Plasma vacuum hot pressing bonding machine for semiconductor wafer surface bonding

Abstract

This invention discloses a plasma vacuum thermopressing bonding machine and method for semiconductor wafer surface bonding. The machine comprises a main body, a vacuum chamber mounted on the main body, and a vacuum pumping device for evacuating the vacuum chamber. The vacuum chamber contains an upper sample stage and a lower sample stage for placing semiconductor wafers to be bonded. The upper and lower sample stages are positioned opposite each other and are capable of relative movement to bring the two semiconductor wafers together. A cathode discharge plate capable of horizontal movement between the two semiconductor wafers is also provided within the vacuum chamber. Heaters are mounted on the upper and lower sample stages, and the heat generated by these heaters is transferred to the semiconductor wafers positioned on the upper and lower sample stages. This plasma vacuum thermopressing bonding machine for semiconductor wafer surface bonding avoids the formation of bubbles and oxide layers at the bonding interface, thus improving bonding quality.

Description

Technical Field

[0001] This invention relates to the field of chip equipment and semiconductor manufacturing technology, and proposes a plasma vacuum in-situ bonding machine and its bonding method for semiconductor wafer surface bonding processing. Background Technology

[0002] Bonding is an indispensable and important step in semiconductor manufacturing. Wafer bonding has a wide range of applications in integrated circuit manufacturing, microelectromechanical system packaging, and multi-functional chip integration. However, due to the different requirements for material bonding performance in different application fields, the functions of bonding equipment vary greatly. Therefore, it is necessary to design the bonding system more rationally and rigorously according to the material preparation requirements.

[0003] Wafer bonding can be performed directly in air, but in an atmospheric environment, the wafer surface will adsorb byproduct precursors such as hydroxyl groups and water vapor from the air, resulting in a large number of bubbles and oxide layers at the bonding interface after bonding, which greatly affects the wafer bonding quality. This is unacceptable for optoelectronic devices with interfacial electrical channels. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a plasma vacuum hot pressing bonding machine and bonding method for semiconductor wafer surface bonding processing. The plasma vacuum hot pressing bonding machine for semiconductor wafer surface bonding processing can avoid the generation of bubbles and oxide layers at the bonding interface and improve the bonding quality.

[0005] This invention relates to a plasma vacuum hot-press bonding machine for semiconductor wafer surface bonding, characterized in that it includes a machine body, a vacuum chamber disposed on the machine body, and a vacuum pumping device for evacuating the vacuum chamber. The vacuum chamber is provided with an upper sample stage and a lower sample stage for placing semiconductor wafers to be bonded, respectively. The upper and lower sample stages are arranged opposite to each other and are capable of relative movement to bring the two semiconductor wafers on them into contact. The vacuum chamber also includes a cathode discharge plate capable of horizontally moving between the two semiconductor wafers. Heaters are provided on the upper and lower sample stages, and the heat generated by these heaters is transferred to the semiconductor wafers positioned on the upper and lower sample stages.

[0006] Furthermore, the upper sample stage and the lower sample stage are arranged opposite each other in the vertical direction. The upper sample stage is driven to descend by a vertically arranged screw and nut mechanism or a cylinder drive mechanism so that the semiconductor wafer on the upper sample stage can be attached to the semiconductor wafer on the lower sample stage.

[0007] Furthermore, the polished surface of the semiconductor wafer located on the upper sample stage faces downwards, while the polished surface of the semiconductor wafer located on the lower sample stage faces upwards.

[0008] Furthermore, the wiring of the aforementioned heater is protected with insulating ceramic to prevent short circuits caused by contact with high temperatures.

[0009] Furthermore, the right side of the aforementioned vacuum chamber is a cathode discharge plate placement area. The cathode discharge plate placement area is connected to an external radio frequency power supply to energize the cathode plate. The cathode discharge plate is driven to move horizontally by a horizontally arranged screw and nut mechanism or a cylinder drive mechanism.

[0010] Furthermore, the lead screw and nut mechanism vertically arranged on the upper sample stage is connected to and controlled by a stepper motor, so that the lead screw steps to adjust the pressure between the upper and lower sample stages.

