Design method of deep trench ohmic contacts with high thermoelectric performance based on microjet laser technology

Abstract

The present invention provides a design method for a deep-groove ohmic contact with high thermoelectric performance based on micro-jet laser technology, which relates to the technical field of semiconductor power devices. The method comprises: a high-thermoelectric-performance deep-groove ohmic contact structure is obtained by a micro-jet laser etching process using an ultrashort pulse laser; a micro-jet laser etching process based on an ultrashort pulse laser precisely etches a positioning area to achieve a deep-groove flow channel that meets the thermal management performance requirements of the microchannel and is compatible with subsequent device processes and research requirements. The method combines a capacitance-voltage ring diode measurement unit prepared using a hard mask process and a thick photoresist process, a transmission line model measurement unit prepared using a hard mask process or a thick photoresist process, and a time-domain thermal reflection measurement unit prepared using a chemical mechanical polishing process to achieve an optimized iterative study of the thermoelectric characteristics of a high-thermoelectric-performance deep-groove ohmic contact structure, thereby achieving a high-thermoelectric-performance deep-groove ohmic contact.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor power devices, and in particular to a method for designing deep-groove ohmic contacts with high thermoelectric performance based on micro-jet laser technology. Background Art

[0002] The low thermal conductivity of gallium oxide (Ga2O3) material is the main obstacle to the application of Ga2O3 power devices. Some experimental and simulation studies have documented thermal management strategies based on adding or changing the bottom and top configurations of Ga2O3 transistors. Bottom cooling methods (microfluidic cooling, substrate thinning, and heterogeneous integration of high thermal conductivity substrates) and top cooling methods (air jet impingement cooling and flip-chip packaging integration) can effectively alleviate the self-heating effect of Ga2O3 transistors. Microfluidic cooling is achieved by etching deep grooves in the substrate, with a depth typically greater than 100μm, ensuring that they are effectively close to the channel heat source area to achieve effective heat dissipation of the device. When the device is operating, the coolant in the deep groove flow channel for horizontal devices and the electrode material and packaging solder with higher thermal conductivity in the deep groove of the substrate ohmic region for vertical devices are used to enhance the heat exchange level between the device heat source area and the outside world, thereby achieving the purpose of improving the overall heat dissipation level of the device. For vertical devices, groove etching can also enhance the surface roughness of the Ga2O3 material in the ohmic region and increase the ohmic contact area, thereby enhancing ohmic tunneling and ohmic interface thermal conductivity, while significantly improving the ohmic contact thermal and electrical properties and enhancing the overall thermoelectric properties of the device.

[0003] At present, microjet laser technology can be applied to the device processing process. During the processing of microjet laser technology, laser is used to irradiate the material to heat it locally. The temperature rises rapidly to make the material sublime, and the impurities are removed by the scouring force generated by the jet. Conventional microjet laser technology can realize the processing of SiC materials. However, due to the high melting point of Ga2O3 material (such as the melting point of β-Ga2O3 is 1820℃) and its special lattice structure, conventional microjet laser technology is not suitable for etching Ga2O3 material. At the same time, after conventional microjet laser etching of Ga2O3 material, its surface roughness is still large (generally on the order of 10μm), and it is impossible to conduct ohmic thermoelectric properties and its optimization iteration research. A time domain thermoreflectance (TDTR) measurement unit for characterizing the thermal resistance characteristics of the ohmic contact interface; a capacitance-voltage ring diode (CV ring) measurement unit for characterizing the ohmic interface characteristics; and a transmission line model (TLM) measurement unit for characterizing the ohmic contact resistance. The above measurement units need to be prepared on the etched surface of the semiconductor material unit after conventional microjet laser etching. Since the surface roughness of the device after conventional microjet laser etching is large, it is difficult to form a uniform film layer using the conventional 1μm thin photoresist process, and the subsequent ohmic evaporation process and device unit preparation cannot be carried out, making it impossible to carry out iterative research on the optimization of the ohmic thermoelectric characteristics, resulting in the ultimate in the inability to achieve thermoelectrically optimized deep trench ohmic contact. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a method for designing deep-groove ohmic contacts with high thermoelectric performance based on micro-jet laser technology to solve the current problems of 1) insufficient etching depth of dry etching and inability to achieve thermal management requirements based on flow channel thermal management technology; 2) poor anisotropy of the wet-etched grooves, and as the etching depth increases, the groove patterning accuracy index deteriorates, resulting in the inability to effectively implement subsequent processes or bringing performance degradation and reliability risks; 3) the surface roughness of micro-jet laser technology is large, and subsequent iterative research on optimization of ohmic thermoelectric characteristics cannot be carried out.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] The present invention provides a method for designing a deep-groove ohmic contact with high thermoelectric performance based on micro-jet laser technology, the method comprising:

[0007] Obtain a high-thermoelectric performance deep-groove ohmic contact structure based on microjet laser technology. The deep groove of the high-thermoelectric performance deep-groove ohmic contact structure is obtained by using a microjet laser etching process using an ultrashort pulse laser. The deep groove is a groove with a depth greater than 100μm.

[0008] According to the high thermoelectric performance deep trench ohmic contact structure, a semiconductor material unit is prepared. The material used in the semiconductor material unit is the target semiconductor material. The parameters and etching process of the semiconductor material unit and the semiconductor material of the high thermoelectric performance deep trench ohmic contact structure are the same;

[0009] A capacitance-voltage ring diode measurement unit is fabricated on an etched surface of a semiconductor material unit using a hard mask process and a thick photoresist process;

[0010] A transmission line model measurement unit is prepared on an etched surface of a semiconductor material unit using a hard mask process or a thick photoresist process;

[0011] Using chemical mechanical polishing, a time-domain thermoreflectance measurement unit is fabricated on the etched surface of a semiconductor material unit. Capacitance-voltage ring diode measurement units, transmission line model measurement units, and time-domain thermoreflectance measurement units are all used for ohmic characteristic evaluation and iterative research on thermoelectric property optimization.

