Negative photoresist edge removing method

Abstract

The invention provides a negative photoresist edge removing method. The negative photoresist edge removing method comprises the following steps: providing a wafer, spin-coating negative photoresist on the surface of the wafer, forming an annular mask on the negative photoresist at the edge of the wafer, shielding the negative photoresist at the edge of the wafer by using the annular mask, and exposing the negative photoresist; and developing to remove the annular mask and the negative photoresist shielded by the annular mask. According to the invention, exposure edge removal of the negative photoresist is realized, the edge contour of the negative photoresist after edge removal is improved, additional hardware does not need to be arranged in the photoetching machine, optical path hardware of the photoetching machine is simplified, and pollution to a machine table of the photoetching machine is avoided.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for removing the edge of negative photoresist. Background Technology

[0002] In the photolithography process, photoresist is usually first uniformly spin-coated on the entire surface of the wafer. After spin-coating, the photoresist at the edge of the wafer is uneven, which can easily lead to defects and contamination. After spin-coating, photolithography is then performed. In order to ensure the quality and stability of the pattern and avoid affecting subsequent processes, it is usually necessary to remove the photoresist at the edge of the wafer after spin-coating and before photolithography, which is called photoresist edge removal.

[0003] Photoresist edge removal methods include Edge Bead Remover (EBR) and Wafer Edge Exposure (WEE). Please refer to [link / reference]. Figure 1 Wafer 10 is placed on wafer carrier stage 20, and negative photoresist 30 is uniformly spin-coated on wafer 10. The edge removal method is to use the nozzle 40 of the cleaning equipment to physically rinse the negative photoresist 30 at a certain angle to remove the photoresist edge. During the edge removal process, wafer 10 will rotate, and the centrifugal force generated during rotation will throw out the dissolved negative photoresist and cleaning agent together. After EBR cleaning, the wafer edge has an uneven slope, which will affect subsequent processes.

[0004] Please refer to Figure 2 Wafer 10 is placed on wafer carrier stage 20, and negative photoresist 30 is uniformly spin-coated on wafer 10. The wafer edge exposure method is to expose the negative photoresist 30 on the edge of wafer 10 with a separate light source 50. After development, the excess negative photoresist on the edge of wafer 10 is removed to achieve photoresist edge removal. After development, the wafer edge contour is better and the wafer edge is vertical. However, in the process of removing the edge of negative photoresist, since the characteristic of negative photoresist is that the exposed area is retained, the edge of negative photoresist cannot be directly removed by WEE method.

[0005] Please refer to Figure 3 Some lithography machines are equipped with a metal ring 60 of fixed width. During exposure, the metal ring 60 is positioned above the wafer 10 to block light from the edge of the wafer 10. However, the metal ring 60 cannot contact the edge of the wafer 10, as this can easily contaminate the machine. A certain distance must be maintained between the metal ring 60 and the wafer 10. This results in strong diffraction interference during exposure, leading to poor edge contours after development. Furthermore, the edge removal width of the metal ring 60 cannot be adjusted, making it difficult to add hardware to the optical path system of the lithography machine. Summary of the Invention

[0006] The purpose of this invention is to provide a method for removing edges from negative photoresist, thereby improving the edge contour of the negative photoresist after edge removal.

[0007] To achieve the above objectives, the present invention provides a method for removing edges from negative photoresist, comprising:

[0008] A wafer is provided, and a negative photoresist is spin-coated on the surface of the wafer;

[0009] A ring-shaped mask is formed on the negative photoresist at the edge of the wafer;

[0010] The negative photoresist at the edge of the wafer is blocked by the annular mask, and the negative photoresist is exposed; and,

[0011] Development removes the annular mask and the negative photoresist it blocks.

[0012] Optionally, the step of forming the annular mask on the negative photoresist at the edge of the wafer includes:

[0013] A nozzle is provided, the outlet width of which is adjustable;

[0014] The nozzle is positioned above the negative photoresist at the edge of the wafer and remains stationary. During wafer rotation, mask material flows out of the nozzle to spin-coat the negative photoresist at the edge of the wafer to form the annular mask.

[0015] Optionally, the nozzle does not contact the negative photoresist at the edge of the wafer.

