Research On ICP Etching In The Fabrication Of GaAs,GaN And SiC Devices

The devices made of GaAs,GaN and SiC compound semiconductors play an excellent position in various military and civil industries,such as information and communication,photoelectric industry,aerospace,radar,new energy vehicles and so on.Dry etching is an essential and complex step in the fabrication of these compound semiconductor devices.In this paper,the etching experiments of GaAs,GaN and SiC materials were carried out by ICP equipment,and various dry etching parameters were studied,such as ICP power,lower electrode bias RF power(RF1),gas ratio,gas flow rate and chamber pressure on the etching results was studied;The relationship between etching rate and ICP power,lower electrode bias RF power RF1,chlorine gas flow rate was analyzed.The causes of residual pillar defects at the bottom of GaAs back via etching were analyzed and eliminated,so as to improve the side wall roughness;The relationship between GaN etching rate and ICP power,lower electrode bias RF power(RF1),gas ratio,gas flow rate and chamber pressure was studied;The relationship between SiC etching rate and ICP power,gas ratio,gas flow rate and chamber pressure was studied.The main research results are summarized as follows:1.The experimental results show that ICP power,Cl2 flow rate and RF power can promote the etching rate in the range of experimental parameters.ICP power and chlorine gas flow rate can inhibit the side wall angle of the back through-hole,and the higher the RF1 power,the more helpful it is to open the side wall angle.The morphology of etched bottom is affected by RFl power,chlorine flow rate and ICP power.The trend of sidewall lateral drilling erosion also changed with the change of ICP power and Cl2 content.In the experiment of GaAs,the reason of grass in the bottom is that the chemical etching and physical etching are not enough to clean the falling GaAs particles/polymer particles/mask layer in time,so that the GaAs under the particles can not be etched.The side wall angle and the roughness of the etched surface are proportional to the physical etching/chemical etching/protection effect.An etching condition with high etching rate and ideal etching morphology was obtained by experiments:under the chamber pressure of 15mTorr,ICP of 1200W and RF1 power of 200W,the etching rate of GaAs can reach 5.1μm/min by using 150sccm main etching gas Cl2 and 30sccm auxiliary etching gas BCl3.The bottom and side walls are relatively smooth and smooth,and the side wall angle is close to 90°.2.In GaN etching,a larger physical bombardment is needed to break the Ga-N bond to assist etching.In the experiment,BCl3/Cl2 gas combination or Ar/Cl2 gas were used to etch GaN.The experimental results show that BCl3/Cl2 combination etching GaN can not form enough strong physical bombardment;under the condition of RF1 power of 50W,increasing ICP power will lead to the decrease of etching rate,which is due to the fact that BCl3 is easy to produce polymers in the reaction,which inhibit the etching rate and etching angle to a certain extent.When Ar/Cl2 gas combination is used instead,the etching rate and etching angle are significantly increased compared with that of BCl3/Cl2 combination under the same conditions,which indicates that the physical bombardment assisted effect of Ar is stronger than that of BCl3.The etching angle of GaN increases with increasing RF1.The following optimized etching menu was obtained by experiments:under 7 mTorr chamber pressure,600 W ICP and 200 W RF1 power,48sccm main etching gas Cl2 and 12sccm ar were used to etch GaN.The etching rate can be as high as 441.3 nm/min and the sidewall inclination angle is 83.6°.3.It is found that the etching rate of SiC increases with the increase of SF6 flow rate,and a higher etching rate can be obtained with a certain proportion of oxygen and argon.At the same time,the ICP power also has a linear positive correlation with the etching rate.When the chamber pressure is belowl5mTorr,the etching rate is positively correlated with it,and when the chamber pressure is higher than 15mTorr,the etching rate is negatively correlated with it,which may be due to the excess pressure in the chamber is higher than 15mTorr,the concentration of etching gas increases,and more and more free radicals occupy the surface of SiC wafer during the reaction,which results in the surface of silicon carbide occupied.The number of active radicals exceeds the amount of SiC that can react with it.The chemical reaction in the cavity reaches the limit,and the extra active radicals can not participate in the reaction to improve the etching rate.The experimental results show that a high etching rate of 560nm/min can be obtained under the chamber pressure of 15 mTorr,ICP of 1200 W and RF1 power of 200 W,and the main etching gas SF6 of 25 sccm combined with O2 of 5 sccm and AR of 6 sccm..