JP2001338879A - Manufacturing method of semiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grow an SiGeC crystal that can be applied to a semiconductor device, and has uniformity (there is no local structure such as an SiC crystal) and excellent crystallinity on a substrate. SOLUTION: After the surface of an Si substrate 1 is subjected to pretreatment, an ultra-high-vacuum chemical vapor deposition device (UHV-CVD device) is used for forming an SiGeC layer 2 on the Si substrate 1. The growth temperature of the SiGeC layer 2 at this time is set to 490 deg.C or less, and Si2H5, GeH4, and SiH3CH3 are used as the raw materials of Si, Ge, and C, respectively, thus forming the SiGeC layer 2 having the excellent crystallinity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to silicon (Si).
The present invention relates to a method for manufacturing a semiconductor crystal including atoms, germanium (Ge) atoms, and carbon (C) atoms.

[0002]

2. Description of the Related Art A mixed crystal semiconductor (SiGe) composed of Si and Ge is well known as a material capable of forming a heterostructure with Si and producing an ultrahigh-speed semiconductor device. But,
Since SiGe has a larger lattice constant than Si, when a SiGe layer is epitaxially grown on the Si layer, SiG
A very large compressive strain occurs in the e-layer. Therefore, when a SiGe layer having a certain film thickness (critical film thickness) or more is deposited on the Si layer, a phenomenon in which a defect such as dislocation is generated in the SiGe crystal and strain in the crystal is relaxed occurs. Get up. Even when there is no defect immediately after crystal growth, when heat treatment indispensable for a semiconductor process is applied, Ge
In a SiGe crystal having a high content of, defects are likely to occur in the crystal. That is, the SiGe crystal also has unfavorable properties such as low thermal resistance from the viewpoint of device fabrication. Also, at the Si / SiGe heterojunction, the energy band offset is
It occurs only in the valence band of the layer. Therefore, carrier confinement occurs only in the valence band. Therefore, when forming a MOS transistor having a SiGe layer having a Si / SiGe heterostructure as a channel, only a p-channel transistor having holes as carriers can be manufactured.

In order to compensate for the above-mentioned weak points of the Si _1-x Ge _x crystal, Si and Ge have recently received special attention.
And C are mixed crystal semiconductors (SiGeC). C is
An element having an atomic radius smaller than that of Si or Ge. By introducing C into a crystal, the lattice constant of the crystal can be reduced, and the strain in the crystal can be reduced. In addition, since the amount of strain accumulated in the crystal can be reduced, the thermal resistance can be improved. Further, at the Si / SiGeC heterojunction,
When the contents of Ge and C are increased (Ge is several tens
%, C is several%), which can cause an energy band offset in both the valence band and the conduction band of the SiGeC layer. In this case, confinement of carriers occurs in both the conduction band and the valence band, so that not only a p-channel transistor but also an n-channel transistor can be manufactured.

Further, by introducing C into the SiGe layer, a function of suppressing diffusion of impurities such as boron is exhibited. In this case, a SiGeC crystal having a C atom content of about 0.1% or less is used.

[0005] This SiGeC crystal has a
Since it cannot be formed by a method performed in a thermal equilibrium state such as a melting method, it has been conventionally known that molecular beam epitaxy (Mole
cular Beam Epitaxy: MBE, chemical vapor deposition (Chem)
Crystal growth techniques performed in a thermally non-equilibrium state, such as chemical vapor deposition (CVD), have been used to form the crystals.

[0006] Among them, the MBE method is a method in which source atoms are evaporated under ultra-high vacuum conditions of 300 to 500 ° C and directed toward a substrate to grow a crystal on the substrate. However, this method has disadvantages such as the necessity of exchanging raw materials, the inability to grow a crystal on a minute concave surface, and the difficulty in increasing the diameter of a substrate, and is particularly unsuitable for mass production of SiGeC crystals. .

Next, in the CVD method, Rapid Thermal Chemic
al Vapor Deposition (RT-CVD)
An action processing (LRP) method is used, in which a source gas is introduced together with a large amount of hydrogen under a medium-high vacuum to grow a crystal on a heated substrate. S
In the case of an iGeC crystal, the raw material of Si is mainly silane (SiH ₄ ), the raw material of Ge is GeH ₄ , and the raw material of C is monomethylsilane (SiH ₃ CH ₃ ), ethylene (C ₂ H ₄ ) or Acetylene (C ₂ H ₂ ) or the like is used. Conventionally, crystal growth has been performed under a temperature condition of 550 to 600 ° C., similarly to the growth of the SiGe layer.

