Semiconductor chip polyimide film forming and curing device

Abstract

The application discloses a kind of semiconductor chip polyimide film-forming curing device, comprising: high-temperature furnace body (1), program temperature control system (2), high-purity quartz cavity (3), airflow pressure stabilizing system (4) and exhaust system (5), high-purity quartz cavity (3) is arranged on high-temperature furnace body (1), and the semiconductor chip to be film-formed and cured is arranged in high-purity quartz cavity (3), and program temperature control system (2) controls the temperature of high-temperature furnace body (1), airflow pressure stabilizing system (4) and exhaust system (5) are all communicated, and the protective gas is introduced into high-purity quartz cavity (3) by airflow pressure stabilizing system (4), and the protective gas after circulation is discharged by exhaust system (5).The application solves the problem that moisture molecules cannot be discharged in time when film-forming by the existing oven method, avoids the degradation reaction of amide group in polyamide acid, and the process cavity of quartz material can better handle and control metal ions.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor chip fabrication equipment and tooling technology, and relates to a semiconductor chip polyimide film forming and curing device, which has the characteristics of highly uniform bottom heating and low mobile ion contamination. Background Technology

[0002] Polyimide is a type of polymer material containing imide rings in its main molecular chain. It possesses superior mechanical, dielectric, insulating, radiation-resistant, corrosion-resistant, and high / low temperature-resistant properties, making it widely used in aerospace, electrical engineering, microelectronics, and chemical industries. In the field of microelectronic devices, polyimide is often used as a dielectric layer for interlayer insulation, as a buffer layer to reduce surface stress, as a passivation layer to reduce the impact of the environment on the device, and as a radiation-resistant layer to shield against alpha ions. Semiconductor chips protected by polyimide films exhibit lower leakage current, stronger moisture resistance, and better chemical corrosion resistance.

[0003] The commonly used process for fabricating polyimide films on the surface of microelectronic chips is as follows: A layer of liquid polyimide prepolymer—polyamic acid—is coated on the surface of silicon, silicon dioxide, or silicon nitride. After thermal pre-curing and photolithography, the film pattern is obtained. Then, the polyimide is subjected to a polyimide thermal curing process to cause the polyamic acid to undergo ring shrinkage and ring-closure dehydration, thereby fully imidizing the polyamic acid and forming a polyimide film.

[0004] The curing process of polyimide involves two thermal curing steps. The first is thermal pre-curing before photolithography, typically controlled at 120℃~140℃. At this temperature, a large amount of solvent in the liquid polyamic acid evaporates and imidization has not yet begun, which is conducive to the formation of film patterns by photolithography. The second is the imidization curing process after photolithography. The imidization rate of polyamic acid generally accelerates above 160℃, basic imidization is achieved at 250℃~300℃, and full imidization is achieved at 300℃~400℃, forming a stable polyimide film. However, as the temperature continues to rise, the polyimide film begins to decompose. Therefore, a stepped heating method is used in the polyimide film formation and curing process.

[0005] The equipment commonly used in the thermosetting process of polyimide includes cleanroom ovens, vacuum ovens, and oxygen-controlled ovens. When applied to semiconductor chip surfaces in the microelectronics field, the quality, uniformity, and control of mobile metal ion content in the polyimide film are relatively demanding. Using oven-type imidization equipment presents several problems: First, metal ions such as Na and K significantly impact the performance of microelectronic devices. The oven's inner wall is made of metal, and the cavity is difficult to thoroughly clean to remove metal ions. At temperatures exceeding 180°C, the diffusion rate of metal ions on the chip surface accelerates, negatively affecting the performance of metal ion-sensitive devices. Second, heat transfer in the oven proceeds gradually from the surface to the inner layers of the film. When the surface layer is heated first to form a polymer, the solvent inside the film cannot be effectively expelled, generating microbubbles and affecting film uniformity. Third, the airflow inside the oven is non-unidirectional. When volatile small-molecule water is not promptly removed, water molecules and amide groups in the polyamic acid undergo degradation reactions, affecting the mechanical strength and electrical insulation properties of the polyimide. Summary of the Invention

[0006] (a) Purpose of the invention

[0007] The purpose of this invention is to provide a device for polyimide film-forming and curing processes that features a highly uniform heating method with a maximum temperature of 350°C from the inside out, a process chamber with low metal ion contamination, and unidirectional displacement of protective gas.

