JPS6322671Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a processing apparatus for forming a protective film on the surface of a - group compound semiconductor wafer in the same container immediately after cleaning it.

(Prior Art) Conventionally, - group compound semiconductor wafers cut from ingots have been completed as substrates for crystal growth by the procedure described below. That is,
The wafer cut from the ingot is subjected to mechanical polishing or mechanochemical polishing to give its surface a mirror finish. Thereafter, the wafer is removed from the polishing jig and cleaned to remove the wax used to secure it to the polishing jig. Wash off with reflux cleaning, boiling cleaning, or ultrasonic cleaning with an organic solvent such as acetone or trichlene, spray with inert gas such as nitrogen gas, and dry. After this, these wafers are stored in an alcohol-filled container or dry box or simply a wafer container. The stored wafers are taken out and subjected to the next processing as needed. For example, when a gallium arsenide wafer is used as a substrate for epitaxial growth, the surface is etched by dipping it in a sulfuric acid-based chemical etching solution to obtain a clean surface.
It is set in the growth apparatus.

(Problems with the Prior Art) The conventional wafer processing method has been described above, but this conventional wafer processing method has the following drawbacks. First, each process is independent and uses separate processing equipment, making the work complicated and time-consuming.

Second, because the processes are independent, the cleaned wafer surface is often exposed to the air between processes, and becomes contaminated by minute dust particles in the air adhering to the surface. . This deposit adversely affects subsequent processing, such as a crystal growth step. Third, the wafer surface is susceptible to damage due to complicated processing operations. Fourth, conventional surface etching treatments using sulfuric acid-based chemicals have the following serious drawbacks. In other words, when the wafer is used as a substrate for crystal growth, the surface of the wafer is etched by about 10 to 100 μm just before it is set in the growth apparatus, but as a result of this process, the periphery of the wafer surface, which had been polished to a mirror finish, is inevitably etched. It causes sagging.

Even if this etching process is performed carefully and while stirring the etching solution, the width of 2 to 8 mm from the periphery of the wafer is rounded compared to the center, and the flatness of the wafer is lost when looking at the wafer as a whole. be exposed.

This poor flatness is caused by various subsequent steps, such as the epitaxial growth step, the exposure of photoresist using a mask, or the device fabrication process that requires high uniformity of the epitaxial film layer within the wafer. This becomes a major hindrance and ultimately causes a deterioration in the effective area utilization rate per wafer.

(Purpose of the invention) By using the processing apparatus of the present invention, all of the above-mentioned drawbacks can be solved, time can be shortened by processing a large number of wafers simultaneously, and the process up to the step of forming a protective film can be performed in a series of continuous steps. An object of the present invention is to provide a novel - group compound semiconductor wafer processing apparatus characterized in that it performs as follows.

(Structure of the invention) According to the invention, an organic solvent, water, inert gas, etc., which cleans a group compound semiconductor wafer to be processed or forms a metamorphic layer as a protective film on its surface,
The upper part is filled with halogen gas, hydrogen halide gas, a mixture of these gases and an inert gas, a solution of these gases, an aqueous solution of sodium hypochlorite, or aqueous hydrogen peroxide, and has a heater on the outside. A processing container is provided with a container main body with an open part and a lid provided to cover this opening part, and the processing container can be used for the cleaning by introducing and discharging the liquid or gas by opening and closing a valve. At least three ports or pipes for successive formation of a protective film are provided, one of which is provided in the container body at a position equal to or higher than the height of the wafer when the wafer is loaded, and the other one is located above the height of the wafer. The bubbles are provided at a high position, and the remaining one is provided at the bottom of the container, and any two of the bubbles are opened when introducing the liquid or gas, forming a protective film with the gas, and discharging the gas, There is obtained an apparatus for surface treatment of - group compound semiconductors, characterized in that the valve at the higher position is opened during cleaning and when forming a protective film using a liquid, and the valve at the bottom of the container is opened when discharging the liquid. .

