JP2003068718A - Plasma processing equipment - Google Patents

Abstract

(57) [Problem] To provide a plasma processing apparatus capable of preventing abnormal discharge in a shower plate serving as a means for introducing gas into a plasma processing chamber and extending its life. SOLUTION: A concave portion is provided in a substantially flat antenna portion 7 for applying an electromagnetic wave to the plasma processing chamber 1. This concave portion is provided at the center of a surface provided close to the antenna section 7 and opposed to the gas introducing means 12 for introducing gas into the plasma processing chamber 1. The dielectric 11 is arranged in the recess.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a metal material such as aluminum, copper and platinum, an insulating material such as silicon oxide and silicon nitride, and a low dielectric constant film (low-k film) in the manufacturing process of a semiconductor device. The present invention relates to a plasma processing apparatus suitable for etching an organic material such as the above using plasma.

[0002]

2. Description of the Related Art DRAMs, microprocessors, ASs
Plasma processing using weakly ionized plasma is widely used in the process of manufacturing semiconductor devices such as ICs. In the plasma process, a wafer is processed by irradiating a wafer to be processed with ions and radicals generated by plasma.

A parallel plate type plasma source has been used for a long time as a plasma source for these plasma devices. The parallel plate type plasma is a CCP (Capacitive Coupled) because the coupling between the plasma and the power source is capacitive.
Plasma) is called.

As a plasma processing apparatus using this parallel plate type plasma source, Japanese Patent Laid-Open No. 7-297175 discloses a narrow electrode parallel plate type reactor having an upper electrode of several tens of meters.
A relatively high density plasma is generated by applying a high frequency of Hz, and a high frequency bias of several hundred kHz to several MHz is applied to the lower electrode on which the wafer to be processed is placed, thereby applying a high frequency bias to the wafer to be processed. An IEM (Ion Energy Modulation) method for controlling the amount of incident ions is disclosed. In addition, the upper electrode of such a plasma processing apparatus has a diameter of 0.3 to 0.8 mm in order to uniformly introduce the processing gas into the low-aspect plasma processing chamber.
A shower plate structure having hundreds of small holes is often used, and silicon is often used as the material for controlling the radical species incident on the wafer to be processed.

[0005]

However, the above-mentioned IEM
Method, the pressure that can generate plasma stably is several tens of P
It is about a to 5 Pa, and it is difficult to cope with further miniaturization of the pattern dimension. In order to generate medium to high density plasma at a lower pressure for fine processing, the frequency for exciting the plasma may be raised to several tens of MHz to several hundreds of MHz. Becomes shorter and approaches the size of the plasma processing chamber, the electric field distribution in the plasma processing chamber becomes uneven. This electric field distribution is analytically expressed as a superposition of Bessel functions, and the central portion has a high electric field distribution.

When the etching process is performed in such a state, the etching rate at the central portion of the wafer to be processed is high and the etching rate at the peripheral portion is low. Furthermore, if etching treatment (discharge) is performed for a long time, gas holes in the upper electrode having a shower plate structure are consumed and abnormal discharge occurs, which shortens the life.

On the other hand, the above-mentioned nonuniformity of the etching rate can be controlled to some extent by applying a magnetic field from the outside. For example, as described in Japanese Patent Application Laid-Open No. 09-321031, a frequency of 300 MHz to 1 GHz.
In the UHF-ECR device using the UHF band, the plasma can be excited by electromagnetic waves in the UHF band, and the etching rate distribution can be controlled by using the interaction between the UHF electric field and the external magnetic field created by the solenoid coil. Also, UHF-E
In the CR device, the electron temperature is relatively low, and the dissociation of the processing gas can be kept in an optimum state.

However, even in the UHF-ECR device,
It is inevitable that the gas holes in the upper shower plate will be consumed when discharging for a long time. When the gas holes are exhausted, abnormal discharge occurs near the central portion of the shower plate, and the shower plate needs to be replaced. Particularly, when the material of the shower plate is expensive silicon for the purpose of controlling the radical species, the shower plate replacement frequency is directly related to the running cost.

Therefore, it is an object of the present invention to provide a plasma processing apparatus capable of preventing abnormal discharge in the shower plate, which serves as a gas introducing means to the plasma processing chamber, and extending its life.

[0010]

The present invention has achieved its object by providing a recess in a substantially flat plate-shaped antenna section for introducing electromagnetic waves into a plasma processing chamber. This recess is preferably provided in the central portion of the surface provided in the vicinity of the antenna portion and facing the gas introduction means for introducing the gas into the plasma processing chamber.

