Radiant energy – Inspection of solids or liquids by charged particles – Positive ion probe or microscope type
Reexamination Certificate
2001-02-07
2003-12-16
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Positive ion probe or microscope type
C073S105000
Reexamination Certificate
active
06664540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microprobe constituted by a cantilever provided with a piezoresistive element on a surface of a semiconductor substrate and a sample surface measuring apparatus observing a very small area (nanometer order) of the sample surface by using the microprobe.
2. Description of the Prior Art
Currently, as a microscope for observing a very small area of nanometer order on a surface of a sample, there is known a Scanning Probe Microscope (SPM). In the field of SPM, an Atomic Force Microscope (AFM) uses a microprobe constituted by a cantilever provided with a stylus at a front end portion thereof and the stylus of the cantilever is made to scan along a surface of a sample constituting an observation object and atomic force (attractive force or repulsive force) caused between the surface of the sample and the stylus is detected as an amount of bending the cantilever to thereby measure the shape of the surface of the sample.
It is known that the above-described microprobe is classified into a microprobe of an optical lever type and a microprobe of a self detection type by a difference in a system of detecting the bending amount of the cantilever. The optical lever type microprobe referes to a microprobe used in a system in which a laser beam is irradiated to an end portion of the cantilever constituting the microprobe and the above-described bending amount is detected by measuring a change in an angle of reflection thereof. This system is also known as an optical lever detection system.
The optical lever type microprobe has the advantage that it is capable of being fabricated inexpensively in comparison with the self detection type microprobe. On the other hand, the optical lever type microprobe has the drawback that when it is used in an atomic force microscope, it is necessary to finely adjust an irradiation angle of a laser beam irradiated to the cantilever and a position of a photodiode for detecting a reflection beam from the cantilever and the like. In particular, which interchanging the cantilever which is frequently carried out, the fine adjustment must be carried out repeatedly, which is troublesome.
Meanwhile, the self detection type microprobe refers to a microprobe forming a piezoresistive element on the cantilever and capable of detecting the bending amount of the cantilever by measuring a variation in a resistance value thereof.
According to the self detection type microprobe, when used in an atomic force microscope, since a detector (piezoresistive element) for detecting the bending amount of the cantilever is formed at the microprobe per se, there is provided an advantage in which in interchanging the cantilever, the troublesome operation of adjusting the position of the detector is not necessary and the observation of a sample can be started swiftly. On the other hand, in comparison with the optical lever type microprobe, there is provided a drawback in which the constitution of the microprobe becomes complicated and the microprobe becomes difficult to provide inexpensively to a user.
FIG. 10
is a block diagram showing an outline constitution of an atomic force microscope using particularly the above-described self detection type microprobe in these microprobes. In
FIG. 10
, an atomic force microscope
200
comprises a microprobe
201
(corresponding to the above-described self detection type microprobe) provided with a sharpened stylus
202
directed toward a surface of a sample
203
at its front end portion, an XYZ actuator
210
for finely moving the sample relative to the microprobe
201
in the horizontal direction (X, Y direction) and the vertical direction (Z direction), an actuator drive amplifier
212
for generating an XYZ control signal for driving the XYZ actuator
210
, a scanning signal generating unit for generating a signal (scanning signal) for finely moving the sample
203
at constant speed in a predetermined range in the above-described X and Y directions, a measuring unit
216
for acquiring a detection signal provided from a bending detecting portion (the above-described detector: piezoresistive element) on the microprobe
201
, a reference value generating unit
128
for generating a detection value in a steady state of the above-described bending detecting portion, that is, a reference value for detecting irregularities of the surface of the sample
203
, a comparator
220
for deriving an actual bending amount of the microprobe
201
by comparing signals respectively provided from the measuring unit
216
and the reference value generating unit
218
and a control unit
222
for generating a signal in correspondence with a displacement of the XYZ actuator
210
in Z direction based on a signal provided from the comparator
220
.
A brief explanation will be given of operation of the atomic force microscope
200
as follows. First, the user fixes the sample
203
constituting the observation object onto a stage on the XYZ actuator
210
and attaches the microprobe
201
at a comparatively remote position above thereof. Normally, the microprobe
201
is arranged with an electrode terminal for taking out a signal from the above-described bending detecting portion at an end portion thereof disposed opposedly to the stylus
202
and on a face opposed thereto in the longitudinal direction, normally, the microprobe
201
is provided separately from the atomic force microscope as an attachable and detachable cartridge type one facilitating electric connection between the electrode terminal and the measuring unit
216
and fixing an end portion thereof on the side of the electrode terminal.
After preparation before observing the sample has been finished in this way, successively, it is necessary to make the microprobe
201
sufficiently proximate to the sample
203
to a degree that the stylus
202
produces atomic force between the stylus
202
and the surface of the sample
203
. The proximity control is carried out firstly, while making the sample
203
being proximate to the stylus
202
by a Z-axis rough movement mechanism (not illustrated) in the XYZ actuator
210
, by monitoring whether a predetermined amount of signal can be acquired from the above-described bending detecting portion by the measuring unit
216
.
The Z-axis rough movement mechanism in the XYZ actuator
210
is instructed by a computer (not illustrated) for controlling operation of the atomic force microscope
200
under a predetermined condition via the user and is operated based on a Z control signal generated via the actuator drive amplifier
212
.
Further, the above-described predetermined amount of signal acquired in the measuring unit
216
is a signal indicating detection of the atomic force between the stylus
202
and the surface of the sample
203
and is actually informed by a signal outputted from the comparator
220
. In this case, the resistance value of the piezoresistive element per se constituting the bending detecting portion is varied by conditions other than bending such as temperature condition or the like and accordingly, the reference value of the reference value generating unit
218
constituting one of comparison objects of the comparator
220
, provides a reference resistance value for removing the unnecessary variation information from a variation in the resistance value measured at the bending detecting portion.
After finishing the above-described proximity control, at the scanning signal generating unit
214
, there is generated a scanning signal for instructing a movement in a predetermined range set on the computer, mentioned above, that is, in a plane range (XY range) in the XYZ actuator. Normally, the scanning signal is a signal for realizing so-to-speak raster scanning in which after finishing scanning operation in X direction while fixing a Y-axis point, the scanning is moved to a successive Y-axis point and the scanning operation in X direction is carried again.
The scanning signal is inputted to the actuator drive amplifier
212
, amplified pertinently to c
Shimizu Nobuhiro
Shirakawabe Yoshiharu
Takahashi Hiroshi
Yasumuro Chiaki
Adams & Wilks
Johnston Phillip A.
Lee John R.
Seiko Instruments Inc.
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