Positive photoresist was characterized by Fourier transform infrared (FTIR) spectroscopy after high dose, high power ion implantation. The concentration of individual components in the resist such as the photosensitizer and organic C--H bonds were determined independently by examining the integrated absorbances at the corresponding infrared absorption peaks: 2040-2200 cm 1 for the sensitizer, and 2820-2995 cm 1 for the stretch of C--H bonds. Degradation of the sensitizer was found to be largely due to the elevated wafer temperature which is dependent on the heat generated by the ion implant and the cooling mechanism of the implanter. The thickness of the carbonized layer can be estimated by the loss of C--H bonds, which is in agreement with SEM results. A study of the implanted resist which was subjected to an oxygen plasma shows that the increased ashing resistance is due to the formation of the carbonized layer. The carbonized layer also reduces the degradation of the sensitizer in the implanted resist when exposed to an oxygen plasma.Over the years, photoresist has been used extensively as an ion implant mask in semiconductor device fabrication. For most practical applications, the ion dose ranges from 1.0Ell to 1.0El5 ions/cm 2. In this range the photoresist mask provides the advantages of process simplicity, effective masking, and ease of removal after implant. At higher dose levels, however, the optical density of the resist increases substantially and the films become more difficult to strip. Okuyama et al.(1) attributed the change to the "graphitization" of resist. In their report, they presented experimental data from the measurements of scratch resistance, optical density, and gas chromatography and showed similarities between high dose ion-implanted photoresist and disordered graphite. They concluded that physical ion bombardment during implant is responsible for the graphitization of the resist, which breaks chemical bonds within the resist. As a result, hydrogen, oxygen, and nitrogen atoms are lost from the base polymer chains and consequently the resist becomes richer in carbon.Later, Smith (2) proposed a model which related the thickness of the carbonized layer to ion dose and ion range within the photoresist. He suggested that there is a critical dose at which the original concentration of hydrogen within the carbonized layer is completely depleted. Below the critical dose, fractional carbonization exists and the thickness of the carbonized layer is determined by the ion range. Above the critical dose, the thickness of the carbonized layer can be estimated from the gas evolved from the resist and should slowly increase with dose. However, application of the model to estimate the thickness of the carbonized layer is limited, since the ion range within the resist will change toward that of amorphous carbon, as the carbonization proceeds.Another concern when using photoresist as an implant mask is the wafer temperature. Wafers can rise in temperature if the heat generated by the ion implant is not di...
Spin-on-glass (SOG) has been characterized using process control techniques that provide in-line monitoring capability. Film composition changes have been observed for different anneal temperatures (300~176 and ambients (oxygen and nitrogen). Fourier transform infrared (FTIR) spectroscopy and x-ray photoelectron spectroscopy (XPS) show a reduction in organic content in the film after annealing at temperatures above 500~ Area integration under the silicon dioxide peak in the FTIR spectrum indicates compositional changes begin at a critical temperature identified as approximately 500~ Both FTIR and XPS data show further densification of SOG takes place at higher temperature anneals (700 ~ 1000~ Refractive index and film stress measurement data correlate well with FTIR and XPS results.
The interstitial oxygen concentration, wafer warpage, and flatness were measured after each step of a typical n-well CMOS process. It is found that a critical oxygen concentration of 30.0 ppm exists below which no appreciable precipitation takes place during the process. Precipitation densities at the end of the process range from approximately 2.0 • 10 s to 2.0 • 10 l~ cm -3 for wafers having initial oxygen concentrations of 30.0-38.0 ppm, respectively. A well-defined denuded zone is absent from wafers at the upper end of this concentration range. Changes in wafer flatness were less than the 1.0 ~m measurement repeatability. Severe warpage was induced by thermal stress during an ion implant anneal step for wafers having an initial oxygen concentration greater than 32.0 ppm. Reduction of the push/pull temperature for this process and a subsequent glass anneal step from 900 ~ to 650~ made the entire process immune to warpage irrespective of initial oxygen concentration.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.38.0.53 Downloaded on 2015-06-13 to IP
A nondestructive, noncontact, optical method was successfully developed to measure thicknesses of titanium and titanium silicide thin films by observing infrared transmissions. These transmissions can be substantial for film thicknesses of up to 850 Å in titanium and 1000 Å in titanium silicide. The technique provides a convenient and reliable means for in-line process monitoring of a Ti-salicide (titanium self-aligned silicide) process module for gate, source, and drain formation in integrated circuits. A linear relationship between absorbance and film thickness was obtained for titanium and titanium silicide films. This behavior can be explained very well by the classical wave propagation theory of metallic films.
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