JP3471077B2 - Vacuum vessel pressure control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control method for a vacuum container.

[0002]

2. Description of the Related Art Various processes such as film formation, etching, ion implantation, etc. are carried out in the manufacture of an object to be processed, for example, a semiconductor wafer.
It is carried out in a vacuum container called a reaction tube or the like.

For example, in the film forming process step, as shown in the time chart of FIG. 10, a semiconductor wafer, which is an object to be processed, is loaded into a reaction tube of a heat treatment apparatus under atmospheric pressure (760 Torr), and then the inside of the reaction tube is predetermined. Pressure of eg 1 × 10 ^-3
A process of reducing the pressure to about Torr and supplying a required process gas under the reduced pressure to form a process film such as a polysilicon film, a silicon nitride film, or a silicon oxide film on the surface of the semiconductor wafer is performed. After the treatment, nitrogen (N ₂ ) gas which is an inert gas is supplied into the reaction tube to return the pressure in the reaction tube to atmospheric pressure, and the semiconductor wafer is unloaded from the reaction tube.

In the film forming process of the semiconductor wafer,
Due to the miniaturization of manufactured semiconductor devices, it is required that less adhesion (contamination) of dust (dust) occurs, and the reaction tubes of the heat treatment equipment are regularly removed and replaced with clean cleaned reaction tubes. I am trying.

[0005]

However, even if a clean reaction tube is used, it has been confirmed that dust adheres to the surface of the semiconductor wafer, which lowers the yield of semiconductor elements formed on the semiconductor wafer. There was a problem to do. Incidentally, as a result of measuring the number of dust particles having a diameter of 0.2 μm or more attached to the surface of the semiconductor wafer with a laser irradiation type dust inspection device, it is confirmed that 100 or more dust particles are attached to each 6-inch wafer.

It is considered that this is due to the pressure control method in the depressurizing process and the normal pressure restoring process in the reaction tube which is the vacuum container. For example, in the depressurizing step in the conventional heat treatment apparatus, as shown by the curve C in FIG. 2, first, the auxiliary exhaust system having a small exhaust flow rate is operated to slowly depressurize the pressure in the reaction tube from atmospheric pressure to a predetermined pressure, for example, about 10 Torr. Then, the main exhaust system having the larger exhaust flow rate was operated to reduce the pressure to the target pressure, for example, 1 × 10 ⁻³ Torr in a short time. Further, in the normal pressure recovery step, as shown by the curve D in FIG. 6, nitrogen gas, for example, 1000 cc /
It was supplied in a large amount as much as a minute to return the inside of the reaction vessel to normal pressure in a short time.

Therefore, since any of the steps is accompanied by a rapid pressure change, it is contained in the gas (in the nitrogen gas in the normal pressure restoring step) by adiabatic expansion as shown in FIGS. 11 (a) to 11 (d). The water content m becomes a water droplet n by using the fine dust component g in the reaction tube as a core, and the water droplet n adheres to the surface of the semiconductor wafer w, and the water content then evaporates, so that only the dust component g that is the core remains. It is thought to be due to. In addition, reaction products and the like attached to the inner wall of the reaction tube in the film forming process, etc. are peeled off from the inner wall of the reaction tube due to a sudden change in pressure and are wound up, which becomes dust and floats in the reaction tube and becomes a semiconductor wafer. It is thought that this is due to the adhesion to the surface of.

In order to solve such a problem, the pressure may be slowly changed as shown by a curve E in FIG. 6 in the normal pressure recovery step so as not to cause a sudden pressure change. If such a control method is adopted, it takes a lot of time, and there is a problem that the operating rate of an expensive heat treatment apparatus is lowered. In the depressurizing step, the pressure may be reduced to a high vacuum, for example, about 1 × 10 ⁻⁵ Torr, but in this case, adsorbed molecules such as water adsorbed on the inner wall of the reaction tube are not easily released, and Due to the released gas, it takes a long time to reduce the pressure, and there is also a problem that the operating rate of the heat treatment apparatus is lowered.

Therefore, an object of the present invention is to reduce the adhesion of dust to the surface of the object to be treated in the depressurizing step and the normal pressure returning step, and further to reduce the time required for these steps. It is to provide a control method.

[0010]

In order to achieve the above object, the invention according to claim 1 sets the pressure of a vacuum container equipped with a main exhaust system having a large exhaust flow rate and an auxiliary exhaust system having a small exhaust flow rate to atmospheric pressure. To a predetermined pressure, the sub-exhaust system is operated to depressurize the inside of the vacuum container, and after the sub-exhaust depressurizing process, the main exhaust system is operated to depressurize the inside of the vacuum container. The main exhaust depressurization step is performed, and at least the main exhaust depressurization step is performed at a maximum depressurization speed at which condensation and liquefaction of water contained in the gas in the vacuum container does not occur.

The invention according to claim 2 has a large exhaust flow rate.
When reducing the pressure of the vacuum container equipped with the main exhaust system and the auxiliary exhaust system with a small exhaust flow rate from atmospheric pressure to a predetermined pressure,
A gas replacement step of replacing the gas in the vacuum container with an inert gas from which water has been removed, and before the gas replacement step.
A secondary exhaust that operates the secondary exhaust system to reduce the pressure inside the vacuum container.
Air depressurization step, and the main exhaust system after the auxiliary exhaust depressurization step
A main exhaust depressurizing step of operating the vacuum container to depressurize the inside of the vacuum container .

According to a third aspect of the present invention, when the pressure of the vacuum container provided with the main exhaust system having a large exhaust flow rate and the auxiliary exhaust system having a small exhaust flow rate is reduced from atmospheric pressure to a predetermined pressure,
The inert gas dewatered is supplied to the vacuum container.
In this state, the auxiliary exhaust system is operated to depressurize the inside of the vacuum container, and the main exhaust system is operated after this auxiliary exhaust depressurizing process to depressurize the inside of the vacuum container. And is provided .

