JPH065523A - Method of manufacturing semiconductor thin film - Google Patents

Abstract

PURPOSE:To suppress density of threading dislocation reaching the surface of a film at a specific numerical value/cm<2> or less. CONSTITUTION:After a Si substrate 5 inclined at 2 deg. in the <110> direction on the (001) plane is appropriately chemical-washed and input into a molecular beam crystal growth (MBE) device, it is heated at about 900 deg.C for 15min. to form an oxide film on the substrate surface. Thereafter, a buffer film 8 of AlAs is grown in an atomic layer at 400 deg.C and a GaAs film 6 is grown at 600 deg.C at a growing speed of about 1mum/hour up to a thickness of 1mum. Thereafter, a thin film 7 of Si is grown at a thickness about 1nm at 250 deg.C and the GaAs film 6 is again grown by 1mum. Thereafter, the Si thin layer 7 is continuously grown by 1nm in the same manner as described above and the GaAs film 6 is grown by 1mum. A sample of the thus-grown heteroepitaxial growing film is taken out from a MBE chamber and input into a short-termed heat-treatment processing chamber and heat-treated at 900 deg.C for 10sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor thin film, and more particularly to a method for manufacturing a semiconductor thin film applicable to the growth of all heteroepitaxial growth films. The semiconductor thin film manufactured by this method is applied to manufacture electronic devices, optical devices, and mixed electron-light devices in all fields.

[0002]

2. Description of the Related Art Generally, when a substance different from a substrate is crystal-grown on a substrate, the following occurs. That is, there is a lattice mismatch between the crystal forming the substrate and the crystal forming the substance grown on the crystal. Here, the substrate is also called a base. Such crystal growth is called heteroepitaxial growth. Lattice mismatch is also referred to as misfit in the art. Based on the misfit between the two crystals, defects, that is, dislocations, occur at the interface. This dislocation is called a misfit dislocation because it is caused by a misfit. Various combinations have been studied for a long time with respect to the generation mechanism, properties, interactions, etc. of this misfit dislocation.

On the other hand, it is also known that this misfit dislocation acts as a driving force to propagate new dislocations into the grown film. The dislocations that propagate into this growth film are called threading dislocations.

The process of forming this threading dislocation will be described below with reference to FIG. 3A shows the initial growth, FIG. 3B shows the middle of growth, and FIG. 3C shows the end of growth. As shown in FIGS. 3A, 3 </ b> B, and 3 </ b> C, the growth layer 2 is grown on the substrate 1, and threading dislocations 3 are generated in the growth layer 2. Figure 3 (a),
As is clear from (b) and (c), it can be seen that the threading dislocation 3 propagates in the growth layer 2 as the time elapses, such as at the beginning of growth, during growth, and at the end of growth.

Threading dislocations adversely affect the properties of various types of devices fabricated into grown films. Therefore, various methods have been proposed so far in order to prevent the formation thereof. For example, a recent journal of Applied Physics (Applied Physics, 1992, Vol. 61 No. 2, p. 126-
(Page 133) summarizes methods of reducing threading dislocations generated during heteroepitaxial growth of GaAs films on Si substrates, which have been tried so far.

Among these heteroepitaxial growths, the growth of the GaAs film on the Si substrate is extremely important for application, and the high quality of the growth film is essential for its application. However, as described in the article of the Journal of Applied Physics, the crystal quality of the GaAs film is still insufficient at present, and it is strongly desired to reduce the dislocation density.

The present invention particularly relates to improvement of the crystal quality of the GaAs film, and an object thereof is to suppress the threading dislocation from reaching the substrate surface.

As shown in FIG. 4, as one of attempts to suppress the movement of threading dislocation propagating in the growth film toward the surface of the growth layer, a thin film of a substance different from the growth film is inserted into the growth film. A method of inserting as layer 4 is known.

For example, in the growth of a GaAs film on a Si substrate, In _x G having a lattice constant slightly different from that of the GaAs film.
It is effective to prevent dislocation rise by alternately inserting the a _{1 -x} As film into the growth film. Such insertion of the insertion layer 4 is called so-called insertion of strained superlattice ... Strained layer super lattice (SLS). This method, as shown in FIGS. 4 (a) and 4 (b), has two effects, that is, a sweeping effect and a blocking effect.
The dislocations are prevented from propagating to the surface of the growth film.