[0008] (II) Technical Solution

[0009] To address the aforementioned technical problems, this invention provides a semiconductor chip polyimide film-forming and curing apparatus, comprising a high-temperature furnace body 1, a programmed temperature control system 2, a high-purity quartz cavity 3, an airflow stabilization system 4, and an exhaust system 5. The high-purity quartz cavity 3 is arranged on the high-temperature furnace body 1, and the semiconductor chip to be film-formed and cured is arranged in the high-purity quartz cavity 3. The programmed temperature control system 2 controls the temperature of the high-temperature furnace body 1. The airflow stabilization system 4 and the exhaust system 5 are both connected. A protective gas is introduced into the high-purity quartz cavity 3 through the airflow stabilization system 4, and the exhaust system 5 discharges the circulated protective gas.

[0010] The bottom furnace plate 1-1 of the high-temperature furnace body 1 is made of high-quality aluminum. The upper surface of the furnace plate is pre-planed flat, and then V-shaped patterns are planed on the surface to increase the heat dissipation surface and improve temperature uniformity. Six heating tubes 1-2 and three thermocouples 1-3 are pre-embedded in the middle of the bottom furnace plate 1-1. The temperature measurement range of the thermocouples is 0.0~500.0℃. The number of heating tubes and thermocouples can be adjusted according to the size of the furnace body and the temperature control accuracy. The side furnace chambers 1-4, which are perpendicular to the furnace plate, are designed with a heat insulation layer. The heat insulation material is selected from... Ceramic fiber cotton and Morgan board provide excellent insulation and are resistant to rapid heating and cooling, without cracking, crystallization, or slagging. The outer shell 1-5 is made of 304 stainless steel plate, and the outer paint layer uses a high-temperature baking process for powder coating, making it resistant to high temperatures, oxidation, and acids and alkalis. The space between the outer shell 1-5 and the lower plane of the bottom furnace plate 1-1, as well as between the furnace chamber 1-4, is filled with heat insulation cotton 1-6 to ensure that heat is not easily lost and to keep the external temperature of the furnace shell close to room temperature during operation, preventing burns from contact with personnel.

[0011] The programmable temperature control system 2 uses a high-precision programmable temperature controller with a temperature control accuracy of 0.1%, connected to the heating tubes 1-2 and thermocouples 1-3 pre-embedded in the furnace plate at the bottom of the high-temperature furnace. It employs multiple independent power-adjustable thyristor outputs, with the power output using a three-phase zero-crossing sequential triggering method to avoid excessive primary current and power surges caused by simultaneous energizing of multiple heating elements. Thermocouples use multiple independent inputs, with each thermocouple input signal employing dynamic correction technology for real-time power output adjustment. Three temperature values ​​are simultaneously displayed on three sets of digital tubes, allowing for real-time monitoring of each temperature segment. It utilizes a programmable PID self-tuning system with over 20 segments, adapting to the characteristics and requirements of the polyimide film stepped curing process, enabling automatic heating and cooling without requiring manual intervention. For safety, it incorporates over-temperature protection, thermocouple breakage protection, and over-current and over-pressure protection functions. When the temperature exceeds the set alarm range, the temperature control system automatically issues an audible and visual alarm and automatically cuts off the control relay for protection, ensuring stable and reliable equipment operation.

