JPH0474792A - Method for forming thin film of semiconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor thin film forming method for forming a compound semiconductor thin film at any location on a substrate with controlled growth rate and composition.

(Prior Art) As semiconductor devices become more sophisticated and functional, their manufacturing processes are becoming more and more complex. Therefore, it is desired to simplify these manufacturing processes. With conventional technology: for example, the Journal of Applied Physics
), Volume 58 (1985), page 1415, only films with varying thicknesses and compositions could be fabricated within the plane.

Therefore, after the film is grown, it is necessary to use sophisticated lithography techniques to fabricate an element structure having five complex in-plane irregularities. Therefore, in order to omit these complicated process steps after film growth, there is a need for a method that allows pattern formation during film growth.

Recently, attempts have been made to control the thickness at some in-plane locations during thin film formation in order to simplify complex process steps. For example, Applied Physics Letters
) Vol. 47, 1985, p. 95, when forming a GaAs film using the metal organic thermal decomposition method (hereinafter abbreviated as MOCVD), the substrate is irradiated with an argon laser, so that the film is formed only on the irradiated area. Techniques have been developed to perform the formation. The reason for the selective growth is that the raw organic metal is decomposed by light irradiation. As for light sources, it has been reported that not only argon lasers but also low-pressure mercury lamps, excimer lasers, etc. are effective.

(Problems to be Solved by the Invention) In conventional selective growth by light irradiation, light is irradiated under conditions where film growth increases as the substrate rises, that is, at a low substrate temperature. The reason for this is that although part of the organic metal supplied onto the low-temperature substrate cannot be decomposed, the undecomposed organic metal is decomposed by light to increase the growth rate. As is well known, as the growth temperature decreases, the quality of the film deteriorates. Therefore, films grown by selective IR using the conventional method are of poor quality and are rarely applied to devices.

In order to solve the above-mentioned problems, the present invention takes into consideration that the film growth rate and composition change greatly depending on the substrate temperature. It is possible to control the growth rate and composition at any location within the thin film surface by irradiating the thin film with a temperature distribution sufficient to locally change the growth rate.

An object of the present invention is to provide a method for forming a semiconductor thin film that can form a high-quality semiconductor thin film that forms a fine pattern without using lithography technology after growing the thin film, and that can simplify complicated process steps for semiconductor devices. do.

(Means and Effects for Solving the Problems) In order to achieve the above object, the first invention of the present invention is to produce a single crystal using organic metal molecular beams and thermally decomposed hydride molecular beams in a vacuum container. When growing compound semiconductor thin films using organometallic molecular beam epitaxy, which forms semiconductor thin films on substrates, light is applied from outside the vacuum chamber under conditions where the film growth rate remains constant or decreases as the substrate temperature rises. A method for forming a semiconductor thin film is characterized in that the film is grown while irradiating the substrate.

In the present invention, when growing a compound semiconductor thin film by organometallic molecular beam epitaxy, light is emitted from outside the vacuum container onto the substrate under conditions where the growth rate of the film is constant or decreases as the substrate temperature rises. By growing the film while irradiating the film, the number of steps can be significantly reduced and the occurrence of interfacial defects can be prevented.

Next, the second invention uses organometallic molecular beam epitaxy to grow a semiconductor thin film on a single crystal substrate, and as the substrate temperature rises, the growth rate of the semiconductor thin film decreases from a certain high constant range. Under the growth conditions that change continuously until the growth rate reaches a constant low region, the substrate temperature is controlled so that the growth rate of the semiconductor thin film falls within the constant high region in the non-irradiated region, and A semiconductor thin film forming method characterized in that a part of the substrate is irradiated with intensely variable light sufficient to heat the semiconductor thin film to a substrate temperature at which the growth rate of the semiconductor thin film becomes the low constant region as the substrate temperature rises. It is characterized by

The second invention is a growth condition in which the growth rate of the semiconductor thin film is constant or decreases as the substrate temperature increases when growing a semiconductor thin film on a single crystal substrate using the organometallic molecular beam Evitaki 7 method. At the desired location on the substrate, the growth rate of the thin film decreases as the substrate temperature rises and then reaches a constant temperature by irradiating a portion of the substrate with light of sufficient light intensity to reach a constant substrate temperature. A thin film having unevenness can be formed.

