Method for controlling adsorption and desorption of wafer and semiconductor processing equipment

Abstract

The application discloses a kind of to wafer is adsorbed and the control method of desorption and semiconductor process equipment, control method includes: wafer is sent to electrostatic chuck, wafer is adsorbed;After wafer is processed, desorption gas is introduced into reaction chamber, chamber pressure is controlled to be first set pressure, and first set power is applied to upper electrode, to excite desorption gas into plasma;In the first set duration after maintaining plasma, wafer is lifted to set height;After lifting, in the second set duration, the power of upper electrode is gradually reduced from first set power to 0, to realize the extinction of plasma;While chamber pressure is gradually reduced from first set pressure to second set pressure, and the desorption of wafer is completed.The application can solve the problem of particle generated in the process of wafer adsorption and desorption during process, improve product yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a method and semiconductor process equipment for controlling the adsorption and desorption of wafers. Background Technology

[0002] An ESC (Electrostatic Chuck) is a fixture that uses electrostatic adsorption to hold a wafer in a vacuum or plasma environment. Its main function is to hold the wafer in place, preventing movement or deformation during etching and controlling its temperature. ESCs are widely used in semiconductor manufacturing. A plasma etching chamber typically includes an upper electrode, a lower electrode, and an ESC. During plasma etching, the wafer is adsorbed onto the ESC, and plasma is generated between the upper electrode and the wafer (the plasma sheath is located near the wafer at the bottom). The plasma then etches the film layer on the wafer surface, forming the desired circuitry. After plasma etching, the wafer is released from the chuck, and a robotic arm removes the wafer from the chamber and returns it to the wafer cassette.

[0003] As chip sizes continue to shrink, particle generation during etching becomes increasingly critical, as the number of particles directly impacts chip yield. In current plasma etching processes, a significant portion of these particles are generated by friction between the wafer and the ESC surface during adsorption and desorption. Simultaneously, during the wafer desorption process after the process, an inert gas plasma needs to be formed within the chamber to neutralize the positive and negative charges carried on the chamber and wafer. At this time, most small particles within the chamber remain suspended in the plasma sheath and do not fall onto the wafer surface. However, current processes often shut off the power and extinguish the plasma immediately after wafer desorption and lifting. At the moment the plasma extinguishes, particles fall onto the wafer surface under gravity, causing chip defects and affecting wafer yield in subsequent processes. Summary of the Invention

[0004] The purpose of this invention is to provide a method and semiconductor process equipment for controlling the adsorption and desorption of wafers, thereby solving the problem of particles generated during the adsorption and desorption of wafers in the process and improving product yield.

[0005] In a first aspect, the present invention proposes a method for controlling the adsorption and desorption of wafers, used in a semiconductor device, the semiconductor device comprising a reaction chamber and an electrostatic chuck disposed in the reaction chamber, including:

[0006] The wafer is transferred to the electrostatic chuck for adsorption.

[0007] After the wafer has been processed, desorption gas is introduced into the reaction chamber, the chamber pressure is controlled to a first set pressure, and a first set power is applied to the upper electrode to excite the desorption gas into plasma.

[0008] Within a first set time after maintaining the plasma, the wafer is raised to a set height;

[0009] After the lifting, within a second set time period, the power of the upper electrode is gradually reduced from the first set power to 0 to extinguish the plasma; at the same time, the chamber pressure is gradually reduced from the first set pressure to the second set pressure to complete the desorption of the wafer.

[0010] Optionally, adsorption of the wafer specifically includes:

[0011] Simultaneously increase the adsorption voltage of the electrostatic chuck and the gas pressure on the back of the wafer.

[0012] Optionally, the simultaneous increase of the electrostatic chuck's adsorption voltage and the gas pressure on the back side of the wafer includes:

[0013] Within a third set time period, the adsorption voltage of the electrostatic chuck is simultaneously controlled to gradually increase from zero to a set voltage, and the gas pressure on the back of the wafer is gradually increased from zero to a third set pressure.

[0014] Optionally, before raising the wafer to a set height within a first set time period after maintaining the plasma, the method further includes:

[0015] During the fourth time period, the adsorption voltage of the electrostatic chuck is controlled to gradually decrease from the set voltage to zero, while the gas pressure on the back side of the wafer is controlled to be maintained at the third set pressure.

