Wafer IPA drying method for improving wafer edge particle aggregation

Abstract

The invention discloses a wafer IPA drying method for improving wafer edge particle aggregation, and belongs to the technical field of semiconductor manufacturing. The method comprises the following steps: after a wafer is cleaned, lifting the wafer from pure water to the 4 / 5 position of the wafer to be separated from the water surface by using a bottom supporting table, and then clamping the 2 / 3 edge position of the wafer by using a top clamp to continuously lift until the wafer is completely separated from the water surface; in the lifting process, the surface of the wafer is purged through mixed gas of N2 and IPA, and the completely-dried wafer is obtained. According to the invention, the wafer is dried by replacing a wafer lifting mode and cooperating with an IPA drying mode, so that the wafer can be completely dried, and the watermark problem caused by local dryness due to contact between the wafer and the supporting table in the medium replacement process can be avoided. The method is wide in practicability, simple in technological process, short in treatment time, low in cost and good in application prospect.

Description

Technical Field

[0001] This invention relates to a wafer IPA drying method to improve the aggregation of particles at the wafer edge, belonging to the field of semiconductor manufacturing technology. Background Technology

[0002] Semiconductor technology has developed rapidly over the past few decades, with silicon wafer sizes gradually increasing from 50 mm to 300 mm, while critical dimensions are continuously shrinking. Due to the shrinking device dimensions and the decreasing depth of focus in optical lithography equipment, the requirements for the silicon wafer surface in integrated circuit manufacturing processes have increased to the nanometer scale. The number and distribution of particles on the wafer surface significantly affect the final yield.

[0003] Isopropanol (IPA) drying of wafers is a key dehydration process in semiconductor manufacturing. Relying on the low surface tension, high volatility and water miscibility of IPA, efficient and damage-free drying of wafer surfaces is achieved through vapor displacement, Marangoni effect and other methods. It is the core method for drying wafers with fine patterns.

[0004] During the drying process, the traditional method involves holding the wafer edge with a stage (usually a chuck on a robotic arm) and slowly, steadily, and uniformly lifting it from the cleaning tank, gradually removing it from the water surface. However, water droplets can easily remain at the contact point between the wafer and the stage when passing over the water surface. This prevents complete drying during IPA (Intense Pulsed Acid) treatment, which can easily cause watermarks at the edges, leading to particle aggregation and affecting the wafer's usability. Summary of the Invention

[0005] The purpose of this invention is to provide a wafer IPA drying method that improves the aggregation of wafer edge particles. This method is used in the pre-cleaning or final cleaning process after fine polishing to solve the problem of wafer edge particle aggregation caused by watermarks at the contact position between the tray and the wafer during the drying process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A wafer IPA drying method to improve wafer edge particle aggregation includes: after wafer cleaning, lifting the wafer from pure water using a bottom support to 4 / 5 of the wafer position above the water surface, then using a top clamp to hold the wafer at 2 / 3 of the edge position and continue lifting until the wafer is completely above the water surface; during the lifting process, purging the wafer surface with a mixture of N2 and IPA gas to obtain a completely dry wafer.

[0007] Preferably, the wafer rises at a speed of 4-8 mm / s during the lifting process.

[0008] Preferably, the temperature of the pure water is 20-50℃.

[0009] Preferably, two purge rods are spaced apart at a position 1 cm above the water surface. The wafer passes between the two purge rods during its ascent. After N2 and IPA are mixed, they are used to purge the wafer surface through the purge rods. The flow rate of N2 is 20-30 slm, and the purge flow rate of IPA is 0.5-1 g / min.

[0010] Preferably, both the support platform and the clamp are made of PEEK material.

[0011] The wafer IPA drying method of the present invention, which improves the particle aggregation at the wafer edge, is applicable to the pre-cleaning stage or the final cleaning stage after wafer polishing.

