JP2006086179A - Distorted silicon wafer and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a distorted silicon wafer with an SiGe layer where a through-dislocation density is reduced and a distortion is relaxed, and a manufacturing method for the distorted silicon wafer. <P>SOLUTION: The distorted silicon wafer has an epitaxial SiGe layer having lattice mismatching properties, a nitride-film layer having a nitrogen concentration of 1×10<SP>19</SP>atoms/cc or more, and a distorted Si layer on a single-crystal silicon substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a strained silicon wafer and a method for manufacturing the same, and more particularly to a strained silicon wafer having a threading dislocation density reduced as compared with the conventional method and a method for manufacturing the same.

  In recent years, there has been an increasing demand for high-speed and low-power consumption semiconductor devices. However, significant scale reduction of devices, that is, further improvement of device performance due to drastic reduction of element dimensions and miniaturization is the limit. Is beginning to be visible.

  For this reason, a semiconductor substrate having a strained silicon layer has attracted attention as a substrate for forming a semiconductor device with high speed and low power consumption. In particular, high-speed devices using a strained silicon layer (hereinafter referred to as a strained Si layer) obtained by epitaxially growing silicon on a single crystal silicon substrate via a silicon-germanium layer (hereinafter referred to as a SiGe layer) are attracting attention. Has been.

  This strained Si layer is tensilely strained by the SiGe layer having a larger lattice constant than silicon. This strain changes the band structure of Si, degenerates and increases the carrier mobility.

  Therefore, by using this strained Si layer for the channel region, it is possible to increase the carrier speed by 1.5 times or more when using bulk silicon.

  In order to obtain a high-quality strained Si layer, it is necessary to epitaxially grow a high-quality SiGe layer on a silicon substrate, that is, a SiGe layer having a smooth surface with threading dislocations and defect density reduced and relaxed.

  However, since there is a difference of about 4.2% in lattice constant between Si and Ge, when the epitaxial growth is performed as it is in the normal state, of course, the Si surface is oxidized before the epitaxial growth and further annealed at a high temperature. However, threading dislocations and stacking faults frequently occur during epitaxial growth, and it is difficult to obtain a good epitaxial growth film.

  Attempts have also been made to improve this problem. For example, epitaxial growth is performed with a Ge concentration gradient in the thickness direction of the SiGe layer, and the strain due to the difference in lattice constant is reduced within the allowable limit of dislocation generation. Has been proposed.

  Further, as a proposal from a similar idea, an invention is disclosed in which SiGe layers are formed in multiple stages, the Ge concentration of each stage layer is changed stepwise, and the occurrence of dislocations due to lattice mismatch is suppressed (for example, Patent Documents 1 and 2).

However, these proposals have not been able to suppress the occurrence of threading dislocations to the extent that they are sufficiently satisfied. Further, the thickness of the SiGe layer formed to avoid the occurrence of threading dislocations reached several μm, and the production efficiency was poor.
JP 2003-78116 A (page 5, column 7) JP 2003-78118 A (page 4, column 5, line 20 to column 6, line 28)

  As described above, in the conventional technique, misfit dislocations are generated from the interface with the silicon substrate even when the SiGe layer is epitaxially grown by increasing the Ge concentration on the surface of the silicon substrate. The threading dislocations resulting from the misfit dislocations reach the surface of the strained Si layer at a high density and exist. The presence of threading dislocations in the strained Si layer is a major cause of an increase in junction leakage current during device element molding.

  Further, the threading dislocations and the residual strain energy cause the formation of cross-hatch pattern irregularities, and the problem arises that the surface roughness Rms of the strained Si layer to be grown thereon increases.

  Therefore, the emergence of an effective means for preventing the generation and elongation of threading dislocation density during epitaxial growth of the composition gradient SiGe layer is strongly demanded.

  Therefore, the present inventors have found that the presence of nitrogen captures threading dislocations and hinders movement, resulting in a decrease in dislocation density on the surface of the strained Si layer.

