Scanning probe microscope with the stage unit

Details Scanning probe microscope with the stage unit Scanning probe microscope with the stage unit

1998-10-06

2001-02-06

Berman, Jack (Department: 2881)

Radiant energy

Inspection of solids or liquids by charged particles

Analyte supports

C073S105000

Reexamination Certificate

active

06184533

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a movement stage unit used for moving a sample or positioning it at a predetermined place, and a scanning probe microscope equipped with the movement stage unit.
2. Description of the Related Art
A scanning probe microscope has high resolution capable of measuring or observing fine objects substantially equal to a size of atoms or molecules. In the scanning probe microscope, a measuring and observing section including a detecting section observes a sample like a wafer mounted on a sample stand.
A typical sample stage mechanism used in the conventional scanning probe microscope is shown in
FIG. 10
, for example. This sample stage mechanism is configured by an X-axis direction stage
901
, a Y-axis direction stage
902
and a Z-axis direction stage
903
, which are piled up so as to make a triple structure. The sample stage mechanism is placed on a surface table
904
. The Z-axis direction stage
904
is equipped with a sample stand
905
, on which a sample
906
such as a wafer and the like is mounted. A probe tip
907
for measuring a sample surface is arranged above the sample
906
. The probe tip
907
is disposed to a frame fixed on the surface table
905
. When each of the X-axis direction stage
901
, the Y-axis direction stage
902
and the Z-axis direction stage
903
operates individually, the sample
906
mounted on the sample stand
905
can be moved toward any place. The probe tip
907
scans the surface of the sample
906
based on a change of the relative positional relationship between the sample
906
and the probe tip
907
.
For the scanning probe microscope, in general, it is preferable to fail to transmit external vibrations into the sample. Therefore, it is desirable to increase the rigidity of the middle structure from the probe tip
907
to the sample
906
. However, in the conventional scanning probe microscope with the sample stage mechanism having the aforementioned triple structure, the entire rigidity of the sample stage mechanism is determined by the structure formed out of combining the X-axis direction stage, the Y-axis direction stage and the Z-axis direction stage in series. This structure of the series combination results in a lowering of the entire rigidity because each rigidity of the three stages are added. Further, since the three stages piled-up structure increases the entire height of the sample stage mechanism, the shape of the frame
908
increases in its size, and therefore the rigidity of the frame
908
is reduced.
As a prior art literature stating the art for increasing the rigidity of the structural section from a detecting section to the sample in the sample stage mechanism of the scanning probe microscope, the publication of Tokko-Hei (Patent) No.1-34746 can be cited. The apparatus stated in the literature is adapted to reduce the structure of movable sections in its size as small as possible and to directly drive the movable sections by driving sections. However, since the driving section in the movable section operates based on the direct driving system and the point end of the driving section has functions of driving and supporting, the apparatus of the prior art poses a problem that the rigidity of the sample stage mechanism is determined by the rigidity of the driving sections. To say concretely, each rigidity of steel balls, floating pads, nut members, feeding screws have an effect on the entire rigidity based on their series relationship. In addition, the structure for the direct driving increases the height of the sample stage mechanism.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a stage unit used for moving a sample, in which its whole rigidity is increased and its height is decreased as low as possible and further the rigidity of driving sections thereof have few effect to the whole rigidity.
Another object of the present invention is to provide a scanning probe microscope having the stage unit.
The stage unit of the present invention is configured as follows in order to achieve the above-mentioned objects.
The stage unit used for moving a sample in accordance with the present invention comprises, if it is arranged on a horizontal surface table, a vertical stage (Z-axis direction stage) for moving a sample stand upward and downward in a vertical direction, a horizontal stage (X-axis and Y-axis direction stages) for moving the vertical stage in a horizontal direction. The stage unit is fixed to a horizontal slide surface of the surface table. The horizontal stage is fixed on the slide surface and the vertical stage is slidably arranged on the slide surface. The vertical stage is coupled with the horizontal stage by means of coupling members (for example, plate spring) having strong rigidity in the horizontal direction and weak rigidity in the vertical direction.
In accordance with the above configuration, the whole rigidity of the stage unit is determined only by the vertical stage and is not subject to the effect of the rigidity of the sections included in the horizontal stage and the rigidity of a driving section as to each axis direction. Consequently, the rigidity of the stage unit can be increased. Further, the standstill rigidity of the stage unit is determined only by the rigidity of the vertical stage. Since all stages of the stage unit are not piled up and further the height of stage unit is determined only by the vertical stage, the height of the stage unit can be lowered as low as possible, and therefore the height of a probe-tip-supporting frame arranged above the sample can be lowered.
The stage unit may have a wedges-combination mechanism operating as an ascent and descent mechanism in the vertical stage. The wedges-combination mechanism performs the upward and downward movement of the sample stand based on the horizontal movement operations of the slope thereof. The wedges-combination mechanism is capable of increasing the rigidity thereof and decreasing the height as the ascent and descent mechanism.
In the stage unit, the wedges-combination mechanism comprises an upper wedge member on which the sample stand is arranged, and a lower wedge member movable in the horizontal direction by a driving section. The upper and lower wedge members are placed so that their slopes face with each other.
In the stage unit, the horizontal stage comprises a first-axis (X-axis) direction stage and a second-axis (Y-axis) direction stage. The first-axis direction stage is fixed on the slide surface of the surface table. The second-axis direction stage is arranged on the first-axis direction stage so as to be movable by a rail guide mechanism and has a moving frame which is movable by another rail guide mechanism. In this case, the vertical stage is coupled with the moving frame by means of the coupling members.
In the stage unit, further, the horizontal stage comprises a first-axis (X-axis) direction stage and a second-axis (Y-axis) direction stage, and the first-axis direction stage is fixed on the slide surface of the surface table, and further the second-axis direction stage is placed in an inside space of the first-axis direction stage so as to be slidable on the slide surface. In this case, the vertical stage is placed in an inside space of the second-axis direction stage so as to be slidable on the slide surface of the surface table.
In the stage unit, a bottom plate of the vertical stage may have an air-emitting mechanism which emits an air through nozzles formed on a lower surface of the bottom plate. This configuration enables the vertical stage to move smoothly on the slide surface of the surface table without having friction.
Further, the scanning probe microscope of the present invention is provided with the above-mentioned stage unit and a detecting section including a probe tip directed to a sample mounted on the sample stand. This scanning probe microscope observes the sample by causing the probe tip to scan the sample surface in accordance with the movement of the sample by means of the stage

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