Method for changing morphology of PI glue side wall

Abstract

The invention belongs to the technical field of PI glue patterns, and particularly relates to a method for changing the appearance of a PI glue side wall. The surface of a wafer is coated with PI glue, the obtained wafer coated with the PI glue is baked, then the wafer with a PI glue layer is subjected to first exposure with a mask and second exposure without the mask, and the dosage of the second exposure accounts for less than or equal to 10% of the dosage of the first exposure; and finally, developing the wafer after the secondary exposure, and obtaining a PI glue pattern on the surface of the wafer. According to the method provided by the invention, smoother PI glue side wall morphology and inclination angles can be obtained, stress concentration of metal connecting wires is reduced, the problems of metal wire breakage and open circuit are reduced, and the yield and reliability of chips are improved; meanwhile, the equipment investment cost is low, and the exposure efficiency is high.

Description

Technical Field

[0001] The invention belongs to the technical field of PI glue graphics, and in particular relates to a method for changing the morphology of a PI glue side wall. Background Art

[0002] In the semiconductor chip manufacturing process, photosensitive PI glue is widely used, and its main function is to fill or passivate the chip surface; however, the pattern of photosensitive PI glue will form steep side walls and sharp corners, which will cause broken wires or unreliable connections during the metal wiring process, ultimately leading to problems such as device open circuit or reliability abnormalities.

[0003] In order to solve this problem, the sidewall morphology of the PI glue must be changed to obtain a relatively gentle sidewall and arc angle to facilitate metal wiring. In the prior art, in order to obtain a gentle inclination angle on the sidewall of the PI glue pattern, it is necessary to use a stepper lithography machine to adjust the exposure focal length during exposure. However, the price of stepper lithography equipment is expensive and the exposure efficiency is lower than that of contact lithography machines. Summary of the invention

[0004] The purpose of the present invention is to provide a method for changing the side wall morphology of PI glue. The method provided by the present invention can obtain a smoother side wall morphology and inclination angle of the PI glue, reduce the stress concentration of metal connections, reduce metal wire breakage and open circuit problems, and improve the yield and reliability of the chip; at the same time, the equipment investment cost is low and the exposure efficiency is high.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for changing the morphology of the sidewall of PI glue, comprising the following steps:

[0007] Coating PI glue on the surface of the wafer to obtain a wafer coated with PI glue;

[0008] Baking the wafer coated with the PI glue to obtain a wafer with a PI glue layer;

[0009] Expose the wafer with the PI adhesive layer for the first time to obtain a wafer after the first exposure; during the first exposure, a mask is arranged between the wafer with the PI adhesive layer and the light source of the first exposure;

[0010] Expose the wafer after the first exposure for a second time to obtain a wafer after the second exposure; during the second exposure, no mask is arranged between the wafer after the first exposure and the light source of the second exposure, and the percentage of the dose of the second exposure to the dose of the first exposure is ≤10%;

[0011] The wafer after the secondary exposure is developed to obtain a PI glue pattern on the wafer surface.

[0012] Preferably, the percentage of the dose of the second exposure to the dose of the first exposure is 5-10%.

[0013] Preferably, the dose of the first exposure is 200-300 mJ / cm 2 .

[0014] Preferably, the first exposure and the second exposure are both performed on a contact photolithography machine.

[0015] Preferably, the light sources for the first exposure and the second exposure are parallel light sources.

[0016] Preferably, the coating is performed by spin coating, the rotation speed of the spin coating is 2500-3000 RPM, and the time is 20-30s.

[0017] Preferably, the baking is performed on a hot plate, the baking temperature is 110-120° C., and the baking time is 1-3 min.

[0018] Preferably, the development time is 60 to 90 seconds.

[0019] Preferably, before coating the PI glue on the surface of the wafer, the method further comprises: cleaning the wafer, wherein the cleaning reagents are acetone, methanol and water in sequence.

[0020] Preferably, after developing the wafer after the secondary exposure, the process further comprises: washing and drying the wafer obtained after development in sequence to obtain a PI glue pattern on the surface of the wafer.

