JP2001196347A - Method of manufacturing III-V compound semiconductor wafer - Google Patents

Abstract

(57) [Problem] To provide a high quality III without colloidal silica remaining on the surface even when the surface is polished using the colloidal silica.
Providing a Group V compound semiconductor wafer; SOLUTION: A step of polishing the surface of the wafer 1 using a polishing liquid 32 containing colloidal silica, a step of immersing the wafer 1 whose surface has been polished in a pool tank 41 of an alkaline solution 42, and a step of immersing the wafer 1 in the pool tank 41. Removing the cleaned wafer 1 and cleaning it with an alkaline solution 52 without drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group III-V compound semiconductor wafer of the periodic table used for semiconductor integrated circuit devices and the like, and more particularly, to a compound semiconductor such as gallium-arsenic (GaAs). The present invention relates to a method for manufacturing a wafer.

[0002]

2. Description of the Related Art Conventionally, III-V group compound semiconductor wafers such as GaAs have been used as a raw material for elements constituting a photodiode or a semiconductor laser. This III
When manufacturing a Group V compound semiconductor wafer, first,
An ingot made of a II-V compound semiconductor is formed. Next, the ingot is sliced into a plate-like body, and a surface treatment such as etching and lapping is performed on the surface of the plate-like body to form a wafer. Next, the surface of the wafer is polished, and the abrasive is washed with water. Thereafter, alkali cleaning is performed. Finally, an epitaxial layer is formed on the surface of the wafer.

[0003]

In recent years, in order to reduce the surface roughness of a wafer, a technique using colloidal silica as an abrasive in the above-mentioned polishing step has been developed. However, when colloidal silica is used as the polishing agent, the colloidal silica may not be completely removed from the wafer surface in the alkaline cleaning after polishing. When an epitaxial layer is grown on the surface of the wafer where the colloidal silica remains, there is a problem that crystal defects occur in the epitaxial layer and cause defects when used as the above-described photodiode or semiconductor laser.

Accordingly, the present invention has been made to solve the above-mentioned problems, and provides a method of manufacturing a high-quality III-V compound semiconductor wafer without leaving colloidal silica on the surface. That is.

[0005]

Means for Solving the Problems The present inventors have proposed III-
When the cause of colloidal silica remaining on the surface of the group V compound semiconductor wafer was studied, the following findings were obtained.

First, colloidal silica is made of silicon dioxide (S
iO ₂ ) is a colloidal suspension of water, and in water, a hydroxyl group (OH group) is present on its surface and is negatively charged. Polishing of the III-V compound semiconductor wafer is completed,
Immediately after washing with water, an alkaline solution is attached to the surface of the wafer, and a large amount of hydroxide ions (OH ^- ions) are present. At this time, although the negatively charged colloidal silica adheres to the surface of the wafer, it does not strongly adhere to the surface of the wafer where many hydroxide ions are present. However, when the pure water covering the washed wafer is exposed to the air, the pure water absorbs carbon dioxide in the air and becomes acidic. As a result, the amount of hydroxide ions in the water covering the wafer surface is reduced, and the colloidal silica is strongly adsorbed on the wafer surface. The colloidal silica strongly adsorbed in this manner is not removed in the subsequent alkali washing.

According to the method for manufacturing a group III-V compound semiconductor wafer according to the present invention, which has been made based on such findings, the surface of the group III-V compound semiconductor wafer is polished using a polishing liquid containing colloidal silica. Immersing a III-V compound semiconductor wafer having a polished surface in a pool of an alkaline solution;
Taking out the group V compound semiconductor wafer and cleaning the surface with an alkaline solution without drying the surface.

According to such a method, first, the wafer is polished using colloidal silica, and then the wafer is immersed in a pool of an alkaline solution. As a result, the surface of the wafer is completely covered with the alkaline solution, so that the colloidal silica remaining on the surface of the wafer does not strongly adhere to the surface of the wafer. Since a large amount of alkaline solution is present in the pool, the alkaline solution does not become acidic even if it absorbs carbon dioxide in the air. Further, in the next step, the wafer immersed in the pool is taken out, and its surface is washed with an alkaline solution without drying. As a result, the alkali cleaning is performed with the hydroxide ions remaining on the surface of the wafer, so that the alkali cleaning can be performed with colloidal silica not strongly adsorbed on the surface of the wafer. As a result, colloidal silica can be completely removed by alkali washing. Therefore, if an epitaxial film is grown on a wafer manufactured by this method, a high quality III-V compound semiconductor wafer without crystal defects in the epitaxial film can be provided.

