JPH09219367A - Method for manufacturing semiconductor device - Google Patents

Abstract

Kind Code: A1 A method for manufacturing a semiconductor device, in which when a semiconductor device is formed by selective growth, the in-plane distribution of carrier density is made uniform. A semiconductor substrate (1) provided with a selective growth mask (2)
A III-V group compound semiconductor layer composed of at least one group III element selected from In, Ga, and Al and at least one group V element selected from As and P is formed on the upper surface of the organic metal. When selective growth is performed by the vapor phase epitaxy method, as the n-type doping material, a doping material in which the dopant diffusion amount from the selective growth mask region cancels out the group III element diffusion amount and the dopant concentration becomes substantially uniform is used.

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, and more particularly to a metal organic chemical vapor deposition method (M
The present invention relates to a method for manufacturing a semiconductor device such as a semiconductor laser using selective growth by the OVPE method).

[0002]

2. Description of the Related Art In recent years, the characteristics of optical semiconductor devices such as semiconductor lasers have been greatly improved by using a multiple quantum well (MQW) structure. Integrating devices having different functions, such as integration.

In such integration, the MQW structure can be formed with good controllability, and by using the dielectric pattern as a selective growth mask, the film thickness distribution and composition distribution in the growth plane can be formed, and a large amount can be formed. The MOVPE method, which is suitable for production, is used.

Now, a conventional semiconductor laser using the MOVPE method will be described with reference to FIG. Note that Fig. 3 (a)
3B is a plan view at the time when the selective growth mask is formed, and FIG. 3B is a cross-sectional view after the growth along the one-dot chain line connecting AA ′ in FIG.

Referring to FIGS. 3A and 3B, first, a SiO ₂ film is provided on the n-type InP substrate 21 and then patterned to form a stripe-shaped opening and spot size for forming the gain region 23. S having a tapered opening for forming the conversion region 24
An iO ₂ mask 22 is formed.

Then, an n-type InP buffer layer 25 which also serves as a cladding layer is deposited by MOVPE using SiH ₄ as a doping material, and then InGaAs is deposited.
P light guide layer 26, InGaAs PMQW active layer 27,
The InGaAsP optical guide layer 28, the p-type InP cladding layer 29, and the p ⁺ -type InGaAsP contact layer 30 are deposited.

[0007] In this case, only grow in the selective growth region of the opening does not occur the growth of the semiconductor layer occurs on the SiO ₂ mask 22, the material of the diffusion amount from the mask region to form a SiO ₂ mask 22 Difference This causes the stripe-shaped opening for forming the gain region 23 to be deposited thicker than the tapered opening for forming the spot size conversion region 24, so that the InG in the gain region 23 is deposited.
The energy gap between the quantum levels of the aAsPMQW active layer 27 depends on the InG in the spot size conversion region 24.
Since it is smaller than the energy gap between the quantum levels of the aAsPMQW active layer 27, an energy gap distribution is formed in the laser cavity direction.

In the spot size conversion region 24, the InGaAsP optical guide layers 26 and 28 are also tapered toward the emitting end face, and the ridge width is expanded in a tapered manner to expand the spot size of the laser beam. To do.

Next, after each electrode (not shown) is formed, by appropriately dividing the element, a spot size converter having an energy gap distribution in the laser resonator direction and a small light absorption loss at the light emitting end face is provided. The semiconductor laser is completed.

Such a semiconductor laser with a spot size converter is excellent in avoiding the cutoff of the guided mode at the emitting end face and reducing the radiation loss.

[0011]

In the manufacturing process of such a semiconductor laser with a spot size converter, an n-type I
When selectively growing the nP buffer layer 25, monosilane (SiH ₄ ) having a good flow rate controllability by a mass flow controller is used as a doping raw material. However, when SiH ₄ is used as a doping raw material, an in-plane carrier concentration is obtained. Since there is a problem that uniformity cannot be obtained, this situation will be generalized and described with reference to FIG.

