Photoresist stripping method

Abstract

The present invention proposes a photoresist stripping method, which uses a wafer with photoresist, comprising: first placing the wafer in an etching chamber; arranging a uniform gas disk with multiple through holes in the etching chamber; placing the wafer between the uniform gas disk and a microwave source; then, from above the wafer, successively introducing oxygen and water into the etching chamber to soften the surface portion of the photoresist; then, both the introduced oxygen and water are discharged; then, from above the wafer, introducing 0.2-0.5g of water into the etching chamber and simultaneously activating the microwave source, the microwave source ionizing the water vapor into an ionic state, the ionic water vapor descending to the wafer through the uniform gas disk to absorb chloride ions attached to the wafer; finally, performing dry stripping according to preset dry stripping parameters to strip the surface portion of the photoresist and the photoresist. The present invention improves the uniformity of photoresist stripping by setting the uniform gas disk, the softening process, and the parameters in the dry stripping process.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor industry, and in particular relates to a photoresist stripping method. Background Art

[0002] The traditional mainstream stripping method uses wet stripping, which is low-cost and highly efficient. However, with the continuous iteration and update of technology, more and more IC manufacturers are beginning to adopt dry stripping. Unlike traditional wet stripping processes, dry stripping does not require immersion in chemical solvents or drying, making the stripping process easier to control, avoiding excessive substrate inclusion, and improving product yield. Dry stripping, also known as plasma stripping, follows a similar principle to plasma cleaning, primarily removing photoresist through the reaction between oxygen nuclei and photoresist in a plasma environment. Since photoresist is basically composed of hydrocarbon organic compounds, under the influence of radio frequency or microwaves, oxygen is ionized into oxygen atoms, which react chemically with the photoresist to produce carbon monoxide, carbon dioxide, and water, which are then vacuumed away by a pump, completing the photoresist removal.

[0003] In the dry stripping process, uniformity is the main factor in determining the stripping quality. However, in traditional dry stripping processes, the photoresist stripping uniformity is too poor, affecting production efficiency and, in turn, the yield of the entire product. Summary of the Invention

[0004] The object of the present invention is to provide a photoresist stripping method, by arranging the parameters in the gas-distributing disk, softening process and dry process stripping process, the stripping uniformity of the photoresist is improved. To achieve the above object, the present invention adopts the following technical solutions:

[0005] A photoresist stripping method uses a wafer with photoresist, comprising the following steps:

[0006] Step 01: placing the wafer in an etching chamber; a uniform gas plate with a plurality of through holes is provided in the etching chamber; the wafer is placed between the uniform gas plate and a microwave source;

[0007] Step 02: Oxygen and water are introduced into the etching chamber from above the wafer to soften the surface of the photoresist;

[0008] Step 03: Expel the oxygen and water introduced in step 02;

[0009] Step 4: 0.2-0.5g of water is introduced into the etching chamber from above the wafer and the microwave source is activated at the same time. The water forms water vapor during its descent process. The microwave source ionizes the water vapor into ions. The ionized water vapor descends to the wafer through the uniform gas plate to absorb the chloride ions attached to the wafer.

[0010] Step 05: performing dry stripping according to preset dry stripping parameters to remove the surface portion of the photoresist and the photoresist; wherein the preset dry stripping parameters include the flow rate of oxygen and the flow rate of nitrogen; the oxygen and nitrogen are both introduced into the etching chamber from above the wafer;

[0011] At the same time, 0.2 to 0.5 g of water is continuously introduced into the etching chamber from above the wafer to absorb chloride ions attached to the wafer.

[0012] Preferably, in step 04, the radio frequency power of the microwave source is 1000-1400 W; and the reaction pressure of the etching chamber is 2000-8000 mtorr.

[0013] Preferably, in step 05, the preset dry stripping parameters further include radio frequency power and reaction pressure of the etching chamber; the radio frequency power of the microwave source is 1000-1400W; and the reaction pressure of the etching chamber is 2000-8000 mtorr.

[0014] Preferably, in step 05, the oxygen flow rate is 2000-4000 sccm, and the nitrogen flow rate is 200-800 sccm.

[0015] Preferably, in step 02, the total flow rate of oxygen introduced is 3500 sccm, and the introduction time is 30 s; the total amount of water introduced is 0.6 g, and the introduction time is 30 s.

[0016] Preferably, in step 01, the gas uniforming disk is made of quartz material.

