A piezoelectric wafer lithography method based on thermally conductive sheet loading unit
By combining the heat-conducting loading unit with the piezoelectric wafer, the problem of wafer cracking caused by sudden temperature changes and photoresist contamination in the photolithography process was solved, achieving temperature uniformity and cleanliness control of the piezoelectric wafer and improving the reliability of the photolithography process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA ELECTRONICS TECH GRP NO 26 RES INST
- Filing Date
- 2023-11-08
- Publication Date
- 2026-05-26
AI Technical Summary
Piezoelectric wafers are susceptible to cracking due to sudden temperature changes and inhomogeneities during photolithography, and photoresist contamination of the hot plate can also cause temperature differences and cracking.
A thermally conductive sheet loading unit is adopted, which combines the thermally conductive sheet with the piezoelectric wafer. The thermally conductive sheet is used for temperature transition, avoiding direct contact with the hot plate, reducing photoresist contamination, and achieving temperature uniformity and cleanliness control.
It effectively prevents piezoelectric wafers from cracking due to sudden temperature changes and inhomogeneities during heat treatment, ensuring the consistency and cleanliness of the photolithography process and improving the reliability of piezoelectric wafers.
Smart Images
Figure CN117412658B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of surface acoustic wave electronic device technology, and specifically to a piezoelectric wafer photolithography method based on a heat-conducting sheet loading unit. Background Technology
[0002] Surface acoustic wave (SAW) filters made from piezoelectric single crystal materials such as lithium tantalate (LiTaO3) and lithium niobate (LiNbO3) feature miniaturization, lightweight design, low power consumption, strong radiation resistance, and a wide dynamic range (up to 100dB). They can operate under various complex and harsh environmental conditions and meet the requirements of modern information systems and equipment for miniaturization, high frequency, digitalization, high performance, and high reliability. They have found wide application in military electronic systems such as satellites, navigation, radar, communications, target simulation, and electronic warfare. Unlike silicon substrates used in semiconductor materials, piezoelectric crystals made from materials like lithium tantalate (LiTaO3) and lithium niobate (LiNbO3) are highly temperature-sensitive. During the four steps of HMDS surface treatment, pre-baking, post-baking, and hard coating in the photolithography process, the alternating hot and cold plates cause sudden temperature changes, leading to the cracking of the piezoelectric wafer.
[0003] Besides rapid heating and cooling, temperature uniformity within the piezoelectric wafer can also lead to cracking. Currently, in semiconductor manufacturing, hot and cold plates are controlled by adjusting the raising / lowering of ejector pins to manage the contact between the piezoelectric wafer and the hot / cold plate, thus achieving the baking or cooling process. Figure 3 As shown. To ensure support for the piezoelectric wafer, at least three or more ejector pins are required. The lifting height or rate of these three or more ejector pins may be inconsistent. Inconsistent pin heights will cause significant temperature differences within the wafer when it contacts the hot plate (the area that contacts the hot plate first will experience a rapid temperature increase). Figure 4 As shown, this can also lead to cleavage of such materials. Simultaneously, because the piezoelectric wafer is in direct contact with the hot plate, the photoresist on the piezoelectric wafer can contaminate the hot plate, forming particles. These contaminants on the hot plate can also cause significant temperature differences within the piezoelectric wafer when it contacts the hot plate, thus leading to cleavage. Figure 5 As shown. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a piezoelectric wafer lithography method based on a thermally conductive sheet loading unit. This method employs a coating and developing machine comprising a wafer transfer module 1, a wafer transfer module 2, and a thermally conductive sheet loading module. The thermally conductive sheet loading module includes a separation unit and a loading unit. The piezoelectric wafer lithography method includes the following steps:
[0005] S1. Using the transfer module 1, the heat-conducting sheet and the piezoelectric wafer are sequentially transferred to the loading unit, so that the heat-conducting sheet is placed at the bottom of the piezoelectric wafer to obtain the first combined device;
[0006] S2. Use the transfer module 2 to transfer the first combined device to the HMDS hot plate for baking; then transfer the baked first combined device to the cold plate for cooling so that its temperature returns to room temperature.
