JP2001060555A - Substrate processing method - Google Patents

Abstract

[PROBLEMS] To prevent generation of turbulent flow in a reduced pressure CVD apparatus in which a wafer is heat-treated in a reaction chamber in a reduced pressure reaction gas atmosphere when the reaction chamber is closed and the atmospheric pressure is maintained. Then, it is ensured that no particles or contaminants such as NH ₄ Cl are mixed due to leakage of N ₂ gas from the seal portion. SOLUTION: A main exhaust line 16 communicating with a reaction chamber 3 is provided.
The secondary exhaust line 2 that bypasses the primary exhaust valve 18
1 is provided. The sub exhaust line 21 includes a sub exhaust valve 22 that opens when the pressure in the reaction chamber 3 becomes atmospheric pressure, and a needle valve 23 that can adjust the exhaust flow rate so that the airflow flowing in the reaction chamber 3 becomes laminar. Provide. In the state of maintaining the atmospheric pressure, the amount of introduction and the amount of exhaust are balanced by the needle valve 23, thereby maintaining the atmospheric pressure and forming a laminar flow in the reaction chamber 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate processing method, and more particularly, to a method suitable for a semiconductor manufacturing method using a low pressure CVD apparatus.

[0002]

2. Description of the Related Art In a low-pressure CVD apparatus, as shown in FIG. 3, a furnace port 10 of a reaction chamber 3 is closed by a shutter 11 or a furnace port lid 9 of a boat 12 not loaded with product wafers. There is a step of introducing N ₂ into 3 to maintain the pressure in the reaction chamber at atmospheric pressure. In this step, a mass flow controller (MF
C) N ₂ gas controlled to an appropriate amount in 27 is introduced from the lower part of the reaction chamber 3 through the reactive gas introduction line 15 to increase the pressure in the reaction chamber 3. On the other hand, the pressure in the reaction chamber 3 is monitored by a pressure detector 25 provided in the main exhaust line 16, and when the pressure in the reaction chamber 3 becomes atmospheric pressure, the pressure is provided in an overpressurization prevention line (atmospheric pressure bend line) 31. When the gate valve 32 is opened and the pressure in the reaction chamber 3 becomes higher than the atmospheric pressure, the check valve 33 operates to exhaust the N ₂ gas. The inside of the reaction chamber 3 is maintained in an atmospheric state while maintaining the balance between the introduction and the exhaust.

When N ₂ gas is introduced from the lower part of the reaction chamber 3, the flow of the N ₂ gas flows from the lower part of the reaction chamber 3 → the upper part of the reaction chamber 3 → the external reaction tube 1 as shown by a dotted arrow. The space 8 between the internal reaction tube 2 and the overpressure prevention line 31
It is preferable that a regular laminar flow is formed in the reaction chamber 3. Here, in order to form a laminar flow, (1) it is necessary to always introduce an appropriate amount of inert gas into the reaction chamber at the time of a leak event (it is essential to flow the inert gas, but it is essential to limit the flow rate) (2) When the pressure in the reaction chamber is 760 Torr / 10
It is necessary to evacuate to maintain the atmospheric pressure of 1,080 Pa. However, in the above-described conventional apparatus, a turbulent flow is generated instead of a laminar flow. The reason is,

(1) Gate valve 32 of overpressurization prevention line 31
The operating pressure of the check valve 33 on the secondary side is not uniform (for example, 0.07 kgf / cm ² and 0.07 kgf / cm ² ).
23kgf / cm ² ), 0.07 in the check valve
If some of kgf / cm ² as the 0.023kgf / cm ^2, or increasingly gas introduction rate than the exhaust capacity,
A case where the exhaust capacity becomes larger than the gas introduction amount may occur. Also, the over-pressurization prevention line 31 is connected to the customer's utility (power supply required externally for system operation,
In the method of exhausting by connecting to a cooling water or the like, the exhaust pressure of the customer changes, and it is not known whether a laminar flow is formed unless the N ₂ flow rate to the reaction chamber is adjusted one by one. Further, whether or not the flow is laminar must be measured by actually measuring the amount of particles attached to the processing substrate. Therefore, exhaust cannot be performed to maintain the pressure in the reaction chamber at atmospheric pressure.