(Operation of the present invention) According to the processing apparatus of the present invention, wafer contamination, damage to the wafer surface, complexity of each process, etc.
The drawbacks of conventional methods, such as surface sag due to etching of the wafer surface, can be eliminated. This is because, according to the processing apparatus of the present invention, after mechanical and chemical polishing, a wafer is cleaned with an organic solvent and a protective film is immediately and uniformly formed on the clean surface in the same apparatus, so that the surface is not contaminated. , and is also protected from damage. Further, if the uniform protective film is removed when the substrate is used, it becomes equivalent to uniform etching, and furthermore, since these steps are performed in series in the same apparatus, the operation becomes very simple.

surface treated by the treatment device of the present invention.
In the case of group compound semiconductor wafers, even when the wafers are used as substrates for crystal growth, the conventional etching treatment using sulfuric acid-based chemicals is not necessarily performed. As a result of studies conducted by the present inventors, it was found that the conventional etching process was not necessarily necessary, and the wafer that had been cleaned with an organic solvent was treated with halogen gas, hydrogen halide gas, an inert gas containing these, or a liquid etching process. When a modified layer is formed on the clean surface by contacting it with a halogen acid, an aqueous solution of sodium hypochlorite, hydrogen peroxide, or pure water, and this is used as a surface protective film, The surface from which the protective film was removed was found to be very good. The properties of the surface protective film vary depending on the treatment chemicals. However, the protective film formed by halogen treatment and the protective film formed by oxidation treatment with sodium hypochlorite etc. are different, but all the steps up to the formation of either protective film are One of the effects of the processing apparatus of the present invention is that a clean surface can be created within the same apparatus and a protective film can be continuously formed while maintaining the clean surface.

In the processing apparatus of the present invention, a protective film formed by halogenating the surface of a group-group compound semiconductor wafer is achieved by introducing halogen gas such as bromine gas or iodine gas, or hydrogen halide gas such as hydrogen fluoride, hydrogen chloride, hydrogen bromide or hydrogen iodide gas, or an inert gas containing at least one of these halogens, or a liquid acid thereof, into the container of the processing apparatus of the present invention, and keeping the temperature inside the container at +10°C to +250°C, and contacting the group-group compound semiconductor wafer. The protective film formed by halogen treatment not only coats the wafer surface for protection, but also transforms a very thin layer of impurities and wafer crystals remaining on the surface into highly volatile compounds. The thickness of this protective film can be changed by, for example, appropriately changing the temperature of the processing container and the processing time during its formation.

On the other hand, in the processing apparatus of the present invention, in order to form a protective film by oxidizing the surface of the - group compound semiconductor wafer, an aqueous solution of sodium hypochlorite or peroxide must be added to the container of the processing apparatus of the present invention. Hydrogen water, pure water, or the vapor of at least one of these, or oxygen gas or inert gas containing the vapor is introduced and kept under a temperature condition of +10°C to +400°C, and the - group compound semiconductor wafer is heated. This is achieved by contacting with.

The protective film formed by oxidation treatment has different characteristics from the above-mentioned protective film formed by halogen treatment, and transforms the wafer surface into a compound that is less susceptible to mechanical damage.

Therefore, a wafer that has been processed to form this protective film is also effective as a passivation for protecting devices processed and provided on the wafer surface. For example, when a gallium arsenide wafer is treated with the above-mentioned chemicals, the surface of the gallium arsenide is transformed into gallium arsenite, and this modified layer is mechanically hard and has good protection against damage and external damage. The thickness of this protective film is determined at the time of its formation, e.g.
It can be changed by appropriately selecting the treatment temperature and time.

A feature of the processing apparatus of the present invention is that all the steps up to the formation of any protective film can be continuously processed within the same apparatus while keeping the surface clean.

Hereinafter, embodiments will be described in detail using the drawings.

(Example 1) FIG. 1 shows a cross-sectional structure of an example of a processing apparatus of the present invention. The container body 1 in which the wafer support stand 3 is housed is provided with pipes 7, 12, 14 and a port 13 for introducing and discharging liquid, vapor, or gas for processing the substrate. Valves 8, 9, 10 for each pipe and mouth
has been established. Similarly, pipe 4 and valve 5 are attached to lid 6.
has been established. Furthermore, a heater 11 was provided around the container to enable the temperature to be raised. Among the above-mentioned inlet/outlet ports and pipes, the inlet/outlet port 13 was provided at a position in the container body 1 at approximately the same height as the pipe 7 which penetrated from the bottom of the container body 1 and extended to the height of the wafer support stand 3.
The processing apparatus of the present invention will be explained using an example of a procedure for surface treatment of a - group compound semiconductor.

A gallium arsenide wafer 2 to be used as a substrate for vapor phase growth is placed on a wafer support stand 3 and placed in a stainless steel container 1 whose inner surface is coated with fluororesin. After that, the fluororesin-coated lid 6, which is equipped with a pipe 4 and a valve 5, was closed, and with the valve 5 open, trichlorethylene was introduced from the pipe 4, which was placed at a position higher than the wafer support 3. Fill the container until it overflows from the pipe 7. At this time valve 8
And valve 9 is closed, and valve 5 or valve 10 is left open.

