Wafer dicing
Wafer dicing is the process by which die
Die (integrated circuit)
A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon or other semiconductor through processes such as...

 are separated from a wafer
Wafer (electronics)
A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...

 of semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 following the processing of the wafer. The dicing process can be accomplished by scribing and breaking, by mechanical sawing
The execution by sawing was a method of execution used in Europe under the Roman Empire, in the Middle East, and in parts of Asia. Some sources say that the method was probably never used. The condemned were hung upside-down and sawn apart vertically through the middle, starting at the groin...

 (normally with a machine called a dicing saw) or by laser cutting
Laser cutting
Laser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to be used by schools, small businesses and hobbyists. Laser cutting works by directing the output of a high-power laser, by computer, at the...

. Following the dicing process the individual silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

 are encapsulated into chip carrier
Chip carrier
A chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...

s which are then suitable for use in building electronic
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 devices such as computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s, etc.

During dicing, wafers are typically mounted on dicing tape
Dicing tape
Dicing tape is a backing tape used during wafer dicing, the cutting apart of pieces of semiconductor material following wafer microfabrication. The tape holds the pieces of semiconductor, known as dies, together during the cutting process, mounting them to a thin metal frame...

 which has a sticky backing that holds the wafer on a thin sheet metal frame. Once a wafer has been diced, the pieces left on the dicing tape are referred to as die, dice or dies. These will be packaged in a suitable package or placed directly on a printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 substrate as a "bare die". The area that has been cut away are called die streets which are typically about 75 micrometres (0.003 inch) wide. Once a wafer has been diced, the die will stay on the dicing tape until they are extracted by die handling equipment, such as a die bonder or die sorter, further in the electronics assembly process.

The size of the die left on the tape may range from 35 mm (very large) to 0.5 mm square (very small). The die created may be any shape generated by straight lines, but they are typically rectangular or square shaped.

Materials diced include:
  • Glass
    Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

  • Alumina
  • Silicon
  • Gallium arsenide (GaAs)
  • Silicon on sapphire
    Silicon on sapphire
    Silicon on sapphire is a hetero-epitaxial process for integrated circuit manufacturing that consists of a thin layer of silicon grown on a sapphire wafer. SOS is part of the Silicon on Insulator family of CMOS technologies...

  • Ceramics
  • Delicate compound semiconductors

Stealth dicing

Dicing of silicon wafers
Wafer (electronics)
A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...

 may also be performed by a laser-based technique, the so-called stealth dicing process. It works as a two-stage process in which defect regions are firstly introduced into the wafer by scanning the beam along intended cutting lines and secondly an underlying carrier membrane is expanded to induce fracture.

The first step operates with a pulsed Nd:YAG laser
Nd:YAG laser
Nd:YAG is a crystal that is used as a lasing medium for solid-state lasers. The dopant, triply ionized neodymium, typically replaces yttrium in the crystal structure of the yttrium aluminium garnet , since they are of similar size...

, the wavelength of which (1064 nm) is well adopted to the electronic band gap
Band gap
In solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the...

 of silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 (1.11 eV
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 or 1117 nm), so that maximum absorption
Absorption (electromagnetic radiation)
In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy for example, to heat. The absorption of light during wave propagation is...

 may well be adjusted by optical focusing
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...

. Defect regions of about 10 µm width are inscribed by multiple scans of the laser along the intended dicing lanes, where the beam is focused at different depths of the wafer. The figure displays an optical micrograph of a cleavage plane of a separated chip of 150 µm thickness that was subjected to four laser scans, compare. The topmost defects are the best resolved and it is realized that a single laser pulse causes a defected crystal region that resembles to the shape of candle flame. This shape is caused by the rapid melting and solidification of the irradiated region in the laser beam focus, where the temperature of only some µm3 small volumes suddenly rise to some 1000 K within nanoseconds and fell to ambient temperature again. The laser is typically pulsed by a frequency of about 100 kHz, while the wafer is moved with a velocity of about 1 m/s. A defected region of about 10 µm width is finally inscribed in the wafer, along which preferential fracture occurs under mechanical loading. The fracture is performed in the second step and operates by radially expanding the carrier membrane to which the wafer is attached. The cleavage initiates at the bottom and advances to the surface, from which it is understood that a high distortion density must be introduced at the bottom.

It is the advantage of the stealth dicing process that it does not require a cooling liquid. Dry dicing methods inevitably have to be applied for the preparation of certain microelectromechanical systems (MEMS), in particular, when these are intended for bioelectronic
Bioelectronics is a recently coined term for a field of research that works to establish a synergy between electronics and biology. One of the main forums for information about the field is the Elsevier journal Biosensors and Bioelectronics, published since 1990...

applications. In addition, stealth dicing hardly generates debris and allows for improved exploitation of the wafer surface due to smaller kerf loss compared to wafer sawing.
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