When the gas holes of the gas introducing means (shower plate) are consumed, abnormal discharge occurs from the gas holes near the central portion of the shower plate, which is caused by the high electric field strength near the central portion described above. To do. Therefore, by providing a concave portion in the central portion of the antenna portion, it is possible to reduce the electric field strength near the central portion and prevent abnormal discharge. Therefore, the life of the silicon shower plate, which is an expensive replacement part, can be extended and the running cost can be reduced.

The mechanism of occurrence of abnormal discharge due to exhaustion of gas holes in the shower plate will be described with reference to FIG. FIG. 3 is an enlarged schematic view of the shower plate and the gas dispersion plate portion of the antenna portion on the back of the shower plate. Figure 3
As shown in (a), when the discharge time is 0 hours, the gas holes are not consumed and abnormal discharge does not occur. When a number of wafers are processed and the total discharge time is about 100 hours, the gas hole diameter in the portion in contact with plasma gradually increases as shown in FIG. 3 (b). Furthermore, when the discharge time is extended and the ions generated by the plasma pass through the gas holes of the shower plate and reach the gas dispersion plate as shown in FIG. More likely.

In addition to the above-mentioned ions, the electric field strength between the shower plate and the gas dispersion plate may be mentioned as a cause of the abnormal discharge. If the electric field strength in the minute gap existing at the connecting portion between the gas holes of the gas distribution plate and the gas holes of the shower plate is large, an abnormal discharge occurs continuously behind the shower plate triggered by ions as a fire source. When this electric field strength is small, the gas holes are consumed and abnormal discharge is less likely to occur even when ions that act as triggers are incident. That is, if the electric field strength in the minute gap existing at the connection between the gas hole of the gas distribution plate and the gas hole of the shower plate can be weakened, the margin for abnormal discharge can be widened and the life of the shower plate can be extended.

As a method of weakening the electric field strength, it is effective to provide a concave portion in a substantially flat antenna portion facing the shower plate as the gas introducing means, and thereby effectively prevent abnormal discharge. You can

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to an example in which the plasma processing apparatus of the present invention is applied to an etching apparatus.

<First Embodiment> FIG. 1 is a vertical sectional view of a UHF type ECR plasma etching apparatus according to the present invention. In the figure, inside the plasma processing chamber 1, a wafer mounting stage 2, a wafer 3, and a substantially annular focus ring 4 electrically insulated from the wafer 3 are installed. Further, a first temperature control device 5 for maintaining the inner wall of the plasma processing chamber 1 at a constant temperature is installed.

A coil 6 is installed outside the plasma processing chamber 1 in order to generate a magnetic field for causing electron cyclotron resonance (ECR) in the plasma processing chamber 1.

An antenna portion 7 is arranged at a position facing the wafer 3. The antenna unit 7 includes a substantially disk-shaped antenna body 7a for radiating electromagnetic waves in the UHF band, and a gas dispersion plate 7b as a gas supply means for uniformly supplying processing gas to a shower plate described later. It consists of Both the antenna body 7a and the gas dispersion plate 7b are made of a conductor. An antenna back dielectric 9 is arranged between the antenna unit 7 and the ceiling of the plasma processing chamber 1.

FIG. 2 shows details of the antenna section. The gas dispersion plate 7b is provided with several hundreds of fine holes each having a diameter of about 0.3 to 1.5 mm.
A buffer chamber 7c for processing gas is provided between b and the antenna body 7a. Below the gas dispersion plate 7b, there is arranged a shower plate 12 as a gas introduction means in which hundreds of fine holes each having a diameter of about 0.3 to 0.8 mm are formed. The processing gas is introduced from the gas supply system 10 (see FIG. 1) into the plasma processing chamber 1 through the buffer chamber 7c, the gas dispersion plate 7b, and the shower plate 12 after being adjusted to a predetermined flow rate. The material of the shower plate 12 is preferably silicon, quartz, polyimide, aluminum oxide, aluminum nitride, carbon, or silicon carbide in order to prevent the plasma processing chamber 1 from being contaminated. In order to control radical species in plasma by positively utilizing the surface reaction of
More preferably, it is silicon. The resistivity of silicon is preferably greater than 0.5 Ωcm. When the resistivity of silicon becomes small, the high frequency current will flow only on the surface of the shower plate due to the skin effect,
This is because the effect of reducing the electric field in the vicinity of the central portion due to the concave portion provided in the central portion of the antenna portion does not appear.

