JPH05335690A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To suppress the effect of an etching stopper on the element characteristics of a semiconductor device by removing the etching stopper from an area which is exposed after a second semiconductor layer is etched. CONSTITUTION:A p-type inner clad layer 35b, etching stopper layer 36, second p-type outer clad layer 35a, and p-type cap layer 37 are successively formed on an active layer 34. Then a silicon nitride layer 45 elongated in the direction perpendicular to the plane of the figure is formed in a pattern and the layers 37 and 35a are etched by using the layer 45 as a mask. As a result, the layer 37 is removed from all areas except the areas where the film 45 is formed and the etching of the layer 35a is stopped by means of the etching stopper layer 36. Thereafter, the layer 36 is removed from all parts except the mesa-like part. Therefore, the second conductor layer can be uniformly etched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms another semiconductor layer on a certain semiconductor layer with an etching stopper interposed therebetween, and when the other semiconductor layer is etched into a predetermined pattern, the etching stopper is used. The present invention relates to a semiconductor device such as a semiconductor laser device which is manufactured so as to be stopped, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A semiconductor laser device has been conventionally used as a light source for image writing of a laser printer and recording / reproducing on an optical disk. However, the image writing speed in the laser printer and the data transfer speed in the optical disk recording / reproducing apparatus are not always sufficient, and higher speed processing is demanded.

Therefore, a multi-beam type semiconductor laser device which can generate two beams which can be independently controlled from close positions is used, and one optical system for drawing and recording / reproducing is used as two beams. It is proposed to be commonly used in. That is, it is expected that a system having a double data transfer rate can be constructed by performing drawing and recording / reproducing processing in parallel with two beams.

FIG. 6 is a sectional view of a multi-beam type semiconductor laser device. An n-type buffer layer 2, an n-type clad layer 3, an active layer 4, and a p-type clad layer 5 are formed on a Si-GaAs substrate 1.
Are stacked. This p-type cladding layer 5 has two mesa-shaped portions 6a and 7 corresponding to the two light emitting regions 21 and 22.
a. P-type cap layers 6b and 7b are formed on the tops of the mesa-shaped portions 6a and 7a, respectively, to form larger overall mesa-shaped portions 6 and 7. The mesa-shaped portions 6 and 7 are formed so as to extend in a stripe shape in a direction perpendicular to FIG. 6, and the active portions of the mesa-shaped portions 6 and 7 are provided on both sides of the mesa-shaped portions 6 and 7. An n-type current blocking layer 8 is formed for concentrating a current on the layer 4 to enhance the luminous efficiency. Then, a p-type contact layer 9 is further laminated so as to cover the cap layers 6b and 7b and the current block layer 8, and an ohmic electrode 10 formed by alloying is formed on the surface of the p-type contact layer 9. There is. The ohmic electrode 11 formed by alloying is also provided on the bottom surface of the substrate 1.

The two light emitting regions 21 and 22 are separated by the current blocking layer 8, and each region of the active layer 4 corresponding to the light emitting regions 21 and 22 generates an independently controlled laser beam. You can By the way, in order to commonly use each beam generated from the light emitting areas 21 and 22 as light for image writing of a laser printer and recording / reproducing for an optical disc, it is important to make the characteristics of the two beams uniform. ..

In order to make the characteristics of the beams generated from the light emitting regions 21 and 22 uniform, it is important to make the layer thickness d of the p-type cladding layer 5 below the current blocking layer 8 uniform in each part. If the layer thickness d is non-uniform in each part, the degree of current confinement differs for each beam, and the characteristics of the generated beam become non-uniform. However, the mesa-shaped portions 6a and 7a of the p-type clad layer 5 are formed in stripes S.
It is formed by etching using an iN film or the like as a mask. At this time, the thin portions sandwiched by the stripes are difficult to etch, so it is difficult to keep the layer thickness d uniform at each portion. Such a tendency is particularly remarkable when forming three or more mesa-shaped portions in order to obtain three or more beams.

An effective method generally applied to improve the etching uniformity and solve the above problem is to replace the p-type cladding layer 5 with the inner cladding layer 5a as shown in FIG. It is divided into the outer cladding layer 5b and the etching stopper layer 15 is provided between the two cladding layers 5a and 5b. Then, the outer cladding layer 5b constitutes the mesa-shaped portions 6a and 7a. By doing so, the etching of the outer cladding layer 5b is surely stopped by the etching stopper layer 15, so that the layer thickness of the inner cladding layer 5a below the current block layer 8 can be reliably made uniform.

