JPH01231321A - Plasma processing device - Google Patents

Abstract

PURPOSE:To remove a deposit in a plasma forming chamber automatically and efficiently by utilizing etching action by gas plasma discharge by installing an electrically insulated conductive protective wall capable of selectively applying the ground potential and/or a plurality of potentials into the plasma forming chamber. CONSTITUTION:The circumferential wall and protective walls 6 of a plasma forming chamber 1 are set previously at ground potential by changeover switches SW1, SW2. Microwaves are introduced into the plasma forming chamber 1 through an introducing port 1c, and a film is formed onto the surface of a sample S to which a specified bias is applied by an RF power 8. When the operating time reaches a fixed value, film formation work is suspended, each changeover, switch SW1, SW2 is changed over respectively from the ground side to the RF power 10 side, and a gas for etching is fed from a gas supply system 1g. Accordingly, when plasma is formed in the plasma forming chamber 1, each protective wall 6 and a sample base 5 are set automatically at negative potential (a self-bias), plasma discharge is dispersed to the periphery, films deposited on the surfaces of the protective films 6 are removed through etching, and removed ions, gas, etc., are discharged through an exhaust port 3a.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electron cyclotron resonance (electron cyclotron resonance) using microwaves.
Electron Cyclotron Re5ona
nce, ECR) manufacturing equipment for highly integrated semiconductor devices, etc. that utilizes plasma generated by excitation, such as CVD.
(Che+++ ica IVapor Deposit
The present invention relates to plasma processing equipment used as etching equipment, etching equipment, and other sputtering equipment.

[Prior art]

Devices that generate plasma by electron cyclotron resonance excitation using microwaves can generate highly active plasma at low gas pressure, allow a wide range of ion energies to be selected, and can generate large ion currents to improve ion flow. It has advantages such as excellent directivity and uniformity, and its research and development are progressing as it is essential for manufacturing highly integrated semiconductor devices.

FIG. 2 is a longitudinal cross-sectional view of a conventional plasma device configured as a CvO device that utilizes electron cyclotron resonance using microwaves, and 31 indicates a plasma generation chamber. The plasma generation chamber 31 has a double structure around the surrounding wall and is equipped with a cooling water passage 31a, and a microwave inlet 31c sealed with a quartz glass plate 31b in the center of one side wall, and a microwave inlet 31c sealed with a quartz glass plate 31b in the center of the other side wall. A circular plasma extraction window 31d is provided at a position facing the microwave introduction port 31c. One end of a waveguide 32, the other end of which is connected to a high frequency oscillator (not shown), is connected to the microwave inlet 31c, and a reaction chamber 33 is disposed facing the plasma extraction window 31d. An excitation coil 34 is disposed concentrically with the chamber 31 and one end of the waveguide 32 connected to the chamber 31 so as to surround the chamber 31 and one end of the waveguide 32 connected thereto.

Inside the reaction chamber 33, a sample stage 35 on which a sample S such as a wafer is mounted is disposed facing the plasma extraction window 31d, and in front of it, a disk-shaped sample S is placed as is or by electrostatic adsorption, etc. It is designed to be removably attached by means of. A cooling water passage (not shown) for cooling is embedded in the sample stage 35, and an electrode 35b for electrostatic adsorption and/or bias application of the sample S is embedded in the mounting position of the sample S, respectively. A cooling water supply pipe 35a is provided in the flow path, and an electrode 35b is also provided.
An RF (radio frequency) power supply 138 is connected through a DC power supply (not shown) and a matching box 37 .

An exhaust port 33a connected to an exhaust device (not shown) is opened in the rear wall of the reaction chamber 33 located on the rear side of the sample stage 35. 31g and 33g are raw material gas supply systems, 31h.

31i is a cooling water supply system and a drainage system.

