JP2002318117A - Semiconductor ring laser gyro and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and high-yield manufacturing method of a semiconductor ring laser gyro wherein the side wall of a ridged optical waveguide is inclined against a substrate and a reflecting mirror is vertical to the substrate. SOLUTION: An etching mask 101 for the semiconductor ring laser gyro is formed as shown in figure (A). In this case, the section shape of an etching mask 102 for the ridged waveguide part is formed to have a shape similar to a hemispheric shape as shown in figure (B), and, on the other hand, an etching mask 104 of the reflecting mirror part is formed to have a rectangular section shape as shown in figure (C). By using the etching mask formed in this way, dry etching is performed in a condition wherein the reflecting mirror part is formed vertically and smoothly as shown in figure (D). The inclined side of the ridged waveguide and the reflecting mirror part vertical to a growing layer can be formed by one-time dry etching in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple and high-yield manufacturing method of a semiconductor ring laser gyro having a ridge-shaped optical waveguide and a reflection mirror.

[0002]

2. Description of the Related Art In recent years, a semiconductor ring laser gyro has been studied as a gyro having a small size and low power consumption. A semiconductor ring laser, which is part of a semiconductor laser gyro,
For example, it is disclosed in JP-A-7-131123. In this semiconductor ring laser, as shown in FIG. 5, 410 is a semiconductor ring laser, 410a is an upper electrode, 410b is a lower electrode, 410c is a laser light emitting surface,
411 is a semiconductor substrate, 412 is an output extraction prism, and 415 is an active layer. As can be seen from the figure, the ridge waveguide of the semiconductor laser 410 is formed by etching deeper than the active layer 415, and the active layer 415 is exposed on the side surface of the waveguide.

According to this publication, since a waveguide is formed by etching and regrowth is not used, a semiconductor ring laser can be manufactured by simple steps.

[0004]

However, in JP-A-7-131123, the side surface of the waveguide is formed almost perpendicular to the growth layer. Such a waveguide is susceptible to backscattering due to the roughness of the waveguide side surface, causing a lock-in phenomenon, which is not preferable as a gyro.

Further, it is preferable to form an electrode having a large area after forming a ridge waveguide for measurement and mounting. However, since the side wall of the waveguide is almost vertical, deposition by resistance heating or electron beam heating is performed. In the case of vapor deposition using, for example, the electrodes are liable to be cut off, and the apparatus and process for forming the electrodes are limited.

Further, before forming an electrode having a large area,
Usually, an insulating layer is provided in a portion other than a portion necessary for conduction. However, in the case of the shape having high perpendicularity, the insulating layer is poorly covered, and current leakage sometimes occurs in an unnecessary portion.

Accordingly, the present invention provides a simple and high-yield manufacturing method of a semiconductor ring laser gyro in which a side wall of a ridge-shaped optical waveguide is inclined with respect to a substrate and a reflection mirror is perpendicular to the substrate. That is the task.

[0008]

According to a method of manufacturing a semiconductor ring laser gyro of the present invention for solving the above-mentioned problems, the cross-sectional shape of the etching mask of the ridge waveguide portion and the cross-sectional shape of the etching mask of the reflection mirror portion are different. By performing dry etching using different etching masks,
A step of simultaneously forming a ridge-shaped optical waveguide having a side surface inclined with respect to a normal line of the growth layer of the substrate and a reflection mirror perpendicular to the growth layer of the substrate.

In the method of manufacturing a semiconductor ring laser gyro according to the present invention, after forming a ridge-shaped optical waveguide and a reflection mirror portion perpendicular to a growth layer, only the ridge-shaped optical waveguide is isotropically etched. Accordingly, the method includes a step of forming a ridge-shaped optical waveguide having a side surface inclined with respect to the normal line of the growth layer and a reflection mirror portion perpendicular to the growth layer.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram best illustrating a method of manufacturing a semiconductor ring laser gyro according to the present invention. In FIG. 1, 100 is a semiconductor substrate, 101 is an etching mask of a semiconductor ring laser gyro, 102 is an etching mask of a ridge-shaped optical waveguide portion, 104 is an etching mask of a reflection mirror portion, 106 is a ridge-shaped optical waveguide portion after etching, 108 is a reflection mirror portion after etching, and 110 is a semiconductor ring laser gyro after etching.

As shown in FIG. 1A, an etching mask 101 of a semiconductor ring laser gyro is formed on a semiconductor substrate 100 having an active layer by using photolithography or the like. At this time, as shown in FIG. 1B, the cross-sectional shape of the etching mask 102 in the ridge-shaped waveguide portion is not rectangular but formed in a shape close to a hemisphere, whereas the etching mask 104 in the reflecting mirror portion is , FIG. 1 (C)
As shown in FIG. 5, the cross section is formed to be rectangular.