(2) There is no designation of the connection position of the over-pressurization prevention line 31 to the main exhaust line 16, and in the installation process of the apparatus, the location is confirmed at the site, and the piping shape and the like are determined and assembled. Therefore, the function of the over-pressurization prevention line 31 cannot be sufficiently exhibited as compared with the case where the position is designated and the piping shape or the like is determined in advance. Therefore, an appropriate amount of inert gas cannot always be introduced into the reaction chamber.

(3) It is difficult to maintain the reaction chamber at atmospheric pressure if there is variation in the exhaust pressure at the connecting point depending on the utility of the customer, and if there is variation in the exhaust pressure. And so on.

In (1), there is a problem that it takes time and cost for adjustment, and in (2), in the installation process of the apparatus, the location is confirmed on site, the piping shape and the like are determined and assembled. Therefore, there is also a problem that the man-hour for manufacturing the device is increased.

When the flow of N ₂ gas does not become laminar,
N ₂ gas leaks from the seal portion of the O-ring 7 between the inlet flange 6 into which the reactive gas introduction line 15 is inserted and the shutter 11 or the furnace cover 9 as shown by the solid line arrow. When the flow of the N ₂ gas is not laminar, NH ₄ Cl attached to the inner wall of the upper part of the inlet flange 6 (the side of the space 8 on the exhaust passage side) or the joint between the gas exhaust port 5 and the main exhaust line 16 NH ₄ Cl adhered to the inner wall of the portion (low temperature portion) gradually sublimates due to the heat of the heater 30,
The chlorine component will stagnate in the upper part of the reaction chamber 3.

Here, the relationship between gas leakage and stagnation will be explained. Leakage of N ₂ gas means that the state of over-pressurization in the reaction chamber 3 progresses and the state where the over-pressurization limit is exceeded. is there. In this state, the gas introduction amount is larger than the exhaust amount,
A gas is created that can move independently of the direction of exhaust.
Therefore, the phenomenon of gas stagnation occurs.

The amount of the chlorine component described above is proportional to the atmospheric state maintaining time, and when the increasing chlorine component is large (that is, when the atmospheric state maintaining time of the apparatus is long), the wafer is inserted when the boat 12 loaded with the product silicon wafer is inserted. After adsorbing to the surface and forming a nitride film, the film is counted as film-forming particles or haze by the lens effect. Table 1 shows the relationship between the atmospheric state maintenance time and the film-forming particles when two device tests were performed. It can be seen that the longer the apparatus maintains the atmospheric state, the more the deposition particles.

[0011]

[Table 1]

In [0005] conventional device described above, when the atmospheric conditions maintained, the pressure detector 25 detects the reaction chamber 3 and atmospheric pressure, or by leaks of N ₂ gas in the check valve 33 reaction Even when the chamber 3 is maintained at the atmospheric pressure, the operating pressure of the check valve 33 is not uniform, the connection position of the overpressurization prevention line 31, the variation of the exhaust pressure at the connection destination, etc. The flow of the N ₂ gas in the reaction chamber 3 does not become laminar,
Turbulence occurs. Therefore, N ₂ gas leaks from the reaction chamber 3, particles adhering to the inner wall or the like of the main exhaust line 16 or NH ₄ Cl remaining in the inlet flange or the like enter the reaction chamber 3 and contaminate the wafer W. There was a problem that caused.

It is an object of the present invention to solve the above-mentioned problems of the prior art by controlling the exhaust flow rate while maintaining the balance with the gas introduction amount to make the reaction chamber air flow laminar in the atmospheric pressure maintaining state. Accordingly, it is an object of the present invention to provide a substrate processing method in which leakage of an inert gas does not occur and contamination of particles or contaminants such as NH ₄ Cl does not occur.

[0013]

According to the present invention, a reaction chamber in which a boat is not inserted is closed with a shutter, or a boat in which a product substrate is not loaded is inserted into the reaction chamber and the reaction chamber is closed with a furnace lid. In a substrate processing method including a step of closing and maintaining the reaction chamber in an atmospheric state, when the reaction chamber is maintained in an atmospheric state, an inert gas is introduced into the reaction chamber, and the pressure of the reaction chamber is reduced to an atmospheric pressure. In this case, the exhaust gas is exhausted from a sub exhaust line provided in parallel with the main exhaust line, and the exhaust amount is controlled such that the pressure in the reaction chamber does not fluctuate.