[0013] The invention of claim 4, wherein, upon evacuating the pressure of the vacuum vessel and a relatively small diameter of the secondary exhaust pipe and a relatively large diameter of the main exhaust pipe from atmospheric pressure to a predetermined pressure, the vacuum chamber A first exhaust step of continuously opening the valve opening of the sub-exhaust pipe, and a second exhaust step of continuously opening the valve opening of the main exhaust pipe after the first exhaust step. And an exhaust step.

According to a fifth aspect of the invention, when the pressure in the vacuum container is returned from a predetermined depressurized state to the atmospheric pressure, a gas from which water has been removed is supplied into the vacuum container while exhausting the inside of the vacuum container. And a main pressure returning step of stopping the exhaust after the initial pressure returning step and supplying the gas into the vacuum container to return to the atmospheric pressure. It is characterized by

The invention of claim 6 is characterized in that, in the invention of claim 5, the supply flow rate of the gas is controlled from small to large from the initial pressure returning step to the main pressure returning step.

The invention according to claim 7 is characterized in that, in the invention according to claim 5 or 6, the gas is an inert gas from which water has been removed by a water removing device.

According to an eighth aspect of the present invention, when the pressure of a vacuum container provided with a main gas supply pipe having a relatively large diameter and a sub gas supply pipe having a relatively small diameter is released from a vacuum state to atmospheric pressure, the vacuum is applied. A first gas supply step of supplying a gas by continuously opening the valve opening degree of the sub gas supply tube in the container, and a continuous valve opening degree of the main gas supply tube after the first gas supply step. And a second gas supply step for opening and supplying gas.

[0018]

According to the first aspect of the invention, at least the main exhaust depressurization step is executed at the maximum depressurization rate at which the condensation and liquefaction of the water contained in the gas in the vacuum container does not occur. It is quickly depressurized without being depressurized. Therefore, the adhesion of dust to the surface of the object to be processed due to the condensation and liquefaction of the water contained in the gas in the pressure vessel is eliminated, and the time required for the depressurizing step is shortened.

According to the second aspect of the present invention, after the gas in the vacuum container is replaced with the inert gas from which water has been removed, the auxiliary exhaust system is operated to reduce the pressure in the vacuum container.
Exhaust decompression process and main exhaust system is operated after this auxiliary exhaust decompression process
And a main exhaust pressure reduction step for reducing the pressure inside the vacuum container.
Since this is performed , the pressure in the vacuum container can be quickly reduced without condensing and liquefying the gas in the vacuum container, and it is possible to prevent dust from adhering to the surface of the object to be processed and shorten the decompression time.

According to the third aspect of the present invention, while supplying the water inert gas removed in the vacuum chamber, said auxiliary exhaust system is operated to reduce the pressure within the vacuum vessel auxiliary exhaust vacuum And a step of depressurizing the main exhaust to depressurize the inside of the vacuum container by operating the main exhaust system after the step of depressurizing the auxiliary exhaust.
Since it is equipped, it is possible to quickly reduce the pressure of the vacuum container by suppressing the condensation and liquefaction of the gas in the vacuum container,
It is possible to reduce the adhesion of dust to the surface of the object to be processed and shorten the decompression time. In this case, the kinetic energy of the gas molecules of the inert gas supplied into the vacuum container causes the gas molecules to collide with the adsorbed molecules adsorbed on the inner wall of the vacuum container, so that the adsorbed molecules are separated from the inner wall of the vacuum container. Since it is released, the vacuum container can be depressurized to a high vacuum in a short time.

According to the fourth aspect of the present invention, the vacuum container
In evacuating the pressure from atmospheric pressure to a predetermined pressure, after the relatively evacuated the valve opening degree of the small-diameter auxiliary exhaust pipe continuously open the vacuum vessel, a relatively large diameter of the valve of the main exhaust pipe Since the opening is continuously opened and the gas is exhausted, it is possible to quickly evacuate the inside of the vacuum container while suppressing the condensate liquefaction of gas and the rolling up of dust without abrupt pressure change.

According to the fifth aspect of the present invention, first, while exhausting the inside of the vacuum container, the gas from which water has been removed is supplied into the vacuum container to restore the pressure to a predetermined level. Even if the dust inside is rolled up, this rolled-up dust is discharged to the outside of the vacuum container. Then, while stopping the exhaust, in order to return to atmospheric pressure by supplying the gas in the vacuum container,
It is possible to quickly return the pressure of the vacuum container to the atmospheric pressure without condensing and liquefying the gas, and it is possible to prevent dust from adhering to the surface of the object to be processed and shorten the normal pressure recovery time.

According to the sixth aspect of the present invention, since the supply flow rate of the gas is controlled from small to large in the pressure returning step, the normal pressure returning time can be further shortened. In addition, claim 7
According to the invention described, since the gas is an inert gas from which water has been removed by the water removing device, it becomes possible to easily supply the inert gas from which water has been easily removed into the vacuum container, The prevention of dust from adhering to the surface of the object to be processed and the shortening of the normal pressure recovery time are further promoted.

According to the invention of claim 8, when the inside of the vacuum container is released from the vacuum state to the atmospheric pressure, the valve opening of the auxiliary gas supply pipe having a relatively small diameter is continuously opened in the vacuum container. After supplying gas, the valve opening of the main gas supply pipe with a relatively large diameter is continuously opened to supply gas, so there is no sudden pressure change, and gas condensation and liquefaction are suppressed. The inside of the vacuum container can be quickly released to atmospheric pressure.

[0025]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a heat treatment apparatus. The heat treatment apparatus 1 is configured to be suitable for batch processing type low pressure CVD, and is provided with a cylindrical manifold 3 made of a heat resistant / corrosion resistant metal such as stainless steel attached to a base plate 2. A reaction tube 4 made of a heat-resistant material, for example, quartz, whose upper end is closed and whose lower end is opened, is hermetically attached to the upper end through an O-ring 5, which is an airtight material, as a vacuum container constituting a vertical furnace. .

