JP2002335043A - Ridge semiconductor element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a right side protective film and a ridge electrode of a semiconductor element having a ridge shape, without complicating the process. SOLUTION: The manufacturing method comprises a step for growing a clad layer 102, an optical guide layer 104, a multi-quantum well layer 106, an optical guide layer 108, a clad layer 110 and a cap layer 112 on a substrate 100 one above another as shown in (a); forming a resist mask 114 on the cap layer 112 as shown in (b); forming a ridge, using a dry etcher as shown in (c) forming a silicon nitride(SiN) protective film 116, using a CVD apparatus, as shown in (d), lifting off to expose the top of the ridge, using a remover, as shown in (e), and forming an anode 118 and a cathode 120, as shown in (f).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a ridge shape such as a semiconductor laser, and more particularly to a method for forming a ridge side face protective film and a method for forming an electrode on a ridge.

[0002]

2. Description of the Related Art In a semiconductor device having a ridge shape, such as a semiconductor laser, a passivation film (protective film) is formed to insulate the side surface of the ridge and to protect it from oxidation and contamination. Conventionally, a method for forming a ridge side surface protective film and a method for forming an electrode on a ridge include forming a ridge by etching, protecting the entire ridge with an insulating film,
In order to form an electrode, a ridge is caught by photolithography, and an electrode is formed by lift-off. However, in this case, it is difficult to control flattening (embedding of the ridge with a resist or the like) or cueing of the ridge by etchback. Further, in photolithography at the time of electrode formation, it is necessary to align the photomask and the ridge, and a positional shift eventually causes a leak current.

As described above, formation of the protective film on the side surface of the ridge and formation of the electrode on the ridge have at least some problems. For example, in Japanese Patent Application Laid-Open No. 8-316579, in order to solve this problem, embedding with excellent flatness can be achieved by controlling the ratio of solute and solvent in spin-on-glass. There is a problem that the length is defined by a constant value. In addition, a method is disclosed in which an auxiliary semiconductor layer is introduced to increase the height of the ridge so that the ridge is not completely buried when the ridge is buried. However, introduction of an auxiliary semiconductor layer that is not necessary as a functional layer complicates the process and causes problems from the viewpoint of cost.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for forming a ridge side face protective film of a ridge-shaped semiconductor device and a method for forming an electrode on a ridge, which can be performed easily and without complicating the process. Is an issue.

[0005]

According to the present invention, there is provided a method for fabricating a semiconductor device having a ridge shape, comprising the steps of: forming a ridge on a semiconductor substrate; A step of covering the ridge including the used resist mask with a protective film, a step of exposing the head of the ridge by lifting off the protective film using the resist mask, and a step of exposing the head of the ridge. The method includes a step of forming an electrode on the entire surface. That is, in the present invention, by using the resist mask used in the dry etching step for lift-off of the protective film, the electrode on the ridge can be formed without the need for the step of locating the ridge by the conventional flattening or etch-back. , The process is simplified.

Further, the method of manufacturing a semiconductor device having a ridge shape according to the present invention includes a step of forming an electrode material on the entire surface of a semiconductor substrate and a dry etching step of forming the ridge on the semiconductor substrate with the electrode material. A step of covering the ridge including the resist mask used in the dry etching step with a protective film, and a step of exposing the head of the ridge by lifting off the protective film using the resist mask. That is, in the present invention, in addition to the simplification of the process, since the electrode material is formed at the beginning of the process, a contact at a clean interface with the semiconductor layer can be realized, and the contact area with the ridge is maximized. Therefore, the contact resistivity is reduced.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

First, as shown in FIG.
, A light guide layer 104, a multiple quantum well layer 106, a light guide layer 108, a clad layer 110,
The cap layer 112 is sequentially grown.

Next, as shown in FIG. 1B, a resist mask 114 is formed on the cap layer 112.

Subsequently, as shown in FIG. 1C, a ridge is formed using a dry etching apparatus.

In this state, as shown in FIG.
Silicon nitride (SiN) protective film 116 using a VD device
To form

Subsequently, as shown in FIG. 1E, lift-off is performed using a remover to expose the head of the ridge.

Next, as shown in FIG.
18 and the cathode 120 are formed.

Next, a gyro using the method for manufacturing a semiconductor device will be described with reference to FIG.

A semiconductor laser having a ring resonator shape 20 is manufactured by using the above dry etching method. When the semiconductor laser oscillates, a clockwise laser light (CW light) 22 and a counterclockwise laser light (CCW light) 24 circling in opposite directions coexist. 26 is a mirror.

