thermal anneal Furnace anneals Thermal oxidation Laser lift-off (for LED production) Electrochemical deposition (ECD). See Electroplating Chemical-mechanical polishing (CMP) Wafer testing (where the electrical performance is verified using Automatic Test Equipment, binning and/or laser trimming may also be carried out at this step) Die preparation Through-silicon via manufacture (For three-dimensional integrated circuits) Wafer mounting (wafer is mounted onto a metal frame using Dicing tape) Wafer backgrinding and polishing (reduces the thickness of the wafer for thin devices like a smartcard or PCMCIA card or wafer bonding and stacking, this can also occur during wafer dicing, in a process known as Dice Before Grind or DBG) Wafer bonding and stacking (For Three-dimensional integrated circuits and MEMS) Redistribution layer manufacture (for WLCSP packages) Wafer Bumping (For Flip chip BGA (Ball grid array), and WLCSP packages) Die cutting or Wafer dicing IC packaging Die attachment (The die is attached to a leadframe using conductive paste or die attach film) IC bonding: Wire bonding, Thermosonic bonding, Flip chip or Tape Automated Bonding (TAB) IC encapsulation or integrated heat spreader (IHS) installation Molding (using special plastic molding compound that may contain glass powder as filler to control thermal expansion) Baking Electroplating (plates the copper leads of the lead frames with tin to make soldering easier) Laser marking or silkscreen printing Trim and form (separates the lead frames from each other, and bends the lead frame's pins so that they can be mounted on a Printed circuit board) IC testing Additionally steps such as Wright etch may be carried out. Prevention of contamination and defects When feature widths were far greater than about 10 micrometres, semiconductor purity was not as big of an issue as it is today in device manufacturing. As devices become more integrated, cleanrooms must become even cleaner. Today, fabrication plants are pressurized with filtered air to remove even the smallest particles, which could come to rest on the wafers and contribute to defects. The ceilings of semiconductor cleanrooms have fan filter units (FFUs) at regular intervals to constantly replace and filter the air in the cleanroom; semiconductor capital equipment may also have their own FFUs. The FFUs, combined with raised floors with grills, help ensure a laminar air flow, to ensure that particles are immediately brought down to the floor and do not stay suspended in the air due to turbulence. The workers in a semiconductor fabrication facility are required to wear