JP2000183047A - Semiconductor processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch a slope cutting means from a V blade to etching so as to provide a semiconductor device at a lower manufacturing cost, by a method wherein a semiconductor substrate having a crystal structure of zinc blende is subjected to a slope anisotropic etching in the direction of a forward mesa by the use of an etching aqueous solution which contains specific wt.% hydrogen chloride and hydrogen bromide, respectively. SOLUTION: A silicon nitride film 11 is formed on the surface of an InP substrate 10 as a semiconductor substrate that has a crystal structure of zinc blende, and a resist film 12 is applied on the silicon nitride film 11 and formed into a prescribed pattern 13. Openings are bored in the silicon nitride film 11 by etching using the pattern 13 as a mask. The substrate 10 is subjected to wet etching together with the silicon nitride film 11. As a result, a groove 14 with a slope of an angle of 45 deg. in the direction of a forward mesa can be cut in the surface of the InP substrate 10. An etching solution contains hydrogen chloride and hydrogen bromide as main components, where 5 to 15 wt.% hydrogen chloride and 5 to 20 wt.% hydrogen bromide are contained in the etching solution. By this setup, a 45⊥ slope forming process can be carried out through etching instead of a physical means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for processing a semiconductor, and more particularly, to a method for processing a semiconductor using an etching solution for processing a semiconductor used for anisotropic etching.

[0002]

2. Description of the Related Art In the field of optical communication systems, up until now, maintenance has mainly been performed on trunk systems, but recently, recently, there has been a growing demand for widespread use in subscriber systems. Research and development of various transmission systems and optical devices corresponding to them have been promoted. However, since the maintenance costs of the subscriber system are borne by the subscriber in principle, it is necessary to promote economical use of the optical system for the subscriber system and to promote the opticalization of domestic optical communication systems. It has become.

[0003] For example, with the aim of economicalization of optical terminals in Japan, as shown in FIG.
tar) method is adopted. According to the PDS method, a star coupler (SC) 50 is used in a transmission path, and a plurality of subscriber ONUs (Optical Network Units) are used.
51, 52, 53 and one station side (OSU: Optical Subs
A criber unit 54 can perform time-division two-way communication with a 1.3 μm signal through one optical fiber (one-fiber transmission) 55. The optical signal transmitted from the OSU 54 is transmitted as a downlink signal (TDM: normal time-division transmission) 56, and is transmitted by the SC 50 to each ONU.
It branches to 51,52,53. Also, each ONU 51,
The signal light transmitted from 52 and 53 is a rising signal (TDM).
A: Same as satellite / PHS etc.) 57 is transmitted to OSU 54 via SC 50.

An optical transceiver module used in this system has, for example, a principle configuration as shown in FIG.
1997 Dentsu Gakkai, C-3-86). That is, the downstream optical signal guided through the optical fiber 58 passes through the half mirror 59 of the prism 64, is focused by the lens 60, and is coupled to the receiving PD 62. On the other hand, LD6
The transmission optical signal emitted from 1 is guided to the total reflection mirror 63 of the prism 64 through the lens 60, and the reflected light is reflected by the half mirror 59, and is coupled to the optical fiber 58 through which the downstream optical signal has passed.

More specifically, an optical receiving module 65 (Mitsubishi Electric, 1997 Dentsu Institute, C-3-
86) have been proposed. In this optical receiving module 65, an optical fiber 66 is fixed by a V-groove 68 formed by anisotropic etching of a silicon substrate 67, and light emitted from the optical fiber 66 is a front-incident PIN-PD.
Binds to 69.

[0006] The substrate used in the above-described light receiving module is usually processed by wet etching in order to achieve a mirror surface that can be used as a BS (beam splitter).

However, a semiconductor substrate (100) having a zinc-blende type structure is placed in a forward mesa direction by, for example, a sulfuric acid-based etchant (H ₂ SO ₄ + H ₂ O ₂ + H ₂ O) or a bromine-based etchant ( When wet etching is performed using HBr + CH ₃ COOH, Br ₂ + MeOH, etc., an angle of 54.7 ° is mainly formed with respect to the substrate surface (100) (1).
11) appears. That is, since the surface of (111) or the like has a high atomic packing ratio, the elution rate becomes extremely slower than that of the other surfaces (generally, about 1/100 at room temperature), and as a result, (100) , (110), and (101) are considered to be retained even if other surfaces with a high elution rate elute. Further, for example, a chlorine-based etching solution (HCl + CH ₃ COOH,
HCl + HNO ₃ ), 35.3 mainly to the substrate surface (100) surface.
An angle of (211) appears. Therefore, it is difficult to form a V-groove having a 45 ° slope that is most suitable for use as described above.

