Plasma diagnostic in an inductively coupled plasma using chlorine chemistry

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1 Plasma diagnostic in an inductively coupled plasma using chlorine chemistry H. Steinmetz, J. Strobl, N. Rohn and T. Werner, Lam Research GmbH M. Klick, W. Rehak, M. Kammeyer, and D. Suchland, Adolf-Slaby-Institute S. Wurm, W. Preis and Ch. Koelbl, Infineon Technologies - 1 -

2 Plasma diagnostics for production tools Comparison of complementary methods Optical emission Self excited electron VI - probe spectroscopy (OES) resonance spectroscopy (rf voltage and power) (SEERS), Hercules Parameters - relative values - absolute values - absolute and relative values - line averaged - volume averaged - no well define averaging - intensities of emission lines - plasma bulk power - peak voltage - identification of species - plasma density - real power in chamber - characterization of excitation - electron collision rate (not in plasma) Measurement - optical - electrical, high frequency - electrical, radio frequency - passive - passive - passive - non-intrusive - non-intrusive - non-intrusive Deposition, contamination - critical - no influence - no influence Sensitivity - high - high - low/medium Endpoint - yes - yes - (strongly) limited Base lining, - strongy limeted - yes - limited tool matching Plasma diagnostics for production tools - 2 -

3 Mechanical analogon of nonlinear effect used for SEERS Sheath (nonlinear part) Sheath (linear part - retarding electric field) million rps (generator) Sinusoidal oscillation (simple sheath model) Inert mass of plasma electrons Oil Collisions with neutrals Nonsinusoidal oscillation (realistic sheath model) - 3 -

4 Experimental setup dielectric window top power TCP coil Coaxial sensor and cable HERCULES plasma rf current Fast ADC 500 MHz, 1 GS/s 50 Ohms input chamber bottom power peak voltage SEERS Process data bank - 4 -

5 HERCULES - Sensor for LAM TCP 9600SE - 5 -

6 HERCULES - Sensor for LAM TCP 9600SE He leakage flange Figure 1 shows window plate of the TCP-System in section Detail figure: mounted sensor in the He leakage flange (principle) Contact spring or thread A

7 electron density [cm -3 ] mtorr 10 mtorr first wafer (cold machine) 13 mtorr Pressure variation,, process time [min] The relative changes between processing a production wafer on a warm and a cold machine as well as between running process at different total pressure are much more evident. The overall curve shape does depend strongly on total pressure and on tool condition

8 Al etching - first wafer effect electron density [1/cm 3 ], collision rate [1/s process time [s] peak voltage [V] peak voltage collision rate electron density (filtered) Process signatures of the first three wafers - 8 -

9 bulk power PBP [mw cm -2 ] electron density ne [cm -3 ] W 150 W 200 W TCP - power P TCP [ W ] Electron density and bulk power vs. TCP power TCP power effects the density and collision rate of electrons and therefore the plasma impedance and the power dissipation of the bottom power (capacitive). Mainly dependent on collision rate, the bulk power (bottom) decreases for increasing TCP power (>250W). This is the reason for the plateau in the electron density.

10 Product wafer - resist mask on Al (appr. 50%) Al etching in Cl 2 - first wafer effect electron density [1/cm 3 ] main etch first wafer second third wafer The behavior of the main etch for the first wafer of a lot is quite different from the following ones process time [s]

11 Wafer fault analysis Fault: no resist, faultless dashed (reference wafer) optical emission (EP) peak voltage [V] process time [s] collision rate [1/s] The break-through is not influenced (here separate step). In case of the main etch the collision rate decreases by one order of magnitude

12 Al etching-with/without barrier (TiN,Ti) each curve averaged from five test wafers collision rate [1/s] break through (Al 2 O 3 ) 800 nm AlSiCu Ti layer Increase of the collision rate due to the larger cross section of Ti (red curve). TiN layer not visible SiO 2 0 with TiN (100 nm), Ti (15 nm) process time [s]

13 Characterization of chamber cleaning First Si wafer (blue curve) after chamber cleaning behaves different. collision rate [1/s] resist wafer (*0.7) Si wafer (*2) product wafer Conditioning is finished after processing 10 resist wafers. Deconditioning due to processing bare Si wafers Wafer No. Charactrization and calibration of machine status possible by measuring and comparing absolute parameter values

14 one lot one point Al etching - trend analysis main etch etch time [s] electron density [1/cm 3 ] Cl 2 -MFC drift/error quick clean Cl 2 -MFC error main clean Lot No collsion rate [1/s] optical emission (EP) *3000 After Cl 2 -MFC adjustments/substitution, the collision rate returned back to normal signal levels. Shows the dramatic effect of the main clean on the collision rate. The endpoint level was adjusted during cleaning procedures

15 one lot one point Al etching - trend analysis barrier etch etch time [s] electron density [1/cm 3 ] Quick clean Cl 2 -MFC drift/error main clean Cl 2 -MFC error Lot No. collsion rate [1/s] optical emission (EP) *500 Trend analysis of a memory product covering 77 lots. Shows the effect of the quick clean on the collision rate. The collision rate is the most sensitive parameter, in particular forecasting MFC error

16 Al etching - trend analysis collision rate main etch (Al) and barrier etch (TiN, Ti) collision rate [1/s] quick clean main clean main etch step barrier etch step One point represents one lot - stepwise analysis. Shows the different dependence of process steps on events, e.g., cleaning procedures Cl 2 -MFC error Lot No

17 Summary Key items Results Monitor / control power coupling into the plasma? Tool matching? Long term tool stability? Developing / optimizing processes? Controlling chamber cleaning procedures? Reduction of test- and monitor wafers? Layer resolution? Spatial resolution? Detection of tool failure? Yes Yes Yes Yes Yes Yes Yes demonstrated forti, SiO 2, ARC and photo resist No Yes (e.g. Cl 2 -MFC failure)

18 Benefit from outfitting LAM TCP with HERCULES /PL increasing decreasing - overall equipment effectiveness - reliability and uptime - statistical analysis - MTBF - yield - throughput - cost of ownership (equipment) - MTBR - time for equipment base lining - time for process development

Real time plasma etch control by means of physical plasma parameters with HERCULES

Real time plasma etch control by means of physical plasma parameters with HERCULES A. Steinbach 1) S. Bernhard 1) M. Sussiek 4) S. Wurm 2) Ch. Koelbl 3) D. Knobloch 1) Siemens, Dresden Siemens at International