JPH07193037A - Method and apparatus for vacuum drying - Google Patents

Abstract

PURPOSE:To decrease the attachment of fine particles to the surface of a substrate strikingly after vacuum drying by conducting washing step and a pressure reducing step in one vacumm drying apparatus, and providing a water draining step for dropping pure water remaining on the substrate after the washing from the substrate between the washing step and the pressure reducing step. CONSTITUTION:A vacuum drying apparatus has an outer tank 4 and an inner tank 3. A carrier setting stage 8 is provided in the inner tank 3. A carrier 1 containing a substrate 2 is provided on the carrier setting stage 8. After the substrate 2 undergoes the washing with chemical, chemical is washed out with pure water in a water washing step. The pure water, which is heated to 80 deg.C, is supplied from a water feeding and draining pipe 6, and the overflowed pure water is drained. After the end of the washing step, the pure water in the inner tank 3 and the outer tank 4 is drained. When the draining of the pure water in the inner tank 3 is finished, the operation is made to wait until the pure water attached to the surfaces of the substrate 2 and the carrier 1 is sufficiently dropped from the substrate 2. The attached amount of the fine particles in the drying step can be made zero by setting the waiting time at 120 seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum drying method and a vacuum drying apparatus. More specifically, the present invention relates to a vacuum drying method and a vacuum drying apparatus suitable for drying after cleaning a semiconductor substrate in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high integration of elements constituting a semiconductor device, the structure of the semiconductor device has become three-dimensional and complicated. In particular, a memory cell of a semiconductor memory device such as a dynamic random access memory (DRAM) has been provided with a capacitive electrode having a complicated structure in order to secure a large electrode area within a small occupied area.
Such capacitance electrodes include a stack type and a trench type. In recent years, the height of the storage electrode of the stack-type capacitance electrode has become higher and higher, and the depth of the trench of the trench-type capacitance electrode has become deeper and deeper.

In the process of manufacturing a semiconductor device having such a fine and complicated structure, if fine particles adhere to the substrate,
There is a problem that the manufacturing yield of semiconductor devices decreases. As a method of removing fine particles from the surface of a substrate, cleaning of the substrate with a chemical solution has been conventionally performed. As a method for drying the washed substrate, there are a spin drying method, an alcohol vapor drying method, a substrate lifting drying method, a vacuum drying method and the like.

In the spin drying method, the pure water for cleaning adhering to the surface of the substrate is shaken off by rotating the substrate at a high speed. In this method, the substrate is charged because the substrate is rotated at a high speed. The electrification not only facilitates the attachment of fine particles, but also deteriorates the characteristics of the semiconductor device. In addition, a drive system that easily becomes a dust source of fine particles must be installed inside the device. Further, since a low dust-generating member such as quartz or Teflon cannot be used due to the fear of damage to the device, a member such as stainless steel which may cause contamination of metal impurities must be used. Moreover, in recent years, the diameter of the substrate has increased to 20 and the diameter of the substrate has increased.
It is designed to exceed 0 mm. When such a large substrate is rotated at high speed, the substrate may be damaged.

In the alcohol vapor drying method, a substrate is inserted into a container filled with alcohol vapor, and pure water remaining on the surface of the substrate is replaced with alcohol having a small latent heat,
It evaporates alcohol on the substrate surface. This method cannot dry semiconductor devices having complicated recesses with a sufficient level of cleanliness. Further, since the used alcohol cannot be discarded unless the waste liquid is treated, there is a problem that a separate device for treating the waste liquid is required and the manufacturing cost increases as the amount of alcohol is increased.

The substrate pulling and drying method is a drying method in which a substrate is pulled up from pure water at an extremely low speed and the surface tension of the pure water is used to prevent the pure water from being left on the substrate. This method, in principle, requires a long time for drying, so that the production efficiency decreases. In addition, the three-dimensional and complicated semiconductor device cannot be dried sufficiently. Further, there is a problem that a natural oxide film grows unevenly on the surface of the substrate.