  That is, the present invention has been made in view of the above circumstances, and an object thereof is to provide a strained silicon wafer having a threading dislocation density lower than the conventional one and a method for manufacturing the same.

In order to achieve the above object, a strained silicon wafer according to the present invention includes an epitaxial SiGe layer having lattice mismatch on a single crystal silicon substrate, a nitride film layer having a nitrogen concentration of 1 × 10 ¹⁹ atoms / cc or more, and And a strained Si layer.

Further, in the strained silicon wafer according to the present invention, the lattice-mismatched epitaxial SiGe layer includes a compositionally graded Si _1-x Ge _x layer epitaxially grown by sequentially increasing the Ge concentration on the single crystal silicon substrate, and a residual strain. Strain relaxed Si _1-x Ge _x layer epitaxially grown on a compositionally-graded Si _1-x Ge _x layer and strained Si layer epitaxially grown on the strain relaxed Si _1-x Ge _x layer It is characterized by being.

Furthermore, according to one aspect of the present invention, a composition-graded Si _1-x Ge _x layer is epitaxially grown on a single crystal silicon substrate by sequentially increasing the Ge concentration, and the composition-graded Si _1-x Ge _x layer is formed on the composition-graded Si _1-x Ge _x layer. least nitrogen to form a nitride layer in a high-temperature gas atmosphere at above about 800 ° C. containing, a strain-relaxed Si _1-x Ge _x layer on the nitride layer is epitaxially grown, the strain relaxed Si _1-x Ge _x layer There is provided a method for producing a strained silicon wafer, wherein a strained Si layer is formed thereon.

Further, according to another aspect of the present invention, a composition gradient Si _1-x Ge _x layer is epitaxially grown on a single crystal silicon substrate by sequentially increasing a Ge concentration, and the composition gradient Si _1-x Ge _x layer is formed. A strain-relaxed Si _1-x Ge _x layer is epitaxially grown thereon, and a nitride film layer is formed on the strain-relaxed Si _1-x Ge _x layer in a high-temperature gas atmosphere of at least about 800 ° C. containing nitrogen. A strained silicon wafer manufacturing method is provided, wherein a strained Si layer is formed on a nitride film layer.

  Further, according to another aspect of the present invention, a lattice mismatched SiGe layer is epitaxially grown on a single crystal silicon substrate, and a first strained Si layer is formed on the lattice mismatched SiGe layer. Is epitaxially grown, and a nitride film layer is formed on the first strained Si layer in a high-temperature gas atmosphere at least about 800 ° C. containing nitrogen, and a second strained Si layer is formed on the nitride film layer. A method of manufacturing a strained silicon wafer is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the distortion silicon wafer with few unevenness | corrugations on the surface by the reduced threading dislocation density, and its manufacturing method can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a strained silicon wafer according to an embodiment of the present invention.

In the embodiment of the present invention, for example, a compositionally graded SiGe layer 2 with a gradually increasing Ge concentration is formed on a single crystal silicon substrate 1 whose surface is mirror-polished. This composition gradient SiGe layer 2 has a Ge concentration increased from 0% to 30%, for example. For example, the Ge concentration gradient is preferably set to 20% / μm or less. A nitride film layer 3 is formed on the composition gradient SiGe layer 2. For example, the nitrogen concentration of the nitride film layer 3 is preferably 1 × 10 ¹⁹ atoms / cc or more. A strain relaxation Si ₇₀ Ge ₃₀ layer 4 is epitaxially grown on the nitride film layer 3. The SiGe layers 2 and 4 have lattice mismatch. Further, a strained Si layer 5 is formed on the strain relaxation SiGe layer 4.

