Detecting thickness variation and quantitative depth utilizing scanning electron microscopy with a surface profiler

Patent metadata

Field	Value
Publication number	US-9372078-B1
Application number	US-201414310294-A
Country	US
Kind code	B1
Filing date	Jun 20, 2014
Priority date	Jun 20, 2014
Publication date	Jun 21, 2016
Grant date	Jun 21, 2016

Abstract

A method and system to detect thickness variation of a subject material are described. In an aspect, tribological wear is assessed for a disk drive memory system at the pole tip region of a magnetic head. Images are obtained of a first region and a second region of a subject material utilizing scanning electron microscopy (SEM). The SEM images are image processed to obtain a differential contrast between the first region and the second region. An image intensity variation is determined between masked SEM images of the first region and the second region by obtaining a surface profiler image of the first region and the second region, and overlaying and calibrating the SEM images with the surface profiler images. In an aspect, image intensity variation is converted to quantified thickness utilizing a fitted relation obtained from the calibration of the surface profiler images with the SEM images.

First claim

We claim:

1. A method for detecting thickness variation of a subject material for a data storage system comprising:
i.) obtaining images of a first region of the subject material and a second region of the subject material utilizing scanning electron microscopy (SEM), wherein the subject material is a material of the data storage system;
ii.) image processing the SEM images to obtain a differential contrast between the first region and the second region, wherein: a.) the first region has less thickness than the second region; b.) the subject material is overlying a second material; and c.) the image processing utilizes the second material to differentially contrast the first region from the second region; and
iii.) determining image intensity variation between the masked SEM images of the first region and the second region by obtaining a surface profiler image of the first region and the second region, and overlaying and calibrating the SEM images with the surface profiler images.

2. The method as in claim 1 , wherein the subject material is one of:
i.) at least a portion of a magnetic read head overcoat and/or write head overcoat, wherein the overcoat is diamond-like carbon; and
ii.) a surface of a data storage disk facing an air bearing surface.

3. The method as in claim 1 , further comprising background leveling the SEM images by at least one of:
i.) top-hat filtering the first region;
ii) two-dimensional spline fitting the first region; and
iii.) flat-frame calibration the first and second region.

4. The method as in claim 1 , further comprising masking thickness variation of the SEM images of the first region and the second region, to obtain a two-dimensional black and white mask including the first region and the second region.

5. The method as in claim 4 , further comprising normalizing contrast variation between a series of SEM images of the second region by mapping an intensity of the series of SEM images of the second region utilizing linear or low-order fitting, and comparing the series of the SEM images of the second region with an intensity of a reference image of the second region.

6. The method as in claim 5 , further comprising secondary masking the thickness variation of the SEM images of the first region and the second region, to obtain a refined two-dimensional black and white mask including the first region and the second region.

7. The method as in claim 1 , wherein the surface profiler images are atomic force microscope (AFM) images of the first region and the second region.

8. The method as in claim 1 , further comprising converting image intensity variation to quantified thickness utilizing a fitted relation obtained from the calibration of the surface profiler images with the SEM images.

9. A method to quantify magnetic read and/or write head tribological wear depth, for a data storage system comprising:
i.) obtaining images of a first region of the magnetic head and a second region of the magnetic head utilizing scanning electron microscopy (SEM);
ii.) background leveling the SEM images;
iii.) image processing the SEM images to obtain a differential contrast between the first region and the second region, wherein: a.) the first region has less thickness than the second region; b.) the magnetic head is overlying a second material; and c.) the image processing utilizes the second material to differentially contrast the first region from the second region;
iv.) masking thickness variation of the SEM images of the first region and the second region, to obtain a two-dimensional black and white mask including the first region and the second region;
v.) determining image intensity variation between the masked SEM images of the first region and the second region by obtaining a surface profiler image of the first region and the second region, and overlaying and calibrating the SEM images with the surface profiler images; and
vi.) converting image intensity variation to quantified thickness utilizing a fitted relation obtained from the calibration of the surface profiler images with the SEM images.

10. The method as in claim 9 , wherein the surface profiler images are atomic force microscope (AFM) images of the first region and the second region.

Assignees

• Western Digital Fremont Llc

Inventors

• Ruthe Kurt C
• Leary Sean P

Classifications

• H01J37/222

  Image processing arrangements associated with the tube · CPC title

• G01B15/02 Primary

  for measuring thickness · CPC title

• G06T7/0008

  checking presence/absence · CPC title

• G06T2207/10061

  from scanning electron microscope · CPC title

• G06T2207/30136

  Metal · CPC title