JPH0139210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a first step of forming an etching mask on a - group compound semiconductor substrate or layer;
The present invention relates to an improvement in a method for manufacturing a semiconductor device, comprising a second step of etching the - group compound semiconductor substrate or layer using the etching mask as a mask.

Conventionally, as a manufacturing method for such a semiconductor device,
- group compound semiconductor substrate or layer, for example, InP,
Ga _x In _1-x , As _1-y P _y (0≦x≦1, 0≦y≦
1), and the etching mask is SiO ₂
Alternatively, for Si ₃ N ₄ , it has been proposed that the etching treatment be carried out using an etching solution made of bromomethanol, a hydrochloric acid-based etching solution, or an aqua regia-based etching solution.

However, in such conventional manufacturing methods for semiconductor devices, the etching solution used in the etching process corrodes the AZ photoresist (manufactured by Shippray), so the etching process is performed using an etching mask made of AZ photoresist as an etching mask. It was not possible to do so using a mask.

For this reason, there is a drawback in that an etching mask cannot be easily and minutely formed on a - group compound semiconductor substrate or layer.

The reason is as follows.

That is, if the etching mask is an etching mask made of AZ photoresist, on the - group compound semiconductor substrate or layer,
An etching mask can be formed simply by forming a layer of AZ photoresist and then exposing and developing that layer.
Moreover, since the etching mask is formed from the AZ photoresist layer, the etching mask can be formed finely.

However, if the etching mask is an etching mask made of SiO ₂ or Si ₃ N ₄ , the
A layer made of SiO ₂ or Si ₃ N ₄ is formed, a photoresist layer is formed on the layer, and exposure and
A mask layer made of photoresist is obtained by developing, and then the photoresist layer is used as a mask.
This is because an etching mask can only be obtained by etching a layer made of SiO ₂ or Si ₃ N ₄ and then removing the mask layer made of photoresist.

Therefore, the present invention proposes a novel method for manufacturing a semiconductor device free from the above-mentioned drawbacks, which will become clear from the detailed description below.

The present inventors confirmed the following as a result of various experiments.

That is, a mixture of bromine, acid, and water is -
Group compound semiconductor crystals, especially InP crystals, GaxIn1−
Although it easily attacks xAsyPy crystals (hereinafter, for the sake of simplicity, it is assumed that - group compound semiconductor crystals are InP crystals) at a relatively high rate, SiO ₂ ,
Si ₃ N ₄ , AZ photoresist, etc. (hereinafter, for simplicity, they will be described as AZ photoresist) are not substantially immersed.

The reason is presumed to be as follows.

In other words, bromine water achieves an equilibrium state using the mechanism expressed as 2H ₂ O + 2Br ₂ 4HBr + 20...(1).If bromine water, which has achieved such an equilibrium state, acts on an InP crystal, Then, the InP crystal is oxidized by the mechanism expressed as 2InP+80→In ₂ O ₃ +P ₂ O ₅ (2).

In addition, In oxide (In ₂ O ₃ ) and P oxide (P ₂ O ₅ ) obtained by such oxidation can be oxidized with acids such as hydrochloric acid (HCl) and phosphoric acid (H ₃ PO ₄ ). , and water, when the acid is hydrochloric acid, In ₂ O ₃ +6HCl→2InCl ₃ +3H ₂ O ……(3a) P ₂ O ₅ +3H ₂ O→2H ₃ PO ₄ ……(3b) InCl ₃ of the formula (3a) is easily dissolved in a mixed solution of acid and water, just as InCl 3 of formula (3a) is easily dissolved in water.

Therefore, InP crystals can be easily formed in a mixture of bromine, acid, and water using the mechanism expressed as InP + 3HCl + 4Br ₂ + 4H ₂ O → InCl ₃ + H ₃ PO ₄ + 8HBr (4) when the acid is hydrochloric acid. It is easily dissolved, as it is dissolved in.

The present inventors also confirmed the following.

That is, if the etching treatment for the InP crystal is performed using a mixed solution of bromine, acid, and water as the etching solution, the InP crystal can be easily etched according to the reaction rate. This means that when the mixed solution is a 22°C liquid containing saturated bromine water, phosphoric acid, and water mixed in a volume ratio of 2:1:15, etching of InP crystals while stirring the mixed solution is possible. When we measured the relationship between the etching depth D (μm) of the InP crystal and the etching time T (seconds) when the etching process was performed and when the etching process was performed without stirring, the results are shown in Figure 1. This is clear from the results shown below. Note that FIG. 1 also shows similar measurement results when the same etching process was performed on Ga _x In _1-x As _1-y P _y .

Furthermore, the present inventors also confirmed the following.

