Rapid thermal processing
Encyclopedia
Rapid Thermal Processing (or RTP) refers to a semiconductor
manufacturing process which heats silicon wafers to high temperatures (up to 1,200 °C or greater) on a timescale of several seconds or less. During cooling, however, wafer temperatures must be brought down slowly so they do not break 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
manufacturing including dopant activation
, thermal oxidation
, metal reflow and chemical vapor deposition.
with the process chamber. One temperature control strategy involves in situ pyrometry to effect real time control.
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
s, change film-to-film or film-to-wafer substrate interfaces, densify deposited films, change states of grown films, repair damage from ion implantation
, 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
s they are short in duration, processing each wafer in several minutes.
To achieve short time annealing time trade off is made in temperature and process uniformity, temperature measurement and control and wafer stress as well as throughput.
Recently, RTP-like processing has found applications in another rapidly growing field — solar cell fabrication. RTP-like processing, in which an increase in the temperature of the semiconductor sample is produced by the absorption of the optical flux, is now used for a host of 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.
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...
manufacturing process which heats silicon wafers to high temperatures (up to 1,200 °C or greater) on a timescale of several seconds or less. During cooling, however, wafer temperatures must be brought down slowly so they do not break 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
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...
manufacturing including dopant activation
Dopant Activation
Dopant Activation is the process of obtaining the desired electronic contribution from impurity species in a semiconductor host. The term is often restricted to the application of thermal energy following the ion implantation of dopants...
, thermal oxidation
Thermal oxidation
In microfabrication, thermal oxidation is a way to produce a thin layer of oxide on the surface of a wafer. The technique forces an oxidizing agent to diffuse into the wafer at high temperature and react with it. The rate of oxide growth is often predicted by the Deal-Grove model...
, 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 equilibriumThermal equilibrium
Thermal equilibrium is a theoretical physical concept, used especially in theoretical texts, that means that all temperatures of interest are unchanging in time and uniform in space...
with the process chamber. One temperature control strategy involves in situ pyrometry to effect real time control.
Rapid thermal anneal
Rapid thermal anneal (RTA) is a subset of Rapid Thermal Processing. It is a process used in semiconductor device fabrication which consists of heating a single waferWafer (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...
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
Dopant
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance in order to alter the electrical properties or the optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that...
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
Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into another solid. This process is used to change the physical, chemical, or electrical properties of the solid...
, 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 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...
s they are short in duration, processing each wafer in several minutes.
To achieve short time annealing time trade off is made in temperature and process uniformity, temperature measurement and control and wafer stress as well as throughput.
Recently, RTP-like processing has found applications in another rapidly growing field — solar cell fabrication. RTP-like processing, in which an increase in the temperature of the semiconductor sample is produced by the absorption of the optical flux, is now used for a host of 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.