JP2003158077A - Vacuum device and baking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum device of high operation efficiency capable of raising a temperature of a cooling trap provided inside a vacuum chamber in a short time and shortening the time required for re-running. SOLUTION: This MBE device is provided with a liquid nitrogen cryopanel 2, a baking panel 10, and a temperature medium circulation device 7, The temperature medium circulation device 7 introduces gaseous nitrogen at a high temperature into the liquid nitrogen cryopanel 2 provided inside the vacuum chamber 1, and raises the temperature on a surface of the liquid nitrogen cryopanel 2 in a short time. Thus, since moisture, white phosphorus, phosphoric acid harmful to semiconductor manufacture adsorbed on the surface of the liquid nitrogen cryopanel 2 are evaporated in a short time, the operation efficiency of the MBE device is improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vacuum device and a baking method.

[0002]

2. Description of the Related Art In a semiconductor growth apparatus and the like, a semiconductor element manufacturing process using a vacuum apparatus occupies an important position.
In recent years, in order to improve the performance of various elements, it is required to improve the degree of vacuum of the above vacuum device, and there is an increasing demand for a process for removing residual impurities with high accuracy.

A molecular beam epitaxy method (MBE) for performing epitaxial growth in ultrahigh vacuum is a typical example of the process required to improve the degree of vacuum. The molecular beam epitaxy method performs high-purity epitaxial growth in a vacuum apparatus evacuated to a very high degree of vacuum of the order of 10 × 10 ⁻¹¹ hPa to obtain high performance of HEMT (high electron mobility transistor) and semiconductor laser. A semiconductor device can be manufactured.

Conventionally, as a vacuum device of this type, there is one shown in FIGS. 2 and 3. As shown in FIG. 2, this vacuum device includes a vacuum chamber 41, a cryopanel 40 provided inside the vacuum chamber 41, and a cryopanel 4
0, a liquid nitrogen inlet 42 for introducing liquid nitrogen from outside the vacuum chamber 41, a nitrogen exhaust port 43 for discharging nitrogen from the cryopanel 40 to the outside of the vacuum chamber 41, and a Ga
Material evaporation sources 44 and 45 for evaporating materials such as As and As,
And a baking panel 46 that covers the vacuum chamber 41 and heats the vacuum chamber 41.

In the above vacuum device, the vacuum chamber 41 is used for filling the material in the vacuum chamber 41 and for maintenance of parts.
The inside of the vacuum chamber 41 and the cryopanel 40 are heated by externally heating the vacuum chamber 41 by the baking panel 46 when the vacuum chamber 41 is evacuated after being exposed to the atmosphere.
The temperature of the surface of (1) is raised to evaporate the gas molecules adsorbed inside the vacuum chamber 41 and on the surface of the cryopanel 40, and discharge the gas molecules outside the vacuum chamber 41. This process is generally called baking.

By the way, the moisture in the atmosphere that enters the vacuum chamber 41 when the vacuum chamber 41 is opened to the atmosphere serves as a source of oxygen which is harmful to the semiconductor element during the growth process of the compound semiconductor thin film requiring high vacuum. , It is necessary to remove it sufficiently. Further, when phosphorus is used in the growth process of the compound semiconductor thin film, phosphorus is oxidized in the vacuum chamber 41 to generate phosphoric acid when exposed to the atmosphere. This phosphoric acid also supplies oxygen which is harmful to the semiconductor element like moisture. Be the source.

