EP0491973A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Integrated pneumatically and electrostatically controlled scanning tunneling microscope and method of making the same
Assignee: International Business Machines Corp
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Filing: 1990-12-21
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Granted: —
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Expires: 2010-12-21
Abstract
Abstract The application describes an integrated scanning tunneling microscope which allows pneumatically controlled coarse approach of a membrane/tip (24,25) assembly to the sample surface, and electrostatically controlled X, Y movement and fine approach of said tip (25) to the sample surface along Z-axis. The at least four electrodes (27,28) of the XY-drive are spaced from a counter-electrode (26). In a first embodiment, the four electrodes form the upper electrodes and are arranged on a glass member (30) which is connected to a silicon frame (21) carrying a membrane (24) with integrated tip (25) with the lower electrode (26) being arranged on said membrane. In a second embodiment, the four electrodes form the lower electrodes (42A,42B) and are arranged on the silicon substrate (41). The counter-electrode is the upper electrode (45) and connected by a dielectric layer (46) and a tunnel contact layer (48) to the membrane/tip assembly. For the coarse approach of the tip to the sample surface the pressure on the membrane is varied. For the fine approach of the tip to the sample surface voltage is applied to the individual electrodes. Two micromechanical processes are described for producing scanning tunneling microscopes in accordance with this invention.
Inventors
- 👤 Johann Dr. Greschner
- 👤 Martin Dr. Nonnenmacher
- 👤 Olaf Dr. Wolter
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 17:11
CPC Classifications
G; G01; G01Q; G01Q10/00; G01Q10/02; G01Q10/04; G01Q60/00; G01Q60/10; G01Q60/16
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
139 words
Scanning tunneling microscope comprising at least one electron-emitting tip maintained at an essentially constant distance along Z-axis from the sample surface, an XY-drive for scanning said tip in a matrix fashion across said sample surface, means for controlling said tunnel current to maintain said distance essentially constant, characterized in that said XY-drive consists of at least four electrodes (27, 28; 37, 38; 42A, 42B) spaced from a counter-electrode (26, 36, 45); said four electrodes (27, 28; 37, 38; 42A, 42B) being upper electrodes arranged on member (40, Fig. 3), or lower electrodes arranged on substrate (41, Fig. 4); said counter-electrode (26, 36, 45) being connected to membrane (24, 34, 49); and said electron-emitting tip (25; 35, 39; 48, 49) capable of moving along Z-axis normal to the sample surface forming an integral part of said membrane (24, 34, 49).
Claim 2
Dependent Claim
20 words
Scanning tunneling microscope of claim 1, characterized in that said STM is fabricated by micromachining using integrated circuit processing steps.
Claim 3
Dependent Claim
22 words
Scanning tunneling microscope of claim 2, characterized in that said STM is fabricated by a planar batch technique (Figs. 4A to 4E).
Claim 4
Dependent Claim
67 words
Scanning tunneling microscope of claims 1 to 3, characterized in that said membrane (24, 34, 49) consists of a dielectric material, and that said tip (25, 35, 49) forming an integral part of said membrane is provided with an electrically conductive material (29, 39, 48) and connected to individual electrodes to which voltage may be applied for moving said tip along Z-axis normal to the sample surface.
Claim 5
Dependent Claim
26 words
Scanning tunneling microscope of claim 4, characterized in that membrane (24, 34, 49) consists of silicon carbide or silicon nitride, and said tip coating is platinum.
Claim 6
Dependent Claim
27 words
Scanning tunneling microscope of claim 1, characterized in that member (30, 40) is a perforated glass block which forms part of a pressure or vacuum generating chamber.
Claim 7
Dependent Claim
65 words
Scanning tunneling microscope of claims 1 to 6, characterized in that for coarse approach of the membrane and integral tip along Z-axis the pressure on said membrane is varied, and that for fine approach of the membrane and integral tip voltage U z is applied to Z-electrode (26, 36, 45), the distance between tip and sample being controlled as a function of U z .
Claim 8
Dependent Claim
43 words
Scanning tunneling microscope of one or several of claims 1 to 7, characterized in that the semiconductor substrate (21, 31, 41) includes electronic devices for the current supply of the distance control of the tip and for processing the signals resulting from scanning.
