JPS6247119A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To grow a crystalline layer parallel to a true crystal surface on a crystal substrate even if the crystal surface is displaced by growing a crystal layer on the substrate formed with a projection on the surface, and forming an element on the layer which includes a region on the projection. CONSTITUTION:A projection 2 is formed on a crystal substrate 1 such as an InP substrate. Then, an n-type InP layer 31 as a buffer layer, an n-type In1-xGaxAs layer 32 as a photoreceiving layer and an n-type InP layer 33 as a multiplying layer are sequentially grown by the first liquid-phase epitaxial growth LPE on the substrate 1. In this case, the surfaces of the respective grown layers become parallel to the true crystal surface. Then, a projection is formed on the layer 33. Then, an n<-> type InP layer 34 is grown as guard ring region layer over the projection by the second LPE. In this case, the surface of the layer grown by the first LPE and the surface of the layer grown by the second LPE become in parallel. Then, a P-type region 35 is formed to arrive at the layer 33 by the surface. A photoreceiving device thus formed as above has a region 35 necessary to form a photoreceptor in parallel at the front with the photoreceiving layer, thereby uniformizing the sensitivity distribution in the plane.

Description

[Detailed Description of the Invention] [Summary] Since the surface of the crystal substrate deviates somewhat from the true plane index,
A device formed on a crystal layer grown on top of this has poor device characteristics. As a countermeasure, a crystal layer is grown parallel to the true crystal plane by forming a step on the substrate, and an element is formed here.

[Industrial application field]

The present invention relates to a semiconductor device, and particularly to a manufacturing method for improving the characteristics of a light receiving/emitting element.

Currently, semiconductor devices formed of mixed crystals are widely used in high-speed integrated circuits and optical semiconductor devices such as light receiving and emitting elements.

In such a semiconductor device, various elements are formed by growing a plurality of crystal layers on a crystal substrate made of a mixed crystal by liquid phase epitaxial growth (LPII).

In this case, since the crystal substrate is created by slicing, mirror processing, etc., the plane index deviates from the true plane by about ±0.1° at most. When LPE is performed on such a substrate,
If a crystal layer with a jagged surface in a terrace pattern grows, or if a convex part is formed on the crystal layer grown by a second LPE and a second LPE is performed on it, as in the case of forming a light receiving element, A problem arises in that the surface of the crystal layer is distorted, and countermeasures are desired.

[Conventional technology]

FIGS. 2(11 to 5) are cross-sectional views illustrating a conventional method for manufacturing a light receiving element in the order of steps.

In FIG. 2 (11), 21 is a crystal substrate, for example an indium phosphide (InP) substrate, and the dotted line indicates a true crystal plane, for example (100) or (111) A plane.

In the figure, the true tilt of the crystal plane is enlarged.

In FIG. 2 (2), the first LPH results in an n-type 1nP (n-1nP) layer 231 as a buffer layer, an n-type indium gallium arsenide (n-In+-GaAs) layer 232 as a light-receiving layer, and an n-1nP layer 23 as double layer
3 are sequentially grown on the substrate.

In this case, the surface of each growth layer develops a terrace pattern;
The entire surface is parallel to the substrate.

In FIG. 2(3), the n-InP layer 233 in the light receiving area
Then, a convex portion is formed by mesa etching.

In FIG. 2(4), by the second LPH, an n-InP layer 23 is formed as a guard ring region layer covering the convex portion.
Grow 4.

In this case, since the substrate has a convex portion, growth is performed perpendicular to the true crystal plane, and the surface of the layer grown in the first LPE is parallel to the surface of the layer grown in the second LPE. do not become.

In Fig. 2 (5), the n
Zinc (Zn) is diffused so as to reach the -1nP layer 233 to form a p-type head region 235.

This completes the formation of the main parts of the light-receiving element, and then electrodes are formed by normal steps.

