JPH05182949A - Method of treating surface of si-doped semiconductor epitaxial growth substrate - Google Patents

Abstract

PURPOSE:To provide a method of treating the surface of an Si-doped semiconductor epitaxial growth substrate, which is capable of etching away selectively an Si crystal deposited on the surface of an epitaxial layer. CONSTITUTION:An Si-doped semiconductor epitaxial growth substrate is dipped in a strong alkali solution and an Si crystal deposited on the surface of an epitaxial layer is etched away. The Si crystal deposited in a mountain range form on the surface of the epitaxial layer can be selectively etched away. Accordingly, the use of a high-cost apparatus can be dispensed with. Moreover, as the Si crystal is not shaved off mechanically from the surface of the epitaxial layer, the surface of the epitaxial layer is never marred, the cause of a failure of cracking a wafer can be eliminated and the yield in the production of the wafer is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for a Si-doped semiconductor epitaxial growth substrate used for manufacturing LED chips.

[0002]

2. Description of the Related Art When a semiconductor material such as GaAs or AlGaAs is epitaxially grown, Si is doped to change the growth temperature to form a P-type layer or an n-type layer. However, when Si is doped, Si crystals are deposited on the surface of the epitaxial layer (hereinafter referred to as an epi layer) in a mountain range. Thus, if the Si crystal remains on the surface of the epi layer, a wafer crack occurs during the exposure process performed in the LED manufacturing process or the like. Therefore, it was mechanically scraped off using a device such as a router.

[0003]

However, when the Si crystal is mechanically removed from the surface of the epilayer, the grown G
The aAs crystal or AlGaAs crystal may be impacted, and the epi layer may be damaged to break the wafer. Further, when the amount of Si crystals precipitated is large, the Si crystals cannot be completely scraped off even by using the above equipment. Therefore, since Si crystals remain on the wafer surface in the form of protrusions, when the wafer on which the mask is stacked is brought into close contact with the exposure machine table in the exposure step, the action of the protrusion-shaped Si crystals causes the wafer to crack.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a surface treatment method for a Si-doped semiconductor epitaxial growth substrate which can selectively remove Si crystals deposited on the epilayer surface by etching. It is a thing.

[0005]

The surface treatment method of the present invention is characterized in that the Si-doped semiconductor epitaxial growth substrate is immersed in a strong alkaline solution to remove the Si crystal deposited on the surface by etching.

Explaining the present invention in more detail, examples of the Si-doped semiconductor epitaxial growth substrate to which the surface treatment method of the present invention is applied include a Si-doped GaAs epitaxial growth layer and a substrate having an AlGaAs epitaxial growth layer formed on the substrate surface. .. AlG above
The aAs epitaxial growth layer is made of Al _X Ga _1-X As.
The crystal of (0 <X ≦ 0.3) is grown.

As a strong alkaline solution for etching away the Si crystals deposited on the surface of the epitaxial layer of the Si-doped semiconductor epitaxial growth substrate, for example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide is used. It can be used preferably. This strong alkaline solution has a pH of 12 to 14, preferably around pH 13, and is capable of selectively etching Si crystals.

As the above-mentioned strong alkaline solution, it is desirable to use a strong alkaline solution composed of an aqueous solution of potassium hydroxide. The concentration is 3% by weight to a saturated solution, preferably 20 to 50% by weight.
It is particularly preferably adjusted to 30 to 40% by weight before use. When the concentration of this strong alkaline liquid is less than 3% by weight,
It is not preferable because it has a weak dissolving power and it takes a long time to remove Si crystals by etching. Although it can be used in a saturated solution, if the concentration is too high, the dissolving power is too strong, and not only Si crystal but also the AlGaAs epilayer tends to be etched. Is desirable.

Further, the ability of the strong alkaline solution to etch Si crystals, that is, the strength of the dissolving power is influenced by not only the concentration of the strong alkaline solution but also the temperature. Then, the dissolving power tends to be weak. Considering these conditions, the temperature of the strong alkaline solution is preferably set to a high temperature because the etching time can be shortened.
It is used at 100 ° C, preferably 30 to 80 ° C. When the temperature of the strong alkaline solution exceeds 100 ° C., the dissolving power is too high to selectively etch Si crystals, and when it is lower than 5 ° C., the dissolving power decreases, which is not preferable.

Therefore, the time for immersing the Si-doped semiconductor epitaxial growth substrate in the strong alkaline solution is appropriately determined according to the strength of the dissolving power of the strong alkaline solution and the amount of Si crystals deposited on the surface. 30-40
It is suitable to use a potassium hydroxide aqueous solution (70 ° C.) of wt% for about 1 to 2 hours.