[0012] The high-purity quartz cavity 3 includes a quartz substrate pot, a uniformly distributed quartz pot lid, a quartz five-way gas distributor, PTFE clips, and a silicone rubber inlet pipe. The high-purity quartz, PTFE, and silicone rubber materials used in the high-purity quartz cavity 3 can all be cleaned using the RCA wet cleaning method. This method utilizes chemical reagents such as acids and alkalis to remove organic matter, particles, and metal ions from the material surface through chemical reactions, ensuring that the chip to be cured with the polyimide film is in a low-metal ion contamination environment and that the product is not contaminated by impurities. The bottom surface of the quartz wafer holder is in close contact with the upper surface of the bottom plate 1-1 of the high-temperature furnace body, and the bottom surface of the quartz wafer holder is in close contact with the bottom surface of the chip to be processed. This close contact between the three provides the polyimide film on the chip surface with low-loss heat conduction from the inside out. Therefore, the bottom of the quartz wafer holder needs to have a high degree of flatness before being placed on the bottom plate 1-1 of the high-temperature furnace body. The contact parts between the uniform flow quartz pot lid and the quartz wafer holder are both designed with ground joints to form a tight, seamless contact. The uniform flow quartz pot lid is designed with four air inlets 3- 2-1. Protective gas enters the conical gas chamber 3-2-2 through the inlet. The bottom of the conical gas chamber 3-2-2 is densely covered with evenly distributed circular micropores. After passing through these micropores, the gas evenly covers and passes through the surface of the chip to be processed, and then exits through the two exhaust holes 3-2-3 designed on the quartz pot lid. The upper inlet hole 3-3-1 of the quartz five-way gas distributor connects to the external gas, and the lower four holes 3-3-2 connect to the four inlet holes on the quartz pot lid. The connectors use PTFE clips and silicone rubber inlet pipes, ensuring that the protective gas is injected smoothly and evenly into the conical gas chamber 3-2-2 of the quartz pot lid. The two-stage flow distribution through the five-way gas distributor 3-3 and the conical gas chamber 3-2-2 ensures more uniform contact between the protective gas and the chip to be processed.

[0013] The airflow stabilization system 4 includes a gas pressure stabilizing valve and a flow meter, which are installed on the connection passage between the external protective gas and the upper air inlet 3-3-1 of the quartz five-way gas distributor. This ensures that the flow rate of the protective gas entering the conical gas chamber 3-2-2 of the quartz pot lid is constant, avoiding the instability of gas flow caused by fluctuations in the external gas pressure. This prevents unstable curing temperature of the polyimide film on the semiconductor chip surface and imbalance between the inlet and outlet flow rates, which would affect the quality of the film curing process.

[0014] The exhaust system 5 adopts a pressure self-exhaust method, connecting the exhaust port 3-2-3 of the high-purity quartz process chamber to an open, negative pressure exhaust hood. The positive pressure of the intake air causes the waste gas carrying the solvent to diffuse to the exhaust port 3-2-3, where it is absorbed and treated by the plant exhaust system 5.

[0015] (III) Beneficial Effects

[0016] The semiconductor chip polyimide film curing device provided by the above technical solution allows the solvent in the polyimide film layer to be pushed from the inside to the outside, avoiding the problem of incomplete solvent discharge during existing oven film formation. The multi-stage unidirectional gas flow effectively discharges the evaporated solvent, solving the problem of water molecules not being discharged in time during existing oven film formation. This avoids the degradation reaction of amide groups in polyamic acid. At the same time, the quartz process chamber can better process and control metal ions, which is essential in the manufacturing process of semiconductor devices that are sensitive to metal ions.

[0017] Using the equipment and tooling described in this invention to carry out the polyimide film deposition and curing process for semiconductor chips, a polyimide passivation film with low metal ion content, high film uniformity, and high reliability can be obtained. It has been successfully applied in projects such as silicon-based avalanche detectors, four-quadrant laser detectors, and monolithic integrated detectors. Tens of thousands of various devices have been manufactured. The devices protected by the passivation film have exhibited excellent performance and high reliability, keeping the surface leakage current of the devices at the nanoampere level. Some aerospace-grade products have been carried on the Chang'e probe for deep space exploration and have undergone rigorous reliability verification.

[0018] The specific advantages of this invention are as follows:

[0019] 1. This equipment adopts bottom thermal radiation heating, which is conducive to the evaporation of solvent in the polyimide coating to be cured from the inside out. It avoids the polyimide coating surface from imidization caused by the overall enclosed thermal radiation of the oven, which forms a polymer and prevents the internal solvent from completely evaporating.

