JPH11307804A - Manufacture of semiconductor photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method by which a wafer can be cleaved near the light entrance end of a semiconductor photodetector with high yield at the time of cutting the photodetector from the wafer. SOLUTION: In a method for manufacturing a refraction type semiconductor photodetector which is constituted to make incident light to pass through a light receiving layer 13 obliquely to the thickness direction of the layer 13 by refracting the incident light at a light entrance end face 11 by providing a light receiving section composed of a multilayered semiconductor structure containing the light receiving layer 13 formed on the surface of a substrate 15 and the light entrance end face 11 the inward inclined angle of which becomes larger as becoming farther from the surface side and which is provided on the end face of the photodetector, the width 2W between the upper ends of an inverted-mesa etched groove is adjusted to 2W<=2(H+Hc)tanδ (where, H, Hc, and δ respectively represent the depth to the deepest bottom of the etched groove, depth of a cleave scratch, and the half of the opening angle 2δ of the front end section of a needle used for forming the cleavage scratch) after an inverted-mesa etched groove forming process for forming the light entrance end face 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor light receiving element.

[0002]

2. Description of the Related Art FIG. 2 schematically shows a refraction type semiconductor light receiving element. In FIG. 2, reference numeral 11 denotes a light incident end face, and 12 denotes a 1 μm thick p.
-InP layer, 13: 1 μm-thick InGaAs light receiving layer, 14: 1 μm
An m-thick n-InP layer, 15 is a semi-insulating InP substrate, 16 is a p-electrode, and 17 is an n-electrode. As shown in FIG.
A chip is formed from the vicinity of the light incident inclined end face by cleavage or the like. When light (L) is incident on the light receiving element from a fiber or the like, the light emitted from the fiber or the like spreads with respect to the distance, and thus depends on how the emitted light spreads.
The light incident end face of the light receiving element needs to be set at a distance of about several tens μm or less from the light exit end face such as a fiber. Therefore, as shown in FIG. 2, it is necessary to manufacture the cleavage end face 18 of the substrate 15 in the vicinity of the light incidence end face 11 with high accuracy.

Usually, the cleavage is performed by reducing the thickness of the substrate to about 100 μm, and as shown in FIG. 3, a wafer having a structure in which a refraction type semiconductor light receiving element portion is arranged in parallel with a groove portion of an inverted mesa is provided at an end of a portion where the groove is cleaved. A part of the part is cleaved by needle 19 etc. 2
When a mechanical shock is applied thereto, the scratch portion becomes a starting point of cleavage, and cleavage is performed over the entire wafer. Here, cleavage 20
The tip of the needle 19 is formed into a conical or pyramid shape, and the tip is processed to be extremely fine. However, when a deep mesa exists as in a refraction type semiconductor light receiving element, the groove width of the mesa portion is set to the needle 19. Is formed sufficiently wide so as not to contact the mesa, and the cleavage flaw 20 is formed. However, in order to prevent the needle from contacting the upper end of the inverted mesa, the cleavage flaw is separated from the upper end of the inverted mesa by several tens μm or more. 20 had to be formed.

When the spread angle of light emitted from a fiber or the like is large, it is important to bring the fiber as close as possible to the vicinity of the incident end face. For this reason, it is necessary to make a cleavage flaw 20 very close to the incident end face. In such a case, the needle 19 is forcibly pressed to the vicinity of the incident end face to form a cleavage flaw, but the conical or pyramid-shaped part of the needle contacts the mesa portion of the incidence end face 11 near the position where the cleavage flaw 20 is formed. The position to be scratched is shifted,
There has been a problem that the position variation becomes large. For these reasons, there is a problem that the yield of chips cut out from the wafer is reduced.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a refraction type light receiving element which can cleave the element near a light incident end with high yield when cutting out the element from a wafer. is there.

[0006]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor light receiving device, comprising: a light receiving portion having a semiconductor multilayer structure including a light receiving layer formed on a surface of a substrate;
By providing a light incident end face that is inclined inward as the end face moves away from the surface side, the incident light is refracted at the light incident end face so that the incident light passes through the light receiving layer obliquely to the layer thickness direction. In the manufacture of the refraction type semiconductor light receiving element, after the step of forming the reverse mesa etching groove for forming the light incident end face, the depth from the upper side of the light incident end face to the bottom of the etching groove is H, and the depth of the cleavage flaw is Hc, and the opening angle of the tip of the needle for forming the cleavage flaw is 2δ,
When the groove width 2W at the upper end of the reverse mesa etching groove is 2W ≦ 2 (H +
Hc) tan δ.

