JP2000036481A - Drying method for semiconductor substrate and drying device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor substrate with superior drying property by fixing recovery time, regardless of the fluctuations of processing capacity and also fixing the exposure time of an object to be processed, based on it. SOLUTION: This drying method is an IPA(isopropyl alcohol) drying method for exposing only the object to be processed or the object to be processed and a dummy member in the saturated vapor of an organic solvent, and the exposure time in the saturated vapor is constituted of the recovery time of the saturated steam and the additional time and is fixed, regardless of the fluctuations in the capacity of the object to be processed. This drying device is provided with a processing tank 2 for processing the object 7 to be processed or an object to be processed and the dummy member 10, an evaporation means 6 for heating and evaporating the organic solvent 8 and forming the saturated vapor 9, a recovery means 3 for cooling, liquefying and recovering the rising saturated vapor 9, a transfer means 4 capable of holding and transferring the object to be processed and a tray 5 for recovering the organic solvent from the surface of the object to be processed. It is desirable to separately provide a tray 12 for recovering the organic solvent from the surface on the lower part of the dummy member 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of drying a semiconductor substrate by steam and a drying apparatus therefor, and more particularly to a method of drying a semiconductor substrate after cleaning with excellent drying properties irrespective of fluctuations in processing capacity. It is about technology that can be.

[0002]

2. Description of the Related Art A substrate used for manufacturing a semiconductor device is washed and washed in a final stage, and then its surface is dried. Usually, as a technique used for such surface drying, isopropyl alcohol (hereinafter, referred to as an organic solvent) is used.
An IPA vapor drying method using "IPA" has been frequently used, and many proposals have been made in relation to the improvement of the drying method (for example, Japanese Patent Application Laid-Open Nos. 5-74753 and 5-74753). 6-196471).

FIG. 6 is a diagram showing a sectional configuration of a conventional IPA drying apparatus. As is apparent from FIG.
Is provided with a processing tank 2 configured to be able to carry an object to be processed 7 from above. An IPA solvent 8 and a heater 6 for heating and evaporating the IPA solvent 8 are disposed below the processing tank 2. On the upper exit side of the processing tank 2, a cooling snake tube 3 is provided to raise
Since the PA vapor 9 can be quickly cooled and liquefied and recovered, no vapor flows out of the cooling coil 3. Therefore, the heated and evaporated IPA vapor 9 is filled in the processing tank to form a saturated vapor layer.

When drying a substrate, a plurality of substrates 7 washed and washed with water are exposed to IPA saturated vapor while being held by a plurality of holders 4, so that the surface of the substrate is saturated due to a temperature difference between the substrate and the saturated vapor. The vapor condenses. At this time, water having a high surface tension and a low vapor pressure remaining on the surface of the substrate due to the cleaning is replaced by a vaporized IPA solvent having a low surface tension and a high vapor pressure, and water is removed from the substrate surface. The coagulating liquid containing water drops from the surface of the substrate and is collected in a tray 5 provided below the substrate. Thereafter, the substrate 7 held by the holder 4 is carried out from above the processing tank 2 and the substrate is dried by volatilizing the IPA solvent on the substrate surface.

[0005]

As described above, in the IPA drying, the surface temperature of the washed substrate (for example, 20 ° C.)
(30 ° C.) and the saturated vapor temperature (80 ° C. to 90 ° C.) cause the saturated vapor to condense on the substrate surface, so that the vapor is rapidly consumed at the same time that the substrate is exposed to the IPA saturated vapor layer. As a result, the IPA vapor layer goes out of saturation, the vapor density decreases, and the volume of the vapor layer also decreases.

As shown in FIG. 6, even after the substrate is exposed to the IPA saturated vapor layer, the IPA solvent 8 is heated to
Since the A vapor 9 is continuously supplied into the processing tank, the state of the saturated vapor layer is restored to the initial state with the lapse of time. Normal,
As described above, the time when the vapor density reduced by exposing the substrate to the IPA saturated vapor layer or the reduced volume of the vapor layer recovers to the initial vapor density or volume of the saturated vapor layer is referred to as a recovery time. . Since the recovery time has a great effect on the drying property of the substrate to be processed, the time for exposing the substrate to the IPA saturated vapor, that is, the exposure time, is determined based on the recovery time.

Although it depends on the processing capacity of the object to be processed, it is usually difficult to replace the water remaining on the substrate surface with the IPA solvent within the recovery time of the IPA vapor in drying the substrate with IPA. Therefore, the exposure time of the substrate is calculated by adding a certain additional time to the recovery time so that the replacement of the water with the IPA solvent is sufficiently completed. For example, a fixed time is selected as the additional time within a range of 0.5 min to 2 min.

