Etch processing system having reflective endpoint detection

A method, comprising:

• mounting a substrate on a substrate support member in an etch chamber, wherein the substrate includes an alignment region, and the etch chamber has a chamber body around the substrate support member, wherein the etch chamber has a chamber lid and a plurality of lid windows, the plurality of lid windows comprising a first lid window located near a perimeter of the chamber lid radially outward from a center of the chamber lid at a first position, and the plurality of lid windows comprising a second lid window located near the perimeter of the chamber lid at a second position, the second position of the second lid window being circumferentially offset from the first position of the first lid window;
• viewing or capturing an image of the alignment region, wherein the image includes a reflection of a beam spot from the substrate, the viewing or capturing comprising emitting, by a light source of an endpoint detection system, a first light toward the alignment region, wherein the beam spot includes the first light, and emitting, by a second light source, a second light toward the alignment region, wherein the image is of the reflection of the first light and the second light from the alignment region;
• determining an endpoint of an etching process by receiving the reflection of the first light from the alignment region by a photodetector, wherein the circumferential offset provides one of the first lid window or the second lid window vertically above the alignment region regardless of an orientation of the substrate on the substrate support member;
• and
• etching an etch layer through the alignment opening in the etch chamber after aligning the beam spot to the alignment opening.