A method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips

Abstract

The invention discloses a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips, comprising the following steps: S1: selecting a certain amount of pyromellitic anhydride, which is also called 2,4,5-pyromellitic anhydride, has a molecular formula of C10H2O6, a molecular weight of 218.1193, and is a white, slightly yellow, blocky, powdery solid crystal, and preparing a certain amount of diaminodiphenyl ether, which has a molecular formula of C12H12N2O, a relative molecular weight of 200.23, and is a crystal precipitated from ethanol; S2: preparing a certain amount of 4% H2 / N2 gas for standby use. The method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips described in the invention realizes the removal of polyimide photoresist of vanadium oxide thermal imaging chips by adopting RF plasma technology, and optimizes the process in combination with the problems existing in traditional RF plasma systems, adds new process gases, and debugs new parameters to meet process requirements and bring better prospects for use.

Description

Technical Field

[0001] The invention relates to the field of semiconductor photoresist and polyimide removal technology, and in particular to a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips. Background Art

[0002] Vanadium oxide thermal imaging chip is the current mainstream uncooled focal plane array imaging technology. It uses the characteristics of objects above absolute zero emitting infrared rays and the change in resistance of vanadium oxide materials after receiving infrared rays for thermal imaging. The resolution of imaging depends on the size and number of pixel units. In the wafer manufacturing process, the three-dimensional structure of vanadium oxide deposited requires polyimide photoresist as support and protection. Therefore, in the post-packaging process, these polyimides need to be removed by plasma etching technology. People's requirements for polyimide removal technology are also getting higher and higher.

[0003] The existing polyimide removal process has certain drawbacks when used. Due to the high frequency of microwave plasma and the characteristics of remote plasma, its etching rate is relatively low and the production efficiency is low. Since the cost of semiconductor equipment is very expensive, if microwave plasma is used to remove polyimide photoresist in vanadium oxide imaging chips, the unit cost will be 3 times that of the RF plasma system degumming process, which is not conducive to people's use and has brought certain adverse effects to people's use process. For this reason, we propose a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the shortcomings of the prior art, the present invention provides a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips. The polyimide photoresist of the vanadium oxide thermal imaging chip is removed by adopting RF plasma technology, and the process is optimized in combination with the problems existing in the traditional RF plasma system. New process gases are added and new parameters are debugged to meet the process requirements, which can effectively solve the problems in the background technology.

[0006] (II) Technical solution

[0007] To achieve the above object, the technical solution adopted by the present invention is: a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips, comprising the following steps:

[0008] S1: Select a certain amount of pyromellitic anhydride, which is also called 2,4,5-pyromellitic anhydride, has a molecular formula of C10H2O6, a molecular weight of 218.1193, and is a white, slightly yellow, blocky, powdery, solid crystal; prepare a certain amount of diaminodiphenyl ether, which has a molecular formula of C12H12N2O, a relative molecular weight of 200.23, and is a crystal precipitated in ethanol;

[0009] S2: prepare a certain amount of photosensitizer, which is a coating with photosensitive properties, usually composed of silver bromide and gelatin, in which silver bromide plays a major photosensitive role, and prepare a certain amount of 4% H2 / N2 gas for standby use;

[0010] S3: Polyimide photoresist is made by polycondensing pyromellitic anhydride and diaminodiphenyl ether, then dehydrating and cyclizing them into polyimide, and then adding photosensitizer. Its long-term temperature resistance can reach above 220°C;

[0011] S4: These polyimides are removed by RF plasma etching technology. The polyimide photoresist removal method in the manufacture of vanadium oxide thermal imaging chips uses a modified RF plasma system1. Microwave plasma is generated in the magnetron and transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist.

