JPH0732133B2 - Semiconductor manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus provided with a vacuum pump such as an oil rotary pump, and particularly to a semiconductor suitable for preventing contamination by oil on the exhausted side. Manufacturing equipment

[Conventional technology]

In semiconductor manufacturing equipment equipped with a vacuum pump that uses oil, a purging method that prevents oil contamination of the vacuum container due to back diffusion of oil from the vacuum pump is described in "Vacuum Technology" (Kyoritsu Shuppan, July 1985). "D. A clean system" (203-2
Page 07). In the purging method according to this known document, the contamination with the oil causes a purge gas pressure of 13 Pa (0.
1 Torr), the pressure rises sharply on the low pressure side, so dry nitrogen purge is provided on the suction side of the oil rotary pump, and the suction pressure of the oil rotary pump is 13-40 Pa (0.1-0.3To
rr).

FIG. 8 shows a conventional vacuum device to which the above-mentioned known purging method is applied. First, in order to evacuate the vacuum chamber 50 from the atmospheric pressure state, the roughing valve 51 and the oil rotary pump valve 52 are opened, and the roughing by the oil rotary pump 53 is started. At this time, the vacuum chamber purge valve 55 is opened so that the oil of the oil rotary pump 53 does not back-diffuse into the vacuum chamber 50, the purge gas from the purge gas source (not shown) is purged into the vacuum chamber 50 through the pipe 56, and the vacuum chamber 50 Pressure is 40Pa (0.
3Torr) Do not fall below. At a pressure near 40 Pa, the oil rotary pump valve 52 and the vacuum chamber purge valve 55 are closed, the sorption pump valve 58 is opened, and the sorption pump 59 performs roughing to a lower pressure.

When the working pressure range of the main exhaust pump (not shown) communicating with the vacuum chamber 50 through the pipe 60 is reached, the roughing valve
51 is closed and the main exhaust pump is exhausted through the pipe 60. Further, in order to prevent the oil of the oil rotary pump 53 from back-diffusing due to an erroneous operation of the valve or the like and contaminating the vacuum chamber 50, a purge gas is caused to flow from the oil rotary pump purge pipe 61 so that the suction port pressure of the oil rotary pump 53 is 13 Pa ( 0.1T
It is desirable to be more than orr). In FIG. 8, 62 is a pump discharge pipe.

[Problems to be solved by the invention]

In recent years, as semiconductors have become highly integrated, a problem has arisen in semiconductor manufacturing equipment due to wafer contamination due to back diffusion of oil in a vacuum pump used for exhausting a vacuum chamber. In particular, in an oil rotary pump operating near the ultimate pressure, oil back diffusion is severely generated. If the amount of back diffusion of oil in the oil rotary pump, which is the source of this oil pollution, is reduced, it is possible to reduce the defective rate of semiconductors due to oil pollution. However, in the above conventional purging method, by suppressing the oil contamination due to the reverse diffusion of the oil of the oil rotary pump 53 into the vacuum chamber 50, the suction port pressure of the oil rotary pump 53 is as high as 13 Pa (0.1 Torr) or more by purging. is doing.
With this, in the semiconductor manufacturing process, the pressure in the vacuum chamber 50 after removing unnecessary gas becomes high, and the oil rotary pump 53 is used to set the pressure in the vacuum chamber 50 to 13 Pa (0.1 Torr).
r) There was a problem that a lower and higher clean environment could not be created.

An object of the present invention is to purify a small amount of purge gas from the suction port side of a vacuum pump such as an oil rotary pump while maintaining the pressure of the processing chamber at 0.1 Torr or less, and to suppress the back diffusion of oil in a semiconductor manufacturing apparatus. To provide.

[Means for solving problems]

To achieve such an object, the present invention, in a semiconductor manufacturing apparatus using a vacuum pump such as an oil rotary pump as a vacuum exhaust system, traces a small amount of purge gas to 0.1 Torr during the process of exhausting the processing chamber to the ultimate pressure. A purge gas micro flow rate supply mechanism for purging from the upstream side of the vacuum pump while maintaining the following is provided.

