Preparation method of GeSn and GePb semiconductor single crystal nanodots

Abstract

The invention discloses a preparation method of GeSn and GePb semiconductor single-crystal nanodots, and relates to the field of preparation of semiconductor single-crystal nanodots. Comprising the following steps: 1) selecting a semiconductor wafer substrate with a crystal structure similar to a grown material and small lattice mismatch, and cleaning the semiconductor wafer substrate; 2) transferring the AAO template to a semiconductor wafer substrate, and dissolving the PMMA substrate with an acetone solution; (3) the substrate with the AAO template transferred in the step (2) and the PMMA dissolved away is fed into a sputtering cavity for magnetron sputtering epitaxial growth of GeSn or GePb, the temperature of the substrate ranges from 250 DEG C to 360 DEG C, and the sputtering speed is larger than 21 nm / min; and 4) mechanically stripping the AAO template to obtain the GeSn and GePb semiconductor single-crystal nanodot. The invention provides a new process method for preparing the high-quality GeSn and GePb single-crystal nanodot, and is expected to be applied to research and development of a silicon-based efficient light-emitting detector in silicon-based photoelectric integration.

Description

Technical Field

[0001] The invention relates to the field of semiconductor single crystal nanodot preparation, and in particular to a method for preparing GeSn and GePb semiconductor single crystal nanodots. Background Art

[0002] Germanium tin (GeSn) and germanium lead (GePb) are a new type of Group IV alloy semiconductor materials. The band gap of GeSn and GePb is adjustable with the change of Sn and Pb components. When the Sn and Pb components exceed 8% and 3.4% respectively, GeSn and GePb alloys transform from indirect band gap materials to direct band gap materials, and the process of GeSn and GePb is compatible with traditional silicon-based CMOS processes, and can be used to prepare ideal silicon-based high-efficiency light sources. Although high-component GeSn and GePb alloys can achieve direct band transition, the emission wavelength exceeds the commonly used band of optical communications due to the overall decrease in the conduction band. Preparing low-dimensional GeSn and GePb structures, such as GeSn nanodots, and using quantum confinement effects to expand the band gap is an effective way to solve the problem of too narrow a band gap. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems in the prior art and provide a method for preparing GeSn and GePb semiconductor single crystal nanodots. The AAO template method is combined with a magnetron sputtering system to epitaxially grow GeSn and GePb single crystal nanodots at a temperature of 250-360°C and a high rate of more than 21 nm / min, thereby improving the crystal quality.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] A method for preparing GeSn and GePb semiconductor single crystal nanodots, comprising the following steps:

[0006] 1) Select a semiconductor wafer substrate with a similar crystal structure and a smaller lattice mismatch to the material being grown, and clean it;

[0007] 2) Transferring the porous anodic aluminum oxide (AAO) template to a semiconductor wafer substrate and dissolving polymethyl methacrylate (PMMA) with an acetone solution;

[0008] 3) The substrate with the AAO template transferred and PMMA dissolved in step 2) is sent into the sputtering chamber for magnetron sputtering epitaxial growth of GeSn or GePb, with the substrate temperature of 250-360 °C and the sputtering rate greater than 21 nm / min;

[0009] 4) Mechanically peel off the AAO template to obtain GeSn and GePb semiconductor single crystal nanodots.

[0010] The semiconductor wafer substrate is Si (001) or Ge (001).

[0011] The Si (001) wafer substrate was cleaned by standard RCA cleaning, or the Ge (001) wafer substrate was ultrasonically cleaned using acetone, ethanol and deionized water in sequence to remove surface particles and organic contamination.

[0012] The cleaned Si (001) wafer substrate or Ge (001) wafer substrate is immersed in a diluted HF solution and rinsed to remove the surface oxide layer.

[0013] Place the AAO template face down on a clean substrate, clamp the AAO template and one corner of the substrate with tweezers and immerse them in acetone solution to dissolve the PMMA supporting the AAO template.

[0014] In step 4), the mechanical peeling method includes tape sticking.

[0015] The GeSn and GePb semiconductor single crystal nanodots prepared by the present invention have a lateral size determined by the micropore diameter of the AAO template (20 nm to micrometer level), and a height determined by the average thickness of the sputtered material (several nanometers to 100 nanometers level). Better collimation is beneficial to the preparation of nanodots with a larger aspect ratio.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] The present invention uses AAO as a template and adopts a magnetron sputtering method to prepare GeSn and GePb single crystal nanodot arrays on Si (001) and Ge (001) substrates under the growth conditions of 276 ° C, 25 nm / min and 360 ° C, 26 nm / min, respectively. The average diameter of the nanodots is 70 nm and the average height is 21 nm.

[0018] In the present invention, the GeSn and GePb components can be controlled by the sputtering rate, and the quality of the single crystal is improved by adjusting the wafer substrate temperature during sputtering. If the temperature is too low, single crystal nanodots cannot be formed, and if the temperature is too high, Sn and Pb are easily segregated, resulting in a decrease in the corresponding components of the nanodots.