Under these circumstances, when a groove having a 45 ° slope is usually formed in a semiconductor substrate having a zinc-blend structure, the side view of FIG. 10A and the front view of FIG. As described above, many methods of cutting the surface of the semiconductor substrate 71 by rotating the V-blade 70 having a right-angled tip at a high speed have been adopted. Also, at this time, since the processed surface becomes rough with only the V blade 70, the processed surface is cut more smoothly while spraying an electrolyte solution (which is considered to be an etching solution in a broad sense) onto the semiconductor substrate 71 (( NTT,
1997 Dentsu Institute, C-3-126).

Further, as another processing method, a method has been proposed in which a 45 ° inclined surface is realized on one surface with a normal etching solution by cutting in advance with an angle offset of 9.7 ° at the time of slicing from an ingot. (JP-A-4-322201).

However, in the case of cutting with a V-blade, the accuracy of the machined surface is largely governed by the roughness of the blade, and it is in principle difficult to achieve optically sufficient specularity even with the use of an electrolyte solution. .

On the other hand, the method of offsetting angularly in advance requires a custom-made slice from an expensive ingot, resulting in an increase in the cost of the PD chip. Further, there is a fundamental problem that the cleavage plane of each chip is inclined by 9.7 ° when the substrate is divided after the formation of the V-groove.

[0012]

According to the present invention, a zinc blende type crystal is prepared by using an etching aqueous solution containing 5 to 15% by weight of hydrogen chloride and 5 to 20% by weight of hydrogen bromide. There is provided a method for processing a semiconductor, comprising etching a semiconductor substrate having a structure in a forward mesa direction by 45 ° anisotropically.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The etching solution used in the semiconductor processing method of the present invention mainly contains hydrogen chloride and hydrogen bromide. Hydrogen chloride is added to the
The content is preferably about 15% by weight,
% By weight is more preferable. Hydrogen bromide is preferably contained in the etching solution in an amount of about 5 to 20% by weight,
About 10 to 20% by weight is more preferable.

The aqueous etching solution used in the present invention may further contain an organic or inorganic weak acid or a lower alcohol. Examples of the organic or inorganic weak acid include acetic acid, phosphoric acid, and a mixture thereof. Examples of the lower alcohol include ethanol, propanol, and a mixture thereof. In addition, a weak acid and a lower alcohol may be mixed and used. Among them, acetic acid is preferably used. This is because, when acetic acid is used, side etching when etching the semiconductor substrate is minimized. When acetic acid is used, it is preferably contained in the etching aqueous solution at about 30 to 70% by weight, more preferably about 30 to 35% by weight.

The etching aqueous solution of the present invention can control the etching rate of the semiconductor to be processed by adjusting the proportion of hydrogen chloride and hydrogen bromide in the etching solution within the above range. In addition, by using an organic or inorganic weak acid or lower alcohol, an intermediate product (eg, InBr ₃ when the semiconductor is an InP substrate) generated by etching the semiconductor can be rapidly dissolved in these aqueous solutions. , Can promote etching.

When an oxidizing solution is mixed with the etching aqueous solution, the solution is made of HCl or HBr.
Reacts with the gas to generate highly toxic chlorine and bromine gases, and furthermore, the molecular chlorine and bromine gases dissolved in the etching solution themselves affect the etching of semiconductors, thereby controlling the etching rate. Therefore, it is preferable to use an organic or inorganic weak acid or a lower alcohol.

The aqueous etching solution may be prepared by using any form of hydrogen chloride or hydrogen bromide as long as the above components are finally contained in the above proportions. Hydrogen gas, hydrogen bromide gas may be dissolved in water or the above weak acid or lower alcohol, and finally contained in the etching solution at the above ratio, or hydrochloric acid, hydrobromic acid may be directly mixed, May be mixed with the above weak acid or lower alcohol. Above all, from the viewpoint of simplicity of preparation, etc.,
It is preferably prepared by mixing commercially available concentrated hydrochloric acid and concentrated hydrobromic acid with a weak acid or lower alcohol. Specifically, commercially available concentrated hydrochloric acid (about 37% by weight): concentrated hydrobromic acid (about 48% by weight): glacial acetic acid = 1: 1: 1 to 4 (volume ratio), concentrated hydrochloric acid: concentrated hydrogen bromide Acid: glacial acetic acid = 1: 2: 1 to 1
4, concentrated hydrochloric acid: concentrated hydrobromic acid: glacial acetic acid = 2: 1: 1 to 4,
Concentrated hydrochloric acid: concentrated hydrobromic acid: commercially available phosphoric acid (about 85% by weight) = 2: 1: 2 to 4 and the like. Among them, commercially available concentrated hydrochloric acid (approximately 37% by weight): concentrated hydrobromic acid (approximately 48% by weight): glacial acetic acid = from the viewpoints of simplicity of preparation, ease of use, and the state of the slope after etching. A 1: 1: 1 aqueous etching solution is preferred.

