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  • H10D62/83—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group IV materials, e.g. B-doped Si or undoped Ge
  • H10D62/832—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group IV materials, e.g. B-doped Si or undoped Ge being Group IV materials comprising two or more elements, e.g. SiGe
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Definitions

• the present invention relates to a method for manufacturing a semiconductor wafer, and more particularly to a method for forming a semiconductor wafer having a semiconductor crystal layer containing strain.
• SiGe silicon and germanium
• SiGeC mixed crystal of silicon, germanium and carbon
• strained Si crystals which adds a new element called strain to Si crystals to reduce the scattering of carrier electrons called inte- valley scatterin and improve mobility. That is the approach.
• the latter strained Si crystal can improve its performance only by distorting the bulk Si crystal and use the existing Si process technology (for example, the technology of the oxidation etching process). Since they can be processed into devices, they are attracting industrial attention.
• such a strained Si crystal is produced by depositing a thick SiGe crystal layer on a Si substrate composed of a bulk Si crystal, and depositing the Si crystal on the thick SiGe crystal layer.
• a SiGe crystal is a crystal having a larger lattice constant than Si. Therefore, when a SiGe crystal is epitaxially grown with a lattice in the substrate plane matched to Si, the following is obtained. Very large compressive strains occur in iGe crystals. When the Si Ge crystal is deposited on the Si substrate beyond a certain thickness (critical thickness), dislocations are generated between the Si substrate and the Si Ge layer, and the strain is relaxed. I do.
• the lattice spacing in the plane of the Si Ge layer becomes larger than the lattice spacing on the Si substrate surface.
• the Si crystal layer is epitaxially deposited on the Si Ge crystal layer, the lattice spacing in the plane of the Si is relaxed and coincides with the lattice spacing of the feSi Ge crystal. It becomes larger than the original lattice constant.
• a strained Si crystal layer subjected to a tensile stress can be produced.
• a crystal layer having lattice relaxation that causes lattice relaxation and has a larger lattice spacing than the Si substrate, as in the above Si Ge crystal will be described below.
• This is called a relaxation buffer layer).
• FIG. 1 is a cross-sectional view of a substrate on which a strained Si crystal layer is formed using a conventional method.
• a Si Ge crystal layer having a thickness exceeding a critical film thickness of at least several m / m is formed on the Si substrate 101 by a CVD method. 3. Epitaxial growth. At this time, dislocations 102 occur between the relaxed Si Ge crystal layers 103, and the Si Ge crystal layers 103 are lattice-relaxed.
• a strained Si crystal layer 104 is obtained by depositing a Si crystal on the Si Ge crystal layer 103 by the CVD method. Solution issues
• An object of the present invention is to provide a structure and a method of manufacturing a buffer layer having a reduced crystal defect density, thereby manufacturing a semiconductor wafer provided with a strained Si layer or the like used as a substrate of a semiconductor device. Is to do.
• a semiconductor wafer according to the present invention includes a substrate made of a Si crystal, and a crystal layer provided on the substrate and having an in-plane lattice constant larger than the lattice constant of the substrate. Some are crystals composed of Si, Ge, and C in which SiC crystals are dispersed.
• a crystal layer having a lattice constant within a plane larger than the lattice constant of the substrate made of Si crystal can be used as a relaxation buffer layer. Therefore, a distorted Si crystal layer can be formed on this relaxation buffer layer.
• the semiconductor wafer manufactured here can also be used as a substrate of a semiconductor device.
• the semiconductor wafer further includes a distorted Si crystal layer provided on the crystal layer, so that when the semiconductor wafer is used as a substrate of a semiconductor device, the distorted Si crystal is Since the carrier mobility in the layer is larger than the carrier mobility in the bulk Si crystal, it is possible to fabricate a semiconductor device with improved performance when the bulk Si crystal is used as a substrate.
• the first method for producing a semiconductor wafer of the present invention comprises the steps of: (a) depositing a crystal layer containing at least partially Si, Ge, and C on a substrate made of Si crystal; (B) thermally annealing the substrate on which the crystal layer is deposited to relax the crystal layer and precipitate a SiC crystal in the crystal layer.