Referring to FIGS. 4A and 4B, that is, a selective growth mask 32 made of a SiO ₂ film is provided on a semiconductor substrate 31, and SiH ₄ is used as a doping material.
When the n-type InP layer is grown by the OVPE method, in the selective growth region 33 sandwiched by the selective growth masks 32, in addition to the original group III source material supply, the selective growth mask 3
There is III group source diffusion from the mask area provided with II, II
Under the conditions of group I raw material supply << group V raw material supply,
Since the growth rate of the n-type InP layer depends on the supply amount of the group III source material, the growth rate distribution on the semiconductor substrate 31 is III.
It has the same shape as the group element flux distribution.

On the other hand, the flux distribution of the dopant depends on the incorporation efficiency of the doping raw material, that is, when the incorporation efficiency is high because diffusion due to the difference in concentration of the dopant occurs to compensate for the amount reduced by the incorporation, the doping efficiency is high. Since the amount of reduction of the raw material is large, the dopant flux 35 becomes large.

The group III element flux and the dopant flux mean the flux of the decomposition species of the group III raw material and the flux of the decomposition species of the doping raw material, and do not mean the flux of the pure group III element or the impurity element. Absent.

Since the incorporation efficiency of SiH ₄ during the growth of the InP layer in the MOVPE method is as low as 1% or less, the dopant flux 35 is also very small, and the diffusion of the dopant from the selective growth mask region is almost the same. This does not occur, and the Si dopant distribution in the gas phase becomes substantially uniform.

Therefore, in the selective growth region 33, although the supply amount of the group III element is larger than that of the other growth regions, the supply amount of the dopant is substantially uniform, so that the carrier density ∝dopant flux / group III element flux. From the above relationship, the carrier density has a distribution form in which the group III element flux distribution is inverted, and in-plane uniformity of carrier density cannot be obtained.

Therefore, it is an object of the present invention to make the in-plane distribution of carrier density uniform when a semiconductor device is formed by selective growth.

[0018]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG. 1 (a) and 1 (b) (1) The present invention relates to a method of manufacturing a semiconductor device, in which In, Ga,
And at least one or more Group III elements of Al,
When selectively growing a III-V group compound semiconductor layer consisting of at least one V group element of As and P by metal organic chemical vapor deposition, as an n-type doping raw material,
It is characterized by using a doping material in which the dopant diffusion amount from the selective growth mask region cancels out the group III element diffusion amount and the dopant concentration becomes substantially uniform.

As described above, the metal organic chemical vapor deposition (MOVP) method
When the n-type III-V compound semiconductor layer is selectively grown by the E method), the dopant diffusion amount from the selective growth mask region as the n-type doping raw material offsets the group III element diffusion amount and the dopant concentration is substantially uniform. By using the doping material that becomes, the in-plane distribution of the dopant concentration, that is,
The in-plane distribution of carrier density can be made substantially uniform, and thus the characteristics of the semiconductor device can be improved.

(2) The present invention also provides the odor according to the above (1).
Si as a doping material_TwoH ₆Specially used
Sign.

Thus, the growth of the III-V group compound semiconductor layer
At this time, Si as a doping material _TwoH₆When using
Has Si_TwoH₆The capture efficiency is several tens of percent.
SiH with efficiency of 1.0% or less_FourVery high compared to
Therefore, the dopant flag in the selective growth region 3 is
Since the cube 5 also becomes large, III in the selective growth region 3
The increase in group 4 element flux was offset and the carrier density
The inner distribution can be made uniform.

(3) Further, the present invention is characterized in that in the above (2), the growth temperature is set to 680 ° C. or higher.

As described above, Si ₂ H is used as a doping raw material.
_{When 6} is used, the in-plane distribution of carrier density can be made uniform by setting the growth temperature to 680 ° C. or higher, and more preferably 700 ° C. or higher.

(4) Further, in the present invention according to the above (1), when R is an alkyl group as a doping material,
It is characterized by using an alkylsilane represented by SiR _n H _4-n (where 1 ≦ n ≦ 4).

Since the decomposition temperature of alkylsilane is lower than that of Si ₂ H ₆ and the incorporation efficiency of the dopant depends on the decomposition temperature, when alkylsilane is used as the doping raw material, the carrier temperature is lower at the lower growth temperature. The in-plane distribution of density can be made uniform.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. 2 (a). First, the width W is 240 μm and the length L is on the InP substrate 11.
A pair of SiO ₂ masks 12 having a thickness
Of 60 μm is formed as a selective growth mask.

