JPH05335238A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor crystalline thin film having excellent light emission characteristics and high quality by setting a temperature of a substrate to a range of a special value when the film having an Si-SiGe heterojunction structure is grown on the substrate and introducing hydrogen into a growing atmosphere. CONSTITUTION:In order to grow a semiconductor crystalline thin film having an Si-SiGe heterojunction structure on an Si substrate A, a pressure of a vacuum chamber X is set to an extra-high vacuum of 10<-11>Torr. Then, the substrate A is heated to 600-900 deg.C by a heater contained in a substrate holder 2. In this state, an Si molecular beam is projected from molecular beam cells 4, 6 toward the substrate A for 60 sec while hydrogen decomposed in atomic state is being projected from an end 7a of a cell 7 toward the substrate A. Then, after it is stopped for 5 sec, it is further projected for 10 sec. In this case, a molecular beam of Ge is projected from molecular beam cells 5-7 for 10sec simultaneously upon projection of the Si molecular beam for 10sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to improve the solid-source molecular beam epitaxial growth method (hereinafter referred to as "solid-source MBE method"), and has a crystalline thin film of Si-SiGe heterojunction structure having a strong light emitting ability on the substrate surface. The present invention relates to a method for manufacturing a semiconductor device (semiconductor device) that can be used as an optoelectronic device or the like by growing (a structure in which a silicon single crystal thin film and a silicon germanium mixed crystal thin film are laminated, the same applies hereinafter).

[0002]

2. Description of the Related Art In recent years, due to the demand for higher performance of elements, it has excellent characteristics as a semiconductor material such as reliability and ease of high integration, and can utilize the technology accumulated over a long period of time. Attempts have been made to manufacture a device having a new structure in a Si-based semiconductor. One of them is S
i-SiGe-based hetero devices, such as high-speed electronic devices such as SiGe hetero bipolar transistors and Si-
There is a new functional device that uses a strained superlattice of SiGe. Furthermore, use in OEICs (photoelectronic ICs) utilizing the light emission characteristics of silicon-based semiconductors is also considered.
For that purpose, a semiconductor crystal thin film is required to have higher performance, and it is desired to establish a crystal growth technique capable of satisfying those requirements.

[0003] As a candidate, an individual source MBE method,
There are a gas source MBE method, a CVD method and the like. Of these, the one that forms the highest quality Si-SiGe heterojunction structure has been considered to be the solid source MBE method.

[0004]

However, even in the best crystalline thin film prepared by the above-mentioned conventional solid source MBE method, strong light emission that can be used for optical devices is not observed. Usually, when a crystalline thin film having such a Si-SiGe heterojunction structure is produced by the solid source MBE method, the substrate is placed in a vacuum chamber of an apparatus, and Si and Ge are placed in a molecular beam state (beam) in the substrate. And crystal thin film is grown. In this case, the crystal thin film is grown in a low temperature range of 300 to 500 ° C. This is for the following reasons. That is, since the crystal lattice constants of Si and Ge are different from each other by 4%, when a Ge or SiGe (or vice versa) film is grown on the Si film, a crystal called dislocation is formed. Defects occur, and the properties of the obtained crystal thin film having a heterojunction structure are significantly deteriorated. Such an inconvenient phenomenon increases as the temperature becomes higher. Therefore, the crystal thin film is grown in the low temperature range as described above. Further, when performed at a high temperature, the surface morphology (surface flatness) tends to deteriorate, and the surface segregation of Ge (Ge
When the Si film is grown on the film, Ge enters the Si film at the interface between the Si film and the / Ge film, and the steepness << steepness of the interface means that when a film is laminated, the newly formed film is The problem is that the mixture of gas is small and the components of the old and new films become strictly different at the bonding interface.), And these can be avoided to prevent the growth of the crystal thin film from the above. This is a major reason for doing it in such a low temperature range.