[0010]

However, the above S
Even with the insertion of LS, at present, the density of threading dislocations reaching the surface of the GaAs film does not fall below 10 ⁶ / cm ² . It is considered that this is because the two effects of the sweeping effect and the blocking effect shown in FIGS. 4A and 4B do not sufficiently act on the suppression of the movement of threading dislocations.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor thin film, which can sufficiently suppress the movement of threading dislocations.

[0012]

Means for Solving the Problems FIGS. 4 (a) and 4 (b)
Let's consider the sweeping effect and blocking effect shown in a little more detail. The sweeping effect is
This is mainly due to the misfit stress due to the difference in lattice constant between the insertion film and the growth film. That is, assuming that the rigidity and thickness of the insertion film are G and h, the misfit is f, and the Burgers vector of the threading dislocation is b, the misfit stress ε is represented by the following formula 1.

[0013]

[Equation 1]

On the other hand, the blocking effect is mainly related to the rigidity G of the insertion film, and the self-energy Ed of dislocations is almost proportional to the rigidity G as shown in the following mathematical formula 2.

[0015]

[Equation 2]

From this fact, the dislocations caused by the insertion film are shown in FIG.
As shown in (b), it is blocked.

As described above, in order to enhance both the sweeping effect and the blocking effect, it is sufficient to select a substance having a large misfit f and a large rigidity modulus G as the insertion film, as can be seen from the above formulas 1 and 2. .

However, GaAs /
When inserting SLS with a combination of Si, these two parameters are small, and especially the rigidity G of the insertion film is small, so that the above two effects cannot be sufficiently obtained. GaA
The hardness of s is 750 kg / mm ² , but the hardness of InAs is 374 kg / mm ² , so In _x Ga _{1 -x} A
The hardness of s falls between these two values.

Instead of such SLS insertion, recently, a method has been proposed in which a Si thin film having a large rigidity G is inserted into a GaAs film to suppress the propagation of dislocations to the film surface (US Electronics). Chemical Society Magazine "Journal of E"
electrochemical Society "13
9, 865 (1992)). Here, the hardness of Si is 11
It is 00 kg / mm ² . However, even with this method, the density of dislocations reaching the surface of the GaAs film is 10
It has not reached below ⁶ / cm ² . It is considered that this is because the above-mentioned two effects do not sufficiently act to suppress the movement of dislocations.

The present inventors passed through the above-mentioned insertion membrane to pass Gs.
The threading dislocation reaching the surface of the As film was analyzed in detail by an electron microscope. As a result of this analysis, it was found that the majority of those moving on the (111) plane in the <211> direction. Other threading dislocations also move on the (111) plane in the <110> direction. However, it was also found that it was blocked by the insertion membrane and did not propagate upwards.

If the dislocations in the <211> direction that have reached above can be moved again and escaped from the epitaxial growth film to the outside, the dislocation density in the epitaxial growth film should decrease significantly. In order to enable this, after the growth of the film or after the growth of the insertion film, the growth may be interrupted and the sample may be heated at a temperature higher than the growth temperature to promote the movement of dislocations.

FIG. 2 shows this process by way of example in the case of heat treatment after film growth. FIG. 2A is a schematic view of threading dislocations in the <211> direction that have passed through the grown film. 2 (b), (b '), and (b ") are diagrams showing the behavior of dislocations in the <211> direction during the heat treatment. The dislocations move along, and in this case, the dislocation motion form is shown in FIG.
As shown in (b), (b '), and (b "), there are three types.

After the heat treatment, the dislocations 3 escape to the outside from the side surface of the film, and the final form of the dislocations is as shown in FIGS.
2 (c), (c '), according to each style of (b "),
There are three types of (c ").