Then, 0.3 sccm of trimethylindium (TMIn) as a group III source gas and 90 sccm of phosphine (PH ₃ ) as a group V source gas were flown to make the group V source gas / group III source gas ratio 300.
Further, the n-type InP layer is grown at a growth pressure of 50 Torr while Si ₂ H ₆ is being used as a dopant material.

The supply amount of Si ₂ H _{6 in} this case is
At each growth temperature, the carrier density at the point B in the region without the SiO ₂ mask 12 is set to be about 1 × 10 ¹⁸ cm ⁻³ .

See FIG. 2 (b). In this case as well, Si is formed in the selective growth region 13 as in the conventional case.
The group III raw material generated by the decomposition of TMIn is diffused from the mask region provided with the O ₂ mask 12, the group III element flux 14 becomes larger than the regions other than the selective growth region 13, and the center of the selective growth region 13 The growth rate at the point A is about 2.5 times the growth rate at the point B in the region without the SiO ₂ mask 12. Therefore, the thickness of the n-type InP layer at the point A is 2. It became 5 times.

See FIG. 2C. In this case, the growth temperatures are 630 ° C., 680 ° C., and 73 ° C.
As a result of growing under three conditions of 0 ° C, the growth temperature was 63
At 0 ° C, the carrier at point A, as shown in
Density is about 6 × 10¹⁷cm^-3And the carrier density at point B is about
1 × 10¹⁸cm ^-3And the key in the selective growth region 13
Carrier density is about 3/5 of the density in the non-selective growth region
Is declining.

When the growth temperature is 680 ° C., the carrier density at the point A is about 8 × 10 ^{17 as shown in.}
At ⁻³ cm ⁻³ , the carrier density at point B is about 1 × 10 ¹⁸ cm ⁻³ , and the carrier density in the selective growth region 13 is reduced to about 4/5 of the density in the non-selective growth region, but this is tolerable. It is within the range.

Further, when the growth temperature is 730 ° C., the carrier density at point A is about 1 × 10 6, as shown in.
^{At 18} cm ⁻³ , it is almost the same as the carrier density at point B, and the in-plane carrier density is very uniform.

Thus, Si ₂ H is used as the n-type dopant.
_{When 6} is used, the uptake efficiency without the selective growth mask is 30% (630 ° C.) to 6 with the growth temperature.
Since the temperature rises to 0% (730 ° C.), when the selective growth mask is used, the diffusion amount due to the concentration difference increases with temperature and a uniform in-plane distribution is gradually obtained. It is considered that the inner distribution can be obtained.

From FIG. 2 (c), it is predicted that at the growth temperature of 700 ° C., a carrier density of about 9 × 10 ¹⁷ cm ^-3 is obtained at point A, and a distribution of about 9:10 is sufficient. Since it is acceptable, a growth temperature of 700 ° C. or higher is more desirable when Si ₂ H ₆ is used.

Here, represents the carrier density distribution when SiH ₄ was used as a dopant for comparison with Si ₂ H ₆ , and B at the growth temperature of 630 ° C.
When the carrier density at the point is 1 × 10 ¹⁸ cm ⁻³ , the carrier density at the point A is 4 × 10.
^{At 17} cm ⁻³ , a distribution with a ratio of 1: 2.5 was formed, and this ratio hardly changed even when the growth temperature was increased.

It is considered that this is because the SiH ₄ incorporation rate is as low as 1% or less, and the change in the dopant flux due to the concentration difference diffusion is very small even if the growth temperature is increased.

In the above description of the embodiment, Si ₂ H ₆ is used as the dopant material,
It is not limited to Si ₂ H ₆ , but R is CH ₃ or C ₂
When an alkyl group such as H ₅ is used, SiR _n H _4-n (1
An alkylsilane represented by ≦ n ≦ 4) may be used.

That is, when silane is used as the dopant raw material, the efficiency of dopant uptake tends to depend on the decomposition temperature, and the decomposition temperature of the alkylsilane is Si ₂ H ₆
Since it is lower than the decomposition temperature of, the carrier density distribution in the growth plane can be made uniform even at a lower growth temperature.