For example, consider the case where the semiconductor laser is driven at a constant current. When the semiconductor laser undergoes rotational movement, a difference occurs between the oscillation frequencies of the CW light 22 and the CCW light 24, and the two laser lights interfere with each other to generate a beat. Since the beat is detected as a frequency change of a voltage applied to the semiconductor laser, the beat can be used as a gyro that can detect an angular velocity of an object using the beat. Furthermore, if a beat signal is obtained even when the gyro is stationary, it is possible to detect the rotation direction by comparing the beat signals when the gyro is stationary and when the gyro is rotating. Specifically, as described in European Patent Publication No. 1020706, by providing an asymmetric tapered shape in a part of a ring-shaped ridge-shaped waveguide, CW light and CCW light can be obtained even at rest. The beat signal resulting from the difference in loss is obtained.

[0017]

FIG. 3 is a schematic view for explaining a method of manufacturing a ring laser gyro having a ring-shaped ridge structure. In the figure, 300 is a substrate, 302 is a cladding layer, 304 is a light guide layer, 306 is a multiple quantum well layer,
308 is a light guide layer, 310 is a cladding layer, 312 is a cap layer, 314 is a resist mask, 316 is a protective film,
318 is an anode, 320 is a cathode, 322 is an output terminal, and 324 is a drive terminal. The cross-sectional view taken along the line AA ′ in FIG. 2 corresponds to the cross-sectional view in FIG.

First, as shown in FIG. 3A, a semiconductor layer constituting a semiconductor laser is laminated on an n-GaAs substrate 300 (thickness: 350 μm) using a metal organic chemical vapor deposition (MOCVD) apparatus. grow up. That is, n-AlGa
As clad layer 302 (1.5 μm thick), undoped AlGaAs optical guide layer 304 (0.1 μm thick)
m), GaAs / AlGaAs having a composition of 0.85 μm
s multiple quantum well layer 306 (well layer thickness 0.01 μm ×
3 layers, barrier layer thickness 0.01 μm × 2 layers), undoped AlGaAs optical guide layer 308 (0.1 μm thickness),
p-AlGaAs cladding layer 310 (1.5 μm thick)
m), p-GaAs cap layer 312 (0.5 μm thick)
m) grow.

Next, a photoresist is applied by using a spin coater in FIG.
As shown in (b), a resist mask 314 is formed.

Subsequently, as shown in FIG. 3C, the substrate is introduced into a reactive ion beam etching (RIBE) apparatus, and a ridge is formed using chlorine gas. The etching conditions at this time are: microwave power: 120 W, pressure: 0.106 Pa (0.8 mTorr), chlorine gas flow rate: 0.02 Pa · m ³ / sec (12 scc)
m), ion extraction voltage: 300 V, substrate temperature: room temperature. As a result, a vertical and smooth ridge (roughness of about 10 nm in scanning electron microscope observation) is formed. When observing the ridge-shaped semiconductor side with a transmission electron microscope, no lattice image disorder was observed.
It was confirmed that etching was achieved without inducing side damage. Also, since there is no difference in the etching rate due to the difference in the constituent elements of each semiconductor layer,
No unevenness due to the laminated structure was observed.

Next, as shown in FIG. 3D, the substrate is introduced into a plasma enhanced chemical vapor deposition (PECVD) apparatus, and a silicon nitride (SiN) protective film (thickness: 200 nm) 316 is formed.
To form

Subsequently, as shown in FIG. 3 (e), the substrate is immersed in a remover solution heated to 80 ° C. and subjected to an ultrasonic cleaner to lift off the protective film on the upper surface of the ridge. As a result, the cap on the upper surface of the ridge is removed. Layer 312 is exposed.

Next, as shown in FIG. 3 (f), the substrate is introduced into a sputtering apparatus, and Ti / Au (Ti thickness: 50
nm, thickness of Au: 500 nm) An anode 318 is formed, and the substrate is introduced into an electron beam evaporation apparatus to form an anode.
A uGe / Au (thickness of AuGe: 0.2 μm, thickness of Au: 0.2 μm) cathode 320 is deposited. Thereafter, rapid heat treatment (RTA) at 375 ° C. in a nitrogen atmosphere
And made ohmic contact.

Thereafter, as shown in FIG. 3 (g), a terminal 322 is provided on the anode 318 in order to detect a beat signal generated in the semiconductor laser as a change in current, voltage or impedance. The beat signal output from the terminal is detected as a change in current, voltage, or impedance by a detection circuit (not shown).
324 is a drive terminal.

Thus, a gyro having the ring-resonant semiconductor laser shown in FIG. 4 is manufactured. FIG.
1 shows only the active layer 306, and the other layers are omitted.

As shown in FIG. 3C, vertical and smooth ridges can be formed by dry etching, so that a mirror having a high reflectance can be manufactured.