As described in Part 2, an embedded photodetector is produced by growing multiple layers including a photodetection layer and a multiplication layer on a flat substrate in the first LPE.
A convex portion is provided on the surface, and a guard ring region layer is grown on the convex portion in a second LPE. At this time, if the substrate is deviated from the true crystal plane, the surface of the layer grown in the first LPE and the surface of the layer grown in the second LPE will not be parallel, making it difficult to complete the photodetector. Necessary Zn
The diffusion front is not parallel to the light-receiving layer, and the in-plane sensitivity distribution tends to be uneven.

FIGS. 4(11 and 2) are cross-sectional views illustrating a conventional method for manufacturing a light emitting device in the order of steps.

In FIG. 4(1), 41 is a crystal substrate, for example, an In
For P substrates, the dotted line indicates the true crystal plane, for example the (100) plane.

In FIG. 4(2), an n-1nP layer 431 is formed as a cladding layer, an indium gallium arsenide phosphorus (In+-xGaJs+-yPy) layer 432 is formed as an active layer, and
A p7InP layer 433 is sequentially grown on the substrate as a cladding layer.

This completes the formation of the main parts of the light emitting element, after which it is separated in a plane parallel to the plane of the paper, and electrodes are formed by a normal process.

In this case, the surface of each growth layer develops a terrace pattern;
The entire surface is parallel to the substrate. Impurities are precipitated in the valleys of the terrace pattern of the active layer 432, and as the impurity concentration deviates from the optimum impurity concentration, the luminous efficiency decreases and luminescence tends to become non-uniform.

[Problem that the invention seeks to solve]

Due to the misalignment of the crystal plane of the crystal substrate, a terrace pattern occurs in the grown layer, reducing the luminous efficiency. Furthermore, in the case of forming a light-receiving element that is grown twice with mesa etching in between, the surfaces of the respective grown layers are not parallel, resulting in non-uniform light-receiving sensitivity.

[Means for solving problems]

The above problem can be solved by growing a crystal layer (3) on a crystal substrate (1) having a convex portion (2) on its surface, and growing the crystal layer (3) including the region above the convex portion (2). ) is achieved by the method of manufacturing a semiconductor device according to the present invention.

This is particularly effective when the element is a light emitting/receiving element.

[Operation] FIG. 5 is a sectional view showing a state when LPE is performed on a substrate having a step.

In the figure, as already mentioned in Figure 2 (4), if there is a step on the substrate, growth will first occur on the true surface of the bottom layer as shown by the dotted line, and the growth will stop at the step. and then 2
It grows on the lowest layer, and its growth stops at a step.
Thereafter, similar growth is repeated one after another, and growth progresses in the direction perpendicular to the true plane.

In the figure, S indicates the surface of the grown layer actually obtained.

The present invention aims to improve device characteristics by forming an element on the growth layer thus obtained.

〔Example〕

FIGS. 1(1) to 1(5) are cross-sectional views illustrating the method for manufacturing a light receiving element according to the present invention in the order of steps.

In FIG. 1 (1), l is a crystal substrate, for example InP
In the substrate, the dotted line indicates the true crystal plane, such as the (100) or (111) A plane.

Convex portions 2 are formed on the substrate by a normal photo process.

In FIG. 1 (2), the buffer layer has a carrier concentration of 1 to 2×10” and a thickness of approximately 3 μm by the first LPH.
n-1nP layer 31 with a carrier concentration of 3 to 1 as a light-receiving layer.
0x1015, about 2μm thick n-In+-8GaXA
S layer 32, carrier concentration 1 to 2 x 10 as a multiplication layer
”, an n-TnP layer 33 with a thickness of about 3 μm is sequentially grown on the substrate.

In this case, the surface of each grown layer is parallel to the true crystal plane.

In FIG. 1(3), a convex portion having a diameter of about 100 μmφ is formed in the n-1nP layer 33 in the light receiving region by mesa etching.

In FIG. 1(4), the second LPH is performed to cover the convex portion and form a guard ring region layer with a carrier concentration of 0.
An n-InP layer 34 having a size of 1 to 8×10 15 and a thickness of about 3 μm is grown.

