CN1739064A - Photoresist Removal - Google Patents

Abstract

Compositions and methods for semiconductor processing are disclosed. In one embodiment, a wet cleaning composition for removing photoresist is provided. The composition comprises a strong base; an oxidizing agent and a polar solvent. In another embodiment, a method of removing photoresist is provided. The method comprises the following steps: the coating comprises from about 0.1 to about 30 weight percent of a strong base; about 1 to about 30 weight percent oxidizing agent; from about 20 to about 95 wt% of a polar solvent; and removing the photoresist.

Description

Photoresist Removal

related application

This application claims priority to US Provisional Application Serial No. 60/434,971, filed December 20,2002.

field of invention

The present invention relates to the processing of semiconductors and, more particularly, to the removal of photoresist.

Background of the invention

Integrated circuits are fabricated through the sequential steps of coating a photoresist on a substrate, forming the photoresist layer by exposure and development, transferring the pattern to the substrate, and removing the photoresist. The above steps are repeated to form a multi-layer patterned circuit. For the photoresist removal step, plasma ashing is often used since it is difficult or impossible to remove etch photoresist residues by wet cleaning alone without damaging other materials.

Positive working photoresists are soluble in aqueous alkaline solutions and compositions of selected organic and inorganic compounds. However, photoresists that have been exposed to a vapor phase ion etchant, such as those used to etch dielectric materials, often form hard crusts or residues on the surface. The residue usually consists of cross-linked organic polymers and may contain small amounts of silicon, metals and halogens or other atoms.

Damascene or dual damascene processes typically use plasma etching as described above. The plasma etch may be a fluorine-based plasma etch for etching silicate inter-layer dielectric (ILD) materials. Such materials may include silicates, organosilicates and fluorosilicates. Fluorine-based plasma etching can fluorinate the cross-linked organic polymers that form the aforementioned residues. Fluorination generally improves chemical resistance. Thus, it is difficult, if not impossible, to remove these residues by conventional wet stripping processes. Ashing with oxidizing or reducing plasma can remove the residue. However, plasma ashing tends to damage ILD materials, especially low dielectric constant ILD materials.

Therefore, the removal of the photoresist needs to be able to remove the photoresist residue without damaging the ILD material.

Summary of the invention

Compositions and methods for semiconductor processing are disclosed. In one embodiment, a wet cleaning composition for removing photoresist is provided. The composition includes a strong base; an oxidizing agent; and a polar solvent.

In another embodiment, a method for removing photoresist is provided. The method comprises the steps of: (i) applying a wet cleaning composition comprising about 0.1 to about 30% by weight of a strong base, about 1 to about 30% by weight of an oxidizing agent, and about 20 to about 95% by weight of a polar solvent; and (ii) removing the light Engraving.

The present invention, together with other features and advantages of the present invention, may be more fully understood by reference to the following detailed description and accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Compositions and methods for semiconductor processing are disclosed herein. According to one aspect of the present invention, there is provided a wet cleaning composition for removing photoresist. The composition includes a strong base. For example, the strong base can result in a solution having a pH greater than about 11.5 even when the strong base constitutes no more than about 3.5% of the solution. That is, the strong base may not exceed about 3.5% by weight of the solution. However, as further described herein, higher strong base concentrations may be desirable. The strong base aids in the removal of photoresist, such as unexposed positive-tone photoresist. The composition also includes an oxidizing agent and a polar solvent. Strong bases of formula I below may be used in accordance with the teachings of the present invention.

Wherein R ¹ , R ² , R ³ and R ⁴ are hydrogen, alkyl or substituted alkyl respectively. Suitable strong bases include, but are not limited to, ammonium hydroxide, tetramethylammonium hydroxide (TMAH), choline hydroxide, and combinations comprising at least one of the foregoing strong bases. In an exemplary embodiment, the strong base includes tetramethylammonium hydroxide.

