JP3188024B2 - Scanning probe microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic force microscope for observing the surface of a sample at an atomic resolution.

[0002]

2. Description of the Related Art An atomic force microscope (AFM) has a flexible cantilever having a probe at a free end and detects displacement of the free end of the cantilever caused by an atomic force acting between the probe and a sample. The apparatus scans the probe along the surface of the sample while keeping it constant, thereby observing the surface shape image of the sample at the atomic resolution.

In such an AFM, methods for detecting the displacement of the free end of the cantilever include an optical interference method, an optical focusing detection method, and an optical lever method. Among them, the optical lever method is generally used because of its simple structure and excellent detection sensitivity.

Recently, there has been a demand for an AFM capable of measuring a large sample such as a silicon wafer. An example of an AFM that meets this demand is disclosed in JP-A-3-296612. In this AFM, as shown in FIG. 5, a displacement detecting system 4 including a cantilever 1, a laser light source 2, and a light detecting element 3 is supported on a free end of a fine moving element 5 using a piezoelectric element. Accordingly, the cantilever 1 is two-dimensionally scanned along the sample 6, and during that time, a displacement signal of the cantilever 1 output from the photodetector 3 is imaged, so that a concave and convex image of the sample surface can be obtained with high resolution.

[0005]

In this AFM, the structure of the portion supported by the free end of the fine moving element 5 including the cantilever 1 and the light detecting element 3 is large.
, And the scanning speed is reduced. Further, it is desired to reduce the size of this portion in order to reduce the load on the fine movement element 5, but it is not possible to simply reduce the size because an appropriate optical path of the laser light must be formed between each element. Further, as in the case of the conventional AFM, at least the position of the laser light source 2 or the light detecting element 3 must be adjusted when the cantilever 1 is replaced. Therefore, an adjusting mechanism must be added substantially in the configuration of FIG.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an AFM capable of performing scanning at a higher speed with less load on a fine movement element. Still another object of the present invention is to provide an AFM that can easily incorporate an adjustment mechanism for an optical element of a light detection system.

[0007]

SUMMARY OF THE INVENTION A scanning probe microscope according to the present invention has a probe at a free end and a reflecting surface on the opposite side, and a fine movement for supporting and scanning the cantilever. The element, a light source for emitting laser light, an irradiating means for irradiating the reflecting surface on the cantilever with laser light from the light source, a deflecting means for deflecting the reflected light from the reflecting surface of the cantilever, and a deflector. A light detecting element that receives the reflected light from the reflecting surface of the cantilever and outputs a signal corresponding to the displacement of the free end of the cantilever; the irradiating means and the deflecting means are provided on the fine movement element; The light source and the light detection element are provided independently of the fine movement element.

[0008]

According to the present invention, the laser light emitted from the light source is deflected by the irradiating means and is irradiated on the free end of the cantilever.
The reflected light is deflected by the deflecting means and enters the light detecting element. During scanning, the cantilever, the irradiating means, and the deflecting means are moved by the fine moving element, but the light source and the light detecting element are not moved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

First, an atomic force microscope according to a first embodiment will be described with reference to FIGS. As shown in FIG. 1, the upper holder 15 is held by a main body (not shown), and the upper holder 15 has a laser light source (LD).
LD supporting member 12 for supporting 2 and fine movement element (cylindrical actuator) 5 for supporting and scanning cantilever 1
And a PD support 11 that supports the photodetector 3 including a position sensor (PSD) 17.
The laser light source 2 is attached to the LD support 12 so as to emit laser light horizontally. Photodetector 3
Is set via the fine adjustment screw 10 by rotating the knob 13.
It is provided to move inside the D support 11 in the Z direction. A ring member 7 made of a material such as iron is attached to the lower end of the fine movement element 5. The cantilever 1 has a probe at its free end, and its fixed end is fixed to a support member 9 made of a material such as iron. The support member 9 is attached to the ring member 7 by the magnetic force of the support member 9 via the magnet 8. Thereby, the cantilever 1 is supported below the ring member 7. Windows 16 </ b> A and 16 </ b> B are provided at the lower end of the fine movement element 5 at portions facing the laser light source 2 and the light detection element 3, respectively. These windows 16
Inside prisms A and 16B, a prism 31 having a mirror surface 31A for reflecting the laser light from the laser light source 2 toward the free end of the cantilever 1 and a light detecting element for detecting the reflected light from the free end of the cantilever 1 Each of the prisms 32 has a mirror surface 32 </ b> A that reflects toward 3. An XY stage 14 for coarse movement is provided below the main body (not shown), on which the sample 6 is placed. The XY stage 14 allows the sample 6 to move greatly, and even if the sample 6 is large, a desired observation point can be arranged below the cantilever 1.

