JP2749264B2 - Plasma processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus using plasma generated by microwave discharge to form a thin film on a sample surface or to perform etching, sputtering, The present invention relates to a plasma processing apparatus suitable for performing plasma oxidation or the like. 2. Description of the Related Art Generally, a plasma processing apparatus utilizing plasma generated by a microwave discharge in a magnetic field includes an electron cyclotron resonance generating position generated by the magnetic field and the microwave in a discharge tube which is a part of a discharge space. And a magnetic flux density distribution that sharply decreases from the electron cyclotron resonance point toward the sample stage provided in the sample chamber.
For this reason, the plasma generated near the resonance point has a density of 1 to 4 while being transported from the discharge tube to the sample stage.
This was reduced by more than two orders of magnitude, and efficient plasma processing could not be performed. Although there is a conventional example in which the above-described resonance position is arranged in the sample chamber, most of the microwaves are absorbed at the resonance position in the discharge tube because of the arrangement of the mirror magnetic field having the resonance position in the discharge tube. In addition, the amount of plasma generated at the resonance position in the sample chamber was restricted. [0004] Even if plasma can be generated at a resonance position in the sample chamber, most of the plasma is generated in the direction of the discharge tube because the magnetic field gradient in the vicinity thereof is directed from the sample chamber to the discharge tube. As a whole, the flow rate of plasma toward the sample stage is reduced, and efficient plasma processing cannot be performed. A description will be given below with reference to the drawings. FIG. 4 is a summary P of the 31st Semiconductor Integrated Circuit Technology Symposium held on December 3 and 1986.
49 to 54 "CVD using ECS plasma" (hereinafter referred to as "CVD using ECS plasma").
A microwave 4 is incident on a discharge tube 2 having a magnetic field coil 1 on the outside through a waveguide 3 from an entrance window 5, and an electron cyclotron in a magnetic field generated by the magnetic field coil 1 is shown. When the motion and the microwaves 4 resonate at the resonance position, resonance electrons collide and ionize the plasma gas 6 to generate plasma. Then, the sample 7 is connected to the discharge tube 2.
The generated plasma is pushed out using a magnetic field gradient in the direction of the sample chamber 9 provided with the sample stage 8 holding the sample. This apparatus excites or ionizes the material gas 10 newly introduced into the sample chamber 9 by the plasma or the plasma to plasma-treat the surface of the sample 7. FIG. 5 shows the magnetic flux density distribution from the microwave entrance window 5 to the sample table 8 in FIG. 4, and the vertical axis is the axial direction with the boundary between the discharge tube 2 and the sample chamber 9 being 0. The distance and the horizontal axis are the magnetic flux density. In the case of the conventional example A, the magnetic flux density causing electron cyclotron resonance corresponding to the frequency (2.45 GHz) of the incident microwave 4 is Be (875 gauss).
In FIG. 5, this position is located about 3 cm in the axial direction from the microwave entrance window 5. For this reason, only the region of 3 cm is effective for plasma generation from the propagation characteristics of microwaves in the plasma and the condition of resonance absorption of microwave energy, and the plasma generated in the region of approximately 3 cm is approximately 3 cm.
It is transported in the direction of the sample table 8 by ambipolar diffusion under the force of the magnetic field gradient between 5 cm. At this time, since the transport distance is long and the magnetic field is rapidly reduced, the density of the plasma transported to the surface of the sample 7 is smaller than the plasma density near the resonance position where the electron cyclotron resonance occurs. Tended to decrease. FIG. 6 is a summary P6 of the 31st Semiconductor Integrated Circuit Technology Symposium held on December 3 and 4, 1986.
1-66 "a-Si: H by ECR plasma CVD method"
FIG. 7 shows the magnetic flux density distribution of the “film” (hereinafter referred to as Conventional Example B). The difference from Conventional Example A is that the magnetic flux density distribution is large as a whole. In addition, the position of the magnetic flux density corresponding to the resonance position is still in the discharge tube 2, and the region where the magnetic flux density is higher than that and effective for the resonance absorption of the microwave is a maximum of 2. / 3. Further, since the magnetic flux density decreases rapidly in the direction of the sample stage 8, the density of the plasma generated in the vicinity of the resonance position becomes smaller than that of the sample 7 as in the conventional example A.
