JPH10308298A - Plasma processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the generation of damage of a sample at the minimum, and while to enable the even plasma processing with the simple structure by providing permanent magnets for forming a magnetic field, which regulates the progress of the plasma, between a sample and an inner wall of a vacuum container so as to surround the sample, and adjusting a space between the sample and the magnets in the circumferential direction of the sample. SOLUTION: Since the predetermined magnetic field is formed between a sample 10, a plasma generating chamber 12 and an inner wall of a reaction chamber 14, dispersion of plasma to the inner wall side is restrained, and a grade of plasma, density to be lowered toward the inner wall is gradually formed so as to even the plasma density on the sample 10 and so as to improve the evenness of the radiating direction toward the inner wall. But in the case where uneven plasma is generated in the circumferential direction of the sample 10 by the magnetic field distribution of the microwave led to the plasma generating chamber 12 and the reaction chamber 14, evenness is hard to be secured. A space between the sample 10 and the permanent magnets 44 is adjusted by the sample 10 in the circumferential direction so as to secure evenness of the plasma on the sample 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing technique for performing processes such as etching and thin film formation in a process of manufacturing electronic parts and semiconductor elements by using plasma.

[0002]

2. Description of the Related Art In a plasma processing apparatus, microwaves are introduced into a vacuum vessel containing a small amount of reaction gas, and a gas discharge is generated in the vacuum vessel to generate plasma. And
By irradiating the surface of the sample substrate with the plasma, processes such as etching and thin film formation are performed. Such a plasma processing apparatus is being studied as being indispensable for manufacturing a highly integrated semiconductor device. Especially,
Electron cyclotron resonance (ECR: El
An ECR plasma processing apparatus using ectron cyclotron resonance has been put to practical use as an apparatus capable of generating highly active plasma under a low gas pressure region.

In order to improve the processing quality in a plasma processing apparatus, it is important that the plasma has a uniform density over the entire range of the sample. In particular, when the processing area of a sample becomes large, such as a semiconductor wafer having a diameter of 300 mm, which has been developed in recent years, it is more important than ever to maintain a uniform plasma (particularly, ion) intensity distribution on the sample. However, it has been difficult to maintain plasma uniformity on the sample. For example, if the sample is irradiated with plasma generated in a vacuum vessel using a divergent magnetic field in which the strength of the magnetic field weakens with an appropriate gradient toward the sample, the processing surface of the sample is used. The distribution of the magnetic flux density above becomes non-uniform. In addition, the plasma in the vacuum container is basically illuminated on the sample by being constrained by the magnetic field (divergent magnetic field) in the vacuum container. Become noticeable.

[0004] If the distribution of plasma particles on the sample is not uniform, a high ion density region and a low ion density region are formed on the sample.
Inconveniences such as deterioration of processing speed uniformity or anisotropy occur. In addition, a potential difference may be generated on the sample, a current may flow, and a semiconductor element formed on the sample may be broken. On the other hand, in the CVD process, the thickness of the film formed on the semiconductor substrate becomes uneven, and uniform film formation becomes difficult. In addition, due to the non-uniformity of the plasma processing of the semiconductor substrate, the quality of the finally manufactured semiconductor device deteriorates.

For this reason, conventionally, Japanese Patent Publication No. 6-4
0542, JP-A-6-210646, JP-A-1-222
As shown by reference numeral 437, a permanent magnet is arranged behind the sample (below the sample stage) with respect to the plasma transport direction to make the magnetic flux density distribution on the sample stage uniform, thereby improving the plasma uniformity. I was planning.

[0006]

However, in the above-described conventional method, the magnetic field formed in the vacuum chamber by the coil for plasma generation is forcibly controlled on the sample, and therefore various problems are caused. There has occurred. For example, when a magnet is arranged below (rearward) the outer peripheral portion of the sample, the divergence of the plasma becomes larger in the central portion of the sample than in the outer peripheral portion of the sample. As a result, the charged particles are accelerated at the center of the sample, causing damage to the sample. Also,
Since the magnetic flux toward the sample surface is locally bent, the magnetic flux density, that is, the plasma density becomes non-uniform. Further, when a high-frequency bias (RF bias) is applied to the sample (sample stage), the impedance of the plasma becomes spatially non-uniform, and the RF bias applied to the sample becomes non-uniform. These various problems have hindered uniform processing of the sample.

