JPH0444219A - Semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain a desired film on which a compressive stress is applied or from which a tensile stress is reduced on a substrate so as to obtain a high- quality film having a low dislocation density by constituting the substrate by utilizing a difference in coefficient of thermal expansion between materials. CONSTITUTION:A silicon nitride (SiNx) film having a film thickness of about 1,000 A is partially formed on the surface of an Si substrate 1. After forming the film, a silicon oxide (SiO2) film 3 having a film thickness of about 5mum is formed on the substrate including the silicon nitride film 1. After removing part of the SiO2 film 3 by partial etching of the SiNx film is exposed ((c), Fig. 1), only the SiNx film is removed by selective etching. Then a GaAs film 4 is selectively formed by vapor growth on the exposed part of the Si substrate 1. Numeral 5 in the figure denotes hollow (cavity) section. Since a relation alpha3>alpha1>alpha2 exists among the coefficients of thermal expansion of Si, SiO2, and GaAs, such a relation that the length of the upper layer is longer than that of the lower layer can be obtained when the length are appropriately selected. Under such condition, the upper layer receives a compressive stress and, therefore, a GaAs layer suffering a compressive stress can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION E-INDUSTRIAL APPLICATION FIELD The present invention relates to a semiconductor substrate made of QaAs, InP or 81, and a structure of a substrate made of a single substance, a compound, or a mixed crystal formed on the semiconductor substrate.

[Prior Art] The properties of a substance largely depend on the stress applied to the substance. For example, in a GaAs film on a Si substrate, tensile stress is applied to the GaAs film due to the difference in thermal expansion coefficient between Sl and GaAs0, and the band gap is different from that of the stress-free bulk G.
It is known from photoluminescence measurements that it is smaller than aAs or the like.

In recent years, strained superlattices have also been used. For example, InP
In the system strain-induced superlattice, under compressive stress, InGa
By changing the valence band structure of semiconductors such as AsP and reducing the effective mass, we can create highly efficient laser diodes (LDs).
) has been created.

[Problems to be Solved by the Invention] On the other hand, in the above-mentioned example of the GaAs/Si substrate, selective growth is performed to grow only on a part of the substrate in order to alleviate thermal stress.

Although it was possible to reduce thermal stress using this method, it was impossible to completely eliminate thermal stress by simply growing it on a portion of the Si substrate.

The purpose of the present invention is to create a film (substance) having a desired compressive or tensile stress by utilizing the difference in thermal expansion coefficients.
Our goal is to provide the following.

[Means to solve the problem]

In order to solve the above problems, the semiconductor substrate of the present invention includes:
A first substance that serves as a substrate (a substrate includes not only a substrate made of a first substance but also a layer made of a first substance formed on a predetermined substrate), and the first substance A thin film made of a second substance different from the first substance formed on the top, and a third substance selectively grown on the part of the thin film where a part of the thin film is removed to the surface of the first substance. In the semiconductor substrate constructed according to the present invention, the vicinity of the third material between the second material and the first material is hollow or is made of a fourth material.

(Function) In the semiconductor substrate of the present invention, the vicinity of the third material is formed between the second material and the first material, and the first, second, and By controlling the difference in thermal expansion coefficient of the third material and its shape, it is possible to obtain a third material having a desired stress and to reduce the dislocation density.

[Example] Example 1 FIGS. 1(a) to 1(e) are process cross-sectional views showing an example of forming a GaAs film having compressive stress on an 81 substrate as Example 1 according to the present invention.

First, a silicon nitride (S i N) film 2 with a thickness of about 1000 nm is formed on a part of the Si substrate 1 (see FIG. 1(a)).
).

After that, silicon oxide (S i O,) with a film thickness of 5 μm was deposited.
A film 3 is formed (FIG. 1(b)).

Thereafter, a part of SiO and Jlj3 was partially removed by etching to expose SiN and film 2 (see Fig. 1(c)).
), then S IN xl! 2 is selectively removed by etching (FIG. 1(d)).

Thereafter, a GaAs layer 4 is selectively grown on this partially exposed substrate 81 by vapor phase growth (Fig. 1(e)
)). 5 is a hollow (cavity) part.

Compressive stress was acting on the selectively grown GaAs layer 4. Next, the reason why compressive stress acts will be explained using FIG. 1(e). Figure 1(e) shows the horizontal length of each layer (<Q, Ω1, Q,). Here, Q represents the horizontal length of the SiNx film 2 before etching removal, Q5 represents the hollow portion 5, and Q represents the horizontal length of the selectively grown GaAs layer 4. Since these are produced by selective growth, Q, = Q, x2
+Ω. The growth temperature is 630°C. Thereafter, when the layer is taken out to the normal operating room temperature of 30° C., the length of each layer decreases according to the respective thermal expansion coefficients αI, α2, and α3. Here, α1 is Sl, α, is S10, α, is G
Indicates the thermal expansion coefficient of aAs, α, = 2.6X10-”
("C-'), α, =0.6 X 10-"(℃-
), α,=sjxlo−” (“C−”). Suppose that the upper GaAs layer, the Si film, and the lower Si substrate are separated. Also, if ΔT is the temperature difference between the growth temperature and room temperature, the length of the upper layer is Q,
(1-α3×△T) The length of the lower layer is Q, (−α3×
△T) -Q,
) x Δ D = <2Q, Cα1-α, )+Q, (α1-α, )) x Δ
The coefficient of thermal expansion of 3i, SiO, GaAs is α
Since there is a relationship of 3>α1>α2, by appropriately selecting Q and ρ, the relationship of upper layer length>lower layer length can be obtained. Under these conditions, it can be understood that in this example where the upper layer and the lower layer are in close contact with each other, the upper layer receives compressive stress, that is, a GaAs layer having compressive stress is obtained.In this example, Q, = 15 μn, Q. ,=10
It is μm.

