A step structure surface graphic processing technology

Abstract

The present invention provides a surface patterning processing technology of a step structure, which includes the following steps: coating the bottom layer glue on the upper surface and the concave part of the step structure of the product, the bottom layer glue on the upper surface of the step structure and the concave part caused by the step structure is continuously coated without breaking and connected as a whole; curing and shaping the bottom layer glue by high temperature baking, coating the color glue, baking, patterning the color glue by photolithography and development and hardening the film, and finally removing the bottom layer glue beyond the edge of the step structure by dry etching process. In order to prevent film defects from occurring when patterning the red color glue on the surface of the step structure, the filling ability of the bottom layer glue is improved by increasing the thickness of the bottom layer glue and reducing the spin coating rate, so that the upper layer of the red color glue does not have film defects at the edge of the step after patterning without changing the viscosity of the red color glue, thereby improving the yield rate and making up for the application disadvantage of the low viscosity of the red color glue, and reducing the cost and improving the efficiency compared with the traditional method of increasing the thickness of the color glue.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, relates to a glue coating process, and specifically to a step structure surface graphic processing technology. Background Art

[0002] After multi-layer coating and lamination, the wafer will have a step structure. When applying glue, the step structure will change the coating state of the glue. The glue is easily thinned and broken by the step structure, especially the glue with low viscosity, which will lead to film defects in the subsequent process and reduce the yield rate. The color glue on the surface of the step structure is patterned. The color glue coating requires the bottom glue as an auxiliary layer so that the color glue can be effectively left on the wafer after development to meet the requirements of patterning processing. The bottom glue has no photosensitivity and will not be affected by photolithography patterning. The red color glue is a negative photoresist. The traditional method is affected by the height difference of the step, so that the red color glue above the edge of the step becomes thinner after spin coating. The thin red color glue will have film defects after exposure and development. The principle of the developer for the red color glue (negative glue) is that the etching rate of the exposed area is much smaller than that of the unexposed part, that is, the exposed part will actually be etched partly, and the thinner red color glue at the edge of the step will have film defects.

[0003] For the patterning of colored glue on the surface of the step structure, most of the industry adopts the method of increasing the thickness of the colored glue, soft-baking after coating, and then exposing and developing to harden the film, so that it can be patterned without film defects on the step surface. The red colored glue has low viscosity, and generally needs to be increased by multiple spin coating methods, which increases costs and reduces efficiency. In addition, as customers' demands for base glue and colored glue are constantly updated, when using red colored glue with low viscosity, the red colored glue becomes thinner at the edge due to the influence of the step, resulting in obvious film defects in the red colored glue at the edge of the step. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides a step structure surface graphic processing technology.

[0005] To achieve the above object, the present invention provides a step structure surface patterning processing method, which comprises the following steps:

[0006] 1) Apply the base glue on the upper surface of the step structure of the product and the depression caused by the step structure. The base glue on the upper surface of the step structure and the depression caused by the step structure should be applied continuously without breaking and connected as a whole;

[0007] 2) Curing the bottom glue by high temperature baking;

[0008] 3) Apply colored glue and bake;

[0009] 4) Use photolithography and development to pattern the color glue and harden the film;

[0010] 5) Use dry etching process to remove the bottom layer glue beyond the edge of the step structure.

[0011] Preferably, in step 1), the angle formed by the surface of the bottom glue layer and the base plane of the step structure of the product after glue coating is less than 50 degrees.

[0012] Preferably, in step 1), the angle formed by the surface of the bottom glue layer and the base plane of the step structure of the product after glue coating is less than 30 degrees.

[0013] Preferably, the base layer is a wafer layer, the product step structure is located on the wafer plane, and after gluing, the angle between the bottom glue surface and the wafer plane is less than 50 degrees.

[0014] Preferably, the base layer is a wafer layer, the product step structure is located on the wafer plane, and after gluing, the angle between the bottom glue surface and the wafer plane is less than 30 degrees.

[0015] Preferably, in step 1), the bottom layer glue is coated by a low-speed spin coating process to increase the thickness of the bottom layer glue, the viscosity of the bottom layer glue is 3-2000cp, and the rotation speed is 250-4700r / min. More preferably, the viscosity of the bottom layer glue is 300cp-400cp, and the rotation speed is 250-500r / min.

[0016] Preferably, in step 1), the thickness of the bottom layer of glue is more than 1 times the height of the step structure.

[0017] Preferably, in step 1), the height of the step structure is 5-8 μm.

