Method for metal stripping of three-layer adhesive for wafer with groove by one-time exposure and one-time development

Abstract

The application discloses a metal stripping method for one-time exposure and one-time development of three layers of photoresist on a wafer with a groove, comprising sequentially spin-coating or spraying a first layer of photosensitive photoresist, non-photosensitive photoresist and another layer of photosensitive photoresist on the surface of the wafer, and then selecting a photoetching plate for one-time exposure, and sequentially performing one-time development, sputtering metal, ultrasonic immersion and stripping. After photoetching and development, the groove photoresist can be completely clean, the horizontal length of the chamfered platform outside the groove can be about 1.1 microns to 2.3 microns, the sputtered metal can not adhere to the chamfered platform during subsequent sputtering, the stripping requirement can be met, and the effect that the pattern edge has no residual metal and is easy to strip can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor metal stripping, and relates to a metal stripping method for three-layer photoresist one-time exposure and one-time development of a wafer with grooves. BACKGROUND

[0002] It is known that a metal stripping process exists in the process of semiconductor wafer processing, and a single-layer negative photoresist is generally used to adjust the chamfer through exposure and development for metal evaporation, but the negative photoresist has the problem that it is difficult to remove residual metal wires and metal debris completely when sputtering is used for stripping. At present, the commonly used method is to use double-layer photoresist for one-time exposure, that is, to use the non-photosensitive photoresist (transparent) of the bottom layer and the photosensitive photoresist of the upper layer for exposure and development, and to adjust the size of the chamfer by adjusting the development time to match the angle of metal sputtering. The double-layer photoresist stripping is much easier than the single-layer negative photoresist stripping, but the non-photosensitive photoresist of the bottom layer has the same dissolution rate in the developing solution after being exposed to light and not being exposed to light, and because the bottom layer is the thickest when spin coating, it is difficult to coordinate the non-photosensitive photoresist and the photosensitive photoresist in the groove to be completely developed, which causes the problem that when the photoresist in the groove is completely developed, the chamfer on the platform outside the groove exceeds the process range, resulting in the collapse of the upper photosensitive photoresist, and after stripping, residual metal wires exist, which leads to poor electrical properties and appearance. SUMMARY

[0003] The purpose of the present application is to provide a metal stripping method for three-layer photoresist one-time exposure and one-time development of a wafer with grooves, which solves the problem that when the photoresist in the groove is completely developed, the chamfer on the platform outside the groove exceeds the process range, resulting in the collapse of the upper photosensitive photoresist, and after stripping, residual metal wires exist, which leads to poor electrical properties and appearance.

[0004] The technical solution adopted by the present application is as follows: a metal stripping method for three-layer photoresist one-time exposure and one-time development of a wafer with grooves, comprising the following steps:

[0005] Step 1: selecting a wafer with uneven etching grooves;

[0006] Step 2: spin coating or spraying a first layer of photosensitive photoresist on the surface of the wafer including the grooves;

[0007] Step 3: spin coating or spraying non-photosensitive photoresist on the solidified photosensitive photoresist of the first layer and performing soft baking;

[0008] Step 4: spin coating or spraying a second layer of photosensitive photoresist on the solidified non-photosensitive photoresist and performing soft baking;

[0009] Step 5: selecting a photoetching plate and performing one-time exposure and one-time development on the second layer of photosensitive photoresist;

[0010] Step 6, after removing the photoetching plate, sputtering metal on the wafer after developing, so that the wafer develops clean pattern area to get corresponding metal pattern;

[0011] Step 7, using organic solution ultrasonic immersion and stripping process, so that the first layer of photosensitive photoresist glue layer, non-photosensitive photoresist glue layer, the second layer of photosensitive photoresist glue layer and the upper metal layer are stripped at the same time.

[0012] The application also has the characteristics of:

[0013] The photosensitive photoresist is positive photoresist or negative photoresist, wherein the first layer of photosensitive photoresist and the second layer of photosensitive photoresist have the same polarity.

[0014] In step 3 and step 4, the temperature is set to 90-200 DEG C, and the time is 30s-2min, and the thickness of the non-photosensitive photoresist and the photosensitive photoresist is 1-10 microns.

[0015] In step 5, i-line or l-line or g-line exposure machine is used for one-time exposure of 5-100 mJ / cm2, and one-time development.

[0016] In step 7, the organic solution ultrasonic immersion and stripping process is as follows: ultrasonic current immersion stripping in stripping solution, and then isopropanol immersion and water washing after stripping is completed.

[0017] The application has the beneficial effects of:

[0018] 1. When the bottom layer of positive photoresist is spun, the trench is filled first, and the depth of the trench is reduced. When the non-photosensitive photoresist is spun, the trench is shallower, and most of the photoresist is easily thrown out of the trench by centrifugal force, and the thickness of the non-photosensitive photoresist in the trench is reduced. Finally, under the condition of light, the dissolution rate of the photoresist in the trench is accelerated.