Growth in this case is also performed in a direction perpendicular to the true crystal plane, and the surface of the layer grown in the first LPE is parallel to the surface of the layer grown in the second LPE.

In Figure 1 (5), the n
−1 Diffuse Zn to reach the nP layer 33 to form the p-type head region 3
form 5.

The crystal layer 3 consists of growth layers 31 to 34, in which elements are formed.

This completes the formation of the main parts of the light-receiving element, and then electrodes are formed by normal steps.

In the embedded photodetector formed as described above, even if the substrate is deviated from the true crystal plane, the surface of the layer grown in the first LPE and the surface of the layer grown in the second LPE are The Zn diffusion front required to complete the light receiving element becomes parallel to the light receiving layer, and the in-plane sensitivity distribution becomes uniform.

FIGS. 3(1) and 3(2) are cross-sectional views illustrating the method for manufacturing a light emitting device according to the present invention in the order of steps.

In FIG. 3 (1), 1 is a crystal substrate, for example InP
On the substrate, the dotted line indicates the true crystal plane, for example the (100) plane.

Convex portions 2 are formed on the substrate by a normal photo process.

In FIG. 3(2), an n-1nP layer 36 as a cladding layer, an In+-)I GaJS+-yPy layer 37 as an active layer, and a p-1nP layer 38 as a cladding layer are successively grown on the substrate by LPH.

In this case, the crystal layer 3 consists of the respective growth layers 36 to 38, in which the elements are formed.

This completes the formation of the main parts of the light emitting element, after which it is separated in a plane parallel to the plane of the paper, and electrodes are formed by a normal process.

In this case, the surface of each growth layer does not have a terrace pattern, and therefore no impurities are deposited in the active layer 32.
Non-uniformity of light emission can be eliminated.

〔Effect of the invention〕

As explained in detail above, according to the present invention, even if there is a misalignment of crystal planes on a crystal substrate, a crystal layer can be grown parallel to the true crystal plane, and by forming an element on this crystal layer, the element characteristics can be improved. can be improved.

For example, in a light emitting device, the formation of a terrace pattern in a crystal layer can be suppressed, and non-uniformity in light emission can be eliminated. Furthermore, in the light receiving element, the bonding surface and the light receiving layer can be formed in parallel, and the in-plane sensitivity distribution can be made uniform.

[Brief explanation of the drawing]

FIGS. 1 (1) to (5) are cross-sectional views explaining the method for manufacturing a light receiving element according to the present invention in the order of steps, and FIGS. 2 (1) to (5) show the method for manufacturing a light receiving element according to the conventional example in the order of steps. 3(1) and (2) are cross-sectional views illustrating the method for manufacturing a light emitting device according to the present invention step by step, and FIGS. 4(1) and (2) are a method for manufacturing a light emitting device according to a conventional example. FIG. 5 is a cross-sectional view showing a state when LPE is performed on a substrate having a step. In the figure, 1 is a crystal substrate, for example an InP substrate, 2 is a convex portion, 3 is a crystal layer, 31 is a buffer layer, 1-InpJW1, 32 is a light-receiving layer, an n-1nl-XGaXAs layer, and 33 is a multiplication layer, n -TnP layer, 34 is a guard ring region layer, n-lnP layer, 35 is a p-type region, 36 is a cladding layer, n-InP layer, 37 is an active layer, Ink-XGaJS+-yPv layer, IN large- 〇～ ) ＼ j (1) [121, InF 扉美bone 1. f1 spitting light + Hitsujiyu cross section 2nd figure tree oR,) All east! υ Cross-sectional diagram Figure 3 (1) B] = Kokan II P

Claims (3)

[Claims] (1) A crystal layer (3) is grown on a crystal substrate (1) having a convex portion (2) on its surface, and an element is attached to the crystal layer (3) including the region above the convex portion (2). 1. A method of manufacturing a semiconductor device, characterized by forming a semiconductor device. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the element is a light receiving element. (3) The method for manufacturing a semiconductor device according to claim 1, wherein the element is a light emitting element.