[0021] The present invention provides a method for changing the sidewall morphology of PI glue, comprising the following steps: coating PI glue on the surface of a wafer to obtain a wafer coated with PI glue; baking the wafer coated with PI glue to obtain a wafer with a PI glue layer; exposing the wafer with the PI glue layer for the first time to obtain a wafer after one exposure; a mask is arranged between the wafer with the PI glue layer and the light source of the first exposure during the first exposure; exposing the wafer after the one exposure for the second time to obtain a wafer after the second exposure; no mask is arranged between the wafer after the one exposure and the light source of the second exposure during the second exposure, and the dosage of the second exposure accounts for ≤10% of the dosage of the first exposure; developing the wafer after the second exposure to obtain a PI glue pattern on the wafer surface. The present invention exposes the wafer with the PI glue layer for the first time (including the mask), then exposes it for the second time (excluding the mask), and controls the dosage of the second exposure to account for ≤10% of the dosage of the first exposure, and then develops it. The second exposure allows the surface area that was not exposed during the first exposure to be properly exposed. The sidewall inclination angle (θ) and curvature radius (R) of the PI glue are optimized after the second exposure. Figure 2 As shown, specifically, the radius of curvature (R) is increased and the sidewall inclination angle (θ) is reduced, so that the graphic area after the first exposure and the second exposure after development forms a gentle transition, and the sidewall inclination angle of the final PI glue graphic has a certain arc, thereby obtaining a smoother PI glue sidewall morphology and inclination angle, reducing the stress concentration of the metal connection, reducing the metal wire breakage and open circuit problems, and improving the chip yield and reliability. At the same time, the present invention adopts a double exposure method, which does not depend on whether the graphic focal length during exposure is adjustable, can greatly reduce the investment cost of the equipment, and improve the exposure efficiency.

[0022] Furthermore, in the present invention, the percentage of the dose of the second exposure to the dose of the first exposure is 5-10%. The present invention further controls the ratio of the exposure dose of the second exposure to the dose of the first exposure by performing the second exposure without a mask, and can further achieve moderate exposure of the surface unexposed area during the second exposure, further optimizing the sidewall inclination angle (θ) and curvature radius (R) of the PI glue.

[0023] Furthermore, in the present invention, the first exposure and the second exposure are both performed on a contact lithography machine. The light sources for the first exposure and the second exposure are parallel light sources. The present invention can be implemented on an ordinary contact lithography machine, and only needs to add a low-dose flood exposure (excluding the second exposure of the mask) after the normal exposure (including the first exposure of the mask), which greatly reduces the investment cost of the equipment and has a higher exposure efficiency than a stepper lithography machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the SEM image of the PI glue sidewall morphology obtained by single exposure in Comparative Example 1;

[0025] Figure 2 This is the SEM image of the PI glue sidewall morphology obtained by double exposure in Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for changing the morphology of the sidewall of PI glue, comprising the following steps:

[0027] Coating PI glue on the surface of the wafer to obtain a wafer coated with PI glue;

[0028] Baking the wafer coated with PI glue to obtain a PI glue layer, thereby obtaining a wafer with a PI glue layer;

[0029] Expose the wafer with the PI adhesive layer for the first time to obtain a wafer after the first exposure; during the first exposure, a mask is arranged between the wafer with the PI adhesive layer and the light source of the first exposure;

[0030] Expose the wafer after the first exposure for a second time to obtain a wafer after the second exposure; during the second exposure, no mask is arranged between the wafer after the first exposure and the light source of the second exposure, and the percentage of the dose of the second exposure to the dose of the first exposure is ≤10%;

[0031] The wafer after the secondary exposure is developed to obtain a PI glue pattern on the wafer surface.

[0032] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0033] The present invention coats PI glue on the surface of a wafer to obtain a wafer coated with PI glue. In the present invention, before coating PI glue on the surface of the wafer, the present invention preferably further comprises: cleaning the wafer, and the reagents used for the cleaning are acetone, methanol and water in sequence, and the water is specifically deionized water. The cleaning preferably comprises: acetone immersion cleaning, methanol immersion cleaning and deionized water rinsing in sequence, and the time for the acetone immersion cleaning is preferably 3 to 5 minutes. The time for the methanol immersion cleaning is preferably 1 to 3 minutes. The time for the deionized water rinsing is preferably 3 to 5 minutes. After the deionized water rinsing, the present invention preferably further comprises: drying the wafer rinsed with deionized water, and the specific implementation method of the drying is preferably nitrogen purging.

[0034] In the present invention, the coating is preferably spin coating, and the spin coating is preferably carried out in a spin coating machine. The rotation speed of the spin coating is preferably 2500-3000 RPM, and the time is preferably 20-30s.

[0035] After obtaining the wafer coated with PI glue, the present invention bakes the wafer coated with PI glue to obtain a PI glue layer, thereby obtaining a wafer with a PI glue layer. In the present invention, the baking is preferably performed on a hot plate, the baking temperature is preferably 110-120° C., and the baking time is preferably 1-3 min.

