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Method for an APSM process

IP.com Disclosure Number: IPCOM000021512D
Publication Date: 2004-Jan-21
Document File: 5 page(s) / 237K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an alternating phase-shifting mask (APSM) process. Benefits include improved yield, improved process simplification, improved throughput, improved support for future technology, and improved cost effectiveness.

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Method for an APSM process

Disclosed is a method for an alternating phase-shifting mask (APSM) process. Benefits include improved yield, improved process simplification, improved throughput, improved support for future technology, and improved cost effectiveness.

Background

         The conventional process of record (POR), is a wet-undercut buffered hydrogen fluoride (HF) etch process (see Figure 1). It creates an undercut structure, altPSM, that is susceptible to defect enlargement (decoration). Pitting and trench defects can enlarge so that they become printable defects. The initial micro-crack under the Cr surface is enlarged to large pits in the contact regions. An AFM scan shows the depth of the defect to be 75 nm (see Figure 2).

         Sharp trenching due to the wet etching makes the Cr more vulnerable to lifting as the feature size decreases and in regions of narrow Cr line widths. Reticle rejection can occur at the end of the mask process when chrome undercutting is performed for image imbalance correction. The loss of the reticle at this step is particularly damaging in view of the long throughput time and the resources invested, especially with the high value-added nature of the reticle.

         Pitting and cracking have plagued the APSM technology since its inception. A viable dielectric material deposition technique repair process is required.

         No effective conventional solution exists that eliminates the high defect rate and low yield issues. One temporary solution is to replace the mechanical spray-type cleans by a gentler megasonic step to reduce the Cr lifting occurrences. However, as the feature sizes reduce in the future generations, the double-sided Qz undercut is likely to increase the vulnerability to a stage where even megasonic cleaning would be unacceptable.

         Another conventional but unsatisfactory solution is the use of a focused ion beam (FIB). However, this technique requires post-repair treatment to remove gallium stains which may have been deposited during the FIB-based defect repair.

General description

         The disclosed method includes two techniques used in the fabrication of APSM reticles. One technique reduces/eliminates nonrepairable quartz (Qz) cracks and pits, which result in printable defects. The method minimizes the process-induced enlargement (decoration) of the cracks and pits. The flaws that are below the printing threshold and do not result in printable defects are not affected.

         The other technique is an improved process for APSM fabrication that includes the following elements:

•         Integration of the post-treatment undercut etch steps with the phase etch steps

•         Architectural change from a two-sided undercut to a single-side undercut with shifter-width sizing, which reduces the occurrence of Cr lifting

Advantages

         The disclosed method provides advantages, including:

•         Improved yield due to the prevention of printable defects and reticule rejection

•         Improved process simplification due to the integration of the post-treatm...