A technique using such an etching stopper is described, for example, in "" HIGH-POWER OPERATION OF A TRANSV.
ERS-MODE STABILISED AlGaInP VISIBLE LIGHT (λ _L )
＝ 683nm) SEMICONDUCTOR LASER ”(ELECTRONICS LETTERS
27th August 1987 Vol.23 No.18, PP 938-939) ". In the technique described in this document, the active layer is
In a semiconductor laser device using GaInP and AlGaInP for the cladding layer, GaInP and
AlGaAs is used. This technique can also be applied to a multi-beam type semiconductor laser device.

[0009]

However, in the technique for achieving uniform etching by using the above-mentioned etching stopper, the crosstalk of the current indicated by reference numeral 16 in FIG. 7 is large, and independent control of each beam is possible. There is the problem of becoming difficult. This problem will be described in more detail. When etching is stopped at the etching stopper layer 15, at least a part of the etching stopper layer 15 remains on the inner cladding layer 5a. If the etching stopper layer 15 thus remains, the etching stopper layer 15
Inner or etching stopper layer 15 and inner cladding layer 5
Current leaks through the interface with a as indicated by reference numeral 16.

Such current crosstalk is increased not only when the etching stopper layer 15 is entirely left as shown in FIG. 7, but also when the etching stopper is left even in a part thereof. .. Further, even in the single-beam type semiconductor laser device, although not as serious as in the case of the multi-beam type semiconductor laser device,
Using an etching stopper increases the spread of current,
There is a problem in that the current cannot be concentrated in a narrow region, and the efficiency of generating laser light deteriorates.

Therefore, an object of the present invention is to solve the above-mentioned technical problem, and a second semiconductor layer is laminated on the first semiconductor layer with an etching stopper interposed, and the second semiconductor layer is predetermined. The present invention is to provide a semiconductor device which is applied to a semiconductor device manufactured by etching into a pattern and can suppress the influence of the etching stopper on element characteristics, and a manufacturing method thereof.

[0012]

In order to achieve the above object, a semiconductor device of the present invention has a structure in which a second semiconductor layer is laminated on a first semiconductor layer with an etching stopper interposed therebetween. In a semiconductor device manufactured by stopping the etching with the etching stopper when the second semiconductor layer is etched into a predetermined pattern, the etching stopper in a region exposed after the etching of the second semiconductor layer is It is characterized by being removed.

The method of manufacturing a semiconductor device according to the present invention is
Manufacturing a semiconductor device in which a second semiconductor layer is stacked on a first semiconductor layer with an etching stopper interposed therebetween, the second semiconductor layer is etched into a predetermined pattern, and the etching is stopped by the etching stopper. The method is characterized in that the etching stopper in a region exposed after the etching of the second semiconductor layer is removed by etching.

According to the present invention, after etching the second semiconductor layer which is laminated on the first semiconductor layer with the etching stopper interposed, the etching stopper in the region exposed after the etching is removed by etching. It Therefore, the influence of the etching stopper on the device characteristics can be suppressed. Further, since the second semiconductor layer can be uniformly etched by using the etching stopper, desired element characteristics can be surely obtained.

In the above semiconductor device, the second semiconductor layer is formed in a predetermined pattern to form a current confinement structure, and the current is concentrated in the current confinement structure portion having the predetermined pattern, so that the current confinement structure portion is formed. A semiconductor laser device that emits light in a corresponding region may be used.

In this case, the current can be prevented from diffusing into the region other than the current confinement structure portion and the current can be favorably confined in the limited region, so that the beam generation efficiency can be improved. .. Further, the semiconductor laser device is capable of generating a plurality of beams by providing a plurality of the current confinement confinement structures on a single chip and causing each of the regions corresponding to each current confinement structure to emit light, and The supply of current to each current confinement structure may be controlled independently.

In this case, since the etching stopper does not exist between the plurality of current confinement structure portions, crosstalk between the current confinement structure portions can be effectively prevented. As a result, independent control of each beam can be favorably performed.

[0018]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view showing the structure of a semiconductor laser device which is an embodiment of the semiconductor device of the present invention. On a GaAs semiconductor substrate 31 to which Si is added, an n-type buffer layer 32 made of GaAs to which Si is added as an n-type dopant, and Si is added (Al _0.7 Ga _0.3 ).
_An n-type clad layer 33 made of _0.5 In _0.5 P is laminated in this order, and undoped GaInP is formed on the n-type clad layer 33.
The active layer 34 of is formed.