FIG. 2 is a diagram showing a change in recovery time (sec) when the number of processed substrates is changed in order to change the processing capacity of a substrate (12-inch wafer) as an object to be processed. As can be seen from the figure, the recovery time of the IPA vapor layer depends on the processing capacity of the substrate, and is substantially linearly reduced as the number of processed sheets to be dried decreases at the same time. Therefore, the proper exposure time of the substrate also depends on the recovery time, and therefore varies according to the processing capacity of the substrate.

In recent years, in response to a demand for higher efficiency in a semiconductor device manufacturing process, the diameter of a substrate to be processed has been increased, and the number of substrates to be simultaneously processed has been increasing. There is a large difference in processing capacity between the maximum processing and the fraction processing that occurs at the end of the processing lot. At this time, if fraction processing is performed while the exposure time of the substrate is set on the basis of the recovery time corresponding to the maximum number of processed sheets, the drying time is secured more than necessary, resulting in an overdry state. That is, when the processing capacity is reduced, the recovery time is shortened, and the condensing action of the IPA vapor on the substrate surface is completed in a short time. Then volatilization of IPA solvent,
Although evaporation occurs, the heat of vaporization lowers the substrate surface and condenses the IPA vapor again. Thereafter, volatilization and condensation are repeated until the drying time ends. Such overdrying significantly deteriorates the wettability of the substrate surface and makes it easier for particles to adhere.

On the other hand, when the exposure time of the substrate is set on the basis of the recovery time corresponding to the fractional processing and the maximum number of processed substrates is processed, the drying time becomes insufficient and the moisture on the surface of the substrate and the IPA solvent become less. Substitution is not reliably performed.
Therefore, drying defects such as watermarks occur on the surface of the substrate.

The adjustment of the recovery time, which serves as a reference for the exposure time, can be achieved by controlling the amount of IPA vapor supplied into the processing tank. Specifically, by controlling the heating temperature of a heater that generates steam by heating the IPA solvent, the supply amount of IPA vapor can be directly adjusted. At the same time, the heating temperature of the heater is kept constant, and the amount of generated steam is not changed, but it is also possible by adjusting the amount of IPA vapor supplied into the processing tank. However, it is difficult to apply the former method of controlling the heater heating temperature without lowering the productivity in a drying step in which the heaters are successively processed. Also, the latter method of directly adjusting the supply amount of IPA vapor has a problem in how to treat excess IPA vapor in a limited processing tank, and cannot be adopted.

As described above, if it is difficult to adjust the recovery time in accordance with the processing capacity of the substrate to be processed in the IPA drying which is continuously processed, the processing capacity of the substrate fluctuates, resulting in overdrying. There is a possibility that the wettability may be deteriorated due to the drying and poor drying due to the watermark or the like may occur.

The present invention has been made in view of such a problem in the conventional IPA drying, and the recovery time of the IPA saturated vapor and the fixed additional time are notwithstanding the fluctuation of the processing capacity of the object to be processed. The purpose of the present invention is to perform IPA drying of a semiconductor substrate as an object to be processed, while keeping the exposure time composed of the following constant.

[0014]

Means for Solving the Problems The present inventor has conducted various studies on IPA drying in order to achieve the above-mentioned object, and as a result, if the processing capacity of the processing object fluctuates, the other It has been found that a semiconductor substrate with excellent drying properties can be obtained even when the exposure time for exposing the substrate to the IPA vapor layer is constant by adjusting the processing capacity by simultaneously processing the dummy members. The present invention is based on the results of such studies, and includes the following drying method (1) and drying apparatus (2).

(1) The object to be treated after the cleaning is exposed to a saturated vapor of an organic solvent for a certain period of time to condense the vapor of the organic solvent on the surface of the object to be treated and replace the remaining moisture with the organic solvent. In the drying method for volatilizing the organic solvent on the surface of the object, the exposure time in the saturated vapor is constituted by the recovery time of the saturated vapor and the additional time, and is constant irrespective of the change in the capacity of the object. A method for drying a semiconductor substrate.

In the drying method (1), the dummy member, in addition to the object to be processed, is exposed to saturated vapor of an organic solvent.
In this case, the dummy member is desirably made of single crystal silicon or quartz. When exposed to the saturated vapor of the organic solvent, the dummy member is held outside to protect the reference surface of the workpiece,
The distance between the dummy member and the object to be processed is the same as the distance between adjacent objects to be processed, and the opposing surfaces of the dummy member and the object to be processed have the same surface area, and the total surface area of the dummy member is insufficient. Is desirably the same as the total surface area. In order to reuse the organic solvent condensed and collected on the surface of the dummy member, it is preferable that the dummy member be subjected to only temperature adjustment and exposed to saturated vapor of the organic solvent.

