The fabrication of an integrated circuit involves a sequence of processes that may be repeated many times before a circuit is complete. The device fabrication steps discussed in this and subsequent sections may be repeated anywhere from six to 15 times to achieve the desired product Robotic arm transfers a wafer
Generally, the first step in semiconductor device fabrication involves the oxidation of the wafer surface in order to grow a thin layer of silicon dioxide (SiO2). This oxide is used to provide insulating and passivation layers.
- The most common method of oxidation is thermal, and can be classified as either "dry" or "wet" oxidation. Wafers are loaded
into quartz boats and slid into a furnace heated to approximately 1200ºC.
- In dry oxidation, thin oxide layers are grown in an environment containing oxygen and hydrogen chloride near atmospheric pressure
- Thicker oxide layers require higher pressures and the use of steam (wet oxidation). Wet oxidation is performed by exposing the wafer to a mixture of oxygen and hydrogen in the furnace chamber. Water vapor is formed when the hydrogen and oxygen react.
The following are the potential hazards of oxidation.
Toxic Exhaust Gases
- Possible employee exposure to corrosive exhaust gases, including hydrogen chloride. Gases such as hydrogen chloride can be irritating and corrosive to the eyes, skin, and mucous membranes. Exposure to high concentrations can cause laryngitis, bronchitis, and pulmonary edema.
Occupational Health Guidelines for Chemical Hazards. US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 81-123, (1981, January). Provides a table of contents of guidelines for many hazardous chemicals. The files provide technical chemical information, including chemical and physical properties, health effects, exposure limits, and recommendations for medical monitoring, personal protective equipment (PPE), and control procedures.