In such a CVD apparatus, raw material gas is supplied from the raw material gas supply system 31g into the plasma generation chamber 311 and the reaction chamber 33 set to a required degree of vacuum, and the excitation coil 34
Microwaves are introduced into the plasma generation chamber 31 while forming a magnetic field in the plasma generation chamber 31, the source gas is resonantly excited using the plasma generation chamber 31 as a cavity resonator, plasma is generated, and the generated plasma is sent to the excitation coil 34. A diverging magnetic field whose magnetic flux density decreases toward the reaction chamber 33 side where it is formed is projected around the sample S on the sample stage 35 in the reaction chamber 33,
The raw material gas supplied from the raw material gas supply system 33g is decomposed and a film is formed on the surface of the sample S (Japanese Patent Laid-Open No. 5
7-133636).

By the way, in the above-mentioned plasma processing apparatus, the peripheral wall of the plasma generation chamber 31 is generally electrically set to a ground potential, and the peripheral wall is cooled with water. When high-density plasma is generated in the plasma generation chamber 31 and taken out as a plasma stream from the plasma extraction window 31d and subjected to film formation or etching treatment in the reaction chamber 33, a secondary reaction also occurs in various parts of the inner surface of the peripheral wall of the plasma generation chamber 31. Accumulation of material cannot be avoided.

For example, when a silicon nitride film is deposited on the surface of the sample S using SiH4 and N2 or NII+ gas as source gases, the inner surface of the peripheral wall of the reaction chamber 33 and the inner wall of the plasma generation chamber 31 are coated with nitride, which is a reaction product. Silicon or surplus 5il
Powdered silicon is deposited due to the decomposition of No. 14. Therefore, if such a film-forming process is repeated, the deposited layer will become thicker.
- When the temperature exceeds that of the chamber, peeling begins to occur from the wall surface, and when a rapid gas flow occurs in the plasma generation chamber 31 or plasma is generated, peeling progresses, and peeled off flakes, etc., adhere to the surface of the sample S during subsequent film formation. , causing defects.

In addition, when etching a silicon oxide film or silicon nitride film with CF4 gas plasma using a photoresist as a mask, fluorinated carbon atoms, C, ionized and decomposed from the CF4 gas are used.
F is bonded to the photoresist, and an organic resin film is deposited on the inner surface of the peripheral wall, and this deposit adsorbs residual gas or becomes a source of contamination, resulting in disadvantages such as lowering the reproducibility of etching.

Conventionally, as a countermeasure against this problem, a method is used in which the inner surface of the peripheral wall of the plasma generation chamber 31 is periodically cleaned by mechanical means every time a certain amount of processing is performed, or an anti-adhesion plate is attached to the inner surface of the peripheral wall of the plasma generation chamber 31. Attempts have been made to remove the deposits on the inner surface of the peripheral wall of the plasma generation chamber 31 or on the adhesion prevention plate using gas plasma such as cp, o, or the like.

[Problem that the invention seeks to solve]

However, with simple cleaning methods or methods that combine cleaning with replacement of the anti-adhesive plate, the deposits become extremely fine particles, so it is difficult to completely remove the deposits, and the It is necessary to stop the operation of the plasma generating chamber 31 and the reaction chamber 33 during this period of time, exposing the plasma generation chamber 31 and the reaction chamber 33 to the atmosphere, which has been a major obstacle in improving production efficiency, such as deteriorating reproducibility.

Furthermore, the current etching method does not have sufficient effect because the plasma generation chamber itself is electrically grounded.

The present invention has been made in view of the above circumstances, and its purpose is to automatically and efficiently remove deposits within the plasma generation chamber by utilizing the etching action of gas plasma discharge. An object of the present invention is to provide a plasma processing apparatus according to the present invention.

[Means for solving problems]

The present invention includes a plasma generation chamber that generates plasma by electron cyclotron resonance excitation, and a sample chamber that introduces the generated plasma through a drawer window and processes a sample placed facing the drawer window. In the plasma processing apparatus, a conductive protection wall is provided in the plasma generation chamber so as to be electrically insulated from the plasma generation chamber, and to which a ground potential and/or a plurality of potentials can be selectively applied.