[0012] Electrical characteristic tests are performed on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic electrical characteristics of the high thermoelectric performance deep trench ohmic contact structure, and time domain thermal reflection tests are performed on the time domain thermal reflection measurement unit to evaluate the ohmic thermal characteristics of the ohmic contact of the high thermoelectric performance deep trench ohmic contact structure.

[0013] In some embodiments, semiconductor materials used in the high thermoelectric performance deep trench ohmic contact structure based on microjet laser technology include Ga2O3 materials, GaN materials, and SiC materials.

[0014] In some embodiments, before obtaining a high thermoelectric performance deep trench ohmic contact structure based on microjet laser technology, the method further includes:

[0015] growing a first Ga2O3 drift layer on the upper surface of the first Ga2O3 substrate layer;

[0016] Spin-coating a photoresist on the upper surface of the first Ga2O3 drift layer;

[0017] Using an ultrashort pulse laser microjet laser etching process, deep grooves are etched on the lower surface of the first Ga2O3 substrate layer according to the graphics designed in AutoCAD software. The deep grooves are evenly arranged and have a depth greater than 100μm. The ultrashort pulse laser has a pulse width of picoseconds and femtoseconds.

[0018] Using organic matter to remove photoresist;

[0019] Anode metal is grown on the upper surface of the first Ga2O3 drift layer using a metal evaporation process to form a Schottky contact, and cathode metal is grown on the lower surface of the etched first Ga2O3 substrate layer and annealed to form an ohmic contact, resulting in a deep-groove ohmic contact structure with high thermoelectric performance based on microjet laser technology.

[0020] In some embodiments, a semiconductor material unit is prepared based on a high thermoelectric performance deep trench ohmic contact structure, including:

[0021] growing a second Ga2O3 drift layer on the upper surface of the second Ga2O3 substrate layer, wherein the second Ga2O3 substrate layer has the same thickness and doping concentration as the first Ga2O3 substrate layer, and the second Ga2O3 drift layer has the same thickness and doping concentration as the first Ga2O3 drift layer;

[0022] Spin-coating a photoresist on the upper surface of the second Ga2O3 drift layer;

[0023] The lower surface of the second Ga2O3 substrate layer is entirely etched using an ultrashort pulse laser microjet laser etching process. The ultrashort pulse laser microjet laser etching process is the same as the etching process used to prepare deep trench ohmic contact structures with high thermoelectric performance.

[0024] The photoresist is removed using organic matter to prepare a semiconductor material unit.

[0025] In some embodiments, the thickness of the thick photoresist used in the thick photoresist process is not less than 10 μm.

[0026] In some embodiments, a capacitance-voltage ring diode measurement unit is fabricated on an etched surface of a semiconductor material unit using a hard mask process and a thick photoresist process, including:

[0027] Using a hard mask process, patterning a first metal on the etched surface of the semiconductor material unit and evaporating the first metal, wherein the material of the first metal is the same as that of the cathode metal;

[0028] Annealing the evaporated first metal to form an ohmic contact;

[0029] Spin coating thick photoresist using a thick photoresist process;

[0030] The second metal is patterned using a thick photoresist process, and the second metal is evaporated to form a Schottky contact to obtain a capacitance-voltage ring diode measurement unit. The material of the second metal is the same as that of the anode metal.

[0031] In some embodiments, a transmission line model measurement unit is fabricated on an etched surface of a semiconductor material unit using a hard mask process or a thick photoresist process, comprising:

[0032] Using a hard mask process, patterning a third metal on the etched surface of the semiconductor material unit and evaporating the third metal, the material of the third metal being the same as that of the cathode metal;

[0033] Annealing the evaporated third metal to form an ohmic contact, thereby obtaining a transmission line model measurement unit;

[0034] Alternatively, a thick photoresist process is used to spin-coat a thick photoresist onto the etched surface of the semiconductor material unit;

[0035] patterning the third metal using a thick photoresist process, and evaporating the third metal;

[0036] The evaporated third metal is annealed to form an ohmic contact, thereby obtaining a transmission line model measurement unit.

[0037] In some embodiments, a time-domain thermoreflectance measurement unit is fabricated on an etched surface of a semiconductor material unit using a chemical mechanical polishing process, comprising:

[0038] Using chemical mechanical polishing process to smooth the etched surface of semiconductor material unit;

[0039] Ohmic contact metal titanium and palladium gold are evaporated in sequence on the smoothed etched surface of the semiconductor material unit to form a time domain thermoreflectance measurement unit.

[0040] In some embodiments, the material of the anode metal is any one of Ni / Au and Mo / Au, and the material of the cathode metal is Ti / Au.

[0041] In some embodiments, the ohmic electrical properties include ohmic contact resistance properties, material sheet resistance properties, and interface defect properties, and the ohmic thermal properties of the ohmic contact include interface thermal resistance and interface thermal expansion coefficient.