Tended to decrease due to loss while diffusing to the surface of. FIG. 8 shows JP-A-59-3018 (hereinafter referred to as Conventional Example C), and FIG. 9 shows the magnetic flux density distribution. The conventional example C shown in FIG. 1 employs a mirror magnetic field configuration which is often used as a plasma confinement method for the purpose of increasing the plasma density, and is used to increase the magnetic body density near the surface of the sample 7 in the sample chamber 9. A permanent magnet 13 is provided. In the conventional example C, the incident microwave 4
Is propagated in a magnetic flux density region (region (I) in FIG. 9) larger than the resonance position and is resonantly absorbed in the plasma near the first resonance position (a in FIG. 9). However, if the magnetic flux density further passes the resonance position and attempts to propagate in a magnetic flux density region (region (II) in FIG. 9) smaller than the resonance position, it becomes difficult for the plasma to propagate. The plasma generated in (b) in FIG. 9 receives a force in the direction of the discharge tube due to the magnetic field gradient.
The density of the plasma incident on the substrate has a tendency to decrease as in the conventional examples A and B, as compared with the plasma density near the first resonance position. As described above, in the above conventional method, no consideration is given to the position where the density of the plasma generated by the electron cyclotron resonance in the microwave and the magnetic field decreases due to the loss while being transported to the sample surface. . In the above prior art, the relationship between the plasma density distribution and the magnetic flux density distribution in the direction from the discharge tube to the sample table is not taken into consideration, and the vicinity of the electron cyclotron resonance generation position to the sample surface is not considered. Since the density of the plasma to be transported tends to decrease, there is a problem that the utilization efficiency of the plasma is low and a high-quality film cannot be obtained, and the processing speed is slow and efficient plasma processing cannot be performed. The present invention has been made in view of the above points,
It is an object of the present invention to provide a plasma processing apparatus capable of improving the quality of a processing film by greatly improving the utilization efficiency of generated plasma and increasing the processing speed. An object of the present invention is to increase the magnetic flux density on the microwave introduction side of a discharge tube to be greater than the magnetic flux density at the position where electron cyclotron resonance occurs due to the magnetic field and the microwave. To at least the sample stage
Has an almost monotonically decreasing magnetic flux density distribution shape,
In the electron cyclotron resonance, the magnetic flux density is on the same surface.
Is formed, and the resonance generating position of the electron cyclotron resonance, plasma processing apparatus located at least in part a sample chamber, also the magnetic flux density of the microwave introduction side of the discharge tube, the electron cyclotron resonance by the magnetic field and the microwave Larger than the magnetic flux density at the resonance occurrence position, and from the discharge tube
At least up to the sample stage position, the magnetic flux density decreases almost monotonically
Electron cyclotron resonance
Auxiliary magnetic flux density is formed in the same plane, and is positioned on at least a portion sample chamber resonance generating position of the electron cyclotron resonance, which generates a weak magnetic field than the magnetic flux density of the magnetic field generated by the magnetic field generating means This is achieved by a plasma processing apparatus having a magnetic field generating means. In general, a microwave that propagates in a plasma and causes electron cyclotron resonance is a clockwise circularly polarized wave, and this wave has a magnetic flux smaller than a magnetic flux density necessary for causing the electron cyclotron resonance. In a dense plasma,
Cut off and cannot propagate. For this reason, according to the present invention, the magnetic flux density at the microwave entrance end of the vacuum vessel is made larger than the magnetic flux density at the electron cyclotron resonance position, so that the
Magnetic flux that decreases almost monotonically from the position of at least the sample stage
In addition to having a density distribution shape, electron cyclotron resonance
