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Several Electrical Measurements of the Concentration of Several (Sodium and Potassium) Ionic Contaminants in Thin Dielectric Films at Constant Temperature

IP.com Disclosure Number: IPCOM000061804D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 4 page(s) / 57K

Publishing Venue

IBM

Related People

Guerin, F: AUTHOR [+2]

Abstract

This article describes a new measurement technique. It is able to measure Na+ and K+ ion densities in MOS structures with the following advantages: 1. short measurement time (N 10 mn) 2. good accuracy : Na+ down to 109 ions/cm 3. does not require the use of very high temperature . price and reliability of tooling are improved . avoid Al/SiO2 reactions which creates current leakages around 400ŒC . keep C-V dip (does not flatten the curve) in the depletion state, still providing information on the electronic state of the interface. Ionic contaminants in thin dielectric films are very detrimental for devices in the microelectronic technology, causing electrical parameter instability.

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Several Electrical Measurements of the Concentration of Several (Sodium and Potassium) Ionic Contaminants in Thin Dielectric Films at Constant Temperature

This article describes a new measurement technique. It is able to measure Na+ and K+ ion densities in MOS structures with the following advantages: 1. short measurement time (N 10 mn) 2. good accuracy : Na+ down to 109 ions/cm 3. does not require the use of very high temperature . price and reliability of tooling are improved . avoid Al/SiO2 reactions which creates current leakages around 400OEC . keep C-V dip (does not flatten the curve) in the depletion state, still providing information on the electronic state of the interface. Ionic contaminants in thin dielectric films are very detrimental for devices in the microelectronic technology, causing electrical parameter instability. It is of vital interest for the semiconductor manufacturing industry to measure, monitor and control the ionic contamination incorporated throughout the processing of integrated circuits. Sodium and potassium are well known as the most important ionic contaminants of thin dielectric films like SiO2, which is the base of the whole planar industry. Several methods have been used to measure sodium and potassium in oxides up to now: -Electrical methods: . The most widely prevalent technique is certainly the so- called "flatband shift" or WVFb measurement at a specific temperature. The main drawback is that the result is global and no value can be separately attributed to sodium and potassium. . TSIC (Thermally Stimulated Ionic Current) This method is fundamentally based on the analysis of the ionic current generated in a MIS (metal insulator silicon) structure under polarization by ionic contaminant motion during a temperature ramp test. Sodium and potassium are well separated, but this technique is very time consuming (N 1 hour). It is mainly useful in laboratories but cannot be used efficiently in manufacturing lines due to its low productivity. . TVS (Triangular Voltage Sweep) See next section. -Physical chemistry methods The main disadvantage of such techniques is that they quantify the chemical form of the contaminant and not the ionic form. However, only the electrical activity of the contaminant is important for the behavior of the devices, thus making physical chemistry methods meaningless. Nevertheless, we can mention SIMS (Secondary Ionic Mass Spectroscopy) and NAA (Neutron Activation Analysis) as the most important physical chemistry methods for analyzing sodium and potassium. The proposed technique is an electrical method which can quantify in only one measurement both sodium and potassium ions like TSIC does but in a much shorter time (10 minutes vs. 1 hour) and using less sophisticated tools because no temperature ramp is needed. .This new method is based on the well-known TVS or IV loop technique and is described hereafter (see Fig. 1 which shows typical IV curves). The whole test sequence...