In addition, when the dislocation density of the Q a As film 4 was measured, it was found that a high quality film was obtained as 1O'an-''.
In conventional GaAs/Si, 10"CIII"" dislocations were introduced during the cooling process from the growth temperature due to tensile stress, whereas in this example, the dislocations were introduced due to compressive stress during the cooling process. This is due to the elimination of dislocation introduction in the process.

Example 2 Next, as Example 2 according to the present invention, I was deposited on an InP substrate.
An example of forming an nP film will be described. FIG. 2 is a sectional view showing the structure of Example 2.

The structure of this example uses the InP substrate 6 instead of the Si substrate and the InP layer 7 instead of the GaAs layer in Example 1, and the manufacturing process is the same as Example 1. It is.

As in Example 1, the upper InP layer 7 was under compressive stress. In addition, the upper InP layer 7 is the DH of an LD consisting of an InGaAs active layer sandwiched between InP layers.
(double heterostructure), the lifetime of the carriers became longer due to the compressive stress, and the emission intensity increased.

Example 3 FIG. 3 is a sectional view showing the structure of Example 3.

In Example 1.2, a hollow portion 5 was provided between the 31 substrate 1 and the Si◯ film 3. In this example, a low melting point glass 8 having a low softening temperature (400° C.) was used for this hollow portion. The manufacturing process was the same as in Example 1, using low melting point glass 8 instead of the SiNx film, but the step of removing SiNJi in Example 1 was omitted.

In the case of this embodiment as well, the strain caused by the difference in thermal expansion coefficient during the cooling process is absorbed by the low melting point glass 8, and the QaA
Compressive stress acted on the s-layer 4, and the same effect as in Example 1 was obtained. In the case of this embodiment, there is an advantage that the step of selectively etching the low melting point glass can be omitted. Furthermore, there is an advantage that a highly reliable substrate can be produced that has no hollow portion in its final form.

Example 4 FIGS. 4(a) to 4(d) are process cross-sectional views of Example 4.

First, a SiO film 3' is deposited on a part of the InP substrate 6.
It is attached under the condition of no r-spatter (Fig. 4(a)).

On top of that, Ar sputtering is performed to form a 5101 film 3 while surface-treating the InP substrate 6 (see Fig. 4 (b).
)). When formed in this way, the adhesion becomes stronger as will be shown later.

Next, as in the previous embodiment, S10. A part of the film 3 is etched (FIG. 4(C)). The completed 5101M
are all the same film, but when considering the interface with the InP substrate 6, the adhesion force is different between the thin line and the thick line in the figure (the thick line has stronger adhesion). ).

Next, an InP layer 7 is selectively grown on this partially wetted InP substrate 6.

In this way, at the InP growth temperature (650'C), the areas without Ar sputtering (thin lines) are
The bond between the film 3 and the InP substrate 6 is broken. The parts marked with thick lines remain connected.

Results such as stress are the same as in Example 2. Furthermore, the resulting structure is the same as in the case of ordinary selective growth.

Although the present invention has been specifically explained based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various changes can be made without departing from the gist thereof. For example, in addition to the above embodiments, the present invention also provides Z
n S S e / S i, G a P / S
i, r n P/S i, AlGaAs/Si, I
m-v (El-v+) compound semiconductor or f on a single crystal substrate such as nGaAsP/Si, GaAs/Ge, etc.
Similar effects can be obtained with II-V (IT-VI) mixed crystal semiconductors. In addition, heterogeneous substrates of different families such as ZnSSe/GaAs, A I Ga As /
Similar effects can be obtained with homologous heterogeneous substrates such as GaAs and InGaAsP/InP.

GaAs/GaAs, InP layer I n P, etc. homo-nibi, QaAs film with compressive stress, InP
Not only can Jlj be obtained, but it also has the advantage of being applicable to strained InP layer devices, strained GaAs layer devices, and the like.

[Effects of the Invention] As described above, according to the semiconductor substrate of the present invention, a desired film with compressive stress or reduced tensile stress can be obtained on the substrate, and a high-quality film with a low dislocation density can be obtained. .

[Brief explanation of the drawing]

1(a) to (e) are process cross-sectional views showing a semiconductor substrate according to Example 1 of the present invention, FIG. 2 is a cross-sectional view showing a semiconductor substrate according to Example 2, and FIG. 3 is a process cross-sectional view showing a semiconductor substrate according to Example 2. FIGS. 4(a) to 4(d) are process sectional views showing the semiconductor substrate of Example 4. FIGS. l...Si substrate 2...SiNx film 3...Sin, film 4...GaAs film 5...hollow part 6...InP substrate 7...InP film 8...low melting point glass Patent applicant Nippon Telegraph II Inc.

Claims (1)

[Claims] 1. A first material serving as a substrate, a thin film formed on the first material and made of a second material different from the first material, and a part of the thin film made of the first material. In a semiconductor substrate composed of a third material selectively grown in a portion removed to the surface, the vicinity of the third material is hollow or a fourth material is formed between the second material and the first material. A semiconductor substrate characterized by being composed of a substance.