Method and apparatus for reducing OPC model errors

• US 7,325,225 B2
• Filed: 10/05/2005
• Issued: 01/29/2008
• Est. Priority Date: 10/05/2005
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Inohara, Masahiro, Tanaka, Yasushi, Angyal, Matthew
• Primary Examiner(s): Chiang; Jack
• Assistant Examiner(s): Doan; Nghia M.
• Application Number:
  US11/243,933
• Publication Number:
  US 20070079278A1
• Time in Patent Office: 846 Days
• Field of Search: 716 19- 21, 703/2, 430/5, 430/30
• 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

It is important to assess and reduce errors that arise in mask correction techniques such as optical proximity correction. A preliminary mask is obtained using an OPC model. An etched wafer is created from the preliminary mask using lithography, and first and second critical dimensions (CD) are measured on the wafer and. An edge placement error (EPE) is determined that corresponds to a difference between a measured value and a desired value of the second CD. These steps are repeated for a plurality of different values of the first CD, and of for each of the values of, the measured value of the second CD is correlated with its corresponding value on the mask as predicted by the OPC model. Δ difference ΔCD is obtained between the difference of the mask CDs calculated by interpolation of wafer CD measurements and by OPC model predictions and is transformed into an OPC model error.

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 first Critical Dimension (CD) on the wafer and a second CD on the wafer;

d. determining a first 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 first CD to obtain an EPE for each of the different values of the first CD;

f. for each of the plurality of values of the first CD, correlating a measured value of the 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 first 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

CD 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;

i. transforming each value of Δ

CD into an OPC model error that each correspond to a particular value of the first CD;

j. obtaining a total residual error for each value of the first CD by summing the EPE corresponding to each particular value of the first CD with the OPC model error corresponding to each of the particular values of the first CD;

k. comparing each value of the total residual error to a predetermined acceptable value of the total residual error; and

l. revising the OPC model based on the OPC model error when the value of the total residual error is greater than the predetermined acceptable value of the total residual error.

2. The method of claim 1 wherein the first CD is pitch.

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

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

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