Piezoresistive pressure sensors are constructed using the piezoresistive effect of single crystal silicon. Using the single crystal silicon diaphragm as the elastic element, the MEMS ion implantation process is used in the specific direction of the single crystal silicon diaphragm, and a certain dose of ions (boron ions, phosphorus ions, arsenic ions, etc.) are implanted to form a set of equivalent resistances, and The resistor is connected into a Wheatstone bridge, and the single crystal silicon diaphragm is placed in the sensor cavity. When the pressure changes, the single crystal silicon produces strain, so that the resistance located on the diaphragm changes in proportion to the measured pressure, and then the bridge circuit obtains the corresponding voltage output signal. The resistance (ie, piezoresistive material) located on the monocrystalline silicon diaphragm is formed by the ion implantation process, and its resistance is related to the concentration distribution of the implanted ions in the depth direction of the monocrystalline silicon and the ambient temperature, as shown in the figure below. The ion concentration distribution of implantation is determined by the process conditions of ion implantation (such as implantation dose, ion species, implantation energy, etc.).

Currently, most multiphysics analysis software can only analyze the performance of devices such as pressure sensors when the piezoresistive coefficient is known. In the actual process, the piezoresistive coefficient is usually difficult to determine, while the concentration distribution of implanted ions is easy to measure, and the process conditions for ion implantation are also easy to know. To this end, the TEM module of IntelliSuite software expands the analysis function of piezoresistive materials. When the concentration distribution of implanted ions or the process conditions of ion implantation are known, simulation analysis of piezoresistive material devices can be performed .

01  Design layout

Design layout files with Blueprint modules

02 Process  flow

Design process flow with IntelliFab modules

03  Process Simulation

Physical-level process simulation with the FabSim module

04  Extract the device-level simulation analysis model

05 Device  -level simulation

◆ To set the analysis type:

◆ To set material parameters:

The TEM module provides three methods for setting up piezoresistive materials:

a. Directly set the piezoresistive coefficients P11, P12, P44 in the form of a table;

b. Calculate the piezoresistive coefficient based on the measured longitudinal ion concentration distribution of the implanted piezoresistive material, semiconductor type and operating temperature;

c. Calculate the piezoresistive coefficient based on the implantation dose, ion species and implantation energy plasma implantation process conditions.

(a) Setting the piezoresistive coefficient

(b) Calculate the piezoresistive coefficient from the measured ion concentration distribution, semiconductor type and temperature, etc.

◆ Set boundary conditions:

◆ To set the load:

06 Analysis  results

(a) Stress

(b) Displacement

07  Extraction resistance analysis

◆ To set the load:

◆ To set the load:

(a) Voltage load: 0V

(b) Voltage load: 5V

(c) Temperature load: 25℃

08  Extract resistance analysis results

(a) Node potential

(b) Node potential

(c) Figures (a) and (b) the relationship between the potential difference between the two nodes and the pressure load on the silicon surface