JPH01315693A - Vacuum discharge pump - Google Patents

Abstract

PURPOSE:To prevent a reaction product in exhaust gas from sticking to the inner surface of a housing for an oil-free vacuum pump by providing a means for heating reactive gas on the inner surface of the housing which makes into contact with the exhaust gas. CONSTITUTION:When a wafer 1 is set on a lower electrode 7 and then a processing chamber 2 is evacuated to a high vacuum by means of a vacuum evacuating device 15, etching gas is fed into a gas supply passage 14. Further, a high frequency power from a power source 12 is applied between electrodes 7, 8. Further, exhaust gas containing the etching gas is discharged from a discharge port 6 by means of the vacuum evacuation device 15, and is led successively into a gas cooling trap 34 and a dry type scrubber 36. In this arrangement, a panel hater 41 is disposed at the inner surface of a housing in a turbo- vacuum pump 20 constituting the vacuum evacuating device 15, which makes into contact with the exhaust gas. With this arrangement, it is possible to prevent a reaction product in the exhaust gas from sticking to the inner surface of the housing 21.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to vacuum evacuation technology, a special feature, and a technology for creating a high vacuum using an oil-free vacuum pump. In contrast, the present invention relates to techniques that are effective when performing plasma etching treatment.

[Conventional technology]

In the manufacturing process of semiconductor devices, a try-etching device that performs etching on a thin film on a wafer consists of a processing chamber, a vacuum evacuation device that evacuates the processing chamber to a high vacuum, and parallel plate electrodes arranged above and below the processing chamber. , and a supply path for supplying etching gas to the processing chamber.The lower electrode of the electrode holds the wafer, and the upper electrode facing the wafer is anode-coupled with a high-frequency power source, and the high-frequency power is applied between the two electrodes. At the same time, by evacuating the processing chamber to a high vacuum, etching processing is performed by a plasma reaction between the plasma formed between the two electrodes and the etching gas supplied to the processing chamber, and by ions accelerated within the electric field. Anode-coupled plasma consisting of
There is an etching device.

The vacuum evacuation equipment used in such dry etching equipment uses mechanical booster pumps and rotary pumps, as well as scrubbers to prevent reaction products from being discharged into the atmosphere. ing.

As an example of dry etching technology,
"Electronic Materials November 1984 Special Edition" published by Kogyo Research Association Co., Ltd., November 20, 1984, P97-P101
There is.

[Problem to be solved by the invention]

However, in the vacuum evacuation equipment used in such dry etching equipment, the oil in the rotary pump deteriorates due to reaction products, requiring periodic replacement. A trap is installed between the mechanical booster pump and the rotary pump to prevent it from sticking, but since it is installed in the vacuum exhaust path, it is easy for leaks to occur (maintenance and The problem is that it is troublesome.

On the other hand, several types of oil-free vacuum pumps that do not use oil are known as high vacuum pumps (for example, Japanese Patent Application No. 60-88624, Japanese Patent Application No. 59-189599).
(Refer to the specification of Japanese Patent Application Laid-open No. 1983-21689). Therefore, by using these oil-free vacuum pumps, it is possible to prevent oil deterioration from occurring.
Conceivable.

However, when an oil-free vacuum pump is used in a dry etching device, there is a problem that foreign matter is generated by the etching gas, and this reaction product accumulates inside the oil-free vacuum pump, causing a malfunction. Revealed by the inventor.

An object of the present invention is to provide a vacuum evacuation device that can prevent failures due to adhesion of reaction products.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

That is, a heating means is installed in a portion of the inner surface of the housing of the oil-free vacuum pump that comes into contact with the gas to be evacuated.

[Effect]

According to the above-mentioned means, since the heating means is installed on the inner surface of the housing of the oil-free vacuum pump, even if the reactive gas in the gas to be exhausted comes into contact with the inner surface of the housing, reaction products will not adhere to it. It will not do anything and will be evacuated immediately. Therefore, reaction products do not accumulate on the inner surface of the housing, and failures caused by such accumulation are prevented.

〔Example〕

FIG. 1 is a schematic diagram showing a dry etching device in which a vacuum evacuation device according to an embodiment of the present invention is used, and FIG. 2 is a longitudinal sectional view showing the overall structure of an oil-free vacuum pump used therein. FIG. 3(a) is a vertical sectional view showing details of the centrifugal compression pump stage in FIG. 2, and FIG. 3(b) and (c)
are the [IIb arrow view and llc arrow view in FIG. 3(a),
Figure 4 (al is a vertical sectional view showing the details of the circumferential flow compression pump stage in Figure 2, and Figures (b) and (C) are views in the direction of the IVb arrow and IVc arrow in Figure 4(a). It is.