The step of maintaining the atmospheric state refers to a step of closing the reaction chamber with a shutter or closing the reaction chamber with a boat in which no product substrate is loaded, and maintaining the reaction chamber at atmospheric pressure. In the atmospheric pressure maintaining step, the inert gas introduced into the reaction chamber is exhausted while controlling the exhaust gas flow rate so as not to fluctuate by the auxiliary exhaust line provided in parallel with the main exhaust line. Then, a steady laminar flow is formed in the reaction chamber. The particles in the reaction chamber are reduced by the laminar flow, and the reaction chamber in the atmospheric state is kept clean. Further, the inert gas does not leak from the seal portion.

As a means for realizing the method of the present invention, an over-pressurization prevention line in which an inert gas cannot always flow and an atmospheric pressure detection is not uniform is eliminated, and a sub-exhaust line is replaced with a main exhaust line instead of a slow exhaust line. Provided separately. An open / close valve and a flow control valve are provided in the sub exhaust line. When the reaction chamber is maintained at the atmospheric pressure, an inert gas is introduced into the reaction chamber to increase the pressure. The pressure in the reaction chamber is detected by a pressure detector. When the pressure reaches atmospheric pressure, an on-off valve provided in the sub exhaust line is opened to exhaust the inert gas from the sub exhaust line. Thus, the inside of the reaction chamber is controlled to the atmospheric pressure state. Further, the flow rate of the exhaust gas is controlled by a flow control valve provided in the sub-exhaust line so that an appropriate amount of the inert gas is constantly flowed into the reaction chamber. Thereby, the inert gas flowing into the reaction chamber can be made laminar.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to an example of a low pressure CVD apparatus comprising a vertical furnace. Decompression CV
The D apparatus forms a thin film such as a nitride film on the surface of a wafer by subjecting the wafer to heat treatment in a reaction chamber in a reduced-pressure reaction gas atmosphere.

In FIG. 1, reference numeral 1 denotes an external reaction tube, and 2 denotes an internal reaction tube which is provided in the external reaction tube 1 and defines a reaction chamber 3. At the lower end of the external reaction tube 1, an inlet flange 6 provided with a gas inlet 4 and a gas outlet 5 is provided in an airtight manner via an O-ring 7. A cylindrical space 8 communicating with the gas exhaust port 5 is formed between the external reaction tube 1 and the internal reaction tube 2, and the lower end of the cylindrical space 8 is closed by a support 6 a provided on the inlet flange 6. The space 8 is an exhaust passage to the gas exhaust port 5.

A boat 12 is charged into the reaction chamber 3 from below.
The product wafers W can be loaded in the boat 12 in multiple stages in a horizontal posture. The boat 12 is placed on the furnace cover 9 via the boat cap 13, and the furnace cover 9 can close the lower opening of the inlet flange 6 which becomes the furnace port 10 of the reaction chamber 3 with the boat 12 loaded. . The furnace cover 9 can be moved up and down by a boat elevator (not shown). Further, a furnace port shutter 11 is provided to close the lower opening after the boat 12 is pulled out. The furnace mouth lid 9 or the furnace mouth shutter 11 hermetically closes the lower opening of the inlet flange 6 via the O-ring 7.

A reactive gas introduction line 15 communicates with the gas introduction port 4 of the inlet flange 6, a main exhaust line 16 communicates with the gas exhaust port 5 at the lower end of the cylindrical space 8, and a main exhaust line 16 communicates with the main exhaust line 16. A vacuum pump 17 is connected.
A main exhaust valve 18 is provided in the middle of the main exhaust line 16,
A slow exhaust line 19 bypassing a main exhaust valve 18 as an on-off valve is connected in parallel to the main exhaust line 16, and an auxiliary valve 20 as an on-off valve is provided on the slow exhaust line 19.

Conventional overpressurization prevention line (reference numeral 3 in FIG. 3)
1) is deleted, and instead, a sub exhaust line 21 for purging N ₂ gas is connected in parallel with the main exhaust line 16, and a sub exhaust valve 22 as an on-off valve and a needle valve 23 as a flow control valve are connected to the sub exhaust line 21. Is provided. The auxiliary exhaust valve 22 is a normally open valve, and prevents the inside of the reaction chamber 3 from being over-pressurized during a power failure. Needle valve 23
Is provided so that the exhaust flow rate of the gas flowing through the sub exhaust line 21 can be adjusted. This sub exhaust line 2
Reference numeral 1 denotes a reaction chamber which is not used for rough evacuation at the time of evacuation from the atmospheric pressure as in the slow exhaust line 19, but is used in a state where the inside of the reaction chamber 3 is at the atmospheric pressure (760 Torr / 101,080 Pa). 3 is a purge line (N ₂ gas laminarization line). A pressure detector 25 is connected to the main exhaust line 16 on the upstream side of the main exhaust valve 18, the auxiliary valve 20, and the sub exhaust valve 22.