Now, when a substrate is irradiated with light and absorbed as heat, the range in which the substrate temperature increases varies depending on the pulse width of the irradiated light. The range in which the substrate temperature increases is determined by the heat diffusion distance, and the -dimensional heat diffusion distance is expressed by the following equation.

1=kt/pCp where 1 is the thermal diffusion distance, k: thermal conductivity, L: light irradiation time (pulse width Lp is density, and Cp is specific heat. As is clear from the above equation, light irradiation Compared to irradiating the substrate with a continuous source such as argon laser light, irradiating the substrate with pulsed laser light suppresses the diffusion of the heat absorbed by the substrate and spreads the heat around the irradiated area. temperature rise can also be suppressed.

Therefore, it is possible to form a semiconductor thin film having a finer pattern than when the above method is applied.

On the other hand, as is clear from the equation expressing the -dimensional heat diffusion distance, when irradiating a pulsed laser with L of 100 nanoseconds or less under the above conditions, the heat diffusion distance is at most 1 μm in the case of InP, for example. Because of this, almost no heat is diffused from the area where the light is irradiated. That is, pulsed laser
The substrate temperature rises only in the area irradiated with light, and crystal growth is suppressed only in that area, making patterning possible. For example, when an InP substrate is irradiated with excimer laser light with a pulse width of 12 nanoseconds, the thermal diffusion distance is approximately 0.3 nanoseconds.
μm, and it is possible to partially grow fine patterns.

The third invention is organometallic molecular beam epitaxy, 2.
When growing a semiconductor thin film on a single crystal substrate using the method, the semiconductor Fi! Under growth conditions in which the film growth rate changes continuously as the substrate temperature increases, it passes through a region where the force is applied and decreases in a certain high constant region, and then settles in a constant low region. The substrate temperature is controlled so that the growth rate of the semiconductor thin film falls within the constant high range, and the growth rate of the semiconductor thin film falls within the constant low range as the substrate temperature rises. A method for forming a semiconductor thin film is characterized by irradiating a pulsed laser beam with sufficient light intensity to cause heating.

Next, the fourth invention is that when a semiconductor thin film is grown on a single crystal substrate using the metal molecular beam Evitakin method, the growth rate of the semiconductor thin film remains constant at a certain high level as the substrate temperature rises. Under growth conditions that change continuously from a decreasing region to a constant low region, for the non-irradiated area, the substrate temperature is adjusted so that the growth rate of the semiconductor thin film is affected by the above-mentioned high constant region force. Regulation? 31
L, and '+ has sufficient light intensity to heat a portion of the substrate to a substrate temperature where the growth rate of the conductive thin film falls into the low constant range as the substrate temperature rises, and has a pulse width of 100 nanoseconds or less. A semiconductor that irradiates light with a pulsed laser m! ! #
Formation method: Synthesis method.

In the third and fourth inventions, 1. Since pulsed laser light is used as the laser light for heating the substrate, it is possible to form fine turns on the micron order and control the composition. .

(Example) Next, an example of the present invention will be described. It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

FIG. 1 is a block diagram for explaining the present invention in detail.
and 6, 8, and 15 are mass flow controllers (MFC),
4 is a pyrolysis cell, 5 and 7 are organic metal bombs, 9 is a molecular beam cell for organic metals, 10 is an InP substrate, 111 is an argon laser, 12 is a lens, 13 is a window, and 14 is a phosphine.