[0007] S3. Use the wafer transfer module 2 to transfer the first combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the coating chamber for spin coating of photoresist, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0008] S4. Use the wafer transfer module 2 to transfer the piezoelectric wafer that has completed photoresist spin coating to the loading unit. At the same time, use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the second combined device.
[0009] S5. Use the transfer module 2 to transfer the second combined device to the PAB hot plate unit for pre-baking; then transfer the pre-baked second combined device to the cold plate for cooling treatment, so that its temperature returns to room temperature.
[0010] S6. Use the wafer transfer module 2 to transfer the second combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the lithography machine for exposure, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0011] S7. Use the wafer transfer module 2 to transfer the exposed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the third combined device.
[0012] S8. Use the transfer module 2 to transfer the exposed third assembly to the PEB hot plate for post-baking; then transfer the post-baked third assembly to the cold plate for cooling treatment so that its temperature returns to room temperature.
[0013] S9. Use the transfer module 2 to transfer the third combined device back to the separation unit for separation; use the transfer module 2 to transfer the separated piezoelectric wafer to the developing chamber for development, and at the same time use the transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0014] S10. Use the wafer transfer module 2 to transfer the developed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the fourth combined device.
[0015] S11. Use the transfer module 2 to transfer the fourth combined device to the HB hot plate for hard film baking; then transfer the hardened fourth combined device to the cold plate for cooling treatment so that its temperature returns to room temperature.
[0016] S12. Use wafer transfer module 2 to transfer the fourth combined device back to the separation unit for separation; use wafer transfer module 1 to transfer the separated piezoelectric wafer to the wafer cassette to complete the photolithography process; then use wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0017] Furthermore, the piezoelectric wafer is made of lithium tantalate or lithium niobate.
[0018] Furthermore, the heat-conducting sheet can be a silicon wafer, a quartz wafer, a ceramic wafer, or a metal wafer.
[0019] Furthermore, the thickness of the heat-conducting sheet is 0.3mm to 1.5mm.
[0020] Furthermore, the diameter of the heat-conducting sheet is greater than or equal to the diameter of the piezoelectric wafer. Furthermore, the loading unit includes a base and four wafer alignment devices, the base having three pinholes for placing ejector pins.
[0021] Furthermore, the separation unit includes a wafer separation base, the upper surface of which is an inclined surface, a wafer limiting groove is provided on the inclined surface, a wafer positioning pin is provided at the lower part of the bottom surface of the wafer limiting groove, and a heat-conducting plate positioning pin is provided at the upper part of the bottom surface of the wafer limiting groove.
[0022] Furthermore, the wafer separation base is equipped with three heat-conducting pad pins and three wafer pins.
[0023] The beneficial effects of this invention are:
[0024] This invention primarily involves incorporating a heat-conducting sheet loading module into the wafer transfer mechanism of the coating and developing machine's track. A robotic arm sequentially feeds the heat-conducting sheet and piezoelectric wafers into this module for alignment. Specifically, during wafer loading, each piezoelectric wafer is stacked on a separate heat-conducting sheet, allowing for temperature conduction during subsequent hot and cold plate processes. Simultaneously, after the process is complete, this module separates the piezoelectric wafer from the heat-conducting sheet and enables the recycling of the sheet. The presence of the heat-conducting sheet prevents sudden temperature changes in the piezoelectric wafer upon contact with the hot or cold plate. Even if the lifting height or rate of the ejector pins is inconsistent during hot or cold plate processes, the heat-conducting sheet ensures relatively uniform temperature conduction to the piezoelectric wafer.
[0025] The presence of the heatsink prevents the piezoelectric wafer from directly contacting the hot plate. The photoresist or other particulate contaminants from the piezoelectric wafer will not directly contaminate the hot plate. Even if there is contamination, it will only contaminate the heatsink. The heatsink can be recycled and cleaned or replaced regularly, thus ensuring the consistency of piezoelectric wafer baking between batches. Attached Figure Description
[0026] Figure 1 This is a flowchart of the piezoelectric wafer photolithography method based on a thermally conductive sheet loading unit according to the present invention;
[0027] Figure 2 This is a temperature timing diagram of the standard process wafer of this invention;
[0028] Figure 3 This is a schematic diagram illustrating the baking process achieved by changing the state of the hot plate ejector pins according to the present invention.
