Preliminary Operations

1. Semiconductor integrated circuit technology is a logical extension of the development of transistor planar technology which embodied the prior experience gained in the production of semiconductor devices. For better understanding of the procedures of IC fabrication, therefore, we should be familiar with typical manufacturing steps of the entire technological cycle. Hybrid technology has its historical roots too. It generalized and perfected the film deposition techniques used earlier in radio engineering, machine-building industry, and optics.

2. Single crystals of silicon and also other semiconductors are generally produced by the techniques of crystal growth from the melt, the most popular being the technique of crystal pulling. For a crystal to be grown, a silicon seed crystal attached to the pulling rod is lowered into contact with the melt and then slowly raised and rotated. The liquid column suspended from the seed gradually solidifies into a single crystal ingot.

3. The crystallographic orientation of the ingot in its cross section is defined by that of the seed. The standard diameter of crystal rods is at present 80 mm; the maximum diameter can be 120 mm and over. The length can be 1 to 1.5 m., but commonly the rods measure only fractions of this size. Silicon ingots are first sawed into wafers, or slices, 0.4 or 0.5 mm in thickness.

4. The surface of blanks is rather uneven: scratches, projections, and pits are far larger in size than the potential integrated elements. Before starting with basic technological steps, therefore, blanks need be repeatedly lapped and polished to produce the smooth and shiny surface. Apart from removing mechanical defects, the aim of the first stage is to bring the blanks to the desired thickness, 200 to 300 µm unattainable in sawing, and render the faces parallel to each other. The lapping agent is the suspension of micro powders chosen for each cycle of lapping in order of decreasing grain size, down to 1 or 2 µm.

5. The wafers lapped in this stage still have a mechanically disrupted surface layer, a few micrometers thick, which covers a yet thinner, physically disturbed layer characterized by “invisible” crystal distortions and mechanical stresses induced in the course of polishing.

6. Finishing polishing is aimed at removing the two disturbed layers and decreasing the surface unevenness to a level characteristic of optical systems – down to hundredths of a micrometer. This polishing can be of the mechanical type (polishing with yet fine-grained suspensions) and of the chemical type (etching of the surface layer with suitable solvents).

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Words to be learnt

1.	to gain experience	приобретать опыт
2.	to be familiar with	ознакомиться
3.	to attach to	прикреплять к
4.	to suspend	подвешивать
5.	to define	определять
6.	to attain	достигать
7.	solid to solidify	твердое вещество затвердевать
8.	to disrupt	нарушать
9.	to cover covering	покрывать покрытие
10.	to disrupt	нарушать, мешать
11.	to induce	вызывать, возникать