JPS63229891A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To realize the formation of a deeply buried layer through a vapor growth method wherein a semiconductor substrate surface exposed by etching is selectively coated with a mask, and a second semiconductor layer is grown after a semiconductor layer is so grown that the layer surface makes an obtuse angle with the mask surface. CONSTITUTION:An n-type clad layer 2, an active layer 3, a p-type clad layer 4, and a p<+>-type contact layer 5 are successively grown on an n-type semiconductor substrate 1. Next, a mask 11 is selectively formed thereon, and etching is performed onto layers 5-2 to reach under the mask 11 for the formation of a recessed part. A process follows, wherein a mask 12 is selectively formed on the mask 11 for the growth of a buried layer 6a. In this case, a vapor growth surface is so controlled that the layer 6a surface is grown to be a trapezoid making an obtuse angle with the mask 12 surface. Next, the mask 12 is removed for the formation of a semiconductor 6b on the layers 6 and 2. By these processes, a deeply buried layer is flatly grown through a vapor growth method.

Description

Detailed Description of the Invention [Summary] The present invention involves performing etching that reaches below a first mask that selectively covers the surface of a semiconductor substrate during buried growth of a semiconductor layer, and etching the exposed surface of the semiconductor substrate by the etching. is selectively covered with a second mask to grow a first semiconductor layer whose surface forms an obtuse angle with the surface of the second mask, and the second mask is removed to grow the first semiconductor layer. By growing a second semiconductor layer on the exposed surface of the layer and the semiconductor body, it is possible to grow a deep buried layer flatly by means of a vapor phase growth method, in particular a MO-CVD method.

[Industrial application field]

The present invention is applicable to a method for manufacturing a semiconductor device, particularly to the buried growth of a semiconductor layer using a metal organic pyrolysis vapor deposition method (MO-CVD).
This invention relates to an improvement in a method for manufacturing a semiconductor device that enables the application of vapor phase growth methods such as the above method.

For example, semiconductor light-emitting devices play an extremely important role in optical application systems such as optical communications, and there is an increasing need to ensure and improve their reliability and better compatibility with electronic circuits. Corresponding productivity improvements have become essential.

[Conventional technology]

Various structures and manufacturing methods have already been developed for semiconductor light emitting devices, but conventionally liquid phase epitaxial growth (LPE) has generally been applied to grow semiconductor layers. 1.3
Indium phosphide/indium gallium arsenide phosphide (InP/InGaAsP)-based BH, whose schematic cross-sectional view is shown in Fig. 2, is known as a semiconductor laser with a band of ~1.6 decoys.
(Buried Heterostructure) lasers are manufactured as follows by applying the LPE method.

That is, for example, first, on the (100) plane of the n-type InP substrate 21, an n-type 1nP cladding layer 22, an InGaAsP active layer 23, a p-type InP cladding layer 24, and a p-type InGa
AsP:1 contact layers 25 are epitaxially grown in sequence.

A stripe-shaped mask whose length direction is in the (011) direction is provided on the surface of the semiconductor substrate, and etched using, for example, a bromine (Br)-methanol solution to form an inverted mesa-shaped stripe region.

For example, a semi-insulating InP layer 26 is formed in this etched region.
is buried and grown so that the upper surface of the semiconductor substrate becomes flat to perform current confinement and refractive index guiding to control the transverse mode of the laser beam, and then the p-side electrode 28 and the n-side electrode 2 are formed.
Place 9.

This LPE method produces fewer crystal defects and allows buried growth to flatten the top surface of the semiconductor substrate described above.
This process is difficult to adapt to productivity improvement, and furthermore, growth may be impossible due to being dominated by phase laws.

On the other hand, the open-CVD method uses an organic compound for group Ⅰ or group Ⅰ elements for which hydrogen compounds that are stable at room temperature cannot be obtained, and a vapor phase method that uses hydrogen compounds as the starting material for group ⑛, Ⅰ, or Ⅰ elements. Epitaxial growth has recently made remarkable progress, not only improving crystal quality and productivity, but also making it possible to grow thin films on the order of monomolecular layers and superlattice structures.

However, it is extremely difficult to grow a semiconductor layer buried in a deep recess on the surface of a semiconductor substrate and to flatten the upper surface of the semiconductor layer, as in the case of the InP layer 26 of the conventional example described above, using the -CVO method.

That is, if the mask 33 protrudes like an eaves as shown in the schematic diagram of FIG. 3(a), and the angle θ formed between the end face 31 of the recess where the filling growth is performed and the bottom face 32 is an obtuse angle,
The growth progresses as shown by the broken line, and for example, when the angle θ is about 135 degrees, a buried semiconductor layer with a substantially flat top surface is obtained in which the depth h of the depression is up to about 5n'.

As shown in the schematic diagram in FIG. 3 (bl), if the end face 31 of the depression in which the buried growth is performed is approximately perpendicular to the bottom surface 32, the depth h of the depression in which the buried growth is performed is within a range of, for example, about 34 mm. As shown in the figure, the depression 3 near the mask 33
In the case other than 4, the upper surface is buried with a substantially flat surface, but if the depth h exceeds this level, the recess 34 becomes so large that it becomes unusable.

