JP2003218087A - Manufacturing method for semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a semiconductor device with superior performance, protecting from crystal defect being introduced in a semiconductor film, as well as repeatedly and controllably etching the semiconductor film used for the semiconductor apparatus. <P>SOLUTION: A substrate provided with a bottom semiconductor film 12 including a lattice constant of which difference from the lattice constant of a semiconductor film 13 is within 10%, as well as including band gap energy smaller than that of the semiconductor film 13, in a bottom layer of an etching region 14 of the semiconductor film 13 is dipped in etching solution. The semiconductor film of the etching area 14 is etched by emitting to this substrate light with band gap energy smaller than that of the semiconductor film 13, and energy larger than the band gap energy of the bottom semiconductor film 13. <P>COPYRIGHT: (C)2003,JPO

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 including a step of wet-etching a semiconductor film on a substrate on which semiconductor films are laminated. .

[0002]

2. Description of the Related Art A large-scale integrated circuit (ULSI) made of silicon (Si), a laser diode (LD) made of a compound semiconductor such as gallium arsenide (GaAs), and an electrostatic effect transistor (FET) are semiconductors. It has a structure in which films are laminated. In forming a semiconductor device, it is necessary to partially etch these semiconductor films to form a fine structure. In the case of a semiconductor device using Si, a dry etching method is mainly used for processing, but there are problems of processing damage and surface contamination. Especially L
When a single crystal film is regrown on the surface after etching as in D, the disorder of the crystal at the regrowth interface is small,
Wet etching, which is expected to have high device reliability, is often applied.

Controlling stopping etching at the interface of semiconductor films having different conductivity types and compositions is important for exhibiting device design performance, suppressing variations in device quality, and improving reliability.

As a method of etching a part or the whole surface of a semiconductor film without using a mask, a semiconductor having a Al ₂ O ₃ film as a base and a part without an Al ₂ O ₃ film has been used so far. A method is known in which a semiconductor film formed on an Al ₂ O ₃ film is selectively etched by utilizing the fact that a difference occurs in crystal defects when a layer is epitaxially grown. FIG. 4 is a diagram illustrating a conventional etching method disclosed in Japanese Patent Laid-Open No. 10-233385. In FIG. 4, (a) to (d) are views showing a cross section in each step. In this conventional etching method, first, an Al ₂ O ₃ film is formed on the surface of the semiconductor substrate 1 by using a vapor deposition device, and only a part of the Al ₂ O ₃ film 2 is left by patterning (FIG. 4A). (B)). Next, a semiconductor film is epitaxially grown on the substrate having the Al ₂ O ₃ film 2 formed on a part of the surface. Crystal defects are different between the semiconductor film 4 formed on the semiconductor substrate and the semiconductor film 3 formed on the Al ₂ O ₃ film 2 (FIG. 4C). A
Since the semiconductor film 3 formed on the l ₂ O ₃ film 2 has more crystal defects, the semiconductor film 3 on the Al ₂ O ₃ film 2 can be selectively wet-etched. The groove 5 can be formed in the semiconductor film (FIG.
(D)).

[0005]

[SUMMARY OF THE INVENTION However, in this way, after forming by vapor deposition an Al ₂ O ₃ film on the underlayer, when epitaxially growing a semiconductor film, Al ₂ O
The crystal defect concentration in the semiconductor film formed on the _three films is high.

When manufacturing a semiconductor device such as an LD, A
In some cases, the semiconductor film on the l ₂ O ₃ film is partially etched, and the remaining semiconductor film has a function of determining device characteristics such as an active layer and a clad layer. In such a case, if there is a crystal defect in the semiconductor film, there is a problem that the performance of a semiconductor device such as an LD is significantly deteriorated. For example, when an LD is manufactured, there is a problem that the light conversion efficiency is lowered.

The present invention has been made in order to solve such a problem, and etches a semiconductor film used in a semiconductor device with good reproducibility and controllability, and introduces crystal defects into the semiconductor film. It is an object of the present invention to provide a method for manufacturing a semiconductor device which prevents the occurrence of defects and has excellent performance.