[0016] Optionally, the third set duration is 0.5s-3s, the fourth duration is 5s, the set voltage is 1000V-4000V, and the third set pressure is 10T-30T.

[0017] Optionally, the first set power is 800W-1000W, the first set pressure is 10mT-30mT; the second set duration is 7s-10s, the second set pressure is 0mT-5mT; and the rate of decrease of the upper electrode power is 100-500W / s.

[0018] Optionally, the first set duration is 2s-5s.

[0019] Optionally, after the desorption of the wafer is completed, purge gas is continuously introduced into the process chamber.

[0020] Optionally, the purging gas is an inert gas or nitrogen, and the flow rate of the purging gas is 100 sccm-500 sccm.

[0021] Secondly, the present invention provides a semiconductor process apparatus, comprising: a process chamber and a wafer transfer mechanism, wherein an electrostatic chuck is provided in the process chamber, the electrostatic chuck includes a base and an insulator disposed on the base, a lower electrode is provided in the insulator, and an upper electrode is provided above the base; the wafer transfer mechanism is used to transfer wafers into or out of the process chamber;

[0022] It also includes a control unit, which is used to execute the control method for adsorbing and desorbing the wafer as described in the first aspect.

[0023] The beneficial effects of this invention are as follows:

[0024] In the desorption process of the wafer, after the wafer is lifted, the plasma is gradually extinguished by gradually reducing the electrode power and chamber pressure. This increases the distance between the plasma sheath and the wafer surface, thereby increasing the distance between the suspended particles in the plasma sheath and the wafer surface. As a result, the particles suspended in the plasma sheath are pumped away by the molecular pump during the extinguishing process instead of falling onto the wafer, effectively preventing particles from falling onto the wafer surface, reducing the number of particles on the wafer surface, and improving the wafer yield.

[0025] Furthermore, during the wafer adsorption process, this invention simultaneously increases the adsorption voltage of the electrostatic chuck and the gas pressure on the back side of the wafer, effectively preventing particle generation from direct friction between the wafer surface and the electrostatic chuck surface, thus reducing particle generation at the source. After plasma quenching, by continuously introducing purge gas into the process chamber, particles that have fallen onto the wafer surface can be blown away from the wafer, further reducing particles on the wafer surface and effectively improving wafer yield.

[0026] The system of the present invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0027] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0028] Figure 1A flowchart illustrating the steps of a method for controlling the adsorption and desorption of a wafer according to Embodiment 1 of the present invention is shown.

[0029] Figure 2 A schematic diagram of the process chamber structure of a semiconductor process apparatus according to Embodiment 2 is shown. Detailed Implementation

[0030] Existing technologies mainly focus on the adsorption and desorption processes, wafer temperature control, and preventing wafer damage from arcing. Few technologies address how to reduce particle generation during adsorption and desorption, or how to prevent such particles from falling onto the wafer surface and causing chip defects.

[0031] Research has shown that the probability of particles falling onto the wafer surface during plasma quenching is related to the height of the particle from the wafer surface. When the height is greater than 6 mm, the particle is usually pumped away by a molecular pump and generally does not fall onto the wafer surface. When the height is less than 6 mm, the particle is highly likely to fall onto the wafer during plasma quenching, causing defects. This invention proposes a wafer adsorption and desorption method. By employing optimization schemes such as controlling the height of the particle from the wafer surface, reducing particles generated by friction between the wafer and the back of the ESC, and adjusting the gas flow rate in the chamber during adsorption and desorption, the particle problem generated during the etching process can be reduced.

[0032] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0033] Example 1: This example proposes a method for controlling the adsorption and desorption of wafers in a semiconductor device. The semiconductor device includes a reaction chamber and an electrostatic chuck disposed in the reaction chamber. The method for controlling the adsorption and desorption of wafers includes:

[0034] Step S1: Transfer the wafer to the electrostatic chuck for wafer adsorption;

[0035] Specifically, the wafer adsorption process in this step includes simultaneously increasing the adsorption voltage of the electrostatic chuck and the gas pressure on the back of the wafer.

