Parametric Rule Editor (PRE)
Flexible Pattern Search
A typical physical layout (GDS/OASIS) consists of patterns and subtle to substantial variations of the patterns. Often it is necessary to search for a pattern while specifying precise constraints for finding variations of the pattern in a controlled, deterministic way.
Full-Chip Pattern Segmentation
Advanced inline inspection tools from the leading vendors have provided array mode inspection and random mode inspection. Array mode inspection significantly enhances sensitivity to defects in memory arrays. Because noise characteristics within an array are fairly uniform throughout the array, the threshold setting can be lowered compared with the threshold in random logic regions. However, even random logic regions can be segmented on the basis of uniform pattern characteristics such as line orientation, line density, pattern complexity, and so on, to generate micro care areas. Segmenting the logic regions into homogeneous subregions allows each subregion to be thresholded individually for best sensitivity and noise rejection.
Anchor’s Parametric Rule Editor (PRE) provides an elegant and user-friendly solution for both of these applications. It is a groundbreaking product that provides supreme flexibility with unmatched ease-of-use.
PRE can be used to build simple or complex search rules on patterns that are either imported from a file or drawn by hand using polygon-editing functions built right into the product. Exact constraints for a number of geometric properties such as line width and line space can be specified, with full support for multiple layers.
Want to check if there is a single-via of a specified width with specified coverage within a specified distance from the end of line that is of a specified width and has a minimum specified run length? No problem. This example combines a via layer and an interconnect layer, yet it is a relatively simple example of the flexibility offered by PRE.
In this section we walk through a sample use case to demonstrate some of the capabilities of the Parametric Rule Editor.
1. It would be more meaningful if there was a via connecting this metal island. You want to avoid ‘floating metal’ that is of no consequence.
2. You feel that there might be several variations of this pattern that might be quite relevant. You decide that this pattern and its variants are ‘Patterns of Interest’ or POI that should be searched.
Within a few seconds we use the PRE GUI to draw the pattern on the right.
Now the base pattern is complete and we move on to specifying the necessary constraints.
This can be achieved by examining the 4 properties illustrated on the right.
On the left we can see 17 variations of the pattern. Each of the 17 variations may have hundreds or thousands of instances. Note the subtle variations in each of these 17 patterns. Note also the variation in the location of the via.
For example, the gallery on the left shows the 3 different values of side edge distance that were found. These values (0.05um, 0.06um, and 0.065um) can be plotted on a histogram to show how many instances had a side distance of 0.05um, how many had a distance of 0.06um, etc. Filtering and sampling operations are also provided to narrow down the population into one or more subsets.