In this embodiment, the dry etching apparatus is equipped with a chamber 3 that constitutes a processing chamber 2 for processing a wafer l as an object to be processed. It is formed from. The chamber main body 4 is formed into a substantially cylindrical shape with a closed bottom and a closed top, and the lid 5 is formed into a substantially disk shape and is detachably placed over the bottom opening of the main body 4 to cover the processing chamber 2. It is designed to be sealed tightly. Further, an IJI-air port 6 for evacuating the inside of the processing chamber 2 is provided in the lid body 5, and a vacuum evacuation device to be described later is connected to this exhaust port 6.

A pair of electrodes 7.8 are horizontally disposed at the lower and upper portions of the processing chamber 2 so as to form parallel plate electrodes. The lower electrode 7 is vertically movably supported by a support shaft 10 slidably inserted into the bottom wall of the lid 5 via an insulator 9, and can hold the wafer 1 on its upper surface. It is configured as follows. The upper electrode 8 is fixedly suspended by a support shaft 11 inserted into the main body 4 via a holder 13 made of an insulating material, and a high frequency power source 12 is anode-coupled to the upper electrode 8.

Further, inside the holder 13, a gas supply path 14 is provided with an etching gas (for example, B(1, ccp,
etc.), and the etching gas inlet, which is the outlet of the supply path 14, faces the back surface of the upper electrode 8 so as to introduce the etching gas into the back space of the upper electrode 8.

The vacuum evacuation device 15 includes a main pump 16 and an auxiliary pump 2, both of which are constructed using oil-free vacuum pumps.
As the main pump 16, a turbo-molecular pump that exhibits a vacuum evacuation action in a relatively high vacuum region is used. The auxiliary pump 20 is a turbo molecular pump 16
It is connected to the discharge side of the turbo molecular pump 16 and serves as an auxiliary pump for the turbo molecular pump 16, so it is configured as shown in FIGS. 2 to 4 in order to achieve vacuum evacuation from near atmospheric pressure. has been done.

That is, this vacuum pump (hereinafter referred to as a turbo vacuum pump) includes a housing 21 having an intake port 21A and an exhaust port 21B, a rotating shaft 22 rotatably supported within the housing 21 via a bearing 25, Intake port 21
It includes a centrifugal compression pump stage 23 and a circumferential flow compression pump stage 24 which are arranged in sequence within the housing 21 from the A side to the exhaust port 21B side. The rotating shaft 22 is driven by a motor 30 connected thereto, and the motor 30 is configured to have its rotation speed controlled by an inverter 31.

As shown in FIGS. 3(a) and 3(b), the centrifugal compression pump stage 23 has a plurality of vanes 26 protruding from its surface facing inward with respect to the rotational direction, and has a plurality of vanes 26 protruding from the rotating shaft 22. The attached open impeller 23A and Fig. 3(a)
)(C), it is attached to the inner wall of the housing 2I, and the back surface of the impeller 23A (
A fixed disk 23B having a plurality of blades 27 protruding inwardly with respect to the direction of rotation is arranged alternately in parallel on the opposing surface.

As shown in FIGS. 4(a) and 4(a), the circumferential flow compression pump stage 24 is attached to a rotating shaft 22 and has a plurality of vanes 28 radially formed on its outer circumferential surface. The impeller 24A and FIGS. 3(a) and (C)
As shown in , a fixed disk is attached to the inner wall of the housing 21 and has a U-shaped groove 29 on the surface facing the surface of the impeller 24A (the surface on which the blades are provided). 24B are alternately arranged in parallel, and as shown in FIGS. 4A and 4C, a hole 29a is bored at the end of the groove 29 to form a ventilation path. It is formed.

Here, the operation of the turbo vacuum pump according to this configuration will be explained.

In a transient state at the beginning of pump operation, the entire inside of the pump is under a high pressure close to atmospheric pressure, and the gas flow becomes a viscous flow, so that the centrifugal compression pump stage 23 acts as a centrifugal compressor. That is, the centrifugal compression pump stage impeller 23A
acts as a compressor impeller, and the impeller 23A and fixed disk 2
The flow path formed between the blades 27 between the blades 3B acts as a return channel that directs the flow from the outer diameter to the inner diameter. Therefore, the function of flowing the large 291 is performed as a compressor rather than as a pressure loss section.

In a steady state, when the compression ratio of the circumferential flow compression pump stage 24 is increased and the pressure at the inlet of the circumferential flow compression pump stage is sufficiently low, that is, this pressure is several T.

