A method for removing thick glue edge on wafer

Abstract

The invention discloses a method for removing the edge of thick photoresist on a wafer, and belongs to the field of semiconductor photolithography technology. The method removes the edge of thick photoresist (7μm-20μm) on the wafer, firstly reduces the thickness of the photoresist film in the edge area of ​​the wafer by chemical means, and then completely removes it by edge exposure. Compared with the prior art, the time for removing the photoresist at the edge of the thick photoresist is shortened, and the production capacity is improved while ensuring the edge removal effect by adjusting various process parameters, and the amount of chemical edge removal liquid and the edge exposure time are reduced, which plays a role in reducing costs and increasing production.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor lithography, and in particular to a method for removing a thick glue edge on a wafer. Background Art

[0002] As the critical dimensions of semiconductor lithography devices become smaller and smaller, the cleaning of the wafer edge becomes more important. The reasons include but are not limited to the following three points: 1. During the coating process, the photoresist will flow to the edge of the wafer due to centrifugal force. Due to its surface tension, a circle of edge glue droplets will be formed. If not removed, these glue droplets will peel off to form particles, causing pollution to the equipment and the wafer itself. More seriously, it may contaminate the lithography machine, causing poor exposure focus, increased overlay error, and increased defect rate; 2. During the coating process, photoresist is prone to accumulation near the edge of the wafer, and these accumulations will affect subsequent etching and other processes; 3. Since photoresist is not conductive, the photoresist on the edge of the wafer also needs to be removed before the packaging electroplating process. From the above reasons, it can be seen that edge photoresist removal is necessary and important. Because these problems are more serious in the coating of thick glue than thin glue, it is very meaningful to improve the edge removal efficiency of thick glue by changing the method and adjusting the parameters.

[0003] At present, there are two methods for removing photoresist from the edge of wafers: chemical removal and edge exposure, each with its own advantages and disadvantages:

[0004] The advantages of edge exposure are high production efficiency, low equipment cost, easy process control, and neat edge contour. The disadvantage is that the scattering of light will cause a slope in the contour (see Figure 1 ) is a big problem. The edge exposure unit is mainly composed of a wafer carrier, a pre-alignment system, a light source (with a shading plate), and a light intensity meter. After the wafer enters, it is vacuum-adsorbed on the carrier. The pre-alignment system first finds the exposure starting position, and then the light spot formed by the light source through the shading plate is irradiated on the edge of the wafer. The edge exposure with controllable width and position is achieved through the rotation of the carrier and the calculation control of the system.

[0005] The advantage of chemical removal over edge exposure is that there is no slope, but the disadvantages are that the edge removal time is long, the cost of solvent consumables is high, the residual area is difficult to clean, and the contour of the removed area is not smooth and neat. In the glue coating unit with chemical removal, the chemical edge removal needle is at a certain angle to the wafer surface. When the wafer enters the unit, it is vacuum adsorbed on the carrier and spin-coated, and the chemical edge removal needle moves to the designated position to spray chemical liquid to rinse the edge.

[0006] The commonly used edge removal width is 0.5mm-1.5mm, but for photoresists with a thickness of 7μm-20μm, the chemical removal method will result in uneven edges, a long time, and a large amount of chemical consumption. The edge exposure method will result in difficult-to-control slopes and a long time. Summary of the invention

[0007] In order to solve the above-mentioned shortcomings in the prior art of removing the edge of thick glue (7μm-20μm), the purpose of the present invention is to provide a method for removing the edge of thick glue on a wafer, which achieves the purpose of increasing production capacity, enhancing removal effect and reducing chemical consumption by adopting a specific process and selecting appropriate process parameters.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A method for removing the edge of thick photoresist on a wafer, the method is to process the photoresist coated on the wafer, the thickness of the coated photoresist is 7μm-20μm; the method specifically comprises the following steps:

[0010] A method for removing the edge of thick photoresist on a wafer, the method is for removing the edge of the photoresist coated on the wafer, and specifically comprises the following steps:

[0011] (1) The wafer is transferred to the coating unit to coat the photoresist and form a film;

[0012] (2) using a chemical method in the adhesive coating unit to partially remove the adhesive film in the edge area of ​​the wafer, that is, to thin the thickness of the adhesive film in the edge area of ​​the wafer and control the size of the thinned area;

[0013] (3) The wafer with edge photoresist thinning is transferred to a hot plate for post-baking;

[0014] (4) The wafer after post-baking is transferred to the edge exposure unit. The remaining film on the edge of the wafer is completely removed by edge exposure of the silicon wafer. The size of the exposure area needs to be controlled during edge exposure of the silicon wafer.