[0042] Compared to the prior art, the present invention provides a method for designing a high-thermoelectric-performance deep-groove ohmic contact based on microjet laser technology, including a high-thermoelectric-performance deep-groove ohmic contact structure based on microjet laser technology. The high-thermoelectric-performance ohmic deep-groove contact structure is obtained using a microjet laser etching process using an ultrashort pulse laser, and the deep groove is a trench with a depth greater than 100 μm. A semiconductor material unit is prepared based on the high-thermoelectric-performance deep-groove ohmic contact structure. The material used in the semiconductor material unit is the target semiconductor material, and the parameters and etching process of the semiconductor material unit and the semiconductor material of the high-thermoelectric-performance deep-groove ohmic contact structure are the same. A capacitance-voltage ring diode measurement unit is prepared on the etched surface of the semiconductor material unit using a hard mask process and a thick photoresist process; a transmission line model measurement unit is prepared on the etched surface of the semiconductor material unit using a hard mask process or a thick photoresist process; and a time-domain thermal reflection measurement unit is prepared on the etched surface of the semiconductor material unit using a chemical mechanical polishing process. The capacitance-voltage ring diode measurement unit, transmission line model measurement unit and time-domain thermal reflection measurement unit are all used for ohmic characteristic evaluation and iterative research on thermoelectric characteristic optimization; electrical characteristic tests are performed on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic electrical characteristics of the deep trench ohmic contact structure with high thermoelectric performance, and time-domain thermal reflection tests are performed on the time-domain thermal reflection measurement unit to evaluate the ohmic thermal characteristics of the ohmic contact of the deep trench ohmic contact structure with high thermoelectric performance. In this way, a deep groove ohmic contact structure with high thermoelectric performance is obtained through the micro-jet laser etching process of an ultrashort pulse laser. The micro-jet laser etching process based on the ultrashort pulse laser can achieve a deep groove flow channel that meets the thermal management performance requirements of the microchannel and is compatible with subsequent device processes and research requirements by precisely etching the positioning area; combined with the capacitance-voltage ring diode measurement unit prepared based on the hard mask process and the thick photoresist process, the transmission line model measurement unit prepared based on the hard mask process or the thick photoresist process, and the time domain thermal reflection measurement unit prepared based on the chemical mechanical polishing process, the iterative research on the thermoelectric characteristics optimization of the deep groove ohmic contact structure with high thermoelectric performance is realized, thereby realizing a deep groove ohmic contact with high thermoelectric performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0044] Figure 1 The flowchart of the design method of deep trench ohmic contacts with high thermoelectric performance based on microjet laser technology is schematically shown;

[0045] Figure 2The following schematically shows the process flow for preparing a deep trench ohmic contact structure with high thermoelectric performance;

[0046] Figure 3 Schematic diagram of growing the first Ga2O3 drift layer;

[0047] Figure 4 Schematic diagram showing the spin coating of photoresist on the upper surface of the first Ga2O3 drift layer;

[0048] Figure 5 Schematic diagram showing the etching of deep grooves on the lower surface of the first Ga2O3 substrate layer;

[0049] Figure 6 Schematically shows a schematic diagram of removing photoresist;

[0050] Figure 7 The structure of the deep trench ohmic contact structure with high thermoelectric performance is schematically shown;

[0051] Figure 8 The flowchart of the preparation of the semiconductor material unit is schematically shown;

[0052] Figure 9 Schematic diagram showing the growth of the second Ga2O3 drift layer;

[0053] Figure 10 Schematic diagram showing the spin coating of photoresist on the upper surface of the second Ga2O3 drift layer;

[0054] Figure 11 Schematic diagram showing the entire surface etching of the lower surface of the second Ga2O3 substrate layer using the same ultrashort pulse laser microjet laser etching process conditions as those used to prepare a high thermoelectric performance deep trench ohmic contact structure;

[0055] Figure 12 Schematically shows the structure of a semiconductor material unit;

[0056] Figure 13 schematically illustrates a schematic diagram of patterning a first metal and evaporating the first metal;

[0057] Figure 14 schematically shows a schematic diagram of annealing the evaporated first metal;

[0058] Figure 15 Schematic diagram of spin coating thick photoresist;

[0059] Figure 16 schematically illustrates a schematic diagram of patterning a second metal and evaporating the second metal;

[0060] Figure 17 The structure of the capacitance-voltage ring diode measurement unit is schematically shown;

[0061] Figure 18 The figure schematically shows a schematic diagram of patterning the third metal using a hard mask process and evaporating the third metal;

[0062] Figure 19 Schematically shows a schematic diagram of spin coating thick photoresist using a thick photoresist process;

[0063] Figure 20 Schematically shows a schematic diagram of patterning the third metal using a thick photoresist process and evaporating the third metal;

[0064] Figure 21 The structure diagram of the transmission line model measurement unit is schematically shown;

[0065] Figure 22 Schematic diagram showing the use of a chemical mechanical polishing process to smooth the etched surface of a semiconductor material unit;

[0066] Figure 23 The figure schematically shows a time domain thermoreflectance measurement unit obtained by sequentially evaporating ohmic contact metal titanium and palladium gold on the etched surface of the smoothed semiconductor material unit. DETAILED DESCRIPTION

[0067] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0068] It should be noted that, unless otherwise specified, the technical or scientific terms used in the present invention should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0069] The method in the embodiment of the present invention is described in detail below.

[0070] Figure 1 The flowchart of the method for designing a deep trench ohmic contact with high thermoelectric performance based on micro-jet laser technology in an embodiment of the present invention is schematically shown. Figure 1 As shown, the method may include:

[0071] S101. Obtain a deep-groove ohmic contact structure with high thermoelectric performance based on micro-jet laser technology.

