IntegraBond™ and MightyBond™ Bonding Technologies
Bonding of sputtering targets to backing plates has been an evolving technology since the beginning of the use of this practice for thin film deposition. With the advent of higher power PVD deposition applications, MRC engineers have responded by developing the IntegraBond and MightyBond™ processes. Both represent significant advancements in bonding technology. These techniques afford the user unprecedented bonding strength for high power sputtering applications, such as reactively sputtered or collimated Ti (-20 kW) and TiW. The IntegraBond and MightyBond™ manufacturing processes permit superior target bond strength and reliability without impairing MRC’s CCH "tuned target microstructure"
The practice of bonding high-purity PVD materials to backing plates, particularly Cu, has been well established. MRC's proprietary solder bonding technology, called PermaBond™ is used for refractory materials. A patented Fixture Immersion Bonding (FIB) method has also been developed for Al or Ti on Cu, which eliminates the problems associated with voids.
In response to the increasingly higher bond strengths required by some applications for advanced cathodes, such as those manufactured by Anelva, Applied Materials, CVC, Novellus, TEL Trikon, and Ulvac, new methods of bonding were required.
Praxair MRC’s high-performance "diffusion" bonding IntegraBond process has been developed for all grades of Ti, and TiW in conjunction with a commercial purity Al backing plate. Classical diffusion bonding techniques, where inter-metallic compounds are formed, tend to weaken the bond strength. The IntegraBond process uses a patented technology which maximizes bond strength by virtually eliminating the formation of inter-metallic compounds in the bond region and minimizing the thickness of the inter-diffusion layer itself (Figure 1).
Praxair MRC has developed a unique testing method to determine the bond strength. Stress is concentrated at the bond interface and a good IntegraBond will induce a failure in the one of the materials being bonded rather than the bond interface itself. MRC's IntegraBond diffusion bonding process produces a bond that is 100% stronger than the current industry standard* (Figure 2).
IntegraBonding enables targets to withstand the higher sputtering powers necessary for collimated deposition processes used to fill high-aspect ratio geometries. In addition, it permits higher deposition rates for Ti and TiW films, increasing wafer throughput. Finally, with Integrabonding, target assemblies can be made lighter without the need for re-useable backing plates.
In applications where the material being bonded to an aluminum or copper backing plate has a low temperature of recrystallization, the patented Praxair MRC MightyBond™™ technology assures that the microstructures developed through its CCH processing are maintained while bond strengths are equivalent those of the IntegraBond. Materials such as aluminum alloys and copper are routinely MightyBond™ed to commercial aluminum alloys. Figure 3 illustrates the microstructure of copper before and after MightyBond™ing, which clearly shows that there is no change in the microstructure.
As with all of Praxair MRC's products, reliability is of utmost importance. The IntegraBond and MightyBond™ processes provide excellent performance at high power. Typically one can operate as high as 20 kW for Ti on an Al backing plate. The bonding process is verified using the latest test methods including ultrasonic and pre-product release sputtering tests,
Figure 4. Bond quality Praxair MRC MightyBond™ (left) as compared to competitive bonding technology (right) as used on and Applied Materials ALPS target assembly. Coloration indicates the depth of reflected ultrasonic sound waves. In the central region, the blue color indicates sound reflected from the back surface of the assembly. Lighter colors indicate discontinuities at the bond interface.
IntergaBond MightyBond™ technologies are ideally suited for processes required in today's state-of-the-art semiconductor devices using PVD systems such as Applied Materials Endura™ Novellus Inova™, M2I™/MB2™/M200O™, TELs ECLIPSE® , Trikon Sigma™, CVC Connexion™, Ulvac Cereaus™and Anelva systems employing advanced cathodes.
Endura is a trademark of Applied Materials Inc.