A method for preparing Ge / Si SACM APD
High-quality Ge/Si SACM APDs were fabricated using high-vacuum in-situ sputtering bonding technology and photolithography and etching processes. This solved the problems of low gain and high dark current in Ge/Si APDs, achieving high gain and low dark current.
Patent Information
- Application Number
- CN202411894125.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-11-14
- Estimated Expiration
- 2044-12-20
AI Technical Summary
Existing techniques for epitaxial Ge films on Si substrates often result in high-density through-dislocations and high roughness, leading to problems such as large dark current, poor stability, reduced gain, and noise in Ge/Si APDs.
Ge/Si SACM APD with a vertical structure was fabricated by sputtering a-Si as an intermediate layer at the Ge/Si bonding interface using high-vacuum in-situ sputtering bonding technology, combined with photolithography, etching and coating techniques. Through-through dislocations and surface roughness were reduced by long-term annealing and polishing processes.
The prepared Ge/Si SACM APD exhibited high responsivity and gain at wavelengths of 1310 nm and 1550 nm, with significantly reduced dark current. The gain reached 1.79 × 10⁶ and 1.69 × 10⁵, respectively, and the dark current was as low as 1.79 μA.
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Figure CN119630109B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a novel method in the field of semiconductor device fabrication, which can prepare ultra-high gain Ge / Si SACM APDs. Specifically, a high-vacuum in-situ sputtering bonding technique is used to in-situ sputter 3 nm a-Si as a bonding intermediate layer at the Ge / Si bonding interface to achieve Ge / Si lattice isolation, suppress the generation of through-dislocations in the Ge thin film, and prepare a high-quality Si-based Ge thin film with zero through-dislocations, no interface oxide layer, and zero bubbles. A high-performance Ge / Si SACM APD with absorption, charge, and multiplication separation is then prepared using photolithography, etching, and deposition techniques. Background Technology
[0002] Ge / Si near-infrared photodetectors are widely used in military reconnaissance, night vision imaging, and communications due to their high carrier mobility and high absorption rate in the communication band. Epitaxy plays a crucial role in the preparation of Si-based Ge thin films because it enables the growth of large-scale single-crystal thin films. However, due to the 4.2% lattice mismatch between Ge and Si, traditional methods for epitaxially growing Ge thin films on Si substrates often result in the formation of high-density penetrating dislocations (10⁻⁶) within the Ge film. 6 cm -2 High surface roughness and through-hole dislocations in Ge thin films lead to problems such as large dark current, poor stability, reduced gain, and noise in epitaxial Ge / Si APDs. Therefore, it is necessary to reduce through-hole dislocations and surface roughness in Ge thin films to reduce device dark current and improve device performance. Summary of the Invention
[0003] The purpose of this invention is to propose a novel fabrication method to address the problems of low gain and high dark current in Ge / Si SACM APDs, successfully solving these issues. First, a Si-based Ge thin film with an oxide-free interface, high bonding strength, and zero bubbles is prepared using high-vacuum in-situ sputtering bonding technology. Then, the Si-based Ge thin film is processed through photolithography, etching, and sputtering to fabricate a Ge / Si SACM APD with a vertical structure and ultra-high gain. The Ge / Si SACM APD fabricated using this method exhibits responsivity of 1.145 A / W and 2.57 A / W at wavelengths of 1310 nm and 1550 nm for a 30 μm mesa, respectively, with gains reaching 1.79 × 10⁻⁶. 6 and 1.69×10 5 The dark current is as low as 1.79 μA; the responsivity of the 50 μm diameter Ge / Si APD device at wavelengths of 1310 nm and 1550 nm is 0.58 A / W and 1.5 A / W, respectively, with a gain of 1.17 × 10⁻⁶. 6 and 2×10 5The dark current is as low as 12.7 μA.
[0004] The present invention provides a method for preparing Ge / Si SACM APD, which includes the following technical features:
[0005] First, after surface treatment of the Si epitaxial wafer and Ge wafer, a-Si is sputtered at the Ge / Si bonding interface as a bonding intermediate layer using high vacuum in-situ sputtering bonding technology, and then directly bonded in-situ under high vacuum; then the bonded Ge / Si is subjected to step-by-step long-term annealing to achieve the peeling of the Si-based Ge thin film.
[0006] Secondly, the stripped Si-based Ge film is placed in a high-vacuum annealing furnace for high-temperature annealing to release the non-uniform strain of the Ge film and repair point defects; then, the repaired Si-based Ge film is polished and ion implanted to prepare a P+ contact layer.
[0007] Finally, Ge / Si SACM APD with vertical absorption, charge and multiplication separation structure was prepared by photolithography, etching and passivation processes.
[0008] The surface treatment of Si epitaxial wafers and Ge wafers includes the following:
[0009] First, ion implantation is performed: SiO2 is deposited on the Ge wafer surface as an ion implantation protective layer using a plasma chemical vapor deposition system, followed by H2O. + Ion implantation;
[0010] A single-crystal Si epitaxial wafer is grown on a Si substrate, and boron ions are implanted on the surface of the Si epitaxial wafer. Then, rapid thermal annealing is used to activate the implanted boron ions to form a lightly doped P-type charge layer.
[0011] After ion implantation, chemical cleaning is performed: the SiO2 on the surface of the Ge wafer is immersed in HF:H2O solution to etch away the SiO2 protective layer, resulting in the processed Si epitaxial wafer and Ge wafer.
