Complex pattern electrode alloying method based on ultraviolet pulse laser

Abstract

The invention relates to a complex pattern electrode alloying method based on ultraviolet pulse laser, and belongs to the technical field of infrared detector chip manufacturing. The method comprises the following steps of: alloying an electrode with a prepared complex pattern on an InAs / InAsSb class-II superlattice infrared medium wave detector chip, spin-coating photoresist on the chip with the electrode with the complex pattern to protect a non-electrode area, heating the chip by using a hot plate in an inert gas protection environment, and scanning the chip by using ultraviolet pulse laser; through the instantaneous high temperature and rapid cooling process generated by laser alloying, a non-equilibrium alloy phase or a metastable phase can be formed at an interface, lower Schottky barrier height or higher carrier concentration can be generated, and contact resistance is reduced, so that noise of the infrared detector is effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of infrared detector chip manufacturing technology, and in particular, it is a method for alloying complex patterned electrodes based on ultraviolet pulsed laser. Background Technology

[0002] In semiconductor device manufacturing, forming low-resistance ohmic contacts is a crucial step in ensuring high performance and reliability. Traditional alloying methods primarily rely on thermal annealing and rapid thermal annealing (RTA) techniques. These methods treat the metal-semiconductor structure at high temperatures for a period of time, inducing atomic interdiffusion and chemical reactions at the interface to form an alloy layer, reducing the contact barrier and achieving ohmic contacts. However, as semiconductor devices evolve towards smaller sizes, more complex structures, and higher performance, these traditional methods have gradually revealed their inherent limitations. The drawbacks of traditional thermal annealing processes are particularly pronounced when processing temperature-sensitive and chemically reactive III-V compound semiconductor materials such as InAs / InAsSb. High-temperature treatment can not only lead to excessive reactions between the metal and semiconductor, forming undesirable compound phases, but also cause semiconductor material decomposition, dopant diffusion, and interface morphology deterioration, thus severely impacting device performance and reliability. For example, in InAs / InAsSb superlattice structures, high-temperature annealing can lead to interdiffusion at the interfaces, disrupting the precisely designed band structure and thus affecting its optoelectronic properties. Therefore, developing a novel alloying technique capable of precisely controlling the heating region and thermal budget has become a critical issue that urgently needs to be addressed in this field.

[0003] InAs / InAsSb, as an important class of narrow-bandgap III-V semiconductor materials, has wide applications in infrared detection, high-speed electronic devices, and other fields. However, fabricating ohmic contacts with low contact resistance on this material system faces unique challenges. Traditional alloying methods, whether hot annealing or rapid hot annealing, have some insurmountable problems when applied to InAs / InAsSb. First, InAs and GaSb materials themselves have relatively poor thermal stability, and high-temperature treatment can easily lead to material decomposition and element volatilization (such as As and Sb), thereby changing the stoichiometry and electrical properties of the material. Second, the interdiffusion problem at the InAs / InAsSb heterojunction interface is particularly prominent. High temperatures exacerbate the interdiffusion between elements such as In, Ga, As, and Sb, destroying the carefully designed heterojunction band structure and seriously affecting device performance. For example, in InAs / AlSb heterojunctions, to achieve good ohmic contacts, specific metal stacks (such as Pd / Ti / Pt / Au) need to be used and alloyed, but traditional annealing processes are difficult to precisely control the interface reaction, which may lead to high contact resistance. Furthermore, for InAs / InAsSb-based devices, electrodes with complex patterns are typically required to achieve specific electrical or optical functions. However, the large-area heating characteristics of traditional annealing methods cannot meet the requirements for selective and localized alloying of complex patterns, easily leading to problems such as blurred pattern edges and lateral metal diffusion. Therefore, developing a new alloying method that can achieve localized, precise, and low thermal budget is crucial for improving the performance and reliability of InAs / InAsSb-based devices. Summary of the Invention

[0004] A method for alloying complex patterned electrodes based on ultraviolet pulsed lasers is proposed. The method involves alloying electrodes with complex patterns on an InAs / InAsSb type-two superlattice infrared mid-wave detector chip. First, photoresist is spin-coated onto the chip with complex patterned electrodes to protect the non-electrode areas. Then, the chip is heated with a hot plate in an inert gas protected environment, and the chip is scanned with an ultraviolet pulsed laser.