The laser light LB1 emitted from the laser light source 2 enters the prism 31 through the window 16A, is reflected by the mirror surface 31A, and irradiates the free end of the cantilever 1. The reflected light LB2 reflected at the free end is
The light enters the prism 32 and is reflected by the mirror surface 32A.
The light enters the position sensor 17 of the light detection element 3 through 6B. At this time, the position of the light detection element 3 is adjusted in advance so that the reflected light LB2 enters an appropriate position of the position sensor 17 when the cantilever 1 is in a predetermined state, for example, a horizontal state. When the free end of the cantilever 1 is displaced as shown by a broken line, the reflected light L from the free end
The incident position of B3 (shown by a broken line) on the position sensor 17 moves upward, and the position sensor 17 outputs a signal indicating the displacement of the free end of the cantilever 1 in response to this.

As shown in FIG. 2, the laser light source 2
An elliptical beam having a long axis in the axial direction is emitted. Thus, even when the cantilever 1 is scanned in the Y direction by the fine movement element 5, the free end of the cantilever 1 is reliably irradiated with the laser beam LB1. As described above, the laser light source 2 emits an elliptical beam having a long axis in the Y-axis direction horizontally (parallel to the X-axis). Therefore, when the cantilever 1 is scanned in the XY directions by the fine movement element 5, the cantilever 1
The free end is always irradiated with the laser beam LB1 in the same state irrespective of its XY position, and its displacement is detected as a vertical difference in the incident position of the reflected light on the position sensor 17. In FIG. 2, the cantilever in the state indicated by the solid line in FIG. 1 is indicated by 1a, and the cantilever in the state indicated by the broken line is indicated by 1b. Due to the difference between these states, the mirror surfaces of the reflected lights LB2 and LB3 are different. 32A
It is shown that the position of incidence on the surface changes.

As described above, in the AFM according to the present embodiment, since the laser light source 2 and the light detecting element 3 are supported by the supports 12 and 11 other than the fine moving element 5, the load applied to the fine moving element 5 is relatively small. Is running low. As a result, the cantilever 1 is scanned at a relatively high speed.

Next, the AF of the second embodiment will be described with reference to FIG.
M will be described. In the drawing, members equivalent to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
In this embodiment, the fine movement element 5 is composed of a parallel spring 5A and a bimorph 5B, and the upper end of the parallel spring 5A is fixed to the upper holder 15, and the lower end thereof can be moved in the X direction by the bimorph 5B. Has become. Parallel spring 5
At the lower end of A, windows 16A and 16
B is provided, and the prism 31
, 32 and the ring member 7 are attached, and the cantilever 1 is attached to the ring member 7 by the magnet 8. The light detecting element 3 is pressed downward by the force of the spring 19 and pressed against the sliding surface 18 by the fine movement screw 10. The fine movement screw 10 is in contact with the slope of the light detecting element 3, and the light detecting element 3 moves in the Z direction by rotating the knob 13. The PD support 11 supporting the light detection element 3 and the LD support 12 supporting the laser light source 2 are attached to the upper holder 15 together with the fine movement element 5. This upper holder 15
Is provided so as to be movable in the Y direction with respect to a main body (not shown), and is scanned by the drive element 20 in the Y direction. Thereby, cantilever 1
Is scanned in the X direction by the fine movement element 5 and in the Y direction by the drive element 20. In this embodiment, since the fine movement element 5 is constituted by the parallel spring 5A and the bimorph 5B, the size and weight are reduced, and the movement in the X direction is kept linear over a wide range.

In this embodiment, the moving part in the Y-direction scanning is not small and light, but the scanning in the Y-direction is originally performed at a low speed. It is not contrary to the gist of the present invention, such as increasing the speed.

Finally, referring to FIG. 4, A of the third embodiment will be described.
FM will be described. In this embodiment, the upper holder 15
Like the second embodiment, is provided on a main body (not shown) so as to be movable in the Y direction.
The scanning is performed in the direction. This upper holder 1
5 is an LD support 12 supporting the laser light source 2
And a support 28 corresponding to the PD support of the above-described embodiment.
And a parallel spring 5A extending downward. As in the second embodiment, a window 16A is provided at the lower end of the parallel spring 5A, a prism 31 and a ring member 7 are attached, and the cantilever 1 is fixed to this ring member 7 via a magnet 8 by magnetic force. Have been. The lower end of the support 28 and the ring member 7 are connected by a laminated piezoelectric element 5C, and a fine movement element is constituted by the parallel spring 5A and the laminated piezoelectric element 5C. The cantilever 1 is scanned in the X direction. In addition, the parallel spring 5
A lens 21 is provided inside A, independently of the fine movement element. A split mirror 24 is provided above the lens 21, and a lens 22 is provided to the right of the split mirror 24. In addition, lens 2
A conjugate surface 27 which is obtained by projecting the back focal plane 25 of one lens by the lens 22
The light detecting element 3 is disposed at the first position.