In a steady state below rr, the gas flow near the inlet of the centrifugal compression pump stage 23, that is, the suction port 21A of the vacuum pump, becomes an intermediate flow or a molecular flow, and the centrifugal compression pump stage 23 becomes a Siegbahn molecular pump. Acts as. That is, the impeller 23A having the blades 26 is
It acts as a rotating disk with spiral grooves, and the fixed disk 23
In combination with the back surface of B (the surface on which the blades 27 are not provided), it functions as a Siegbahn molecular pump that compresses from the inner diameter side toward the outer diameter side. In addition, multiple blades 2
The fixed disk 23B provided with the impeller 23B acts as a fixed disk having a cape spiral groove formed thereon, and is attached to the back surface of the impeller 23A
When used in combination with the surface (without a surface), it acts as a Siegbahn molecular pump that compresses from the outer diameter side toward the inner diameter side.

Similarly, in the steady state, the gas flowing into the circumferential compression pump stage 24 is sufficiently compressed in the centrifugal compression pump stage 23, so that the volumetric flow rate is almost zero. In other words, the circumferential flow compression pump stage 24 is operated in a state close to the closed state, but since the circumferential flow compression pump has the characteristic of obtaining a high compression ratio in the closed state, a small number of stages is sufficient. Reaching a low ultimate pressure 6 Centrifugal compression pump stage 23 as well as circumferential flow compression pump stage 24
The number of stages and pump rotation speed are as follows under steady operating conditions:
The pressure at the boundary between the two stages is set to be the switching point between the viscous flow and the intermediate flow, that is, several Torr. Usually 1 to 3 centrifugal compression pump stages and 6 to 1 circumferential compression pump stages.
Depending on the combination of 0 stages, the pressure at the pump intake port 2+A will be between 10-3 and 1, which can realize the CVD process described later.
0-'Torr is reached.

As is clear from the above, according to this vacuum pump,
The centrifugal compression stage pump stage installed on the inlet side works as a centrifugal compressor in a transient state and as a Siegbahn molecular pump in a steady state (it has a dual function, so it keeps the exhaust port pressure close to atmospheric pressure). This allows a large pumping speed to be obtained in the transient state at the beginning of pump operation.

Exhaust port 21B of the turbo vacuum pump 20 according to the above configuration
is fluidly connected to a trap 34 via a pipe 32, and a heater 33 as a heating means is provided in the pipe 32 to heat the exhaust gas passing through the pipe 7!32 to a predetermined temperature. As such, from the exhaust port 21 [3 to the cooling Trump 3
It is laid out over 4. The heater 33 is controlled by a temperature controller or the like (not shown) to a predetermined temperature that can prevent reaction products from adhering to the piping 32 or the like, for example,
It is configured to be controlled to heat the gas above about 180'C.

The gas cooling trap 34 to which the pipe 32 is connected cools the exhaust gas heated by the heater 33 of the pipe 32 to about room temperature by being supplied with a refrigerant such as clean air or nitrogen gas from the refrigerant supply device 35. is configured to do so.

A dry scrubber 36 is connected to the outlet of the gas cooling trap 34, and although detailed explanation and illustration are omitted, this dry scrubber 36 applies inertia, collision, obstruction, etc. to the exhaust gas to remove the gas in the gas. It is configured to physically collect reaction products and foreign substances.

In this embodiment, the inner surface of the housing 21 of the turbo vacuum pump 20 according to the above configuration has an hI region where the panel heater 41 as a heating means comes into contact with the gas to be evacuated, and an area that does not interfere with the pumping action. , and is laid with a heat insulating material 42 in between. This panel heater 4■ is a temperature controller, etc. (not shown)
A predetermined temperature that can prevent reaction products from adhering to the inner surface of the housing 21, for example, a temperature corresponding to the Y atmospheric pressure of the etching gas, vJr ao'
It is configured to be controlled so as to heat the gas that is about to be heated above IJP.

Next, the action will be explained.

When the wafer l is placed on the lower electrode 7 and the inside of the processing chamber 2 is brought to a high vacuum by the evacuation device 15, an etching gas (for example, BCI, C(1) is supplied to the gas supply path 14).
4, etc.) is supplied and blown out from the outlet, and at the same time, high frequency power is applied between the picture electrodes 7 and 8 by the electric current tX12. The dirt causes a plasma etching reaction and ion sputtering, and a desired etching process is performed depending on the selectivity between the resist (not shown) deposited on the wafer I and the underlying layer.

Then, the exhaust gas containing the etching gas supplied to the processing chamber 2 is exhausted from the exhaust port 6 by the vacuum exhaust device I5, and is then exhausted from the gas cooling trap 34 and the dry scrubber 3.
After the reaction products and the like are reduced and collected in step 6, they are exhausted to a predetermined waste treatment section.

By the way, if the panel heater 41 is not installed on the inner surface of the housing 21 in the oil-free vacuum pump 20, reaction products in the exhaust gas will adhere to the inner surface of the housing 21, resulting in a problem that the exhaust path will quickly become clogged. The inventor has revealed that there is a point.

