JPH07254730A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form three-dimensionally a plurality of layers of quantum boxes which are excellent in crystallinity and have the same form, by forming a polygonal pyramid type trench with defects or fine grains deposit as nuclei, on a first semiconductor layer of a semiconductor substrate surface. CONSTITUTION:By irradiating an InP substrate 11 of face orientation with a specified laser light, defect or disturbance is generated in the face orientation. An Fe-doped InP layer 12 is grown to be 300nm thick on the InP substrate 11, at a growth rate of 20nm/min. On the Fe-doped InP layer 12, an In0.52Al0.48As layer 14 which lattice-matches with InP is grown to be 50nm thick, at a growth rate of 20nm/min. Next In0.53Ga0.47As which lattice-matches with InP is grown. Dots of InGaAs are formed in the bottom of a trench. An InAlAs film is grown to be 50nm thick, at a growth rate of 20nm/min. By repeating the above process 4 times, quantum boxes are formed three-dimensionally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device having a semiconductor quantum well structure.

[0002]

2. Description of the Related Art Quantum boxes for confining carriers to zero dimensions are known by utilizing semiconductor fine processing technology and heterostructure growth technology. There are the following two methods as the main creation methods.

(A) After forming a superlattice structure in which two kinds of semiconductor layers are alternately deposited on a semiconductor substrate, a fine mask is attached to the surface, and the superlattice structure is partially removed and removed by etching.

(B) A polygonal window is opened on the substrate surface with a mask, a semiconductor layer is formed in the opening under growth conditions such that the shape becomes a polygonal pyramid, and a quantum box is formed at the apex of the polygonal pyramid.

For the method (b), for example, Japanese Patent Laid-Open No. 2-1 is used.
There is an application of 63928.

However, the above method has the following problems. Both of the methods (a) and (b) require a step of forming a mask by a technique such as photography. In order to create this mask, it is necessary to perform fine processing with a size of about several tens nm. Therefore, very expensive equipment and sophisticated technology are required, and it takes time because a plurality of steps are performed before production. Further, in the method (a), it is difficult to align the shapes of the quantum boxes by etching, and the portions of the quantum boxes are directly exposed during etching, so that the surface is contaminated or damaged. On the other hand, the method (b) has a problem that the substrate surface before the semiconductor layer growth is contaminated during mask formation. Further, in order to create a quantum box three-dimensionally as well as in a two-dimensional plane, that is, to create a quantum box in multiple layers, in the method of (b), mask creation → quantum box creation → mask and quantum A quantum box cannot be created three-dimensionally unless the process of embedding on the box is repeated.

[0007]

The production of the quantum box by the above-mentioned conventional method requires expensive equipment, sophisticated fine processing and crystal growth technology, and it takes time. Also, in the process of etching or mask formation, the surface of the semiconductor layer is likely to be contaminated or damaged, and it is difficult to determine the conditions for etching and growth to make the quantum box shape uniform. There is a problem that a large number of steps are required to create a quantum box.

An object of the present invention is to provide a method of manufacturing a semiconductor device that solves the above problems.

[0009]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention comprises forming a defect or a fine grain precipitate on the surface of a semiconductor substrate, then forming a first semiconductor layer, Alternatively, a step of forming a polygonal pyramidal groove in the first semiconductor layer using fine grain precipitates as a nucleus, and the growth rate at the apex of the groove on the first semiconductor layer is higher than the growth rates of other portions. And forming a second semiconductor layer of a different type from the first semiconductor layer by laminating a desired number of atomic layers, and forming a third semiconductor layer on the second semiconductor layer. It is characterized by doing.

In the method of manufacturing a semiconductor device according to the present invention, a crystal defect is formed on the surface of a semiconductor substrate, or fine particles made of a metal or a substance in which an atom and a metal forming the semiconductor substrate are bonded are deposited. Step, a second step of forming the first semiconductor layer under the growth conditions in which a groove having a polygonal shape with the vertex directly above the fine particles is formed, and the growth rate at the top of the groove is the growth of other portions. A third step of forming a predetermined number of atomic layers of a second semiconductor of a type different from that of the first semiconductor under a growth condition larger than the speed, and a step of forming the first semiconductor again on the second semiconductor layer. It is characterized by comprising four steps.

