A method for exposing and opening circular ring patterns in negative polymer films

Abstract

The present application relates to a method for exposing and opening circular ring patterns in negative polymer films in wafer-level packaging, comprising the following processes: attaching a first layer of negative polymer film to a prepared wafer, designing a circular pattern of a certain radius at the electrode opening for exposure and development, baking and curing, measuring the opening radius of the first layer of film, and designing a concentric ring-shaped mask pattern according to a certain method; attaching a second layer of negative polymer film to the above wafer, using a photolithography machine to align the wafer for exposure at a certain exposure dose based on the designed mask pattern; performing static development and dynamic development for a period of time after exposure, and washing and drying with deionized water to obtain membrane holes. Compared with conventional second-layer membrane circular pattern exposure and opening, the present application achieves a change in the morphology of the second-layer membrane hole wall by designing a concentric ring pattern for exposure and development. Furthermore, the steepness of the second-layer membrane hole wall is controlled by designing the relevant parameters of the concentric rings.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing, and in particular to a method for exposing and opening circular ring-shaped patterns in negative polymer films. Background Art

[0002] In wafer-level packaging (WLP), polymer films are used to create sealed cavities on the wafer surface to protect the device. Metal is then filled into the polymer film's through-holes through electroplating or other methods to provide electrical connections. This packaging method offers advantages such as reduced substrate usage, smaller device size, high processing efficiency, low packaging production facility and design costs, and a reduced number of steps. Negative polymer films exhibit excellent sealing and exposure-polymerization properties, allowing them to create a sealed cavity for the chip while also allowing electrodes to be exposed for external connections through photolithography. Therefore, they are widely used in wafer-level packaging in semiconductor manufacturing. In wafer-level packaging of surface acoustic wave devices, creating a sealed cavity typically requires two layers of organic film. The first layer primarily acts as a cushion and is typically half the thickness of the second layer. Under certain process conditions, the two layers adhere tightly and are both insoluble in developer after exposure and polymerization. However, negative polymer films have a distinct color. During exposure, light intensity gradually decreases with increasing penetration depth, with the bottom of the film receiving less light than the top, resulting in varying degrees of polymerization. Conventional photolithography aperture technology uses a circular mask pattern, resulting in a greater degree of corrosion at the bottom of the aperture than at the top, creating an undercut appearance. This effect is particularly pronounced with thicker negative polymer films. This pore wall morphology negatively impacts subsequent processes such as electroplating metal filling and package bumping. Ideally, a steep or slightly bowl-shaped pore wall morphology is desirable, facilitating final electrode connection and packaging. Summary of the Invention

[0003] Negative polymer films have a certain color. During the exposure process, the light intensity gradually decreases with the increase of penetration depth. The light intensity received by the bottom of the film is less than that at the top, resulting in different degrees of polymerization. After using conventional circular pattern exposure to open holes, the degree of development and corrosion at the bottom of the film hole is greater than that at the top, showing an inverted concave morphology. In particular, the thicker the negative polymer film, the more obvious this effect is. This pore wall morphology has a negative impact on electroplating metal filling, packaging and ball planting, etc. In order to solve the technical problems described in the background technology, the present application provides a circular ring pattern exposure and opening method for negative polymer films, which includes the following steps performed in sequence:

[0004] S1. Apply a first layer of thin negative polymer film to the prepared wafer, controlling the film application parameters to ensure good adhesion between the first layer and the wafer. Cut and separate the first layer at the edge of the wafer. Design a photolithographic pattern for the first layer, including a circular pattern at the wafer where the external electrode is required. Expose and develop the pattern to obtain the first layer film holes, measure the hole radius r, and bake to cure.

[0005] S2. Apply a second layer of negative polymer film to the wafer, controlling key process parameters such as film application temperature, pressure, and vacuum to ensure good adhesion between the first and second layers, and then cut and separate the films.

[0006] S3. Draw a circle 1 with the required hole radius R in the layout software. R should be slightly larger than r.

[0007] S4. Draw a circle 2 with a radius of r within a circle 1 with a radius of R in the layout. The non-overlapping area between circles 1 and 2 forms a ring with a width of D2 = Rr. The ring is shaded.

[0008] S5. Draw a circle 3 with a radius of t inside a circle 2 with a radius of r in the layout. The non-overlapping area between circles 2 and 3 forms a ring with a width of D1 = rt. The ring is set as a blank area, and the inner circle 3 is set as a shaded area.

[0009] S6. Based on the designed mask pattern, use a photolithography machine to expose the wafer at a certain exposure dose;

[0010] S7. Perform static development and dynamic development for a period of time, rinse with deionized water, dry, and bake to solidify to obtain membrane pores.

[0011] The concentric ring-shaped pattern of the present invention includes: the concentric ring-shaped pattern is in the mask, the shadow area is the light-shielding area in actual exposure, and the blank area is the light-transmitting area in actual exposure.