Using the etching mask thus formed, dry etching is performed under the condition that the reflection mirror portion is vertically and smoothly formed as shown in FIG. The ridge-shaped waveguide portion is smooth due to the shape of the etching mask, but is not etched vertically, and has a side surface inclined with respect to the normal of the growth layer as shown in FIG. Having. In this manner, the ridge-shaped waveguide portion has a side surface inclined with respect to the normal of the growth layer, and the reflection mirror portion can be formed in a shape perpendicular to the growth layer by a single dry etching. I can do it. Thereafter, necessary steps such as formation of an anode and a cathode are performed to complete the device. In this element, since the reflection mirror portion is perpendicular to the growth layer, reflection loss is small and laser oscillation can be performed at a low threshold. Further, since the ridge-shaped optical waveguide portion has a side surface inclined with respect to the growth layer, the ridge-shaped optical waveguide portion is hardly affected by irregularities on the side surface, and lock-in hardly occurs. In addition, disconnection of the electrode and disconnection of the passivation film hardly occur.

As described above, according to the manufacturing method of the present invention, the ridge-shaped optical waveguide having a side surface inclined with respect to the normal line of the growth layer and the reflecting mirror portion perpendicular to the growth layer are provided. With low power consumption,
A semiconductor ring laser gyro with few steps in the electrodes and the passivation film can be manufactured by a simple manufacturing method.

[0014]

[First Embodiment] As a first embodiment of the present invention, G
An example in which a semiconductor ring laser gyro made of an aAs-based compound semiconductor is formed will be described. The production process will be described with reference to FIG.

FIG. 2A is a bird's-eye view in which a ring laser gyro etching mask 101 is formed on a semiconductor substrate, and FIG. 2B is an AA of the ring laser gyro etching mask 101 in FIG. 2A. 2A and 2B are cross-sectional views of the etching mask 101 of the ring laser gyro taken along line BB 'in FIG. 2A.

First, as shown in FIG. 2A, n-Ga
N-AlGaAs cladding layer 20 on As substrate 200
2. n-AlGaAs optical guide layer 204, multiple quantum well (MQW) active layer 206, p-AlGaAs optical guide layer 208, p-AlGaAs cladding layer 210, p-Ga
A photoresist having a novolak resin as a main component is applied using a spin coater or the like to a thickness of 1.7 μm on an LD wafer 100 having a laminated structure in which an As cap layer 212 is sequentially epitaxially grown.
After pre-baking at 30 ° C for 30 minutes, a mask is applied.
Exposure and development are performed using ep UV light to form an etching mask 101.

Next, as shown in FIG. 2B, after irradiating only the reflecting mirror portion 104 with UV light using a mask,
Heating was performed in an oven at 180 ° C. for 30 minutes. In this state, the cross-sectional shape of the etching mask 102 in the optical waveguide portion was nearly hemispherical due to softening by heat as shown in FIG. Also, the etching mask 10 of the reflection mirror portion
The cross-sectional shape of 4 is to improve the heat resistance by UV light.
The change in the shape was small, and a substantially rectangular shape was maintained as shown in FIG. After forming etching masks having different cross-sectional shapes in the waveguide section and the reflection mirror section in this manner, an inductively coupled ICP (ICP) is formed.
d Plasma) etching was performed. Etching was performed using a gas consisting of chlorine and xenon as an etching gas and applying an ICP power of 300 W and a substrate RF power of 100 W at an etching pressure of 0.5 Pa. This condition is a condition in which the etching is performed perpendicularly and smoothly to the etching mask shape of the reflection mirror portion. After the etching, the etching mask was removed by oxygen plasma.

At this time, the reflection mirror portion is vertically etched as shown in FIG.
As shown in (E), the etched shape had a side surface inclined with respect to the normal to the growth layer. This is due to the effect that the cross-sectional shape of the etching mask 102 in the waveguide portion is close to a hemisphere. After forming a ridge-shaped optical waveguide having a side surface inclined with respect to the normal of the growth layer and a reflection mirror portion perpendicular to the growth layer in this way, using a plasma CVD apparatus, 500 nm of silicon nitride is deposited on the entire surface. To form a passivation film 214. afterwards,
The passivation film 214 is partially removed, and Au / Ti is used as the anode 216 and Au is used as the cathode 218.
Ge / Ni / Au was formed, and ohmic contact was made between the electrodes by heat treatment to complete the device shown in FIG.

[Second Embodiment] As a second embodiment of the present invention, an example is shown in which a semiconductor ring laser gyro made of a GaAs compound semiconductor is formed. The creation process will be described with reference to FIG.

FIG. 3A is a bird's-eye view in which a ring laser gyro etching mask 101 is formed on a semiconductor substrate, and FIG. 3B is an AA of the ring laser gyro etching mask 101 in FIG. 3A. FIG. 3C is a cross-sectional view of the etching mask 101 of the ring laser gyro in FIG.