In the vacuum drying method, a substrate having pure water on its surface is placed in a reduced pressure atmosphere to promote the evaporation of pure water from the substrate surface (Electrochemical Society Meeting).
91 Proceedings, I.Oki, et.al.). In this method, since the device is not driven, it is possible to use a low dust-generating member such as quartz or Teflon, and since there is no drive system inside the device, no dust is emitted from the device. Further, since pure water is used, the cost for waste liquid treatment does not occur. Moreover, since the substrate is exposed to a reduced pressure and dried, a three-dimensional and complicated semiconductor device can be sufficiently dried.

At present, this vacuum drying method is regarded as the most promising. The conventional vacuum drying method will be described below with reference to FIGS. 4 (a) to 4 (h).

In step (a), the inner tank is filled with pure water heated to 80 ° C. with the lid of the outer tank opened. The heated pure water continues to be supplied from the water supply / drain port of the inner tank and overflows from the inner tank. In step (b), the substrate is soaked in pure water in the inner tank together with the carrier. Pure water continues to be supplied from the water supply / drain port and overflows the inner tank. In the step (c), in order to remove contaminants such as fine particles remaining in the substrate, the carrier, and the inner tank, the heated pure water is sufficiently supplied from the water supply / drain port on the bottom surface of the inner tank to perform cleaning. During this time, the lid of the outer tank is closed. In step (d), the cleaning step is completed, and then the pure water in the inner tank and the outer tank is drained.

In step (e), the depressurization step is started when the pure water in the inner tank is drained. As the pressure is reduced, the pure water remaining on the substrate surface is evaporated and the substrate is dried. In step (f), the inert gas is supplied again to the inside of the outer tank to return the pressure inside the outer tank to almost atmospheric pressure. In step (g), the lid of the outer tank is opened, and in step (h), the carrier is taken out of the apparatus.

[0011]

However, the above-mentioned prior art has a problem that the number of fine particles remaining on the substrate surface after drying cannot be reduced to a sufficiently low level for manufacturing semiconductor devices with a high yield. .

FIG. 5 shows 0.2 remaining on the surface of a silicon substrate having a diameter of 150 mm dried by the above conventional drying method.
The distribution of fine particles having a particle size of μm or more is shown. This distribution was measured using a laser surface inspection device. The peripheral portion (width 10 mm) of the substrate is outside the measurement target.

The silicon substrate was first washed with a mixed liquid of ammonia water and hydrogen peroxide water, and then washed with water and dried. The silicon substrate to be measured is washed with water, dried, washed again with pure water, and dried by a vacuum drying method. The number of fine particles on the surface of the substrate before washing again was 10 or less, but the number of fine particles on the surface of the substrate after vacuum drying was 624. The number of adhered fine particles increased by washing with water again and vacuum drying. The adhesion of these fine particles lowers the manufacturing yield of semiconductor devices having a fine pattern of 0.5 μm or less.

The present invention has been made in order to solve the above problems, and an object of the present invention is to significantly reduce the number of fine particles attached to the surface of a substrate after vacuum drying, and to manufacture a semiconductor device. It is an object of the present invention to provide a vacuum drying method and a vacuum drying device that can contribute to an improvement in yield.

[0015]

In the vacuum drying method of the present invention, a cleaning step for cleaning a substrate with pure water and an atmosphere of the substrate are depressurized from atmospheric pressure, whereby the substrate remains on the substrate. A vacuum drying method for a substrate, comprising: a depressurizing step for evaporating the pure water, the method comprising: performing the cleaning step and the depressurizing step in one vacuum drying apparatus, and The method further includes a draining step of dropping a part of the pure water remaining on the substrate from the substrate between the cleaning step and the depressurizing step, whereby the above object is achieved. To be achieved.

[0016] In the embodiment, the vacuum drying device has a lid, and an outer tank capable of blocking the inside from the atmosphere by closing the lid, and an inner tank installed inside the outer tank. The cleaning step comprises: a preparatory step of filling the inner tank with pure water; an inserting step of inserting the substrate into the pure water filled in the inner tank; A drainage step of discharging the pure water to the outside of the outer tank.

