Electrostatic charge removal method for semiconductor wafer

Abstract

To provide a method for reducing an amount of static electricity charging on a semiconductor wafer in a semiconductor manufacturing process.SOLUTION: An electrostatic charge removal method for semiconductor wafers W1 and W2 applied to a semiconductor manufacturing process is provided, including: supplying argon gas 30 to the semiconductor wafers W1 and W2 having been subjected to plasma processing; and reducing an amount of static electricity charged on the semiconductor wafers W1 and W2. The method further includes: supplying mixed gas including argon and hydrogen to the semiconductor wafers W1 and W2 having been subjected to the plasma processing; and subsequently supplying oxygen gas, thereby omitting cleaning processing to the semiconductor wafers W1 and W2, consequently reducing the charge amount of static electricity charged on the semiconductor wafers W1 and W2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for reducing the amount of static electricity that accumulates on a semiconductor wafer during, for example, a semiconductor manufacturing process. [Background technology]

[0002] Hybrid bonding, which is part of a conventional semiconductor manufacturing process, includes, for example, a plasma treatment step, a cleaning step, a drying step, and a bonding step.

[0003] In the plasma treatment process, atmospheric pressure plasma or vacuum plasma is applied to the semiconductor wafer to activate the surface of the semiconductor wafer. In the cleaning process, for example, a cleaning liquid (pure water or chemical liquid) is dropped onto the semiconductor wafer while rotating the semiconductor wafer around its central axis to clean the surface of the semiconductor wafer. In the drying process, centrifugal force is used to disperse water droplets from the surface of the semiconductor wafer while rotating the semiconductor wafer at high speed around its central axis. In the bonding process, two semiconductor wafers, one above the other and one below the other, that have been through the plasma treatment process and the drying process are placed opposite each other and bonded together. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-181337 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, after activating the surface of the semiconductor wafer in the plasma processing process and attaching OH groups (hydroxyl groups) to the surface of the semiconductor wafer in the cleaning process, when the semiconductor wafer is rotated at high speed in the drying process, static electricity is generated due to friction between the semiconductor wafer and the air, and the surface of the semiconductor wafer is charged with static electricity. As a result, particles floating in the vicinity are attracted by the static electricity and attach to the surface of the semiconductor wafer. The semiconductor wafers with the particles attached are bonded together in the bonding process. For example, if a particle of about 1 μm adheres to the surface of the semiconductor wafer, it grows into an air bubble of about 1 cm when two semiconductor wafers are bonded together, which causes a quality defect in the semiconductor wafer and a decrease in the yield of the semiconductor manufacturing process.

[0006] In view of the above problems, an object of the present invention is to provide a method for reducing the amount of static electricity that builds up on a semiconductor wafer during a semiconductor manufacturing process. [Means for solving the problem]

[0007] A first invention is a method for removing static electricity from a semiconductor wafer, which is applied to a semiconductor manufacturing process, in which argon gas is supplied to the semiconductor wafer after plasma processing, thereby reducing the amount of static electricity charged on the semiconductor wafer.

[0008] The third invention is a method for removing electrostatic charge from a semiconductor wafer, which is applied to a semiconductor manufacturing process, in which a mixed gas containing argon and hydrogen is supplied to the semiconductor wafer after plasma processing, and then oxygen gas is supplied, thereby omitting a cleaning process for the semiconductor wafer and reducing the amount of static electricity charged to the semiconductor wafer.

[0009] In this case, it is preferable that the argon gas or mixed gas is supplied from the center of the plane of the semiconductor wafer toward the outside in the radial direction.

[0010] In this case, the argon gas or mixed gas is preferably supplied using a swingable nozzle. Effect of the Invention

[0011] According to the present invention, the amount of static electricity that builds up on a semiconductor wafer in a semiconductor manufacturing process can be reduced. [Brief description of the drawings]

[0012] [Figure 1] 1 is a process diagram of a semiconductor manufacturing process according to an embodiment of the present invention; [Diagram 2] 1 is an example of a plasma chamber for use in one embodiment of the present invention. [Diagram 3] 1 is an example of a cleaning machine according to an embodiment of the present invention. [Figure 4] 1A to 1C are diagrams illustrating a cleaning process, an argon gas supply process, and a drying process in a semiconductor manufacturing process according to an embodiment of the present invention. [Diagram 5] 1 is a flow chart of a semiconductor manufacturing process according to an embodiment of the present invention. [Figure 6] 1 is a process flow diagram of an improved semiconductor manufacturing process according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A method for removing electrostatic charges from a semiconductor wafer, which is applied to a semiconductor manufacturing process according to an embodiment of the present invention, will be described. For example, an embodiment applied to a semiconductor manufacturing process employing hybrid bonding will be described.

