Method for improving electrostatic distribution on the backside of a wafer in a lithography machine

Abstract

The application discloses a method for improving electrostatic distribution of a silicon wafer back surface of a photoetching machine, which comprises the following steps: step one, installing an electrostatic eliminator on the side of a pre-alignment unit of the photoetching machine; step two, blowing plasma wind to the surface of the silicon wafer through compressed air; and step three, when pre-alignment, rotating the silicon wafer, and the positive and negative particles in the plasma wind neutralize the surface charge of the silicon wafer uniformly. The application can slow down the abrasion of an exposure wafer table of the photoetching machine.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine. Background Technology

[0002] Photoresist coating is a process in integrated circuit and discrete device manufacturing where photoresist is applied to the surface of chips. It belongs to the photolithography process and, together with the developing and exposure systems, constitutes the most critical and frequently repeated process in the entire IC manufacturing process. As a key process in the front-end of large-scale integrated circuit production, it has a significant impact on improving product integration and yield.

[0003] When silicon wafers are coated with adhesive, the oxide layer on the back side rubs against the non-conductive liquid, generating static electricity. Because the nozzle position is fixed, such as... Figure 1 As shown, static electricity accumulates at fixed locations, creating a unique distribution. When the silicon wafer is transferred to the lithography machine, the static electricity on the back side accelerates the wear of the lithography machine's wafer carrier platform, causing pits to appear at fixed locations. These pits ultimately affect the focusing and overlay accuracy of the lithography machine's exposure. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: a method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine, characterized in that it includes the following steps:

[0006] Step 1: Install the electrostatic eliminator on the side of the pre-alignment unit of the lithography machine;

[0007] Step two: Plasma air is blown onto the surface of the silicon wafer using compressed air;

[0008] Step 3, during pre-alignment, the silicon wafer rotates, and the positive and negative particles in the plasma wind uniformly neutralize the surface charge of the silicon wafer.

[0009] Preferably, the lithography machine pre-alignment unit includes a liftable temperature control platform. When the silicon wafer is pre-aligned, the lithography machine pre-alignment temperature control platform will be lowered to expose the lower surface of the silicon wafer.

[0010] Preferably, the static eliminator includes multiple nozzles, which are installed on the side of the pre-alignment temperature control platform of the lithography machine. The nozzle outlet angle of the static eliminator is adjusted to align with the lower surface of the silicon wafer.

[0011] Preferably, the step two uses temperature-controlled compressed clean air inside the photoetching machine as the air source, which is introduced into the static eliminator through the air pipe, and at least one electromagnetic valve is used to control the compressed air. When the compressed air passes through the static eliminator, part of the compressed air is ionized by the high-voltage electrode inside the static eliminator, and the compressed air forms a plasma wind and is sprayed from the nozzle to neutralize the charge on the lower surface of the silicon wafer.

[0012] Preferably, the diameter of the air pipe is six millimeters.

[0013] Preferably, the temperature-controlled platform is provided with a micro switch on the side to detect and adjust the state of the temperature-controlled platform.

[0014] Preferably, when the photoetching machine pre-alignment unit is pre-aligned, the temperature-controlled platform is lowered, the micro switch is triggered to close, the electromagnetic valve is turned on, the compressed air forms a plasma wind, the plasma wind blows towards the lower surface of the silicon wafer, and the static neutralization process begins.

[0015] Preferably, after the pre-alignment is completed, the temperature-controlled platform will rise and be close to the silicon wafer, the micro switch will be opened, the electromagnetic valve will be closed, the plasma wind will be closed, and the static neutralization process will be completed.

[0016] Preferably, the silicon wafer rotates around its center when pre-alignment is performed.

[0017] The positive progress effect of the present application is that the present application can slow down the wear of the photoetching machine exposure wafer stage, and the service life is increased from the original 500,000 pieces to more than 1,000,000 pieces. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the distribution of static electricity on the coated silicon wafer along the diameter direction of the silicon wafer in the prior art.

[0019] Figure 2 It is a structural schematic diagram of the method for improving the distribution of static electricity on the back surface of the silicon wafer in the photoetching machine.

[0020] Figure 3 It is a schematic diagram of the distribution of static electricity on the coated silicon wafer along the diameter direction of the silicon wafer in the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments.