Preferably, the pure water in the inner tank is heated. Preferably, the depressurizing step includes the step of depressurizing the pressure in the outer tank to 1 Torr or less after closing the lid of the outer tank.

Preferably, a step of introducing an inert gas into the outer vessel after the depressurizing step, thereby increasing the pressure in the outer vessel above atmospheric pressure, and then opening the lid of the outer vessel. Is further included.

Preferably, the draining step includes a waiting step of delaying the start of depressurization in the depressurizing step from the end of washing in the washing step by 10 seconds or more.

Preferably, the draining step includes a step of moving the substrate so as to have acceleration in the vertical direction.

Another vacuum drying method of the present invention has a lid,
After cleaning the substrate with pure water in a vacuum drying apparatus equipped with an outer tank capable of shutting off the atmosphere from the atmosphere by closing the lid, and an inner tank installed inside the outer tank, A vacuum drying method of depressurizing the atmosphere of the substrate from atmospheric pressure to evaporate the pure water remaining on the substrate, wherein the pure water filled in the inner tank is used to clean the substrate. A step of draining the pure water from the inner tank to the outside of the outer tank while introducing an inert gas into the outer tank with the lid closed. Even after the water is completely discharged, the inert gas is continuously introduced into the outer tank until a certain period of time elapses, and a part of the pure water remaining on the substrate during that period is dropped from the substrate. And a step of stopping the introduction of the inert gas into the outer tank after the lapse of the certain period of time. Discharging the inert gas of the internal to the external tank outside, thereby and includes a depressurizing step of reducing the pressure in the outer chamber, the objects can be achieved.

Preferably, the fixed period is 10 seconds or more. Preferably, after the depressurizing step, an inert gas is reintroduced into the outer tank, thereby increasing the pressure in the outer tank above atmospheric pressure, and then opening the lid of the outer tank. Inclusive.

Preferably, the draining step includes a step of moving the substrate so as to have an acceleration in the vertical direction.

The vacuum drying apparatus of the present invention has an outer tank capable of blocking the inside from the atmosphere, an inner tank provided in the outer tank and capable of storing pure water therein, and an outer tank in the outer tank. A vacuum drying apparatus comprising: a depressurizing unit for depressurizing the pressure, wherein the inner tank further has at least one water supply / drainage port for supplying and draining the pure water. The apparatus further comprises means for moving the outer tank so as to have acceleration in the vertical direction before the start of the depressurization step, whereby the above object is achieved.

Another vacuum drying apparatus of the present invention is an outer tank capable of blocking the inside from the atmosphere, an inner tank provided inside the outer tank and capable of storing pure water therein, and the outer tank. A vacuum drying apparatus comprising: a decompression unit for decompressing the internal pressure, wherein the inner tank further comprises at least one water supply / drainage port for supplying and draining the pure water, and at least a vacuum drying step. Prior to the start of (1), a draining member for guiding the pure water left on the substrate to the water supply / drainage port, thereby achieving the above object.

In the embodiment, the draining member is arranged in the inner tank so as to substantially contact the lower end of the substrate at least before the start of the depressurizing step.

[0027]

According to the vacuum drying method of the present invention, the cleaning step and the depressurizing step are performed in one vacuum drying apparatus, and moreover, the cleaning step and the depressurizing step remain on the cleaned substrate. It includes a draining step of dropping pure water from the substrate.

This draining process is a process for removing pure water from the substrate as much as possible from the end of drainage in the cleaning process to the substantial start of evaporation of pure water in the depressurizing process. . The draining process brings a particularly remarkable effect by setting the waiting time from the end of drainage to the start of decompression to 10 seconds or more. In addition, during the draining process, the draining member can be brought into contact with the substrate or the substrate can be accelerated in the vertical direction to achieve draining more quickly. By introducing such a draining process, the number of fine particles left on the substrate by vacuum drying is reduced, and the cleanliness of the substrate surface after vacuum drying is enhanced.

