Online information source for semiconductor professionals

Product Briefing Outline: Novellus Systems has introduced a new patent-pending ashable hard mask (AHM) process technology on the ‘VECTOR Express' plasma-enhanced chemical vapor deposition (PECVD) platform. The technology has been designed to address the challenges in advanced technology nodes that utilize 193nm lithography for high aspect patterning etch, where thinning photoresist material makes it difficult to extend conventional patterning.  Novellus has already delivered tools with this new capability to major memory manufacturers.

Problem: With the heavy dependence on 193nm optical lithography for critical process steps, problems are generated when fabricating high aspect ratios such as structure collapse and sidewall striation. This can limit aggressive scaling of critical dimensions using conventional processes and films. The problem becomes compounded with the migration below 60nm that requires six hard mask levels achieving required thicknesses between 2000 and 8000 angstroms for advanced DRAM devices.

Solution: The AHM process has been developed with a unique chemistry and enhanced plasma capability. The AHM film maintains correct transparency to the light source used for wafer alignment during photoresist exposure. In key customer evaluations, AHM on the VECTOR Express has demonstrated superior film performance, excellent CD control, low defectivity and improved device yield, according to Novellus. Cost-of-ownership has also been reduced by more than 30 percent from prevailing industry benchmarks, the company claims.  In addition, a new post-deposition edge bevel film removal capability has been integrated on the VECTOR Express platform to provide process flexibility and to resolve reliability, throughput and defect performance issues associated with conventional in-chamber edge exclusion techniques. Edge bead removal takes place in the outbound loadlock, using atomic O2 generation, eliminating chamber contamination issues and negating any throughput issues and improving bevel-edge profile repeatability in the 2nm exclusion range, according to Novellus.

Applications: High aspect ratio etching of memory devices.

Platform: The VECTOR Express PECVD platform, introduced earlier this year, is used to deposit a variety of films for memory and logic devices. VECTOR Express includes the ‘SmartSoak' processing feature. SmartSoak takes advantage of the VECTOR platform's multi-station sequential processing (MSSP) architecture to control wafer heat-up independently from film deposition. This enables a more stable and consistent wafer temperature at the start of film deposition while simultaneously reducing thin film processing time. Novellus has received orders for more than 50 VECTOR Express systems.

Availability: June 2007 onwards.