JPH02118426A - Method for measuring internal strain of alumina ceramics material - Google Patents

Abstract

PURPOSE:To directly measure the internal strain of an alumina ceramics sample without contact by measuring the phase difference DELTA of the above-mentioned sample by a polarization analysis method and contrasting the measured value with the reference value of the phase difference DELTA which is set by the previously determined correlation between the internal strain and phase difference DELTA of the sample. CONSTITUTION:The phase difference DELTA of the alumina ceramics sample which is precisely polished to <=50Angstrom surface roughness is first estimated by the polarization analysis method. This measured value is then contrasted with the reference value of the phase difference DELTA set by the previously determined correlation between the internal stress and phase difference DELTA of the sample, by which the internal strain of the work is relatively decided. A method for immersing the sample in HNO3 and treating the sample while oscillating the sample to prevent the generation of unequal etching is preferable as the method of precisely polishing the surface of this material to <=50Angstrom surface roughness. The rate of etching is controllable by the concn. of the NHO3 and the etching time.

Description

[Detailed Description of the Invention] Field of Application This invention relates to a method for measuring internal strain in alumina-based ceramic materials, in which internal strain is relatively measured non-destructively from a mirror-finished surface of the material using ellipsometry. Regarding the method.

BACKGROUND ART Today, there is a strong demand for higher recording density and improved wear resistance for various types of magnetic heads, including those for computers and audio VTRs. A magnetic head is considered optimal.

Generally, Mn-Zn is used as thin film magnetic head substrate material.
Nonmagnetic materials with excellent wear resistance and precision machinability, such as soft magnetic materials such as ferrite, Ni--Zn ferrite, and sendust, or alumina-based ceramic materials such as Al2O3-TiC, are used as substrates.

In addition, the reduction of the flying height of the thin film magnetic head slider and the flatness of the slider surface require processing accuracy of about 1/1100p, and in order to obtain such a high-precision flat surface, it is necessary to
As with processing techniques such as grinding and lapping, and flatness measurement techniques, it is also necessary to fully consider the internal strain of the workpiece.

The causes of warpage that occurs in the workpiece during such processing can be broadly classified into the following two types. One is when warpage occurs due to the strain difference between the front and back surfaces due to the presence of a strained layer on the surface of the workpiece, and the other is when the internal strain inherent in the workpiece is released by surface treatment. This is a case where warping occurs.

To counter the above warping, in the former case, methods are used to process the material into a distortion-free flat surface using etching or mechanochemical polishing, or by developing materials with a high Young's modulus.

However, if the latter internal strain is inherent in the substrate, it cannot be removed by the above process, and it is necessary to measure the degree of the internal strain and take measures.

Generally, methods for measuring internal strain include a direct method, which measures the amount of warpage that occurs during machining of the workpiece;
Methods used include measuring changes in warpage due to heat treatment, and observing dislocations, microcracks, impurities, etc. that depend on internal defects and grain boundaries based on etching rate and etch bit.

Further, as an indirect method, there is a method of measuring internal strain based on the amount of change in the lattice spacing of the workpiece using an X-ray stress measuring device.

Such measurement methods mainly involve destructive testing, and 100% testing for quality control purposes is not possible during actual operations or mass production.

In addition, a plate-shaped photoelastic body with holes is adhesively fixed to the member to be measured in advance, and while an external pressure is applied to this member, light is irradiated onto the photoelastic body, and an interference fringe image of the reflected light is obtained. A method of measuring the stress of the member by comparing it with a plurality of reference interference fringe images was proposed (Japanese Patent Laid-Open No. 58-22372).
Publication No. 5).

The above measurement method is a method in which the stress of the member is indirectly measured via a photoelastic body in a state where an external pressure is applied, and it is not possible to measure the internal strain of the member to be measured before the external pressure is applied.

Purpose of the Invention The present invention provides Al2O3-TiC, Al203-Ti0
The purpose is to develop an internal strain measurement method that can directly measure the internal strain of alumina-based ceramic materials such as 2 and those with additives added, without contact. The purpose is to measure the

Summary of the Invention This invention measures the phase difference Δ of an alumina ceramic sample that has been precisely polished to a surface roughness of 50A or less by ellipsometry, and compares the measured value with the predetermined internal strain of the sample and the phase difference Δ. This is a method for measuring internal strain in an alumina-based ceramic material, which is characterized in that internal strain in a workpiece is relatively determined by comparing a reference value of a phase difference Δ set based on the correlation.

