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      The process flow of wafer fabrication in a chip

      The wafer goes through a series of processes to form a silicon substrate, known as a wafer, that meets the requirements of semiconductor manufacturing. The basic processing process is: appearance finishing, slicing, chamfering, grinding and polishing, etc.

      Exterior finishing

      (1) cutting section

      The seed portion, shoulder portion, tail portion, and the portion that does not meet the diameter requirements after visual inspection, as well as the portion that does not meet the specifications for electrical resistivity and structural integrity, shall be removed.

      (2) Radial grinding

      The diameter of the crystal rod can not meet the diameter requirements very accurately, and it is generally a little larger, so it is necessary to carry out radial grinding.

      (3) positioning surface grinding

      Once the crystal is oriented on the cutting block, a reference plane is rolled along the axis, its position along an important crystal plane, which is determined by crystal orientation inspection.

      slice

      Slicing determines several characteristics of wafer: thickness, slope, parallelism and warping. The process of sectioning is as follows:

      Wafer fixation — X ray positioning — Slicing — Wafer disassembly — Cleaning — X ray positioning

      chamfering

      Chamfering is to grind the sharp edges and corners around the wafer. Its purpose is to prevent the rupture of the edge of the wafer, prevent the damage caused by thermal stress, and increase the flatness of the epitaxial layer and the photoresist at the edge of the wafer.

      grinding

      The purpose of grinding is to remove the knife marks on the surface; Eliminate damage layer; Improve the flatness, make the wafer thickness uniform; Increase surface flatness, etc.

      polishing

      (1) Polishing. The goal of polishing is to remove the subtle damage layer on the surface and get a smooth surface with high flatness. There are two kinds of polishing methods: mechanical polishing and chemical mechanical polishing. The efficiency of mechanical polishing is too low, and the amount of consumables is large. The speed of chemical mechanical polishing is greatly improved and the surface quality is also improved.

      (2) Inspection of defects and flatness

      The polished chip needs to be inspected for surface defects and surface roughness. Surface defect inspection, with the resolution accurate to 0.05μm “magic mirror” to observe the surface of wafer concave and convex situation, detect the defective products. Surface roughness inspection, Wafer surface roughness measured by atomic microscope, surface roughness parameters are as follows:

      TTV, difference between maximum and minimum Wafer thickness, TTV=a-b;

      Tir, the sum of the distance between the highest point and the reference surface and the distance between the lowest point and the reference surface on the wafer surface, Tir =a + b; FPD, the maximum distance between a point on the wafer surface and the reference surface, if A > B, FPD= A, otherwise, FPD= B.

      cleaning

      Wafer has gone through slicing, grinding, polishing and other processing procedures from the drawing of monocrystalline silicon rod. In the middle, it is exposed to the pollution of various chemical reagents and particles such as polishing agent and abrasive, and finally these impurities need to be cleaned up.

      Traditionally, Wet Chemical Cleaning has been used for Wafer cleaning. Wet Chemical Cleaning has been used in the field for many years and has proven to be the most effective and cost effective cleaning technology. The most widely used wet chemical cleaning technique is RCA cleaning.