[0012] The process involves using high-vacuum in-situ sputtering bonding technology to sputter a-Si onto a Si epitaxial wafer, followed by in-situ bonding; and employing a step-by-step, long-term annealing process to peel off the Si-based Ge thin film.
[0013] After surface treatment, the Si epitaxial wafers and Ge wafers are spun dry using a spin coater and then quickly placed into the cavity of a double-sided magnetron thermosetting sputtering machine. The sputtering chamber vacuum level is then reduced to less than 1×10⁻⁶. -4 At Pa, Ar gas is introduced into the sputtering chamber, and the gas pressure in the sputtering chamber is adjusted by changing the Ar gas flow rate, thus depositing an a-Si thin film on the Si epitaxial wafer.
[0014] After sputtering the a-Si thin film, the Si epitaxial wafer is directly bonded to the Ge wafer in the cavity of the double-sided magnetron thermopressing sputtering machine.
[0015] The sample with completed Ge / Si bonding was placed in a tube furnace and subjected to step-by-step long-term annealing under a N2 atmosphere to achieve the exfoliation of the Si-based Ge film.
[0016] The process of releasing the non-uniform strain and repairing point defects in Ge thin films includes:
[0017] The stripped Si-based Ge film was placed in a high-vacuum annealing furnace and annealed under high vacuum to release the non-uniform strain and repair point defects in the Ge film.
[0018] Among them, polishing and ion implantation will be used to prepare P + The contact layer process includes:
[0019] The surface of the Ge thin film was polished using a chemical mechanical polishing machine;
[0020] After polishing, the Ge film was placed in a quartz beaker, an appropriate amount of alcohol was poured in, and the beaker was placed in a water bath to remove the paraffin on the back of the Si substrate. After the alcohol water bath, the Si-based Ge film was ultrasonically treated with acetone, ethanol and deionized water in sequence to remove the particulate matter adsorbed on the surface of the Ge film.
[0021] Boron ions were implanted onto the cleaned Ge film surface, and then SiO2 film was deposited on the Ge film surface using PECVD. Finally, the sample was placed in a tube annealing furnace and annealed under a N2 atmosphere to activate the implanted boron ions.
[0022] The process of fabricating Ge / Si SACM APDs with vertical absorption, charge multiplication, and separation structures through photolithography, etching, and passivation includes:
[0023] Step 1: Remove moisture from the Si-based Ge thin film sample implanted with boron ions. After moisture removal, perform photolithography to form a hard film of photoresist. After hard film formation, etch the sample. After etching, clean and remove the photoresist.
[0024] Step 2: After hardening the film, etch the Si-based Ge thin film sample. After etching, clean and remove the photoresist. Then, deposit and grow the compound on the Si-based Ge thin film sample. After compound growth, harden the Si-based Ge thin film sample with photoresist again. After hardening the film, etch the Si-based Ge thin film sample. After etching, remove the photoresist. Then, dry and develop the sample.
[0025] Step 3: Magnetron sputtering is used to sputter both the front and back sides of the Si-based Ge thin film sample after photolithography and development. After sputtering, the Ge / Si sample is immersed in acetone solution and peeled off with adhesive to finally prepare the Ge / Si SACM APD photodetector.
[0026] Step 1 includes the following process:
[0027] The ion-activated Ge film was immersed in HF:H2O solution to etch away the SiO2 protective layer. Then, the Ge film was ultrasonically cleaned with acetone, ethanol and deionized water in sequence, rinsed with deionized water, and then spun dry using a spin coater. Finally, the sample was placed in an oven to remove moisture.
[0028] After removing moisture, the Si-based Ge thin film sample was spin-coated with a tackifier and photoresist using a spin coater. The sample was then placed on a heating stage for pre-baking of the photoresist. Next, the sample was subjected to the first photolithography using an ultraviolet lithography machine to define the upper stage. After the photolithography was completed, the sample was developed using a developer. Finally, the developed sample was placed in an oven to achieve photoresist hardening.
[0029] Step 2 includes the following process:
[0030] The Ge thin film was etched using dry and wet methods after the hard film was completed. First, the sample was placed in an ICP etching machine for dry etching using sulfur hexafluoride gas. Then, the sample was placed in an H3PO4:H2O2=3:1 etching solution for wet etching.
[0031] After etching, the sample is placed in an ICP etching machine to etch the Si. The etching gas is sulfur hexafluoride to achieve device isolation.
[0032] The photoresist was removed from the etched sample by sequentially ultrasonically cleaning the sample with acetone, ethanol and deionized water, followed by rinsing with deionized water to remove the photoresist.
[0033] The cleaned Ge / Si sample was spin-dried using a spin coater, and then Al2O3 was deposited on the surface of the Ge thin film using an atomic layer deposition system. After the growth was completed, the sample was placed into the chamber of the atomic layer deposition system, and SiO2 and Si3N4 were deposited sequentially.
[0034] After the growth is completed, a spin coater is used to spin coat the Si-based Ge thin film surface with a thickener and photoresist. Then, the sample is placed on a heating stage to pre-bake the photoresist. Next, the sample is photolithographically etched using an ultraviolet lithography machine to define the electrode hole positions. Then, the sample is developed using a developer. Finally, the developed sample is placed in an oven to achieve photoresist hardening.
