JP2003045805A - Method of manufacturing semiconductor film containing dielectric film and porous film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming high quality semiconductor material with few defects even with a semiconductor film having a lattice constant different from those of substrates mass-produced so far such as Si, GaAs, GaP, and InP, and its configuration. SOLUTION: This method comprises the steps of forming a dielectric film partially on a substrate, forming a first semiconductor film having a lattice constant different from that of the substrate to sandwich the dielectric film, making the first semiconductor film porous, cleaning the surface of the porous semiconductor film, and forming a second semiconductor film having the same composition as that of the first semiconductor film on the cleaned surface.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a structure of a semiconductor device using a compound semiconductor material.

[0002]

2. Description of the Related Art Single crystal compound semiconductor materials represented by GaAs and InP are widely used and important materials for high speed transistors, photodetectors, semiconductor lasers, light emitting diodes and the like. More recently, MOCVD method, M
By improving the crystal growth method such as the BE method and the CBE method,
An ultra-thin film structure has been realized, realizing a device with outstanding characteristics that has never been achieved. However, many compound semiconductor materials are still undeveloped despite being materials having such excellent properties. The reason is that the substrates for growing compound semiconductors are limited.

In order to manufacture a compound semiconductor device having excellent characteristics, it is necessary to grow a semiconductor material having few defects. If the lattice constant of the substrate and the lattice constant of the growing compound semiconductor material are deviated from each other, the grown compound semiconductor material will have defects and the desired characteristics cannot be obtained. Substrates currently in practical use include Si and GaA
Although s, InP, InAs, InSb, etc. can be mentioned, the compound semiconductor materials that can be used by these substrates are few in the whole compound semiconductor, and the technology for growing compound semiconductor materials having an arbitrary lattice constant will be developed in the future. It is thought that it will have a great influence on the development of the compound semiconductor material technology of.

As an example of studying growth of a material having a lattice constant different from that of the substrate, there is one in which GaAs and devices are formed on a Si substrate. G with few defects on Si substrate
A method of forming a layer having an intermediate lattice constant of these two materials at the interface between Si and GaAs film to grow aAs, or a method of introducing a superlattice structure to reduce threading transition,
Further, several lattice relaxation methods and defect reduction methods have been proposed, such as a two-step growth method in which GaAs is once formed at a low temperature and then the temperature is increased to crystallize to confine crystal defects in the low temperature layer. As a result of these studies, a GaAs semiconductor laser that continuously oscillates at room temperature is realized on a Si substrate. However, unfortunately, it has a short life and has a large difference in characteristics from a laser manufactured on a GaAs substrate, and has not been put into practical use. The root cause of this is that the defects caused by the difference in lattice constant and thermal stress cannot be reduced.

Recently, as another method, ELO (Epitaxial Lateral Over growth) has been performed on a silicon substrate.
Has been proposed (Y. Ujiie and T. Nishina
ga: Japan Journal Applied Physics 28 (1989) L337).

A window is opened in the SiO ₂ mask formed on the Si substrate by photolithography, and the exposed semiconductor surface is used as a seed. The GaAs crystal grown from this window is grown laterally. In this case, G formed directly on the window
The aAs film A number of defects introduced by the difference in lattice constant between GaAs / Si, Ga on SiO ₂ extending laterally
Defects are less likely to enter the As film.

However, this method has a drawback that it takes a long time to grow. In addition, there is a problem that defects are partially concentrated in a portion corresponding to the window. In order to provide a high quality film on the entire surface, it is necessary to reduce defects concentrated in the seed crystal portion.

[0008]

DISCLOSURE OF THE INVENTION The present invention is directed to mass-produced substrates, Si, GaAs, GaP, InP.
The present invention provides a method and a structure for forming a high-quality semiconductor material with few defects even in a semiconductor film having a different lattice constant as described above.