An example will be described in which argon laser is not irradiated while growing an InGaAs film on an InP substrate. First, vacuum container 1
0-'' TorrO high vacuum; was drawn. Arsine with a concentration of 100% was used as the hydride gas for the arsenic raw material. The flow rate of arsine was increased to 1 using MFC3 for 2 hours.
An arsenic molecular beam was formed in a pyrolysis cell 4 heated to 950° C. and set at 7' occ. Since hydrogen is generated during thermal decomposition, the degree of vacuum in the vacuum container is approximately 2 x 10-'Tor.
increased to r. Triethyl gallium (abbreviated as TEG) was used as the organometallic gallium raw material. TEG Ponbe 5
was opened and the flow rate was adjusted to 0.47 cc/min using MFC6. Trimethylindium (TMI) was used as the organic metal of the indium raw material. 7 was opened to the bottle and the flow rate was adjusted to 0.53 cc/min using MFC8. These organometallic gases are mixed and guided to an organometallic molecular beam cell 9, from which a mixed molecular beam of TEG and TMI is transferred to an InP substrate 1.
I irradiated towards 0. In this way, growth of the InGaAs film was started. After several minutes, a laser beam with an intensity of 500+W was emitted from the argon laser 11. The laser beam was focused using a lens 12 and irradiated perpendicularly to the InP substrate 10 through a window 13 . At that time, the diameter of the laser beam was adjusted to 400 μm. - TEG after hours
Then, the supply of TMI was stopped, and the growth of the InGaAs film was completed. At the same time, the laser beam irradiation also stopped. In the laser irradiated area of the film thus produced, irregularities in the form of grooves and grooves were observed depending on the substrate temperature.

That is, in the range below about 500° C., convex spots 7) were formed in the irradiated area, and the height of the convex portions increased as the temperature decreased. However, as a result of examining the optical characteristics of the convex portion using cathode luminescence, the luminescence intensity decreases as the substrate temperature decreases. In other words, it was found that the film quality had deteriorated.

On the other hand, when the substrate temperature is 500°C or higher, the laser irradiation part
The growth was suppressed, resulting in a concave shape. The depth of this recess increased as the temperature of the base VI layer increased. Its surface was mirror-like to the same extent as the non-irradiated area. Also, increase the substrate temperature to 530
When the laser intensity was increased while maintaining the temperature at °C, the depth of the recess also increased.

lnP using an organometallic molecular beam Evita Kinyal device.
On the S plate - 2 1nGaAsF! The growth rate when growing the film and the substrate temperature dependence of the Ga composition in InGaAs are
Figures 22 and 3 are shown.

Figure 2: The horizontal axis represents the substrate temperature, and the vertical axis represents the growth rate of InGaAs. In Figure 3, the horizontal axis represents the substrate temperature, and the vertical axis represents 1n1.
- The composition X of Ga in aJs is shown in x. The raw materials used were trimethylindium 5, triethylgallium and arun. Growth conditions other than substrate temperature were kept constant. From Figures 2 and 3, the substrate temperature ranges from 500°C to 55°C.
At 0'C, the growth rate and Ga&[l growth rate are almost constant.

Above 550°C, both the growth rate and the Ga composition begin to decrease, and above 600°C, both the growth rate and the Ga content become constant. This result shows that the growth rate and composition can be controlled by keeping other growth conditions constant and changing only the substrate temperature to an appropriate value.

Therefore, when the substrate temperature is in the range of 500'C or more and less than 600°C, if a part of the substrate surface is irradiated with light and the substrate temperature is partially increased to 600°C or more, the light irradiated area will grow. Since both the velocity and the GaMi formation are reduced compared to the non-irradiated area, pattern formation and changes in the Gal[l formation are possible.

The light intensity required to change the growth rate and composition changes depending on the temperature of the substrate in the non-irradiated area or the ratio of the supply amount of the group V raw material to the group II raw material (~'/'III ratio). If the substrate temperature of the non-irradiated part is higher, or V1m
The smaller the ratio, the less light intensity is required to change the growth rate and composition.

FIG. 4 shows a situation in which when the ~'/■ ratio is made small, the portion of the downward curve to the right becomes 1-1 on the low temperature side, as shown by the broken line. In other words, substrate temperature, laser intensity and V/I [
The l ratio is an equivalent parameter, which means that by fixing two of these parameters and changing the remaining one, it is possible to change the growth rate and composition of the light irradiated area.

The above results are for InGaAs film, but InG
Almost the same tendency was obtained in the growth of the aAsP film. Regarding the composition of the In[;aAsP film: Well, the composition of P in addition to Ga can be controlled by increasing the substrate temperature.

(Example 1) Using the above-mentioned apparatus, the substrate temperature was set to 540°C, and 1
Argon laser (514,5 nm) with light intensity of w
1nGaAs was grown without partial irradiation.

As a result, the growth rate in the irradiated area decreased to about 50% of that in the non-irradiated area, and the Ga&ll composition decreased from 0.5 to 0.1. In other words, pattern formation and Gai[l formation were achieved.

