F4280: Background information to PECVD-CCP laboratory excercise Miroslav Michl íček, Lenka Zajíčková michlicekm@mail. mu ni. cz, lenkaz@physics. muni. cz F4280 PECVD deposition Summary Miroslav Michlíček, Lenka 2/16 Details of PECVD-CCP laboratory excercise The goal of this excercise is to understand low pressure radio frequency (RF) capacitive coupled plasmas (CCP) that are used for PECVD (including plasma polymerization). Here is the list of areas that you should understand: ► Vacuum systems. Useful hints can be found later in the presentation. If necessary check literature on vacuum technology - D. Smith book, chapter 2, uploaded to IS study materials. ► What is plasma and how to generate it. ► Types of reactions occuring in plasma. ► What is plasma sheath. ► Generation and basic properties of RF capacitively coupled plasmas. Important terms: RF generator, matching box, blocking capacitor, capacitive plasma sheath, capacitive voltage divider, dc self-bias ► Plasma enhanced CVD F4280 PECVD deposition ummary iroslav Michlicek, Lenka 3/16 Experimental PECVD system F4280 PECVD deposition ummary iroslav Michlicek, Lenka 4/16 E hamber ► What will be the pressure? - LP - glass, PMMA, stainless steel... all with appropriate sealings - KF and CF standards, swagelok ► design is more of an engineering problem - size of samples, windows + much more ► geometry affects electric fields, gas flow patterns, possibly temperature distribution ► =>Chamber itself influences process - standard - GEC reference cell F4280 PECVD deposition ummary iroslav Michlicek, Lenka 5/16 Vacuum sealing ► KF/QF/DN - Klein Flange (KF), Quick Flange (QF) - elastomer O-rign + clamp, lower vacuum ► CF - Conflat - single-use copper gasket - bakeable - UHV vacuum F4280 PECVD deposition Summary Miroslav Michlicek, Lenka 6/16 Vacuum sealing II ► Swagelok systems - mainly for gas delivery - beware of inch-related measures (Anglo-American) ► others - ISO flange, Wheeler flange F4280 PECVD deposition Summary Miroslav Michlíček, Lenka 7/16 Pumping ► what types of pumps do we have? Which of them are relevant? ► oil vs dry pumps - tricks? ► it is rather useful to know principle and limitations of different types of pumps... there is not enough space for that. Vacuum Pump Pressure Ranges Ultra-High Vacuum High Vacuum Rough Vacuum ROTARY VANE ROTARY PISTON MECHANICAL PU DRY MECHAN MECHANICAL PUMP SORPTION PUMP B LOW E F •■'BOOST E F. PUMP IMP ICAL YSSSSSA VENTURI PUMP S/SA vrssss/SA LIQUID NITROGEN TRAP ÚP Y////////A DIFFUSION PU Y////A YSS/S/S/SSS* Y//S/////////7m CRYOPUMP Y////////* TURBOPqiMP ION PUMP Tl SUBLIMATION PUMP -12 -10 -8 -6 -4 -2 0 +2 Pressure in Torr (units are exponents of ten) F4280 PECVD deposition Summary Miroslav Michlicek, Lenka 8/16 Pumping II example ► what type of pump is this? ► can it pump atmospheric pressure? RPS Systems / MS-301 - Pumping Speed | 600 200 D 10 10 ■2 101 1 ID1 10s Pressure (mbar) 104 RPS 751/301 RPS-1001/301 RPS 1401/301 65 F4280 PECVD deposition Summary Miroslav Michlicek, Lenka 9/16 Pressure measurement ► U tube? Absolute vs relative gauges ► a single wide range gauge is often used (usually consists of Pirani + Ionization) ► additionally, absolute measurement by a capacitron (Baratron) -zero error McLeod Convection/Pirani__ nometer Thermocouple Cold Cathode Hot Cathode (Ionization Residual Gas AialvzerfRG e-Range Combination ► how to deliver gases? gas bottle « 200 bar ► mass flow meters - K-factors ► Internal structure Flaw rate gengor Bypass Inlet Power supply Flow rate oulput signal Flow rate setting signal □river/ Receiver D/A - A/D converter _^- CPU Valve driver circuit AJD converter jar Piezo actuator Flow rate control valve Meial diaphragm l'i'iii|iiTjitLiri£_— Operated (Jnuirnl Vulvc IfoltlT 'PIZP Outlet Mil hi for a high flow - a floating ball flow meter 1 H 4j ■ \. Hi Wiltini Int» 1 ■df-r^i lLt-p 1 p.'= 11 ~l 11h1 t KlllM- -1*1 r-if 1 r»ntij v*iw. 0*c; et rhnw ► homogeneity of the gas mixture - gas mixers ► inlet of gases into the chamber - shower head ► depending on the gas, pressure and geometry we can distinguish degree of mixing ► plug flow ► back-mixing flow ► well mixed flow ► Throttling valves to adjust pumping speed and working pressure For independent measurement of the gas flow (leak rate, liquid vapors): (1) (2) F4280 PECVD deposition Electric Power Summary Miroslav Michlicek, Lenka 12/16 ► Choosing a frequency - DC and AC Aston Dark Space (AD) Cathode Negative Glow (NG) Faraday Space self-bias F4280 PECVD deposition Summary Miroslav Michlicek, Lenka 15/16 Optional accessories ► Temperature control - both cooling and heating + feedback ► Leak detection ► Various characterization and process control techniques ► Light - spectroscopy using emission or absorption ► Charged particles + electric fields - ► Neutral species - mass spectrometry laser induced fluorescence ► Power signal ► Sample movement and manipulation - mechanical clamping and electrostatic chuck Wafer:Conductive Substrata + + + + + + + Dielectric _ — v — ±5000V ±600V '— V —' '□' Electrodes (Thick Film) Concentric Rings (Thin Film) F4280 PECVD deposition S ummary M iroslav Michlíček, Lenka 16/16 ■ 11 III III III 11 llil I I.I llili I^^^M Books covering similar topics: ► General thin film deposition (easy) - Thin-Film Deposition: Principles and Practise, D. Smith ► General plasma (easy) - Principles of Plasma Processing, F Chen and J. Chang ► General plasma (difficult) - Principles of Plasma Discharges and Materials Processing, Lieberman M. and Lichtenberg A. ► CCP (difficult) - Physics of Radio-Frequency Plasmas, Pascal Chabert Courses - Vakuová fyzika 1, 2 (Czech only), Fyzika plazmatu 3 (CCP mainly)