(2) A processing tank 2 capable of processing while holding the object 7 after cleaning, an evaporating means 6 for heating and evaporating the organic solvent 8 to form saturated vapor in the processing tank, A collection unit 3 provided at an upper portion of the processing tank and configured to cool and liquefy the rising saturated steam 9 for collection, a transfer unit 4 capable of holding and transferring an object to be processed, and provided at a lower portion of the container; A saucer 5 for recovering the organic solvent from the surface of the object to be treated is provided, and the exposure time of the object to be treated in the saturated vapor is constituted by the recovery time of the saturated vapor and the additional time, and the capacity of the object to be treated is reduced. An apparatus for drying a semiconductor substrate, which is constant regardless of fluctuations (see FIG. 1).

In the drying apparatus of the above (2), the dummy member 10 as well as the object to be processed is exposed to the saturated vapor 9 of the organic solvent. In this case, it is desirable to separately provide a tray 12 below the dummy member 10 for collecting the organic solvent from the surface.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The drying method of the present invention is a method of exposing only an object to be treated or an object and a dummy member to IPA saturated vapor to replace the surface moisture with an organic solvent.
The steam drying method is characterized in that the exposure time in the saturated steam is made constant as the recovery time of the saturated steam and the additional time, regardless of the fluctuation of the capacity of the object to be treated.

The drying apparatus of the present invention is an apparatus for performing the above-described drying method, and includes a processing tank capable of processing the object to be cleaned or a processing tank capable of holding the object and the dummy member, and an IPA. Evaporating means for forming saturated vapor, collecting means for liquefying and recovering the rising IPA saturated vapor, transferring means capable of holding and transferring the object to be processed, and removing the organic solvent from the surface of the object to be processed. A collecting tray is provided.

According to the drying method and the apparatus of the present invention, even when the exposure time in the saturated steam is kept constant regardless of the fluctuation of the processing capacity of the processing object, the drying property of the surface of the processing object may be impaired. Absent. In particular, even in fractional processing that occurs at the end of a processing lot in which the processing capacity fluctuates greatly with the increase in the diameter of the semiconductor substrate, it is possible to prevent overdrying and avoid particle adhesion due to reduced surface wettability. become.

FIG. 3 shows the relationship between the substrate position and the surface contact angle (°) when ten substrates (12-inch wafers) to be processed are simultaneously dried by using the heating temperature of the IPA solvent as a parameter. I have. As is clear from the figure,
The outermost first substrate is susceptible to the action of the IPA vapor, and the wettability due to overdrying is significantly reduced as compared to the third and fifth substrates.

At this time, in order to adjust the processing capacity of the object to be processed, the dummy member exposed to the saturated vapor of the organic solvent includes:
Desirably, it is made of single crystal silicon or quartz. This is because a material equivalent to that of the substrate is effective in appropriately adjusting the processing capacity of the substrate to be processed.

Further, when the dummy member is exposed to the IPA saturated vapor, the dummy member is held outside the reference surface so as to protect the reference surface of the object to be processed. And the dummy member are arranged so as to have a uniform interval. The semiconductor substrate has a “front surface” and a “back surface”, and the reference surface of the object to be processed means the “front surface” of the semiconductor substrate. Therefore, the dummy member is disposed outside the substrate surface to prevent a decrease in the non-defective product rate in the fraction processing, and to maintain uniform spacing between the adjacent workpiece and the dummy member, thereby achieving uniform drying properties. .

FIG. 4 is a view for explaining the holding state of the dummy member and the object to be processed when exposed to IPA saturated vapor. As shown in FIG. 4, the dummy member 10 is held outside the substrate 7 which is the object to be processed. To effectively protect the outermost object to be processed and make the drying property uniform, It is desirable to satisfy the following condition.

First, the distance between the dummy member 10 and the substrate 7 to be processed is the same as that of the adjacent substrate 7 (c in the figure).
= D or e = f) holds. Next, the dummy member
The surfaces (the X and Y surfaces or the Z and W surfaces in the figure) where the substrate 10 and the substrate 7 face each other have the same surface area. Then, in order to adjust the processing capacity of the substrate, the total surface area of the dummy member 10 is made equal to the total surface area of the insufficient substrate. Specifically, when processing an object to be processed with six substrates in a processing tank having a processing capacity of ten substrates, the insufficient substrate 4
A dummy member having a total surface area for the number of sheets is required. At this time, as shown in FIGS. 4 (a) and 4 (b), the shape of the dummy member is such that the surface area of the opposite surface is the same as that of the object to be processed, and the total surface area of the substrate whose total surface area is insufficient. The shape is not particularly limited as long as it has a surface area equivalent to that of.

