Measuring and testing – Surface and cutting edge testing – Roughness
Reexamination Certificate
2002-01-08
2004-06-08
Raevis, Robert (Department: 2856)
Measuring and testing
Surface and cutting edge testing
Roughness
Reexamination Certificate
active
06745617
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning probe microscope, and more particularly, relates to a scanning probe microscope making it possible to shorten a contact time for a probe tip being contact with a sample surface and thereby perform measurement with smooth movement of the probe tip on the sample surface.
2. Description of the Related Art
A scanning probe microscope (SPM) is a measurement equipment capable of measuring objective samples of an atomic size level in its resolution. The scanning probe microscope is being used in various kinds of wide fields, such as measurement of the surface shape of substances or materials and measurement of the surface shape of semiconductor-chips including LSI. The scanning probe microscope is provided with a cantilever having a probe tip at its pointed end. The scanning probe microscope measures the sample by detecting a physical amount generated between the probe tip and the sample when making the probe tip approached to the sample to be measured with a required distance. There are various kinds of the scanning probe microscopes responding to the physical amounts used for the detection, such as a scanning tunneling microscope (STM), an atomic force microscope (AFM) and a magnetic force microscope (MFM). For this reason, the applicable field for the scanning probe microscope is being enlarged presently.
Among the above-mentioned microscopes, the atomic force microscope is suitable when detecting the surface shape of the sample with high resolution, and it actually becomes useful in the fields of the semiconductor devices, the optical disks and so on. Hereinafter, the atomic force microscope will be explained.
The principles of the measurement based on the atomic force microscope are roughly divided into “contact mode” and “non-contact mode” in response to the relationship produced between the probe tip and the sample surface. In the current stage, the measurement of the contact mode is mainly used in the technical field of industrial surface form measurement, because the measurement of the non-contact mode is slow in a measuring speed.
The outline of fundamental structure of the atomic force microscope performing the surface shape measurement in the contact mode is as follows.
In the atomic force microscope, a coarse movement mechanism section is fixed to a fixing part such as a support frame, and a fine movement mechanism section is attached to the lower part of the coarse movement mechanism section, and a cantilever is further attached to the lower end of the fine movement mechanism section. A probe tip is formed at the tip of the cantilever. The probe tip is directed to the surface of the sample placed at a lower spot in the state of approaching it to the sample. The above-mentioned coarse movement mechanism section is a means for approaching the probe tip to the surface of the sample in the height direction (Z direction) with a comparatively large distance, and it is used for an early approach movement of the probe tip. The fine movement mechanism section is a means for moving the probe tip to three-dimensional directions (each axis direction of X-axis, Y-axis and Z-axis intersecting perpendicularly mutually) in a comparatively fine distance. The fine movement mechanism section is comprised of a XY fine movement section for moving the probe tip along the sample surface directions (XY directions) as a scanning movement, and a Z fine movement section for moving the probe tip to the height direction. A control section controls operations of the coarse and fine movement mechanism sections. The cantilever is moved downward by the operations of the coarse and fine movement mechanism sections. When the probe tip approaches the sample surface sufficiently, the atomic force given from the sample surface to the probe tip causes the cantilever to be bent to make the cantilever deformation. Displacement detection means comprised of a laser light source and an optical detector detects the deformation of the cantilever. The laser light emitted from the laser light source is irradiated onto the back of the cantilever, and then the laser light reflected on the back of the cantilever enters the light-receiving surface of the optical detector. In accordance with the arrangement of the displacement detection means, when the deformation arises in the cantilever, the displacement of the probe tip in the Z direction can be detected, since the laser light incidence position on the light-receiving surface of the optical detector changes. The information on the position of the probe tip in the height direction, which is detected by the optical detector, is compared with a standard position (target standard value) set up beforehand, and the difference obtained by the above comparison is inputted into the above-mentioned control section. On the basis of the information on the difference, the control section gives a signal used for controlling the operation of Z fine movement section to the Z fine movement section so that the height of the probe tip to the sample surface (the difference between the sample and the probe tip) may be consistent with the standard position.
The configuration mentioned above makes the probe tip of the cantilever scan the shape of the sample surface to follow it, detecting the atomic force produced between the sample surface and the probe tip and controlling the distance between the sample surface and the probe tip to be constant (target standard value). In this measurement operation, the control section is usually configured by a proportion and integration control (PI control). In order to keep the distance between the sample surface and the probe tip constant, the atomic force between the sample surface and the probe tip can be kept contact.
When measuring the shape of the sample surface by following it based on the scanning operation while the distance between the sample and the probe tip is kept constant, as mentioned above, the contact mode is used. There are some modes in the contact mode, and they are shown in
FIGS. 4A
,
4
B and
4
C.
FIG. 4A
shows a static contact mode and
FIGS. 4B and 4C
show dynamic contact modes. In
FIGS. 4A-4C
, a reference number
101
designates the pointed end of the probe tip, and
102
the sample.
The static contact mode measurement is a most general method. In this measurement, the probe tip is continuously moved between each two of measuring points {circle around (1)}-{circle around (5)} along the surface of the sample
102
as shown by an arrow
103
. The measurement of this method makes it possible to perform a high-speed measurement in a viewpoint of time and space because it is performed with the continuous operation.
The Dynamic contact mode is arranged so that the probe tip
101
may once be separated from the surface of the sample
102
with the advance of the scanning movement. As to the dynamic contact mode,
FIG. 4B
shows the method of contacting the probe tip
101
onto the sample surface only at the measuring points {circle around (1)}-{circle around (5)} as shown by an arrow
104
, and
FIG. 4C
shows the method of repeating the contact and separation by making the probe tip
101
or the cantilever resonate in the Z direction as usually shown by arrow
105
using a sine wave etc. (several tens to several hundreds kHz). In
FIG. 4C
, the movements of contact and separation are also repeated in spots other than the measuring point {circle around (1)}-{circle around (5)}.
The measurement method by the above-mentioned static contact mode is unsuitable for samples which have steep level differences or generate large frictional forces, because the probe tip receives the force in the scanning direction or the frictional force with the advance of the scanning movement. Furthermore, if a large lateral force is operated to the probe tip, the sample surface is damaged, and therefore it is also unsuitable for the measurement of soft samples.
The above-mentioned dynamic contact mode shown in
FIGS. 4B and 4C
can solve the problem abou
Hitachi Kenki FineTech. Co., Ltd.
Mattingly Stanger & Malur, P.C.
Raevis Robert
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