[0072] Among them, the deep groove of the high thermoelectric performance deep groove ohmic contact structure is obtained by using a micro-jet laser etching process of an ultrashort pulse laser, and the deep groove is a groove with a depth greater than 100μm.

[0073] High thermoelectric performance means that the doping concentration of the drift layer is 1×10 16 cm -3 For a Ga2O3 diode device with a thickness of 10μm and an anode metal area of ​​1mm×1mm, the forward current can reach 2A when the forward voltage is 2V, and the junction temperature of the Ga2O3 diode device does not exceed 90 degrees.

[0074] The groove depth of the deep groove may be 100 μm-300 μm, and the deep groove has a micron-level roughness.

[0075] The materials used in the high-thermoelectric-performance deep trench ohmic contact structure include Ga2O3, GaN, and SiC. Other semiconductor materials, particularly those sensitive to high temperatures, may also be used. The materials used in the high-thermoelectric-performance deep trench ohmic contact structure are not specifically limited.

[0076] Figure 2 The following schematically illustrates a flow chart for preparing a deep trench ohmic contact structure with high thermoelectric performance. Specifically, before obtaining the deep trench ohmic contact structure with high thermoelectric performance based on microjet laser technology, the method further includes:

[0077] Step A1: growing a first Ga2O3 drift layer on the upper surface of the first Ga2O3 substrate layer.

[0078] Figure 3 The schematic diagram of growing the first Ga2O3 drift layer is shown schematically. The first Ga2O3 drift layer can be grown on the first Ga2O3 substrate layer by Halide Vapor Phase Epitaxy (HVPE). Here, the growth method is not specifically limited.

[0079] Step A2: Spin-coat photoresist on the upper surface of the first Ga2O3 drift layer.

[0080] Figure 4 The schematic diagram of spin coating photoresist on the upper surface of the first Ga2O3 drift layer is schematically shown. The photoresist is spin coated on the upper surface of the first Ga2O3 drift layer to protect the upper surface of the first Ga2O3 drift layer.

[0081] Step A3: using an ultrashort pulse laser microjet laser etching process, deep grooves are etched on the lower surface of the first Ga2O3 substrate layer according to the graphics designed by AutoCAD software.

[0082] The deep grooves are evenly arranged and have a depth greater than 100 μm. The ultrashort pulse laser is a laser with a pulse width in the order of picoseconds and femtoseconds.

[0083] The principle of the micro-jet laser etching process of ultrashort pulse lasers is as follows: an advanced technology that uses a fine water jet to guide the laser to achieve material processing. This technology focuses the laser beam and couples it into a high-speed water jet. The laser beam focused at the nozzle position forms a total reflection on the inner wall of the fine water column, generating an energy beam with uniform cross-sectional energy distribution and is guided to the surface of the workpiece for processing. During the micro-jet laser processing process, the water flow ejected by high pressure can continuously cool the etching area and effectively remove the Ga2O3 debris generated by laser etching. The water flow ejected by high pressure can continuously cool the etching area and effectively remove the debris generated by laser etching. After optimizing the etching process using ultrashort pulse lasers such as picosecond and femtosecond lasers, the etching area can be precisely located to achieve the groove morphology and reliability required for deep groove thermal management of the first Ga2O3 substrate layer.

[0084] Figure 5 The schematic diagram of etching deep grooves on the lower surface of the first Ga2O3 substrate layer is shown schematically. Using the micro-jet laser etching process of an ultrashort pulse laser, two 100μm deep grooves can be etched on the lower surface of the 650μm first Ga2O3 substrate layer.

[0085] Step A4: removing the photoresist using organic matter.

[0086] Figure 6 The schematic diagram of removing the photoresist is shown schematically. Using the micro-jet laser etching process of the ultrashort pulse laser, two 100 μm deep grooves can be etched on the lower surface of the first 650 μm Ga2O3 substrate layer, and then the photoresist spin-coated in step A2 can be removed using organic matter.

[0087] Step A5: Anode metal is grown on the upper surface of the first Ga2O3 drift layer using a metal evaporation process to form a Schottky contact, cathode metal is grown on the lower surface of the etched first Ga2O3 substrate layer and annealed to form an ohmic contact, thereby obtaining a deep-groove ohmic contact structure with high thermoelectric performance based on microjet laser technology.

[0088] The anode metal material is any one of Ni / Au and Mo / Au, and the cathode metal material is Ti / Au. The anode metal and cathode metal materials may also be other materials, and are not specifically limited herein.

[0089] Figure 7The schematic diagram of a high-thermoelectric-performance deep-trench ohmic contact structure shows the structure, which, from top to bottom, comprises: a nickel / gold (Ni / Au) anode, a first Ga2O3 drift layer, a first Ga2O3 substrate layer with deep trenches, and a titanium / gold (Ti / Au) cathode. The deep trench on the lower surface of the first Ga2O3 substrate layer is etched using an ultrashort-pulse laser microjet etching process. There is at least one deep trench with a micron-level roughness.

[0090] S102. Prepare a semiconductor material unit based on a deep trench ohmic contact structure with high thermoelectric performance.

[0091] Among them, the material used in the semiconductor material unit is the target semiconductor material, and the parameters and etching process of the semiconductor material unit and the semiconductor material of the high thermoelectric performance deep trench ohmic contact structure are the same.

[0092] The parameters of the semiconductor material include the thickness of the semiconductor material and the doping concentration of the semiconductor material. The etching process of the semiconductor material unit is the same as the etching process conditions of the high thermoelectric performance deep trench ohmic contact structure.