[0035] After the hardening process is completed, the sample is etched with trifluoromethane and argon to remove Si3N4 and SiO2 from the surface of the Ge film. Then, SiO2 and Al2O3 will remain on the sample surface. Then, BOE solution is used to etch away the SiO2 and Al2O3 on the sample surface.
[0036] After etching, the photoresist is removed from the sample. The steps are as follows: the sample is ultrasonically cleaned with acetone, ethanol and deionized water in sequence, rinsed with deionized water, then the sample is spun dry using a spin coater, and finally the sample is placed in an oven to dry.
[0037] After drying, the sample is first spin-coated with a tackifier and photoresist on the surface of the Si-based Ge thin film using a spin coater. Then, the sample is placed on a heating stage for pre-baking of the photoresist. Next, the sample is photolithographically etched to define the positions of the electrodes. Then, the sample is placed on a heating stage for post-baking of the photoresist. The sample is then exposed using a photolithography machine, and finally, the sample is developed.
[0038] Step 3 includes the following process:
[0039] After development, Ti and Al were sputtered on both the front and back sides of the Ge / Si sample using magnetron sputtering. Finally, the Ge / Si sample was immersed in acetone solution and the adhesive was removed to prepare the Ge / Si SACM APD photodetector.
[0040] In summary, a Ge / Si SACM APD is characterized by being prepared by the method according to any one of claims 1 to 9; the Ge / Si SACM APD possesses the following features:
[0041] Ge / Si SACM APDs exhibit vertically structured absorption, charge, and multiplication separation characteristics. Furthermore, a 30 μm diameter Ge / Si SACM APD device demonstrates responsivity of 1.145 A / W and 2.57 A / W at 1310 nm and 1550 nm wavelengths, respectively, with gains reaching 1.79 × 10⁻⁶. 6 and 1.69×10 5 The dark current is as low as 1.79 μA.
[0042] When the diameter of the Ge / Si SACM APD is 50 μm, the Ge / Si SACM APD device exhibits responsivity of 0.58 A / W and 1.5 A / W at wavelengths of 1310 nm and 1550 nm, respectively, with gains reaching 1.17 × 10⁻⁶. 6 and 2×10 5 The dark current is as low as 12.7 μA.
[0043] To achieve the above method, the present invention employs the following detailed technical steps:
[0044] A novel method for preparing ultra-high gain Ge / Si SACM APDs includes the following steps:
[0045] 1) After ion implantation of boron ions into the Si epitaxial wafer, rapid thermal annealing at 1000 ℃ for 25 s was performed;
[0046] 2) The Si epitaxial wafer and Ge wafer were ultrasonically cleaned sequentially with acetone, ethanol and deionized water for 10 min to remove adsorbed particulate matter and organic matter from the substrate surface.
[0047] 3) After cleaning, the Si epitaxial wafer is first boiled in a H2SO4 / H2O2 solution with a volume ratio of 4:1 for 10 min, rinsed with deionized water 15 times, then soaked in an HF / H2O solution with a volume ratio of 1:20 for 4 min, and rinsed with deionized water 15 times.
[0048] 4) After cleaning, the Si epitaxial wafer is first boiled in a 1:1:4 NH4OH / H2O2 / H2O solution for 10 min, rinsed with deionized water 15 times, then soaked in a 1:20 HF / H2O solution for 4 min, and rinsed with deionized water 15 times.
[0049] 5) After cleaning, the Si epitaxial wafer is first boiled in a HCl / H2O2 / H2O solution with a volume ratio of 1:1:4 for 10 min, rinsed with deionized water 15 times, then soaked in an HF / H2O solution with a volume ratio of 1:20 for 4 min, and rinsed with deionized water 15 times.
[0050] 6) The Si epitaxial wafers cleaned in 5) and the Ge wafers cleaned in 2) are soaked in a solution with a volume ratio of HF:H2O=1:20 for 4 minutes and rinsed with deionized water 10-15 times.
[0051] 7) After cleaning, the Si epitaxial wafer and Ge wafer are spun dry using a spin coater, and then placed into a double-sided magnetron sputtering thermosetting machine. The sputtering chamber background vacuum level is kept below 1×10⁻⁶. -4 Pa, Ar gas with a purity of 5N is introduced into the sputtering chamber, and the gas pressure in the sputtering chamber is adjusted to maintain the gas pressure at 0.7 Pa.
[0052] 8) At room temperature, a 3 nm a-Si thin film was sputtered onto the surface of a Si epitaxial wafer, and then the Si epitaxial wafer and the Ge wafer were rapidly bonded together in the cavity. Then, in-situ hot pressing bonding was performed with a pressure of 12 MPa, a hot pressing temperature of 300 ℃, a hot pressing time of 1 h, and a heating and cooling rate of 1 ℃ / min.
[0053] 9) The bonded Ge / Si wafers are placed in an annealing furnace for low-temperature thermal annealing to achieve intelligent peeling of the Si-based Ge film, that is, to peel off a layer of Ge film from the Ge wafer and cover it on the Si-based amorphous Si.
[0054] 10) The prepared Si-based Ge thin film was placed in a high-vacuum annealing furnace and annealed at 500 °C in a vacuum environment for 1 h with a heating and cooling rate of 0.5 °C / min.