Preferably, the alkaline solution contains an organic alkaline solution. In this case, since the organic alkaline solution is generally composed of carbon, hydrogen, oxygen, and nitrogen, it does not remain on the surface of the wafer as compared with the inorganic alkaline solution containing metal. As a result, if an epitaxial layer is grown on the surface of this wafer, the leakage current at the interface with the epitaxial layer is suppressed, and a higher quality III-
A group V compound semiconductor wafer can be provided.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a method of manufacturing a group III-V compound semiconductor wafer according to the present invention. FIG. 1A is a diagram for explaining a first step of the manufacturing method of the present invention, and FIG.
It is a figure for explaining a 2nd process, and (C) is a figure for explaining a 3rd process. Referring to FIG. 1A, according to the present invention, first, an ingot of a GaAs compound semiconductor is sliced into a disk-shaped plate. By subjecting the surface of the plate-like body to a surface treatment such as etching and lapping, III
A wafer 1 as a group V compound semiconductor wafer is prepared. The wafer 1 has a diameter of 2 to 6 inches (5.08 to 1).
5.2 cm), and the thickness is 25 to 650 μm
It is. The wafer 1 is fixed to a wafer holding jig 23. The wafer holding jig 23 is fixed to a disk-shaped rotary pad 21.
It is possible to rotate in the direction shown by.

The wafer 1 is in contact with the polishing pad 13. The polishing pad 13 is made of foamed polyurethane and has a disk shape with a diameter of 23 inches (58 cm).
The polishing pad 13 is fixed to a disk-shaped support plate 11, and the support plate 11 can rotate together with the rotating shaft 12 in a direction indicated by an arrow R <b> 1. A nozzle 31 is positioned above the polishing pad 13, and a polishing liquid 32 is ejected from the nozzle 31.

Using such an apparatus, first, the nozzle 3
The polishing liquid 32 is ejected from 1. The polishing liquid contains 0.5% by weight of colloidal silica and 2% by weight of INSEC manufactured by Fujimi Incorporated. The flow rate of the polishing liquid 32 is set to 0.5 liter / minute. In this state, the rotating shaft 12
And 22 are rotated in the directions indicated by arrows R1 and R2. The rotation speed of both the rotation shafts 12 and 22 is 60 rotations per minute. Further, a load is applied to the rotating shaft 22 so that the load applied to the wafer 1 per unit area is 150 gf / cm ² . As a result, the surface of the wafer 1 is polished by the polishing pad 13 and then washed with pure water.

After the polishing and washing, the plurality of wafers 1 are held by a wafer holding jig 43 with reference to FIG. In this state, the wafer holding jig 43 and the wafer 1 are immersed in a pool tank 41 as a pool containing an alkaline solution 42. The alkaline solution 42 is composed of an aqueous amine solution as an organic alkaline solution. As the amine aqueous solution, an aqueous solution of an amine as shown below can be used.

Ethylhydroxylamine C ₂ H ₅ ONH ₂ 2-ethoxyethylamine C ₂ H ₅ OCH ₂ CH ₂ NH ₂ triethanolamine (HOCH ₂ CH ₂ ) ₃ N diethanolamine (HOCH ₂ CH ₂ ) ₂ NH ethylamine C ₂ H ₅ NH ₂ trimethylamine (CH ₃ ) ₃ N diethylamine (C ₂ H ₅ ) ₂ NH dimethylamine (CH ₃ ) ₂ NH ethanolamine HOCH ₂ CH ₂ NH ₂ trimethyl (2-hydroxymethyl) ammonium hydroxide: (choline) ( ^{_{CH 3) 3 N + CH 2}} CH 2 OH · OH - tetraethylammonium hydroxide _{(C 2 H 5) 4 N} + · OH - tetramethylammonium hydroxide ^{_{(CH 3) 4 N + ·}} OH - also in the air In order not to become acidic even if carbon dioxide is absorbed, the content of the amine is 0.1%. It is preferable that the weight% or more. By immersing the wafer 1 in the alkaline solution 42 for several minutes, the surface of the wafer 1 is covered with hydroxide ions. Therefore, the negatively charged colloidal silica does not strongly adhere to the surface of the wafer 1.

