US 11,784,077 B2
Wafer overlay marks, overlay measurement systems, and related methods
Denzil S. Frost, Lehi, UT (US); Richard T. Housley, Boise, ID (US); David S. Pratt, Meridian, ID (US); and Trupti D. Gawai, Boise, ID (US)
Assigned to Micron Technology, Inc., Boise, ID (US)
Filed by Micron Technology, Inc., Boise, ID (US)
Filed on Dec. 18, 2019, as Appl. No. 16/719,366.
Prior Publication US 2021/0193493 A1, Jun. 24, 2021
Int. Cl. H01L 23/544 (2006.01); H01L 21/68 (2006.01); G06T 7/00 (2017.01); G06T 7/73 (2017.01); G03F 7/00 (2006.01)
CPC H01L 21/681 (2013.01) [G06T 7/0004 (2013.01); G06T 7/73 (2017.01); H01L 23/544 (2013.01); G03F 7/70633 (2013.01); G06T 2207/10056 (2013.01); G06T 2207/30148 (2013.01); H01L 2223/544 (2013.01); H01L 2223/54426 (2013.01); H01L 2223/54493 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A method, comprising:
orienting a wafer to align lines of a first region of a pattern of an overlay mark with a direction in which an illumination source emits light at the wafer, the overlay mark comprising the pattern defining an array of columns, each column of the array of columns respectively comprising some of the lines oriented parallel to each other and individually continuously extending in a non-linear path from an end of the column in a first direction to an additional end of the column in the first direction, the some of the lines comprising:
regions each linearly extending in a second direction acutely angled relative to the first direction and defining bar marks of the column, the bar marks each having substantially the same width in the first direction and oriented parallel to one another in a third direction perpendicular to the first direction; and
additional regions alternating with the regions in the first direction and each linearly extending in a fourth direction obtusely angled relative to the first direction, the additional regions defining space marks of the column each having substantially the same additional width in the first direction and oriented parallel to one another in the third direction;
emitting light at the wafer via the illumination source;
capturing at least one image of the wafer via an imager sensor; and
based at least partially on the captured at least one image, determining a contrast of a second region of the pattern of the overlay mark where additional lines of the pattern are not aligned with the direction in which the illumination source emits light at the wafer and determining a contrast of the first region of the pattern of the overlay mark.