# US 2014/0152976 A1 · System and Method for Detecting Cracks in a Wafer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152976 A1 - Document ID: US20140152976A1 - Status: Published application - Kind: A1 - Application number: 14/073,535 - Filed: 2013-11-06 - Published: 2014-06-05 - Earliest claimed: 2012-11-09 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: William VanHoomissen; Sean Wheeler - Web page: https://patentgrep.com/patent/US20140152976A1 ## CPC - G01N 21/9505: {Wafer internal defects, e.g. microcracks} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A wafer crack detection system includes a rotational wafer stage assembly configured to secure a wafer and selectively rotate the wafer, a light source positioned on a first side of the wafer and configured to direct a light beam through the wafer, a sensor positioned on a second side of the wafer and configured to monitor one or more characteristics of light transmitted through the wafer as the wafer is rotated, and a controller communicatively coupled to the sensor and a portion of the rotational wafer stage assembly, the controller configured to: determine the presence of one or more cracks in the wafer based on the monitored one or more characteristics of light transmitted through the wafer, and, responsive to the determination of the presence of one or more cracks in the wafer, direct the rotational stage assembly to adjust the rotational condition of the wafer. ## Claims ### Claim 1 A system for detecting cracks in a wafer comprising: a rotational wafer stage assembly configured to secure a wafer and selectively rotate the wafer; a light source positioned on a first side of a surface of the wafer and configured direct at least a portion of a light beam through the wafer, wherein the light beam is at least partially transmittable through the wafer; a sensor positioned on a second side of the wafer opposite the first side and configured to monitor one or more characteristics of light transmitted through the wafer as the rotational wafer stage assembly rotates the wafer, wherein the rotational wafer stage assembly and the light source are configured to cause the light beam to trace a pattern across the wafer; a controller communicatively coupled to the sensor and a portion of the rotational wafer stage assembly, the controller configured to: determine the presence of one or more cracks in the wafer based on the monitored one or more characteristics of light transmitted through the wafer; and responsive to the determination of the presence of one or more cracks in the wafer, direct the rotational stage assembly to adjust the rotational condition of the wafer. ### Claim 2 (depends on 1) The system of claim 1, wherein the rotational wafer stage assembly includes: a wafer chuck configured to secure the wafer; and a spindle configured to selectively rotate the wafer. ### Claim 3 (depends on 1) The system of claim 1, wherein the rotational wafer stage assembly is configured to rotate the wafer about an axis perpendicular to the wafer surface. ### Claim 4 (depends on 1) The system of claim 1, wherein the rotational wafer stage assembly and the light source are configured to cause the light beam to trace substantially a circle pattern over the surface of the wafer. ### Claim 5 (depends on 4) The system of claim 4, wherein the light source is configured to direct a light beam onto the wafer at a location between the laser scribe line of the wafer and the bevel of the wafer such that the light beam substantially traces a circle pattern over the surface of the wafer bounded by the laser scribe of the wafer and the bevel of the wafer. ### Claim 6 (depends on 1) The system of claim 1, wherein the rotational wafer stage assembly and the light source are configured to cause the light beam to trace substantially a spiral pattern over the wafer. ### Claim 7 (depends on 6) The system of claim 6, wherein the light source is disposed on a linear stage, wherein the combined operation of the rotational wafer stage assembly and the linear stage of the light source cause the light beam to trace substantially a spiral pattern over the wafer. ### Claim 8 (depends on 6) The system of claim 6, wherein the light source is fixed, wherein the rotational wafer stage assembly is configured cause the light beam to trace substantially a spiral pattern over the wafer. ### Claim 9 (depends on 1) The system of claim 1, wherein the one or more characteristics of the transmitted light include the intensity of transmitted light. ### Claim 10 (depends on 1) The system of claim 1, wherein the light source comprises: an infrared laser. ### Claim 11 (depends on 1) The system of claim 1, wherein the light source emits at least 1550 nm light. ### Claim 12 (depends on 1) The system of claim 1, wherein the sensor comprises: at least one of a photodiode, a CCD detector and a CMOS detector. ### Claim 13 (depends on 1) The system of claim 1, wherein the plane of the wafer is located at least proximate to the focus of the light beam. ### Claim 14 (depends on 1) The system of claim 1, wherein the control system is further configured to compare the monitored one or more characteristics of the light beam to a selected response threshold. ### Claim 15 (depends on 1) The