Using the VWF Production Tools - Technology Objects

Overview of the Production Tools

A typical simulation design sequence for a technology consists of specifying certain values for input parameters (such as implant dose, diffusion temperature) and extracting design parameters (oxide thickness, threshold voltage) at key points in the process flow and at parametric device test.

By using the VWF to automatically run the process simulation with statistical combinations of input parameter values, response surface models (RSMs) can be generated for each extracted design parameter.

With an RSM for each extracted design parameter, an entire process flow's design parameter set can be analyzed in real time. This means it is possible to instantly see the effect of any processing parameter upon any design parameter in a realtime graphical environment.

This functionality forms the basis of in the Production Tools, the latest new software layer of the Virtual Wafer Fab. When enabled, it also provides capabilities such as yield analysis, multi-variant and multi-dimensional process calibration and interactive design parameter analysis.

 

How RSMs Are Used

When the VWF has generated all the RSMs required for a particular process flow (one RSM for each extracted design parameter), they are passed as objects to the VWF Production Tools.

RSM objects can then be plotted as 1D graphs (showing design parameter variation with respect to one process parameter), 2D contour plots or 3D surface plots (output with respect to two process variables).

With Production Tools, the RSMs provide even more functionality. With the ability to calculate values for the design parameters, Production Tools can compute yield distributions, find calibration coefficients to match multiple measured data values, and synthesize input values to obtain any desired design parameter set. In this simple to use form it is a valuable tool to the non-expert user.

 

Technology Objects in the VWF

For any given process, once a given technology's nominal experimentally measured design parameters have been found, they remain essentially constant. VWF therefore provides a way of storing these values, and then automatically passing them to the Production Tools allowing the side by side use of empirical measured data and physically based simulation data. This technique uses a "Technology Object".

 

What Are Technology Objects?

Technology objects are used primarily to store experimental data, measured in the fab. This data is used to calibrate each RSM to exactly match the nominal processing case. In this manner, Physical Simulation is only used for the 'Trend' or the slope of the RSM.

Further, statistical process control (SPC) limits are stored to act as guidelines for a technology designer, to be superimposed over graphs of simulated RSM results. The process parameter statistical variations are also stored, for subsequent design parameter yield distribution analysis.

A technology object editor from the VWF RSM library archive screen allows the Technology Object to be defined. After having been defined in the VWF, Technology Objects are passed to the Production Tools. Alternatively, a Technology Object may be defined as a simple ascii text file which can then be read by the Production Tools.

Technology Object files can be loaded into Tonyplot Production Mode at any time, redefining the current technology parameters. When plotting from the VWF, the Technology Object (if defined) is passed automatically.

 

Figure 1. Here, 6 CMOS design parameters are shown in the slider
controlled interactive environment. This versatile graphical tool
can be used to explore, analyze and optimize the design of multiple devices.

 

 

Figure 2. The Production Tools offer a simple to use
slider driven control over process parameters.

 

 

Figure 3. The Technology Object Editor is found in the RSM archive
area of the VWF library. It offers a simple Graphical User Interface
for inputing experimentally measured Fab data.