Patent ID: 8537213

Claim:
A method for measuring a via bottom profile, for obtaining a profile of a bottom of a via in a front side of a substrate, the method comprising: using an IR-microscope to transmit an infrared (IR) light source from a back of the substrate to the bottom of the via through an objective; using an image capturing device to capture lights scattered from the bottom of the via to generate an image, wherein the image displays a diameter (2E a ) of the via bottom profile and a diameter (2E c ) of a maximum receivable base area of the via for the IR-microscope; and using an elliptic equation to obtain a minor axis radius (E b ) of the elliptic equation, so that the via bottom profile is obtained from a radius (E a ) of the via bottom profile and the minor axis radius (E b ) of the elliptic equation, wherein the elliptic equation is represented by an equation (1): x 2 E a 2 + z 2 E b 2 = 1 ( 1 ) in the equation (1), E a is the radius of the via bottom profile, and E b is the minor axis radius of the elliptic equation; a slope equation (2) is obtained according to the equation (1): ⅆ z ⅆ x = m = E b 2 ⁢ x E a 2 ⁢ E b 2 - ( E b E a ⁢ x ) 2 ( 2 ) in the equation (2), m is the slope of the equation (1), and when x is a radius (E c ) of the maximum receivable base area of the via for the IR-microscope, the slope is M, so that the minor axis radius E b is represented by an equation (3): E b = M · E a ⁢ E a 2 - E c 2 E c ( 3 ) in the equation (3), M is a fixed parameter of the IR-microscope.