Wafer level alignment structures using subwavelength grating polarizers

• US 20090002706A1
• Filed: 06/26/2007
• Published: 01/01/2009
• Est. Priority Date: 06/26/2007
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Blanton, William T., Weiss, Martin, Koffas, Telly, Kinnear, Brian, Yang, Ming-chuan, Fryer, David
• Granted Patent: US 8,004,678 B2
• Time in Patent Office: Days
• US Class Current: 356/369
• CPC Class Codes: G03F 9/7065 Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength
• CPC Class Codes: G03F 9/7076 Mark details, e.g. phase grating mark, temporary mark

Abstract

In one embodiment, a wafer alignment system, comprises a radiation source to generate radiation, a radiation directing assembly to direct at least a portion of the radiation onto a surface of a wafer, the radiation having a polarization state, an optical analyzer to collect at least a portion of the radiation reflected from the wafer, the wafer including at least a first region having a first grating pattern oriented in a first direction and at least a second region having a second grating pattern oriented in a second direction, different from the first direction.

Claims

1. A wafer alignment system, comprising:

a radiation source to generate radiation;

a radiation directing assembly to direct at least a portion of the radiation onto a surface of a wafer, the radiation having a polarization state;

an optical analyzer to collect at least a portion of the radiation reflected from the wafer;

the wafer including at least a first region having a first grating pattern oriented in a first direction and at least a second region having a second grating pattern oriented in a second direction, different from the first direction.

2. The system of claim 1, wherein:

the radiation source generates radiation having a wavelength;

the first grating pattern has a pitch that is less than the wavelength; and

the second grating pattern has a pitch that is less than the wavelength.

3. The system of claim 1, wherein the radiation directing assembly comprises at least one polarizer to polarize the radiation to a linear polarization state or an elliptical polarization state.

4. The system of claim 1, wherein the first grating pattern and the second grating pattern are formed in the same layer of material of the wafer.

5. The system of claim 1, wherein the first grating pattern and the second grating pattern are formed in different layers of material of the wafer.

6. The system of claim 1, wherein the first direction is substantially perpendicular to the second direction.

7. The system of claim 1, wherein the wafer comprises a plurality of regions having a first grating pattern oriented in a first direction and a plurality of regions having a second grating pattern oriented in a second direction, substantially perpendicular to the first direction.

8. The system of claim 1, wherein radiation reflected from the first grating pattern has a first polarization orientation and radiation reflected from the second grating pattern has a second polarization orientation.

9. The system of claim 8, wherein the optical analyzer distinguishes between radiation reflected from the first grating pattern and radiation reflected from the second grating pattern.

11. The method of claim 9, wherein:

forming a first grating pattern in a region of the wafer during a fabrication process comprises performing a first lithographic etching process; and

forming a second grating pattern in a region of the wafer during a fabrication process comprises performing a second lithographic etching process, different from the first process.

12. The method of claim 9, wherein directing radiation onto a surface of a wafer comprises:

generating radiation having a wavelength; and

polarizing the radiation to have an elliptical polarization state or a linear polarization state.

13. The method of claim 11 wherein:

the first grating pattern has a pitch that is less than the wavelength; and

the second grating pattern has a pitch that is less than the wavelength.

14. The method of claim 12, wherein radiation reflected from the first grating pattern has a first intensity and radiation reflected from the second grating pattern has a second intensity, the difference in those intensities providing the optical contrast to differentiate the two grating patterns.

15. The method of claim 13, wherein detecting an orientation of the wafer using a characteristic of radiation reflected from the first region and the second region comprises distinguishing between the first intensity and the second intensity.

10. A method to detect an alignment of a wafer, comprising:

forming a first grating pattern in a region of the wafer during a fabrication process, the first pattern including a plurality of gratings oriented in a first direction;

forming a second grating pattern in a region of the wafer during a fabrication process, the second pattern including a plurality of gratings oriented in a second direction, different from the first direction;

directing radiation onto a surface of a wafer, the radiation having a polarization state;

collecting at least a portion of the radiation reflected from the wafer; and

detecting an orientation of the wafer using a characteristic of radiation reflected from the first region and the second region.