Wafer etching method
By controlling the pressure and gas flow in the process chamber, and combining radio frequency devices and heat conduction gas treatment, the problems of wafer misalignment and machine downtime caused by polymer accumulation on the surface of the electrostatic chuck were solved, achieving accurate wafer positioning and efficient etching.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUA HONG SEMICON WUXI LTD
- Filing Date
- 2023-01-05
- Publication Date
- 2026-06-05
AI Technical Summary
In the zero-layer etching process of power MOSFETs, the accumulation of reaction byproducts on the surface of the electrostatic chuck can cause problems such as wafer misalignment, scratches, fragmentation, and machine downtime.
By controlling the pressure and gas flow rate within the process chamber, plasma ignition is performed using an RF device to pre-treat the electrostatic chuck and heat its surface. Simultaneously, the flow rate of heat-conducting gas is increased to remove polymers from the surface of the electrostatic chuck, ensuring that the wafer fully releases its charge.
It effectively removes polymer buildup on the surface of the electrostatic chuck, ensuring accurate wafer positioning, preventing wafer scratches, fragmentation, and machine downtime, and improving work efficiency.
Smart Images
Figure CN116825629B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor manufacturing technology, specifically to a wafer etching method. Background Technology
[0002] In semiconductor etching processes, wafers are electrostatically attached to an electrostatic chuck (ESC) within the machine. After etching, the charge is released through a de-chuck step, the wafer is lifted by a pin, and then transported to the target position by a robotic arm.
[0003] However, in the zero-layer etching process of power MOSFETs, a large number of reaction byproducts are generated, such as polymer impurities. Some of these byproducts accumulate on the ESC surface. As the etching time increases, the accumulation of reaction byproducts becomes thicker and thicker, resulting in insufficient charge release in the De-chuck step. When the ejector pin lifts the wafer, it is affected by the electrostatic adsorption force, causing the wafer position to shift. This can even cause wafer scratches, fragmentation, etc., and at the same time, it can cause the machine to crash, affecting the uptime (the time for the machine to run normally). Summary of the Invention
[0004] This application provides a wafer etching method that can solve at least one of the following problems caused by insufficient electrostatic discharge of the wafer: wafer position displacement, wafer front scratches, wafer fragments, and machine downtime.
[0005] On one hand, embodiments of this application provide a wafer etching method. The wafer etching equipment includes: a process chamber, an electrostatic chuck disposed within the process chamber, and a pin disposed within the electrostatic chuck. The wafer etching method includes:
[0006] The wafer to be etched is held in place by the electrostatic chuck;
[0007] The wafer is etched to form alignment marks on the front side of the wafer;
[0008] The pressure inside the process chamber is controlled at 25 mTorr to 35 mTorr, and the flow rate of the gas involved in etching is controlled at 80 sccm to 120 sccm.
[0009] Plasma ignition is performed using a radio frequency device to pre-treat the wafer by releasing its charge.
[0010] The electrostatic chuck is heated to raise the temperature of its surface to a preset temperature threshold range, while the flow rate of the heat-conducting gas is increased to a preset flow rate threshold range.
[0011] The wafer is subjected to charge release treatment;
[0012] The wafer is lifted from the surface of the electrostatic chuck using a push pin.
[0013] Optionally, in the wafer etching method, the temperature threshold range is 20°C to 30°C.
[0014] Optionally, in the wafer etching method, the gas involved in the etching includes helium.
[0015] Optionally, in the wafer etching method, the flow rate threshold range is 2 sccm to 3 sccm.
[0016] Optionally, in the wafer etching method, the duration of plasma ignition using a radio frequency device is 1.5s to 2.5s.
[0017] Optionally, in the wafer etching method, the heat-conducting gas is helium.
[0018] Optionally, in the wafer etching method, the electrostatic chuck is provided with multiple gas lines, through which the heat-conducting gas is sprayed onto the back side of the wafer.
[0019] Optionally, in the wafer etching method, a plasma etching process is used to etch the wafer to form alignment marks on the front side of the wafer.
[0020] Optionally, in the wafer etching method, the etching equipment for etching the wafer further includes a retractable and rotatable robotic arm located on the process chamber side.
[0021] Optionally, in the wafer etching method, after the wafer is lifted from the surface of the electrostatic chuck using a pusher pin, the wafer etching method further includes:
[0022] The wafer is transferred out of the process chamber by the robotic arm.