[0036] The specific method for simultaneously increasing the adsorption voltage of the electrostatic chuck and the gas pressure on the back side of the wafer is as follows:

[0037] Within a third set time period, the adsorption voltage of the electrostatic chuck is simultaneously controlled to gradually increase from zero to a set voltage, and the gas pressure on the back side of the wafer is simultaneously controlled to gradually increase from zero to a third set pressure. Preferably, the third set time period is 0.5s-3s, the set voltage is 1000V-4000V, and in this embodiment, it is preferably 1800V. The third set pressure is 10T-30T, and in this embodiment, it is preferably 10T.

[0038] The wafer adsorption process in this embodiment is as follows: within 2 seconds, the adsorption voltage of the electrostatic chuck is gradually increased from 0 to 1800V, while the gas pressure (back pressure) on the back of the wafer is gradually increased from 0 to 10T. The adsorption voltage and wafer back pressure can be increased linearly or in a stepwise manner. The gas introduced into the electrostatic chuck and the back of the wafer is generally helium.

[0039] During wafer adsorption, the adsorption voltage and back gas pressure are increased simultaneously. The pressure of the introduced helium gas gradually increases with the increase of the adsorption voltage, which can always form an air cushion between the back of the wafer and the surface of the electrostatic chuck, thereby avoiding direct friction between the wafer surface and the surface of the electrostatic chuck, and reducing the generation of particles from the source.

[0040] After the wafer is adsorbed, the pre-set process conditions are run on the wafer, such as performing a plasma etching process on the wafer. After the process is completed, step S2 is executed.

[0041] S2: After the wafer has been processed, desorption gas is introduced into the reaction chamber, the chamber pressure is controlled to a first set pressure, and a first set power is applied to the upper electrode to excite the desorption gas into plasma.

[0042] Specifically, after the process is completed, before desorption of the wafer, the chamber needs to be adjusted from the previous process conditions to the desorption set conditions. This includes: introducing a desorption gas into the reaction chamber, which can be any one of argon, oxygen, or nitrogen; then controlling the chamber pressure to a first set pressure; and applying a first set power to the upper electrode to excite the desorption gas into plasma. Preferably, the first set power is 800W-1000W, and in this embodiment, it is preferably 1000W. The first set pressure is 10mT-30mT, and in this embodiment, it is preferably 30mT.

[0043] S3: Within the first set time after maintaining the plasma, raise the wafer to the set height;

[0044] Before executing step S3, during the fourth time period, the adsorption voltage of the electrostatic chuck is gradually reduced from the set voltage to zero, while the gas pressure on the back of the wafer is maintained at the third set pressure to release the electrostatic adsorption of the wafer by the electrostatic chuck, after which step S3 is executed. Preferably, the fourth time period is 5 seconds.

[0045] Specifically, the process of the electrostatic chuck releasing the electrostatic adsorption of the wafer and completing the wafer lifting is generally 7-10 seconds. First, the electrostatic chuck performs normal desorption and releases static electricity on the wafer in about 5 seconds. This process is achieved by reducing the adsorption voltage of the electrostatic chuck, that is, gradually reducing the adsorption voltage of the electrostatic chuck from the set voltage (e.g., 1800V) to 0. During this process, the gas pressure introduced into the back of the wafer needs to be maintained at the third set pressure (e.g., 10T) to ensure that there is always an air cushion between the wafer and the electrostatic chuck, and that no particles are generated in contact between the wafer surface and the electrostatic chuck.

[0046] After releasing the electrostatic adsorption of the wafer, a lifting motion is performed within a first set time period before plasma extinguishing, preferably 2-5 seconds. The lifting motion can be accomplished by the ejector pin assembly below the electrostatic chuck. During the wafer lifting process, plasma needs to be maintained until the wafer is completely lifted. After the wafer is completely lifted to the set height, the plasma begins to extinguish. The set height at which the wafer is lifted is the set value of the machine tool, which is the set height at which the transfer mechanism (such as a robot arm) transfers the wafer out of the process chamber.

[0047] During the process of the electrostatic chuck releasing the electrostatic adsorption of the wafer and completing the wafer lifting, since the plasma is in a held state, the flow rate of the desorption gas introduced into the chamber remains unchanged, the pumping force of the molecular pump remains constant, and the chamber pressure remains at the first set pressure. The particles suspended in the plasma sheath do not fall directly onto the wafer surface. Instead, the particles suspended in the plasma sheath are carried away to the molecular pump as the plasma diffuses, thus preventing the particles from falling onto the wafer.