A magnetic flux density is formed on the same surface, and the electron cyclotron resonance position is at least partially located in the sample chamber, so that a region where high-density plasma is generated in a magnetic flux density region higher than the resonance magnetic flux density is evacuated. It can be extended to the vicinity of the sample stage in the container, and the distance that the plasma is pushed out by the magnetic field gradient and transported to the sample stage can be reduced to zero. With this, the distance between the resonance position and the sample table can be made sufficiently small with respect to the plasma density which rapidly decreases on the magnetic flux density side smaller than the resonance magnetic flux density, so that high-density plasma is transported to the sample surface. It becomes possible. An embodiment of the plasma processing apparatus according to the present invention will be described below with reference to FIGS. 1, 2 and 3. FIGS. 1 and 2 show an example in which the present invention is applied to a plasma processing apparatus for performing a sample surface treatment (film formation) by magnetic field microwave discharge. FIG. 1 shows a structure, in which a microwave 4 is introduced through a waveguide 3 into a discharge tube 2 forming a vacuum vessel provided with a magnetic field coil 1 on the outside. The plasma is generated by exciting or ionizing the gas 6 by electron cyclotron motion in the magnetic field generated by the magnetic field coil 1 and electron cyclotron resonance by the microwave 4. Then, the plasma is generated by the gradient of the magnetic field generated by the magnetic field coil 1 in the direction of the sample chamber 9 forming a vacuum vessel provided with a sample stage 8 holding the sample 7 to be processed, which is connected to the discharge tube 2. And the material gas 10 newly introduced into the front surface of the sample 7 in the sample chamber 9 is excited by the plasma flow or transported to the surface of the sample 7 while being ionized. This is a plasma processing apparatus that generates a thin film having a composition using the application gas 6 and the material gas 10. FIG. 2 shows the magnetic flux density distribution in the axial direction from the discharge tube 2 to the sample table 8 in this embodiment. The horizontal axis indicates the axial distance, and the vertical axis indicates the magnetic flux density. The present invention is characterized in that the distribution shape of FIG.
FIG. 2 shows a magnetic flux density distribution shape when the electron cyclotron resonance generated magnetic field position is at the boundary point between the sample chamber 9 and the sample chamber 9. FIG. 2 shows an example of a known magnetic flux density distribution. In FIG. 1, a microwave (2.45 GHz) 4 introduced into the discharge tube 2 by the waveguide 3 has a magnetic flux density (Be = corresponding to the resonance position) in the magnetic flux density distribution shape of FIG. 875 gauss) is located near the sample table 8 in the sample chamber 9 (point a in FIG. 1).
Propagating in the magnetic flux density region equal to or higher than the magnetic flux density corresponding to the resonance position in the discharge tube 2 and entering the sample chamber 9 and approaching the resonance position, ionization and excitation by electron cyclotron resonance are activated, and the plasma is proportionally increased. The density also increases, and the plasma generation probability reaches a maximum value at the resonance position. But,
When the microwave tries to propagate in a plasma having a magnetic flux density smaller than the magnetic flux density (875 gauss in this embodiment) corresponding to the resonance position, the microwave rotates right-handed circularly polarized, causing the electron cyclotron resonance. Due to the nature of the wave, it is cut off and cannot be propagated, and the microwave that has not been resonantly absorbed in the plasma is reflected at this resonance position. For this reason, in the low magnetic flux density region on the sample stage 8 side from the resonance position, almost no plasma is generated, and the plasma reaching the surface of the sample 7 is accompanied by a magnetic field that gradually decreases from the resonance position toward the sample stage 8. The plasma transported by ambipolar diffusion and the material gas 10 introduced in the vicinity of the resonance position become atoms and molecules ionized and excited by the plasma flow. Therefore, the sample table 8 is moved from the resonance position.