• a crystal wafer containing Si, Ge, and C is used as a relaxation buffer layer, and a semiconductor wafer capable of forming a strained Si crystal layer having almost no dislocation on the relaxation buffer layer is manufactured. Can be.
• the occurrence of threading dislocations in the crystal layer serving as the relaxation buffer layer is suppressed by precipitating SiC by thermally annealing the substrate.
• the thickness of the relaxation buffer layer which previously required a thickness of several m / m, can be made smaller than before, mass production of semiconductor wafers capable of forming a strained Si crystal layer is possible. It becomes possible to do.
• the method for manufacturing a first semiconductor wafer further includes a step (c) of forming a distorted Si crystal layer on the crystal layer after the thermal annealing including the Si C crystal. Accordingly, it is possible to manufacture a semiconductor wafer provided with a relaxation buffer layer containing Si, Ge, and C, and a strained Si crystal layer. By using this semiconductor wafer as a substrate of a semiconductor device, it is possible to manufacture a semiconductor device with improved performance as compared with a case where a bulk Si crystal is used as a substrate.
• the method comprises the steps of: (a) depositing a crystal layer containing at least part of Si, Ge and C on a substrate made of Si crystal; and forming a Si crystal shoulder on the crystal layer. (B) depositing Si and thermally annealing the substrate to deposit SiC crystals in the crystal layer and distorting the Si crystal layer (c). I have.
• a semiconductor wafer having a relaxation bath containing 3%, 06 and C, a sofa layer, and a strained Si crystal layer is manufactured in the same manner as the above-described method of manufacturing the first semiconductor wafer. can do.
• this semiconductor wafer as a substrate of a semiconductor device, it is possible to manufacture a semiconductor device with improved performance as compared with a case where a bulk Si crystal is used as a substrate.
• FIG. 1 is a cross-sectional view showing a conventional substrate structure for obtaining a strained Si crystal.
• FIG. 2 shows a semiconductor having a strained Si crystal layer formed according to an embodiment of the present invention. It is sectional drawing of one wafer.
• 3 (a) to 3 (d) are cross-sectional views illustrating the steps of manufacturing a semiconductor wafer according to an embodiment of the present invention.
• FIG. 4 shows an X-ray diffraction spectrum of a SiGeC crystal immediately after deposition on a Si substrate and a SiGeC crystal after thermal annealing in a semiconductor wafer according to an embodiment of the present invention.
• FIG. 5 is a diagram showing an X-ray diffraction spectrum of a Si substrate having a strained Si crystal layer formed on a relaxation buffer layer proposed in the present invention.
• FIG. 6 is a transmission electron micrograph of the SiGeC layer formed on the Si substrate according to the present invention after thermal annealing.
• FIG. 7 is a transmission electron micrograph of the Si Ge crystal formed on the substrate after thermal annealing. Best Embodiment
• FIG. 2 is a cross-sectional view showing one semiconductor wafer according to the present embodiment.
• a semiconductor wafer according to an embodiment of the present invention includes a Si substrate 1 which is a bulk Si crystal, and an annealing having a thickness of about 130 nm formed on the Si substrate 1.
• a Si Ge crystal layer 10 a Si crystal layer 9 having a thickness of about 4 nm formed on the anneal Si G iC crystal layer 10, and a Si crystal layer 9 formed on the Si crystal layer 9.
• a strained Si crystal layer 4 is a strained Si crystal layer 4.
• the anneal SiGeC crystal layer 10 has a diameter of about scattered in the matrix SiGeC crystal layer 7 formed on the Si substrate 1 and in the matrix SiGeC crystal layer 7. It consists of SiC microcrystals 6 of 2 to 3 nm.
• a region 2 within 20 nm from the interface between the Si substrate 1 and the matrix SiGeC crystal layer ⁇ ⁇ contains a defect 2 which is considered to be a dislocation.
• One feature of the wafer according to the present embodiment is that an annealing SiGeC crystal layer 10 composed of a SiC microcrystal 6 and a matrix SiGeC crystal layer 7 is used as a relaxation buffer layer. It is to be.