The cleaning composition or solution is particularly suitable for cleaning photoresist residues on semiconductor substrates. For example, in one embodiment, a semiconductor substrate is patterned to form trenches. This is done by using a photoresist method. The cleaning solution can be used to remove photoresist and any residue from the trenches and substrate. Semiconductor features, such as metal lines, can be formed in the trenches, and then the metal lines are insulated by chemical mechanical planarization. Further semiconductor processing follows to form a complete semiconductor device.

In exemplary embodiments, the compositions of the present invention include greater than or equal to about 0.1 wt % strong base, preferably greater than or equal to about 1 wt % strong base, more preferably greater than or equal to about 5 wt % strong base. In exemplary embodiments, the compositions of the present invention further comprise less than or equal to about 30 wt % strong base, preferably less than or equal to about 20 wt % strong base, more preferably less than or equal to about 10 wt % strong base.

The composition further includes an oxidizing agent. Suitable oxidizing agents include, without limitation, inorganic oxidizing agents, organic oxidizing agents, such as amine-N-oxides, perborates, persulfates, percarbonates, and combinations comprising at least one of the foregoing oxidizing agents. In exemplary embodiments, the oxidizing agent includes an organic oxidizing agent. According to the teaching of the present invention, organic oxidizing agents of the following general formula II can be used.

Wherein R ¹ , R ² and R ³ can be hydrogen, methyl or other substituted or unsubstituted alkyl groups. ^R1 and ^R2 may form the two ends of an alkyl chain.

Although peroxides such as hydrogen peroxide and substituted alkyl or aryl peroxides can be used in accordance with the teachings of the present invention, amine-N-oxides have the advantage of being milder oxidizing agents compared to common peroxides . Also, amine-N-oxides decompose more slowly than ordinary peroxides. In particular, it is known that hydrogen peroxide decomposes rapidly in an alkaline environment to produce oxygen and water, and the above conditions will lead to short bath life, especially at temperatures greater than room temperature. Furthermore, hydrogen peroxide is unstable in the presence of oxidizable organic species such as amines and alcohols. Therefore, according to the teachings of the present invention, non-peroxide oxidizing agents are preferred.

In exemplary embodiments, the compositions of the present invention include greater than or equal to about 1 wt % oxidizing agent, preferably greater than or equal to about 5 wt % oxidizing agent, more preferably greater than or equal to about 10 wt % oxidizing agent. In exemplary embodiments, the compositions of the present invention further comprise less than or equal to about 30 wt % oxidizing agent, preferably less than or equal to about 20 wt % oxidizing agent, more preferably less than or equal to about 15 wt % oxidizing agent.

The compositions of the present invention further comprise polar solvents. The polar solvent dissolves ionic components in the photoresist and photoresist residue. Suitable polar solvents include, without limitation, water, ethylene glycol, propylene glycol, other glycol solvents, glycol ethers, alcohols, amides, carbonates, and combinations comprising at least one of the foregoing polar solvents. In an exemplary embodiment, the polar solvent includes water due to its low cost and non-toxicity.

In exemplary embodiments, the compositions of the present invention comprise greater than or equal to about 20 wt % polar solvent, preferably greater than or equal to about 30 wt % polar solvent, more preferably greater than or equal to about 40 wt % polar solvent. In an exemplary embodiment, the composition of the present invention further comprises less than or equal to about 95 wt % polar solvent, preferably less than or equal to about 85 wt % polar solvent, more preferably less than or equal to about 75 wt % polar solvent.

The compositions of the present invention may further comprise a chelating agent. Suitable chelating agents include, but are not limited to, unsubstituted triazoles, substituted triazoles, thiazoles, tetrazoles, imidazoles, phosphates, thiols and azines, glycerols, amino acids, carboxylic acids , alcohols, amides, quinolines, and combinations comprising at least one of the foregoing chelating agents.