[Action]

According to the above configuration, when the process chamber is evacuated to the ultimate pressure with a vacuum pump such as an oil rotary pump, the minimum amount sufficient to prevent the back diffusion of oil used in the vacuum pump to the suction port side. Is purged from the upstream side of the vacuum pump through the minute flow rate supply mechanism while maintaining the pressure of the processing chamber at 0.1 Torr or less. The purge amount at this time is about several tenths of the conventional purge amount, and the ultimate pressure of the vacuum exhaust system is hardly affected, and a clean vacuum can be obtained. As a result, a semiconductor manufacturing apparatus in which the oil in the exhaust system is less contaminated can be obtained.

〔Example〕

 Hereinafter, the present invention will be described based on embodiments shown in the drawings.

FIG. 1 shows a semiconductor manufacturing apparatus 1 according to the present invention in a batch depressurization CV.
1 shows the first embodiment applied to the D apparatus. The semiconductor manufacturing apparatus 1 includes a reaction tube 2 that is a processing chamber, an oil rotary pump 3 that is a vacuum pump, a gas supply unit 5, and a purge gas micro flow rate supply. And a mechanism 6.

The reaction tube 2 is closed at one end with a cover 9 via a seal member 8 and is configured to introduce the wafer 10 therein. The oil rotary pump 3 is connected to the other end of the reaction tube 2 by an exhaust pipe 11, and in the exhaust pipe 11, a cooling trap 12 and a main exhaust valve 13 are sequentially arranged from upstream to downstream.
And mechanical booster 15 is located. In addition, the exhaust pipe 11A between the cooling trap 12 and the main exhaust valve 13 branches off from the exhaust pipe 11 between the main exhaust valve 13 and the mechanical booster 15.
An auxiliary exhaust valve 18 is arranged in the branch pipe 16 connected to 11B. The gas supply unit 5 is connected to one end of the reaction tube 2 by a pipe 19, and a gas valve 20 is arranged in the pipe 19.

The purge gas micro flow rate supply mechanism 6 includes a purge gas source 21 and
It comprises a purge gas pipe 22 connecting the purge gas source 21 and the exhaust pipe 11B, a minute flow rate supply flow meter 23 and a minute flow rate supply purge valve 25 arranged in the purge gas pipe 22.

In FIG. 1, a leak valve 26 and a pressure gauge 28 are connected to the pipe 11A, and the outer peripheral surface of the reaction tube 2 is covered with a heater 29. Further, a dilution gas line 30 and a discharge pipe 31 are connected to the oil rotary pump 3, respectively.

Next, the operation of the first embodiment of the present invention will be described.

In the batch type low pressure CVD cycle, after the wafer 10 is introduced into the reaction tube 2, first the auxiliary exhaust valve 18 is opened and then the main exhaust valve 13 is opened to remove the air in the reaction tube 2 from the exhaust tube 11 and the branch tube 16. Through the mechanical booster 15 and the oil rotary pump 3. Next, the gas valve 20 is opened and nitrogen gas is introduced from the gas supply unit 5 into the reaction tube 2 through the pipe 19 and is replaced with air. Then, only the auxiliary exhaust valve 18 is closed to perform further exhaust, and the reaction gas is supplied to the gas supply unit 5.
Is introduced into the reaction tube 2 through the pipe 19 to cause the reaction, and after completion of the reaction, nitrogen gas is again introduced into the reaction tube 2 to replace the reaction gas. Then, after closing the main exhaust valve 13 and the gas valve 20, the leak valve 26 is opened to introduce the atmosphere into the reaction tube 2 to return it to the atmospheric pressure state, and the wafer 10 is carried out of the reaction tube 2.