As shown in FIG. 2A or 2B, a recess having a diameter of 40 to 120 mm and a depth of 3 to 10 mm is provided in the center of the gas dispersion plate 7b. Antenna center dielectric 11 to control strength
Are arranged. A gas hole having a diameter of about 0.3 to 1.5 mm is formed in the antenna central dielectric 11. The diameters of the holes formed in the gas dispersion plate 7b and the antenna central dielectric 11 are set so that the gas in the shower plate 12 as shown in FIG. 2 (c) or (d) is absorbed so as to absorb the positional deviation of the gas holes during assembly. The diameter is made slightly larger than the hole diameter, or the portion contacting the shower plate 12 is chamfered. Further, the antenna central dielectric 11 is preferably made of a material such as polyimide, quartz, or Teflon so as not to cause contamination in the plasma processing chamber 1.

Returning to FIG. 1, the antenna main body 7a is connected with a UHF power source 13 for supplying electric power for generating plasma to the processing chamber through a first matching box 14. Further, since the gas dispersion plate 7b and the antenna main body 7a are made to function as a counter earth electrode, the antenna main body 7a
Is grounded through the filter 15. Filter 15
Is designed so that electromagnetic waves in the UHF band for exciting plasma do not pass, but only frequencies in the band used for wafer bias pass.

The frequency of the UHF power source 13 is preferably in the band of 100 MHz to 500 MHz so that the electron temperature of plasma can be lowered in order to prevent excessive dissociation of the processing gas. In this embodiment, a frequency around 450 MHz is used.

A second high frequency power supply 17 is connected to the wafer mounting stage 2 via a second matching unit 16, and by applying a high frequency bias to the wafer 3, ions generated by plasma are transferred to the wafer. Can be pulled into 3. At the same time, it is possible to apply a high frequency bias to the focus ring 4. The amount of radicals contributing to etching can be controlled by the high frequency bias applied to the focus ring 4. The focus ring 4 is preferably made of silicon, carbon, silicon carbide, quartz or the like.

The frequency of the high frequency bias is UHF-EC.
It is selected between 400 kHz and 3 MHz so as not to affect the plasma distribution generated by R so much.
With such a frequency, the plasma generation due to the bias can be ignored, and most of the applied power can be used to attract ions to the wafer 3. In this embodiment, 80
A frequency of 0 kHz was used.

A second temperature controller 18 is installed on the wafer mounting stage 2 so that the wafer temperature can be kept constant during etching.

The plasma processing chamber 1 has an exhaust speed of 100.
A turbo molecular pump 19 of 0 to 3000 L / s,
A conductance control valve 20 is installed so that the plasma processing chamber 1 can be set to a predetermined pressure while the processing gas is being flown. Further, when the plasma processing chamber 1 is opened to the atmosphere, the plasma processing chamber 1 and the turbo molecular pump 19
A valve 21 is installed to isolate the and.

When an etching process is performed by using the plasma processing apparatus having the above-described structure, conventionally, the shower plate has a life of several hundred hours in total, and an abnormal discharge occurs from the central portion of the shower plate. However, no abnormal discharge was observed even when the total discharge time exceeded about 1.5 times the conventional discharge time. That is, the life of the shower plate can be extended to about 1.5 times.

FIG. 4 shows the results of a numerical simulation of the electric field intensity immediately below the electrodes in the embodiment of the present invention shown in FIG. 2A and a conventional planar example having no recess in the center. As can be seen from this figure, in the embodiment of the present invention (central concave antenna), the electric field strength at the central portion is reduced. From this result, it is understood that the present invention can extend the margin for the abnormal discharge near the central portion of the shower plate and extend the life of the shower plate.

The change in the electric field distribution affects the uniformity of etching results, which can be corrected by applying a magnetic field from the outside. Even in a plasma processing apparatus that does not apply a magnetic field, the uniformity of the electric field distribution is improved rather than the conventional example (planar antenna), and more uniform etching processing can be performed.

<Second Embodiment> In the first embodiment, U
Although the HF-ECR device has been described as an example, the present invention is UH.
It is not limited to the F-ECR device. Next, a second embodiment of the present invention will be described.

FIG. 5 is a vertical sectional view showing a second embodiment of the present invention, showing a plasma etching apparatus using a narrow gap parallel plate type plasma source. For simplification, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

A first high frequency power supply 22 is connected to the upper antenna 7 as an antenna section via a first matching unit 14. The frequency of the first high-frequency power source 22 is set so that medium to high density plasma can be generated even at a pressure of several Pa or less.
A frequency of about MHz to 100 MHz is used. Although not shown in detail in FIG. 5, the upper antenna 7 is also provided with a concave portion in the central portion thereof as in the first embodiment shown in FIG. 2, and the antenna central dielectric 11 is arranged in the concave portion. There is.