[Effect]

According to the present invention, the plasma generated in the plasma generation chamber is dispersed and projected onto the inner surface of the peripheral wall of the plasma generation chamber, thereby etching and removing deposits on the inner surface of the peripheral wall.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention configured as a CVO device will be specifically described below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of a plasma device according to the present invention (hereinafter referred to as the device of the present invention), in which 1 is a plasma generation chamber, 2 is a waveguide, and 3 is a sample chamber in which film formation is performed on a sample S. A barrel reaction chamber, 4 indicates an excitation coil.

The plasma generation chamber l is made of stainless steel and is formed to constitute a cavity resonator for microwaves,
Furthermore, the surrounding wall has a double structure to form a hollow cylindrical shape with a water-cooled jacket (la), and a microwave inlet 1c closed with a quartz plate 1b is provided in the center of one side wall, and the microwave inlet 1c is provided in the center of the other side wall. A plasma extraction window 1d is provided at a position facing the plasma. The microwave inlet 1c
One end of the waveguide 2 is connected to the plasma extraction window 1d, and a reaction chamber 3 is arranged in addition to the plasma extraction window 1d. 2
An excitation coil 4 is disposed concentrically around one end of the coil.

The other end of the waveguide 2 is connected to a high frequency oscillator (not shown), and microwaves emitted by the high frequency oscillator are introduced into the plasma generation chamber 1 through the microwave introduction port 1c.

The excitation coil 4 is connected to a DC power source (not shown),
By passing a direct current, a magnetic field is formed so that plasma can be generated by introducing microwaves into the plasma generation chamber 1, and a diverging magnetic field whose magnetic flux density decreases toward the reaction chamber 3 side is formed, thereby generating plasma. The plasma generated in chamber 1 is introduced into reaction chamber 3.

The reaction chamber 3 is formed in the shape of a hollow rectangular parallelepiped, and an exhaust port 3a connected to an exhaust device (not shown) is opened in the side wall facing the plasma extraction window 1d. A sample stage 5 is arranged to face the
A sample S is removably mounted on the front surface of the sample stage 5, facing the plasma extraction window 1d. Inside the sample stage 5, there is a cooling water supply pipe for cooling and a sample S that is electrostatically attracted and/or
Alternatively, an electrode 5b for applying a bias is buried, a cooling water supply pipe 5a is provided in the flow path, and a DC power supply (not shown) and a matching box 7 are interposed in the electrode 5b to provide RF (radio high frequency) power. ) Power supply 8 is connected.

And inside the plasma generation chamber 1 there is a plasma extraction window 1d.
A conductive protective wall 6 is maintained in an electrically insulated state with a required gap between it and the surrounding wall to cover the inner surface of the surrounding wall except for the surrounding wall 6.
, 6 are arranged. The protective walls 6, 6 are made of, for example, stainless steel plates, and each of the protective walls 6, 6 is connected to an RF power source 10 with a changeover switch SW+ and a SWz matching box 9 interposed therebetween.

The changeover switches SW+ and SWz are formed so that their changeover pieces can be selectively switched between a position where they are connected to the RF power source 1o via a matching box 9 and a position where they are grounded, and during film formation, they are connected to the ground side. Also, when removing the deposited film on the wall, use RF
It is connected to the power supply 10 side.

The changeover switches SW, SWt are connected to the ground potential with respect to the protective wall 6.6, and to another negative potential (RF power source 10. Even when connected to a high frequency power source, the protective wall automatically changes to a negative potential when plasma for etching is generated. Although the case where the potential is set to a potential (self-bias) is shown, the present invention is not limited to this. For example, a configuration may be adopted in which the potential can be selectively set to a plurality of negative potentials other than the ground potential.

Further, the power source is not limited to the RF power source 1o, but may be a high frequency power source or a DC power source, for example.

When using a DC power supply, connect its negative terminal to the protective wall.

In addition, 1g and 3g indicate a gas supply system, and lh and li indicate a cooling water supply system and a drainage system, respectively.

