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A new resin system, comprising a thermoplastic polymer backbone with chemically stable imide functionality, has been adapted for use in three different positive resist product types. These include an advanced bilayer system, a near, mid and deep UV monolevel resist; and an antireflective coating.The key features of the imide polymer system which are utilized for the new resist products are:1.Novolac -like solubility in aqueous base.This property allows formulation of resists, including the planarizing layer of a bilevel system, with conventional types of positive resist photoactive compounds and aqueous base developers, unlike the situation with PMMA which is not base soluble. 2.Transparency to wavelengths above 260nm.This permits use of the polymer as the matrix for systems which utilize mid and deep UV exposure, including the planarizing layer for a bilevel system and mid and deep UV monolayer resists. This is in contrast to novolac resin which absorbs strongly in the deep UV region. 3.Insolubility in solvents used for conventional positive resists. This property is critical to use of the resin in planarizing layers of bilevel systems, including antireflective coatings. It eliminates the intermixing problems which represent a major problem in conventional PMMA bilevel systems. 4. High Tg (185 °C).This value is about 80 °C higher than that of PMMA and allows higher temperature processing without pattern distortion. 5.Chemical stability and plasma resistance.Unlike conventional reactive polyimide resins the subject polymer is chemically unreactive and is stable to temperatures above 300 °C. Further, the polymer has significantly greater resistance to plasma than does PMMA.

A high resolution, easy to implement bilayer PMGI [poly[dimethylglutarimide)] process has been developed for producing polysilicon gates for high density CMOS. One micron wide, proximity effect free, and very uniform poly lines were obtained. Unbiased mask dimensions were reproduced easily with optimum process latitude.A focus latitude of 5 microns for 1 micron dense (repeating line /space) pattern is reported.This was achieved using a conventional stepper with a nominal resolution of 1.1 microns and a depth of focus of +/ -1.3 microns.The delta between the mask and the final wafer dimensions was virtually the same for lines ranging from 5 all the way to 1 micron, as well as for all single and dense lines showing no proximity effects. The after -etch linewidths were uniform to within a sigma of 0.04 microns across a 4 inch wafer.The process consisted of the following: The polysilicon was coated with a planarizing and antireflecting PMGI layer of about 1 micron. A 0.7 micron layer of conventional novolak resist was put on top. The image was formed in the top resist and transferred to the bottom by a deep UV flood exposure. The PMGI was developed in a aqueous -based solution completely removing the top resist in the process.The etching was done in a single wafer RIE machine. All the linewidth measurements were made on final poly structures using electrical techniques.The advantages of using PMGI over conventional materials such as PMMA are no interlayer mixing, aqueous -based developer chemicals, and better etch resistance.The process is very flexible and different schemes can be implemented as needed. A novolak cap can be retained for increased etch resistance by changing to a different aqueous developer solution; however, the simple uncapped approach was found to be already far superior to any single layer resist technique and it was easily implemented on conventional production equipment.

A discussion of the general parameters used in resist formulation is given. Characterization of the resist and its metal and non -metal developers includes: resist chemistry, coating properties and film thickness control, photospeed at two major wavelengths, contrast parameters, resolution capability, thermal flow properties, dry etch resistance, adhesion and removal characteristics. The new system emphasizes a higher degree of manufacturing control to increase yields in high resolution device manufacturing.