In other words, if an InP crystal is etched using a mixed solution of bromine, acid, and water as the etching solution, the InP crystal can be etched relatively quickly within a range of a relatively large volume ratio of acid to bromine and water. Etched quickly and easily. This means that the mixed solution is a mixture of saturated bromine water, phosphoric acid, and water at a volume ratio of 2:n:15 (where n is an arbitrary number) at 22°C, and a saturated bromine water and hydrochloric acid solution. When the relationship between the etching speed V (μm/min) and the value of n was measured in the case of a solution at 22°C in which 2:n:15 and water were similarly mixed at a volume ratio of 2:n:15, the relationship between the etching rate V (μm/min) and the value shown in Figure 2 was obtained. This is clear from the results shown below.

However, even if a similar etching process is performed on the AZ photoresist, the AZ photoresist is not substantially etched.

The present inventors also confirmed the following.

In other words, if the etching process for InP crystals is performed using a mixed solution of bromine, acid, and water as the etching solution, the InP crystals will be etched at a relatively high rate within a relatively large volume range of bromine and acid relative to water. , easily etched. This means that the mixed solution contains saturated bromine water, phosphoric acid, and water in 2 parts.
When the relationship between the etching rate V and the value of m was measured in the case of 22°C liquids mixed at a volume ratio of 1:m (where m is an arbitrary number),
This is clear from the results shown in FIG. 3.

However, even if a similar etching process is performed on the AZ photoresist, the AZ photoresist is not substantially etched.

Furthermore, the present inventors performed selective etching on a substrate made of InP crystal using an etching mask made of AZ photoresist, using a mixed solution of bromine, acid, and water as the etching solution.

In such cases, the mixed solution is a mixture of saturated bromine water, phosphoric acid, and water in a volume ratio of 2:1:15.
In the case of the solution at 22° C., the substrate 1 made of InP crystal was easily anisotropically etched as shown by the reference numeral 2 in FIGS. 4 and 5.

In addition, Figure 4 shows that the main surface of the substrate made of InP crystal is
When the etching mask is made of the (100) plane of InP crystal and the etching mask is made of AZ photoresist, it has a lattice pattern extending in the [110] axis direction of the InP crystal on the main surface of the substrate made of InP crystal. , shows the results of the etching process. In Fig. 4, the direction parallel to the paper surface is the [110] direction of the InP crystal.
It is axial.

Figure 5 also shows that the main surface of the substrate made of InP crystal is
Similar results are shown for the (001) plane of an InP crystal. Note that in FIG. 5, the direction perpendicular to the paper surface is the [110] axis direction.

Based on the above, the inventors and others (A)
A first step of forming an etching mask on the - group compound semiconductor substrate or layer, and a second step of performing an etching process on the - group compound semiconductor substrate or layer using the etching mask as a mask. In a method for manufacturing a semiconductor device having
(B) We have proposed the present invention, in which the etching treatment in the second step is performed using an etching solution consisting of a mixture of bromine and an acid, which may be composed of hydrochloric acid or phosphoric acid, and water. Ivy.

From the above, the method for manufacturing a semiconductor device according to the present invention has been clarified.According to the method for manufacturing a semiconductor device according to the present invention, as is clear from the above, detailed explanation will be omitted, but the etching solution is bromine and bromine. Since it is a mixed solution of acid and water, it has the great feature that an etching mask can be easily and minutely formed on a - group compound semiconductor substrate or layer.

This is even more so in this case since the etching mask can be made of AZ photoresist.

Further, the method for manufacturing a semiconductor device according to the present invention includes -
InP crystal or Ga _x In _1-x As _1-y compound semiconductor substrate or layer suitable for forming an optical semiconductor device
When it is made of _Py crystal, it has the characteristics that it is suitable for use in manufacturing optical semiconductor devices.

[Brief explanation of drawings]

FIG. 1 shows the etching depth D versus the etching time T (seconds) when a semiconductor crystal is etched using a mixed solution of bromine, acid, and water to explain a semiconductor device according to the present invention. (μ
It is a figure showing the relationship of (m). Figure 2 shows a similar
FIG. 3 is a diagram showing the relationship between the etching rate V and the ratio of acid to bromine and water when a semiconductor crystal is etched using a mixed solution of bromine, acid, and water. FIG. 3 is a diagram showing the relationship between the etching rate V and the ratio of water to bromine and acid when a semiconductor crystal is etched using a similar mixed solution of bromine, acid, and water. . Figures 4 and 5 show a - group compound semiconductor substrate after an etching process using an etching mask is performed on the - group compound semiconductor substrate using a mixed solution of bromine, acid, and water as an etching solution. FIG. 1... - group compound semiconductor substrate, 2... etched portion.

Claims (1)

[Claims] 1. A first step of forming an etching mask on the - group compound semiconductor substrate or layer;
a second step of performing an etching process using the etching mask as a mask; A method for manufacturing a semiconductor device characterized by using the method. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the acid constituting the mixed solution as the etching solution is hydrochloric acid. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the acid constituting the mixed solution as the etching solution is phosphoric acid.