[0009]

A method of manufacturing a semiconductor substrate of the present invention comprises a step of partially forming a dielectric film on the substrate,
A step of forming a first semiconductor film having a lattice constant different from that of the substrate with the dielectric film interposed therebetween, a step of making the first semiconductor film porous, and a surface of the porous semiconductor film cleaned. And a step of forming a second semiconductor film having the same composition as the first semiconductor film on the cleaned surface.

Here, it is preferable that a superlattice is formed in the second semiconductor layer. Further, it is preferable that the first semiconductor layer is doped with impurities of 10 ²⁰ cm ⁻³ or more. Furthermore, it is preferable that the first semiconductor layer is heat-treated during growth. Further, it is preferable that the first semiconductor layer is doped with impurities and the impurities are Se.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to a first embodiment of the present invention, a semiconductor film which is not lattice-matched to sapphire is formed on a sapphire substrate by lateral growth, and then a porous film is formed on the top of the semiconductor film. By forming and again forming a film having the same composition as the semiconductor film before being made porous on this porous film,
A method of reducing defects is provided.

According to a second aspect of the present invention, a semiconductor film which is not lattice-matched with GaAs is formed on a GaAs substrate by lateral growth, and then a porous film is formed on the uppermost part of the semiconductor film, and the porous film is formed again. A film having the same composition as the semiconductor film before being made porous is formed on this porous film. At this time, a method of reducing defects by including a superlattice structure is proposed.

According to a third aspect of the present invention, a first semiconductor film which is not lattice-matched with Si is formed on a Si substrate by lateral growth, and then a porous film is formed on the uppermost part of the first semiconductor film. In the method of forming a film, again forming a film having the same composition as the semiconductor film before being made porous on this porous film, by doping the first semiconductor film with an impurity at a high concentration,
A method of reducing defects is provided.

According to a fourth aspect of the present invention, after the first semiconductor film which is not lattice-matched with GaAs is formed on the GaAs substrate by lateral growth, the first semiconductor film is formed on the uppermost part of the first semiconductor film. In the method of forming a porous film and forming a film having the same composition as the semiconductor film before being made porous again on the porous film, defects are generated by repeating heat treatment when forming the first semiconductor film. It provides a way to reduce.

[0015]

EXAMPLE 1 An example of the present invention will be described with reference to FIG. In FIG. 1A, reference numeral 1 indicates a sapphire substrate. This substrate has a C surface. SiNx is formed on the sapphire substrate as shown in 2 and a window is opened.
The window is formed in <1-101>. GaN is grown on this by the MOVPE method. Decompression MOVP
The pressure is set to around 100 Torr using the E method. TEG and NH ₃ are used as raw material gases. Substrate temperature is 1
The temperature is 000 ° C. GaN shown in 3 grown under these conditions
Start to grow from the window and grow and bond in the lateral direction as shown by 4. The reason why the window stripe direction is <1-101> is that the growth rate in the lateral direction is higher than in the film thickness direction. When the GaN film is laterally grown in this manner, GaN is bonded as shown by 3 in FIG. 1B, and GaN on SiNx has few defects and forms a good film. on the other hand,
Defects are concentrated and formed in GaN indicated by 5 corresponding to the window. Furthermore, the lateral growth collides with each other and the surface 8
A defect is also formed. It is necessary to reduce defects in these two areas. Therefore, as shown in 6, the problem is solved by a porous layer of GaN. As a method of forming a porous material, G
A substrate having an aN layer is placed in HF and anodized while applying ultraviolet light. The thickness of the porous layer is 10 μm. Defects tend to be more positively etched in this anodization. As a result, a good film remains with few defects in the region formed by the anodization. First, a thin GaN film is formed on the surface of this porous GaN. As a method of forming this, a thin film is formed by filling the porosity of the surface with a GaN growth rate of 0.05 μm / h. GaN is formed on this thin film. The substrate temperature is 1000 ° C. and the growth is about 20 μm. The GaN film 7 thus formed can reduce defects even in the portion corresponding to the window where defects are conventionally concentrated due to the effect of reducing defects due to anodization and the stress reduction due to the porous layer. It is possible to reduce defects to the same extent as the InGaAs film laterally grown on SiNx.