[0015] (5) After the edge of the wafer is exposed, it is sent to the photolithography machine for pattern exposure, then transferred to the hot plate for post-exposure baking, then transferred to the cold plate for cooling, and finally transferred to the developing unit for development, so as to completely remove the photoresist at the edge of the wafer, and finally transferred back to the silicon wafer storage unit.

[0016] In the above step (1), the thickness of the adhesive film formed on the wafer is 7 μm-20 μm.

[0017] In the above step (2), in the process of partially removing the adhesive film in the edge area of ​​the wafer by chemical means: the removal width is W1, W1 is the distance from the circular line POS1 on the wafer to the outer edge of the wafer, POS2 is set as the circular line outside the edge of the wafer (POS2 is outside the edge of the wafer, and POS1 and POS2 are concentric with the wafer), and the needle for spraying chemicals (removal liquid) scans back and forth between POS1 and POS2. By controlling the chemical flow, scanning speed and scanning time, the photoresist on the edge of the wafer is thinned by 70 to 80% of its thickness.

[0018] In the above step (2), the removal width W1 is determined according to actual needs, and the distance between POS2 and the edge of the wafer is 2-4 mm; the chemical flow, scanning speed and scanning time in EBR need to be determined according to the thickness and characteristics of the glue on the wafer.

[0019] In the above step (3), the temperature of the post-baking treatment needs to be determined according to the thickness and characteristics of the glue spin-coated on the wafer.

[0020] In the above step (4), the width W2 of the exposure area refers to the distance from the circular line POS1 on the wafer to the outer edge of the wafer, W2 = W1.

[0021] In the above step (4), the exposure power and exposure time need to be determined according to the thickness and characteristics of the glue spun on the wafer.

[0022] The method of the present invention is carried out by using a film edge removal device, which includes a silicon wafer storage unit, a glue coating unit, a hot plate, an edge exposure unit and a developing unit, wherein: the silicon wafer storage unit is used to store silicon wafers, the glue coating unit is used for spin coating of photoresist, the hot plate is used for post-baking treatment of silicon wafers, the edge exposure unit is used for exposing the edges of silicon wafers, and the developing unit is used for development.

[0023] The advantages and beneficial effects of the present invention are as follows:

[0024] 1. The method of the present invention reduces the amount of chemicals used: the chemical removal method is changed from the needle fixed at POS1 for a long time spraying and flushing to the needle scanning back and forth at POS1-POS2-POS1-POS2 for a short time. Figure 2 Because the purpose of the chemical removal step in the present invention has changed from thorough cleaning in the prior art to uniform thinning of the edge area film, it is not required to completely remove (the required thinning amount is achieved by controlling the process parameters), and by adjusting the flow rate and the position parameters of POS1 and POS2, the scanning speed of the needle and other parameters, the purpose of shortening the process time and reducing chemical consumption can be achieved.

[0025] 2. Productivity improvement: After chemical edge removal, the film in the edge area of ​​the wafer is thinned. For the same material, the thicker the film thickness, the longer the exposure time required. Therefore, the exposure time required for the edge area after thinning will be reduced accordingly, and it can also produce the additional effect of reducing the slope width.

[0026] 3. Enhanced edge removal effect: The combination of chemical removal and edge exposure for edge removal not only combines the advantages of the two, but also produces new advantages: During the chemical removal process, the POS2 position is required to exceed the edge of the wafer, so that the glue drop residue at the edge can be completely removed by scanning and the bevel area can be cleaned at the same time; during the edge exposure process, the film in the area to be exposed becomes thinner, the exposure time is shortened, and the slope width generated after exposure is reduced. Therefore, the process effect of this method can achieve clean edges, neat contours, and narrower slope widths, while having high production efficiency and low chemical usage.

[0027] 4. For photoresists of different components and thicknesses, the best cleaning effect and higher production capacity can be achieved by adjusting parameters such as chemical removal time, flow, edge exposure time, and light intensity, and coordinating with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of edge exposure.

[0029] Figure 2 Schematic diagram of chemical deflanging.

[0030] Figure 3 It is a schematic diagram of the photoresist edge removal process of the present invention.

[0031] Figure 4 Schematic diagram of the edge removal process with only chemical deflashing.