The reason why the sub exhaust line 21 is not used for roughing is that, conversely, the slow exhaust line 19 used for roughing cannot supply an appropriate amount of N ₂ gas. That is, the slow exhaust line 19, since it is intended to be advanced as much as possible the exhaust time, the use also when N ₂ gas purge, if increasing the supply amount of the purge N ₂ gas reaction chamber 760Torr / 101,080Pa
If the supply amount of the purge N ₂ gas is too large, particles may be wound up. Therefore, the auxiliary exhaust line 21 is provided separately from the slow exhaust line 19 so that an appropriate amount of N ₂ gas can be supplied.

The sub exhaust valve 22 is set to be opened when the pressure detector 25 detects the atmospheric pressure (760 Torr / 101, 080 Pa). The needle valve 23 adjusts the valve opening so that the pressure value of the pressure detector 25 does not increase or decrease, and adjusts the N ₂ gas flow rate used in the main leak event to return the inside of the reaction chamber 3 from reduced pressure to atmospheric pressure. Introduce into 3. The appropriate value of the N ₂ gas flow introduced here is 1
-10 SLM / min, more preferably 2-3 SLM / m
in.

In the film forming process, the boat 12 loaded with the product wafer W is loaded into the heated reaction chamber 3, the furnace cover 9 closes the furnace port 10, the main exhaust valve 18, the sub exhaust valve 22
When the auxiliary valve 20 of the slow exhaust line 19 is open, the vacuum pump 17 slowly evacuates the reaction chamber 3 through the slow exhaust line 19. When the pressure in the reaction chamber 3 drops to a required pressure, the main exhaust valve 18 is opened to exhaust the gas through the main exhaust line 16. When the pressure in the reaction chamber 3 reaches a predetermined pressure and the temperature of the wafer W is stabilized, a reactive gas is introduced from the reactive gas introduction line 15 and the wafer W is heated to form a film.

After the completion of the film formation by the heat treatment, an inert gas is caused to flow into the reaction chamber 3 and gas purge is performed. Next, the main exhaust valve 1
8. The auxiliary valve 20 is closed, the inert gas N ₂ is further introduced from the reactive gas introduction line 15, and the pressure in the reaction chamber 3 is increased to atmospheric pressure. When the atmospheric pressure is detected by the pressure detector 25, the sub exhaust valve 22 is opened. When the pressure in the reaction chamber 3 becomes higher than the atmospheric pressure, N ₂ is exhausted from the needle valve 23 through the sub exhaust line 21.

When the atmospheric pressure is confirmed, the boat 12 is pulled out by a boat elevator (not shown). With the boat 12 pulled out, the furnace opening 10 is closed by the furnace shutter 11. The state in which the furnace port 10 is closed by the furnace port shutter 11 is shown in FIG. Instead of closing with the shutter 11, a boat 12 in which the product wafer W is not loaded may be inserted into the reaction chamber 3 and closed with the furnace cover 9. The state in which the empty boat 12 is closed by the furnace cover 9 is substantially the same as that in FIG. The boat 12 may be loaded with a wafer other than the product wafer, for example, a monitor wafer.

After being closed by the shutter 11 or the furnace cover 9, the apparatus enters an atmospheric state maintaining step. During this atmospheric state maintaining step, the appropriate amount of N ₂ gas described above is supplied to the reactive gas introduction line 1.
5, the reaction chamber 3 is introduced from the lower part of the reaction chamber 3, and the pressure in the reaction chamber 3 is increased to atmospheric pressure.

