JPS5969934A - Etching method - Google Patents

Abstract

PURPOSE:To form a narrow deep groove to a substrate consisting of a GaAlAs group single crystal by forming a mask composed of a material, a thermal expansion coefficient thereof differs from the substrate, and dipping the mask in an ammonia-hydrogen peroxide aqueous solution. CONSTITUTION:The mask 12 laminated on the GaAs substrate 11 consists of SiO2, the thermal expansion coefficient thereof differs from the substrate 11, etc. When the substrate 11 to which the mask 12 is formed is dipped in the solution composed of 30wt% hydrogen peroxide water containing 1% ammonia, the narrow deep V-shaped groove 13 is obtained along the mask 12. Stress is generated in a section along the mask 12 because the thermal expansion coefficients of the substrate 11 and the mask 12 differ, bonding power among crystals weakens, and the substrate is etched in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an etching method, particularly for GaAl! This invention relates to a method for etching AB-based materials.

<Prior Art> FIGS. 1 to 3 are for explaining the entire conventional etching method.

In the figure, (11 is, for example, a GaA, 8 (gallium arsenide) single crystal substrate, and I21 is, for example, a 5
102, and a window (3) is formed in the mask so that a part of the substrate il+ is exposed. After that, fold the mask (21) on the substrate 11J, Y suitable for example sulfuric acid: hydrogen oxide water: water 3:
Etching solution with a ratio of 1:1 [by dipping twice,
As shown in FIG. 2, a groove (4) whose surface opening corresponds to the shape of the window (3) is obtained.

However, in the conventional method, the groove width is iB and the R depth is iD.
However, it was impossible to obtain a groove such that B<D. In other words, even if an attempt is made to obtain a groove of depth D by immersing it in an etching solution as shown in FIG. becomes larger.

For example, if you make a groove with a groove width of 2 meters and a groove depth of about 10 mm, the depth of the groove will be 10/Im. The width near the opening of the under-etching C2 is about 8 to 10 mm.

Therefore, in the past, grooves with narrow groove widths and deep groove depths could not be obtained.

<Object of the invention> The present invention was made in view of the above points, and GaAl! A
The present invention aims to provide an etching method capable of forming narrow and deep grooves in a substrate made of S-based single crystal.

<Structure of the Invention> A feature of the etching method of the present invention is that a mask is formed along one end of a groove to be formed in the future on a substrate made of a GaAJAs-based saliva crystal material, and a mask made of a material having an expansion coefficient different from that of the substrate is at least The forming step consists in immersing the substrate on which the mask is formed in an ammonia-hydrogen peroxide aqueous solution.

<Example> FIG. 4 and FIG. 5 show an example of the present invention, and tl 1
1 caAs substrate whose main surface is the (100) plane, 02
is a mask laminated on the substrate (11), and the mask is made of a material such as 5i02 having a different coefficient of thermal expansion from that of the substrate (11). The substrate (1) on which such a mask O2 is formed is treated with an ammonia-hydrogen peroxide aqueous solution, preferably containing 1% ammonia. When the fish is immersed in vocal fluid made of hydrogen peroxide solution for 6 minutes, as shown in Fig. 5, Tm<, depth D==1.
[], am, groove width B-=2 pm, and a narrow and deep V-shaped groove 031 was obtained along the above mask (121).The etching power of the above solution on the GaAs substrate was very weak.

The mechanism by which the V-groove is formed is not clear, but because the thermal expansion coefficients of the substrate 0υ and the mask Oa are different, there is a difference in the thermal expansion coefficient between the substrate 0υ and the mask Oa. It is thought that this is because the bonding force between the crystals in such a region is weakened by the occurrence of stonos, and therefore only such a region is etched by the above solution.Although CaAs was used as the substrate in the example, GaAJ
A similar effect can be obtained using a substrate made of As. Further, the mask material is not limited to SiO2, but may be any material that has a thermal expansion coefficient of P with respect to the GaARAB material and is not etched by the above solution.

Application Example A preferred example of the application of the present invention is used to separate into pellet units a GaJ'As-based 43 photodiode wafer in which a pn junction is formed between the substrate and the substrate. When the present invention is applied to such '1NIt, the groove width can be made smaller and separation is possible, so the effective area ratio of the pellet obtained from one sea urchin becomes larger. As shown in Fig. 2, it is used to form grooves for narrowing grooves in semiconductor lasers. 211 in the diagram
is an n-type GaAs substrate, +721 is an oscillation layer laminated on the substrate, and the oscillation layer consists of an active layer Q, (l) and a second cladding layer f2111251 sandwiching the active layer. Such an active layer (231 and the first and second cladding layers (lrht2511d GaAlAs yarn material collar 71 iJ, first and second cladding layers 124+
1251 is an active cycle), the bandgap is human.
type and P type. C26) is a cap layer made of P-type GaAS formed on the oscillation layer (221), and the opening is an ohmic electrode formed on the cap layer, and the electrode is a stripe extending in the direction perpendicular to the plane of the paper. T shape t,
f281 is a groove provided on both sides of the electrode C2L,
The groove reaches the second cladding layer. The C291 insulating layer is an insulating layer, and the U insulating layer consists of the surface of the cap layer on which the electrode C27+ is not formed, and the groove (formed inside the cap layer 5).

In such a semiconductor laser, the electrode (
27) Since the applied magnetic current is constricted, the active layer I2
Highly efficient laser oscillation can be obtained at 31.

Further, since the trench 12 & described above can be made smaller in width using the electrode (z7) as a mask, the amount of 5 iOz trench needed to fill the trench is reduced.

As is clear from the above description, according to the present invention, grooves with a small width and a large depth can be easily obtained, so that the present invention can be applied to separation of pellets, etc., and is very effective.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views showing a conventional example 7, FIGS. 4 and 5 are cross-sectional views showing an embodiment of the present invention, and FIG. 6 is a cross-sectional view showing an example of an application of the present invention. old]... board, 0 cap... mask, (131...
・Groove Fig. 1j Fig. 3 Fig. 5 Fig. 2 Fig. 4 Ie? Figure 6 135-

Claims (1)

[Claims] a step of forming a mask along one end of a groove to be formed in the future on a substrate made of IllGaAIAs single crystal nanocrystalline material, and made of a material having a coefficient of thermal expansion at least different from that of the substrate; The substrate on which the above mask was formed? Ammonia hydrogen peroxide solution ζ2 immersion T
An etching method characterized by