[0029]

EXAMPLES The present invention will be described below with reference to examples.

First, the structure of the vacuum drying apparatus according to the present invention will be described with reference to FIG. This device is the outer tank 4
And an inner tank 3 installed in the outer tank 4. The outer tub 4 has a lid 7, and by closing the lid 7, the inside can be shut off from the atmosphere.

The upper part of the inner tank 3 is open, and
It has a structure that can store pure water inside. A carrier installation table 8 is provided inside the inner tank 3.
A carrier 1 containing at least one substrate 2 is installed on the carrier installation table 8.

On the bottom surface of the inner tank 3, one or more water supply / drainage pipes 6 are provided.
Are connected. Pure water passes through this water supply / drainage pipe 6,
It is supplied into the inner tank 3 and is drained from the inner tank 3 to the outside. The number of the water supply / drainage pipes 6 is arbitrary. Instead of the water supply / drainage pipe 6, the water supply pipe and the drainage pipe may be separately connected to the inner tank 3. In this case, the drain pipe needs to be connected to the bottom surface of the inner tank 3, but the water supply pipe does not necessarily have to be provided on the bottom surface. In the vacuum drying apparatus of the present invention, after the pure water is drained, the gas in the outer tub 4 can be discharged (exhausted) to the outside through the water supply / drain pipe 6. In this embodiment, the water supply / drainage pipe 6 also serves as the exhaust pipe in this way.

Since the substrate 2 to be cleaned is completely immersed in the pure water supplied to the inner tank 3, the size and shape of the inner tank 3 are the same as those of the substrate 2. It will be designed considering the number. The substrate 2 accommodated in the carrier 1 undergoes a cleaning process and a drying process.
Therefore, it is preferable that the inner tank 3 has a size capable of accommodating at least one carrier 1.

The outer tank 4 has a drainage port and a drainage pipe connected to the drainage port on the bottom surface thereof. Through this drain pipe, the pure water overflowing from the inner tank 3 into the outer tank 4 is drained to the outside of the outer tank 4. Further, the outer tank 4 is provided with a gas introduction port (not shown). An inert gas can be supplied into the outer tub 4 through this gas inlet. The introduction of the inert gas is controlled by a control device (not shown).

When pure water and gas are continuously discharged from the apparatus via the water supply / drain pipe 6 of the inner tank 3 and the drain pipe of the outer tank 4 with the lid 7 of the outer tank 4 closed, The pressure decreases to a non-negligible level compared to atmospheric pressure. But,
If the inert gas is continuously introduced into the outer tub 4 through the gas introduction port, the pressure in the outer tub 4 can be prevented from being substantially lowered (at least, maintained at a pressure at which evaporation does not occur). can do).

The vacuum drying method of the present invention using the above vacuum drying apparatus will be described below with reference to FIGS. 3 (a) to 3 (i). Note that, in FIG. 3, reference numerals given to the vacuum dryer and the like are omitted.

First, the substrate (silicon wafer) 2 in a state of being inserted in the carrier 1 is subjected to cleaning treatment with a chemical solution, and then the chemical solution is washed off with pure water in a water washing step. On the surface of the substrate 2, a film of pure water attached in the washing step is formed.

In step (a), the inner tank 3 is filled with pure water heated to 80 ° C. with the lid 7 of the outer tank 4 opened. The heated pure water continues to be supplied from the water supply / drainage pipe 6 of the inner tank 3 and overflows from the inner tank 3. The overflowed pure water is drained from the drain pipe provided in the outer tank 4.

In step (b), the substrate 2 is the carrier 1
At the same time, it is soaked in pure water in the inner tank 3. Pure water continues to be supplied from the water supply / drainage pipe 6 and overflows the inner tank 3.