[0093] The semiconductor material unit does not include anode metal and cathode metal of a deep trench ohmic contact structure with high thermoelectric performance.

[0094] Figure 8 The following schematically illustrates a process flow for preparing a semiconductor material unit. Specifically, the process for preparing a semiconductor material unit based on a deep trench ohmic contact structure with high thermoelectric performance includes:

[0095] Step B1: growing a second Ga2O3 drift layer on the upper surface of the second Ga2O3 substrate layer.

[0096] The second Ga2O3 substrate layer has the same doping concentration and thickness as the first Ga2O3 substrate layer, and the second Ga2O3 drift layer has the same doping concentration and thickness as the first Ga2O3 drift layer.

[0097] Figure 9 The schematic diagram of growing the second Ga2O3 drift layer is schematically shown. The second Ga2O3 drift layer is grown on the second Ga2O3 substrate layer by using HVPE.

[0098] Step B2: Spin-coat photoresist on the upper surface of the second Ga2O3 drift layer.

[0099] Figure 10 The schematic diagram of spin coating photoresist on the upper surface of the second Ga2O3 drift layer is schematically shown. The photoresist is spin coated on the upper surface of the second Ga2O3 drift layer to protect the surface of the second Ga2O3 drift layer.

[0100] Step B3: using a microjet laser etching process using an ultrashort pulse laser to entirely etch the lower surface of the second Ga2O3 substrate layer.

[0101] Among them, the micro-jet laser etching process of the ultrashort pulse laser is the same as the etching process for preparing the deep groove ohmic contact structure with high thermoelectric performance.

[0102] Figure 11 The figure schematically shows the entire surface etching of the lower surface of the second Ga2O3 substrate layer using the same micro-jet laser etching process conditions as those used to prepare the high thermoelectric performance deep groove ohmic contact structure. The lower surface of the second Ga2O3 substrate layer is entirely etched using the same etching process conditions as those used to prepare the high thermoelectric performance deep groove ohmic contact. After etching, the lower surface of the second Ga2O3 substrate layer has a micron-level roughness.

[0103] Step B4: using organic matter to remove the photoresist to prepare a semiconductor material unit.

[0104] Figure 12 The structure of the semiconductor material unit is schematically shown. The semiconductor material unit includes, from top to bottom, a second Ga2O3 drift layer and a second Ga2O3 substrate layer after full-surface etching. The lower surface of the second Ga2O3 substrate layer has a micron-level roughness.

[0105] The measurement units used for ohmic characteristic evaluation and iterative research for thermoelectric characteristic optimization include CV loop measurement unit, TLM measurement unit, and TDTR measurement unit.

[0106] S103 , using a hard mask process and a thick photoresist process to prepare a capacitance-voltage ring diode measurement unit on the etched surface of the semiconductor material unit.

[0107] The capacitance-voltage ring diode measurement unit is used to characterize the interface properties of ohmic contacts.

[0108] The thickness of the thick photoresist used in the thick photoresist process is not less than 10 μm.

[0109] The CV ring measurement unit is prepared on the etched surface of a semiconductor material unit after being etched using an ultrashort pulse laser. The hard mask process uses a metal material as a mask to accurately transfer complex, high-precision patterns. Compared to conventional photoresist mask processes, the hard mask process does not require a pre-photolithography stripping process and can accurately replicate the pattern on the mask onto the material surface, ensuring high pattern precision. The thick photoresist process uses an unconventional thick photoresist (10μm thick) process to form a uniform film layer on materials with high surface roughness, facilitating the formation of ideal device electrode structures with good contact in subsequent processes.

[0110] Specifically, a capacitance-voltage ring diode measurement unit is prepared on an etched surface of a semiconductor material unit using a hard mask process and a thick photoresist process, including:

[0111] Step C1: patterning a first metal on the etched surface of the semiconductor material unit and evaporating the first metal using a hard mask process.

[0112] The material of the first metal is the same as that of the cathode metal.

[0113] The material of the first metal is Ti / Au, and the first metal may also be other materials. The material of the first metal is not specifically limited here.

[0114] Figure 13 The schematic diagram of patterning the first metal and evaporating the first metal is schematically shown. The first metal Ti / Au is patterned and evaporated on the etched surface of the semiconductor material unit using a hard mask process.

[0115] Step C2: annealing the evaporated first metal to form an ohmic contact.

[0116] Figure 14 The schematic diagram of annealing the evaporated first metal is schematically shown. The evaporated first metal Ti / Au is annealed to form an ohmic contact.

[0117] Step C3: spin-coating thick photoresist using a thick photoresist process.

[0118] Figure 15 The schematic diagram of spin-coating thick photoresist is schematically shown. Using the thick photoresist process, thick photoresist is spin-coated on the etched surface of the first metal Ti / Au and semiconductor material unit after annealing to protect the etched surface of the first metal Ti / Au and semiconductor material unit after annealing that does not require subsequent processes.

[0119] Step C4: patterning the second metal using a thick photoresist process, and evaporating the second metal to form a Schottky contact, thereby obtaining a capacitance-voltage ring diode measurement unit.

[0120] The material of the second metal is the same as that of the anode metal.

[0121] The material of the second metal is any one of Ni / Au and Mo / Au. The second metal may also be other materials. The material of the second metal is not specifically limited here.

[0122] Figure 16The schematic diagram of patterning the second metal and evaporating the second metal is schematically shown. The second metal Ni / Au is patterned using a thick photoresist process, and the second metal Ni / Au is evaporated to obtain a capacitance-voltage ring diode measurement unit.

