THE ENERGY INFLUX FROM AN RF PLASMA TO A …从RF离子体的能量涌入…

1、the energy influx from an rf plasma to a substrate during plasma processingw.w. stoffels, e. stoffels, h. kersten*, m. otte*, c. csambal* and h. deutschdepartment of physics, eindhoven university of technology,po box 513, 5600 mb eindhoven* institute for physics, university of greifswald, domstr. 10

2、a, d-17487 greifswald, germany.the work has been supported by the royal dutch academy of sciences (knaw) and the deutsche forschungsgemeinschaft (dfg) under sfb198/a14. 13 nabstractlaim: determine the energy flux to a substrate in an low pressure rf plasmalmethod: calorimetric probelresults: argon:

3、heat flux is few times 10-3 w/cm2 heating mainly due to ions and electrons oxygen 50% higher heat flux than argon molecular surface processes are important as wellsubstrate heating: csdt/dt = fin-fout lf fin = heat flux jx times probe surface: ions: kinetic recombination electrons:kinetic neutrals:

4、kinetic, internal, association, chemical photons: blackbody, plasmalf fout: thermal conduction of gas and substrate radiationthe ion and electron heating depends on surface potential: =separation of neutral component possible by using a bias voltagecs: heat capacity substrate; ji,je ion/electron flu

5、x; vpl -vfl acceleration voltage of ions in sheath eeflpleeeektktvvemktnj2)(exp20recirecejjjj ej e vvn ve vvnktme vviiiiplfleambplfleeiplfl00005()()exp.()thermal probelprinciple: heat flux determines the heating time of the probetcoolsheatsssindtdtdtdtmccoolhheathq)()(the probe is a cu plate, diamet

6、er 3.4 cm, height 0.002 cm. mounted to a thermocouple and shielded from below (see picture). it can be moved (x,y,z) and rotated.dshsubstratefig.4photograph of the thermal probe placed in the glow at substrate position.thermal probe: raw data0100200300400262830323436fig.5-95v-46v0vts ctime sts(t)-cu

7、rves as measured during the argon plasma process (p=1pa, p=15w) for three substrate voltages (0, -46, -95v).rising edge plasma on, decreasing edge plasma off. the plasma heat flux is determined from the derivative signal-120-100-80-60-40-20020-10-8-6-4-202fig.6 ar, 1pa o2, 1pais mavs vcurrent-voltag

8、e characteristic of the thermal probe for argon and oxygen.the measured electron and ion flux is used to separate ion and electron heating from neutral heating. rf-matchrfargoni-vpowderinjectionccdplangmuir-probe thermal probeoxygen fig.1experimental setuplcapacitively coupled 13.56 mhz plasma. al e

9、lectrode d=130mm spherical reactor d=400mm.ldiagnostics: thermal probe langmuir probe ccd cameraltypical conditions: 1pa, 15w ar or o2 argon: te = 3.5 ev ne = 2 1015 m-3 results: argoncalculated contributions by ions (ji, jrec) and electrons (je) to the thermal balance of the substrate. the calculat

10、ions are based on ne measured by the langmuir probe and a bohm flux. for the electron current (right branch) the measured substrate current is used. measured data fitted by the model results.-100-80-60-40-200200,000,050,100,150,20fig.10 ji+je+jrec (probe) ji (probe) je (probe) jrec (probe) je+jrec (

11、substrate)qin j/svs v-100-80-60-40-200200,000,050,100,150,20fig.11 measurement: ar, 15w, 1pa model: vs*is model: ji+je+jrec probe model: ji+je+jrec substrateqin j/svs v results: oxygen similar trends for oxygen and argon overall higher heat flux in oxygen due to neutral heating ne(oxygen) ne(argon)

12、so electron branch is smaller -100-80-60-40-200200,000,050,100,150,20fig.12 o2, 1pa, 15w ar, 1pa, 15wqin j/svs vmeasured integral energy influx (qin) for argon and oxygen, respectively, for the same macroscopic discharge conditions.conclusionslthermal heat flux to a substrate can be measured by probelelectron, ion and neutral heating can be separatedlargon 15w, 1pa: heat flux few times 10-3 w/