[0012] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: (1) The present invention uses a two-stage lifting method to ensure that the wafer does not come into contact with other substances when it leaves the water surface and passes through the N2 and IPA mixed gas. This avoids the accumulation of edge particles caused by watermarks due to water droplets remaining at the contact point or insufficient drying of IPA.

[0013] (2) The method provided by the present invention has wide applicability and can be used in the pre-cleaning or final cleaning process after fine polishing; the process flow is simple, the processing time is short, and the cost is low; at the same time, it causes little damage to the wafer and the metal content on the wafer surface is low, which can completely solve the problem of edge particle aggregation caused by the wafer drying process, improve the subsequent final cleaning effect, and has good application prospects. Attached Figure Description

[0014] Figure 1 This is an image showing the output of a wafer particle inspection instrument used in Example 1 to detect defects in wafer particles.

[0015] Figure 2 for Figure 1 Enlarged view of the integrated output channel of the DC converter.

[0016] Figure 3 The image shown is an output image of wafer particles detected using the SP5 XP wafer defect inspector, used for comparison.

[0017] Figure 4 for Figure 3 Enlarged view of the integrated output channel of the DC converter. Detailed Implementation

[0018] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below.

[0019] The wafer IPA drying method for improving wafer edge particle aggregation provided by the present invention includes: after wafer cleaning, lifting the wafer from pure water using a bottom support to the position of 4 / 5 of the wafer above the water surface, and then using a top clamp to hold the edge of the wafer at 2 / 3 of the wafer and continue lifting until the wafer is completely above the water surface; during the lifting process, the wafer surface is purged with a mixture of N2 and IPA gas to obtain a completely dry wafer.

[0020] This invention provides a wafer IPA drying method to improve edge particle aggregation. This method is applicable to the pre-cleaning or final cleaning stage after wafer polishing. During the IPA drying process, the wafer is raised using two methods: either by a support platform or by clamping it. The wafer is lifted through a mixture of N2 and IPA steam. This relay method ensures that the wafer does not come into contact with other substances when leaving the water surface or passing through the mixed steam stage, preventing watermark formation at contact points and thus preventing edge particle aggregation during the drying process, which affects particle quality.

[0021] In one specific embodiment of the present invention, during the wafer lifting process, the wafer rises at a speed of 4-8 mm / s in pure water, for example, 4 mm / s, 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, etc. can be selected.

[0022] In one specific embodiment of the present invention, two purge rods are spaced apart at a position 1 cm above the water surface. During the wafer's ascent, it passes between the two purge rods. N2 and IPA are mixed and then pass through the purge rods to become mixed steam to purge the wafer surface. The preferred flow rate of N2 is 20-30 slm, such as 20 slm, 22 slm, 25 slm, 28 slm, 30 slm, etc.; the preferred purge flow rate of IPA is 0.5-1 g / min, such as 0.5 g / min, 0.6 g / min, 0.7 g / min, 0.8 g / min, 0.9 g / min, 1.0 g / min, etc.

[0023] In one specific embodiment of the present invention, the support platform and the clamp are made of PEEK.

[0024] Example 1 The processing object involved in this embodiment is a 300mm wafer, and the method used includes the following steps: (1) Place the wafer in pure water and use a PEEK support to lift the wafer at a speed of 4 mm / s until the wafer is 4 / 5 of the way up from the water surface.

[0025] (2) Use a wafer jig to clamp the wafer at 2 / 3 of its edge and lift the wafer off the water surface at a speed of 4 mm / s.

[0026] (3) Two purge rods are set 1 cm above the water surface, and the wafer passes through the middle of the purge rods.

[0027] (4) N2 is mixed at a rate of 20 slm and IPA at a rate of 0.5 g / min. After mixing, the wafer is purged by a blower.

[0028] (5) The drying process can be completed after the wafer has passed through the blow bar, resulting in a clean wafer without edge particle aggregation.

[0029] Example 2 The processing object involved in this embodiment is a 300mm wafer, and the method used includes the following steps: (1) Place the wafer in pure water and use a PEEK support to lift the wafer at a speed of 6 mm / s until it is 4 / 5 of the way up from the water surface.

