JPH05166785A - Storing method for semiconductor wafer - Google Patents

Abstract

PURPOSE:To make it possible to omit etching which is usually done as pretreatment immediately before the epitaxial growth is provided, by polishing the surface of a semiconductor wafer to mirror-finished level, cleaning, washing the wafer and then storing it in an inactive gas. CONSTITUTION:After cutting a single crystal into 1mm thick wafers 2, etching lapping, and polishing it, the wafer is cleaned organically, and then washed by water. Next, the wafer 2 is immersed in a container containing cleaning mixed liquid chiefly composed of phosphoric acid, and the surface of the wafer 2 is cleaned. After washing the wafer 2 with water and drying it, it is housed in a wafer case 1a, and a holding tool 1c is placed on the wafer case, and further a cap 1b is put on the wafer case. The wafer case is put in a bag consisting of aluminum laminated sheets, and sealed by filling the inside of the bag with N2 gas. As a result, it is made possible to take out the wafer immediately before epitaxial growth, and to make epitaxial growth for it without etching and cleaning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer storage method, and more particularly to a wafer storage method suitable for use in the case where an InP wafer for epitaxial growth is mirror-polished and then stored until it is subjected to epitaxial growth. is there.

[0002]

2. Description of the Related Art InP compound semiconductors have been attracting attention in recent years as materials for light emitting devices or microwave devices. An InP wafer used as a substrate for such devices or elements is obtained by slicing an InP single crystal into thin pieces, and lapping or other polishing steps to finally obtain a mirror surface. The mirror-polished InP wafer has various epitaxial layers laminated according to the application to form a semiconductor device or an optical element. For example, the most promising field of InP is application to semiconductor lasers, and at present, a fiber having a wavelength range of 1.3 μm to 1.55 μm in which the transmission loss of a quartz optical fiber is the smallest is put into practical use. A substrate having an InGaAsP layer formed on an InP wafer is used as a substrate for an element that generates laser light in this wavelength range. Such a semiconductor layer is generally formed by growing an epitaxial layer on a substrate. However, the mirror-polished I
It is considered that a work-affected layer of about submicron is formed on the surface of the nP wafer during mirror polishing. Therefore, there has been proposed a method of obtaining a clean surface by cleaning an InP wafer after mirror polishing with a mixed solution of phosphoric acid-hydrogen peroxide-water or hydrofluoric acid-hydrogen peroxide-water. (JP-A-62-252140).

[0003]

However, conventionally, mirror-polished InP wafers are usually stored for several months after being cleaned and before being actually epitaxially grown. It was saved. Therefore, there is a possibility that the oxides of In and P and organic substances adhere to the surface of the InP wafer and are contaminated during storage. As a result, an etching process is indispensable just before the epitaxial growth of a wafer that has been washed and stored, as a pretreatment for creating a more perfect mirror-free surface. Note that this etching treatment is performed, for example, by H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 5: 1: 1 (volume ratio).
Or a 1% by volume Br ₂ -methanol solution.

The present invention has been made to solve the above problems, and an object of the present invention is to save an InP wafer storage technique capable of omitting an etching step as a pretreatment performed immediately before epitaxial growth. To provide.

[0005]

In order to achieve the above object, the present invention is such that an InP wafer used for epitaxial growth is mirror-polished, washed, washed with water, and then stored in an inert gas. .. The above washing is preferably performed with a mixed solution of phosphoric acid-hydrogen peroxide-water or hydrofluoric acid-hydrogen peroxide-water. The wafer is stored, for example, in a resin-made wafer case made of polypropylene or the like and sealed in an aluminum laminate sheet together with an inert gas.

[0006]

According to the above-described means, since the InP wafer is stored in an inert gas after cleaning, even if it is left for several months before the epitaxial growth, the InP wafer is newly oxidized during that period. In addition, organic substances do not adhere to the surface and are contaminated, and if taken out immediately before epitaxial growth, it is possible to grow a good-quality epitaxial layer on the wafer surface even if epitaxial growth is performed without etching or cleaning as a pretreatment. Will be able to. In addition, a clean InP surface can be obtained with a mixed solution of phosphoric acid-hydrogen peroxide-water or a mixed solution of hydrofluoric acid-hydrogen peroxide-water, which can be stored in an inert gas for several months. The cleanliness of the surface can be maintained. Further, the above-mentioned means can
Not only is it effective in suppressing the adhesion of n and P oxides, but it is also effective in preventing the deterioration of the wafer case made of polypropylene or the like that houses the wafer, and the adhesion of organic substances can be greatly reduced.