Further, the electric field intensity distribution of the microwave introduced into the vacuum vessel is, for example, a circular TE which is a fundamental mode.
If you have a distribution that is not axisymmetric like ₁₁ modes,
The distribution of the plasma generated by the microwave is not axially symmetric. As a result, the distribution of the processing speed of the sample also differs in the X and Y directions. Such inconvenience can be avoided by converting the mode of the microwave before the microwave is introduced into the vacuum vessel, but it involves an increase in the configuration and size of the plasma processing apparatus.

[0008] The present invention has been made in view of the above situation, and while minimizing damage to a sample,
It is an object of the present invention to provide a plasma processing apparatus that can realize uniform plasma processing with a simple configuration.

[0009]

In order to solve the above-mentioned problems, a plasma processing apparatus according to the present invention comprises a sample (10) provided between a sample (10) and inner walls of vacuum vessels (12, 14).
And a permanent magnet (44) that forms a magnetic field that regulates the progress of the plasma. Then, the distance between the sample (10) and the magnet (44) is adjusted in the circumferential direction of the sample (10).

For example, the permanent magnet (44) is composed of a plurality of permanent magnet pieces (44a) and these permanent magnet pieces (44)
The distance between a) and the sample (10) can each be adjusted. Further, the distance from the sample (10) can be adjusted by using a ring-shaped integral permanent magnet (48) arranged so as to surround the sample (10) and adjusting the diameter thereof.

[0011]

As described above, in the present invention, the sample (1
0) and the inner wall of the vacuum vessel (12, 14), a predetermined magnetic field is formed, so that the diffusion of plasma to the inner wall side of the vacuum vessel (12, 14) is suppressed, and the vacuum vessel (12, 14) 1
4) The plasma density gradient decreasing toward the side can be moderated, which can contribute to the improvement of the uniformity of the plasma density on the sample (10). Such a method improves the uniformity in the radial direction from the center of the sample (10) toward the inner wall of the vacuum vessel (12, 14), and the plasma density in the circumferential direction on the sample (10) is reduced. Great effect when uniform. However, vacuum containers (12, 14)
When a non-uniform plasma is generated in the circumferential direction of the sample (10) due to the influence of the magnetic field intensity distribution of the microwave introduced into the sample, the uniformity of the plasma on the sample (10) is sufficiently ensured. It becomes difficult. In the present invention, the distance between the sample (10) and the magnet (44) is set to the distance between the sample (1) and the magnet (44).
Since the adjustment is performed in the circumferential direction of the sample (10), the sample (1) is not affected even when an uneven plasma is generated in the circumferential direction of the sample (10) due to the influence of the magnetic field intensity distribution of the microwave.
0) The uniformity of the plasma above can be ensured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to examples. In each of the embodiments described below, the technical idea of the present invention is applied to plasma processing of a silicon wafer, which is a part of a manufacturing process of a semiconductor device.

[0013]

FIG. 1 shows a configuration of a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus of the present embodiment includes:
A predetermined plasma process such as etching is performed on a silicon wafer 10 having a diameter of 300 mm. The silicon wafer 10 includes a plasma generation chamber 12 having a hollow cylindrical shape for generating plasma, and a reaction chamber 14 communicating with the plasma generation chamber 12. I have.
Samples processed by this apparatus include a silicon wafer 10 having a diameter of 300 mm, a wafer having a diameter of 200 m, and an LC.
Various samples requiring uniform plasma treatment, such as a glass substrate for D, can be targeted. Plasma generation chamber 1
A circular waveguide 16 connected to a microwave oscillator (not shown) such as a magnetron is connected to an upper portion of the circular waveguide 2 to transmit microwaves (2.45 GHz) to the circular waveguide 1.
6 to the plasma generation chamber 12.