Fill with trichlorethylene and heat heater 1
1, the temperature inside the container is set to about 60° C., and steam is exhausted from pipe 4 or pipe 7 connected to valve 5 or valve 10, whichever is open. After washing in a heated state for about 20 minutes, open the valve 8 and discharge the trichlorethylene in the container from the port 14 provided at the bottom of the container, and close the valve 8 again.
Fresh trichlorethylene is introduced from pipe 4 and cleaning is performed again in a heated state. Another method of performing the above trichlorethylene cleaning is to close valves 5 and 10, and close valves 8 and 9.
Using a pump or other means such as raising the trichlorethylene to a higher level than the container and allowing it to flow by gravity, introduce the trichlorethylene through the opening provided at the bottom of the container, and then pour the trichlorethylene into the container until it overflows from pipe 7. fill the inside. Thereafter, the valve 8 is closed, the temperature is raised by the heater 11, and the boiling cleaning is performed, and the trichlorethylene vapor is exhausted from the pipe 7. In this case, since the pipe 4 and the valve 5 have no function, the lid 6 may be a simple lid without the pipe 4 and the valve 5. The pipe 7 for overflowing and discharging steam may be replaced by a port 13 provided on the side wall of the container at a position higher than the wafer (for example, at a position as shown in FIG. 27). After repeating the same washing operation 2 to 3 times, the solution is replaced as necessary, and acetone washing and alcohol washing are performed. Thereafter, valves 5 and 10 are closed, valve 8 is opened, and valve 9 is further opened to introduce drying nitrogen gas from pipe 12 through pipe 7 to sufficiently dry the inside of the container. Thereafter, bromine vapor evaporated from liquid bromine is mixed with the drying nitrogen gas to fill the container with bromine vapor. After the bromine gas and wafer are reacted under heating for about 30 minutes, the supply of bromine vapor mixed in the nitrogen gas is stopped, and the residual bromine gas in the container is discharged.
During this time, the power to the heater 11 is turned off to lower the temperature inside the container. After cooling, the wafer is taken out and
Saved. The wafers that underwent such processing in the processing apparatus of the present invention were taken out of the storage container, placed directly in the growth apparatus, and epitaxially grown, but the surface condition of the growth layer was good and the film thickness was not uniform. The effective utilization rate within the wafer surface was extremely high, exceeding 95%.

(Example 2) As the processing apparatus, the example apparatus shown in FIG. 1 was used again. Other functions of the processing apparatus of the present invention will be explained using another example of the surface treatment procedure for - group compound semiconductors.

A gallium arsenide wafer 2 used as a substrate for vapor phase growth was placed on a wafer support 3 and placed in a container 1 in the same manner as in Example 1. Subsequent washing with an organic solvent was performed in the same manner as in Example 1, and the inside of the container was sufficiently dried in the same manner. After that, valves 8 and 9 are closed, valves 5 and 10 are opened, and a 0.3N aqueous solution of sodium hypochlorite is introduced from pipe 4, which is passed through the pipe to a position above wafer support 3. Fill the container until the overflow liquid starts to drain from step 7. With the valve 5 closed, the temperature inside the container is brought to about 70° C. using the heater 11. After processing for about 5 minutes, open the valves 8 and 9, and with the valve 10 closed, introduce pure water from the pipe 7 through the pipe 12, and pour the water into the port 1 provided at the bottom of the container.
4, and the wafer 2 and the inside of the container are washed with running water to quickly replace it with sodium hypochlorite. Note that in the case of using only hydrogen peroxide solution and pure water, the treatment temperature must be increased and the treatment time must be increased. The processing temperature exceeds 100℃,
When processing at temperatures below about 400°C, do not fill the container 1 with the solution, close valves 9 and 10, open valves 5 and 8, and pipe the solution vapor or oxygen gas containing vapor or inert gas into the pipe. It was also possible to introduce it from No. 4 and treat it by reacting with the wafers in the container. When treated with either solution, turn off the heating heater and
When the wafer temperature drops to about 50° C. or less, drying nitrogen gas is introduced from the pipe 12 instead of pure water to sufficiently dry the inside of the container and the wafer. The lid 6 was opened and the processed wafer was taken out.

An apparatus as shown in FIG. 2, which shows another embodiment of the present invention, can also be used for these processes.