Unsubstituted triazoles include, but are not limited to, 1,2,3-triazole and 1,2,4-triazole. In addition, triazoles may be substituted with alkyl, amino, benzo, thiol, mercapto, imino, carboxyl, nitro, and combinations comprising at least one of the foregoing substituents. Substituted triazoles include, but are not limited to, benzotriazole, polytriazole, 5-phenyl-benzotriazole, 5-nitro-benzotriazole, 1-amino-1,2,3-triazole, 1-amino-1,2,4-triazole, 1-amino-5-methyl-1,2,3-triazole, hydroxybenzotriazole, 2-(5-amino-phenyl)-benzo Triazole, 3-amino-1,2,4-triazole, 3-isopropyl-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 5-phenylthio - Benzotriazoles, halobenzotriazoles, naphthotriazoles. Thiazoles, tetrazoles, imidazoles, phosphates, thiols, and azines include, without limitation, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 5-aminotetrazole, 5-amino-1 , 3,4-thiadiazole-2-thiol, thiazole, triazine, methyltetrazole, 1,3-dimethyl-2-imidazolidinone, 1,5-pentylidenetetrazole, 1- Phenyl-5-mercaptotetrazole, diaminomethyltriazine, mercaptobenzothiazole, imidazolinthione, mercaptobenzimidazole, 4-methyl-4H-1,2,4-triazole-3-sulfur Alcohols, benzothiazoles, tricresyl phosphates, indiazoles, and combinations comprising at least one of the foregoing. Glycerols, amino acids, carboxylic acids, alcohols, amides, quinolines include but are not limited to guanine, adenine, glycerol, thioglycerol, nitrilotriacetic acid, salicylamide, iminodiacetic acid, benzene Guanamine, melamine, thiocyanuric acid, anthranilic acid, 8-hydroxyquinoline, 5-carboxylic acid-benzotriazole, 3-mercaptopropanol, boric acid and iminodiacetic acid.

Chelating agents may be added to the composition to prevent etching or corrosion of metal surfaces such as copper, tungsten, aluminum and alloys thereof when exposed to the composition. Therefore, chelating agents can be used to improve the compatibility of the composition with metals and insulating materials used in semiconductor devices.

In exemplary embodiments, the compositions of the present invention comprise less than or equal to about 10 wt % chelating agent, preferably less than or equal to about 7 wt % chelating agent, more preferably less than or equal to about 4 wt % chelating agent.

The compositions of the present invention may further comprise co-solvents. Co-solvents may be added to improve the performance of the composition, ie the ability of the composition to swell, dissolve and strip photoresist residue. Suitable co-solvents include, but are not limited to, N,N-dimethyl diglycolamine, 1,8-diazabicyclo[5.4.0]undecene, aminopropylmorpholine, triethanolamine, methyl Substituted alkylamines or alkanolamines of ethanolamines, diols such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, such as diethylene glycol monoethyl ether, dipropylene glycol propyl ether, ethylene glycol phenyl ether , dipropylene glycol butyl ether, diethylene glycol monobutyl ether, glycol ethers of polyethylene glycol ether, and combinations comprising at least one of the above co-solvents.

Furthermore, the co-solvent should be polar. Polar compounds will be miscible with polar solvents and will dissolve ionic species, such as tetramethylammonium hydroxide. In exemplary embodiments, the compositions of the present invention include less than or equal to about 50 wt % co-solvent, preferably less than or equal to about 30 wt % co-solvent, more preferably less than or equal to about 20 wt % co-solvent.

The composition may further include a surfactant. Surfactants may be added to help strip insoluble photoresist residue and reduce silicon etch that may occur when exposed to strong bases. Suitable surfactants include, but are not limited to, anionic, cationic and nonionic surfactants, such as fluoroalkyl surfactants, polyethylene glycols, polypropylene glycols, polyethylene glycol or polypropylene glycol ethers, carboxylates dodecylbenzenesulfonic acid or its salts, polyacrylate polymers, siloxane or modified siloxane polymers, acetylene glycols or modified acetylene glycols, alkylammonium salts Class or modified alkyl ammonium salts, and combinations comprising at least one of the foregoing surfactants.

