CN102315246A - Relaxation SiGe virtual substrate and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of semiconductor materials, and relates to a relaxed SiGe dummy substrate with high germanium content and a preparation method thereof. The SiGe virtual substrate includes a Si substrate, a Ge seed layer epitaxially grown on the Si substrate from inside to outside, a Ge buffer layer, a SiGe buffer layer with a graded composition, and a SiGe layer with a constant composition; the Ge The seed layer and the Ge buffer layer constitute a Ge relaxation buffer layer. The SiGe virtual substrate has the characteristics of high Ge content, complete relaxation, low dislocation density, thin thickness, smooth surface and the like. The preparation method of the SiGe dummy substrate is to sequentially grow each epitaxial layer on the Si substrate by adopting a decompression chemical vapor deposition method. The relaxed SiGe virtual substrate with high germanium content prepared by the invention can be widely used in Ge channel strain engineering and high mobility channel material preparation in CMOS technology, and further improves the performance of CMOS devices.

Description

A relaxed SiGe virtual substrate and its preparation method

technical field

The invention belongs to the technical field of semiconductor materials, and relates to a high-quality relaxed SiGe dummy substrate with high germanium content and a preparation method thereof. the

Background technique

In the semiconductor industry, Si material has been developed as a dominant semiconductor device for nearly half a century. With the development of science and technology and people's pursuit of the performance of microelectronic devices, the feature size of semiconductor devices has been continuously reduced, and the size of a single transistor has gradually reached the dual limits of physics and technology. The performance of CMOS devices using traditional Si as the channel material It has been unable to meet the requirements of continuous improvement in the performance of semiconductor devices. People are stepping up the search for new methods and materials to maintain the pace of rapid growth of microelectronic devices. It is known that introducing strained Si or Ge into a CMOS device can significantly improve the performance of the device, because the carrier mobility of Si and Ge under strain can be significantly improved. Strained Si and strained Ge are considered to be the most promising channel materials. Due to the large lattice mismatch (4.2%) between Ge and Si, it is not possible to directly epitaxially grow Ge on Si wafers or directly grow Si epitaxially on Ge wafers to introduce strain as channel material, between them The lattice mismatch between them makes the epitaxial layer relax when it is very thin, resulting in defects and dislocations, which seriously reduce the mobility of carriers. Therefore, it is necessary to develop new technologies to obtain high-quality buffer layers suitable for channel materials on Si substrates. The development of virtual substrates is considered a very promising research project. The virtual substrate generally obtains a layer of high-quality film layer on the Si substrate through various methods, which is less different from the properties of the required channel material, as the substrate of the new material, and prepares a high-quality layer of channel material. If strained Si is used as the channel material, a SiGe virtual substrate with high quality and low germanium content is required; if strained Ge is introduced as the channel material, a SiGe virtual substrate with high quality and high germanium content is required. The traditional method of preparing a dummy substrate is mainly to obtain a dummy substrate by epitaxy of a SiGe layer with a gradient composition, which is feasible on a SiGe dummy substrate with a low germanium content, but if a dummy substrate with a high germanium content is prepared, it will be difficult A very thick SiGe composition graded layer is required. For example, the virtual substrate thickness of Si _1-x Ge _x (0.7≤x≤0.9) prepared by SiGe composition graded layer is more than 5 μm, and some even 10 μm, resulting in long processing time and high cost, and thicker SiGe The graded composition layer makes the surface of the virtual substrate have severe cross hatching (cross hatch), making the surface rougher, requiring chemical mechanical polishing (CMP) to obtain a relatively flat surface, which increases the complexity of the process. Therefore, obtaining high-quality thin SiGe virtual substrates with high germanium content is still a research hotspot with practical applications in the field of Si-based semiconductor material preparation.

Contents of the invention

The purpose of the present invention is to provide a SiGe virtual substrate with a relaxed high germanium content and a preparation method thereof, so as to overcome the shortcomings of the SiGe virtual substrate with a high germanium content prepared in the prior art such as large thickness, rough surface, and complicated process. . The present invention provides a high-quality SiGe dummy substrate prepared by reversely changing the Ge content in the SiGe composition. The dummy substrate has high Ge content, complete relaxation, low dislocation density, thin thickness, Features such as smooth surface. the

In order to solve the problems of the technologies described above, the technical scheme of the present invention is as follows:

A kind of relaxed SiGe dummy substrate, described SiGe dummy substrate comprises Si substrate, the Ge crystal seed layer that grows epitaxially from inside to outside on Si substrate successively, Ge buffer layer, the SiGe buffer layer of composition gradient and The SiGe layer with constant composition, the Ge seed layer and the Ge buffer layer constitute a Ge relaxation buffer layer. the

Each epitaxial growth layer on the Si substrate is a fully strain-relaxed buffer layer. the

The dislocations and defects in the relaxed SiGe dummy substrate with high germanium content are mainly concentrated in the SiGe buffer layer with a graded composition, and the SiGe layer with a constant composition has a lower dislocation and defect density (<10 ⁶ cm ^-2 ).