The dummy member is exposed to saturating vapor of an organic solvent only by controlling the temperature without being washed, that is, without being wetted with the cleaning liquid, and is placed under the dummy member from the surface thereof. A separate tray for collecting the solvent is provided, and the organic solvent condensed and collected on the surface of the dummy member is reused. If the dummy member is washed and then subjected to IPA drying in order to make the same surface conditions with the object to be treated, a large amount of water will be mixed in the IPA solvent recovered from the dummy member. It becomes difficult. Therefore, the dummy member was dried by IPA without being washed.
The solvent A does not contain water, and can be reused by filtering after recovery. However, if the temperature of the object to be treated and the temperature of the dummy member are significantly different, the condensation reaction of the IPA vapor is completely different. I am adjusting.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific structure of the present invention will be described below with reference to the drawings, and further, the remarkable effects of the present invention will be shown by examples. In the drawings showing the device, common members are denoted by the same reference numerals.

FIG. 1 is a diagram showing an example of a sectional configuration of a drying apparatus according to the present invention. The drying apparatus of the present invention has an IP shown in FIG.
A processing tank 2 similar to the A drying apparatus is provided. An IPA solvent 8 and a heater 6 for heating and evaporating the IPA solvent 8 are disposed below the processing tank 2, and a cooling snake tube 3 is provided above the processing tank 2. These operations are the same as those of the conventional IPA drying apparatus.

In the drying apparatus shown in FIG. 1, the number of processed substrates that can be simultaneously dried is set to a maximum of 10, and a configuration is shown in which the dummy member 10 is exposed to the IPA saturated steam 9 in addition to the four substrates.
The surface (reference plane) of the substrate 7 is directed rightward in the drawing, and the dummy member 10 is located outside (right side in the drawing) so as to protect the surface of the substrate, and at the same interval as the adjacent substrate,
The opposing surfaces of the dummy member 10 are held by the dummy transfer means 11 so as to have the same surface area as the substrate. In the embodiment, each dummy member has a processing capacity of 2.5 substrates, and the correction procedure is as shown in Table 1. That is, when processing four substrates with a maximum of ten substrates, two dummy members for correction were prepared at the same time. The material of the dummy member is quartz, and the total surface area of each is 2.
The surface area is adjusted so that the total surface area is equivalent to five sheets. If necessary, the surface may be slit or uneven.

[0031]

[Table 1]

FIG. 5 shows actual measurement results of the recovery time when the number of substrates to be simultaneously dried by the drying apparatus of the present invention is changed from one to ten. It is preferable that the correction dummy member be divided and managed so as to be as close as possible to the processing capacity of the substrate. However, even with the correction procedure shown in Table 1, the recovery time can be adjusted to be as small as 23 seconds to 25 seconds. Thus, it was confirmed that the drying property was sufficiently ensured uniformly.

As shown in FIG. 1, in the drying apparatus of the present invention, a collecting tray 12 is provided below the dummy member 10. In the case where only the temperature adjustment is performed and the IPA drying is performed without washing the dummy member 10, the IPA solvent condensed on the surface of the dummy member can be recovered by the receiving tray 12, filtered, and reused as it is. It is. On the other hand, since the IPA solution recovered from the substrate contains water, a regeneration treatment by a gas-liquid separation membrane or distillation is required.

As described above, in order to make the condensation of the IPA vapor uniform, it is necessary to adjust the temperature so that the surface temperatures of the substrate and the dummy member are the same. Usually, the drying of the dummy member is limited as in the case of the fraction processing, and therefore, the temperature is kept at the same temperature as the cleaning temperature of the substrate outside the drying device. At this time, since the dummy member does not leave moisture on the surface as compared with the cleaned substrate, absorption of the latent heat of saturated steam is reduced when the dummy member is exposed to IPA saturated steam. For this reason, it is desirable to maintain the surface temperature of the dummy member slightly lower than the substrate cleaning temperature.