In exemplary embodiments, the compositions of the present invention comprise less than or equal to about 20 wt % surfactant, preferably less than or equal to about 15 wt % surfactant, more preferably less than or equal to about 10 wt % surfactant.

Another aspect of the invention provides a method of removing photoresist. The method includes applying a wet cleaning composition comprising about 0.1 to about 30 wt % strong base, about 1 to about 30 wt % oxidizing agent, and about 20 to about 95 wt % polar solvent; and (ii) removing the photoresist.

All the terms photoresist herein can be applied generally to any layer containing photoresist. Thus, photoresist and photoresist residues can be removed using the compositions and methods herein, for example, in accordance with the teachings of the present invention. Additionally, the teachings of the present invention are applicable to the removal of any photoresist residue, ie, from an etching process including, but not limited to, fluorine-based plasma etching.

Although exemplary embodiments of the present invention have been described, it should be understood that the present invention is not limited to the above-mentioned specific embodiments, and various other changes or modifications may be made by those skilled in the art without departing from the scope or spirit of the present invention. The following examples are provided to illustrate the scope and spirit of the invention. The invention embodied in the examples should not be limited by the examples given as examples only.

Example

The following formulations substantially clean photoresist from semiconductor substrates. According to the teachings of the present invention, substantially cleaned means that more than 80% of the photoresist is removed from the semiconductor device, which can be detected by optical microscopy. The substrate used herein comprises a chemically amplified photoresist coated on an organosilicate insulating coated silicon wafer. In addition, the photoresist is exposed to patterning radiation and developed, and then the pattern is transferred to the insulator by plasma etching.

Example 1

Composition A was prepared as follows: Composition A components weight percent N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 water 79.2

In this example N-methylmorpholine-N-oxide was provided and used as a 50 wt% solution, while tetramethylammonium hydroxide (TMAH) was provided and used as a 25 wt% solution, and in other examples N- Methylmorpholine-N-oxide and tetramethylammonium hydroxide (TMAH).

The photoresist substrate was rinsed by dipping in Composition A at 70°C for 20 minutes. All photoresist and etch residues were removed from the substrate as observed by light microscopy. No significant etching of the insulating material was observed.

Example 2

Compositions containing 13.5 wt% N-methylmorpholine-N-oxide, 7.3 wt% TMAH, 78.9 wt% water and 0.3 wt% inhibitor 2-mercaptobenzimidazole (2-MBI) were prepared as shown below B, C and D. 2-MBI was included in the formulation to retard the etching of copper or other materials by the solution as seen in Example 3. combination additive B 2,4-Diamino-6-methyl-1,3,5-triazine C 5-amino-1,3,4-thiadiazole-2-thiol D. 2-Mercaptobenzimidazole

The photoresist substrate was cleaned by dipping in a stripper at 70°C for 20 minutes.

Example 3

The etch rate of uncoated copper (Cu) on silicon wafers was measured using the compositions AD prepared above. A copper layer was deposited by physical vapor deposition to a thickness of about 1000 Angstroms (Å). The samples were dipped in the composition for a fixed period of time, and the thickness before and after dipping was measured using four-point probe electrometry. The etch rate was calculated by dividing the difference in thickness before and after etching by the time in minutes. The etch rates of compositions AD are shown below. combination Cu etching rate at 70°C (Å/min) A 15.8 B 1.5 C 3.2 D. 1.1

Example 4

Composition E was prepared as follows: Composition E components weight percent N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.5 2-Mercaptobenzimidazole 0.08 water 64.1 N,N-Dimethyl diglycolamine 15.0 Polyethylene glycol 4-nonylphenyl ether 0.05

Polyethylene glycol 4-nonylphenyl ether is a surfactant containing about 5 ethylene glycol repeat units. After immersion in Composition E for 15 minutes at 70°C, 100% of the photoresist residue was removed from the entire area of the semiconductor.