[0017] Preferably, in step 01, the gas uniforming disk includes N circles of through-hole units, wherein N≥1; the through-hole units include a plurality of through-holes distributed along the circumference; and the radii of the through-hole units are different.

[0018] Preferably, after step 05, return to step 04.

[0019] Preferably, step 01 specifically includes:

[0020] Step S1: a robotic arm device is used to deliver the wafer in the wafer loading chamber to a position directly above a hot stage in an etching chamber;

[0021] Step S2: The ceramic ejector mechanism located below the heat stage is raised and passes through the hollow area of ​​the heat stage and the robotic arm device in sequence to lift the wafer on the hollow area; the distance between the wafer and the heat stage is 9 mm.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) First, during the softening process, oxygen and water are introduced to physically soften the photoresist and the surface layer of the photoresist, so that the photoresist and the surface layer of the photoresist contain water; then, the oxygen and water used for softening are discharged from the etching chamber; then, the chloride ions on the wafer are dissolved by using ionic water to remove the chloride ions; finally, by setting the dry stripping parameters, the surface layer of the photoresist and the photoresist are stripped. Therefore, through the above process, the uniformity of the stripping can be improved.

[0024] (2) During the softening process and dry stripping process, oxygen, nitrogen and water are introduced into the etching chamber from above the wafer. The oxygen, nitrogen and water are ionized into ions by the microwave source and then evenly sprinkled onto the wafer by the action of the uniform gas plate to react with the photoresist and the surface part of the photoresist, thereby finally removing the photoresist and stripping the photoresist evenly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. 4 is a flow chart of a photoresist stripping method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be described in more detail below with reference to schematic diagrams, which illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art may modify the present invention as described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a general guide for those skilled in the art and not as a limitation of the present invention.

[0027] like Figure 1 As shown, a photoresist stripping method uses a wafer with photoresist and includes the following steps 01 to 06.

[0028] Step 01: Place the wafer in an etching chamber; set up a uniform gas plate with multiple through holes in the etching chamber; and place the wafer between the uniform gas plate and the microwave source.

[0029] The gas-distributing disk is made of quartz material; the gas-distributing disk comprises N circles of through-hole units, wherein N is a positive integer and N≥1; the through-hole units comprise a plurality of through-holes distributed along the circumference; and the radii of the through-hole units are different.

[0030] The function of the gas-distributing plate is to homogenize the oxygen and water introduced into the etching chamber. In step 02, the gas-distributing plate is used to uniformly contact the photoresist and the surface layer of the photoresist to improve the softening effect. In step 04, the gas-distributing plate is used to uniformly contact the water vapor formed by microwave ionization, so that the water vapor uniformly contacts the photoresist and the surface layer of the photoresist to uniformly absorb the chloride ions attached to the wafer. In step 05, the gas-distributing plate is used to uniformly contact the oxygen ions, nitrogen ions, and water ions formed by microwave ionization, so that the oxygen ions, nitrogen ions, and water ions uniformly contact the photoresist and the surface layer of the photoresist to improve the uniformity of the stripping.

[0031] The specific operation of placing the wafer in the etching chamber is as follows: first, a robotic arm device is used to send the wafer in the wafer loading chamber to the top of a hot plate in the etching chamber; then, the ceramic ejector mechanism located below the hot plate is raised and passes through the hollow area of ​​the hot plate and the robotic arm device in sequence to lift the wafer on the hollow area; the distance between the wafer and the hot plate is 9mm. It is known to those skilled in the art that the operating method of how to place the wafer in the etching chamber belongs to the prior art. In addition, since the temperature of the hot plate is relatively high, in order to prevent the photoresist on the wafer from sticking, the wafer and the hot plate do not contact each other, thereby reducing the difficulty coefficient of debonding.

[0032] Step 02: Oxygen and water are introduced into the etching chamber from above the wafer to soften the surface of the photoresist.

[0033] Specifically, oxygen and water are introduced through the wafer. As the amount of oxygen introduced increases, the oxygen gradually completely covers or, in turn, completely submerges the photoresist and its surface layer on the wafer. The oxygen softens the photoresist and its surface layer, preventing it from drying out during subsequent stripping. The water physically softens the photoresist and its surface layer, ensuring that water is contained within them, preventing the 250°C heating stage from drying out the resist and its surface layer.