[0029] Figure 4 This is a schematic diagram illustrating the temperature difference within the wafer when the wafer contacts the hot plate due to inconsistent lifting and lowering rates of the hot plate ejector pins.
[0030] Figure 5 This is a schematic diagram illustrating the temperature difference within the wafer when the wafer contacts the hot plate due to particulate contamination on the hot plate, as described in this invention.
[0031] Figure 6 This is a schematic diagram of the adhesive coating and developing machine structure of the present invention, which includes a film transfer module 1, a film transfer module 2, and a heat-conducting sheet loading module;
[0032] Figure 7 This is a top view of the loading unit structure of the present invention;
[0033] Figure 8 This is a cross-sectional schematic diagram of the loading unit structure of the present invention;
[0034] Figure 9 This is a top view of the separate unit structure of the present invention;
[0035] Figure 10 This is a flowchart illustrating the use of the separation unit in this invention. Detailed Implementation
[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0037] In the standard semiconductor lithography process, apart from the exposure process which uses a lithography machine, all other steps are executed sequentially on a coating and developing machine track. Furthermore, the four steps of HMDS surface treatment, pre-baking, post-baking, and hardening all involve thermal processing. The thermal processing flow is as follows: a robotic arm transfers the wafer to a hot plate for heating and baking; after baking, the robotic arm transfers the wafer to a cold plate for rapid cooling; after cooling, the robotic arm removes the wafer. During this process, the temperature timing diagram of the piezoelectric wafer is shown below. Figure 2 As shown.
[0038] The semiconductor industry primarily uses silicon wafers as substrate materials. Silicon wafers are not sensitive to temperature shocks, making this heat treatment process a standard procedure in the semiconductor industry. However, piezoelectric wafers are highly sensitive to temperature and are prone to cracking during heat treatment. To address this issue, this invention provides a piezoelectric wafer photolithography method based on a heat-conducting sheet loading unit. This method improves upon traditional coating and developing machines (generally including a coating unit, developing unit, wafer transfer system, hot and cold plate unit, temperature and humidity control system, exhaust system, draining system, and power supply system), employing methods such as... Figure 6 The coating and developing machine shown includes a film transfer module 1, a film transfer module 2, and a thermally conductive sheet loading module. The thermally conductive sheet loading module includes a separation unit and a loading unit.
[0039] Specifically, such as Figure 1 As shown, the piezoelectric wafer lithography method includes the following steps:
[0040] S1. The heat-conducting sheet and the piezoelectric wafer are sequentially fed into the loading unit of the heat-conducting sheet loading module, so that the heat-conducting sheet is placed at the bottom of the piezoelectric wafer to obtain the first combined device.
[0041] Specifically, such as Figure 7 , Figure 8 As shown, the loading unit includes a base and four wafer alignment devices. The base has three pin holes for placing ejector pins. In use, the ejector pins are in the UP state. The wafer transfer module 1 first places the heat-conducting sheet on the ejector pin, then places the piezoelectric wafer on the heat-conducting sheet. Subsequently, the ejector pins descend to be flush with the surface of the base. Then, the four wafer alignment devices are used to align the heat-conducting sheet and the piezoelectric wafer, and finally, a combined device consisting of the heat-conducting sheet and the piezoelectric wafer is obtained.
[0042] S2. Use the transfer module 2 to transfer the first combined device to the HMDS hot plate for baking (baking temperature is 90-250 degrees); then use the transfer module 2 to transfer the first combined device after HMDS surface treatment to the cold plate for cooling treatment, so that its temperature returns to room temperature.