[0008]

The SiGeC crystal is a material capable of realizing various and high-performance devices more than the SiGe crystal because the degree of freedom in controlling distortion and band offset is greatly expanded. Is not easy to produce due to the properties described below.

First, the solid solubility of C atoms in Si and Ge is very low (about 10 ¹⁷ / cm ³ in Si in a thermal equilibrium state,
e is about 10 ⁸ / cm ³ ), and it is impossible to produce SiGe crystals having a high C content (% order) by a method performed in a thermal equilibrium state such as a melting method.

Further, C atoms have a property that they can easily enter not only the lattice positions of the crystal but also the lattices, and the C atoms between the crystal lattices become recombination centers of carriers.
It is thought to have an adverse effect on device characteristics.

Further, C has a tendency to selectively bond with Si in the SiGeC crystal, so that crystalline silicon carbide (Si)
C) tends to occur locally. SiC may have a structure close to amorphous. Also, depending on the crystal growth conditions, aggregates of C are likely to be formed. These local structures cause a decrease in crystallinity.

As described above, the content of C is relatively high, and it has uniformity that can be applied to semiconductor devices (S
SiGeC crystal having no local structure such as iC crystal, that is, high quality S having a relatively high C content and a low defect density
It is very difficult to epitaxially grow an iGeC layer on a Si layer.

For example, it has been difficult to form a high-quality SiGeC crystal containing a high content of C and having a low defect density even by the above-described CVD method performed under thermally non-equilibrium conditions.

An object of the present invention is to provide a method for growing a SiGeC crystal having uniformity (having no local structure such as SiC crystal) and good crystallinity on a substrate, which can be applied to a semiconductor device. Is to provide.

[0015]

According to the method of manufacturing a semiconductor crystal of the present invention, silicon (S) is placed in a container holding a substrate.
A raw material gas containing i), a raw material gas containing germanium (Ge), and a raw material gas containing carbon (C) are introduced, and the raw material gas is thermally decomposed to obtain Si atoms and Ge atoms. A method for producing a semiconductor crystal containing C atoms on the substrate, wherein the thermal decomposition is performed at a temperature of 490 ° C. or lower.

Thus, a semiconductor crystal containing Si, Ge and C and having good crystallinity can be formed on the substrate.

In the method of manufacturing a semiconductor crystal, by forming the semiconductor crystal by a thermal CVD method, a semiconductor crystal having good crystallinity can be efficiently formed on a substrate. Further, a semiconductor crystal having good crystallinity can be formed even on a substrate having a patterned member.

In the method of manufacturing a semiconductor crystal, the source gas of Si contained in the semiconductor crystal may be Si ₂ H
490 ° C by using ₆ or Si ₃ H ₈
The growth rate of the semiconductor crystal is about 4-8 even at the following low temperature.
It can be about nm / min. Therefore, it becomes possible to mass-produce a semiconductor device having a semiconductor crystal having good crystallinity.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) show heat C on a Si substrate.
FIG. 4 is a diagram showing a step of forming a SiGeC layer using a VD method.

First, in the step shown in FIG. 1A, pretreatment of the Si substrate 1 is performed. When a crystal such as SiGeC is grown on the Si substrate 1, the pretreatment of the Si substrate 1 is very important and must be performed. Here, as the substrate, (0
The Si wafer having the 01) plane is used.

First, the surface of the Si substrate 1 is washed with a mixed solution of sulfuric acid and hydrogen peroxide to remove organic substances and metal contaminants on the surface of the Si substrate 1. Next, the surface of the Si substrate 1 is washed with an ammonia-hydrogen peroxide aqueous solution to remove deposits on the surface of the Si substrate 1. Subsequently, the natural oxide film on the surface of the Si substrate 1 is removed using hydrofluoric acid.
Next, the Si substrate 1 is again placed in the ammonia-hydrogen peroxide aqueous solution.
To form a thin protective oxide film on the surface of the Si substrate 1.

Next, in the step shown in FIG. 1B, the pretreated Si substrate 1 is introduced into a crystal growth apparatus. In this embodiment, an ultra-high vacuum chemical vapor deposition apparatus (UHV-CVD apparatus) is used as a crystal growth apparatus. This method
The crystal growth was 1.3 × 10 ⁻⁸ Pa (1.0 × 10 ⁻¹⁰ To
rr) This is a method for producing a semiconductor crystal performed by reducing the pressure to an ultra-high vacuum as described below. In the present embodiment, the pressure in the crystal growth chamber is temporarily reduced to 2.66 × 10 ⁻⁷ Pa (2.0 × 10 ⁻⁹ Torr) after the Si substrate 1 is introduced into the crystal growth chamber.

