Process control monitors for interferometric modulators

• US 7,869,055 B2
• Filed: 08/20/2007
• Issued: 01/11/2011
• Est. Priority Date: 09/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gally, Brian, Cummings, William
• Primary Examiner(s): Lee; Hwa S. A
• Application Number:
  US11/841,633
• Publication Number:
  US 20080002206A1
• Time in Patent Office: 1,240 Days
• Field of Search: 356/503, 356/506, 356/517, 356/519
• US Class Current: 356/506
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 99/004 during manufacturing
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

Process control monitors are disclosed that are produced using at least some of the same process steps used to manufacture a MEMS device. Analysis of the process control monitors can provide information regarding properties of the MEMS device and components or sub-components in the device. This information can be used to identify errors in processing or to optimize the MEMS device. In some embodiments, analysis of the process control monitors may utilize optical measurements.

Claims

1. A wafer, comprising:

a plurality of interferometric modulators used in a display, the interferometric modulators comprising a plurality of material layers comprising a first mechanical membrane having a plurality of holes; and

a process control monitor that reflects incident light and provides information regarding processes used to manufacture the interferometric modulators, wherein the process control monitor comprises one or more of the material layers but less than all of the plurality of material layers, wherein the process control monitor comprises a second mechanical membrane with more holes than the first mechanical membrane of the interferometric modulators.

2. The wafer of claim 1, wherein the process control monitors includes an etalon.

3. The wafer of claim 2, wherein no substantial air gap exists between reflecting surfaces in the etalon.

4. The wafer of claim 1, wherein a final layer formed in the process control monitor is substantially reflective.

5. The wafer of claim 4, wherein layers other than the final layer formed in the process control monitor are substantially transparent.

6. The wafer of claim 1, wherein the process control monitor comprises a non-modulating interferometer.

7. The wafer of claim 1, wherein the process control monitor comprises at least three layers of material that are also present in the plurality of interferometric modulators.

8. The wafer of claim 1, wherein the plurality of interferometric modulators and the process control monitor are disposed on a substantially transparent substrate.

9. The wafer of claim 8, wherein the process control monitor substantially reflects light incident through the substrate.

10. The wafer of claim 1, wherein the plurality of interferometric modulators and the process control monitor each comprise conductive partial mirrors and conductive mirrors.

11. The wafer of claim 1, wherein the plurality of interferometric modulators and the process control monitor each comprise substantially transparent layers.

12. The wafer of claim 1, additionally comprising:

a plurality of other interferometric modulators used in the display, the plurality of other interferometric modulators comprising the plurality of material layers, wherein the plurality of interferometric modulators reflect light of a different color than the plurality of other interferometric modulators;

another process control monitor that reflects light of a color substantially the same as the plurality of other interferometric modulators, wherein the another process control monitor comprises one or more but less than all of the plurality of material layers.

13. The wafer of claim 12, wherein the another process control monitor comprises another etalon.

14. The wafer of claim 13, wherein no substantial air gap exists between reflecting surfaces in the another etalon.

15. The wafer of claim 12, wherein the plurality of interferometric modulators and the process control monitor reflect substantially red light.

16. The wafer of claim 15, wherein the plurality of other interferometric modulators and the another process control monitor reflect substantially blue light.

17. The wafer of claim 15, wherein the plurality of other interferometric modulators and the another process control monitor reflect substantially green light.

18. The wafer of claim 1, wherein the interferometric modulators each comprise a sacrificial layer and the process control monitor comprises a sacrificial layer, and wherein at any given time during an etching process the process control monitor comprises a greater amount of sacrificial layer than each interferometric modulator.