[0012] The shadow area of ​​the inner circle 3 in the concentric ring pattern of the present invention can be changed into a circular grating and connected to the middle transparent ring D1 in alternating light and dark patterns.

[0013] The dimensions of the concentric ring pattern described in the present invention include: the width D1 of the middle light-transmitting area is less than 16% of the total opening radius, the width D2 of the outer light-shielding area is not less than 20% of the total opening radius, the ratio of D2 / D1 is not less than 1.67, the radius t of the inner light-shielding area is not less than 72% of the total opening radius, and the total opening radius R is not less than 50um.

[0014] In the present invention, the thickness of the first layer of negative polymer film is less than or equal to 1 / 2 of the second layer of negative polymer film, and the first layer and the second layer of negative polymer film are made of different materials.

[0015] The exposure wavelength of the photolithography machine used in the present invention is i-line, and the exposure dose should be controlled so that the negative polymer film is just polymerized and hardly soluble in the developer.

[0016] The development of the present invention requires a certain vibration friction such as ultrasound or swing-arm developer washing.

[0017] The developer concentration and development time of the present invention need to be controlled within a certain range. A conventional developer containing 2.38%-2.58% TMAH can be used, and the static development time is 5 minutes. The dynamic development time takes into account multiple factors such as film thickness and opening diameter, and is based on the fact that the surface morphology and color of the wafer no longer change.

[0018] The center of the concentric ring pattern described in the present invention is consistent with the center of the hole in the first layer of polymer membrane.

[0019] When the ratio D2 / D1 of the circular ring pattern designed in the present invention is not less than 1.67, increasing the ratio D2 / D1 can improve the steepness of the sidewall of the opening of the negative polymer film.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a method for exposing and opening circular ring patterns in negative polymer films, which can prevent the appearance of a concave morphology on the film hole wall caused by the gradual weakening of the exposure light intensity as the penetration depth of the polymer film increases in wafer packaging technology, realize the change of the hole wall morphology and the regulation of the steepness after the negative polymer film is photolithographically opened, improve the yield of subsequent electroplating and packaging ball planting processes, and reduce the chip manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 A flow chart showing a method for photolithographically opening holes in a negative polymer film according to the present invention is shown;

[0024] Figure 2 The figure shows the structure diagram of the wafer level packaging of the surface acoustic wave device;

[0025] Figure 3 The second layer of the negative polymer film aperture mask pattern of the embodiment is shown;

[0026] Figure 4 The photomask patterns for different D2 / D1 ratios are shown;

[0027] Figure 5 The exposure and development results corresponding to different mask patterns are shown;

[0028] Figure 6 Shows a schematic diagram of the fabrication of a single layer and a second layer of film in wafer-level packaging;

[0029] Figure 7 A schematic diagram of the exposure and development process of a conventional circular pattern is shown;

[0030] Figure 8 A schematic diagram of the exposure and development process of a circular ring pattern of the present invention is shown;

[0031] Figure 9 The exposure and development results of Example 1 of the present invention with D1=4 μm, D2=10 μm, t=36 μm, r=40 μm, and R=50 μm are shown;

[0032] Figure 10 The exposure and development results of Example 1 of the present invention with D1=6um, D2=10um, t=36um, r=42um, and R=52um are shown;

[0033] Figure 11 The mask pattern of Example 2 is shown;

[0034] Figure 12 The exposure and development results of Example 2 are shown. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0036] Example 1

[0037] In wafer-level packaging technology, polymer films are used to construct a sealed cavity on the surface of the wafer, allowing the device to operate normally within it, while at the same time exposing electrode through-holes through photolithography for electrical connection with the outside world. This packaging method has the advantages of saving the use of substrates and reducing the size of the device. In the wafer-level packaging technology of surface acoustic wave devices, it generally requires two layers of organic films to construct a sealed cavity. One layer of the film mainly serves to raise the height of the second layer of the organic film, such as Figure 2 The present invention provides a method for photolithographically opening holes by changing the morphology of the sidewall of the second layer of negative polymer film. The flow chart is as follows: Figure 1 The detailed steps of this method are as follows:

[0038] S1. Apply the first layer of 10 micron thick negative polymer film to the prepared wafer. Control the film application temperature, pressure and vacuum to ensure good adhesion between the first layer of film and the wafer. Cut and separate the first layer of film at the edge of the wafer. Design the photolithography pattern of the first layer of film. The external electrode area of ​​the wafer is designed into a circular pattern. The device functional area is designed into a certain shape. Expose and develop. The circular hole at the electrode and the device functional area are exposed. The negative film in other areas is exposed and polymerized. The whole film application process is as follows: Figure 6 As shown, the first layer of membrane pores is obtained and the pore radius r is measured, and the membrane is baked and solidified. Optionally, r is 40 microns, and the process proceeds to step S2;

[0039] Step S2: Apply a second layer of 20-μm-thick negative polymer film to the wafer. Key process parameters, such as temperature, pressure, and vacuum, are controlled to ensure good adhesion between the first and second layers. The second layer is cut and separated at the wafer edge, and the process proceeds to step S3.

