A method for preparing a silicon-based suspended relaxation GeSn structure

Abstract

The application discloses a preparation method of a silicon-based suspended relaxation GeSn structure, which comprises the following steps: step 1, performing a standard photolithography step on an epitaxial silicon-based GeSn film; step 2, etching the GeSn film and part of a Ge buffer layer by using an oxidizing acid vertical etching solution; step 3, performing lateral etching on the Ge buffer layer by using F-based plasma; and step 4, soaking in a acetone solution for glue removal, and completing the structure preparation. The GeSn suspended structure can relax the strain of the GeSn alloy and realize a direct band gap; the process for preparing the suspended structure is simple; the prepared GeSn suspended structure has the characteristics of a smooth sample surface, low roughness and small GeSn loss compared with other processes; and the application provides a novel process method for preparing a silicon-based GeSn light-emitting device, and is expected to play a huge role in the field of silicon-based optoelectronics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of GeSn passive light-emitting device preparation, and particularly relates to a preparation method of a silicon-based suspended relaxed GeSn structure. BACKGROUND

[0002] High-efficiency Si-based light-emitting devices are one of the most challenging devices in Si-based optoelectronic integrated circuits. Germanium tin (GeSn) alloy materials can be converted into direct bandgap materials under certain conditions and are compatible with Si-based complementary metal-oxide-semiconductor (CMOS) technology, making them one of the most promising candidate materials for Si-based light sources. 1- x Sn x ) alloy materials can be converted into direct bandgap materials under certain conditions and are compatible with Si-based complementary metal-oxide-semiconductor (CMOS) technology, making them one of the most promising candidate materials for Si-based light sources.

[0003] Due to the temperature sensitivity of GeSn alloy, low-temperature epitaxy technology is often used, so that the epitaxial fully strained GeSn material is almost an indirect band material. GeSn alloy can be converted into a direct bandgap material by increasing the Sn component and strain engineering. Theoretical calculations show that Ge 1-x Sn x alloy materials can be converted into direct bandgap materials under certain conditions and are compatible with Si-based complementary metal-oxide-semiconductor (CMOS) technology, making them one of the most promising candidate materials for Si-based light sources.

[0004] Etching suspended structure relaxed GeSn is an effective means for preparing GeSn light sources. The compressive strain of GeSn material mainly comes from the lattice mismatch between GeSn material and Ge virtual substrate. By selectively removing Ge material and retaining GeSn material, a fully relaxed GeSn suspended structure can be manufactured. In the preparation process of GeSn alloy suspended structure, the following difficulties need to be overcome: 1) large-scale etching is not uniform; 2) the sample surface roughness is high; 3) the mask is difficult to remove. Therefore, it is difficult to use a simple process to prepare a fully relaxed GeSn suspended structure with low surface roughness. SUMMARY

[0005] The present application aims to solve the above-mentioned problems in the prior art, and provides a preparation method of a silicon-based suspended relaxed GeSn structure, which combines wet etching and dry etching processes.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A preparation method of a silicon-based suspended relaxed GeSn structure, comprising the following steps:

[0008] 1) performing a standard photolithography process on an epitaxial silicon-based GeSn film;

[0009] 2) etching the GeSn film and part of the Ge buffer layer using an oxidizing acidic vertical etching solution;

[0010] 3) using F-based plasma to perform lateral etching of the Ge buffer layer to form a Ge column to support the microdisk;

[0011] 4) soaking in an acetone solution to remove the photoresist, thereby completing the structure preparation.

[0012] In step 1), the silicon-based GeSn thin film is epitaxially grown on the Ge buffer layer on the silicon substrate.

[0013] In step 1), the photoresist used in the standard photolithography process is AZ-5214E.

[0014] Before step 2), a hardening treatment at 105-135 ℃ for 10-15 min is further included.

[0015] In step 2), the oxidizing acid vertical etching solution is a solution configured with HCl:H2O2:H2O in a volume ratio of 1:1:5-1:1:10.

[0016] Before step 3), a hardening treatment at 105-135 ℃ for 10-15 min is further included.

