Field of Invention

The present invention relates to a photoresist stripping composition.

Background of the Invention

In the production of semiconductor devices, such as semiconductor integrated circuits (1C) and large-scale integrated circuits (LSI); display devices, such as liquid crystal displays (LCD) and light-emitting diode (LED) displays; MEMS (Micro Electro Mechanical Systems) and sensor devices; and other electronic equipment, a microelectronic circuit is produced, for example, by the following steps: a conductive metal film or a dielectric film is formed on a silicon, glass, or ceramic substrate; subsequently, after the surface of the conductive metal film or the dielectric film is coated with a photosensitive polymer composition called a photoresist, a photomask is used for selective exposure to form a resist pattern; and dry etching or wet etching is then performed using the obtained resist pattern as an etching mask. Further, a process of forming an electronic circuit by wet plating or vacuum deposition using, as a template, a resist pattern formed on a substrate, is also known.

A photoresist stripping agent is used to strip the remaining photoresist and dry etching residue from the substrate after the dry etching step. A photoresist stripping agent is also used to strip the photoresist from the substrate after an electronic circuit is formed by wet etching, wet plating, or vacuum deposition.

For typical semiconductor devices, a multi-level interconnect structure is widely applied. Copper interconnects are mainly used in a multi-level interconnect structure of advanced semiconductor devices. Considering the economics of the manufacturing process, it is desirable that one kind of photoresist stripping composition is used not only for copper interconnect structures, but also for other types of interconnect structures.

As a photoresist stripping agent that exhibits excellent stripping performance, a non-aqueous photoresist stripper solution containing tetramethylammonium hydroxide (TMAH) and an organic solvent, such as dimethyl sulfoxide, has been proposed (U.S. Patent Application Publication No. 2010/0104824 A1).

Summary of the Invention

Technical Problem

An object of the present invention is to provide a photoresist stripping composition that causes reduced damage on copper interconnects while retaining sufficient stripping ability.

Solution to Problem

The present inventor conducted extensive research to solve the above problem. As a result, the inventor found that known photoresist stripping compositions comprising an organic solvent, tetramethylammonium hydroxide (TMAH), and alkanolamine have problems regarding either insufficient photoresist stripping ability, or damage on copper. Surprisingly, however, a photoresist stripping composition comprising an organic solvent, choline hydroxide, and triethanolamine significantly suppressed damage on copper. The present invention has been accomplished by further research based on this finding, and includes the following embodiments.

Item 1. A photoresist stripping composition comprising:

(A) at least one organic solvent;

(B) choline hydroxide; and

(C) triethanolamine.

Item 2.

The photoresist stripping composition according to Item 1, containing the choline hydroxide in an amount of 0.8 to 20 wt% based on the total weight of the photoresist stripping composition.

Item 3.

The photoresist stripping composition according to Item 1 or 2, containing triethanolamine in an amount of 5 to 20 wt% based on the total weight of the photoresist stripping composition.

Item 4.

The photoresist stripping composition according to any one of Items 1 to 3, containing the organic solvent in an amount of 50 wt% or more based on the total weight of the photoresist stripping composition.

Item 5.

The photoresist stripping composition according to any one of Items 1 to 4, wherein the organic solvent is an aprotic polar solvent.

Item 6.

The photoresist stripping composition according to any one of Items 1 to 5, wherein the organic solvent is dimethyl sulfoxide and/or N-methylpyrrolidone.

Item 7. Use of a composition comprising:

(A) at least one organic solvent;

(B) choline hydroxide; and

(C) triethanolamine, for stripping a photoresist on an electronic device having copper interconnects.

Item 8.

A photoresist stripping method, comprising applying a composition to a photoresist on an electronic device having copper interconnects, the composition comprising:

(A) at least one organic solvent;

(B) choline hydroxide; and

(C) triethanolamine.

Advantageous Effects of Invention

According to the present invention, a photoresist stripping composition that causes reduced damage on copper interconnects, while retaining sufficient stripping ability, can be provided.

