Browse Prior Art Database

Non-Contact And Dynamic Flying Height Control for Thin Film Sensors Using a Differential AC Phase Measuring Interferometer

IP.com Disclosure Number: IPCOM000120779D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 89K

Publishing Venue

IBM

Related People

Kulkarni, M: AUTHOR [+3]

Abstract

A method is developed to accurately (within a few angstroms) and repeatedly control the distance between two surfaces. These two surfaces can be the bottom surface of a partially coated glass slide and a polished ferrite surface. Any surface of known reflective properties can be substituted for either of these surfaces. The glass slide is mounted parallel to the object surface and with bottom surface at the focal plane of the microscope lens. Computer-controlled PZT stages can be used to move the object surface in the x, y, and z directions.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Non-Contact And Dynamic Flying Height Control for Thin Film Sensors
Using a Differential AC Phase Measuring Interferometer

      A method is developed to accurately (within a few
angstroms) and repeatedly control the distance between two surfaces.
These two surfaces can be the bottom surface of a partially coated
glass slide and a polished ferrite surface.  Any surface of known
reflective properties can be substituted for either of these
surfaces.  The glass slide is mounted parallel to the object surface
and with bottom surface at the focal plane of the microscope lens.
Computer-controlled PZT stages can be used to move the object surface
in the x, y, and z directions.  A linearly polarized laser beam is
split into two orthogonally polarized beams and these two beams are
projected through an optical system so that one of the beams is
radiated onto the thin film/glass interface and the other passes
through the glass and is reflected back at the object surface.  A
phase shift interferometer examines the irradiated light from the
surfaces and calculates the phase change.  This phase change is a
function of the distance between the bottom surface of the glass
slide and materials of the object surfaces.

      The phase change can be directly correlated to the distance
between the objects.  This method provides a contactless measurement
of the distance between the bottom of the glass slide (glass/air
interface) and the sample surface.

      The zero reference plane is established beforehand by the
following procedure.  The two beams of the differential phase
interferometer are focussed on the bottom surface of the glass slide
while making sure that one of the beam spots was on the glass/metal
interface while the other was in the clear area and was reflected at
the glass/air interface only (no object).  The phase difference
between the two beams is measured by the interferometer (which is
computer controlled).  The computer stores the phase difference...