Быстрый термический процесс (RTP)

What is Rapid Thermal Processing (RTP)?

Rapid Thermal Processing (RTP) is a semiconductor manufacturing technology that allows for the rapid heating of samples to high temperatures in order to complete short processes in a few minutes or less.

High intensity lamps controlled by pyrometers and thermocouples that detect sample temperature are used to generate such rapid heating rates.

To avoid dislocations and sample breakage, cooling must be precisely controlled.

Rapid Thermal Processing was originally developed for ion implant annealing, but its applications have expanded to include oxidation, silicide formation, chemical vapor deposition, and advanced applications such as modifying the crystallographic phase of elements, compounds, or alloys to improve properties, lattice interface, or stress relaxation.

RTP is a flexible technology that provides rapid heating and cooling to process temperatures ranging from 200 to 1300°C, with ramp rates typically ranging from 20 to 200°C/sec, and excellent gas ambient control, allowing the creation of sophisticated multistage processes within a single processing recipe.

Rapid Thermal Anneal

Rapid Thermal Anneal (RTA) is a process used in semiconductor device manufacture that includes heating a single wafer at a time to influence its electrical characteristics.

Different heat treatments are created for different effects.

Wafers can be heated to activate dopants, modify the film-to-wafer substrate interface, densify deposited films, change the states of grown films, repair ion implantation damage, shift dopants from one film to another, or form a film into the wafer substrate.

Other Applications

•Implant annealing

•Ohmic contact annealing

•Rapid Thermal Oxidation (RTO)

•Rapid Thermal Nitridation (RTN)

•Rapid Thermal Evaporation (RTE)

•Densification and crystallization

•Diffusion of dopants

•Selenization (CIGS solar cells)

•RTCVD of graphene and HBN

Implant Annealing

By directly bombarding dopants into a substrate, high energy ions are deposited on it. The collision of high energy ions with the atoms of the substrate during this process produces changes and damages to the substrate’s material structure. Damages of ion implantation can be formation of crystal defects, creating local zones of amorphous material within crystalline structure and formation of continuous amorphous layers. Annealing heat treatment applied to material in order to restoring the structure of the substrate to condition before ion implantation process.

Ohmic Contact Annealing

The main steps for ohmic contact fabrication are surface cleaning of semiconductor, metal deposition, patterning and annealing as a last step. Surface cleaning may be done by various ways such as sputter etching, chemical ething, reactive gas etching or ion milling. After that, metals are deposited on the semiconductor by CVD, sputter deposition or evaporation. Patterning of contacts can be done with photolithographic methods. The annealing process is applied to relieve any stress that may occur on the materials during the previous steps or to accelerate any reaction that is desired to occur between the metal and the semiconductor.

Rapid Thermal Oxidation

In order to make semiconductor devices smaller, it is necessary to perfectly control oxidation and minimize the effects of oxidation on silicon. Very short times on high temperatures required to prevent these impurities which could affect electrical properties of device and achieve oxide film growth. This can be achieved by rapid thermal oxidation and RTO process tends to produce silicon dioxide films with the highest quality electrical and material characteristics. It is possible to precisely control the oxidation temperature and reducing the thermal budget of the heat cycle required for an oxide film growth.

Rapid Thermal Nitridation

In terms of chemical and electrical properties, nitrided thermal SiO₂ films shows better results than pure thermal oxides. The nitridation of oxides was previously carried out with excessively long furnace times or plasma-enhanced treatments. However, nitrogen distribution in the oxides could not be controlled in these methods, and as a result, nitride oxides could not be used at their full potential. Now nitride oxides can be effectively controlled and used with RTN.

Rapid Thermal Evaporation

In a rapid thermal evaporation (RTE) system, the powdered source material is evaporated and deposited on the substrate located within 10 mm from the source. This design in the RTE system allows high deposition rates (~2 µm/min), effective use of source materials, high uniformity in thickness and composition of thin films. Therefore, RTE has been successfully used in synthesizing photovoltaic-grade thin films.

Densification and Crystallization

When sintering porous, amorphous materials there is a competition between densification and crystallization. When a material crystallizes prior to full densification, transport by diffusion is slowcr through the impinging crystals than by viscous flow through the matrix. Crystal formation during sintering retards the densification rate. Thus, a porous, crystalline material results. However, when the nucleation of crystals is avoided, such as by heating rapidly through the region where nucleation rate is fast, densification will occur prior to extensive crystallization. A dense, crystalline material results.

Diffusion of Dopants

Diffusion and ion implantation are the two key processes to introduce a controlled amount of dopants into semiconductors and to alter the conductivity type. The doping concentration decreases monotonically from the surface, and the in-depth distribution of the dopant is determined mainly by the temperature and diffusion time. Generally speaking, diffusion and ion implantation complement each other. Diffusion is used to form a deep junction, such as an n-tub in a CMOS device, while ion implantation is utilized to form a shallow junction, like a source / drain junction of a MOSFET.

Selenization (CIGS Solar Cells)

The chalcopyrite structure of Cu(In, Ga)Se2 (CIGS) has the potential to make it a major candidate for new and more efficient solar cells due to its favorable band gap, high absorption coefficient for solar radiation and stability against photo-degradation. The two-step process is the most promising for fabricating high efficiency solar cells at low cost manner on an industrial scale. This type of process consists of the sputter deposition of metallic precursor layers on back electrode (Mo films), followed by selenization using an elemental Se vapor ambient. Many parameters require optimization in order to obtain a high quality CIGS solar cell absorber by a selenization process, including the Cu/Ga/In metal stacking order, Se layer thickness, temperature ramp rate, annealing temperature, annealing time, and partial pressure of Se.