The 65nm technology node will require a more detailed assessment of the tradeoffs between performance, manufacturability and cost than any previous generation of technology. Circuits fabricated at the 65nm technology node need to use Strong Phase shifting techniques such as Full-Phase and Model based OPC in order to guarantee printability of critical layers, such as the poly layer. We presents a methodology whereby layouts are genrated base don a preliminary set of design rules for 65nm and the process latitude determined using image simulation software. Mask costs were also estiamted base donfigure counts of the required masks. Tradeoffs between mask costs, manufacturibility and density were made by small changes to the design rules. The simultaneous use of tools that integrate the design creation process with mask generation allows far better optimization than current methodology where physical design is separated from the downstream data preparation and processing.
The 2001 ITRS roadmap identified the need for tight coupling of design technology with manufacturing technology in order to ensure the successful production of circuits fabricated at the 65nm technology node. The design creation process for 65nm needs to efficiently explore the interaction between device, cell design and manufacturability. Using fast simulation tools for device and lithography simulation and an automated tool for standard cell generation, various process and cell architectural options were investigated. The average and standard deviation of line width had to be matched to the type of application because of the direct relationship between leakage current and performance. Best process latitude for poly line widths is achieved with Full Phase technology. It is shown that by matching design rules to the Full Phase capabilities and using automated layout tools, manufacturabilty could be optizmed without hurting density or performance.
The ITRS roadmap for the 65nm technology node, targets poly gate lengths of 65nm and poly pitches between 140-180nm. In addition, contact overlaps and spacing to diffusion contacts will need to be scaled down. It is very likely that the poly layer will be printed using 193nm high NA steppers and Strong Phase Shift Technologies. Attempts to capture the effect of RET on layout by adding more constraints to the desing rules make it difficult to lay out cells using manual tools and can also lead to sub optimal designs. In this paper we describe a methodology that couples automatic cell generation with Phase shifter insertion and image simulation to allow the design space to be explored more fully.
It is suggested that the high cost of mask sets for 90nm and below technologies may restrict the application of technologies to a handful of high volume chips. Most of the cost for mask production is a result of the increased time to write and inspect (including defect disposition) a mask due to the large files that are created prior to mask writing. Stringent mask specifications needed for low k factor imaging drive protracted and costly yield learning curves for a
mask maker. The cost of different steps in the flow from design tape-out to final wafer test are analyzed and it is shown that limiting the reticle field size on critical layers could reduce net costs. The net die cost is lower as long as the number of processed wafers stays below a cutoff number. Costs can be further decreased by reducing the overall "figure count" (and hence writing time) for an ASIC chip by restricting the amount of OPC done on critical layers.
An integrated shallow trench isolation process utilizing HDP (High Density Plasma) oxide and a highly manufacturable corner oxidation is described. The choice of trench corner oxidation temperature is shown to be critical in reducing silicon stress, and hence junction leakage, to the levels required by multi-million gate designs. This STI process is shown to be extremely robust and manufacturable. Optimal design of the trench depth and well profiles is shown to provide well-edge isolation adequate for sub-0.18 micrometer technologies.
KEYWORDS: Aluminum, Metals, Diffusion, Oxides, Very large scale integration, Ion beams, Semiconducting wafers, Reliability, Chemical species, Microscopy
A Focussed Ion beam Microscope has been used to image the grains as well voids formed in Al- 1%Cu/TiW fine line conductors . Void formation has been compared between laser annealed Al and non laser annealed Al and it has been shown that the laser annealed Al is more prone to voiding. A TiW layer placed over the Al is effective in suppressing the voids.
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