According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor light receiving element, comprising: a light receiving portion having a semiconductor multilayer structure including a light receiving layer formed on a surface of a substrate; In the manufacture of a refraction-type semiconductor light receiving element in which an inclined light incident end face is provided to refract incident light at the light incident end face so that the incident light passes through the light receiving layer obliquely to the layer thickness direction. A method of manufacturing a semiconductor light receiving element, wherein after the step of forming a reverse mesa etching groove for forming a light incident end face, a groove width of an upper end of the mesa etching groove is 30 μm or less.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor light receiving device according to the present invention is directed to a method of manufacturing a refraction type semiconductor light receiving device, in which a groove width at an upper end of a reverse mesa etching groove after a step of forming a reverse mesa etching groove for forming a light incident end face. Is set narrow, a groove having a shape as shown in FIG. 1 is formed after etching for forming the end face.

FIG. 1 also schematically shows a needle for simultaneously forming a cleavage flaw. As shown in FIG. 1, the depth from the upper side to the bottom surface of the light incident end face 11 is H,
Assuming that the depth of the cleavage flaw is Hc and the opening angle of the tip of the needle for forming the cleavage flaw is 2δ, the groove width of the upper end of the inverted mesa after manufacturing the light incident end face is 2W ≦ 2 (H + H
c) When the cleavage needle 19 is lowered from above to the vicinity of the center of the groove so as to have tan δ, the upper sides of the opposite mesas serve as guides, and a cleavage flaw can be formed almost at the center with high reproducibility. In addition, even if the groove width is narrowed and the upper portions of both mesas are damaged by the contact of the inclined portions of the needle 19, the portions always function as guides, and therefore, the cleavage flaws can be formed in the central portion with good reproducibility. For this reason, by applying a mechanical shock, the cleavage occurs with good reproducibility starting from the portion with the cleavage flaw. Further, if the groove width 2W is set to 10 μm or less, cleavage can be performed very close to 5 μm or less from the light incident end face.

FIG. 4 shows an InP substrate 1 having a (001) surface by bromide etching when the etching groove width is sufficiently large.
FIG. 5 is a schematic view of an etched cross section when an inverted mesa shape (θ = 55 degrees) is formed by etching 5 to expose a (111) plane. The depth of the cleavage flaw is assumed to be Hc, and the groove width 2W at the upper end of the inverted mesa after manufacturing the light incident end face is set to 2W ≦ 2 (H + H
c) When tan δ is set, inverted mesa portions are formed on both sides of the needle. When the cleavage needle is lowered from above to the vicinity of the center of the groove, the upper sides of both inverted mesas serve as guides, and the center of the inverted mesa is almost at the center. Cleavage flaws can be formed with good reproducibility.

Here, as a typical example, when light from a silica-based single mode fiber (SMF) is highly efficiently received without a lens system by a refractive semiconductor light receiving element, a silica-based single mode fiber (SMF: spot) is used. Size is 1
0 μm), the beam diameter is 15 μm and the light intensity includes 99% or more, so the depth D of the light incident end face 11 needs to be at least 15 μm. According to experiments, 26 μm was required for H in order to make D 15 μm. Usually, the tip opening angle of a needle used in an automatic cleavage flaw forming apparatus is often 2δ = about 60 degrees or more.

Here, when 2δ = 60 degrees and the cleavage flaw depth Hc is set to zero, the groove width at the upper end of the inverted mesa after the manufacture of the light incident end face is 30 μm or less (2 × (26 × tan).
(30 degrees)) = 30), and the cleaving needle is lowered from above to near the center of the groove. Can be formed. In reality, the needle is further lowered by a finite cleavage flaw depth Hc, so that the inclined portion of the needle comes into contact with and guides the inverted mesa portion without fail. For this reason, by applying a mechanical shock, the cleavage occurs with good reproducibility starting from the portion with the cleavage flaw.

The difference from the prior art is that, in the formation of cleavage flaws, there is almost no displacement of the flaws, and the cleavage can be performed with a desired accuracy near the incident end face.