As described above, by introducing a porous layer, it becomes possible to reduce the number of defects in GaN corresponding to the window region portion, which is a problem due to lateral growth in the related art.

As the substrate, GaN was directly formed on the sapphire substrate, but once GaN was formed on the sapphire substrate.
May be formed, and this GaN may be used as the substrate. Further, not only sapphire but also Si, SiC or the like may be used as the substrate.

(Embodiment 2) Embodiment 2 shows an example in which a GaAs substrate is used and InGaAs which is not matched with the GaAs substrate is formed. In FIG. 2A, reference numeral 11 denotes Ga, which is a substrate.
It is As. A dielectric film (here, SiNx) 12 is formed on this. Here, SiNx is 100
nm is formed. The SiNx film is provided with an opening 19 as shown in FIG. 9 by using ordinary photolithography to expose the GaAs layer. In this example, the width of the openings is 100 μm and the pitch is 2000 μm. The substrate thus formed is placed in an LPE apparatus, and InGaAs (In composition 0.38) is selectively epitaxially grown to a thickness of 10 μm as shown in FIG. The growth start temperature is 800 ° C., and the slow cooling rate is 10 ° C./h. The growth rate of InGaAs is slow on the (111) vertical surface but on the side surface (11
1) A surface, (111) B surface, etc. can obtain high speed. The InGaAs thus formed also has a defect density higher than that of the other portions in the portion 15 corresponding to the window shown in FIG. 2B. Therefore, in this method, the porous layer 16 is formed by immersing this substrate in the HCl solution. As a method for forming a porous layer, first, a substrate having an InGaAs layer is cleaned by organic cleaning or the like, and then an electrode that makes electrical contact with In on the back surface of the substrate is manufactured. After that, anodization treatment is performed in an HCl solution to form a porous layer on the surface of the InGaAs substrate. The porous InGaAs was prepared by anodizing by applying a current of 10 M / cm ² for 5 minutes. The thickness of the porous layer was 5 μm and the porosity was 30%.
Is.

Subsequently, an intended InGaAs film is formed on the porous InGaAs film. The procedure will be described. First, thin InGaAs is formed on the surface of the porous layer. Substrate with porous InGaAs Figure 2 (b)
Put in a growth device. Here, a molecular beam epitaxy apparatus (MBE apparatus) is used. The substrate temperature is heated to about 600 ° C. while irradiating with As, and held for 20 minutes. As a result, the oxide film on the surface of InGaAs is removed, and porous InGa is removed.
On the outermost surface of As, migration of Ga and In occurs in the direction of flattening the unevenness and lowering the surface energy. As a result, the porous surface is flattened. During this planarization, a small amount of Ga or In beam may be irradiated to promote the planarization.
The thickness of the InGaAs single crystal layer formed on the surface is extremely thin and is approximately the same as or less than the diameter of the hole, specifically 100 nm or less, and more preferably 30 nm or less. That is, the thickness of the layer filling the holes is preferably sufficiently smaller than the thickness of the semiconductor layer formed thereabove, for example, 1/5 or less, more preferably 1/100 or less. Specifically, 1 nm to 100 nm
It is desirable to consider the film thickness of the compound semiconductor within the range.

Here, as a method for sealing the holes, a migration enhanced epitaxy (MEE) method is effective in addition to this method. Further, as a growth method, a chemical beam method (CBE method) or a MOCVD method may be used. On this thin InGaAs thin film,
(C) The superlattice layer 17 is formed. The structure of the superlattice layer is InGaAs10 nm and InGaAsP10n.
m is repeatedly formed 5 times. The purpose of this layer is to promote planarization of the film formed on the porous material. Finally 1
InGaAs shown in 8 is formed to a thickness of 10 μm and the growth is completed.