As described above, conventionally, it has been considered that low-temperature growth is an essential condition for forming a crystal thin film having a heterojunction structure of Si-SiGe system, and this has been common technical knowledge. A high quality SiGe / Si quantum well structure produced based on this idea << Si thin film is formed on Si substrate, thin SiGe film is formed on it, and further Even in the case of a film having a structure in which a Si thin film is formed and a SiGe film is sandwiched between upper and lower Si thin films (heterojunction structure crystalline thin film), a strong light emission phenomenon that can be considered to be used as an optoelectronic device is recognized. I couldn't do it.

Further, gas source MBE method and other CVD
Also in the method, similarly, a crystal thin film that exhibits a strong light emission phenomenon has not been produced. However, if a semiconductor crystal thin film having a Si—SiGe heterojunction structure that produces strong light emission can be manufactured, a semiconductor device including the semiconductor thin film has not only basic performance as a semiconductor device but also performance as an optical element or the like. As a result, it will play an important role in areas such as optical communication.

The present invention has been made in view of such circumstances, and is a high-quality Si-S showing strong light emission which has never been obtained.
It is an object of the present invention to provide a method for growing a semiconductor crystal thin film having an iGe heterojunction structure and manufacturing a semiconductor device having the performance used for an optoelectronic device or the like.

[0008]

In order to achieve the above object, the method of manufacturing a semiconductor device of the present invention is a solid source M
A method of manufacturing a semiconductor device by growing a semiconductor crystal thin film having a Si-SiGe heterojunction structure on a substrate by using the BE method, wherein the temperature of the substrate is 600 when the semiconductor crystal thin film is grown. The temperature is set to ˜900 ° C. and hydrogen is introduced into the growth atmosphere.

[0009]

The inventors believe that the crystallinity of the semiconductor crystal thin film is insufficient in that the semiconductor crystal thin film having the Si-SiGe heterojunction structure does not generate strong light emission that can be used for optical devices. Inspired and repeated a series of studies. In the course of this research, the above-mentioned idea of the inventors was proved to be correct, and as a result of repeated research to realize the above-mentioned idea, the individual source MBE method was used.
When a semiconductor crystal thin film (Si—SiGe / Si quantum well structure film) having a Si—SiGe heterojunction structure is formed in a high temperature range of 1800 to 900 ° C., which has not been heretofore known, strong light emission (light emission of a compound semiconductor) that has never been achieved. The inventors have reached the present invention by discovering that a strong light emission comparable to that of (1) can be obtained.

To explain this in more detail, the gas source MBE method gives a step to the solid source MBE method in terms of the uniformity of the film formed. Therefore, conventionally, the individual source MBE method has been favored. However, it is common general knowledge that the growth of the semiconductor crystal thin film in the solid source MBE method is performed at a low temperature of 300 to 500 ° C.

As described above, the present inventors doubted such common technical knowledge and thought that the film growth itself at a low temperature might inhibit the light emission phenomenon. That is, at a low temperature, active movement of atoms (SiGe) forming a crystal is suppressed, the above atom cannot be contained in the original crystal lattice position, and the crystallinity is expected to decrease. The present inventors anticipate that good crystallinity and the like are essential conditions for strong light emission. Conventionally, the solid-source MBE method has performed low-temperature growth, resulting in a decrease in crystallinity of the grown SiGe itself. It should be noted that the quality of crystallinity is usually determined by PL (photoluminescence) measurement using a light emission phenomenon. According to this method, it is possible to easily determine if it is a compound semiconductor such as GaAs that easily emits light, but it is not easy to determine whether the crystallinity is good or bad because the Si-based crystal originally does not emit light easily. Furthermore, the conventional individual source M
Semiconductor crystal thin film of the resulting Si-SiGe heterojunction structure in BE method was often form a absolutely several thousand Å or more thick film for application to the electronic device is a little. However, when a SiGe film is grown on a Si film, since Si and SiGe have lattice constants different by 4% from each other, such a thick film causes dislocation and crystallinity as described above. become worse. That is, in order to form a hetero interface with good crystallinity without generating dislocations, SiG
Although the e film is made to match the lattice constant of the Si film smaller than the lattice constant of the SiGe film in the state where the strain is contained therein, the thicker the film thickness, the more the internal strain of the SiGe film. When the energy increases and the film thickness exceeds a certain value, dislocations occur. Such a film thickness is called a critical film thickness,
Usually less than 1000Å. In the conventional solid source MBE method, as described above, the obtained semiconductor crystal thin film inevitably exceeds this critical film thickness, so that the crystallinity is automatically lowered. Thus, the conventional individual source MBE
In the semiconductor crystal thin film formed by the method, dislocations are automatically generated and the crystallinity is deteriorated. This means that it is not easy to determine whether the crystallinity is good or bad by PL measurement. It is considered that he did not notice that the luminescence phenomenon and the crystallinity have a correlation in combination with the fact that the method has excellent film forming performance and is said to have few defects.