Next, the Si substrate 1 is placed in an atmosphere of hydrogen gas for 8 hours.
Heating to 50 ° C. removes the protective oxide film formed on the Si substrate 1 to expose a clean surface of the Si substrate 1.

Subsequently, the temperature of the Si substrate 1 is lowered to 490 ° C. where crystal growth is performed, and a source gas is introduced.
A SiGeC layer 2 of about 00 nm is grown on the Si substrate 1. In this embodiment, the crystal is grown at 490 ° C.
At the following temperature, a SiGeC layer having good crystallinity can be formed.

Also, Si ₂ H _6, which is easily decomposed at a relatively low temperature, is used as a Si source gas, and GeH ₄
And SiH ₃ CH ₃ as a raw material of C.
The pressure of each gas is 9.1 × 10 ⁻³ Pa for Si ₂ H _6.
(7 × 10 ⁻⁵ Torr), GeH ₄ is 4.2 × 10 ⁻²
Pa (3 × 10 ⁻⁴ Torr), Si ₃ H ₈ is 1.1 ×
It is fixed at 10 ⁻³ Pa (9 × 10 ⁻⁶ Torr).

Here, Si ₂ H is used as a raw material gas for Si.
_In addition to ₆ , low temperature decomposable Si ₃ H ₈ can also be used. However, silane (SiH ₄ ), which is generally used as a raw material gas for Si, is not used in this embodiment because its crystal growth at low temperatures (about 490 ° C.) is poor. The pressure of the raw material gas used here is set lower than the pressure conditions in the SiGeC crystal growth method reported so far. This is because Si ₂ H ₆
This is because the source gas is an explosive gas, and in the growth step of the SiGeC crystal, a lower pressure of the source gas is preferable from the viewpoint of safety. Further, since the pressure of the source gas is low, the source gas can be saved, which is advantageous in terms of cost.

In the present embodiment, the SiGeC layer 2 is deposited on the Si substrate 1 by using an ultra-high vacuum chemical vapor deposition apparatus (UHV-CVD apparatus).
A device D may be used.

In this embodiment, the substrate (00
1) Although a Si wafer having a plane is used, a Si wafer having a plane orientation other than the above may be used, and a Si wafer having good crystallinity can be formed on a substrate having an already patterned member.
It is possible to form a GeC layer. Through the above steps, the SiGeC layer 2 having good crystallinity on the Si substrate 1
Can be formed.

In the present embodiment, the growth temperature of the SiGeC crystal was set at 490 ° C., which is a temperature derived from the results of the following study for the purpose of searching for the optimum temperature for crystal growth.

First, after pretreatment of the Si substrate is performed in the same manner as in the present embodiment, the Si substrate is subjected to the UHV-CVD method.
A SiGeC layer was deposited on the substrate. The crystal growth temperature was between 480 ° C. and 520 ° C. The raw material gas is also Si ₂ H ₆ as the Si raw material as in the present embodiment.
, GeH ₄ as a Ge source, and Si as a C source.
H ₃ CH ₃ was used, and the pressure of each gas was the same as in this embodiment.

Next, the SiG of the sample produced by the above operation was
The crystallinity of the eC layer was investigated by measuring the X-ray diffraction spectrum. FIG. 2 shows the result. Here, the thickness of the SiGeC layer in each sample was all set to about 100 nm.

First, in FIG. 2, the peak around 34.56 degrees observed in all the samples is the peak of S used for the substrate.
This is a peak due to diffraction of the (004) plane of i, and has nothing to do with the epitaxially grown SiGeC layer. The peak of the SiGeC crystal layer to be noted here is 34.0-
It is a peak that appears between 34.1 degrees.

From FIG. 2, in the spectrum of the sample grown at 525 ° C., a diffraction peak due to the (004) plane of the SiGeC crystal is observed at an angle of about 34.0 degrees.
However, the peak shape is very broad and weak. In general, it is known that the peak intensity and half width (peak width at half the peak intensity) of the X-ray diffraction spectrum have a very strong correlation with the crystallinity. That is, when the crystallinity is good, the peak intensity becomes strong and the half width becomes narrow. Conversely, when the crystallinity is poor, the peak intensity is weak and the half width tends to be wide. From this, 52
The SiGeC layer of the sample grown at 5 ° C. has very poor crystallinity, and it is assumed that there are many defects and the like in the crystal.

The observation of the crystal surface with a Nomarski microscope also revealed that the SiG of the sample grown at 525 ° C.
The eC layer had irregularities, and it was also found that the surface morphology was very poor (not shown).