[0043] HMDS surface treatment: Typically, hexamethyldisilazine vapor is introduced at 90°C to 250°C to replace the hydrophilic hydroxide (OH) on the surface of the piezoelectric wafer with hydrophobic OSi(CH3)3, thereby achieving the purpose of hydrophobic treatment of the piezoelectric wafer surface and increasing the adhesion of photoresist to the wafer surface.
[0044] S3. Use the wafer transfer module 2 to transfer the first combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the coating chamber for spin coating of photoresist, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0045] Specifically, such as Figure 9 , Figure 10 As shown, the separation unit includes a wafer separation base, the upper surface of which is an inclined surface, a wafer limiting groove is provided on the inclined surface, a wafer positioning pin is provided at the lower part of the bottom surface of the wafer limiting groove, and a heat-conducting plate positioning pin is provided at the upper part of the middle of the bottom surface of the wafer limiting groove; a heat-conducting plate pin and a wafer pin are provided inside the wafer separation base. In operation, the heat-conducting pad pin and the wafer pin are in the UP state. The wafer transfer module 2 places the assembled device on the heat-conducting pad pin. Subsequently, the heat-conducting pad pin and the wafer pin descend, and the assembled device contacts the bottom surface of the wafer positioning groove. Due to the inclined design of the wafer separation base, the piezoelectric wafer slides due to gravity. At this time, the heat-conducting pad is fixed by the heat-conducting pad positioning pin (the heat-conducting pad positioning pin is thinner than the heat-conducting pad, and the height of the heat-conducting pad positioning pin is ≤0.3mm). Therefore, the piezoelectric wafer will slide down to the wafer positioning pin (the height of the wafer positioning pin is 1mm~3mm), realizing the automatic separation of the heat-conducting pad and the piezoelectric wafer. Then, the heat-conducting pad pin and the wafer pin rise simultaneously, lifting the heat-conducting pad and the piezoelectric wafer respectively, making it easy for the robot to pick them up.
[0046] S4. Use the wafer transfer module 2 to transfer the piezoelectric wafer that has completed photoresist spin coating to the loading unit. At the same time, use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the second combined device.
[0047] S5. Use the transfer module 2 to transfer the second combined device to the PAB hot plate unit for pre-baking; then use the transfer module 2 to transfer the pre-baked second combined device to the cold plate for cooling treatment, so that its temperature returns to room temperature.
[0048] S6. Use the wafer transfer module 2 to transfer the second combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the lithography machine for exposure, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0049] S7. Use the wafer transfer module 2 to transfer the exposed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the third combined device.
[0050] S8. Use the transfer module 2 to transfer the exposed third assembly device to the PEB hot plate for post-baking; then use the transfer module 2 to transfer the post-baked third assembly device to the cold plate for cooling treatment, so that its temperature returns to room temperature.
[0051] S9. Use the transfer module 2 to transfer the third combined device back to the separation unit for separation; use the transfer module 2 to transfer the separated piezoelectric wafer to the developing chamber for development, and at the same time use the transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0052] S10. Use the wafer transfer module 2 to transfer the developed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the fourth combined device.
[0053] S11. Use the transfer module 2 to transfer the fourth combined device to the HB hot plate for hard film baking; then transfer the hardened fourth combined device to the cold plate for cooling treatment so that its temperature returns to room temperature.
[0054] S12. Use wafer transfer module 2 to transfer the fourth combined device back to the separation unit for separation; use wafer transfer module 1 to transfer the separated piezoelectric wafer to the wafer cassette to complete the photolithography process; then use wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
[0055] Specifically, the piezoelectric wafer is made of lithium tantalate or lithium niobate.
[0056] Specifically, the heat sink can be made of silicon, quartz, ceramic, or metal.
[0057] Specifically, the thickness of the heat-conducting sheet is 0.3mm to 1.5mm.
[0058] Specifically, the diameter of the heat-conducting plate is greater than or equal to the diameter of the piezoelectric wafer.
