SPRINTCAD QUARTERLY SUMMARY

January 1 - March 31, 1995

ORGANIZATION:

SUB-CONTRACTORS:

PRINCIPAL INVESTIGATORS:

PROJECT LEADER

TITLE OF EFFORT:

RELATED INFORMATION:

OBJECTIVE:

APPROACH:

1. deposition/etching module---of special interest are CVD and plasma assisted processes that result in high aspect ratio structures such as trenches and filling/planarization of structures for metal interconnects. Algorithmic work focuses on geometric manipulations and surface evolution.
2. thermal/stress analysis module---that can solve nonlinear constitutive models for key process steps involving growth of dielectric layers and impurity redistribution as well as the resulting stress fields. Advanced formulations for finite elements are being developed that support: parallel computation, adaptive gridding and domain decomposition.

PROGRESS:

The dial-an-operator finite element analysis program has been named as a-la-mode (A Layered Approach MODEling) since the user has layered access to the built-in physical model and parameters, physical formulations, numerical schemes, geometry and field manipulation, etc. to maximize both software configurability and user friendliness. The object model of TCL (tool control language) has been implemented and the user can now describe the physical definition, numerical schemes and various input and control in the TCL extension language. We have demonstrated that a reactive-diffusive model for Phosphorous diffusion in 2D containing five interacting specifies (i.e., five coupled PDEs) can be completely described in a simple TCL script. The results have been benchmarked and compared favorably with the 1D PEPPER diffusion simulation tool. The code has been ported to the ALPHA machine and is currently used by several graduate students and research staffs to study the transient-enhanced-diffusion (TED) effect. One of the main authors (D. Yergeau) will work as an intern in Intel this summer, where a-la-mode will be applied to realistic processes and a set of diffusion coefficients for TED will be calibrated.

The new finite-deformation oxidation model has been originally tested in the the FEAP (finite element analysis program) environment. However, to reduce future duplicated efforts in integration with the geometry/field server and the parallelized linear solver, the interface of element calculation to FEAP is carefully analyzed and encapsulated, so that the basic element functions for this new oxidation model can become an operator-like description in the a-la-mode code.

The 3D etch/depo simulation using the physical models in SPEEDIE is under way. Presently we chose to wrap the SAMPLE-3D (Berkeley photo-lithography tool) by the minimal SWR specification and used it as a surface mesh field server. To prevent undercut in thin metal interconnect lines, more careful etch time control is necessary. However, this produces stringer problems on crossover. To model this phenomenon accurately, physical etching models in SPEEDIE will be extended to 3D. The interface to the wrapped SAMPLE-3D code is completed and various physical etch models are under investigation.

RECENT ACCOMPLISHMENTS:

• Geometry modeling utilities have been used on a commercial RF application to extract intermodulation distortion.
• TCL handles for the a-la-mode code (dial-an-operator finite element program) have been implemented.
• The a-la-mode code has been benchmarked with SUPREM IV on Boron segregation and PEPPER on a five-species Phosphorous diffusion model.
• The 3D SPEEDIE for physical etch/depo simulation has been built on SAMPLE-3D wrapped in the minimal SWR specification.

FY-`96 PLANS:

• Test 3D Thermal Module and integration of parallel solver technology.
• Implementation of 3D Oxidation within Thermal Module and transition into unified capabilities (both diffusion and oxidation).
• Implementation of complete server for 3D Deposition/Etching Module, including 3D parallel solver to support flux calculations.
• Benchmark the overall SPRINT-CAD modules in terms of a deep submicron MOS technology. The Thermal Module will demonstrate 3D analysis of locally oxidized isolation and shallow junction diffusion steps. The Deposition/Etching Module will demonstrate first-time functionality of a 3D server-based architecture and implementation.

TECHNOLOGY TRANSITION:

Ongoing development of the object-oriented PDE solver continues to create enthusiasm within the research and industrial communities. Intel has offered to be a "beta" test site this summer and one of the key developers of the Dial-an-Operator module will be directly involved with the implementation and testing at Intel. Within the SUPREM project at Stanford, supported through SRC, the Dial-an-Operator module will be tested internally as a replacement for the present diffusion module within SUPREM 4GS. This application based testing of the new object-oriented module also provides the basis for creating completely new applications, for example in support of computational prototyping of 21st century semiconductor devices (under separate ARPA support).

SIGNIFICANT EVENTS:

TECHNOLOGY-DEPENDENCE OF INTERMODULATION (IM) DISTORTION OF BIPOLAR RF DEVICE DETERMINED USING COMPUTATIONAL PROTOTYPING.

Researchers at Stanford have demonstrated for the first time the ability to go directly from IC device specification to electrical extraction of distortion in radio frequency (RF) circuits based on computational prototyping. Using IC layout-based specification of a complex RF bipolar power transistor, including both 3D and 2D computational models of devices, a new harmonic balance (HB) simulator directly supports the analysis and extraction of exactly which regions in the device contribute to harmonic and IM distortion. This new computational approach now allows the circuit designer and the IC technologist to communicate directly and unambiguously about the trade-offs being made in development of new structures for RF and other wireless applications. As an example, the Stanford team demonstrated the extraction of distortion for a 1.5 GHz bipolar cellular phone application. The IM tones can now directly be correlated with internal device effects such as collector and base doping parameters, thereby setting the stage for optimizations that will improve overall system performance.

Date prepared: 4/27/95