FIG. 5 shows the cross-sectional shape of the irradiation part. In FIG. 5, the horizontal axis represents the width, and the joint axis represents the height. As shown in the figure, the cross-sectional shape of the irradiation part is rectangular. In case 2, the substrate temperature at the laser irradiation part has increased to 600°C or more.

(Comparative Example 1) Next, using the same equipment as in Example 1, the substrate temperature was 540°C1.
The InGaAs film was grown by keeping the ~'/■ ratio the same and changing only the laser intensity of the argon laser to 200 mW. As a result, the growth rate of the irradiated area was no different from that of the non-irradiated area. In other words, a pattern could not be formed. In this case, the substrate temperature increase due to laser irradiation is 10°C or less, and the substrate temperature at the irradiation part has not reached 550°C.

(Example 2) Next, using the same equipment as in Comparative Example 1, the laser intensity (200
11W), V/I [[ratio is equal, substrate temperature)
InGaAs growth was performed by raising the temperature to 580"C. As a result, the growth rate in the irradiated area was reduced to about 60% of that in the non-irradiated area, and the Ga1l composition was also reduced from 0.4 to 0.1. In other words, Pattern formation and Ga composition change were achieved.

The cross-sectional shape of the irradiation part was the same as that in FIG. 5, and was rectangular.

(Example 3) Next, using the same equipment as in Comparative Example 1, the laser intensity (200
mW), the substrate temperature (540°C) is the same, and V1m
InGaAs was grown with only the ratio reduced to 1/3. As a result, the growth rate in the irradiated area was reduced to about 50% of that in the non-irradiated area, and the Ga composition was also reduced from 0.5 to 0.1.

In other words, pattern formation and Gai[l formation were achieved.

The cross-sectional shape of the irradiation part is almost the same as that shown in FIG.
Argon laser (514,5 nm) with light intensity of W
Partially 1-nGaAsP growth was performed.

As a result, the growth rate in the irradiated area decreased by about 30% compared to the non-irradiated area5, and the Ga composition increased from 0.4 to O,l! The P composition decreased from 0.3 to 0.2. In other words, pattern formation and changes in Ga&P composition were achieved.

The cross-sectional shape of the irradiation part is substantially the same as the fifth section, and is rectangular.

(Comparative Example 2) Next, Example 4, equipment, substrate temperature (520°C), ~・'
1nGaAsP Wit was grown by keeping the /■ ratio the same and changing only the laser intensity of the argon laser to 501. As a result, the growth rate of the irradiated area was no different from that of the non-irradiated area. In other words, a pattern could not be formed.

(Example 5) Next, the apparatus, laser intensity, v, 'nl ratio were the same as in Comparative Example 2, and only the substrate temperature was increased to 560'C.
AsP growth was performed. As a result, the growth rate in the irradiated area decreased by about 30% compared to the non-irradiated area, and the Ga composition decreased from 0.4 to 0.
．． ■The PI ratio decreased from 0.3 to 9.2.

In other words, pattern formation and changes in Ga1l and Pm formations were achieved.

The cross-sectional shape of the irradiation part was almost the same as that in FIG. 5, which was a rectangle.

(Example 6) Next, Comparative Example 2 and a bag! InGa
AsP growth was performed. As a result, the growth rate in the irradiated area was reduced to about 30% of that in the non-irradiated area, the Ga&[l content also decreased from 0.4 to 0.1, and the Pmu content decreased from 0.3 to 0.2.

In other words, pattern formation and change in Ga&[l and P&[l formations were achieved.

The cross-sectional shape of the irradiation part was almost the same as that in FIG. 5, and was rectangular.

In addition, although an argon laser was used here, any light source that increases the substrate temperature may be used, such as a mercury lamp or an infrared lamp.
It goes without saying that the same effect can be obtained with YAC laser, CO2 laser, helium neon laser, etc.

(Example 7) An excimer laser (308 nm) with a substrate temperature of 540°C, a pulse width of 20 nanoseconds, a repetition frequency of 20 Hz, and a pulse energy of 100 J was heated using a mask.
InGaAs growth was performed while irradiating with a pair of projections. As a result, the growth rate of the irradiated area was reduced to about 50% of that of the non-irradiated area, and the smallest area was 3 μm.

