Key Process Design Of High Temperature CMOS Integrated Circuit Based On 4H-SiC

The third generation wide band gap semiconductor Si C materials mainly composed of 4H-Si C have the characteristics of high working temperature,high thermal conductivity and high compressive strength,etc.Its application in the most popular fields in the new era,such as petroleum exploration,high-speed railway,aerospace and so on,will be the key to the development of high-tech industry in the future.As everyone knows,CMOS structure is one of the most important structure in integrated circuit system,but no physical limits make it Si based CMOS can adapt to bad working environment,such as high temperature,and the domestic research on high temperature resistance of Si C materials CMOS circuit is seldom reported,so the study of 4H-Si C high temperature CMOS process and critical process steps of design is of great importance in the field of high temperature integrated circuit.This paper focuses on the design and research of doping resistance and metal interconnection process in 4H-Si C CMOS process,and finally designs and maps the complete CMOS process based on these key processes.Then specific work contents are as follows:1.Firstly,the basic structure and working principle of CMOS are introduced,and the N-type substrate and epitaxial parameters of 4H-Si C CMOS circuit are designed,and the injection parameters of Gaussian P-well,P+and N+region are simulated by SRIM software.Then through Agient B1505A tester and Cascade probe for the same injection parameters but different channel width long than NMOS and PMOS devices for temperature change test,get output characteristic and transfer characteristic,and the effective migration rate and the threshold voltage are extracted,found that before 475K effective migration rate with the increase of temperature,the threshold voltage with the temperature decreases,and will become an important theoretical basis for process design;Finally,the CMOS process of 4H-Si C material is described in detail,with emphasis on the difference between it and Si-based process in temperature control,oxide-semiconductor interface defect control,etc.,and the design of doping resistance and metal interconnection two key processes are proposed.2.For the doping resistance process,its advantages over other integrated resistors are firstly defined.Then,the doping parameters in the CMOS process are designed,and a method based on Kelvin method to measure the total resistance and TLM method to extract the doping resistance is proposed.4H-Si C doping was divided into uniform doping and Gaussian-injected non-uniform doping for high temperature modeling.For uniform doping,a basic model at room temperature was established based on the Caughey-Thomas equation,and the theoretical resistance values,Sentaurus TCAD simulation values and test values were compared to verify the validity of the basic model.And the physical model with temperature coefficient was added to the simulation,and the comparison showed that the simulation value and the test value were in the same order of magnitude and had the same change trend with temperature.The resistance value would decrease first and then increase before and after475K.Finally,the mobility relationship was extracted from the simulation,and the high temperature model of 4H-Si C uniformly doped resistance was established based on the mobility.For non-uniform doped,the parameters of the extracted from SRIM generation into Sentaurus TCAD simulation,compared with the test values are:N+resistance test and the simulation values are not more than 10%,have the same variation law with temperature,suitable for absolute value request more accurate ten or hundred European levels of the circuit,and P-Well resistance for k?level,the test values due to the ohmic contact and holes ion the reason such as the activation rate and simulation value but still have the same trend of temperature difference,so it is suitable for the absolute value is not strict big resistance in the circuit.Finally,based on the relationship between the injection parameters and the resistivity,a high temperature model of 4H-Si C non-uniformly doped resistance was established,and the modeling process was summarized.3.For metal interconnection process,Pt/Tasi₂ alloy layer is added between Al and Si O₂ to prevent the mutual diffusion of metal and barrier layer at high temperature by its blocking effect on O element,and the interconnection process in 4H-Si C CMOS process is improved to make Pt/Tasi₂ encapsulate Al as much as possible.Then use Auto CAD software drawing and making the physical sputtering metal mask version,compared to 100 nm,with 20/40/100nm Pt/Ta Si₂/Al resistance high temperature properties,get a quadratic increase the resistance varies with temperature,while the latter is the temperature coefficient of resistance has a fixed,and proved that the high temperature influence O elements in diffusion into Al layers interconnect reliability.Finally,the characteristics of line width,spacing and corner of metal interconnection are analyzed,and it is proved that Pt/Tasi₂/Al system makes the interconnection have high temperature stability,and then the selection of appropriate line width,spacing and corner shape can make the interconnection process to achieve the optimal.4.Finally,the doping resistor and Pt/Tasi₂/Al interconnection are applied in the actual circuit,and the most basic integrated circuits such as common source co-gate amplifier,current mirror and CMOS transmission gate are designed,and their high temperature characteristics and process are analyzed.Finally,the detailed technological process of high temperature 4H-Si C CMOS is designed by combining the previous ion implantation parameters,key process research and circuit device design,and the complete layout is designed by using L-Edit software,which is of great significance to the future CMOS flow sheet based on 4H-Si C material.