During the subsequent growth process, in order to achieve a high degree of vacuum in the vacuum chamber 41, as shown in FIG. 3, the cryopanel 40, which is a cooling trap, is supplied from the liquid nitrogen inlet 42 to the liquid nitrogen 47. Is introduced into the vacuum chamber 41
Gas molecules remaining or generated inside are adsorbed on the surface of the cryopanel 40. On the surface of the cryopanel 40, not only the molecules of the residual gas but also the molecules of the process material are adsorbed, and in many cases, they are solidified. Among these, white phosphorus, when the vacuum chamber 41 is opened to the atmosphere,
It is very dangerous because it oxidizes and burns inside the vacuum chamber 41.
In addition, white phosphorus becomes an oxide such as phosphoric acid after burning, and serves as a supply source of oxygen which is a harmful substance to the semiconductor during the subsequent semiconductor element manufacturing process. Therefore, especially in a vacuum apparatus using phosphorus, it is necessary to perform baking before opening to the atmosphere to sufficiently evaporate and remove white phosphorus.

[0008]

However, in the above-described conventional vacuum apparatus, the cryopanel 40 for realizing a high vacuum during the manufacture of semiconductor elements is inside the vacuum chamber 41 and is vacuum insulated from the outside. Therefore, the vacuum chamber 41
It takes a long time to increase the temperature of the cryopanel 40 by baking the above from the outside. Therefore, it takes a long time to vaporize the gas molecules adsorbed on the surface of the cryopanel 40, and there is a problem that the operation efficiency of the vacuum device is poor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vacuum device having a high operating efficiency which can raise the temperature of the cooling trap in the vacuum chamber in a short time and shorten the time required for re-operation.

[0010]

In order to achieve the above object, the vacuum apparatus of the present invention is a vacuum apparatus having a cooling trap for adsorbing gas in the vacuum chamber, and a baking means for baking the vacuum chamber and the cooling unit. The trap is characterized in that the trap is provided with a heating medium supply means for supplying the heating medium.

According to the present invention, the vacuum chamber is baked by the baking means, and the heating medium is placed inside the cooling trap by the heating medium supply means. Therefore, even if the inside of the vacuum chamber is vacuum-insulated, the temperature of the cooling trap rises in a short time due to the heating medium. Therefore, it is possible to surely evaporate the molecules adsorbed on the surface of the cooling trap in a short time, thereby shortening the regeneration time of the vacuum device and increasing the operating efficiency of the vacuum device.

In the vacuum apparatus of one embodiment, the temperature of the heating medium is equal to or higher than the temperature at which white phosphorus evaporates.

According to the above embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which white phosphorus evaporates, the temperature of the cooling trap becomes equal to or higher than the evaporation of white phosphorus, and the temperature of the cooling trap surface is increased. White phosphorus evaporates. Therefore,
By discharging the white phosphorus to the outside of the vacuum device, it is possible to prevent the white phosphorus from performing dangerous oxidative combustion in the vacuum device when the vacuum device is opened to the atmosphere.

In the vacuum device of one embodiment, the temperature of the heating medium is equal to or higher than the temperature at which water vaporizes.

According to the above embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which moisture evaporates, the temperature of the cooling trap becomes equal to or higher than the evaporation of moisture, so that the moisture is removed from the surface of the cooling trap. Evaporate. Therefore, it is possible to efficiently discharge the water, which supplies harmful oxygen to the semiconductor, to the outside of the vacuum device during the growth process of the compound semiconductor thin film.

Further, in the vacuum apparatus of one embodiment, the temperature of the heating medium is equal to or higher than the temperature at which phosphoric acid evaporates.

According to the above embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which phosphoric acid evaporates, the temperature of the cooling trap becomes equal to or higher than the evaporation of phosphoric acid, and The phosphoric acid evaporates. Therefore,
The phosphoric acid, which supplies harmful oxygen to the semiconductor during the growth process of the compound semiconductor thin film, can be efficiently discharged to the outside of the vacuum apparatus. Therefore, the quality of the semiconductor device can be improved.

In the vacuum device of one embodiment, the heating medium is nitrogen.

Since the nitrogen is inexpensive, the operating cost of this vacuum device is low. In addition, since the nitrogen is chemically stable and does not oxidize the material of the cooling trap, the life of the cooling trap can be extended.

The vacuum apparatus of one embodiment is a molecular beam epitaxy apparatus.

