Controlling thermal expansion of mask substrates by scatterometry

• US 6,654,660 B1
• Filed: 11/04/2002
• Issued: 11/25/2003
• Est. Priority Date: 11/04/2002
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Subramanian, Ramkumar, Singh, Bhanwar, Phan, Khoi A., Rangarajan, Bharath, Lyons, Christopher F.
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US10/287,292
• Time in Patent Office: 386 Days
• Field of Search: 438/14, 700/121, 716/4, 356/630, 356/301, 356/328, 430/30, 430/313, 382/144
• US Class Current: 700/121
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 7/70875 Temperature, e.g. temperature control of masks or workpieces via control of stage temperature

Abstract

One aspect of the present invention relates to a system and method for controlling thermal expansion on an EUV mask during EUV photolithography. The system includes an EUV photolithography system for irradiating one or more layers of a wafer through one or more gratings of a patterned EUV mask, whereby heat accumulates on at least a portion of the patterned EUV mask during the irradiation of the one or more layers of the wafer; an EUV mask inspection system for monitoring the one or more gratings on the mask to detect expansion therein, the inspection system producing data relating to the mask; and a temperature control system operatively coupled to the inspection system for making adjustments to the EUV photolithography system in order to compensate for the detected expansion on the mask. The method involves employing feedback and feed forward control to optimize the current and future EUV photolithography processes.

Claims

1. A system for controlling thermal expansion on a mask during photolithography of an underlying wafer comprising:

a photolithography system comprising an irradiation source and a mask, whereby heat accumulates on at least a portion of the mask while irradiating one or more layers of the underlying wafer;

a mask inspection system for monitoring one or more gratings on the mask to detect expansion therein, the mask inspection system producing data relating to the mask;

a temperature control system operatively coupled to the mask inspection system and the photolithography system for making adjustments to the photolithography system in order to control the detected expansion on the mask and to mitigate undesirable pitch changes on the mask; and

a mask cooling system operatively connected to the temperature control system such that the temperature control system signals the cooling system to treat the mask in order to compensate for the detected expansion on the mask.

2. The system of claim 1, wherein the data from the mask inspection system is fed forward to a subsequent photolithography process to facilitate forming features on a subsequent wafer using the mask such that thermal expansion on the mask is substantially mitigated.

3. The system of claim 1, wherein the data from the mask inspection system comprises numerical data and calculated values associated with an amount of thermal expansion at the one or more gratings of the mask.

4. The system of claim 1, wherein the mask inspection system comprises a scatterometer.

5. The system of claim 4, wherein the mask inspection system comprises a processor for computing measurements collected by the scatterometer.

6. The system of claim 1, wherein the temperature control system adjusts the photolithography system according to the data received from the mask inspection system.

7. The system of claim 1, wherein the mask inspection system communicates the data back to the photolithography system in order to control the detected expansion on the mask during a subsequent exposure of the wafer.

8. The system of claim 1, wherein the photolithography system comprises a wafer exposure system.

9. The system of claim 1, wherein the temperature control system signals the cooling system to treat the mask with cooling sufficient to control an undesired amount of the thermal expansion detected on the mask.

10. The system of claim 1, wherein the mask is anyone of a EUV mask, an I-line mask, a DUV mask and a G-line mask.

11. A system for controlling thermal expansion on a mask during photolithography of an underlying wafer comprising:

a photolithography system comprising an irradiation source and a mask, whereby heat accumulates on at least a portion of the mask while irradiating one or more layers of a wafer;

a mask inspection system for monitoring and measuring one or more gratings on the mask to detect expansion therein, the mask inspection system producing data relating to the mask;

a processor operatively connected to the mask inspection system for processing and analyzing the data produced by the inspection system, thereby generating output related to the detected expansion on the mask;

a mask temperature control system for receiving output generated by the processor in order to make an adjustment to one or more photolithography components to thereby compensate for the detected thermal expansion in the one or more of gratings on the mask; and

a mask cooling system operatively connected to the mask temperature control system and the photolithography system for controlling and mitigating the accumulated heat on the mask such that the thermal expansion is controlled.

12. The system of claim 11, wherein the data from the mask inspection system is fed forward to a subsequent photolithography process to facilitate forming features on a subsequent wafer using the mask such that thermal expansion on the mask is substantially mitigated.

13. The system of claim 11, wherein the output from the processor comprises numerical data and calculated values relating to an amount of thermal expansion detected on the mask.

14. The system of claim 11, wherein the mask inspection system comprises a scatterometer for measuring one or more gratings on the mask to determine an occurrence of expansion at one or more gratings on the mask.

15. The system of claim 11, wherein the processor communicates the output back to the photolithography system in order to compensate for an undesired amount of the thermal expansion detected on the mask during a subsequent exposure of the wafer.

16. The system of claim 11, wherein the photolithography system comprises a wafer exposure system.

17. The system of claim 11, wherein the mask is anyone of a EUV mask, an I-line mask, a DUV mask and a G-line mask.

18. A method for controlling thermal expansion on a mask during a photolithography process comprising:

providing a semiconductor structure having a mask thereover, the mask having one or more gratings therein;

exposing the semiconductor structure through the one or more gratings of the mask with a wavelength of light during a wafer exposure process;

monitoring the one or more gratings of the mask for thermal expansion in order to generate data related to the one or more gratings; and

signaling a cooling chamber to treat the one or more gratings of the patterned mask where thermal expansion is detected in order to control an amount of thermal expansion on the mask.

19. The method of claim 18, wherein monitoring the one or more gratings of the patterned mask comprises:

directing a beam of incident light at the one or more gratings on the mask;

collecting light reflected from the one or more gratings on the mask; and

analyzing the reflected light with respect to the incident light to determine whether the one or more gratings are affected by thermal expansion to facilitate controlling an amount of thermal expansion on the mask.

20. The method of claim 18, further comprising wherein monitoring the one or more gratings on the mask is performed by a scatterometer.

21. The method of claim 18, wherein etching of the semiconductor substrate is performed by a wafer exposure system via one or more photolithography components.

22. The method of claim 18, further comprising feeding data corresponding to the determined thermal expansion back to the etch process so as to effect a change in one or more photolithography components in order to mitigate the occurrence of thermal expansion in future photolithography processes.

23. The method of claim 18, further comprising feeding data corresponding to the thermal expansion forward to subsequent photolithography processes in order to mitigate thermal expansion during future processing.

24. The method of claim 18, further comprising feeding data corresponding to the thermal expansion back to the wafer exposure process in order to make an adjustment to one or more photolithography components so as to control an amount of thermal expansion on the mask for a subsequent exposure process.

25. The method of claim 18, further comprising cooling the mask during the photolithography process to control an amount of thermal expansion detected on the mask.

26. The method of claim 18, wherein the mask is anyone of a EUV mask, an I-line mask, a DUV mask and a G-line mask.