Gas Purification for Thin Film Deposition CIGS Photovoltaic Cells
The thin film active layers in copper indium Potential Problems gallium diselenide (CIGS) solar cells are These trace contaminating gases can cause frequently formed using sputter deposition. defects in the thin film layers in addition to During this vacuum-based process, a plasma increasing chamber pump-down times. Both of electrons and ions are created from the vacuum and cryo pumps may be affected. inert argon gas. These ions dislodge atoms from the surface of a crystalline material Oxygen contamination can lead to uncontrolled which is then deposited to form an extremely oxidation of metal layers and metal targets thin coating on a substrate. Multicomponent within the sputter or PVD tools. Trace water films can be deposited with excellent vapor can contribute both hydrogen and stoichiometric accuracy. oxygen molecules to process chambers and metal layers. Carbon contamination might Pall argon purification products remove result in the formation of thin polymer films on moisture, oxygen, carbon monoxide, carbon process chambers and metal surface layers. dioxide and hydrocarbons thereby: Virtually all gaseous contaminants found in • improving film quality and gas delivery systems and process gases can • reducing outgassing, leading to faster lead to upsets and longer process times, pump-down times ultimately resulting in manufacturing yield losses and lower tool throughput. These The Challenge factors can negatively impact overall tool Typical argon impurity levels found in physical cost-of-ownership (COO). vapor deposition (PVD) / sputtering tools are: moisture (0.5 ppm), oxygen (2 ppm), and The control and reduction of trace oxygen total hydrocarbons (0.4 ppm). Furthermore, and hydrocarbon species can be achieved the following contaminants, emanating from using Pall purifiers with AresKleen ™ INP the process gases and gas delivery system medium. components, are often present in the vacuum chambers: H 2O, O 2, CO, CO 2, H 2, N 2, methane The Solution and non-methane hydrocarbons. These The recommended Pall argon purification contaminants are often adsorbed to the and filtration products are: chamber walls under atmospheric conditions, but tend to desorb at the operating pressures • Gaskleen ® II purifier assembly typically used during sputter deposition P/N GLP2INPVMM4 (for ≤3 slpm) (< 200 mT). Furthermore, the elevated • Gaskleen ST purifier assembly temperatures required for thermal processing P/N GLP5INPVMM4 (for ≤5 slpm) can exacerbate the release of gases from chamber walls. The Gaskleen gas purifier assemblies combine AresKleen media with Ultramet-L ™ stainless steel filter media. APIMS test data molecular species in argon, effectively removing show AresKleen INP medium has a strong these impurities to sub-100 ppt levels. affinity for oxygen and carbon containing
Test Results
102 102 Mixed challenge of 20 ppb each Challenge of 55 ppm n-butane ) ) 02, H2O, CO2 and CO b b 1 p p 10 p p 1 ( (
H2O 10 n n o o i i O2 t t a a CO r
r 0 t t 10 n n CO2 e e c c 0 n n 10 o o c c
10-1 m m a a e e r r t t s s -1 n n 10 -2 w w 10 o o D D
10-3 10-2 0 5101520 0 24 48 72 Time (h) Time (h) Figure 1. Removal of oxygen-containing Figure 2. Removal of carbon-containing compounds by Gaskleen II purifier compound by Gaskleen II purifier
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25 Harbor Park Drive Pall Corporation has offices and plants throughout the world. For Pall representatives in your area, please go to www.pall.com/contact Port Washington, NY 11050 +1 516 484 3600 telephone Because of technological developments related to the products, systems, and/or services +1 800 360 7255 toll free US described herein, the data and procedures are subject to change without notice. Please consult your Pall representative or visit www.pall.com to verify that this information remains valid. Products in this document may be covered by one or more of the following Portsmouth - UK patent numbers: US 7,465,692; EP 1 105 201. +44 (0)23 9230 3303 telephone +44 (0)23 9230 2507 fax [email protected] © Copyright 2010, Pall Corporation. Pall, , AresKleen, Gaskleen, and Ultramet-L are trademarks of Pall Corporation. ® Indicates a trademark registered in the USA. is a service mark of Pall Corporation.
MECIGSEN Printed in the USA February 2010