A cylindrical inner tube 6 made of, for example, quartz is coaxially provided in the reaction tube 4 for the purpose of soaking and prevention of heavy metal contamination. The reaction tube 4 is surrounded by a high temperature inside the reaction tube 4, for example. A heater 7, which is a heating means for heating to about 800 to 1200 ° C., which is formed by spirally winding a heating resistance wire such as Kanthal wire, a heat insulating material 8, and a shell 9 having a water cooling jacket structure are sequentially provided.

Lower end opening (furnace opening) of the manifold 3
A lid 10 made of, for example, stainless steel that opens and closes the lid 10 is vertically movable by an elevating mechanism 11, and a large number of, for example, about 150 semiconductor wafers W to be processed are horizontally placed on the lid 10. The wafer boat 12 that is held in multiple stages at intervals in the up-and-down direction is a heat insulating tube 13 made of quartz.
Is placed through. In addition, the heat insulating cylinder 1 is provided on the lid 10.
A rotation mechanism 14 and the like for rotating and driving 3 are provided.

Further, the manifold 3 has a gas introduction pipe 15
A processing gas supply source 16 is connected to the gas introduction pipe 15 via an opening / closing valve 17 and a flow rate controller 18, and a supply source of an inert gas such as nitrogen (N ₂ ) gas. 19 is connected via an on-off valve 20, a flow rate controller 21, and a water removing device 22. The moisture removing device 22 is composed of, for example, a liquid nitrogen cooler, and moisture contained in the supplied nitrogen gas is condensed on the pipe wall of the pipe cooled to −100 ° C. or less by the liquid nitrogen so that the moisture content of the nitrogen gas is increased. Is reduced to, for example, 10 ppm or less. The water removing device 22 may be a device that uses a purifier to reduce the water content to 1 ppb or less.

Further, a relatively large-diameter main exhaust pipe 23 is connected to the manifold 3 as a main exhaust system leading to a factory exhaust system and having a large exhaust flow rate. The main exhaust pipe 23 is provided with an opening / closing valve 24 from the upstream side. , Pressure regulator 25 and pressure reducing pump 26
And a relatively small diameter auxiliary exhaust pipe (bypass pipe) as an auxiliary exhaust system with a small exhaust flow rate that bypasses the on-off valve 24 and the pressure regulator 25 upstream of the pressure reducing pump 26. 27 is connected. An opening / closing valve 28 and a pressure regulator 29 are provided in the sub exhaust pipe 27. The flow rate regulators 18 and 21 and the pressure regulators 25 and 29 do not have the function of completely shutting off the gas and thus require the on-off valves 17, 20, 24 and 28, but the function of shutting off the gas completely. On-off valves 17, 20, 24, 28 are not necessarily required as long as they have the above-mentioned features.

A pressure sensor 30 for detecting the pressure inside the main exhaust pipe 23 is provided upstream of the main exhaust pipe 23. And
A control device 31 is used to control the pressure in the reaction tube 4, and the control device 31 receives the pressure signal from the pressure sensor 30, and the flow rate controller based on previously input data and program. 18, 21, pressure regulators 25 and 29, and on-off valves 17, 20, 24 and 28 are configured to be controlled as described later.

Next, the reaction tube 4 in the heat treatment apparatus 1
Regarding the internal pressure control method, a pressure reducing step of reducing the pressure in the reaction tube 4 from atmospheric pressure to a predetermined pressure and a normal pressure returning step of returning the pressure in the reaction tube 4 from a predetermined reduced pressure state to atmospheric pressure. I will explain separately. In the depressurizing step, a total of three examples of the depressurizing steps 1 to 3 will be described.

[Decompression Step 1] In carrying out this step,
The flow rate controllers 18, 21, the pressure controllers 25, 29 and the opening / closing valves 17, 20, 24, 28 are closed, and the wafer boat 1
A large number of semiconductor wafers W supported by
Thus, the lid body 10 is closed while being carried into the reaction tube 4 (hereinafter, this is referred to as a preparation step). Then, the control device 31 first opens the opening / closing valve 28 of the auxiliary exhaust pipe 27 which is the auxiliary exhaust system, and the pressure sensor 30 detects the pressure in the main exhaust pipe 23 (which is almost the same as the pressure in the reaction pipe 4). However, the inside of the reaction tube 4 is controlled by controlling the opening degree of the pressure regulator 29 so as to have a predetermined depressurization characteristic, that is, the maximum depressurization rate at which condensation of water contained in the gas (atmosphere) in the reaction tube 4 does not occur. Is reduced to a predetermined pressure, for example, about 10 Torr (hereinafter, this is referred to as a sub-exhaust pressure reducing step).

Next, the control device 31 closes the opening / closing valve 28 and the pressure regulator 29 of the auxiliary exhaust system, and opens the opening / closing valve 24 of the main exhaust system so that the same predetermined depressurization characteristic is obtained. Control the opening of the pressure regulator 25 to the reaction tube 4
The internal pressure is reduced to a target pressure, for example, about 1 × 10 ⁻⁵ Torr (hereinafter referred to as the main exhaust pressure reduction step).
The relationship between the pressure and the time in such a depressurization step is shown by the curve A1 in FIG. Then, when the pressure inside the reaction tube 4 reaches the target pressure, the on-off valve 17 of the processing gas supply source 16 is opened and the opening degree of the flow rate controller 18 is controlled while maintaining this reduced pressure state, and the processing gas is controlled. Source 16
Process gas is supplied into the reaction tube 4 through the gas introduction tube 15 and the semiconductor wafer W is subjected to a predetermined film forming process.

As described above, since the auxiliary exhaust depressurization step and the main exhaust depressurization step are executed at the maximum depressurization rate at which the condensation of the water contained in the gas (atmosphere) in the reaction tube 4 does not occur, the pressure in the reaction tube 4 is reduced. The pressure is quickly reduced without sudden pressure reduction. Therefore, it is possible to eliminate the adhesion of dust to the surface of the semiconductor wafer W due to the condensation and liquefaction of the water contained in the gas in the reaction tube 4, and even if the dust adheres to the inner wall of the reaction tube 4. The dust does not wind up and adheres to the surface of the semiconductor wafer W, and the time required for the depressurizing step can be shortened. In addition,
In this process, pressure control with a predetermined depressurization characteristic was performed in both the auxiliary exhaust depressurization process and the main exhaust depressurization process. It is also possible to perform the pressure control with which the predetermined pressure reducing characteristic is obtained.

