JP3164188B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 for performing processing such as etching or thin film formation on a sample such as a semiconductor device substrate using plasma.

[0002]

2. Description of the Related Art Microwaves are introduced into a vacuum vessel under reduced pressure and low gas pressure to generate gas discharge to generate plasma, and the plasma is irradiated onto the surface of a substrate as a sample. Research and development of plasma processing apparatuses for performing processes such as etching and thin film formation have been promoted as being indispensable for the manufacture of highly integrated semiconductor elements and the like. In particular, a plasma processing apparatus that can independently control the generation of plasma and the acceleration of ions in the generated plasma has been desired in the dry etching technique and the embedding technique in forming a thin film.

FIG. 4 shows a conventional plasma processing apparatus 400, and is a cross-sectional view schematically showing a plasma etching apparatus capable of independently controlling generation of plasma and acceleration of ions in the plasma. It is. In the figure, reference numeral 40 denotes a hollow rectangular reactor. Reactor 4
Numeral 0 is formed of a metal such as aluminum or stainless steel, and its peripheral wall has a double structure. Inside the double structure, a cavity 50 serving as a passage for cooling water is formed. A reaction chamber 41 is formed inside the cavity 50,
The upper portion of the reactor 40 has microwave permeability, and has a small dielectric loss and heat resistance. For example, microwave introduction formed using a heat-resistant plate such as quartz glass or Al ₂ O ₃ is used. The window 45 is hermetically sealed.

A microwave introduction window 4 is provided above the reactor 40.
5 and a microwave introduction window 45
Is provided, and a dielectric line 44 large enough to cover is provided.
The dielectric line 44 is composed of a dielectric layer 44a made of a dielectric material such as fluororesin, polystyrene, polyethylene or the like having a small dielectric loss, and an A disposed on the upper surface of the dielectric layer 44a.
1 and other metal plates 44b. Dielectric line 4
Microwaves 4 are introduced into the waveguide 4 from the microwave oscillator 47 via the waveguide 46.
4 is sealed with a metal plate 44b.

A sample table 42 having a sample holder 42a for holding a sample S to be processed is provided inside the reaction chamber 41. The sample holder 42a applies a bias voltage to the surface of the sample S. A high frequency power supply 43 for generating power is connected. Further, the sample holding unit 42a is also provided with a mechanism for adsorbing the sample S using an electrostatic chuck or the like (not shown) and a mechanism for cooling the sample S using a circulating refrigerant or the like (not shown). On the lower surface of the microwave introduction window 45 facing the sample S, a metal plate 51 connected to the earth 52 via the reactor 40 is disposed in close contact with the metal plate 51. A large number of slits or holes 51a are formed so that they can enter the reaction chamber 41. This metal plate 51
Is a cathode (sample holding unit 4) to which a high-frequency power supply 43 is supplied.
As an anode for 2a), a clear bias voltage can be generated for the sample S mounted on the cathode.

An exhaust pipe 49 connected to an exhaust device (not shown) for evacuating the reaction chamber 41 to a vacuum is connected to a lower wall of the reactor 40. A gas supply pipe 48 for supplying a gas required for plasma generation into the reaction chamber 41 is connected.

In the plasma processing apparatus 400 configured as described above, the surface of the sample S is subjected to an etching process as follows. First, the inside of the reaction chamber 41 is set to a required pressure by exhausting air from the exhaust pipe 49, and then the reaction gas is supplied from the gas supply pipe 48. Cooling water is supplied from the cooling water inlet 50a and discharged from the cooling water outlet 50b to be circulated in the cavity 50. Next, the microwave is oscillated in the microwave oscillator 47 and introduced into the dielectric line 44 via the waveguide 46. Then, an electric field is formed below the dielectric line 44, and the formed electric field passes through the microwave introduction window 45, passes through the slit or hole of the grounded metal plate 51, and generates plasma in the reaction chamber 41. At the same time, in order to control the anisotropy and acceleration energy of the ions in the plasma,
To apply a high-frequency electric field to the sample holding unit 42a on which the sample S is mounted, thereby generating a bias voltage on the surface of the sample S. The bias voltage allows ions to be incident perpendicularly to the sample S and optimizes etching conditions while controlling the energy of the ions incident to the sample S.