[0020] 2. All materials in contact with semiconductor chips in this equipment are made of high-purity quartz glass. This material is resistant to high temperatures and acids and alkalis, and can be cleaned using the RCA wet cleaning method. This method uses chemical reagents such as acids and alkalis to remove organic matter, particles, metal ions, etc. from the surface of the material through chemical reactions, thus preventing various impurities, especially metal ions, from diffusing into the interior of the semiconductor material at high temperatures and damaging the product performance.

[0021] 3. The quartz fixture adopts a two-stage flow distribution system consisting of a five-way gas distributor and a conical gas chamber. This allows the incoming gas to flow out evenly from the uniformly distributed circular holes at the bottom of the conical chamber and through the surface of the chip to be processed, thus avoiding large temperature differences on the chip surface caused by uneven or overly concentrated airflow, which could damage product performance.

[0022] 4. The ground quartz cap and the ground quartz pot are matched to form a tight and seamless contact. Together with the one-way air intake and exhaust channels, a one-way gas flow channel is formed. The gas passes through the chip surface, allowing the small molecule moisture volatilized during the imidization process to be discharged in time, thus preventing the polyimide from undergoing degradation in a humid and hot environment.

[0023] 5. The conical gas cylinder design, with its conical base close to the bottom of the quartz pot and a diameter slightly smaller than the pot's diameter, allows the protective gas to flow evenly from the conical cylinder, quickly displacing any moisture-laden molecules on the chip surface. This ensures the chip surface is consistently protected by high-purity gas. Simultaneously, the moisture-laden gas, under positive pressure, rapidly diffuses to the furnace edge, enters the furnace space outside the conical cylinder, and is exhausted through the exhaust port.

[0024] 6. The connection between the air tube and the quartz five-way air inlet, the connection between the quartz five-way air outlet and the air tube, and the connection between the air tube and the quartz pot lid air inlet all use PTFE sleeves. This material is resistant to high temperature and acid and alkali, and can be cleaned using the RCA wet cleaning method, which removes organic matter, particles, metal ions, etc. from the surface of the material through chemical reaction, thus avoiding contamination.

[0025] 7. The addition of a pressure stabilizing device to the equipment can stabilize the airflow into the quartz cavity, which is beneficial for adjusting the airflow and maintaining positive pressure inside the quartz cavity. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the layout of the device of the present invention.

[0027] Figure 2 This is a schematic diagram of the high-temperature furnace body in the device of the present invention.

[0028] Figure 3 Figure I is a schematic diagram of the quartz plate pot in the device of the present invention, and Figure II is a top view of Figure I.

[0029] Figure 4 Figure 1 is a schematic diagram of the uniform flow-dividing quartz pot lid in the device of the present invention. Figure 2 is the A-A' view of Figure 1, and Figure 3 is the B-B' view of Figure 1.

[0030] Figure 5 Figure II is a schematic diagram of the quartz five-way gas distributor in the device of the present invention. Figure I is a view along line A-A' of Figure I.

[0031] In the diagram: 1 High-temperature furnace body, 2 Programmable temperature control system, 3 High-purity quartz cavity, 4 Airflow stabilization system, 5 Exhaust system; 1-1 Furnace plate, 1-2 Heating tube, 1-3 Thermocouple, 1-4 Furnace chamber, 1-5 Outer shell, 1-6 Insulation cotton; 3-2-1 Air inlet, 3-2-2 Conical air chamber, 3-2-3 Exhaust port, 3-3-1 Upper air inlet, 3-3-2 Lower four holes. Detailed Implementation

[0032] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0033] Reference Figures 1 to 4As shown, the semiconductor chip polyimide film-forming and curing apparatus of this embodiment includes a high-temperature furnace body 1, a programmable temperature control system 2, a high-purity quartz cavity 3, an airflow stabilization system 4, and an exhaust system 5. The high-purity quartz cavity 3 is arranged on the high-temperature furnace body 1, and the semiconductor chip to be film-formed and cured is arranged in the high-purity quartz cavity 3. The programmable temperature control system 2 controls the temperature of the high-temperature furnace body 1. The airflow stabilization system 4 and the exhaust system 5 are connected. Protective gas is introduced into the high-purity quartz cavity 3 through the airflow stabilization system 4, and the protective gas after circulation is discharged through the exhaust system 5.

