Monday, July 5th, 2010
With the world now manufacturing nanoscale ICs and MEMS, new devices require the formation of thin-film coatings from exotic material precursors. Atomic-layer depostion (ALD) as an extension of chemical vapor deposition (CVD) technology can be used to form both dielectric barriers and metal connections. With a tool designed to deposit almost any thin film, French OEM Altatech Semiconductor S.A., has recently received orders for ALD/CVD systems that will be used for the R&D of 3D and high-mobility ICs.
In May of this year, the Fraunhofer Research Institution for Electronic Nano Systems (Fraunhofer ENAS) in Chemnitz, Germany, ordered an AltaCVD system (figure) from Altatech to deposit advanced silicon stressor materials on 200mm wafers. Silicon stressor materials are used to increase the channel mobility of transistors, enabling higher processing speeds.
Fraunhofer ENAS is scheduled to install the new AltaCVD system in its back-end-of-line (BEOL) cleanroom facility in Chemnitz during the second quarter. A previously installed system is being used to deposit diffusion barrier and copper layers for advanced copper damascene interconnects and through-silicon-via (TSV) features.
“After evaluating Altatech’s innovative technology and its AltaCVD equipment, we have ordered a system for our lab, where we’re developing nanometric thin films to advance the state of semiconductor processing. The use of liquid-phase precursor injection and evaporation is a key enabling technology for this work,” said Prof. Stefan E. Schulz, head of back-end-of-line operations at Fraunhofer ENAS.
Altatech also won an order by Fraunhofer IZM’s new All Silicon System Integration Dresden (ASSID) group for a 300mm AltaCVD system. Just opened on 31 May 2010, the ASSID is specially designed for projects in 3D wafer-level system integration (200/300 mm) and prototype development for manufacturing partners in industry. As part of the Fraunhofer IZM Institute, which specializes in transferring IC advanced packaging and system integration research results to industry, ASSID is integrated into a technology network of applied research institutes and universities.
The equipment is scheduled to go online in the third quarter of this year at ASSID. The site’s Class 1,000 cleanroom is equipped with a complete 300mm wafer fabrication line for TSV formation and post-processing on both the frontside and backside of wafers, wafer thinning, 3D device stacking, and package assembly and testing. ASSID will use the AltaCVD system to create through silicon vias (TSV), processing both standard and thin silicon wafers. The low-temperature AltaCVD tool will deposit stacks of film layers and ultrathin, conformal isolation layers inside deep vias and trenches with aspect ratios as high as 40:1.
In addition to handling either 200 mm or 300 mm wafers, AltaCVD’s flexible architecture allows it to be used in volume production for plasma-enhanced deposition (PECVD) of dielectric materials, stacks and metal films as well as in R&D for metal-organic processing (MOCVD) in back-end-of-line (BEOL) applications such as creating direct-platable barriers.
Altatech Semiconductor’s AltaCVD platform uses direct injection of liquid precursors and an advanced flash-vaporization system in processing wafers up to 300 mm. The modular system can accommodate a wide range of vaporization and deposition temperatures, enabling users to select the optimal process windows for their specific applications, which can include deposition of advanced materials for high-k gate dielectrics, metal gate electrodes, capacitors and 3D integration. For thermal CVD or RF-enhanced deposition steps, a low-frequency plasma enables tuning of the thin film’s mechanical, electrical and optical properties.
“Through our partnerships with Fraunhofer ENAS and other leading research centers, we are continuing to develop liquid-precursor deposition processes for high-k/metal gates, through-silicon-vias, memory and capacitor applications,” said Jean-Luc Delcarri, president of Altatech Semiconductor. “We’re also working with IDMs and foundries to bring liquid-precursor deposition to their high-volume 300 mm fabs. And we’ve begun applying our CVD technology to create advanced thin films for solar cells, high-brightness LEDs and other microelectronics markets.”
Key features of Altatech’s low-pressure injection (LPI) vaporizer (figure):
-
Improved atomization, due to carrier gas “blasting” the flow into claimed 5-40µm droplet diameter range with maximum population at 10µm (compared to 6 to 60µm with max population at 22µm for high-pressure direct injection),
-
Longer droplet residence time inside the vaporizer due to low liquid pressure (2 to 5 bar), and
- Sequential or co-injection from 2-4 injection heads provides for binary or higher order alloy deposition, and the ability to form nano-laminates in a single-chamber.
With the above capabilities in the source injector, the company claims that the system can work with any of the following liquid precursors:
-
TEOS,
-
n-octadecyl trimethoxysilane,
-
glycidil methacrylate,
-
n-hexadecane,
-
III/V precursors (TMGa, TMAl, Cp2Mg, etc.), and
- Proprietary organometallics (Cupraselect™ for Cu, Chorus™ for Ru, etc.).
Diluted solid precursors such as ß-diketonates, Alkoxides, and proprietary molecules can also be vaporized by the system.
“Through our partnerships with Fraunhofer ENAS and other leading research centers, we are continuing to develop liquid-precursor deposition processes for high-k/metal gates, through-silicon-vias, memory and capacitor applications,” said Jean-Luc Delcarri, president of Altatech Semiconductor. “We’re also working with IDMs and foundries to bring liquid-precursor deposition to their high-volume 300 mm fabs. And we’ve begun applying our CVD technology to create advanced thin films for solar cells, high-brightness LEDs and other microelectronics markets.”
No deposited film exists independently, and the smaller the device structure the tighter the integration required. Films that play an active role in the device function—such as high-k metal gates (HKMG) for 32nm node CMOS ICs—must be carefully integrated with various physical and electrical barrier layers. High-volume manufacturing (HVM) necessarily changes as little as possible, and so any new material must always fit into old flows, and any new tool must be proven as reliable.
Liquid-precursors have always been challenging to handle in CVD systems: bubblers tend to lack precision, and vaporizers generally lack reliability. Vaporizers have been used for decades, yet nozzles still get clogged, and interior walls still build-up particle contamination. Encouragingly, in an email exchange with BetaSights, Altatech claimed that it’s low-pressure injector design allows for 6 months of “production mode” use between preventative maintenance (PM) cleanings of the vaporizer.–E.K.
Tags: 22nm, 32nm, 3DIC, 45nm, ALD, BEOL, CVD, IC, LED, materials, R&D, TSV