The mole percentage of germanium in the relaxed SiGe dummy substrate is Ge%≥70%, which is a SiGe dummy substrate with high germanium content. the

The average roughness of the relaxed SiGe dummy substrate is 1.3-1.9nm, which is lower than the requirement of the prior art technology level (<2.0nm). The dislocation density after etching the relaxed SiGe dummy substrate with high germanium content is on the order of 10 ⁶ cm ^-2 , which meets the requirements of the semiconductor device processing technology for the substrate.

The Si substrate in the SiGe virtual substrate adopts a Si wafer; the Si wafer is an industrial wafer of a standard size, and the size of the Si wafer is selected from 4 inches, 6 inches, 8 inches, 12 inches, etc. Dimensions. the

The Ge seed layer and the Ge buffer layer in the SiGe virtual substrate form a fully relaxed Ge relaxation buffer layer; the thickness of the Ge seed layer is 50-100nm, and the thickness of the Ge buffer layer is 300-600nm , the thickness of the whole Ge relaxation buffer layer is 350-700nm. the

The components in the SiGe buffer layer with gradual composition and the SiGe layer with constant composition are Si and Ge, and their respective contents are in mole percent. the

In the SiGe buffer layer with gradually changing composition, starting from the side adjacent to the Ge relaxation buffer layer and ending at the side adjacent to the SiGe layer with constant composition, the mole percentage of Ge gradually decreases from 100% to the composition The Ge mole percentage content in the constant SiGe layer is the same. In the SiGe buffer layer with graded composition, the mole percentage of Ge varies by 5% of the Ge content per 200-250 nm thickness. the

For example, the mole percentage of Ge in the SiGe buffer layer with a graded composition gradually changes from 100% to 95% and from 95% to 90% as the thickness of the SiGe buffer layer with a graded composition increases. By analogy, the Ge content is reduced by 5% every 200-250 nm thickness until it gradually becomes the same as the Ge content in the next SiGe layer with constant composition. the

The thickness of the SiGe layer with constant composition is 500-1000 nm, which can be adjusted according to the required thickness of the virtual substrate. the

A strained Ge channel layer can be epitaxially grown on the SiGe constant composition layer for use as a channel material in a CMOS device. the

A preparation method of a SiGe dummy substrate with a relaxed high germanium content, according to the composition of the SiGe dummy substrate with a relaxed high germanium content, the decompression chemical vapor deposition method is used on the Si substrate, with GeH ₄ and SiH ₂ Cl ₂ is used as the gas phase precursor, and H ₂ is used as the carrier gas to grow each epitaxial layer sequentially.

In the preparation method of the SiGe virtual substrate with high germanium content in the relaxation, the epitaxial growth of the Ge seed layer and the Ge buffer layer all use _GeH4 as a gas phase precursor, and the SiGe buffer layer with a gradual composition and a constant composition The epitaxial growth of the SiGe layer used GeH ₄ and SiH ₂ Cl ₂ as gas phase precursors.

The preparation method specifically includes the following steps:

1) Epitaxially growing a Ge seed layer on a Si substrate, the growth temperature of the Ge seed layer is 350-400° C., the growth chamber pressure is 50-150 Torr, and the growth thickness is 50-100 nm. the

The growth of the Ge seed layer uses GeH ₄ as a gas phase precursor, a flow rate of 100-200 sccm, and H ₂ as a carrier gas.

2) Epitaxially growing a Ge buffer layer on the grown Ge seed layer, the growth temperature of the Ge buffer layer is 650-700° C., the growth chamber pressure is 50-150 Torr, and the growth thickness is 300-600 nm. the

The growth of the Ge buffer layer uses GeH ₄ as a gas phase precursor, a flow rate of 100-200 sccm, and H ₂ as a carrier gas.