Example 5

Composition F was prepared as follows: Composition F components weight percent N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 6.5 2-Mercaptobenzimidazole 0.01 water 76.09 Nonionic Fluorinated Surfactant 0.1

The potential etching effects of Compositions A and F on polysilicon were determined by immersing 1000 Å wafer sections of polysilicon in Compositions A and F, respectively, at 70°C for 15 minutes. Composition F exhibited no observable etching or roughening of the polysilicon surface. Composition A made the polysilicon surface slightly observablely rough.

Example 6

Composition G was prepared as follows: Composition G components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 6.5 2-Mercaptobenzimidazole 0.01 water 79.9 Modified Alkyne Diol Surfactant 0.1

The photoresist substrate was cleaned by immersion in Composition G at 70°C for 20 minutes. All photoresist and etch residues were removed from the substrate as observed by light microscopy. However, etching or roughening of polysilicon was observed under the same conditions.

Example 7

Composition H was prepared as follows: Composition H components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 3.5 components wt% 2-Mercaptobenzimidazole 0.01 water 82.89 2,4,7,9-Tetramethyl-5-decyne-4,7-diol 0.1

As described in Example 5, polysilicon-coated wafers showed no observable etching or roughening after immersion in Composition H for 15 minutes at 70°C. However, Composition H was unable to remove most of the photoresist crust from the substrate.

Example 8

Composition I was prepared as follows: Composition I components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.2 water 43.9 Nonionic Fluorinated Surfactant 0.1 Diethylene glycol monobutyl ether 5 N,N-Dimethyl diglycolamine 15 1,8-diazabicyclo[5.4.0]undecene 15

The use of Composition I removed the photoresist while moderately protecting the polysilicon. The polysilicon showed some etching or roughening when immersed in the sample for 15 minutes at 70°C. The copper etch rate remained at 0.15 Å/min, while the tungsten etch rate was 0.67 Å/min. The above copper and tungsten samples were dipped at 70°C for 40 minutes.

Example 9

Composition J was prepared as follows: Composition J components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.2 water 49 pentamethyldiethylenetriamine 30

Composition J completely removed the photoresist and residue from the trench features and removed about 40% of the photoresist residue from the connection pad area. The trench features described above consist of 1:1 line/space pairs of approximately 0.2 microns, while the connection pad areas consist of a square array of approximately 2 micron square dummy features.

Example 10

Composition K was prepared as follows: Composition K components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.2 water 58.0 pentamethyldiethylenetriamine 20.0 boric acid 1.0

After immersion in Composition K for 20 minutes at 70°C, Composition K produced some residual photoresist in the trench features while cleaning off 5% of the connection pad area.

Example 11

Composition L was prepared as follows: Composition L components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.2 water 49.0 N-(3-aminopropyl)-morpholine 30.0

Composition L completely removed the photoresist from the trench features and greater than 99.9% of the photoresist from the connection pad areas after 16 minutes of immersion at 70°C.

Example 12

Composition M was prepared as follows: Composition M components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.2 water 49.0 N-Hydroxyethylmorpholine 30.0

Composition L removed 10% of the photoresist from the trench features and no photoresist from the connection pad areas after 16 minutes of immersion at 70°C.

Example 13

Composition N was prepared as follows: Composition N components wt% N-methylmorpholine-N-oxide (50wt% solution) 13.5 TMAH (25wt% solution) 7.3 2-Mercaptobenzimidazole 0.08 water 64.1 N,N-Dimethyl diglycolamine 15.0

Composition N completely removed the photoresist crust from the trench features and removed 95% of the photoresist from the connection pad area after 20 minutes of immersion at 70°C.

Example 14

Composition O was prepared as follows: Composition O components wt% N-methylmorpholine-N-oxide (50wt% solution) 12.6 TMAH (25wt% solution) 11.7 2-Mercaptobenzimidazole 0.08 water 75.3 Polyethylene glycol dinonylphenyl ether 0.3

Polyethylene glycol dinonylphenyl ether is a surfactant containing about 150 repeating units of ethylene glycol. After immersion at 70°C for 20 minutes, Composition O completely removed the photoresist crust from the trench features and completely removed the photoresist from the connection pad areas.