[0023] The technical solution of this application has at least the following advantages:
[0024] After forming alignment marks, this application controls the pressure in the process chamber to 25 mTorr to 35 mTorr and the flow rate of the etching gas to 80 sccm to 120 sccm. After plasma ignition using an RF device and pre-treating the wafer to release charge, the surface temperature of the electrostatic chuck is raised to a preset temperature threshold range by heating the electrostatic chuck and increasing the flow rate of the heat-conducting gas. This effectively removes a large amount of polymer accumulated on the surface of the electrostatic chuck, improves the reliability of the electrostatic chuck, and ensures that the electrostatic discharge is fully completed during the final charge release process on the wafer. This avoids problems such as wafer position displacement, wafer front scratches, wafer fragmentation, and machine downtime caused by insufficient electrostatic discharge, thus improving work efficiency. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0026] Figure 1 This is a flowchart of a wafer etching method according to an embodiment of the present invention;
[0027] Figure 2 This is a schematic diagram of the etching equipment after the etching process generates reaction byproducts, according to an embodiment of the present invention.
[0028] Figure 3 This is a schematic diagram of the etching apparatus after the elimination of reaction byproducts in an embodiment of the present invention;
[0029] The reference numerals in the attached figures are explained as follows:
[0030] 11-Electrostatic chuck, 12-Ejector pin, 21-Wafer, 22-Reaction byproduct. Detailed Implementation
[0031] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0032] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0033] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0034] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0035] This application provides a wafer etching method, referencing... Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of the etching equipment after the etching process generates reaction byproducts, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of an etching apparatus after the elimination of reaction byproducts according to an embodiment of the present invention. The etching apparatus for etching wafers includes: a process chamber, an electrostatic chuck 11 disposed in the process chamber, and a pin 12 disposed in the electrostatic chuck 11.
[0036] refer to Figure 1 , Figure 1 This is a flowchart of a wafer etching method according to an embodiment of the present invention, the wafer etching method comprising:
[0037] Step S10: The wafer 21 to be etched is held in place by the electrostatic chuck 11.
[0038] Step S20: Etch the wafer 21 to form alignment marks on the front side of the wafer 21. Specifically, in this embodiment, a plasma etching process can be used to etch the wafer to form alignment marks on the front side of the wafer.
[0039] like Figure 2As shown, after alignment marks are formed on the front side of the wafer 21, a large amount of reaction byproducts 22 accumulate on the surface of the electrostatic chuck 11 and / or the back side of the wafer 21. The subsequent steps S30-S60 effectively remove the large amount of reaction byproducts 22 accumulated on the surface of the electrostatic chuck 11 and / or the back side of the wafer 21.
[0040] Step S30: Control (stabilize) the pressure within the process chamber within the range of 25 mTorr to 35 mTorr, and control the flow rate of the etching gas within the range of 80 sccm to 120 sccm. Specifically, the etching gas includes helium, which enters the process chamber through a specific gas pipeline and acts on the entire internal space of the process chamber.
[0041] In this embodiment, the pressure inside the process chamber is controlled at 30 mTorr, 32 mTorr, etc.; and the flow rate of the gas involved in etching is controlled at 90 sccm, 100 sccm, 110 sccm, etc.
[0042] Furthermore, in step S30, the temperature within the process chamber can be controlled within the range of 55°C to 60°C. At a temperature of 55°C to 60°C within the process chamber, helium is more easily converted into plasma.
[0043] Step S40: Use a radio frequency device (plasma ignition device) to perform plasma ignition in order to pre-process the wafer 21 to release charges.
[0044] Preferably, the duration of plasma ignition using a radio frequency device can be 1.5s to 2.5s, for example, 2s.
[0045] It is worth noting that plasma ignition operation is applicable to Twin Star equipment as well as to all other models of equipment with radio frequency devices (plasma ignition devices).
[0046] Step S50: Heat the electrostatic chuck 11 to raise the surface temperature of the electrostatic chuck 11 to a preset temperature threshold range, and simultaneously increase the flow rate of the heat-conducting gas to a preset flow rate threshold range. Specifically, the heat-conducting gas can be helium. The electrostatic chuck 11 is provided with multiple gas lines (not shown), through which the heat-conducting gas is injected onto the back side of the wafer 21.