[0014] [Semiconductor manufacturing process] First, the semiconductor manufacturing process will be described. As shown in Figures 1 and 5, the semiconductor manufacturing process includes, for example, a particle removal process P100 for semiconductor wafers W1 and W2, a plasma treatment process P200, an atmosphere exposure process P300, a cleaning process P400, a drying process P500, an alignment process P600, a bonding process P700, an inspection process P800, and an annealing process P900.

[0015] In the particle removal step P100, particles adhering to the semiconductor wafers W1 and W2 are removed mechanically or chemically.

[0016] In the plasma treatment step P200, the surfaces of the semiconductor wafers W1 and W2 are activated by vacuum plasma treatment, atmospheric pressure plasma treatment, or the like.

[0017] The vacuum plasma treatment can be carried out using a known device. Examples of the vacuum plasma treatment include a high-frequency induction method, a capacitively coupled electrode method, a corona discharge electrode-plasma jet method, a parallel plate method, a remote plasma method, and an ICP type high-density plasma method. Examples of the gas used in the vacuum plasma treatment include oxygen gas, nitrogen gas, a rare gas (such as argon gas), hydrogen gas, and ammonia gas, and rare gas or nitrogen gas is preferable. The gas may be used alone or in a mixture of two or more types. For example, the gas may be 100% by volume of argon gas, may be a mixed gas of hydrogen gas / nitrogen gas at 70 / 30 (volume ratio), or may be a mixed gas of hydrogen gas / nitrogen gas / argon gas at 35 / 15 / 50 (volume ratio).

[0018] The atmosphere for the vacuum plasma treatment is preferably an atmosphere with a volume fraction of rare gas or nitrogen gas of 50 volume % or more, more preferably an atmosphere with a volume fraction of 70 volume % or more, further preferably an atmosphere with a volume fraction of 90 volume % or more, and particularly preferably an atmosphere with a volume fraction of 100 volume %. If the volume fraction of rare gas or nitrogen gas is equal to or more than the lower limit of the above range, the surface of the treatment object can be sufficiently roughened.

[0019] The gas flow rate, degree of vacuum, and treatment time in the vacuum plasma treatment are appropriately selected depending on the composition of the inorganic layer to be surface-treated and the structure of the vacuum plasma treatment apparatus.

[0020] Atmospheric pressure plasma treatment can also be carried out using a known device. In atmospheric pressure plasma treatment, a glow discharge is generated by discharging in an inert gas (argon gas, nitrogen gas, helium gas, etc.) at 0.8 to 1.2 atm. A small amount of active gas (oxygen gas, hydrogen gas, carbon dioxide gas, ethylene, tetrafluoroethylene, etc.) is mixed into the inert gas. As the gas, a mixture of nitrogen gas and hydrogen gas is preferable, since the surface of the treatment object can be sufficiently roughened.

[0021] The plasma chamber is shown in Figure 2. The gate valve 12 of the plasma chamber 10 is opened, and the semiconductor wafers W1 and W2 are transported by a robot into the chamber 14 and placed on the stage 16. The gate valve 12 is then closed to seal the inside of the chamber 14. The inside of the chamber 14 is then evacuated. Plasma processing is performed on the semiconductor wafers W1 and W2 to activate the surfaces of the semiconductor wafers W1 and W2.

[0022] Here, it is preferable to further include an atmosphere exposure step P300 of placing the semiconductor wafers W1 and W2 in an atmospheric environment after the plasma treatment step P200.

[0023] In the atmosphere opening process P300, the gate valve 12 of the plasma chamber 10 may be opened to expose the inside of the chamber 10 to the atmosphere, or an atmosphere opening chamber (not shown) that is open to the atmosphere may be provided separately from the plasma chamber 10, and the semiconductor wafers W1 and W2 may be transported to the atmosphere opening chamber and then placed in an atmospheric environment.

[0024] In the atmosphere release step P300, argon gas 30 is supplied to the semiconductor wafers W1 and W2. The argon gas 30 is preferably supplied by spraying it from the center of the plane of the semiconductor wafers W1 and W2 toward the radially outward (outer periphery) side using a predetermined swing nozzle 32.

[0025] The reason why the argon gas 30 is supplied to the semiconductor wafers W1 and W2 in the atmospheric release step P300 is that, for example, when nitrogen (N2) is purged during atmospheric release as in the conventional method, the surfaces of the semiconductor wafers W1 and W2 are charged with static electricity due to friction between the semiconductor wafers W1 and W2 and the purge gas, and particles fly up due to pressure fluctuations during purging, and the particles are attracted to the static electricity and tend to adhere to the surfaces of the semiconductor wafers W1 and W2. To prevent this, in this embodiment, instead of nitrogen (N2) purging, argon gas 30 is sprayed onto the semiconductor wafers W1 and W2, thereby reducing the amount of static electricity on the surfaces of the semiconductor wafers W1 and W2. As a result, the particles adhering to the surfaces of the semiconductor wafers W1 and W2 can be reduced.

