ICPMS Analysis of Bulk & Process Chemicals for Semiconductor Processes Ann O Connell Chemical Analysis Eng Intel Corporation 1
Overview of Presentation Impact of Trace Metal contamination on Semiconductor Manufacture More Transistors, Less Trace Metals Analysis lab, Applications, Tools and Validation Benefits of onsite system Future requirements for ICPMS 2
The Impact of Tracemetal contamination Semiconductor Mfg In the semiconductor industry, high purity reagents are used in manufacturing devices. The analysis of metallic impurities in these reagents has become more important than ever before. The development of ultra scale integration devices (ULSI) requires higher component densities. This in turn increases the probability of device failure caused by the mobility of metallic impurities within the device. 3
Trace metal effects on Semiconductor devices The main elemens of Integrated chips are the transistor (basically on/off switches) When the gate is biased by an applied voltage, the electric field at the Silicon substrate under the gate inverts allowing the current to flow (the on, state). A transistor is produced using a range of processing techniques. These techniques necessitate that the device comes into direct contact with process chemicals. The mobility of metallic impurities within the wafer could result t in device failure at the gate dielectric. The race for manufacturing of ultra large scale integration (ULSI) devices requires higher component densities, within smaller dimensions. The shrinking of the gate dielectric area makes the devices more sensitive to the same concentration of metal impurities. A A direct consequence of Moore s s law ( Transistors( doubling every 2 years toward the billiontransistor microprocessor ) is the strong demand for a continuous reduction in the concentration of metallic impurities. A lower concentration c is required for every new process generation. 4
Trace metal limits (ppb) More Transistors, less Trace metals 100,000 10,000 1,000 100 10 Processor 4004 Moore s Law 8008 1 Pentium 4 Processor 4004 1970 1975 1980 1985 1990 1995 2000 Transistors doubling every 2 years toward the billiontransistor microprocessor The exponential relationship of number components per chip and the reduction in the trace metal levels allowable in process chemicals. 5
Chemical Analysis Lab ICPMS 4500 System for 0.18 micron technology is setup in a class 100 clean room (less than 100 particles >0.5 µm diameter/ft 3 of air) environment. PFA Sample Introduction Certified ISO9002. Sample prep done in class 10 hood. Wall mounted ultrapure water systems hooked up to fume hoods 6
Trace Metal Analysis by ICPMS Trace metal levels are determined in Process & Bulk Chemicals by either ICPMS or GFAA Since the development of the benchtop systems, routine tracemetal analysis by ICPMS has become the norm, Concentration levels from parts per million (i.e ppm = 1mg/L) to parts per trillion (i.e ppt = 1ng/L) can be measured Quantifiable data for most elements across the mass spectrum can be collected Speed of analysis, 7
Common Applications Trace Metal analysis of Chemicals such as H 2 O 2, HCl, NH 4 OH, TMAH, HNO 3, H 2 SO 4 from process & support tools for 1. Tool Qualification During process startup trace metal levels in the chemical and the process & support tools are measured and deemed fit for process or not based on specification levels. 2. Monitoring the quality control process chemicals, process tools and support tools. typically 50+ samples p/w are analysed, results recorded and tracked. Wafer Surface analysis Surface Metal extraction combined with ICPMS to characterise trace metal contaminants on Si Wafer surfaces. SWAB Analysis Clean room quality check, (e.g. Cu Migration check) 8
Bulk & Process Tools Bulk Chemical Delivery System (BCDS) Supply the Process Benches with Chemicals Tote (Chemical storage) CDM (Chemical distribution manifold) TVB (Tool Valve Box) Process Benches The tools in the Fabrication facility where wafers are processed. Contain various Acid/Base/Solvent and Water baths. Used in the Front End and Back End of the process. Hooked up to the BCDS system after the TVB 9
Element Li B Na Mg Al K Ca Cr Mn Fe Ni Co Cu Sn Ba Pb Ti Zn Process & Bulk Chemicals, Analysis Procedure Plasma Normal Normal Normal Normal Normal Normal Table # 1 elementplasma conditions Samples are taken from the tool using the SOP for the area Samples, when received by the lab, are diluted to specified concentrations. Analysis is carried out using Standards prepared in an identical matrix to the sample Samples are analysed in both hot & normal plasma conditions (see Table #1) PreCleaned PFA bottles are used for all sample storage. Number of elements measured, vary between 8 & 35 elements, defined by: step in process (i.e. Front End or Back End Process) distribution of chemical throughout fabrication facility ( for e.g ultra pure water analysed for 35 elements, it is used throughout the process) 10
Element Al B Ba Ca Co Cr Cu Fe K Li Mg Mn Na Ni Pb Sn Ti Zn AWS Nitric 0.0166 0.0973 0.0183 0.0155 0.0299 0.0025 0.0241 0.0315 0.0168 0.143 0.0005 0.0282 0.0167 0.0306 Analysis Validation HNO3 ICB 0.0122 0.0973 0.0181 0.0146 0.060 0.0237 0.0156 0.175 0.0004 0.0273 0.0180 0.0084 HNO3 ICV 1.91 2.04 2.04 1.98 2.01 2.01 1.95 1.81 1.68 2.13 1.94 2.00 2.00 1.76 2.02 2.08 2.01 1.98 Table # 2 Typical Analysis results LOD 0.009 0.08 0.0002 0.01 0.0003 0.02 0.001 0.05 0.05 0.003 0.001 0.001 0.1 0.0001 0.001 0.001 0.007 0.003 Quantative analysis of this type is relatively new to the semiconductor industruy and the need for analysis validation of results has become apparent. For each process generation the ICP MS tool is qualified in accordance with a qualification plan and approved by a process control board. On each analysis run, standards are used to validate analysis. (see Table # 2) RoundRobin Robin standards are purchased by one site quarterly. This standard is shipped to each site for crosssite site matching. All limits of detection LOD are quoted at the 3 sigma level. 11
Benefits of the onsite vs. contract ICPMS analysis The outstanding benefit of onsite ICPMS capability is: Real time analysis, Speed of analysis turn around Engineering and lab personnel working together on issues with the benefit of historical data to identify problems. Ongoing investigations requiring ICPMS analysis is facilitated Logistical issues are simplified 12
Future requirements for ICPMS As future technologies are moving to nm levels the challenge to ICPMS Manufacturers is to design systems to continue to meet the changing requirements of the Semiconductor Industry 13