[0019] 2. After the three-layer glue is completely spun and baked, one-time exposure and one-time development can achieve the required chamfer size, and repeated exposure is not required, which is simple to operate and saves cost.

[0020] 3. After photoetching and development, the development rates of the photoresist inside and outside the trench are almost the same, and the chamfer transverse length can reach 1.1-2.3 microns.

[0021] 4. The large chamfer can meet the requirements of no metal adhesion at the chamfer during sputtering metal, and can meet the stripping requirements, achieving the effect of easy stripping and no residual metal at the pattern edge. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the topography diagram of the metal stripping method of the three-layer glue of the wafer with a trench after soft baking according to the application;

[0023] Figure 2 This is a topographic image of the metal after metal deposition in the metal stripping method of the present invention, which uses a three-layer resist with one exposure and one development.

[0024] Figure 3 This is a beveled photograph after development according to Embodiment 1 of the present invention;

[0025] Figure 4 This is a beveled photograph after development, as shown in Embodiment 2 of the present invention;

[0026] Figure 5 This is a photograph of the stripped area in Embodiment 2 of the present invention.

[0027] In the diagram, 1. wafer, 2. non-photosensitive photoresist, 3. photosensitive photoresist, 4. chamfer, 5. metal layer. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] This invention relates to a method for metal stripping of trenched wafers using a single exposure and development process with three layers of adhesive, comprising the following steps:

[0030] Step 1, select wafer 1 with uneven etching grooves;

[0031] Step 2: Spin-coat or spray the first layer of photoresist 3 onto the surface of wafer 1, including the grooves; perform soft baking at 90℃-200℃ for 30s-2min, with a photoresist thickness of 1μm-10μm;

[0032] Step 3: Spin-coat or spray non-photosensitive photoresist 2 onto the cured photoresist; perform soft baking at 90℃-200℃ for 30s-2min, with a photoresist thickness of 1-10 micrometers;

[0033] Step 4: Spin-coat or spray-coat a second layer of photosensitive photoresist 3 onto the cured non-photosensitive photoresist 2; perform a soft bake at 90℃-200℃ for 30s-2min, with a photoresist thickness of 1-10 micrometers. Figure 1 ;

[0034] Step 5: Select a photomask and expose it to the second layer of photoresist 3 using an i-line, l-line, or g-line exposure machine at a concentration of 5mJ / cm2-100mJ / cm2. Then, develop it once using a positive or negative developer.

[0035] Step 6: Sputter metal to form a metal layer 5 on the second photoresist layer 3. The cleaned patterned area on wafer 1 yields the corresponding metal pattern, such as... Figure 2 ;

[0036] Step 7, using the organic solution ultrasonic immersion and peeling process, the first layer of photoresist 3, the non-photosensitive glue 2 layer and the other layer of photosensitive photoresist 3 glue layer and the upper metal layer 5 are peeled off at the same time, the specific method is: ultrasonic current immersion peeling in the stripping solution, after stripping, isopropanol is soaked and then washed with water. The first layer of photoresist 3 and the other layer of photosensitive photoresist 3 adopt positive photoresist or negative photoresist, and the first layer of photoresist 3 and the other layer of photosensitive photoresist 3 have the same polarity.

[0037] Example 1

[0038] The wafer 1 etched groove is baked and metal peeled off by the method of the application, and the specific steps include:

[0039] Step 1, select the wafer 1 with high and low uneven etched groove, the groove depth-width ratio is 4:1;

[0040] Step 2, spin-coat the first layer of i-line positive photoresist AZ-12XT on the surface of the wafer 1 including the groove at 3000r, and soft-bake at 110℃ for 50s by hot plate;

[0041] Step 3, spin-coat LOL2000 photoresist on the first layer of solidified photoresist at 6000r; soft-bake at 150℃ for 1min by hot plate;

[0042] Step 4, spin-coat the third layer of positive photoresist, which is i-line photoresist AZ-12XT, on the solidified LOL2000 at 3000r, and soft-bake at 110℃ for 50s by hot plate;

[0043] Step 5, select the photoetching plate, and use the double-sided exposure machine H94-16 i-line exposure machine to perform one-time 10mw-18s exposure on the third layer of photoresist, and use SUN-238D developing solution to develop for one time for 1min, the size of the inverted corner after developing is shown in the figure, the inverted corner transverse size is 1.19 microns; Figure 3

[0044] Step 6, select the sputtering machine JCP-550 to sputter 100nm Ti and 300nm Au according to the sputtering rate The wafer 1 is developed clean, and the corresponding metal pattern is obtained;

[0045] Step 7, the wafer 1 is immersed in NMP stripping solution for 10min by ultrasonic current 0.7, and then is immersed in isopropanol for 5min after stripping, and then is washed with water, and is spin-dried;

