JP2002064237A - Cleaving method of crystalline substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out cleavage with higher positional accuracy than before. SOLUTION: After an element, such as an active region 102 has been formed on a crystalline substrate 101, a sub guide groove 108 is successively formed on a main guide groove 107, the blade of a wedge-like tool 106 is applied to the back of the substrate 101 at the forming section, and prescribed force is applied to the direction of the tool 106 from the upper section of the substrate 101, thus cleaving the substrate 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaving a crystalline substrate used for manufacturing a semiconductor laser.

[0002]

2. Description of the Related Art In an optical device using a semiconductor substrate such as a semiconductor laser, a semiconductor optical amplifier, a semiconductor optical modulator, and an optical waveguide device, it has been proposed to use a cleavage plane as an optical input / output end face. As a method of manufacturing a cleavage plane that becomes an optical input / output end face, there is a method of forming a groove in a part of a substrate on which a predetermined semiconductor layer is laminated with a diamond scriber or the like and performing cleavage along the groove. A method has also been proposed in which a groove is formed in a part of the substrate by etching, and cleavage is performed using the groove as a guide groove.

In this cleavage method, as shown in FIG. 7, a substrate 701 made of a compound semiconductor on which elements such as an active layer 702 are formed is prepared. A groove 703 is formed at a position where a line on the surface and one end of the substrate 701 intersect. Next, a wedge-shaped jig 7 is formed on the back surface of the substrate 701 in the groove 703 forming portion.
06 is applied to the jig 706 from above the substrate 701.
The substrate 701 is cleaved by applying a predetermined force in the direction.

[0004]

However, in the above-mentioned conventional cleaving method, since the position accuracy of the cleaving includes an error of ± 1 μm or more, it is very difficult to precisely control the position of the cleaved surface. was there. Therefore, it is difficult to cleave at the designed position, and for example, it has not been possible to form an element such that the element length of the optical element is equal to the designed value with an accuracy within ± 1 μm.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to enable cleavage with higher positional accuracy than in the past.

[0006]

According to the present invention, there is provided a method for cleaving a crystalline substrate, comprising: a main guide groove extending from an end of a main surface of a crystalline substrate to a central portion of the substrate; The narrower auxiliary guide groove is deeper than the main guide groove,
In addition, the main guide groove and the sub guide groove are formed so that the central axes thereof coincide with each other and are continuous, and a stress is applied to a position on the back surface of the substrate opposite to the main guide groove forming portion, and the main guide groove and the sub guide groove are formed. This is to cleave the substrate in the extending direction. According to the present invention, the tip of the sub guide groove on the substrate center side is a cleavage start position. In the above invention, the main guide groove and the sub guide groove may be formed by selective etching.

[0007] The method for cleaving a crystalline substrate of the present invention comprises:
A guide groove of a triangular prism extending in a direction from the edge of the main surface of the substrate having crystallinity to the center of the substrate and having a base whose bottom is a triangle overlapping the edge is formed in a guide groove forming portion on the back surface of the substrate. In this method, stress is applied to opposing positions to cleave the substrate in the direction in which the guide grooves extend. According to the invention,
The tip of the guide groove of the triangular prism on the substrate center side is the cleavage start point. In the above invention, the triangle may be an isosceles triangle having two adjacent sides having the same length. Further, the guide groove may be formed by selective etching.

The method for cleaving a crystalline substrate according to the present invention comprises the steps of:
A triangular prism portion extending from the edge of the main surface of the substrate having crystallinity to the center of the substrate and having a base whose bottom is a triangle whose base overlaps the end, and a vertex portion which is an intersection of two adjacent sides of the triangle. A guide groove consisting of a continuous rectangular shape and a rectangular groove portion having a bottom surface is formed, stress is applied to a position opposite to the guide groove forming portion on the back surface of the substrate, and the substrate is cleaved in the extending direction of the guide groove. Things. According to the present invention, the tip of the rectangular portion of the guide groove on the center side of the substrate serves as a cleavage site. In the above invention, the guide groove may be formed by selective etching.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a perspective view (a) and a cross-sectional view (b) illustrating a cleavage method according to an embodiment of the present invention.
It is. In the first embodiment, as shown in FIG. 1A, an element such as an active region 102 is formed on a crystalline substrate 101 made of, for example, n-type InP.
A main guide groove 107 and a sub guide groove 108 are formed in a state continuous with the main guide groove 107 so as to extend from an end of the main surface of the substrate 1 toward the center of the substrate. By applying a predetermined force in the direction of the jig 106 from above the substrate 101 by applying the blade portion of the tool 106,
1 is cleaved.