The moving speed of dislocations in the GaAs film is 800
It is about 0.1 cm / sec at ℃ and about 1 cm / sec at 900 ℃. That is, the dislocations can move from one end to the other end of a wafer having a diameter of about 4 inches (about 10 cm) in a heat treatment time of 1 to 2 minutes at 800 ° C. and about 10 seconds at 900 ° C. . Therefore, as shown in FIG.
It is easy to realize (c ′) and (c ″).

Therefore, in the method for manufacturing a semiconductor thin film according to the present invention, the single crystal thin film having the first lattice constant and the first rigidity is changed to the second lattice constant and the first rigidity different from the first lattice constant. And a step of growing the semiconductor heteroepitaxial growth film at a predetermined growth temperature in a state of being sandwiched between the semiconductor heteroepitaxial growth films having a second rigidity different from the elastic modulus, and growing during and after the growth of the semiconductor heteroepitaxial growth film. And subjecting the semiconductor heteroepitaxial growth film to heat treatment at a temperature higher than the growth temperature to obtain a semiconductor thin film.

In the method of manufacturing a semiconductor thin film, the single crystal thin film is, for example, a Si thin film, and the semiconductor heteroepitaxial growth film is, for example, a GaAs film.

[0027]

As described above, according to the present invention, the effect obtained by inserting a single crystal thin film having a large rigidity and a large misfit into a semiconductor heteroepitaxial growth film and performing a heat treatment at a temperature higher than the crystal growth temperature after the insertion is achieved. It is used to prevent the movement of dislocations in the film and to reduce the dislocation density.

A substance having a large rigidity and a large misfit has an effect of suppressing the movement of dislocations in the film, and the heat treatment has an effect of ejecting dislocations from the film to the outside of the film. These two
Together, these two effects have a great effect on reducing the dislocation density. Needless to say, the effect is reduced only by the independent actions.

[0029]

EXAMPLES Next, examples of the present invention will be described with reference to FIGS.

Example 1 The Si substrate 5 tilted by 2 ° in the <110> direction on the (001) plane was appropriately chemically cleaned and placed in a molecular beam crystal growth (MBE) apparatus. The substrate was heated for a minute to remove the oxide film on the substrate surface. Thereafter, the AlAs buffer film 8 was grown at 10 atomic layers at 400 ° C., and then the GaAs film 6 was grown at 600 ° C. at a growth rate of about 1 μm / hour to a thickness of 1 μm. After that, the Si thin film 7 is formed to a thickness of about 1 nm 250
The GaAs film 6 was grown at 1 ° C. again at a temperature of ℃. Thereafter, the Si thin layer 7 was grown to 1 nm in the same manner as described above, and then the GaAs film 6 was grown to 1 μm. The result produced in this way is shown in FIG.

The heteroepitaxial growth film sample thus grown was taken out of the MBE chamber, placed in a heat treatment apparatus chamber for a short time, and heat-treated at 900 ° C. for 10 seconds to determine the number of dislocations that escaped to the surface of the heteroepitaxial growth film by the etch pit method. It was evaluated by. As a result of the evaluation, it was confirmed that the dislocation density was approximately 10 ⁴ / cm ² or less. Further, when the morphology of threading dislocations was observed with an electron microscope, it was confirmed that it was the same as in FIG. 2 (c ″).

Example 2 A Si substrate 5 having the same plane orientation as in Example 1 was treated in the same manner as in Example 1 above, and immediately after the first growth of the Si thin layer 7 was completed, immediately under As pressure at 800 ° C. for 30 minutes. Was heat treated. Then, after repeating the same growth as in Example 1, the growth film was taken out from the MBE chamber and the dislocation density was evaluated by the etch bit method. As a result of this evaluation, it was found that the dislocation density was about 10 ⁴ / cm ² or less. Moreover, when the morphology of dislocations was examined with an electron microscope,
It was also found that it was similar to (c).

In the growth described in Examples 1 and 2, the maximum thickness of the Si thin layer 7 is 1 nm at maximum, and if the thickness is more than that, dislocations are generated from the Si thin layer, which is desirable. Absent. Further, the growth temperature of the Si thin layer is preferably between room temperature and 500 ° C. when there is no As pressure. Further, regarding the growth temperature of the Si thin layer, it was found that under the As pressure, the upper limit of the temperature is 700 ° C. without any problem.

