by Amanda Hartnett , Jacques Matteau , Ronnie Spraker, Omar Knio
As semiconductor processing has moved to 300mm wafers, the size of
deposition targets, including tungsten, tantalum, and molybdenum has grown,
and process complexity has increased as well. This added size and complexity
contributes to the stress on a target assembly during the physical vapor deposition
(PVD) process, and the target assembly’s ability to withstand this stress has
a large effect on the resulting deposition rates, yields, and film properties.
One of the major sources of stress is the coefficient of thermal expansion
(CTE) mismatch between metal targets in semiconductor processes, such as
tungsten (CTE of 4.5*10-6/°C), tantalum (6.5*10-6/°C), and molybdenum
(5.1*10-6/°C) compared with their backing plates, which are typically made
of aluminum (23*10-6/°C), brass (21.2*10-6/°C), or copper-chrome (17.6*10-
6/°C). Standard soldering and solid state joining processes have difficulty
controlling stress produced by the CTE-mismatch. We will demonstrate how the
NanoBond® process can be used to control stresses during the bonding and
deposition processes. Modeling will be conducted to compare standard bonding
processes to the NanoBond process, accounting for CTE mismatches.
SVC Tech Con 2011, NanoFoil, NanoBond, sputtering target, CTE mismatch
[Permanent Link to this Paper ]
Posted on 19 Apr 2011
by Jacques Matteau
Indium Corporation has commercialized a new technology with NanoFoil® that will revolutionize how manufacturers join components using solder materials (see Figure 1). The joining process is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano- engineered materials in which self-propagating exothermic reactions can be ignited at room temperature through an ignition process. By inserting a multilayer foil between two solder layers and two components, heat generated by the reaction in the foil melts the solder and, consequently, bonds are completed at room temperature in air, argon, or vacuum in approximately one second. The resulting metallic joints exhibit thermal conductivities two orders of magnitude higher, and thermal resistivity an order of magnitude lower than current commercial Thermal Interface Materials (TIMs).
The use of reactive foils as a local heat source eliminates the need for torches, furnaces or lasers, speeds the soldering processes and dramatically reduces the total heat that is needed. Thus, temperature-sensitive or small components can be joined without thermal damage or excessive heating. In addition, mismatches in thermal contraction on cooling can be avoided because
components see very small increases in temperature. This is particularly beneficial for joining metals to ceramics. The fabrication and characterization of the reactive foils is described and the value proposition for NanoBonding is presented. This paper also shows the applicability of this platform technology to many areas of packaging, including TIMs, microelectronics, optoelectronics and Light Emitting Diodes (LEDs).
Thermal transfer, TIM, NanoFoil, NanoBond, solder bonding
[Permanent Link to this Paper ]
Posted on 14 Nov 2011