3) In-situ annealing in the growth chamber after the growth of the Ge buffer layer in step 2), the annealing temperature is 800-900° C. to obtain a fully relaxed Ge buffer layer. the

The thickness of the Ge relaxation buffer layer is 350-700nm, which can be adjusted according to the thickness requirements of the required virtual substrate;

The annealing time may be, for example, 10 minutes. the

4) Epitaxially growing a SiGe buffer layer with a graded composition on the grown Ge relaxation buffer layer, the epitaxial growth temperature is 800-900° C., and the growth chamber pressure is 20-100 Torr. the

The growth of the composition-graded SiGe buffer layer uses _H2 as the carrier gas and _GeH4 and _SiH2Cl2 as the gaseous precursors, and dynamically adjusts the gaseous precursors _GeH4 and _SiH2Cl during _the epitaxial growth process ₂ flow rate ratio to prepare.

5) Epitaxially grow a SiGe layer with a constant composition on the grown SiGe buffer layer with a gradient composition, the epitaxial growth temperature is 800-900°C, the growth chamber pressure is 20-100Torr, and the growth thickness is 500-1000nm . the

The SiGe layer with constant composition uses _H2 as carrier gas, _GeH4 and _SiH2Cl2 as gas phase precursors, the flow rate _{of GeH4} is _300-500sccm , and the flow rate of _SiH2Cl2 is 14-80sccm;

Wherein the flow rate of SiH ₂ Cl ₂ is preferably 14-62 sccm.

In the preparation method of the SiGe dummy substrate of relaxation high germanium content of the present invention, wherein said whole Ge relaxation buffer layer is the necessary condition for the SiGe buffer layer of epitaxial growth composition gradient, so obtaining Ge relaxation buffer layer is also One of the key factors affecting the quality of the virtual substrate. The epitaxial growth temperature of the Ge seed layer in the entire Ge relaxation buffer layer cannot be too low, otherwise polycrystalline growth will occur, and the thickness of the entire Ge relaxation buffer layer can be adjusted within a certain range according to the thickness requirements of the virtual substrate;

The SiGe buffer layer whose composition is gradually changed is the most critical part of the high-quality SiGe virtual substrate of the present invention. Every 200-250nm thickness changes 5% Ge content. Too fast or too slow Ge composition gradient rate has a great impact on the quality and total thickness of the virtual substrate. This buffer layer is to limit the dislocations and defects in the virtual substrate. Area;

The SiGe buffer layer with a constant composition is a fully relaxed buffer layer. Generally, a fully relaxed SiGe layer can be obtained by epitaxial growth at a high temperature. The epitaxial growth temperature is 800-900° C., and an annealing process is required for low temperature growth, and Growth rate is slow. the

The relaxed SiGe dummy substrate with high germanium content of the present invention is limited by introducing the Ge relaxation buffer layer composed of the Ge seed layer and the Ge buffer layer, and adopting the content of Ge in the SiGe buffer layer with reverse gradient composition. Dislocations and defects, especially suitable for preparing thin SiGe virtual substrates with high germanium content. Adopting the preparation method of the present invention can not only obtain the SiGe dummy substrate with thinner thickness and high germanium content, but also effectively reduce the surface roughness and dislocation density of the SiGe dummy substrate without additional processing technology, such as CMP, etc. shorten the epitaxy time and save costs. The high-quality SiGe virtual substrate prepared by the invention has the characteristics of high Ge content, complete relaxation, low dislocation density, thin thickness, flat surface, etc., and meets the application requirements of device-level strained Ge channel materials. the

Description of drawings

Fig. 1 is a schematic structural representation and a preparation flow chart of the high germanium content SiGe dummy substrate of the present invention

Fig. 2 High-resolution X-ray diffraction reciprocal space pattern of Si _0.2 Ge _0.8 virtual substrate c in Example 1

Figure 3 Transmission electron microscope (TEM) photograph of the cross-section of Si _0.2 Ge _0.8 virtual substrate c in Example 1

Surface atomic force microscope (AFM) photo of Si _0.2 Ge _0.8 virtual substrate c in Fig. 4 embodiment 1

Fig. 5 Optical microscope photo of Si _0.2 Ge _0.8 dummy substrate c etched in Example 1

Detailed ways

The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention. the

Example 1

The preparation process of a SiGe dummy substrate with high germanium content is shown in Figure 1. Taking the preparation of Si _0.2 Ge _0.8 dummy substrate as an example, it includes the following steps:

In step s100, four 4-inch, 6-inch, 8-inch and 12-inch Si wafers are respectively prepared as Si substrates. the