[0055] 11) After annealing, the Ge thin film was polished for 5 min using a chemical mechanical polishing (CMP) machine at a speed of 30 r / min and a swing arm speed of 15 r / min. The polished Ge thin film was then placed in a quartz beaker, an appropriate amount of alcohol was added, and the beaker was placed in a water bath at 80 °C for 20 min to remove the paraffin wax from the back of the Si substrate. The Ge thin film was then ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 10 min each to remove adsorbed particles from the Ge thin film surface.
[0056] 12) After cleaning, boron ion implantation was performed on the Si-based Ge thin film at a dose of 4 × 10⁻⁶. 15 cm -2 The injection energy was 30 keV. Then, the injected Ge thin film sample was placed in the PECVD vacuum chamber and a 100 nm SiO2 layer was grown on the surface of the Ge thin film as an annealing protective layer.
[0057] 13) After SiO2 growth is completed, the Ge film is placed in a tube annealing furnace and annealed at 400 °C for 1 h in a N2 atmosphere.
[0058] 14) After annealing, the Ge film was soaked in a solution with a volume ratio of HF:H2O=1:20 for 15 min to etch away the SiO2 layer. Then, it was ultrasonicated with acetone, alcohol and water for 10 min respectively. Finally, it was rinsed with deionized water 15 times. After the Ge film was spin-dried by a spin coater, it was placed in an oven and dried at 135 ℃ for 1 h to remove moisture.
[0059] 15) After the sample drying is completed, a spin coater is first used to spin-coat the Ge film with a tackifier and photoresist. Then, a heating stage at 96 ℃ is used to pre-bake the photoresist for 5 min, performing the first photolithography on the sample to define the upper stage. Next, development is performed with a developer for 55 s, followed by hardening in an oven at 120 ℃ for 15 min to harden the photoresist. Then, the sample is placed in an ICP etching machine, where the Ge film is etched using both dry and wet methods. The etching gas is sulfur hexafluoride (10 sccm), the etching time is 180 s, and the electrode power (upper / lower) is 100 / 40 W. Finally, the sample is immersed in an H3PO4:H2O2 = 3:1 etching solution for 1 min 30 s. Next, the sample was placed in an ICP etching machine to etch Si. The etching gas was sulfur hexafluoride (30 sccm), the etching time was 29 s, and the electrode power (upper / lower) was 200 / 15 W to achieve device isolation. Finally, the photoresist was removed from the sample using acetone, alcohol, and water.
[0060] 16) After the sample is cleaned, the sample is spun dry using a spin coater and then placed in an ALD to deposit 10 nm Al2O3. Then the sample is placed in a PECVD chamber to deposit 400 nm SiO2 and 200 nm Si3N4.
[0061] 17) After sample growth, a spin coater was first used to spin-coat the Ge / Si sample surface with a tackifier and photoresist. Then, the photoresist was pre-baked for 5 min using a heating stage at 96 ℃. Next, a third-stage photolithography was performed on the sample using a UV lithography machine to define the positions of the electrode holes. Then, the sample was baked in an oven at 120 ℃ for 15 min to achieve a hard film of the photoresist. The sample was then placed in an ICP etching machine to etch Si3N4 and SiO2. The etching gases were trifluoromethane (100 sccm) and argon (20 sccm), with etching times of 125 s and 300 s, and electrode power (upper / lower) of 200 / 20 W. Afterward, 20 nm of SiO2 and 10 nm of Al2O3 remained on the sample surface. These were etched away with a BOE solution (3 ml HF: 6 g NH4F: 10 ml H2O) for 10 s. Finally, acetone, alcohol and water were used to remove the photoresist. After the sample was dried by spin coating, it was placed in an oven at 135 °C for 1 h to remove moisture.
[0062] 18) After sample baking, the photoresist was first patterned using third-layer photolithography to define the electrode positions. Then, it was post-baked for 4 minutes, followed by 20 seconds of exposure, and then developed with a developer for 55 seconds. Next, 10 nm Ti / 300 nm Al electrodes were magnetron sputtered onto the sample surface. Finally, the sample was immersed in acetone solution for 24 hours for stripping with the photoresist, ultimately fabricating a Ge / Si SACM APD photodetector. Figure 4 As shown.
[0063] 19) The fabricated Ge / Si SACM APD photodetector was tested for dark current using a monochromator. The Ge / Si SACM APD fabricated by this method showed responsivity of 1.145 A / W and 2.57 A / W at wavelengths of 1310 nm and 1550 nm for a 30 μm mesa, respectively, with gains reaching 1.79 × 10⁻⁶. 6 and 1.69×10 5 The dark current is as low as 1.79 μA; the responsivity of the 50 μm diameter Ge / Si APD device at wavelengths of 1310 nm and 1550 nm is 0.58 A / W and 1.5 A / W, respectively, with a gain of 1.17 × 10⁻⁶. 6 and 2×10 5 The dark current is as low as 12.7 μA.
[0064] The advantages of this invention are:
[0065] This invention innovatively proposes a novel method for fabricating ultra-high gain Ge / Si SACM APDs. Employing high-vacuum sputtering bonding, it can prepare Si-based Ge thin films with zero bubbles, no oxide layer at the interface, and high bonding strength. The Ge / Si SACM APDs are then fabricated using photolithography, etching, and deposition techniques. The Ge / Si SACM APDs fabricated using this method exhibit responsivity of 1.145 A / W and 2.57 A / W at 1310 nm and 1550 nm wavelengths, respectively, with gains reaching 1.79 × 10⁻⁶. 6 and 1.69×10 5 The dark current is as low as 1.79 μA; the responsivity of the 50 μm diameter Ge / Si APD device at wavelengths of 1310 nm and 1550 nm is 0.58 A / W and 1.5 A / W, respectively, with a gain of 1.17 × 10⁻⁶. 6 and 2×10 5 The dark current is as low as 12.7 μA. Attached Figure Description
[0066] Figure 1This is a schematic diagram of the Ge / Si bonding process in Embodiment 1 of the present invention.