Detailed Description of the Invention

1. Photoresist Stripping Composition

The photoresist stripping composition of the present invention comprises:

(A) at least one organic solvent;

(B) choline hydroxide; and (C) triethanolamine.

1.1. Organic Solvent (A)

The photoresist stripping composition of the present invention comprises at least one organic solvent. The photoresist stripping composition of the present invention may comprise only one kind of organic solvent; or may comprise a combination of two or more kinds of organic solvent.

The photoresist stripping composition of the present invention may comprise at least one organic solvent preferably selected from aprotic polar solvents, more preferably selected from aprotic polar solvents having a relative permittivity measured at 20 °C and 1 kHz of 20 to 50, even more preferably selected from the group consisting of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), methyl diglycol (MDG), buthyl diglycol (BDG), N,N- dimethylformamide, N,N-dimethylacetamide, g-butyrolactone, ethylene glycol, propylene glycol, and mixtures thereof. The photoresist stripping composition of the present invention may preferably comprise at least one organic solvent selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and mixtures thereof. DMSO is preferred in view of the fact that DMSO promotes solubility of etching residue, residual photoresist, and photoresist by-products on a semiconductor, a display substrate, and the like.

DMSO is, for example, but not limited to, a product commercially available from Toray Fine Chemicals Co., Ltd.

In view of cleaning performance of the photoresist stripping composition, the total content of the organic solvent(s) in the photoresist stripping composition of the present invention is preferably more than 50 wt%, and more preferably more than 60 wt%, based on the total weight of the composition. The upper limit of the total content of the organic solvent(s) in the composition is not limited as long as a sufficient level of photoresist stripping ability is achieved, and damage on metals such as copper is sufficiently suppressed when the photoresist stripping composition is used. The upper limit is preferably 95 wt% or less, and more preferably 90 wt% or less, in view of suppression of damage on metals such as copper. 1.2. Choline Hydroxide (B)

The photoresist stripping composition of the present invention comprises choline hydroxide.

Choline hydroxide is also known as (2-hydroxyethyl)trimethylammonium hydroxide. Choline hydroxide is, for example, but not limited to, a product commercially available from Huntsman Corporation.

In view of photoresist stripping ability, the content of the choline hydroxide in the photoresist stripping composition of the present invention is preferably 1 wt% or more, based on the total weight of the composition. In view of damage on metals such as copper, the upper limit is preferably 10 wt% or less, and more preferably 5 wt% or less.

1.3. Triethanolamine (C)

The photoresist stripping composition of the present invention comprises triethanolamine. Because of the presence of triethanolamine in the photoresist stripping composition of the present invention, damage on metals such as copper can be suppressed when the photoresist stripping composition is used.

In view of damage on metals such as copper, the content of the triethanolamine in the photoresist stripping composition of the present invention is usually 0.1 wt% or more, preferably 1 wt% or more, and more preferably 5 wt% or more, based on the total weight of the composition. In view of photoresist stripping ability, the upper limit is preferably 50 wt% or less, and more preferably 30 wt% or less.

Triethanolamine is, for example, but not limited to, a product commercially available from Dow Chemical Company and Nippon Shokubai Co., Ltd.

1.4. Other Components The photoresist stripping composition of the present invention may further contain, in addition to the above components, components commonly used as components of a photoresist stripping agent, which are at least one component selected from the group consisting of surfactants, organic acids, hydrogen fluoride or salts thereof, chelating agents, corrosion inhibition agents, anti-foaming agents, and preservative agents. Such components may be commercially available products.

1.5. Uses

The photoresist stripping composition of the present invention is used to strip the remaining photoresist and dry etching residue from a substrate after a dry etching step in the production of semiconductor devices, such as semiconductor integrated circuits (IC) and large-scale integrated circuits (LSI); display devices, such as liquid crystal displays (LCD) and light- emitting diode (LED) displays; MEMS (Micro Electro Mechanical Systems) and sensor devices; or other electronic equipment.

2. Photoresist Stripping Method

The photoresist stripping method of the present invention is a method for stripping a photoresist using the photoresist stripping composition of the present invention.