In step (c), with the lid 7 of the outer tank 4 closed, heated pure water is continuously supplied from the water supply / drain pipe 6 on the bottom surface of the inner tank 3, and the substrate 2 is washed with pure water for about 5 minutes. To be done. During this time, the temperature of the substrate 2 is raised to about the temperature of the heated pure water, which accelerates the drying in the subsequent steps. The cleaning time is adjusted as needed.

In step (d), the washing step is completed,
Then, the pure water in the inner tank 3 and the outer tank 4 is drained through the water supply / drainage pipe 6 and the drainage pipe, respectively. At this time, the outer tank 4
If the inside is in a depressurized state, it is difficult for the pure water to be drained, and in addition, boiling of the pure water may occur. In order to prevent such a situation, an inert gas such as nitrogen is introduced into the outer tub 4 so that the pressure in the outer tub 4 is not reduced. By doing so, boiling of pure water can be prevented and the drainage rate of pure water can be stabilized.

In the present embodiment, drainage is performed by using an aspirator. However, pure water may be naturally dropped from the water supply / drainage pipe 6. Further, pure water may be pushed out through the water supply / drainage pipe 6 by introducing an inert gas into the outer tank 4. The pure water was drained at a speed of about 5 cm / min. However, if this speed is too slow, the number of particles adhering to the surface of the substrate 2 tends to increase. From the viewpoint of preventing adhesion of fine particles and shortening the time required for drying, it is desirable.

In step (e), after the pure water in the inner tank 3 has been drained, the process waits until the pure water adhering to the surface of the substrate 2 or the carrier 1 drops from the substrate 2 to a sufficient extent. In the prior art, the pressure inside the outer tub 4 began to fluctuate at the end of the drainage of pure water, and the pressure reduction was substantially started. Further, conventionally, the introduction of an inert gas was stopped immediately after the drainage of pure water, and thereby the pressure reduction was promoted. As described above, according to the conventional technique, the depressurization step was started immediately after the drainage was completed. However, in this embodiment, the introduction of the inert gas is not stopped immediately after the pure water is drained. In this embodiment, the flow rate of the inert gas introduced is adjusted according to the fluctuation of the pressure inside the outer tank 4 from the end of the drainage of pure water, and the outer tank 4 is adjusted.
The inside is kept in a depressurized state.

In the present specification, the time from the end of drainage of pure water to the start of the depressurizing step inside the outer tank 4 is referred to as "waiting time". According to the present invention, pure water is removed from the surface of the substrate 2 as much as possible before the pressure reduction is started. Therefore, in this embodiment, a “standby time” is provided before the depressurization step, so that the pure water remaining on the surface of the substrate 2 at the end of the drainage step naturally flows downward from the substrate 2. Has been secured.

As a result of the experiment, it was found that by setting the "standby time" to 120 seconds, the amount of adhered fine particles in the drying step can be almost eliminated. FIG. 6 shows the relationship between the waiting time and the amount of increase in the number of adhered fine particles, which is obtained by the experiment. It can be seen from the graph of FIG. 6 that the number of fine particles can be halved by waiting for about 10 seconds as compared with the case of waiting time of 0 seconds. From this result, according to the vacuum drying method,
It can be seen that the pure water remaining on the surface of the substrate 2 at the start of decompression contains a small amount of fine particles, and the fine particles remain on the surface of the substrate 2 even after such pure water is evaporated under reduced pressure. . However, according to the present invention, due to the presence of the waiting step, the amount of pure water remaining on the surface of the substrate 2 at the time of starting depressurization can be sufficiently removed. Therefore, the number of fine particles remaining on the surface of the substrate 2 after the drying is sufficiently reduced.

In the present embodiment, after the predetermined "waiting time" has elapsed, in step (f), the introduction of the inert gas is stopped and the inside of the outer tank 4 is kept until the inner tank 4 reaches about 1 Torr. Decompress. If a means for heating the substrate 2 is provided inside or outside the outer tank 4 so that the substrate 2 is heated during the depressurization step, the drying is further promoted, and thus 1 Torr
Even at pressures above r, sufficient drying is possible. Moreover, the drying time can be shortened by using such a heating means.

