A wafer is a thin slice of semiconductor material (also called substrate) used in the fabrication of integrated circuits and in photovoltaics for wafer based solar cells. The microelectronic devices are built in and over the wafer through a series of fabrication steps. The whole process takes place in an ultra-clean environment. As a wafer is sent through the manufacturing facility, it is subject to intense vacuums, chemical baths, high energy plasmas, UV light and hundreds of processing steps required to turn it into a functioning product. Micro-contamination control is a huge challenge that needs to be addressed to achieve a defect free product and improved yields. Cleanliness at every step is crucial to maintain an ultra-clean process.
Why Monitor Trace Metals on Bevel Edge?
Trace metals around the edge exclusion area and bevel of silicon is another source of contamination that needs to be controlled. There are numerous pathways for contamination: incomplete etching of a film at the edge during a backside-cleaning process; edge handling of wafers during (edge bead removal (EBR) and wafer edge exposure (WEE); wafer alignment, direct contact between the wafer's edge and the cassette and from contact to the contaminated chuck.
Historically, it has been difficult or impossible to quantify metal contamination in the bevel and edge exclusion region of silicon wafers by traditional analytical methods. Total reflection x-ray fluorescence spectroscopy cannot operate close to the edge of a wafer due to scattering effects of the incident radiation and typically has a built in edge exclusion area of 10 mm. Localized metal contamination such as Bevel edge exclusion zone radial and backside contamination capabilities are offered for verifying bevel edge and backside cleaning efficacy in removing novel metallic elements with precision.
Monitoring and qualifying the raw materials, bare silicon substrates in this case for cleanliness before they make their way into the manufacturing cycle is a prudent step. Trace metal contaminants can diffuse along the surface or into the substrate of the silicon leading to electrical instability of the IC’s. A significant degradation of the recombination carrier lifetime has been demonstrated on the wafers with trace metal impurities. Alkali metals such as Na, K, and Li, can cause threshold voltage shifts on the transistors due to mobile ionic contamination. Trace metals such as Cu, Au, Ag, Zn and Cd are known to poison the devices.
Comprehensive Wafer Analysis
At ChemTrace, we utilize vapor phase decomposition (VPD) inductively coupled plasma-mass spectrometry (ICP-MS) for fully quantitative measurement of trace metals on wafer surfaces with superior method sensitivity and capability to analyze low to high z elements. We have developed a technique that will allow us to precisely measure the metallic contamination on whole wafer or customer specified regions on 200, 300 and 450 mm wafers. Standard edge exclusion is 2mm; however, we can provide zero and larger exclusions upon request.
Available Scanning Modes
Standard elements offered
40E to include Al, As, Sb, Ba, Be, Bi, B, Cd, Ca, Cs, Cr, Co, Cu, Ga, Ge, Hf, Fe, Pb, Li, Mg, Mn, Mo, Ni, Nb, K, Re, Rb, Na, Sr, Sn, Ta, Th, Tl, Ti, W, U, V, Y, Zn, Zr
*Other elements are offered upon request
ANIONS AND CATIONS ANALYSIS
Ultrapure water extraction of anions and cations on wafer surface followed by ion chromatography (IC)
Ionics are a leading factor in IC reliability. For example, residual fluoride on Al bond causes bond pad corrosion and staining. Poor rinsing of wafers during SC1, SC2, and dilute HF cleaning processes causes formation of haze on the wafer surface.
Residual anions or cations from cleaning chemistries, process gas, process chamber, and cleanroom environment
Standard ionics offered
Anions to include F-, Cl-, NO2-, Br-, NO3-, SO42-, PO43-
Cations to include Li+, Na+, NH4+, K+, Mg2+, Ca2+
VOLATILE ORGANICS ANALYSIS
Organic outgassing of wafer by automated thermal desorption gas chromatography - mass spectrometry (ATD GC-MS, SEMI MF 1982-1103 for detection of C7-C30 chained volatile organics
Speciation and semi-quantitative analysis of volatile organics collected on processed and witness wafers
Electronics and Nanotechnology
For more information, please contact us:
Technology Center and Principal Laboratory
44050 Fremont Blvd
Fremont, California 94538
12130 NE Ainsworth Circle Suite 210
Portland, Oregon 97220
Paltan myeon, Hwaseong-si,
Office: 031 703 3669
Mobile: 010 8993 0081
ChemTrace Hsinchu, Taiwan
No.9, Datong Road
Hukou Township Hsinchu County
ChemTrace Tainan, Taiwan
No.7, Gongye 3rd Road
Annan District, Tainan