However, in this embodiment, a panel heater 41 is installed on the inner surface of the housing 21 of the turbo vacuum pump 20 that comes into contact with the gas to be exhausted, and this heater 41 increases the vapor pressure of the etching gas in the exhaust gas. a predetermined temperature corresponding to, for example, about 180°
Since it is heated above C, reaction products do not adhere to the inner surface of the housing 21. That is, by maintaining the etching gas in the gas to be exhausted at a high temperature, it becomes difficult for the reaction products to grow or become pulverized.

According to the embodiment described above, the following effects can be obtained.

(1) By providing a heating means for heating the reactive gas on the inner surface of the housing of the oil-free vacuum pump that comes into contact with the gas to be exhausted, reaction products in the gas to be exhausted adhere to the inside of the housing. Therefore, it is possible to prevent failures due to clogging, etc., and maintain proper exhaust conditions.

(2) By providing a heating means for heating the exhaust gas in the piping connected to the exhaust port of the oil-free vacuum pump, and by providing a gas cooling means after the heating means, the heated exhaust gas is brought back to a low temperature. Therefore, by effectively exerting the collection action of the scrubber, the exhaust gas can be properly cleaned.

(3) By realizing the use of only oil-free vacuum pumps, it is possible to avoid oil deterioration due to reaction products and the accompanying oil replacement work, thereby reducing oil replacement costs and maintenance. As a result, the operating efficiency of the equipment can be increased,
The productivity of the entire manufacturing process can be increased.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the heating means installed on the inner surface of the housing of the oil-free vacuum pump is not limited to a panel heater, but may also be a steam heating pipe or the like.

The oil-free vacuum pump is not limited to a turbo-molecular pump or a turbo-type oil-free vacuum pump as in the above embodiments, but may also be a scroll vacuum pump or the like.

In the above explanation, the invention made by the present inventor was mainly applied to a vacuum evacuation device used in a dry etching device, which is the background field of application, but the invention is not limited to this. The present invention can be applied to all vacuum evacuation devices used in processing equipment such as CVD equipment.

In particular, the present invention exhibits excellent effects when applied to a vacuum evacuation device connected to a processing device that uses processing gas.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

By providing a heating means for heating the reactive gas on the inner surface of the housing of the oil-free vacuum pump that comes into contact with the gas to be exhausted, the reaction products in the gas to be exhausted into the housing are Therefore, it is possible to prevent failures due to clogging, etc., and maintain proper exhaust conditions.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a dry etching device in which a vacuum evacuation device according to an embodiment of the present invention is used, and Fig. 2 is a vertical sectional view showing the overall structure of an oil-free vacuum pump used therein. , Fig. 3(a) is a vertical sectional view showing details of the centrifugal compression pump stage in Fig. 2, and Fig. 3(b) and (C) are m in Fig. 3(a).
b arrow view and mc arrow view 1 and 4 [ff1 (a) is a vertical sectional view showing details of the circumferential flow compression pump stage in Fig. 2;
Figure (a) is a view in the direction of the IVc arrow. 1... Wafer (workpiece), 2... Processing chamber, 3...
・Chamber, 4...Main body, 5...Lid, 6...Exhaust port, 7...Lower electrode, 8...Lower electrode (electrode to which the power source is connected to the anode), 9... Insulator, l01II
... Support shaft, I2 ... High frequency power supply, I3 ... Holder, 14 ... Gas supply path, 15 ... Vacuum exhaust device, 1
6...Turbo molecular pump C main pump), 20...Oil-free vacuum pump (auxiliary pump), 21...Housing, 21A...Intake port, 21B...Exhaust port, 2
2...Rotating shaft, 23...Centrifugal compression pump stage, 23A
...Open impeller, 23B...Fixed disc, 24
... Circumferential flow compression pump stage, 24Δ... Impeller, 24
■3...Fixed disc, 26.27.28...Blade, 3
0... Motor, 31... Inverter, 32... Piping, 33... Heater (heating means), 34... Gas cooling trap (cooling means), 35... Refrigerant supply device, 3
6...Dry scrubber, 41...Panel heater (heating means), 42...Insulating material. N Ward C Castle

Claims (1)

[Scope of Claims] 1. A vacuum evacuation device characterized in that a heating means is installed in a portion of the inner surface of the housing of an oil-free vacuum pump that comes into contact with the gas to be evacuated. 2. The vacuum according to claim 1, wherein the heating means is configured to be temperature-controlled in accordance with the vapor pressure of a component in the exhaust gas that is likely to generate a reaction product. Exhaust device. 3. The vacuum evacuation device according to claim 1, wherein a heating means is provided at the exhaust port of the oil-free vacuum pump so as to heat the exhaust gas.