[0012] S5: Add 4% H2 / N2 gas to the original microwave plasma stripping process, and use the characteristics of hydrogen in this gas to more easily form hydrides that can be easily pumped away by the vacuum pump during plasma stripping, so that the stripping is cleaner and more thorough, and the efficiency is also improved, meeting the process standards of polyimide photoresist in the production of vanadium oxide thermal imaging chips;

[0013] S6: Add two aluminum alloy grid plates with staggered holes as plasma buffers. On the one hand, the conductivity of aluminum alloy can remove some messy charges in the early stage of plasma generation. On the other hand, it can block the plasma and prevent it from directly acting on the wafer surface, thereby minimizing the formation of DC BIAS. This can effectively prevent plasma damage of the wafer and increase production efficiency by 3 to 5 times.

[0014] As a preferred technical solution, the frequency of the improved RF plasma system is 13.56 MHz, the gas added to the improved RF plasma system is 4% H2 / N2 gas, and the gas flow rate is 3000 SCCM.

[0015] As a preferred technical solution, the etching rate of the improved RF plasma system is 62,000 angstroms per minute.

[0016] As a preferred technical solution, the time for the improved RF plasma system to remove polyimide is 20 minutes.

[0017] As a preferred technical solution, the plasma generation characteristic in the improved RF plasma system is remote plasma.

[0018] As a preferred technical solution, the temperature in the improved RF plasma system is 160-200 degrees Celsius, the power in the improved RF plasma system is 750-900W, and the pressure in the improved RF plasma system is 0.9-1.2TOrr.

[0019] As a preferred technical solution, the temperature in the improved RF plasma system is 170 degrees Celsius, the power in the improved RF plasma system is 800W, and the pressure in the improved RF plasma system is 1TOrr.

[0020] As a preferred technical solution, the temperature in the improved RF plasma system is 180 degrees Celsius, the power in the improved RF plasma system is 820W, and the pressure in the improved RF plasma system is 1.1TOrr.

[0021] (III) Beneficial effects

[0022] Compared with the prior art, the present invention provides a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips, which has the following beneficial effects: the method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips realizes the removal of polyimide photoresist of vanadium oxide thermal imaging chips by adopting RF plasma technology, optimizes the process in combination with the problems existing in traditional RF plasma systems, adds new process gases, and debugs new parameters to meet the process requirements, replaces the original microwave plasma technology, uses advanced RF plasma technology for product production, and improves the production efficiency by 3 to 5 times, changes the hardware structure of the transmission system of the traditional RF plasma degumming machine, adds a double-layer aluminum alloy grid plate to reduce the plasma bombardment in the initial stage of the reaction, and can effectively prevent the collapse of the vanadium oxide three-dimensional structure and the instability of the resistivity, changes the traditional RF plasma degumming process, adds new process gases, and debugs new process conditions, which can effectively prevent the occurrence of photoresist residues and unqualified resistivity, removes these polyimides by RF plasma etching technology, and the method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips adopts the improved RF plasmasystem1, microwave plasma is generated in the magnetron, and the plasma is transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist. On the basis of the original microwave plasma degumming process, 4% H2 / N2 gas is added. The hydrogen element in this gas is more likely to form hydrides that are easily pumped away by the vacuum pump during plasma degumming, making the degumming cleaner and more thorough, and the efficiency is also improved. The process standards of polyimide photoresist in the production of vanadium oxide thermal imaging chips are met. Two grid plates with staggered holes made of aluminum alloy are added as plasma buffers. On the one hand, some messy charges in the early stage of plasma generation are removed through the conductivity of aluminum alloy. On the other hand, the plasma is blocked to prevent it from directly acting on the wafer surface, and the formation of DC BIAS is reduced as much as possible, which can effectively prevent plasma damage to the wafer and improve production efficiency by 3 to 5 times. The entire polyimide photoresist removal structure is simple, easy to operate, and the effect of use is better than that of traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic diagram of the plasma action mode of a method for removing polyimide photoresist in the manufacture of a vanadium oxide thermal imaging chip.

[0024] Figure 2 The present invention is a schematic structural diagram of adding two aluminum alloy grid plates with mutually staggered holes in a polyimide photoresist removal method in the manufacture of a vanadium oxide thermal imaging chip.