The plasma density distribution in the direction shows a sharp decrease. However, according to the present invention, since the distance from the resonance position to the sample surface can be reduced to substantially zero, it is possible to arrange the surface position of the sample 7 before the plasma density sharply decreases. 7 The ion density which gives an ion bombardment which has an effect on the density at the time of film formation can be appropriately selected without reducing the processing speed which is almost proportional to the electron density near the surface. Can be generated. FIG. 3 shows the film formation rate when a thin film is formed on the sample surface according to the present embodiment, and is measured under the condition that the film composition is constant. The lower part of the horizontal axis in FIG. 3 shows the magnetic flux density distribution shape (〜) shown in FIG.
The upper part of the horizontal axis shows the corresponding electron density on the sample surface in an arbitrary unit (electron density ratio), and the vertical axis shows the film forming rate in arbitrary units (film forming rate ratio). As is clear from this figure, when the resonance position is located in the sample chamber 9 (in FIG. 3) and closer to the surface of the sample 7, the electron density increases, and as a result, It can be seen that the film forming speed is greatly increased. FIGS. 10 and 11 show another embodiment of the present invention. FIG. 10 shows that an auxiliary magnetic field generating means 21 for generating a magnetic field on the sample chamber 9 side is provided outside the sample chamber 9 as means for positioning the position of the electron cyclotron resonance generated magnetic field in the sample chamber 9. FIG. 11 shows the magnetic flux density distribution in the axial direction of the embodiment of FIG. The broken line in FIG. 11 shows a magnetic flux density distribution curve obtained only by the magnetic field coil 1 in FIG. 10, and the broken line in FIG. 11 shows a magnetic flux density distribution curve obtained only by the auxiliary magnetic field generating means in FIG. As a result, the curve in FIG. 11 becomes a superposition of and, and the position of the resonance generating magnetic field is
It is pulled out in the direction indicated by the arrow in the middle, and is located in the sample chamber 9. In order for the auxiliary magnetic field generating means 21 to position the resonance generating position in the sample chamber 9, the magnetic flux density may be approximately 50 gauss or more. In this embodiment, the size of the magnetic field coil 1 can be reduced, the same effect as that of the embodiment shown in FIGS. 1 to 3 can be obtained, and by adjusting the auxiliary magnetic field generating means 21,
The resonance generation position can be moved and adjusted without significantly affecting the magnetic field distribution in the discharge tube 2 due to the magnetic field coil 1, and the flow diameter, density, etc., of the plasma extracted by the auxiliary magnetic field generation means 21 can be adjusted. There is an effect that it can be controlled. According to the plasma processing apparatus of the present invention described above, the magnetic flux density on the microwave introduction side of the discharge tube is larger than the magnetic flux density at the position where the electron cyclotron resonance occurs due to the magnetic field and the microwave. And less from the discharge tube
Magnetic flux density distribution almost monotonically decreasing up to the sample stage
And the electron cyclotron resonance has the shape
It is formed on the magnetic flux density the same surface, and the resonance generating position of the electron cyclotron resonance, plasma processing apparatus located at least in part a sample chamber, also the magnetic flux density of the microwave introduction side of the discharge tube, and a magnetic field The magnetic flux density at the position where the electron cyclotron resonance is generated by microwaves is made larger than the magnetic flux density, and at least the position from the discharge tube to the position of the sample stage is almost
It has a monotonously decreasing magnetic flux density distribution shape and the electron
In cyclotron resonance, the magnetic flux density is formed on the same plane.
