JPH08111380A - Fabrication of semiconductor structure - Google Patents

Abstract

PURPOSE: To obtain a semiconductor structure excellent in the interface characteristics by growing a polycrystal on a mask set on a semiconductor substrate whereas growing a single crystal on a part not covered with the mask and setting the thickness of a mask layer thinner than the level difference. CONSTITUTION: A resist pattern 2 is formed on a semiconductor substrate 1 which is then etched using the resist pattern 2 as a mask thus forming a level difference. Subsequently, an SiO2 mask 3 is formed at the etched part on the semiconductor substrate 1. A high resistance polycrystal 5 is then grown on the mask 3 whereas a single crystal 3 is grown on a part not covered with the SiO2 mask 3. The SiO2 mask layer 3 is set thinner than the level difference. This method provides a semiconductor structure excellent in the interface characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor structure manufacturing method using a processed substrate and a selective crystal growth method, which is necessary for manufacturing a fine structure device having good characteristics.

[0002]

2. Description of the Related Art Conventionally, quantum effects such as quantum wires have been studied in order to fabricate semiconductor parts (fine structure devices) such as transistors, ICs, diodes, thermoelectric elements, solar cells, Hall elements and photoconductive elements. For III-
Research on selective crystal growth on group V compound semiconductors has been actively conducted.

In this selective growth, the following two types of mask materials are used. That is, i) An oxide film made of an insulating material such as SiO ₂ , SiN, GaAs is used to electrically isolate the elements.
Ii) A metal having a high melting point such as W or WSi is used as an embedded electrode.

The case where an insulating film is used will be described below.

Selective growth is the growth of crystals only at selected locations on the substrate. In a broad sense, it also includes selectively growing a substance having a property different from that on the non-selected place.

First, metal organic chemical vapor deposition (MOCVD)
In the case of performing selective growth using the method or a growth method similar thereto, Si is selectively epitaxially grown only on the exposed Si portion of the substrate using an insulating film such as SiO ₂ or SiN as a growth mask. In this selective growth, a single crystal grows on the compound semiconductor not covered with the mask.

Next, a case where selective growth is performed by using a molecular beam epitaxy (MBE) method for forming a single crystal thin film in an ultrahigh vacuum will be described. For example, when GaAs is selectively grown, a single crystal grows on a compound semiconductor not covered with a mask, whereas a polycrystal is deposited on the mask. Since this polycrystal exhibits high resistance, it can be used as an insulating material. In this case, since the crystal properties (whether it is single crystal or polycrystal) on the mask and on the portion not covered by the mask are different, it is considered to be selective growth in a broad sense. In this selective growth using the MBE method, as shown in FIG. 6, an interface is formed between the regrown layer and a mask such as SiO ₂ . In FIG.
A mask 32 is partially formed on the GaAs substrate 1. High-resistance polycrystal is grown in the portion where the mask is formed. On the other hand, the single crystal 4 has grown in the portion where the mask 32 is not formed. Further, a mask is formed between the single crystal 4 and the mask 32.

[0008]

However, in the above semiconductor structure, since the portion where the single crystal 4 starts to grow is below the mask 32, the single crystal 4 and the mask 3 are initially formed at the beginning of growth.
There are two interfaces 61. The characteristics of this interface are poor, and this interface 61 also adversely affects the interface between the single crystal 4 and the high resistance polycrystal 5.

Generally, the above metal organic chemical vapor deposition (MOCV) is used.
When selective growth is performed using the method D) or a growth method similar to it, it is important not to grow single crystals and polycrystals on the mask. Therefore, in order to obtain good selectivity, it is necessary to determine appropriate growth conditions (growth temperature, growth pressure, source gas, etc.). The growth conditions suitable for selective growth may be different from the conditions for growing a good single crystal, or the electrode formation may become difficult even if a fine structure can be produced.

Further, the molecular beam epitaxy (MB
When the selective growth is performed using the method E), the device characteristics are deteriorated due to the poor interface characteristics. Furthermore, the properties of this interface also adversely affect the interface between the single crystal and the high resistance polycrystal. Therefore, the characteristics of these interfaces adversely affect the characteristics of the device as the device size decreases.