[0123] Figure 17 The structural diagram of the capacitance-voltage ring diode measurement unit is schematically shown. The capacitance-voltage ring diode measurement unit includes, from top to bottom, a second Ga2O3 drift layer, a second Ga2O3 substrate layer after full-surface etching, and a first metal Ti / Au and a second metal Ni / Au arranged at intervals on the lower surface of the second Ga2O3 substrate layer after full-surface etching.

[0124] S104 , using a hard mask process or a thick photoresist process to prepare a transmission line model measurement unit on the etched surface of the semiconductor material unit.

[0125] The transmission line model measurement unit is used to characterize ohmic contact resistance and square resistance.

[0126] The following steps D1a and D2a may be selected to prepare a transmission line model measurement unit on the etched surface of the semiconductor material unit, or steps D1b, D2b and D3b may be selected to prepare a transmission line model measurement unit on the etched surface of the semiconductor material unit.

[0127] Specifically, a transmission line model measurement unit is prepared on an etched surface of a semiconductor material unit using a hard mask process or a thick photoresist process, including:

[0128] Step D1a: patterning a third metal on the etched surface of the semiconductor material unit using a hard mask process and evaporating the third metal.

[0129] The material of the third metal is the same as that of the cathode metal.

[0130] The material of the third metal is Ti / Au, and the third metal may also be other materials. The material of the third metal is not specifically limited here.

[0131] Figure 18 The diagram schematically shows the patterning of the third metal and evaporation of the third metal using the hard mask process. The third metal Ti / Au is patterned on the etched surface of the semiconductor material unit using the hard mask process and the third metal Ti / Au is evaporated.

[0132] Step D2a: Annealing the evaporated third metal to form an ohmic contact, thereby obtaining a transmission line model measurement unit.

[0133] Alternatively, step D1b: using a thick photoresist process, spin-coating a thick photoresist on the etched surface of the semiconductor material unit.

[0134] Figure 19 The schematic diagram of spin coating thick photoresist using thick photoresist process is schematically shown. Using thick photoresist process, thick photoresist is spin coated on the etched surface of semiconductor material unit to protect the etched surface of semiconductor material unit from being subjected to subsequent processes.

[0135] Step D2b: patterning the third metal using a thick photoresist process, and evaporating the third metal.

[0136] Figure 20 The diagram schematically shows the process of patterning the third metal using a thick photoresist process and evaporating the third metal, and the process of patterning the third metal Ti / Au using a thick photoresist process and evaporating the third metal Ti / Au.

[0137] Step D3b: Annealing the evaporated third metal to form an ohmic contact, thereby obtaining a transmission line model measurement unit.

[0138] Figure 21 The structural diagram of the transmission line model measurement unit is schematically shown. The transmission line model measurement unit includes, from top to bottom, a second Ga2O3 drift layer, a second Ga2O3 substrate layer after full-surface etching, and a third metal Ti / Au arranged at intervals on the lower surface of the second Ga2O3 substrate layer after full-surface etching.

[0139] S105 , using a chemical mechanical polishing process to prepare a time domain thermoreflectance measurement unit on the etched surface of the semiconductor material unit.

[0140] Among them, the capacitance-voltage ring diode measurement unit, the transmission line model measurement unit and the time-domain thermal reflection measurement unit are all used for ohmic characteristic evaluation and iterative research on thermoelectric characteristic optimization.

[0141] The time-domain thermoreflectance measurement unit is used to characterize the ohmic contact interface thermal resistance and interface thermal expansion coefficient.

[0142] The main principle of the chemical mechanical polishing process is to first allow the chemical components in the polishing liquid to react slightly with the debris on the surface of the material to soften it, and then apply pressure to the polishing head to physically grind the surface of the material, thereby reducing the surface roughness of the material.

[0143] Specifically, a time domain thermoreflectance measurement unit is prepared on an etched surface of a semiconductor material unit using a chemical mechanical polishing process, including:

[0144] Step E1: Smoothing the etched surface of the semiconductor material unit by using a chemical mechanical polishing process.

[0145] Figure 22A schematic diagram of smoothing the etched surface of a semiconductor material unit using a chemical mechanical polishing process is shown. The chemical mechanical polishing process is used to smooth the etched surface of the semiconductor material unit to meet the requirements of TDTR measurement. After polishing, the etched surface roughness of the semiconductor material unit is nanometer-level roughness.

[0146] Step E2: sequentially evaporating ohmic contact metal titanium and palladium gold on the smoothed etched surface of the semiconductor material unit to form the time-domain thermoreflectance measurement unit.

[0147] The roughness of the time domain thermoreflectance measurement unit is at the nanometer level.

[0148] Figure 23 A schematic diagram of a time-domain thermoreflectometry cell, resulting from the sequential evaporation of ohmic contact titanium and palladium onto the smoothed etched surface of a semiconductor material cell. The cell comprises, from top to bottom, a second Ga2O3 drift layer, a smoothed second Ga2O3 substrate layer, and ohmic contact titanium and palladium.

[0149] S106. Perform electrical characteristic tests on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic electrical characteristics of the high thermoelectric performance deep trench ohmic contact structure, and perform time domain thermal reflection tests on the time domain thermal reflection measurement unit to evaluate the ohmic thermal characteristics of the ohmic contact of the high thermoelectric performance deep trench ohmic contact structure.

[0150] The ohmic characteristics include electrical characteristics such as ohmic contact resistance, material sheet resistance, and interface defect characteristics, and thermal characteristics such as interface thermal resistance and interface thermal expansion coefficient.