• the lattice constant of the lattice-relaxed matrix Si Ge C crystal layer 7 is larger than the lattice constant of Si, even if the relaxation buffer layer has a thickness of about 130 nm, the anneal si Ge C By growing the Si crystal layer 9 above the crystal layer 10, the strained Si crystal layer 4 can be formed.
• the crystal defects 2 which are regarded as dislocations are caused by the Si substrate 1 and the anneal Si GeC crystal layer 1 in the anneal SiGeC crystal layer 10.
• the region is within 20 nm from the interface with 0, and no threading dislocation is seen. The evidence and the inference of the inventor for this reason will be described later.
• a highly reliable and high-performance semiconductor device can be manufactured using the semiconductor wafer according to the present embodiment.
• a field-effect transistor having a Si / SiGeC heterostructure in which a gate oxide film and a gate electrode are provided on the strained Si crystal layer 4 can be manufactured.
• the thickness of the Si crystal layer 9 is 4 nm, but the thickness of the Si crystal layer 9 is not particularly limited. Further, the Si crystal layer 9 may not be formed on the anneal SiGeC crystal layer 10, and the strained Si crystal layer 4 may be formed directly on the anneal SiGeC crystal layer 10. Alternatively, a SiGe crystal or a SiGeC crystal may be formed below the strained Si crystal layer 4 and on the Si crystal layer 9.
• a wafer provided with the strained Si crystal layer 4 has been described.
• a wafer in which the strained Si crystal layer 4 is not formed can be provided to the user.
• the composition of the SiGeC crystal is, as described later, 68.3% for Si, 30.5% for Ge, and 1.2% for C.
• the content of each atom is not limited to this.
• the thickness of the anneal Si Ge C crystal layer 10 serving as the relaxation buffer layer is 13 O nm.
• the anneal S The thickness of the iGeC crystal layer 10 may be greater than 20 nm.
• the thickness of the anneal SiGeC crystal layer 10 may be 130 nm or more.
• the (001) surface of the Si substrate 1 is cleaned as follows. 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 the attached matter on the surface of the Si substrate 1. Subsequently, the native oxide film on the surface of the Si substrate 1 is removed using hydrofluoric acid. Next, the Si substrate 1 is immersed again in an aqueous solution of ammonia and hydrogen peroxide to form a thin protective oxide film on the surface of the Si substrate 1.
• the Si substrate 1 whose surface has been cleaned is put into an ultra-high vacuum chemical vapor deposition apparatus (UHV-CVD apparatus), and once inside the UHV-CVD apparatus. . to 6 X 1 0- 7 P a ( 2 xl O- 9 T orr) under reduced pressure. Next, by heating the Si substrate 1 to a temperature of 800 ° C. in a hydrogen gas atmosphere, the above-mentioned protective oxide film is removed, and a clean surface of the Si substrate 1 is exposed.
• UHV-CVD apparatus ultra-high vacuum chemical vapor deposition apparatus
• disilane (Si 2 H 6 ) gas which is a source gas of Si, Ge, and C, and germane (GeH 4 )
• SiChe germane
• S i 2 H 6 gas 9. 1 X 1 0- 3 P a (7 x 1 0- 5 T orr), a GeH 4 gas 4.
• the thickness of the Si crystal layer 9 deposited on the Si Ge C crystal layer 8 was set to 4 nm.
• the deposition of the Si crystal layer 9 may be omitted.
• a Si Ge crystal or a Si Ge C crystal may be deposited on the Si crystal layer 9.
• the UHV-C VD method is used for crystal growth, but an LRP device, an RT-CVD device, or the like may be used instead.
• one Si wafer having the (001) plane is used as the substrate.
• an Si wafer having a plane orientation other than this may be used.
• FIG. 4 is an XRD spectrum diagram of the SiGeC crystal immediately after being grown on the Si substrate and the SiGeC crystal after the thermal annealing.
• the peak observed at around 34.56 degrees is a peak due to the diffraction of the (004) plane of S soil used as the substrate, and the peak around 34.06 degrees is the Si substrate.
