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  Two-layer film and method of forming pattern with the sameUSPTO Application #: 20070248905Title: Two-layer film and method of forming pattern with the same Abstract: sequentially applying positive radiation-sensitive resin compositions 1 and 2 to form a two-layer laminate; subjecting the two-layer resist to single exposure and development to produce fine patterns having an undercut cross section; depositing and/or sputtering an organic or inorganic thin layer with use of the resist pattern as a mask; and lifting off the resist pattern to leave a pattern of the thin layer in desired shape.
The invention concerns a lift-off process for patterning layers that are deposited and/or sputtered. The invention provides a two-layer resist and a patterning method using the resist. The patterning method can readily produce burr-free layers on a substrate. The method comprises the steps of: (end of abstract)
Agent: Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US Inventors: Masaru OHTA, Atsushi ITO, Isamu Mochizuki, Katsumi INOMATA, Shin-ichiro IWANAGA USPTO Applicaton #: 20070248905 - Class: 430141000 (USPTO) Related Patent Categories: Radiation Imagery Chemistry: Process, Composition, Or Product Thereof, Diazo Reproduction, Process, Composition, Or Product The Patent Description & Claims data below is from USPTO Patent Application 20070248905. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to photofabrication, in other words precision microfabrication by photolithography technique. More particularly, the invention relates to a lift-off process using a two-layer resist. BACKGROUND OF THE INVENTION [0002] Lift-off is a general term for a process of forming a pattern of organic or inorganic thin layers by: [0003] applying a resist onto a workpiece surface; [0004] patterning the resist layer by a photolithography technique; [0005] depositing and/or sputtering an organic or inorganic substance over the resist layer and areas in which the resist has been cleared; and [0006] releasing the resist layer together with the overlying organic or inorganic thin layer. [0007] As a consequence, the organic or inorganic substance found in the orifices of the resist layer remains there to form a desired pattern. [0008] In this lift-off process, the resist pattern profile is very important. For example, positive resists will typically produce a pattern which tapers forward as shown in FIG. 2(c) Releasing of this forward tapered resist will result in a pattern of layers having burrs on their edges as shown in FIG. 2(d). [0009] A specific example will be given with respect to the processing of MR magnetic head sliders. Here, the aforesaid lift-off process is used to form a DLC (diamond like carbon) layer on an ABS (air bearing surface) for the purpose of pad protection As described above, the lift-off process can produce burrs on the edges of DLC layers. The burrs on the DLC layers can scratch the magnetic recording disks of HDD (hard disk drive) or can be a foreign object to cause HDD failures. [0010] With such problems, it will be effective to use negative resists or image reversal resists which can be formed into a reverse tapered pattern. As shown in FIG. 3(c), the orifices of this reverse tapered layer have a larger size in the bottom than in the top, so that the formation of burrs can be prevented. However, this method in general has a difficult control of the resist pattern profile. Further, it is difficult to observe the resist pattern with a light microscope and also to release the resist layer which has been hardened. [0011] In respect to the workpiece surface as a substrate, it will usually have irregularities, which are relatively large for the thickness of applied resist, as a result of the process steps the workpiece has undergone. Because of this, it has been difficult to form a resist layer in uniform thickness. [0012] In the above processing of MR magnetic heads, a number of strip pieces called row bars are processed as being stuck on a jog with their ABS upward. Since these row bars have a gap between the neighboring ones, a direct application of a liquid resist is impossible; therefore, a resist film such as a dry film is generally employed instead. [0013] From the viewpoint of improving the productivity of workpieces, there has been a need for a technology which can be incorporated into the production process without disrupting the flow of process steps and by which a pattern can be readily formed on a workpiece surface. [0014] The present inventors studied earnestly in view of the aforesaid circumstances. As a result, they have developed a two-layer laminate that comprises a resist layer (I) formed from a specific positive radiation-sensitive resin composition 1 and a resist layer (II) formed from a specific positive radiation-sensitive resin composition 2. This two-layer laminate can be formed into an undercut resist pattern by single photoexposure and development. Thus, the patterning method using the two-layer laminate can produce a burr-free layer with ease. The present invention has been completed based on these findings. [0015] It is an object of the invention to provide a resist layer which can leave a burr-free layer on a substrate with ease, and a patterning method using the same. SUMMARY OF THE INVENTION [0016] The two-layer laminate according to the invention comprises: [0017] a resist layer (I) formed from a positive radiation-sensitive resin composition 1 which comprises a radical polymer containing a hydroxyl group and/or a carboxyl group (A), a quinonediazido group-containing compound (B) and a solvent (C); and [0018] a resist layer (II) formed from a positive radiation-sensitive resin composition 2 which comprises a polymer containing a phenolic hydroxyl group (D), a quinonediazido group-containing compound (E) and a solvent (F). [0019] The patterning method according to the invention comprises a step of forming a two-layer laminate comprising: [0020] a resist layer (I) formed from a positive radiation-sensitive resin composition 1 which comprises a radical polymer containing a hydroxyl group and/or a carboxyl group (A), a quinonediazido group-containing compound (B) and a solvent (C); and [0021] a resist layer (II) formed from a positive radiation-sensitive resin composition 2 which comprises a polymer containing a phenolic hydroxyl group (D), a quinonediazido group-containing compound (E) and a solvent (F) The patterning method preferably comprises the steps of: Continue reading... 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