Further, a total reflection surface could be formed over the entire ring resonator. In addition, the protective film served as an insulator, and an element having no leak was produced with good reproducibility. As a result, a gyro having a small oscillation threshold current was realized, a beat signal could be obtained stably, and an angular velocity could be detected.

Although the shape of the ring resonator is a square here, it may be circular, triangular or polygonal.

Although RIBE is shown here as a dry etching apparatus, the present invention is not limited to this, and ICP-RIE, CAIBE or the like may be used.

Further, although the chlorine gas as an etching gas, BCl ₃ is not limited to this, Si
It may be Cl ₄ or the like.

Although SiN is shown here as the protective film, the present invention is not limited to this, and silicon dioxide (SiO ₂ ) may be used.

In this case, P is used as a protective film forming apparatus.
Although ECVD has been described, the present invention is not limited to this, and sputtering may be used.

Also, here, a ring laser gyro having a ring-shaped ridge structure is shown as an example of a semiconductor element.
Any semiconductor element such as a light emitting element such as a semiconductor laser or a light emitting diode, or a light receiving element such as a photodiode may be used.

[Second Embodiment] FIG. 5 is a schematic view for explaining another method of manufacturing a ring laser gyro having a ring-shaped ridge structure. 400 is a substrate, 402 is a cladding layer, 404 is a light guide layer, 406 is a multiple quantum well layer,
408 is a light guide layer, 410 is a cladding layer, 412 is a cap layer, 414 is an anode, 416 is a protective film, 420
Is a cathode, 422 is an output terminal, and 424 is a drive terminal. The cross-sectional view taken along the line AA ′ in FIG. 2 corresponds to the cross-sectional view in FIG.

First, as shown in FIG. 5A, a semiconductor layer constituting a semiconductor laser is laminated on an n-GaAs substrate 400 (thickness: 350 μm) using a metal organic chemical vapor deposition (MOCVD) apparatus. grow up. That is, n-AlGa
As clad layer 402 (1.5 μm thick), undoped AlGaAs optical guide layer 404 (0.1 μm thick)
m), GaAs / AlGaAs having a composition of 0.85 μm
s multiple quantum well layer 406 (well layer thickness 0.01 μm ×
3 layers, barrier layer thickness 0.01 μm × 2 layers), undoped AlGaAs optical guide layer 408 (0.1 μm thickness),
p-AlGaAs cladding layer 410 (1.5 μm thick)
m), p-GaAs cap layer 412 (0.5 μm thick)
m) grow. Subsequently, the substrate is immersed in a mixed solution of hydrochloric acid: phosphoric acid: water to perform a pretreatment, and introduced into a sputtering apparatus for T
i / Au (Ti thickness: 50 nm, Au thickness: 50
0 nm) Anode 414 is deposited.

Next, as shown in FIG. 5B, a photoresist is applied using a spin coater, and after exposure and development processes, a resist mask 416 is formed. In this state, the substrate is introduced into a reactive ion etching (RIE) apparatus, and the Ti / Au anode 414 is etched.
The etching condition at this time is RF power: 500 W
(Both Ti and Au etching), pressure: 0.5 Pa
(3.7 mTorr), gas flow rate: BCl ₃ ... 0.1
5 Pa · m ³ / sec (90 sccm, at the time of Au etching), SF ₆ ... 0.05 Pa · m ³ / sec (30
sccm, Ti etching). as a result,
A vertical and smooth Ti / Au anode 414 ridge was formed.

Further, as shown in FIG. 5C, the substrate in this state is subjected to reactive ion beam etching (RIBE).
The semiconductor device is introduced into the apparatus, and the semiconductor multilayer structure is etched using chlorine gas to form a ridge. The etching conditions at this time were as follows: microwave power: 120 W, pressure: 0.10
6 Pa (0.8 mTorr), chlorine gas flow rate: 0.
02 Pa · m ³ / sec (12 sccm), ion extraction voltage: 300 V, substrate temperature: room temperature. As a result, a vertical and smooth ridge (roughness of about 10 nm in scanning electron microscope observation) was formed. Observation of the side surface of the ridge-shaped semiconductor with a transmission electron microscope confirmed that etching was achieved without inducing damage to the side surface since no disturbance of the lattice image was observed. Further, no difference in etching rate due to a difference in constituent elements of each semiconductor layer appears, and thus no unevenness due to the stacked structure is observed.

Next, as shown in FIG. 5D, the substrate is introduced into a plasma enhanced chemical vapor deposition (PECVD) apparatus, and a silicon nitride (SiN) protective film (thickness: 200 nm) 41 is formed.
8 is formed.