Step s101, growth of Ge relaxation buffer layer: based on 4-inch, 6-inch, 8-inch and 12-inch Si substrates, respectively, at 400 ° C with GeH ₄ as the gas phase precursor, the GeH ₄ flow rate is 150 sccm, and _H2 is the carrier gas, the pressure of the growth chamber is 100Torr, deposit a layer of Ge seed layer with a thickness of 50nm, 60nm, 100nm, and 100nm respectively; keep the growth atmosphere unchanged, and then deposit on the deposited four Ge seed layers Ge buffer layers with a thickness of 300nm, 340nm, 400nm and 600nm were deposited at 700°C, and annealed in situ (epitaxy growth chamber) at 850°C for 10 minutes after completion, and the growth chamber pressure was kept at 100 Torr during annealing to obtain four fully strained Relaxed Ge relaxation buffer layer. The four Ge relaxation buffer layers are respectively a Ge relaxation buffer layer with a thickness of 350 nm on a 4-inch Si substrate, marked as a1, a Ge relaxation buffer layer with a thickness of 400 nm on a 6-inch Si substrate, marked as b1, and an 8-inch Si substrate. The Ge relaxation buffer layer with a thickness of 500 nm is marked as c1 and the Ge relaxation buffer layer with a thickness of 700 nm on the 12-inch Si substrate is marked as d1.

Step s102, growth of SiGe buffer layer with graded composition: on the basis of the relaxed Ge buffer layers a1, b1, c1 and d1 obtained in step s101, respectively epitaxially grow SiGe buffer layers with graded composition, with _H2 as the carrier Gas, GeH ₄ and SiCl ₂ H ₂ are gaseous precursors, the growth temperature is 850°C, the growth chamber pressure is 20Torr, the change of Ge content in the SiGe buffer layer with gradual composition changes, by adjusting the flow rate of GeH ₄ and SiH ₂ Cl ₂ Ratio realizes the gradual change of SiGe composition, the flow rate of GeH ₄ is kept at 500 sccm, and the flow rate of SiCl ₂ H ₂ increases linearly with the growth time. The composition-graded SiGe buffer layer realizes the reduction of 5% Ge every 250nm thickness, until the content ratio of Ge and Si is gradually changed to 0.8:0.2, and the composition-graded Si _0.2 Ge _0.8 buffer layer a2 with a thickness of 1000nm is obtained respectively , b2, c2 and d2.

Step s103, growth of a SiGe layer with a constant composition: on the basis of the Si _0.2 Ge _0.8 buffer layers a2, b2, c2 and d2 obtained in step s102 with a gradient composition, GeH ₄ and SiCl ₂ H ₂ are used as gas phase precursors The GeH ₄ flow rate is 500 sccm, the SiCl ₂ H ₂ flow rate is 33 sccm, H ₂ is the carrier gas, the epitaxial growth temperature is 850 ° C, the growth chamber pressure is 20 Torr, and the growth thickness is 500 nm Si _0.2 Ge _0.8 layer with constant composition, Relaxed SiGe virtual substrates a, b, c and d with high germanium content were respectively obtained, and the total thickness of the epitaxial layer was detected to be 1850nm, 1900nm, 2000nm and 2200nm respectively.

The schematic diagram of the structure of the relaxed SiGe dummy substrate with high germanium content obtained in Example 1 is shown in FIG. A SiGe buffer layer with a graded composition and a SiGe layer with a constant composition, the Ge seed layer and the Ge buffer layer form a Ge relaxed buffer layer. the

Figure 2 is the high-resolution X-ray diffraction reciprocal space map of the Si _0.2 Ge _0.8 virtual substrate c obtained in Example 1. The layers of epitaxial growth have been marked in the figure, and it can be seen that the Ge seed layer and the Ge buffer layer have occurred Complete strain relaxation, the SiGe composition graded layer and the SiGe composition constant layer are also in a complete relaxation state.

Fig. 3 is the cross-sectional transmission electron microscope (TEM) photo of Si _0.2 Ge _0.8 dummy substrate c obtained in Example 1, as can be seen from the TEM photo in Fig. 3, each epitaxial layer of Si _0.2 Ge _0.8 dummy substrate c is total When the thickness is 2μm, the dislocations and defects are mainly concentrated in the Si _0-0.2 Ge _1-0.8 composition gradient layer with a thickness of 1μm, while there are no obvious dislocations and defects in the Si _0.2 Ge _0.8 constant composition layer. In addition, it should be noted that the upper part of the SiGe layer with a constant composition in Figure 3 is the colloid used to prepare the TEM sample, as a reference for the topmost layer.