[0019] The GeSn and GePb single crystal nanodots prepared on Si (001) substrates and Ge (001) substrates of the present invention have high crystal quality and no obvious dislocations at the interface. The method of the present invention provides a new process scheme for preparing high-quality GeSn and GePb single crystal nanodot structures, and is expected to be applied to the research and development of silicon-based high-efficiency light-emitting detection devices in silicon-based optoelectronic integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1(a) is a schematic diagram of the AAO template structure, and (b) is a schematic diagram of the AAO template being transferred to a substrate in an acetone solution;

[0021] Figure 2 Schematic diagram of the process of transferring the AAO template to the Si(001) or Ge(001) substrate and dissolving the PMMA;

[0022] Figure 3 Schematic diagram of the preparation of GeSn and GePb single crystal nanodots by magnetron sputtering;

[0023] Figure 4 The present invention shows GeSn nanodots on a Ge(001) substrate with a sputtering temperature of 276 °C and a sputtering rate of 25 nm / min; (a) is a surface SEM image; (b) is a HRTEM image; (c) is an enlarged image of the Ge / GeSn interface, corresponding to the inside of the white box in Figure (b); (d) is a (111) crystal plane image obtained by performing IFFT transformation on Figure (c); (e) is an EDS scan of the Ge element; (f) is an EDS scan of the Sn element;

[0024] Figure 5 TEM images of GeSn nanodots on Si(001) substrates at sputtering temperatures of (a) 124°C, (b) 164°C, (c) 212°C, and (d) 276°C and a sputtering rate of 8 nm / min according to embodiments of the present invention;

[0025] Figure 6 This is an optical microscope picture of GePb on a Ge(001) substrate at a sputtering temperature of 400° C. and a sputtering rate of 22 nm / min according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] Example 1

[0028] The finished AAO template used in this example is a commercially available double-pass ultra-thin AAO, adhered to a PMMA substrate, see Figure 1 In (a), the magnetron sputtering equipment used is a conventional high vacuum multi-target sputtering instrument. The target material used for GeSn sputtering can be a customized GeSn alloy target with a Sn content of 12% (atomic ratio) and a purity of 99.999%. The target material used for GePb sputtering can be a customized GePb alloy target with a Pb content of 3% (atomic ratio) and a purity of 99.999%. Ge, Sn or Ge, Pb co-sputtering can also be used for sputtering.

[0029] 1. Si(001) and Ge(001) substrate cleaning

[0030] Si (001) substrate cleaning steps:

[0031] 1) Place the Si(001) substrate into liquid III (H 2 SO 4 :H 2 O 2 =4:1) for 10 minutes, rinse with deionized water, dilute hydrofluoric acid solution (HF:H 2 O=1:20) soak for 4 minutes;

[0032] 2) Then add liquid Ⅰ (NH 4 OH:H 2 O 2 : H 2 O=1:1:4) heated to 85 °C for 10 minutes, rinsed with deionized water, and soaked in dilute hydrofluoric acid solution for 2 minutes;

[0033] 3) Finally, add solution II (HCl:H 2 O 2 :H 2 O=1:1:4) heated to 85 ℃ for 10 minutes, rinsed with deionized water. Before sputtering, Si(001) substrate was immersed in dilute hydrofluoric acid solution for 30 s to remove the surface oxide layer.

[0034] Ge(001) substrate cleaning steps:

[0035] 1) Ultrasonic treatment in acetone and ethanol for 10 minutes, repeated three times, can remove particles and organic matter on the surface of Ge (001) substrate;

[0036] 2) Rinse with deionized water, then ultrasonicate in deionized water for 10 minutes;

[0037] 3) Soak the Ge(001) substrate in a dilute hydrochloric acid solution (HCl:H 2 O = 1:4) for 30 s to remove some surface oxides and metal impurities, and then rinse with deionized water;

[0038] 4) Repeat step 3) 3 times;

[0039] 5) Soak the Ge(001) substrate in a dilute hydrofluoric acid solution (HF:H 2 O = 1:50) for 15 s to remove some surface oxides, and then rinsed with deionized water;

[0040] 6) Repeat step 5) 3 times.

[0041] 2. See Figure 1~2, the AAO template is transferred to the Si(001) or Ge(001) substrate and PMMA is dissolved

[0042] 1) Place the AAO template with its front side facing down on a clean substrate, and use tweezers to hold the AAO template and one corner of the substrate and immerse them in the acetone solution. Figure 1 As shown in (b). (The entire AAO template cannot be immersed in the acetone solution, because the surface of the Si(001) substrate and the Ge(001) substrate is hydrophobic after cleaning and removing the surface oxide, but the AAO template is hydrophilic, and immersion will cause the AAO template to fall off the substrate)

[0043] 2) After immersion for 3 to 5 minutes, PMMA is dissolved by acetone, leaving the AAO template attached to the substrate, which is then taken out and dried;

[0044] 3) Use tweezers to clamp the other side of the sample, and also clamp the substrate and AAO template at the same time to prevent the AAO template from falling off, then immerse the side not immersed in acetone in acetone for 3-5 minutes, then take it out and dry it;

[0045] 4) Place the sample vertically on the flower basket and immerse it in new acetone solution for 5-10 minutes, then take it out and dry it;

[0046] 5) Repeat the above steps until there is no PMMA residue on the sample surface.