Further, in the selective growth using the MBE method, a method has been reported in which the GaAs surface is oxidized to form a mask of a GaAs oxide film, the mask is partially scraped off, and then regrowth is performed. Before performing recrystallization, the native oxide film on the GaAs surface not covered with the mask must be removed. However, when removing the natural oxide film,
The GaAs oxide film on the mask is also removed. And GaA
There is also a problem that the s-oxide film is thermally unstable and thus deteriorates during growth.

In the MBE method or MOCVD method, Al
It is difficult to grow a single crystal on the GaAs layer. This is A
This is because it is difficult to remove the natural oxide film formed on lGaAs. This is considered to indicate that, on the contrary, the AlGaAs oxide film is thermally stable and the AlGaAs oxide film can be used as a mask. In order to prevent the oxidation of the surface of the AlGaAs layer, Al
A thin GaAs cap layer is grown and protected on the GaAs layer. This GaAs cap layer has a temperature (7 ° C) higher than the normal growth temperature (600 ° C to 700 ° C).
It can be peeled off by applying (50 ° C.). By peeling off the GaAs cap layer immediately before regrowth, a single crystal can be grown on the unoxidized AlGaAs layer. By partially removing the GaAs cap layer, a single crystal is formed in the part with the cap layer.
Polycrystals can grow in the non-existing portion, and selective growth becomes possible. However, in order to peel off the GaAs cap layer, heat treatment at a high temperature is necessary, which causes deterioration of the buried structure and accumulation and diffusion of impurities during the heat treatment.
Further, the oxide film of the AlGaAs layer, on which the polycrystal should be grown, may be removed, and the polycrystal may not have a high resistance, and the elements may not be separated.

Therefore, an object of the present invention is to solve the above problems and provide a method for manufacturing a semiconductor structure having good interface characteristics.

[0014]

In order to solve the above-mentioned problems, a semiconductor structure manufacturing method according to the present invention comprises:
In a semiconductor structure manufacturing method for selectively growing crystals on a semiconductor substrate, a step of forming a resist pattern on the semiconductor substrate, and a step of forming a step on the semiconductor substrate by etching using the resist pattern as a mask, Forming a mask made of an insulator on the etched portion of the semiconductor substrate, and growing a polycrystal on the mask, while growing a single crystal on a portion not covered by the mask In addition, the thickness of the layer including the insulating mask is lower than the height of the step. Therefore, the region for growing the single crystal on the semiconductor substrate is located above the surface of the mask layer made of an insulating material. Therefore, since the single crystal growth layer and the mask layer do not come into contact with each other, the adverse effect of the interface formation between the single crystal growth layer and the mask layer, which has been a problem in the related art, can be avoided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor structure manufacturing method according to the present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 is a schematic cross-sectional view for explaining each step of an example of a method for manufacturing a semiconductor structure according to the present invention. FIG. FIG. 3A is a diagram for explaining each step of substrate etching, (c) a SiO ₂ film formed by a sputtering method, (d) a lift-off of a resist film, and (e) a growth step by an MBE method.

First, a resist is applied on the surface of a GaAs substrate to form a resist pattern (FIG. 1 (a)). The substrate is etched over a predetermined thickness using this resist pattern as an etching pattern. As a result, a step is formed on the surface of the substrate (FIG. 1 (b)). After the etching is completed, a SiO ₂ film is formed by sputtering on the entire surface of the substrate including the portion covered with the resist mask (FIG. 1C). Further, the resist mask is removed with acetone to leave SiO ₂ only in the recessed portion of the GaAs substrate (FIG. 1 (d)). Then, GaAs is grown on the substrate thus processed (FIG. 1E). In this example, crystal growth was performed by the MBE method at a substrate temperature of 600 ° C. In this case, the crystal on the SiO ₂ mask was polycrystalline 5 and exhibited high resistance. On the other hand, the crystal on the GaAs layer is a single crystal 4. Further, as shown in FIG. 1E, the single crystal growth layer 4 is located above the SiO ₂ mask 3. Therefore, the single crystal 4 forms an interface 6 adjacent to the polycrystal, but does not contact the SiO ₂ mask 3. Therefore, a good interface was obtained.

It is not always necessary to use the MBE method for growth, and if the polycrystalline layer has high resistance, MOCVD is performed.
It is also possible to use a growth method or a growth method based on it.

