Online information source for semiconductor professionals

Product Briefing Outline: Integrated Materials has added to its range of pure poly silicon furnace products with the introduction of a ‘SiFusion' liner for semiconductor furnace processes. According to the company the new product is now available in limited quantities for "beta" phase validation with the liner fixture completeing the SiFusion suite of furnaceware, which includes furnace boats, injectors and pedestals. SiFusion liners are already under qualification at fabs in Japan, Korea and Singapore. Initial performance data indicate unparalleled low particle levels when the SiFusion liner and boat are used together, according to the company.

Problem: Vertical furnace processes, including high temperature diffusion, deposition and rapid thermal processing, comprise up to 30 percent of the major process steps in wafer manufacturing. In these processes, particle defects are caused by properties inherent to traditional quartz or silicon carbide (SiC) furnace consumables, including the boats, liners, pedestals and injectors. Quartz and silicon carbide furnace consumables have been the only source material options for the last 20 years; consequently, most IC makers do their best to minimize these defects, but see them as unavoidable. While recent improvements in furnace cleaning have helped to remediate particle defects induced by quartz or SiC consumables, engineers still have not achieved the overall reduction of defect rates required for state-of-the-art manufacturing environments. Moreover, the cleaning process itself is costly in terms of cleaning chemicals and environmental safeguards.


Solution: Poly silicon is elemental silicon in a non-oriented crystalline form. Unlike single crystal silicon, polycrystalline silicon is a high-strength, structural material with excellent high-temperature stability. Unlike silicon carbide, it is non-porous and non-absorbing, making it ideal for extremely high furnace temperatures because its Coefficient of Thermal Expansion (CTE) matches that of the wafer. Additionally, poly silicon's elemental purity is measured in parts per billion and parts per trillion, compared to quartz and silicon carbide, which are measured for purity in parts per million. Furnace liners are an essential element of the semiconductor LPCVD furnace. Liners provide a uniform path for the gas flow from inlet to exhaust and act as an ultra pure barrier preventing particles from the outer furnace tube from affecting product yields.  SiFusion liners feature a patented surface treatment that diffuses thermal stress and allows the structure to maintain its integrity through high temperature cycling, positively impacting furnace uptime, defect rates and yield.

Applications: The liners are available for 200 and 300 mm vertical furnace process applications, including high temperature, LPCVD and HTO.

Platform: SiFusion furnaceware survives severe temperature cycling and performs without deformities in demanding processes that reach temperatures of up to 1350°C. This characteristic enables increased thermal ramp rates and reduced thermal stabilization times. SiFusion technology's thermal shock resistance means fixtures maintain their mechanical tolerances at temperatures far above normal furnace processes. Also newly installed quartz towers may be used for 17 to 34 cycles before particles exceed limits, and customers must remove the fixture for cleaning. This process is time-consuming and results in significant furnace downtime.By comparison, Integrated Materials claims that SiFusion poly silicon furnaceware require no routine cleaning, thus minimizing downtime and its associated productivity losses. Moreover, by not needing cleaning chemicals, wafer fabs save the costs of purchase and their disposal, which reduces the environmental footprint, according to the company.

Availability: July 2006 onwards.