[0067] Figure 2 This is a physical image of the Ge / Si bond obtained in Example 1 of the present invention.
[0068] Figure 3 This is a bicrystalline XRD diffraction pattern of the Si-based Ge thin film after annealing at 350 °C and 500 °C in Example 1 of the present invention.
[0069] Figure 4 This is a three-dimensional device structure and cross-sectional view of the Ge / Si SACM APD in Embodiment 1 of the present invention.
[0070] Figure 5 This is the dark current IV curve of Ge / Si SACM APD obtained in Example 1 of the present invention.
[0071] Figure 6 The photoresponsivity, responsivity, and gain of the Ge / Si SACM APD 30 μm mesa obtained in Example 1 of this invention at wavelengths of 1310 nm and 1550 nm are shown.
[0072] Figure 7 The photoresponsivity, responsivity, and gain of the Ge / Si SACM APD 50 μm mesa obtained in Example 1 of this invention at wavelengths of 1310 nm and 1550 nm are shown. Detailed Implementation
[0073] To make the content of this invention easier to understand, the technical solution of this invention will be further described below in conjunction with specific embodiments.
[0074] The equipment used was a DM300 thermostatic sputtering machine, with two DC target positions installed in the growth chamber. The target material used was a 5N (99.999%) high-purity Si circular target. The Si film epitaxially grown on the Si substrate had a thickness of 1.65 μm, a crystal orientation of (111), an N-type impurity, and a resistivity of 0.72 Ω•cm. The single-crystal Ge substrate used had a crystal orientation of (100), was single-sided polished, and had a resistivity >30 Ω•cm.
[0075] The tackifier used is AZ AD PROMOTER, whose main component is hexamethyldisilazane (HMDS). The photoresist used is AZ5214E, and the developer is JAZX-238.
[0076] 1) First, a 100 nm SiO2 protective layer was deposited on the Ge wafer surface using a plasma chemical vapor deposition (PECVD) system, followed by H... + Ion implantation. The implantation dose was 5 × 10⁻⁶. 16cm -2 The implantation energy was 150 keV, and the ion beam was deflected 7° from the sample normal to prevent channeling effects. Boron ion implantation was performed on the Si epitaxial wafer at a dose of 2 × 10⁻⁶. 12 The implantation energy was 15 keV, and the ion beam was deviated from the sample normal by 7° to avoid channeling effects. After boron ion implantation, rapid thermal annealing at 1000 °C for 25 s was performed to activate the implanted boron ions and form a 100 nm charge layer.
[0077] 2) After activation, the Si epitaxial wafer and Ge wafer were subjected to organic sonication with acetone, alcohol and water for 10 min respectively to remove particulate matter and organic matter adsorbed on the substrate surface.
[0078] 3) After cleaning, the Si epitaxial wafer is first boiled in a 4:1 H2SO4 / H2O2 solution for 10 min, rinsed with deionized water 15 times, then soaked in a 1:20 HF / H2O solution for 4 min, and rinsed with deionized water 15 times.
[0079] 4) After cleaning, the Si epitaxial wafer is first boiled in a 1:1:4 NH4OH / H2O2 / H2O solution for 10 min, rinsed with deionized water 15 times, then soaked in a 1:20 HF / H2O solution for 4 min, and rinsed with deionized water 15 times.
[0080] 5) After cleaning, the Si epitaxial wafer is first boiled in a solution of HCl / H2O2 / H2O with a volume ratio of 1:1:4 for 10 min, and then rinsed with deionized water 15 times.
[0081] 6) The cleaned Si epitaxial wafer and the cleaned Ge wafer were soaked in a solution with a volume ratio of HF:H2O=1:20 for 4 minutes and rinsed with deionized water 15 times.
[0082] 7) Reference Figure 1 The bonding process diagram shows that after the Si epitaxial wafer and Ge wafer are cleaned and dried using a spin coater, they are placed into a double-sided magnetron sputtering thermopressing machine until the background vacuum level in the sputtering chamber is less than 1×10⁻⁶. -4 Ar gas with a purity of 5N was introduced into the sputtering chamber, and the pressure inside the sputtering chamber was controlled at 0.7 Pa. At room temperature, a 3 nm a-Si thin film was sputtered on the surface of a Si epitaxial wafer, and then the Si epitaxial wafer and the Ge wafer were rapidly bonded together in the cavity. Then, in-situ hot pressing bonding was performed, with a pressure of 12 MPa, a hot pressing temperature of 300 ℃, a hot pressing holding time of 1 h, and a heating and cooling rate of 1 ℃ / min.
[0083] 8) After bonding, the Ge / Si bonded wafer is placed in a tube annealing furnace for low-temperature hot annealing. The bubble diagram of the annealed Ge / Si sample is shown below. Figure 2As shown, the effect of full bonding can be achieved. Then, the sample is annealed at 350 °C for 10 h in a nitrogen atmosphere to achieve intelligent peeling of the Si-based Ge film, that is, to peel off a layer of Ge film from the Ge wafer and cover it on the Si-based a-Si.