The above-mentioned molecular beam epitaxy apparatus can surely evaporate the molecules attached to the surface of the cooling trap in a short time at the time of baking, so that the operation efficiency becomes high.

In the vacuum apparatus of one embodiment, the cooling trap is a liquid nitrogen cryopanel.

According to the above embodiment, liquid nitrogen is used as a refrigerant in the liquid nitrogen cryopanel, and gas molecules in the vacuum device are adsorbed on the surface of the liquid nitrogen cryopanel to realize a high vacuum. Since the liquid nitrogen can be easily handled and is inexpensive, the vacuum device is easy to handle and the operating cost is low.

In the baking method of the present invention, the step of opening the inside of a vacuum apparatus having a cooling trap for gas adsorption to the atmosphere, the step of evacuating the vacuum apparatus whose inside is opened to the atmosphere, And a step of introducing a heating medium into the cooling trap in order to desorb molecules adsorbed in the cooling trap of the vacuum apparatus that has been evacuated.

According to the baking method of the present invention, during the period from the opening of the vacuum device to the atmosphere until the start of operation,
There is the step of introducing the heating medium into the cooling trap. According to this step, since the heating medium is supplied into the cooling trap, the time required for baking can be significantly shortened and the molecules adsorbed to the cooling trap can be reliably secured even if the cooling trap is vacuum-insulated. Can be released. Therefore, according to the baking method of the present invention, it is possible to shorten the regeneration time of the vacuum device and improve the operation efficiency.

Further, in the baking method of the present invention, before the vacuum device having the cooling trap for adsorbing gas is opened to the atmosphere, in order to desorb the material adsorbed in the cooling trap, a temperature is kept in the cooling trap. It is characterized by including a step of introducing a medium.

According to the baking method of the present invention, the heating medium is introduced into the cooling trap before the vacuum chamber is opened to the atmosphere. Therefore, even if the vacuum chamber is vacuum-insulated, the surface temperature of the cooling trap can be quickly raised by the heating medium, and the material adsorbed on the surface of the cooling trap can be surely and quickly evaporated. it can.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an MBE apparatus (molecular beam exhaustion apparatus) as an example of a vacuum apparatus according to the first embodiment of the present invention. This MBE device includes a vacuum chamber 1, a liquid nitrogen cryopanel 2 as an example of a cooling trap provided inside the vacuum chamber 1, and a heating medium inside the liquid nitrogen cryopanel 2 from outside the vacuum chamber 1. A nitrogen inlet 3 for introducing nitrogen gas at about 160 ° C. as an example,
The nitrogen gas is discharged from the inside of the liquid nitrogen cryopanel 2 to the outside of the vacuum chamber 1, and the nitrogen gas is sent to the nitrogen inlet 3 and the nitrogen gas is recovered from the nitrogen outlet 4. A heating medium circulation device 7 as an example of a heating medium supply means, material evaporation sources 8 and 9 for evaporating materials such as Ga and As, and an example of baking means for covering the vacuum chamber 1 and heating the vacuum chamber 1 from the outside. As a baking panel 10.

Although not shown, the heating medium circulating device 7 is provided with a heater and a fan.

The following baking is performed in the MBE apparatus having the above-mentioned structure.

First, the inside of the vacuum chamber 1 of the MBE apparatus is opened to the atmosphere for the purpose of material filling and maintenance of parts. Next, the vacuum chamber 1 is evacuated. Thereafter, the entire vacuum chamber 1 is covered with a heat insulating panel (not shown), the vacuum chamber 1 is baked by the baking panel 10 located outside the vacuum chamber 1, and the liquid nitrogen cryopanel 2 of the liquid nitrogen cryopanel 2 is heated by the heating medium circulating device 7. About 160 ℃ inside
Is sent to heat the liquid nitrogen cryopanel 2.