Comparative example 1

Comparative Example 1 consisted of 10 wt% hydroxylamine, 10 wt% water and 80 wt% diglycolamine. The etched photoresist substrates were immersed in the composition at 70°C for 30, 50 and 60 minutes, respectively, and then rinsed with water. Examination by light microscopy showed that Comparative Composition 1 dissolved the photoresist from below the upper layer of photoresist residue, but the remaining layer of photoresist residue cracked and adhered to the sample in all areas.

Claims (23)

1. cleaning solution comprises:

Polar solvent; With

When account for described solution be no more than about 3.5wt% the time, the pH that makes described solution is greater than about 11.5 alkali.

2. the cleaning solution of claim 1, wherein said polar solvent are one of in water, alcohol, ethylene glycol, acid amides, propylene glycol, carbonic ester and the glycol.

3. the cleaning solution of claim 1, wherein said alkali are the nitrogen-containing compounds that one of contains in hydrogen, alkyl and the substituted alkyl as side chain.

4. the cleaning solution of claim 1, wherein said polar solvent accounts for about 20% to about 95% of described solution weight.

5. the cleaning solution of claim 1, wherein said alkali are one of in ammonium hydroxide and the tetramethylammonium hydroxide.

6. the cleaning solution of claim 1, wherein said alkali accounts for about 0.1% to about 30% of described solution weight.

7. the cleaning solution of claim 1, it one of further comprises in oxygenant, cosolvent and the sequestrant.

8.pH the cleaning solution greater than about 11.5 comprises:

Polar solvent;

Alkali; With

One of in oxygenant, cosolvent, surfactant and the sequestrant.

9. the cleaning solution of claim 8, wherein said oxygenant accounts for about 1% to about 30% of described solution.

One of 10. the cleaning solution of claim 8, wherein said oxygenant is amine-N-oxide, perborate, in percarbonate and the superoxide.

11. the cleaning solution of claim 8, wherein said oxygenant are the nitrogen-containing compound that comprises one of hydrogen, methyl and pendent alkyl groups.

12. the cleaning solution of claim 8, it is the highest by about 50% that wherein said cosolvent accounts for described solution weight.

13. the cleaning solution of claim 8, wherein said cosolvent are one of in alkyl amine, alkanolamine and the glycol.

14. the cleaning solution of claim 8, the described solution weight of wherein said surfactant comprise is the highest by about 20%.

15. the cleaning solution of claim 8, wherein said surfactant are one of in fluoroalkyl, glycol, carboxylate, dodecylbenzene sulfonic acid, dodecyl benzene sulfonate, siloxane polymer, polypropylene salt polymkeric substance, acetylenic glycols, alkylammonium and the alkylammonium salt.

16. the cleaning solution of claim 8, it is the highest by about 10% that wherein said sequestrant accounts for described solution weight.

17. the cleaning solution of claim 8, wherein said sequestrant are one of in triazole, thiazole, tetrazolium, imidazoles, phosphate, mercaptan, azine, glycerine, amino acid, carboxylic acid, alcohol, acid amides and the quinoline.

18. device comprises:

The semiconductor chip that has the patterning groove on it; With

The metal wire that comprises in the groove cleans groove to comprise metal wire with solution, and the pH of solution is greater than about 11.5.

19. the device of claim 18, wherein solution one of comprises in polar solvent, oxygenant, cosolvent, surfactant and the sequestrant.

21. method comprises:

With the photoresist patterning on the semiconductor chip; With

Clean semiconductor chip with pH greater than about 11.5 cleaning solution.

22. the method for claim 20, wherein cleaning solution one of comprises in polar solvent, oxygenant, cosolvent, surfactant and the sequestrant.

23. the method for claim 20, wherein said cleaning comprises from semiconductor chip removes photoresist.

24. the method for claim 20 further comprises:

Behind described patterning, on semiconductor chip, form groove;

At described cleaning back plated metal line in groove; With

Semiconductor chip is carried out chemical-mechanical planarization.