US 12,140,752 B2
Thermal control of MEMS mirrors to limit resonant frequency shift
Sae Won Lee, Mountain View, CA (US); Youmin Wang, Mountain View, CA (US); and Anan Pan, Mountain View, CA (US)
Assigned to Beijing Voyager Technology Co., Ltd., Beijing (CN)
Filed by Beijing Voyager Technology Co., Ltd., Beijing (CN)
Filed on Dec. 29, 2020, as Appl. No. 17/137,211.
Prior Publication US 2022/0206285 A1, Jun. 30, 2022
Int. Cl. B81B 3/00 (2006.01); G01S 7/481 (2006.01); G01S 17/931 (2020.01); G02B 26/08 (2006.01); G02B 26/10 (2006.01); H05K 1/02 (2006.01)
CPC G02B 26/0841 (2013.01) [B81B 3/0018 (2013.01); G01S 7/4814 (2013.01); G01S 7/4817 (2013.01); G01S 17/931 (2020.01); G02B 26/105 (2013.01); H05K 1/0203 (2013.01); B81B 2201/042 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A micro-electromechanical system (MEMS) apparatus for beam steering in a Light Detection and Ranging (LiDAR) system of an autonomous vehicle, the apparatus comprising:
a mirror having a reflective surface and at least first and second respective sides;
first and second supporting torsion springs, wherein the first and second supporting torsion springs have first ends, respectively, connected to the first and second respective sides of the mirror, on opposite sides, to support the mirror;
first and second common terminals connected to the first and second supporting torsion springs, respectively, on second ends of the first and second supporting torsion springs;
a plurality of first fingers extending from the mirror on first and second sides orthogonal to the first and second supporting torsion springs;
first and second bias terminals opposite the first and second sides of the mirror;
a plurality of second fingers extending from the first and second bias terminals, the plurality of second fingers being interleaved with the plurality of first fingers and partially overlapping the plurality of first fingers;
a control circuit for rotating the mirror around an axis of the first and second supporting torsion springs at a resonant frequency;
an oxide layer below the first and second common terminals and the first and second bias terminals;
a die substrate below the oxide layer having a first Coefficient of Thermal Expansion (CTE);
a die attach material coupled to the die substrate having a second CTE;
a chip package coupled to the die attach material and having a chip package substrate with a third CTE;
a printed circuit board coupled to the chip package, the printed circuit board having a fourth CTE; and
means for reducing changes in the resonant frequency due to changes in temperature causing stresses due to a mismatch between the first, second, third and fourth CTE.