In the apparatus of the present invention, the sample S is mounted on the sample stage 5 in the reaction chamber 3, and the plasma generation chamber 11 is connected to the reaction chamber 3.
After setting the inside to the required degree of vacuum, the gas supply system 1g, 3g
A raw material gas is supplied into the plasma generation chamber 12 and the reaction chamber 3 through the waveguide 2. Microwaves are introduced into the plasma generation chamber 1 through the microwave introduction port 1c. The microwave introduced into the plasma generation chamber 1 resonates within the plasma generation chamber 1 which functions as a plasma cavity resonator, decomposes the source gas, and excites it resonantly to generate plasma. The generated plasma is introduced into the reaction chamber 3 by a divergent magnetic field formed by an excitation coil 4, and a film is formed on the surface of the sample S to which a predetermined bias is maintained by an RP power source 8. .

At this time, the peripheral wall of the plasma generation chamber 1 is set to the ground potential, and the protective walls 6, 6 are similarly set to the ground potential by the changeover switch S-1°SWt.

This can prevent the protection walls 6, 6 from becoming floating potential due to the plasma in the plasma generation chamber 1 and affecting the film-forming ion flow.

When the operating time reaches a predetermined value, the film forming operation is temporarily stopped and each selector switch SWI, swt is turned from the ground side to R.
Switch to the F power source 10 side, and supply 10% 02-added CF and gas for etching from the gas supply system 1g.

As a result, when plasma is generated in the plasma generation chamber 1, each of the protective walls 6, 6 and the sample stage 5 are automatically set to a negative potential (self-bias), and the plasma discharge is dispersed around the four circumferences and spreads on the surface of the protective wall 6. Ions removed by etching the deposited film.

Gas etc. are exhausted through the exhaust port 3a.

[Numerical example]

Using the apparatus shown in Fig. 1, Nt gas is supplied from 1 g of the gas supply system at a rate of 105 CCH, and 5 rH from 3 g of the gas supply system.
a at a rate of 8 SCCM, the plasma generation chamber 11
A silicon nitride film with a thickness of about 1 μm was deposited on the sample surface by setting the vacuum level in the reaction chamber 3 to 0.7 mTorr and the microwave power to 200 mTorr. Adhesion of the film was observed at a thickness of 0.4 μm. Further, at this point, the number of particles of 0.3 μm or more attached to the wafer was 10 particles/cd.

Next, the changeover switches SW, SW, and SW were respectively applied to the high frequency power supply lO side, 10% 0□ added CF4 gas was introduced into the plasma generation chamber 1 at a rate of 405 CCM, and the degree of vacuum was set to 0°5 mTorr, and the RF power was set to Etching was performed by generating plasma at 200W. Immediately after this, the number of particles was less than 1/d, confirming that the attached film was removed by etching for about 10 minutes, and the protective wall 6.6 was restored to the luster of the stainless steel it is made of. did it.

As a result, the time required for cleaning was reduced to 1710 times compared to the conventional method.

Although the above-mentioned embodiment shows a structure in which the apparatus of the present invention is applied to a CVD apparatus, it is not limited to this in any way, and it goes without saying that the apparatus can also be applied to, for example, an etching apparatus, a sputtering apparatus, and the like.

〔effect〕

As described above, in the present invention, a conductive protective wall is provided in the plasma generation chamber in a manner that covers it and maintains an electrically insulated state from the plasma generation chamber, and can be set at a ground potential and/or a plurality of negative potentials. Because of this, the present invention has excellent effects such as being able to perform the purification process of the plasma generation chamber automatically while maintaining a high vacuum, resulting in high production efficiency.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the device of the present invention, and FIG. 2 is a longitudinal sectional view of the conventional device. 1... Plasma generation chamber 2... Waveguide 3... Reaction chamber 4... Excitation coil 5... Sample stage 6... Protective wall 7... Matching box 8... RF main Power supply 9... Matching box 10... RF power IS... Sample SWI, S switch 2... Changeover switch patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 2 Figures

Claims (1)

[Claims] 1. In a plasma processing apparatus equipped with a plasma generation chamber that generates plasma by electron cyclotron resonance excitation, and a sample chamber that introduces the generated plasma through a drawer window and processes a sample placed facing the drawer window. . A plasma processing apparatus, characterized in that a conductive protection wall is provided in the plasma generation chamber so as to be electrically insulated from the plasma generation chamber and capable of selectively applying a ground potential and/or a plurality of potentials.