The inventors of the present invention thought that a strong light emission phenomenon could be obtained by producing a SiGe / Si quantum well structure having excellent crystallinity as described above. Therefore, in order to improve the crystallinity, research has been repeated on a growth method that allows growth at high temperature and does not cause adverse effects of high temperature growth. As a result, the individual source MBE method was improved, and 600-900
SiGe / Si while introducing hydrogen into the growth atmosphere such as in a vacuum chamber in a high temperature range of ℃, which is unprecedented.
If a quantum well structure is manufactured and the film thickness is suppressed to a critical film thickness or less at which crystallinity deterioration due to dislocation does not occur,
The inventors have found that strong light emission comparable to that of a compound semiconductor can be obtained, and have reached the present invention. Therefore, in the present invention, the thin film in the semiconductor crystal thin film of the Si-SiGe heterojunction structure is a critical film thickness or less, and usually 10
It means a film thickness of 00Å or less.

The semiconductor device of the present invention can be obtained by directly using a conventionally known semiconductor manufacturing apparatus used in the solid source MBE method. In this case, during the growth of the semiconductor crystal thin film, hydrogen is introduced into the vacuum chamber of the semiconductor manufacturing apparatus, and the substrate temperature and the thickness of the semiconductor crystal thin film to be produced are controlled as described above. ..

Next, the present invention will be described in detail based on embodiments.

[0015]

1 shows a semiconductor manufacturing apparatus used in the present invention. That is, this semiconductor manufacturing apparatus is a conventionally known semiconductor manufacturing apparatus used for the solid source MBE method.
This semiconductor manufacturing device is a cylindrical stainless steel vacuum chamber X.
The magnet coupling device 1 is provided in the vacuum chamber X. A substrate holder 2 is attached to an end surface of the magnet coupling device 1, and a disc-shaped Si substrate is detachably attached to the substrate holder 2. The disk-shaped Si substrate A is rotated in the circumferential direction at a rotational speed of 100 prm or more by the magnet coupling device 1. 3 is a manipulator. The manipulator 3 is connected to the magnet coupling device 1 to properly adjust the position of the Si substrate A. Disc-shaped Si substrate A
In the portion of the vacuum chamber X opposite to, three molecular beam source cells 4 to 6 containing a solid source and one cell 7 for projecting hydrogen are provided at predetermined intervals. Of these molecular beam source cells 4 to 6, cells 4 and 6 have Si sources built in, and cells 5 have Ge sources built-in. A heat gun (not shown) is built in each of the molecular beam source cells 4 to 6, and the cells 4 to 6 are heated in a state of a molecular beam (beam state) by heating and vaporizing the Si source or Ge source. 6 tips 4a, 5
Projection is performed from a, 6a toward the Si substrate A. Further, a heater (not shown) made of a tantalum filament is built in the cell 7 for hydrogen projection.
It is designed to be heated to 00 ° C. Then, hydrogen is introduced into the cell through the hydrogen introducing pipe 7b, is decomposed into atoms by the heat of the heater, and is projected from the tip 7a of the cell 7 toward the Si substrate A. Those cells 4-7
A cell shutter 8 is provided in front of each of the cells 4 to 7, and a main shutter 9 is provided in front of the cell shutter 8. A liquid nitrogen shroud 10 is provided on the inner wall surface of the vacuum chamber X. 11 is a molecular beam monitor ion gauge, 12 is a quadrupole mass spectrometer (QMS), 13 is a reflection electron beam diffractometer (RHEE).
D). 14 is an ultrahigh vacuum (10 ^-11 T
orr) is a communication pipe that communicates with a vacuum pump (getter hoop) for suction, and 15 is a gate valve thereof.

