Beam Processing in Silicon Device Technology
- PDF / 2,071,211 Bytes
- 14 Pages / 415.8 x 637.2 pts Page_size
- 45 Downloads / 248 Views
Hess,
and Sigmon,
eds.
Laser and Electron-Bean Solid Interactions
361
and Materials Processing
BEAM PROCESSING IN SILICON DEVICE TECHNOLOGY
C. HILL Plessey Research (Caswell) Limited, Towcester, Northants., England.
Allen Clark Research Centre,
Caswell,
ABSTRACT Three modes of beam processing are distinguished, characterised by the heat pulse duration. The suitability of each of these modes as a process step in integrated circuit fabrication is discussed with reference to six criteria for applicability. Some conclusions are made as to the eventual application of each mode of processing.
INTRODUCTION As compared with the conventional heat treatment techniques available to solid state device technologists, beam processing offers an enormously increased range of processing times (10-8 to 10+1 secs), selectivity of heating both laterally and in depth with a resolution on the scale of the smallest device structures currently produced, and the option of transient liquid phase formation to effect material changes when required. These new degrees of freedom have been intensively applied to produce novel material changes, structures and even devices in silicon and some of these applications look very promising. However, in considering beam processing as an integral part of a complete silicon device technology reliably producing structures in large numbers, a number of additional criteria become important. These are Mi) is the heat treatment process sufficiently well controlled to achieve the required tolerances in the structure being fabricated? (ii) is the process compatible with other processing steps, e.g. can multi-material integrated circuits be processed? (iii) can secondary effects be tolerated or minimised, e.g. high point defect concentrations causing high recombination/generation currents?(iv) can large slices be processed and processed rapidly? (v) is the process cost effective? (vi) are the advantages of beam processing sufficient to justify changing from the well established successful conventional heat treatment techniques for the particular device under consideration? The possibility of meeting these criteria with the existing beam processing techniques and the expected problem areas are discussed in this paper. MODES OF BEAM PROCESSING There are three main modes of beam processing, characterised by the duration of the heating cycle responsible for the change in material properties. These will be referred to as the adiabatic, thermal flux and isothermal modes of beam processing. The typical experimental arrangement and resulting temperature profiles (laterally and in depth on a silicon slice) are shown schematically in Fig.l. In the adiabatic mode the radiation pulse is sufficiently short (less than 200 nS) that little heat is lost by diffusion from the absorption layer (about 2 microns deep) during the pulse, and so essentially all the energy absorbed is utilised in raising the absorption layer temperature. The temperature profile in depth is consequently very shallow and steep: laterally the prof
Data Loading...