As described above, according to the present manufacturing method, there is almost no variation in the positional shift in the formation of the cleavage flaw, and the cleavage can be performed in the vicinity of the incident end face. Therefore, it is possible to easily cut out the element while sufficiently satisfying the distance to the light incident end face required for optical coupling with a fiber or the like. In addition, since both sides of the etched groove can be cut out as light incident end faces, the yield of the elements from the wafer is greatly improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[Embodiment 1] FIG. 5 is a view for explaining a first embodiment of the present invention. 11 is a light incident end face, 12 is 1 μm
A thick p-InP layer, 13 is a 1 μm thick InGaAs light receiving layer, 14 is a 1 μm thick n-InP layer, 15 is a semi-insulating InP substrate, 16 is a p electrode, and 17 is an n electrode. The light-receiving layer area of the device is 14
μm × 20 μm. The light incident end face 11 was formed by wet etching using bromomethanol using a silicon nitride film mask. At this time, the light incident end face 11
The (001) surface was formed by utilizing the fact that the (111) A surface was formed in an inverted mesa shape as shown in the figure by wet etching using bromomethanol. The groove width at the upper end of the reverse mesa etching groove after this step is 7 μm.
It is. Even if the groove width at the upper end of the reverse mesa etching groove is as narrow as 7 μm, the depth D of the light incident end face 11 is 20 μm.
The depth H to the bottom is about 35 μm, and a good incident end face can be formed.

When a thin needle 19 having an opening angle of about 2δ = 20 degrees at the tip of the cone of the needle is lowered from above to the vicinity of the center of the groove, and the cleavage flaw depth Hc is set to about 10 μm, the conical part becomes a double inverted mesa. The portion contacted the upper side, and this portion served as a guide, and a cleavage flaw could be formed almost at the center with good reproducibility. This is because the condition 2W = 7 <2 × (35 + 10) ×
tan (10 degrees) = 15.9 μm is satisfied. The cleavage flaw Hc was formed on a part of the wafer edge over a length of about 200 μm. Of course, since the strength of the semiconductor is lower than that of the needle, the reverse mesa portion where the needle contacts is finely broken, but the mesa portion still functions as a guide, and the cleavage flaws are reproduced with good reproducibility in the center of the groove. Could be formed. Therefore, by applying a mechanical shock here, good cleavage could be performed over several centimeters starting from the cleavage flaw, and both sides of this cleavage could be used as light incident end faces of the light receiving element.

In the present embodiment, the groove width at the upper end of the reverse mesa etching groove after the step of forming the reverse mesa etching groove for forming the light incident end face is 7 μm. It was possible. The reverse mesa portion may be formed by using another wet etching solution or a dry etching method, may be formed by using another crystal plane, or may be formed by controlling an angle by using adhesion of an etching mask. .

When a non-reflective film is formed on the incident end face and light having a wavelength of 1.55 μm is introduced using a spherical fiber, a large value of light receiving sensitivity of 0.9 A / W or more can be obtained with an applied reverse bias of 3 V. And a high-speed operation in a 3 dB band of 40 GHz was possible. At this time, the protrusion of the substrate portion immediately below the light incident end face portion is as small as several microns, and hardly hinders the proximity of the fiber.

In this embodiment, the grooves of the etching mask are formed by the linear stripe-shaped etching mask 21 as shown in FIG. 7 (a), but the grooves are formed as shown in FIGS. 7 (b) and 7 (c). Various shapes, such as the etching mask 22 and the etching mask 23 having an uneven shape with a taper, may be used, as long as the groove width of a portion where a cleavage flaw is formed conforms to the gist of the present invention.

In this embodiment, the p-InP layer on the surface side is formed by crystal growth. However, in the crystal growth, an undoped InP layer is used. It may be determined by an ion implantation method and subsequent annealing.

The semiconductor light receiving element portion is on the semiconductor layer having the first conductivity type, and is formed of an intrinsic or first conductivity type semiconductor layer, a superlattice semiconductor layer or a multiple quantum well semiconductor layer. And a semiconductor layer having a high Schottky barrier height having a Schottky barrier higher than the Schottky barrier between the light receiving layer and the Schottky electrode between the light receiving layer and the Schottky electrode. or a semiconductor light receiving element formed by constructed on a substrate a multilayer structure in which the Schottky barrier height with high semiconductor _{layer, in 1-xy Ga x Al} y As (0 ≦ x ≦ 1,0 ≦ y ≦ 1)
Or In _1-xy Ga _x Al _y As (0 ≦ x ≦ 1, 0 ≦ y ≦ 1)
And a thin In _1-u Ga _u As _1-v P _v (0 ≦ u ≦ 1,0
.Ltoreq.v.ltoreq.1).

In this embodiment, the semi-insulating InP is used as the substrate and the n-InP layer is used on the substrate side. However, even if a p-InP layer is used, the above p and n are reversed. It can be manufactured similarly using an n-InP or p-InP substrate.