  According to the silicon wafer according to the present embodiment, the composition is obtained by interposing the nitride film layer 3 between the composition-graded SiGe layer 2 in which the Ge concentration is sequentially increased and the relaxed SiGe layer 4 in the final composition having the Ge concentration. Since the threading dislocation generated in the tilted SiGe layer 2 is captured by the nitrogen immediately above the threading dislocation, the threading dislocation that should originally extend further does not reach the relaxed SiGe layer 4 and the strained Si layer 5.

Next, another embodiment of the present invention will be described. FIG. 2 is a schematic cross-sectional view of a strained silicon wafer according to an embodiment of the present invention. As shown in FIG. 2, for example, a composition gradient SiGe layer 12 with a gradually increasing Ge concentration is formed on a single crystal silicon substrate 11 whose surface is mirror-polished. This composition gradient SiGe layer 12 has a Ge concentration increased from 0% to 30%, for example. For example, the Ge concentration gradient is preferably set to 20% / μm or less. A strain relaxation Si ₇₀ Ge ₃₀ layer 13 is epitaxially grown on the composition gradient SiGe layer 12. The SiGe layers 12 and 13 have lattice mismatch. Further, a nitride film layer 14 is formed on the strain relaxation Si ₇₀ Ge ₃₀ layer 13. For example, the nitrogen concentration of the nitride film layer 14 is preferably 1 × 10 ¹⁹ atoms / cc or more. A strained Si layer 15 is formed on the nitride film layer 14. In the silicon wafer according to the present embodiment, since the nitride film layer 14 is present at the interface between the strained Si layer 15 and the strain relaxation Si ₇₀ Ge ₃₀ layer 13, the single crystal silicon substrate 11 and the composition gradient SiGe layer 12 are formed. Misfoot dislocations and threading dislocations generated and extended from the interface are suppressed.

Next, another embodiment of the present invention will be described. FIG. 3 is a schematic cross-sectional view of a strained silicon wafer according to an embodiment of the present invention. As shown in FIG. 3, for example, a Si ₈₀ Ge ₂₀ layer 22 having a Ge concentration of 20% is formed on a single crystal silicon substrate 21 whose surface is mirror-polished. A first strained Si layer 23 is epitaxially grown on the lattice mismatched Si ₈₀ Ge ₂₀ layer 22. A nitride film layer 24 is formed on the first strained Si layer 23. For example, the nitrogen concentration of the nitride film layer 24 is preferably 1 × 10 ¹⁹ atoms / cc or more. Further, a second strained Si layer 25 is formed on the nitride film layer 24. According to the silicon wafer according to the present embodiment, threading dislocations generated at the interface between the Si ₈₀ Ge ₂₀ layer 22 and the first strained Si layer 23 are trapped by the nitrogen immediately above, so that if it is originally, further above The threading dislocation to be extended does not reach the second strained Si layer 25.

  Next, an outline of a method for producing the above-described strained silicon wafer will be described.

  First, the epitaxial growth of the SiGe layers 2 and 4 formed on the mirror-polished silicon substrate 1 is performed by, for example, a CVD method using lamp heating or a CVD method (UHV-CVD) in an ultrahigh vacuum. It can be performed by a phase epitaxial growth method, a molecular beam epitaxial growth method (MBE), or the like.

  The growth conditions are appropriately set depending on the Si: Ge composition ratio and film thickness of the SiGe layer to be grown, depending on the growth method and apparatus used.

  For example, an example in the case of a CVD method by lamp heating is as follows when the composition is Ge = 0.3.

Carrier gas: H ₂ , source gas: SiH ₄ , GeH ₄ , chamber pressure: 10-100 Torr, temperature: 650-680 ° C., growth rate 10-50 nm / min.

  The nitride film layer 3 is formed on the surface portion of the composition gradient SiGe layer 2 by high-temperature heat treatment at 800 ° C. or higher with a gas containing nitrogen. A relaxed SiGe layer 4 is formed thereon.

