Method and apparatus for reducing OPC model errors

• US 20070079278A1
• Filed: 10/05/2005
• Published: 04/05/2007
• Est. Priority Date: 10/05/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Tanaka, Yasushi, Angyal, Matthew, Inohara, Masahiro
• Granted Patent: US 7,325,225 B2
• Time in Patent Office: Days
• US Class Current: 716/53
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 1/68 Preparation processes not covered by groups G03F1/20 - G03F1/50

Abstract

A method is provided of accessing model error in an optical proximity correction (OPC) model. The method begins by obtaining a preliminary mask using an OPC model, creating an etched wafer from the preliminary mask using lithography, and measuring a specified critical dimension (CD) on the wafer and a second CD on the wafer. An edge placement error (EPE) is determined that corresponds to a difference between a measured value of the second CD on the wafer and a desired value of the second CD on the wafer. The aforementioned steps are repeated for a plurality of different values of the specified CD to obtain an EPE for each of the different values of the specified CD. For each of the plurality of values of the specified CD, a measured value of a second CD on the wafer is correlated with a corresponding value of the second CD on the mask. For each of the plurality of values of the specified CD, the measured value of the second CD on the wafer is correlated with its corresponding value of the second CD on the mask as predicted by the OPC model. For each of the immediately preceding correlations that are obtained, and at a selected measured value of the second CD on the wafer, a difference Δ is obtained between the difference of the mask CDs calculated by interpolation of wafer CD measurements and by OPC model predictions. Each value of Δ is transformed into an OPC model error that each correspond to a particular value of the specified CD.

Claims

1. A method of accessing model error in an optical proximity correction (OPC) model, comprising:

a. obtaining a preliminary mask using an OPC model;

b. creating an etched wafer from the preliminary mask using lithography;

c. measuring a specified CD on the wafer and a second CD on the wafer;

d. determining an edge placement error (EPE) that corresponds to a difference between a measured value of the second CD on the wafer and a desired value of the second CD on the wafer;

e. repeating steps a-d for a plurality of different values of the specified CD to obtain an EPE for each of the different values of the specified CD;

f. for each of the plurality of values of the specified CD, correlating a measured value of a second CD on the wafer with a corresponding value of the second CD on the mask;

g. for each of the plurality of values of the specified CD, correlating the measured value of the second CD on the wafer with its corresponding value of the second CD on the mask as predicted by the OPC model;

h. for each correlation obtained in step (g) and at a selected measured value of the second CD on the wafer, obtaining a difference Δ

between the measured second CD on the mask and the corresponding value of the second CD on the mask as predicted by the OPC model; and

i. transforming each value of Δ

into an OPC model error that each correspond to a particular value of the specified CD.

2. The method of claim 1 further comprising the step of obtaining a total residual error for each value of the specified CD by summing the EPE corresponding to each particular value of the specified CD with the OPC model error corresponding to each of the particular values of the specified CD.

3. The method of claim 2 further comprising the step of comparing each value of the total residual error to a predetermined acceptable value of the total residual error.

4. The method of claim 1 wherein the specified CD is pitch.

5. The method of claim 1 wherein the second CD is line width.

6. The method of claim 1 wherein the second CD is line width at end-of-line.

7. The method of claim 1 wherein the second CD is spacing at end-of-line.

8. The method of claim 1 further comprising the step of revising the OPC model based on the OPC model error.