[0084] 9) The prepared Si-based Ge thin films were annealed in a high-vacuum annealing furnace at 500 °C for 1 h in a vacuum environment, with a heating and cooling rate of 0.5 °C / min.
[0085] 10)Reference Figure 3 The double-crystal XRD diffraction patterns of the samples were measured after annealing at 350 °C and 500 °C. The figures show that the full width at half maximum (FWHM) of the samples decreased from 100 arcseconds to 84 arcseconds with increasing temperature. This is because the disordered internal structure enables lattice isolation, suppresses mismatch dislocation nucleation, and repairs midpoint defects in the Ge thin film under high-temperature annealing, thereby improving the crystal quality of the Ge thin film.
[0086] 11) After annealing, the Ge film was polished using a chemical mechanical polishing machine for 5 min at a speed of 30 r / min and a swing arm speed of 15 r / min. The polished Ge film was then placed in a quartz beaker, an appropriate amount of alcohol was added, and the beaker was placed in a water bath at 80 °C for 20 min to remove the paraffin wax on the back side of the Si substrate.
[0087] 12) After cleaning, the Si-based Ge film was subjected to boron ion implantation at a dose of 4 × 10⁻⁶. 15 cm -2 The implantation energy was 30 keV. The implanted Ge thin film sample was then placed in a PECVD vacuum chamber to grow a 100 nm SiO2 layer on the Ge thin film surface as an annealing protective layer.
[0088] 13) The Ge thin film after SiO2 growth was placed in a tube annealing chamber and annealed at 400 °C for 1 h in a N2 atmosphere;
[0089] 14) After annealing, the Ge film sample was soaked in a solution with a volume ratio of HF:H2O=1:20 for 15 min to etch away the SiO2 layer. Then, it was sonicated with acetone, alcohol and water for 10 min respectively. Finally, it was rinsed with deionized water 15 times. The Ge film sample was then dried by spin coating and placed in an oven at 135 ℃ for 1 h to remove moisture.
[0090] 15) After drying, a spin coater was first used to spin-coat the Ge / Si sample surface with a tackifier and photoresist. Then, the sample was pre-baked for 5 minutes. Next, a UV lithography machine was used to perform the first photolithography on the sample, defining the pattern on the upper platform. After photolithography, the sample was developed with a developer for 55 seconds, followed by baking in an oven at 120°C for 15 minutes to harden the photoresist. Then, dry and wet etching of the Ge thin film were performed. First, the sample was placed in an ICP etching machine for dry etching. The etching gas was sulfur hexafluoride (10 sccm), the etching time was 180 seconds, and the electrode power (upper / lower) was 100 / 40 W. Next, the sample was placed in an H3PO4:H2O2=3:1 etching solution for wet etching for 1 min 30 s. Then, the sample was placed in an ICP etching machine to etch Si using sulfur hexafluoride (30 sccm) as the etching gas, with electrode power (upper / lower) of 200 / 15 W and an etching time of 29 s to isolate each device. Finally, the photoresist was removed from the sample using acetone, alcohol, and water.
[0091] 16) After cleaning, the sample was dried using a spin coater and then placed in an ALD to deposit 10 nm Al2O3. Then the sample was placed in a PECVD to deposit 400 nm SiO2 and 200 nm Si3N4.
[0092] 17) After growth, the sample was first spin-coated with a tackifier and photoresist using a spin coater, then pre-baked for 5 min. Next, the sample was lithographically patterned using a second photolithography plate to define the electrode hole positions. It was then baked in an oven at 120 ℃ for 15 min to achieve a hardened photoresist film. Then, the sample was placed in an ICP etching machine to etch Si3N4 and SiO2 separately using trifluoromethane (100 sccm) and argon (20 sccm) as etching gases, with etching times of 125 s and 300 s respectively. The electrode power (upper / lower) was set to 200 / 20 W. The remaining 20 nm of SiO2 was then etched with BOE solution (3 ml HF: 6 g NH4F: 10 ml H2O) for 10 s. The sample was then sequentially treated with acetone, alcohol, and water to remove the photoresist. After spin-drying the sample using a spin coater, it was placed in an oven at 135 ℃ for 1 h to remove moisture.
[0093] 18) After baking, the Ge / Si sample surface was first spin-coated with a tackifier and photoresist using a spin coater. Then, the photoresist was pre-baked for 4 minutes using a heating stage at 96 ℃. The sample was then etched using a third-generation photolithography plate to define the electrode positions, followed by a 4-minute post-baking. The sample was then exposed for 20 seconds and developed with a developer for 55 seconds. Next, 10 nm Ti / 300 nm Al electrodes were sputtered onto the sample surface using magnetron sputtering. Finally, the sample was immersed in acetone solution for 24 hours and then peeled off with the photoresist, ultimately fabricating the Ge / Si SACM APD photodetector.
[0094] 19) The fabricated Ge / Si SACM APD photodetector was tested for dark current using a monochromator. The Ge / Si SACM APD device with a 30 μm diameter mesa achieved gains of 1.79 × 10⁻⁶ at wavelengths of 1310 nm and 1550 nm, respectively. 6 and 1.69×10 5 The responsivity is 1.145 A / W and 2.57 A / W, respectively, and the dark current is as low as 1.79 μA.