[0040] S3. Draw a circle 1 with the required aperture radius R in the layout software. R is slightly larger than r. Optionally, set R to 50 μm and proceed to step S4.

[0041] S4. Draw a circle 2 with a radius of r within the circle 1 with a radius of R in the layout. The non-overlapping area between circles 1 and 2 forms a ring with a width of D2 = Rr, where D2 is not less than 20% of the total aperture radius. Optionally, D2 is set to 10 μm, the ring is set as a shadow area, and the process proceeds to step S5.

[0042] S5. Draw a circle 3 with a radius of t inside a circle 2 with a radius of r in the layout. The non-overlapping area between circles 2 and 3 forms a ring with a width of D1 = rt. The width D1 of the ring in the middle light-transmitting area is less than 16% of the total opening radius, and the radius t of the inner light-shielding area is not less than 72% of the total opening radius. Optionally, set D1 to 0um, 2um, 4um, 6um, 8um, 10um, etc. Figure 3 As shown, the inner circle radius t = r-D1, the ring is set as a blank light-transmitting area, and the inner circle 3 is set as a shadow shading area. The entire designed pattern is as shown Figure 4 As shown. And enter step S6;

[0043] S6. Based on the designed mask pattern, use a photolithography machine to align and expose at a certain exposure dose. The exposure wavelength is i-line. The exposure dose should be controlled so that the negative polymer film is just polymerized and difficult to dissolve in the developer. Optionally, the exposure dose is set to 1000mJ / cm 2 , and enter step S7;

[0044] S7. After exposure, the film is allowed to stand for development. Optionally, the development time is 5 minutes, and the film proceeds to step S8.

[0045] S8. Perform dynamic development for a period of time, set a certain vibration friction, and optionally, perform ultrasonic development for 5 minutes in the developer, rinse with deionized water, dry, bake and solidify to obtain membrane pores. The final cross-sectional view of the negative polymer membrane pore wall is as follows: Figure 5 As shown, the conventional circular opening pattern is as follows Figure 4 Solution A in the photolithography process reference Figure 7 , the opening results are as follows Figure 5 The result A( Figure 5 The final result is a hole with poor steepness and concave morphology. Figure 4 The exposure and opening process of schemes B, C, D, E, and F is as follows: Figure 8 As shown in Figure 2, the final result is a hole wall with better steepness and bowl-shaped morphology in solution C. The results under the optimal conditions of D1 = 4um, D2 = 10um, t = 36um, r = 40um, and R = 50um are as follows: Figure 9 As shown; under the optimal conditions, the results of D1 = 6um, D2 = 10um, t = 36um, r = 42um, and R = 52um are as follows Figure 10 As shown in FIG. 1 , the optimal condition of D2 / D1=2.5 has a better steepness than that of D2 / D1=1.67.

[0046] Example 2

[0047] The present invention provides a photolithographic pore-forming method for changing the morphology of the sidewall of the pores in the second layer of negative polymer film. The detailed steps of the method include the following:

[0048] S1. Paste the first layer of 10 micron thick negative polymer film on the prepared wafer, control the film pasting temperature, pressure and vacuum to make the first layer of film and wafer well adhered, and cut and separate the first layer of film at the edge of the wafer; design the first layer of film photolithography pattern, where the external electrode needs to be designed with a circular pattern in the shot, and the device functional area is designed with a certain shape. Expose and develop, the circular hole at the electrode and the device functional area are exposed, and the negative film in other areas is exposed and polymerized. The whole film pasting process is as follows: Figure 6 As shown, the first layer of membrane pores is obtained and the pore radius r is measured, and the membrane is baked and solidified. Optionally, r is 40 microns, and the process proceeds to step S2;

[0049] Step S2: Apply a second layer of 20-μm-thick negative polymer film to the wafer. Key process parameters, such as temperature, pressure, and vacuum, are controlled to ensure good adhesion between the first and second layers. The second layer is cut and separated at the wafer edge, and the process proceeds to step S3.

[0050] S3. Draw a circle 1 with the required aperture radius R in the layout software, where R is greater than r. Optionally, set R to 60 μm and proceed to step S4.

[0051] S4. Draw a circle 2 with a radius of r within the circle 1 with a radius of R in the layout. The non-overlapping area between circles 1 and 2 forms a ring with a width D2 = Rr, where D2 is not less than 20% of the total aperture radius. Optionally, D2 is set to 20 μm. The ring is set as a shadow area, and the process proceeds to step S5.