[Decompression Step 2] First, after the preparation step, the control device 31 opens the on-off valve 20 of the nitrogen gas supply source 19, and the opening degree of the flow rate regulator 21 is set to, for example, about 500 cc / min. Water removal device 22 from gas supply source 19
The dry nitrogen gas from which most of the water has been removed is supplied into the reaction tube 4 via. In this state, the opening / closing valve 28 of the auxiliary exhaust system is opened, and the opening of the pressure regulator 29 is controlled so as to maintain the pressure in the main exhaust pipe at 760 Torr. ) Is replaced with dry nitrogen gas (hereinafter, this is referred to as a gas replacement step).

After the gas replacement step, for example, the above-described auxiliary exhaust depressurization step and main exhaust depressurization step are carried out in order to carry out the reaction tube 4.
The inside pressure may be reduced to the target pressure. The relationship between the pressure and the time in the depressurizing step is shown by the curve A2 in FIG. In this way, the gas (atmosphere) in the reaction tube 4
Since the inside of the reaction tube 4 is depressurized after the gas is replaced with dry nitrogen gas from which water is removed, the pressure in the reaction tube 4 can be quickly depressurized without condensing and liquefying the gas in the reaction tube 4. It is possible to prevent dust from adhering to the surface of the semiconductor wafer W and shorten the decompression time. In this depressurization step, the dry nitrogen gas from which water has been removed is exhausted from the reaction tube 4 to reduce the pressure, so that condensation liquefaction is less likely to occur. It can be performed by exhausting.

[Decompression Step 3] First, after the preparation step, the opening / closing valve 20 of the nitrogen gas supply source 19 is opened by the controller 31, and the opening degree of the flow rate controller 21 is set to, for example, about 100 cc / min. Water removal device 22 from gas supply source 19
The dry nitrogen gas from which most of the water has been removed is supplied into the reaction tube 4 via. In this state, the auxiliary exhaust depressurizing step and the main exhaust depressurizing step are sequentially performed to reduce the pressure in the reaction tube 4 to a predetermined pressure, for example, about 1 × 10 ⁻¹ . Next, the on-off valve 20 and the flow rate controller 21 of the nitrogen gas supply source 19 are closed, and the pressure in the reaction tube 4 is adjusted to the target pressure (1 ×) while controlling the opening degree of the pressure controller 25 of the main exhaust system. The pressure is reduced to about 10 ⁻⁵ Torr). The relationship between the pressure and time in the depressurizing step is shown by the curve A3 in FIG.

Since the pressure inside the reaction tube 4 is reduced while supplying the dry nitrogen gas from which water has been removed to the reaction tube 4 as described above, the condensation and liquefaction of the gas inside the reaction tube 4 is suppressed and the pressure in the reaction tube 4 is suppressed. The pressure can be quickly reduced, and the adhesion of dust to the surface of the semiconductor wafer W and the pressure reduction time can be shortened. Further, in this case, the kinetic energy of the gas molecule of the nitrogen gas supplied into the reaction tube 4 causes the gas molecule to collide with the adsorbed molecule of the water adsorbed on the inner wall of the reaction tube 4, whereby the adsorbed molecule is Since it is released from the inner wall of 4,
The reaction tube 4 can be depressurized to a high vacuum in a short time. In this depressurizing step, the supply of the dry nitrogen gas may not be continuously performed, and for example, as shown in FIG. 5, the supply and the stop may be repeated in a pulsed manner, and this may be performed while the target pressure is reached. You can go. Further, the supply amount of the dry nitrogen gas may not be constant, but may be changed gently (including increase / decrease) with the progress of the depressurizing step, or may be changed stepwise.

[Normal Pressure Return Step] When the predetermined film forming process of the semiconductor wafer W is completed, the on-off valve 17 and the flow rate controller 18 of the process gas supply source 16 are closed and the operation of the main exhaust system is continued to react. The processing gas remaining in the pipe 4 is discharged. Then, the pressure in the reaction tube 4 is set to the predetermined depressurized state (1 ×
At the time of returning from 10 ^-5 Torr) to atmospheric pressure, the control device 31 first closes the main exhaust system on-off valve 24 and the pressure regulator 25, and opens the sub-exhaust system on-off valve 28 and adjusts the pressure. The on-off valve 2 of the nitrogen gas supply source 19 while exhausting the inside of the reaction tube 4 in a state where the vessel 29 is at a predetermined opening degree.
0 is opened, and the opening degree of the flow rate controller 21 is set to, for example, 10
The dry nitrogen gas from which most of the water has been removed is supplied from the nitrogen gas supply source 19 through the water removing device 22 to the reaction tube 4 at a setting of about 00 cc / minute, and this state is continued for a predetermined time, for example, about 1 minute. As a result, the pressure in the reaction tube 4 is returned to a predetermined pressure, for example, about 5 Torr (hereinafter, this is referred to as an initial pressure returning step).

Next, the opening / closing valve 28 and the pressure controller 29 of the auxiliary exhaust system are closed to stop the exhaust, and the opening degree of the flow rate controller 21 of the nitrogen gas supply source 19 is set to 5000 cc, for example.
/ Min to supply dry nitrogen gas into the reaction tube 4, and this state is continued for a predetermined time, for example, about 20 minutes to return the pressure in the reaction tube 4 to atmospheric pressure (hereinafter,
This is called a main pressure recovery step. ). The relationship between the pressure and time in the normal pressure recovery process is shown by the curve B in FIG.
As shown in. When the pressure in the reaction tube 4 returns to atmospheric pressure, the on-off valve 20 and the flow rate controller 21 of the nitrogen gas supply source 19 are closed to stop the supply of nitrogen gas, and the lifting mechanism 1
The semiconductor wafer W may be unloaded from the inside of the reaction tube 4 by opening the lid body 10 downward by 1.