Subsequently, as shown in FIG. 5 (e), the substrate is immersed in a remover solution heated to 80 ° C. and subjected to an ultrasonic cleaner to lift off the protective film on the ridge upper surface. As a result, the Ti on the ridge upper surface is lifted off. / Au anode 414 is exposed. Further, the substrate is introduced into an electron beam evaporation apparatus and Au is introduced.
A Ge / Au (AuGe thickness: 0.2 μm, Au thickness: 0.2 μm) cathode 420 is deposited. Thereafter, rapid heat treatment (RTA) is performed at 375 ° C. in a nitrogen atmosphere,
Ohmic contact was made.

Thereafter, as shown in FIG. 5F, a terminal 422 is provided on the anode 414 in order to detect a beat signal generated in the semiconductor laser as a change in current, voltage or impedance. The beat signal output from the terminal is detected as a change in current, voltage, or impedance by a detection circuit (not shown).
424 is a drive terminal.

Thus, a gyro having the ring-resonant semiconductor laser shown in FIG. 6 is manufactured. FIG.
In FIG. 7, only the active layer 406 is shown, and other layers are omitted.

As shown in FIG. 5C, vertical and smooth ridges can be formed by dry etching, so that a mirror having high reflectivity could be manufactured. Further, a total reflection surface could be formed over the entire ring resonator. In addition, the protective film served as an insulator, and an element having no leak was produced with good reproducibility. As a result, a gyro having a small oscillation threshold current was realized, a beat signal could be obtained stably, and an angular velocity could be detected. Further, since the anode was formed at an early stage of the process, a contact with a clean semiconductor interface was obtained, so that the contact resistivity was reduced.

Although the shape of the ring resonator is square here, it may be circular, triangular or polygonal.

Although RIBE is shown here as a dry etching apparatus, the present invention is not limited to this and may be ICP-RIE, CAIBE, or the like.

Further, although the chlorine gas as an etching gas, BCl ₃ is not limited to this, Si
It may be Cl ₄ or the like.

Although SiN is shown here as the protective film, the present invention is not limited to this, and may be silicon dioxide (SiO ₂ ).

In this case, the protective film forming apparatus is P
Although ECVD has been described, the present invention is not limited to this, and sputtering may be used.

Although a ring laser gyro having a ring-shaped ridge structure is shown here as an example of a semiconductor device,
Any semiconductor element such as a light emitting element such as a semiconductor laser or a light emitting diode, or a light receiving element such as a photodiode may be used.

[0049]

According to the present invention described above, the ridge side surface protective film and the ridge upper electrode of the semiconductor element having the ridge shape can be formed easily and without complicating the process.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a ring resonator shape manufactured by using the manufacturing method according to the present invention.

FIG. 3 is a schematic cross-sectional view for explaining a method for manufacturing a semiconductor device having a ridge shape according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a gyro having a ring resonator type semiconductor laser having a ridge shape according to the first embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view for explaining a method for manufacturing a semiconductor device having a ridge shape according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a gyro having a ring resonator type semiconductor laser having a ridge shape according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 20 ring resonator 22 clockwise laser light (CW light) 24 counterclockwise laser light (CW light) 26 mirror 100, 300, 400 substrate 102, 302, 402 clad layer 104, 304, 404 light guide layer 106, 306, 406 Multiple quantum well active layer 108, 308, 408 Light guide layer 110, 310, 410 Cladding layer 112, 312, 412 Cap layer 114, 314, 416 Resist mask 116, 316, 418 Protective film 118, 318, 414 Anode 120, 320, 420 Cathode 322, 422 Output terminal 324, 424 Drive terminal

Claims (4)

[Claims] 1. A method for manufacturing a semiconductor device having a ridge shape, comprising: a dry etching step of forming the ridge on a semiconductor substrate; and a step of covering the ridge including a resist mask used in the dry etching step with a protective film. A step of exposing the head of the ridge by lifting off the protective film using the resist mask; and forming an electrode over the entire surface with the head of the ridge exposed. Method of manufacturing a semiconductor device. 2. A method for manufacturing a semiconductor device having a ridge shape, comprising: forming an electrode material on the entire surface of a semiconductor substrate; dry etching forming the ridge on the semiconductor substrate with electrodes; A step of covering the ridge including the resist mask used in the step with a protective film, and a step of exposing the head of the ridge by lifting off the protective film using the resist mask. A method for manufacturing a semiconductor element. 3. The method for manufacturing a ridge-type semiconductor device according to claim 1, wherein the semiconductor substrate is a compound semiconductor substrate having a laminated structure of heterogeneous semiconductor layers. 4. A ring laser gyro having a ring-shaped ridge type structure formed by using the method for manufacturing a ridge type semiconductor device according to claim 1.