[0008]

A method of manufacturing a semiconductor device according to the present invention comprises:
A substrate provided with a base semiconductor film having a bandgap energy smaller than that of the semiconductor film and having a lattice constant within 10% of the lattice constant of the semiconductor film is immersed in an etching solution to form a semiconductor film. The step of etching the semiconductor film in the etching region by irradiating with light having an energy smaller than the band gap energy of the base semiconductor film and larger than the band gap energy of the base semiconductor film.

Further, the semiconductor film is a GaN film and the base semiconductor film is a GaInN-based film.

The semiconductor film and the base semiconductor film are made of GaA.
The film is one of an InnN-based film, an InGaAsP-based film, an AlGaAs-based film, and an AlGaAsSb-based film.

Further, etching is carried out with a negative voltage applied to the substrate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are views for explaining a method of manufacturing a semiconductor device according to a first embodiment of the present invention. In FIG. 1, (a) to (d) are views showing a cross section in each step. First, the base semiconductor film 12 having a desired pattern is formed on the substrate 11 (FIGS. 1A and 1B). A crystalline substrate such as a sapphire substrate is used as the substrate 11. The base semiconductor film 12 is
It is formed by epitaxial growth. Epitaxial growth is based on MOCVD (Metalorganic Chemical Vapor Depo
sition), MBE (Molecular Beam Epitaxy), MOV
It is carried out by a method such as PE (Metalorganic Vapor Phase Epitaxy). The underlying semiconductor film 12 is epitaxially grown on the entire surface of the substrate 11 and then patterned, or
Alternatively, a base material semiconductor film having a predetermined pattern is formed by epitaxial growth using a mask material.

Next, a semiconductor film 13 is formed by epitaxial growth on the substrate 11 having the underlying semiconductor film 12 formed on a part of the surface (FIG. 1C). Here, the underlying semiconductor film 12 is selected to have a bandgap energy smaller than the bandgap of the semiconductor film 13 and a lattice constant within 10% from the lattice constant of the semiconductor film 13. The thickness of the base semiconductor film 12 is set to be equal to or less than the thickness of the semiconductor film 13 epitaxially grown on the base semiconductor film 12. By setting the difference in the lattice constant between the semiconductor film 13 and the base semiconductor film 12 to be within 10%, the misfit dislocation exists only at the interface between the semiconductor film 13 and the base semiconductor film 12, and the thickness is 0.1 μm or more. In, there is no crystal defect.

Next, the substrate having the semiconductor film 13 formed on the surface thereof is immersed in an etching solution so that energy lower than the band gap energy of the semiconductor film 13 and higher than the band gap energy of the base semiconductor film 12 is applied. When the semiconductor film 13 is irradiated with the light, it is possible to etch only the semiconductor film in the etching region 14 in which the base semiconductor film 12 is formed.
5 can be formed (FIG. 1 (d)). In this method, etching can be performed without a mask without forming a mask on the semiconductor film. As the etching liquid, a liquid that can consume holes and dissolve the semiconductor film in the etching liquid is used.

Next, a mechanism capable of etching the semiconductor film in the etching region 14 in which the base semiconductor film 12 is formed as the base will be described. FIG. 2 is an energy band model diagram in the etching according to the first embodiment of the present invention. (A) is an energy band model diagram when a voltage is not applied to the substrate, and (b) is a negative voltage to the substrate. It is an energy band model figure when applying it. In FIG. 2, Ec is a conduction band edge, Ef is a Fermi level, Ev is a valence band edge, 16 is an electron, and 17 is a hole.

First, etching when no voltage is applied to the substrate will be described with reference to FIG. Figure 2
As shown in (a), when light having energy smaller than the band gap energy of the semiconductor film and larger than the band gap energy of the base semiconductor film is irradiated while the semiconductor film and the etching solution are in contact with each other, the inside of the semiconductor film is irradiated. In the above, light-absorption occurs inside the underlying semiconductor film without generating electron-hole pairs, and electron-hole pairs are generated. The holes 17 generated in the valence band of the base semiconductor film have an energy corresponding to one half of the difference in bandgap energy between the semiconductor film and the base semiconductor film, as indicated by an arrow in FIG. It diffuses in the semiconductor film beyond the barrier and reaches the surface of the semiconductor film. The holes that have reached the surface of the semiconductor film cause a reaction between the semiconductor film and the etching liquid at the semiconductor film / etching liquid interface, whereby the semiconductor film is dissolved in the etching liquid and etching proceeds.