[0008]

In such a plasma processing apparatus, the reaction gas is introduced into the reaction chamber 41 from one side wall of the reactor 40 via the gas supply pipe 48, and the sample S It was not fed directly in the direction.
Therefore, it is difficult to increase the utilization efficiency of the reaction gas, and the gas flow to the processing surface of the sample S becomes non-uniform, thereby improving the uniformity of the processing such as the uniformity of the etch rate and the selection ratio. It was difficult to make it.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to increase the utilization efficiency of a reaction gas and to make the flow of the reaction gas uniform so that the etching rate can be improved.
It is an object of the present invention to provide a plasma processing apparatus capable of improving processing uniformity, such as uniformity of processing and selectivity.

[0010]

In order to achieve the above object, a plasma processing apparatus according to the present invention comprises a microwave oscillator, a waveguide for transmitting microwaves, and a dielectric connected to the waveguide. A line, a reactor having a microwave introduction window disposed opposite to the dielectric line, a sample holder provided in the reactor, and a means for applying a high-frequency electric field or a DC electric field to the sample holder. A plasma processing apparatus provided between the microwave introduction window and the sample holding unit and having a grounded electrode means, wherein a gas buffer chamber is provided inside the electrode means, and the sample of the electrode means is provided. A plurality of holes for blowing gas from the gas buffer chamber toward the sample holding unit are formed on a surface facing the holding unit, and further, the microwave is introduced into the electrode unit.
Penetrates the surface that contacts the window and the surface that faces the sample holder
Characterized in that a microwave transmitting hole is formed .

[0011]

In order to improve the utilization efficiency of the reaction gas and the uniformity of the processing in the plasma processing apparatus, it is desirable that the reaction gas be perpendicularly incident on the processing surface of the sample. In particular, Si which increases the selectivity by using CVD or a deposited film
In the case of the O ₂ etching process, the uniformity of the process is greatly affected by the flow of the reaction gas. In the plasma processing apparatus according to the above configuration, a gas buffer chamber is provided inside the electrode unit, and a surface of the electrode unit facing the sample holding unit is arranged from the gas buffer chamber toward the sample holding unit. A plurality of holes for blowing out gas are formed, and the electrode means is provided in the microwave introduction window.
Penetrates the contact surface and the surface facing the sample holder
Since the microwave transmission holes are formed , the reaction gas is once introduced into the gas buffer chamber, and then supplied from the plurality of holes vertically and uniformly to the processing surface of the sample held in the sample holding unit. Is done. As a result, the reaction gas does not efficiently reach the processing surface of the sample directly and reach the processing surface of the sample without being depleted on the side walls and the like until the reaction gas reaches the processing surface of the sample. The use efficiency of the reaction gas can be improved as compared with the plasma processing apparatus of the above, and the flow of the reaction gas to the processing surface of the sample can be made uniform. It is possible to improve the uniformity of the treatment, such as the uniformity of the ratio.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma processing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view schematically showing a plasma processing apparatus 100 according to the embodiment. The configuration of the plasma processing apparatus 100 according to the embodiment shown in FIG. 1 is different from the configuration of the conventional plasma processing apparatus 400 shown in FIG. 4 in the following points. That is, in the case of the plasma processing apparatus 400, an arc having a microwave transmission hole is used.
Although the metal plate 51 is disposed as a contacted electrode means in contact with the lower surface of the microwave introduction window 45, in the case of the plasma processing apparatus 100, the metal plate in which the gas buffer chamber 11 a is formed as the electrode means is used. The plate 11 is disposed in contact with the lower surface of the microwave introduction window 45, and the gas buffer chamber 11
The point is that the gas supply pipe 48 is connected to a. The other configuration is the same as the configuration of the conventional plasma processing apparatus 400 shown in FIG. 4, so that the detailed description is omitted here, and only the configuration of the metal plate 11 will be described below with reference to FIG.