[Embodiment 2] FIG. 2 is a schematic cross-sectional view of a hetero-bipolar transistor manufactured by a semiconductor structure manufacturing method according to the present invention. In this figure, reference numeral 1 is a GaAs substrate processed by the same method as in Example 1, a high-resistance polycrystal 5 is laminated in a recessed portion of the substrate 1, and a plurality of single crystals is formed in a convex portion. The layers are stacked. That is, the single crystal layer 4 of Example 1
The n-GaAs collector electrode layer 14, the n-GaAs collector layer 11, the p-GaAs base layer 15, and the N-AlG.
aAs emitter layer 16, n-GaAs emitter electrode layer 1
It was set to 7. Further, in FIG. 2, reference numeral 19 is an emitter electrode, 20 is a base electrode, and 21 is a collector electrode. In this example, after the growth by the MBE method, a process is performed to form a metal electrode.

Even if SiN was used as the mask layer, the resistance between the elements was high, and the polycrystal 5 showed good insulation characteristics. Further, even if the emitter electrode is formed on the high-resistance polycrystal 5, the elements can be separated from each other, so that the size of the emitter can be reduced. Therefore, the degree of integration is increased and the high frequency characteristics are improved. Furthermore, since one of the interfaces between the p-GaAs base layer 15 and the N-AlGaAs emitter layer 16 is in contact with the polycrystal 5 and is not in contact with the atmosphere, the recombination current at the base / emitter interface is reduced. . Although the example of AlGaAs / GaAs is used here, the present invention can be applied to all semiconductors such as Si / Ge and InGaAs / InP.

[Embodiment 3] FIG. 3 is a schematic cross-sectional view of a micro-resonant tunnel diode manufactured by the method for manufacturing a semiconductor structure according to the present invention. Reference numeral 1 is n-G
aAs substrate, 3 is a SiO ₂ mask, 5 is a high resistance polycrystal,
22 is a GaAs layer, 23 is an AlAs layer, and 24 is n-Ga.
The As electrode layer, 25 is a metal electrode. Single crystal layer 4 of FIG.
The GaAs layer 22, the AlAs layer 23, the n-GaAs layer 2
4 corresponds to this case, and this portion forms a resonant tunneling diode structure. Despite being a small diode, the electrode formation is very easy and the negative resistance characteristic can be observed.

[Embodiment 4] FIG. 4 is a schematic cross-sectional view for explaining each step of an example of a method for manufacturing a semiconductor structure according to the present invention, in which an Al-based natural oxide film is used instead of a mask such as SiO ₂ . Shows the case of using. In FIG.
(A) is a GaAs / AlGaAs substrate, (b) is a resist film formed on the substrate and etching, (c) is A
FIG. 3D is a diagram corresponding to each step of the growth by the MBE method after the resist is removed, and FIG. In the figure, reference numeral 31 is a GaAs layer, 32 is an AlGaAs layer, 2 is a resist, 33 is an Al-based oxide film, 4 is a single crystal, and 5 is a high resistance polycrystal.

First, the GaAs layer 31 and the AlGaAs layer 3
This facilitates a substrate 30 formed by stacking two (FIG. 2 (a)).
Next, the resist 2 is applied on the GaAs layer 31. A step is formed by etching the substrate using the resist mask as a pattern (FIG. 4B). Here, GaA
It can be performed by using selective etching for the s layer. However, the GaAs layer 31 and the AlG
It is not necessary to stop etching at the interface of the aAs layer 32,
The etching may be stopped in the AlGaAs layer 32. An Al-based oxide film is formed on the entire surface by the oxidation process (FIG. 4C). Here, an oxide film formed when reacting with oxygen in the atmosphere is used. Other methods may be used for the oxidation process. Next, G on the processed substrate
An aAs layer is grown (FIG. 4 (d)). After removing the resist, the GaAs layer is also oxidized. However, Al
The GaAs layer is more easily oxidized than the GaAs layer, and the oxide film is difficult to remove. Utilizing this property, heat treatment was performed at 650 ° C. before growth in order to remove only the oxide film on the GaAs layer. At this temperature, the oxide film on the surface of the AlGaAs layer is not removed and is thermally stable, so it can be used as a mask. After that, re-growth is 600 ° C MBE
Went by law. The crystal on the AlGaAs layer was polycrystalline 5 and had high resistance. On the other hand, the crystal on the GaAs layer is the single crystal 4. Further, as shown in FIG. 4D, the Al-based oxide film 3 in which the single crystal growth layer serves as an oxide film mask layer
Since it is located above 3, the interface with the single crystal layer 4 is not the Al-based oxide film 33 but the polycrystal 5. Therefore, a good interface was obtained.

