JPH01101624A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the flat buried growth of a crystal layer even if a mesa pattern has steps higher than 1mum so as to make a manufacturing process of a laser simple and the degree of freedom of design improve by a method wherein the mesa pattern is made to be formed in such a manner than an orientation of a mesa stripe is made to deviate from orientation <110> by a specified degree. CONSTITUTION:A mesa pattern is formed on a semiconductor substrate 10 with plane face {100} and then a semiconductor crystal layer 40 is selectively formed on the semiconductor substrate 10 through a vapor phase growth method, where the mesa pattern in formed in an orientation that deviates from orientation <110> by 5 degrees or more. Therefore, the semiconductor crystal layer 40 can be made to grow flat in a buried state on the semiconductor substrate 10 provided with the mesa pattern on it, moreover even if the mesa pattern has a step 1mum or more in height the flat buried growth can be made because the speed of crystal growth is dependent on the face orientation. By these processes, in case of the manufacture of a semiconductor laser or the like, a manufacturing process can be simplified and the degree of freedom of design can be also improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device, and particularly to a semiconductor device in which a semiconductor crystal layer is embedded into a substrate on which a mesa pattern is formed. Relating to a manufacturing method.

(Prior art) In the process of manufacturing devices such as semiconductor lasers,
It is necessary to epitaxially form a semiconductor crystal layer on a semiconductor substrate having a step such as a mesa. It is known that when this crystal growth is performed using a liquid phase growth method, it is possible to achieve flat buried growth in which a semiconductor crystal layer is grown so as to bury the mesa portion. However, when attempting to perform this by vapor phase growth, flat buried growth can be achieved if the step difference in the substrate is approximately 1 μm or less, but flat buried growth cannot be achieved if the step difference is 1 μm or more. In other words, protruding growth occurs from the side of the mesa, which prevents flat buried growth (IEICE,
Spring 1987 86S: Japan Society of Applied Physics.

Spring 1987 3 Op, ZH-8).

In the above steps, the surface of the substrate on which crystal growth is performed is (1001 plane), and the mesa pattern is <11
0> direction. When creating a laser, the direction of the mesa pattern is determined so that the mesa stripe direction is perpendicular to the cavity end face (110) plane formed by crystal cleavage, etc., so the above direction is inevitably selected. .

When the stripe direction of the mesa is in the <110> direction, a +1111 plane appears on the side surface of the mesa, and protrusion-like growth occurs in a direction parallel to the (1111 plane).

Conventionally, in order to avoid the above problem, a method has been used in which the process is subdivided so that when crystal growth is performed on a substrate surface on which a mesa pattern is formed, the step difference in the mesa is 1 μm or less. However, in this method, crystal growth is required multiple times in the process of manufacturing the device, which not only complicates the process, but also requires various constraints to be placed on the structure when designing the device. There wasn't.

(Problems to be Solved by the Invention) Conventionally, when a mesa pattern with a step of 1 μm or more in the <110> direction is formed on the [10] plane, a flat buried growth layer is formed on the substrate using a vapor phase growth method. could not be done. Furthermore, for the above reasons, there have been problems such as complicating the manufacturing process and reducing the degree of freedom in design in a semiconductor laser having a mesa portion.

The present invention has been made in consideration of the above circumstances, and its purpose is to enable a semiconductor crystal layer to be buried and grown flat on a substrate on which a mesa pattern with a step difference of 1 μm or more is formed. An object of the present invention is to provide a method for manufacturing a semiconductor device that can contribute to simplifying the manufacturing process and improving the degree of freedom in design when creating a laser or the like.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to set the stripe direction of the mesa pattern to (1)
10> The purpose is to actively deviate from the direction.

That is, the present invention provides a method for manufacturing a semiconductor device in which a mesa pattern is formed on a semiconductor substrate having a (100) surface, and then a semiconductor crystal layer is selectively formed on the semiconductor substrate by a vapor phase growth method. This is a method in which the mesa pattern is formed in a direction shifted by 5 degrees or more from the <110> direction.

