Novel method for removing mask photoresist

Abstract

The invention relates to the technical field of semiconductor wet cleaning, in particular to a novel method for removing mask photoresist. The novel method for removing the photoresist on the mask comprises the following steps: carrying out UV light irradiation treatment on the mask, carrying out plasma gas bombardment treatment on the mask, spraying a developing solution on the surface of the mask, washing with high-temperature hot water, and spin-drying. Compared with a traditional SPM solution, the novel method for removing the photoresist of the mask has the advantages that the photoresist removal effect is better, meanwhile, the concentration residue of sulfate ions of the mask can be reduced, the generation of the Haze defect of the mask is reduced, and the service life of the mask is prolonged; the problem that in the prior art, dirt generated due to incomplete photoresist removal cannot be removed is solved, and product scrapping caused by the dirt is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor wet cleaning, and in particular to a novel method for removing mask photoresist. Background Art

[0002] A mask is a mold required for the semiconductor industry and integrated circuit manufacturing. It uses the pattern on the mask to replicate the pattern on the wafer through an exposure process. Common types of mask substrates include binary masks and phase-shift masks. The binary mask is composed of a quartz substrate, a chrome layer, and a photoresist, while the phase-shift mask has an additional phase-shift layer between the quartz substrate and the chrome layer.

[0003] The template is a micro-processing process, which involves exposure, development, etching, degumming and other processes. Patent technology document CN104252103A discloses a method for removing residual photoresist after photolithography rework, including the following steps: soaking the wafer with residual photoresist in a hydrofluoric acid solution; cleaning the wafer with residual photoresist with an SPM solution; and cleaning the wafer with residual photoresist with an APM. The present invention can remove the photoresist that still remains on the wafer after rework, thereby reducing production costs, improving the utilization rate of production raw materials, and avoiding waste.

[0004] However, the traditional SPM degumming is to use sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) to mix and produce carboxylic acid (H2SO5), H2SO4+ H2O2, H2SO5+ H2O2. H2SO5 has a very strong oxidizing power and can oxidize and decompose organic matter (photoresist) into CO2 for removal. However, due to the introduction of sulfuric acid in the degumming process, although it has been rinsed with hot water, some sulfate ions will still remain on the surface of the mask. Under the conditions of exposure, the sulfate ions remaining on the surface of the mask and the ammonia ions in the environment react chemically to produce crystals. The crystals gradually grow into defects and are then printed on the wafer by photolithography, which has a great impact on the wafer yield. With the continuous development of semiconductor technology, the wavelength of photolithography is getting shorter and shorter, and the haze defect is becoming more and more serious. The frequency of occurrence is getting higher and higher, and the number of masks affected by it is as high as 15%-20%. HAZE defects cause a local transmittance loss of about 10% in the mask in the early stage, and can be as high as 50% or more in the later stage, which seriously affects the yield of wafer products. Therefore, effectively controlling mask HAZE defects is particularly important for mask production at 40nm and higher-end process nodes. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a new method for removing mask photoresist, so as to provide a new method for removing mask photoresist, which can reduce the generation of mask HAZE defects, extend the service life of the mask, and solve the difficulty of removing dirt caused by incomplete degumming in the prior art, thereby reducing the problem of product scrapping and low yield rate caused by dirt.

[0006] Based on the above purpose, the present invention provides a novel method for removing mask photoresist, which is suitable for 40nm mask stripping requirements and includes the following steps: S1: UV light irradiation treatment of the mask; S2: Plasma gas bombardment treatment is performed on the mask after UV pretreatment; S3: spraying a developing solution on the mask surface after the plasma gas treatment; S4: Rinse the mask obtained in step S3 with deionized water and spin dry.

[0007] Preferably, the UV light irradiation treatment in step S1 is irradiation with 172nm UV light for 8-15min, the purpose of which is to break the chemical bonds of organic matter, improve the hydrophilicity of the mask surface, oxidize the mask surface, and protect the pattern from damage in the subsequent stripping process.

[0008] Preferably, the ionization gas source for the plasma gas bombardment treatment in step S2 is high-purity oxygen, and the treatment time is 6-10 minutes. The purpose is that after O2 is ionized, the oxygen atom loses an electron to form oxygen ions, and the generated oxygen ions bombard the mask photoresist, generating physical and chemical reactions to remove the photoresist.

[0009] Preferably, the developer in step S3 is a TMAH solution with a concentration of 1%-5%, and the cleaning time is 5-10 minutes, the purpose of which is to dissolve residual organic matter and photoresist.

[0010] Preferably, the developer is sprayed in step S3 in a mist-like manner.

[0011] Preferably, the temperature of the deionized water in step S4 is 70-80° C. and the cleaning time is 8-12 min, the purpose of which is to rinse the TMAH solution remaining on the mask.

[0012] Preferably, the drying process in step S4 is to use a high speed to generate centrifugal force to dry the water stains on the mask.

[0013] The beneficial effects of the present invention are as follows: the photoresist removal method of UV irradiation + plasma gas bombardment + TMAH washing is adopted, which has a better photoresist removal effect, and can reduce the residual sulfate ion concentration of the mask, reduce the generation of mask Haze defects, and extend the service life of the mask.