Claim 9
Dependent Claim
268 words
Method of making a scanning tunneling microscope using pneumatic and electrostatic control of tip motion as claimed in claims 1 to 8, comprising the following steps: a) depositing masking layers (32) on either side of a semiconductor substrate (31); etching a pit of several µm depth into the front masking layer (32) and into substrate (31) in a size which corresponds to the future membrane size (Fig. 3A); b) removing said front side masking layer (32); depositing a resistent masking layer (33) on said fine etched pit (Fig. 3B); c) providing an opening in layer (33) in the center of said pit; etching a hole (35) through substrate (31, Fig. 3C); d) removing the remaining masking layer (33); and covering the front side of substrate (31) including said hole (35) with a tensile stressed film (34, Fig. 3D); e) opening said back side masking layer (32); thinning down substrate (31) to expose future membrane (34) and tip (35); applying a metal layer (36) to said tensile stressed film (34) on the front side and patterning a first electrode so as to extend over said pit (Fig. 3E); f) applying a metal layer to member (40) and patterning second electrodes (37, 38, Fig. 3F); g) bonding member (40) with second electrodes (37, 38) to substrate frame (31, 34) with second electrodes (37, 38) being positioned above first electrode (36) on membrane (34); and removing the remaining mask (32) from the back side of substrate (31); thinning the substrate frame (31) by etching; and applying a metal coating (39) on tip (35) and a part of substrate (31, Fig. 3G).
Claim 10
Dependent Claim
29 words
Method of claim 9 wherein step a) of depositing masking layer (32) comprises forming layers of silicon dioxide or silicon nitride on either side of a silicon substrate (31).
Claim 11
Dependent Claim
20 words
Method of claim 9 wherein step b) of depositing a resistent mask material (33) comprises depositing silicon dioxide or aluminum.
Claim 12
Dependent Claim
37 words
Method of claim 9 wherein step d) of covering the front side of substrate (31) including hole (35) with a tensile stressed film (34) comprises depositing silicon carbide or silicon nitride by plasma enhanced chemical vapor deposition.
Claim 13
Dependent Claim
22 words
Method of claim 9 wherein the etching steps of the masking layers comprise wet-etching steps using buffered hydrofluoric acid for silicon dioxide.
Claim 14
Dependent Claim
35 words
Method of claim 9 wherein the etching steps of the silicon substrate comprise wet-etching using a 37.5 % b. w. aqueous KOH (steps a, e, g) or dry-etching using chlorine or bromine chemistry (step c).
Claim 15
Dependent Claim
27 words
Method of claim 9 wherein depositing and patterning of first and second electrodes comprise vapor depositing a metal, preferably platinum, using an aperture mask (steps e, f).
Claim 16
Dependent Claim
231 words
Method of making a scanning tunneling microscope using pneumatic and electrostatic control of tip motion as claimed in claims 1 to 8, comprising the following steps: a) applying a metal layer to substrate (41) and patterning first electrodes (42A, 42B); and applying a dielectric layer (44) to the surface of electrodes (42A, 42B) overlapping said electrodes (Fig. 4A); b) applying a metal layer to said dielectric layer (44) and patterning to form an annular conductor (45) which covers approximately the same area as first electrodes (42A, 42B) and forms the second electrode; deposition a dielectric layer (46) on top of said annular conductor (45, Fig. 4B); c) providing an opening in the center of the circular sandwich and etching a hole (47) through substrate (41, Fig. 4C); d) covering the circular sandwich including the hole with tunnel contact material (48); applying dielectric layer (49) to tunnel contact material layer (48) and to the entire structure (Fig. 4D); e) removing the substrate material surrounding the tip by etching using a structured oxide mask; thinning the substrate by etching; and etching off dielectric layer (44) so as to provide clearance space for the sandwich, comprising membrane (49), tunnel contact layer (48) with tip (47) as integral part of said layers (49, 48), dielectric layer (46), and annular conductor (45), for moving along X, Y, and Z-axes upon application of electrical fields (Fig. 4E).
Claim 17
Dependent Claim
40 words
Method of claim 16 wherein step a) of depositing dielectric layer (44) comprises depositing silicon dioxide which acts as a spacer material and which is removed by etching with buffered hydrofluoric acid at a later stage (step e, Fig. 4E).
Claim 18
Dependent Claim
40 words
Method of claim 16 wherein steps a, b, and d of depositing and patterning of first electrodes (42A, 42B), of annular conductor (45), and of tunnel contact material (48) comprise vapor depositing a metal, preferably platinum, using an aperture mask.
Claim 19
Dependent Claim
35 words
Method of claim 16, wherein steps b and d of depositing dielectric layers (44) and (49) comprise depositing silicon carbide or silicon nitride by plasma enhanced chemical vapor deposition, with layer (49) representing the membrane.
Claim 20
Dependent Claim
45 words
Method of claims 16 to 19 further comprising: providing a glass block on top of the scanning tunneling microscope, leaving a cavity between said glass block and membrane (49), to allow pneumatic coarse approach of the membrane/tip assembly along Z-axis normal to the sample surface.
References Cited (Backward Citations)
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