JPH0467334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device in which a crystal layer is formed on a substrate whose surface has irregularities such as steps and grooves.

Epitaxial growth is one of the methods for manufacturing semiconductor devices. In this method, a semiconductor layer is formed on the surface of a certain substrate using a material different from the substrate or a material of the same type as the substrate. When forming this semiconductor layer, there are the following problems.

The thickness of the semiconductor epitaxial growth layer may vary within the substrate plane, and sometimes the semiconductor epitaxial growth surface has a square pyramid shape,
What is usually called a step or swirl occurs. As a result of the above, the formation of a uniform semiconductor epitaxial growth layer on a certain substrate is hindered.

In addition to the above-mentioned problems, in a substrate having steps, grooves, and similar unevenness formed on the surface, the growth cross-sectional shape of the semiconductor epitaxial growth layer formed on the substrate varies significantly in the direction along the substrate surface.

In addition to the above-mentioned problems, the cross-sectional shape of a semiconductor epitaxially grown film formed on the same step, groove, or similar unevenness becomes asymmetrical as shown in FIGS. 1 and 2. Note that FIG. 1 shows a GaAs single crystal substrate 12 with a stepped portion formed on its surface, and a semiconductor growth layer 31 is formed from above the stepped portion. As is clear from the figure, the semiconductor growth layers on the left and right sides of the stepped portion are asymmetrical.

FIG. 2 shows a GaAs single crystal substrate 12 with grooves formed on its surface, and a semiconductor growth layer 31 is formed from the top of the groove, but the semiconductor growth layer inside and outside the groove is clearly visible from the figure. The left and right sides are asymmetrical.

As one method to solve the above problems, in the vapor phase growth method, a plane with a plane index deviation of several degrees from the 100 plane is used as the growth plane of a Si single crystal substrate or a GaAs single crystal substrate, and a uniform thickness is obtained. There is an example of obtaining a growth layer and manufacturing a semiconductor device.

However, no method has been proposed to solve all of the above-mentioned problems, and furthermore, there is no example in which the above-mentioned problems have been solved in a substrate having steps, grooves, and similar unevenness formed on the surface.

The present invention involves forming a semiconductor layer on the substrate using the shape of the steps, grooves, and similar unevenness on the surface of the substrate, and determining the shape of the semiconductor layer. The purpose is to manufacture semiconductor devices with desired electrical and optical properties through control. In other words, in a semiconductor device using a substrate having steps, grooves, and similar unevenness formed on the surface, the substrate surface is 100, 111, 110 or an equivalent surface [moo, nnm, kko;
m, n, k are integers of 2 or more], specify the surface index deviation in two directions. That is, the present invention provides a semiconductor device characterized in that the surface index deviation θ ₂ of the step, groove, etc. in the ridgeline direction is larger than the surface index deviation θ ₁ in the direction perpendicular to the ridgeline direction.

The present invention will be specifically described below with reference to Examples.

Here, 100 planes are used as the substrate planes. As shown in the plane and cross-sectional views of Figures 4a and 4b, a step is formed on the substrate surface so that the cross-sectional shape becomes an inverted mesa, and as shown in Figures 3 and 4a and b, the step is The plane index deviation from the 100 plane in the ridge direction is θ ₂ ,
Let θ ₁ be the plane index deviation from the 100 plane in the direction perpendicular to the ridgeline direction of the step.

GaAs single-crystal substrates are cut out accurately by fixing a GaAs ingot with a jig and determining the crystal plane. In the GaAs single crystal substrate of the semiconductor device of the present invention that utilizes the 100 crystal plane, the deviations from the 100 crystal plane in the <011> direction and the <011> direction perpendicular thereto are defined as θ ₁ and θ ₂ , respectively. The settings of θ ₁ and θ ₂ are determined by determining the values of θ 1 ′ and θ 2 ′ by analyzing the surface of a GaAs substrate cut out from an ingot fixed in advance by X-ray diffraction, and then determining the values of θ ₁ ′ and θ ₂ ′. Based on this, the ingot fixing jig is adjusted so that θ ₁ ′→θ ₁ and θ ₂ ′→θ ₂ are set, and the substrate is cut out. And for these 100 crystal planes, the ridgeline direction of the step is θ ₂
By adjusting the angles θ 1 and θ 2 of the plane indices in the two directions, it is possible to determine the deviation angles θ ₁ and θ ₂ of the plane indexes in the two directions.

