# US 7,461,543 B2 · Overlay measurement methods with firat based probe microscope > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,461,543 B2 - Document ID: US7461543B2 - Status: Granted - Kind: B2 - Application number: 11/548,531 - Filed: 2006-10-11 - Published: 2007-05-17 - Granted: 2008-12-09 - Earliest claimed: 2005-06-17 - Assignees: Georgia Tech Research Corporation - Inventors: Fahrettin Levent Degertekin - Web page: https://patentgrep.com/patent/US7461543B2 ## CPC - G01Q 70/02: Probe holders - G01Q 20/04: Self-detecting probes, i.e. wherein the probe itself generates a signal representative of its position, e.g. piezoelectric gauge - G01Q 60/38: Probes, their manufacture, or their related instrumentation, e.g. holders - G01Q: SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM] ## Abstract A method, system and unit for determining alignment in a layered device such as a semiconductor device includes providing a first layer having detectable surface and subsurface material properties and positioning a patterned photoresist layer over the first layer, patterned photoresist layer having detectable surface and subsurface material properties. The layers are imaged with a FIRAT probe to detect the material properties, and the detectable material properties are compared for mapping an alignment of the compared detectable material properties. The first layer may be a substrate or have a previously processed layer formed thereon. A surface topography may be included over the substrate and an etchable layer formed over the substrate or first layer. The FIRAT probe may be a single tip probe or a dual tip probe. ## Claims ### Claim 1 A method for determining alignment of layers in a semiconductor device comprising the actions of: providing a first layer having detectable surface and subsurface material properties: positioning a photoresist layer over said first layer, said photoresist layer having detectable surface and subsurface material properties; imaging said first layer and said photoresist layer with a dual tip probe device comparing the detectable material properties; and mapping an alignment of the compared detectable material properties, wherein the dual tip probe comprises: a detection surface; a force sensor attached to said detection surface, said force sensor comprising: a pair of flexible mechanical structures each disposed a first distance above the detection surface so as to form a gap between the flexible mechanical structure and the detection surface, wherein each flexible mechanical structure is configured to independently deflect upon exposure to an external force, thereby changing the first distance; a probe tip disposed on an outer surface of each flexible mechanical structure; an actuator coupled to each flexible mechanical structure configured to apply force to the flexible mechanical structure; and a detector configured to measure deflection of each said flexible mechanical structure. ### Claim 2 (depends on 1) The method according to claim 1, wherein said first layer includes a combination of materials and features from prior processing. ### Claim 3 (depends on 2) The method according to claim 2, wherein said first layer is planarized by chemical mechanical polishing. ### Claim 4 (depends on 1) The method according to claim 1, further comprising: providing an etchable layer between said first layer and said photoresist layer, said photoresist layer defining patterns in said etchable layer that are aligned to the features in said first layer. ### Claim 5 (depends on 1) The method according to claim 1, wherein the material properties include surface properties and subsurface properties. ### Claim 6 (depends on 1) The method according to claim 1, wherein the material properties include adhesion, Van der Waals forces, electrostatic forces, elastic, and viscoelastic properties. ### Claim 7 (depends on 1) The method according to claim 1, wherein said photoresist layer has been exposed to a lithographic process, thereby defining exposed and unexposed portions thereof. ### Claim 8 (depends on 1) The method according to claim 1, further comprising: providing features from prior processing to define a surface topography. ### Claim 9 (depends on 1) The method according to claim 1, wherein each flexible mechanical structure is defined by a clamped-clamped beam. ### Claim 10 (depends on 1) The method according to claim 1, wherein one said probe tip is positioned on each clamped-clamped beam, whereby probe tips are positioned in proximity to each other. ### Claim 11 (depends on 1) The method according to claim 1, wherein a reflective diffraction grating faces an inner surface of the flexible mechanical structure. ### Claim 12 (depends on 1) The method according to claim 1, wherein each probe tip includes an independent actuator and detector. ### Claim 13 (depends on 1) The method according to claim 1, wherein the probe tips are positioned with a separation of from about 10 nm to about 100 μm. ### Claim 14 (depends on 1) The method according to claim 1, wherein the probe tips are positioned with a separation of from about 10 nm to about 100 nm. ### Claim 15 (depends on 1) The method according to claim 1, wherein a radius of curvature of one probe tip is greater than the remaining probe tip. ### Claim 16 (depends on 15) The method according to claim 15, wherein a relatively sharper probe tip records surface topography and surface conditions with a high lateral resolution. ### Claim 17 (depends on 16) The method according to claim 16, wherein the relatively sharper probe tip is defined by a radius of curvature of about 3 nm to about 20 nm. ### Claim 18 (depends on 15) The method according to claim 15, where a relatively less sharp probe tip generates elastic stress fields for deeper penetration into a sample. ### Claim 19 (depends on 18) The method according to claim 18, wherein the relatively less sharp probe tip generates information about structure surface, topography, and subsurface features at multiple sample depths. ### Claim 20 (depends on 18) The method according to claim 18, wherein a relatively less sharp probe tip is defined by a radius of curvature of about 30 nm to about 300 nm. ### Claim 21 (depends on 15) The method according to claim 15, wherein the probe tips are used in parallel to simultaneously form images. ### Claim 22 (depends on 1) The method according to claim 1, wherein subsurface imaging is from about 100 nm to about 500 nm. ### Claim 23 (depends on 1) The method of claim 1, wherein subsurface imaging is from about 100 nm to about 200 nm. ### Claim 24 (depends on 1) The method according to claim 1, wherein a lateral resolution of subsurface imaging is from about 1 nm to about 5 nm. ### Claim 25 (depends on 1) The method according to claim 1, wherein imaging is conducted with a single scanning of said dual tip sensor over a surface of said semiconductor device. ### Claim 26 (depends on 1) The method according to claim 1, wherein imaging is conducted with multiple scanning of said dual tip sensor over a surface of said semiconductor device. ### Claim 27 (depends on 26) The method according to claim 26, wherein subsequent scans apply different force levels for extracting information from the semiconductor device.