[0059] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "rotation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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 or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A piezoelectric wafer photolithography method based on a heat conduction sheet loading unit, characterized by, A coating and developing machine is used, comprising a wafer transfer module 1, a wafer transfer module 2, and a thermally conductive sheet loading module. The thermally conductive sheet loading module includes a separation unit and a loading unit. The piezoelectric wafer lithography method includes the following steps: S1. Using the transfer module 1, the heat-conducting sheet and the piezoelectric wafer are sequentially transferred to the loading unit, so that the heat-conducting sheet is placed at the bottom of the piezoelectric wafer to obtain the first combined device; S2. Use the transfer module 2 to transfer the first combined device to the HMDS hot plate for baking; then transfer the baked first combined device to the cold plate for cooling so that its temperature returns to room temperature. S3. Use the wafer transfer module 2 to transfer the first combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the coating chamber for spin coating of photoresist, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box. S4. Use the wafer transfer module 2 to transfer the piezoelectric wafer that has completed photoresist spin coating to the loading unit. At the same time, use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the second combined device. S5. Use the transfer module 2 to transfer the second combined device to the PAB hot plate unit for pre-baking; then transfer the pre-baked second combined device to the cold plate for cooling treatment, so that its temperature returns to room temperature. S6. Use the wafer transfer module 2 to transfer the second combined device back to the separation unit for separation; use the wafer transfer module 2 to transfer the separated piezoelectric wafer to the lithography machine for exposure, and at the same time use the wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box. S7. Use the wafer transfer module 2 to transfer the exposed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the third combined device. S8. Use the transfer module 2 to transfer the third assembly device to the PEB hot plate for post-baking; then transfer the post-baked third assembly device to the cold plate for cooling treatment so that its temperature returns to room temperature. S9. Use the transfer module 2 to transfer the third combined device back to the separation unit for separation; use the transfer module 2 to transfer the separated piezoelectric wafer to the developing chamber for development, and at the same time use the transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box. S10. Use the wafer transfer module 2 to transfer the developed piezoelectric wafer to the loading unit, and at the same time use the wafer transfer module 1 to transfer a new thermal conductive sheet to the loading unit, so that the new thermal conductive sheet is placed at the bottom of the piezoelectric wafer to obtain the fourth combined device. S11. Use the transfer module 2 to transfer the fourth combined device to the HB hot plate for hard film baking; then transfer the hardened fourth combined device to the cold plate for cooling treatment so that its temperature returns to room temperature. S12. Use wafer transfer module 2 to transfer the fourth combined device back to the separation unit for separation; use wafer transfer module 1 to transfer the separated piezoelectric wafer to the wafer cassette to complete the photolithography process; then use wafer transfer module 1 to transfer the separated thermal conductive sheet to the thermal conductive sheet recycling box.
2. The piezoelectric wafer lithography method based on a thermally conductive sheet loading unit as described in claim 1, characterized in that, The loading unit includes a base and four wafer alignment devices. The base has three pinholes for placing ejector pins.
3. The piezoelectric wafer lithography method based on a thermally conductive sheet loading unit as described in claim 1, characterized in that, The separation unit includes a wafer separation base, the upper surface of which is an inclined surface. A wafer positioning groove is provided on the inclined surface. A wafer positioning pin is provided at the lower part of the bottom surface of the wafer positioning groove, and a heat-conducting plate positioning pin is provided at the upper part of the bottom surface of the wafer positioning groove.
4. A piezoelectric wafer lithography method based on a thermally conductive sheet loading unit according to claim 3, characterized in that, The wafer separation base contains three heat-conducting pad pins and three wafer pins.
5. The piezoelectric wafer lithography method based on a thermally conductive sheet loading unit according to claim 1, characterized in that, The heat-conducting plate can be a silicon wafer, a quartz wafer, a ceramic wafer, or a metal wafer.
6. The piezoelectric wafer lithography method based on a thermally conductive sheet loading unit according to claim 1, characterized in that, The thickness of the heat-conducting sheet is 0.3mm to 1.5mm.
7. The piezoelectric wafer lithography method based on a thermally conductive sheet loading unit according to claim 1, characterized in that, The diameter of the heat-conducting plate is greater than or equal to the diameter of the piezoelectric wafer.