The semiconductor substrate that can be processed using the etching solution of the present invention is not particularly limited as long as it has a zinc-blende type crystal structure.
BN, BP, BAs, AlP, AlAs, AlSb, G
Examples thereof include III-V compound semiconductors such as aP, GaAs, InAs, and InSb.

The semiconductor processing method of the present invention can be realized by bringing the semiconductor into contact with the etching solution. At that time, the contact time between the semiconductor and the etching solution is about 15 to 120 minutes. The temperature of the solution is preferably about room temperature. Further, it is preferable that the semiconductor to be processed is left in an etching solution. Further, the semiconductor and the etching solution are preferably brought into contact in a dark place.

According to the semiconductor processing method of the present invention, four
Although the processing can be performed so as to form a 5 ° slope, this method can be applied to various uses such as processing of a light receiving / light emitting element and processing of a V-groove of a semiconductor substrate for fixing an optical fiber.

Hereinafter, the semiconductor processing method of the present invention will be described. Example 1: Application as a processing method of a receiving PD for an optical transmitting / receiving module First, as shown in FIG. 1A, a semiconductor substrate having a zinc-blende type crystal structure has a (100) surface. I
Using the nP substrate 10, a silicon nitride film 11 is formed to a thickness of 200 nm on the surface of the InP substrate 10. Then
As shown in FIG. 1B, a resist 12 is coated on the silicon nitride film 11 to a thickness of 600 nm, and as shown in FIG. The resist pattern 13 is formed by patterning into a shape.

Thereafter, as shown in FIG. 1D, an opening is formed in the silicon nitride film 11 using the obtained resist pattern 13 as a mask, and then, as shown in FIG. The InP substrate 1 is formed by using the opened resist pattern 13 and the silicon nitride film 11 as a mask.
0 is wet-etched. The etching solution used for the wet etching is a concentrated hydrochloric acid solution (37% by weight of hydrochloric acid,
50 ml of a concentrated hydrogen bromide solution (48% by weight of hydrogen bromide, manufactured by Kishida Chemical Co., Ltd.)
Glacial acetic acid (acetic acid 99.7%, manufactured by Kishida Chemical Co., Ltd.) 50
ml of an etching solution. During the etching, the InP substrate 10 is allowed to stand in a dark place at a temperature of 15 to 25 ° C. for about 90 minutes.

As described above, it is possible to form the groove 14 having a 45 ° slope in the forward mesa direction in the InP substrate 10. That is, in the etching solution obtained by mixing concentrated hydrochloric acid and concentrated hydrogen bromide and diluting with acetic acid, chlorine ions and bromine ions are randomly present therein. Each of these ions has a monovalent charge, and has an equal electrostatic attraction to the semiconductor substrate, ie, the InP substrate, and thus makes random contact with the InP substrate. For this reason, as shown in FIG. 2, at the portion where the chlorine ions have come into contact,
The (211) plane of the nP substrate appears, and the (111) plane of the InP substrate appears by bromide ion etching at the site where the bromine ions are in contact. Since such random contact and etching of chlorine ions and bromine ions occur consistently from before the V-groove is formed until after the V-groove is formed, observing the slope of the groove after the etching shows that the size of the crystal lattice is large. At the level, minute slopes of (211) and (111) are formed at almost the same ratio. As a result, I
The slope of the groove of the nP substrate has 45 ° which is an average value of 35.3 ° and 54.7 °. Further, since the slope of the groove has a size of a crystal lattice level, it is optically sufficiently smooth.

The obtained silicon nitride film 11 and the resist pattern 1 on the InP substrate 10 having the 45 ° groove 14
3 is removed, and as shown in FIG. Thereafter, a desired chamfered incident type photodiode (PD) 20 is utilized by utilizing the divided individual InP substrates 10.
Then, as shown in FIG. 4, an optical transceiver module 33 was fabricated by mounting the tapered waveguide laser diode (LD) 31 and the waveguide 32 on the PLC 30.