As described above, according to the first embodiment, the vacuum chamber 1 is baked by the baking panel 10 and about 16 by the heating medium circulating device 7.
Nitrogen gas at 0 ° C. is sent to the inside of the liquid nitrogen cryopanel 2. Therefore, even if the inside of the vacuum chamber 1 is vacuum-insulated, the temperature of the liquid nitrogen cryopanel 2 rises in a short time due to the nitrogen gas. Therefore, the moisture adsorbed on the surface of the liquid nitrogen cryopanel 2 and supplying harmful oxygen to the semiconductor during the growth process of the compound semiconductor thin film can be surely evaporated in a short time. The time can be shortened and the operating efficiency of this MBE device can be improved.

In the case of the first embodiment, it took about 3 hours to elevate the temperature of the liquid nitrogen cryopanel 2 to evaporate the water adsorbed on the surface of the liquid nitrogen cryopanel 2. On the other hand, in the case of baking using only the baking panel 10 as in the conventional MBE apparatus, the surface of the liquid nitrogen cryopanel 2 is heated to a high temperature and the moisture adsorbed on the surface of the liquid nitrogen cryopanel 2 is evaporated. It took about 24 hours or more to perform. Therefore, in the first embodiment, the time required for evaporation is 1/8 of that in the conventional case.

As described above, since the time required for baking can be greatly shortened, the reproduction time of the MBE apparatus of the first embodiment can be shortened and the operating efficiency of the MBE apparatus can be improved.

Further, in the first embodiment, since nitrogen gas is used as the heating medium, the operating cost is low, oxidation of the welded portion of the liquid nitrogen cryopanel 2 is prevented, and the life of the liquid nitrogen cryopanel 2 is reduced. Can be lengthened.

In the first embodiment, nitrogen gas at about 160 ° C. is used as the heating medium for evaporating water, but air may be used as the heating medium instead of nitrogen gas. The temperature of the nitrogen gas and the air is 150 ° C
The above is desirable, but it can be used even at a temperature of less than 150 ° C.

Next, using the MBE apparatus shown in FIG.
The baking method of the embodiment will be described.

In the second embodiment, phosphorus is used as the material of the semiconductor element. A large amount of white phosphorus adheres to the inside of the vacuum chamber 41, and particularly on the surface of the liquid nitrogen cryopanel 2 which is cooled to an extremely low temperature during the growth of the compound semiconductor thin film,
A lot of white phosphorus adheres. Therefore, it is necessary to sufficiently remove white phosphorus by baking before the growth of the compound semiconductor thin film is completed and before the vacuum chamber 1 is opened to the atmosphere for filling the semiconductor element material and maintaining the parts. Otherwise, very dangerous spontaneous firing of white phosphorus will occur inside the vacuum chamber 1 when opening to the atmosphere.

In order to prevent this efficiently, in this second embodiment, the temperature of the heating medium circulating device 7 is about 210 ° C. from the outside of the vacuum chamber 1 to the inside of the liquid nitrogen cryopanel 2.
Is sent to heat the surface of the liquid nitrogen cryopanel 2. By doing so, the white phosphorus adsorbed on the surface of the liquid nitrogen cryopanel 2 can be surely evaporated in a short time. Since the evaporated white phosphorus can be exhausted to the outside of the vacuum chamber 1, dangerous spontaneous ignition of white phosphorus can be prevented.

In the second embodiment, the heating medium circulating device 7 sends nitrogen gas at about 210 ° C. from the outside of the vacuum chamber 1 to the inside of the liquid nitrogen cryopanel 2 to clean the surface of the liquid nitrogen cryopanel 2. It's warming up. Therefore, as compared with the case of baking only from the outside of the conventional vacuum chamber 1 using only the baking panel 10, the time during which the surface of the liquid nitrogen cryopanel 2 becomes hot can be shortened significantly. In the case of baking only from the outside of the conventional vacuum chamber 1, it takes about 24 hours to elevate the surface of the liquid nitrogen cryopanel 2 to evaporate the white phosphorus adsorbed on the surface of the liquid nitrogen cryopanel 2. Although the above was required, in the case of the present embodiment, the white phosphorus could be evaporated in about 3 hours.