[0046] Example 2

[0047] The wafer 1 etched groove is baked and metal peeled off by the method of the application, and the specific steps include: ​

[0048] Step 1, select the wafer 1 with high and low uneven etching groove, groove depth ratio 4:1;

[0049] Step 2, use 3000r spin coating the first layer of i-line positive photoresist AZ-12XT on the surface of wafer 1 including the groove, and use hot plate to soft-bake at 110℃ for 50s;

[0050] Step 3, spin coating LOL2000 photoresist on the first layer of solidified photoresist at 6000r, and use hot plate to soft-bake at 150℃ for 1min;

[0051] Step 4, spin coating the third layer of positive photoresist, i-line photoresist AZ-12XT, on the solidified LOL2000 at 3000r, and use hot plate to soft-bake at 110℃ for 50s;

[0052] Step 5, select the photoetching plate, and use double-sided exposure machine H94-16 i-line exposure machine to expose for 10mw-18s on the third layer of photoresist, and use SUN-238D developer to develop for 1min30s, the size of the inverted corner of the groove outside the platform after development Figure 4 as shown, the inverted corner transverse size is 2.24 microns;

[0053] Step 6, select sputtering machine JCP-550 to sputter metal 100nm Ti and 300nm Au, and the wafer 1 with clean developed pattern area gets the corresponding metal pattern;

[0054] Step 7, the wafer 1 is immersed in NMP stripping liquid for 10min under ultrasonic current 0.7 for stripping, and after stripping is completed, it is immersed in isopropanol for 5min, then water flushing is carried out after isopropanol immersion time is over, and spin-drying is carried out;

[0055] The stripping effect of this embodiment 2 is shown in the microscope as Figure 5 It can be seen that the metal pattern edge after stripping is regular, and there is no residual metal effect.

[0056] This embodiment uses one layer of positive photoresist plus LOL2000 plus one layer of positive photoresist; one-time exposure and one-time development are adopted, the bottom is the positive photoresist which is easy to develop after exposure, and then is the LOL2000 which has the same development rate whether exposed or not, so this combination reduces the groove depth of LOL2000 on one hand, and on the other hand, the bottom positive photoresist which is sensitive to light will quickly dissolve as soon as it comes into contact with the developer, which speeds up the development rate in the groove, so that the development rate in the groove and the platform outside the groove is almost the same.

[0057] Secondly, in this embodiment, only one-time exposure and one-time development are adopted, without repeated etching exposure, which is simple to operate and saves cost. When stripping, ultrasonic immersion in traditional organic solution can meet the effect of easy stripping and no residual metal at the pattern edge.​

Claims

1. A method for metal stripping of trenched wafers using a single exposure and development of three layers of adhesive, characterized in that, Includes the following steps: Step 1, select a wafer with uneven etching grooves (1); Step 2: Spin-coat or spray-coat the first layer of photoresist on the surface of the wafer (1), including the grooves, and perform soft baking; Step 3: Spin-coat or spray non-photosensitive photoresist (2) onto the cured first layer of photosensitive photoresist and perform soft baking; Step 4: Spin-coat or spray a second layer of photosensitive photoresist onto the cured non-photosensitive photoresist (2) and perform soft baking; Step 5: Select a photomask and perform one exposure and one development on the second layer of photosensitive photoresist; Step 6: Remove the photomask and sputter metal onto the developed wafer (1) so that the patterned area of ​​the developed wafer (1) obtains the corresponding metal pattern. Step 7: Using an organic solution ultrasonic soaking and peeling process, the first photosensitive photoresist layer, the non-photosensitive photoresist (2) layer, the second photosensitive photoresist layer, and the upper metal layer (5) of the area to be peeled off are simultaneously peeled off.

2. The metal stripping method for trenched wafers with three layers of resist in a single exposure and development process as described in claim 1, characterized in that, The photoresist is either a positive or negative photoresist, wherein the first and second photoresist layers have the same polarity.

3. The metal stripping method for trenched wafers with three layers of resist in a single exposure and development process as described in claim 1, characterized in that, During the soft baking process in steps 2, 3 and 4, the temperature is set to 90℃-200℃ and the time is 30s-2min. The thickness of the non-photosensitive photoresist (2) and the photosensitive photoresist is 1 micrometer-10 micrometers.

4. The metal stripping method for trenched wafers with three layers of resist in a single exposure and development process as described in claim 1, characterized in that, In step 5, an i-line, l-line, or g-line exposure machine is used to perform a 5mJ / cm exposure. 2 -100mJ / cm 2 Exposure, one development.

5. The metal stripping method for trenched wafers with three layers of resist in a single exposure and development process as described in claim 1, characterized in that, The specific steps of the ultrasonic soaking and peeling process in step 7 are as follows: ultrasonic current soaking and peeling are performed in the peeling solution, and after peeling, the solution is soaked in isopropanol and then rinsed with water.

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