In step (g), the inert gas is supplied again to the inside of the outer tank 4 to return the pressure inside the outer tank 4 to almost atmospheric pressure. Then, in step (h), the lid 7 of the outer tank 4 is opened. At this time, if the pressure inside the outer tub 4 is slightly lower than the atmospheric pressure, an air flow from the outside to the inside of the outer tub 4 is generated, and water droplets remaining on the seal portion between the outer tub 4 and the lid 7 thereof are generated. May fly to the surface of the substrate 2 and adhere to the substrate 2. Therefore, when the lid 7 is opened, it is preferable that the atmospheric pressure inside the outer tub 4 be higher than the outside by about 1 mmH2O. In step (i), the carrier 1 in which the substrate 2 is finally inserted is taken out of the apparatus, whereby the drying is completed.

According to this embodiment, as shown in FIG. 6, it can be seen that the amount of adhered fine particles can be markedly reduced as compared with the conventional method which does not involve the standby process after the drainage process. Although the standby time for draining water was 120 seconds in the present embodiment, it may be set to the minimum standby time according to the device to be manufactured.

In the case of the present embodiment, the method of waiting while operating the pump during the waiting step has been described, but the same effect can be obtained by stopping the introduction of the pump and the inert gas at the end of the draining step and waiting. It is possible.

In this embodiment, the standby method is adopted as the draining method. However, if another method of applying an upward acceleration to the substrate 2 is adopted, the time required for draining can be shortened. . For example, when the drainage is completed, the entire vacuum drying apparatus is lifted up with an acceleration of about 5 cm / sec 2, whereby the pure water film adhering to the surface can be removed in a short time. Practically, as in the vacuum drying device shown in FIG. 7, a vibration generator 9 such as a spring is connected to the outer tank 4 and the vibration generator 9 is operated at the time of completion of drainage to generate a vacuum. You may vibrate the whole drying apparatus up and down.

Further, in the present embodiment, the cleaning and drying are carried out in a state where the main surface of the substrate 2 is parallel to the vertical direction, but the present invention is not limited to this.
By tilting the substrate 2, the vertical direction and the main surface of the substrate 2 may form an angle larger than 0 degree.
For example, cleaning and drying by arranging the substrate 2 so that the back surface side (the side on which the semiconductor element is not formed) is upward is performed by cleaning the substrate 2 on the front surface side (the side on which the semiconductor element is formed). Further reduce the amount of water. Such an arrangement can be easily obtained by inclining the carrier installation table 8.

(Embodiment 2) Next, another vacuum drying apparatus and vacuum drying method according to the present invention will be described.

First, the structure of the vacuum drying apparatus will be described with reference to FIG. 1 and 2, corresponding parts are given the same reference numerals. Below,
Differences between the apparatus shown in FIG. 2 and the apparatus shown in FIG. 2 will be described.

The feature of this vacuum drying apparatus is that it is provided with a draining member 5. This draining member 5 has a diameter of 6 mm
It is provided on the carrier installation table 8 including the cylindrical part of. The position and height of the draining member 5 are adjusted so that when the carrier 1 is placed on the carrier installation table 8, the draining member 5 contacts the lower end of the substrate 2 in the carrier 1.

During the draining process, most of the pure water remaining on the surface of the substrate 2 gathers near the lower end of the substrate 2 and flows down to the bottom of the inner tank 3. At this time, the water draining member 5 comes into contact with the pure water remaining on the surface of the substrate 2 and functions to quickly drop the pure water downward. It suffices for the draining member 5 to be in contact with pure water that hangs from the lower end of the substrate 2 in the form of water droplets, and it is not necessary that the lower end of the substrate 2 and the draining member 5 are in complete contact. Specifically, a gap of about 0.1 mm may be provided between the two. On the contrary, the height of the draining member 5 may be set so that the substrate 2 is pushed up from below when the carrier 1 is placed on the carrier installation table 8.