(Function) According to the present invention, it is possible to flatten and bury a semiconductor crystal layer on a semiconductor substrate on which a mesa pattern is formed,
Furthermore, even if the mesa pattern has a step difference of 1 μm or more, flat buried growth can be achieved in the same way. As described above, the reason why flat buried growth is possible even though the mesa pattern has a step difference of 1 μm or more is the dependence of the crystal growth rate on the plane orientation. That is, in the case of the conventionally used mesa pattern in the <110> direction, the substrate surface is the (1001 plane), so the mesa side faces are the il 11 planes. Since the crystal growth rate in the direction along the 11111 plane is high, protrusion-like growth occurs along the side surface direction of the mesa. On the other hand, by shifting the stripe direction of the mesa pattern from the <110> direction, the 11111 plane does not appear on the side surface of the mesa, suppressing protruding growth and allowing flat buried growth. In this case, since the resonator end face is not completely perpendicular to the stripe direction of the mesa pattern, the reflection efficiency at the resonator end face slightly decreases, but experiments by the present inventors have shown that sufficient laser oscillation is possible. Confirmed by.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

First, as shown in Fig. 1, InP with plane orientation (100),
Forming Si02 film 20 (21, 22, 23, 24) as a striped mask on W plate 10]7.5i0
2 selectively etching the substrate 10 using the film 20 as a mask,
A striped mesa 30 (31°32.33.34) was formed. Note that the width and step height of the mesa pattern are each approximately 2 μ711. Also, the stripe direction of mesa 31 is the [011) direction, and the stripe direction of mesa 32 is [)11
] direction, the stripe direction of mesa 33 is a direction tilted 15 degrees from the [011] direction, and the stripe direction of mesa 34 is [
This is a direction tilted 15 degrees from the 011F direction.

Here, each cross section of FIG. 1 is shown in FIG. 2.

The cross section taken along arrow A-A and the cross section taken along arrow C-C in Figure 1 are shown in Figure 2 (
The mesa becomes an inverted mesa as shown in a), and the cross section taken along arrows BB and DD in FIG. 1 becomes a forward mesa as shown in FIG. 2(b). And at Mesa 31.32, the side is +111
1 side, and at mesa 33°34, that side is +111)
It will be out of place. In addition, in the above example, the mesa part is
Although it is formed only of nP, when producing a semiconductor laser or the like, it is actually sufficient to form a heterostructure consisting of InP and another compound semiconductor that is lattice-matched to this mesa portion.

Using the substrate 10 described above, an InP layer 40 was grown by metal organic chemical vapor deposition (MOCVD) in order to fill the side surfaces of the mesa 30 with a semiconductor crystal layer. As raw material gas,
A mixed gas of TML (trimethylindium) and PH (phosphine) was used. The thickness of the grown film is approximately 2 μm.
It is.

FIG. 3 shows the state in which the InP layer 40 is deposited.

In Fig. 3, (a) is a cross section taken along arrow A-A in Fig. 1, and (b)
) is a cross section taken along arrow B-B in Figure 1, and (c) is a cross section taken along arrow C in Figure 1.
-C section and (d) respectively correspond to the arrow DD section in FIG.

The stripe direction of the mesa 30 is the same as the conventional [0111 direction or [0111 direction, that is, in the mesas 31 and 32,
As shown in FIGS. 3(a) and 3(b), growth occurred on protrusions along the sides of the mesa, and the InP layer 40 could not be buried flatly. On the other hand, when the striped mesa of mesa 30 is inclined by 15 degrees from the [0111 direction, that is, mesa 33 and 34, flat buried growth without protrusions is possible as shown in FIGS. 3(c) and 3(d). Ta. This is Mesa 3
While the side of 1.32 is +1111 side,
This is because the side surfaces of the mesas 33 and 34 are deviated from the +1111 plane, and crystal growth in the direction parallel to the side surfaces is not very fast.

Further, the stripe direction of the mesa 30 is set at 4 degrees, 5 degrees, and 15 degrees from the [)11] direction and the [011] direction.

When we conducted experiments at various angles of 30 degrees and 45 degrees, we found that [0
1μ for less than 5 degrees from the [1,1] direction and the [011] direction
The above-mentioned protrusion-like growth occurs with a step difference of m or more, but if the step is shifted by more than 5 degrees (i.e., 5 degrees to 85 degrees when viewed from either the [0111 direction or the [011] direction), the protrusion-like growth occurs. It was confirmed that it was almost never seen.

When a semiconductor laser was fabricated using the mesas 33 and 34, good characteristics as a laser were obtained although the stripe direction and the (110) plane cavity end face were not completely perpendicular. Furthermore, by forming the resonator end face by etching rather than cleaving, it was also possible to make the resonator end face perpendicular to the stripe direction, which is shifted by 5 degrees or more from the [0111 direction and the [011] direction.

