John L. Mauer

Mechanism of silicon etching by a CF4 plasma

The mechanisms for the reactive ion etching of silicon by CF4 plasma are investigated. A model is proposed whereby silicon is etched by chemical reaction with free fluorine to produce a volatile species, and also by physical sputtering. The chemical etching is shown to be enhanced by ion bombardment of the reacting surface. This etching process, together with a model for cracking CF4 in the plasma, is evaluated by comparison to actual etch rates. Experimentally, the silicon etch rate is observed to decrease with increasing silicon area, by what is called the loading effect. The functional form of the loading effect, as predicted by the model, is fitted to experimental loading curves. The contributions of the various etching components are separated, to yield empirical values for the enhancement of the chemical reaction by physical sputtering.

Reactant supply in reactive ion etching

In reactive ion etching, the etch rate may be reactant limited, so that a measurement of reactant supply is neccessary to understand the details of the etching process. A quantitative determination of reactant supply can be obtained by measuring the total dissociation of the etching gas. In particular, this paper reports the total dissociation of CF4 as a function of input power and pressure in a diode system. A quadrupole mass spectrometer measuring the CF3+ peak indicates the presence of CF4 as well as other molecules containing the (CF3) radical. A transient technique is used to separate the contributions of the other molecules from CF4 so that the total CF4 number density can be calculated. The production of reactant by the dissociation of Cf4 causes etching of silicon and SiO2 on the cathode of the system. Possible reaction sequences of these etching processes are modelled by using the known supply of reactant. The partial pressures of the etching products are calculated and correlated with the etch ...

Using simulation to analyze integrated tool performance in semiconductor manufacturing

Abstract The use of integrated tools in semiconductor manufacturing has increased rapidly over the last few years. Increased clustering of process modules can make the sequential process steps more reliable. But the advent of clustering also made parallel processing possible. The combined effect is usually increased manufacturing productivity through lower cycle times and/or greater throughput. However, this difference in productivity can be difficult to quantify. Detailed simulation models of integrated tools provided a means to evaluate the various performance characteristics as a function of application specific process and equipment parameters.

The simulation of integrated tool performance in semiconductor manufacturing

Integrated tools in semiconductor manufacturing have become increasingly complex; the throughput and cycle time are no longer easily related to the individual process times. Detailed simulation models of these tools provide a means to evaluate the various performance characteristics. Further, proper planning for integrated tools requires flexible simulation models in the hands of line engineers themselves.

X-ray mask repair

A method for repairing X-ray lithographic masks using focused ion beam technology is described and demonstrated. The ion beam is used for mask imaging, for absorber milling for opaque repair, and for deposition of X-ray-opaque material for clear repair. Solutions to the unique problems faced in executing these tasks on the high-resolution, high-aspect-ratio patterns characteristic of X-ray masks are discussed. Several effects of material redeposition during opaque repair are explored. The significance of this same redeposition during clear repair and the resulting advantage gained in using a high-yield deposition process are illustrated. Examples of repairs and printed images of these repairs are shown for feature sizes smaller than 0.25 µm.

X-ray transmission through low atomic number particles

Abstract Defect printability studies have been carried out using low atomic number particles mounted on thin silicon membranes. Transfer of the particle image to a resist-coated wafer was accomplished using synchrotron radiation from the VUV electron storage ring at Brookhaven National Laboratory and subsequent resist development. Residual resist images resulting from the particles on the membrane were measured with an SEM. A semi-empirical model has been developed that can approximately predict the size of the printed image on the wafer. Data is presented which shows that over-development of the photoresist, which removes the residual particulate images, can be achieved while maintaining exceptional line-width control in x-ray lithography.