  On the surface of the SiGe layer thus obtained, the single crystal Si layer 5 is grown by, for example, the CVD method. The formed single crystal Si layer 5 becomes a strained Si layer 5 because the lattice constant is different from that of the underlying SiGe layer. Since this strained Si layer becomes a device active region, it is preferably formed to a thickness of 5 to 30 nm, for example.

  Furthermore, an example of the growth conditions of single crystal Si by the CVD method is as follows.

Carrier gas: H ₂ , source gas: SiH ₂ Cl ₂ or SiH ₄ , chamber pressure: 10 to 760 Torr, temperature: 650 to 1000 ° C.

"Example 1"
A compositionally-graded Si ₈₀ Ge ₂₀ layer having a Ge concentration increased from 0% to 20% was epitaxially grown to a thickness of 500 nm at a film forming temperature of 900 ° C. on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, a silicon nitride film (Si ₃ N ₄ ) layer was grown on the composition graded Si ₈₀ Ge ₂₀ layer by a CVD method at a generation temperature of 1000 ° C. to a thickness of 2 nm. Further, a relaxed Si ₈₀ Ge ₂₀ layer was epitaxially grown on the silicon nitride film layer at a film forming temperature of 900 ° C. to a thickness of 200 nm. Finally, a strained Si layer was grown at a production temperature of 700 ° C. to a thickness of 10 nm.

"Example 2"
A compositionally-graded Si ₈₀ Ge ₂₀ layer having a Ge concentration increased from 0% to 20% was epitaxially grown to a thickness of 500 nm at a film forming temperature of 900 ° C. on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, high-temperature heat treatment at 1200 ° C. was performed on the composition-gradient Si ₈₀ Ge ₂₀ layer with a gas containing 95% argon gas and 5% nitrogen gas to diffuse nitrogen on the surface of the SiGe layer. Further, a relaxed Si ₈₀ Ge ₂₀ layer was epitaxially grown on the silicon nitride film layer at a film forming temperature of 900 ° C. to a thickness of 200 nm. Finally, a strained Si layer was grown at a production temperature of 700 ° C. to a thickness of 10 nm.

"Example 3"
A compositionally graded Si ₇₀ Ge ₃₀ layer having a Ge concentration increased from 0% to 30% was epitaxially grown to a thickness of 2 μm at a film forming temperature of 900 ° C. on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, a relaxed Si ₇₀ Ge ₃₀ layer was epitaxially grown on the composition gradient SiGe layer to a thickness of 1 μm at a film forming temperature of 900 ° C. Further, nitrogen gas was diffused on the relaxed SiGe layer for 10 seconds. Finally, a strained Si layer was grown at a production temperature of 700 ° C. to a thickness of 20 nm.

Example 4
A Si ₈₀ Ge ₂₀ layer having a Ge concentration of 20% was epitaxially grown at a film forming temperature of 900 ° C. to a thickness of 500 nm on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, a first strained Si layer is epitaxially grown on the SiGe layer to a thickness of 10 nm at a film formation temperature of 700 ° C., and a silicon nitride film is formed thereon to a thickness of 2 nm at a film formation temperature of 1000 ° C. by CVD. did. Further, a second strained Si layer was grown on the silicon nitride film at a generation temperature of 700 ° C. to a thickness of 10 nm.

"Example 5"
A Si ₈₀ Ge ₂₀ layer having a Ge concentration of 20% was epitaxially grown at a film forming temperature of 900 ° C. to a thickness of 500 nm on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, a first strained Si layer is epitaxially grown on the SiGe layer to a thickness of 5 nm at a film forming temperature of 700 ° C., and then subjected to a high temperature heat treatment at 1200 ° C. with a gas containing 95% argon gas and 5% nitrogen gas. Nitrogen was diffused on the surface of the SiGe layer. Further, a second strained Si layer was grown on the nitride film at a generation temperature of 700 ° C. to a thickness of 10 nm.