The cross-sectional shape of the draining member 5 is not limited to a circle, and may be any shape such as an ellipse, a rectangle, and a rhombus. The material of the draining member 5 is preferably a material that does not harm the semiconductor, and in addition to quartz, a low dust-generating resin such as Teflon, silicon, or the like is used.

The drying method performed by using this apparatus is substantially the same as the method of Example 1. However, the time required for draining (waiting time) is remarkably shortened by the action of the draining member 5, and the effect of reducing the number of adhered fine particles can be obtained with a waiting time of about 1 to 2 seconds.

(Example 3) Silicon substrate (diameter 150 m
m) was immersed in an aqueous solution of hydrofluoric acid, the silicon substrate was washed with water and dried by the vacuum drying method of Example 1. The aqueous solution of hydrofluoric acid removes the natural oxide film (hydrophilic) formed on the surface of the silicon substrate, thereby exposing the hydrophobic silicon to the surface of the substrate. In this manner, when the substrate having a hydrophobic surface was vacuum dried in this example, the number of fine particles (particle size 0.2 μm) observed on the dried substrate was 10 or less. there were.

During the process of manufacturing a semiconductor device, cleaning and drying are often performed with silicon partially exposed on the surface of the substrate. In this case, i.e.
Even when a hydrophobic portion such as silicon and a hydrophilic portion such as a silicon oxide film are both exposed on the surface of the substrate, according to the present invention, vacuum drying can be performed on both of those portions in a clean state. To be executed.

The drying method according to the present invention is carried out, for example, in the range of about 0.
It is most suitable for manufacturing large-scale integrated circuits including a large number of fine elements such as megabit DRAM designed based on the design rule of 5 μm. In particular, it is possible to dry a substrate having a hydrophobic surface, which has been difficult by the conventional spin drying method or alcohol substitution method, while maintaining an extremely clean state. The present invention is also applicable to drying after cleaning with a liquid such as alcohol or choline instead of pure water.

As is clear from the principle, the present invention is not applied only to the drying of semiconductor substrates. The present invention can be applied to manufacturing that requires cleaning substrates made of various materials such as glass substrates or resin substrates.

[0062]

According to the present invention, the introduction of the draining step can significantly reduce the number of fine particles attached to the substrate surface after vacuum drying, which contributes to the improvement in the manufacturing yield of semiconductor devices.

Further, according to the vacuum drying apparatus of the present invention, it is possible to shorten the time of the draining process, thereby improving the throughput and reducing the manufacturing cost of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a sectional view showing a vacuum drying apparatus used in a vacuum drying method of the present invention.

FIG. 2 is a cross-sectional view showing another vacuum drying apparatus used in the vacuum drying method of the present invention.

3 (a) to (i) are diagrams showing each step of the vacuum drying method according to the present invention.

4A to 4H are diagrams showing each step of a conventional vacuum drying method.

FIG. 5: Diameter 150 dried by a conventional vacuum drying method
showing a distribution of fine particles having a particle diameter of 0.2 μm or more remaining on the surface of a silicon substrate having a size of 0.3 mm

FIG. 6 is a characteristic diagram showing the relationship between the waiting time and the increase in the number of adhering particles in the vacuum drying method of the present invention, obtained by an experiment.

FIG. 7 is a sectional view showing another vacuum drying apparatus used in the vacuum drying method of the present invention.

[Explanation of symbols]