A second high frequency power source 17 is connected to the wafer mounting stage 2 via a second matching unit 16, and by applying a high frequency bias to the wafer 3, ions generated by plasma are transferred to the wafer. Can be pulled into 3. The frequency of the high frequency bias applied to the wafer 3 is 400 kHz to 3 MHz so as not to affect the plasma distribution generated by the electric field of the upper antenna 7 so much.
Will be selected among. With such a frequency, the plasma generation due to the bias can be ignored, and most of the applied power can be used to attract ions to the wafer 3.

Even when the plasma processing apparatus having the above-mentioned structure is used for the etching process, the central portion of the shower plate 12 is exhausted due to the exhaustion of the gas holes and the high electric field distribution in the central portion after long-time discharge. The effect of suppressing abnormal discharge was confirmed. Further, the high electric field distribution in the central portion was alleviated by the concave portion in the center of the upper antenna 7, and the uniformity of the etching process was also improved.

[0035]

As described above, the present invention has the following effects.

By providing the concave portion in the central portion of the antenna, the high electric field distribution in the central portion can be relaxed. As a result, it is possible to suppress abnormal discharge that occurs near the center of the shower plate as the gas introducing means when the gas holes are consumed by performing discharge for a long time, and it is possible to extend the life of the shower plate.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing details of an antenna unit.

FIG. 3 is a schematic view showing consumption of gas holes in a shower plate.

FIG. 4 is a diagram showing a result of a numerical simulation of electric field strength in a lower portion of an antenna unit.

FIG. 5 is a vertical sectional view showing a second embodiment of the plasma processing apparatus according to the present invention.

[Explanation of symbols]

1: Plasma processing chamber, 2: Wafer mounting stage, 3:
Wafer, 4: focus ring, 5: first temperature controller,
6: coil, 7: antenna part, 7a: antenna body, 7
b: gas dispersion plate (gas supply means), 7c: buffer chamber,
9: Antenna back dielectric, 10: Gas supply system, 11: Antenna central dielectric, 12: Shower plate (gas introducing means), 13: UHF power supply, 14: First matching unit, 15:
Filter, 16: second matching device, 17: second high frequency power supply, 18: second temperature controller, 19: turbo molecular pump, 2
0: conductance control valve, 21: valve, 22:
First high frequency power supply

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masatsugu Arai             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center (72) Inventor Tsutomu Tsukasa             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center F term (reference) 5F004 AA01 AA16 BA04 BA06 BB11                       BB13 BB28 BB32

Claims (11)

[Claims] 1. A plasma processing apparatus comprising: a substantially flat plate-shaped antenna section for injecting electromagnetic waves into a plasma processing chamber; and a gas introduction means for introducing gas into the plasma processing chamber, which is provided in the vicinity of the antenna section. A plasma processing apparatus, wherein a recess is provided in the antenna section. 2. The plasma processing apparatus according to claim 1, wherein the concave portion of the antenna portion is provided on a surface facing the gas introducing unit. 3. The plasma processing apparatus according to claim 1, wherein the concave portion of the antenna portion is provided in a central portion of the antenna portion. 4. The plasma processing apparatus according to claim 1, wherein a dielectric is mounted in the recess of the antenna section. 5. The plasma processing apparatus according to claim 4, wherein a small hole for introducing gas is provided in the dielectric filled in the recess of the antenna section. 6. The plasma processing apparatus according to claim 4 or 5, wherein the material of the dielectric material mounted in the recess of the antenna portion is quartz, polyimide, aluminum oxide, aluminum nitride, silicon or Teflon (registered trademark). A plasma processing apparatus characterized by the above. 7. The plasma processing apparatus according to claim 1, wherein a portion of the gas introducing means that comes into contact with plasma is made of silicon, quartz, polyimide, aluminum oxide, aluminum nitride, carbon or silicon carbide. A plasma processing apparatus, which is a shower plate. 8. The plasma processing apparatus according to claim 7, wherein the shower plate is made of silicon, and the silicon has a resistivity of more than 0.5 Ωcm. 9. The plasma processing apparatus according to claim 1, wherein the antenna unit has a gas supply unit that supplies a gas to the gas introduction unit. 10. The plasma processing apparatus according to claim 9, wherein the gas supply unit has a gas dispersion plate provided with a small hole for supplying gas to the gas introduction unit. 11. The plasma processing apparatus according to claim 1, wherein the antenna portion has a diameter larger than that of the wafer to be processed.