As described above, the white phosphorus adsorbed on the surface of the liquid nitrogen cryopanel 2 can be evaporated and exhausted in a short time, so that the regeneration time of the MBE device can be shortened and the operation efficiency of the MBE device can be improved. be able to.

In the second embodiment, nitrogen gas at about 210 ° C. is used as the heating medium, but air may be used as the heating medium instead of nitrogen gas. The temperature of nitrogen gas or air is preferably 200 ° C. or higher in order to evaporate the white phosphorus deposited on the other vapor deposition material in a short time, but 100 ° C. or higher to evaporate the white phosphorus. It may be any temperature.

Next, using the MBE apparatus shown in FIG.
The baking method after opening the atmosphere of the MBE apparatus of the embodiment will be described.

Even when the white phosphorus is removed according to the second embodiment, some phosphorus components remain inside the vacuum chamber 1. When released to the atmosphere, these react with oxygen in the atmosphere to produce phosphoric acid. During maintenance of the MBE device, red phosphorus may be ignited and oxidized due to friction and the like to generate phosphoric acid. These phosphoric acids serve as a supply source of oxygen into the crystal during the growth of the compound semiconductor thin film in the MBE device, and are extremely harmful to the semiconductor element.

In the third embodiment, at the time of baking the vacuum chamber 1 after releasing it to the atmosphere, the heating medium circulating device 7 introduces nitrogen gas at about 250 ° C. from the outside of the vacuum chamber 1 into the inside of the liquid nitrogen cryopanel 2. By sending, the phosphoric acid adsorbed on the surface of the liquid nitrogen cryopanel 2 can be evaporated.

In the third embodiment, nitrogen gas at about 250 ° C. is used as the heating medium, but air may be used as the heating medium instead of nitrogen gas. The temperature of nitrogen gas or air is preferably about 250 ° C. or higher in order to evaporate phosphoric acid in a sufficient time in a short time.
It is effective if the temperature is ℃ or more.

In the above first, second and third embodiments, the MBE device is given as an example of the vacuum device.
D device (chemical vapor deposition device) or the like may be used, and any device may be used as long as the inside is evacuated and baking is required.

Further, in the first, second and third embodiments, the liquid nitrogen cryopanel is used as the cooling trap, but the liquid nitrogen cryopanel is not necessarily required and the cavity into which the refrigerant and the heating medium can be introduced. As long as it has the internal structure of

[0050]

As is apparent from the above, since the vacuum device of the present invention is provided with the heating medium supply means for supplying the heating medium into the cooling trap in the vacuum chamber, even if the vacuum chamber is vacuum-insulated, The temperature of the cooling trap can be raised in a short time to evaporate the molecules adsorbed on the surface of the cooling trap in a short time. Therefore, according to the present invention, the regeneration time of the vacuum device can be shortened and the operating efficiency can be improved.

Further, according to one embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which white phosphorus is vaporized, white phosphorus is vaporized from the surface of the cooling trap in a short time, and the white phosphorus is surely placed outside the vacuum device. Can be discharged. Therefore, it is possible to prevent the white phosphorus from performing dangerous oxidative combustion in the vacuum device when the vacuum device is opened to the atmosphere.

Further, according to one embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which water is evaporated, the water can be evaporated from the surface of the cooling trap in a short time. Therefore, the moisture that supplies harmful oxygen to the semiconductor during the growth process of the compound semiconductor thin film can be reliably discharged to the outside of the vacuum device, and the quality of the semiconductor element can be improved.