As described above, first, while the inside of the reaction tube 4 is being evacuated, the dry nitrogen gas from which water has been removed is supplied into the reaction tube 4 to return it to a predetermined pressure. Therefore, the reaction tube 4 is supplied with the nitrogen gas. Even if the internal waste is rolled up, this rolled-up waste is discharged outside the reaction tube. Then, since the exhaust is stopped and the dry nitrogen gas is supplied into the reaction tube 4 to return it to the atmospheric pressure, the pressure in the reaction tube 4 is quickly returned to the atmospheric pressure without condensing and liquefying the atmosphere. Therefore, it is possible to prevent dust from adhering to the surface of the semiconductor wafer W and shorten the normal pressure recovery time. Moreover, since the supply flow rate of the nitrogen gas is controlled from small to large from the initial pressure returning step to the main pressure returning step, the normal pressure returning time can be further shortened. Further, since the nitrogen gas is supplied into the reaction tube 4 via the water removing device 22, the nitrogen gas from which the water is sufficiently removed can be easily and quickly supplied into the reaction tube 4.

In the initial pressure returning step, the exhaust capacity is gradually reduced by, for example, gradually closing the opening degree of the pressure regulator 29 of the sub exhaust system from the fully open state, and abruptly changing the exhaust capacity. May not be generated.
Further, the supply of dry nitrogen gas into the reaction tube 4 in the initial pressure returning step and the main pressure returning step is not continuous,
It may be intermittently performed by repeatedly supplying and stopping. Furthermore,
The dry gas used in the step of returning to normal pressure may be dry air instead of dry nitrogen gas. Further, as the inert gas used in the depressurizing step and the normal pressure returning step, for example, argon gas, helium gas, etc. can be applied in addition to nitrogen gas.

FIG. 7 is a schematic block diagram showing another embodiment of the present invention. The apparatus of this embodiment, for example, the heat treatment apparatus as a whole is provided with a treatment chamber for a target object, for example, a heat treatment furnace 40, and a preliminary chamber as a vacuum container for transferring the target object, for example, a semiconductor wafer W to the heat treatment furnace 40 after vacuuming it in advance. 41,
The vacuum pumping mechanism 42 and the atmospheric pressure releasing mechanism 43 are mainly configured. The heat treatment furnace 40 and the auxiliary chamber 41 are opened / closed by a shutoff valve (gate valve) 44. The vacuum evacuation mechanism 42 is mainly composed of a decompression pump (vacuum pump) 45 and a vacuum evacuation piping mechanism 46 that connects the decompression pump 45 and the preliminary chamber 41. The vacuum evacuation piping mechanism 46 includes a main exhaust pipe 47 having a relatively large diameter.
And the auxiliary exhaust pipes 48 having a relatively small diameter are connected in parallel. A vacuum degree measuring terminal (pressure sensor) 49 for measuring the degree of vacuum inside the tube is provided in the main exhaust pipe 47 near the decompression pump 45. Main exhaust pipe 4
7 and the sub-exhaust pipe 48 are provided with shut-off valves 50 and 51 for shutting off their respective vacuuming capabilities, and the sub-exhaust pipe 48 is provided with a variable control valve 52 capable of continuously adjusting the vacuuming capability, that is, the opening. A variable control valve 53 that can continuously adjust the opening degree is attached to the main exhaust pipe 47 connected to the decompression pump 45.

On the other hand, the atmospheric pressure release mechanism 43 is a mechanism similar to the vacuum evacuation mechanism 42, and the difference between the atmospheric pressure release mechanism 43 and the vacuum evacuation mechanism 42 is that of the vacuum pump 45 of the vacuum evacuation mechanism 42. Instead, a gas supply mechanism 54 for supplying a gas for releasing the preliminary chamber 41 to the atmospheric pressure, for example, nitrogen (N ₂ ) gas is connected. The atmospheric pressure release mechanism 43 is a main gas supply pipe 5 having a relatively large diameter.
5 is provided with an atmospheric pressure release pipe mechanism 57 in which a sub gas supply pipe 56 having a relatively small diameter is connected in parallel, and shutoff valves 57 and 58 are attached to the main gas supply pipe 55 and the sub gas supply pipe 56. There is. A variable control valve 60 capable of continuously adjusting the opening is attached to the sub gas supply pipe 56, and the gas supply mechanism 54
Similarly, a variable control valve 61 capable of continuously adjusting the opening is attached to the main exhaust pipe 55 connected to. 6
Reference numeral 2 is an atmospheric pressure measuring terminal (pressure sensor) provided in the gas supply mechanism 54, and 63 is a vacuum degree measuring terminal (pressure sensor) provided in the auxiliary chamber 41. The valves 44, 50, 51, 5
2, 53, 58, 59, 60, 61 and the like are automatically controlled by a control device 64 including a microcomputer having a program stored in advance.

In the heat treatment apparatus having the above-described structure, first, the atmosphere shutoff valve (gate valve, not shown) provided between the preliminary chamber 41 and the outside is opened to open the preliminary chamber 41.
Is released to the atmospheric pressure in advance, and then the semiconductor wafer W is loaded into the preliminary chamber 41 by a transfer mechanism (not shown). After that, the transport mechanism is returned to the original position, that is, the predetermined position outside the preliminary chamber 41. After that, the atmosphere shutoff valve is closed and the preliminary chamber 41 is made airtight. At this time, the opening and closing of the atmosphere shutoff valve and the control of the transfer mechanism are all executed by the controller 64.