“Comparative Example 1”
A compositionally-graded Si ₈₀ Ge ₂₀ layer having a Ge concentration increased from 0% to 20% was epitaxially grown to a thickness of 500 nm at a film forming temperature of 900 ° C. on the surface of a single crystal silicon substrate whose surface was mirror-polished. Further, a relaxed Si ₈₀ Ge ₂₀ layer was epitaxially grown to a thickness of 200 nm at a film forming temperature of 900 ° C. Finally, a strained Si layer was grown at a production temperature of 700 ° C. to a thickness of 10 nm.

Table 1 shows the threading dislocation density of each of the wafers of Examples 1 to 5 and Comparative Example 1 using the Secco solution.

As is apparent from Table 1, the threading dislocation concentration existing on the strained silicon wafer surface is less than 10 ³ / cm ² when the nitride film is present, and the threading dislocation concentration is as high as 10 ⁵ / cm when the nitride film is not present. End up.

FIG. 4 shows the relationship between the nitrogen concentration and the threading dislocation density of the strained Si layer. As apparent from FIG. 4, when the nitrogen concentration is 1 × 10 ¹⁹ atoms / cc or more, the threading dislocation density tends to be as low as less than 10 ³ / cm ² , while the nitrogen concentration is 1 × 10 ¹⁸ atoms / cc. In the following, it can be seen that the threading dislocation density tends to increase.

  As described above in detail, the strained silicon wafer according to the present invention has a very low dislocation density such as threading dislocations in the strain relaxation layer and is sufficiently strain relaxed, so that the strained silicon layer formed thereon is of good quality. is there.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment.

1 is a schematic cross-sectional view of a strained silicon substrate wafer according to an embodiment of the present invention. It is a schematic sectional drawing of the distortion | strained silicon wafer which concerns on another embodiment of this invention. It is a schematic sectional drawing of the distortion | strained silicon wafer which concerns on another embodiment of this invention. It is a diagram which shows the relationship between a nitrogen concentration and the threading dislocation density of a strained Si layer.

Explanation of symbols

1, 11, 21: single crystal silicon substrate, 2, 12: composition gradient SiGe layer,
3, 14, 24: nitride film layer, 4, 13: relaxed SiGe layer,
5, 15, 23, 25: strained Si layer.

Claims (4)

An epitaxial SiGe layer having lattice mismatch on a single crystal silicon substrate;
A nitride film layer having a nitrogen concentration of 1 × 10 ¹⁹ atoms / cc or more;
A strained silicon wafer comprising a strained Si layer. A compositionally graded Si _1-x Ge _x layer is epitaxially grown on a single crystal silicon substrate by sequentially increasing the Ge concentration, and a high-temperature gas at least about 800 ° C. containing at least nitrogen on the composition graded Si _1-x Ge _x layer. characterized in that to form a nitride layer in an atmosphere, by epitaxially growing a strained relaxed Si _1-x Ge _x layer on the nitride layer, forming a strained Si layer on the strained relaxed Si _1-x Ge _x layer A method for producing a strained silicon wafer. A compositionally graded Si _1-x Ge _x layer is epitaxially grown on a single crystal silicon substrate by sequentially increasing the Ge concentration, and a strain-relaxed Si _1-x Ge _x layer is epitaxially grown on the composition graded Si _1-x Ge _x layer. Forming a nitride film layer on the strain-relaxed Si _1-x Ge _x layer in a high-temperature gas atmosphere containing at least nitrogen and at least about 800 ° C., and forming a strained Si layer on the nitride film layer A method for producing a strained silicon wafer characterized by   A lattice mismatched SiGe layer is epitaxially grown on the single crystal silicon substrate, and a first strained Si layer is epitaxially grown on the lattice mismatched SiGe layer. A method for producing a strained silicon wafer comprising: forming a nitride film layer in a high-temperature gas atmosphere containing at least nitrogen containing at least about 800 ° C .; and forming a second strained Si layer on the nitride film layer.

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