Referring to FIG. 1C, the wafer 1 is taken out of the alkaline solution 42 by using a wafer holding jig 43.
Next, without drying the alkaline solution on the surface of the wafer 1,
The wafer 1 is immersed in a cleaning tank 51 filled with an alkaline solution 52. The alkaline solution 52 is composed of an aqueous solution of an amine similar to the alkaline solution 42 of FIG. Next, from the ultrasonic oscillator 54 attached to the cleaning tank 51,
Generates ultrasonic waves. This ultrasonic wave is applied to the surface of the wafer 1 to remove colloidal silica and other foreign substances on the surface of the wafer 1. At this time, since the negatively charged colloidal silica is not strongly adsorbed on the surface of the wafer 1 covered with hydroxide ions, when the colloidal silica is irradiated with ultrasonic waves, the colloidal silica immediately Removed from the surface. Thus, the surface cleaning of the wafer 1 is completed. Next, the wafer 1 is taken out from the cleaning tank 51 and the surface of the wafer 1 is dried. Thereafter, an epitaxial film is grown on the surface of the wafer 1 and the wafer 1 is cleaved into a predetermined shape to be used as a semiconductor laser or a photodiode.

According to the manufacturing method configured as described above,
First, in the step shown in FIG. 1B, the polished wafer 1 is immersed in a pool tank 41 filled with an alkaline solution 42 immediately after washing with running water. Thereby, the surface of the wafer 1 is completely covered with hydroxide ions. Next, wafer 1
Is taken out of the pool tank 41 and the wafer 1 is immersed in the cleaning tank 51 for alkali cleaning before the alkaline solution on the surface of the wafer 1 is dried.
The hydroxide ions will be present. Therefore, the colloidal silica does not strongly adhere to the surface of the wafer 1. As a result, the colloidal silica can be easily removed by washing in the step shown in FIG.
Thereafter, by growing an epitaxial film on the surface of the wafer, a high-quality wafer having an epitaxial film without crystal defects can be obtained.

In the step shown in FIG. 1B, a plurality of wafers 1 are immersed in a pool tank 41. As described above, by immersing the wafers 1 in the pool tank 41, a large amount of wafers 1 can be processed in a short time, and the production capacity can be improved and the increase in the manufacturing cost can be minimized. If the manufacturing cost is not considered, the present invention can be implemented by flowing an alkaline solution over the surface of the wafer 1.

Although the embodiment of the present invention has been described above, the embodiment shown here can be variously modified.

First, a GaAs compound semiconductor substrate was used as a III-V compound semiconductor substrate, but the present invention is not limited to this, and an InP compound semiconductor substrate, an AlG
An aAs compound semiconductor substrate can also be used.

The amount of colloidal silica in the polishing liquid 32 and the number of rotations of the rotating shafts 12 and 22 can be appropriately changed according to the size of the wafer to be polished.

Although the amount of the alkaline substance in the alkaline solutions 42 and 52 is not particularly limited, it is preferable that the alkaline substance is kept at a concentration that can maintain the alkalinity even when absorbing carbon dioxide in the atmosphere. desirable.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0023]

According to the present invention, even if the surface is polished using colloidal silica, the colloidal silica can be completely removed by subsequent washing, and high quality II can be obtained.
An IV compound semiconductor wafer can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of manufacturing a group III-V compound semiconductor wafer according to the present invention.

[Explanation of symbols]

1 wafer, 32 polishing liquid, 41 pool tank, 42, 5
2 Alkaline solution, 51 cleaning tank, 54 ultrasonic generator.

Claims (2)

[Claims] 1. A step of polishing a surface of a group III-V compound semiconductor wafer using a polishing liquid containing colloidal silica; and dipping the group III-V compound semiconductor wafer whose surface has been polished into a pool of an alkaline solution. A method for producing a group III-V compound semiconductor wafer, comprising: a step of taking out the group III-V compound semiconductor wafer immersed in the pool, and washing the surface with an alkaline solution without drying the surface. 2. The method for manufacturing a group III-V compound semiconductor wafer according to claim 1, wherein said alkaline solution includes an organic alkaline solution.