The 16 porous layers enable selective etching of defects in the region indicated by 15, and the In formed on the defects.
The defects of the GaAs layer 18 can be reduced. Further, the flattening is promoted by the InGaAs / InGaAsP superlattice formed in 17 and the reduction of defects can be realized by changing the direction of dislocation.

Although GaAs is used as the substrate in this embodiment, the same effect can be obtained by using a substrate made of Si, InP, GaP, GaN or the like.

(Embodiment 3) Embodiment 3 shows an example in which a Si substrate is used and InGaAs which is not aligned with the Si substrate is formed. Reference numeral 21 in FIG. 3A is Si which is a substrate.
A dielectric film (here, SiO ₂ ) 22 is formed on this. Here, SiO ₂ is formed to 100 nm. The Si layer is exposed by forming an opening 28 in the SiO ₂ film using ordinary photolithography. 23, InGaAs is selectively epitaxially grown to a thickness of 10 μm. At this time, S is added to this InGaAs layer.
e is doped with 10 ²⁰ cm ⁻³ . This doping reduces defects in the grown film. As a result, the defects in the InGaAs 25 corresponding to the window are greatly reduced as compared with the conventional one. Furthermore, the effect of porosity is used to reduce defects.
This substrate is placed in an HCl solution to form the porous layer 26.
As a method for forming a porous layer, first, a substrate having an InGaAs layer is cleaned by organic cleaning or the like, and then an electrode that makes electrical contact with In on the back surface of the substrate is manufactured. After this, anodization treatment is carried out in an HCl solution, and I
A porous layer is formed on the surface of the nGaAs substrate.

Subsequently, an intended InGaAs film is formed on this porous InGaAs film. The procedure will be described. First, thin InGaAs is formed on the surface of the porous layer. Substrate with porous InGaAs, FIG. 3 (b)
Put in a growth device. Here, a chemical beam epitaxy device (CBE device) is used. While irradiating with AsH ₃ , the substrate temperature is heated to about 600 ° C. and kept for 20 minutes. As a result, the oxide film on the surface of InGaAs is removed, and Ga and In migrate in the direction of flattening the unevenness and lowering the surface energy on the outermost surface of the porous InGaAs. As a result, the porous surface is flattened. Further, as the growth method, the MOCVD method or the like may be used. InGa shown on 27 is formed on this thin InGaAs thin film.
Growth is completed after forming As of 10 μm.

The high density doping of Se in 23 can reduce the defect density of InGaAs 25 corresponding to the window. Further, the 26 porous layers can selectively etch the defects in the region indicated by 25, and the defects of the InGaAs layer 27 formed thereon can be further reduced as compared with the prior art.

(Embodiment 4) Embodiment 4 shows an example in which a GaAs substrate is used and InGaAs which is not matched with the GaAs substrate is formed. In FIG. 4A, reference numeral 31 denotes GaA which is a substrate.
s. A dielectric film 32 (here, S
iNx) is formed. The SiNx film is provided with an opening 39 as shown in FIG.
Expose the layer. As shown in 33, selective InGaAs
Are epitaxially grown to a thickness of 10 μm. Here, the growth is temporarily stopped and the InGaAs layer is heat-treated.
The heat treatment temperature is raised and lowered by repeating 400 ° C. and 600 ° C. three times. As a result, the defects in the InGaAs 35 corresponding to the window are greatly reduced as compared with the prior art. Further, the effect of porosity reduces defects. This substrate is placed in an HCl solution to form the porous layer 36. As a method for forming a porous material, first, I
After the substrate having the nGaAs layer is cleaned by organic cleaning or the like, an electrode that makes electrical contact with In is formed on the back surface of the substrate. After that, anodization treatment is performed in an HCl solution to form a porous layer on the surface of the InGaAs substrate.