Although the light-receiving layer is made of a bulk having a uniform composition, a separate-absorption-graded-multiplic used in an avalanche photodiode is used here.
ation (SAGM) structure and Separate absorption and mu
It goes without saying that a semiconductor layer having an ltiplication superlattice (SAM-SL) structure or another superlattice structure may be used. InGaAlAs / InGaA other than InGaAsP / InP
It goes without saying that a material system such as sP or AlGaAs / GaAs system or a material system having intrinsic strain may be used.

[Embodiment 2] FIG. 6 is a view for explaining a second embodiment of the present invention. 11 is a light incident end face, 12 is 1 μm
A thick p-InP layer, 13 is a 1 μm thick InGaAs light receiving layer, 14 is a 1 μm thick n-InP layer, 15 is a semi-insulating InP substrate, 16 is a p electrode, and 17 is an n electrode. The light-receiving layer area of the device is 30
μm × 50 μm. The light incident end face was formed by wet etching using bromomethanol using a silicon nitride film mask. At this time, the light incident end face is (00
1) The wafer on the surface is formed by utilizing the fact that the (111) A plane is formed in an inverted mesa shape as shown in the figure by wet etching using bromomethanol. The groove width at the upper end of the reverse mesa etching groove after this step is 30 μm.
Even if the groove width at the upper end of the reverse mesa etching groove is 30 μm,
The depth D of the light incident end face is as deep as 20 μm, and a good incident end face can be formed. The depth H to the bottom is about 35 μm.
is there. When an automatic cleavage flaw forming apparatus having a pyramidal needle is used, the needle 19 whose tip opening angle is about 2δ = 60 degrees in a plane perpendicular to the direction in which the cleavage flaw is formed is lowered from above to near the center of the groove. The pyramid-shaped portion was in contact with the upper sides of the opposite mesas, and this portion served as a guide, and a cleavage flaw could be formed almost at the center with good reproducibility.

In this case, the needle 19 is symmetrical in the left and right directions. However, even if the needle 19 is asymmetrical in the left and right directions, if the groove width is set so that the upper ends of both mesas serve as guides, the cleavage flaw position will be the same as that of the groove. It can be formed with good reproducibility by being intentionally shifted from the center. Cleavage flaws were formed on a part of the wafer edge at about 200 μm. Of course, since the strength of the semiconductor is lower than that of the needle, the reverse mesa portion where the needle contacts is finely broken, but the mesa portion still functions as a guide, and the cleavage flaws are reproduced with good reproducibility in the center of the groove. Could be formed.

Therefore, by applying a mechanical shock, good cleavage could be performed over several centimeters starting from the cleavage flaw, and both sides of this cleavage could be used as the light incident end face of the light receiving element. The reverse mesa portion may be formed by using another wet etching solution or a dry etching method, may be formed by using another crystal plane, or may be formed by controlling an angle by using adhesion of an etching mask. . When a non-reflective film was formed on the incident end face and light having a wavelength of 1.55 μm was introduced using a single mode fiber (SMF), a large value of light receiving sensitivity of 0.9 A / W or more was obtained with an applied reverse bias of 3 V. . At this time, the protrusion of the substrate portion immediately below the light incident end face portion is 10 μm or more, but the misalignment tolerance in the optical axis direction at which the light receiving sensitivity of the light receiving element with respect to SMF is reduced by 1 dB is 80 μm, which is practically a problem. No.

In this embodiment, the grooves of the etching mask have a linear stripe shape as shown in FIG. 7 (a). However, the grooves and the taper as shown in FIGS. 7 (b) and 7 (c) are used. In addition to the concavo-convex shape with, various shapes may be used,
It is only necessary that the groove width of the portion where the cleavage flaw is formed conforms to the gist of the present invention. In this embodiment, the p-InP layer on the surface side is formed by crystal growth. However, in the crystal growth, an undoped InP layer is used. And subsequent annealing. Also, the semiconductor light receiving element part
A light-emitting layer on the semiconductor layer having the first conductivity type, the light-receiving layer comprising an intrinsic or first conductivity type semiconductor layer, a superlattice semiconductor layer or a multiple quantum well semiconductor layer, and the Schottky electrode; A multi-layer structure including a semiconductor layer having a high Schottky barrier height having a Schottky barrier higher than the Schottky barrier between the light receiving layer and the Schottky electrode is formed on the substrate. and a semiconductor light receiving device, the Schottky barrier height with high semiconductor _{layer, in 1-xy Ga x Al} y As (0 ≦ x ≦ 1,0
≦ y ≦ 1) or In _1-xy Ga _x Al _y As (0 ≦ x ≦ 1,0
≦ y ≦ 1) and a thin In _1-u Ga _u As _{1-v Pv} (0 ≦
u ≦ 1, 0 ≦ v ≦ 1). Further, in this embodiment, the semi-insulating InP is used as the substrate, and the n-InP layer is used on the substrate side. Manufacturable, n-InP and p-
It can be manufactured similarly using InP substrate. Also, here, the bulk of the uniform composition is used as the light receiving layer,
Separate-a used for avalanche photodiode
bsorption-graded-multiplication (SAGM) structure and Separate absorption and multiplication superlatt
It goes without saying that a semiconductor layer having an ice (SAM-SL) structure or another superlattice structure may be used. Also, InGaAs
It goes without saying that a material system other than the P / InP system, such as InGaAlAs / InGaAsP or AlGaAs / GaAs system, or a material system having intrinsic strain may be used.