[0026] The inside of the chamber 14 may be filled with argon gas 30 to create an argon gas atmosphere, so that the semiconductor wafers W1, W placed in the argon gas atmosphere are not charged with static electricity.

[0027] 4, for example, the semiconductor wafers W1 and W2 after the plasma processing are placed on a turntable 20 and rotated at a predetermined speed while cleaning water 28 is dropped onto the surfaces of the semiconductor wafers W1 and W2. As the cleaning water 28, for example, pure water or a chemical liquid can be used.

[0028] Here, when supplying the cleaning water 28 to the semiconductor wafers W1, W2, it is preferable to drip the cleaning water 28 onto the center of the plane of the rotating semiconductor wafers W1, W2 and guide the cleaning water 28 radially outward by the centrifugal force of the rotating semiconductor wafers W1, W2. This makes it possible to clean the entire surfaces of the semiconductor wafers W1, W2 and prevent uneven cleaning with the cleaning water 28.

[0029] The cleaning machine is shown in FIG. 3. The cleaning machine 18 is used in the cleaning process P400. The cleaning machine 18 has a rotating table 20, a rotary motor 22 that rotates the rotating table 20, and a cleaning nozzle 24 that supplies cleaning water 28 (see FIG. 4) to the semiconductor wafers W1 and W2. The cleaning nozzle 24 ejects the cleaning water 28 and is configured to be oscillated by driving a swing motor 26. As a result, while the semiconductor wafers W1 and W2 are placed on the rotating table and rotated by the rotary motor 22, the cleaning water 28 can be dropped from the cleaning nozzle 24 onto the center of the plane of the semiconductor wafers W1 and W2. As a result, the semiconductor wafers W1 and W2 are cleaned, and OH groups (hydroxyl groups) are attached to the surfaces of the semiconductor wafers W1 and W2.

[0030] Here, it is preferable to provide a drying step P500 after the cleaning step P400.

[0031] In the drying step P500, for example, the cleaning machine 18 is used as it is. Specifically, the turntable 20 is rotated at a speed faster than that in the cleaning step, and the argon gas 30 is sprayed toward the semiconductor wafers W1 and W2 from the cleaning nozzle 24 or another gas supply nozzle (not shown). In this case, as shown in FIG. 4, when the argon gas 30 is supplied from the center of the plane of the rotating semiconductor wafers W1 and W2 toward the radially outward (outer periphery), the argon gas 30 spreads as if pushing the cleaning water 28 under the action of the centrifugal force of the rotating semiconductor wafers W1 and W2. In other words, the cleaning water 28 attached to the surfaces of the semiconductor wafers W1 and W2 is peeled off from the surfaces of the semiconductor wafers W1 and W2 while being agitated by the centrifugal force of the rotating semiconductor wafers W1 and W2. This allows the argon gas 30 to come into contact with the entire surfaces of the semiconductor wafers W1 and W2, and prevents uneven contact of the argon gas 30.

[0032] Another reason for supplying argon gas 30 to the semiconductor wafers W1 and W2 in the drying step P500 is that when the cleaned semiconductor wafers W1 and W2 are rotated at high speed to dry, the surfaces of the semiconductor wafers W1 and W2 are charged with static electricity due to friction between the semiconductor wafers W1 and W2 and the air. Therefore, by exposing the surfaces of the semiconductor wafers W1 and W2 to argon gas 30 in the drying step P500, the amount of static electricity on the surfaces of the semiconductor wafers W1 and W2 can be reduced. As a result, the number of particles adhering to the surfaces of the semiconductor wafers W1 and W2 can be reduced.

[0033] As described above, by supplying the argon gas 30 to the semiconductor wafers W1, W2 in the drying step P500, the cleaning water 28 is removed from the surfaces of the semiconductor wafers W1, W2, and the surfaces are dried, and the amount of static electricity on the surfaces of the semiconductor wafers W1, W2 can be reduced.

[0034] In addition, in the atmosphere release step P300, a mixed gas obtained by appropriately mixing small amounts of hydrogen and oxygen into argon gas 30 may be supplied to the semiconductor wafers W1 and W2. For example, a mixed gas obtained by mixing argon with about 3 volume % hydrogen may be sprayed onto the surfaces of the semiconductor wafers W1 and W2 to remove static electricity and particles, and then oxygen gas may be sprayed onto the surfaces of the semiconductor wafers W1 and W2 to attach OH groups (hydroxyl groups) to the surfaces of the semiconductor wafers W1 and W2.