[Embodiment 5] FIG. 5 is a schematic cross-sectional view of a hetero-bipolar transistor manufactured by a semiconductor structure manufacturing method according to the present invention. Reference numeral 11 is an n-GaAs collector layer, 41 is n-GaAs
Substrate, 32 is an AlGaAs substrate, 33 is an Al-based oxide film,
15 is a p-GaAs base layer, 16 is N-AlGaAs
An emitter layer, 17 is an n-GaAs emitter electrode layer, 5 is a high resistance polycrystal, 19 is an emitter electrode, 20 is a base electrode, and 21 is a collector electrode. The single crystal layer 4 of FIG.
-GaAs collector layer 11, p-GaAs base layer 1
5, N-AlGaAs emitter layer 16 and n-GaAs emitter electrode layer 17. In addition, the GaAs / AlGaAs substrate 30 in FIG.
N-GaAs / consisting of the layer 41 and the AlGaAs layer 32
This corresponds to the case of using an AlGaAs substrate. And MB
After the growth by the E method, a process is performed to form a metal electrode.

Even if an Al-based oxide film is used, the same advantages as those of the hetero bipolar transistor obtained in the second embodiment can be obtained.

[0026]

As described above, since the substrate surface of the region where the single crystal is to be grown is located above the mask layer surface, a good interface can be obtained, and the fine device can be manufactured well. There is an effect.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining each step of an example of a semiconductor structure manufacturing method according to the present invention, in which (a) is Ga.
Forming a resist film on the As substrate, (b) etching the substrate, (c) forming a SiO ₂ film by sputtering,
(D) lift-off of resist film, (e) MB
It is a figure for demonstrating each process of the growth by E method.

FIG. 2 is a schematic cross-sectional view of a hetero-bipolar transistor manufactured by a semiconductor structure manufacturing method according to the present invention.

FIG. 3 is a schematic cross-sectional view of a micro-resonant tunnel diode manufactured by a semiconductor structure manufacturing method according to the present invention.

FIG. 4 is a schematic cross-sectional view for explaining each step of an example of a semiconductor structure manufacturing method according to the present invention, in which (a) is Ga.
Drawings corresponding to the steps of forming an As / AlGaAs substrate, (b) forming and etching a resist film on the substrate, (c) forming an Al-based oxide film, and (d) growing by the MBE method after resist removal. Is.

FIG. 5 is a schematic cross-sectional view of a hetero-bipolar transistor manufactured by a semiconductor structure manufacturing method according to the present invention.

FIG. 6 is a schematic cross-sectional view of a semiconductor structure manufactured by a conventional semiconductor structure manufacturing method.

[Explanation of symbols]

1 GaAs substrate (n-GaAs substrate) 2 Resist 3 SiO ₂ mask 4 Single crystal 5 High resistance polycrystal 6 Interface between single crystal and polycrystal 11 n-GaAs collector layer 13 SiN mask 14 n-GaAs collector electrode layer 15 p -GaAs base layer 16 N-AlGaAs emitter layer 17 n-GaAs emitter electrode layer 19 emitter electrode 20 base electrode 21 collector electrode 22 GaAs layer 23 AlAs layer 24 n-GaAs electrode layer 25 electrode 30 semiconductor substrate 31 GaAs layer 32 AlGaAs layer ( Mask) 33 Al-based oxide film 41 n-GaAs layer 61 Interface between single crystal 4 and mask 32

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/331 29/73

Claims (1)

[Claims] 1. A semiconductor structure manufacturing method for selectively growing crystals on a semiconductor substrate, the method comprising: forming a resist pattern on the semiconductor substrate; and etching the semiconductor substrate by using the resist pattern as a mask. A step of forming a step,
Forming a mask made of an insulator on the etched portion of the semiconductor substrate; growing a polycrystal on the mask; and growing a single crystal on a portion not covered by the mask. The method of manufacturing a semiconductor structure, further comprising: a step of forming the insulating mask, wherein the thickness of the insulating mask layer is lower than the height of the step.