Furthermore, the end surface 31 of the depression where the filling growth is performed is the bottom surface 3.
If the slope is at an acute angle with respect to 2, the depth h of the depression in which the buried growth is performed is, for example, about 1, and a (111)8 plane 35 appears as shown in the schematic diagram in FIG. 3(C). Growth hardly progresses near the corners of the bottom surface 32.

Since buried growth is difficult in the MO-CVD method, a semiconductor laser shown in FIG. 4, for example, has been provided as a structure that can be manufactured by the MO-CVD method.

In this conventional example, 31 is an n-type semiconductor substrate, 32 is an n-type cladding layer, 33 is an active layer, 36 is a p-type cladding layer, 3
7 is a p-type contact layer, and current confinement and loss guiding are performed by the n-type semiconductor layer 34 and the n-type semiconductor layer 35. First, the semiconductor layers 32 to 35 are sequentially grown on the substrate 31. Etching is carried out so as not to reach the active layer 33, and the p-type rad layer 36 filling this groove and the p-type
A mold contact layer 37 is grown. Note that the p-side electrode 3
8 is provided on this groove.

[Problem that the invention seeks to solve]

As mentioned above, vapor phase growth methods such as the MO-CVO method have many difficulties in selective growth and cannot realize the semiconductor light emitting device conventionally manufactured by the LPE method. Although such a structure has been provided, its characteristics are inferior, and the optical/electronic integrated circuit device (OEIC)
) etc., the fact that the semiconductor substrate surface is not flat becomes an obstacle.

Under these circumstances, deep buried growth for current confinement and mode control required for semiconductor light emitting devices with good characteristics such as the conventional example shown in FIG.
There is a strong demand for a method for manufacturing semiconductor devices that can be realized using a vapor phase growth method, particularly an MO-CVD method.

[Means for solving problems]

The problem is as follows: (1) After etching the portion of the semiconductor substrate to be replaced with the buried growth layer to create an overhang state in which the first mask protrudes like an eave, (2) etching the exposed surface of the semiconductor substrate with the second mask; selectively coated with
Also covering the first mask, a first semiconductor layer is first grown whose surface forms an obtuse angle with respect to the surface of the second mask on the semiconductor substrate surface by etching. Next, (1) the second mask is removed, and a second layer is formed on the etched semiconductor substrate surface that was covered with the first semiconductor layer and the second mask.
The problem is solved by a manufacturing method that grows a semiconductor layer and completes the buried growth.

[For production]

In the manufacturing method according to the present invention, the buried growth is performed in two stages, for example, as in the embodiment described later.

In the first step, in addition to the overhanging first mask 11, a second mask 12 is placed on the etched exposed surface of the semiconductor substrate, and the outer periphery of the opening is in contact with the first mask 11 of the semiconductor substrate. The first semiconductor layer 68 is grown so that the plane passing through the upper end has a slope similar to, for example, the (111)B plane of the semiconductor substrate. By restricting the epitaxial growth surface in this way, the first semiconductor layer 6A
is grown into a trapezoidal shape whose surface forms an obtuse angle with respect to the surface of the second mask 12 by a vapor phase growth method such as MO-CVD.

Then, in a second step, the second mask 12 is removed and the first mask 12 is removed.
A second semiconductor layer 6B is formed on the etched semiconductor substrate surface that has been covered with the semiconductor layer 6A and the second mask 12.
grow. In this second stage of growth, since the inclined surface is shaped as described above, the etching depth is, for example, 5-5.
Even if the amount exceeds this, growth proceeds by a vapor phase growth method such as MO-CVD, and embedding can be achieved without any problem.

〔Example〕

The present invention will be specifically explained below with reference to an example shown in FIG. 1, which is a schematic cross-sectional view of the process order.

Refer to FIG. 1(a) = (10
0) On the surface, for example, tin (Sn) is applied at a concentration of 1×1018a6
An n-type 1nP cladding layer 2 doped to approximately 3 μm and having a thickness of approximately 3 μm, for example, an undoped InGaAsP active layer 2 having a thickness of approximately 0.15 μm and a luminescence peak wavelength of 1.3 μm.
W3, for example cadmium (Cd) at a concentration of I
P-type InP doped to about m-' and about 2.0 μm thick
Cladding layer 4, for example, zinc (Zn) with a concentration of 5×1011
A p+ pear-shaped 1nGaAsP contact layer 5 doped to about Ia14 and having a thickness of about 0.5 μm is sequentially epitaxially grown.

In this example, this growth was carried out by the No-CVD method at a pressure cuff of 60 torr and a substrate temperature of 650°C, and as a raw material, In was trimethylindium (In(CHs) 3).
, Ga is trimethylgallium (Ga(Ctb)s)
, As is arsine (Astl+), P is phosphine (P
H3), Si doped as an impurity is monosilane (S
iH4), Cd is dimethyl cadmium (ca (CH:
l) z) and hydrogen (H2) is used as the carrier gas.