FIG. 2A is a perspective view showing the metal plate 11 viewed from the microwave introduction window 45 side.
(B) is a bottom view showing a surface of the metal plate 11 facing the sample holding unit 42a. As shown in FIG. 2A, a slit-shaped microwave transmission hole 12 penetrating the metal plate 11 through a surface in contact with the microwave introduction window 45 and a surface in opposition to the sample holder 42a. The gas inlet 11 is connected to a gas supply pipe 48 for introducing gas into the gas buffer chamber 11a.
b is formed. On the other hand, the sample holder 4 of the metal plate 11
A large number of small holes 13 for blowing out the gas introduced into the gas buffer chamber 11a toward the processing surface of the sample S are formed on the surface facing 2a. The small hole 13 has a predetermined diameter (for example, 1
mm).

Since the metal plate 11 is formed of a conductive material such as Al and is connected to the earth 52 via the reactor 40, the metal plate 11 has a sample holder 42a to which the high frequency power supply 43 is applied. (Cathode electrode). The metal plate 11 has microwave transmitting holes 1.
2 is formed, the microwave is supplied to the reaction chamber 41 through the microwave introduction window 45 and the microwave transmission hole 12.
Will be introduced. A gas inlet 11b connected to a gas supply pipe 48 is formed at the center of one side surface of the metal plate 11, and a number of small holes 13 having a predetermined diameter are formed on a surface facing the sample table 42. Therefore, the gas supplied from the gas supply pipe 48 is temporarily stored in the gas buffer chamber 11a, and then blown out from the small holes 13 toward the processing surface of the sample S.

As can be seen from the above description, in the plasma processing apparatus 100 according to the embodiment, the earth 52
The metal plate 11 connected to the electrode acts as a counter electrode (anode electrode) for the sample holder 42a (cathode electrode) to which the high-frequency power supply 43 is applied. The plasma potential can be stabilized, and a stable bias voltage can be generated on the surface of the sample S. As a result, the ion energy in the plasma can be optimized, and the processing surface of the sample S can be irradiated with ions perpendicularly. In addition, in the plasma processing apparatus 100, gas is blown out from a large number of small holes 13 having a predetermined diameter, so that the gas can be blown out uniformly and perpendicularly to the processing surface of the sample S. The gas flow to the processing surface can be kept uniform. Thereby, the plasma processing apparatus 100
By using the method, the gas use efficiency can be improved as compared with the case where the plasma processing apparatus 400 is used, and the uniformity of the processing such as the uniformity of the etch rate and the uniformity of the selection ratio can be improved. The above contents will be demonstrated with specific numerical values.

The silicon oxide film (SiO ₂ film) was etched using the plasma processing apparatus 100 shown in FIG. As a sample S, an 8-inch silicon wafer was
An O ₂ film having a thickness of 1 μm was used. As a discharge gas, CF ₄ , CHF ₃ , and Ar were each 30 scc.
m, 30 sccm, 100 sccm, gas pressure is 3
Performed at 0 mTorr. Microwave frequency 2.45G
Hz, and plasma was generated at a power of 1 kW. Further, a high frequency of 400 kHz was supplied to the sample holding unit 42a with a power of 600W. Then, a case where the SiO ₂ film was etched under the same conditions as above using the plasma processing apparatus 400 shown in FIG. 4 was set as a comparative example, and the result was compared. The comparison result is shown in FIG.

FIG. 3A is a graph showing a result in the plasma processing apparatus 100, and FIG. 3B is a graph showing a result in the plasma processing apparatus 400. 3 (a) and 3 (b), the graphs indicated by Δ indicate the etch rate of the SiO ₂ film, and the graphs indicated by Δ indicate the selectivity to Si. The horizontal axis indicates the distance from the center (= 0 mm) of the silicon wafer.