A p-type dopant is formed on the active layer 34.
Zn was added (Al_0.7Ga_0.3)_0.5In_{0 .Five}The first consisting of P
Add p-type inner cladding layer 35b, which is a semiconductor layer, and Zn
Ga_0.5In_0.5Etching stopper layer 36 made of P,
Zn was added (Al_0.7Ga_0.3) _0.5In_0.5The second consisting of P
P-type outer cladding layer 35a, which is a semiconductor layer, and Zn
Ga with addition_0.5In_0.5P-type cap layer 37 made of P
They are stacked in order.

Part of the p-type cap layer 37, the p-type inner clad layer 35b, the etching stopper layer 36, and the p-type outer clad layer 35a are etched in stripes in the direction perpendicular to the plane of FIG. The mesa-shaped portions 41 and 42 which are trapezoidal current confinement structures are configured. On both sides of each of the mesa-shaped portions 41 and 42, an n-type current block layer 38 for concentrating current in the mesa-shaped portions 41 and 42 is formed. The n-type current blocking layer 38 is made of, for example, GaAs to which Si is added.

The surfaces of the p-type cap layer 37 and the n-type current blocking layer 38 are covered with a p-type contact layer 39 made of GaAs to which Zn is added. The surface of the p-type contact layer 39 is made of, for example, Ti. A p-side electrode 40 made of / Pt / Au is formed. The electrode 40 is separated by the silicon nitride film 43 into the mesa-shaped portions 41 and 42. Therefore, currents can flow through the mesa-shaped portions 41 and 42 independently of each other. The n-side electrode 44 formed on the bottom surface of the semiconductor substrate 31 is, for example, AuGe.
It is composed of / Ni / Au.

The silicon nitride film 43 is embedded in a groove formed to a depth reaching the inside of the current block layer 38, and the contact layer 3 is formed by the silicon nitride film 43.
8 and a part of the current blocking layer 38 are separated.
As a result, crosstalk is reduced (see Japanese Patent Application No. 4-33334). With the above configuration, by selectively passing a current through the mesa-shaped portions 41 and 42, individually controlled laser beams can be generated from the respective regions of the active layer 34 indicated by reference characters A1 and A2. In this way, a multi-beam type semiconductor laser device capable of controlling each beam independently is realized.

In the semiconductor laser device of this embodiment, the etching stopper layer 36 between the mesa-shaped portions 41 and 42 is removed, so that the active layer 34 in the regions corresponding to the mesa-shaped portions 41 and 42 is removed. The generation of the beams can be well controlled independently without affecting each other. In other words, since the etching stopper layer 36 does not exist between the mesa-shaped portions 41 and 42, current crosstalk, which is a problem in the conventional configuration shown in FIG. 5, does not occur.

2 to 5 are sectional views showing a method of manufacturing the semiconductor laser device described above in the order of steps. First, Fig. 2 (a)
As shown in, for example, (100) Si with a thickness of about 70 μm
On the GaAs semiconductor substrate 31, an n-type buffer layer 32 having a layer thickness of 0.2 μm, an n-type clad layer 33 having a layer thickness of 1 μm, an active layer 34 having a layer thickness of 0.08 μm, and a layer are formed on the GaAs semiconductor substrate 31 by a metal organic chemical vapor deposition method or the like. 0.3 μm thick p-type inner cladding layer 35
b, the etching stopper layer 36 having a layer thickness of 70Å, the layer thickness of 0.
7 μm p-type outer cladding layer 35a and layer thickness 0.1
A 35 μm p-type cap layer 37 is sequentially epitaxially grown.

Next, as shown in FIG. 2B, a stripe-shaped silicon nitride film 4 extending in a direction perpendicular to the plane of FIG.
5 is patterned and the silicon nitride film 45 is used as a mask to form the cap layer 37 and the p-type outer cladding layer 3
5a is etched. The following etchants I and II are used for this etching. Etchant I ... Concentrated sulfuric acid, hydrogen peroxide solution and water are mixed in concentrated sulfuric acid: hydrogen peroxide solution: water = 5: 1: 1 and heated to 50 ° C. Etchant II ... Concentrated sulfuric acid is heated to 60 ° C. The etching rates of GaInP and AlGaInP of each etchant I and II are shown in Table 1 below.

