Low-temperature anodic bonding of silicon to silicon wafers by means of intermediate glass layers

Abstract

Silicon wafers have been anodically bonded to sputtered lithium borosilicate glass layers (Itb 1060) at temperatures as low as 150-180°C and to sputtered Corning 7740 glass layers at 400°C. Dependent on the thickness of the glass layer and the sputtering rate, the sputtered glass layers incorporate compressive stresses which cause the wafer to bow. As a result of this bowing, no anodic bond can be established especially along the edges of the silicon wafer. Successful anodic bonding not only requires plane surfaces, but also is determined very much by the alkali concentration in the glass layer. The concentration of alkali ions as measured by EDX and SNMS depends on both the sputtering rate and the oxygen fraction in the argon process gas. In Itb 1060 layers produced at a sputtering rate of 0.2 nm/s, and in Corning 7740 layers produced at sputtering rates of 0.03 and 0.5 nm/s, respectively, the concentration of alkali ions in the glass layers was sufficiently high, at oxygen partial pressures below 10\4 Pa, to achieve anodic bonding. High-frequency ultrasonic microanalysis allowed the bonding area to be examined non-destructively. Tensile strengths between 4 and 14 MPa were measured in subsequent destructive tensile tests of single-bonded specimens.

Transformation and patterning of supermicelles using dynamic holographic assembly

“…To enable ease of use with a range of solvents, for the deposition experiments an adhesive-free fabrication process known as anodic bonding was used for the cell's preparation 41 42 43 .…”

Contributed Review: The feasibility of a fully miniaturized magneto-optical trap for portable ultracold quantum technology

“…Several bonding techniques are available and we highlight eutectic and direct bonding as the most suitable methods due to their low outgassing and high hermeticity, with anodic bonding as a suitable alternative if the oxygen released during bonding can be pumped away. Lowering the temperatures of these bonding techniques should be investigated as they can reduce the outgassing limitations by two or three orders of magnitude 171,174,175,181,[243][244][245][246][247][248] .…”

“…Moreover, thin films, such as gold on silicon, can diffuse at moderate temperatures if additional barrier layers are not used 170 . In these situations one must use lower temperature degassing, such as UV desorption or plasma cleaning, and also develop lower temperature bonding methods 171,174,175,181,[243][244][245][246][247][248] .…”

Reliability of MEMS packaging: vacuum maintenance and packaging induced stress

“…Therefore, package stress must be controlled and maintained at a level low enough to avoid impact to the sensor performance. In anodic bonding, a difference in the thermal expansion between the silicon and glass induces stress when they are bonded together at a high temperature (Gerlach et al 1999). After dicing, MEMS devices go through conventional electronic packaging such as die-bonding, wire-bonding and plastic molding.…”