Next, the vacuuming mechanism 42 causes the controller 6 to
4 automatically operates, and the preliminary chamber 4 is operated by the procedure described later.
Evacuate 1. When the pressure in the preliminary chamber 41 reaches a predetermined degree of vacuum, which is almost the same as that in the heat treatment furnace 40, the shut-off valve 44 is opened and the semiconductor wafer W is transported in the preliminary chamber 41 by a transfer robot, that is, a vacuum chamber transfer mechanism (not shown). No.) is carried into the heat treatment furnace 40. In this case, if the heat treatment furnace 40 is set to have a slightly positive pressure than the preliminary chamber 41, it is possible to prevent dust from being trapped in the heat treatment furnace 40 during the loading operation. Then, the shutoff valve 44 is automatically and airtightly closed under the control of the control device 64. Then, heat treatment furnace 40
In the inside, predetermined processing of the semiconductor wafer W, for example, thermal oxidation processing is performed. In this process, for example, steam generated by combusting oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas is introduced into the heat treatment furnace 40 and supplied to the surface of the semiconductor wafer W heated to 600 to 700 ° C. Then, a surface oxide film is formed.

Such processing and monitoring are performed by the control device 6
4 automatically, and when the processing is completed, the shutoff valve 44 is opened, and the processed semiconductor wafer W is transferred to the preliminary chamber 41 by the vacuum chamber transfer mechanism. After that, the shutoff valve 44 is automatically closed, the preliminary chamber 41 is released to the atmosphere by the atmospheric pressure release mechanism 43 by the procedure described later, the atmosphere shutoff valve is opened, and the processed semiconductor wafer W is transferred by the transfer mechanism. Reserve room 4
Carry out from 1. When carrying in and out like this, the spare room 4
By setting 1 to a slightly positive pressure than the outside, it is possible to prevent the inclusion of dust in the atmosphere. Then, the air shutoff valve is closed. The procedure for vacuuming (reducing pressure) and releasing atmospheric pressure (returning to normal pressure) in the preliminary chamber 41 and the heat treatment furnace 40 will be described below.

[Vacuating Step] First, the vacuuming step will be described. First, all of the valves 50, 51, 5 will be described.
2, 53, 58, 59, 60, 61 and the like are in a closed state. When the evacuation process is started based on the program stored in advance in the control device, the shutoff valve 51 of the auxiliary exhaust pipe 48 is opened, and the variable control valve 52 is automatically opened little by little with the preliminary operation. The evacuation of the chamber 41 is started via the auxiliary exhaust pipe 48. Note that the variable control valve 53 may be left as it is if it cannot be completely shut off even in a closed state due to its structure, and if it can be completely shut off, for example, it may be about the same as the maximum opening degree of the variable control valve 52. Leave it open. In this state, the variable control valve 52
The variable control valve 5 is evacuated, i.e., evacuated while gradually opening the opening (first evacuation step), and reaches a predetermined degree of vacuum after a predetermined time has elapsed.
2 (or shutoff valve 51) automatically closes and the auxiliary exhaust pipe 4
The evacuation by 8 is completed. Then, the shutoff valve 50 of the main exhaust pipe 47 is opened, and the main exhaust pipe 47 by the variable control valve 53 is opened.
Move to the vacuuming process via. At this time, the variable control valve 53 is in an opened state by a predetermined amount. That is, the opening degree of the variable control valve 53 is set in advance by the control mechanism 64 so that a sudden change in the degree of vacuum with respect to the degree of vacuum in the auxiliary chamber 41 reached by the auxiliary exhaust pipe 48 does not occur.

Then, the variable control valve 53 is gradually and continuously opened to a predetermined open value to proceed with evacuation by the main exhaust pipe 47 (second evacuation step), and finally to a processable vacuum degree. Reach This processable vacuum degree means the next step, that is, the semiconductor wafer W into the heat treatment furnace 40.
The degree of vacuum that can be carried in. The state of these vacuuming steps is shown in a graph as shown by the curve A4 in FIG. In this graph, the time zone a shows the vacuuming process by the auxiliary exhaust pipe 48 after the evacuation is started, and the time zone b shows the vacuuming process by the main exhaust pipe 47. Also,
A point c on the graph is a contact point between the time zone a and the time zone b, and the last vacuum degree of the preliminary chamber 41 in the time zone a and the first vacuum degree of the preliminary chamber 41 in the time zone b are set. It is a point where they coincide with each other, that is, it indicates that the pressure in the preliminary chamber 41 continuously decreases.

The control method of the evacuation step shown in FIG. 7 is based on two conditions preliminarily obtained by experiments, that is, moisture condensation in the gas in the auxiliary chamber 41 does not occur due to sudden evacuation, and It is preset to satisfy the condition that the dust inside the chamber 41 is not rolled up, and to realize the maximum vacuuming capability, that is, the minimum vacuuming time under this condition. And the execution control is
The control device 64 feeds back the detected values from the vacuum degree measuring terminals 49 and 63 to comprehensively control the shutoff valves 50 and 51 and the variable control valves 52 and 53. When the inside of the auxiliary chamber 41, which is a vacuum container, is evacuated in this way, the inside of the auxiliary chamber 41 has a relatively small diameter.
Since the valve opening of No. 8 is continuously opened and exhausted, and then the valve opening of the main exhaust pipe 47 having a relatively large diameter is continuously opened and exhausted, the gas is condensed and liquefied without sudden pressure change. It is possible to quickly evacuate the inside of the auxiliary chamber 41 by suppressing the winding of dust.

[Atmospheric Pressure Releasing Step] Next, the atmospheric pressure releasing step will be described. When releasing the preliminary chamber 41 from the vacuum state to the atmospheric pressure, the valves 50, 51, 52, 53, 5
8, 59, 60, 61 and the like are in a closed state. Then, when the atmospheric pressure release step is started based on the predetermined program of the control device 64, the shutoff valve 59 of the sub gas supply pipe 56 is opened first. Next, the variable control valve 60
Continuously opens little by little at a pre-stored speed of the controller 64 to introduce the atmospheric pressure releasing gas, for example, nitrogen (N ₂ ) gas into the preliminary chamber 41 (first gas supply step). Note that the variable control valve 61 may be left as it is if it cannot be completely shut off even in the closed state due to its structure.
Open it to the same degree as the maximum opening of 0. In this state, after a certain time has passed, the shutoff valve 59 (or the variable control valve 60)
Is closed, and then the shutoff valve 58 is opened to proceed to the atmospheric pressure releasing step via the main gas supply pipe 55. In this step, the variable control valve 61 is gradually and continuously opened (second gas supply step), and the preliminary chamber 41 is finally released to atmospheric pressure.