When the plasma processing apparatus 100 is used, S
450 nm / mi as average etch rate of iO ₂ film
The etch rate uniformity of the n-inch, 8-inch silicon wafer was ± 5%, and the uniformity of the selectivity to Si was ± 5%. On the other hand, when the plasma processing apparatus 400 is used, the average etch rate of the SiO ₂ film is 400 nm / mi.
n, the etch rate uniformity on an 8-inch silicon wafer was ± 5%, but the uniformity of the selectivity to Si was ± 15%. This is because, in the etching of the SiO ₂ film, ions obtain energy by a bias voltage, and the etching proceeds by the energy. Thus, if the distribution of the plasma and the bias voltage is uniform, a uniform etching distribution can be obtained. Since the etching of Si proceeds by a chemical reaction due to neutral radicals, the influence of the bias is small and the distribution is considered to be due to the gas flow.

In the above embodiment, the plasma processing apparatus 10
0 was applied to the etching apparatus,
The present invention is not limited to this, and can be applied to, for example, a thin film forming apparatus.

[0020]

As described above in detail, in the plasma processing apparatus according to the present invention, a gas buffer chamber is provided inside the electrode means, and the gas buffer chamber is provided on the surface of the electrode means facing the sample holding section. A plurality of holes for blowing out a reaction gas from the gas buffer chamber toward the sample holding section are formed, and the electrode means is applied to the microwave introduction window.
A mask that penetrates the contacting surface and the surface facing the sample holder.
Since the microwave transmission holes are formed , the reaction gas is once introduced into the gas buffer chamber and then blown out from the plurality of holes, whereby the reaction gas is blown out uniformly and perpendicularly to the processing surface of the sample. be able to. This allows the reaction gas to directly reach the processing surface of the sample efficiently, preventing the reaction gas from being depleted on the side walls and the like until it reaches the processing surface of the sample and wasted. Prevention, and the utilization efficiency of the reaction gas can be improved. Further, the flow of the reaction gas to the processing surface of the sample can be made uniform, and the uniformity of the processing such as the uniformity of the etch rate and the uniformity of the selection ratio can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2A is a perspective view illustrating a metal plate 11 serving as an electrode unit, and FIG. 2B is a bottom view illustrating a surface of the metal plate 11 serving as an electrode unit facing a sample holding unit 42a. .

FIG. 3 (a) is a graph showing an etch rate of a SiO ₂ film and a selectivity of a SiO ₂ film to Si in a plasma processing apparatus according to an embodiment, and FIG. 3 (b) is a graph showing a conventional plasma processing apparatus. Etch rate of SiO ₂ film and Si
4 is a graph showing a selectivity of an O ₂ film to Si.

FIG. 4 is a schematic sectional view showing a conventional plasma processing apparatus.

[Explanation of symbols]

 Reference Signs List 11 metal plate (grounded electrode means) 11a gas buffer chamber 11b gas inlet 12 microwave transmission hole 13 small hole 40 reactor 41 reaction chamber 42 sample table 42a sample holder 43 high frequency power supply 44 dielectric line 44a dielectric Body layer 44b Metal plate 45 Microwave introduction window 46 Waveguide 47 Microwave oscillator 48 Gas supply pipe 49 Exhaust pipe 50 Cavity 52 (to serve as cooling water passage) 52 Earth S sample 100, 400 Plasma processing apparatus

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-263725 (JP, A) JP-A-1-120810 (JP, A) JP-A-6-104098 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) H01L 21/3065 H01L 21/205

Claims (1)

(57) [Claims] 1. A reactor having a microwave oscillator, a waveguide for transmitting microwaves, a dielectric line connected to the waveguide, and a microwave introduction window disposed opposite to the dielectric line. A sample holder provided in the reactor, means for applying a high-frequency electric field or a DC electric field to the sample holder, provided between the microwave introduction window and the sample holder, and grounded. A plasma processing apparatus comprising: a gas buffer chamber provided inside the electrode means; and a surface of the electrode means facing the sample holding part, the gas buffer chamber being directed from the gas buffer chamber to the sample holding part. A plurality of holes for blowing gas are formed, and the electrode means further comprises
The surface contacting the microwave introduction window and the sample holding unit
A plasma processing apparatus, wherein a microwave transmission hole penetrating an opposing surface is formed .