system of claim 1, wherein the control system is further configured to direct the rotational stage assembly to stop the rotation of the wafer. ### Claim 16 (depends on 1) The system of claim 1, wherein the control system is further configured to direct the rotational stage assembly to reduce the speed of rotation of the wafer. ### Claim 17 (depends on 1) The system of claim 1, wherein the light source and the sensor are fixed. ### Claim 18 (depends on 1) The system of claim 1, wherein at least one of the light source and the sensor are disposed on an actuatable stage. ### Claim 19 An inspection tool equipped with crack detection capabilities comprising: a light source configured to illuminate an area of a surface of a wafer disposed on a rotational wafer stage assembly configured to secure a wafer and selectively rotate the wafer; a detector configured to detect light reflected or scattered from the illuminated area of the wafer; a crack detection light source positioned on a first side of a surface of the wafer and configured direct at least a portion of a light beam through the wafer, wherein the light beam is at least partially transmittable through the wafer; a crack detection sensor positioned on a second side of the wafer opposite the first side and configured to monitor one or more characteristics of light transmitted through the wafer as the rotational wafer stage assembly rotates the wafer, wherein the rotational wafer stage assembly and the light source are configured to cause the light beam to trace a pattern across the wafer; a controller communicatively coupled to the sensor and a portion of the rotational wafer stage assembly, the controller configured to: determine the presence of one or more cracks in the wafer based on the monitored one or more characteristics of light transmitted through the wafer; and responsive to the determination of the presence of one or more cracks in the wafer, direct the rotational stage assembly to adjust the rotational condition of the wafer. ### Claim 20 (depends on 19) The inspection tool of claim 19, wherein the inspection tool is configured as at least one of a bright-field inspection tool and a dark-field inspection tool. ### Claim 21 A method for detecting cracks in a wafer comprising: generating a light beam at least partially transmittable through the wafer; selectively rotating a wafer disposed on a rotational wafer stage assembly in order to trace the light beam across the surface of the wafer; monitoring one or more characteristics of light transmitted through the wafer; determining the presence of one or more cracks in the wafer based on the monitored one or more characteristics of light transmitted through the wafer; and responsive to the determination of the presence of one or more cracks in the wafer, directing the rotational stage assembly to adjust the rotational condition of the wafer. ### Claim 22 A system for monitoring centering of wafer on a rotational wafer stage comprising: a rotational wafer stage assembly configured to secure a wafer and selectively rotate the wafer; a light source positioned on a first side of a surface of the wafer and configured direct at least a portion of a light beam through the wafer, wherein the light beam is at least partially transmittable through the wafer; a sensor positioned on a second side of the wafer opposite the first side and configured to monitor an edge bevel location of the wafer based on one or more characteristics of light transmitted through the wafer as the rotational wafer stage assembly rotates the wafer, wherein the rotational wafer stage and the light source are configured to cause the light beam to trace a pattern across the wafer proximate to the bevel of the wafer; a controller communicatively coupled to the sensor and a portion of the rotational wafer stage assembly, the controller configured to: determine a centering condition of the wafer based on the monitored one or more characteristics of light transmitted through the wafer; and responsive to the determination an off-center condition, direct the rotational stage assembly to adjust the rotational condition of the wafer. ### Claim 23 A system for monitoring wafer slippage on a rotational wafer stage comprising: a rotational wafer stage assembly configured to secure a wafer and selectively rotate the wafer; a light source positioned on a first side of a surface of the wafer and configured direct at least a portion of a light beam through the wafer, wherein the light beam is at least partially transmittable through the wafer; a sensor positioned on a second side of the wafer opposite the first side and configured to monitor changes in at least one of a wafer notch location and a spindle axis location as the rotational wafer stage assembly rotates the wafer; a controller communicatively coupled to the sensor and a portion of the rotational wafer stage assembly, the controller configured to: determine a slippage condition of the wafer based on the monitored changes in at least one of the wafer notch location and the spindle axis location; and responsive to the determination of a slippage condition exceeding a selected slippage threshold, direct the rotational stage assembly to adjust the rotational condition of the wafer.