After the wafer 10 is introduced into the reaction tube 2, when the reaction tube 2 is evacuated from the atmospheric pressure state by the mechanical booster 15 and the oil rotary pump 3, or when the reaction gas is replaced with the nitrogen gas, the reaction gas is supplied. When the reaction gas is stopped and the reaction gas is exhausted from the inside of the reaction tube 2, reverse diffusion of oil rapidly progresses in the vicinity of the ultimate pressure to contaminate the inside of the reaction tube 2, so that the purge gas micro flow rate supply mechanism 6 is provided from the beginning of exhaust. The minute flow rate supply purge valve 25 is opened, and the flow rate of the purge gas is confirmed by the minute flow rate supply flow meter 23 from the purge gas source 21 through the purge gas pipe 22 and a small amount of purge gas is flowed. As the gas to be purged at this time, an inert gas that does not affect the reaction is preferable, but nitrogen gas or the like is also sufficiently effective, and as a result of the experiment, a gas having a larger molecular weight is more effective, as shown in Table 1. Is proved by.

FIG. 2 shows a residual gas spectrum measured by a quadrupole mass spectrometer in the vicinity of the ultimate pressure in the reaction tube 2 when purging with nitrogen gas, in which the vertical axis is the ion current value and the horizontal axis is the mass. Is a number. The obtained spectrum is the residual gas spectrum of air, and it can be seen that an extremely clean state was obtained.

FIG. 3 is a residual gas spectrum in the reaction tube 2 when the purging at the minute flow rate is stopped. The peak due to the component of the oil (hydrocarbon system) used in the oil rotary pump 3 is the mass number 39.
A large number are detected as described above, and it can be seen that the oil contamination in the reaction tube 2 is significantly advanced.

FIG. 4 shows changes in the amount of purge gas and residual gas component detection peaks when purging nitrogen gas, and changes in oil rotary pump suction port pressure (hereinafter simply referred to as suction port pressure). The left vertical axis represents the ion current value with respect to the residual gas detection peak, the right vertical axis represents the suction port pressure, and the horizontal axis represents the purge amount.

Comparing the above, when looking at each component of oil by a slight amount of purge, the peak when a minute flow rate is purged is about 1/100 of that when no purge is performed, and a sufficiently clean vacuum is obtained. You can see that it is being done. At this time, when the total amount of purging and the conventional purging amount are compared, it can be seen that the purging amount of the present invention is extremely small. As an example, the purging amount of the oil rotary pump 3 having an evacuation speed of 240 l / min will be compared between the conventional method and the present invention.

When the exhaust speed of the oil rotary pump 3 is S, the exhaust amount is Q, and the suction port pressure is P, the respective relationships are given by the following equations.

Q = SP ... (1) S = 240 l / min, and the purge amount Q ₁ by the conventional method is P =
Assuming that 0.1 Torr, Q ₁ = 0.4 Torrl / S≈32 SCCM from equation (1), and the purge amount Q ₂ according to the present invention is 0.6 S according to FIG.
Since CCM (at the ultimate pressure of 7 × 10 ^-3 Torr) is also sufficiently effective, setting Q ₂ = 0.6 SCCM is about 1/53 of the conventional value. Therefore, the ultimate pressure of the vacuum exhaust system becomes lower than the pressure of 0.1 Torr by the conventional purging method, and a clean vacuum can be obtained. Therefore, according to the present embodiment, a vacuum with less oil contamination can be obtained by modifying the device with a relatively small number.

FIG. 5 relates to a second embodiment of the present invention, which is a semiconductor manufacturing apparatus 1
Is another example in which is applied to a batch type low pressure CVD apparatus.
In this embodiment, a minute flow rate supply control mechanism 35 for automatically controlling the purge gas minute flow rate supply mechanism 6 for purging according to the pressure on the upstream side of the oil rotary pump 3 is provided. The mechanism 35 includes a suction port pressure monitor vacuum gauge 36 for monitoring the suction port pressure and a minute flow rate supply purge valve control signal line 38.

When the suction port pressure becomes equal to or lower than a predetermined pressure, the suction port pressure monitor vacuum gauge 36 detects this, and outputs a signal for opening the minute flow rate supply purge valve 25 through the minute flow rate supply purge valve control signal line 38. Then, the valve 25 is opened and purging is performed. When the suction port pressure becomes higher than a predetermined pressure, the suction port pressure monitor vacuum gauge 36 detects this and sends a signal for closing the minute flow rate supply purge valve 25 through the minute flow rate supply purge valve control signal line 38.
25, which causes the valve 25 to close. As described above, in the second embodiment, purging can be automatically performed according to the suction port pressure, and the reliability and economy of the device are improved.