In this optical transmitting / receiving module 33,
The signal light that has passed through the waveguide 32 is converted into a tapered waveguide LD3.
1 and enters from the chamfered portion of the InP substrate together with the monitor light emitted from the rear part of the tapered waveguide LD31.
Signal PD provided on the opposite side of light receiving element through P crystal
Join the parts.

Example 2: Application as a processing method of an optical transceiver module for pickup A 45 ° slope formed substantially in the same manner as in Example 1 except that a silicon substrate is used instead of an InP substrate and the etching time is shortened. Using a silicon substrate 35 having four surfaces, a pickup hologram unit 34 shown in FIG. 5 was prepared.

The unit 34 has a concave portion in which an integrated circuit 37 and a PD 38 are provided on a silicon substrate 35 and four micromirrors 36 each having a 45-degree inclined surface are formed on the surface of the silicon substrate 35. An LD 39 is provided in the recess, and the LD 39 and the PD 38 are optically and efficiently coupled by the micromirror 36 having a 45-degree slope.

Embodiment 3 Etching of V-groove in Silicon Substrate for Fixing Optical Fiber As shown in FIG. 6, a plurality of grooves 40 of 45 ° slope formed substantially in the same manner as in Embodiment 1 41. The arrow M in FIG. 6 indicates the forward mesa direction.

By fixing the optical fiber in the groove 40 of the silicon substrate 41, the position accuracy of the optical fiber of several μm is secured. The light emitted from the optical fiber is a surface-incident PIN formed on the silicon substrate 41.
-PD (not shown), but because of high positional accuracy when fixing the optical fiber, PD for receiving light
Can also be improved.

[0030]

According to the present invention, a zinc blende type crystal structure is formed by using an etching solution containing 5% by weight or more of hydrogen chloride, 5% by weight or more of hydrogen bromide, and a diluent. Since the semiconductor substrate is etched 45 degrees anisotropically in the forward mesa direction, the concentration of hydrogen chloride and hydrogen bromide in the etching solution is adjusted to an appropriate value, and while controlling the etching rate, the forward mesa direction of the semiconductor is controlled. 45 ° anisotropic etching becomes possible. Therefore, it is possible to switch the processing of forming a 45 ° slope of a semiconductor, which has conventionally depended on physical means such as cutting with a V-blade combined with an electrolyte solution and inclined slices of an ingot, to an easier etching method. . Therefore, the mass productivity can be further improved, the manufacturing cost can be reduced, and a more reliable semiconductor device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining one embodiment of a semiconductor processing method according to the present invention.

FIG. 2 is a diagram for explaining a processing state of a processing surface according to the semiconductor processing method of the present invention.

FIG. 3 is a perspective view showing a semiconductor substrate having a 45 ° slope formed by the semiconductor processing method of the present invention.

FIG. 4 is a schematic sectional view of an optical transceiver module using a semiconductor substrate having a 45 ° slope formed by the semiconductor processing method of the present invention.

FIG. 5 is a perspective view of a hologram unit for pickup using a semiconductor substrate having a 45 ° slope formed by the semiconductor processing method of the present invention.

FIG. 6 is a perspective view of a semiconductor substrate for explaining a semiconductor substrate having a 45 ° slope formed by the semiconductor processing method of the present invention.

FIG. 7 is a configuration diagram showing wavelength division two-way communication according to a conventional PDS method.

FIG. 8 is a schematic configuration diagram showing a conventional optical transceiver module.

FIG. 9 is a schematic perspective view showing a conventional planar mounting type (PLC type) optical receiving module.

FIG. 10 is an etching process diagram for explaining a conventional method for forming a 45 ° inclined surface of a semiconductor substrate.

[Description of Reference Numerals] 10 InP substrate (semiconductor substrate) 11 silicon nitride film 12 resist 13 resist pattern 14, 40 groove 20 chamfered incident photodiode 30 PLC 31 tapered waveguide laser diode 32 waveguide 33 optical transceiver module 34 pickup Hologram unit 35, 41 silicon substrate 36 micromirror 37 integrated circuit 38 PD 39 LD

Claims (3)

[Claims] 1. A semiconductor substrate having a zinc-blende type crystal structure in a forward mesa direction using an etching aqueous solution containing 5 to 15% by weight of hydrogen chloride and 5 to 20% by weight of hydrogen bromide. A semiconductor processing method comprising performing 45 ° anisotropic etching. 2. The semiconductor processing method according to claim 1, wherein the etching aqueous solution further contains an organic or inorganic weak acid or a lower alcohol. 3. An etching aqueous solution containing 30 to 70 acetic acid.
2. The method for processing a semiconductor according to claim 1, wherein the semiconductor material is contained by weight.