A microwave introduction window 20 is arranged between the circular waveguide 16 and the plasma generation chamber 12. The microwave introduction window 20 is made of a microwave transmitting material such as quartz glass, and is designed to hermetically seal the plasma generation chamber 12. Outside the plasma generation chamber 12, three-stage main coils 22, 24, and 26 are arranged so as to include a connection part of the circular waveguide 16 and concentrically surround the connection part. Below the main coils 22, 24, 26, a one-stage sub coil 28 is arranged. The main coils 22, 24, 26 and the sub-coils 28 receive a necessary current from the current supply unit 40 and
A region (100) having a magnetic flux density of 875 gauss satisfying the ECR condition is formed therein. In the reaction chamber 14 connected to the plasma generation chamber 12, a sample table 32 for holding the silicon wafer 10 by a fixing means such as electrostatic suction is provided.

Around the sample table 32, a silicon wafer 1
A permanent magnet 44 is provided so as to be concentric with zero. As will be described later, the permanent magnet 44 includes a plurality of magnet pieces 44a (FIG. 2), and each of the magnet pieces 44a can be adjusted in the radial direction of the silicon wafer 10.

On the side wall of the reaction chamber 14, the plasma generation chamber 1
An exhaust pipe 34 for exhausting the gas in the reaction chamber 14 and the reaction chamber 14 is provided, and the plasma generation chamber 12 and the reaction chamber 14 are maintained in a high vacuum state by evacuation from the exhaust pipe 34. The reaction chamber 14 is provided with a gas supply pipe 36 for supplying a reaction gas required for plasma generation. Although not shown, a coolant path is formed around the plasma generation chamber 12, and the plasma generation chamber 12 is cooled by cooling water (coolant) circulating through the coolant path.

In the apparatus shown in FIG. 1, a high-frequency power supply 48 having one end grounded is connected to the sample table 32,
By applying RF power to the sample stage 32, a chemical reaction occurring near the surface of the silicon wafer 10 can be promoted. As a result, it is possible to improve the efficiency of the plasma processing, such as an improvement in the thin film deposition rate.

FIG. 2 shows the structure of the permanent magnet 44 disposed around the sample table 32. The permanent magnet 44 is connected to the sample table 32.
Magnet pieces 44a arranged at equal intervals so as to surround
It is composed of The 16 magnet pieces 44a have the same strength (magnetic force), and are arranged such that the inscribed circle of these magnet pieces 44a is elliptical with respect to the center of the silicon wafer 10. That is, they are arranged such that the diameter in the Y direction is slightly smaller than the diameter in the X direction. It is needless to say that the number of the magnet pieces 44a is not limited to 16 and can be increased or decreased as needed. The ratio of the arrangement of the magnet pieces 44a (ellipticity: vertical diameter / horizontal diameter) and the interval between the silicon wafers 10 is appropriately changed according to the plasma intensity distribution.

Each of the magnet pieces 44a and the silicon wafer 1
The distance to 0 is also set in consideration of various effects. A magnet 44 is provided inside the magnet piece 44a (on the sample stage 32 side).
The magnetic field in the opposite direction to the magnetic field on the upper surface (magnetic field from bottom to top)
May be formed, and may act to lower the plasma density on the silicon wafer 10. Such a magnetic field is a relatively weak magnetic field as compared with the magnetic field on the upper surface of the magnet piece 44a. However, when the magnet piece 44a is too close to the sample table 32, the plasma at the end of the silicon wafer 10 (sample) is generated. May reduce density. Therefore, in the present embodiment, the influence of the magnetic field in the opposite direction (from bottom to top) does not appear.
At an appropriate distance from the sample table 32, each magnet piece 44a
Place.

The distance between the magnet piece 44a and the inner wall of the reaction chamber 14 is also set to an appropriate value. Since the plasma density has a gradient that decreases toward the inner wall of the reaction chamber 14, when the plasma contacts the inner wall, electrons and ions recombine and disappear, and the plasma density becomes zero. Therefore, if the magnet piece 44a is too close to the inner wall of the reaction chamber 14, the plasma cannot be sufficiently trapped and escapes to the wall 12a side. Therefore, in this embodiment, the magnet pieces 44a are arranged at an appropriate distance from the inner wall so that the plasma can be sufficiently trapped and the inner wall of the reaction chamber is not affected.