In addition, when manufacturing a buried semiconductor laser or integrating fine elements such as 0EIC, it is necessary to obtain a good mesa pattern with a steep slope. It has been experimentally confirmed that if the etching direction is exceeded, it becomes difficult to obtain a good slope of the mesa pattern by wet etching (for example, etching an InP substrate using hydrochloric acid). Therefore, in such a case, a better semiconductor device can be obtained by setting the stripe direction of the mesa pattern within a range of 5 degrees to 40 degrees from the <110> direction.

Thus, according to this embodiment, the stripe directions are aligned in the [0111 direction and [011] direction on the (100) plane InP substrate 10.
By forming the mesa 30 at a deviation of 5 degrees or more from one direction, it is possible to prevent the +1111 plane from appearing on the side surface of the mesa 30.

Therefore, even if a vapor phase growth method such as MOCVD is used, no protruding growth occurs in the direction parallel to the side surfaces of the mesa 30, and the side surfaces of the mesa 30 are flatly buried and grown with the InP layer 40. Can be done. Therefore, semiconductor lasers with various buried structures can be easily manufactured, and their usefulness is enormous. In addition, there is no need to basically change the conventional process, just the direction of the mesa stripe, and there is a great advantage beyond practical use that it is easy to implement.

Note that the present invention is not limited to the embodiments described above. For example, the semiconductor substrate and the semiconductor crystal layer to be grown are not limited to InP, but may be made of Ga InAs, Ga
I nAsP, A, i' I nAs.

AI nP, AI! I nGaP, A1Ga I
nAs.

Other compound semiconductor materials such as GaAs may also be used. It is also effective even in the case of hetero-growth where the semiconductor on the substrate and the semiconductor crystal layer to be grown are different types. Further, the mesa portion of the substrate is not limited to a single semiconductor, and may be a heterostructure in which different types of semiconductors are stacked. Also,
For the growth of the semiconductor crystal layer, it is also possible to use not only the MOCVD method but also other vapor phase growth methods. Furthermore, the mesa stripes are not necessarily limited to rectangular shapes, but may also be square stripes.

Furthermore, the surface orientation of the substrate surface is not limited to (100), but may be any orientation equivalent to (100), that is, the +1001 plane.

Similarly, the crystal axis orientation serving as a reference for shifting the stripe direction is not limited to the [011] direction and the [0111 direction, but may be any orientation equivalent to these, that is, the <110> direction.

In other words, the reference axis direction is among the <110> directions,
The direction is parallel to the substrate surface. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by forming the mesa pattern so that the mesa stripe direction is deviated from the <110> direction by 5 degrees or more, the step difference in the mesa pattern can be reduced. Even if the thickness is 1 μm or more, flat buried growth can be performed. Therefore, it is effective for producing a semiconductor laser with a buried structure, and can contribute to simplifying the manufacturing process and improving the degree of freedom in design of the laser.

[Brief explanation of the drawing]

1 to 3 are for explaining a method according to an embodiment of the present invention. FIG. 1 is a plan view showing the mesa stripe direction, FIG. 2 is a sectional view showing the mesa etched state, and FIG. FIG. 3 is a cross-sectional view showing a state in which an InP layer is deposited. 10-1 n P substrate (semiconductor substrate), 20 (21
゜22.23.24)...5i02 film (stripe mask), 30 (31, 32, 33, 34)... Mesa, 40... InP layer (semiconductor crystal layer). Applicant's representative Patent attorney Takehiko Suzue Figure 1 (a) (Q) (C) Figure 31 (b) Figure (b) (d)

Claims (6)

[Claims] (1) A step of forming a mesa pattern on a semiconductor substrate whose surface is a (100) plane in a direction shifted by 5 degrees or more from the <110> direction parallel to the substrate surface, and a step of forming a mesa pattern on the semiconductor substrate using a vapor phase growth method. A method of manufacturing a semiconductor device, comprising the step of selectively forming a semiconductor crystal layer. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the mesa pattern is formed in a stripe shape, and the stripe direction is deviated from the <110> direction by 5 degrees or more. (3) The mesa pattern is formed in a stripe shape, and the stripe direction is deviated from the <110> direction by 5 degrees to 40 degrees.
A method for manufacturing a semiconductor device according to section 1. (4) The method of manufacturing a semiconductor device according to claim 1, wherein the step of the mesa pattern is 1 μm or more. (5) In the step of forming the mesa pattern, a striped mask is formed on the substrate, and then the substrate is selectively etched using the mask. A method for manufacturing a semiconductor device. (6) The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor substrate and the semiconductor crystal layer are made of InP.