[0017] In step 3), the F-based plasma etching of the Ge column under the microdisk is an etching process performed in an inductively coupled plasma etching system with an ICP power of 80-120 W, a flow ratio of CF4 to O2 of 3:1-6:1, and an etching time of 30-60 s.

[0018] A silicon-based suspended relaxed GeSn structure prepared by using the preparation method.

[0019] The present application controls the size of the Ge column under the microdisk by regulating the etching time in step 3), thereby achieving control of the relaxation degree and relaxation area of the GeSn thin film.

[0020] The silicon-based suspended relaxed GeSn structure can be completely relaxed to achieve a direct bandgap.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The GeSn suspended structure can achieve complete relaxation of the GeSn thin film to achieve a direct bandgap.

[0023] (2) The prepared GeSn suspended structure has a small surface roughness and has smaller surface scattering loss than other processes.

[0024] (3) The present application provides a new process method for preparing a silicon-based GeSn light-emitting device, which is expected to play a huge role in the field of silicon-based optoelectronics. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 SEM image of the sample obtained in Example 1 of the present application.

[0026] Figure 2 Raman Mapping strain distribution of the sample obtained in Example 1 of the present application.

[0027] Figure 3 SEM image of the sample obtained in Example 2 of the present application.

[0028] Figure 4 Raman line scan and strain distribution of the sample obtained in Example 2 of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear, explicit, the present application is further described in detail below in combination with the drawings and examples.

[0030] Example 1

[0031] The photoetching equipment used is MA6 contact photoetching machine (resolution 2 μm) manufactured by Suss Company in Germany, and AZ-5214E photoresist is selected to make the mask of disc structure. The transverse F-based selective etching equipment used is SENTECH SI 500 inductive coupling plasma etching system. The model of the oxygen plasma stripping machine used is Q150. The epitaxial thickness of the GeSn sample selected is ~ 370 nm. 0.91 Sn 0.09 thin film material is etched.

[0032] I. Standard photoetching process of AZ5214E photoresist

[0033] 1) Ge 0.91 Sn 0.09 thin film sample is ultrasonically cleaned with acetone, ethanol and deionized water for 10 min in sequence to remove surface adhered particulate matter and organic matter;

[0034] 2) Oven 135℃ baking 1h to remove water vapor;

[0035] 3) Uniform coating: place the sample on the spin coater, and coat AZ5214E photoresist. Rotate AZ5214E photoresist at a speed of 3500 rd / min for 30 s to form a film;

[0036] 4) Pre-baking: after spin coating the photoresist, place the sample on a hot plate at 96℃ for 4 min;

[0037] 5) Photoetching: use a regular round column photoetching plate with a diameter of 10 μm, and the power parameters of the photoetching machine are 10.8 and the exposure time is 13 s;

[0038] 6) Post exposure bake: The exposed sample was placed on a hot plate at 96 °C for 4 min to bake again, which produced cross-linked polymer and the photoresist layer formed a trapezoidal structure required for lift-off;

[0039] 7) Lithography machine power parameter 10.8, exposed for 13.5 s in flood exposure mode, the first large area of unexposed AZ5214E photoresist reacted with ultraviolet light after irradiation, the AZ5214E photoresist no longer reacted with ultraviolet light after the first exposure due to post exposure bake.

[0040] 8) Development: placed in the developing solution for 60 s, fixed for 15 s, and the sample was blown dry with nitrogen;

[0041] II. Oxidizing acidic etching solution wet vertical etching

[0042] 1) The dried sample was placed in a 110 °C oven for 15 min to harden the film. The sample after hardening was taken out and cooled to room temperature, and the etching solution HCl:H2O2:H2O was prepared with a volume ratio of 1:1:5. The mixed solution is an acidic vertical etching solution, which has almost the same etching rate for GeSn alloy material and Ge material, and does not affect the etching rate with the change of Sn component.

[0043] 2) The average etching rate of the solution is ~ 180 nm / min (23 °C). The thickness of the GeSn sample is ~ 370 nm, and the GeSn layer is completely etched off, and the etching time is ~ 2 min. The sample was placed horizontally and immersed in the etching solution for 3.5 min to etch off part of the Ge buffer layer under the GeSn, and the etching morphology was a tilted mesa.