[0034] The total flow rate of oxygen introduced was 3500 sccm, and the introduction time was 30 s; the total amount of water introduced was 0.6 g, and the introduction time was 30 s.

[0035] Step 03: Completely discharge the oxygen and water introduced in step 02.

[0036] Specifically, an exhaust pipe and a drain pipe connected to the etching chamber can be installed at the bottom of the etching chamber. When the softening time reaches a preset value, the valves on the exhaust pipe and drain pipe are opened to discharge oxygen and water from the etching chamber respectively. The purpose of step 3 is to prevent residual oxygen or water. If residual oxygen or water occurs, it will cause an imbalance in the ratio of process gas to water in steps 4 and 5, affecting the uniformity of degumming.

[0037] Step 4: 0.2-0.5g of water is introduced into the etching chamber from above the wafer while the microwave source is activated. As the water descends, it forms vapor. The microwave source ionizes the vapor into ions, which then descend through the uniform gas plate onto the wafer, absorbing chloride ions attached to the wafer. This step also serves as a debonding step. Chlorine is required for dry etching of aluminum in the previous step. Therefore, residual chloride ions are present during this debonding step. Chloride ions are corrosive and therefore need to be removed beforehand.

[0038] The radio frequency power of the microwave source is 1000-1400W; the reaction pressure of the etching cavity is 2000-8000mtorr.

[0039] Step 05: Dry stripping is performed according to preset dry stripping parameters to remove the surface portion of the photoresist and the photoresist; wherein the preset dry stripping parameters include the flow rate of oxygen and the flow rate of nitrogen; oxygen and nitrogen are both introduced into the etching chamber from above the wafer; oxygen and nitrogen serve as reactive gases, and after ionization, react with the photoresist and the surface portion of the photoresist to remove the photoresist and the surface portion of the photoresist.

[0040] While dry stripping is being performed, 0.2 to 0.5 g of water is continuously introduced into the etching chamber from above the wafer to further absorb the chloride ions attached to the wafer.

[0041] The oxygen flow rate is 2000-4000 sccm, and the nitrogen flow rate is 200-800 sccm.

[0042] Among them, the preset dry stripping parameters also include RF power and reaction pressure of the etching chamber; the RF power of the microwave source is 1000-1400W; and the reaction pressure of the etching chamber is 2000-8000mtorr.

[0043] Step 06: After step 05, return to step 04. Repeat steps 04 and 05 multiple times to completely remove the photoresist and the surface portion of the photoresist.

[0044] Example 1

[0045] Parameter settings in Step 04: 6-10mm gas plate aperture size, 5 layers from the inside out, increasing by 2mm or remaining constant; RF power 1000-1400W, chamber pressure 2000-8000mtorr, water flow 0.2-0.5g. Experimental results show a stripping uniformity of 10.5% and a stripping rate of 49190A / min.

[0046] Parameter settings in Step 05: 6-10mm gas plate aperture size, 5 layers from the inside out, increasing by 2mm or remaining constant; upper RF power 1000-1400W, etch chamber pressure 2000-8000mtorr, water flow 0.2-0.5g, oxygen flow 2000-4000sccm, and nitrogen flow 200-800sccm. Experimental results show a stripping uniformity of 14.8% and a stripping rate of 31470A / min.

[0047] Example 2

[0048] Parameter settings in Step 04: 6-10mm gas plate aperture size, 4 layers from the inside out, increasing by 2mm or remaining constant; upper RF power 1000-1400W, chamber pressure 2000-8000mtorr, water flow 0.2-0.5g. Experimental results show a 14.2% stripping uniformity and a stripping rate of 55,230A / min.

[0049] Parameter settings in Step 05: 6-10mm gas plate hole size, 4 layers from the inside out, increasing by 2mm or remaining constant; RF power 1000-1400W, chamber pressure 2000-8000mtorr, water flow 0.2-0.5g, oxygen flow 2000-4000sccm, and nitrogen flow 200-800sccm. Experimental results show a stripping uniformity of 14.4% and a stripping rate of 30,600A / min.

[0050] Example 3

[0051] Case 3:

[0052] Parameter settings in Step 04: 6-10mm perforation size of the uniforming disk, four layers from the inside out, increasing in 2mm increments or remaining constant; RF power of 800-1000W, chamber pressure of 2000-8000mtorr, and water flow rate of 0.2-0.5g. Experimental results show a debonding uniformity of 12.2% and a debonding rate of 29190A / min.

