Dual endpoint detection for advanced phase shift and binary photomasks

Patent metadata

Field	Value
Publication number	US-10453696-B2
Application number	US-201715726233-A
Country	US
Kind code	B2
Filing date	Oct 5, 2017
Priority date	Oct 12, 2012
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

The present invention provides a method and apparatus for etching a photomask substrate with enhanced process monitoring, for example, by providing for optical monitoring at certain regions of the photomask to obtain dual endpoints, e.g., etch rate or thickness loss of both a photoresist layer and an absorber layer. By monitoring transmissity of an optical beam transmitted through areas having photoresist layer and etched absorber layer at two different predetermined wavelength, dual process endpoints may be obtained by a signal optical detection.

First claim

The invention claimed is:

1. A method of determining a thickness loss of a photoresist layer during an etching process, comprising:
performing an etching process on an absorber layer disposed on a first surface of a substrate through a patterned photoresist layer in a plasma etch chamber;
directing radiation having at least two wavelengths greater than 400 nm to a first area of the absorber layer covered by the patterned photoresist layer and a second area of the absorber layer uncovered by the patterned photoresist layer during the etching process;
collecting an optical signal transmitted through the first area of the absorber layer covered by the patterned photoresist layer;
analyzing a waveform obtained from the optical signals at the wavelengths greater than 400 nm;
determining a thickness loss of the photoresist layer for etching the photoresist layer based on the transmitted optical signal; and
determining dual endpoints for etching the absorber layer and the photoresist layer in response to the optical signal becoming substantially horizontally flat.

2. The method of claim 1 , wherein the substrate is a photomask reticle.

3. The method of claim 1 , wherein analyzing the waveform further comprises:
analyzing a waveform as a function of time verses intensity at the wavelengths greater than 400 nm.

4. The method of claim 1 , wherein the absorber layer is a Cr containing layer.

5. The method of claim 1 , further comprising:
determining an endpoint for etching the photoresist layer in response to the optical signal becoming substantially horizontally flat.

6. The method of claim 1 , wherein the photoresist layer has a thickness between about 100 nm and about 1000 nm.

7. The method of claim 1 , wherein the wavelengths are between about 400 nm and about 800 nm.

8. The method of claim 1 , further comprising:
determining an endpoint for etching the photoresist layer in response to a signal intensity of the optical signal reaching to a peak value.

9. The method of claim 8 , wherein the endpoint is reached when the signal intensity is between about 50 percent and about 90 percent below a peak of the signal intensity of the optical signal.

10. The method of claim 8 , wherein the endpoint is reached when the signal intensity remains in a steady state condition.

Assignees

• Applied Materials Inc

Inventors

• Grimbergen Michael

Classifications

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• H10P74/23

  characterised by multiple measurements, corrections, marking or sorting processes · CPC title

• H10P50/694

  characterised by their behaviour during the process, e.g. soluble masks or redeposited masks · CPC title

• H10P50/242 Primary

  of Group IV materials · CPC title

• G03F1/80

  Etching · CPC title