[0016] Optionally, the nozzle outlet is provided with a baffle, and the nozzle outlet width is adjusted by moving the baffle.

[0017] Optionally, a robotic arm can be used to hold the nozzle in place.

[0018] Optionally, the maximum exit width of the nozzle is the same as the maximum edge removal width of the negative photoresist.

[0019] Optionally, the nozzle outlet width can be adjusted within the range of 1μm to 3μm.

[0020] Optionally, the mask material is a non-photosensitive flexible liquid material.

[0021] Optionally, the mask material includes polydimethylsiloxane.

[0022] Optionally, after forming the annular mask, the process further includes baking the annular mask.

[0023] The negative photoresist edge removal method provided by the present invention includes: providing a wafer, spin-coating negative photoresist on the surface of the wafer, forming an annular mask on the negative photoresist at the edge of the wafer, using the annular mask to block the negative photoresist at the edge of the wafer, exposing the negative photoresist; and developing to remove the annular mask and the negative photoresist blocked by the annular mask. This invention forms an annular mask on the negative photoresist at the wafer edge. Due to the obstruction of the annular mask, during exposure, the non-edge areas of the wafer are exposed, while the negative photoresist at the wafer edge is not exposed. The negative photoresist is retained in the exposed area. After development, both the annular mask and the negative photoresist it obstructs are removed, thus achieving edge removal of the negative photoresist through exposure. The annular mask blocks light in contact with the negative photoresist, resulting in minimal diffraction interference during exposure and improving the edge contour of the negative photoresist after edge removal, i.e., a better edge contour. Furthermore, it eliminates the need for additional hardware in the lithography machine, simplifying the optical path hardware of the lithography machine and avoiding contamination of the lithography machine. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of edge removal using the EBR method in existing technologies.

[0025] Figure 2 This is a schematic diagram of edge removal using the WEE method in existing technologies.

[0026] Figure 3 This is a schematic diagram of edge removal using a metal ring method in the prior art.

[0027] Figure 4 This is a flowchart of a negative photoresist edge removal method provided in an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of the negative photoresist after spin-coating in a negative photoresist edge removal method provided in an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the formation of a ring-shaped mask in a negative photoresist edge removal method according to an embodiment of the present invention.

[0030] Figure 7 This is a top view of the negative photoresist edge removal method provided in an embodiment of the present invention after forming a ring-shaped mask.

[0031] Figure 8 This is a schematic diagram of the nozzle in a negative photoresist edge removal method provided in an embodiment of the present invention.

[0032] Figure 9 This is a schematic diagram of the exposure process in a negative photoresist edge removal method according to an embodiment of the present invention.

[0033] Figure 10This is a schematic diagram after development in a negative photoresist edge removal method according to an embodiment of the present invention.

[0034] in, Figures 1-3 The attached figures are labeled as follows:

[0035] 10 - Wafer; 20 - Wafer stage; 30 - Negative photoresist; 40 - Nozzle; 50 - Light source; 60 - Metal ring;

[0036] Figures 5-10 The attached figures are labeled as follows:

[0037] 100 - Wafer; 200 - Wafer stage; 300 - Negative photoresist; 400 - Annular mask; 500 - Nozzle; 510 - Clamping part; 540 - Discharge part; 530 - Baffle; 500a - Outlet. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The accompanying drawings are all in a very simplified form and are not drawn to scale, only used to conveniently and clearly assist in illustrating the objectives of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structures; in particular, different proportions are sometimes used because different drawings need to show different focuses.

[0039] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0040] In the description of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the equipment or component 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.

[0041] Furthermore, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0042] Please refer to Figure 4 This embodiment provides a method for removing the edge of negative photoresist, including:

[0043] Step S1: Provide a wafer and spin-coat a negative photoresist onto the surface of the wafer;

[0044] Step S2: Form a ring-shaped mask on the negative photoresist at the edge of the wafer;

[0045] Step S3: Use a ring-shaped mask to block the negative photoresist at the edge of the wafer and expose the negative photoresist.

[0046] Step S4: Development removes the annular mask and the negative photoresist blocked by the annular mask.

