A process for attaching first and second wafers, at least one wafer having a microstructure, comprising: - making a first wafer having low-temperature microelectronics, having a first connection (23, 27) including the steps of: - applying a polyimide layer on a topside of said first wafer and patterning said polyimide layer to produce an opening above and extending to a connection; - depositing metal across the entire surface of said polyimide layer; - forming a planarised metal post in the opening by means of a chemical mechanical polish whereby the polyimide is re-exposed; and - depositing a further polyimide layer across the surface of the planarised metal post, - making a second wafer at a high temperature having a second connection mirrored to match the first connection (23, 27) including the step of: - applying a polyimide layer on a topside of said second wafer; - soft-baking the first and second wafers; - thereafter, facing the topsides of said first and second wafers with each other and aligning the first and second connections and bonding said first and second wafers together by bonding the polyimide layers (19, 28) on the topside of each wafer (2, 22) under a pressure at a temperature in a non-oxidising environment; - etching a hole through said polyimide layers (19, 24, 28) down to the metal post; and - forming a contact in the hole which makes electrical contact with the metal post. - making a first wafer having low-temperature microelectronics, having a first connection (23, 27) including the steps of: - applying a polyimide layer on a topside of said first wafer and patterning said polyimide layer to produce an opening above and extending to a connection; - depositing metal across the entire surface of said polyimide layer; - forming a planarised metal post in the opening by means of a chemical mechanical polish whereby the polyimide is re-exposed; and - depositing a further polyimide layer across the surface of the planarised metal post, - applying a polyimide layer on a topside of said first wafer and patterning said polyimide layer to produce an opening above and extending to a connection; - depositing metal across the entire surface of said polyimide layer; - forming a planarised metal post in the opening by means of a chemical mechanical polish whereby the polyimide is re-exposed; and - depositing a further polyimide layer across the surface of the planarised metal post, - making a second wafer at a high temperature having a second connection mirrored to match the first connection (23, 27) including the step of: - applying a polyimide layer on a topside of said second wafer; - applying a polyimide layer on a topside of said second wafer; - soft-baking the first and second wafers; - thereafter, facing the topsides of said first and second wafers with each other and aligning the first and second connections and bonding said first and second wafers together by bonding the polyimide layers (19, 28) on the topside of each wafer (2, 22) under a pressure at a temperature in a non-oxidising environment; - etching a hole through said polyimide layers (19, 24, 28) down to the metal post; and - forming a contact in the hole which makes electrical contact with the metal post.