Thermal processes in semiconductor technology, tube furnaces and RTP systems
Koyo Thermo Systems

Koyo Thermo Systems Co., Ltd. is represented in Europe by
Crystec Technology Trading GmbH

Crystec
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Diffusion   Oxidation   H2-Anneal   Polyimide   Copper   low-k   polySilicon   Nitride   TEOS   BPSG   LPSOG

Thermal processes in semiconductor technology

In semiconductor technology many thermal processes are used at atmospheric pressure and at low pressure. Atmospheric processes are used for diffusion of dopands, annealing and oxidation of semiconductor materials, mainly silicon. Low pressure processes use a vacuum pump to evacuate the furnace chamber but still keep a continues gas flow of process gas. They are mainly used for deposition of dielectric layers like silicon oxide, silicon nitride or for depostion of poly-silicon films.
In the past horizontal tube furnace have been used for those processes, but nowadays almost only vertical tube furnaces are used in the semiconductor industry. Short time heating can be done in lamp heated furnaces, so called (rapid thermal anneal) RTP systems. Koyo Thermo Systems furnaces are available for all of those processes. Koyo Thermo Systems has an application laboratory in Tenri, Nara, Japan and an application center in Uppsala, Europe in cooperation with the University of Uppsala.

horizontal furnace vertical furnace RTP system
Horizontal Furnace Vertical Furnace RTP system
Overview and listing of the thermal, semiconductor processes that are available on Koyo Thermo Systems semiconductor tube furnaces:
Atmospheric processes LPCVD-processes

Crystec Technology Trading GmbH, Germany, www.crystec.com, +49 8671 882173, FAX 882177
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Atmospheric Processes

Diffusion and Doping

Doping can be achieved by solid source doping (doping-wafers), by liquid source doping  as e.g. TMB (Trimethoxyboran, Trimethylborate, (CH3O)3B ) or TMP (Trimethoxyphosphine, Trimethylphosphite, (CH3O)3P) or Phosphorus Oxychloride POCl3 and by gaseous doping like Boran BH3, Phosphane PH3. TMB and TMP have gained significant acceptance. Benefits are the ease of handling a liquid source, less health hazards and improved purity levels. Anneal steps allow the activation and diffusion of dopants in the silicon. Using LGO heating elements, Koyo Thermo Systems can achieve excellent temperature uniformity in their furnaces and gets excellent process results for doping processes.

Dry and Wet Oxidation

Koyo Thermo Systems has well developed furnace versions for dry and wet oxidation. Thin gate oxides can be prepared with a very high uniformity over the wafer and from wafer to wafer. Thicker field oxides or oxides used for masking can be grown faster by wet oxidation. An external torch with a very high process safety makes sure that you can run this furnace without risk. HCl can be used in order to prevent metallic contamination and helps avoiding defects in the oxidation layer. A special air tight quartz to quartz seal (see picture) avoids the leaking of corrosive materials (like HCl) and protects the scavenger from corrosion. The high performance of these furnaces can be shown especially at very thin oxides. We can send you measurement results on request for dry and wet oxidation with and without HCl.

vertical furnace boat move in

Of course, we can also supply a TCA (1,1,1-Trichoroethane) or a trans-LC bubbler as a liquid source substitute for cylinder HCl gas. TCA and trans-LC are much less corrosive compared to HCl.

Koyo Thermo Systems furnaces with LGO heating elements show the biggest advantages in low temperature applications. Meanwhile Koyo developed also high temperature versions of the vertical furnace for temperature up to 1350°C, using special heating elements, SiC tubes and boats (see picture).

move in SiC boat

Forming Gas and Hydrogen Anneal

Hydrogen can cover dangling bonds and can heal defects. These processes are operated at temperatures around 400°C. This is a rather low temperature for a semiconductor tube furnace and standard heating elements (HGC, heavy gauge coil), used in these furnaces are different to control. Koyo Thermo Systems has special LGO heating elements, that have a low thermal mass and can be used from 140°C already. Using these LGO heaters, you will have better temperature stability, better temperature uniformity on your wafers and from wafer to wafer and last but not least, you have no over-swing of the temperature after boat move actions or after temperature ramping.

temperature overshoot

Furnaces are available with top exhaust and bottom exhaust. A vertical furnace that combines hydrogen anneal and polyimide process is available now also (see below).

Polyimide Cure

Koyo Thermo Systems is a real specialist for baking of polyimide. For non-photosensitive polyimide, you can use our clean oven type CLH. A special version has been developed for polyimide baking.
Photosensitive polyimide has a much better performance and can help saving several process steps and therefore reduce the costs for preparing a polyimide layer. However it creates by-products during the curing process that are very difficult to remove after the deposition. Together with one of the largest producers of photosensitive polyimide, the company of Asahi Chemicals, Japan, Koyo Thermo Systems developed this special model of a vertical furnace. Special LGO heating elements make sure that you will get an excellent temperature control and temperature uniformity at low temperatures (350°C - 400°C) that are used normally for this bake process. In addition Koyo Thermo Systems installs a special quartzware in this furnace for this process, that avoids the deposition of curing by-products.

polyimide exhaust

The furnace is maintenance free and we can prove the superior performance of this furnace type by a very long reference list of satisfied customers.  Please check also our special page, describing the polyimide cure process.

