Radiant energy – Inspection of solids or liquids by charged particles
Reexamination Certificate
1999-01-20
2002-04-02
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
C073S105000
Reexamination Certificate
active
06365895
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a micro surface measuring apparatus preferably used for measuring a three-dimensional configuration of a machine component in the submillimeter order. For example, this measuring apparatus is applicable to the microstructural measurement for the micro machine parts as well as measurement of an inner surface configuration for the fuel injector nozzles employed in the internal combustion engines or the ink jet nozzles of various printers. More specifically, the present invention relates to a contact-type micro surface configuration measuring apparatus using a probe directly brought into contact with an objective surface to be measured, and also relates to a related method for manufacturing the probe.
The unexamined Japanese patent application No. Kokai 5-264214 or 6-323845 discloses a conventional contact-type micro surface measuring apparatus which is capable of inserting a probe into a narrow or deep portion in a microstructural body or member. Its detailed structure will be explained, hereinafter.
FIG. 15
shows a first conventional arrangement represented by the unexamined Japanese patent application No. Kokai 5-264214. A probe
101
, when actuated by an actuator
102
, oscillates in a direction shown by an arrow. The probe
101
is placed closely to a measuring object
103
. The measuring object
103
is mounted on an X stage
105
which is shiftable in the X-axis direction. The X stage
105
is mounted on a Z stage
104
which is shiftable in the Z-axis direction. The Z stage
104
is connected to and driven by a Z-axis feed mechanism
106
. The X stage
105
is connected to and driven by an X-axis feed mechanism
107
. A duty cycle measuring device
108
, interposed between the probe
101
and the measuring object
103
, measures the duty cycle. A computer
109
controls the Z-axis feed mechanism
106
, the X-axis feed mechanism
107
, and the duty cycle measuring device
108
.
According to this arrangement, the actuator
102
causes the probe
101
to oscillate at a predetermined position with a constant amplitude as shown by the arrow in FIG.
15
. Electrical conduction between the probe
101
and the measuring object
103
is detectable as short-circuit current measured when a DC voltage is applied between the probe
101
and the measuring object
103
. The duty cycle measuring device
108
detects the ratio of a conductive duration to the oscillation period.
For example, when the oscillating probe
101
exceeds a certain displacement “s” as shown in
FIG. 16A
, the electrically conductive condition is maintained between the probe
101
and the measuring object
103
as shown in FIG.
16
B.
FIG. 17
shows a relationship between the measured duty cycle and the relative distance between the probe
101
and the measuring object
103
. By recording the duty cycle in this manner, the Z-axis feed mechanism
106
is driven to detect the surface configuration of the measuring object
103
.
As understood from
FIG. 17
, the obtained relationship is not completely proportional. It is, however, possible to improve the proportionality when the sine wave in the oscillation of the probe
101
is changed to a triangular wave. When the undulation on the objective surface of the measuring object
103
exceeds the amplitude of the probe
101
, the X-axis drive mechanism
107
is controlled to re-position the measuring object
103
for the measurement of the surface configuration of the measuring object
103
.
A second conventional arrangement is based on the AFM (scanning-type atomic force microscope) techniques which have been rapidly developed and applicable to the micro configuration measurement. The unexamined Japanese patent application No. Kokai 6-323845 discloses an advanced AFM probe having a simplified structure and applicable to the micro configuration measurement for mechanical parts, whereas many of conventional AFM systems require a large-scale optical system to detect an interatomic force acting on the probe.
FIGS. 18 and 19
show the schematic arrangement of the second conventional arrangement. A probe
201
is made of an elastic filmy plate of SiO
2
or the like whose size is 200~300 &mgr;m in length, 40~50 &mgr;m in width, and 1.8 &mgr;m in thickness. A pointed tip
201
a,
made of ZnO whiskers, is bonded at the distal end of the probe
201
.
A piezoelectric film
202
b,
made of ZnO, is sandwiched between electrodes
202
a
and
202
c
and located on the surface of the probe
201
. The probe
201
is provided on the surface of a silicon wafer
203
.
FIG. 19
shows a practical arrangement of a measuring apparatus using the above-described probe
201
. A sample
206
is placed on a base body
204
via a Z-axis shift mechanism
205
. The probe
201
is attached to the base body
204
via an XYZ piezoelectric scanner
207
and a piezoelectric plate
208
as shown in the drawing.
According to this practical arrangement, the piezoelectric plate
208
causes the probe
201
to oscillate at its resonance frequency. The sample
206
approaches the pointed tip
201
a
of the probe
201
so closely that the oscillating condition of the probe
201
is significantly influenced by an interatomic force. A distortion signal, detectable by the piezoelectric film
202
b,
has the amplitude and phase variable in response to the detected oscillation. The position of the XYZ piezoelectric scanner
207
in the Z-axis direction is controlled so as to maintain the changes in the amplitude and phase of the distortion signal, thereby detecting the surface configuration of the sample
206
.
The AFM detection mode is roughly classified into a contact mode (tapping mode) and a non-contact mode, as introduced in the journal of society of precision engineering, Vol. 62, No. 3, 1996, pp.345~350. The non-contact mode is a measurement mode preferable in that no damage is given to the surface of the sample. However, an absorbing layer, such as water on the sample surface, gives adverse influence in this measurement mode. Thus, the measurement is performed in the vacuum.
On the other hand, the tapping mode is free from such problems derived from the absorbing layer. The AFM measurement according to this mode is generally performed in the air and is, therefore, applicable to the micro configuration measurement for many of mechanical parts.
FIGS. 20A and 20B
cooperatively show the principle of the contact detection in the tapping mode.
In the condition shown in
FIG. 20A
, the piezoelectric film
202
b
detects a distortion waveform
211
of the probe
201
whose phase is delayed 90° with respect to the exciting waveform
210
of the probe
201
. In the condition shown in
FIG. 20B
, the pointed tip
201
a
is brought into contact with the sample
206
. In such contact condition, the oscillation of the probe
201
is restricted so as to cause the distortion waveform
211
varied in the amplitude. The configuration of the sample
206
is thus measured based on the amplitude change of the distortion waveform
211
. Although not shown in the drawing, it will be possible to detect the configuration of the sample
206
based on the phase change in addition to the amplitude change.
The above-described two conventional measurements are applicable to the configuration measurement of a nozzle hole or a micro groove. However, they have the following problems.
According to the former case represented by the unexamined Japanese patent application No. Kokai 5-264214, the detection of contact condition basically relies on the electrical conduction between the probe
101
and the measuring object
103
. Thus, this measuring method is not applicable to the non-conductive members. Furthermore, even if the measuring object is electrically conductive, the measurement accuracy will be deteriorated by oxide films covering the surface or dusts on the surface.
On the other hand, the latter case represented by the unexamined Japanese patent application No. Kokai 6-323845 has the capability of detecting the internal micro configuration regardless of conductiveness o
Nguyen Kiet T.
Woo Louis
LandOfFree
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