Further, it is desirable to appropriately change the insertion position of the Si thin layer depending on the thickness of the growth layer. For example, if the total film thickness is d, 0.2d and 0.6 from the substrate surface
It was found that the effect was highest when it was inserted at the position of d. It was also found that the effect can be further enhanced by inserting a plurality of Si thin layers according to the purpose.

Needless to say, in the growth of Examples 1 and 2, if the substance to be inserted is a material having a high rigidity and a misfit other than Si, it is effective in reducing the dislocation density. .

As described in Examples 1 and 2, the application of heat treatment is effective both during and after growth. Further, the heat treatment temperature and the heat treatment time can be selected as desired according to the purpose. In particular, the effect was remarkable in the range of heat treatment time of 10 seconds to 10 minutes at the heat treatment temperature of 800 to 900 ° C. It was also found that when applying heat treatment for a short time, repeating it a plurality of times has a further effect.

Examples 1 and 2 above show examples of growth of the most general semiconductor heteroepitaxial growth film. In other systems such as the growth of Ge on a Si substrate or the growth of InP on a Si substrate,
It goes without saying that the Si insertion film and the heat treatment are effective. In general, it has been found that it has a great effect on suppressing the propagation of dislocations in the heteroepitaxial growth film on the Si substrate to the film surface.

In the heteroepitaxial growth on all semiconductor substrates other than the Si substrate, the effect of suppressing the dislocations by the insertion film in the heteroepitaxial growth film and the heat treatment is, for example, InP / GaAs, GaAs / InP, I.
It goes without saying that it is also effective in systems such as nAs / GaAs and GaAs / InAs.

[0039]

As described above, according to the present invention, a semiconductor heteroepitaxial growth film is formed by inserting a single crystal thin film having greatly different lattice constant and rigidity into the film.
By performing heat treatment at a temperature higher than the growth temperature of the semiconductor heteroepitaxial growth film during and after the growth, the dislocation density on the surface of the semiconductor heteroepitaxial growth film can be suppressed to 10 ⁴ / cm ² or less.

[Brief description of drawings]

FIG. 1 is a schematic view showing a semiconductor thin film manufactured by a method for manufacturing a semiconductor thin film according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an effect of an insertion film of threading dislocation.

FIG. 3 is a schematic diagram showing the occurrence of threading dislocations that occur during the growth of a heteroepitaxial growth film.

FIG. 4 is a schematic diagram showing two effects of preventing an increase in threading dislocation.

[Explanation of symbols]

 1 Substrate 2 Growth Film 3 Threading Dislocation 4 Insertion Layer 5 Si 6 GaAs 7 Si Thin Layer 8 AlAs

Claims (5)

[Claims] 1. A single crystal thin film having a first lattice constant and a first rigidity is provided with a second lattice constant different from the first lattice constant and a second rigidity different from the first rigidity. A step of growing the semiconductor heteroepitaxial growth film at a predetermined growth temperature in a state of being sandwiched between the semiconductor heteroepitaxial growth film having And a step of performing heat treatment at a temperature higher than the growth temperature. 2. A step of growing the GaAs film on a Si substrate at a predetermined growth temperature with a Si thin film sandwiched between the GaAs films, and the growth of the GaAs film during and after the growth of the GaAs film. G
A method of manufacturing a semiconductor thin film, comprising the step of performing a heat treatment on the aAs film at a temperature higher than the growth temperature. 3. The method of manufacturing a semiconductor thin film according to claim 2, wherein the thickness of the Si thin film is 1 nm or less. 4. The grown Si thin film is formed on the grown GaAs.
The method for producing a semiconductor thin film according to claim 2, wherein the film is inserted at positions of 0.2 and 0.6 from the substrate surface with respect to the film thickness of the entire film. 5. The step of applying the heat treatment is 800 to 90.
The method for producing a semiconductor thin film according to claim 2, wherein the heat treatment temperature is 0 ° C., and the heat treatment time is 10 seconds to 10 minutes.