Research On Single-chip Integrated CMOS 3D Micro Hall Magnetic Sensor

With the advancement of intelligence,sensor plays an important role in the whole intelligent system as a necessary part of sensing layer.In the field of sensors,magnetic sensor can not only detect the magnetic field,but also measure pressure,position,displacement,velocity,acceleration,angle,angular velocity,current and so on.In recent years,the size of magnetic sensor's market hits billions of dollars a year in the world,with Hall effect sensor occupying a large portion.The main reason is that the range covered by Hall effect sensor's detection is consistent with that of magnetic field produced by various permanent magnetic materials.In addition,Hall effect sensor is compatible with CMOS technology,since compared to other magnetic sensors,Hall sensor requires less cost to be integrated to a single chip with the signal conditioning circuit and digital processing circuit.In the previous study and development of the CMOS 3D Hall sensor,those important parts affecting the sensor performance,such as device structure,circuit model and layout design,are studied separately and cannot fuse together,because of the disconnection of the research tools and methods.So the research is time-consuming and the experience and data is different to pass to and participate in the design and iteration.In this paper,we focus on the above problems from device modeling,simulation optimization,accurate circuit model to layout design,tap-out,performance characterization.Afterwards,by multiple iterative verification and optimization of sensor design,a complete rapid research and development method for single-chip Hall magnetic sensor is formed.This paper focuses on how to improve the performance of 3D Hall devices.First,a detailed study of the horizontal Hall sensor,an important component of a 3D Hall device,is carried out.The tap-outs are completed twice to implement various structures in 0.18?m BCDliteTM technology provided by GLOBALFOUNDRIES.The advantages and disadvantages of every structure are analyzed in detail according to Silvaco TCAD.Then,the sensitivity is improved by optimizing the process parameters.Moreover,the resistance,sensitivity and offset of the devices are analyzed and characterized at different temperatures.As a result,a 90° symmetrical circuit model of horizontal Hall device is proposed and described by Verilog-A hardware description language and verified in Spectre simulator.Based on the 2-pulse spinning current method,the signal conditioning circuit for cross-shaped horizontal Hall sensor is designed.Secondly,the width,length,and contacts' location of 5CVHD(Five-contact Vertical Hall Device)are studied with the aid of COMSOL simulator using parameters of GLOBALFOUNDRIES' 0.18?m BCDliteTM technology and the performance is improved.A circuit model of 5CVHD,taking into full account various physical effects,is proposed using JEFT to simulate characteristic of resistors and capacitors.The circuit model is described by Verilog-A hardware description language and verified in Spectre simulator.According to the 4-pulse spinning current method,conditioning circuit is designed for 5CVHD.Finally,3D Hall sensor is studied and two structures are proposed.The first one is the multi-device structure combining the horizontal Hall device and the vertical Hall device,which is the product of studying two kinds of discrete devices.The second one is a single-device structure.Such cross-shaped 3D Hall sensor is proposed with the following advantages:small area of 120?m2;concentrated in a tiny point to effectively eliminate non-orthogonal error;strong-compatibility with the study of horizontal and vertical Hall sensors.The circuit model of the cross-shaped 3D Hall device is designed with not only the basic characteristics such as resistance and Hall voltage simulated accurately but also the physical effects such as nonlinearity,geometric effect,temperature effect,and AC characteristics fully considered.The cross-shaped 3D Hall device is analyzed with the help of circuit model while the corresponding conditioning circuit is designed.The main innovations of the paper are as follows:1.When the horizontal Hall sensor is under design,through the design process of multiple iterations,the sensitivity is improved from 81.6V/AT to 402V/AT.Meanwhile,various temperature parameters of sensitivity,offset and resistance are extracted to be prepared for the design of vertical and 3D Hall sensors.In the study of the vertical and 3D Hall sensors,COMSOL simulator,which substitutes multiple tap-outs(3?4 tap-outs in 2-3 years),helps to iterate the structures,to generate the corresponding circuit model,and to optimize the device structure based on the model in COMSOL by the horizontal Hall device research experience.This method can reduce the development cycle from 2-3 years into months.2.A cross-shaped 3D Hall device is proposed,which has the following advantages:small area of 120?m2;concentrated in the tiny point,to effectively eliminate non-orthogonal error;strong-compatibility with the study of horizontal and vertical Hall sensors.The sensitivity of three directions are improved and balanced as following:90.7V/AT,90.7V/AT and 86.9V/AT respectively,through the optimization of process and device structure.3.The high-precision circuit models for cross-shaped horizontal Hall device,5CVHD and cross-shaped 3D Hall device are proposed and design.Those three circuit models have the following advantages:full consideration of the physical effects such as the voltage-dependent nonlinear,geometric effects temperature effect;taking into account the depletion layer above and under the active area to improve the accuracy of the model;using the JFET to simulate the resistance and capacitance to improve the AC performance of the model.