[0044] III. F-based dry selective lateral etching

[0045] 1) The GeSn cylindrical structure manufactured by wet etching was placed in a 105 °C oven for 10 min to make the photoresist mask more solid.

[0046] 2) The baked sample was placed in a SENTECH SI 500 inductively coupled plasma etching system for F-based etching, with ICP power 100 W, CF4flow rate 30 sccm, O2flow rate 5 sccm, and etching time set to 60 s.

[0047] IV. Acetone soaking for glue removal

[0048] 1) The etched sample was placed in a Q150 oxygen plasma glue removal machine to remove the surface denatured glue mask, with power 150 W, O2flow rate 100 sccm, Ar flow rate 50 sccm, and etching time set to 360 s, with an expected glue removal of 90 nm.

[0049] 2) The sample after oxygen plasma stripping was inverted and immersed in acetone for one hour at room temperature for stripping.

[0050] 3) The prepared structure was tested by SEM, and the size of the structure microdisk was measured from Figure 1 It can be seen that the GeSn microdisk with almost perfect morphology is obtained, and the size of the structure microdisk is finally ~ 9.5 μm. The size reduction is caused by the characteristics of the reverse glue. The size of the Ge column under the GeSn microdisk is less than 1 μm, and the purpose of manufacturing the GeSn microdisk cavity is achieved. Then the sample was subjected to Raman line scanning to determine its relaxation. From Figure 2 It can be seen that the strain in the microdisk gradually relaxes along the radial distribution and even applies a tensile strain. The highest tensile strain applied at the edge of the microdisk is 1.5%, reaching the direct bandgap.

[0051] Example 2

[0052] The lithography equipment used was a MA6 contact lithography machine (resolution 2 μm) manufactured by Suss Company in Germany, and AZ-5214E photoresist was selected as the mask for manufacturing waveguide structure. The transverse F-based selective etching equipment used was a SENTECH SI 500 inductively coupled plasma etching system. The oxygen plasma stripping machine used was a Q150. The GeSn sample selected was a Ge 0.91 Sn 0.09 thin film material with an epitaxial thickness of ~ 370 nm.

[0053] I. Standard photoetching process of AZ5214E photoresist

[0054] 1) The Ge 0.91 Sn 0.09 thin film sample was ultrasonically cleaned with acetone, ethanol and deionized water for 10 min, respectively, to remove surface attached particulate matter and organic matter;

[0055] 2) Oven drying at 135℃ for 1h to remove moisture;

[0056] 3) Glue uniformity: the sample was placed on a spin coater, and AZ5214E photoresist was coated at a speed of 3500 rd / min for 30s to form a film;

[0057] 4) Pre-baking: after spin coating the photoresist, the sample was placed on a hot plate at 96℃ for 4 min;

[0058] 5) Photoetching: a waveguide array photoetching plate with a width of 9 μm and a length of 6 mm was used, and the power parameters of the photoetching machine were 10.8 and the exposure time was 13s;

[0059] 6) Post-exposure baking: the exposed sample was placed on a hot plate at 96℃ for 4 min again to produce cross-linked polymers, and the photoresist layer formed a ladder-shaped structure required for stripping

[0060] 7) Lithography machine power parameter 10.8, exposure 13.5s with flood mode, the first large area of AZ5214E photoresist not exposed reacts with UV light after irradiation, the AZ5214E photoresist after the first exposure no longer reacts with UV light after post-exposure bake.

[0061] 8) Development: Place in developer for 60s, fix for 15s, use nitrogen to dry the sample;

[0062] II. Oxidizing acid etching solution vertical etching

[0063] 1) Put the dried sample into a 110°C oven, harden the film for 10 min. Take out the sample after hardening and cool it to room temperature. Prepare the etching solution HCl:H2O2:H2O with a volume ratio of 1:1:5. This mixture is an acid vertical etching solution, which has almost the same etching rate for GeSn alloy materials and Ge materials, and does not affect the etching rate with the change of Sn component.

