JP2862018B2 - Semiconductor substrate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a semiconductor substrate such as GaAs, InP, or Si, and a substrate made of a simple substance, a compound, or a mixed crystal formed on the semiconductor substrate.

[Conventional technology]

The properties of a material are highly dependent on the stress on the material. For example, in a GaAs film or the like on a Si substrate, a tensile stress is included in the GaAs film due to a difference in thermal expansion coefficient between Si and GaAs. It is known from measurements and the like.

In recent years, strained superlattices and the like have been used. For example, InP
In a strained superlattice, InGaAsP
High-efficiency laser diodes (LDs) have been manufactured by changing the valence band structure of semiconductors and reducing the effective mass.

[Problems to be solved by the invention]

On the other hand, in the above-described example of the GaAs / Si substrate, selective growth in which the substrate is grown only on a part of the substrate is performed to reduce thermal stress.

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

An object of the present invention is to provide a film (substance) having a desired arbitrary compressive or tensile stress by utilizing a difference in thermal expansion coefficient.

[Means for solving the problem]

In order to solve the above problems, a semiconductor substrate according to the present invention includes a first material to be a substrate and a thin film formed on the first material and composed of a second material different from the first material. A semiconductor substrate formed of a third material different from the second material selectively grown on a portion where the part of the thin film has been removed to the surface of the first material;
Between the substance and the first substance, the vicinity of the third substance is hollow or a fourth substance different from the first, second, and third substances.
Wherein the length of the hollow or fourth material and the length of the removed portion are controlled, and the stress applied to the third material is controlled.

Further, the semiconductor substrate of the present invention includes a first substance to be a substrate, a thin film formed on the first substance, the second substance being different from the first substance, and a part of the thin film. Is a semiconductor substrate composed of a third material different from the second material selectively grown on a portion removed to the surface of the first material, wherein the second material and the first material are The adhesive has a weak portion in the vicinity of the third material, the length of the weak portion and the length of the removed portion are controlled, and the stress applied to the third material is controlled. Features.

[Action]

In the semiconductor substrate of the present invention, the second substance and the first
A hollow or a fourth substance different from the first, second, and third substances in the vicinity of the third substance among the substances;
Controlling the length of the hollow or fourth material and the length of the removed portion, or the portion where the adhesion between the second material and the first material is weak in the vicinity of the third material. By controlling the length of the weak portion and the length of the removed portion to control the stress applied to the third material, a third material having a desired stress can be obtained. In addition, dislocation density can be reduced.

〔Example〕

Embodiment 1 FIGS. 1A to 1E are process cross-sectional views showing an example of forming a GaAs film having a compressive stress on a Si substrate as Embodiment 1 according to the present invention.

First, a silicon nitride (SiN _x ) film 2 having a thickness of about 1000 ° is formed on a part of an Si substrate 1 (FIG. 1A).

Thereafter, a silicon oxide (SiO ₂ ) film 3 having a thickness of about 5 μm is formed (FIG. 1B).

Thereafter, a part of the SiO ₂ film 3 is partially removed by etching to expose the SiN _X film 2 (FIG. 1C), and then only the SiN _X film 2 is selectively removed by etching (FIG. 1C). FIG. 1 (d).

Thereafter, a GaAs film 4 is selectively grown on the partially exposed Si substrate 1 by a vapor deposition method (FIG. 1 (e)). 5 is a hollow (hollow) part. Selectively grown Ga
A compressive stress was acting on the As film 4. Next, the reason why a compressive stress acts will be described with reference to FIG. FIG. 1 (e) shows the horizontal length of each layer (l ₁ , l ₂ ,
l ₃ ). Here, l ₁ indicates the lateral length of the SiN _X film 2 before etching removal, l ₂ indicates the hollow portion 5, and l ₃ indicates the lateral length of the selectively grown GaAs film 4. Because of their close contact due to the selective growth, l ₁ = l ₂ × 2 + l ₃ . The growth temperature is 630 ° C. After that, take it out at room temperature 30 ° C for normal operation,
The length of each layer decreases according to its respective coefficient of thermal expansion α1, α2, α3. Here, α ₁ is Si, α ₂ is SiO ₂ , α ₃
Indicates the thermal expansion coefficient of GaAs, and α ₁ = 2.6 × 10
⁻⁶ (° C. ⁻¹ ), α ₂ = 0.6 × 10 ⁻⁶ (° C. ⁻¹ ), α ₃ = 5.7 × 10
⁻⁶ (° C. ⁻¹ ). It is assumed that the upper GaAs layer and the SiO ₂ film are separated from the lower Si substrate. When ΔT is the temperature difference between the growth temperature and room temperature, the length of the upper layer is l ₂ × (1−α2 × ΔT) × 2 + l ₃ ×
(1−α3 × ΔT) The length of the lower layer is l ₁ × (1−α1 × ΔT), and the length of the upper layer−the length of the lower layer is l ₂ × (−α2 × ΔT) × 2 + l ₃ × ( _{-α3 × ΔT) -l 1 × (} -α1 × ΔT) = {α1 × l 1 - (α2 × l 2 × 2 + α3 × l 3)} × ΔT = {2l 2 (α 1 -α 2) + l 3 ( α ₁ −α ₃ )｝ ΔT. The thermal expansion coefficients of Si, SiO ₂ and GaAs are α3>α1>
Since there are relationship between [alpha] 2, by choosing l ₂ and l ₃ appropriately, it is possible to obtain a top layer of length> lower length relationship. Under these conditions, it can be understood that in this embodiment in which the upper layer and the lower layer are in close contact with each other, the upper layer receives a compressive stress, that is, a GaAs layer having a compressive stress can be obtained. In this embodiment, l ₂ = 15 μm and l ₃ = 10 μm.