In order to grow a desired semiconductor crystal thin film on the Si substrate A using the above apparatus, the pressure in the vacuum chamber X is set to an ultrahigh vacuum of 10 ^-11 Torr. Then, the Si substrate A is heated by the heater built in the substrate holder 2.
Is heated to a temperature of 600 to 900 ° C, preferably 620 to 800 ° C. Then, in this state, the tip 7 of the cell 7 is
While projecting atomically decomposed hydrogen from a toward the Si substrate A, a molecular beam of Si from the molecular beam source cells 4 and 6 is projected toward the Si substrate A for 60 seconds, and then stopped for 5 seconds. , Project for another 10 seconds (if necessary, this projection is 60 seconds → 5 seconds (stop) → 10 seconds → 5 seconds (stop) →
It is repeated 60 seconds → 5 seconds (stop) → 10 seconds → 5 seconds (stop) →). At this time, the molecular beam of Ge from the molecular beam source cells 5 to 7 is overlapped with the flow of the above-mentioned Si molecular beam for 10 seconds, and
Shed for 0 seconds. That is, S toward the Si substrate A
By flowing the molecular beam of i for 60 seconds, a thin film of Si is first formed on the Si substrate A, then stopped for 5 seconds and then flowed for 10 seconds (the molecular beam of Ge overlaps in this 10 seconds). By being projected)
A SiGe thin film is overlaid on the thin film. In this way, Si thin films and SiGe thin films are alternately formed. In this case, the presence of atomically decomposed hydrogen improves the steepness of the bonding interface between the Si thin film and the SiGe thin film, and improves the purity of both thin films near the bonding interface (for example, near the bonding interface). Ge does not mix into the Si thin film).

Using the above apparatus, while introducing hydrogen,
Si _0.84 Ge _0.16 (36 which is one of the semiconductor crystal thin films having a SiGe / Si heterostructure manufactured at 20 ° C.)
Å) / Si (54Å) quantum well structure (5 on Si substrate
A 4 Å Si crystal thin film is formed, a SiGe crystal thin film with a ratio of Si to Ge of 0.84 to 0.16 is formed on the Å thickness of 36 Å, and a Si crystal thin film is further formed on it is 54 Å) PL. The (photoluminescence) spectrum is shown by the curve A in FIG. A curve B shows a PL spectrum of a thin film having the same structure, which was manufactured using the same device at a temperature of 500 ° C. without introducing hydrogen. In curve A, X
^The strong peaks designated as ^TO and X ^NP are the light emission from the SiGe film, which has not been obtained conventionally. The large peak on the right side is the light emission from the Si substrate. In the case of the same structure manufactured at 500 ° C., the emission peak is completely disappeared, and a broad peak indicating the presence of crystal defects is detected on the lower energy side.

A curve A in FIG. 3 is obtained by using the above apparatus,
SiGe / Si produced at 620 ° C. while introducing hydrogen
3 is a SIMS analysis data curve obtained by measuring the steepness of the junction interface between the SiGe film and the Si film having the quantum well structure. Similarly, the curve B in FIG.
SiGe of SiGe / Si quantum well structure manufactured at 0 ° C.
It is a SIMS analysis curve which measured the steepness of the junction interface of a film and a Si film. From the comparison between the curves A and B in FIG. 3, it can be seen that in the above-mentioned embodiment of the present invention, Ge is attenuated at an extremely short distance and the steepness of the bonding interface is excellent. On the other hand, Ge produced at 500 ° C. without introducing hydrogen has Ge distributed over a long distance, indicating that the steepness is poor.