The photoresist stripping method of the present invention may be performed by any cleaning system. The cleaning system to be used can be selected, for example, from ultrasonic cleaning, shower cleaning, spray cleaning, high-pressure jet cleaning, brush cleaning, immersion cleaning, swing cleaning, single-wafer cleaning system, and combinations thereof. In view of cleaning effects and work efficiency, the cleaning system is preferably immersion cleaning by an ultrasound system. The photoresist stripping method of the present invention comprises a step of applying the photoresist stripping composition of the present invention to the surface comprising a photoresist, and further comprises a step of stripping the photoresist by a cleaning system as described above. The photoresist stripping method of the present invention can be performed using the photoresist stripping composition of the present invention at various temperatures. This temperature can usually be from 10°C to 90°C. When the temperature is 10°C or higher, freezing of the photoresist stripping composition can be avoided. When the temperature is 90°C or less, evaporation of the photoresist stripping composition can be avoided. The temperature of the photoresist stripping composition at the time of cleaning is preferably 40°C to 80°C, in view of the photoresist stripping effect.

Examples

The components shown in Table 1 were mixed in glass beakers at room temperature to obtain compositions of the formulations shown in Table 1. Unless otherwise specified, commercially available products were used without any further purification.

A commercially available THMR-iP5700 photoresist composition, provided by Tokyo Ohka Kogyo Co., Ltd., was used to prepare test wafers. A photoresist composition was coated on 6-inch silicon wafers treated with 1,1,1,3,3,3-hexamethyldisilazane. The photoresist coated on the wafers was exposed to 365 nm UV light through a line-hole pattern mask using an i- line stepper. After development and post-baking steps, the test wafers were cut into small pieces for a photoresist stripping test.

The compositions of Examples 1 to 4, and the compositions of Comparative Examples 1 to 6, each individually contained in glass beakers, were heated to 60°C. Test wafer pieces coated with THMR-iP5700 were individually immersed in the compositions for 5 minutes. Afterward, the test wafer pieces were rinsed with deionized water, and dried by nitrogen stream. The photoresist stripping results were determined by visual inspection.

Metal damage on copper was assessed by etching rate of photoresist stripping compositions for Cu film formed on Si substrates. Commercially available test wafers formed with Cu films used for the examples were provided by Philtech Inc. The etching rate of copper (Cu ER) was determined from process time and thickness loss of copper film formed on silicon wafer. The thickness of copper film was measured by using an RT-70 four-point probe, manufactured by Napson Corporation. After determining the initial copper thickness, test wafers were immersed in the test solution at 60°C. After 30 minutes, the test wafers were removed from the test solution, rinsed with deionized water, and dried completely under nitrogen. Subsequently, the copper thickness was measured to determine the thickness loss by immersion in the test solutions.

Table 1.

The components used in the above examples are shown below.

DMSO: Dimethyl sulfoxide, produced by Toray Fine Chemicals Co., Ltd.

TEA: Triethanolamine, produced by Dow Chemical Company.

Choline hydroxide, produced by Tokyo Chemical Industry Co., Ltd., in the form of a 49 wt% aqueous solution of 2-hydroxyethyltrimethylammonium hydroxide.

Tetramethylammonium hydroxide (TMAH), produced by Tokyo Chemical Industry Co., Ltd., in the form of pentahydrate.

The test wafers used in the above examples are shown below.

Cu-coated wafer: 8-inch silicon wafers coated with 300 nm vapor-deposited copper film, provided by Philtech Inc.

As shown in Table 1, all of the compositions of Comparative Examples 2 to 6, which contained TMAH, showed problems regarding insufficient photoresist stripping ability or high Cu ER.

As shown in Table 1, the composition of Comparative Example 1, which contained a small amount of choline hydroxide, showed insufficient photoresist stripping ability. In contrast, the compositions of Examples 1 to 4, which contained a suitable amount of choline hydroxide, showed sufficient photoresist stripping ability and controlled Cu ER.

Based on this result, it can be said that the behavior of the compositions containing choline hydroxide is surprisingly different from that of the compositions containing TMAH.