The state of the above atmospheric pressure releasing step is shown in a graph as shown by the curve B2 in FIG. In this graph, the time zone d shows the atmospheric pressure releasing step by the sub gas supply pipe 56, and the time zone e shows the atmospheric pressure releasing step by the main gas supply tube 55. The point f on the graph is the contact point between the time zone d and the time zone e, and the final vacuum degree of the preliminary chamber 41 in the time zone d and the first vacuum degree of the preliminary chamber 41 in the time zone e. Are coincident with each other, which means that the pressure in the preliminary chamber 41 is continuously increased.

The control method of the atmospheric pressure releasing step shown in FIG. 8 is such that the condensation of water in the gas does not occur in the preliminary chamber 41 due to two conditions preliminarily obtained by experiments, that is, the rapid atmospheric pressure release. It is preset so as to satisfy the condition that the dust in the spare chamber 41 is not rolled up and to realize the maximum atmospheric pressure release capability, that is, the minimum atmospheric pressure release time under this condition. The execution control is performed by the control device 64 feeding back the detection values from the vacuum degree measurement terminal 63 and the atmospheric pressure measurement terminal 62, and comprehensively controlling the cutoff valves 58 and 59 and the variable control valves 60 and 61. Is going. As described above, when the inside of the preliminary chamber 41, which is a vacuum container, is released from the vacuum state to the atmospheric pressure, the auxiliary gas supply pipe 56 having a relatively small diameter is provided in the preliminary chamber 41.
Is continuously opened to supply gas, and then the valve opening of the main gas supply pipe 55 having a relatively large diameter is continuously opened to supply gas, so that gas is not abruptly changed. It is possible to quickly release the inside of the preparatory chamber 41 to the atmospheric pressure while suppressing the condensation and liquefaction of the above and the winding of dust.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention. For example, the object to be processed may be at least a planar object to be processed, and in addition to the semiconductor wafer W,
For example, an LCD substrate or the like can be applied. Further, the present invention is not limited to the heat treatment apparatus 1, but is an apparatus for preventing the adhesion of dust such as a semiconductor wafer W or an LCD substrate to reduce the atmospheric pressure to a predetermined pressure, or vice versa. So you can apply it to anything,
For example, it can be applied to an etching device, a sputtering device, an ion implantation device, a single-wafer processing CVD device, a PVD device, a load lock chamber (preliminary chamber) of these devices, and the like. In particular, it is effective for vacuuming each chamber of the cluster roll structure.

[0055]

In summary, according to the present invention, the following excellent effects can be obtained.

(1) According to the first aspect of the invention, at least the main evacuation depressurization step is executed at the maximum depressurization speed at which the condensation and liquefaction of the water contained in the gas in the vacuum vessel does not occur, so that the pressure in the vacuum vessel is reduced. Will be decompressed rapidly without being decompressed rapidly, and the adhesion of dust to the surface of the object to be processed due to the condensation and liquefaction of the water contained in the gas in the pressure vessel is eliminated, and the decompression step is performed. The time required is reduced.

(2) According to the invention of claim 2, after replacing the gas in the vacuum container with an inert gas from which water has been removed, the auxiliary exhaust system is operated to reduce the pressure in the vacuum container.
Sub-exhaust depressurization process and the main exhaust system after this sub-exhaust depressurization process
Main exhaust depressurization step to depressurize the inside of the vacuum container by operating the
To perform the bets, it is possible to quickly reduce the pressure of the vacuum container without condensation liquefaction of gas in the vacuum chamber, it can be shortened to prevent and decompression time of dust adhering to the surface of the object.

[0058] (3) According to the third aspect of the present invention, while supplying the water removal inert gas into the vacuum vessel, depressurizing the vacuum vessel by operating the auxiliary exhaust system Since the auxiliary exhaust depressurizing step and the main exhaust depressurizing step of operating the main exhaust system to depressurize the inside of the vacuum container after the auxiliary exhaust depressurizing step are provided, it is possible to suppress condensation and liquefaction of gas in the vacuum container. It is possible to quickly reduce the pressure in the vacuum container, and it is possible to reduce the adhesion of dust to the surface of the object to be processed and the time for reducing the pressure. In this case, the kinetic energy of the gas molecules of the inert gas supplied into the vacuum container causes the gas molecules to collide with the adsorbed molecules adsorbed on the inner wall of the vacuum container, so that the adsorbed molecules are separated from the inner wall of the vacuum container. Since it is released, the vacuum container can be depressurized to a high vacuum in a short time.

(4) According to the invention described in claim 4, when exhausting the pressure of the vacuum container from atmospheric pressure to a predetermined pressure , the valve opening of the auxiliary exhaust pipe having a relatively small diameter is continuously maintained in the vacuum container. after evacuating to open, in order to relatively exhausting valve opening of the large diameter of the main exhaust pipe continuously open, without rapid pressure changes, by suppressing the winding condensed and dust gas It is possible to quickly evacuate the inside of the vacuum container.

(5) According to the fifth aspect of the present invention, first, while the vacuum container is being evacuated, the gas from which moisture has been removed is supplied to the vacuum container to restore the pressure to a predetermined level. Even if the dust in the vacuum container is rolled up by the, the rolled up dust can be discharged to the outside of the vacuum container, and then the exhaust is stopped and the gas is supplied into the vacuum container. Since the pressure is returned to atmospheric pressure, the pressure in the vacuum container can be quickly returned to atmospheric pressure without condensing and liquefying the gas, preventing dust from adhering to the surface of the object to be processed and shortening the normal pressure return time. Can be achieved.

(6) According to the sixth aspect of the invention, since the supply flow rate of the gas is controlled from small to large in the pressure returning step, the normal pressure returning time can be further shortened.

