Various technologies are described herein pertaining to electrochemical etching of a semiconductor controlled by way of a laser that emits light with an energy below a bandgap energy of the semiconductor.

A method for producing a planar semiconductor surface includes forming a workpiece that has a carrier substrate, one or more insulating layers, a semiconductor layer, a first etch stop layer, and a second etch stop layer; forming a contact on the workpiece; biasing the workpiece to a second voltage through the contact; etching the second etch stop layer and part of the first etch stop layer with a photo-electrochemical etching and the second voltage that selectively removes the second etch stop layer faster than the first etch stop layer; biasing the workpiece to a first voltage through the contact; and etching the first etch stop layer and part of the semiconductor layer with the photo-electrochemical etching and the first voltage that selectively removes the first etch stop layer faster than the semiconductor layer to produce a semiconductor device with a planar surface on the semiconductor layer.

A package substrate includes: a sheet including glass; build-up layers respectively on a top surface and on a bottom surface of the sheet; structures defining electrically conductive pathways within the sheet and within the build-up layers; and a ribbon-shaped edge structure in recesses defined at lateral edges of the sheet and defined with respect to lateral edges of the build-up layers, the ribbon-shaped edge structure extending in a direction along a thickness of the sheet, having a lateral edge surface facing away from the sheet, and comprising an edge structure material not including glass and not including metal.