[0047] The following is combined Figures 5-10 The negative photoresist edge removal method provided in this embodiment will be described in detail.

[0048] Please refer to Figure 5 Step S1: Provide wafer 100 and place it on wafer stage 200. Use a photoresist coating device to spin-coat negative photoresist 300 onto the surface of wafer 100. During the coating process, wafer 100 is rotated by wafer stage 200 to ensure that the negative photoresist is evenly spin-coated onto the surface of wafer 100. Because the uniformity of the negative photoresist 300 at the edges of wafer 100 is poor after spin-coating, it is necessary to remove the negative photoresist 300 at the edges of wafer 100 to avoid affecting subsequent processes.

[0049] Please refer to Figure 6 and Figure 7Step S2: A nozzle 500 is provided, the outlet width of which is adjustable. A robotic arm holds the nozzle 500, and the nozzle 500 is used to spin-coat a ring-shaped mask 400 onto the negative photoresist 300 at the edge of the wafer 100. During the spin-coating process, the robotic arm holds the nozzle 500 stationary, the nozzle 500 is positioned above the negative photoresist 300 at the edge of the wafer 100, and the nozzle 500 does not contact the negative photoresist 300 at the edge of the wafer 100; the wafer 100 is rotated by the wafer carrier stage 200, and during the rotation of the wafer 100, the nozzle 500 continuously flows out mask material, thereby forming a ring-shaped mask 400 on the edge of the negative photoresist 300 (e.g., ...). Figure 7 (As shown). In this embodiment, the material of the annular mask 400 (mask material) is a non-photosensitive flexible liquid material. During the rotation of the wafer 100, the nozzle 500 continuously flows out the flexible liquid onto the negative photoresist 300 at the edge of the wafer 100. The flexible liquid does not flow easily and adheres to the negative photoresist 300 at the edge of the wafer 100. The material of the annular mask 400 (mask material) includes polydimethylsiloxane, but is not limited to this.

[0050] Please refer to Figure 8 The nozzle 500 includes a clamping part 510, a discharge part 520, and a baffle 530. An external robotic arm is connected to the clamping part 510 to control the nozzle 500 to move to a set position. The top of the clamping part 510 and the discharge part 520 are connected and communicate with each other. Material can be added into the discharge part 520 through the clamping part 510. The outlet 500a of the nozzle 500 is located at the bottom of the discharge part 520, and the baffle 530 is disposed at the outlet 500a. The baffle 530 moves in a direction perpendicular to the outlet 500a (horizontal direction in the figure) to control the outlet width of the nozzle 500. The baffle 530 is preferably disposed on the inner side of the bottom of the discharge part 520 (the discharge part 520 is transparent in the figure to show the part of the baffle 530 located inside the discharge part 520). The discharge section 520 can hold flexible liquid materials. When it is necessary to discharge the flexible liquid, the baffle 530 is opened for discharge. The outlet width of the nozzle 500 is adjusted by moving the opening width of the baffle 530. Figure 8 The baffle 530 is opened, the outlet width of the nozzle 500 is D1, and the maximum outlet width of the nozzle 500 is D2. The length of the baffle 530 along the horizontal direction of the outlet 500a is greater than the maximum outlet width of the nozzle 500, which facilitates the control of the moving baffle 530. In this embodiment, the maximum outlet width of the nozzle 500 is the same as the maximum edge removal width of the negative photoresist 300; the adjustment range of the outlet width of the nozzle 500 can be 1μm~3μm, and is not limited to this. In this embodiment, by setting an outlet width-adjustable nozzle 500 and using the nozzle 500 to form an annular mask 400, it is easy to obtain annular masks 400 of different widths according to actual conditions, which has high utilization and is easy to implement.

[0051] Furthermore, after forming the annular mask 400, the process also includes baking the annular mask 400 to harden it.

[0052] Please refer to Figure 9 Step S3 is executed: the negative photoresist 300 at the edge of wafer 100 is blocked by an annular mask 400, and the negative photoresist 300 is exposed; due to the blocking by the annular mask 400, during exposure, the negative photoresist 300 in the non-edge area of ​​wafer 100 (area other than the edge of wafer 100) is exposed, and the negative photoresist 300 at the edge of wafer 100 is not exposed.