When the dislocation density of the GaAs film 4 was measured, the dislocation density was 10 ⁵ cm.
^-2 and a high quality film were obtained. This is the traditional GaAs / Si
In the example, in the cooling process from the growth temperature, the dislocation of 10 ⁶ cm ⁻² was introduced due to the tensile stress, whereas in the present embodiment, the dislocation was introduced in the cooling process due to the compressive stress. It is due to disappearance.

Embodiment 2 Next, as Embodiment 2 according to the present invention, InP was formed on an InP substrate.
An example of forming a film will be described. FIG. 2 is a sectional view showing the structure of the second embodiment.

The structure of this embodiment is the same as that of the first embodiment except that the InP substrate 6 is used instead of the Si substrate and the InP film 7 is used instead of the GaAs layer.

As in Example 1, the upper InP layer 7 was subjected to compressive stress. The upper InP layer 7 is sandwiched between the InP layers.
When the DH (double heterostructure) of the LD composed of the GaAs active layer was used, the carrier life was extended due to compressive stress, and the emission intensity was increased.

Third Embodiment FIG. 3 is a sectional view showing a structure of a third embodiment. In the first and _second embodiments, the hollow portion 5 is provided between the Si substrate 1 and the SiO ₂ film 3. In the present embodiment, a low melting point glass (400 ° C.) having a low softening temperature (400 ° C.) is used for the hollow portion. The manufacturing process is almost the same as that of the first embodiment using the low melting point glass 8 instead of the SiN _X film, but the step of removing the SiN _X film in the first embodiment is omitted.

Also in the case of the present embodiment, the strain caused by the difference in thermal expansion coefficient during the cooling process is absorbed by the low melting point glass 8 and
A compressive stress acts on the layer 4, and the same effect as in the first embodiment is obtained. In the case of this embodiment, there is an advantage that the step of selective etching of the low melting point glass can be omitted. Further, there is an advantage that a hollow substrate is not formed in the final form, and thus a highly reliable substrate can be manufactured.

Fourth Embodiment FIGS. 4A to 4D are process cross-sectional views of a fourth embodiment.

First, a SiO ₂ film 3 ′ is formed on a part of the InP substrate 6 under the condition without Ar sputtering (FIG. 4A).

Then, an SiO ₂ film 3 is formed on the InP substrate 6 while Ar sputtering is performed this time (FIG. 4B).
When formed in this manner, the adhesion becomes stronger as will be described later.

Next, similarly to the previous embodiment, a part of the SiO ₂ film 3 is etched (FIG. 4C). Although the completed SiO ₂ films are all the same, considering the interface with the InP substrate 6,
In the drawing, the adhesive force is different between the portion shown by the thin line and the portion shown by the thick line (the thicker line has stronger adhesive force).

Next, an InP film 7 is selectively grown on the partially exposed InP substrate 6.

In this manner, at the growth temperature of InP (650 ° C.), the portion between the SiO ₂ film 3 and the InP substrate 6 is broken at a portion (thin wire) where no Ar sputtering is performed. Bold lines remain connected.

The results such as stress are the same as those in the second embodiment. The resulting structure is the same as in the case of normal selective growth.

As described above, the present invention has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment.
Of course, various changes can be made without departing from the scope of the invention. For example, the present invention provides, in addition to the above embodiments,
ZnSSe / Si, GaP / Si, InP / Si, AlGaAs / Si, InGaAsP / Si, G
A similar effect can be obtained in a III-V (II-VI) compound semiconductor or a III-V (II-VI) mixed crystal semiconductor such as aAs / Ge on a single crystal substrate. A similar effect can be obtained in a hetero-epitaxial substrate of a different group such as ZnSSe / GaAs or a hetero-epitaxial substrate of a similar group such as AlGaAs / GaAs or InGaAsP / InP. Even in the case of homoepitaxy such as GaAs / GaAs and InP / InP, it is possible to obtain a GaAs film and an InP film having a compressive stress, as well as to apply the invention to a strained InP layer device, a strained GaAs layer device, and the like.

〔The invention's effect〕

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

[Brief description of the drawings]

1 (a) to 1 (e) are process sectional views showing a semiconductor substrate of Example 1 of the present invention, FIG. 2 is a sectional view showing a semiconductor substrate of Example 2, and FIG. 4 (a) to 4 (d) are process cross-sectional views showing a semiconductor substrate of Example 4. FIG. 1 ...... Si substrate 2 ...... SiN _X film 3 ...... SiO ₂ film 4 ...... GaAs layer 5 ...... hollow section 6 ...... InP substrate 7 ...... InP layer 8 ...... low melting glass

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/20 H01L 21/205

Claims (2)

(57) [Claims] A first material to be 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 formed by the first material. A semiconductor substrate composed of a third substance different from the second substance selectively grown on the portion removed to the surface of the substance,
In the vicinity of the third substance between the second substance and the first substance, the vicinity of the third substance is hollow or a fourth substance different from the first, second, and third substances, and the hollow or fourth substance is used. 4. The semiconductor substrate according to claim 4, wherein the length of the substance and the length of the removed portion are controlled, and the stress applied to the third substance is controlled. 2. A first substance to be a substrate, a thin film formed on the first substance and made of a second substance different from the first substance, and a part of the thin film is formed on the first substance. A semiconductor substrate composed of a third substance different from the second substance selectively grown on the portion removed to the surface of the substance,
The adhesive force between the second substance and the first substance has a weak part near the third substance, and the length of the weak part and the length of the removed part are controlled. 3. A semiconductor substrate, wherein the stress applied to the substance is controlled.