Thin semiconductor device having embedded die support and methods of making the same
AssigneeTemic Automotive of North America, Inc.
InventorsXIAOYI DING, JEFFREY J. FRYE, GREGORY A. MILLER
Life of this patent
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Abstract
Ultra-thin semiconductor devices, including piezoresistive sensing elements can be formed in a wafer stack that facilitates handling many thin device dice at a wafer level. Three embodiments are provided to form the thin dice in a wafer stack using three different fabrication techniques that include anodic bonding, adhesive bonding and fusion bonding. A trench is etched around each thin die to separate the thin die from others in the wafer stack. A tether layer, also known as a tether, is used to hold thin dice or dice in a wafer stack. Such as wafer stack holds many thin dice together at a wafer level for handling and enables easier die picking in packaging processes.
Claims70
A wafer stack comprising:
- a silicon device wafer and a silicon substrate wafer;
- a silicon die having a circuit formed thereon the device wafer, the die extending over a cavity in the device wafer and having an outer perimeter defined by a trench formed in the device wafer, the trench separating the die from the device wafer;
- and
- a single tether attached to the die, extending across the trench and ending on the device wafer.
A wafer stack comprising:
- a silicon device wafer and a silicon substrate wafer;
- a silicon die having a circuit formed thereon the device wafer, the die extending over a cavity in the device wafer and having an outer perimeter defined by a trench formed in the device wafer, the trench separating the die from the device wafer;
- and
- a die tether layer attached to the die, extending across the trench and ending on the device wafer.
A wafer stack comprising:
- a thin silicon device layer having top and bottom surfaces and a cap wafer;
- at least one die formed on a portion of the thin silicon device layer, and having a circuit on the die;
- a tether covering at least a portion of the top surface of the die and extending over the die;
- wherein the cap wafer is over the die and forms a sealed gap between the top surface of the die and the cap wafer;
- wherein the die has an outer perimeter defined by a trench formed from a bottom surface of the thin silicon device layer and surrounding the die, the die being attached to the wafer stack by the tether extending over the trench, said tether extending across the trench.
A wafer stack comprising:
- a thin silicon device layer having top and bottom surfaces and a cap wafer;
- a die formed on a portion of the thin silicon device layer and having a circuit on the top surface of the die;
- a tether covering at least a portion of the top surface of the die and extending over the die;
- wherein the cap wafer is suspended over the die and forms a sealed gap, and wherein the die has an outer perimeter defined by a trench formed from the bottom surface of the thin silicon device layer and surrounding the die, the die being attached to the wafer stack by the passivation layer extending over the trench;
- wherein said tether extends across the trench attaching the die to the wafer stack.
A method of forming a die from a wafer stack, the wafer stack being comprised of a silicon device wafer having first and second sides and a silicon substrate wafer, the method comprised of:
- forming a cavity from the first side of the silicon device wafer, the cavity having an outer perimeter defined by a cavity wall and a cavity bottom surface;
- forming a tether layer on the bottom surface, the tether layer comprising at least one of silicon oxide, silicon nitride or poly silicon;
- attaching a silicon substrate wafer to the first side of the silicon device wafer, the silicon substrate wafer extending over the cavity and beyond the outer perimeter of the cavity;
- thinning the silicon device wafer by removing silicon from the second side of the silicon device wafer thereby forming a die top surface;
- forming a circuit on the die top surface;
- forming a trench from the die top surface to the tether layer and which surrounds a region having the circuit, the trench having an inner perimeter and an outer perimeter, the outer perimeter of the trench being less than the outer perimeter of the cavity, the trench having a width defined by its inner and outer perimeters and a depth extending from the die top surface to the tether layer.
(canceled)
A method of forming a die from a wafer stack, the wafer stack comprising a silicon device wafer having first and second sides and a cap wafer having top and bottom sides, the method comprised of:
- forming a circuit on the first side of the silicon device wafer, within a die region, which has a die outer perimeter;
- forming a tether layer on the first side of the silicon device wafer which at least partially covers and extends beyond the circuit;
- attaching the cap wafer to the first side of the device wafer to form a gap over the circuit and over a first area extending beyond the circuit;
- thinning the silicon device wafer from the second side of the silicon device wafer forming a die back side;
- forming a trench from the back side of the die to the tether layer, the trench having an inner perimeter substantially aligned with the die outer perimeter, the trench having an outer perimeter greater than the inner perimeter, the trench having a width defined by its inner and outer perimeters at the tether layer and a depth extending from the back side of the die to the tether layer.
(canceled)
Dependencies are inferred from the claim text.