 1 carrier 2 substrate 3 inner tank 4 outer tank 5 drainer 6 water supply / drainage pipe 7 lid 8 carrier installation stand 9 vibration generator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Teruhito Onishi, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Yuichi Hirofuji, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. A cleaning process for cleaning a substrate with pure water; a decompression process for reducing the atmosphere of the substrate from atmospheric pressure, thereby evaporating the pure water remaining on the substrate.
A method for vacuum-drying a substrate, comprising: performing the cleaning step and the depressurizing step in a single vacuum drying apparatus; and the method comprising: The vacuum drying method further includes a draining step of dropping a portion of the pure water remaining on the substrate from the substrate. 2. The vacuum drying device comprises an outer tank having a lid, the inside of which can be shut off from the atmosphere by closing the lid, and an inner tank installed inside the outer tank. Using the apparatus described above, the cleaning step includes a preparatory step of filling the inner tank with pure water, an inserting step of inserting the substrate into the pure water filled in the inner tank, and an inner tank Drainage step of discharging the pure water from the outside to the outside of the outer tank,
The vacuum drying method according to claim 1, which comprises: 3. The vacuum drying method according to claim 2, wherein pure water in the inner tank is heated. 4. The depressurizing step includes a step of depressurizing the pressure in the outer tank to 1 Torr or less after closing the lid of the outer tank. Vacuum drying method. 5. A step of introducing an inert gas into the outer vessel after the depressurizing step, thereby increasing the pressure in the outer vessel above atmospheric pressure, and then opening the lid of the outer vessel. The vacuum drying method according to claim 4, further comprising: 6. The dewatering step starts the depressurization in the depressurizing step from the end of the washing in the washing step,
The vacuum drying method according to claim 1, further comprising a waiting step of delaying the time by 0 seconds or more. 7. The draining step starts the depressurization by the depressurizing step, and starts 10 times after the draining in the draining step.
The vacuum drying method according to claim 2, further comprising a standby step of delaying by at least 2 seconds. 8. The vacuum drying method according to claim 1, wherein the draining step includes a step of moving the substrate so as to have an acceleration in a vertical direction. 9. A vacuum drying apparatus comprising: an outer tank having a lid, which can be shut off from the atmosphere by closing the lid, and an inner tank installed inside the outer tank. After cleaning the substrate with pure water, the atmosphere of the substrate is depressurized from atmospheric pressure, thereby evaporating the pure water remaining on the substrate by a vacuum drying method, in which the inner tank is filled. And a step of cleaning the substrate with the pure water, and draining the pure water from the inner tank to the outer tank while introducing an inert gas into the outer tank with the lid closed. And, after the pure water is completely discharged from the inner tank, the inert gas is continuously introduced into the outer tank until a certain period of time elapses.
In the meantime, a step of draining a portion of the pure water remaining on the substrate from the substrate, and a step of stopping the introduction of the inert gas into the outer tank after the elapse of the certain period of time, A vacuum drying method comprising: a step of discharging the inert gas in the outer tank to the outside of the outer tank, thereby reducing the pressure in the outer tank. 10. The vacuum drying method according to claim 9, wherein the certain period is 10 seconds or more. 11. A step of reintroducing an inert gas into the outer vessel after the depressurizing step, thereby increasing the pressure in the outer vessel above atmospheric pressure, and then opening the lid of the outer vessel. 10. The vacuum drying method according to claim 9, further comprising: 12. The vacuum drying method according to claim 9, wherein the draining step includes a step of moving the substrate so as to have an acceleration in a vertical direction. 13. An outer tank capable of shutting off the inside from the atmosphere, an inner tank provided in the outer tank and capable of storing pure water therein, and a pressure for reducing the pressure in the outer tank. A vacuum drying device provided with a depressurizing means, wherein the inner tank further has at least one water supply / drainage port for supplying and draining the pure water, and the vacuum drying device includes the depressurizing means. The vacuum drying apparatus further comprising means for moving the outer tank so as to have an acceleration in the vertical direction before starting the depressurization by. 14. An outer tank capable of shutting off the inside from the atmosphere, an inner tank provided in the outer tank and capable of storing pure water therein, and a pressure reducing means for reducing the pressure in the outer tank. A vacuum drying apparatus comprising decompression means, wherein the inner tank further comprises at least one water supply / drainage port for supplying and draining the pure water, and at least before starting the vacuum drying process, A draining member for guiding the pure water remaining in the inlet to the water supply / drainage port,
A vacuum drying apparatus having: 15. The vacuum according to claim 14, wherein the draining member is arranged in the inner tank so as to substantially contact the lower end of the substrate at least before the depressurizing step is started. Drying device.