[0095] 20) Schematic diagram of Ge / Si sample bonded by high vacuum in-situ sputtering and as shown below. Figure 1 As shown in the image, the actual bubble structure of the bonded Ge / Si sample is as follows. Figure 2 As shown in the figure, this method can achieve the effect of complete bonding of Ge / Si samples. Figure 3 These are the double-crystal XRD diffraction patterns of the tested Si-based Ge thin films after annealing at 350 °C and 500 °C. The Si-based Ge thin film exfoliated at 350 °C has a full width at half maximum (FWHM) of 100 arcseconds, which is due to H... + The point defects formed by the injection in the Ge film are the cause. After annealing at 500 °C, the full width at half maximum (FWHM) of the Si-based Ge film decreased to 84 arcseconds. This is because the point defects in the Ge film were repaired under high-temperature annealing, resulting in improved crystal quality of the Ge film. Figure 4 This is a three-dimensional structure diagram of a Ge / Si SACM APD. Figure 5 Figure 6 shows the IV curves of the tested Ge / Si SACM APD at diameters of 30 μm and 50 μm, respectively. From Figure 6, it can be seen that the gain of the 30 μm diameter Ge / Si APD device at wavelengths of 1310 nm and 1550 nm can reach 1.79 × 10⁻⁶. 6 and 1.69×10 5The responsivity is 1.145 A / W and 2.57 A / W, respectively, with a dark current as low as 1.79 μA. Figure 7 shows that the responsivity of the 50 μm diameter Ge / Si APD device at wavelengths of 1310 nm and 1550 nm is 0.58 A / W and 1.5 A / W, respectively, with a gain of 1.17 × 10⁻⁶. 6 and 2×10 5 The dark current is as low as 12.7 μA.
[0096] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for preparing Ge / Si SACMAPD, characterized in that, include: First, the Si epitaxial wafer and Ge wafer are surface treated. Then, a-Si is sputtered as an intermediate bonding layer at the Ge / Si bonding interface using high-vacuum in-situ sputtering bonding technology, and then directly bonded in-situ under high vacuum. Then, the bonded Ge / Si is annealed in steps for a long time to achieve the peeling of the Si-based Ge film. Secondly, the stripped Si-based Ge film was placed in a high-vacuum annealing furnace for annealing to release the non-uniform strain and repair point defects in the Ge film. Then, the repaired Si-based Ge film was polished and ion-implanted to prepare P… + Contact layer; Finally, a Ge / SiSACMAPD with a vertical absorption, charge, and multiplication separation structure was fabricated through photolithography, etching, and passivation processes. The surface treatment of Si epitaxial wafers and Ge wafers includes: First, ion implantation is performed: SiO2 is deposited on the Ge wafer surface as an ion implantation protective layer using a plasma chemical vapor deposition system, followed by H2O. + Ion implantation; A single-crystal Si epitaxial wafer is epitaxially grown on a Si substrate, and boron ions are implanted into the surface of the Si epitaxial wafer. Then, rapid thermal annealing is used to activate the implanted boron ions to form a lightly doped P-type charge layer. After ion implantation, chemical cleaning is performed: the SiO2 on the surface of the Ge wafer is immersed in HF:H2O solution to etch away the SiO2 protective layer, and the processed Si epitaxial wafer and Ge wafer are obtained. The process includes: sputtering a-Si onto Si epitaxial wafers and Ge wafers using high-vacuum in-situ sputtering bonding technology, followed by in-situ bonding; and peeling off Si-based Ge thin films using step-by-step long-term annealing. After surface treatment, the Si epitaxial wafers and Ge wafers are spun dry using a spin coater and then quickly placed into the cavity of a double-sided magnetron thermosetting sputtering machine. The sputtering chamber vacuum level is then reduced to less than 1×10⁻⁶. -4 At Pa, Ar gas is introduced into the sputtering chamber, and the gas pressure in the sputtering chamber is adjusted by changing the Ar gas flow rate, thus depositing an a-Si thin film on the Si epitaxial wafer. After sputtering the a-Si thin film, the Si epitaxial wafer is directly bonded to the Ge wafer in the cavity of a double-sided magnetron thermopressing sputtering machine to obtain a bonded Ge / Si sample. The sample with completed Ge / Si bonding was placed in a tube furnace and annealed in a step-by-step long time under a N2 atmosphere to achieve the peeling of the Si-based Ge film. The process of releasing the non-uniform strain and repairing point defects in Ge thin films includes: The stripped Si-based Ge film was placed in a high-vacuum annealing furnace and annealed in a high-vacuum environment to release the non-uniform strain and repair the point defects in the Ge film. Among them, polishing and ion implantation were used to prepare P + The contact layer process includes: The surface of the Ge thin film was polished using a chemical mechanical polishing machine; After polishing, the Ge film was placed in a quartz beaker, an appropriate amount of alcohol was poured in, and the beaker was placed in a water bath to remove the paraffin on the back of the Si substrate. After the alcohol water bath, the Si-based Ge film was ultrasonically treated with acetone, ethanol and deionized water in sequence to remove the particulate matter adsorbed on the surface of the Ge film. Boron ions were implanted onto the cleaned Ge film surface, and then SiO2 film was deposited on the Ge film surface using a plasma chemical vapor deposition system. Finally, the sample was placed in a tube annealing furnace and annealed under a N2 atmosphere to activate the implanted boron ions.