FIG. 6 relates to a third embodiment of the present invention, which is a semiconductor manufacturing apparatus 1
Is another example in which is applied to a batch reduced pressure CVD apparatus. In this embodiment, in the mechanism for purging the purge gas, the purge gas source is shared with a part of the gas in the gas supply unit 5. As described above, in this embodiment, the purge gas micro flow rate supply mechanism 6 is shared with a part of the gas in the gas supply section 5, and the structure is simplified.

FIG. 7 relates to a fourth embodiment of the present invention and relates to a semiconductor manufacturing apparatus 1
Is another example in which is applied to a batch type low pressure CVD apparatus.
In this embodiment, among the constituent elements of the purge gas micro flow rate supply mechanism 6, a micro flow rate supply mass flow controller 39 in which a micro flow rate supply purge valve 25 and a micro flow rate supply flow meter 23 are integrated is used (this structure and principle are Measurement Technology "86, Special Issue, pages 55-62). This simplifies the structure of the purge gas micro flow rate supply mechanism 6.

〔The invention's effect〕

As described above, according to the present invention, during the process of exhausting the processing chamber to the ultimate pressure with a vacuum pump such as an oil rotary pump, a slight amount of purge gas maintains the pressure of the processing chamber below 0.1 Torr and Purged from the upstream side. Therefore, the back diffusion of the oil used in the vacuum pump to the suction port side is suppressed, so that the inside of the processing chamber is in a clean vacuum state, whereby a semiconductor manufacturing apparatus in which the exhaust system oil is less contaminated can be obtained.

[Brief description of drawings]

1 to 4 relate to the first embodiment of the present invention, FIG. 1 is a configuration diagram in which a semiconductor manufacturing apparatus according to the present invention is applied to a batch type low pressure CVD apparatus, and FIG. 2 is a residual gas in a reaction tube. FIG. 3 is a spectrum, FIG. 3 is a spectrum of residual gas in the reaction tube when purging is not performed, and FIG. 4 is a relationship diagram between the amount of purge gas, changes in the detection peak of residual gas components, and changes in pump suction port pressure. FIG. 7 to FIG. 7 relate to the second to fourth embodiments of the present invention, and are configuration diagrams of other embodiments in which the semiconductor manufacturing apparatus according to the present invention is applied to a batch type low pressure CVD apparatus, and FIG.
FIG. 1 is a block diagram of a vacuum device to which the conventional purging method is applied. 1 ... Semiconductor manufacturing equipment, 2 ... reaction tube which is a processing chamber, 3
…… Oil rotary pump, which is an example of a vacuum pump, 6 …… Purge gas micro flow rate supply mechanism, 36 …… Suction port pressure monitor vacuum gauge, which is a pressure detector.

Claims (4)

[Claims] 1. In a semiconductor manufacturing apparatus using a vacuum pump such as an oil rotary pump as a vacuum exhaust system, a slight amount of purge gas is maintained at a pressure of 0.1 Torr or less during the process of exhausting the process chamber to the ultimate pressure. A semiconductor manufacturing apparatus provided with a purge gas micro flow rate supply mechanism for purging from the upstream side of the vacuum pump. 2. The purge gas micro flow rate supply mechanism has a pressure detector for detecting the upstream pressure of the vacuum pump,
2. The semiconductor manufacturing apparatus according to claim 1, wherein purging is performed when the pressure on the upstream side of the vacuum pump falls below a predetermined pressure by the pressure detector, and purging is stopped when the pressure rises above a predetermined pressure. 3. The semiconductor manufacturing apparatus according to claim 1, wherein a part of the purge gas minute flow rate supply mechanism is shared with a mechanism for supplying a reaction gas to the processing chamber. 4. The semiconductor manufacturing apparatus according to claim 1, wherein the purge gas species for performing the purging is an inert gas or a nitrogen gas.