[0052] S5. Draw a circle 3 with a radius of t inside a circle 2 with a radius of r in the layout. The non-overlapping area between circles 2 and 3 forms a ring with a width of D1 = rt. The width D1 of the middle light-transmitting ring is less than 16% of the total aperture radius, and the radius t of the inner circle light-blocking area is not less than 72% of the total aperture radius. Optionally, set D1 to 4 microns, t to 36 microns, set the ring as a blank light-transmitting area, and set the inner circle 3 as a circular grating with light and dark alternating at equal intervals and connected to the middle light-transmitting ring. The entire designed pattern is as follows: Figure 11 As shown. And enter step S6;

[0053] S6. Based on the designed mask pattern, use a photolithography machine to align and expose at a certain exposure dose. The exposure wavelength is i-line. The exposure dose should be controlled so that the negative polymer film is just polymerized and difficult to dissolve in the developer. Optionally, the exposure dose is set to 1000mJ / cm 2 , and enter step S7;

[0054] S7. After exposure, the film is allowed to stand for development. Optionally, the film is allowed to stand for development for 5 minutes and then proceeds to step S8.

[0055] S8. Perform dynamic development for a period of time, set a certain vibration friction, and optionally, perform ultrasonic development for 5 minutes in the developer, rinse with deionized water, dry, and bake to solidify. The cross-sectional view of the negative polymer film sidewall is shown below. Figure 12 shown.

[0056] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.

Claims

1. A method for exposing and opening a circular ring pattern in a negative polymer film, characterized in that: The method comprises sequentially Follow these steps: S1. Lay the first layer of negative polymer film on the prepared wafer, control the laminating process parameters to make the first layer of film adhere well to the wafer, and cut and separate the first layer of film at the edge of the wafer; design the photolithography pattern of the first layer of film, where the wafer needs to be connected externally. The electrodes are designed into circular patterns, exposed and developed to obtain the first layer of membrane pores and measure the pore radius r, and then baked and cured; S2. Paste the second layer of negative polymer film on the wafer, and control the film process parameters to make the first layer of film and the second layer of film The bonding is good, and the second layer of film is cut and separated at the edge of the wafer; S3. Draw a circle 1 with the required hole radius R in the layout software. R should be slightly larger than r. S4. Draw a circle 2 with a radius of r inside a circle 1 with a radius of R in the layout. The non-overlapping area between circles 1 and 2 forms a ring. The width is D2 = Rr, and the ring is set as a shaded area; S5. Draw an inner circle 3 with a radius of t inside a circle 2 with a radius of r in the layout. The non-overlapping area between circle 2 and inner circle 3 constitutes a The ring has a width of D1 = rt, the ring is set as a blank area, and the inner circle 3 is set as a shadow area; thus forming a concentric ring pattern; S6. Based on the designed mask pattern, use a photolithography machine to expose the wafer at a certain exposure dose; S7. Perform static development and dynamic development for a period of time, rinse with deionized water, dry, and bake to solidify to obtain membrane pores.

2. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, characterized in that: The shadow area of ​​the concentric ring pattern is a light-shielding area during actual exposure, and the blank area is a light-transmitting area during actual exposure.

3. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The shadow area of ​​the inner circle 3 in the concentric ring pattern is a circular grating and is connected to the middle transparent ring D1 in alternating light and dark colors.

4. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The dimensions of the concentric ring pattern include: the width D1 of the blank area serving as the middle light-transmitting area is less than 16% of the total opening radius, the width D2 of the shadow area serving as the outer light-shielding area is not less than 20% of the total opening radius, the ratio of D2 / D1 is not less than 1.67, the radius t of the inner circle 3 is not less than 72% of the total opening radius, and the total opening radius R is not less than 50um.

5. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The thickness of the first negative polymer film layer is less than or equal to 1 / 2 of the second negative polymer film layer, and the first negative polymer film layer and the second negative polymer film layer are made of different materials.

6. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The exposure wavelength of the photolithography machine matches the inherent photosensitivity wavelength of the negative polymer film, and the exposure dose should be controlled so that the negative polymer film just polymerizes and is difficult to dissolve in the developer.

7. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: Development requires setting a certain amount of vibration friction.

8. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The developer concentration and development time need to be controlled within a certain range.

9. The method for exposing and opening a circular ring pattern in a negative polymer film according to claim 1, wherein: The center of the concentric ring pattern is consistent with the center of the first layer of membrane hole.

10. The method for exposing and opening holes in a circular ring pattern of a negative polymer film according to claim 1, characterized in that: Under the condition that the ratio of D2 / D1 is not less than 1.67, D1 and D2 in the mask are designed to increase the ratio of D2 / D1, thereby improving the steepness of the pore wall of the negative polymer film.

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