By the way, FIG. 5 shows a cross section of a stepped substrate type semiconductor laser (hereinafter referred to as TS laser) manufactured by liquid phase crystal growth on a GaAs single crystal substrate surface with steps as shown in FIG. 4 above. Show shape. The crystal growth initiation temperature was 850°C, and the crystal growth was performed at a cooling rate of 0.5C/min. 10 is the surface formed on the substrate surface to form a step, and 11 is the surface of 100°C.
There is a plane index deviation of θ ₁ and θ ₂ from the plane.
This is the surface of a GaAs single crystal substrate. 12 is a GaAs single crystal substrate, 17 is an n-type Ga _x A _1-x As cladding layer, 1
8 is Ga _y A _1-y As active layer, 19 is p-type Ga _x A _1-
x As clad layer, 20 is n-type GaAs layer, 21 is n
It is a Ga _z A _1-z As layer, and is a semiconductor laser device with a five-layer structure. The area within the circle surrounded by the broken line 23 is the laser oscillation area. The distance d indicated by 22 is
This distance is important for the electrical and optical characteristics of the TS laser.

If the growth conditions are exactly the same, but the plane index deviations θ ₁ and θ ₂ from the 100 plane of the growth plane of the GaAs single crystal substrate take various values, the shape of the grown layer near the step of the layer grown on the step substrate will change. , changes as shown in FIG. 6a to FIG. 6b. Such a change also occurs when multilayer crystal growth is performed on a step, resulting in a change in the distance d shown at 22 of the p-type Ga _x A _1-x As cladding layer 19 of the semiconductor laser device in Fig. 5. It appears,
This impairs the electrical and optical characteristics of this element, making it impossible to obtain a promising semiconductor device.

Therefore, on a GaAs single crystal substrate surface with various sets of plane index deviation values (θ ₁ , θ ₂ ) from the 100 plane,
When the TS laser device shown in Fig. 5 was fabricated, the following things became clear.

FIGS. 7a, b, c, and d show a typical example of a set of plane index deviation values (θ ₁ , θ ₂ ) from the 100 plane of the GaAs single crystal substrate used. 100
When the TS type semiconductor laser shown in Fig. 3 is fabricated on the growth substrate surface where the set of plane index deviation values from the plane has a relationship of θ ₁ < θ ₂ , the TS type semiconductor laser shown in Fig. 7 a and b is 2
If the distance d of 2 is almost never more than 5 μm, and the variation in d has the relationship θ ₁ > θ ₂ , then Fig. 7c,
It is less than d.

Therefore, from 100 planes, we experimentally found a set of plane index deviation values (θ ₁ , θ ₂ ) with the relationship θ ₁ < θ ₂ .
It is better to grow crystals on the GaAs single crystal substrate surface.
Experiments have shown that on a substrate with a step, it is optimal for manufacturing elements that utilize the shape near the step due to the controllability and reproducibility of the semiconductor layer shape, as seen for example at a distance d of 22. After various attempts, I found out. Note that the set of surface index deviation values (θ ₁ , θ ₂ ) shown in FIG. 7 is an example, and can be applied to all (θ ₁ , θ ₂ ) that satisfy the relationship θ ₁ < θ ₂ , and θ ₁ ≦ The effect is particularly remarkable at 1 _p .