A pressure detector 25 provided in the main exhaust line 16
The pressure inside the reaction chamber 3 becomes atmospheric pressure (760 Torr / 101,08
When it is detected that 0 Pa), secondary exhaust line 21 auxiliary exhaust valve 22 is opened becomes a stream of N ₂ laminarization line.
At this time, the needle valve 23 constantly monitors the pressure value of the pressure detector 25 provided in the main exhaust line 16 and adjusts the opening so that the pressure value becomes the above-mentioned atmospheric pressure. Therefore, the operating pressure of the non-return valve, the connection position of the over-pressure prevention line, and the variation of the exhaust pressure at the connection destination are affected compared to the case where the over-pressurization is prevented by the check valve. By adjusting the opening of the needle valve 23, the flow rate of the exhaust gas drawn by the vacuum pump 17 is reduced.
The flow rate is controlled so as to be the same as the flow rate of the N ₂ gas introduced into the inside, and the balance between the introduced amount and the exhaust amount is maintained. as a result,
The N ₂ gas introduced into the reaction chamber 3 during the state of maintaining the atmospheric pressure is exhausted from the sub exhaust line 21 as a laminar flow, and the inside of the reaction chamber 3 is maintained at the atmospheric pressure. In addition, since the flow becomes laminar, the O flow between the inlet flange 6 and the shutter 11 or the furnace cover 9 is prevented.
There is no leakage of N ₂ gas from the seal portion of the ring 7.

According to the above embodiment, the main exhaust line 16
Remove the over-pressurization prevention line from
A sub-exhaust line 21 provided with a needle valve 23 is provided.
When the pressure is maintained, the opening is adjusted according to the value detected by the pressure detector 25.
The reaction chamber 3 is maintained at the atmospheric pressure by the adjusted needle valve 23.
Turbulence caused by the overpressurization prevention line
Can be effectively prevented. Laminar air flow in the reaction chamber
Adheres to the inner wall of the main exhaust line 16
Particles or residual NH _FourCl etc.
Contamination of the product wafer W due to by-products of
You. As a result, it is not affected by the atmospheric state maintenance time of the device,
You can keep the particle level at a low level all the time.
Particles or particles adsorbed on the silicon wafer surface
Reduces the haze count as much as one hour in Table 1.
be able to.

Further, according to the above-described embodiment, since piping can be designed in advance, there is no problem that the installation is troublesome and the adjustment is expensive as in the conventional overpressurization prevention line. In the installation process of the apparatus, the place is not checked on site, the piping shape and the like are not determined and assembled, so that the number of manufacturing steps of the apparatus can be reduced.

In the above-described embodiment, the case where the needle valve 23 is provided in the sub-exhaust line 21 has been described. However, other means may be used as long as the exhaust flow rate can be adjusted. FIG. 2 shows a configuration in which a mass flow controller 26 is attached in place of the needle valve 23 as exhaust flow rate adjusting means. Regarding the opening degree of the mass flow controller 26, the same setting value as the setting signal of the N ₂ gas flow rate of the MFC 27 used in the main leak event for returning the pressure in the reaction chamber 3 from the reduced pressure to the atmospheric pressure is given to the MFC 26. With this setting, laminarization of the N ₂ gas stream flowing from the reaction chamber to the exhaust line is realized.

Although the above embodiment has been described with reference to a vertical furnace, the present invention can be similarly applied to a semiconductor manufacturing apparatus having a horizontal reactor.

[0032]

According to the present invention, gas is introduced and exhausted without pressure fluctuation, so that a steady laminar flow is formed in the reaction chamber. For this reason, since the reaction chamber in the atmospheric state is kept clean, particles adhering to the product wafer during substrate processing can be reduced, and the quality of the manufactured semiconductor element can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a low pressure CVD apparatus for performing a substrate processing method according to an embodiment.

FIG. 2 is a schematic cross-sectional view of a reduced-pressure CVD apparatus for performing a substrate processing method according to another embodiment.

FIG. 3 is a schematic sectional view of a reduced-pressure CDV device according to a conventional example.

[Explanation of symbols]

 3 Reaction chamber 9 Furnace lid 11 Shutter 12 Boat 16 Main exhaust line 21 Sub exhaust line 23 Needle valve (flow control valve) W Product wafer

Claims (1)

[Claims] 1. A reaction chamber in which a boat is not inserted is closed with a shutter, or a boat in which no product substrate is loaded is inserted into the reaction chamber and closed with a furnace lid of the boat, and the reaction chamber is opened to the atmosphere. In the substrate processing method including the step of maintaining a state, when the reaction chamber is maintained in an atmospheric state, an inert gas is introduced into the reaction chamber, and when the pressure of the reaction chamber becomes atmospheric pressure, a main exhaust line A substrate processing method, wherein exhaust is performed from a sub exhaust line provided in parallel with the apparatus, and a flow rate of the exhaust is controlled so as not to cause a pressure change in the reaction chamber.