[Measurement of Steepness] Secondary ion mass spectrometer (oxygen ion O ₂ ⁺ is injected with an acceleration energy of 6 kV at an angle of 60 ° with respect to the sample surface, and due to the physical sputtering effect, the depth of Ge in Si is increased. Direction analysis.
The distribution of Ge in the vicinity of the Si / SiGe interface was measured using an MS apparatus >>). <SIMS: Atomika 6500, ultra-high vacuum compatible (10 ^-11 Torr), helium cryopanel for light element analysis, quadrupole mass spectrometer type>

[Measurement of PL] manufactured by JOBIN YVON,
It measured using the 1-m spectroscope (JHR-1000).

As described above, according to the above-described embodiment, a high-quality semiconductor crystal thin film having good crystallinity, good steepness at the heterojunction interface between the Si thin film and the SiGe thin film, and excellent emission characteristics is formed. be able to. That is, according to the present invention, when the semiconductor crystal thin film is grown, not only the substrate temperature is raised, but also hydrogen is added, so that the adverse effect of the high temperature growth can be prevented. The adverse effect of high temperature growth is that the steepness of the heterojunction interface becomes poor. When the steepness of the heterojunction interface deteriorates, there will be fluctuations at what should originally be the interface between dissimilar metals, which is caused by shifting the emission wavelength of the quantum well from the designed value (if there is no fluctuation, the emission wavelength Causes a variety of obstacles in device fabrication, such as causing the well width. This surface segregation is a phenomenon in which supplied atoms replace atoms in the underlying crystal at the interface. In order to suppress it, it is necessary to suppress the movement of surface atoms. One of the methods is to lower the growth temperature, which is a conventional low temperature growth method. However, this also reduces the crystallinity. It is necessary to suppress the surface segregation without reducing the crystallinity. The present inventors have conceived that the surface energy should be suppressed for that purpose. That is, it is sufficient to reduce the number of Ge dangling bonds (the hands that can bond atoms, but are open without being used for bonding). As the method, hydrogen is supplied and the dangling bond is terminated with hydrogen to prevent the steepness of the heterojunction interface from being deteriorated. The presence of hydrogen does not adversely affect the crystallinity. In the above embodiment, hydrogen gas is passed through a heater heated to about 2000 ° C., decomposed into atomic hydrogen and introduced into the growth surface, but the invention is not limited to this. For example, hydrogen gas may be decomposed into atomic hydrogen by plasma and introduced into the growth surface, or a hydride of atoms (atoms other than Si and Ge) that do not form a growing crystal, such as a doping gas, may be used as a heater or plasma. May be decomposed and introduced.

[0022]

As described above, the present invention is an improvement of the solid source MBE method. When the semiconductor crystal thin film having the Si--SiGe heterojunction structure is grown on the substrate, the substrate temperature is 600 to 900. The temperature is set to ℃, hydrogen is introduced into the growth atmosphere, and the semiconductor crystal thin film is
Since the film thickness is set to a critical film thickness or less at which crystal defects do not occur due to dislocations, it is possible to manufacture high-quality semiconductor crystal thin films with unprecedentedly excellent light-emitting characteristics. It is possible to manufacture a semiconductor device having a combination of performances such as a light-emitting element in addition to the desired performance. Therefore, using this semiconductor device, it becomes possible to fabricate an ultra-high-performance Si electronic device and a completely new optoelectronic device incorporating photochemical functions such as light emission, light reception, and light treatment.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view of a growth chamber of a semiconductor manufacturing apparatus used in the present invention.

FIG. 2 is a diagram for comparatively explaining the light emission characteristics of the semiconductor crystal thin film obtained by the manufacturing method of the present invention and the conventional manufacturing method.

FIG. 3 is a diagram for comparing and explaining the steepness of the semiconductor crystal thin film obtained by the manufacturing method of the present invention and the conventional manufacturing method.

[Explanation of symbols]

 X vacuum chamber A Si substrate 4,5,6,7 Molecular beam source cell 10 Liquid nitrogen shroud

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[Procedure amendment]

[Submission date] June 24, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. A method for producing a semiconductor device by growing a semiconductor crystal thin film having a Si—SiGe heterojunction structure on a substrate by using a solid source molecular beam epitaxial growth method, the method comprising the steps of: At this time, the temperature of the substrate is set to 600 to 900 ° C., and hydrogen is introduced into the growth atmosphere.