Particularly, in the case of alkylsilane, the higher the molecular weight of the alkyl group is, the lower the decomposition temperature is, but tetraethylsilane [(C ₂ H ₅ ) ₄ Si is used because of its ease of handling or availability. ] Is most preferable, or tetramethylsilane [(CH ₃ ) ₄ Si] may be used.

As a specific film forming condition, the group V source gas / group III source gas ratio is 300 and the growth pressure is 50 Torr, but the present invention is not limited to such conditions, and the group V source is not limited. Source gas / Group III source gas ratio is 10
The growth pressure may be 10 to 500.
It may be in the range of 200 Torr.

Further, in the description of the embodiment of the present invention, only the growth process of the n-type InP layer is described, but an actual semiconductor device such as the semiconductor laser with a spot size converter shown in FIG. 3 is used. When manufacturing n, Si ₂ H ₆ or alkylsilane may be used as a dopant material when growing the n-type layer.

In the example shown in FIG. 3, the MQW structure of the active layer is provided with a film thickness distribution by selective growth, an energy gap distribution is formed in the laser cavity direction, and the layer thickness in the spot size conversion region is set. Although thinned in a taper shape, when forming an optical modulator integrated DFB laser using a p-type substrate, when growing an n-type cladding layer and an n ⁺ -type contact layer to be grown on an active layer You may apply.

In addition, although InP-based semiconductors have been described in the above-mentioned embodiments, the present invention is not limited to InP, and In, Ga, and
Alternatively, at least one element of Al and V
It is applied to a III-V group compound semiconductor composed of at least one element of As or P as a group element.

Further, in the above description, only the integrated semiconductor laser device is referred to as the semiconductor device to which the present invention is applied, but the invention is not limited to the integrated semiconductor laser device, and the integrated light receiving semiconductor device or the integrated semiconductor laser device is used. It is also applied to other semiconductor devices such as a compound semiconductor transistor device that performs element isolation by selective growth.

[0045]

According to the present invention, in the step of forming the film thickness distribution or composition distribution by selective growth, when the n-type layer is grown, Si ₂ H ₆ (disilane) or alkylsilane is used as a doping material. Since a raw material having a low decomposition temperature and a high uptake efficiency is used, the dopant concentration in the entire layer, that is, the carrier density can be made uniform. When manufacturing a semiconductor device in which elements having different functions are integrated, a semiconductor device having stable characteristics can be manufactured with good reproducibility.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional semiconductor laser.

FIG. 4 is an explanatory diagram of problems in conventional selective growth.

[Explanation of symbols]

1 semiconductor substrate 2 selective growth mask 3 selective growth region 4 group III element flux 5 dopant flux 11 n-type InP substrate 12 SiO ₂ mask 13 selective growth region 14 group III element flux 15 dopant flux 21 n-type InP substrate 22 SiO ₂ mask 23 Gain region 24 Spot size conversion region 25 n-type InP buffer layer 26 InGaAsP optical guide layer 27 InGaAsPMQW active layer 28 InGaAsP optical guide layer 29 p-type InP clad layer 30 p ⁺ type InGaAsP contact layer 31 semiconductor substrate 32 SiO ₂ mask 33 selective growth Region 34 Group III element flux 35 Dopant flux

Claims (4)

[Claims] 1. A semiconductor substrate provided with a selective growth mask, wherein at least one group III element of In, Ga, and Al and at least one group V element of As and P are provided. When the group III-V compound semiconductor layer consisting of and is selectively grown by metalorganic vapor phase epitaxy, the dopant diffusion amount from the selective growth mask region is used as an n-type doping material by canceling the group III element diffusion amount. A method of manufacturing a semiconductor device, which uses a doping material having a substantially uniform concentration. 2. Si ₂ H ₆ as the doping raw material
The method for manufacturing a semiconductor device according to claim 1, wherein the method is used. 3. The method for manufacturing a semiconductor device according to claim 2, wherein the growth temperature when Si ₂ H ₆ is used as the doping raw material is set to 680 ° C. or higher. 4. The alkylsilane represented by SiR _n H _4-n (where 1 ≦ n ≦ 4) is used when R is an alkyl group as the doping raw material. Of manufacturing a semiconductor device of.