JPH0722146B2 - Etching method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an etching solution and an etching method suitable for manufacturing an end face mirror of a semiconductor laser, an optical IC, and the like.

2. Description of the Related Art Conventionally, as etching solutions used for wet etching of InP crystals, etching solutions such as hydrochloric acid-based, ball water-based, hydrobromic acid-based, and bromine-methanol-based are known.

Hereinafter, conventional wet etching using the above etching solution will be described with reference to FIG.

In FIG. 3, 11 is an etching mask, 12 (100) InP
Crystal substrate, 13 forward mesa {111} plane, 14 forward mesa {211}
Plane, 15 is the (100) plane, and 16 is the (01) plane.

When the (100) InP crystal substrate 12 on which the etching mask 11 of the [01] direction line was formed was etched using the above etching solution, the forward mesa {111} plane 1 was formed as shown in FIG.
3, or the forward mesa {211} plane 14 is formed. The forward mesa {111} plane 13 forms an angle of 55 ° with the (100) plane 15,
The forward mesa {211} plane 14 forms an angle of 35 ° with the (100) plane 15.

That is, when the (100) InP crystal substrate 12 is etched using the above etching solution, the etching surface formed perpendicular to the (01) plane 16 is (100) plane 15 and 55 ° or 35 °. Make a tilt angle.

However, in the InP crystal, the conventional wet etching forms an angle of 45 ° with the (100) plane and (01)
It was very difficult to form an etched surface perpendicular to the surface.

It is an object of the present invention to provide an etching method for forming an etching surface on an InP crystal substrate that forms an angle of 45 ° with the (100) plane and is perpendicular to the (01) plane.

Means for Solving the Problems The first aspect of the present invention for achieving the above object is, firstly, the volume percentages x%, y% and z% of hydrochloric acid, hydrogen peroxide and acetic acid, respectively.
When 3 ≦ z ≦ 93 and 3 ≦ z ≦ 60 When 60 <z ≤ 93 The etching solution is a mixed solution of hydrochloric acid, hydrogen peroxide, and acetic acid represented by

Secondly, a mixed solution of hydrochloric acid, hydrogen peroxide and acetic acid having a volume percentage of hydrochloric acid of 7% to 60% and a volume percentage of hydrogen peroxide of 1% to 10% is etched. It is a liquid.

Furthermore, as a third, InGaAsP on a (100) InP crystal substrate
After forming a layer and forming an etching mask on which a pattern including a line in the [01] direction is patterned on the (100) plane of the InGaAsP layer, the above-mentioned first etching solution,
Alternatively, using the second etching solution, the above-mentioned InGaAsP
An etching method for etching an InP crystal substrate provided with a layer and an etching mask.

The InGaAsP layer is formed on the (100) InP substrate by adjusting the mixing ratio of hydrochloric acid, hydrogen peroxide and acetic acid as in the case of the first etching solution or the second etching solution described above. The rate at which the layer is etched back in the horizontal direction of the substrate and the rate at which InP is etched in the vertical direction of the substrate form an etched surface that is perpendicular to the (01) plane and forms 45 ° with the (100) plane. The InP crystal substrate is etched while maintaining a good balance. That is, InGaA
The etching rate in the horizontal direction of the sP layer and the etching rate in the perpendicular direction of the substrate of InP are adjusted by the above-mentioned etching solution, and the InP crystal substrate is perpendicular to the (01) plane and the (100) plane.
An etched surface of 45 ° is formed.

Embodiments Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of (10) with respect to the volume mixing ratio of hydrochloric acid, hydrogen peroxide, and acetic acid in the etching solution.
It is a figure showing an angle θ formed by a (0) plane and an etching plane formed by etching.

Further, FIG. 2 is a perspective view of the wafer, and FIG.
Is a perspective view before etching, and FIG. 2B is a perspective view after etching.