[0048] Step S4: After the lifting, within the second set time period, the power of the upper electrode is gradually reduced from the first set power to 0 to extinguish the plasma; at the same time, the chamber pressure is gradually reduced from the first set pressure to the second set pressure to complete the desorption of the wafer.

[0049] Specifically, after the wafer is lifted, the plasma quenching process begins: within a second set time period, the power of the upper electrode is gradually reduced from a first set power to 0, and simultaneously, the chamber pressure is gradually reduced from a first set pressure to a second set pressure, completing the desorption of the wafer. Preferably, the second set time period is 7s-10s, the second set pressure is 0mT-5mT, and the rate of decrease of the upper electrode power is 100-500W / s.

[0050] In this embodiment, the preferred first set power is 1000W, the preferred first set pressure is 30mT, and the preferred second set pressure is 5mT. This means that within 7-10 seconds, the upper electrode power decreases from 1000W to 0W, and the pressure decreases from 30mT to 5mT. The upper electrode power needs to gradually decrease from 1000W to 0W to ensure complete plasma extinguishing. The chamber pressure is reduced to 5mT primarily to account for the pressure limits of the instrument, and can be set according to the instrument's pressure control capabilities.

[0051] During plasma quenching, by gradually reducing the power of the upper electrode and the chamber pressure, the distance from the bottom of the plasma sheath to the wafer surface can be increased. This allows control over the height of particles suspended in the plasma sheath above the wafer surface. As the upper electrode power and chamber pressure gradually decrease during quenching (and the flow rate of desorption gas and the pumping force of the molecular pump also gradually decrease), particles suspended in the plasma sheath are more susceptible to gravity and tend to fall downwards. However, because the distance between the wafer surface and the plasma sheath gradually increases and the molecular pump maintains a certain pumping force, falling particles are drawn away by the molecular pump before reaching the wafer surface, thus effectively preventing particle contamination of the wafer surface during desorption and improving wafer yield.

[0052] In this embodiment, after desorption of the wafer is completed, the process further includes:

[0053] Step S5: Continuously introduce purge gas into the process chamber.

[0054] Preferably, the purge gas can be any gas that does not react with the wafer material, preferably an inert gas such as argon or nitrogen, and the flow rate of the purge gas is preferably 100 sccm-500 sccm.

[0055] Specifically, after plasma quenching, the wafer has been desorbed, and purge gas is continuously introduced into the process chamber, forming a continuous flow of gas on the wafer surface. Preferably, in this embodiment, the gas flow rate introduced into the chamber is 200-300 sccm; the purge gas is an inert gas, such as Ar or N2. The airflow introduced into the process chamber can blow particles that have fallen onto the wafer surface away from the wafer, and finally be pumped away by a molecular pump. This can further reduce the particles on the wafer surface and further improve the wafer yield.

[0056] In this embodiment, after continuously introducing purge gas into the process chamber, the method further includes:

[0057] Step S6: Transfer the wafer out of the process chamber.

[0058] Specifically, after completing wafer desorption and chamber purging, and minimizing particulate contamination on the wafer surface, the wafer can then be transferred to the process chamber via a transport mechanism.

[0059] The method of this invention reduces particle generation at its source by simultaneously increasing or decreasing the adsorption voltage and the helium pressure on the back of the wafer, preventing hard contact friction between the wafer and the ESC during adsorption and desorption. Furthermore, by adjusting the upper electrode power and chamber pressure, the height of particles suspended in the plasma sheath above the wafer surface is controlled, thereby reducing or preventing particles from falling onto the wafer surface. Moreover, continuously supplying gas to the wafer surface after desorption further reduces the number of particles on the wafer surface. Experiments have verified that the method of this invention can reduce particles generated on the wafer surface by more than 90% during adsorption and desorption.

[0060] Example 2

[0061] like Figure 2 As shown, this embodiment proposes a semiconductor process apparatus, including: a process chamber 1 and a wafer transfer mechanism. The process chamber 1 is provided with an electrostatic chuck 2, which includes a base 3 and an insulator 4 disposed on the base 3. A lower electrode 5 is disposed inside the insulator 4. An upper electrode 6 is disposed above the base 3. The wafer transfer mechanism is used to transfer a wafer 7 into or out of the process chamber.

