Rapid thermal processing (RTP) is a
semiconductor manufacturing process which heats
silicon wafers to temperatures exceeding 1,000°C for not more than a few seconds. During cooling wafer temperatures must be brought down slowly to prevent dislocations and wafer breakage due to thermal shock. Such rapid heating rates are often attained by high intensity lamps or lasers. These processes are used for a wide variety of applications in
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
manufacturing including
dopant activation,
thermal oxidation, metal reflow and chemical vapor deposition.
Temperature control
One of the key challenges in rapid thermal processing is accurate measurement and control of the wafer temperature. Monitoring the ambient with a thermocouple has only recently become feasible, in that the high temperature ramp rates prevent the wafer from coming to
thermal equilibrium
Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in ...
with the process chamber. One temperature control strategy involves ''in situ''
pyrometry
A pyrometer is a type of remote-sensing thermometer used to measure the temperature of distant objects. Various forms of pyrometers have historically existed. In the modern usage, it is a device that from a distance determines the temperature o ...
to effect real time control. Used for melting iron for welding purposes.
Rapid thermal anneal
Rapid thermal anneal (RTA) in rapid thermal processing is a process used in
semiconductor device fabrication
Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuit (IC) chips such as modern computer processors, microcontrollers, and memory chips such as NAND flash and DRAM that are ...
which involves heating a single
wafer at a time in order to affect its electrical properties. Unique heat treatments are designed for different effects. Wafers can be heated in order to activate
dopant
A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. Whe ...
s, change film-to-film or film-to-wafer substrate interfaces, densify deposited films, change states of grown films, repair damage from
ion implantation
Ion implantation is a low-temperature process by which ions of one element are accelerated into a solid target, thereby changing the physical, chemical, or electrical properties of the target. Ion implantation is used in semiconductor device fa ...
, move dopants or drive dopants from one film into another or from a film into the wafer substrate.
Rapid thermal anneals are performed by equipment that heats a single wafer at a time using either lamp based heating, a hot chuck, or a hot plate that a wafer is brought near. Unlike
furnace anneal
Furnace annealing is a process used in semiconductor device fabrication which consist of heating multiple semiconductor wafers in order to affect their electrical properties. Heat treatments are designed for different effects. Wafers can be heate ...
s they are of short duration, processing each wafer in several minutes.
To achieve short annealing times and quick throughput, sacrifices are made in temperature and process uniformity, temperature measurement and control, and wafer stress.
RTP-like processing has found applications in another rapidly growing field: solar cell fabrication. RTP-like processing, in which the semiconductor sample is heated by absorbing optical radiation, has come to be used for many solar cell fabrication steps, including phosphorus diffusion for N/P junction formation and impurity gettering, hydrogen diffusion for impurity and defect passivation, and formation of screen-printed contacts using Ag-ink for the front and Al-ink for back contacts, respectively.
See also
*
Tamman and Hüttig temperature
References
{{Reflist
External links
IEEE RTP Conference Proceedings Different Heating Systems with Microwaves/Plasma
Semiconductor device fabrication