Printing the Metal and Contact Layers for the 32 and 22 nm Node: Comparing positive and negative Tone Development Process

摘要

A strong demand exists for techniques that can further extend the application of ArF immersion lithography. Besides techniques like litho-friendly design, dual exposure or patterning schemes, customized illumination modes, also alternative processing schemes are viable candidates to reach this goal. One of the most promising alternative process flows uses image reversal by means of a negative tone development (NTD) step with a FUJIFILM solvent-based developer. Traditionally, the printing of contacts and trenches is done by using a dark field mask in combination with positive tone resist and positive tone development. With NTD, the same features can be printed in positive resist using a light field mask, and consequently with a much better image contrast.In this paper, we present an overview of applications for the NTD technique, both for trench and contact patterning, comparing the NTD performance to that of the traditional positive tone development (PTD). This experimental work was performed on an ASML Twinscan XT:1900i scanner at 1.35 NA, and targets the contact/metal layers of the 32 & 22 nm node. For contact hole printing, we consider both single and dual exposure schemes for regular arrays and 2D patterns. For trench printing, we compare the NTD and PTD performance for one-dimensional patterns, line ends and two-dimensional structures. We also assess the etch capability and CDU performance of the NTD process. This experimental study proves the added value of the NTD scheme. For contacts and trenches, it allows achieving a broader pitch range and/or smaller litho targets, which makes this process flow attractive for the most advanced lithography applications, including double patterning.