[0018] Preferably, in step 3), the spin coating speed of the color glue can be adjusted according to product requirements.

[0019] Preferably, in step 3), the baking temperature is 70-120°C and the time is 30-300s. More preferably, the soft baking temperature is 80-100°C and the time is 60-180s.

[0020] Preferably, the film hardening temperature is 140-250°C and the time is 180-900s. More preferably, the film hardening temperature is 180-220°C and the time is 300-600s.

[0021] Preferably, in step 3), the color glue has a viscosity of less than 10 cp, and a spin coating process is used with a spin coating speed of 250-400 r / min.

[0022] Preferably, the spin coating speed of the color glue is 400 rpm.

[0023] Preferably, the colored glue is red glue.

[0024] The present invention provides a step structure product obtained by the above-mentioned step structure surface graphic processing method, which comprises a base layer, a step structure, a bottom layer glue and a color glue in sequence, and the color glue is graphic.

[0025] Preferably, the base layer is a wafer layer.

[0026] The beneficial effects of the present invention are as follows:

[0027] The bottom layer glue has no photosensitivity, and its thickness is affected by the step structure, but it is still an integral whole with the bottom layer glue outside the step. In order to prevent film defects when patterning the red color glue on the surface of the step structure, the present invention increases the thickness of the bottom layer glue and reduces the spin coating rate to improve its filling ability, so that the upper layer of red color glue does not have film defects at the edge of the step after patterning without changing the viscosity of the red color glue, thereby improving the yield rate and making up for the application disadvantage of the low viscosity of the red color glue. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram showing the state of the missing film layer of the product with a step structure of the present invention when the color glue is applied by the traditional method;

[0029] Figure 2 It is a schematic diagram of the structure after the process method of the present invention performs low-speed large-area spin coating of the base glue and then coats the color glue (before dry engraving);

[0030] Figure 3 This is a picture of the product result after dry engraving is completed in the process method of the present invention. DETAILED DESCRIPTION

[0031] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present application will be further described below in conjunction with specific embodiments.

[0032] The process of the present invention is applied to the optical path layer processing of image sensors and the optical path layer processing of under-screen fingerprint sensors.

[0033] like Figure 1 , although the bottom glue coating area in the figure is sufficient to meet the product requirements of color glue coating, there are obvious glue layer missing areas on both sides after the color glue (red glue) is coated. The technical solution adopted by the present invention is a step structure surface graphic processing technology, wherein the step structure product includes a base layer, a step structure, a bottom glue layer and a color glue layer from bottom to top, and the step structure includes at least a first step layer and a second step layer. There is a step or gap between the step structure and the base layer. The bottom glue is coated on the upper surface of the step structure and between the step structure and the base layer, and the continuous coating forms an unbroken and connected whole to achieve leveling. The specific processing technology includes:

[0034] 1) Spin-coat the bottom layer glue on the upper surface of the product step structure. The viscosity of the bottom layer glue is 3cp-2000cp, the spin-coating speed is 250-4700r / min, and the thickness of the bottom layer glue is more than 1 times the height of the step structure; after coating, the angle between the bottom layer glue surface and the wafer plane is less than 50 degrees;

[0035] 2) Curing the bottom glue by high temperature baking;

[0036] 3) Spin coating the colored glue. The speed of the colored glue is adjusted according to the product requirements. After spin coating, it is baked at a temperature of 70-120°C for 30-300s.

[0037] 4) Use photolithography and development to pattern the color glue and harden the film. The hardening temperature is 140-250℃ and the time is 180-900s.

[0038] 5) Use dry etching process to remove the bottom layer glue beyond the edge of the step structure.

[0039] Example 1

[0040] like Figure 2-Figure 3 For products with step structures, the base layer is the wafer layer as an example. The two layers of the step structure, the part between the step structure and the base layer, and the part between the wafer layer and the pad are all filled with the bottom glue. The step height is 5-8μm, the step layer height difference is 0.5-2μm, the bottom glue viscosity is 300-400cp, and the color glue is red glue with a viscosity of less than 10cp. The specific processing technology in this embodiment includes:

[0041] 1) Spin-coat the bottom layer glue on the upper surface of the step structure of the product. The viscosity of the bottom layer glue is 300cp-400cp, the spin-coating speed is 400r / min, the step structure height is 7um, and the thickness of the bottom layer glue is more than 1 times the height of the step structure. In this embodiment, the thickness is 7-8um; after coating, the angle between the bottom layer glue surface and the wafer plane is less than 30 degrees;

[0042] 2) Curing the bottom glue by high temperature baking;

[0043] 3) Spin coating the colored glue. The spin coating speed of the colored glue is adjusted according to the product requirements. After spin coating, soft baking is performed at a temperature of 80-100°C for 60-180s.