[0032] Figure 5 Schematic diagram of the process where only the edge is exposed. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0034] The process of the method for removing the thick glue edge on the wafer provided by the present invention is shown in Figure 3 The specific process of this method is as follows:

[0035] In the first step, the wafer enters the cold plate for cooling, and then is transferred to the glue coating unit for spin coating to form a glue film;

[0036] In the second step, chemical removal is performed in the glue coating unit. The removal width W1 is set as the distance between the inner ring line POS1 on the wafer and the edge of the wafer. The position of the outer ring line POS2 on the edge of the wafer is required to exceed the outermost edge of the wafer. During the removal process, the needle repeatedly scans and sprays chemicals between POS1 and POS2. The scanning speed and chemical flow rate are adjusted according to the specific situation. After chemical removal, the adhesive film on the edge of the wafer is thinned.

[0037] In the third step, the wafer enters the hot plate for post-baking treatment, and then is transferred to the edge exposure unit for exposure. The exposure area is set to a width of W2, where W2 is the distance from the inner ring line POS1 on the wafer to the edge of the wafer, and W2 = W1. The exposure time is adjusted according to the specific situation;

[0038] The fourth step is to send the wafer into the photolithography machine for exposure and then transfer it to the hot plate for post-exposure baking, then transfer it to the cold plate for cooling, and finally transfer it to the developing unit for development. At this point, the edge removal is completed.

[0039] Comparative Example 1:

[0040] A photoresist PI is used, the coating thickness is 7.7μm, the edge removal target is W1=W2=1±0.1mm, the chemical removal liquid is OK73, and the wafer is a 300mm diameter silicon wafer. Figure 4 As shown, after the photoresist is formed, only chemical removal is used ( Figure 2 ), and various parameters were adjusted to obtain the best removal effect of this method, which was recorded as follows: when only chemical removal was used, the film-forming time of the glue coating unit was 95.5s, the chemical edge removal time was 40s, the total time was 135.5s, the required amount of chemical liquid was 13.3ml, the edge removal basically reached the spec, the slope width was about 0.02mm, but the edge contour was uneven, showing irregular jagged or wavy shapes;

[0041] Comparative Example 2:

[0042] A certain photoresist PI (same as comparative example 1) is used, the coating thickness is 7.7 μm, the edge removal target is W1=W2=1±0.1 mm, and the wafer is a silicon wafer with a diameter of 300 mm. Figure 5 As shown, only edge exposure is used after film formation ( Figure 1 ), and adjusted various parameters to obtain the best removal effect of this method, which is recorded as follows: when only the edge is exposed, the film forming time of the glue coating unit is 106.5s, the edge exposure time is 120s, the total time is 226.5s, and the edge removal basically reaches the spec, but the slope is wider, about 0.09mm.

[0043] Embodiment 1:

[0044] A certain photoresist PI (same as comparative example 1) is used, the coating thickness is 7.7 μm, the edge removal target is W1=W2=1±0.1 mm, the chemical removal liquid is OK73, and the wafer is a silicon wafer with a diameter of 300 mm. Figure 3 As shown, chemical removal is combined with edge exposure, various parameters are adjusted and various time combinations are tried to obtain the best removal effect of this method, which is recorded as follows: Combining the two, the film formation time of the glue coating unit is 95.5s, the chemical removal time is 11s, the edge exposure time is 42s, the total time is 148.5s, the required amount of chemical liquid is 3.6ml, the edge removal effect is better, reaching the spec, and the slope width is about 0.02mm.

[0045] By recording the data, it can be found that for this embodiment, the method of the present invention has the best effect. Considering the duration, amount of chemicals used, and removal effect, the method achieves the purpose of the invention.

[0046] Comparative Example 3:

[0047] A positive photoresist is used, the coating thickness is 15μm, the edge removal target is W1=W2=1.3±0.15mm, the chemical removal liquid is OK73, and the wafer is a 300mm diameter silicon wafer. Figure 4 As shown, after film formation, only chemical removal is used, and various parameters are adjusted to obtain the best removal effect of this method, which is recorded as follows: when only chemical removal is used, the film formation time of the glue coating unit is 78s, the chemical edge removal time is 25s, the total time is 103s, the required amount of chemical liquid is 8.3ml, the edge removal basically reaches the spec, the slope width is about 0.01mm, but the edge contour is jagged, showing irregular serrated or wavy shapes.