In FIG. 2, 1 is a (100) InP crystal substrate, 2 is InGaAs
P layer, 3 is SiO ₂ film, 4 is (100) plane, 5 is (01) plane, 6
Is an etching surface formed by etching.

In this embodiment, first, as shown in FIG.
The InGaAsP layer 2 is formed on the crystal substrate 1. Next, InGaA
A SiO ₂ film 3 is formed on the (100) surface 4 of the sP layer 2, and a line in the [01] direction is patterned on the SiO ₂ film 3. Then, the wafer shown in FIG.
When the respective volume percentages x%, y%, z% of acetic acid are the following formula (1) 3 ≦ z ≦ 93, 3 ≦ z ≦ 60 When 60 <z ≤ 93 Alternatively, a mixed solution of hydrochloric acid, hydrogen peroxide and acetic acid that satisfies the following formula (2) 7 ≦ x ≦ 60, 1 ≦ y ≦ 10 (2) (in the shaded area in FIG. 1) When the mixed liquid) is used as an etching liquid, etching is performed as shown in FIG. 2B to form the etching surface 6. That is, when etching is performed with a mixed solution of hydrochloric acid, hydrogen peroxide, and acetic acid whose volume percentages x%, y%, and z% satisfy the formula (1) or the formula (2) as an etching solution, the InGaAsP layer 2 becomes horizontal to the substrate. The rate of etching in the direction and the rate of etching the (100) InP crystal substrate 1 in the vertical direction of the substrate are 45 ° with the (100) plane such as the etching plane 6, and (01) An etching surface perpendicular to the surface can be formed.

Further, as shown in FIG. 1, the angle θ can be adjusted in the range of 25 ° to 50 ° by changing the volume mixing ratio of hydrochloric acid, hydrogen peroxide and acetic acid, and the tilt angle of the etching surface can be controlled. it can.

In addition, in FIG. 1, in a region where horizontal parallel lines are applied,
Only the InGaAsP layer 2 can be etched, and the InP crystal is not etched. Further, two etched surfaces can be formed in the region where the lattice film is formed.

EFFECTS OF THE INVENTION As described above, according to the present invention, (100)
An etching surface that makes an angle of 45 ° with the surface and is perpendicular to the (01) surface can be formed by wet etching.

[Brief description of drawings]

FIG. 1 shows the angle θ between the (100) plane and the etching plane in the cross section of the (01) plane with respect to the volume mixing ratio of hydrochloric acid, hydrogen peroxide and acetic acid in the etching solution according to the embodiment of the present invention. FIG. 3 is a perspective view showing the state of the wafer before etching and the state of the etching solution in the embodiment of the present invention, and FIG. 3 is a perspective view of the wafer in the conventional wet etching. 1,12 …… (100) InP crystal substrate, 2 …… InGaAsP layer, 3 ・ ・ ・
… SiO ₂ film, 4,15 …… (100) plane, 5,16 …… (01) plane,
6 ... Etching surface, 11 ... Etching mask, 13 ...
Forward mesa {111} plane, 14 …… Forward mesa {211} plane.

Claims (1)

[Claims] 1. When the volume percentage of hydrochloric acid x%, the volume percentage of hydrogen peroxide y%, and the volume percentage of acetic acid z% are 3≤z≤93 and 3≤z≤60. When 60 <z ≤ 93 The first etching solution in which hydrochloric acid, hydrogen peroxide, and acetic acid are mixed at x, y, and z satisfying the above, or the volume percentage of hydrochloric acid is 7% to 60%, and the volume percentage of hydrogen peroxide is 1% to 10%. %, An etching method using a second etching solution in which the hydrochloric acid, the hydrogen peroxide, and the acetic acid are mixed, wherein a step of forming an InGaAsP layer on a (100) InP crystal; Forming an etching mask in which a pattern including a line in the [01] direction is patterned on the (100) surface, and using the first etching liquid or the second etching liquid to form the InGaAsP layer and the etching mask. And a step of etching the (100) InP crystal.