Is, and is positioned on at least a portion sample chamber resonance generating position of the electron cyclotron resonance, plasma processing apparatus comprising an auxiliary magnetic field generating means for generating a weak magnetic field than the magnetic flux density of the magnetic field generated by the magnetic field generating means Because the distance between the high-density plasma generation position and the surface of the sample is reduced, high-density plasma can be transported to the sample surface, and plasma processing with good film quality and high processing speed can be performed. It is very effective for the seed plasma processing method.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a magnetic field microwave discharge plasma processing apparatus showing one embodiment of the present invention. FIG. 2 is a characteristic diagram showing an axial magnetic flux density distribution in the apparatus of FIG. FIG. 3 is a characteristic diagram showing a relationship between a film forming speed ratio, a magnetic flux density distribution shape, and a corresponding electron density ratio when a film is formed by the apparatus of FIG. FIG. 4 is a cross-sectional view showing a plasma processing apparatus of Conventional Example A. FIG. 5 is a characteristic diagram showing an axial magnetic flux density distribution in the device of FIG. FIG. 6 is a sectional view showing a plasma processing apparatus of Conventional Example B. FIG. 7 is a characteristic diagram showing an axial magnetic flux density distribution in the device of FIG. 6; FIG. 8 is a sectional view showing a plasma processing apparatus of Conventional Example C. FIG. 9 is a characteristic diagram showing an axial magnetic flux density distribution in the apparatus of FIG. FIG. 10 is a sectional view showing another embodiment of the present invention. 11 is an axial magnetic flux density distribution diagram in the device of FIG. [Description of Signs] 1 ... magnetic field coil, 2 ... discharge tube, 3 ... waveguide, 4 ... microwave, 5 ... incident window, 6 ... plasma gas, 7 ... sample, 8
... sample stage, 9 ... sample room, 10 ... material gas, 11a, 11b
... cooling water, 12 ... evacuation.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/302 B (72) Inventor Tadashi Sonobe 3-chome, Saimachi, Hitachi-shi, Ibaraki Pref. No. 1 Hitachi, Ltd. Hitachi Plant (72) Inventor Atsushi Chiba 3-1-1, Sakaimachi, Hitachi City, Ibaraki Prefecture Hitachi Ltd.Hitachi Plant (72) Inventor Naohiro Kadoma 4026 Kujicho, Hitachi City, Ibaraki Prefecture Address Hitachi, Ltd.Hitachi Laboratory (72) Inventor Yasuhiro Mochizuki 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Laboratory (72) Inventor Shigeru Takahashi 4026 Kuji-cho, Hitachi City, Ibaraki Hitachi, Ltd. In the laboratory (72) Inventor Takuya Fukuda 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Research Laboratory (56) References JP-A-60-1 34423 (JP, A) JP-A-61-125133 (JP, A) JP-A-57-79621 (JP, A)

Claims (1)

(57) [Claims] A discharge gas is introduced, a discharge tube forming a part of the discharge space, a magnetic field generating means for generating a magnetic field in the discharge space of the discharge tube, and a microwave introduced into the discharge space of the discharge tube. Means, and a plasma processing apparatus comprising: a sample chamber connected to the discharge tube, and a sample stage for holding a sample to be processed is disposed, wherein the magnetic flux density on the microwave introduction side of the discharge tube is Larger than the magnetic flux density at the position where the electron cyclotron resonance occurs due to the magnetic field and the microwave, and at least from the discharge tube.
The magnetic flux density component that decreases almost monotonically up to the position of the sample stage
It has a cloth shape and the electron cyclotron resonance is
Serial magnetic flux density is formed in the same plane, and, a plasma processing apparatus resonance generation position of the electron cyclotron resonance, characterized in that located in at least part the sample chamber. 2. A discharge gas is introduced, a discharge tube forming a part of the discharge space, a magnetic field generating means for generating a magnetic field in the discharge space of the discharge tube, and a microwave introduced into the discharge space of the discharge tube. Means, and a plasma processing apparatus comprising: a sample chamber connected to the discharge tube, and a sample stage for holding a sample to be processed is disposed, wherein the magnetic flux density on the microwave introduction side of the discharge tube is Larger than the magnetic flux density at the position where the electron cyclotron resonance occurs due to the magnetic field and the microwave, and at least from the discharge tube.
The magnetic flux density component that decreases almost monotonically up to the position of the sample stage
It has a cloth shape and the electron cyclotron resonance is
Serial magnetic flux density is formed in the same plane, and a resonance generating position of the electron cyclotron resonance is located at least partially said sample chamber, to generate a weak magnetic field than the magnetic flux density of the generated magnetic field of the magnetic field generating means A plasma processing apparatus comprising an auxiliary magnetic field generating means.