[0011] Furthermore, silicon wafers, germanium wafers, or indium phosphide wafers are attached to the surfaces of the upper and lower sample stages and the cathode discharge plate to remove the influence of the stainless steel of the sample stage and cathode discharge plate on the semiconductor wafer surface during plasma treatment, so as to achieve high-quality bonding of different semiconductor wafers.

[0012] Furthermore, the aforementioned vacuum chamber is also connected to an air inlet channel for introducing nitrogen and argon gas.

[0013] The bonding method of the present invention is characterized by comprising the following steps:

[0014] S1. Open the vacuum chamber, place the two semiconductor wafers to be bonded on the upper and lower sample stages respectively, and align and position them.

[0015] S2. Turn on the vacuum pumping device to complete the high-vacuum extraction of the vacuum chamber;

[0016] S3. When the vacuum level reaches the target value, argon gas is introduced. After the gas pressure control is stable, the cathode discharge plate is driven to move to the middle area of ​​the vacuum cavity between the upper and lower sample stages. The radio frequency power supply is turned on to perform plasma treatment on the semiconductor wafers on the upper and lower sample stages. After plasma treatment, the radio frequency power supply is turned off and the cathode discharge plate is driven to be extracted from the bonding area.

[0017] S4. By driving the upper sample stage to descend, the two semiconductor wafers on the upper sample stage and the lower sample stage are brought into contact and the contact pressure between them is maintained.

[0018] S5. In-situ heating of the two semiconductor wafers under pressure;

[0019] S6. After heating for a certain period of time, annealing is performed in situ. After annealing is completed, the sample stage is raised, the pressure applied to the two semiconductor wafers is removed, the cavity is opened, and the sample is taken out to complete the in-situ bonding.

[0020] Furthermore, in step S3 above, the target vacuum level is 10⁻⁴ Pa, the vacuum chamber pressure is 2.5 Pa, the pressure between the two semiconductor wafers is 1000 N-3000 N, and the temperature during in-situ heating of the two semiconductor wafers is 300-600 °C.

[0021] The bonding method of this invention can perform semiconductor wafer bonding in a high vacuum environment, preventing the introduction of an oxide layer at the bonding interface and avoiding the problem of forming bubbles due to the adsorption of hydroxyl groups on the wafer surface, which affects the bonding quality. Before bonding, the wafer surface is plasma treated to form semiconductor dangling bonds as an adhesive layer. After in-situ hot pressing, the semiconductor dangling bonds are tightly connected together, which can achieve high-strength bonding. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a partial three-dimensional structure of a plasma vacuum hot pressing bonding machine;

[0023] Figure 2 This is a schematic diagram of a partial front view cross-section of a plasma vacuum hot pressing bonding machine.

[0024] Figure 3 This is a schematic diagram of the overall three-dimensional structure of the plasma vacuum hot pressing bonding machine;

[0025] Figure 4 This is a flowchart of the bonding method of the present invention. Detailed Implementation

[0026] The present invention provides a plasma vacuum in-situ bonding machine and bonding method. The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description.

[0027] The present invention relates to a plasma vacuum hot pressing bonding machine for semiconductor wafer surface bonding processing, comprising a body 1 and a vacuum chamber 2 disposed on the body 1. The vacuum chamber 2 is a vertical chamber with a full stainless steel copper ring sealing structure. Its front is a chamber sealing door with an observation window, which provides a high vacuum environment for the bonding process. The body 1 contains circuits for various modules. The front side of the body 1 is provided with a pressure gauge 10 with a disc, a pressure adjustment knob 11, etc.

[0028] The machine body is equipped with a vacuum pumping device 3 for evacuating the vacuum chamber. The vacuum pumping device 3 is an existing device, which consists of a molecular pump, a mechanical pump, a compound vacuum gauge, a slide valve, a butterfly valve, a resistance gauge, an ionization gauge, and a diaphragm gauge, etc., and is used to extract the gas in the vacuum chamber 2 to create a high vacuum environment.

[0029] The vacuum chamber is equipped with an upper sample stage 4 and a lower sample stage 5 for placing semiconductor wafers to be bonded. Both the upper sample stage 4 and the lower sample stage 5 are provided with positioning grooves for fixing the semiconductor wafers to be bonded.