[0022] As shown in Figure 2 the method for improving the distribution of static electricity on the back surface of the silicon wafer in the photoetching machine includes the following steps:

[0023] Step one, install the static eliminator on the side of the pre-alignment unit of the lithography machine; the pre-alignment unit of the lithography machine contains a temperature-controlled platform (TSU) that can be lifted down to expose the lower surface of the wafer when the wafer is pre-aligned. The static eliminator includes multiple nozzles installed on the side of the pre-alignment temperature-controlled platform of the lithography machine. The angle of the nozzle outlet of the static eliminator is adjusted to align with the lower surface of the wafer, facilitating subsequent blowing and neutralization.

[0024] Step two, blow the plasma wind to the surface of the wafer by compressed air; use the temperature-controlled (22°C) compressed clean air inside the lithography machine as the air source, introduce it into the static eliminator through the air pipe, and use at least one solenoid valve to control the compressed air. When the compressed air passes through the static eliminator, part of it will be ionized by the high-voltage electrode inside, forming a plasma wind that is blown out of the nozzle and neutralizing the charge on the lower surface of the wafer. The diameter of the air pipe is six millimeters, which facilitates air flow and subsequent compression.

[0025] Step three, during pre-alignment, the wafer rotates, and the positive and negative particles in the plasma wind uniformly neutralize the surface charge of the wafer.

[0026] The temperature-controlled platform is equipped with a micro switch to detect and adjust the state of the temperature-controlled platform. When the pre-alignment unit of the lithography machine is pre-aligned, the temperature-controlled platform is lowered, the micro switch is triggered to close, the solenoid valve is turned on, the compressed air forms a plasma wind, the plasma wind is blown to the lower surface of the wafer, and the static neutralization process begins. To find the gap at the fixed position of the wafer, the wafer rotates around its center when it is pre-aligned. Since the nozzle outlet of the static eliminator is fixed and does not change, the plasma gas flow can uniformly blow to the entire lower surface of the wafer during the rotation process, and the entire pre-alignment process takes three seconds. After the pre-alignment is completed, the temperature-controlled platform will rise to adhere to the wafer, the micro switch will be turned off, the solenoid valve will be closed, the plasma wind will be turned off, and the static neutralization process will be completed. As shown in Figure 3 The average voltage of the static electricity is reduced from 86.3V to 0.4V, and the voltage difference inside the wafer is reduced from 20V to 5V.

[0027] The above specific embodiments are preferred embodiments of the present application and cannot limit the present application. Any changes or other equivalent replacement methods that do not deviate from the technical solutions of the present application are included in the protection scope of the present application.

Claims

1. A method for improving the electrostatic distribution on the back side of a silicon wafer in a photolithography machine, characterized in that, It includes the following steps: Step 1: The lithography machine pre-alignment unit includes a liftable temperature control platform; The static eliminator includes multiple nozzles, which are installed on the side of the pre-alignment temperature control platform of the lithography machine. The nozzle outlet angle of the static eliminator is adjusted to align with the lower surface of the silicon wafer. Step 2: Use temperature-controlled compressed clean air from inside the lithography machine as the air source. Introduce it into the electrostatic eliminator through an air pipe. When the compressed air passes through the electrostatic eliminator, some of it will be ionized by the internal high-voltage electrodes. The compressed air forms plasma wind and is ejected from the nozzle, blowing onto the silicon wafer surface. Step 3: When the silicon wafer is pre-aligned, the pre-alignment temperature control platform of the lithography machine is lowered to expose the lower surface of the silicon wafer. At the same time, the silicon wafer rotates around its center, and the positive and negative particles in the plasma wind evenly neutralize the surface charge of the silicon wafer.

2. The method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine as described in claim 1, characterized in that, The diameter of the trachea is six millimeters.

3. The method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine as described in claim 2, characterized in that, The temperature control platform is equipped with a micro switch on its side to detect and adjust the status of the temperature control platform.

4. The method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine as described in claim 3, characterized in that, When the photolithography machine pre-alignment unit performs pre-alignment, the temperature control platform descends, the micro switch is triggered and closed, the solenoid valve is activated, compressed air forms plasma wind, the plasma wind blows towards the lower surface of the silicon wafer, and the electrostatic neutralization process begins.

5. The method for improving the electrostatic distribution on the back side of a silicon wafer in a lithography machine as described in claim 3, characterized in that, After pre-alignment is completed in step three, the temperature control platform will rise and press against the silicon wafer, the microswitch will be turned off, the solenoid valve will be closed, the plasma air will be shut off, and the electrostatic neutralization process will end.

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