[0035] Here, in a configuration in which the semiconductor wafers W1, W2 are rotatable, the mixed gas and oxygen gas are preferably supplied from the center of the plane of the rotating semiconductor wafers W1, W2 toward the outside in the radial direction by a swing nozzle or the like. This causes the mixed gas and oxygen gas to be agitated by the centrifugal force acting on the rotating semiconductor wafers W1, W2, so that the mixed gas and oxygen gas can be evenly exposed to the entire surfaces of the semiconductor wafers W1, W2.

[0036] As a result, as shown in Figures 5 and 6, the cleaning step P400 and the drying step P500 can be omitted, improving the throughput in the semiconductor manufacturing process. Also, it is possible to prevent microbubbles from being generated in the semiconductor wafers W1 and W2 after the annealing step P900. Furthermore, fusion bonding becomes possible by attaching OH groups (hydroxyl groups) to the surfaces of the semiconductor wafers W1 and W2 activated by the plasma treatment, and a dry process can be realized.

[0037] In the alignment step P600, two semiconductor wafers W1 and W2 facing each other are positioned.

[0038] In the bonding process P700, the two semiconductor wafers W1 and W2 that have been through the alignment process P600 are bonded together. At this time, since the semiconductor wafers W1 and W2 with few particles are bonded together, the size of the air bubbles generated between the semiconductor wafers W1 and W2 becomes extremely small, which makes it possible to avoid quality defects of the semiconductor wafers W1 and W2 and to prevent a decrease in the yield of the semiconductor manufacturing process.

[0039] In the inspection process P800, shape observation, defect inspection, etc. are performed on the bonded semiconductor wafers W1 and W2.

[0040] In the annealing step P900, the surfaces of the semiconductor wafers W1 and W2 are heated and then cooled to modify the material surfaces, for example, by heating in a furnace or lamp, laser annealing, or the like.

[0041] As described above, according to this embodiment, the amount of static electricity charged to the semiconductor wafers W1 and W2 in the semiconductor manufacturing process can be reduced, thereby reducing particles attracted by static electricity and adhering to the surfaces of the semiconductor wafers W1 and W2.

[0042] Moreover, while the cleaning water 28 adhering to the surfaces of the semiconductor wafers W1, W2 is removed, the semiconductor wafers W1, W2 can be modified to have properties that make them less susceptible to static electricity.

[0043] In addition, fusion bonding of the semiconductor wafers W1 and W2 becomes possible, and the generation of microbubbles (air bubbles) can be prevented, which in turn prevents defects in the semiconductor wafers W1 and W2.

[0044] It should be noted that the present embodiment and examples are merely illustrative of one aspect of the present invention, and the present invention is not limited thereto. Any design changes to the present embodiment and examples are naturally included within the scope of the technical idea of ​​the present invention. [Explanation of symbols]

[0045] 10 Plasma chamber 12 Gate valve 14 Chamber 16 Stages 18 Cleaning Machine 20 Rotating Table 22 Rotary Motor 24 Cleaning nozzle 26 Swing motor 28 Washing Water 30 Argon gas 32 Swinging nozzle W1 Semiconductor wafer W2 Semiconductor wafer

Claims

1. A method for removing electrostatic charge from a semiconductor wafer, which is applied to a semiconductor manufacturing process, comprising the steps of: A method for removing electrostatic charges from a semiconductor wafer, comprising: supplying argon gas to the semiconductor wafer after plasma processing, thereby reducing the amount of static electricity charged on the semiconductor wafer.

2. A method for removing electrostatic charge from a semiconductor wafer, which is applied to a semiconductor manufacturing process, comprising the steps of: A method for removing electrostatic charge from a semiconductor wafer, comprising: supplying a mixed gas containing argon and hydrogen to the semiconductor wafer after plasma processing, and then supplying oxygen gas to the semiconductor wafer, thereby omitting a cleaning process for the semiconductor wafer and reducing the amount of static electricity charged to the semiconductor wafer.

3. 2. The method for removing electrostatic charges from a semiconductor wafer according to claim 1, wherein the argon gas is supplied from the center of the plane of the semiconductor wafer toward the outside in the radial direction.

4. 3. The method for removing electrostatic charges from a semiconductor wafer according to claim 2, wherein the mixed gas is supplied from the center of the plane of the semiconductor wafer toward the outside in the radial direction.

5. 5. The method for removing electrostatic charges from a semiconductor wafer according to claim 3, wherein the argon gas or the mixed gas is supplied by using a swingable nozzle.

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