[0005] Laser alloying (LA) is a non-equilibrium heat treatment technique that uses a high-energy pulsed laser beam to instantaneously and locally heat the surface of a material. The technical solution of this invention utilizes the high energy density of the laser beam to deposit energy into an extremely thin region on the material surface within an extremely short time (nanoseconds, picoseconds, or even femtoseconds), rapidly raising its temperature above the melting point. Subsequently, due to the rapid heat conduction into the matrix, this region cools at an extremely high rate (up to 10⁻⁶). 9Rapid cooling (K / s) enables rapid solidification. This "heat-cooling" process is highly localized in both time and space. During the metal-semiconductor contact formation process, laser energy is absorbed by the metal layer and the semiconductor surface layer, causing melting at the interface. Metal and semiconductor atoms mix thoroughly in the liquid state, forming a new alloy phase. By precisely controlling laser parameters (such as wavelength, pulse width, energy density, and repetition frequency), the thickness, composition, microstructure, and interface morphology of the alloy layer can be precisely controlled, thereby optimizing the contact's electrical properties. Compared to traditional thermal annealing, the greatest advantage of lasers lies in their extremely small heat-affected zone, which effectively avoids thermal damage to other areas of the substrate, making them particularly suitable for temperature-sensitive flexible electronic devices and semiconductor devices with complex structures.

[0006] Protecting complex patterned electrodes requires patterning them using photolithography and lift-off processes after the deposition of multilayer metal thin films to form the desired complex electrode pattern. This process is a crucial step in realizing "complex patterned electrodes." The alloying process for the fabricated complex patterned electrodes involves the following steps: First, a layer of photoresist is spin-coated onto the surface of the metal thin film. The pattern on the pre-designed mask is transferred onto the photoresist using contact lithography or projection lithography. After exposure, the photoresist in the exposed areas is removed using a developer, thereby forming a photoresist mask on the non-metallic surface that complements the electrode pattern.

[0007] Then, the Au / Pt / Cr electrodes with complex patterns, which have been fabricated, are subjected to laser scanning on an InAs / InAsSb type-two superlattice infrared mid-wave detector chip. Specifically, the chip is heated to a temperature range of (100~150)℃ ± 1℃ using a hot plate in an inert gas argon or nitrogen atmosphere, and then scanned using a pulsed ultraviolet laser. In this method of alloying complex patterned electrodes based on pulsed ultraviolet lasers, the wavelength range of the pulsed ultraviolet laser is 200-400nm.

[0008] Complex patterned electrodes fabricated on InAs / InAsSb type-II superlattice detector chips can be Au / Pt / Cr electrodes, Au / Pt / Ni electrodes, or Au / Pt / Ti electrodes.

[0009] In addition to shielded scanning, ultraviolet pulsed lasers can also be used for alloying in a direct-write mode under two-dimensional platform control, following complex electrode patterns. The direct-write mode features a laser spot diameter of 0.5-5 μm, a writing speed of 20-500 mm / s, and a controlled spot energy density of 50-300 mJ / cm². 2The inert gas is argon or nitrogen, with a purity of not less than 99.999% and a dew point temperature of -65℃ or lower. The photoresist protecting the non-electrode areas is i-line photoresist, i.e., positive or negative photoresist suitable for a 365nm wavelength light source, with a thickness of 3-5µm after baking at 80±1℃. The laser pulse duration of the ultraviolet pulsed laser is 50-120ns.

[0010] The laser spot diameter used is 5-40µm, and the spot energy density is controlled to be 50-300mJ / cm². 2 The complex patterned electrodes are either Au / Pt / Cr electrodes or Au / Pt / Ni electrodes. The thicknesses of the Au / Pt / Cr electrodes are Au: 100-300nm, Pt: 30-100nm, and Cr: 50-80nm, respectively; the thicknesses of the Au / Pt / Ni electrodes are Au: 100-300nm, Pt: 30-100nm, and Ni: 50-80nm, respectively.

[0011] The technical solution of the present invention has the following advantages compared with the prior art: 1. One advantage of the ultraviolet pulsed laser-based alloying method is that the energy is precisely focused on the electrode region at the micrometer or even nanometer scale, generating instantaneous high temperatures only at the interface, while the surrounding area and most of the substrate remain at a controlled low temperature. This "point heating" mode greatly reduces the heat-affected zone (HAZ), effectively avoiding damage to other temperature-sensitive areas in the device from high temperatures; 2. The laser alloying technology of this invention provides better flexibility and precision for fabricating electrodes with complex geometries and irregular patterns. For three-dimensional structures, the laser beam can irradiate from different angles to achieve processing and alloying of non-planar surfaces, which is difficult to achieve with traditional rapid thermal annealing techniques; 3. Lower contact resistance can be achieved. After alloying based on the method provided by this invention, the ohmic contact resistance is reduced to one-tenth. By optimizing the laser parameters, the laser alloying technology can achieve lower contact resistance than traditional thermal annealing, resulting in a lower Schottky barrier height or a higher carrier concentration. Secondly, laser treatment can effectively "activate" the doped atoms at the interface, improving their ionization efficiency, thereby forming a steeper doping gradient, promoting carrier tunneling transport, and reducing contact resistance; 4. High process flexibility and controllability: Laser alloying technology has extremely high process flexibility and controllability. Through computer software, all key parameters such as the scanning path, speed, energy density, and pulse frequency of the laser beam can be precisely controlled. Attached Figure Description