Fig. 4 is the surface atomic force microscope (AFM) photo of the Si _0.2 Ge _0.8 virtual substrate c obtained in Example 1, as can be seen from the surface topography AFM photo, the average roughness of the Si _0.2 Ge _0.8 virtual substrate c It is 1.7±0.1nm, which is lower than the requirement of the prior art technology level (<2.0nm).

Figure 5 is the photomicrograph of the etched Si _0.2 Ge _0.8 dummy substrate c obtained in Example 1. The dislocation density of the Si _0.2 Ge _0.8 dummy substrate obtained after etching is 1×10 ⁶ cm ^-2 , to meet the requirements of the semiconductor device processing technology for the substrate.

Example 2

The preparation of a Si _0.15 Ge _0.85 dummy substrate with high germanium content comprises the following steps:

In step s100, an 8-inch Si wafer is prepared as a Si substrate. the

Step s101, growth of a Ge relaxation buffer layer: based on an 8-inch Si substrate, first use GeH ₄ as a gas phase precursor at 350°C, the flow rate of GeH ₄ is 200 sccm, and H ₂ is used as a carrier gas, and the growth chamber pressure is 100Torr, deposit a Ge seed layer with a thickness of 100nm; keep the growth atmosphere unchanged, then deposit a Ge buffer layer with a thickness of 400nm at 650°C on the deposited Ge seed layer, and in situ at 850°C ( (epitaxial growth chamber) annealing for 10 minutes, maintaining the pressure of the growth chamber at 100 Torr during annealing, and obtaining a Ge relaxation buffer layer with a thickness of 500 nm and complete strain relaxation.

Step s102, growth of a composition-graded SiGe buffer layer: on the basis of the relaxed Ge buffer layer obtained in step s101, epitaxially grow a composition-graded SiGe buffer layer, using H ₂ as a carrier gas, GeH ₄ and SiCl ₂ H ₂ It is a gas phase precursor, the growth temperature is 900°C, the growth chamber pressure is 20Torr, the SiGe buffer layer thickness increases with the composition gradient, and the SiGe composition gradient is realized by adjusting the flow ratio of GeH ₄ and SiH ₂ Cl _2. The flow rate of GeH ₄ Keeping at 500 sccm, the flow rate of SiCl ₂ H ₂ increases linearly with the growth time. The composition-graded SiGe buffer layer achieves a reduction of 5% Ge every 200 nm thickness until the content ratio of Ge and Si is 0.85:0.15, and a composition-graded Si _0.15 Ge _0.85 buffer layer with a thickness of 600 nm is obtained.

Step s103, growth of SiGe layer with constant composition: on the Si _0.15 Ge _0.85 buffer layer with gradual composition obtained in step s102, using GeH ₄ and SiCl ₂ H ₂ as gas phase precursors, GeH ₄ flow rate is 300 sccm, SiCl ₂ H ₂ flow rate is 18sccm, H ₂ is carrier gas, epitaxial growth temperature is 800°C, growth chamber pressure is 50Torr, and a Si _0.15 Ge _0.85 layer with constant composition is grown with a thickness of 500nm to obtain a SiGe virtual substrate with a relaxed high germanium content At the bottom, the total thickness of the epitaxial layer was detected to be 1600nm.

After testing, the obtained relaxed SiGe virtual substrate with high germanium content is based on the Si substrate, including a Ge relaxation buffer layer epitaxially grown from the inside out, a SiGe buffer layer with a gradient composition, and a SiGe buffer layer with a constant composition. layer, the Ge relaxation buffer layer includes a Ge seed layer and a Ge buffer layer from inside to outside. the

After testing, the high-resolution X-ray diffraction reciprocal space spectrum of the Si _0.15 Ge _0.85 virtual substrate obtained in Example 2 shows that complete strain relaxation has taken place in the Ge crystal seed layer and the Ge buffer layer, and the SiGe composition graded layer and SiGe The composition constant layer is also in a fully relaxed state.

After testing, the Si _0.15 Ge _0.85 virtual substrate cross-sectional transmission electron microscope (TEM) photos obtained in Example 2 show that the total thickness of each epitaxial layer of the Si _0.15 Ge _0.85 virtual substrate is 1.6 μm, and the dislocations and defects are mainly Concentrated on the Si _0-0.15 Ge _1-0.85 composition graded layer with a thickness of 0.6 μm, it effectively reduces the dislocation and defect density in the Si _0.15 Ge _0.85 constant composition layer, and the TEM photo shows that the Si _0.15 Ge _0.85 composition constant layer There are no obvious dislocations and defects.