[0053] Please refer to Figure 10 Step S4: Development to remove the annular mask 400 and the negative photoresist 300 blocked by the annular mask 400. Specifically, the negative photoresist 300 blocked by the annular mask 400 can be removed by developing with a developer. The negative photoresist 300 under the annular mask 400 is removed by side-penetrating development from the side edge of the wafer 100. After the negative photoresist 300 under the annular mask 400 is removed, the annular mask 400 is suspended and can be removed by rinsing. Alternatively, the annular mask 400 and the negative photoresist 300 it blocks can be removed through stepwise development. For example, the annular mask 400 can be removed first, followed by the negative photoresist 300 it blocks. Different developing solutions are used for the two developments. The developing solution for the first development is a solution for dissolving the annular mask 400 and will not affect the negative photoresist 300 below the annular mask 400; it only removes the annular mask 400. The developing solution for the second development is a negative photoresist developing solution, which removes the negative photoresist 300 at the edge of the wafer 100. In this embodiment, since the negative photoresist 300 is the exposed area and the negative photoresist 300 it blocks is not exposed, it is removed after development, thus achieving edge removal of the negative photoresist.

[0054] In summary, the negative photoresist edge removal method provided by the present invention includes: providing a wafer, spin-coating negative photoresist on the surface of the wafer, forming an annular mask on the negative photoresist at the edge of the wafer, using the annular mask to block the negative photoresist at the edge of the wafer, exposing the negative photoresist; and developing to remove the annular mask and the negative photoresist blocked by the annular mask. This invention forms an annular mask on the negative photoresist at the wafer edge. Due to the obstruction of the annular mask, during exposure, the non-edge areas of the wafer are exposed, while the negative photoresist at the wafer edge is not exposed. The negative photoresist is retained in the exposed area. After development, both the annular mask and the negative photoresist it obstructs are removed, thus achieving edge removal of the negative photoresist through exposure. The annular mask blocks light in contact with the negative photoresist, resulting in minimal diffraction interference during exposure and improving the edge contour of the negative photoresist after edge removal, i.e., a better edge contour. Furthermore, it eliminates the need for additional hardware in the lithography machine, simplifying the optical path hardware of the lithography machine and avoiding contamination of the lithography machine.

[0055] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A method for removing edges from negative photoresist, characterized in that, include: A wafer is provided, and a negative photoresist is spin-coated on the surface of the wafer; A ring-shaped mask is formed on the negative photoresist at the edge of the wafer; The negative photoresist at the edge of the wafer is blocked by the annular mask, and the negative photoresist is exposed. as well as, Development removes the annular mask and the negative photoresist it blocks.

2. The negative photoresist edge removal method as described in claim 1, characterized in that, The step of forming the annular mask on the negative photoresist at the edge of the wafer includes: A nozzle is provided, the outlet width of which is adjustable; The nozzle is positioned above the negative photoresist at the edge of the wafer and remains stationary. During wafer rotation, mask material flows out of the nozzle to spin-coat the negative photoresist at the edge of the wafer to form the annular mask.

3. The negative photoresist edge removal method as described in claim 2, characterized in that, The nozzle does not come into contact with the negative photoresist at the edge of the wafer.

4. The negative photoresist edge removal method as described in claim 2, characterized in that, The nozzle outlet is equipped with a baffle, and the nozzle outlet width can be adjusted by moving the baffle.

5. The negative photoresist edge removal method as described in claim 2, characterized in that, The nozzle is held in place by a robotic arm.

6. The negative photoresist edge removal method as described in claim 2, characterized in that, The maximum exit width of the nozzle is the same as the maximum edge removal width of the negative photoresist.

7. The negative photoresist edge removal method as described in claim 6, characterized in that, The nozzle's outlet width can be adjusted within the range of 1μm to 3μm.

8. The negative photoresist edge removal method as described in claim 2, characterized in that, The mask material is a non-photosensitive flexible liquid material.

9. The negative photoresist edge removal method as described in claim 8, characterized in that, The mask material includes polydimethylsiloxane.

10. The negative photoresist edge removal method as described in claim 2, characterized in that, After forming the annular mask, the process also includes baking the annular mask.

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