• This SiGeC crystal is considered to be in a completely strained state, that is, a state in which the lattice constant of the SiGeC crystal in each direction parallel to the Si substrate completely matches the lattice constant of the Si substrate. .
• the composition of the crystal is estimated from the peak angle of the X-ray diffraction spectrum using a crystal analysis method called the Vegard rule, it is found that S containing about 30.5% of Ge and about 1.2% of C is contained. It can be seen that this is an i GeC crystal. Looking at the lower spectrum in Fig. 4 in detail, a small peak is observed around the peak of the Si Ge C crystal at around 34.06 degrees. This small peak forms fringe in the X-ray diffraction image, indicating that the crystallinity and flatness of the SiGeC crystal formed in the present embodiment are very good. The crystallinity was confirmed by cross-sectional observation with a transmission electron microscope (TEM). No defects were observed at all.
• TEM transmission electron microscope
• the substrate is taken out of the UHV-CVD apparatus and subjected to thermal annealing in a nitrogen atmosphere using a halogen lamp annealing apparatus or an electric furnace annealing apparatus.
• thermal annealing is performed at 1 050 ° C for 15 seconds.
• the SiGeC crystal layer 8 is finely formed by the SiC as described later. Layer separation occurs between crystal 6 and matrix SiGeC crystal layer 7. As will be described later, lattice relaxation occurs simultaneously, and the lattice constant in the plane of the matrix Si GeC crystal layer 7 becomes larger than the lattice constant of the Si substrate 1. Accordingly, when the Si crystal layer is deposited on the anneal Si GeC crystal layer 10 in a later step, the Si crystal layer can be distorted, and the strained Si crystal layer 4 can be formed. Becomes possible.
• the SiC microcrystals 6 are deposited by thermally annealing the substrate at 150 ° C., no threading dislocation is observed in the anneal SiGeC crystal layer 10. This indicates that a highly reliable semiconductor device can be manufactured using the semiconductor wafer manufactured according to the present embodiment.
• the thermal annealing of the substrate is performed at 150 ° C., but the thermal annealing may be performed at a temperature at which SiC is deposited, that is, at a condition of about 950 ° C. or more.
• the substrate is once taken out of the crystal growth apparatus and subjected to thermal annealing.
• a thermal annealing process may be continuously performed in the crystal growth apparatus.
• the strained Si crystal layer 4 is formed in a later step. However, this is not performed, and as a substrate for forming an arbitrary semiconductor device, 31 substrate 1 and anneal Si Ge A thermally annealed substrate provided with the C crystal layer 10 may be manufactured. That is, a wafer provided with a Si substrate and a SiGeC crystal layer in which a SiC crystal is dispersed may be provided to a user without forming the strained Si crystal layer 4.
• FIG. 6 is a TEM photograph showing the result of TEM observation of the cross section of the substrate after the thermal annealing in the step shown in FIG. 3 (c).
• SiC microcrystals 6 having a diameter of about 2-3 nm are precipitated in the portion where the uniform SiGeC crystal was present.
• the SiC microcrystals 6 are generated because the metastable SiGeC crystal is phase-separated into stable SiC and SiGe crystals by thermal annealing. it is conceivable that.
• the SiC microcrystals 6 are shown larger than the actual volume ratios for easy understanding, but in reality, the anneal SiGeC crystal layers The volume ratio of SiC microcrystals 6 in 10 is quite small.
• the TEM photograph shown in FIG. 6 shows the matrix Si GeC crystal layer 7 within about 20 nm from the interface between the Si substrate 1 and the anneal SiGeC crystal layer 10. Only in the region of, defect 2 considered to be dislocation is seen. However, in the matrix SiGeC crystal layer 7, almost no defect is observed in a region 20 nm or more away from the interface between the Si substrate 1 and the anneal S106 crystal layer 10. In general, it is known that when a simple Si Ge crystal is deposited on a Si substrate and subjected to thermal annealing, large threading dislocations and the like are generated.
