Takahisa Namiki

A New Single-Layer Resist for 193-nm Lithography

A positive chemically amplified resist for 193-nm lithography has been developed. The resist consists of a copolymer of tetrahydro-4-methyl-2-oxo- 2H-pyran-4-yl methacrylate and 2-methyl-2-adamantyl methacrylate and a photoacid generator. The acid-catalyzed deprotection of the protective groups leads to a large polarity change in the exposed region of the resist films and it allows for high-contrast patterning with high sensitivity. Using an ArF excimer laser exposure system, a 0.17-µ m lines and spaces pattern has been resolved.

High-performance EB chemically amplified resists using alicyclic protective groups

The impact of alicyclic protective groups on acid-labile substituents in a vinylphenol-methacrylate-based chemically amplified positive resist was investigated. The resist consists of the copolymer of vinylphenol and adamantyl methacrylate (VP/AdMA) with triflate onium salt as a photo- acid generator. The alicyclic protective groups in our system show a higher reactivity and higher hydrophobicity than those of the tert-butyl group, which is widely used in chemically amplified resists. The resists containing the alicyclic protective group resolved 0.09-micrometer hole patterns at 6 (mu) C/cm2, and a resist with a base additive resolved 0.12-micrometer line and space patterns at 9.0 (mu) C/cm2 using a 50-keV EB lithography system with a 2.38% TMAH aqueous solution as the developer. The dry etching durability of resists containing the alicyclic group was also compared with resists containing the tert-butyl group and with polyvinylphenol (PVP). The dry etching durability of our resists for a C4F8 plasma was 1.3 times superior to that of resist containing the tert-butyl group, and 1.1 times better than that of PVP. This means the thickness of film in pattern fabrication can be reduced to obtain a higher sensitivity and higher resolution.

High-performance chemically amplified positive electron-beam resist

The effect of an alkali decomposable additive on a chemically amplified (CA) positive electron-beam (EB) resists was studied. HalogenoMethylEster (HME), 1,4- bis(bromoacetoxy) benzene was synthesize and used as an alkali decomposable additive. The hydrophobic HME decomposed with an alkali solution and changed into a hydrophilic, which in turn increased the alkali dissolution rate of the exposed region of the resist and enhanced the resist contrast. In addition, the bromomethyl groups and ester groups are hydrolyzed with a high degree of polarity change. HME having the large dissolution acceleration effect at an exposed region is suitable for application as a positive resist. HME was added to 2-component CA positive EB resist consisting of a base polymer and a photoacid generator. As a result of a high degree of polarity change, HME enhanced the resist contrast with no loss in sensitivity. The delineation of a fine 0.13 micrometers hole-pattern was possible with the addition of HME. The addition of HME rendered the sidewalls smooth and vertical.

Environmentally stable chemically amplified resist effects of organic salt additives

Incorporation of organic salt additives consisting of an organic acid and organic base improves the resist stability. The sensitivity of a t-BOC resist without the salt decreased to 1/4 after standing for one hour after deep-UV exposure. Typical T-top patterns were obtained on this resist by a KrF excimer laser stepper (NA equals 0.45), and a half-micron resolution was barely obtained. On the other hand, a t-BOC resist, with an organic salt, consisting of p- toluenesulfonic acid and dicyclohexylamine (PTS/DCHA), showed no change in sensitivity after one hour. The resist with the PTS/DCHA achieved a 0.3-micrometers resolution line-and- space pattern without environmental control or a protective topcoat.