In addition, when we experimentally determined the effects on crystal growth depending on the positive and negative values of θ ₁ and θ ₂ of the set of plane index deviation values (θ ₁ , θ ₂ ), we found that the difference in level difference (and As shown in the figure, there is an asymmetry in the shape of the semiconductor growth layer on both sides (inside and outside the trench), and the degree of this asymmetry changes depending on the sign and negative of θ ₁ , the magnitude of the absolute value, and the magnitude relationship with θ ₂ . Under the condition θ ₁ < θ ₂ , the eighth
It has become clear from experiments that semiconductor growth layers are formed symmetrically as shown in FIGS.

Although GaAs is used as the semiconductor material in this example, it can be easily inferred that other semiconductor materials such as Si, Ge, and compound semiconductors can be similarly applied. As explained above, the semiconductor device of the present invention has the following advantages.

In a substrate having steps, grooves, and similar unevenness formed on the surface, a semiconductor device can be manufactured with good reproducibility under the same growth conditions with the cross-sectional shape of a semiconductor epitaxial growth layer formed on the substrate.

It is possible to fabricate a semiconductor device in which the cross-sectional shape of the semiconductor epitaxial growth layer is symmetrical in the vicinity of steps, grooves, and similar uneven portions as shown in FIGS. 1 and 2 as examples.

In the case of multilayer growth on a substrate, in addition to controlling the growth shape of layers on the substrate, it is also possible to control the growth shape of layers that are not in direct contact with the substrate, and a semiconductor device can be manufactured by applying this.

When using a substrate with steps, grooves, and similar unevenness formed on the surface, the thickness of the semiconductor growth layer can be made uniform on the flat portion of the substrate that is not affected by the steps, grooves, etc., and the desired thickness can be achieved. A semiconductor device formed with good reproducibility can be manufactured.

Furthermore, as can be seen from the examples described above,
The present invention is applicable to semiconductor integrated circuits including three-dimensional semiconductor integrated circuits and optical integrated circuits.

[Brief explanation of drawings]

Figures 1 and 2 show a set of plane index deviation values (θ ₁ ,
Figure ₃ is a cross-sectional view of a conventional semiconductor device showing the asymmetrical shape of the semiconductor growth layer near the step and groove when θ ₁ > θ ₂ at θ 2 ). A diagram showing the definition of the values (θ ₁ , θ ₂ ), FIG. FIGS. 6a and 6b are cross-sectional views of a stepped substrate type semiconductor laser which is a semiconductor device according to an embodiment of the invention.
Figure 7 a, b, c, and d are cross-sectional views showing that the growth shape near the step changes depending on the plane index deviation value (θ ₁ , θ ₂ ) from the 100 plane of the single crystal substrate plane. The value of friction (θ ₁ , θ ₂ ) determines the electrical
Figures 8 and 9, which show the distribution of the size of distance d as one of the figures of merit of optical properties and the range of its dispersion, show the set of surface index deviation values (θ ₁ , θ ₂ )
FIG. 2 is a cross-sectional view showing the symmetrical shape of the semiconductor growth layer near the step and groove when θ ₁ >θ ₂ . 10... Surface excavated to form a step, 11...
...GaAs single crystal substrate surface with plane index deviation from 100 plane, 12...GaAs single crystal substrate, 15,1
6, 31... Semiconductor growth layer, 17... n-type Ga _x A
_1-x As clad layer, 18...Ga _y A _1-y As active layer, 19...p-type Ga _x A _1-x As clad layer, 2
1... n-type Ga _z A _1-z As layer, 20... GaAs layer,
22...Distance d, 23...Laser oscillation area.

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device in which a crystal layer is formed on a substrate having irregularities such as steps and grooves on the surface, the surface of the substrate is 100, 110, 11
1 or an equivalent surface index, after confirming that the surface index deviation parallel to the ridgeline direction of the uneven portion is larger than the surface index deviation in the direction perpendicular to the ridgeline direction, a semiconductor is placed on the uneven portion. A method for manufacturing a semiconductor device characterized by growing a film.