The laser light emitted from the laser light source 2 is reflected by the prism 31 and irradiates the free end of the cantilever 1, and the reflected light is incident on the lens 21 and is deflected, reflected by the split mirror 24 and reflected by the lens 22. The light passes through the light detecting element 3. In the optical system 23 from the lens 21 to the light detecting element 3, the reflected lights LBp1 and LBp2 from the two positions p1 and p2 in the X direction of the cantilever 1 enter the lens 21 when the cantilever 1 is not displaced. Are parallel to each other and converge on one point (Q0) of the back focal plane 25 of the lens 21 after passing through the lens 21. If the cantilever 1 is displaced by an atomic force or the like even if the cantilever 1 is displaced by the same amount, if the cantilever 1 is located at any position during the scanning, a predetermined value on the focal plane 25 corresponding to the displacement is obtained. Pass through a point. Although the photodetector 3 may be disposed on the rear focal plane 25, in this embodiment, the photodetector 3 is disposed on a conjugate surface 27 where the rear focal plane 25 is projected by the lens 22, and Is provided with an imaging optical system, so that an optical image of the sample 6 can be obtained using the lens 21 via the split mirror 24.

In this embodiment, the portion moved by the fine moving element is smaller and lighter than the above-described embodiment, so that the load on the fine moving element is reduced. 15, the load on the driving body 20 in the Y direction is also reduced. As a result, higher-speed scanning can be performed.

[0019]

According to the present invention, there is provided an AFM capable of performing scanning at a higher speed with a smaller load on the fine moving element. Further, since the light detection system is provided independently of the scanning system, the adjustment mechanism of the optical element of the light detection system can be easily incorporated.

[Brief description of the drawings]

FIG. 1 shows the configuration of an AFM according to a first embodiment of the present invention.

FIG. 2 shows a positional relationship when each optical element of FIG. 1 is viewed from above.

FIG. 3 shows a configuration of an AFM according to a second embodiment of the present invention.

FIG. 4 shows a configuration of an AFM according to a third embodiment of the present invention.

FIG. 5 shows a configuration of a conventional example of an AFM using an optical lever method for a light detection system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cantilever, 2 ... Laser light source, 3 ... Photodetection element, 5 ... Fine movement element, 31, 32 ... Prism.

Claims (6)

(57) [Claims] 1. A cantilever having a probe at a free end and a reflecting surface on the opposite side, a fine movement element supporting the cantilever and scanning the same, a holding body holding the fine movement element, A light source that emits a laser beam, an irradiating unit that irradiates the reflecting surface on the cantilever with the laser beam from the light source, a deflecting unit that deflects the reflected light from the reflecting surface of the cantilever, and a reflection of the cantilever deflected by the deflecting unit A light detection element that receives the reflected light from the surface and outputs a signal corresponding to the displacement of the free end of the cantilever; the irradiation means and the deflection means are provided on the fine movement element; A scanning probe microscope in which the detection element is provided independently of the fine movement element. 2. The fine movement element is a cylindrical actuator.
The scanning probe microscope according to claim 1. 3. The fine movement element is composed of a parallel spring and a bimorph.
The scanning probe microscope according to claim 1, which is configured. 4. The apparatus according to claim 3, wherein said holding member is movable.
A scanning probe microscope as described. 5. A probe having a probe at a free end and a reflection at the opposite side.
A cantilever with a surface, A fine movement element that supports and scans the cantilever; A holder for holding the fine movement element, A light source for emitting laser light, Laser light from the light source illuminates the reflective surface on the cantilever
Irradiating means; A first lens provided independently of the fine movement element; A conjugate projection of the rear focal plane of the lens with a second lens
On the surface, corresponding to the displacement of the free end of the cantilever
A light detection element for outputting a signal, Irradiation means is provided on the fine movement element, The light source and the light detection element are provided independently of the fine movement element
Scanning probe microscope. 6. The light source emits an elliptical laser beam.
A scanning program according to any one of claims 1 to 5,
Probe microscope.