Such a dissolution reaction of a semiconductor is represented by the following equation (1) in the case of silicon, for example. Since holes are involved in the dissolution reaction as in the following formula (1), the hole concentration at the semiconductor film / etching liquid interface determines the dissolution rate of the semiconductor film. Si (bulk) + 4h ⁺ → Si ⁴⁺ (sol.) (1) Here, Si (bulk) is Si in the solid state, h ⁺ is a hole, and Si ⁴⁺ (sol.) Is dissolved in the etching solution. The ionized Si is shown.

Next, etching when a negative voltage is applied to the substrate will be described with reference to FIG. The negative voltage is applied to the substrate by providing an electrode facing the substrate and connecting the electrode to the positive side of the power source and the substrate to the negative side of the power source (not shown). When a negative voltage is applied to the substrate, the Fermi level in the semiconductor film decreases as shown in FIG. 2 (b). Similar to when no voltage is applied,
When the semiconductor film and the etching solution are in contact with each other, when light having an energy smaller than the band gap energy of the semiconductor film and larger than the band gap energy of the base semiconductor film is irradiated, electron-hole pairs are generated inside the semiconductor film. Without generating, light absorption occurs inside the underlying semiconductor film,
Electron-hole pairs are generated. The holes 17 generated in the valence band of the base semiconductor film are pulled by the negative voltage and drift toward the semiconductor film side. As indicated by the arrow in FIG. 2B, the holes 17 drift toward the semiconductor film side beyond the energy barrier at the interface between the semiconductor film and the base semiconductor film, but this energy is applied when a negative voltage is applied. Since the barrier becomes lower, more holes 17 drift toward the semiconductor film side than when no voltage is applied, and the hole concentration on the surface of the semiconductor film (interface with the etching solution) increases. The holes reaching the surface of the semiconductor film are
The reaction between the semiconductor film and the etching solution is caused, whereby the semiconductor film is dissolved in the etching solution. By applying a negative voltage, the hole concentration on the surface of the semiconductor film can be increased, so that the etching rate of the semiconductor film can be increased.

In the etching method of the present invention, the etching rate can be controlled by controlling the conductivity type of the semiconductor film, the conductivity type of the base semiconductor film, and the carrier concentration of the semiconductor film and the base semiconductor film. .
Also, by controlling the power of the light to be emitted,
The etching rate can be controlled.

As described above, according to the etching method of the present invention, the semiconductor film can be etched at a desired etching rate. Therefore, even when the semiconductor film is partially etched, the etching amount can be reproduced with good reproducibility. ,
And it can be controlled with high accuracy. Further, since the semiconductor film can be etched without a mask, manufacturing of the semiconductor device can be simplified. Furthermore, since it is possible to prevent defects from occurring in the semiconductor film, it is possible to prevent deterioration of the characteristics of the semiconductor device, and it is possible to obtain a semiconductor device with excellent performance. For example, when it is used for an LD, it is possible to prevent a bad influence due to a defect such as a decrease in light conversion efficiency.

Next, an example of a combination of a semiconductor film and a base semiconductor film when performing the above-described etching method of the present invention will be described. Even in the case of the combinations described below, the above effects can be obtained. FIG. 3 is a diagram showing the relationship between the band gap and the lattice constant of various semiconductors. In FIG. 3, WZ and ZB indicate that the crystal structures are Wurtzite structure and Zincblende structure, respectively.
A and B are Wurtzite structure and Zincblen, respectively.
This is a region showing the relationship between the band gap and the lattice constant of a GaAlInN-based semiconductor having a de structure.

Of the various semiconductors shown in FIG. 3, the semiconductor film has a band gap larger than that of the base semiconductor film, and the difference in lattice constant between the semiconductor film and the base semiconductor film is within 10%. What satisfies the above conditions can be selected as a combination of the semiconductor film and the base semiconductor film.