[0034] The high-temperature furnace body 1 includes a bottom furnace plate 1-1, heating tubes 1-2, thermocouples 1-3, furnace chamber 1-4, outer shell 1-5, and insulation cotton 1-6. The bottom furnace plate 1-1 is made of high-quality aluminum, with the upper surface pre-planed flat and then V-shaped grooves planed on the surface. Heating tubes 1-2 and thermocouples 1-3 are pre-embedded in the furnace plate. The side furnace chamber 1-4 is insulated with ceramic fiber cotton and Morgan board. The outer shell 1-5 is made of 304 stainless steel plate, and the outer paint layer uses a high-temperature baking process for powder coating. Insulation cotton 1-6 is filled between the inner layer and the lower surface of the furnace plate 1-1 and between the furnace chamber 1-4.

[0035] The programmable temperature control system 2 uses a high-precision programmable temperature controller with a temperature control accuracy of one-thousandth, connected to the heating tubes 1-2 and thermocouples 1-3 pre-embedded in the furnace plate at the bottom of the high-temperature furnace body. It employs multiple independent power-adjustable thyristor outputs and multiple independent thermocouple inputs. Each thermocouple input signal uses dynamic correction technology, enabling real-time control and adjustment of power output. Three temperature values ​​are simultaneously displayed on three sets of digital tubes, allowing for real-time monitoring of each temperature segment. It utilizes a programmable PID self-tuning system with more than 20 segments and incorporates over-temperature protection, thermocouple breakage protection, and over-current and over-pressure protection functions. When the temperature exceeds the set alarm range, the temperature control system automatically issues an audible and visual alarm and automatically cuts off the control relay for protection.

[0036] The high-purity quartz cavity 3 includes a quartz plate pot, a uniformly distributed quartz pot lid, a quartz five-way gas distributor, a PTFE buckle, and a silicone rubber gas inlet pipe. The bottom of the quartz substrate pot needs to be highly flat and is placed on the bottom plate 1-1 of the high-temperature furnace. The contact parts between the uniformly distributed quartz pot lid and the quartz substrate pot are all ground to form a tight seal. The uniformly distributed quartz pot lid is designed with 4 air inlets 3-2-1. The protective gas enters the conical gas chamber 3-2-2 through the air inlets. The bottom of the conical gas chamber 3-2-2 is evenly covered with circular micropores. After passing through the micropores, the gas evenly covers and passes through the surface of the chip to be processed, and then exits through the two exhaust holes 3-2-3 designed on the quartz pot lid. The upper air inlet 3-3-1 of the quartz five-way gas distributor connects to the external gas, and the lower four holes 3-3-2 connect to the 4 air inlets on the quartz pot lid. The connector uses PTFE clips and silicone rubber air inlet pipes to ensure that the protective gas can be injected smoothly and evenly into the conical gas chamber 3-2-2 of the quartz pot lid.

[0037] The airflow stabilization system 4 includes a gas pressure stabilizing valve and a flow meter, which are installed on the connection passage between the external protective gas and the upper air inlet 3-3-1 of the quartz five-way gas distributor.

