# US 10,372,113 B2 · Method for defocus detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,372,113 B2 - Document ID: US10372113B2 - Status: Granted - Kind: B2 - Application number: 15/669,030 - Filed: 2017-08-04 - Published: 2018-03-29 - Granted: 2019-08-06 - Earliest claimed: 2016-09-23 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: Xuguang Jiang; Shifang Li; Yong Zhang - Web page: https://patentgrep.com/patent/US10372113B2 ## CPC - G05B 19/418: Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM] - G06T 7/0004: {Industrial image inspection} - G06T 7/11: Region-based segmentation - G06T 7/174: involving the use of two or more images - G05B 2219/45027: Masking, project image on wafer semiconductor, photo tracer - G05B 2219/45031: Manufacturing semiconductor wafers - G06T 2207/10024: Color image - G06T 2207/10148: Varying focus - G06T 2207/10152: Varying illumination - G06T 2207/30148: Semiconductor; IC; Wafer - G06T 2207/30168: Image quality inspection - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract Two or more color data can be combined to form a new data source to enhance sensitivity to defocus signal. Defocus detection can be performed on the newly formed data source. In a setup step, a training wafer can be used to select the best color combination, and obtain defocus detection threshold. This can include applying a segment mask, calculating mean intensities of the segment, determining a color combination that optimizes defocus sensitivity, and generating a second segment mask based on pixels that are above a threshold to sensitivity. In a detection step, the selected color combination is calculated, and the threshold is applied to obtain defocus detection result. ## Claims ### Claim 1 A method comprising: applying, using a controller, a segment mask on a die of a wafer thereby forming a segment on the die; calculating, using the controller, a mean intensity of the segment in red, green, and blue colors using a bright field mode and in red, green, and blue colors using a dark field mode; comparing, using the controller, defocus value against the mean intensities; determining, using the controller, a color combination that optimizes defocus sensitivity; determining, using the controller, sensitivity to defocus for each pixel in the segment; applying, using the controller, a threshold to the sensitivity for each pixel; and generating, using the controller, a second segment mask on the die based on pixels that are above the threshold to the sensitivity. ### Claim 2 (depends on 1) The method of claim 1, wherein the wafer is a training wafer with focus modulations. ### Claim 3 (depends on 1) The method of claim 1, wherein the wafer includes a plurality of the dies, and wherein the generating and the calculating are repeated for each of the dies on the wafer. ### Claim 4 (depends on 1) The method of claim 1, wherein the segment mask is configured to cover part of the die. ### Claim 5 (depends on 1) The method of claim 1, wherein the comparing includes generating a scatter plot of defocus value versus the mean intensity. ### Claim 6 (depends on 1) The method of claim 1, further comprising adjusting the threshold using the controller. ### Claim 7 (depends on 1) The method of claim 1, wherein an average intensity of all pixels within a die is used when applying the threshold to the sensitivity for each pixel. ### Claim 8 A non-transitory computer readable medium storing a program configured to instruct a processor to: apply a segment mask on a die thereby forming a segment on the die; calculate a mean intensity of the segment with data including red, green, and blue colors using a bright field mode and with data including red, green, and blue colors using a dark field mode; compare defocus value against the mean intensities; determine a color combination that optimizes defocus sensitivity; determine sensitivity to defocus for each pixel in the segment; apply a threshold to the sensitivity for each pixel; and generate a second segment mask on the die based on pixels that are above the threshold to the sensitivity. ### Claim 9 (depends on 8) The non-transitory computer readable medium of claim 8, wherein a wafer includes a plurality of the dies, and wherein the generating and the calculating are repeated for each of the dies on the wafer. ### Claim 10 (depends on 8) The non-transitory computer readable medium of claim 8, wherein the segment mask is configured to cover part of the die. ### Claim 11 (depends on 8) The non-transitory computer readable medium of claim 8, wherein comparing the defocus value includes generating a scatter plot of the defocus value versus the mean intensity. ### Claim 12 (depends on 8) The non-transitory computer readable medium of claim 8, wherein the program is further configured to adjust the threshold. ### Claim 13 (depends on 8) The non-transitory computer readable medium of claim 8, wherein an average intensity of all pixels within a die is used when applying the threshold to the sensitivity for each pixel. ### Claim 14 A system comprising: a chuck configured to hold a wafer; a measurement system configured to measure a surface of the wafer, wherein the measurement system provides an image of the wafer using a bright field mode and a dark field mode; and a controller in electronic communication with the measurement system, wherein the controller includes a processor, an electronic data storage unit in electronic communication with the processor, and a communication port in electronic communication with the processor, and wherein the controller is configured to: apply a segment mask on a die of the wafer thereby forming a segment on the die; calculate a mean intensity of the segment with data including red, green, and blue colors using the bright field mode and with data including red, green, and blue colors using the dark field mode; compare defocus value against the mean intensities; determine a color combination that optimizes defocus sensitivity; determine sensitivity to defocus for each pixel in the segment; apply a threshold to the sensitivity for each pixel; and generate a second segment mask on the die based on pixels that are above the threshold to the sensitivity. ### Claim 15 (depends on 14) The system of claim 14, wherein the wafer includes a plurality of dies. ### Claim 16 (depends on 14) The system of claim 14, wherein the segment mask applied by the controller is configured to cover part of the die. ### Claim 17 (depends on 14) The system of claim 14, wherein comparing the defocus value includes generating a scatter plot of the defocus value versus the mean intensity. ### Claim 18 (depends on 14) The system of claim 14, wherein the controller is further configured to adjust the threshold. ### Claim 19 (depends on 14) The system of claim 14, wherein an average intensity of all pixels within a die is used when applying the threshold to the sensitivity for each pixel.