[0048] Comparative Example 4:

[0049] A positive photoresist (same as comparative example 3) is used, the coating thickness is 15 μm, the edge removal target is W1=W2=1.3±0.15 mm, and the wafer is a silicon wafer with a diameter of 300 mm. Figure 5 As shown, after film formation, only edge exposure is used, and various parameters are adjusted to obtain the best removal effect of this method, which is recorded as follows: when only edge exposure is used, the film formation time of the glue coating unit is 86s, the edge exposure time is 40s, the total time is 126s, and the edge removal basically reaches the spec, but the slope is wider, about 0.08mm.

[0050] Embodiment 2:

[0051] A positive photoresist (same as comparative example 3) is used, the coating thickness is 15 μm, the edge removal target is W1=W2=1.3±0.15 mm, the chemical removal liquid is OK73, and the wafer is a silicon wafer with a diameter of 300 mm. Figure 3As shown, chemical removal is combined with edge exposure, various parameters are adjusted and various time combinations are tried to obtain the best removal effect of this method, which is recorded as follows: Combining the two, the film formation time of the glue coating unit is 78s, the chemical removal time is 8s, the edge exposure time is 15s, the total time is 101s, the required amount of chemical liquid is 2.6ml, the edge removal effect is better, reaching the spec, and the slope width is about 0.02mm.

[0052] By recording the data, it can be found that for this embodiment, the method of the present invention has the best effect. Considering the duration, amount of chemicals used, and removal effect, the method achieves the purpose of the invention.

[0053] Through the above embodiments, it can be proved that the method of the present invention is suitable for removing the edge of thick glue of 7μm-20μm, with good effect, and has the additional effects of saving chemicals, reducing slope and improving production capacity.

Claims

1. A method for removing thick glue edges on a wafer, characterized in that: The method is to remove the edge of the photoresist coated on the wafer, and specifically includes the following steps: (1) The wafer is transferred to the coating unit to coat the photoresist and form a film; (2) using a chemical method in the adhesive coating unit to partially remove the adhesive film in the edge area of ​​the wafer, that is, to thin the thickness of the adhesive film in the edge area of ​​the wafer and control the size of the thinned area; (3) The wafer with edge photoresist thinning is transferred to a hot plate for post-baking; (4) The wafer after post-baking is transferred to the edge exposure unit. The remaining film on the edge of the wafer is completely removed by edge exposure of the silicon wafer. The size of the exposure area needs to be controlled during edge exposure of the silicon wafer. (5) After the wafer edge is exposed, it is sent to the photolithography machine for pattern exposure, then sent to the hot plate for post-exposure baking, then sent to the cold plate for cooling, and finally sent to the developing unit for development to achieve complete removal of the photoresist at the wafer edge, and finally sent back to the silicon wafer storage unit; In step (2), in the process of partially removing the adhesive film in the wafer edge area by chemical means: the removal width is W1, W1 is the distance from the circular line POS1 on the wafer to the outer edge of the wafer; in step (4), the width W2 of the exposure area refers to the distance from the circular line POS1 on the wafer to the outer edge of the wafer, W2 = W1; In step (1), the thickness of the adhesive film formed on the wafer is 7 μm-20 μm; In step (2), POS2 is set as a circular ring outside the edge of the wafer, and the needle for spraying the removal liquid scans back and forth between POS1 and POS2. By controlling the chemical flow, scanning speed and scanning time, the photoresist on the edge of the wafer is thinned by 70% to 80% of its thickness.

2. The method for removing the edge of thick adhesive on a wafer according to claim 1, characterized in that: In step (2), the removal width W1 is determined according to actual needs, and the distance between POS2 and the edge of the wafer is 2-4 mm.

3. The method for removing the thick glue edge on the wafer according to claim 1, characterized in that: In step (3), the temperature of the post-bake treatment needs to be determined based on the thickness and characteristics of the glue spin-coated on the wafer.

4. The method for removing thick glue edge on wafer according to claim 1, characterized in that: In step (4), the exposure power and exposure time need to be determined based on the thickness and characteristics of the glue spun on the wafer.

5. The method for removing thick glue edge on wafer according to claim 1, characterized in that: The method is carried out by using a film edge removal device, which includes a silicon wafer storage unit, a glue coating unit, a hot plate, an edge exposure unit and a developing unit, wherein: the silicon wafer storage unit is used to store silicon wafers, the glue coating unit is used for spin coating of photoresist, the hot plate is used for post-baking treatment of silicon wafers, the edge exposure unit is used for exposing the edges of silicon wafers, and the developing unit is used for development.

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