Further, in the step of forming the polygonal pyramidal groove in the first semiconductor layer in the method of manufacturing a semiconductor device, the semiconductor layer is epitaxially grown on the semiconductor substrate while doping metal atoms above the solid solution limit. This is a method of precipitating fine particles made of a substance in which the metal or the atoms constituting the semiconductor are bound to the metal.

[0012]

[Action]

First step: a crystal defect is formed on the surface of a III-V compound semiconductor substrate such as GaAs or InP, or a metal, or a substance in which an atom and a metal forming the semiconductor substrate are bonded to each other,
For example, fine particles of Fe or a substance in which P and Fe are combined are deposited. This method includes vapor deposition and the like, but the same metal organic chemical vapor deposition method (MOCVD method) as in the second and subsequent steps.
And molecular beam epitaxy method (MBE method)
The whole process can be carried out continuously, and the time can be greatly shortened, and at the same time contamination of impurities on the surface can be prevented. M
In the OCVD method and the MBE method, a metal raw material is supplied to the surface together with a group V raw material while the semiconductor substrate is kept at a high temperature, or a semiconductor layer is grown while being doped with a metal having a solid solubility limit or more. Can be deposited on the surface.

Second step ... A first semiconductor layer is grown by MOCVD or MBE on a semiconductor substrate having a metal or the like deposited on the surface in the first step. At this time, depending on the type of semiconductor, a groove having a polygonal pyramid shape with a metal as a vertex is formed. The semiconductor species having a groove are, for example, AlGaAs,
It is often a semiconductor containing Al such as ZnAlAs.
This is considered to be because the distance (migration) for moving around the substrate surface before the group III raw material is taken into the semiconductor layer is shorter in the case of Al than in Ga or In, and the growth rate depends largely on the plane orientation. The shape of the groove varies depending on the semiconductor type, the plane orientation of the substrate, and the growth conditions. However, when the plane orientation of the substrate is (100), the groove is a pyramid and the angle between the ridgeline and the substrate surface may be 30 ° or more. Many. The growth rate of the groove portion is slower than the growth rate of the flat portion but is not 0. Therefore, as the growth proceeds, the metal portion is covered with the first semiconductor and the bottom portion (apex portion) of the groove rises.
However, the shape near the bottom of the groove remains unchanged and constant. Further, even if the size of the fine particles varies, the shape near the bottom of the groove can be the same.

Third step ... A second semiconductor layer of a kind different from that of the first semiconductor is grown on the semiconductor layer having the groove formed in the second step. When a semiconductor not containing Al is used as the second semiconductor, the growth rate at the bottom of the groove is often higher than the growth rate at the part of the slope, and by adjusting the growth time, a dot of a predetermined size is formed at the bottom. Can be formed. Since the shape near the bottom of the groove is the same, the dot shape is also the same.

Fourth step ... The second semiconductor layer can be surrounded by the first semiconductor by growing the first semiconductor again on the semiconductor layer after the third step.

When the electron affinity of the second semiconductor is made larger than that of the first semiconductor, a quantum box capable of confining electrons in the second semiconductor is obtained.

In the present invention, an LED or a semiconductor laser using this quantum box as a light emitting layer can be provided.

The steps from the first to the fourth are MOC
Since the VD method or the MBE method can be continuously performed, the quantum box can be formed with the same ease as the formation of a normal semiconductor thin film. Further, if the growth conditions are properly selected in the fourth step, the groove portion can be completely covered with the first semiconductor, and the flatness of the surface can be restored. Therefore, it is possible to stack three or more quantum boxes three-dimensionally by repeating the first to fourth steps with one growth.

By continuously performing the above-mentioned first to fourth steps by MOCVD or MBE as described above, it is much easier than the conventional method to prevent impurity contamination and damage, and to have the same shape. It is possible to create three-dimensional layers of quantum boxes.