[0047] In this embodiment, before step S50, the surface temperature of the electrostatic chuck 11 is set at approximately -10°C. In step S50, the surface temperature of the electrostatic chuck 11 is increased from -10°C to a preset temperature threshold range, preferably 20°C to 30°C, for example, 25°C or 30°C. This application increases the surface temperature of the electrostatic chuck 11 to 20°C to 30°C, reducing the adhesion of the reaction byproduct 22 to the surface of the electrostatic chuck 11. The reaction byproduct 22 is less likely to adhere to the surface of the electrostatic chuck 11 and is easily blown away and removed by gas.
[0048] Furthermore, in step S50, the flow rate of the heat-conducting gas is increased to a preset flow rate threshold range, preferably 2 sccm to 3 sccm. This application controls (stabilizes) the pressure within the process chamber within the range of 25 mTorr to 35 mTorr, controls the flow rate of the etching gas (helium) within the range of 80 sccm to 120 sccm, and further increases the flow rate of the heat-conducting gas to 2 sccm to 3 sccm. This increases the gas flow rate within the process chamber and on the back side of the wafer 21, thereby enhancing the ability to remove reaction byproducts and other impurities, and making it easier to remove reaction byproducts 22 generated during the etching of the wafer 21 and adhering to the surface of the electrostatic chuck 11.
[0049] In this application, by controlling the pressure in the process chamber to 25 mTorr to 35 mTorr and the flow rate of the gas involved in etching to 80 sccm to 120 sccm, and after pre-treating the wafer by plasma ignition using an RF device to release the charge, the surface temperature of the electrostatic chuck 11 is raised to a preset temperature threshold range by heating the electrostatic chuck 11 and increasing the flow rate of the heat-conducting gas. This effectively removes a large amount of polymer accumulated on the surface of the electrostatic chuck 11, improves the reliability of the electrostatic chuck 11, and ensures that the electrostatic discharge is fully completed when the wafer 21 is finally discharged. This avoids problems such as wafer position displacement, wafer front scratches, wafer fragmentation, and machine downtime caused by insufficient electrostatic discharge, thus improving work efficiency.
[0050] Step S60: Perform a charge release process on the wafer 21. Specifically, the charge release process on the wafer 21 can last for 7s to 8s.
[0051] Step S70: As Figure 3 As shown, the wafer 21 is lifted from the surface of the electrostatic chuck 11 using the ejector pin 12.
[0052] Furthermore, the etching equipment for etching the wafer also includes a retractable and rotatable robotic arm (not shown) located on the side of the process chamber.
[0053] In this embodiment, after step S70: using the ejector pin 12 to lift the wafer 21 from the surface of the electrostatic chuck 11, the wafer etching method may further include: using the robotic arm to transfer the wafer 12 out of the process chamber.
[0054] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.
Claims
1. A wafer etching method, characterized in that, The wafer etching equipment includes: a process chamber, an electrostatic chuck disposed within the process chamber, and ejector pins disposed within the electrostatic chuck; the wafer etching method includes: The wafer to be etched is held in place by the electrostatic chuck; The wafer is etched to form alignment marks on the front side of the wafer; The pressure inside the process chamber is controlled at 25 mTorr~35 mTorr, and the flow rate of the gas involved in etching is controlled at 80 sccm~120 sccm; Plasma ignition is performed using a radio frequency device to pre-treat the wafer by releasing its charge. The electrostatic chuck is heated to raise the temperature of its surface to a preset temperature threshold range, while the flow rate of the heat-conducting gas is increased to a preset flow rate threshold range. The wafer is subjected to charge release treatment; The wafer is lifted from the surface of the electrostatic chuck using a push pin; The temperature threshold range is 20℃~30℃, the flow rate threshold range is 2sccm~3sccm, and the electrostatic chuck is provided with multiple gas lines through which the heat-conducting gas is injected to the back side of the wafer.
2. The wafer etching method according to claim 1, characterized in that, The gas involved in the etching includes helium.
3. The wafer etching method according to claim 1, characterized in that, The duration of plasma ignition using a radio frequency device is 1.5s to 2.5s.
4. The wafer etching method according to claim 1, characterized in that, The heat-conducting gas is helium.
5. The wafer etching method according to claim 1, characterized in that, The wafer is etched using a plasma etching process to form alignment marks on the front side of the wafer.
6. The wafer etching method according to claim 1, characterized in that, The etching equipment for etching the wafer also includes a retractable and rotatable robotic arm located on the side of the process chamber.
7. The wafer etching method according to claim 6, characterized in that, After the wafer is lifted from the surface of the electrostatic chuck using a pusher pin, the wafer etching method further includes: The wafer is transferred out of the process chamber by the robotic arm.