[0047] 3. See also Figure 3 , GeSn / GePb nanodots grown by magnetron sputtering

[0048] 1) The Si(001) and Ge(001) substrates with the AAO template transferred and PMMA dissolved are sent into the vacuum chamber for sputtering;

[0049] For GeSn sputtering, the sputtering chamber vacuum is 7×10 −5 Pa, the substrate temperature was set to 276 °C, the working gas argon flow rate was controlled to 5.6 sccm, the corresponding pressure was 0.5 Pa, and the sputtering rate of GeSn was 25 nm / min.

[0050] For GePb sputtering, the sputtering chamber vacuum is 5.0×10 -5 Pa, the substrate temperature is set to 360 °C, the working gas argon flow rate is controlled to 2.2 sccm, the corresponding pressure is 0.3 Pa, and the sputtering rate of GePb is 26 nm / min.

[0051] On the basis of the above sputtering condition parameters, if the sputtering rate of each component material is further increased and the substrate temperature is slightly increased, it will be beneficial to further improve the quality of the nanodot single crystal. A higher sputtering rate is beneficial to suppress the Sn and Pb segregation of GeSn and GePb nanodots and increase the Sn and Pb components.

[0052] 2) Remove the sample from the sputtering chamber and mechanically peel off the AAO template by tape or other means.

[0053] The prepared GeSn nanodots on the Ge(001) substrate were tested by SEM and TEM respectively. Figure 4 (a) is a SEM image of GeSn single crystal nanodots on Ge(001) substrate. Since the AAO template used in this embodiment is a circular porous structure, the nanodots normally present a circular appearance after the pattern is replicated on the nanodots. The nearly square GeSn single crystal nanodots observed here are obviously related to the anisotropy of crystal growth. Figure 4 (b) is the HRTEM image of the sample. It can be seen that each GeSn single crystal nanodot is a large grain with a complete structure and forms a good single crystal epitaxial relationship with the Ge (001) substrate. Figure 4 In (c), the GeSn single crystal nanodots are integrated with the Ge(001) substrate interface, and almost no obvious dislocations or other defects can be seen. Figure 4 (d) is Figure 4 The inverse fast Fourier transform of (c) shows that there is no break or bifurcation in the atomic arrangement of the (111) plane at the interface between Ge and GeSn, indicating that a good interface is an important guarantee for the formation of single-crystal nanodot arrays. Figure 4 In (e) and (f), it can be clearly seen that the Ge and Sn elements in the GeSn single crystal nanodots are distributed very evenly, and no obvious Sn element segregation phenomenon is observed. The EDS data calculates that the Sn element content in the sample is 16%.

[0054] from Figure 5 TEM images of GeSn nanodots on Si(001) substrate at different sputtering temperatures and sputtering rates of 8 nm / min show that at lower sputtering temperatures and lower sputtering rates, crystallization failed or only polycrystalline nanodots were formed. Figure 6 From the optical microscope image of GePb with a sputtering temperature of 400 °C and a sputtering rate of 22 nm / min, it can be seen that too high a temperature can also lead to the segregation of GePb (the black dots in the image are precipitated lead).

[0055] In the present invention, high substrate temperature is conducive to promoting the layered growth of GeSn and GePb layers, improving the density of the film layer, and thus improving the crystal quality. The AAO template method is combined with a magnetron sputtering system at a temperature of 250-360 ° C and a high rate of more than 21 nm / min to epitaxially grow GeSn and GePb single crystal nanodots, and epitaxy of GeSn and GePb nano single crystal nanodots on Si (001) and Ge (001) substrates is achieved. On Si (001) substrates and Ge (001) substrates, due to the good epitaxial interface between the nanodots and the substrate, there are almost no visible defects such as dislocations, and nanodots with high crystal quality are obtained.

[0056] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing GeSn and GePb semiconductor single crystal nanodots, characterized in that: The following steps are involved: 1) Select a semiconductor wafer substrate with a similar crystal structure and a smaller lattice mismatch to the material being grown, and clean it; 2) Transfer the AAO template to the semiconductor wafer substrate and dissolve the PMMA substrate with acetone solution; 3) The substrate with the AAO template transferred and PMMA dissolved in step 2) is sent into the sputtering chamber for magnetron sputtering epitaxial growth of GeSn or GePb, with the substrate temperature of 250-360 °C and the sputtering rate greater than 21 nm / min; 4) Mechanically peel off the AAO template to obtain GeSn and GePb semiconductor single crystal nanodots.

2. The method for preparing GeSn and GePb semiconductor single crystal nanodots according to claim 1, characterized in that: The semiconductor wafer substrate is Si (001) or Ge (001).

3. The method for preparing GeSn and GePb semiconductor single crystal nanodots according to claim 1, characterized in that: In step 4), the mechanical peeling method includes tape sticking.

4. A GeSn and GePb semiconductor single crystal nanodot, characterized in that: Prepared by any preparation method of claims 1 to 3.

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