FIG. 3 shows an electric field intensity distribution of a microwave (circular TE ₁₁ mode) transmitted through the microwave introduction window 20 and introduced into the plasma chamber 12. As can be seen from the figure, the electric field intensity distribution of the microwave differs between the X direction and the Y direction, and the plasma density distribution in the circumferential direction on the silicon wafer 10 becomes non-uniform. The apparatus of the present invention corrects such non-uniformity of the plasma density distribution.

Next, the overall operation of this embodiment will be described. When etching the polysilicon film formed on the silicon wafer 10 using the apparatus of the present embodiment, first, the silicon wafer 10 to be processed is set on the sample stage 32, By evacuation,
The internal pressure of the plasma generation chamber 12 and the reaction chamber 14 is reduced to a predetermined pressure. Next, a reaction gas (Cl ₂ ) is introduced from the gas supply pipe 36 into the plasma generation chamber 12 and the reaction chamber 14,
The internal pressure of the plasma generation chamber 12 and the reaction chamber 14 is set to 1 × 10 ⁻³
Keep around Torr.

Thereafter, a magnetic field is formed inside the plasma generation chamber 12 by energizing the main coils 22, 24, 26 and the sub-coil 28, and the magnetic field is formed from the circular waveguide 16 through the microwave introduction window 20 into the plasma generation chamber 12. Introduce microwave. This microwave has a frequency f = 2.45.
GHz (wavelength λ = about 12.2 cm), power 1500 W
Is set to

When microwaves are introduced into the plasma generation chamber 12, the reaction gas is resonantly excited on the ECR surface 100 to generate plasma. Main coil 22, 24, 2
The magnetic field formed by the sub-coil 6 and the sub-coil 28 is a divergent magnetic field whose magnetic flux density decreases toward the reaction chamber 14 side, and the plasma generated in the plasma generation chamber 12 is drawn into the reaction chamber 14 by the action of the divergent magnetic field. Then, the surface of the silicon wafer 10 on the sample stage 32 is irradiated and etched.

As described above, the main coils 22, 2
4, 26 and the plasma radiated along the divergent magnetic field generated by the sub-coil 28, the permanent magnet 44 (44a)
Therefore, plasma directed to the inner wall of the reaction chamber (vacuum vessel) 14 can be greatly reduced. In addition, no abrupt change in the magnetic field occurs on the silicon wafer 10, and no local change in the plasma density on the silicon wafer 10 occurs. Further, since the distance between the magnet piece 44a and the silicon wafer 10 is adjusted in the circumferential direction of the silicon wafer 10, for example, the microwave (circular TE) transmitted through the microwave introduction window 20 and introduced into the plasma chamber 12 _{In the case where} the electric field intensity distribution of ( ₁₁ mode) is different between the X direction and the Y direction and the plasma density distribution in the circumferential direction of the silicon wafer 10 is not uniform, the plasma density distribution on the silicon wafer 10 can be corrected. it can.

As a method of adjusting the strength of the magnetic field formed between the silicon wafer 10 and the inner wall of the reaction chamber 14,
The strength of the plurality of permanent magnets surrounding the silicon wafer 10 can be adjusted (changed) in advance. However, this method has a disadvantage that a large number of costs are required to manufacture a large number of magnets having slightly different strengths. Therefore, as described in the above embodiment, the above-described disadvantage can be solved by keeping the strength of each magnet piece 44a constant and adjusting the distance between the magnet piece 44a and the silicon wafer 10 in the circumferential direction of the silicon wafer 10. .

Next, when a thin film is formed on the silicon wafer 10 using the apparatus of the present embodiment, a predetermined source gas is introduced through a gas supply pipe 36 in addition to the above procedures.
The plasma generated by the gas is applied to the silicon wafer 1
Irradiate to zero. As a result, a thin film of a substance generated by the reaction of the source gas is formed on the surface of the silicon wafer 10. Also in such thin film formation, plasma having a uniform density is generated, and the film thickness distribution of the thin film formed on the surface of the silicon wafer 10 is equalized. As a result, the quality and performance of the finally manufactured semiconductor device are improved. Here, the semiconductor device includes a semiconductor element itself such as a transistor, a completed semiconductor device such as a RAM, and the like.

