TABLE OF CONTENTS In this chapter, the preparation of semiconductor-grade silicon from sand, its conversion into crystals and wafers (material preparation stage), and the processes required to produce polished wafers (crystal growth and wafer preparation) are explained.
Upon completion of this chapter, you should be able to:
Explain the difference between crystalline and noncrystalline materials.
Explain the differences between a polycrystalline and a single crystalline material.
Draw a diagram of the two major wafer crystal orientations used in semiconductor processing.
Explain the Czochralski, float zone and liquid crystal encapsulated Czochralski methods of crystal growing.
Draw a flow diagram of the wafer preparation process.
Explain the use and meaning of the flats or notches ground on wafers.
Describe the benefits in the wafer fab process that come from edge-rounded wafers.
Describe the benefits in the wafer fab process that come from flat and damage-free wafer surfaces.
The evolution of higher-density and larger-size chips has required the delivery of larger diameter wafers. Starting with 1-in diameter wafers in the 1960s, the industry is now introducing 300-mm (12-in) diameter wafers into production lines. According the International Technology Roadmap for Semiconductors, 300-mm wafers will be the standard diameter until about 2007, and 400- or 450-mm diameter wafers are predicted for the far future (Figure 3.1). Larger-diameter wafers are necessary to accommodate increasing chip sizes with cost effective wafer fabrication processes (see Chaps. 6 and 15). The challenges in wafer preparation are formidable. In crystal growth, the...