First, as shown in FIG.
N-AlGaAs cladding layer 20 on As substrate 200
2. n-AlGaAs optical guide layer 204, multiple quantum well (MQW) active layer 206, p-AlGaAs optical guide layer 208, p-AlGaAs cladding layer 210, p-Ga
A photoresist having a novolak resin as a main component is applied to a thickness of 1.7 μm using a spin coater or the like on an LD wafer 100 having a laminated structure in which the As cap layer 212 is sequentially epitaxially grown.
After pre-baking at 30 ° C for 30 minutes, a mask is applied.
After performing exposure and development using ep UV light to form an etching mask 102 for the waveguide portion, the substrate was heated in an oven at 180 ° C. for 30 minutes. In this state, as shown in FIG. 3B, the cross-sectional shape of the etching mask 102 in the optical waveguide portion was nearly hemispherical due to softening due to heat.

Next, a photoresist containing a novolak resin as a main component is coated with a photoresist having a thickness of 1.7 μm using a spin coater or the like.
m, pre-baked at 80 ° C. for 30 minutes, masked, exposed and developed using Deep UV light, and etched mask 104 for the reflection mirror.
Was formed. At this time, the etching mask 10 of the mirror portion is used.
The cross-sectional shape of No. 4 was a substantially rectangular shape as shown in FIG.

After forming etching masks having different cross-sectional shapes in the waveguide portion and the reflection mirror portion in this manner,
ICP (Inductively Coupled P)
lasma) etching was performed. A gas consisting of chlorine and xenon is used as an etching gas.
Etching was performed by applying 100 W as electric power. This condition is a condition under which the etching is performed perpendicularly and smoothly to the etching mask shape of the reflection mirror portion.

After the etching, the etching mask was removed by oxygen plasma. At this time, the reflection mirror is
As shown in FIG. 3D, etching was performed vertically, and the waveguide portion had an etched shape having a side surface inclined with respect to the normal to the growth layer, as shown in FIG. 3E.
This is due to the effect that the cross-sectional shape of the etching mask 102 in the waveguide portion is close to a hemisphere. Thus, after forming a ridge-shaped optical waveguide having a side surface inclined with respect to the normal of the growth layer and a reflection mirror portion perpendicular to the growth layer, 50 nm of silicon nitride is formed using a plasma CVD apparatus.
A passivation film 214 was formed on the entire surface with a thickness of 0 nm.

Thereafter, the passivation film 214 is partially removed, Au / Ti is formed as the anode 216, and AuGe / Ni / Au is formed as the cathode 218. Ohmic contact between the electrodes is made by heat treatment.
The device shown in (F) was completed.

[Third Embodiment] As a third embodiment of the present invention, G
An example in which a semiconductor ring laser gyro made of an aAs-based compound semiconductor is formed will be described. The creation process will be described with reference to FIG. FIG. 4A is a bird's-eye view in which an etching mask 101 of a ring laser gyro is formed on a semiconductor substrate.
FIG. 4B is a sectional view taken along line AA ′ of the etching mask 101 of the ring laser gyro in FIG. 4A.

First, as shown in FIG.
N-AlGaAs cladding layer 20 on As substrate 200
2. n-AlGaAs optical guide layer 204, multiple quantum well (MQW) active layer 206, p-AlGaAs optical guide layer 208, p-AlGaAs cladding layer 210, p-Ga
A photoresist having a novolak resin as a main component is applied using a spin coater or the like to a thickness of 1.7 μm on an LD wafer 100 having a laminated structure in which an As cap layer 212 is sequentially epitaxially grown.
After pre-baking at 30 ° C for 30 minutes, a mask is applied.
Exposure and development were performed using ep UV light to form an etching mask 101. In this state, the cross-sectional shapes of the etching mask 102 and the reflection mirror portion 104 of the optical waveguide portion were substantially rectangular as shown in FIG. 4B.

After forming the etching mask 101 in this way, an ICP (Inductively Cou) is formed.
Pled Plasma) etching was performed. As an etching gas, a gas composed of chlorine and xenon is used,
ICP power 300 at etching pressure 0.5Pa
Etching was performed by applying 100 W as W and substrate RF power. This condition is a condition under which the etching is performed vertically and smoothly on the etching mask having a substantially rectangular shape. After the etching, the etching mask was removed by oxygen plasma. At this time, the reflection mirror portion and the optical waveguide portion were vertically etched as shown in FIG.

Thereafter, only the reflection mirror portion was protected by a resist, and only the waveguide portion was wet-etched using an etchant composed of sulfuric acid, hydrogen peroxide and water.
As shown in FIG. 4D, the cross-sectional shape of the waveguide portion after the wet etching was a shape having a side surface inclined with respect to the normal line of the growth layer.