Using a conventional IPA drying apparatus and the drying apparatus of the present invention, the drying condition was confirmed. The substrate was washed before drying with IPA by rinsing with a mixed solution of aqueous ammonia and hydrogen peroxide, followed by rinsing with pure water. The exposure time of the substrate in IPA saturated vapor is 1 with the maximum number of substrates processed being 10 and the additional time of 95 seconds based on the recovery time of 25 seconds.
4 substrates and 10 substrates dried simultaneously in 20 sec (2 min)
It was a sheet. In the conventional IPA drying apparatus, only the substrate is dried without using the dummy member. In the drying apparatus of the present invention, the substrate and the dummy member are dried using the dummy member according to the correction procedure shown in Table 1 above. At this time, the particle value (> 0.25 μm) of the dried substrate surface was measured, and the results are shown in Table 2.

[0036]

[Table 2]

As is clear from Table 2, the number of particles was increased in the conventional IPA drying apparatus in the case of processing four sheets having a small processing capacity, but in the drying apparatus of the present invention, regardless of the fluctuation in the processing capacity, the number of particles increased. It can be seen that the generation of particles is small and the drying property is excellent.

[0038]

According to the drying method and the drying apparatus of the present invention, the recovery time of the saturated vapor of IPA is kept constant, regardless of the fluctuation of the processing capacity of the processing object, and the exposure of the processing object based on the recovery time. With a constant time, a semiconductor substrate having excellent drying properties can be provided. Moreover, the collected I
Since the water contained in the PA solvent can be eliminated,
It is possible to efficiently reuse the IPA solvent.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a cross-sectional configuration of a drying device of the present invention.

FIG. 2 is a recovery time (se) when the number of processed substrates is changed in order to change the processing capacity of a substrate to be processed.
It is a figure which shows the change of c).

FIG. 3 is a diagram illustrating a relationship between a substrate position and a surface contact angle (°) when ten substrates to be processed are simultaneously dried.

FIG. 4 is a diagram illustrating a holding state of a dummy member and a workpiece when exposed to IPA saturated steam.

FIG. 5 is a diagram showing actual measurement results of the recovery time when the number of substrates to be simultaneously dried by the drying apparatus of the present invention is changed from one to ten.

FIG. 6 is a diagram showing a cross-sectional configuration of a conventional IPA drying apparatus.

[Explanation of symbols]

 1: Drying device 2: Processing tank 3: Cooling means 4: Transfer means for substrate, holder 5: Receiving tray, 6: Heating means, heater 7: Workpiece, substrate 8: IPA solvent, 9: IPA vapor 10: Dummy member 11: Dummy member transfer means 12: Dummy member tray

Claims (8)

[Claims] An object to be treated after the cleaning is exposed to a saturated vapor of an organic solvent for a certain period of time to condense the vapor of the organic solvent on the surface of the object to be treated and replace the remaining moisture with the organic solvent.
In the drying method of evaporating the organic solvent on the surface of the workpiece,
A method for drying a semiconductor substrate, wherein the exposure time in the saturated vapor is constituted by a recovery time of the saturated vapor and an additional time thereof, and is constant irrespective of a change in the capacity of the object to be processed. 2. The method for drying a semiconductor substrate according to claim 1, wherein the dummy member is exposed to a saturated vapor of an organic solvent in addition to the object to be processed. 3. The method for drying a semiconductor substrate according to claim 2, wherein said dummy member is made of single crystal silicon or quartz. 4. When exposed to saturated vapor of an organic solvent,
The dummy member is held outside to protect the reference surface of the object to be processed. The distance between the dummy member and the object to be processed is the same as the distance between adjacent objects to be processed. 3. The method for drying a semiconductor substrate according to claim 2, wherein the surface facing the object has the same surface area, and the total surface area of the dummy member is the same as the total surface area of the insufficient substrate. 5. The method according to claim 2, wherein the dummy member is exposed to the saturated vapor of the organic solvent only by adjusting the temperature, and the organic solvent condensed and recovered on the surface of the dummy member is reused. A method for drying a semiconductor substrate according to the above. 6. A processing tank capable of processing while holding an object to be processed after cleaning, an evaporating means for heating and evaporating an organic solvent to form a saturated vapor in the processing tank, and A collecting means for cooling and liquefying the rising saturated vapor, and a transferring means capable of holding and transferring the object to be processed; and an organic solvent provided at a lower portion of the container and provided on the surface of the object to be processed. Is provided, and the exposure time of the object to be treated in saturated steam is made up of the recovery time of the saturated steam and the additional time, and that the exposure time is constant irrespective of the change in the capacity of the object to be treated. Characteristic device for drying semiconductor substrate. 7. The apparatus for drying a semiconductor substrate according to claim 5, wherein the dummy member is exposed to a saturated vapor of an organic solvent in addition to the object to be processed. 8. An apparatus for drying a semiconductor substrate according to claim 7, wherein a tray for recovering an organic solvent from the surface is separately provided below said dummy member.