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Use of Sub-Ambient Temperatures to Improve Radiation Durability of Polymer-Based Pellicles

IP.com Disclosure Number: IPCOM000010800D
Publication Date: 2003-Jan-22
Document File: 3 page(s) / 179K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that keeps the temperature of soft pellicles under the controlled sub-ambient temperature by purging sub-ambient nitrogen through the reticle chamber of the stepper. Benefits include an improvement in irradiation durability and stability.

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Use of Sub-Ambient Temperatures to Improve Radiation Durability of Polymer-Based Pellicles

Disclosed is a method that keeps the temperature of soft pellicles under the controlled sub-ambient temperature by purging sub-ambient nitrogen through the reticle chamber of the stepper. Benefits include an improvement in irradiation durability and stability.

Background

Currently, existing pellicles rapidly degrade (i.e. darken) and become opaque when subjected to higher energy irradiation at a wavelength of 157 nm. This wavelength is required for the next generation 65 and 45 nm node technology (see Figure 1). The target requirements for successful integration of 157 nm technology is a transmission loss of less than 1 % at an irradiation dose of 4000  J/cm2, corresponding to the exposure of 16,600 wafers. As such, pellicles created using the  current state of art do not satisfy the technology requirements.

Presently, no solution exists for the wavelength below 193nm.  One potential solution for a wavelength below 193 nm could use “hard” pellicles made from inorganic fluorine-doped silica. These pellicles do not degrade when exposed to 157 nm irradiation; however, the cost associated with hard pellicle implementation is tremendous, due to the inspection tools and stepper optics modifications required to accommodate the thick inorganic hard pellicles (300-500um). In addition to optical aberrations, thickness errors, and deformation (caused by mounting force), the sagging of the thick membrane results in refraction induced distortion effects. Currently, using soft pellicles is the industry-preferred solution.

General Description

The disclosed method purges sub-ambient nitrogen through the upper chamber of the stepper, which contains pellicles, a photo mask, and a heater. The combined action of heater and purged sub-ambient nitrogen cools the chamber to the predetermined sub-ambient temperatures. The electrical and mechanical design of the heater, the valves, and other essential parts can be similar to the design of the Dynamic Mechanical Analyzer manufactured by TA Instruments, Inc., which is used for mechanical tests of polymers under a wide range of the temperatures.  The irradiation of the pellicles at the required wavelength of 157 nm is con...