[0011]

According to the surface treatment method of the present invention, Si crystals deposited in a mountain range on the epilayer surface by the dissolving power of the strong alkaline solution can be selectively removed by etching. Therefore, it is not necessary to mechanically remove the Si crystal from the surface of the epi layer,
It does not damage the epi layer and eliminates the cause of cracking the wafer.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 FIG. 1A shows a scanning electron microscope (hereinafter, S) of an epilayer surface of a Si-doped AlGaAs epitaxial growth substrate.
(EM) photograph, (b) represents a schematic diagram of this SEM photograph. In FIG. 1B, 1 is Si
It is a crystal deposited on the surface of the AlGaAs epilayer 2 in a mountain range. The AlGaAs epilayer 2 is
A crystal of l _X Ga _1-X As (0 <X ≦ 0.3) was grown. The substrate 1 was immersed in a potassium hydroxide aqueous solution (70 ° C.) of pH 13 adjusted to a concentration of 33% by weight for 2 hours, then washed with water and dried, and then SEM.
When the surface was observed at a magnification of 75 times, the Si crystal 1 shown in FIG. 1 was selectively removed by etching without damaging the surface of the AlGaAs epilayer 2 as shown in the SEM photograph shown in FIG. Was there. Thus, this potassium hydroxide aqueous solution showed excellent Si crystal dissolving power and selective solubility.

Examples 2 to 4 The same procedure as in Example 1 was repeated except that the concentration of the aqueous potassium hydroxide solution, the temperature and the immersion time of the substrate were as shown in Table 1. Also in the example, the aqueous potassium hydroxide solution shows excellent Si
It exhibits a crystal dissolving power and a selective dissolving property, and does not damage the surface of the AlGaAs epilayer as in the case of the above-mentioned Example 1, and Si
A Si-doped GaAs epitaxial growth substrate having an AlGaAs epilayer in which crystals were selectively etched away was obtained.

Comparative Examples 1 to 4 Comparative Example 1 was carried out by the same method as in Example 1 except that the concentration of the aqueous potassium hydroxide solution, the temperature and the immersion time of the substrate were as shown in Table 1. In Nos. 3 and 3, the aqueous solution of potassium hydroxide had a poor ability to dissolve Si crystals, and the Si crystals were not selectively removed by etching. As shown in the SEM photograph of FIG.
s remained on the surface of the epi layer. On the other hand, in Comparative Examples 2 and 4, since the Si crystal dissolving power of the potassium hydroxide aqueous solution was too strong, the selective etching property of the Si crystal was poor, and S shown in FIG.
As in the EM photograph, the AlGaAs epilayer was etched and the surface was damaged.

[0015]

[Table 1]

Example 5 In the method of Example 1, when a Si-doped GaAs epitaxial growth substrate was used in place of the Si-doped AlGaAs epitaxial growth substrate, Si-like Si deposited on the surface of the GaAs epilayer as in Example 1 was used. A Si-doped GaAs epitaxial growth substrate in which the crystal was selectively removed by etching was obtained.

[0017]

EFFECTS OF THE INVENTION According to the present invention, the Si crystals that are deposited in the form of protrusions on the surface of the epilayer can be selectively removed by etching due to the dissolving power of the strong alkaline aqueous solution. Therefore, the use of expensive equipment can be eliminated. Further, since the Si crystal is not mechanically cut off from the epi layer surface, the epi layer surface is not damaged, the cause of defects that break the wafer can be eliminated, and the production yield is improved.

[Brief description of drawings]

FIG. 1A is a SEM photograph of the surface of an epilayer formed on a Si-doped semiconductor epitaxial growth substrate, and FIG. 1B is a schematic view thereof.

FIG. 2 S of the epilayer surface after the surface treatment of the present invention
It is an EM photograph.

FIG. 3 is an S of the epilayer surface after the surface treatment of the comparative example.
It is an EM photograph.

FIG. 4 is an SEM photograph of the surface of the comparative example, in which the epilayer is etched after the surface treatment.

[Explanation of symbols]

 1 Si crystal 2 Epitaxial layer

Claims (5)

[Claims] 1. An Si-doped semiconductor epitaxial growth substrate is dipped in a strong alkaline solution to deposit S on the surface thereof.
A surface treatment method for a Si-doped semiconductor epitaxial growth substrate, which comprises removing an i crystal by etching. 2. The surface treatment method for a Si-doped semiconductor epitaxial growth substrate according to claim 1, wherein the Si-doped semiconductor epitaxial growth substrate is formed with a Si-doped GaAs epitaxial growth layer or a Si-doped AlGaAs epitaxial growth layer. 3. The surface treatment method for a Si-doped semiconductor epitaxial growth substrate according to claim 1, wherein the strong alkaline solution is an aqueous solution of an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide and lithium hydroxide. 4. The surface treatment method for a Si-doped semiconductor epitaxial growth substrate according to claim 1, wherein the strong alkaline solution is an aqueous potassium hydroxide solution having a concentration of 3% by weight or more. 5. The surface treatment method for a Si-doped semiconductor epitaxial growth substrate according to claim 1, wherein the temperature of the strong alkaline solution is 5 to 100 ° C.