For example, a GaInN-based film obtained by mixing a GaN film with a predetermined mixing ratio of In has a smaller band gap than the GaN film and has a difference of 1 from the lattice constant of the GaN film.
It can be within 0%. Therefore, when a GaN film is etched as a semiconductor film, a GaInN-based film mixed with In is used as a base semiconductor film having a band gap smaller than that of the GaN film and having a difference from the lattice constant of the GaN film within 10%. Can be used. When a GaN film is used as the semiconductor film, a KOH aqueous solution or the like can be used as an etchant capable of etching while consuming holes.

In addition, in a GaAlInN-based semiconductor containing Ga, Al, and In which are group III, Ga, Al, In
Since the mixing ratio can be arbitrarily changed, the band gap and the lattice constant can be arbitrarily selected within the region A or the region B of FIG. Therefore, when a GaAlInN-based film is etched as the semiconductor film, the band gap of the GaAlInN film is smaller than that of the GaAlInN film, and the difference from the lattice constant is within 10%.
A GaAlInN-based film having a different Al / In mixture ratio can be used. In this case, it is possible to select a combination of the semiconductor film and the base semiconductor film in which only the band gap energy is changed by making the lattice constants exactly the same, and therefore, a mistake existing at the interface between the semiconductor film and the base semiconductor film can be selected. Almost no dislocations due to fit can be eliminated.

Further, InGaAsP-based film, AlGaAs
Also for semiconductor films such as Al-based films and AlGaAsSb-based films, as in the case of GaAlInN-based films, the combination of the semiconductor film and the underlying semiconductor film is selected by changing the mixing ratio of the elements forming these semiconductors. be able to. Also in the case of these semiconductor films, the same effect as in the case of the GaAlInN-based film can be obtained.

[0026]

According to the method of manufacturing a semiconductor device of the present invention, the lower layer of the etching region of the semiconductor film has a bandgap energy smaller than the bandgap energy of the semiconductor film and a difference from the lattice constant of the semiconductor film. A substrate provided with a base semiconductor film having a lattice constant of 10% or less is immersed in an etching solution and irradiated with light having energy smaller than the band gap energy of the semiconductor film and larger than the band gap energy of the base semiconductor film. By doing so, the semiconductor film in the etching region is etched, so that the semiconductor film used for the semiconductor device can be etched with good reproducibility and controllability. Further, even when the etching of the semiconductor film is stopped midway, crystal defects occurring in the remaining semiconductor film can be reduced, so that a semiconductor device having excellent performance can be obtained.

Further, when the GaN film is etched as the semiconductor film, by using the GaInN type film as the underlying semiconductor film, the GaN film can be etched with good reproducibility and controllability.

Ga is used for the semiconductor film and the base semiconductor film.
By using any of the AlInN-based film, the InGaAsP-based film, the AlGaAs-based film, and the AlGaAsSb-based film, these semiconductor films can be etched with good reproducibility and controllability. Further, the band gap and lattice constant of the semiconductor film and the base semiconductor film can be selected by changing the mixing ratio of the elements forming these semiconductor films.

By applying a negative voltage to the substrate for etching, the etching rate of the semiconductor film can be improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is an energy band model diagram in etching according to the first embodiment of the present invention, in which (a) is an energy band model diagram when a voltage is not applied to the substrate,
(B) is an energy band model diagram when a negative voltage is applied to the substrate.

FIG. 3 is a diagram showing a relationship between band gaps and lattice constants of various semiconductors.

FIG. 4 is a diagram illustrating a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

12 underlying semiconductor film, 13 semiconductor film, 14 etching region.

Claims (4)

[Claims] 1. An underlayer having a bandgap energy smaller than the bandgap energy of the semiconductor film and having a lattice constant within a difference of 10% or less from the lattice constant of the semiconductor film below an etching region of the semiconductor film. The substrate provided with the semiconductor film is dipped in an etching solution to have a band gap energy smaller than that of the semiconductor film,
And by irradiating with light having an energy larger than the band gap energy of the underlying semiconductor film,
A method of manufacturing a semiconductor device, comprising the step of etching the semiconductor film in the etching region. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor film is a GaN film, and the base semiconductor film is a GaInN-based film. 3. The semiconductor film and the base semiconductor film are GaAlI.
nN-based film, InGaAsP-based film, AlGaAs-based film, A
The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is any one of 1GaAsSb-based films. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the etching is performed while a negative voltage is applied to the substrate.