[0151] Specifically, electrical characteristic tests are performed on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic characteristics of the deep trench ohmic contact structure with high thermoelectric performance (including electrical characteristics such as ohmic contact resistance characteristics, material square resistance characteristics, and interface defect characteristics, and a time domain thermal reflection test is performed on the time domain thermal reflection measurement unit to evaluate the thermal characteristics such as the interface thermal resistance and interface thermal expansion coefficient characteristics of the ohmic contact of the deep trench ohmic contact structure with high thermoelectric performance).

[0152] The Ga2O3 drift layer can be grown not only by the Halide Vapor Phase Epitaxy (HVPE) method, but also by other epitaxial methods such as Molecular Beam Epitaxy (MBE).

[0153] The tests performed on the time-domain thermoreflectance measurement unit are not only applicable to time-domain thermoreflectance testing, but also to other thermal characterization techniques based on optical measurements, such as the structure function method, the 3ω method, laser photothermal method, laser flash method, frequency-domain thermoreflectance method, and steady-state heat flow method.

[0154] The micro-jet laser etching process using an ultrashort pulse laser is used to etch a deep groove structure at the bottom of the Ga2O3 material. This is not only limited to the flow channel preparation of vertical structure devices, but is also applicable to the flow channel preparation of horizontal structure devices.

[0155] The depth of the deep etched trench is not limited to 100 μm. The specific etch depth can be adjusted according to the thermal management goals and actual process requirements.

[0156] The layout of the deep grooves is not limited to the uniform rectangular groove layout. Within the accuracy range of the microjet laser etching of the ultrashort pulse laser (25μm), the deep groove morphology (such as hexagonal, circular, etc.) and layout are optional.

[0157] The chemical mechanical polishing process, hard mask process and thick photoresist process (10μm thick) are not limited to the preparation of Ga2O3 materials and their electrical measurement units such as capacitance-voltage ring diode measurement units and transmission line model measurement units, but are also applicable to all semiconductor materials such as gallium nitride (GaN) and silicon carbide (SiC) and all their characterization structures (for example, Hall bridge structures).

[0158] The present invention provides a method for designing a high-thermoelectric-performance deep-trench ohmic contact based on microjet laser technology. The method comprises obtaining a high-thermoelectric-performance deep-trench ohmic contact structure based on microjet laser technology. The high-thermoelectric-performance deep-trench ohmic contact structure is obtained using a microjet laser etching process using an ultrashort pulse laser, wherein the deep trench is a groove having a depth greater than 100 μm. A semiconductor material unit is prepared based on the high-thermoelectric-performance deep-trench ohmic contact structure. The semiconductor material unit is made of the target semiconductor material, and the parameters and etching process of the semiconductor material of the semiconductor material unit and the high-thermoelectric-performance deep-trench ohmic contact structure are the same. A capacitance-voltage ring diode measurement unit is prepared on the etched surface of the semiconductor material unit using a hard mask process and a thick photoresist process; a transmission line model measurement unit is prepared on the etched surface of the semiconductor material unit using a hard mask process or a thick photoresist process; a time domain thermal reflection measurement unit is prepared on the etched surface of the semiconductor material unit using a chemical mechanical polishing process. The capacitance-voltage ring diode measurement unit, the transmission line model measurement unit and the time domain thermal reflection measurement unit are all used for ohmic characteristic evaluation and iterative research on thermoelectric characteristic optimization; electrical characteristic tests are performed on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic electrical characteristics of the deep trench ohmic contact structure with high thermoelectric performance, and a time domain thermal reflection test is performed on the time domain thermal reflection measurement unit to evaluate the ohmic thermal characteristics of the ohmic contact of the deep trench ohmic contact structure with high thermoelectric performance. In this way, a deep groove ohmic contact structure with high thermoelectric performance is obtained through the micro-jet laser etching process of an ultrashort pulse laser. The micro-jet laser etching process based on an ultrashort pulse laser can realize a deep groove flow channel that meets the thermal management performance requirements of the microchannel and is compatible with subsequent device processes and research requirements by precisely etching the positioning area; combined with the subsequent capacitance-voltage ring diode measurement unit prepared based on the hard mask process and the thick photoresist process, the transmission line model measurement unit prepared based on the hard mask process or the thick photoresist process, and the time domain thermal reflection measurement unit prepared based on the chemical mechanical polishing process, the iterative research on the thermoelectric characteristics optimization of the deep groove ohmic contact structure with high thermoelectric performance is realized, thereby realizing a deep groove ohmic contact with high thermoelectric performance.

[0159] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology, characterized in that: The method for designing a deep trench ohmic contact with high thermoelectric performance based on microjet laser technology includes: Obtaining a high-thermoelectric-performance deep-groove ohmic contact structure based on microjet laser technology, wherein the deep groove of the high-thermoelectric-performance deep-groove ohmic contact structure is obtained by using a microjet laser etching process using an ultrashort pulse laser, and the deep groove is a groove having a depth greater than 100 μm; According to the high thermoelectric performance deep trench ohmic contact structure, a semiconductor material unit is prepared, wherein the material used in the semiconductor material unit is the target semiconductor material, and the parameters and etching process of the semiconductor material of the semiconductor material unit and the semiconductor material of the high thermoelectric performance deep trench ohmic contact structure are the same; Using a hard mask process and a thick photoresist process, a capacitance-voltage ring diode measurement unit is prepared on the etched surface of the semiconductor material unit; preparing a transmission line model measurement unit on the etched surface of the semiconductor material unit by using a hard mask process or a thick photoresist process; A time-domain thermoreflectance measurement unit is prepared on the etched surface of the semiconductor material unit by using a chemical mechanical polishing process. The capacitance-voltage ring diode measurement unit, the transmission line model measurement unit, and the time-domain thermoreflectance measurement unit are all used for ohmic characteristic evaluation and iterative research on thermoelectric characteristic optimization; Electrical characteristic tests are performed on the capacitance-voltage ring diode measurement unit and the transmission line model measurement unit to evaluate the ohmic electrical characteristics of the high thermoelectric performance deep trench ohmic contact structure, and time domain thermal reflection tests are performed on the time domain thermal reflection measurement unit to evaluate the ohmic thermal characteristics of the ohmic contact of the high thermoelectric performance deep trench ohmic contact structure.

2. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 1, characterized in that: The semiconductor materials used in the high thermoelectric performance deep trench ohmic contact structure based on micro-jet laser technology include Ga2O3 material, GaN material and SiC material.

3. The method for designing deep trench ohmic contacts with high thermoelectric performance based on microjet laser technology according to claim 2, characterized in that: Before obtaining a high thermoelectric performance deep trench ohmic contact structure based on microjet laser technology, the method further includes: growing a first Ga2O3 drift layer on the upper surface of the first Ga2O3 substrate layer; Spin-coating a photoresist on the upper surface of the first Ga2O3 drift layer; Using the microjet laser etching process of the ultrashort pulse laser, deep grooves are etched on the lower surface of the first Ga2O3 substrate layer according to the graphics designed by AutoCAD software, wherein the deep grooves are evenly arranged and have a depth greater than 100 μm. The ultrashort pulse laser has a pulse width of the picosecond or femtosecond order. removing the photoresist by using organic matter; Anode metal is grown on the upper surface of the first Ga2O3 drift layer using a metal evaporation process to form a Schottky contact, cathode metal is grown on the lower surface of the etched first Ga2O3 substrate layer and annealed to form an ohmic contact, thereby obtaining the high thermoelectric performance deep groove ohmic contact structure based on microjet laser technology.

4. The method for designing deep trench ohmic contacts with high thermoelectric performance based on microjet laser technology according to claim 3, characterized in that: The semiconductor material unit is prepared according to the high thermoelectric performance deep trench ohmic contact structure based on microjet laser technology, comprising: growing a second Ga2O3 drift layer on the upper surface of the second Ga2O3 substrate layer, wherein the second Ga2O3 substrate layer has the same thickness and doping concentration as the first Ga2O3 substrate layer, and the second Ga2O3 drift layer has the same thickness and doping concentration as the first Ga2O3 drift layer; Spin-coating a photoresist on the upper surface of the second Ga2O3 drift layer; The lower surface of the second Ga2O3 substrate layer is entirely etched using the micro-jet laser etching process of the ultrashort pulse laser. The micro-jet laser etching process of the ultrashort pulse laser is the same as the etching process for preparing the deep trench ohmic contact structure with high thermoelectric performance. The photoresist is removed by using organic matter to prepare the semiconductor material unit.

5. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 1, characterized in that: The thickness of the thick photoresist used in the thick photoresist process is not less than 10 μm.

6. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 3, characterized in that: The method of fabricating a capacitance-voltage ring diode measurement unit on an etched surface of the semiconductor material unit by using a hard mask process and a thick photoresist process comprises: Using the hard mask process, patterning a first metal on the etched surface of the semiconductor material unit and evaporating the first metal, wherein the material of the first metal is the same as that of the cathode metal; Annealing the evaporated first metal to form an ohmic contact; spin coating thick photoresist using the thick photoresist process; The second metal is patterned using the thick photoresist process, and the second metal is evaporated to form a Schottky contact to obtain the capacitance-voltage ring diode measurement unit, wherein the material of the second metal is the same as that of the anode metal.

7. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 3, characterized in that: The method of preparing a transmission line model measurement unit on an etched surface of the semiconductor material unit by using a hard mask process or a thick photoresist process comprises: Using the hard mask process, patterning a third metal on the etched surface of the semiconductor material unit and evaporating the third metal, wherein the material of the third metal is the same as that of the cathode metal; Annealing the evaporated third metal to form an ohmic contact, thereby obtaining the transmission line model measurement unit; Alternatively, using the thick photoresist process, spin-coating thick photoresist on the etched surface of the semiconductor material unit; patterning the third metal using the thick photoresist process, and evaporating the third metal; The evaporated third metal is annealed to form an ohmic contact, thereby obtaining the transmission line model measurement unit.

8. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 3, characterized in that: The method of preparing a time-domain thermoreflectance measurement unit on the etched surface of the semiconductor material unit by using a chemical mechanical polishing process comprises: Smoothing the etched surface of the semiconductor material unit by using the chemical mechanical polishing process; Ohmic contact metal titanium and palladium gold are evaporated in sequence on the smoothed etched surface of the semiconductor material unit to form the time domain thermoreflectance measurement unit.

9. The method for designing deep trench ohmic contacts with high thermoelectric performance based on microjet laser technology according to claim 3, characterized in that: The material of the anode metal is any one of Ni / Au and Mo / Au, and the material of the cathode metal is Ti / Au.

10. The method for designing deep trench ohmic contacts with high thermoelectric performance based on micro-jet laser technology according to claim 1, characterized in that: The ohmic electrical properties include ohmic contact resistance properties, material sheet resistance properties, and interface defect properties. The ohmic thermal properties of the ohmic contact include interface thermal resistance and interface thermal expansion coefficient.

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