[0036] After obtaining a wafer with a PI adhesive layer, the present invention performs a first exposure on the wafer with a PI adhesive layer to obtain a wafer after one exposure; during the first exposure, a mask is arranged between the wafer with a PI adhesive layer and the light source of the first exposure. In the present invention, the mask used for the first exposure is a mask with a pattern. The first exposure is preferably performed on a contact photolithography machine. The light source for the first exposure is preferably a parallel light source. The dose of the first exposure is preferably 200 to 300 mJ / cm 2 , more preferably 230 to 260 mJ / cm 2 .

[0037] After obtaining a wafer after a single exposure, the present invention performs a second exposure on the wafer after the single exposure to obtain a wafer after a double exposure; during the second exposure, no mask is arranged between the wafer after the single exposure and the light source of the second exposure, and the percentage of the dose of the second exposure to the dose of the first exposure is ≤10%. In the present invention, the second exposure is preferably performed on a contact lithography machine. The light source of the second exposure is preferably a parallel light source. The percentage of the dose of the second exposure to the dose of the first exposure is preferably 5 to 10%, and more preferably 6 to 8%.

[0038] After obtaining the wafer after the first exposure, the present invention develops the wafer after the second exposure to obtain a PI glue pattern on the wafer surface. In the present invention, the development time is preferably 60 to 90 seconds, more preferably 70 to 80 seconds.

[0039] In the present invention, after developing the wafer after the secondary exposure, the present invention preferably further comprises: washing and drying the wafer obtained after the development in sequence. The washing is preferably washing with deionized water. The specific implementation of the washing is preferably rinsing with water, and the washing time is preferably 3 to 5 minutes. The specific implementation of the drying is preferably drying with nitrogen.

[0040] According to the method provided by the present invention, after the photosensitive PI glue is exposed for the first time (including the mask), it is exposed for the second time (excluding the mask), and the dose of the second exposure is preferably 5 to 10% of the dose of the first exposure. Then development is performed to obtain a smoother PI glue sidewall morphology and inclination angle.

[0041] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] Example 1

[0043] (1) Clean the wafer to be processed by soaking it in acetone for 5 minutes, then soaking it in methanol for 3 minutes, and finally rinsing it with deionized water for 5 minutes and purging it with N2.

[0044] (2) Place the wafer in a spin coating machine and spin coat the PI glue, setting the speed to 3000 RPM and the time to 30 s.

[0045] (3) Place the wafer with PI glue spin-coated on a 120°C hot plate and bake for 3 minutes.

[0046] (4) Place the wafer with PI glue in a contact photolithography machine for exposure, using a parallel light source. There is a mask with a pattern made between the wafer and the light source. The dose of the first exposure is 300mJ / cm 2 .

[0047] (5) The wafer that has been exposed for the first time is placed in a contact photolithography machine for exposure again, using a parallel light source. At this time, there is no mask between the wafer and the light source (which can be called flood exposure). The dose of the second exposure is 10% of the dose of the first exposure.

[0048] (6) The wafer after the second exposure is developed with developer for 90 seconds, and finally rinsed with deionized water for 5 minutes and dried with N2.

[0049] Example 2

[0050] The preparation method is basically the same as that of Example 1, except that: in step (5), the dose of the second exposure is 5% of the dose of the first exposure.

[0051] Example 3

[0052] The preparation method is basically the same as that of Example 1, except that: in step (5), the dose of the second exposure is 8% of the dose of the first exposure.

[0053] Example 4

[0054] The preparation method is basically the same as that of Example 1, except that: in step (4): the dose of the first exposure is 200 mJ / cm 2 .

[0055] Example 5

[0056] The preparation method is basically the same as that of Example 1, except that: in step (4): the first exposure dose is 250 mJ / cm 2 .

[0057] Example 6

[0058] The preparation method is basically the same as that of Example 1, except that: in step (2): the rotation speed is set to 2500RPM.

[0059] Comparative Example 1

[0060] (1) Clean the wafer to be processed by soaking it in acetone for 5 minutes, then soaking it in methanol for 3 minutes, and finally rinsing it with deionized water for 5 minutes and purging it with N2.

[0061] (2) Place the wafer in a spin coating machine and spin coat the PI glue, setting the speed to 3000 RPM and the time to 30 s.

[0062] (3) Place the wafer with PI glue spin-coated on a 120°C hot plate and bake for 3 minutes.

