Process control monitors for interferometric modulators

• US 20060066872A1
• Filed: 11/17/2005
• Published: 03/30/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Cummings, William, Gally, Brian
• Granted Patent: US 7,403,323 B2
• Time in Patent Office: Days
• US Class Current: 356/504
• 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 method of measuring thicknesses of layers deposited during manufacture of a micro-electro-mechanical system (MEMS), comprising:

forming a process control monitor that comprises two or more layers successively deposited on top of each other, wherein the layers are formed using a process that is used for forming those layers during manufacture of the MEMS, wherein the layers are patterned such that at least two steps are formed in a profile of the structure; and

measuring the height of the steps by sweeping a profilometer across the structure.

2. The method of claim 1, wherein forming the process control monitor comprises applying an identical sequence of material deposition and patterning steps as used in the manufacturing of the MEMS.

3. The method of claim 1, wherein the profilometer is swept once across the structure.

4. The method of claim 1, wherein the MEMS is an interferometric modulator.

5. A process control monitor for measuring the thicknesses of a plurality of layers deposited during manufacturing of an interferometric modulator, comprising the layers stacked on top of each other so as to form at least two steps in a profile of the process control monitor.

6. The process control monitor of claim 5, wherein steps in the process control monitor monotonically increase and then monotonically decrease from one side of the profile to the other.

7. The process control monitor of claim 5, comprising a plurality of sacrificial layers, said sacrificial layers determining the depth of gaps formed in the interferometric modulators.

8. The process control monitor of claim 5, comprising a sacrificial layer and a mechanical membrane, wherein the mechanical membrane is adapted to protect the sacrificial layer during a release etch process.

9. The process control monitor of claim 5, comprising a cut in at least one layer such that the cut forms a step down in the profile of the process control monitor.

10. The process control monitor of claim 5, wherein at least one step in the process control monitor consists of one or more dielectric layers.

11. The process control monitor of claim 5, wherein at least one step in the process control monitor consists of a mechanical membrane structure.

12. The process control monitor of claim 5, wherein the height of at least one step in the process control monitor is substantially determined by the thickness of a sacrificial layer.

13. The process control monitor of claim 5, wherein the height of at least one step in the process control monitor is substantially determined by the thickness of planar material.

14. A wafer, comprising:

a plurality of reflective display elements adapted for use in a display, the reflective display elements comprising a plurality of material layers; and

a process control monitor comprising the plurality of material layers stacked on top of each other so as to form at least two steps in a profile of the process control monitor.

15. A method of manufacturing a combined micro-electro-mechanical system (MEMS) and process control monitor structure, comprising:

forming a MEMS structure, wherein forming the MEMS structure includes one or more material deposition and patterning steps, wherein the MEMS structure comprises a plurality of layers; and

simultaneously forming a process control monitor, wherein forming the process control monitor includes said one or more material deposition and patterning steps, wherein the process control monitor comprises the plurality of layers so as to form at least two steps in a profile of the process control monitor.

16. A wafer, comprising:

a plurality of first means for reflecting light for use in a display; and

second means for measuring thickness of at least one material deposited during manufacture of said first means.

17. The wafer of claim 16, wherein said first means comprises interferometric modulators.

18. The wafer of claim 16, wherein said second means comprises a process control monitor comprising a plurality of material layers stacked on top of each other so as to form at least two steps in a profile of the process control monitor.

19. A wafer produced by a process comprising:

depositing and patterning a series of material layers on a substrate to form a MEMS structure; and

simultaneously depositing and patterning the series of material layers on the substrate to form a process control monitor, wherein layers of material remaining in the process control monitor after the patterning form at least two steps in a profile of the process control monitor.

20. A method of testing a process used to manufacture a polychromatic interferometric modulator display, wherein different color interferometric modulators in the display are manufactured by forming different depth gaps between a partial reflector and a reflective mechanical membrane, wherein the depths of the gaps are determined by deposition of one or more sacrificial layers, wherein the depth of at least one gap is determined by deposition of a plurality of sacrificial layers, the method comprising:

forming a process control monitor that comprises the one or more sacrificial layers, wherein at least one region of the process control monitor comprises the plurality of sacrificial layers deposited on top of each other;

measuring a profile of the process control monitor; and

determining a cumulative thickness of the plurality of sacrificial layers from the profile.

21. The method of claim 20, wherein forming the process control monitor comprises:

sequentially depositing the plurality of sacrificial layers; and

patterning each sacrificial layer after its deposition and before depositing another sacrificial layer so that regions of the process control monitor are formed where less than all of the plurality of sacrificial layers are present.

22. The method of claim 20, wherein forming the process control monitor comprises depositing the mechanical membrane on top of the process control monitor so as to protect the sacrificial layers during an interferometric modulator release etch.

23. The method of claim 20, wherein measuring the profile of the process control monitor comprises:

measuring the thickness of the process control monitor in a region comprising a single sacrificial layer;

measuring the thickness of the process control monitor in a region comprising two sacrificial layers; and

measuring the thickness of the process control monitor in a region comprising three sacrificial layers.

24. A process control monitor for use in testing a process used to manufacture a polychromatic interferometric modulator display, wherein different color interferometric modulators in the display are manufactured by forming different depth gaps between a partial reflector and a reflective mechanical membrane, wherein the depths of the gaps are determined by deposition of one or more sacrificial layers, wherein the depth of at least one gap is determined by deposition of a plurality of sacrificial layers, the process control monitor comprising a plurality of material layers on top of each other, wherein one region of the process control monitor includes a single sacrificial layer, a second region of the process control monitor includes two sacrificial layers on top of each other, and a third region of the process control monitor includes three sacrificial layers on top of each other.

25. The method of claim 24, wherein the process control monitor comprises the mechanical membrane deposited on the top of the process control monitor so as to protect the sacrificial layers during an interferometric modulator release etch.

26. The method of claim 24, wherein the process control monitor comprises planar material between regions comprising sacrificial layers.