Method to derive the location and size of oxide spacing area

A method to derive the location and size of oxide spacing area, comprising:

• dividing a tested region in a GDS file into a grid composed of a plurality of grid units with a specified dimension, wherein each said grid unit consists of a plurality of sub-grid units with a specified dimension and arranged in a plurality of sub-grid columns and a plurality of sub-grid rows;
• extracting layout data in said tested region;
• calculating a pattern density difference of every said grid unit based on said layout data, wherein said pattern density difference is equal to a pattern density of one of said sub-grid units with maximum pattern density in said grid unit minus a pattern density of one of said sub-grid units with minimum pattern density in said grid unit;
• calculating a minimum row/column pattern density of every said grid unit based on said layout data, wherein said minimum row/column pattern density is a pattern density of one of said sub-grid columns and said sub-grid rows with minimum pattern density in said grid unit;
• calculating a row/column pattern density difference of every said grid unit based on said layout data, wherein said row/column pattern density difference is equal to a pattern density of one of said sub-grid rows with minimum pattern density in said grid unit minus a pattern density of one of said sub-grid columns with minimum pattern density in said grid unit;
• and
• determining said grid unit as where an oxide spacing area locates at when said pattern density difference of said grid unit is greater than a first predetermined value, said minimum row/column pattern density of said grid unit is less than a second predetermined value and said row/column pattern density difference of said grid unit is greater than a third predetermined value.