[0020]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

1 to 3 illustrate a process of making a quantum box according to an embodiment of the present invention. Figure 1
(A), (b), and FIG. 3 (a), (b) are diagrams showing the first to fourth steps, respectively. All steps are M
It was continuously performed by the OCVD method. The reaction chamber pressure during growth was 70 torr, and the raw material used for growth was group III In (
CH3 _{) 3} , Ga (CH3 _{) 3} , Al (CH3 _{) 3} , V group is P
H ₃ , AsH ₃ , and Fe (C ₅
H _{5) 2} .

In the first step, In having a plane orientation (100) is used.
Predetermined laser irradiation is applied to the P substrate 11 to cause defects in this crystal orientation or disorder in the crystal. Alternatively, after heating the InP substrate 11 to 650 ° C. in a PH ₃ atmosphere, Fe
The doped InP layer 12 was grown to a thickness of 300 nm at a growth rate of 20 nm / min. The doping concentration of Fe was set to 3 × 10 ¹⁷ cm ⁻³ . The solid solution limit of Fe in InP is 5 × 10
¹⁶ cm ⁻³ , and excess Fe was deposited on the surface as fine particles 13 having a Fe—P bond and a size of 10 to 30 nm.

In the second step, the Fe-doped InP layer 12 is used.
Above, In _{0. 52} Al _0.48 As layer 1 which is lattice-matched to InP
4 at 650 ° C., V / III molar ratio of 400, growth rate of 20 nm
It grew to 50 nm at / min. When the cross section and the surface were observed with a scanning electron microscope, a large number of quadrangular pyramid pits 15 were formed. Almost all the pits had the same shape, and when viewed from the surface, the (011) direction was 80 nm, the (011) direction was 50 nm rhombus, and the depth was 20 nm. The slope of the pit had a smooth surface. The pit density was 2 × 10 ⁷ cm ^-2 (FIG. 1 (b)). It should be noted that as the concentration of Fe doped in the first step was lowered, the density of pits also decreased, and when the concentration fell below the solid solution limit, the pits disappeared. Then, as shown in FIG. 2A, the density of fine particles deposited with respect to the Fe doping concentration changes linearly.

In the third step, I which is lattice-matched to InP is used.
n _0.53 Ga _0.47 As was grown at 650 ° C. and a V / III molar ratio of 40. The fact that the InGaAs dots 16 are formed at the bottom of the groove (FIG. 2B) and that the size of the dots can be controlled in proportion to the growth time of InGaAs is determined by the photoluminescence method after the fourth step. This could be confirmed by measuring the emission peak wavelength (Fig. 3
(A)).

In the fourth step, InAlAs is added to 700
A film thickness of 50 nm was grown at 40 ° C., a V / III molar ratio of 400, and a growth rate of 20 nm / min. InAlAs layer 17 formed by growth
The surface after the growth was flattened as shown in FIG. Further, as shown in FIG. 3B, the above steps can be repeated four times to form a quantum box three-dimensionally. In the first step, Fe on the InP substrate
Planar doping, the second to fourth steps are shown in FIG.
And a quantum box was prepared by the same method as in the example of FIG.
Repeating the first to fourth steps four times,
A quantum box of InGaAs 16 could be three-dimensionally formed in the InAlAs layer 14. According to this embodiment, a semiconductor light emitting device can be manufactured by forming electrodes.

(Embodiment 2) FIG. 4 is a sectional view showing the structure of a semiconductor laser according to another embodiment of the present invention.

In FIG. 4, M is formed on the n-type InP substrate 11.
When the n-type InP buffer layer 21, the Fe planar doped layer 12, and the n-type InGaAsP layer 14 are sequentially grown by the OCVD method, many pits are formed on the surface. A non-doped InGaAs layer 16 is grown on the pits to form dots having a thickness of 10 nm. After that, p-type InGa
An Asp layer 22 and a p-type InP layer 23 are grown. After the growth, the electrode 3 is formed on the n-type InP substrate 11 and the p-type InP layer 23.
1, 33 were formed and a current was passed to obtain laser oscillation.