[0053] Parameter settings in Step 05: 6-10mm gas plate hole size, 4 layers from the inside out, increasing by 2mm or remaining constant; RF power 800-1000W, chamber pressure 2000-8000mtorr, water flow 0.2-0.5g, oxygen flow 2000-4000sccm, and nitrogen flow 200-800sccm. Experimental results show a stripping uniformity of 11% and a stripping rate of 41190A / min.

[0054] It can be seen from the dry stripping uniformity and stripping rate of Example 1 and Example 2 that by adjusting the structure of the gas distribution disk (number of turns and aperture size), the uniformity can be controlled within 15% and the etching rate can be above 25,000 A / min.

[0055] It can be seen from the dry degumming uniformity and degumming rate of Example 2 and Example 3 that by adjusting the process parameters based on the optimized structure of the gas uniformizing disk (number of turns and aperture size), the uniformity can be stably controlled within 15% and the etching rate can be above 25,000 A / min.

[0056] In addition, as shown in Tables 1 and 2, the present invention also verifies the effect of via size on dry stripping etch rate and stripping uniformity. In Table 2, stripping uniformity is calculated using the industry's range method. In this embodiment, "uniformity" refers to "stripping uniformity."

[0057] Table 1 Dimensional data of 10 groups of through holes

[0058]

[0059] Table 2 Output parameters of the 10 experiments corresponding to Table 1 (uniformity < 15)

[0060]

[0061] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. A photoresist stripping method, using a wafer with photoresist, wherein the wafer is dry-etched using chlorine gas in a process before the photoresist stripping, characterized in that: The following steps are involved: Step 01: Placing the wafer in an etching chamber; a uniform gas plate with multiple through holes is provided in the etching chamber; the wafer is placed between the uniform gas plate and a microwave source; the uniform gas plate includes N circles of through hole units, where N ≥ 1; the through hole units include a plurality of through holes distributed along a circumference; the through hole units have different radii; Step 02: Oxygen and water are introduced into the etching chamber from above the wafer to soften the surface of the photoresist; Step 03: Expel the oxygen and water introduced in step 02; Step 4: 0.2-0.5g of water is introduced into the etching chamber from above the wafer and the microwave source is activated at the same time. As the water descends, it forms water vapor. The microwave source ionizes the water vapor into ions. The ionized water vapor descends to the wafer through the uniform gas plate to absorb chloride ions attached to the wafer. Step 05: Dry stripping is performed according to preset dry stripping parameters to remove the surface portion of the photoresist and the photoresist; wherein the preset dry stripping parameters include oxygen flow rate and nitrogen flow rate; the oxygen and nitrogen are both introduced into the etching chamber from above the wafer, the oxygen flow rate is 2000-4000 sccm, and the nitrogen flow rate is 200-800 sccm; At the same time, 0.2-0.5 g of water is continuously introduced into the etching chamber from above the wafer to absorb chloride ions attached to the wafer.

2. A photoresist stripping method according to claim 1, characterized in that: In step 04, the RF power of the microwave source is 1000-1400 W; the reaction pressure of the etching chamber is 2000-8000 mtorr.

3. A photoresist stripping method according to claim 1, characterized in that: In step 05, the preset dry stripping parameters also include radio frequency power and reaction pressure of the etching chamber; the radio frequency power of the microwave source is 1000-1400W; and the reaction pressure of the etching chamber is 2000-8000 mtorr.

4. The photoresist stripping method according to claim 1, wherein: In step 02, the total flow rate of oxygen introduced is 3500 sccm, and the introduction time is 30 s; the total amount of water introduced is 0.6 g, and the introduction time is 30 s.

5. A photoresist stripping method according to claim 1, characterized in that: In step 01, the gas uniformity disk is made of quartz material.

6. A photoresist stripping method according to claim 1, characterized in that: After step 05, return to step 04.

7. A photoresist stripping method according to claim 1, characterized in that: Step 01 specifically includes: Step S1: a robotic arm device is used to deliver the wafer in the wafer loading chamber to a position directly above a hot stage in an etching chamber; Step S2: The ceramic ejector mechanism located below the heat stage is raised and passes through the hollow area of ​​the heat stage and the robotic arm device in sequence to lift the wafer on the hollow area; the distance between the wafer and the heat stage is 9 mm.

Images