US 5,866,469 A · Method of anodic wafer bonding

Abstract

A process is provided for protecting, containing, and/or completing fragile microelectronic and microelectromechanical (MEM) structures on a low conductivity substrate during anodic wafer bonding of a covering wafer. The wafer includes raised areas that contact the substrate at selected bonding regions to support the wafer as a covering structure over the substrate. The covering wafer includes additional raised areas, such as pillars or posts, that contact selected electric circuit lines on the substrate to form temporary shorts through the wafer. During anodic bonding of the wafer to the substrate, the temporary shorts maintain the connected circuit lines and microstructures at nearly the same electric potential to prevent unwanted arcing and electrostatic forces that could damage the fragile structures. The pillars or posts can be formed at the same time as the raised bonding areas, but on unwanted and otherwise unused portions of the covering wafer. Anodic bonding produces only weak bonds between the wafer posts and the metallic conductor material of the circuit lines. After anodic bonding, the unwanted portions of the covering wafer can be removed to leave covering structures over the selected microstructures. Because of the weak bonds, removal of the unwanted portions of the wafer also removes the posts and eliminates the temporary shorts, with no additional processing needed to electrically separate the circuit lines on the substrate.

Claims15

Dependent claims

A method of anodic wafer bonding, comprising the steps of:

providing a low conductivity substrate having an electric circuit formed thereon;
providing a covering wafer having first and second raised areas;
placing said covering wafer atop said substrate with said first raised area contacting a bonding region of said substrate and said second raised area contacting said electric circuit;
applying a sufficient electric potential across said substrate and said covering wafer for bonding said first raised area of said covering wafer to said bonding region of said substrate;
said second raised area of said covering wafer forming a temporary electric short for maintaining said electric circuit at substantially the same electric potential as said covering wafer;
and
removing unwanted portions of said covering wafer including said second raised area forming said temporary electric short.

4 more elements

Dependencies are inferred from the claim text.

Method of anodic wafer bonding

Life of this patent

Method of anodic wafer bonding

Life of this patent

Abstract

Claims15