After testing, the surface atomic force microscope (AFM) photo of the Si _0.15 Ge _0.85 virtual substrate obtained in embodiment 2, as can be seen from the surface topography atomic force photo, the average roughness of this Si _0.15 Ge _0.85 virtual substrate is 1.5 ±0.1nm, which is lower than the requirement of the prior art technology level (<2.0nm).

After testing, the optical microscope photo of the etched Si _0.15 Ge _0.85 dummy substrate obtained in Example 2 shows that the dislocation density of the Si _0.15 Ge _0.85 dummy substrate obtained after etching is 6×10 ⁶ cm ^-2 , It meets the requirements of the semiconductor device processing technology for the substrate.

Example 3

The preparation of a Si _0.1 Ge _0.9 dummy substrate with high germanium content comprises the following steps:

In step s100, a 6-inch Si wafer is prepared as a Si substrate. the

Step s101, growth of the Ge relaxation buffer layer: based on a 6-inch Si substrate, first use GeH ₄ as the gas phase precursor at 400°C, the flow rate of GeH ₄ is 100 sccm, H ₂ is used as the carrier gas, and the growth chamber pressure is 50Torr, deposit a Ge seed layer with a thickness of 100nm; keep the growth atmosphere unchanged, then deposit a Ge buffer layer with a thickness of 500nm at 650°C on the deposited Ge seed layer, and in situ at 800°C ( epitaxial growth chamber) annealed for 10 minutes, and kept the growth chamber pressure at 100 Torr during annealing to obtain a Ge relaxation buffer layer with a thickness of 600 nm and complete strain relaxation.

Step s102, growth of a composition-graded SiGe buffer layer: on the basis of the relaxed Ge buffer layer obtained in step s101, epitaxially grow a composition-graded SiGe buffer layer, using H ₂ as a carrier gas, GeH ₄ and SiCl ₂ H ₂ It is a gaseous precursor, the growth temperature is 800°C, the pressure of the growth chamber is 100Torr, the SiGe buffer layer thickness increases with the composition gradient, and the SiGe composition gradient is realized by adjusting the flow ratio of GeH ₄ and SiH ₂ Cl _2. The flow rate of GeH ₄ Keeping at 300 sccm, the flow rate of SiCl ₂ H ₂ increases linearly with the growth time. The composition-graded SiGe buffer layer achieves a reduction of 5% Ge every 250 nm thickness until the content ratio of Ge and Si is 0.9:0.1, and a composition-graded Si _0.1 Ge _0.9 buffer layer with a thickness of 500 nm is obtained.

Step s103, growth of SiGe layer with constant composition: on the Si _0.1 Ge _0.9 buffer layer with gradual composition obtained in step s102, using GeH ₄ and SiCl ₂ H ₂ as gas phase precursors, GeH ₄ flow rate is 500 sccm, SiCl ₂ The flow rate of H ₂ is 14sccm, H ₂ is the carrier gas, the epitaxial growth temperature is 900°C, the pressure of the growth chamber is 100Torr, and a Si _0.1 Ge _0.9 layer with a constant composition is grown with a thickness of 1000nm to obtain a relaxed SiGe dummy substrate with high germanium content. At the bottom, the total thickness of the epitaxial layer was detected to be 2100nm.

After testing, the obtained relaxed SiGe virtual substrate with high germanium content is based on the Si substrate, including a Ge relaxation buffer layer epitaxially grown from the inside out, a SiGe buffer layer with a gradient composition, and a SiGe buffer layer with a constant composition. layer, the Ge relaxation buffer layer includes a Ge seed layer and a Ge buffer layer from the inside out. the

After testing, the high-resolution X-ray diffraction reciprocal space map of the Si _0.1 Ge _0.9 virtual substrate obtained in Example 3 shows that the Ge crystal seed layer and the Ge buffer layer have undergone complete strain relaxation, and the SiGe composition graded layer and SiGe The composition constant layer is also in a fully relaxed state.

After testing, the Si _0.1 Ge _0.9 virtual substrate cross-sectional transmission electron microscope (TEM) photo obtained in Example 3 shows that the total thickness of each epitaxial layer of the Si _0.1 Ge _0.9 virtual substrate is 2.1 μm, and the dislocations and defects are mainly Concentrated on the Si _0-0.1 Ge _1-0.9 composition graded layer with a thickness of 0.5 μm, effectively reducing the dislocation and defect density in the Si _0.1 Ge _0.9 constant composition layer, TEM photos show that the Si _0.1 Ge _0.9 constant composition layer There are no obvious dislocations and defects.