FIG. 4 shows the configuration of a permanent magnet 48 according to another embodiment of the present invention. This permanent magnet 48 is used in place of the permanent magnet 44 shown in FIGS. 1 and 2, and its basic operation and effects are the same as those of the above-described embodiment.
Same as 4. The permanent magnet 48 is integrally formed in a ring shape, has a width w of 10 mm, and a diameter a =
The diameter is set to 450 mm and the diameter b in the Y direction is set to 400 mm.

FIG. 5 shows the distribution of ion current density on the silicon wafer 10 when the permanent magnet 48 of the embodiment of FIG. 4 is used. The data shown in FIG.
Using a microwave of W, the pressure in the plasma generation chamber 12 and the reaction chamber 14 was maintained at 2 × 10 ⁻³ Torr, and
This is a result of a test performed using l ₂ gas. FIG. 6 shows the distribution of ion current density on the silicon wafer 10 when a ring-shaped permanent magnet designed to have a diameter of 450 mm in both the X and Y directions is used. As can be seen from FIGS. 5 and 6, when the permanent magnet 48 of this embodiment is used, the ion current density uniformity on the silicon wafer 10 is more excellent. Furthermore, according to the present embodiment, not only the uniformity of the ion current but also the absolute value of the ion current on the silicon wafer 10 (sample) is high, and it is expected that the processing speed is increased in addition to the uniform processing. it can.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and does not depart from the gist of the technical idea of the present invention shown in the claims. Various changes are possible within the scope.

[0031]

As described above, according to the present invention, a magnetic field is formed between the sample (10) and the inner walls of the vacuum vessels (12, 14), and the inner wall side of the vacuum vessels (12, 14) is formed. Since the diffusion of plasma into the sample is suppressed, there is an effect that uniform plasma processing can be performed without damaging the sample. The sample (10) and the magnet (4
4) is adjusted in the circumferential direction of the sample (10). Therefore, when an uneven plasma is generated in the circumferential direction of the sample (10) due to the influence of the magnetic field intensity distribution of the microwave or the like. Also, the uniformity of the plasma on the sample (10) can be sufficiently ensured. As a result, finally, the quality of the semiconductor device manufactured through the plasma processing method of the present invention is improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a schematic configuration of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a permanent magnet used in the plasma processing apparatus shown in FIG.

Figure 3 is a graph showing the microwave electric field intensity distribution of the TE ₁₁ mode introduced into the vacuum chamber of the plasma processing apparatus of the embodiment.

FIG. 4 is a plan view showing a configuration of a permanent magnet according to another embodiment of the present invention.

FIG. 5 is a graph showing experimental data for explaining the effect of the embodiment shown in FIG. 4;

FIG. 6 is a graph showing experimental data for a comparative example used to explain the effect of the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Silicon wafer (sample) 12 ... Plasma generation chamber 14 ... Reaction chamber 22, 24, 26 ... Main coil 28 ... Sub coil 44, 48 ... Permanent magnet 44a ... Magnet Piece

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05H 1/10 H01L 21/302 B

Claims (4)

[Claims] 1. A plasma processing apparatus for performing a predetermined process by irradiating a sample placed in a vacuum container with plasma, wherein the sample is surrounded between the sample and an inner wall of the vacuum container. And a permanent magnet that forms a magnetic field that regulates the progress of the plasma and that adjusts a distance between the sample and the magnet in a circumferential direction of the sample. 2. The plasma processing apparatus according to claim 1, wherein the permanent magnet includes a plurality of permanent magnet pieces, and a distance between the plurality of permanent magnet pieces and the sample is adjusted. 3. The permanent magnet is a ring-shaped integral permanent magnet arranged so as to surround the sample. The diameter of the permanent magnet is adjusted by adjusting the distance between the sample and the permanent magnet. The plasma processing apparatus according to claim 1, wherein a permanent magnet is formed. 4. The plasma processing apparatus according to claim 1, further comprising an exciting coil for exciting electron cyclotron resonance in the vacuum vessel.