[0038] The exhaust port 3-2-3 of the high-purity quartz process chamber is connected to an open, negative-pressure exhaust hood through a silicone rubber tube, and the exhaust is absorbed and treated by the plant ventilation system 5.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A semiconductor chip polyimide film forming and curing apparatus, characterized in that, include: The high-temperature furnace body (1), the program temperature control system (2), the high-purity quartz cavity (3), the airflow stabilization system (4) and the exhaust system (5) are arranged on the high-temperature furnace body (1). The semiconductor chip to be film-formed and cured is arranged in the high-purity quartz cavity (3). The program temperature control system (2) controls the temperature of the high-temperature furnace body (1). The airflow stabilization system (4) and the exhaust system (5) are connected. The airflow stabilization system (4) introduces protective gas into the high-purity quartz cavity (3), and the exhaust system (5) discharges the protective gas after it has been circulated. The high-temperature furnace body (1) includes a bottom furnace plate (1-1), a heating tube (1-2), a thermocouple (1-3), a furnace chamber (1-4), and an outer shell (1-5); the bottom furnace plate (1-1) is installed inside the outer shell (1-5), the heating tube (1-2) and the thermocouple (1-3) are pre-embedded in the bottom furnace plate (1-1), the furnace chamber (1-4) is vertically installed above the bottom furnace plate (1-1), and the semiconductor chip to be solidified is placed in the cavity formed by the bottom furnace plate (1-1) and the furnace chamber (1-4); The outer shell (1-5) is made of 304 stainless steel plate, and the side fireplace (1-4) is insulated with ceramic fiber cotton and Morgan board. The inner layer of the outer shell (1-5) is filled with heat insulation cotton (1-6) between the bottom surface of the bottom furnace plate (1-1) and the furnace chamber (1-4). The bottom furnace plate (1-1) is made of aluminum. The upper surface of the bottom furnace plate (1-1) is pre-planed flat, and then V-shaped patterns are planed on the surface. The bottom furnace plate (1-1) has a hole drilled in the middle to pre-embed 6 heating tubes (1-2) and 3 thermocouples (1-3), with the thermocouples having a temperature measurement range of 0.0 to 500.0℃; The programmable temperature control system (2) uses a high-precision programmable temperature controller with a temperature control accuracy of one-thousandth, and connects to the heating tube (1-2) and thermocouple (1-3) pre-embedded in the bottom furnace plate (1-1). The high-purity quartz cavity (3) includes a quartz substrate pot and a uniformly distributed quartz pot lid; the lower bottom surface of the quartz substrate pot is in close contact with the upper surface of the bottom furnace plate (1-1), and the upper bottom surface of the quartz substrate pot is in close contact with the bottom surface of the semiconductor chip to be solidified; the uniformly distributed quartz pot lid is placed on top of the quartz substrate pot, and a conical air cavity (3-2-2) is provided at the bottom of the uniformly distributed quartz pot lid, with evenly distributed circular micropores at the bottom of the conical air cavity (3-2-2), and the uniformly distributed quartz... The top of the quartz pot lid has four air inlets (3-2-1) and two exhaust outlets (3-2-3). The air inlets (3-2-1) are connected to the airflow stabilization system (4), and the exhaust outlets (3-2-3) are connected to the exhaust system (5). The contact parts between the uniformly diverting quartz pot lid and the quartz pot are all designed with ground joints. The air inlets (3-2-1) are connected to the inside of the conical air cavity (3-2-2), and the exhaust outlets (3-2-3) are connected to the outside of the conical air cavity (3-2-2). The high-purity quartz cavity (3) also includes a quartz five-way gas distributor, a polytetrafluoroethylene (PTFE) clip, and a silicone rubber gas inlet pipe; the upper gas inlet hole (3-3-1) of the quartz five-way gas distributor is connected to the external gas, and the lower four holes (3-3-2) are connected to the four gas inlets on the quartz pot lid. The connector uses a PTFE clip and a silicone rubber gas inlet pipe to ensure that the protective gas is evenly injected into the conical gas cavity (3-2-2) of the quartz pot lid. The airflow stabilization system (4) includes a gas pressure stabilizing valve and a flow meter, which are installed on the connection passage between the outer protective gas and the upper air inlet (3-3-1) of the quartz five-way gas distributor to keep the flow rate of the protective gas entering the conical gas cavity (3-2-2) of the quartz pot lid constant; the exhaust system (5) adopts a pressure self-exhaust method, connecting the exhaust port (3-2-3) of the high-purity quartz cavity to an open, negative pressure exhaust hood, and using positive pressure to diffuse the waste gas carrying the solvent to the exhaust port (3-2-3), which is then absorbed and treated by the plant exhaust system (5).

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