An example of the main part layer thickness of the above semiconductor laser is shown below.

P-type InP layer (23) 200 nm p-type InGaAsP layer (22) 100 nm undoped InGaAs (16) -n-type InGaAsP layer (14) 100 nm Fe planar-doped layer (12) -n-type InP buffer layer (21) 500 nm n-type InP substrate (11) − The following is further added to the above.

(1) Even if a transition metal such as Ti, Cr, or Co other than Fe is doped to the solid solution limit or more, a pyramidal groove is similarly formed.

(2) In the second embodiment, the non-doped InGaAs 16 is replaced by non-doped InGaAs.
A semiconductor laser with higher oscillation efficiency can be obtained by using a structure in which several layers of non-doped InGaAs dots are three-dimensionally inserted in the P layer.

(3) It is also possible to form a polygonal pyramidal groove using a crystal defect such as a spiral transition or an edge transition as a nucleus and form a dot structure at the bottom thereof.

[0033]

As described above, according to the present invention, the first step of causing defects or disorder in the crystal structure on the semiconductor substrate, or depositing fine particles such as metal, the disorder of the fine particles or the crystal structure is prevented. The second step of growing the first semiconductor layer so as to form a groove at the top, the third step of forming dots of the second semiconductor layer at the bottom of the groove, the first step of covering the dots with the first semiconductor layer. MOCVD method or MBE
A quantum box can be formed by continuously performing the method. This method is much easier than the conventional method of forming a quantum box, and is free from impurity contamination and damage, and (1) it can be continuously manufactured by the same apparatus and is easy to manufacture. (2) Since the groove is formed without using a mask, the manufacturing process is simple, and contamination and damage associated with mask formation and removal can be prevented.
(3) According to the above (1) and (2), it is possible to form three-dimensionally a quantum box having good crystallinity and the same shape.

[Brief description of drawings]

1A and 1B are cross-sectional views each showing a part of a manufacturing process of a quantum box according to an embodiment of the present invention in process order,
(C) is a top view of (b).

2A is a diagram for explaining the present invention, FIG.
FIG. 2 is a cross-sectional view showing a part of the manufacturing process of the quantum box according to the embodiment of the present invention in the order of processes continuing from FIG. 1.

3A is a cross-sectional view showing a part of the manufacturing process of the quantum box according to the embodiment of the present invention in the order of the processes continued from FIG. 2, and FIG.
FIG. 4 is a cross-sectional view of a semiconductor substrate having a quantum box according to an embodiment of the present invention.

FIG. 4 is a sectional view of a semiconductor laser having a quantum box according to an embodiment of the present invention.

[Explanation of symbols]

 11 ... InP substrate 12 ... Fe-doped InP layer 13 ... Fe-P fine particle 14 ... n type InGaAsP layer 17 ... InAlAs layer 15 ... pit (groove) 16 ... InGaAs dot 21 ... n type InP buffer layer 22 ... p type InGaAsP layer 23 ... p-type InP layer 31, 33 ... electrode

Claims (2)

[Claims] 1. A first semiconductor layer is formed after forming a defect or fine grain precipitate on the surface of a semiconductor substrate, and a polygonal pyramidal groove is formed in the first semiconductor layer using the defect or fine grain precipitate as a nucleus. And a second semiconductor layer of a kind different from that of the first semiconductor layer, in which the growth rate at the apex of the groove is higher than the growth rates of other portions on the first semiconductor layer and desired atoms are formed. A method of manufacturing a semiconductor device, comprising: stacking and forming a number of layers; and forming a third semiconductor layer on the second semiconductor layer. 2. The step of forming a polygonal pyramid-shaped groove in the first semiconductor layer is carried out by epitaxially growing the semiconductor layer on a semiconductor substrate while doping metal atoms above the solid solution limit with the metal or the metal. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the method is a method of depositing fine particles made of a substance in which atoms constituting a semiconductor are bound to the metal.