[0010] The active region 102, as shown in FIG. 1 (b), n formed on the substrate 101 ^- and the lower cladding layer 121 made of InP in the form, the band gap wavelength of InGaAsP of 1.5μm Active layer 122,
p ^- becomes the upper clad layer 123 consisting of the shape of InP, are filled with the buried layer 124 surroundings become semi-insulating InP. That is, a plurality of double hetero embedded laser structures (semiconductor lasers) are formed on the substrate 101.
Are formed at equal intervals. Lower cladding layer 121,
The active layer 122 and the upper clad layer 123 are formed by crystal-growing compound semiconductors constituting each layer on the substrate 101 by metal organic chemical vapor deposition and selectively etching these by dry etching using a hydrocarbon-based etching gas. Can be formed.

Here, the main guide groove 107 and the sub guide groove 1
08 will be described. First, the main guide groove 107 and the sub guide groove 108 are formed so that their center lines in plan view coincide with each other and are continuous. The width w of the sub guide groove 108 is
It is smaller than the width W of the main guide groove 107. For example, the width w of the sub guide groove 108 is 1 μm or less. Also, the sub guide groove 1
The length l of 08 may be 1 μm or more. In addition, the sub guide groove 108 and the main guide groove 107 are formed at the same depth, and the depth D of the main guide groove 107 is formed deeper than the width W of the main guide groove 107 (D> W).

Next, the main guide groove 107 and the sub guide groove 1
08 will be described. First, as shown in FIG. 2A, a substrate 101 on which the above-described active region 102 and buried layer 124 are formed is prepared. Then, about 0,
A silicon oxide film having a thickness of about 2 μm is formed, and an opening having a width of 10 μm and a length of 1000 μm for forming a main guide groove and a width of 1 μm and a length of 5 μm for forming a sub guide groove are formed thereon.
A resist pattern having an opening of m is formed by a known photolithography technique. Then, for example, CF
Using reactive ion etching with ₄ as an etching gas, the silicon oxide film is selectively etched away using the resist pattern as a mask, and then the resist pattern is removed, as shown in FIG. Layer 12
4, a mask pattern 201 is formed.

Next, the buried layer 1 is formed by reactive ion beam etching using the mask pattern 201 as a mask and a mixed gas of bromide gas and nitrogen as an etching gas.
24 and the substrate 101 are etched to a predetermined depth (about 19 μm). Thereafter, as shown in FIG. 2C, the mask pattern 201 is removed, an electrode 109 is formed on the active region 102 by using a lift-off method, and an electrode 11 is formed on the back surface of the substrate.
0 was formed. As described above, a plurality of main guide grooves 107 and a plurality of sub guide grooves 108 are formed at the end of the substrate 101 parallel to the extending direction of the active region 102.

Thereafter, the blade portion of the jig 106 shown in FIG. 1A is applied to the back surface of the substrate 101 where the main guide groove 107 is formed, and the substrate 101 is cleaved. Cleavage is performed with a positional accuracy within ± 1 μm from the formation position, and a laser array shape is formed. According to the present embodiment, the sub guide groove 108 formed by connecting to the main guide groove 107 serves as a positioning guide, and the tip of the sub guide groove 108 serves as a cleavage start point. For this reason,
According to the present embodiment, the position of the cleavage start point can be set to a very high accuracy of about 程度 of the width w of the tip of the sub guide groove 108.

Second Embodiment Next, another embodiment of the present invention will be described. FIG. 3 is a perspective view for explaining a cleavage method according to another embodiment of the present invention. In the present embodiment, as shown in FIG. 3, after forming an active region 102 and a buried layer 124 on a substrate 101, a guide groove 301 having a triangular shape (triangular prism) in plan view is formed.
The blade of the jig 106 is applied to the back surface of the substrate 101 at the formation portion, and a predetermined force is applied from above the substrate 101 toward the jig 106 to cleave the substrate 101. In addition, a guide groove 302 having a shape in which a rectangle is connected to a vertex of a triangle is formed on the substrate 101 (embedded layer 124), and a blade portion of the jig 106 is applied to the back surface of the substrate 101 where the guide groove 301 is formed. The cleavage of the substrate 101 is performed.