[0025] Figure 3It is a structural schematic diagram of a parameter comparison table in a method for removing polyimide photoresist in manufacturing a vanadium oxide thermal imaging chip according to the present invention.

[0026] Figure 4 This is a schematic diagram of the conventional photoresist residue in a method for removing polyimide photoresist in the manufacture of a vanadium oxide thermal imaging chip according to the present invention.

[0027] Figure 5 This is a schematic diagram of the photoresist residue in a polyimide photoresist removal method in the manufacture of a vanadium oxide thermal imaging chip according to the present invention.

[0028] Figure 6 It is a schematic diagram of a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chip according to the present invention, in which the traditional method has serious residues.

[0029] Figure 7 It is a schematic diagram of a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips in the present invention, in which the technology leaves no residue. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0031] Embodiment 1:

[0032] A method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips, comprising the following steps:

[0033] S1: Select a certain amount of pyromellitic anhydride, which is also called 2,4,5-pyromellitic anhydride, with a molecular formula of C10H2O6 and a molecular weight of 218.1193, and is a white, slightly yellow, blocky, powdery, solid crystal; prepare a certain amount of diaminodiphenyl ether, which has a molecular formula of C12H12N2O and a relative molecular weight of 200.23, and is a crystal precipitated in ethanol;

[0034] S2: prepare a certain amount of photosensitizer, which is a coating with photosensitive properties, usually composed of silver bromide and gelatin, in which silver bromide plays a major photosensitive role. Prepare a certain amount of 4% H2 / N2 gas for standby use;

[0035] S3: Polyimide photoresist is made by polycondensing pyromellitic anhydride and diaminodiphenyl ether, then dehydrating and cyclizing them into polyimide, and then adding photosensitizer. Its long-term temperature resistance can reach above 220°C;

[0036] S4: These polyimides are removed by RF plasma etching technology. The polyimide photoresist removal method in the manufacture of vanadium oxide thermal imaging chips uses a modified RF plasma system1. Microwave plasma is generated in the magnetron and transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist.

[0037] S5: Add 4% H2 / N2 gas to the original microwave plasma stripping process, and use the characteristics of hydrogen in this gas to more easily form hydrides that can be easily pumped away by the vacuum pump during plasma stripping, so that the stripping is cleaner and more thorough, and the efficiency is also improved, meeting the process standards of polyimide photoresist in the production of vanadium oxide thermal imaging chips;

[0038] S6: Add two aluminum alloy grid plates with staggered holes as plasma buffers. On the one hand, the conductivity of aluminum alloy can remove some messy charges in the early stage of plasma generation. On the other hand, it can block the plasma and prevent it from directly acting on the wafer surface, thereby minimizing the formation of DC BIAS. This can effectively prevent plasma damage of the wafer and increase production efficiency by 3 to 5 times.

[0039] Furthermore, the frequency of the improved RF plasma system is 13.56 MHz, the gas added to the improved RF plasma system is 4% H2 / N2 gas, and the gas flow rate is 3000 SCCM.

[0040] Furthermore, the etching rate of the improved RF plasma system is 62,000 angstroms per minute.

[0041] Furthermore, the time required for the improved RF plasma system to remove polyimide is 20 minutes.

[0042] Furthermore, the plasma generation characteristic in the improved RF plasma system is remote plasma.

[0043] Furthermore, the temperature in the improved RF plasma system is 160-200 degrees Celsius, the power in the improved RF plasma system is 750-900W, and the pressure in the improved RF plasma system is 0.9-1.2TOrr.

[0044] Furthermore, the temperature in the improved RF plasma system is 180 degrees Celsius, the power in the improved RF plasma system is 820 W, and the pressure in the improved RF plasma system is 1.1 TOrr.