[0064] 2) The average etching rate of the solution is ~ 180 nm / min (23°C). The thickness of the GeSn sample is ~ 350 nm, and the GeSn layer is completely etched, with an etching time of ~ 2 min. The sample is placed horizontally and immersed in the etching solution for 3.5 min to etch part of the Ge buffer layer under the GeSn. The etching morphology is a tilted mesa.

[0065] III. F-based dry selective lateral etching

[0066] 1) Put the GeSn waveguide structure produced by wet etching into a 105°C oven for 10 min to make the photoresist mask more robust.

[0067] 2) Dissociate the sample along the waveguide end face to obtain a smooth cross section as a waveguide resonant cavity.

[0068] 3) Put the dissociated sample into a SENTECH SI 500 inductively coupled plasma etching system for F-based etching. The etching conditions are ICP power 100 W, CF4 flow rate 30 sccm, O2 flow rate 5 sccm, and etching time set to 60 s.

[0069] IV. Acetone soaking for glue removal

[0070] 1) Put the etched sample into a Q150 oxygen plasma glue removal machine to remove the surface denatured glue mask. The glue removal conditions are power 150 W, O2 flow rate 100 sccm, Ar flow rate 50 sccm, and etching time set to 360 s, with an expected glue removal of 90 nm.

[0071] 2) Invert the sample after oxygen plasma glue removal and place it in acetone at room temperature for one hour for glue removal.

[0072] 3) The prepared structure is tested by SEM, from Figure 3 It can be seen that the suspended structure with smooth surface and no impurities is obtained, and the size of the ridge waveguide is finally ~ 8.5 μm, and the size reduction is caused by the characteristics of the reverse glue, and the size of the Ge support under the GeSn suspended ridge waveguide is less than 3 μm, and the manufacturing purpose of the GeSn suspended ridge waveguide is achieved. Then the sample is subjected to Raman line scanning to determine its relaxation, from Figure 4 It can be seen that the Raman shift from the center of the waveguide to the edge part is ~ 4.5 cm -1 , and the strain gradually relaxes from the middle to the edge, and the strain at the edge is quickly released to achieve complete relaxation.

Claims

1. A method for fabricating a silicon-based suspended GeSn structure, characterized in that, The preparation method comprises the following steps: 1) performing a standard photolithography process on an epitaxial silicon-based GeSn film; 2) etching the GeSn film and part of the Ge buffer layer using an oxidizing acid vertical etching solution; 3) performing lateral etching of the Ge buffer layer to form a Ge column to support the microdisk using F-based plasma; 4) soaking in a acetone solution to remove the photoresist and complete the structure preparation.

2. The method of claim 1, wherein the method further comprises: In step 1), the silicon-based GeSn film is epitaxial on a Ge buffer layer on a silicon substrate.

3. The method of claim 1, wherein the method further comprises: In step 1), the photoresist in the standard photolithography process is AZ-5214E.

4. The method of claim 1, wherein the method further comprises: Before step 2), the film is hardened at 105-135 DEG C for 10-15 min.

5. The method of claim 1, wherein the method further comprises: In step 2), the oxidizing acid vertical etching solution is a solution prepared by mixing HCl, H2O2 and H2O in a volume ratio of 1:1:5-1:1:

10.

6. The method of claim 1, wherein the method further comprises: Before step 3), the film is hardened at 105-135 DEG C for 10-15 min.

7. The method of claim 1, wherein the method further comprises: In step 3), the F-based plasma etching of the Ge column under the microdisk is performed in an inductively coupled plasma etching system by using an ICP power of 80-120 W, a flow ratio of CF4 to O2 of 3:1-6:1, and an etching time of 30-60 s.

8. A silicon-based suspended relaxed GeSn structure, characterized by: The silicon-based suspended relaxed GeSn structure is prepared by the preparation method in any one of claims 1-7.

9. A silicon-based suspended relaxed GeSn structure as claimed in claim 8, wherein: The size of the Ge column under the microdisk is controlled by adjusting the etching time in step 3), so that the relaxation degree and relaxation area of the GeSn film are controlled.

10. A silicon-based suspended relaxed GeSn structure as claimed in claim 8, wherein: The silicon-based suspended relaxed GeSn structure can be completely relaxed to realize a direct band gap.

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