[0044] 4) Use photolithography and development to pattern the color glue and harden the film, the hardening temperature is 180-220℃, and the time is 300-600s;

[0045] 5) Use dry etching process to remove the bottom layer glue beyond the edge of the step structure.

[0046] The process of the present invention first reduces the rotation speed of the bottom layer glue during spin coating so as to increase the thickness of the bottom layer glue. When the viscosity of the glue is 300-400cp, 400 revolutions / min is used to allow the bottom layer glue to form a relatively gentle slope at the outer edge of the step structure, reduce the height difference caused by the step structure, and provide a large range of support for the red glue. When the red glue is spin coated, the thickness of the edge of the step structure is consistent with the thickness in the middle of the step. The angle formed by the surface of the bottom layer glue and the base plane of the product step structure is less than 50 degrees, ensuring that the spin-coated red glue is not stretched and non-uniform thinning is avoided, thereby ensuring that there is no film defect after exposure and development, and the yield rate is improved by 100%. The bottom layer glue is cured and fixed by high-temperature baking.

[0047] Figure 2 It is to reflect the effect after the bottom glue fills the platform step. The bottom glue coating area in the figure is expanded, such as to the entire base layer (wafer) plane. The bottom glue rotates during coating, and the edge drop and the middle gap (wafer + pad) between the step structure and the base layer are filled by slow spin coating. Because of the drop and gap, the relative inclination of the glue layer needs to be reduced when ensuring the coating thickness. The bottom glue layer, the drop and gap filling control, and each layer of the product are controlled as a whole to provide multiple supports for the subsequent coating of color glue, and adapt to the efficient spin coating of low-viscosity color glue required by the product. The red color glue is spin-coated on the product surface and soft-baked without changing the viscosity and ensuring that the uniformity of the glue thickness meets the requirements. It is patterned through photolithography and development, and then hardened. The existing viscosity red color glue can meet customer needs. The effective area of ​​the product is scanned by the testing equipment to confirm that there are no film defects on the edges of the step structure. Figure 3 The final form of the product is that part of the bottom layer above the pad needs to be removed by dry etching. The bottom glue that is not needed in the product design is not photosensitive. It provides a filling effect when the red color glue is spin-coated. Finally, the bottom glue above the PAD and the aisle of the chip needs to be removed by dry etching, leaving only the bottom glue above the effective area of ​​the chip.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for processing a stepped structure surface pattern, characterized in that: The following steps are included: 1) Apply the base glue on the upper surface of the step structure of the product and between the step structure and the base layer. The thickness of the base glue should be more than 1 times the height of the step structure. The base glue should be applied continuously without breaking and connected as a whole. 2) Curing the bottom glue by high temperature baking; 3) Apply colored glue and bake; 4) Use photolithography and development to pattern the color glue and harden the film; 5) Use dry etching process to remove the bottom layer glue beyond the edge of the step structure.

2. The method for patterning a stepped structure surface according to claim 1, characterized in that: In step 1), after the glue is applied, the angle formed by the surface of the bottom glue layer and the base plane of the product step structure is less than 50 degrees.

3. The step structure surface patterning processing method according to claim 1, characterized in that: In step 1), the bottom layer glue is applied by a low-speed spin coating process, the viscosity of the bottom layer glue is 3-2000cp, and the rotation speed is 250-4700r / min.

4. The method for patterning a stepped structure surface according to claim 1, characterized in that: In step 1), the height of the step structure is 5-8 μm.

5. The method for patterning a stepped structure surface according to claim 1, characterized in that: In step 3), the spin coating speed of the color glue can be adjusted according to product requirements.

6. The method for patterning a stepped structure surface according to claim 1, characterized in that: In step 3), the baking temperature is 70-120°C and the time is 30-300s.

7. The method for patterning a stepped structure surface according to claim 1, characterized in that: In step 4), the film hardening temperature is 140-250°C and the time is 180-900s.

8. The method for processing a stepped structure surface pattern according to claim 1, characterized in that: The colored glue is red glue.

9. The step structure product obtained by the step structure surface patterning processing method according to claim 1 is characterized in that: It comprises a base layer, a step structure, a bottom layer glue and a color glue in sequence, and the color glue is in a graphical form.

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