Preparation of Semiconductor Substrates for Sensor Based on Porous Layers

Porous semiconductors are obtained by the process of anodizing the substrates. Based on porous semiconductors, a wide class of electronic devices is manufactured, in particular, sensors for gases, temperature, and humidity. A uniform porous layer is required for manufacturing of sensors. Semiconductor substrates have internal thermoelastic stresses arising during ingot growth, which, during anodization, lead to uneven etching depth. Particularly significant stresses arise in gallium arsenide substrates. The paper considers an improvement in the process of preparing substrates for porous semiconductors, which makes it possible to reduce internal thermoelastic stresses. A change in the annealing process is proposed, and the parameters of the technological process that reduce the stress level are determined. By mathematical modeling, it was found that the best results are obtained with preheating with a temperature gradient of 100 OC to a final temperature of 1000 °C, maintaining this temperature for 5 hours, and subsequent controlled cooling with a temperature gradient of 120 °C. A reduction in the level of internal thermoelastic stresses from 6,8 x 10
⁶
Pa to 4,0 x 10
⁶
Pa was achieved. The study of the outer surface of the porous layer by the microscopic method, and the internal structure of the layer by the photoluminescence method showed an increase in the uniformity of the layer. The study shows that the proposed method of substrate preparation can improve the parameters of sensors based on porous semiconductors.