[0014] A novel method for removing mask photoresist is provided, which solves the difficulty of the prior art that dirt generated by incomplete photoresist removal cannot be removed, reduces product scrapping due to dirt, saves production costs, and shortens product delivery cycle. The invention is simple and convenient to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description. Figure 1 Embodiment 2 of the present invention is a photoresist removal process flow chart; Figure 2 A mask with photoresist used in Example 2 of the present invention; Figure 3 This is the mask after photoresist removal in Example 2 of the present invention. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0017] Embodiment 1: A novel method for removing mask photoresist, the specific implementation steps are as follows: (1) Take a mask with glue after exposure, development and etching, irradiate it with 172nm UV light, and expose it for 8 minutes; (2) Placing the UV pretreated mask in a vacuum environment and using high-purity oxygen as the ionization gas source, and subjecting it to plasma gas bombardment for 6 minutes; (3) Place the mask after plasma gas treatment on a rotating chuck, and spray 1% TMAH developer onto the mask surface through a mist nozzle for 5 minutes; (4) The mask rinsed with TAMH was rinsed with deionized water at 70°C for 8 minutes, and then dried to obtain a cleaned mask.

[0018] Embodiment 2: A novel method for removing mask photoresist, the specific implementation steps are as follows: (1) Take a mask with glue after exposure, development and etching, irradiate it with 172nm UV light, and expose it for 12 minutes; (2) Placing the UV pretreated mask in a vacuum environment and using high-purity oxygen as the ionization gas source, and subjecting it to plasma gas bombardment for 10 minutes; (3) Place the mask after plasma gas treatment on a rotating chuck, and spray 3% TMAH developer onto the mask surface through a mist nozzle for 7 minutes; (4) The mask rinsed with TAMH was rinsed with deionized water at 75°C for 10 minutes, and then dried to obtain a cleaned mask.

[0019] Embodiment 3: A novel method for removing mask photoresist, the specific implementation steps are as follows: (1) Take a mask with glue after exposure, development and etching, irradiate it with 172nm UV light, and expose it for 15 minutes; (2) Placing the UV pretreated mask in a vacuum environment and using high-purity oxygen as the ionization gas source, and subjecting it to plasma gas bombardment for 10 minutes; (3) Place the mask after plasma gas treatment on a rotating chuck, and spray 5% TMAH developer onto the mask surface through a mist nozzle for 8 minutes; (4) The mask rinsed with TAMH was rinsed with deionized water at 80°C for 12 minutes, and then dried to obtain a cleaned mask.

[0020] Comparative Example 1: A method for removing mask photoresist, the specific implementation steps are as follows: (1) Take a mask with glue after exposure, development and etching, and soak it in SPM solution (the molar ratio of H2SO4 and H2O2 is 5:1) for 10 minutes; (2) Then, the mixture was treated in SC1 solution (NH4OH:H2O2:DI water in a molar ratio of 1:1:10) for 10 min; (3) The mask was rinsed with deionized water at 70°C for 10 minutes, and then dried to obtain a cleaned mask.

[0021] Comparative Example 2: A method for removing mask photoresist, the specific implementation steps are as follows: (1) Take a mask with glue after exposure, development and etching, and soak it in SPM solution (the molar ratio of H2SO4 and H2O2 is 5:1) for 10 minutes; (2) Then, the sample was cleaned with ozone water at a concentration of 85 mg / l, a temperature of 30 °C, and a flow rate of 500 ml / min for 5 min. (4) Place the ozone-cleaned mask on a rotating chuck, and spray 3% TMAH developer onto the mask surface through a mist nozzle for 10 minutes; (5) The mask rinsed with TAMH was rinsed with deionized water at 80°C for 10 minutes, and then dried to obtain a cleaned mask.

[0022] Performance Testing Cleaning yield: KLA's 5xx series was used to detect contaminant particles on the photomask surface. The test results are shown in Table 1. Phase loss: MPM248 phase measurement equipment is used, and the test results are shown in Table 1; Ion Residual Degree (SO4 2- ): The test was carried out using 850 ion chromatograph, and the test results are shown in Table 1.

[0023] Haze defect: After the sample is stored for 180 days, observe whether crystallization occurs and the probability of crystallization. The test results are shown in Table 1.

[0024] Table 1 Performance test results From the data analysis, it can be seen from Examples 1-3 in Table 1 that the novel method for removing mask photoresist of the present invention can finally obtain a mask with high yield, and both phase loss and ion residue can reach very excellent levels. At the same time, no Haze defect phenomenon occurs after 180 days.

[0025] It can be seen from the embodiments and comparative examples in Table 1 that the present invention greatly reduces the residual sulfate ion concentration of the mask and the generation of mask Haze defects by adopting the photoresist removal method of UV irradiation + plasma gas bombardment + TMAH washing, and has low loss, greatly extending the service life of the mask, while having a high yield rate and saving production costs.

[0026] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A novel method for removing mask photoresist, suitable for 40nm mask photoresist removal requirements, characterized in that: The steps include: S1: UV light irradiation treatment of the mask; S2: Plasma gas bombardment treatment is performed on the mask after UV pretreatment; S3: spraying a developing solution on the mask surface after the plasma gas treatment; S4: Rinse the mask obtained in step S3 with deionized water and spin dry.

2. The novel method for removing mask photoresist according to claim 1, characterized in that: The UV light irradiation treatment in step S1 is performed by irradiating with 172 nm UV light for 8-10 min.

3. The novel method for removing mask photoresist according to claim 1, characterized in that: The ionized gas source for the plasma gas bombardment treatment in step S2 is high-purity oxygen, and the treatment time is 6-10 minutes.

4. The novel method for removing mask photoresist according to claim 1, characterized in that: The developer in step S3 is a TMAH solution with a concentration of 1%-5%, and the cleaning time is 5-10 minutes.

5. The novel method for removing mask photoresist according to claim 1, characterized in that: The developer solution in step S3 is sprayed in a mist-like manner.

6. The novel method for removing mask photoresist according to claim 1, characterized in that: The temperature of the deionized water in step S4 is 70-80° C., and the cleaning time is 8-12 minutes.

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