A vertical furnace that combines hydrogen anneal and polyimide process is available now also (see below).

Hybrid Furnace

Due to the demand of our customers, Koyo Thermo Systems developed a new type of vertical furnace for the combination of hydrogen anneal and polyimide cure process. Within short time, the furnace can be switched to another process. Production peaks can be minimized with a minimum number of vertical furnaces and the backup situation for the process of polyimide cure improves a lot. It is no longer necessary to keep so much free capacity for backup reasons and production costs can be reduced finally using Koyo Thermo Systems’s new hybrid furnace. Several existing installation can prove the cost saving effect of this new machine already.

Copper Anneal

In the manufacturing of semiconductor devices copper lines and copper vias are used more and more instead of aluminium, although the metal contamination risk is much higher, the wall adhesion on dielectrics is worse, and the corrosion resistance of Cu is poor. However the conductivity of copper is much higher, which is an important fact for high-integrated devices. Electromigration resistance is higher for copper.
In order to improve the properties of the copper layer an anneal step is absolutely necessary. It has been found that the best conditions in order to get good copper properties are low temperature anneals (<200C) for longer time (45s in RTP or 30 Min. in oven or furnace). It has to be considered that recrystallization in small structures takes longer time than in larger ones. You can find more details on our special page describing the copper anneal process.

Low-k Cure

Low-k materials can be deposited either by spin-on or CVD methods. Porous materials are typically spun on, with controlled evaporation of solvent providing the desired pore structure. The necessary baking of the material is normally done in a batch furnace. Today, in most cases vertical furnaces are used for this application. However, the bake temperature is typically between 350°C - 400°C, which is quite demanding to standard vertical furnaces.

Kioyo Thermo Systems has long years experience with the similar SOG bake process and developed a special furnace with a very low thermal mass LGO heating element for this process. Now KLL has designed again a special vertical furnace for low-k dielectric bake. The same type of LGO heating element is used also successfully since years in Kioyo Thermo Systems semiconductor tube furnaces for other typical low temperature processes like polyimide bake and hydrogen anneal. The atmospheric Kioyo Thermo Systems furnaces can guarantee very low oxygen levels of <20ppm as required for many low-k material bake processes (as well as for polyimide cure). Expensive low pressure setups incl. vacuum pumps are not required. You can find more details on our special page describing the low-k anneal process.

Crystec Technology Trading GmbH, Germany, www.crystec.com, +49 8671 882173, FAX 882177
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LPCVD Processes

poly-Silicon

Poly-silicon layers have many applications for gate electrode building, for the formation of resistors and capacitors as well as for getter layers. Doped and undoped poly-silicon processes are available from Koyo Thermo Systems. Using LGO heating elements, Koyo Thermo Systems can achieve excellent temperature uniformity in their furnaces and gets excellent process results for poly-silicon deposition. We will send you measurement results on demand.

Silicon Nitride

Silicon nitride is an excellent diffusion barrier. It can be used also as a mask for oxidation, as a dielectric for capacitors and for passivation. Using LGO heating elements, Koyo Thermo Systems can achieve excellent temperature uniformity in their furnaces and gets excellent process results for silicon nitride deposition. Particle values can be kept low. We will send you measurement results on demand.

TEOS (Tetraethoxysilan, Tetraethylorthosilicate) and BPSG (Boron Phosphorous Silicon Glass)

Deposited oxide layers do not use silicon from the wafer during growth. The silicon oxide is built completely from the gas phase. TEOS oxide is used for applications like spacer formation or grave filling. TEOS is a stable, nonpyrophoric, noncorrosive liquid, and thereby is a preferable alternative to processing technologies employing silane or dichlorsilane compounds.

Using LGO heating elements, Koyo Thermo Systems can achieve excellent temperature uniformity in their furnaces and gets excellent process results for CVD oxide deposition. We will send you measurement results on demand.

BPSG (Boron Phosphorous Silicon Glass)

Phosphorous glasses can be used for doping applications and for planarization. They flow already at 1000°C and also have a good getter effect on alkaline and heavy metal contaminants. TMB and TMP can be used in order to deposit BSG, PSG or BPSG.

Using LGO heating elements, Koyo Thermo Systems can achieve excellent temperature uniformity in their furnaces and gets excellent process results for CVD oxide deposition. We will send you measurement results on demand.

LGO heating element

SOG Anneal

Spin on glass (SOG) is produced by curing solved silicontetraacetate. It is used for planarization and sometimes for doping purposes. Today more common planarization technology is chemical mechanical polishing CMP.
This process is again a low temperature process that requires a very good control of the heater, installed in the furnace. The LGO heating elements (see picture) have a very low thermal mass and can achieve much better results for this process, compared to other furnaces equipped with standard heaters.

Hydrogen Anneal

Hydrogen Anneal can also be done in a low pressure furnace for special applications. Since short time, Koyo Thermo Systems can also offer a furnace for atmospheric and LPCVD hydrogen anneal, to be used on one machine. By changing the exhaust tube, you can switch between the two types of process.


Overview and listing of the processes that are available on Koyo Thermo Systems semiconductor tube furnaces:
Atmospheric processes LPCVD-processes
Crystec Technology Trading GmbH will be pleased to further discuss details with you.
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