Semiconductor manufacturers employ capacitance-based inspection and metrology systems for semiconductor wafers. In the front end of the wafer processing procedure, these systems can measure disc geometry to ensure that wafers, which are often valued at thousands of dollars, are suitable for additional operations. The most advanced testing technologies provide inspection and measurement solutions that are fast, easy to use and cost-effective. The benefits of using these systems include increased profitability through reduced waste and costs. This presentation describes how manufacturers can leverage capacitance-based inspection systems for measuring semiconductor wafers. Using illustrations and photos, the presentation is divided into three areas, as outlined in the following paragraphs. Why Disc Geometry Matters in Wafer Production Semiconductor wafers are cut from cylindrical silicon crystals, or ingots. The flatness of these disc-shaped wafers is controlled to tight tolerances to ensure that the entire wafer surface is suitable for integrated circuit (IC) production. If disc geometry is out-of-spec after cutting, it may be possible to reprocess the wafer. However, cutting is only the first step in wafer processing. Subsequent steps such as lapping and polishing, thin film deposition and lithography can add costs that result in significant waste if a wafer fails to meet dimensional specifications. This section of the presentation explains why disc geometry matters at each step during wafer processing – and what can go wrong. The Cost of Failing to Inspect Semiconductor Wafers Semiconductor wafers are usually made of silicon and gallium-based compositions, which are common elements in the earth’s crust. Yet, these elements’ abundance does not mean that wafers are inexpensive. The pure form of silicon (and its neighbors in the periodic chart) used in semiconductors do not occur naturally and must be refined, then mixed with a dopant that alters material properties and electrical characteristics. Ingots of the substrate are formed, wafers are cut, and more costs are added during subsequent processing steps that include lapping and polishing, thin film deposition, and lithography. This section discusses the costs associated with wafer fabrication and explains why it is worth inspecting and measuring wafers during each processing step. The Benefits of Manual, Semi-Automated and Fully Automated Systems for Semiconductor Wafer Inspection & Metrology Fully automated systems wafer inspection and metrology systems are fast, convenient and efficient at high volumes. They are also expensive. In comparison, semi-automated and manual systems generally used for lower volumes cost significantly less. Plus, they are easy to use when making fast, accurate measurements that support production flow. Within the semiconductor industry, there are applications for each type of system. Fully automated systems may be required for inspecting and measuring critical, high-value components such as CPUs, GPUs and high-density memory devices, a manufacturer may elect to perform 100% inspection of wafers prior to lithography. For less complex microelectronics, or for less valuable semiconductor products, a manufacturer may decide that it’s more cost-effective to sample representative wafers instead. This section of the presentation discusses how fully automated, manual or semi-automated systems provide the best solution depending on the application.