(7) According to the invention of claim 7, since the gas is an inert gas from which water has been removed by a water removing device, the inert gas from which water has been easily removed is placed in a vacuum container. It can be promptly supplied, and it is possible to further promote the prevention of adhesion of dust to the surface of the object to be processed and the shortening of the normal pressure recovery time.

(8) According to the invention described in claim 8, when the inside of the vacuum container is released from the vacuum state to the atmospheric pressure, the valve opening of the auxiliary gas supply pipe having a relatively small diameter is continuously set in the vacuum container. After the gas is opened and supplied with gas, the valve opening of the main gas supply pipe with a relatively large diameter is continuously opened to supply the gas, so there is no sudden pressure change, and the gas does not condense and liquefy. It is possible to suppress the winding and quickly release the inside of the vacuum container to the atmospheric pressure.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment in which the present invention is applied to a heat treatment apparatus.

FIG. 2 is a graph showing the relationship between pressure and time in the depressurization step.

FIG. 3 is a graph showing a relationship between pressure and time in a depressurizing step.

FIG. 4 is a graph showing a supply method and a relationship between pressure and time when supplying nitrogen gas in a depressurizing step.

FIG. 5 is a graph illustrating a supply method when supplying nitrogen gas in the depressurizing step.

FIG. 6 is a graph showing the relationship between pressure and time in the normal pressure recovery step.

FIG. 7 is a schematic block diagram showing another embodiment of the present invention.

FIG. 8 is a graph showing a relationship between pressure and time in a vacuuming process.

FIG. 9 is a graph showing a relationship between pressure and time in an atmospheric pressure releasing step.

FIG. 10 is a diagram showing a time chart when a semiconductor wafer is processed by a heat treatment apparatus.

FIG. 11 is a diagram illustrating a situation in which dust adheres to the surface of a semiconductor wafer.

[Explanation of symbols]

1 Heat treatment equipment W Semiconductor wafer (Processing object) 4 Reaction tube (vacuum container) 23 Exhaust pipe (main exhaust system) 27 Sub exhaust pipe (sub exhaust system) 31 Control device 41 Spare chamber (vacuum container) 47 Main exhaust pipe 48 auxiliary exhaust pipe 55 Main gas supply pipe 56 Sub gas supply pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-99051 (JP, A) JP-A-6-93427 (JP, A) JP-A-3-144281 (JP, A) JP-A-2- 305383 (JP, A) JP-A-6-179063 (JP, A) JP-A-4-362712 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01J 3/00-3 / 08

Claims (8)

(57) [Claims] 1. When reducing the pressure of a vacuum container having a main exhaust system having a large exhaust flow rate and a sub exhaust system having a small exhaust flow rate from atmospheric pressure to a predetermined pressure, the sub exhaust system is operated to operate the vacuum container. A sub-exhaust depressurizing step for depressurizing the inside, and a main exhaust depressurizing step for depressurizing the inside of the vacuum container by operating the main exhaust system after the sub-exhaust depressurizing step, at least a main exhaust depressurizing step in the vacuum container A pressure control method for a vacuum container, which is executed at a maximum depressurization rate at which condensation of water contained in gas does not occur. 2. When reducing the pressure of a vacuum container equipped with a main exhaust system with a large exhaust flow rate and a sub exhaust system with a small exhaust flow rate from atmospheric pressure to a predetermined pressure, the gas in the vacuum container is dewatered. A gas replacement step of replacing with an inert gas, an auxiliary exhaust pressure reducing step of operating the auxiliary exhaust system to reduce the pressure in the vacuum container after the gas replacement step, and an operation of the main exhaust system after the auxiliary exhaust pressure reducing step. And a main exhaust depressurization step of depressurizing the inside of the vacuum container. 3. When reducing the pressure of a vacuum container equipped with a main exhaust system with a large exhaust flow rate and a sub-exhaust system with a small exhaust flow rate from atmospheric pressure to a predetermined pressure, the water content in the vacuum container is not removed. while supplying the inert gas, the pressure reducing and auxiliary exhaust depressurizing step of auxiliary exhaust system is operated to reduce the pressure within the vacuum vessel, the auxiliary exhaust reduced pressure after the step to operate the main exhaust system wherein the vacuum chamber comprising a main exhaust decompression step of
A method for controlling pressure in a vacuum container, comprising: 4. When the pressure of a vacuum container provided with a main exhaust pipe having a relatively large diameter and a sub exhaust pipe having a relatively small diameter is exhausted from atmospheric pressure to a predetermined pressure, the inside of the vacuum container is the auxiliary exhaust pipe. A first exhaust step of continuously opening the valve opening of the main exhaust pipe and a second exhaust step of continuously opening the valve opening of the main exhaust pipe after the first exhaust step A method for controlling a pressure in a vacuum container, comprising: 5. When returning the pressure of the vacuum container from a predetermined depressurized state to atmospheric pressure, while exhausting the inside of the vacuum container, a gas from which moisture has been removed is supplied to the vacuum container to return to the predetermined pressure. A vacuum characterized by comprising an initial pressure restoring step of: and a main pressure restoring step of stopping the exhaust after the initial pressure returning step and supplying the gas into the vacuum container to restore the atmospheric pressure. Container pressure control method. 6. The pressure control method for a vacuum container according to claim 5, wherein the supply flow rate of the gas is controlled from small to large from the initial pressure returning step to the main pressure returning step. 7. The pressure control method for a vacuum container according to claim 5, wherein the gas is an inert gas from which water has been removed by a water removing device. 8. When releasing the pressure of a vacuum container provided with a main gas supply pipe having a relatively large diameter and a sub gas supply pipe having a relatively small diameter from a vacuum state to atmospheric pressure, the sub gas in the vacuum container A first gas supply step of continuously supplying the gas by opening the valve opening of the supply pipe, and a gas being supplied by continuously opening the valve opening of the main gas supply tube after the first gas supplying step. And a second gas supply step for controlling the pressure of the vacuum container.