First, the guide groove 301 is, for example,
4 is an isosceles triangle having a base at a side (end) parallel to the active region 102 formed in a stripe pattern of FIG.
(B) A triangular prism having a bottom surface. The guide groove 3
The triangle on the bottom surface of 01 does not need to be an isosceles triangle, and the lengths of two adjacent sides may be different. In addition, the triangle on the bottom surface of the guide groove 301 is, for example, as long as the extension direction on the vertex side of a line connecting the midpoint and the vertex of the base of the triangle is the cleavage direction which is the direction of the central portion of the substrate 101. Good. If the bottom of the triangular prism is an isosceles triangle, the cleavage direction is
Active region 102 formed in a stripe shape on substrate 101
Perpendicular to the side (end) parallel to.

The cleavage plane formed by the cleavage operation by the jig 106 is guided while connecting the parts where the stress is most intense on the surface where the guide groove is formed. In the case of the guide groove 301 of a triangular prism, stress concentrates along the sides of the triangle (intersecting line between the side surface and the bottom surface of the groove), and the stress becomes strongest at the vertex of the triangle (the upper end portion where the two groove side surfaces intersect). . Since the cleavage plane is guided along the side of the guide groove 301 of the triangular prism and is terminated at the apex of the triangle, the site where the cleavage plane is induced is uniquely determined geometrically. Therefore, according to the guide groove 301 of the triangular prism, the cleavage position can be determined with high accuracy.

In the case where the accuracy of the cleavage plane formation position may deviate from the set position by ± α, the guide groove 302
As shown in FIG. 4, a rectangular groove having a width of 2α may be provided continuously to the vertex of the triangle (FIG. 4B). In this case, the cleavage position can be controlled within a range of half (α) of the width 2α of the rectangular portion provided at the tip of the guide groove 302. When a triangular-shaped guide groove is used, the stress applied for cleavage is concentrated at one point, so that it is not necessary to form the guide groove deeper than the width. Further, when the crystalline substrate is cleaved using the guide grooves 301 and 302 as in the present embodiment, the position of the blade of the wedge-shaped jig used for the cleaving operation is brought into contact with high precision. Even if you do not
The cleavage plane formation position can be determined with high accuracy.

Next, formation of the guide groove 301 will be described. First, as shown in FIG. 5A, the substrate 101 on which the above-described active region 102 and the buried layer 124 are formed.
Prepare Next, a silicon oxide film having a thickness of about 0.2 μm is formed, and a resist having an isosceles triangular opening of 1000 μm from the bottom to the tip at a tip angle of 4 ° for forming a guide groove thereon is formed. The pattern is formed by a known photolithography technique. Then, for example, C
Using reactive ion etching using F ₄ as an etching gas, the silicon oxide film is selectively etched away using the resist pattern as a mask, and then the resist pattern is removed, as shown in FIG. Buried layer 1
24, a mask pattern 501 is formed.

Next, using the mask pattern 501 as a mask, the buried layer 124 and the substrate 101 are etched to a predetermined depth (about 3 μm) by reactive ion beam etching using a halogen-based mixed gas as an etching gas. Thereafter, as shown in FIG. 5C, the mask pattern 501 was removed, an electrode 109 was formed on the active region 102 using a lift-off method, and an electrode 110 was formed on the back surface of the substrate. By the above, the active region 102 of the substrate 101
A plurality of guide grooves 301 are formed at an end parallel to the extending direction of.

Thereafter, the substrate 1 at the portion where the guide groove 301 is formed is formed.
The substrate 101 is cleaved from the vertex position of the guide groove 301 by applying the blade portion of the jig 106 (FIG. 3) to the back surface of the substrate 101 to form a laser arrayer shape.
According to the present embodiment, the guide groove 301 of the triangular prism serves as a positioning guide, and the vertex of the triangle of the guide groove 301 serves as a cleavage start point. For this reason, according to the present embodiment, the position of the cleavage start point can be uniquely determined as the vertex position, and extremely high accuracy can be achieved. The guide groove 302 shown in FIGS. 3 and 4B can be formed in the same manner as the guide groove 301 as described above.