[0030] The upper and lower sample stages are vertically opposite each other. The upper sample stage is driven to rise and fall by a vertically arranged lead screw and nut mechanism or a cylinder drive mechanism 8, so that the semiconductor wafer on the upper sample stage can be attached to the semiconductor wafer on the lower sample stage. The polished surface of the semiconductor wafer on the upper sample stage faces down, and the polished surface of the semiconductor wafer on the lower sample stage faces up. Preferably, the vertically arranged lead screw and nut mechanism on the upper sample stage can be connected to and controlled by a stepper motor, so that the lead screw can step to adjust the pressure between the upper and lower sample stages.

[0031] A cathode discharge plate 6, capable of horizontally moving between two semiconductor wafers, is installed inside the vacuum chamber. The right side of the vacuum chamber is the cathode discharge plate placement area. Initially, the cathode discharge plate 6 is located in the cathode discharge plate placement area. During operation, the cathode discharge plate 6 moves between the two semiconductor wafers. The cathode discharge plate 6 can be driven to move horizontally by a horizontally set screw and nut mechanism or a cylinder drive mechanism 9. The cathode discharge plate placement area is connected to an external radio frequency power supply, which can energize the cathode plate to generate plasma. The generated plasma can bombard and remove the oxide layer on the bonding surface of the semiconductor wafers and introduce dangling bonds on the bonding surface.

[0032] During the plasma treatment step, a horizontally positioned screw and nut mechanism or cylinder drive mechanism moves the cathode discharge plate to the left, translating it to the center of the cavity for plasma treatment. After treatment, the cathode discharge plate is controlled to move to the right and reset, moving it to the right side of the cavity, thus enabling in-situ thermo-press bonding in the center of the cavity.

[0033] Heaters 7 are provided on the upper and lower sample stages. The heat generated by the heaters is transferred to the semiconductor wafers positioned on the upper and lower sample stages. The heaters 7 can be electric heating wires or the like embedded in the upper and lower sample stages. The semiconductor wafers after plasma treatment are hot-pressed and bonded under high vacuum, which effectively avoids the introduction of oxide layers and bubbles at the bonding interface and improves the bonding quality.

[0034] To protect the wires, the wires of the aforementioned heater are protected with insulating ceramic, thereby preventing short circuits caused by the wires coming into contact with high temperatures.

[0035] For optimal design, silicon wafers, germanium wafers, or indium phosphide wafers (i.e., semiconductor materials of the same composition as the semiconductor wafers to be bonded) are attached to the surfaces of the upper and lower sample stages and the cathode discharge plate. This is to remove the influence of the stainless steel of the sample stage and cathode discharge plate on the surface of the semiconductor wafers during plasma treatment, thereby achieving high-quality bonding of different semiconductor wafers.

[0036] Furthermore, the aforementioned vacuum chamber is also connected to an air inlet channel for introducing nitrogen and argon. The actual vacuum chamber is equipped with a vacuum pumping port, a discharge gas inlet port (i.e., an air inlet channel), a general nitrogen venting port, a resistance gauge port, an ionization gauge port, and a thin film gauge port. These ports are used to meet the requirements of vacuuming, introducing nitrogen, and ensuring stable gas pressure.

[0037] The bonding method of the present invention is characterized by comprising the following steps:

[0038] S1. Open the vacuum chamber, place the two semiconductor wafers to be bonded on the upper and lower sample stages respectively, and align and position them.

[0039] S2. Turn on the vacuum pumping device to complete the high-vacuum extraction of the vacuum chamber;

[0040] S3. When the vacuum level reaches the target value, argon gas is introduced. After the gas pressure control is stable, the cathode discharge plate is driven to move to the middle area of ​​the vacuum cavity between the upper and lower sample stages. The radio frequency power supply is turned on to perform plasma treatment on the semiconductor wafers on the upper and lower sample stages. After plasma treatment, the radio frequency power supply is turned off and the cathode discharge plate is driven to be extracted from the bonding area.

[0041] S4. By driving the upper sample stage to descend, the two semiconductor wafers on the upper sample stage and the lower sample stage are brought into contact and the contact pressure between them is maintained.

[0042] S5. In-situ heating of the two semiconductor wafers under pressure;

[0043] S6. After heating for a certain period of time, annealing is performed in situ. After annealing is completed, the sample stage is raised, the pressure applied to the two semiconductor wafers is removed, the cavity is opened, and the sample is taken out to complete the in-situ bonding.