[0007]

[Example] A Fe-doped InP single crystal having a diameter of 2 inches, which was pulled up by the liquid-encapsulated Czochralski method, was cut into a 1 mm-thick wafer, subjected to etching, lapping, and polishing, and then organically washed with trichlene, acetone, and methanol. After that, it was washed with water. After this, phosphoric acid: hydrogen peroxide: water = 20: 5: 1 ratio (volume ratio)
The surface of the wafer was cleaned by immersing the above-mentioned wafer in a container containing the mixed solution of (5) for 5 minutes. Then, after washing with water and drying, the wafer 2 is housed in a case body 1a of a polypropylene wafer case having a shape as shown in FIG. 1, a supporting tool 1c is put on, a lid 1b is put on, and an aluminum laminated sheet is then put on. The above-mentioned wafer case was placed in a bag made of, and the inside of the bag was filled with N ₂ gas and sealed.

After the above-mentioned wafer case was stored at room temperature for 3 months, the bag was opened and the wafer was taken out. The MBE method (molecular beam epitaxy) was performed without pretreatment (etching).
Doped In _{0. 53} Ga _0. And the ₄₇ As epitaxial layer grown to a thickness of 0.5μm on the wafer surface by. For comparison, after opening, normal pretreatment _{(H 2 SO 4: H 2} O 2:
H ₂ O = 5: 1: 1 mixed solution), and then an InGaAs epitaxial layer was grown by the MBE method. When the surface of the epitaxial layer of these wafers was observed with a differential interference microscope, both were similarly good mirror surfaces. Furthermore, was evaluated the electrical characteristics of the epitaxial layer of the wafer surface, showed good values mobility 6030cm ² / V · s, the sheet carrier density 8.36 × ^{10 10} cm- ² at room temperature.

In the above embodiment, the InP wafer is housed in a wafer case made of polypropylene or the like and enclosed in an aluminum laminate sheet together with N ₂ gas. However, it may be enclosed in an airtight container together with N ₂ gas. Instead of N ₂ gas, Ar gas or other inert gas may be used as the filling gas. In addition, the washing solution before storage is phosphoric acid:
It is not limited to the mixed solution of hydrogen peroxide: water = 20: 5: 1 (volume ratio), and a mixed solution of hydrofluoric acid-hydrogen peroxide-water may be used. Furthermore, in the above embodiment, the method of storing the InP wafer has been described. However, the present invention is not limited to this, and can be applied to the storage of general semiconductor wafers used for epitaxial growth such as GaAs wafers. In that case, an appropriate cleaning liquid may be selected and used according to the type of semiconductor.

[0010]

As described above, according to the present invention, the InP wafer used for epitaxial growth is mirror-polished, washed, washed with water, and then stored in an inert gas. Even if it is left for a while, the oxides and organic substances of In and P will not be newly attached to the surface during that period to be contaminated. If it is taken out just before the epitaxial growth, etching or cleaning as a pretreatment should be performed. Even if the epitaxial growth is performed as it is, there is an effect that a good quality epitaxial layer can be grown on the wafer surface. In addition, a clean InP surface can be obtained with a mixed solution of phosphoric acid-hydrogen peroxide-water or a mixed solution of hydrofluoric acid-hydrogen peroxide-water, which can be stored in an inert gas for several months. The cleanliness of the surface can be maintained. Furthermore, the method of the present invention is not only effective in suppressing the adhesion of In and P oxides on the wafer surface, but also can prevent the deterioration of the wafer case made of polypropylene or the like for housing the wafer. There is an advantage that the adhesion of organic substances can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a wafer case suitable for use in a wafer storage method according to the present invention.

[Explanation of symbols]

 1a Case body 1b Lid 1c Support tool 2 Wafer

Claims (3)

[Claims] 1. A method for storing a semiconductor wafer, which comprises mirror polishing a semiconductor wafer to be epitaxially grown, washing it with water, and then storing it in an inert gas. 2. When the semiconductor wafer is an InP wafer, it is washed with a mixed solution of phosphoric acid-hydrogen peroxide-water or a mixed solution of hydrogen fluoride-hydrogen peroxide-water. 1. The method for storing a semiconductor wafer according to 1. 3. The semiconductor wafer according to claim 1, wherein the semiconductor wafer after cleaning is housed in a resin case and enclosed in an inert gas in a metal laminate sheet for storage. Preservation method.