Determining relationship between electron-beam dose and etching depth by empirical formula of contrast

According to the sensitivity curves of resists, the empirical formula of contrast was adopted to determine the relationship between exposure dose and etching depth accurately. Exposure experiments were carried out with positive resist PMMA. With curve fitting of the calculated results, the depth-dose curve is obtained and keeps consistent with the experimental results basically. When the doses are in the range of 20~35 μC/cm2, the difference between the experimental results and the calculated ones is least. Using the contrast method in the etching can save experimental time and raise the etching efficiency.