Next, when the growth temperature is lowered to about 510 ° C. to 500 ° C., the peak intensity is slightly increased, but the half width is still large. From this, 510 ℃ -5
In the sample SiGeC layer grown near 00 ° C., 52
Although the crystallinity is slightly improved as compared with the SiGeC layer of the sample grown at 5 ° C., it is unlikely that the crystallinity is good enough to be used as an active region of a semiconductor device. When the surface of the sample whose growth temperature was around 510 ° C. to 500 ° C. was observed with a Nomarski microscope, the surface morphology was not improved (not shown).

However, when the temperature of the SiGeC layer is lowered to 490 ° C., the shape of the peak shape changes completely, and a very sharp peak appears around 34.05 °. Furthermore, in the spectrum when the growth temperature of the SiGeC layer is 490 ° C., many small peak groups are observed before and after the peak near 34.05 degrees. This small peak forms Fringe in an X-ray diffraction image, and is observed only in a crystal having extremely good crystallinity. From these facts, it is understood that the SiGeC layer of the sample grown at 490 ° C. has good crystallinity.

Further, the sample Si grown at 480 ° C.
Also in the GeC layer, the same sharp diffraction peak as in the case of growing at 490 ° C. is observed at almost the same diffraction angle position. This is because the crystallinity of the SiGeC layer grown at 480 ° C. is very good, and the C
Shows that there is no change in the content of the compound when grown at 490 ° C. Here, when the composition of the sample manufactured at 490 ° C. and 480 ° C. was estimated using Vegard's rule, Ge atoms were 30%, C atoms were 1.2%, and Ge was
It has been found that a SiGeC layer having both high C and C contents was produced. In addition, observation of the surfaces of the samples prepared at 490 ° C. and 480 ° C. with a Nomarski microscope showed that no irregularities were observed on the surfaces of the respective SiGeC layers, and that the surface morphology was also improved (not shown). ).

Here, the Vegard's law is a law regarding the relationship between the lattice constant of a mixed crystal and the mixing ratio.
For example, the lattice constant A _SiGe of a Si _x Ge _1-x crystal in which the content of Si is x and the content of Ge is (1-x) is such that the lattice constant of _Si is A _Si and the lattice constant of _Ge is A _Ge . Then A _SiGe =
xA _Si + (1-x) A _Ge . If the lattice constant of each crystal is known, it can be used to determine the composition of the crystal.

Next, a study of the relationship between the crystallinity of the SiGeC layer and the growth temperature was performed on various SiGeC layers having different contents of Ge and C, as described above. Where S
The content of Ge and the content of C in the iGeC layer are determined by Si ₂ H
And ₆ pressure constant, and controlled by changing the pressure of GeH ₄ and SiH ₃ CH _3. Other conditions were the same as in the present embodiment. FIG. 3 summarizes the results.

FIG. 3 shows the growth temperature of the SiGeC layer on the vertical axis,
The horizontal axis shows the content of C in the produced SiGeC layer, and shows the quality of each crystallinity. The quality was determined by measuring the X-ray diffraction spectrum and observing with a Nomarski microscope as in the above method. Ge in the figure
Are indicated by the types of marks, solid marks indicate good crystallinity, and white marks indicate poor crystallinity.

In FIG. 3, for example, a circle or a circle plotted where the C content on the horizontal axis is about 1.2% indicates that Ge contains 30.5% and C contains 1.2%. Si
This is the result when a GeC layer was produced, and the growth temperature was 49
At 0 ° C. or lower, the crystallinity is good (●), and at 500 ° C. or higher, the crystallinity is poor (○). Also, when the content of C is 1.4%, it is indicated by □ or Δ,
SiG having a Ge content of 26.8% and a C content of 1.4%
In the case of the eC layer, the crystallinity is good (■) at 490 ° C. or lower, but the crystallinity is not good (□) at a growth temperature higher than 490 ° C. The dotted line in the figure is
This is an approximate curve connecting the growth temperatures at the boundary where the crystallinity changes from good to poor in each SiGeC layer having a different C content.

Comprehensively looking at the results, the quality of the crystallinity does not depend much on the Ge content, and although there is some variation, it changes with the temperature range of 490 ° C.-500 ° C. You can see that it is. That is, SiGe
If the growth temperature of the C crystal is higher than this temperature range, SiG
This result clearly shows that the crystallinity of the eC crystal deteriorates, and the crystallinity of the SiGeC crystal improves when the crystallinity is low. In particular, for the SiGeC samples having a C content of more than 1%, when the growth temperature of the SiGeC layer was lower than 490 ° C., all the SiGeC samples showed good crystallinity.

