Research On Uniaxial Strained Silicon On Wafer Level By Mechanical Method

sSOI(strained Silicon On Insulator) technology combine the straining of silicon with silicon on insulator technology combine mobility enhancement and reduced parasitics. Wafer-leval uniaxially sSOI by prestrained wafer bonding and Smart-cut technology with simple process, the enhancement of carrier mobility and no degradation at large vertical electric fields will become a new focus point in the sSOI research.The paper will present an a approach that allows to create uniaxial strain flexibly in tension or compression on wafer-level by exploiting mechanical straining of the material upon bending and focus on the experiment that will induce uniaxial strain along [110]direction in the upper layer of 4inch p-type SOI wafer fabricated by Smart-cut processingThe paper has detailedly studied the key technologies(Ion Implantation,wafer direct bonding, Smart-cut) which would play important role in the mechanical strain induction both in process and principles. Especially focused on the mechanism of the wafer bonding and the weaken layer's effect during the process of anneal in order of splitting. The paper set up the lattice mismatch model in the ideal bending situations which also may be used to calculate the degree of uniaxial strain. A scientific and rational plan including every procedures has been made in accordance with the actual level of domestic micro-electronics technology.For mechanical uniaxial straining, two wafers were bent over the experimental equipment whose surface was a part of cylinder(respectively R=0.75,0.5m). Then, the bent wafers are brought into contact via direct wafer bonding and covalent bonds across the bonded interface form upon annealing(200℃,15h) in the bent state. By thinning one of the wafers to about 500nm using Smart-cut the bonded pair assumes an almost flat surface and substantial strain is transferred to the thinned wafer. Finally, the compressive strain in the upper Si layer of p-type (100) sSOI wafer was successfully induced by this mechanical method with the strain along the [110]direction.In the paper, the quality of the upper Si layer in SOI sample was investigated by HRXRD spectroscopy and AFM. And it showed that, the lattice constant was 0.54178nm (paralleled to the interface), RMS 9nm. The result this mechanical method was promising..Through comparing the wafer surface quality in the different stage (after bonding, annealing and splitting),studied and analysised conformation and the diversification of the blister and unbonded area theoretically.