[0012] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1This is a schematic diagram of the structure of an InAs / InAsSb chip that undergoes complex pattern electrode alloying based on the method provided in this invention.

[0013] Figure 2 for Figure 1 A partial schematic diagram of the surface electrode shape of the chip shown.

[0014] Explanation of reference numerals in the attached figures: 1. InAs substrate; 2. InAs buffer transition layer; 3. InAs / InAsSb superlattice layer; 4. Superlattice surface passivation layer; 5. Au / Pt / Cr metal electrode; 6. Chip array mesa structure pixel; 7. Mesa metal electrode area; 8. Mesa passivation layer opening; 9. Mesa alloy pattern area, stripe filling area is photoresist mask; 10. Common electrode alloy pattern area. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0016] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0017] In an optional embodiment, refer to Figure 1 and Figure 2 As shown, in this embodiment, the protection of the complex patterned electrode is achieved after the deposition of multiple metal thin films (see attached diagram). Figure 1 Middle structure 5 and appendix Figure 2 Region 7 in the middle area needs to be patterned using photolithography to form the shape shown in the attached image. Figure 2 The complex electrode patterns required for regions 9 and 10. This process is a key step in realizing "complex patterned electrodes." Here, complex patterns include, but are not limited to, attached... Figure 2 The circular and rectangular arrays shown in regions 9 and 10, and other complex patterns, are designed and modified according to the shape and distribution of the infrared detector pixels and the form of the common electrode metal. First, a layer of positive photoresist is spin-coated onto the metal film surface. Then, the pattern on the pre-designed mask is transferred onto the photoresist using contact lithography or projection lithography. After exposure, the photoresist in the exposed areas is removed using a developer, thereby forming a photoresist mask on the non-metallic surface that complements the electrode pattern.

[0018] Then, on an InAs / InAsSb type-II superlattice detector chip, Au / Pt / Cr electrodes with complex patterns (attached) were fabricated. Figure 2Laser scanning is performed on regions 9 and 10. In an environment protected by inert argon or nitrogen, the chip is heated to 100℃±1℃ using a hot plate, and then scanned using a pulsed ultraviolet laser. The wavelength of the pulsed ultraviolet laser used in this complex pattern electrode alloying method is 266nm.

[0019] The inert gas is argon or nitrogen with a purity of 99.999% and a dew point temperature of -65℃. The photoresist protecting the non-electrode areas is positive photoresist AZ6130, with a thickness of 4µm after baking at 80±1℃. The ultraviolet pulse laser has a pulse duration of 90ns.

[0020] The laser used has a spot diameter of 20µm and the spot energy density is controlled at 100mJ / cm². 2 The complex patterned electrode is an Au / Pt / Cr electrode with thicknesses of 300 nm for Au, 40 nm for Pt, and 50 nm for Cr.

[0021] In an optional embodiment, refer to Figure 1 and 2 As shown, in this embodiment, the protection of the complex patterned electrode is achieved after the deposition of multiple metal thin films (see attached diagram). Figure 1 Middle structure 5 and appendix Figure 2 Region 7 in the middle area needs to be patterned using photolithography to form the shape shown in the attached image. Figure 2 The complex electrode patterns required for regions 9 and 10 are shown. This process is a key step in realizing "complex patterned electrodes." First, a layer of positive photoresist is spin-coated onto the surface of a metal thin film. Then, the pattern on the pre-designed mask is transferred onto the photoresist using contact lithography or projection lithography. After exposure, the photoresist in the exposed areas is removed using a developer, thereby forming a photoresist mask on the non-metallic surface that complements the electrode pattern.

[0022] Then, on an InAs / InAsSb type-II superlattice detector chip, Au / Pt / Cr electrodes with complex patterns (attached) were fabricated. Figure 2 Laser scanning is performed on regions 9 and 10. In an environment protected by inert argon or nitrogen, the chip is heated to 120℃±1℃ using a hot plate, and then scanned using a pulsed ultraviolet laser. The wavelength of the pulsed ultraviolet laser used in this complex pattern electrode alloying method is 355nm.