After testing, the surface atomic force microscope (AFM) photo of the Si _0.1 Ge _0.9 virtual substrate obtained in Example 3 can be seen from the surface topography AFM photo, and the average roughness of the Si _0.1 Ge _0.9 virtual substrate is 1.4 ±0.1nm, which is lower than the requirement of the prior art technology level (<2.0nm).

After testing, the optical microscope photo of the etched Si _0.1 Ge _0.9 virtual substrate obtained in Example 3 shows that the dislocation density of the Si _0.1 Ge _0.9 virtual substrate obtained after etching is 8.5×10 ⁶ cm ^-2 , It meets the requirements of the semiconductor device processing technology for the substrate.

Example 4

The preparation of a Si _0.25 Ge _0.75 dummy substrate with high germanium content comprises the following steps:

In step s100, a 12-inch Si wafer is prepared as a Si substrate. the

Step s101, growth of the Ge relaxation buffer layer: based on a 12-inch Si substrate, first use GeH ₄ as a gas phase precursor at 400°C, the flow rate of GeH ₄ is 150 sccm, H ₂ is used as a carrier gas, and the growth chamber pressure is 150Torr, deposit a Ge seed layer with a thickness of 100nm; keep the growth atmosphere unchanged, then deposit a Ge buffer layer with a thickness of 400nm at 700°C on the deposited Ge seed layer, and in situ at 900°C ( (epitaxial growth chamber) annealing for 10 minutes, maintaining the pressure of the growth chamber at 100 Torr during annealing, and obtaining a Ge relaxation buffer layer with a thickness of 500 nm and complete strain relaxation.

Step s102, growth of a composition-graded SiGe buffer layer: on the basis of the relaxed Ge buffer layer obtained in step s101, epitaxially grow a composition-graded SiGe buffer layer, using H ₂ as a carrier gas, GeH ₄ and SiCl ₂ H ₂ It is a gas phase precursor, the growth temperature is 850°C, the growth chamber pressure is 50Torr, the SiGe buffer layer thickness increases with the composition gradient, and the SiGe composition gradient is realized by adjusting the flow ratio of GeH ₄ and SiH ₂ Cl _2. The flow rate of GeH ₄ Keeping at 500 sccm, the flow rate of SiCl ₂ H ₂ increases linearly with the growth time. The composition-graded SiGe buffer layer achieves a reduction of 5% Ge every 200nm thickness until the content ratio of Ge and Si is 0.75:0.25, and a composition-graded Si _0.25 Ge _0.75 buffer layer with a thickness of 1000nm is obtained.

Step s103, growth of SiGe layer with constant composition: on the Si _0.25 Ge _0.75 buffer layer with gradual composition obtained in step s102, using GeH ₄ and SiCl ₂ H ₂ as gas phase precursors, GeH ₄ flow rate is 400 sccm, SiCl ₂ The flow rate of H ₂ is 62 sccm, H ₂ is the carrier gas, the epitaxial growth temperature is 850°C, the growth chamber pressure is 20Torr, and a Si _0.25 Ge _0.75 layer with constant composition is grown with a thickness of 500nm to obtain a SiGe dummy substrate with a relaxed high germanium content. At the bottom, the total thickness of the epitaxial layer was detected to be 2000nm.

After testing, the obtained relaxed SiGe virtual substrate with high germanium content is based on the Si substrate, including a Ge relaxation buffer layer epitaxially grown from the inside out, a SiGe buffer layer with a gradient composition, and a SiGe buffer layer with a constant composition. layer, the Ge relaxation buffer layer includes a Ge seed layer and a Ge buffer layer from inside to outside. the

After testing, the Si _0.25 Ge _0.75 virtual substrate high-resolution X-ray diffraction reciprocal space pattern obtained in embodiment 4 shows that complete strain relaxation has taken place in the Ge crystal seed layer and the Ge buffer layer, and the SiGe composition graded layer and SiGe The composition constant layer is also in a fully relaxed state.

After testing, the Si _0.25 Ge _0.75 virtual substrate cross-sectional transmission electron microscope (TEM) photo obtained in Example 4 shows that the total thickness of each epitaxial layer of the Si _0.25 Ge _0.75 virtual substrate is 2 μm, and dislocations and defects are mainly concentrated In the Si _0-0.25 Ge _1-0.75 composition gradient layer with a thickness of 1 μm, the dislocation and defect density in the Si _0.25 Ge _0.75 constant composition layer are effectively reduced, and the TEM photos show that the Si _0.25 Ge _0.75 constant composition layer is No obvious dislocations and defects.

