Sintered Porous Metal Filter

Dozens of special procedure gases such as silane, ammonia, argon, tungsten hexafluoride, etc. used in semconductor procedures are the media that directly contact the core procedures of wafer lithography, etching, and deposition. Even nanometer granule impurities in the gas at the billionth level can form fatal circuit defects on the wafer surface. Traditional fiberglass and polymer percolators are prone to fiber detachment and insufficient high-temperature resistance under long-term erosion by high-purity specialty gases, becoming new sources of impurity pollution. However, percolators are completely formed by high-temperature sintering of metal powders such as 316L stainless steel, high-purity nickel, and titanium, with no risk of fiber detachment. The three-dimensional interconnected porous structure can achieve an interception efficiency of over 99.99999% for 0.003 μ m nanoscale granules, cutting off the granule pollution path in the procedure gas from the source.

At the end of the silane gas delivery pipeline in the chemical vapor deposition (CVD) procedure, it is directly installed at the inlet position of the reaction chamber to completely intercept the residual nanoscale silicon powder granules in the silane gas, avoiding the formation of randomly distributed small granule defects on the wafer surface. The operation data of a domestic advanced procedure production line for 12 inch wafers shows that after using high-precision percolators to purify silane gas at the terminal, the number of granule defects on the wafer surface in the CVD procedure decreased by more than 85%, and the yield of chips directly increased by 7 percentage points. Unlike ordinary percolator materials, its gradient pore structure design gradually reduces the aperture of the percolator element from the inlet side to the outlet side, which not only has ultra-high dust holding capacity, but also achieves ultimate colation accuracy.

In the long-term operation of high flow special gases, there will be no problem of granule penetration, and the continuous and stable service life can reach more than 3 years, which is more than 6 times that of traditional polymer percolators.

In the high-purity argon shielding gas system of the photolithography procedure, not only can solid granules in the gas be intercepted, but it can also withstand occasional instantaneous high temperature impacts in the pipeline, without the problem of material deformation and release of organic volatiles at high temperatures like polymer percolators, avoiding organic impurities from contaminating the surface of the photoresist and preventing fatal defects such as distortion and pinholes in the photolithography pattern. In the highly corrosive special gas pipelines such as tungsten hexafluoride used in the etching procedure, high-purity nickel percolators are used, which can withstand the long-term erosion of highly corrosive fluorine gas. The percolator itself will not corrode and precipitate metal ions, completely eliminating the risk of ion pollution of wafer circuits by metal ions.

In the wet procedure loop of semconductor manufacturing, the cleanliness of various ultrapure fluids such as ultrapure water, photoresist, developer solution, and etching solution directly determines the surface quality of the wafer. Traditional polymer percolator membranes are prone to membrane dissolution and additive precipitation in highly corrosive wet electronic chemicals, releasing trace amounts of organic impurities and metal ions into the fluid, directly affecting the circuit performance of the chip. After special ultra pure electrolytic polishing and passivation treatment, the percolator element controls the overall metal ion precipitation at ppb level, without introducing additional impurities into the ultra pure fluid. At the same time, it can withstand long-term immersion in high-temperature wet chemicals at 180 ℃, which is suitable for the purification needs of all semconductor procedure wet chemicals.

In the circulation purification system of wet etching solution, it can withstand the corrosion of strong acidic and strong alkaline etching solution for a long time, continuously intercept the metal etching product granules generated during the etching procedure, avoid these granules from forming re deposition defects on the wafer surface, extend the circulation life of the etching solution by more than three times, and significantly reduce the chemical consumption cost of wet procedure. Unlike disposable polymer colation membranes, regeneration can be achieved through reverse ultrapure water flushing and high-temperature nitrogen blowing. The difference in colation flux after regeneration compared to a brand new percolator element is less than 2%, and it can be repeatedly regenerated and used more than 100 times, significantly reducing the long-term comprehensive cost of semconductor procedure colation consumables and minimizing the generation of colation waste, in line with the green production requirements of the semconductor manufacturing industry.

The wafer transfer carriers and vacuum reaction chambers in semconductor procedures are the areas where wafers are exposed for the longest time. Once tiny granules in these areas fall onto the surface of the wafer, they can directly cause circuit failure. In these scenarios, a comprehensive dynamic clean protection system is established. In the micro environment gas circulation system of the FOUP (Front Open Wafer Transfer Box) for wafer transfer, a miniaturized burn-in percolator serves as the purification core of the circulating air, continuously percolatoring the protective gas inside the transfer box, and maintaining the granule concentration inside the transfer box at the ultra clean level of ISO 1 for a long time.

Even if the wafer is briefly exposed to a non ultra clean environment during the transfer procedure, there will be no granule pollution problem. In the exhaust system of the high vacuum reaction chamber of the ion implantation machine, it is installed at the inlet end of the vacuum pump to intercept a large amount of high-energy metal granules and dopant dust generated during the ion implantation procedure. On the one hand, it prevents these granules from flowing back into the vacuum chamber and contaminating the wafer. On the other hand, it also protects the expensive vacuum pump blades from being eroded and worn by high-speed granules, greatly extending the maintenance cycle of the vacuum pump. The actual operation data of an advanced procedure production line shows that after installing a sintered porous metal filter at the vacuum inlet of the ion implantation machine, the average maintenance cycle of the vacuum pump has been extended from 6 months to 24 months.

At the same time, the background concentration of granules inside the vacuum chamber has decreased by two orders of magnitude, and the number of wafer granule defects in the ion implantation procedure has decreased by 75%. In the polishing solution supply system of chemical mechanical polishing (CMP) procedure, percolator is used to intercept large-sized polishing granules that aggregate in the polishing solution online, avoiding deep scratch defects caused by large granules in the wafer polishing procedure, and reducing the surface roughness of the polished wafer to below 0.1nm, fully meeting the requirements of advanced procedure wafer surface flatness. At the end of the FFU fan colation unit in the clean room of semconductor manufacturing, a high-temperature resistant percolator element with a metal sintered porous structure is used, which can withstand the high-temperature steam disinfection conditions in the workshop and will not cause fiber breakage and detachment after repeated high-temperature disinfection like fiberglass percolators. It can maintain the stable granule concentration in the clean room for a long time to meet the standard.