In this invention, methods for precision polishing the surface of the alumina ceramic material to a surface roughness of 50A or less include, for example, diamond polishing and mechanochemical polishing, and there are various methods for etching, which can be adopted as appropriate. Immerse the sample in
It is preferable to use a method in which etching is performed by rocking motion to prevent uneven etching, and the amount of etching can be adjusted by adjusting the concentration of HNO3, etching temperature, and etching time.

Disclosure based on drawings of the invention FIG. 1 is an optical path diagram showing the principle of ellipsometry.

The ellipsometry method will be explained below. The ellipsometry method uses a sample (Sa
) Polarized light is projected onto a surface and the change in polarization state that occurs upon reflection is observed.

To find the phase difference (Δ) of the sample (Sa), first tilt the compensator (C) fastt'llll by n/4, and then tilt the polarizer (P
I) and the analyzer (A1) are rotated together so that the light transmitted through the analyzer becomes zero in a so-called crossed nicol state, and the polarizer azimuth (P azimuth) θ at this time is measured, and the following (
Obtain the phase difference (Δ) of the sample (Sa) from 1).

Δ=n/2-20 ・・・・・・・・・・・・(1)
Further, the polarizer azimuth (S azimuth) Φ is an observed value necessary to obtain the reflection coefficient ratio.

Next, the phase difference (Δ) of the sample obtained by ellipsometry
A method for relatively measuring the internal strain of a sample by comparing it with a set phase difference (Δ) based on the reference will be described in detail based on an embodiment of the present invention.

The sample materials include Al2O362wt%, TiC37wt%
, an Al2O3-TiC material having a composition of 1 wt% MgO was used.

The above samples are fired by hot pressing, but the internal strain varies depending on the firing conditions and heat treatment conditions, so the following three types of samples were prepared.

First, sample A was heated at 130°C after hot pressing at 1700°C.
The B sample was as-hot pressed at 1700°C, and the C sample was annealed at 0°C. It was hot pressed at 700°C and then annealed at 1400°C.

The above three types of samples are 25 mm wide, 5 mm thick, and 25 mm long.
The surface layer of each fired product was cut into 2 mm.
Diamond powder 7 with a particle size of 05 yen 1 m, ground over mm
Diamond polished using.

At this time, in order to make the process-affected layer formed on the surface layer of each sample the same, each sample was attached to the same lap substrate and lapped under the same processing conditions until the surface roughness was 50 mm.

After that, each sample was subjected to a polarimeter and the θ and Φ of each sample were measured.
Observed value. The observation conditions were a polarized light incident angle of 70°,
The measurement wavelength was 5461A.

Table 1 shows the observed values of each sample and the surface roughness measured by a surface step measuring device.

Accordingly, by comparing the above-mentioned effects, we determined the correlation between the phase difference and internal distortion of the lapped sample and the etched sample, set a reference value for the phase difference, and used this reference value to compare the lapping and internal distortions in the mass production process. By comparing the phase difference (Δ−Δ2) with the etched workpiece,
It is possible to relatively determine the internal strain of the workpiece, which is extremely effective in determining the quality of product lofts in terms of quality control, and is expected to improve yields in mass production.

Margin below Table 1

[Brief explanation of drawings]

FIG. 1 is an optical path diagram showing the principle of ellipsometry. In the figure, A1... analyzer, C... compensator, Pl...
Polarizer, Sa...sample, θ...polarizer azimuth, φ・
...Polarizer azimuth.

Claims (1)

[Claims] 1. Measure the phase difference Δ of an alumina ceramic sample that has been precisely polished to a surface roughness of 50 Å or less by ellipsometry,
The method is characterized in that the internal strain of the workpiece is relatively determined by comparing the measured value with a reference value of the phase difference Δ set based on the correlation between the internal strain of the sample and the phase difference Δ determined in advance. Method for measuring internal strain in alumina ceramic materials.