Moore's Law switching to a subwavelength track
08/01/2000
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A huge transition from above-wavelength to subwavelength design and manufacturing is taking place in the semiconductor industry. Subwavelength features leave little margin for equipment error, making it difficult or impossible to control the critical dimensions of a process. This directly affects yield, making it difficult and cost-prohibitive to produce high-performance ICs reliably.
One significant driver for this transition is the availability of lithography equipment — or the lack thereof.
Tools for 193nm lithography are approaching production readiness, but it will still be at least two years before resist and process development reach a point where 193nm tools are ready to be widely deployed in a silicon production environment. The timeframe for next-generation lithography solutions is more difficult to predict, since optimistic estimates place tool availability 5-7 years away.
This means that manufacturing will have to creep along with 248nm steppers to manufacture today's 0.18mm ICs. And just around the corner are ICs with sub-100nm features. What happens then?
By applying techniques such as optical proximity correction (OPC) and phase shifting, the industry will continue decreasing feature sizes. But point solutions (physical verification tools) that provide OPC and phase shifting alone won't close the subwavelength gap. Such point tools applied only at the layout, tape out, or maskmaking stage will just push the problem to another stage in the design-to-manufacturing flow.
For next-generation feature sizes to be manufactured with existing processes, a complete subwavelength infrastructure integrated into every step of the flow is needed. That's the only way to achieve sub-100nm silicon on an existing process. In addition to working silicon, adopting a subwavelength infrastructure provides an increase in IC performance, enhanced process yields, and extended life for existing fab equipment, resulting in greater competitive advantage and additional revenue for the customer. A complete subwavelength infrastructure includes:
- process model calibration, automatic phase shifting and OPC of a GDSII layout, and software tools that verify the layout of a subwavelength IC against the silicon it is intended to produce — all integrated with automated design tools for process simulation and analysis.
- mask data preparation technology linked with design tools incorporating OPC and phase shifting early in the design flow. The adoption of OPC and phase shifting generates an exponential increase in the amount of data contained in a design database, making the task of preparing manufacturing data much more difficult. Seamless integration between design and data preparation enables a fast hand-off from design to manufacturing at a critical point in the process.
- mask manufacturing and inspection tools that embed industry-standard phase-shifting solutions. In the subwavelength realm, the mask creation and inspection challenges expand exponentially. With the increase in chip capacity, mask complexity increases and the mask no longer looks like the end silicon or the GDSII layout.
- semiconductor manufacturers who have committed to run test chips and set up process models that support industry-standard phase-shifting technology on their existing equipment. It includes design teams that can access the process through design tools, or that work with their foundry to incorporate phase shifting into their mask sets.
After incorporating phase shifting, Motorola successfully fabricated a microprocessor with 0.1mm feature sizes using a standard 0.18mm silicon production process. Lucent Technologies' Bell Labs developed what they believe is the fastest DSP chip operating off a 1V supply after incorporating phase shifting and adopting a subwavelength infrastructure. And MIT Lincoln Laboratories has used phase shifting to generate working 25nm transistors with an existing 248nm process.
The subwavelength infrastructure exists and is in the process of refinement today. With continued adoption of subwavelength technologies and the tools to support them, the semiconductor industry will continue its growth path. Moore's Law can live a while longer.