Active solid-state devices (e.g. – transistors – solid-state diode – Organic semiconductor material
Reexamination Certificate
1998-01-09
2001-04-03
Mintel, William (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Organic semiconductor material
C257S053000, C257S466000, C250S310000, C250S559060, C250S559070
Reexamination Certificate
active
06211532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microprobe chip for detecting evanescent waves which is used in near-field scanning optical microscopes and a method for making the same, a probe including a thin film cantilever provided with the microprobe chip and a method for making the same, an evanescent wave detector, a near-field scanning optical microscope, and an information regenerator provided with the microprobe chip. In particular, the present invention relates to a microprobe chip having a tip with a small curvature, which is suitable for these apparatuses, and a method for making the same which is capable of producing the microprobe chip with high productivity.
2. Related Background Art
A scanning tunnel microscope (hereinafter referred to as an STM) was developed by G. Binning et al. in 1983 (Phys. Rev. Lett., 49, 57 (1983)). The STM can directly observe electronic structures of surface atoms on conductive materials, such as single crystals and amorphous materials and can obtain real space images with high resolution. Thus, various scanning probe microscopes (hereinafter referred to as SPMs) have been intensively investigated in microstructure analysis of materials.
Examples of SPMs include scanning tunnel microscopes, atomic force microscopes (AFMs), magnetic force microscopes (MFMs), and near-field scanning optical microscopes (NSOMs), which detect the surface structure of a material by means of changes in tunnel currents, atomic forces, magnetic forces, and light intensities, respectively. Such changes occur when scanning near the surface of the material with probes provided with microprobe chips.
Among these SPMs, NSOMs permit nondestructive measurement of fine patterns on tested materials with high resolution, that is, a positional resolution of less than &lgr;/2, which has not been achieved by conventional optical microscopes, by using evanescent light radiated from a fine pinhole. Further, NSOMs are applicable to various materials which have not been observed by any conventional method, such as organisms and biological cells.
The evanescent waves are detected by the following three methods.
The first method was developed by E. Betzig, et al. (“Collection Mode Near-Field Scanning Optical Microscopy”, Appl. Phys. Lett. 51(25), pp. 2088-2090 (1987)). Illuminating light is incident on the back surface of a test piece so as to satisfy the total reflection condition, and the evanescent waves occurring on the front surface of the test piece due to the illuminating light are detected with a microprobe chip provided with a fine aperture. This method is capable of obtaining evanescent wave images with high resolution, and thus has been most intensively studied.
The microprobe chip is composed of a glass pipette or optical fiber of which the tip is pointed. It is therefore fabricated by mechanical polishing or the like, with low productivity and high production costs. Further, the aperture is hardly ever formed with satisfactory reproducibility and high accuracy.
The second method uses a thin film cantilever composed of a silicon nitride thin film used in AFMs instead of the aperture to detect the scattered light of evanescent waves (N. F. van Hulst, et al., “Near-Field Optical Microscope Using a Silicon-Nitride Probe”, Appl. Phys. Lett. 62(5), pp. 461-463 (1993)).
A typical microprobe chip used in the second method and a method for making the microprobe chip are disclosed in U.S. Pat. No. 5,221,415, in which the microprobe chip is formed by anisotropic etching of single-crystal silicon in the crystal axes by means of a semiconductor production process. As shown in
FIG. 1
, a pit
518
is formed on a silicon wafer
514
covered with silicon dioxide masks
510
and
512
by an anisotropic etching process, the silicon dioxide masks
510
and
512
are removed, and then the silicon wafer
514
is covered with silicon nitride layers
520
and
521
. The silicon nitride layer
520
has a pyramidal pit
522
directly on top of the pit
518
. After the silicon nitride layer
521
on the bottom surface is removed, a glass plate
530
provided with a sawcut
534
and a Cr layer
532
is joined to the silicon nitride layer
520
. The silicon wafer
514
is removed by etching. As a result, a probe consisting of a microprobe chip and a cantilever which are composed of silicon nitride is replicated on a mounting block. When the probe is used in an optical lever-type AFM, a metal film
542
as a reflecting film is formed on the bottom surface. The probe can be produced with high productivity and reproducibility and has a pointed tip. The probe, however, forms a lower resolution NSOM image than that formed by a probe with an aperture produced by the first method.
In the first and second methods, the microprobe chip is used as an optical pickup and the scattered evanescent-wave light is amplified by a photomultiplier cell provided above the microprobe chip. On the other hand, the third method involves direct detection of scattered evanescent-wave light using a photodiode on a thin film cantilever (S. Akamine, et al., “Development of a Microphotocantilever for Near-Field Scanning Optical Microscopy”, Proceedings of the IEEE MicroElectro Mechanical Systems Workshop 1995, pp. 145-150).
FIG. 2
is a cross-sectional view of a microprobe chip produced by the third method. The microprobe chip consists of a p-silicon thin film cantilever
601
of which one end is supported by a silicon substrate
600
, a photodiode of pn junction
603
formed by providing an n layer
602
, a silicon oxide film
604
provided thereon, and an aluminum wiring layer
605
provided on the silicon oxide film
604
which extracts scattered light signals from the photodiode. The lower face of the thin film cantilever is provided with an etch stop layer
606
which is used for producing the cantilever.
It is possible for the photodiode optical detector provided on the free end of the cantilever to approach the test piece, and hence the SN ratio and resolution can be improved. Further, the photodiode optical detector can simplify the system configuration. In the third method, however, the thin film cantilever, as a microprobe chip, is produced by a photolithographic process and an etching process with poor reproducibility, and hence microprobe chips having the same shape cannot be produced in the same production lot.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems of the prior art technologies.
It is another object of the present invention to provide a microprobe chip for detecting evanescent waves having a high SN ratio and a high resolution and a method for making the same, a probe provided with the microprobe chip and a method for making the same, an evanescent wave detector, a near-field scanning optical microscope, and an information regenerator which are provided with the microprobe chip and which have simplified system configurations.
It is a further object of the present invention to provide a method for making, with high reproducibility, a microprobe chip having a pointed tip for detecting evanescent waves, and a method for making a probe provided with the microprobe chip.
It is still another object of the present invention to provide a method for making a microprobe chip for detecting evanescent waves which permits reuse of a female mold and provides high yield and low cost production, and a method for making a probe in which the microprobe chip is provided on a thin film cantilever.
A first aspect of the present invention is a microprobe chip for detecting evanescent waves comprising a photoconductive material and a substrate for supporting the photoconductive material, the photoconductive material being connected to electrodes formed on the substrate.
A second aspect of the present invention is a method for making a microprobe chip for detecting evanescent waves comprising the following steps of: forming a film composed of a photoconductive material on a peeling layer of a first substrate, the film having t
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mintel William
LandOfFree
Microprobe chip for detecting evanescent waves probe... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microprobe chip for detecting evanescent waves probe..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microprobe chip for detecting evanescent waves probe... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2462934