Patent ID: 9656858
Date: 2017-05-23
CPC Classifications: B81B,B81C,H01L

Claim:
1. A method of reactive ion etching a substrate to form at least a first and a second etched feature, wherein the first etched feature has a greater aspect ratio (depth:width) than said second etched feature, the method comprising the steps of: in a first etching stage etching said substrate so as to etch only said first feature to a predetermined depth, wherein a ratio of a variation in said width of said second etched feature from a top of said second etched feature to a bottom of said second etched feature is at least one of less than or equal to 0.015, and wherein said first etched feature comprises a narrower width than said second etched feature; thereafter in a second etching stage etching said substrate so as to etch both said first and said second features to a respective depth; applying a masking material to a surface of the substrate to define first and second apertures corresponding to the shape of said first and second etched features; in said first etching stage selectively etching said substrate only through said first aperture to etch the first etched feature to the predetermined depth; thereafter in said second etching stage, etching said substrate through both said apertures thereby to etch both said first and second features to the respective depth; wherein said first etching stage includes the step of occluding said second aperture and exposing said masked substrate to a reactive etching process, whereby etching occurs only through said first aperture; and wherein said step of occluding includes selectively applying a second masking material directly on the masking material to cover said second aperture while said first aperture remains exposed, and removing said second masking material from said second aperture after said first stage etching process and prior to said second stage etching process.