[0026]

[Table 1]

After the silicon nitride film 45 is formed, an etching process is first performed with the etchant I for 100 seconds. As a result, the cap layer 37 in the region other than the region where the silicon nitride film 45 is formed is removed, and the outer cladding layer 35a is slightly etched. Next, an etching process is performed using the etchant II for 85 seconds. The etching by the etchant II stops at the etching stopper layer 36. As a result, the state shown in FIG.

Conventionally, the etching process was completed in this state, but in the present embodiment, etching is further performed for 10 seconds using the etchant I from the state shown in FIG. 2B, except for the mesa-shaped portions 41 and 42. The etching stopper layer 36 in the area of is removed by etching, and the inner cladding layer 35b is slightly etched. This state is shown in Figure 3.
It is shown in (c). In this state, there is no etching stopper between the adjacent mesa-shaped portions 41 and 42.

From the state of FIG. 3 (c), next, the mesa-shaped portion 4
For example, a silicon nitride film (not shown) is formed on the top portions 41a, 42a of the first and second portions 42, 42, and the current blocking layer 38 is formed into a mesa-shaped portion 41, by a metal organic chemical vapor deposition method using the silicon nitride film as a mask. 42 is selectively epitaxially grown on each side of 42. Then, after the silicon nitride film is removed, the contact layer 39 is epitaxially grown, and the state shown in FIG. 3 (d) is obtained.

Next, as shown in FIG. 4 (e), a silicon nitride film 46 is patterned to form the silicon nitride film 46.
By etching using the mask as a mask, the mesa-shaped portions 41, 4
A groove 47 having a depth reaching the current block layer 38 is formed between the two. After forming the groove 47, the silicon nitride film 4 is formed.
6 is removed, and a new silicon nitride film 48 is formed on the entire surface as shown in FIG. 4 (f).

Then, a resist film 49 is patterned on the groove 47 by photolithography, and the silicon nitride film 48 is patterned using the resist film 49 as a mask. As a result, the patterned silicon nitride film 43 is obtained as shown in FIG.
With the resist film 49 being formed on the silicon nitride film 43, a metal film 40a made of a three-layer film of Ti / Pt / Au is further formed on the entire surface. A portion of the metal film 40a on the silicon nitride film 43 is removed together with the resist film 49 by etching. As a result, the p-side electrode 40 separated by the silicon nitride film 43 as shown in FIG.
Is obtained.

Finally, the n-side electrode 44 made of a three-layer film of AuGe / Ni / Au is formed on the back surface, whereby the semiconductor laser device of FIG. 1 is obtained. In the semiconductor laser device manufactured by the method as described above, the etching stopper layer 36 between the mesa-shaped portions 41 and 42 is completely removed, so that the active layer 34 corresponding to the mesa-shaped portions 41 and 42 is generated. Current crosstalk does not occur when independently controlling the scanning beam.

Further, by stopping the etching of the outer cladding layer 35a at the etching stopper layer 36,
The etching of the outer cladding layer 35a is made uniform in each part. Then, after this, the thin etching stopper 36 is removed by etching, so that the layer thickness d of the lower inner cladding layer 35b between the mesa-shaped portions 41 and 42 is kept uniform at each portion. As a result, the characteristics of the beams generated from the active layer 34 in the portions corresponding to the mesa-shaped portions 41 and 42 are made uniform.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the AlGaInP-based laser device has been described, but the present invention can be applied to semiconductor laser devices of other materials. Specifically, for the combination of the clad material and the etching stopper material of the semiconductor laser device, the etchants having the roles corresponding to the above etchants I and II are listed in Table 2 below.
It is preferable to use the etchant shown in.

[0035]

[Table 2]

Further, it is needless to say that the numerical values such as the composition ratios of the constituent materials of the respective layers and the layer thicknesses shown in the above embodiments are examples, and these may be appropriately changed. The semiconductor laser device currently used for recording / reproducing on / from a laser printer or an optical disk is AlGaAs.
GaInP has a wavelength of 0.78 to 0.84 μm.
Alternatively, an AlGaInP-based material capable of generating light having a wavelength of 0.6 to 0.7 μm has advantages that a light spot can be easily narrowed down and that a laser printer can use a highly sensitive photosensitive material.

