Step structure surface graphical processing technologyTechnical Field
The invention belongs to the technical field of semiconductors, relates to a gluing process, and particularly relates to a step structure surface graphical processing technology.
Background
The step structure can appear after the wafer is through multilayer coating film, tectorial membrane, and during the rubber coating, step structure can change the coating state of glue, and glue is drawn thin, break off by step structure easily, especially the lower glue of viscosity to lead to appearing the condition that the membrane lacks in the later process, the yields reduces. The step structure surface color glue is patterned, the color glue is used as an auxiliary layer, the color glue can be effectively left on the wafer after being developed, so that the patterning processing requirement is met, the bottom glue has no photosensitivity and cannot be influenced by photoetching patterning, and the red color glue is negative photoresist. The traditional mode is to thin the red color glue above the step edge after spin coating due to the height difference of the steps, the thin red color glue can be in film shortage after exposure and development, and the development principle of the developing solution on the red color glue (negative glue) is that the etching rate of an exposure area is far smaller than that of an unexposed part, namely the exposure part can be actually etched by a part, and the thin red color glue at the step edge can be in film shortage.
The color glue on the surface of the step structure is patterned, most of industries adopt the method that the thickness of the color glue is increased, after the glue is coated, the film is hardened after soft baking, exposure and development, and the patterned film can be formed on the surface of the step without film shortage. The red color glue is low in adhesiveness, the thickness is generally required to be increased through a multiple spin coating mode, the cost is increased, the efficiency is reduced, in addition, along with continuous updating of the requirements of customers on the bottom glue and the color glue, when the red color glue with low viscosity is used, the thickness of the edge glue is thinned due to the influence of steps on the red color glue, and obvious film defects appear in the red color glue at the edges of the steps.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a step structure surface patterning processing technology.
In order to achieve the above object, the present invention provides a method for patterning a surface of a step structure, comprising the steps of,
1) Coating bottom layer glue on the upper surface of the step structure of the product and the concave position caused by the step structure, wherein the bottom layer glue on the upper surface of the step structure and the concave position caused by the step structure are continuously coated and are not broken, and are connected into a whole;
2) Solidifying and shaping the bottom glue by high-temperature baking;
3) Coating color glue and baking;
4) Patterning and hardening the color glue by adopting photoetching and developing;
5) And removing the bottom glue beyond the edge of the step structure by adopting a dry etching process.
Preferably, in step 1), the included angle formed by the glue surface of the bottom layer after glue coating and the plane of the base layer of the product step structure is smaller than 50 degrees.
Preferably, in step 1), the included angle formed by the glue surface of the bottom layer after glue coating and the plane of the base layer of the product step structure is smaller than 30 degrees.
Preferably, the base layer is a wafer layer, the product step structure is positioned on a wafer plane, and the included angle between the surface of the glue on the bottom layer and the wafer plane after glue coating is less than 50 degrees.
Preferably, the base layer is a wafer layer, the product step structure is positioned on a wafer plane, and the included angle between the surface of the glue on the bottom layer and the wafer plane after glue coating is less than 30 degrees.
Preferably, in the step 1), the primer is coated by adopting a low-speed spin coating process, so that the thickness of the primer is increased, the viscosity of the primer is 3-2000cp, and the rotating speed is 250-4700r/min. Further preferably, the viscosity of the primer is 300cp-400cp and the rotating speed is 250-500r/min.
Preferably, in the step 1), the thickness of the bottom layer glue is more than 1 time of the height of the step structure.
Preferably, in step 1), the step structure height is 5-8 μm.
Preferably, in the step 3), the spin-coating speed of the spin-coating color glue is adjusted according to the product requirement.
Preferably, in step 3), the baking temperature is 70-120 ℃ and the baking time is 30-300s. Further preferably, the soft baking temperature is 80-100 ℃ and the time is 60-180s.
Preferably, the hardening temperature is 140-250 ℃ and the hardening time is 180-900s. Further preferably, the hardening temperature is 180-220 ℃ and the hardening time is 300-600s.
Preferably, in the step 3), the color adhesive is less than 10cp, and a spin coating process is adopted, and the spin coating rotating speed is 250-400r/min.
Preferably, the spin coating rotational speed of the color glue is 400 rpm.
Preferably, the color glue is red glue.
The invention provides a step structure product obtained by the step structure surface patterning processing method, which sequentially comprises a base layer, a step structure, bottom glue and color glue, wherein the color glue is patterned.
Preferably, the base layer is a wafer layer.
The beneficial effects of the invention are as follows:
The bottom layer glue has no photosensitivity, the step structure influences the thickness of the bottom layer glue, but the bottom layer glue is still integrated with the steps, so that the red color glue is patterned on the surface of the step structure, and the filling capacity of the bottom layer glue is improved by increasing the thickness of the bottom layer glue and reducing the spin coating rate.
Drawings
FIG. 1 is a diagram showing a state of a film-lacking layer coated with color glue by a traditional method of a product with a step structure;
FIG. 2 is a schematic diagram of the structure of the process of the present invention after spin coating the primer at low speed and large area and applying the color paste (before dry etching);
FIG. 3 is a graph showing the results of the dry etching process of the present invention.