[0045] Embodiment 2:

[0046] Based on Example 1, a method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips includes the following steps:

[0047] S1: Select a certain amount of pyromellitic anhydride, which is also called 2,4,5-pyromellitic anhydride, with a molecular formula of C10H2O6 and a molecular weight of 218.1193, and is a white, slightly yellow, blocky, powdery, solid crystal; prepare a certain amount of diaminodiphenyl ether, which has a molecular formula of C12H12N2O and a relative molecular weight of 200.23, and is a crystal precipitated in ethanol;

[0048] S2: prepare a certain amount of photosensitizer, which is a coating with photosensitive properties, usually composed of silver bromide and gelatin, in which silver bromide plays a major photosensitive role. Prepare a certain amount of 4% H2 / N2 gas for standby use;

[0049] S3: Polyimide photoresist is made by polycondensing pyromellitic anhydride and diaminodiphenyl ether, then dehydrating and cyclizing them into polyimide, and then adding photosensitizer. Its long-term temperature resistance can reach above 220°C;

[0050] S4: These polyimides are removed by RF plasma etching technology. The polyimide photoresist removal method in the manufacture of vanadium oxide thermal imaging chips uses a modified RF plasma system1. Microwave plasma is generated in the magnetron and transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist.

[0051] S5: Add 4% H2 / N2 gas to the original microwave plasma stripping process, and use the characteristics of hydrogen in this gas to more easily form hydrides that can be easily pumped away by the vacuum pump during plasma stripping, so that the stripping is cleaner and more thorough, and the efficiency is also improved, meeting the process standards of polyimide photoresist in the production of vanadium oxide thermal imaging chips;

[0052] S6: Add two aluminum alloy grid plates with staggered holes as plasma buffers. On the one hand, the conductivity of aluminum alloy can remove some messy charges in the early stage of plasma generation. On the other hand, it can block the plasma and prevent it from directly acting on the wafer surface, thereby minimizing the formation of DC BIAS. This can effectively prevent plasma damage of the wafer and increase production efficiency by 3 to 5 times.

[0053] Furthermore, the frequency of the improved RF plasma system is 13.56 MHz, the gas added to the improved RF plasma system is 4% H2 / N2 gas, and the gas flow rate is 3000 SCCM.

[0054] Furthermore, the etching rate of the improved RF plasma system is 62,000 angstroms per minute.

[0055] Furthermore, the time required for the improved RF plasma system to remove polyimide is 20 minutes.

[0056] Furthermore, the plasma generation characteristic in the improved RF plasma system is remote plasma.

[0057] Furthermore, the temperature in the improved RF plasma system is 160-200 degrees Celsius, the power in the improved RF plasma system is 750-900W, and the pressure in the improved RF plasma system is 0.9-1.2TOrr.

[0058] Furthermore, the temperature in the improved RF plasma system is 170 degrees Celsius, the power in the improved RF plasma system is 800W, and the pressure in the improved RF plasma system is 1TOrr.

[0059] Working principle: Polyimide photoresist is made by polycondensing pyromellitic acid anhydride and diaminodiphenyl ether, then dehydrating and cyclizing them into polyimide, and then adding photosensitizer. Its long-term temperature resistance can reach above 220°C. These polyimides are removed by RF plasma etching technology. The polyimide photoresist removal method in the manufacture of vanadium oxide thermal imaging chips uses improved RF plasma System 1, microwave plasma is generated in the magnetron, and the plasma is transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist. On the basis of the original microwave plasma degumming process, 4% H2 / N2 gas is added. The hydrogen element in this gas is more likely to form hydrides that are easily pumped away by the vacuum pump during plasma degumming, making the degumming cleaner and more thorough, and the efficiency is also improved. The process standard of polyimide photoresist in the production of vanadium oxide thermal imaging chips is met. Two aluminum alloy grid plates with staggered holes are added as plasma buffers. On the one hand, the conductivity of the aluminum alloy is used to remove some messy charges in the early stage of plasma generation. On the other hand, the plasma is blocked to prevent it from directly acting on the wafer surface, and the formation of DC BIAS is reduced as much as possible, which can effectively prevent the wafer from plasma. damage, and the production efficiency is improved by 3 to 5 times. The polyimide photoresist of the vanadium oxide thermal imaging chip is removed by adopting RF plasma technology, and the process is optimized in combination with the problems existing in the traditional RF plasma system, new process gases are added, and new parameters are debugged to meet the process requirements, replacing the original microwave plasma technology. The advanced RF plasma technology is used for product production, and the production efficiency is improved by 3 to 5 times. The hardware structure of the transmission system of the traditional RF plasma stripping machine is changed, and a double-layer aluminum alloy grid plate is added to reduce the plasma bombardment in the early stage of the reaction, which can effectively prevent the collapse of the vanadium oxide three-dimensional structure and the instability of the resistivity. The traditional RF plasma stripping process is changed, new process gases are added, and new process conditions are debugged to effectively prevent the occurrence of photoresist residues and unqualified resistivity.