[0044] Furthermore, in step S3 above, the target vacuum level is 10⁻⁴ Pa, the vacuum chamber pressure is 2.5 Pa (adjustable as needed), the pressure between the two semiconductor wafers is 1000 N (adjustable as needed, maximum pressure 3000 N), and the temperature when the two semiconductor wafers are heated in situ is 300 ℃ (adjustable as needed, maximum 600 ℃).

[0045] The bonding method of this invention can perform semiconductor wafer bonding in a high vacuum environment, preventing the introduction of an oxide layer at the bonding interface and avoiding the problem of forming bubbles due to the adsorption of hydroxyl groups on the wafer surface, which affects the bonding quality. Before bonding, the wafer surface is plasma treated to form semiconductor dangling bonds as an adhesive layer. After in-situ hot pressing, the semiconductor dangling bonds are tightly connected together, which can achieve high-strength bonding.

Claims

1. A plasma vacuum hot pressing bonding machine for semiconductor wafer surface bonding processing, characterized in that, The device includes a main body, a vacuum chamber mounted on the main body, and a vacuum pumping device for evacuating the vacuum chamber. The vacuum chamber contains an upper sample stage and a lower sample stage for placing semiconductor wafers to be bonded. The upper and lower sample stages are positioned opposite each other and are capable of relative movement to bring the two semiconductor wafers together. The vacuum chamber also contains a cathode discharge plate that can move horizontally between the two semiconductor wafers. Heaters are mounted on the upper and lower sample stages, transferring heat to the semiconductor wafers positioned on them. The upper and lower sample stages are vertically opposite each other, with the upper sample stage driven downwards by a vertically positioned screw and nut mechanism or cylinder drive mechanism to bring the semiconductor wafers on the upper and lower sample stages together. The polished surface of the semiconductor wafer on the upper sample stage faces downwards, while the polished surface of the wafer on the lower sample stage faces downwards. The polished surface of the semiconductor wafer faces upwards; the heater's wires are protected with insulating ceramic to prevent short circuits caused by contact with high temperatures; the right side of the vacuum chamber is the cathode discharge plate placement area, which is connected to an external radio frequency power supply to energize the cathode plate; the cathode discharge plate is driven to move horizontally by a horizontally arranged lead screw and nut mechanism or a cylinder drive mechanism; the vertically arranged lead screw and nut mechanism on the upper sample stage is connected to and controlled by a stepper motor to adjust the pressure of the upper and lower sample stages; silicon wafers, germanium wafers, or indium phosphide wafers are attached to the surfaces of the upper and lower sample stages and the cathode discharge plate to remove the influence of the stainless steel of the sample stage and cathode discharge plate on the semiconductor wafer surface during plasma treatment, thereby achieving high-quality bonding of different semiconductor wafers; the vacuum chamber is also connected to an air inlet channel for introducing nitrogen to open the vacuum chamber and argon for inlet pressure control. The bonding method includes the following steps: S1. Open the vacuum chamber, place the two semiconductor wafers to be bonded on the upper and lower sample stages respectively, and align and position them. S2. Turn on the vacuum pumping device to complete the high-vacuum extraction of the vacuum chamber; S3. When the vacuum level reaches the target value, argon gas is introduced. After the gas pressure control is stable, the cathode discharge plate is driven to move to the middle area of ​​the vacuum cavity between the upper and lower sample stages. The radio frequency power supply is turned on to perform plasma treatment on the semiconductor wafers on the upper and lower sample stages. After plasma treatment, the radio frequency power supply is turned off and the cathode discharge plate is driven to be extracted from the bonding area. S4. By driving the upper sample stage to descend, the two semiconductor wafers on the upper sample stage and the lower sample stage are brought into contact and the contact pressure between them is maintained. S5. In-situ heating of the two semiconductor wafers under pressure; S6. After heating for a certain period of time, annealing is performed in situ. After annealing, the sample stage is raised, the pressure applied to the two semiconductor wafers is removed, and the sample is removed from the cavity to complete the in-situ bonding. In step S3, the target vacuum level is 10⁻⁴ Pa, the vacuum chamber pressure is 2.5 Pa, the pressure between the two semiconductor wafers is 1000 N-3000 N, and the temperature of the two semiconductor wafers during in-situ heating is 300℃-600℃.

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