Then, an intended InGaAs film is formed on the porous InGaAs film. The procedure will be described. First, thin InGaAs is formed on the surface of the porous layer. The substrate having porous InGaAs shown in FIG. 4 (b) is put into a growth apparatus. Here, a chemical beam epitaxy device (CBE device) is used. While irradiating with AsH ₃ , the substrate temperature is heated to about 600 ° C. and kept for 20 minutes to remove the oxide film. As a result, the oxide film on the surface of InGaAs is removed, and Ga and In migrate in the direction of flattening the unevenness and lowering the surface energy on the outermost surface of the porous InGaAs. This thin InGa
InGaAs shown in 38 is formed to a thickness of 10 μm on the As thin film to complete the growth.

The heat treatment applied during the formation of 33 can reduce the defect density. Further, the 36 porous layers can selectively etch the defects in the region indicated by 35, and the defects of the InGaAs layer 38 formed thereon can be further reduced as compared with the conventional case.

[0029]

As a first aspect of the present invention, a semiconductor film which is not lattice-matched to sapphire is formed on a sapphire substrate by lateral growth, and then a porous film is formed on the uppermost part of the semiconductor film. The defects can be reduced by forming a film having the same composition as the semiconductor film before being made porous again on the porous film.

In a second embodiment of the present invention, a semiconductor film which is not lattice-matched to GaAs is formed on a GaAs substrate by lateral growth, and then a porous film is formed on the uppermost part of the semiconductor film, and the porous film is formed again. When a film having the same composition as the semiconductor film before being made porous is formed on this porous film, the defects can be reduced by including the superlattice structure.

According to a third aspect of the present invention, after a semiconductor film which is not lattice-matched with Si is formed on the Si substrate by lateral growth, a porous film is formed on the uppermost part of the semiconductor film and the semiconductor film is formed again. In the method of forming a film having the same composition as that of the semiconductor film before being made porous on this porous structure, by reducing the number of defects by heavily doping the semiconductor film grown directly on Si with a high concentration of impurities. You can

According to a fourth aspect of the present invention, after a semiconductor film which is not lattice-matched with GaAs is formed on a GaAs substrate by lateral growth, a porous film is formed on the uppermost part of the semiconductor film and the semiconductor film is formed again. In the method of forming a film having the same composition as the semiconductor film before being made porous on this porous structure, it is possible to reduce defects by repeating heat treatment when forming the first semiconductor film directly grown on GaAs. You can

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 sapphire substrate, 2 SiNx, 6 GaN porous layer, 7 GaN film, 11 GaAs substrate, 12 Dielectric film, 13 InGaAs 16 porous layer, 17 superlattice layer, 18 InGaAs layer, 21 Si substrate, 22 Dielectric film, 23 InGaAs layer, 26 porous layer, 27 InGaAs layer, 28 openings, 31 GaAs substrate, 32 dielectric film, 33 InGaAs layer, 36 porous layer, 38 InGaAs layer, 39 Opening.

Continued front page    F-term (reference) 5F045 AA04 AB14 AB17 AC09 AC12                       AD14 AF03 AF04 AF09 AF19                       BB12 DA54 DA59 DB01 HA04

Claims (5)

[Claims] 1. A step of partially forming a dielectric film on a substrate, a step of forming a first semiconductor film having a lattice constant different from that of the substrate sandwiching the dielectric film, and the first semiconductor film. And a step of cleaning a surface of the porous semiconductor film, and a second semiconductor film having the same composition as that of the first semiconductor film is formed on the cleaned surface. And a method for manufacturing a semiconductor substrate. 2. The method for manufacturing a semiconductor substrate according to claim 1, wherein a superlattice is formed in the second semiconductor layer. 3. An impurity of 10 in the first semiconductor layer.
^The method for manufacturing a semiconductor substrate according to claim 1 or 2, wherein the semiconductor substrate is doped with ²⁰ cm ^-3 or more. 4. The heat treatment according to claim 1, wherein the first semiconductor layer is heat-treated during growth.
A method for manufacturing a semiconductor substrate according to item. 5. The method of manufacturing a semiconductor substrate according to claim 1, wherein the first semiconductor layer is doped with an impurity, and the impurity is Se.