[0060] It should be noted that, in this article, relational terms such as first and second (number one, number two), etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0061] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for removing polyimide photoresist in the manufacture of vanadium oxide thermal imaging chips, characterized in that: The steps include: S1: Select a certain amount of pyromellitic anhydride, which is also called 2,4,5-pyromellitic anhydride, has a molecular formula of C10H2O6, a molecular weight of 218.1193, and is a white, slightly yellow, blocky, powdery, solid crystal; prepare a certain amount of diaminodiphenyl ether, which has a molecular formula of C12H12N2O, a relative molecular weight of 200.23, and is a crystal precipitated in ethanol; S2: prepare a certain amount of photosensitizer, which is a coating with photosensitive properties, usually composed of silver bromide and gelatin, in which silver bromide plays a major photosensitive role, and prepare a certain amount of 4% H2 / N2 gas for standby use; S3: Polyimide photoresist is made by polycondensing pyromellitic anhydride and diaminodiphenyl ether, then dehydrating and cyclizing them into polyimide, and then adding photosensitizer. It has a long-term temperature resistance of more than 220°C. S4: These polyimides are removed by RF plasma etching technology. The polyimide photoresist removal method in the manufacture of vanadium oxide thermal imaging chips uses a modified RF plasma system1. Microwave plasma is generated in the magnetron and transmitted through the waveguide. The plasma flows downstream with the initial kinetic energy of the gas and gravity to act on the wafer surface and react with the photoresist. S5: Add 4% H2 / N2 gas to the original microwave plasma stripping process, and use the characteristics of hydrogen in this gas to more easily form hydrides that can be easily pumped away by the vacuum pump during plasma stripping, so that the stripping is cleaner and more thorough, and the efficiency is also improved, meeting the process standards of polyimide photoresist in the production of vanadium oxide thermal imaging chips; S6: Add two aluminum alloy grid plates with staggered holes as plasma buffers. On the one hand, the conductivity of aluminum alloy can remove some random charges in the early stage of plasma generation. On the other hand, it can also block the plasma and prevent it from directly acting on the wafer surface, reducing the formation of DC BIAS and effectively preventing plasma damage to the wafer. The production efficiency has increased by 3 to 5 times. The frequency of the improved RF plasma system is 13.56 MHz, the gas added to the improved RF plasma system is 4% H2 / N2 gas, and the gas flow rate is 3000 SCCM; The etch rate of the modified RF plasma system is 62,000 angstroms per minute; The time for the improved RF plasma system to remove polyimide is 20 minutes; The plasma generation characteristic in the improved RF plasma system is remote plasma; The temperature in the improved RF plasma system is 160-200 degrees Celsius, the power in the improved RF plasma system is 750-900W, and the pressure in the improved RF plasma system is 0.9-1.2TOrr; The temperature in the improved RF plasma system is 170 degrees Celsius, the power in the improved RF plasma system is 800W, and the pressure in the improved RF plasma system is 1TOrr; The temperature in the improved RF plasma system is 180 degrees Celsius, the power in the improved RF plasma system is 820W, and the pressure in the improved RF plasma system is 1.1TOrr.

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