In addition, SiGeC having a C content of less than 1%
As for the layer, the lower the content of C, the higher the temperature at the boundary where the crystallinity changes from good to poor.

Here, it is considered why good crystals can be obtained when the temperature of crystal growth is lowered to about 490 ° C. Literature (J.Mi et al., J.Vac.Sci.Technol.B1
According to 4,166, '96), in the process in which C atoms are incorporated into a SiGeC crystal during its growth, S
It is believed that iCH ₄ is produced. When the growth temperature of the crystal is low, this intermediate product is decomposed at the surface site without moving much on the growing crystal surface, and Si or C
It is considered that atoms are taken into lattice positions of the crystal. Then, it is considered that the Si and C atoms once taken into the lattice position of the crystal are hardly desorbed due to the low temperature.
However, when the crystal growth temperature is high, the intermediate product SiCH ₄ is likely to move around the growth surface and penetrate into the interstitial space or the like, and inhibit normal crystal growth. Also, even if this intermediate product is decomposed at the surface site and once incorporated into the crystal surface during epitaxial growth,
It is supposed that normal crystal growth is hindered by easily desorbing due to heat energy and entering interstitial positions and the like. Therefore, when combined with the results obtained above, 4
At a growth temperature exceeding 90 ° C., it is considered that the crystallinity deteriorated because SiCH ₄ easily moved around and the C atom at the lattice position was easily desorbed.

From the above examination results, the crystal growth temperature was set to 4
When the temperature is suppressed to 90 ° C. or less, it can be determined that a SiGeC crystal having good crystallinity can be produced even under a condition in which the Si source gas pressure is low. In particular, in order to produce a SiGeC crystal having a carbon content exceeding 1% and good crystallinity, it is effective to perform crystal growth at a low temperature of 490 ° C. or lower. From this examination result, the temperature condition for crystal growth in the present embodiment was derived.

In general, when a semiconductor crystal is grown by the CVD method or the like, if the growth temperature is set low, there is a problem that the growth rate of the crystal is reduced and the throughput of the crystal growth process is reduced.

However, in this embodiment, Si ₂ H ₆ which is easily decomposed at a low temperature is used as the Si source gas instead of SiH ₄ which has conventionally been the mainstream gas, so that SiH ₄ at 490 ° C.
When a GeC crystal is produced, the crystal growth rate is about 4-8.
A growth rate of about nm / min, which is comparable to a case where SiGe crystals are produced by a mass-production type growth apparatus, can be realized. Therefore, it is considered that there is no defect in the crystal growth rate even during mass production.

According to the present invention, SiG having good crystallinity
Since an eC crystal can be formed, for example, a SiGeC layer is deposited on a Si substrate based on the present embodiment,
By further depositing a Si layer on the iGeC layer and forming a gate electrode on the Si layer, n operating at an ultra-high speed
Channel-type and p-channel-type MOS transistors can be manufactured.

[0050]

According to the method of manufacturing a semiconductor crystal of the present invention, a crystal containing Si, Ge, and C is epitaxially grown on a substrate at a temperature of 490 ° C. or less, thereby forming a SiGeC crystal layer having good crystallinity. Can be formed on substrate

[Brief description of the drawings]

1 (a) and 1 (b) show S according to an embodiment of the present invention.
It is sectional drawing which shows the formation process of an iGeC layer.

FIG. 2 is a diagram showing an X-ray diffraction spectrum of a SiGeC layer grown at each temperature from 480 to 525 ° C.

FIG. 3 is a diagram showing the relationship between crystallinity and growth temperature in various SiGeC layers having different C and Ge contents.

Claims (3)

[Claims] A source gas containing silicon (Si) and germanium (Ge) are placed in a container holding a substrate.
By introducing a raw material gas containing carbon and a raw material gas containing carbon (C), and thermally decomposing the raw material gas to obtain S
A method for producing a semiconductor crystal containing i-atoms, Ge-atoms and C-atoms on the substrate, wherein the thermal decomposition
A method for producing a semiconductor crystal performed at a temperature of not more than ° C. 2. The method of manufacturing a semiconductor crystal according to claim 1, wherein the formation of the semiconductor crystal is performed by a thermal CVD method. 3. The semiconductor crystal according to claim 1 or 2,
In the manufacturing method, Si is used as a source gas of Si contained in the semiconductor crystal.
_Two H₆ Or Si_Three H ₈ Characterized by the use of semi
A method for producing a conductor crystal.