Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2001-11-30
2004-09-28
Webb, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S176000, C438S692000, C438S693000
Reexamination Certificate
active
06797682
ABSTRACT:
The present invention relates to a stripper to strip a photoresist layer and a titanium oxide in production process of e.g. semiconductor integrated circuits, printed wiring boards and liquid crystals.
A semiconductor integrated circuit is produced by such a method that a photoresist is coated on a substrate, followed by exposure and development, then etching is carried out to form a circuit, and then the photoresist is stripped from the substrate, or ashing is carried out after formation of the circuit, the resist is removed, and then the remaining resist residue is stripped. To strip the photoresist from the substrate, or to strip the resist residue from the substrate, various resist strippers have conventionally been proposed.
For example, JP-A-62-49355 discloses a resist stripping liquid composition employing an alkanolamine. However, the stripping liquid composition employing an alkanolamine is insufficient for stripping of a resist residue degenerated to have inorganic properties by a treatment such as dry etching, ashing or ion implantation. Further, in a latest submicron treatment technique, a metal material containing e.g. TiN or TiSi is used, but in a case of using such a metal material, a stable by-product such as a titanium oxide tends to form during the treatment. A titanium oxide could not be stripped with a conventionally used alkanolamine.
Accordingly, as a resist stripping liquid composition having more excellent stripping properties, one containing hydroxylamine has been proposed in recent years. For example, JP-A-4-289866 proposes a resist stripping liquid composition containing hydroxylamine and an alkanolamine, and JP-A-6-266119 proposes a resist stripping liquid composition containing hydroxylamine, an alkanolamine and catechol. Although this resist stripping composition containing hydroxylamine provides excellent titanium oxide stripping properties, it is an unstable compound, and accordingly there is a risk or e.g. decomposition or explosion.
In addition to the above amine type resist stripper showing basicity, a resist stripper by a combination of hydrogen peroxide and an acid has also been proposed (e.g. JP-A-64-15740). A titanium oxide is generally known to dissolve in hydrogen peroxide in an acidic condition, however, combination of hydrogen peroxide and an acid is not optimal for stripping of an alkali development type photoresist which is likely to be stripped in a basic condition.
As described above, conventionally proposed resist strippers have insufficient stripping properties, particularly stripping properties of a titanium oxide, and with which there is a risk of decomposition or explosion. Accordingly, it is an object of the present invention to provide a resist stripper containing no hydroxylamine having a high risk of explosion and providing excellent resist stripping properties and titanium oxide stripping properties.
The present inventors have conducted extensive studies on a resist stripper and as a result, found that a resist stripper comprising a peroxide and a quaternary ammonium salt is useful as a resist stripper having excellent resist stripping properties and titanium oxide stripping properties, and the present invention has been accomplished on the basis of this discovery.
Namely, the present invention resides in a resist stripper comprising a peroxide and a quaternary ammonium salt.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the present invention, stripping is to remove a resist or a resist residue remaining after formation of a circuit, obtained by coating a photoresist on a substrate, followed by exposure and development, then carrying out a treatment such as etching. Namely, development is removal of a resist solubilized in liquid by exposure of a photoresist, and stripping is removal of a portion remaining after the development or a portion which becomes hardly soluble in liquid by means of a treatment such as etching or ashing.
The resist stripper of the present invention is useful to strip a photoresist or its residue. Namely, a photoresist is coated on a substrate, followed by exposure and development, and then a treatment such as etching is carried out to form a circuit, and then the photoresist is stripped by the stripper of the present invention. Otherwise, after formation of the circuit, ashing is carried out to remove the resist, and then the remaining resist residue is stripped by the stripper of the present invention.
The resist stripper of the present invention strips a titanium oxide which is a by-product in formation of a circuit, as well as the resist. A titanium oxide, particularly a tetravalent titanium oxide is an extremely stable compound and is hardly soluble in water. As the titanium oxide, one having various valency such as tetravalent, trivalent or bivalent may be mentioned, and it is the tetravalent titanium oxide (titanium dioxide) that is most insoluble. On the other hand, a most soluble titanium species is Ti
2+
, and a solid phase titanium oxide is known to easily be dissolved by reduction in an acidic region. However, the resist stripper of the present invention reduces and dissolves, and strips various titanium oxides including titanium dioxide which is most insoluble in an alkaline region at which the resist can be stripped.
Essential components of the resist stripper of the present invention are a peroxide and a quaternary ammonium salt.
The peroxide to be used in the resist stripper of the present invention acts as a reducing agent.
The peroxide to be used in the resist stripper of the present invention is at least one member selected from the group consisting of hydrogen peroxide, a persulfate, a perborate, a percarbonate, an organic peracid and an organic hydroperoxide. Among them, hydrogen peroxide is industrially preferred since it is available at a lowest cost.
Hydrogen peroxide may be used as an anhydride or an aqueous solution, or as a peroxyhydrate of e.g. urea or a quaternary ammonium salt (one having hydrogen peroxide coordinated to urea or a quaternary ammonium salt, such as water in water of crystallization).
The inorganic per salt such as persulfate, perborate or percarbonate is used preferably as a salt with ammonia or an amine or as a quaternary ammonium salt. Other salts such as sodium salt or potassium salt may be used, however, removal of metal ions is required, such being unfavorable industrially.
The organic peracid is not particularly limited so long as it is stable when mixed with a quaternary ammonium salt, and it may, for example, be performic acid, peracetic acid, benzoyl peroxide or m-chloroperbenzoic acid.
The organic hydroperoxide is a compound represented by a general formula R—OOH (wherein R is an alkyl or aryl) and examples of which include butyl hydroperoxide and cumyl hydroperoxide.
The quaternary ammonium salt to be used for the resist stripper of the present invention may be any one showing alkalinity. Examples of the quaternary ammonium salt include quaternary ammonium hydroxide, a quaternary ammonium carbonate, a quaternary ammonium carboxylate and a quaternary ammonium peroxycarboxylate. They are all alkaline substances and they may be used alone or as a mixture. Among these quaternary ammonium salts, particularly preferred is hydroxide or a carboxylate. As a carboxylic acid, either aliphatic carboxylic acid or aromatic carboxylic acid may be used, but an aromatic carboxylic acid is preferred industrially since it has a good stability. The aromatic carboxylic acid may, for example, be benzoic acid, salicylic acid or phthalic acid. The aliphatic carboxylic acid may, for example, be acetic acid, lactic acid, adipic acid or propionic acid.
The cation moiety in the quaternary ammonium salt to be used for the resist stripper of the present invention, i.e. the quaternary ammonium, may be a tetraalkylammonium such as tetramethylammonium, tetraethylammonium, tetra n-propylammonium, triethylmethylammonium or dodecyltrimethylammonium, a benzyl trialkylammonium such as benzyl trimethylammonium, or an
Aoki Masahiro
Hara Yasushi
Hayashi Hiroaki
Sughrue & Mion, PLLC
Tosoh Corporation
Webb Gregory
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