[0030] (2) Use a wafer jig to clamp the wafer at 2 / 3 of its edge and lift the wafer off the water at a speed of 6 mm / s.

[0031] (3) Two purge rods are set 1 cm above the water surface, and the wafer passes through the middle of the purge rods.

[0032] (4) N2 is mixed at 25 slm and IPA at 0.7 g / min. After mixing, the wafer is purged by a blower.

[0033] (5) The drying process can be completed after the wafer has passed through the blow bar, resulting in a clean wafer without edge particle aggregation.

[0034] Example 3 The processing object involved in this embodiment is a 300mm wafer, and the method used includes the following steps: (1) Place the wafer in pure water and use a PEEK support to lift the wafer at a speed of 8 mm / s until the wafer is 4 / 5 of the way up from the water surface.

[0035] (2) Use a wafer jig to clamp the wafer at 2 / 3 of its edge and lift the wafer off the water at a speed of 8 mm / s.

[0036] (3) Two purge rods are set 1 cm above the water surface, and the wafer passes through the middle of the purge rods.

[0037] (4) N2 is mixed at 30 slm and IPA at 1.0 g / min. After mixing, the wafer is purged by a blower.

[0038] (5) The drying process can be completed after the wafer has passed through the blow bar, resulting in a clean wafer without edge particle aggregation.

[0039] Comparative Example The difference between this comparative example and Example 1 is that in this comparative example, a stage is used to lift the wafer off the water surface at a speed of 8 mm / s.

[0040] Performance Test 1: Appearance Morphology Analysis The SP5 XP wafer defect inspector was used to inspect the edge particles of a polished wafer. The output patterns of the SP5 XP test correspond to four channels: DC, DW1, DW2, and DN, with the DC channel being the comprehensive output channel. Figures 1-4 As shown, Figure 1 , 2 This is a particle map image of the wafer after polishing and drying in Example 1. Figure 3 , 4 The image shown is a particle map of the comparative example after the wafers were not polished and dried according to the present invention. Figure 1 and Figure 3 The graphics are numbered sequentially from left to right and top to bottom. Graphics 1 and 7 correspond to the DC channel, graphics 2 and 8 correspond to the DW1 channel, graphics 3, 5, 9, and 11 correspond to the DW2 channel, and graphics 4, 6, 10, and 12 correspond to the DN channel. The comparison shows that after drying using this invention, there is no aggregation of edge particles on the wafer surface.

[0041] In summary, as can be seen from the embodiments, comparative examples, and performance test results, the method provided by the present invention can completely solve the edge aggregation problem caused by the wafer drying process, and within the preferred scope of the present invention, the aggregation problem can be solved.

Claims

1. A wafer IPA drying method to improve wafer edge particle aggregation, characterized in that, The method includes: after cleaning the wafer, lifting the wafer from pure water using a bottom support to 4 / 5 of the wafer's position above the water surface, and then using a top clamp to hold the wafer at 2 / 3 of its edge position and continue lifting until the wafer is completely above the water surface; during the lifting process, the wafer surface is purged with a mixture of N2 and IPA gas to obtain a completely dry wafer.

2. The method according to claim 1, characterized in that, During the lifting process, the wafer rises at a speed of 4-8 mm / s.

3. The method according to claim 1, characterized in that, The temperature of the pure water is 20-50℃.

4. The method according to claim 1, characterized in that, Two purge rods are placed at intervals 1 cm above the water surface. The wafer passes between the two purge rods during its ascent. N2 and IPA are mixed and then blown onto the wafer surface through the purge rods. The flow rate of N2 is 20-30 slm, and the purge flow rate of IPA is 0.5-1 g / min.

5. The method according to claim 1, characterized in that, Both the support platform and the clamp are made of PEEK material.

6. The method according to any one of claims 1-5, characterized in that, It is suitable for the pre-cleaning stage or the final cleaning stage after wafer polishing.

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