Silicon Wafer Inspection and Cleaning Process

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Silicon Wafer Inspection and Cleaning
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• Silicon Specialist LLC

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• A good way to assess the quality of a Silicon
  Wafer is through a comprehensive characterization
  test. In a characterization test, a bare wafer is
  a baseline that is prequalified at the
  semiconductor fab or wafer manufacturer.
• The process uses the bare wafer before and after
  a process environment to establish a baseline for
  particle contributions to the defects. If you are
  evaluating a wafer for use in an IC, the process
  is called a silicon wafer inspection.

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Wafer Cleaning
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• In a process known as silicon Wafer Inspection
  and cleaning, particles on the surface must be
  removed from the surface. The process is a
  repetitive one, and with the increasing
  complexity of technology, it becomes more
  complex. The contaminants on the surface of the
  silicon wafer can range from 0.1 to 20 microns in
  size, and they can be both inorganic and organic.
  Various methods of cleaning the wafers can be
  categorized as wet or dry cleaning. Wet cleaning
  methods use solvents or aerosols, while dry
  cleaning involves ozonated chemistries.
• The first stage of silicon cleaning involves the
  use of solvents. Solvents are effective at
  removing oil and organic particles. However,
  solvents tend to leave residues on the surface of
  the wafer. This step generally requires two
  solvents to clean the surface, one for the
  cleaning solvent, and the other to return the
  substrate to its original state. Cleaners used in
  silicon cleaning are suitable for cleaning a wide
  variety of different materials.

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Wafer Etch
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• The etch process is performed on a
  300-mm-diameter silicon wafer in a reducing
  atmosphere. This chemical process results in a
  shallow structure where defects are formed. A
  laser light scattering tool is used to detect
  defects and identify their sizes. However, this
  technique is not as effective for post-inspection
  defect analysis. In this article, we will discuss
  the benefits and limitations of this method.
• The process of etching a silicon wafer can be
  complex. Etching is a process whereby unwanted
  materials are removed from a wafer while the
  protective layer is left intact. Etches can be
  anisotropic or isotropic. Anisotropic etching
  means that the etching rate is constant in all
  directions. Anisotropic etching, on the other
  hand, results in a variable rate along the
  lateral and vertical axes. Various websites sell
  silicon wafers and can provide you with samples
  in different quantities. Some websites can
  provide you with prompt feedback if there is any
  problem.

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Wafer Laser Marking
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• In the early 1990s, lasers used in semiconductor
  manufacturing began to improve insensitivity. A
  bright-field system could resolve defects and
  determine their size. Dark-field systems detected
  defects smaller than the system's spot size. They
  compared the signal to a calibration curve, which
  could determine the size of the defects. The new
  tools had a much higher throughput than the early
  methods. At the time, the rate of the inspection
  was about one wafer per hour.
• The method is based on the scattering of light
  from a laser beam to a defect on a wafer. The
  defect can be detected directly, or it can be
  detected by comparing images of adjacent dies. In
  digital processing, the image of the die to be
  inspected is subtracted from those of the
  adjacent die. The result is zero if no defects
  were detected, and if a defect is present on die
  (2), it will be seen on the subtracted image.

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Wafer Grinding
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• In the semiconductor and optical industries,
  single-crystal silicon (Si) is critical material.
  The material is highly brittle and is susceptible
  to grinding-induced subsurface cracks (SSCs).
  Studying SSCs during the grinding process is
  important to improve the surface integrity of
  silicon wafers. Subsurface cracks can be
  investigated by statistical methods. They tend to
  form on the cleavage planes when the abrasive
  grain is coarser than the silicon wafer surface.
• In semiconductor device fabrication, the process
  of backgrounding removes unwanted material from
  the surface of a silicon wafer. It combines
  chemical and mechanical polishing and reduces the
  thickness of a silicon wafer to a minimum. Wafer
  thinning is done to achieve desired device
  properties and prevent excessive TTV. Silicon
  wafers typically start with a thickness of 775
  um, but the amount of material removed will vary
  depending on the device.

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Wafer Polishing
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• When a silicon wafer is produced, it must undergo
  several stages of cleaning, drying, and
  polishing. A single-stage polishing process
  produces high-quality silicon wafers, while
  two-stage polishing requires a higher level of
  equipment and more technicians. Both polishing
  processes require clean rooms. Listed below are
  some of the steps in the process. The final steps
  of the process depend on the quality of silicon
  wafers.
• The process of silicon Wafer Polishing starts
  with removing any defects. If new material is
  used to produce a silicon wafer, it can create
  roughness on the surface. This is an important
  step in the process before a wafer reaches the
  fabrication facility (fab). Once at the silicon
  wafer house, imperfect wafers can be cleaned and
  reworked. If they do not meet specifications,
  they are rejected for processing.

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THANK YOU
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• Address 2487 Industrial Pkwy W, Hayward, CA
  94545
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