FIG. 6 shows the result of measuring the distance in which the cleavage start position deviated from the set position in the case of cleavage as described above. First, FIG. 6A shows a case where the main guide groove 107 and the sub guide groove 108 shown in FIG. 1 are formed and cleaved. Main guide groove 107, sub guide groove 10
In the case of using No. 8, as shown in FIG. 6A, cleavage could be performed with a positional accuracy within ± 1 μm from the set position.

FIG. 6 (b) is a view similar to FIG. 3 and FIG.
3A shows a case where a triangular prism guide groove 301 shown in FIG. When the triangular prism guide groove 301 was used, as shown in FIG. 6B, cleavage could be performed with a positional accuracy within ± 1 μm from the set position.
FIG. 6C shows a case where the guide groove 302 shown in FIGS. 3 and 4B is formed and cleaved.
A guide groove 3 of a triangular prism with a rectangular groove of 1 μm width connected to the tip
In the case of using No. 02, as shown in FIG. 6C, cleavage could be performed with a positional accuracy within ± 0.5 μm from the set position. In the above description, the case of forming a semiconductor laser using InP as a substrate has been described as an example. However, the present invention is not limited to this. For example, a cleavage for forming an emission end face of a semiconductor laser using GaAs as a substrate. Needless to say, it can be applied to

[0024]

As described above, according to the present invention,
Since the cleavage start position can be controlled with high accuracy, an excellent effect that the cleavage can be performed with higher positional accuracy than before can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view (a) and a cross-sectional view (b) illustrating a cleavage method according to an embodiment of the present invention.

FIG. 2 is a process chart for explaining a cleavage method according to the embodiment of the present invention.

FIG. 3 is a perspective view for explaining a cleavage method according to another embodiment of the present invention.

FIG. 4 is a plan view showing a shape of a guide groove according to another embodiment of the present invention.

FIG. 5 is a process chart for explaining a cleavage method in another embodiment of the present invention.

FIG. 6 is a statistical diagram showing an effect in the embodiment of the present invention.

FIG. 7 is a perspective view for explaining a conventional cleavage method.

[Explanation of symbols]

101: substrate, 102: active area, 106: jig, 10
7: Main guide groove, 108: Sub guide groove, 109, 110
... electrodes, 121 ... lower cladding layer, 122 ... active layers, 1
23 ... upper clad layer, 124 ... buried layer, 301,
302: guide groove.

Claims (7)

[Claims] 1. A main guide groove extending from an end of a main surface of a substrate having crystallinity to a center portion of the substrate, and a sub guide groove having a width smaller than the main guide groove. The main guide groove and the sub guide groove are formed in a state where they are deeper than the width and the central axes of the sub guide grooves coincide with each other, and a stress is applied to a position on the back surface of the substrate facing the main guide groove forming portion. A method for cleaving a crystalline substrate, comprising cleaving the substrate in a direction in which the main guide groove and the sub guide groove extend. 2. The method for cleaving a crystalline substrate according to claim 1, wherein the main guide groove and the sub guide groove are formed by selective etching. 3. A triangular prism guide groove extending from an end of the main surface of the substrate having crystallinity to the center of the substrate and having a base whose bottom is a triangle overlapping the end is formed. Cleaving the substrate in a direction in which the guide groove extends, by applying stress to a position on the back surface of the substrate opposite to the guide groove forming portion. 4. The method for cleaving a crystalline substrate according to claim 3, wherein said triangle is an isosceles triangle having two adjacent sides equal in length. 5. The method for cleaving a crystalline substrate according to claim 3, wherein said guide groove is formed by selective etching. 6. A triangular prism portion extending from an end of a main surface of a substrate having crystallinity to a direction toward the center of the substrate and having a base whose bottom is a triangle overlapping with the end, and two adjacent to the triangle. Forming a guide groove comprising a rectangular groove portion having a rectangular shape as a bottom surface which is continuous with a vertex portion which is an intersection of sides, and applying stress to a position on the back surface of the substrate facing the guide groove forming portion; Cleaving the substrate in the extending direction of the substrate. 7. The method for cleaving a crystalline substrate according to claim 6, wherein said guide groove is formed by selective etching.