In-line overlay measurement using charged particle beam system
A method and system for controlling an overlay shift on an integrated circuit is disclosed. The method and system comprises utilizing a scanning electron microscope (SEM) to measure the overlay shift between a first mask and a second mask of the circuit after a second mask and comparing the overlay shift to information about the integrated circuit in a database. The method and system includes providing a control mechanism to analyze the overlay shift and feed forward to the fabrication process before a third mask for error correction. A system and method in accordance with the present invention advantageously utilizes a scanning electron microscope (SEM) image overlay measurement after the fabrication process such as etching and chemical mechanical polishing (CMP).
1. A method for controlling an overlay shift on an integrated circuit, the method comprising:
utilizing an scanning electron microscope (SEM) to measure the overlay shift between a first mask and a second mask of the integrated circuit after the second mask;
comparing the overlay shift to information about the integrated circuit in a database; and
providing a control mechanism to analyze the overlay shift and feed forward to the fabrication process before a third mask to adjust for error correction.
2. The method of claim 1 , wherein database contains pattern images of operation steps.
3. The method of claim 1 wherein the database contains an average value of asymmetry of symmetric structure within the integrated circuit.
4. The method of claim 1 wherein the first mask is an active area mask, the second mask is a gate mask, and the third mask is a contact mask.
5. The method of claim 1 wherein the comparing is performed utilizing a plurality of overlay measurement algorithms.
6. The method of claim 4 wherein the contact mask is adjusted to reduce the risk of a contact-to-gate short.
7. A system for controlling an overlay shift on an integrated circuit, the method comprising:
means for utilizing a scanning electron microscope (SEM) to measure the overlay shift between a first and a second mask of the integrated circuit after the second mask;
means for comparing the overlay shift to information about the integrated circuit in a database; and
providing a control mechanism to analyze the overlay shift and feed forward to the fabrication process before a third mask to adjust for error correction.
8. The system of claim 7 wherein database contains pattern images of operation steps.
9. The system of claim 7 wherein the database contains an average value of asymmetry of symmetric structure within the integrated circuit.
10. The system of claim 7 wherein the first mask is an active area mask, the second mask is a gate mask, and the third mask is a contact mask.
11. The system of claim 7 wherein the means for comparing includes a means for utilizing a plurality of overlay measurement algorithms.
12. The system of claim 10 wherein the contact mask is adjusted to reduce the risk of a contact-to-gate short and/or striation.
13. A system for controlling an overlay shift on an integrated circuit, the system comprising:
a scanning electron microscope (SEM) to measure the overlay shift between a first and a second mask of the integrated circuit after a second mask; and
a processing system including a database, wherein the processing system compares the measured overlay shift to overlay shift information within the data base and provides a control mechanism to analyze the overlay shift and feed forward to the fabrication process before a third mask to adjust for error correction.