FIG. 1 (see bl) A first mask 11 is formed in a stripe shape in the (011) direction on this semiconductor substrate using, for example, silicon dioxide (SiOz) and has a width W of about 1=3 iIm.

The InGaAsP contact layer 5 of this semiconductor substrate is first etched with a nitric acid (HNO3) based solution, and then etched with a diluted hydrochloric acid (HCI) based solution to reach the n-type 1nP cladding layer 2 to a depth as shown by the broken line. is 3.5I
About rm, overhang width. h = about 1.5-,
The end face forms a nearly vertical depression.

Then, for example, (1
11) Perform etching to develop the A side, and
Width of P active layer 3 - a = approximately 1.5 IIm, depth h =
An inverted mesa-like stripe region of about 5 prn is formed.

1 (see C1: For example, aluminum oxide (Ah(h)) is sputtered onto this semiconductor substrate and patterned by lithography to form a second mask 12. In this embodiment, this second mask 12 is For example, the width of the opening is w, z = 12 μm, and the slope of the plane that passes between the outer periphery 12E of this opening and the upper end 5E of the semiconductor substrate in contact with the first mask 11 is approximately the (111)B plane of the semiconductor substrate. .

FIG. 1 (see dl: The first stage of epitaxial growth of the semi-insulating 1nP buried layer 6 is performed.

In this example, iron (Fe) is doped as an acceptor impurity that forms a deep level, and the pressure is set to 760 TorrS and the substrate temperature is 650°C by the MO-CVD method.
0% hydrogen dilution P)13 was made into 460cc for 7 minutes, and In
(CI Ris) was fed with 50 cc of H2 aeration for 7 minutes at 25°C, and ferrocene iron (Fe(CzHs)) was fed with 5 cc/min of H2 aeration at 0°C, with a total flow rate of 10β/min of H2.

In this growth, the (111) B plane is likely to develop, and in this embodiment, the (111) B plane facet is formed as shown in the figure, and the growth of the InP buried layer 6^ is completed.

1 (see el): The mask 12 is selectively removed with respect to the mask 11, and a second stage of epitaxial growth of the semi-insulating InP buried layer 6 is performed.

This growth is also carried out by the MO-CVD method under the same conditions as the first stage of growth, but by making the overhang width of the mask 11 (Figure (the location of bl) approximately the same as in this example), InP is buried. A substantially flat buried growth of layer 6B is achieved.

Among the above growth conditions, In(CH3)z was 300cc.
By setting the distance to about 1/min, it is possible to reduce the tendency for facets of the (111)B plane to appear and create a slight step in the vicinity of the mask 11.

See FIG. 1(f): Remove the mask 11 and remove the p-side electrode 8.
and n-side electrode 9 are formed, and the device of this example is completed through processes such as inter-folding. However, since the semiconductor substrate according to the present invention has a flat upper surface, it is similar to the semiconductor light emitting device using the LPE method. It can be formed into any shape.

In this example, a dark value current of about 15 mA and an external differential efficiency of about 25% in the rated operating state are obtained, and it has been demonstrated that the laser has performance equivalent to or better than that of the BH laser based on the LPE method shown in FIG. 2.

Although the above description refers to an InP/InGaAsP laser, similar effects can be obtained by the present invention with respect to other semiconductor materials such as GaAs/AlGaAs and various semiconductor devices other than lasers.

〔Effect of the invention〕

As explained above (according to the present invention), for example, the growth of a deep buried layer for current confinement and mode control of a semiconductor light emitting device can be realized by a vapor phase growth method, particularly an MO-CVD method, and the growth of a deep buried layer for current confinement and mode control of a semiconductor light emitting device can be realized using a vapor phase growth method, in particular an MO-CVD method, and a conventional LPE method. The growth process, which has become a bottleneck in the manufacturing process due to
Improvements can be achieved in the manufacturing method of semiconductor devices by switching to vapor phase growth methods such as MO-CVD methods.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view of the process order of the embodiment of the present invention, Figures 2 and 4 are schematic sectional views of the conventional example, and Figure 3 is a MO-CVD
FIG. 2 is a schematic diagram of embedded growth by the method. In the figure, 1 is an n-type InP semiconductor substrate, 2 is an n-type 1nP cladding layer, 3 is an InGaAsP active layer, 4 is a p-type InP cladding layer, 5 is an f-type 1nGaAsP contact layer, 5E is the end thereof,
6.6A and 6B are semi-insulating 1nP buried layers, 8.9 is an electrode, 11.12 is a mask, and 12E is an end of the mask 12. [Aff de It12
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Claims (1)

[Claims] Selectively covering the surface of the semiconductor substrate with a first mask,
etching the semiconductor substrate to reach below the first mask; selectively covering the first mask and the exposed surface of the semiconductor substrate by the etching with a second mask; growing a first semiconductor layer forming an obtuse angle with the surface of the mask; removing the second mask; and growing a second semiconductor layer on the etched exposed surface of the first semiconductor layer and the semiconductor substrate; 1. A method for manufacturing a semiconductor device, characterized by growing a semiconductor device.