Further, according to one embodiment, since the temperature of the heating medium is equal to or higher than the temperature at which phosphoric acid evaporates, phosphoric acid can be evaporated from the surface of the cooling trap in a short time.
Therefore, the phosphoric acid, which supplies harmful oxygen to the semiconductor during the growth process of the compound semiconductor thin film, can be reliably discharged to the outside of the vacuum apparatus, and the quality of the semiconductor element can be improved.

Further, according to one embodiment, since the heating medium is inexpensive nitrogen, the operating cost of this vacuum device can be reduced. Further, nitrogen is chemically stable and does not oxidize the material of the cooling trap, so that the life of the cooling trap can be extended.

Further, since the vacuum apparatus of one embodiment is a molecular beam epitaxy apparatus, it has an advantage that the molecules attached to the surface of the cooling trap can be surely evaporated in a short time and the operation efficiency is high. .

Further, in one embodiment, since the cooling trap is a liquid nitrogen cryopanel, the vacuum device can be easily handled and the operating cost of the vacuum device can be reduced.

Further, in the baking method of the present invention, after the inside of the vacuum device is opened to the atmosphere, the vacuum device is evacuated, and then the heating medium is introduced into the cooling trap, so that it is adsorbed to the cooling trap. Water and phosphoric acid can be removed in a short time, the regeneration time of the vacuum device can be shortened, and the operation efficiency of the vacuum device can be increased.

Further, in the baking method of the present invention, before the vacuum device having the cooling trap for adsorbing gas is opened to the atmosphere, in order to desorb the material adsorbed in the cooling trap, a temperature is kept in the cooling trap. Since the step of introducing the medium is provided, the material such as white phosphorus adsorbed in the cooling trap can be desorbed from the surface of the cooling trap in a short time before opening the vacuum chamber to the atmosphere.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a vacuum device of the present invention.

FIG. 2 is a conceptual diagram of a conventional vacuum device.

FIG. 3 is a conceptual diagram of a conventional vacuum device.

[Explanation of symbols]

1 vacuum chamber, 2 liquid nitrogen cryopanel, 3 nitrogen inlet, 4 nitrogen outlet, 7 Heat medium circulation device, 8,9 Material evaporation source, 10 baking panels.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4K029 CA01 DA09 FA09                 5F045 AB09 AE01 AF04 BB08 CA07                       DQ08 EB02 EB06                 5F103 AA04 BB25 DD01 GG01 HH03                       LL03 LL09 RR01

Claims (9)

[Claims] 1. A vacuum apparatus having a cooling trap for adsorbing gas in a vacuum chamber, comprising: baking means for baking the vacuum chamber; and heating medium supply means for supplying a heating medium into the cooling trap. Characteristic vacuum device. 2. The vacuum apparatus according to claim 1, wherein the temperature of the heating medium is equal to or higher than a temperature at which white phosphorus is evaporated, equal to or higher than a temperature at which moisture is evaporated, or equal to or higher than a temperature at which phosphoric acid is evaporated. Vacuum device. 3. The vacuum apparatus according to claim 1, wherein the heating medium is nitrogen. 4. The vacuum apparatus according to any one of claims 1 to 3, wherein the vacuum apparatus is a molecular beam epitaxy apparatus. 5. The vacuum apparatus according to any one of claims 1 to 4, wherein the cooling trap is a liquid nitrogen cryopanel. 6. A step of opening the interior of a vacuum apparatus having a cooling trap for adsorbing gas to the atmosphere, a step of evacuating the vacuum apparatus whose interior is open to the atmosphere, and a step of evacuating the vacuum apparatus. And a step of introducing a heating medium into the cooling trap in order to desorb molecules adsorbed in the cooling trap. 7. The baking method according to claim 6, wherein the adsorbed molecules are mainly water or phosphoric acid. 8. A step of introducing a heating medium into the cooling trap in order to desorb the material adsorbed to the cooling trap before opening the vacuum device having the cooling trap for adsorbing gas to the atmosphere. A baking method characterized by the above. 9. The baking method according to claim 8, wherein the adsorbed material is mainly white phosphorus.