[0023] The inert gas is argon or nitrogen with a purity of 99.9999% and a dew point temperature of -65℃. The photoresist protecting the non-electrode areas is positive photoresist AZ5214, with a thickness of 3µm after baking at 80±1℃. The ultraviolet pulse laser has a pulse duration of 60ns.

[0024] The laser used has a spot diameter of 30µm and the spot energy density is controlled at 200mJ / cm². 2 The complex patterned electrode is an Au / Pt / Cr electrode with thicknesses of Au: 200 nm, Pt: 50 nm, and Cr: 60 nm.

[0025] In an optional embodiment, refer to Figure 1 and 2 As shown, in this embodiment, the protection of the complex patterned electrode is achieved after the deposition of multiple metal thin films (see attached diagram). Figure 1 Middle structure 5 and appendix Figure 2 Region 7 in the middle area needs to be patterned using photolithography to form the shape shown in the attached image. Figure 2 The complex electrode patterns required for regions 9 and 10 are shown. This process is a key step in realizing "complex patterned electrodes." First, a layer of negative photoresist is spin-coated onto the surface of a metal thin film. Then, the pattern on the pre-designed mask is transferred onto the photoresist using contact lithography or projection lithography. After exposure, the photoresist in the unexposed areas is removed using a developer, thereby forming a photoresist mask on the non-metallic surface that complements the electrode pattern.

[0026] Then, on an InAs / InAsSb type-II superlattice detector chip, Au / Pt / Cr electrodes with complex patterns (attached) were fabricated. Figure 2 Laser scanning is performed in regions 9 and 10. The chip is heated to 150℃ ± 1℃ in an inert gas environment (argon or nitrogen), and then scanned using a pulsed ultraviolet laser. The wavelength of the pulsed ultraviolet laser used in this complex pattern electrode alloying method is 365nm.

[0027] The inert gas is argon or nitrogen with a purity of 99.9995% and a dew point temperature of -70℃. The photoresist protecting the non-electrode areas is a negative resist SUN1306, with a thickness of 5µm after baking at 80±1℃. The ultraviolet pulse laser has a pulse duration of 120ns.

[0028] The laser used has a spot diameter of 40µm and the spot energy density is controlled at 300mJ / cm². 2 The complex patterned electrode is an Au / Pt / Cr electrode with thicknesses of 300 nm for Au, 100 nm for Pt, and 80 nm for Cr.

Claims

1. A method for alloying complex patterned electrodes based on ultraviolet pulsed laser, characterized in that, On an InAs / InAsSb type-two superlattice infrared mid-wave detector chip, electrodes with pre-fabricated complex patterns are alloyed. First, photoresist is spin-coated onto the chip with complex patterned electrodes to protect the non-electrode areas. Then, the chip is heated with a hot plate in an inert gas protected environment, and the chip is scanned with an ultraviolet pulsed laser.

2. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The heating temperature of the hot plate is controlled at (100~150)℃±1℃.

3. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The wavelength range of the ultraviolet pulsed laser is 200-400nm.

4. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The inert gas is argon or nitrogen, with a purity of not less than 99.999% and a dew point temperature of not less than or equal to -65°C.

5. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The photoresist protecting the non-electrode area is an i-line photoresist, which is a positive or negative photoresist suitable for a 365nm wavelength light source, and has a thickness of 3-5µm after baking at a temperature of 80±1℃.

6. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The duration of the ultraviolet pulsed laser pulse is 50-120 ns.

7. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The laser spot diameter used is 5-40µm, and the spot energy density is controlled to be 50-300mJ / cm². 2 .

8. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The complex patterned electrode is an Au / Pt / Cr electrode, with thicknesses of Au: 100-300nm, Pt: 30-100nm, and Cr: 50-80nm, respectively.

9. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, The complex patterned electrode is an Au / Pt / Ni electrode, with thicknesses of Au: 100-300nm, Pt: 30-100nm, and Ni: 50-80nm, respectively.

10. The method for alloying complex patterned electrodes based on ultraviolet pulsed laser according to claim 1, characterized in that, Alloying was performed in direct writing mode according to the complex pattern of the electrode under the control of a two-dimensional platform. The laser spot diameter in direct writing mode was 0.5-5μm, the direct writing speed was 20-500mm / s, and the spot energy density was controlled to be 50-300mJ / cm². 2 .

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