Development and research of microelectromechanical systems and semiconductor sensors

The aim of the work is to develop technical principles for creating strain-resistant pressure transducers based on a circuit design solution to increase sensitivity and minimize overall dimensions while maintaining input conditions for the geometry of the mechanical structure of the membrane, supply voltage and low error rates. Instead of the classical application of an electrical circuit in the form of a Wheatstone strain-resistive bridge, it is proposed to use a circuit in the form of a strain-sensitive differential cascade with negative feedback, where eight p-type conductivity strain gages are located at the places of maximum concentration of mechanical stresses on the membrane of the pressure sensor crystal, which are combined by two bipolar transistors with a vertical structure of n-p-n type of conductivity on a non-deformable crystal regions.

Semiconductor temperature sensors are one of the most demanded elements of the analysis of physical and chemical processes for a wide range of industries and research. Today, temperature sensors are used in nuclear, oil and gas, medical, automotive, aviation, space, metallurgical and many other industries. As a development for joint use with the pressure sensor, the structure of a separate crystal of the temperature sensor in the form of a Schottky diode was chosen, which is formed according to planar technology with the location of the anode and cathode on the same surface (a PDSH crystal with overall dimensions 0,8*0,8*0,4 mm^3). The characteristic of the direct branch of the Schottky diode VAC is determined by the work of the electron output between Mo and n-Si, where, with a supply current Ip = 1 mA, a direct voltage drop of Upr = 208 ± 6 mV is achieved and the temperature coefficient ST = -1.635 ± 0.015 mV/⁰C with linearity kT < 0.4% for the temperature range from -65 to +85 ⁰C. Due to the structure of two p-type guard rings around the perimeter of the anode of the Schottky diode for the reverse branch of the VAC, high breakdown voltage values of Upv > 85 V and low leakage current readings of Iut < 5 µA at 25 ⁰C and Iut < 130 µA at 85 ⁰C (Uobr = 20 V) were obtained.

Pressure sensors (DD) manufactured by FSUE VNIIA are the product of one of the main directions for the serial production of the enterprise for the nuclear and oil and gas industries. The need for continuous improvement of products for specific applications allows us to permanently find and develop new design and technological solutions. The proposed solutions in the vast majority of cases relate to the main element of the DD, which is the DD tensomodule. The DD strain gauge is an assembly structure containing a pressure converter into an electrical signal, made in the form of a microelectromechanical system (MEMS) made of silicon. The pressure converter is manufactured using planar technology with the structure of the electrical circuit of the resistive bridge on the front side and with the formation of a mechanical structure in the form of a complexly profiled membrane on the reverse side. The project solves the main issues related to the causes of the main and additional errors in measuring pressure in the elements, which in fact can be divided into two components - the quality of the implementation of the DD crystal itself and the correctness of the structure of the assembly structure.