JP2832770B2 - Surface treatment method for Si-doped semiconductor epitaxial growth substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art When epitaxially growing a semiconductor material such as GaAs or AlGaAs, a P-type layer or an n-type layer is prepared by changing the growth temperature by doping with Si. 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-like manner. As described above, if the Si crystal remains on the surface of the epi layer, the wafer is cracked during an exposure process performed in an LED manufacturing process or the like, and thus the Si crystal is mechanically scraped off using a device such as a router.

[0003]

However, when the Si crystal is mechanically scraped off from the surface of the epitaxial layer, the grown G
The aAs crystal or AlGaAs crystal may be impacted and the epilayer may be damaged, breaking the wafer. Further, when the precipitation of the Si crystal is large, the Si crystal cannot be completely removed even by using the above equipment. Therefore, since the Si crystal remains on the wafer surface in the form of protrusions, when the wafer on which the mask is superimposed is brought into close contact with the exposure machine table in the exposure step, the wafer crystal is broken by the action of the protrusion-like Si crystal.

An object of the present invention is to solve 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 an Si crystal deposited on the surface of an epitaxial layer by etching. Things.

[0005]

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

The present invention will be described in more detail. As the Si-doped semiconductor epitaxial growth substrate to which the surface treatment method of the present invention is applied, for example, a Si-doped GaAs epitaxial growth layer, a substrate having an AlGaAs epitaxial growth layer formed on the substrate surface, and the like can be mentioned. . The above AlG
The aAs epitaxial growth layer is made of Al _x Ga ₁ -x As.
(0 <X ≦ 0.3).

As the strong alkaline solution for etching and removing 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 suitably used. This strong alkaline solution has a pH of 12 to 14, preferably around pH 13, and can selectively etch Si crystals.

[0008] As the strong alkaline solution, it is desirable to use a strong alkaline solution composed of an aqueous solution of potassium hydroxide in particular, having a concentration of 3% by weight to a saturated solution, preferably 20 to 50% by weight.
Particularly preferably, it is used after adjusting to 30 to 40% by weight. When the concentration of the strong alkaline liquid is less than 3% by weight,
It is not preferable because the dissolving power is weak and it takes a long time to remove the Si crystal by etching. Although a saturated solution can be used, if the concentration is too high, the dissolving power is too strong, and it tends to etch not only the Si crystal but also the AlGaAs epilayer, for example. Is desirable.

Further, the ability of the strong alkaline solution to etch the Si crystal, that is, the strength of the dissolving power is affected by the temperature as well as the concentration of the strong alkaline solution. If so, the dissolving power tends to be weak. In consideration of 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 100C, preferably at 30-80C. If the temperature of the strong alkali liquid exceeds 100 ° C., the dissolving power is too high to selectively etch the Si crystal, and if it is lower than 5 ° C., the dissolving power is undesirably reduced.

[0010] 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 appropriate to use a 1 wt% aqueous solution of potassium hydroxide (70 ° C) for about 1 to 2 hours.

[0011]

According to the surface treatment method of the present invention, Si crystals precipitated in the form of mountain ridges on the surface of the epilayer due to the dissolving power of the strong alkaline solution can be selectively removed by etching. Therefore, there is no need to mechanically scrape the Si crystal from the epi layer surface,
The cause of breaking the wafer can be eliminated without damaging the epi layer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to an embodiment. Example 1 FIG. 1A shows a scanning electron microscope (hereinafter, referred to as S) of the epilayer surface of a Si-doped AlGaAs epitaxial growth substrate.
EM), and (b) shows a schematic view of this SEM photograph. In FIG. 1B, 1 is Si
It is a crystal which is deposited on the surface of the AlGaAs epilayer 2 in a mountain range. The AlGaAs epilayer 2 is composed of A
A crystal of l _x Ga ₁ -x As (0 <X ≦ 0.3) is grown. The substrate 1 was immersed in an aqueous solution of potassium hydroxide (pH 13) adjusted to a concentration of 33% by weight (70 ° C.) for 2 hours, washed with water and dried, and then subjected to SEM.
Observation of the surface with a magnification of 75 (magnification: 75) showed that the Si crystal 1 shown in FIG. 1 was selectively etched away without damaging the surface of the AlGaAs epilayer 2 as shown in the SEM photograph shown in FIG. I was Thus, this aqueous potassium hydroxide solution exhibited excellent Si crystal dissolving power and selective solubility.

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

Comparative Examples 1 to 4 The procedure of Example 1 was repeated except that the concentration, temperature and immersion time of the aqueous potassium hydroxide solution were as shown in Table 1. In Nos. 3 and 3, the aqueous solution of potassium hydroxide had poor Si crystal dissolving power, and the Si crystal was not selectively removed by etching. As shown in the SEM photograph shown in FIG.
It remained on the surface of the s epi layer. On the other hand, in Comparative Examples 2 and 4, the aqueous solution of potassium hydroxide had an excessively high Si crystal dissolving power, resulting in poor selective etching of Si crystals.
As shown 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, a Si-doped GaAs epitaxial growth substrate was used in place of the Si-doped AlGaAs epitaxial growth substrate. A Si-doped GaAs epitaxial growth substrate from which crystals were selectively removed by etching was obtained.

[0017]

According to the present invention, it is possible to selectively remove, by etching, Si crystals deposited in the form of protrusions on the epilayer surface by the dissolving power of a strong alkaline aqueous solution. Therefore, use of expensive equipment can be eliminated. In addition, since the Si crystal is not mechanically scraped off from the surface of the epi layer, the cause of the defect that breaks the wafer can be eliminated without damaging the surface of the epi layer, thereby improving the yield in production.

[Brief description of the drawings]

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

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

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

FIG. 4 is an SEM photograph of a surface etched up to an epi layer after performing a surface treatment of another comparative example.

[Explanation of symbols]

 1 Si crystal 2 Epitaxial layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int.Cl. ⁶ , DB name) H01L 21/306-21/3063 H01L 21/308 H01L 33/00 H01L 21/203 H01L 21/205 H01L 21 / 208 H01L 21/18-21/20 H01L 21/34-21/36

Claims (5)

(57) [Claims] 1. An Si-doped semiconductor epitaxial growth substrate is immersed in a strong alkaline solution to deposit S
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 by forming a Si-doped GaAs epitaxial growth layer or a Si-doped AlGaAs epitaxial growth layer. 3. The method according to claim 1, wherein the strong alkaline liquid is an aqueous solution of an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide. 4. The method according to claim 1, wherein the strong alkaline solution is an aqueous solution of potassium hydroxide having a concentration of 3% by weight or more. 5. The method according to claim 1, wherein the temperature of the strong alkaline solution is 5 to 100 ° C.