[0063] (4) Place the wafer with PI glue in a contact photolithography machine for exposure, using a parallel light source. There is a mask with a pattern made between the wafer and the light source. The dose of the first exposure is 300mJ / cm 2 .

[0064] (5) The wafer after the first exposure is developed with developer for 90 seconds, and finally rinsed with deionized water for 5 minutes and dried with N2.

[0065] Test Case

[0066] Figure 1 This is the SEM image of the PI glue sidewall morphology obtained by single exposure in Comparative Example 1. Figure 2 The SEM images of the PI adhesive sidewall morphology obtained by double exposure in Example 1. The SEM images of the PI adhesive sidewall morphology obtained by double exposure in Examples 2 to 6 are basically consistent with that in Example 1. Table 1 shows the parameters and effect data of the PI adhesive sidewall obtained in Example 1 and Comparative Example 1.

[0067] Table 1 Parameters and effect data of PI glue sidewall obtained in Example 1 and Comparative Example 1

[0068] Exposures <![CDATA[Exposure dose (mJ / cm 2 )]]> Sidewall inclination angle θ Curvature radius R Disconnection rate (%) Comparative Example 1 Single Exposure 300 75° 1.1μm 40％ Example 1 Double exposure 300+30 60° 22.8μm 3％

[0069] Depend on Figures 1-2As shown in Table 1, the present invention does not depend on whether the focal length of the pattern during exposure is adjustable, and can be used on a relatively inexpensive contact lithography machine, using a parallel light source, which greatly reduces the investment cost of the equipment, and the exposure efficiency of the contact lithography machine is also higher. The second exposure in the present invention allows the surface area that was not exposed during the first exposure to be moderately exposed, so that there is a smooth transition between the pattern area that has been exposed for the first time and the second time after development, and the sidewall inclination angle of the final PI glue pattern has a certain curvature.

[0070] It can be seen from the above embodiments that the method for controlling the sidewall morphology of the PI glue pattern provided by the present invention optimizes the sidewall inclination angle (θ) and the radius of curvature (R) of the PI glue through the second exposure method. The larger radius of curvature reduces the stress concentration of the metal connection, reduces the problem of metal wire breakage and open circuit, and improves the yield and reliability of the chip. At the same time, the method provided by the present invention does not depend on whether the focal length of the pattern during exposure is adjustable, and can be used on a relatively low-priced contact lithography machine, using a parallel light source, which greatly reduces the investment cost of the equipment, and the exposure efficiency of the contact lithography machine is also higher.

[0071] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for changing the sidewall morphology of PI glue, characterized in that: The following steps are involved: Coating PI glue on the surface of the wafer to obtain a wafer coated with PI glue; Baking the wafer coated with the PI glue to obtain a wafer with a PI glue layer; Expose the wafer with the PI adhesive layer for the first time to obtain a wafer after the first exposure; during the first exposure, a mask is arranged between the wafer with the PI adhesive layer and the light source of the first exposure; Expose the wafer after the first exposure for a second time to obtain a wafer after the second exposure; during the second exposure, no mask is arranged between the wafer after the first exposure and the light source of the second exposure, and the percentage of the dose of the second exposure to the dose of the first exposure is ≤10%; The wafer after the secondary exposure is developed to obtain a PI glue pattern on the wafer surface.

2. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: The percentage of the dose of the second exposure to the dose of the first exposure is 5-10%.

3. The method for changing the sidewall morphology of PI glue according to claim 1 or 2, characterized in that: The dose of the first exposure is 200-300 mJ / cm 2 .

4. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: The first exposure and the second exposure are both performed on a contact photolithography machine.

5. The method for changing the sidewall morphology of PI glue according to claim 4, characterized in that: The light sources for the first exposure and the second exposure are parallel light sources.

6. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: The coating is performed by spin coating, the rotation speed of the spin coating is 2500-3000 RPM, and the time is 20-30s.

7. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: The baking is performed on a hot plate at a temperature of 110 to 120° C. for 1 to 3 minutes.

8. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: The development time is 60 to 90 seconds.

9. The method for changing the morphology of the sidewall of PI glue according to claim 1, characterized in that: Before coating the PI glue on the surface of the wafer, the method further includes: cleaning the wafer, wherein the cleaning reagents are acetone, methanol and water in sequence.

10. The method for changing the sidewall morphology of PI glue according to claim 1, characterized in that: After developing the wafer after the secondary exposure, the method further includes: washing and drying the wafer obtained after the development in sequence to obtain a PI glue pattern on the surface of the wafer.

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