Further, in the above embodiment, the multi-beam type semiconductor laser device in which two beams are generated has been taken as an example, but for the multi-beam type semiconductor laser device in which three or more beams are generated. However, the present invention can be easily applied. Furthermore, the present invention is not limited to the multi-beam type semiconductor device, and may be applied to a single-beam type semiconductor device. In this case, by removing the etching stopper in the region other than the current confinement structure, It is possible to prevent the diffusion and improve the generation efficiency of the laser light.

Further, although the semiconductor laser device is taken as an example in the above-mentioned embodiment, the present invention relates to a semiconductor device manufactured by patterning a semiconductor layer using an etching stopper in order to improve etching uniformity. The present invention can be widely applied to semiconductor devices in which the blocking characteristics may change due to the presence of the etching stopper.

Besides, various design changes can be made without departing from the scope of the present invention.

[0040]

As described above, according to the present invention, the etching stopper exposed after forming the second semiconductor layer in a desired pattern is removed by etching. As a result, the second semiconductor layer can be uniformly etched using the etching stopper, and the influence of the etching stopper on the device characteristics can be suppressed.

When the present invention is applied to a semiconductor laser device formed by patterning the second semiconductor layer into a current confinement structure, the current is prevented from diffusing into a region other than the current confinement structure. The current can be concentrated well, and the beam generation efficiency can be improved. Furthermore, if the present invention is applied to a semiconductor laser device in which a plurality of the current confinement confinement structures are provided on a single chip and light emission from each current confinement structure is independently controlled, the current confinement structures can be obtained. It is possible to prevent current crosstalk due to the etching stopper between the two. As a result, independent control of each beam can be favorably performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a semiconductor laser device which is an embodiment of a semiconductor device of the present invention.

FIG. 2 is a cross-sectional view showing the method of manufacturing the semiconductor laser device of the above embodiment in the order of steps.

FIG. 3 is a cross-sectional view showing the method of manufacturing the semiconductor laser device of the above embodiment in the order of steps.

FIG. 4 is a cross-sectional view showing the method of manufacturing the semiconductor laser device of the above embodiment in the order of steps.

FIG. 5 is a cross-sectional view showing the method of manufacturing the semiconductor laser device of the above embodiment in the order of steps.

FIG. 6 is a sectional view showing a configuration of a conventional multi-beam type semiconductor laser device.

FIG. 7 is a cross-sectional view showing the structure of a semiconductor laser device manufactured using an etching stopper to make the beam characteristics uniform.

[Explanation of symbols]

 34 active layer 35a outer clad layer (second semiconductor layer) 35b inner clad layer (first semiconductor layer) 36 etching stopper layer 38 current blocking layer 41 mesa shape part (current confinement structure part) 42 mesa shape part (current confinement) Structure)

Claims (6)

[Claims] 1. A second semiconductor layer is laminated on a first semiconductor layer with an etching stopper interposed, and the etching is stopped by the etching stopper when the second semiconductor layer is etched into a predetermined pattern. A semiconductor device manufactured as described above, wherein the etching stopper in a region exposed after etching the second semiconductor layer is removed. 2. The semiconductor device according to claim 1, wherein the second semiconductor layer is formed in a predetermined pattern to form a current confinement structure, and current is concentrated in the current confinement structure part having the predetermined pattern to form the current confinement structure part. 2. The semiconductor device according to claim 1, wherein the semiconductor laser device emits light in a region corresponding to. 3. The semiconductor laser device according to claim 1, wherein a plurality of the current confinement confinement structures are provided on a single chip, and light is emitted in a region corresponding to each current confinement structure to generate a plurality of beams. 3. The semiconductor device according to claim 2, wherein the semiconductor device can be controlled and the supply of current to each current confinement structure can be controlled independently. 4. A second semiconductor layer is stacked on the first semiconductor layer with an etching stopper interposed therebetween, the second semiconductor layer is etched into a predetermined pattern, and the etching is stopped by the etching stopper. In the method of manufacturing a semiconductor device, the etching stopper in a region exposed after etching the second semiconductor layer is removed by etching. 5. The semiconductor device is a semiconductor laser device, wherein the second semiconductor layer is formed in a predetermined pattern having a current confinement structure for concentrating a current in a light emitting region. Of manufacturing a semiconductor device of. 6. The method of manufacturing a semiconductor device according to claim 5, wherein a plurality of the current closed confinement structures are formed on a single chip.