Detailed Description
For a better description of the objects, technical solutions and advantages of the present application, the present application will be further described with reference to the following specific examples.
The process is applied to processing of the optical path layer of the image sensor and processing of the optical path layer of the fingerprint sensor under the screen.
As shown in fig. 1, although the primer coating area is sufficient to meet the product requirement of color coating, there is a distinct lack of adhesive layer area on both sides after color (red) coating. The technical scheme adopted by the invention is that the surface graphical processing technology of the step structure is characterized in that the step structure product sequentially comprises a base layer, a step structure, a bottom adhesive layer and a color adhesive layer from bottom to top, the step structure at least comprises a first step layer and a second step layer, a step or gap is formed between the step structure and the base layer, the bottom adhesive is coated on the upper surface of the step structure and between the step structure and the base layer, and the whole without fracture and connection is formed by continuous coating, so that filling and leveling are realized. The specific processing technology comprises the following steps:
1) Spin coating the bottom layer glue on the upper surface of the step structure of the product, wherein the viscosity of the bottom layer glue is 3cp-2000cp, the spin coating rotating speed is 250-4700r/min, the thickness of the bottom layer glue is more than 1 time of the height of the step structure, and the included angle between the surface of the bottom layer glue and a wafer plane after glue coating is less than 50 degrees;
2) Solidifying and shaping the bottom glue by high-temperature baking;
3) Spin-coating color glue, wherein the spin-coating speed of the color glue is adjusted according to the product requirement, and the color glue is baked after spin-coating at 70-120 ℃ for 30-300s;
4) And (3) patterning and hardening the color glue by adopting photoetching and developing, wherein the hardening temperature is 140-250 ℃ and the hardening time is 180-900s.
5) And removing the bottom glue beyond the edge of the step structure by adopting a dry etching process.
Example 1
As shown in fig. 2-3, the product with the step structure takes the wafer layer as an example, and the two-layer structure 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 layer glue. The height of the step is 5-8 mu m, the height difference of the step layer is 0.5-2 mu m, the adhesiveness of the bottom layer is 300-400cp, and the color adhesive is red adhesive with the viscosity less than 10 cp. The specific processing technology in the embodiment comprises the following steps:
1) Spin coating the bottom layer glue on the upper surface of the step structure of the product, wherein the viscosity of the bottom layer glue is 300cp-400cp, the spin coating rotating speed is 400r/min, the height of the step structure is 7um, the thickness of the bottom layer glue is more than 1 time of the height of the step structure, the thickness of the bottom layer glue is 7-8um in the embodiment, and the included angle between the surface of the bottom layer glue and a wafer plane after glue coating is less than 30 degrees;
2) Solidifying and shaping the bottom glue by high-temperature baking;
3) Spin-coating color glue, wherein the spin-coating speed of the color glue is adjusted according to the product requirement, and soft baking is performed after spin-coating, wherein the soft baking temperature is 80-100 ℃ and the time is 60-180s;
4) Patterning and hardening the color glue by adopting photoetching and developing, wherein the hardening temperature is 180-220 ℃ and the hardening time is 300-600s;
5) And removing the bottom glue beyond the edge of the step structure by adopting a dry etching process.
According to the process, the thickness of the bottom layer glue is increased by reducing the rotating speed when the bottom layer glue is spin-coated, when the glue viscosity is 300-400cp, 400 rpm is adopted, the bottom layer glue forms a gentle slope on the outer edge of the step structure, the height difference caused by the step structure is reduced, a large-scale support is provided for red glue, the thickness of the edge of the step structure is consistent with the thickness of the middle of the step when the red glue is spin-coated, the included angle formed by the surface of the bottom layer glue and the base layer plane of the step structure of a product is less than 50 ℃, the spin-coated red glue is prevented from being stretched, uneven thinning is avoided, the film shortage is avoided after exposure development is ensured, the yield is improved by 100%, and the bottom layer glue is solidified and fixed through high-temperature baking.
Fig. 2 shows that the spreading area of the primer in the graph is enlarged to the whole plane of the substrate (wafer) in order to show the effect of the primer after filling the steps, the primer is rotated during spreading, the step structure and the edge drop and the middle gap (wafer+pad) of the substrate are fully filled by slow spin coating, because the drop and the gap exist, the relative gradient of the glue layer needs to be reduced during ensuring the spreading thickness, and the glue layer, the drop and gap filling control and the product layers are integrally controlled to provide multiple supports for the subsequent spreading of the color glue, so that the efficient spin coating of the low-viscosity color glue according to the product needs is adapted. The red color adhesive is spin-coated on the surface of a product and soft baked on the premise of not changing the viscosity and ensuring the uniformity of the thickness of the adhesive to meet the requirements, is patterned by photoetching and developing, is then hardened, and can meet the requirements of customers by the existing viscosity red color adhesive. And carrying out appearance scanning on the effective area of the product by detection equipment to confirm that the edges of the step structure are not provided with film defects. As shown in fig. 3, the final form of the product is such that the underlying layer above the pad has a portion that needs to be removed by dry etching. The primer which is not needed in the product design is etched, the primer has no photosensitivity, after the filling effect is provided for the spin coating of the red color primer, the primer above the PAD and the channel of the chip is finally required to be etched and removed, and only the primer above the effective area of the chip is reserved.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.