• Figure 7 is a transmission electron micrograph of the SiGe crystal formed on the substrate after thermal annealing, showing that threading dislocations have occurred in the SiGe layer after thermal annealing. I understand. On the other hand, such a defect is not generated at all in the wafer provided with the SiGeC layer manufactured according to the present embodiment.
• Fig. 4. 3 The result of X-ray diffraction measurement of the substrate after the thermal annealing process (see Fig. 3 (c)) is the upper spectrum in Fig. 4. 3 3.
• the peak appearing at 95 degrees corresponds to the diffraction peak due to the matrix S i G ⁇ C crystal layer 7.
• a detailed analysis using this peak angle and Vegard's law shows that relaxation occurs in the matrix SiGeC crystal layer 7, and the in-plane lattice spacing of the matrix SiGeC crystal layer 7 is 0 from lattice constant. It can be seen that this is about 6% larger, about 0.5494 nm.
• this value is a value of only the matrix SiGeC crystal layer 7 and not a lattice constant of the anneal SiGeC crystal layer 10 containing the SiC crystal.
• the volume ratio of the SiC crystal is quite small, it is considered to be equivalent to the lattice constant of the anneal SiGeC crystal layer 10.
• the structure of the present invention including the Si substrate and the SiGeC crystal layer in which the SiC crystal is dispersed functions as a buffer layer with few defects.
• the crystal structure defect is caused by the Si substrate 1 and the anneal Si GeC crystal layer 10 in the matrix SiGeC crystal layer ⁇ . Since it occurred only in a region within 20 nm from the interface of, it can be understood that a wafer having no defects such as threading dislocations can be manufactured using only a considerably thinner deposited layer than in this example.
• the surface of the substrate provided with the Si substrate 1, the anneal Si Ge C crystal layer 10 and the Si crystal layer 9 was moved to the step shown in FIG. Wash in the same way.
• a clean substrate surface is exposed.
• the temperature of the substrate to the 5 5 0 ° C, 1 5 minutes with a pressure of S i 2 H 6 gas 3. 2 x 1 0 one 2 P a (2. 4 xl O- 4 T orr)
• an Si crystal layer having a thickness of about 30 nm is epitaxially grown on the Si crystal layer 9.
• the Si crystal layer deposited here has a lattice
• the constant is larger than that of the Si substrate 1 and the strained Si crystal layer 4 has a strain.
• a semiconductor substrate having a strained Si crystal layer is manufactured by the above steps.
• a semiconductor device using a conventional Si crystal can be obtained.
• High-performance semiconductor devices can be manufactured.
• a field-effect transistor having a Si / SiGeC heterostructure in which a gate oxide film and a gate electrode are provided on the strained Si crystal layer 4 can be manufactured. You.
• the relaxation buffer layer is as thin as 130 nm, so that the time and cost required for manufacturing can be significantly reduced as compared with the conventional method. . This enables mass production of semiconductor wafers having the strained Si crystal layer 4.
• the Si Ge C crystal layer 8 is deposited on the Si substrate 1 and before the step of depositing the Si crystal layer, heating is performed. After the Si crystal layer is deposited on the crystal layer 8, thermal annealing may be performed. According to this method as well, it is possible to manufacture a semiconductor wafer provided with the strained Si crystal layer 4.
• FIG. 5 is a view showing a result of measuring an X-ray diffraction spectrum of the Si substrate 1 provided with the anneal S soil 06 ⁇ crystal layer 10 and the strained Si crystal layer 4. From this figure, it can be seen that the diffraction peak of Si substrate 1 at around 34.56 degrees and the diffraction beak of relaxed Si Ge C crystal (anneal Si Ge C crystal layer 10) at around 3.3.95 degrees. In addition, a weak broad peak is observed around 34.7 degrees. The peak around 34.7 degrees has an in-plane lattice constant larger than that of the Si substrate 1.
• the Si crystal layer is deposited on the aniline Si Ge C crystal layer 10. This is probably due to the fact that the layer was distorted by the tensile stress.
• a strained Si crystal can be produced by depositing a Si crystal on a SiGeC crystal layer in which a SiC crystal is dispersed.
• the present invention is used for an effect transistor having a Si / SiGeC heterostructure and a strained Si crystal.

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