After forming a ridge-shaped optical waveguide having a side surface inclined with respect to the normal line of the growth layer and a reflection mirror portion perpendicular to the growth layer in this manner, silicon nitride is formed using a plasma CVD apparatus. A passivation film 214 was formed over the entire surface to a thickness of 500 nm. After that, the passivation film 214 is partially removed, and A
u / Ti as AuGe / Ni / A
u was formed, and ohmic contact was established between the electrodes by heat treatment to complete the device shown in FIG.

The present invention is not limited to the material system, the material of the etching mask, and the etching method described in the embodiment, but is a material capable of laser oscillation and whose etching shape depends on the etching mask. Any method is applicable.

[0032]

According to the present invention described above, a semiconductor ring laser gyro having a side wall of a ridge-shaped optical waveguide inclined with respect to a substrate and a reflecting mirror perpendicular to the substrate has a simple and high yield. A manufacturing method can be provided. Thus, it is possible to provide a gyro in which the influence of the backscatter due to the roughness of the waveguide side surface is suppressed and the lock-in phenomenon does not occur. In addition, since the waveguide sidewalls are inclined, the occurrence of electrode breakage is reduced even by vapor deposition using resistance heating or vapor deposition using electron beam heating. An insulating layer can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the concept of the present invention.

FIG. 2 is a view showing a manufacturing process of the semiconductor ring laser gyro according to the first embodiment of the present invention;

FIG. 3 is a view showing a manufacturing process of a semiconductor ring laser gyro according to a second embodiment of the present invention;

FIG. 4 is a view showing a manufacturing process of a semiconductor ring laser gyro according to a second embodiment of the present invention;

FIG. 5 is a diagram showing a conventional manufacturing process.

[Explanation of symbols]

 100: Laser substrate 101: Laser gyro etching mask 102: Waveguide portion etching mask 104: Reflection mirror portion etching mask 106: Waveguide having an inclined side surface with respect to the normal of the growth layer 108: Perpendicular to the growth layer Reflecting mirror section 200: n-GaAs substrate 202: n-AlGaAs cladding layer 204: n-AlGaAs optical guide layer 206: multiple quantum well (MQW) active layer 208: p-AlGaAs optical guide layer 210: p-AlGaAs cladding layer 212 : P-GaAs cap layer 214: passivation film 216: anode 218: cathode 410: semiconductor ring laser 410 a: upper electrode 410 b: lower electrode 410 c: laser emission surface 411: semiconductor substrate 412: output extraction prism 415: active layer

Continued on the front page F-term (reference) 2F105 BB03 BB15 DD07 2H047 KA05 KA12 LA09 NA08 PA06 PA21 PA24 QA02 RA08 TA11 TA42 TA43 5F004 AA16 DA00 DA04 DB21 EA10 EA25 EB08 5F073 AA13 AA74 CA05 CB02 DA22 DA27 DA31 DA35

Claims (6)

[Claims] 1. A method for manufacturing a semiconductor ring laser gyro having a ridge-shaped optical waveguide and a reflection mirror, wherein a cross-sectional shape of an etching mask of the ridge-shaped waveguide portion and a cross-sectional shape of an etching mask of the reflection mirror are different. Simultaneously forming the ridge-shaped optical waveguide having a side surface inclined with respect to the normal line of the substrate growth layer and the reflection mirror perpendicular to the substrate growth layer by dry etching. A method for manufacturing a semiconductor ring laser gyro characterized by the following. 2. The method according to claim 1, wherein only the etching mask of the ridge-shaped optical waveguide is selectively deformed.
A method for manufacturing the semiconductor ring laser gyro according to the above. 3. The method for manufacturing a semiconductor ring laser gyro according to claim 1, wherein the entire etching mask is heated after irradiating only the reflection mirror portion with UV light. 4. The semiconductor ring laser according to claim 1, wherein the etching mask for the ridge-shaped optical waveguide portion and the etching mask for the reflection mirror portion are formed separately using different materials or different forming conditions. Gyro manufacturing method. 5. A method of manufacturing a semiconductor ring laser gyro having a ridge-shaped optical waveguide and a reflection mirror, wherein the ridge-shaped optical waveguide and the reflection mirror are formed perpendicularly to the growth layer, and then only the ridge-shaped optical waveguide is formed. A semiconductor ring comprising isotropic etching to form a ridge-shaped optical waveguide having a side surface inclined with respect to the normal of the growth layer and a reflection mirror portion perpendicular to the growth layer. Manufacturing method of laser gyro. 6. A semiconductor ring laser gyro manufactured by the method of manufacturing a semiconductor ring laser gyro according to any one of claims 1 to 5.