[0029]

As described above, the method of manufacturing a semiconductor photodetector according to the present invention is directed to a method of manufacturing a refraction type semiconductor photodetector, in which a reverse mesa etching groove is formed after a step of forming a reverse mesa etching groove for forming a light incident end face. By setting the groove width of the end to be narrow, when the needle for making a cleavage flaw is lowered from above after the end face formation etching, the cone or pyramid of the needle is formed in the mesa part of the incident end face. This portion contacts and functions as a guide, and a cleavage flaw can be formed with high accuracy at almost the center. Therefore, by applying a mechanical shock thereto, cleavage can be performed with good reproducibility starting from the cleavage flaw portion. As described above, according to the present manufacturing method, a cleavage flaw can be formed accurately at the center of the groove, cleavage can be performed with good reproducibility starting from the cleavage flaw, and the protrusion of the substrate from the light incident end face is short. it can. Therefore, the element can be easily and reproducibly cut out while sufficiently satisfying the distance to the light incident end face required for optical coupling with a fiber or the like. Further, the device can be cut out with both sides of the etched groove both as light incident end faces, and the area of the groove portion wasted on the wafer can be reduced, so that the yield of the device from the wafer is greatly improved.

[Brief description of the drawings]

FIG. 1 schematically shows a shape after etching for forming an end face according to the present invention.

FIG. 2 is a diagram illustrating a refraction type semiconductor light receiving element.

FIG. 3 is a schematic diagram of a wafer structure in which a refraction type semiconductor light receiving element portion is arranged in parallel with a groove portion of an inverted mesa.

FIG. 4 shows In of (001) surface by brom etching.
FIG. 3 schematically shows an inverted mesa shape in which P is etched to expose a (111) plane.

FIG. 5 is a diagram illustrating a first embodiment of the present invention.

FIG. 6 is a diagram illustrating a second embodiment of the present invention.

FIG. 7 is an example of a groove shape of an etching mask.

[Explanation of symbols]

 Reference Signs List 11 light incident end face 12 1 μm thick p-InP layer 13 1 μm thick InGaAs light receiving layer 14 1 μm thick n-InP layer 15 semi-insulating InP substrate 16 p electrode 17 n electrode 18 cleavage end face 21 etching mask 22 etching mask 23 etching mask

Claims (2)

[Claims] 1. A light-receiving part comprising a semiconductor multilayer structure including a light-receiving layer formed on a surface of a substrate, and a light-incident end face which is inclined inward as the distance from the front side increases, the light-incident end face being provided. In the manufacture of a refraction type semiconductor light receiving element in which the incident light is refracted so that the incident light passes through the light receiving layer obliquely with respect to the layer thickness direction, a reverse mesa etching groove forming step for forming a light incident end face is performed. Later, when the depth from the upper side of the light incident end face to the bottom of the etching groove is H, the depth of the cleavage flaw is Hc, and the opening angle of the tip of the needle for forming the cleavage flaw is 2δ, The groove width 2W at the upper end of the mesa etching groove is 2W ≦ 2 (H + H
c) A method for manufacturing a semiconductor light receiving element, characterized by tan δ. 2. A light receiving portion comprising a semiconductor multilayer structure including a light receiving layer formed on a surface of a substrate, and a light incident end surface which is inclined inward as the distance from the front surface increases, so that the light incident end surface is provided. In the manufacture of a refraction type semiconductor light receiving element in which the incident light is refracted so that the incident light passes through the light receiving layer obliquely with respect to the layer thickness direction, a reverse mesa etching groove forming step for forming a light incident end face is performed. A method of manufacturing a semiconductor light receiving device, wherein the width of the upper end of the mesa etching groove is 30 μm or less.