(Example 8) The substrate temperature was set to 520"C, and a Q-switched YAC laser (1064n stiffness) with a pulse width of 12 nanoseconds, a repetition frequency of 10Hz, and a pulse energy of 150mJ was irradiated with one-to-one projection using a mask. As a result, the growth rate of the irradiated part was reduced to about 50% of that of the non-irradiated part, and the smallest region was 5 μm.

(Comparative Example 3) Under the same conditions as in Example 7, a 1nGaAs film was grown using an argon laser having a light intensity of IW. As a result, the smallest region in which the growth rate of the irradiated area decreased was about 100 μm.

In the above example, the excimer laser (308rv) and Y
Although the case where an AG laser is used is shown, a sufficiently short pulse necessary for forming a fine pattern can be obtained by using an excimer laser or a dye laser of other wavelengths.

(Effects of the Invention) As described above, according to the present invention, a micron-order fine pattern having unevenness at a desired location on a substrate can be formed without using lithography technology after film growth. Furthermore, the composition of the pattern area can also be controlled. Therefore, it has become a useful method for forming semiconductor thin films in the production of semiconductor devices that require complicated process steps, such as optoelectronic integrated circuits (OETC).

In the above examples, examples of fabrication of InGaAs and InGaAsP were shown, but similar effects were confirmed for InGaP and InAsP.

[Brief explanation of drawings]

Figure 1 is a block diagram of the device used in the present invention, Figure 2 is an
The dependence of the growth rate of the GaAs film on the substrate temperature, Figure 3 shows the dependence of the growth rate on the substrate temperature.
The results of investigating the GaMi formation in the InGaAs film shown in the figure are shown. Figure 4 shows the situation when the V/III ratio is reduced, and Figure 5 shows the situation when the substrate temperature is 540°C and the argon laser (514, 5n,) with the light intensity of IW is partially irradiated. The cross-sectional shape of the irradiated part of InGaAs1llj grown during the process is shown. 1... Vacuum vessel 2... To Arunbong 3.6.8.15... Mass flow controller 4...
...Thermal decomposition cell 57...The organometallic cylinder 9...The molecular beam cell for machine metal 10...[nP substrate 11...Argon laser 12...Lens 13] ...Sky 14...Phosphine 1st figure mass 0 collector 4th degree (0C) Chest board - 4th house (1C)

Claims (4)

[Claims] (1) When growing a compound semiconductor thin film using the organometallic molecular beam epitaxy method, which forms a semiconductor thin film on a single crystal substrate using organometallic molecular beams and thermally decomposed hydride molecular beams in a vacuum container, A method for forming a semiconductor thin film, which comprises growing the film while irradiating the substrate with light from outside the vacuum chamber under conditions in which the growth rate of the film is constant or decreases as the substrate temperature increases. (2) When growing a semiconductor thin film on a single crystal substrate using organometallic molecular beam epitaxy, the growth rate of the semiconductor thin film goes through a region where it decreases from a certain high constant region as the substrate temperature increases. , under the growth conditions that change continuously until it settles in a constant low region, the substrate temperature is controlled so that the growth rate of the semiconductor thin film is included in the constant high region in the non-irradiated area, and the growth rate of the semiconductor thin film is controlled to be within the constant high region. A method for forming a semiconductor thin film, characterized in that a part of the substrate is irradiated with light having an intensity sufficient to heat the substrate to a temperature in which the rate becomes the constant low region as the substrate temperature increases. (3) When growing a semiconductor thin film on a single crystal substrate using organometallic molecular beam epitaxy, the growth rate of the semiconductor thin film goes through a region where it decreases from a certain high constant region as the substrate temperature increases. , under the growth conditions that change continuously until it settles in a constant low region, the substrate temperature is controlled so that the growth rate of the semiconductor thin film is included in the constant high region in the non-irradiated area, and the growth rate of the semiconductor thin film is controlled to be within the constant high region. A method for forming a semiconductor thin film, comprising irradiating a pulsed laser beam having a light intensity sufficient to heat a portion of the substrate to a substrate temperature whose speed falls within the constant low range as the substrate temperature rises. (4) The semiconductor thin film forming method according to claim 3, wherein the pulse width is 100 nanoseconds or less.