(Embodiment 3) FIG. 2 is a sectional view of an apparatus showing another embodiment of the present invention. The container body 21 has an inlet and discharge pipe 2.
5, 27, and 28 were established. In addition, the inlet and outlet pipes 25 and 27 were provided at different levels in the container body at positions higher than the height of the wafer. The inlet and discharge pipe 28 was provided at the bottom of the container. Valve 29,3 for each pipe
0,31 are provided. Furthermore, the lid 26 is provided with a cooling hollow portion 32. A heater 24 for heating the container was provided around the container and at the bottom.

Next, the apparatus according to another embodiment of the present invention shown in FIG. 2 will be explained using an example of a processing procedure. wafer 2
2 is placed on a wafer support stand 23 and housed in the container 21. After that, the lid 26 that allows cooling water to pass through the hollow part 32 of the lid is closed, the valve 31 is closed, and the valves 29 and 30 are opened.
Processing liquid is introduced through a pipe 25 provided on the upper end of the side wall of the container 21, and the processing liquid overflows from a pipe 27 provided on the side wall of the container 21 at a position higher than the height of the wafer 22 housed in the container 21. Fill the container until it begins to drain. The treated waste liquid is discharged from the pipe 28 provided at the bottom of the container by opening the valve 31. On the other hand, when processing with gas, valve 30 is closed and valve 2 is closed.
9 and 31 are opened, processing gas is introduced through either pipe 25 or 28, and processing gas is discharged through either pipe 25 or 28 through which no processing gas is introduced. Further, the treatment can be performed by heating from the heater 24 at an appropriate time. A uniform degraded layer is formed on any wafer obtained from the processing apparatus shown in FIGS. 1 and 2 in which the present invention is implemented, and the wafer is stored as is.

(Effect of the invention) After forming an altered layer in this way, the number of stored substrates required for vapor phase growth is removed from the storage container, and the oxide film of the altered layer is grown using another prescribed method. It was removed just before being installed in the apparatus and immediately inserted into the growth apparatus. When crystal growth was performed, the epitaxial growth layer had no irregularities due to abnormal growth, and there was no dust attached to the surface, clearly demonstrating the effect of the processing apparatus of the present invention in eliminating damage to the surface. Furthermore, the effect of the processing apparatus of the present invention, which improves uniformity and flatness due to no surface sag and simplifies the processing method, was very clearly demonstrated.

Although an embodiment using the apparatus shown in FIGS. 1 and 2 has been described above, the processing apparatus of the present invention is not particularly limited to the shape of the apparatus shown in FIGS. 1 and 2.

[Brief explanation of drawings]

Figures 1 and 2 show an example of a surface treatment apparatus for - group compound semiconductors in which the present invention is implemented.
It is an explanatory view mainly showing a cross section. In the figure, 1 and 21 are container bodies in which a series of procedures can be carried out, 2 and 22 are - group compound semiconductor wafers to be processed, and 3 and 23 are wafer support stands.
4, 7, 25 and 27 are inlet/outlet pipes provided in the containers 1, 21 higher than the height of the wafers 2, 22; 13 is an inlet/outlet port also provided in a location higher than the wafer height; 14. 28 is the inlet/outlet pipe provided at the bottom of the container; 12 is the inlet/outlet pipe provided at the bottom of the container;
is the branched introduction and discharge pipe, 6 and 26 are the lids of the container, and 32 is the hollow part of the lid through which water flows.
Reference numerals 5, 8, 9, 10, 29, 30, and 31 indicate valves for controlling various gases, vapors, and liquids. 1
1 and 24 are heaters for heating the wafer support stands 3 and 23, and arbitrarily control the temperature inside the container.

Claims (1)

[Scope of utility model registration request] Organic solvents, water, inert gases, halogen gases, hydrogen halide gases, or combinations of these gases and inert gases to clean the target compound semiconductor wafer or to form a metamorphosed layer as a protective film on its surface. The container body is filled with a mixed gas or a solution of these gases, an aqueous solution of sodium hypochlorite, or hydrogen peroxide, has a heater on the outside, and has an open top, and a lid that covers this open part. Furthermore, this processing container is provided with at least three ports or pipes through which the cleaning and protective film formation are successively performed by introducing and discharging the liquid or gas by opening and closing a valve. One of them is provided in the container body at a position above the height of the wafer when the wafer is loaded, and the other one is provided at a higher position,
The remaining one is provided at the bottom of the container, and when the liquid or gas is introduced, the gas forms a protective film, and the gas is discharged, one of the two valves is used.
- group compound semiconductor, wherein the valve at the higher position is opened during cleaning and when forming a protective film with liquid, and the valve at the bottom of the container is opened when discharging the liquid. Surface treatment equipment.