[0062] It also includes a control unit, which is used to execute the control method for adsorption and desorption of wafers in Example 1.

[0063] In this embodiment, the wafer transport mechanism includes a robotic arm, and a base is also provided with a lifting pin assembly for lifting the wafer. The semiconductor process equipment in this embodiment also includes the gas supply lines and pressure control system found in existing plasma process equipment.

[0064] The semiconductor process equipment in this embodiment includes plasma equipment such as plasma etching machines, etc. Figure 2 As shown, during the wafer desorption process after the process is completed, desorption gas is introduced into the process chamber, and plasma 8 is excited between the upper electrode and the wafer. The bottom of the plasma is a plasma sheath layer 9, and there are suspended particles in the plasma sheath layer 9.

[0065] The semiconductor process equipment of this embodiment adopts the wafer adsorption and desorption control method of Embodiment 1. It can avoid the generation of particles between the wafer and the electrostatic chuck during the wafer adsorption process. During the wafer desorption process, the height of the particles suspended in the plasma sheath from the wafer surface is controlled by gradually reducing the upper electrode power and the chamber pressure during the plasma quenching process, thereby reducing or avoiding particles falling onto the wafer surface. After the wafer desorption is completed, the particles on the wafer surface can be further reduced by introducing purge gas into the chamber. This effectively solves the particle problem generated by the wafer during the adsorption and desorption process and improves the product yield.

[0066] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for controlling the adsorption and desorption of a wafer, used in a semiconductor device, the semiconductor device comprising a reaction chamber and an electrostatic chuck disposed in the reaction chamber, characterized in that, include: The wafer is transferred to the electrostatic chuck for adsorption. After the wafer has been processed, desorption gas is introduced into the reaction chamber, the chamber pressure is controlled to a first set pressure, and a first set power is applied to the upper electrode to excite the desorption gas into plasma. Within a first set time after maintaining the plasma, the wafer is raised to a set height; After the lifting, within a second set time period, the power of the upper electrode is gradually reduced from the first set power to 0 to extinguish the plasma; during the plasma extinguishing process, the chamber pressure is gradually reduced from the first set pressure to the second set pressure to complete the desorption of the wafer.

2. The control method according to claim 1, characterized in that, The adsorption of the wafer specifically includes: Simultaneously increase the adsorption voltage of the electrostatic chuck and the gas pressure on the back of the wafer.

3. The control method according to claim 2, characterized in that, The simultaneous increase in the adsorption voltage of the electrostatic chuck and the gas pressure on the back side of the wafer includes: Within a third set time period, the adsorption voltage of the electrostatic chuck is simultaneously controlled to gradually increase from zero to a set voltage, and the gas pressure on the back of the wafer is gradually increased from zero to a third set pressure.

4. The control method according to claim 3, characterized in that, Before raising the wafer to a predetermined height within a first predetermined time period after maintaining the plasma, the process further includes: During the fourth time period, the adsorption voltage of the electrostatic chuck is controlled to gradually decrease from the set voltage to zero, while the gas pressure on the back side of the wafer is controlled to be maintained at the third set pressure.

5. The control method according to claim 4, characterized in that, The third set duration is 0.5s-3s, the fourth duration is 5s, the set voltage is 1000V-4000V, and the third set pressure is 10T-30T.

6. The control method according to claim 1, characterized in that, The first set power is 800W-1000W, the first set pressure is 10mT-30mT; the second set duration is 7s-10s, the second set pressure is 0mT-5mT; the rate of decrease of the upper electrode power is 100-500W / s.

7. The control method according to claim 1, characterized in that, The first set duration is 2s-5s.

8. The control method according to claim 1, characterized in that, After the desorption of the wafer is completed, purge gas is continuously introduced into the reaction chamber.

9. The control method according to claim 8, characterized in that, The purging gas is an inert gas or nitrogen, and the flow rate of the purging gas is 100 sccm-500 sccm.

10. A semiconductor process apparatus, comprising: The reaction chamber and an electrostatic chuck disposed within the reaction chamber, the electrostatic chuck having a lower electrode and an upper electrode above it, characterized in that it further includes a control unit, the control unit being used to execute the control method for adsorbing and desorbing wafers as described in any one of claims 1-9.

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