in the chamber. Further, the connection between the inner coil and the outer coil is achieved at out of the plane (s) containing the inner coil and the outer coil, which makes an integrated antenna, provides a smooth flow of a refrigerant. Moreover, it has an additional merit that any additional components such as a capacitor and an inductor other than a resonance- circuit are not required, and this provides additional advantages such as a simple structure and an easy manufacture .

Claims

1. An antenna for large area inductively coupled plasma comprising an inner coil and an outer coil, wherein one end of the inner coil is connected to one end of the outer coil at out of a plane containing the inner coil as well as a plane containing the outer coil, each of the other ends of the inner coil and the outer coil is connected to a terminal of a power source terminal and to a ground, respectively, and the one ends of the two coils through which the two coils are connected each other and the other ends of the two coils through which the terminal of the power source and the ground are connected are placed in an opposite side.

2. The antenna as set forth in claim 1, further comprising two connection auxiliary coils and a connection coil as well as the inner coil and the outer coil, each of the one ends of the inner coil and the outer coil is derived to out of a plane containing the inner coil as well as a plane containing the outer coil by the two connection auxiliary coils and are connected through the connection coil, and the one ends of the two coils through which the two coils are connected each other and the other ends of the two coils through which the terminal of the power source and the ground are connected are placed in an opposite side.

3. The antenna as set forth in claim 1, the current on the inner coil flows in an opposite direction to that of the outer coil .

4. The antenna as set forth in claim 1, the inner coil and the outer coil are open shape.

5. The antenna as set forth in claim 1, the inner coil and the outer coil are closed shape.

6. The antenna as set forth in claim 1, the plane containing the inner coil and the plane containing the outer coil is the same or different.

7. The antenna, set forth in claim 1, the centers of the inner coil and the outer coil are same or different .

8. The antenna as set forth in claim 1, the inner coil and the outer coil have each independently circle, quadrangle or oval shape .

9. A plasma source comprising the antenna for the large area inductively coupled plasma according to any one of the claims 1 to 8.

10. The apparatus as set forth in claim 9, comprises a chamber inside which a plasma is generated, a gas inlet through which a reacting gas is introduced into the chamber, a vacuum pump which evacuate the chamber by exhausting the effluent gas produced after the treatment with the plasma has been completed, a substrate holder to load a substrate to be processed, and a dielectric window to which an antenna is placed proximate. The apparatus as set forth in claim 9, the antenna is installed inside the chamber or outside the chamber.