After testing, the surface atomic force microscope (AFM) photo of the Si _0.25 Ge _0.75 dummy substrate obtained in Example 4, as can be seen from the surface topography AFM photo, the average roughness of the Si _0.25 Ge _0.75 dummy substrate is 1.8 ±0.1nm, which is lower than the requirement of the prior art technology level (<2.0nm).

After testing, the optical microscope photo of the etched Si _0.25 Ge _0.75 dummy substrate obtained in Example 4 shows that the dislocation density of the Si _0.25 Ge _0.75 dummy substrate obtained after etching is 1.5×10 ⁶ cm ^-2 , It meets the requirements of the semiconductor device processing technology for the substrate.

Claims (9)

1. A relaxed SiGe dummy substrate, said SiGe dummy substrate comprising Si substrate, a Ge crystal seed layer, a Ge buffer layer, and a gradually changing SiGe buffer layer on the Si substrate from the inside to the outside. SiGe layer with constant layer and composition; the Ge seed layer and the Ge buffer layer constitute a Ge relaxation buffer layer. 2. relaxation SiGe dummy substrate as claimed in claim 1, is characterized in that: described Ge crystal seed layer, Ge buffer layer, the SiGe buffer layer of composition gradient and the constant SiGe layer of composition are all strained Relaxed buffer layer. 3. The relaxed SiGe virtual substrate according to claim 1, characterized in that: the thickness of the Ge seed layer is 50-100nm, the thickness of the Ge buffer layer is 300-600nm; the composition is constant The thickness of the SiGe layer is 500-1000nm. 4. The relaxed SiGe dummy substrate as claimed in claim 1, characterized in that: in the SiGe buffer layer with gradually changing composition, the side adjacent to the Ge relaxed buffer layer is the starting point, and the SiGe buffer layer adjacent to the constant composition is used as the starting point. The side of the layer is the endpoint, and the Ge mole percent gradually decreases from 100% to the same Ge mole percent as in a constant composition SiGe layer. 5. The relaxed SiGe dummy substrate according to claim 4, characterized in that: in the SiGe buffer layer with graded composition, the mole percentage of Ge varies by 5% per thickness of 200-250 nm. 6. The application of the relaxed SiGe dummy substrate according to any one of claims 1-5 in Ge channel strain engineering and high mobility channel material in CMOS process. 7. A method for preparing the relaxed SiGe dummy substrate according to any one of claims 1-5, characterized in that, adopting decompression chemical vapor deposition with GeH ₄ and SiH ₂ Cl ₂ are gas phase precursors, with _H2 is the carrier gas to grow each epitaxial layer sequentially on the Si substrate, specifically including the following steps: 1) Epitaxial growth of a Ge seed layer on a Si substrate; 2) epitaxially growing a Ge buffer layer on the grown Ge seed layer; 3) In-situ annealing in the growth chamber after the growth of the Ge buffer layer in step 2), the annealing temperature is 800-900°C, to obtain a fully relaxed Ge relaxation buffer layer; 4) epitaxially growing a SiGe buffer layer with a graded composition on the Ge relaxation buffer layer grown in step 3); 5) epitaxially growing a SiGe layer with a constant composition on the SiGe buffer layer with a graded composition grown in step 4). 8. the preparation method of relaxation SiGe dummy substrate as claimed in claim 7, is characterized in that: In the step 1) the growth temperature of the Ge seed layer is 350-400° C., the growth chamber pressure is 50-150 Torr, and the growth of the Ge seed layer uses GeH ₄ as a gas phase precursor; In the step 2) the growth temperature of the Ge buffer layer is 650-700° C., the growth chamber pressure is 50-150 Torr, and the growth of the Ge buffer layer uses GeH ₄ as a gas phase precursor; In the step 4) the epitaxial growth temperature of the SiGe buffer layer with gradually changing composition is 800-900° C., the growth chamber pressure is 20-100 Torr, and GeH ₄ and SiH ₂ Cl ₂ are used as gas phase precursors; Step 5) SiGe layer with constant composition, the epitaxial growth temperature is 800-900° C., the growth chamber pressure is 20-100 Torr, and GeH ₄ and SiH ₂ Cl ₂ are used as gas phase precursors. 9. The method for preparing a relaxed SiGe dummy substrate as claimed in claim 7 or 8, characterized in that, in said step 4), the SiGe buffer layer with gradually changing composition is dynamically adjusted in the epitaxial growth process by said gas phase Precursor GeH ₄ and SiH ₂ Cl ₂ flow rate ratio to prepare.

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