2. The method for preparing Ge / Si SACMAPD according to claim 1, characterized in that, The process of fabricating Ge / Si SACMAPDs with vertical absorption, charge multiplication, and separation structures through photolithography, etching, and passivation includes: Step 1: Remove moisture from the Si-based Ge thin film sample implanted with boron ions. After moisture removal, perform photolithography to form a hard film of photoresist. After hard film formation, etch the sample. After etching, clean and remove the photoresist. Step 2: After hardening the film, etch the Si-based Ge thin film sample. After etching, clean and remove the photoresist. Then, deposit and grow the compound on the Si-based Ge thin film sample. After compound growth, harden the Si-based Ge thin film sample with photoresist again. After hardening the film, etch the Si-based Ge thin film sample. After etching, remove the photoresist. Then, dry and develop the sample. Step 3: Magnetron sputtering is used to sputter both the front and back sides of the Si-based Ge thin film sample after photolithography and development. After sputtering, the Ge / Si sample is immersed in acetone solution and the adhesive is removed to finally prepare the Ge / Si SACM APD photodetector.
3. The method for preparing Ge / Si SACMAPD according to claim 2, characterized in that, Step 1 includes the following process: The ion-activated Ge film was immersed in HF:H2O solution to etch away the SiO2 protective layer. Then, the Ge film was ultrasonically cleaned with acetone, ethanol and deionized water in sequence, rinsed with deionized water, and then spun dry using a spin coater. Finally, the sample was placed in an oven to remove moisture. After removing moisture, the Si-based Ge thin film sample was spin-coated with a tackifier and photoresist using a spin coater. The sample was then placed on a heating stage for pre-baking of the photoresist. Next, the sample was subjected to the first photolithography using an ultraviolet lithography machine to define the upper stage. After the photolithography was completed, the sample was developed using a developer. Finally, the developed sample was placed in an oven to achieve photoresist hardening.
4. The method for preparing Ge / Si SACMAPD according to claim 3, characterized in that, Step 2 includes the following process: The Ge thin film was etched using dry and wet methods after the hard film was completed. First, the sample was placed in an ICP etching machine for dry etching using sulfur hexafluoride gas. Then, the sample was placed in an H3PO4:H2O2 = 3:1 etching solution for wet etching. After etching, the sample is placed in an ICP etching machine to etch the Si. The etching gas is sulfur hexafluoride to achieve device isolation. The photoresist was removed from the etched sample by sequentially ultrasonically cleaning the sample with acetone, ethanol and deionized water, followed by rinsing with deionized water to remove the photoresist. The cleaned Ge / Si sample was spin-dried using a spin coater, and then Al2O3 was deposited on the surface of the Ge thin film using an atomic layer deposition system. After growth, the sample was placed in the cavity of a plasma-enhanced chemical vapor deposition system to deposit SiO2 and Si3N4 in sequence. After the growth is completed, a spin coater is used to spin coat the Si-based Ge thin film surface with a thickener and photoresist. Then, the sample is placed on a heating stage to pre-bake the photoresist. Next, the sample is photolithographically etched using an ultraviolet lithography machine to define the electrode hole positions. Then, the sample is developed using a developer. Finally, the developed sample is placed in an oven to achieve photoresist hardening. After the hardening process is completed, the sample is etched with trifluoromethane and argon to remove Si3N4 and SiO2 from the surface of the Ge film. Then, SiO2 and Al2O3 will remain on the sample surface. The SiO2 and Al2O3 on the sample surface are then etched away with BOE solution. After etching, the photoresist is removed from the sample. The steps are as follows: the sample is ultrasonically cleaned with acetone, ethanol and deionized water in sequence, rinsed with deionized water, then the sample is spun dry using a spin coater, and finally the sample is placed in an oven to dry. After drying, the sample is first spin-coated with a tackifier and photoresist on the surface of the Si-based Ge thin film using a spin coater. Then, the sample is placed on a heating stage for pre-baking of the photoresist. Next, the sample is photolithographically etched to define the positions of the electrodes. Then, the sample is placed on a heating stage for post-baking of the photoresist. The sample is then exposed using a photolithography machine, and finally, the sample is developed.
5. The method for preparing Ge / Si SACMAPD according to claim 4, characterized in that, Step 3 includes the following process: After the sample was developed, Ti and Al were sputtered on both the front and back sides of the Ge / Si sample using magnetron sputtering. Finally, the Ge / Si sample was immersed in acetone solution and the adhesive was removed to prepare the Ge / Si SACMAPD photodetector.
6. A Ge / Si SACMAPD, characterized in that, The Ge / Si SACMAPD is prepared according to any one of claims 1 to 5 and has the following characteristics: Ge / Si SACMAPD exhibits absorption, charge, and multiplication separation parameter characteristics of a vertical structure; When the diameter of the Ge / Si SACMAPD is 30 μm, the responsivity of the Ge / Si SACMAPD device at wavelengths of 1310 nm and 1550 nm is 1.145 A / W and 2.57 A / W, respectively, and the gain reaches 1.79 × 10⁻⁶. 6 and 1.69×10 5 Dark current as low as 1.79μA; When the diameter of the Ge / Si SACMAPD is 50 μm, the Ge / Si SACMAPD device exhibits responsivity of 0.58 A / W and 1.5 A / W at wavelengths of 1310 nm and 1550 nm, respectively, with gains reaching 1.17 × 10⁻⁶. 6 and 2×10 5 The dark current is as low as 12.7μA.