Integrated passive device and fabrication method using a last through-substrate via
A method for making an integrated passive device (IPD) die includes grinding a backside of a semiconductor substrate to reduce a thickness of a central portion of the semiconductor substrate while leaving a mechanical support ring on an outer portion of the substrate, and forming a through-substrate via (TSV) from the backside of the substrate. The TSV defines interconnect access to at least one passive component embedded in an insulator material disposed on a front surface of the semiconductor substrate. The substrate has a thickness less than three-quarters of an original thickness of the substrate.
1. A method comprising:
embedding at least one passive device in an insulator material disposed on a front surface of a substrate, the at least one passive device having a device body between two device terminals;
back grinding the substrate to thin a central portion of the substrate and to form a support ring on an outer circumference of the substrate;
forming a through-substrate via (TSV) from a backside of the substrate by dry etching through a thickness of the substrate to a TSV bottom at the front surface of the substrate and etching an opening through the TSV bottom by dry or wet etching through a portion of the insulator material to expose at least a first of the two device terminals in the insulator material,
the TSV having a tapered wall sloping in from a wider width of the TSV at the backside of the substrate to a narrower width of the TSV bottom at the front surface of the substrate; and
removing the support ring on the outer circumference of the substrate after forming the TSV.
2. The method of claim 1 , wherein the device body includes at least one of:
an inductive wire or line structure of an inductor, a resistive material pad of a resistor, or capacitor gap material pad of a capacitor.
3. The method of claim 1 , further comprising:
forming a copper layer on the backside of the substrate, in the TSV along the tapered wall, and in an insulator material cavity formed by the TSV, the copper layer defining an electrical connection to at least one of the two device terminals of the at least one passive device having the device body that is embedded in the insulator material.
4. The method of claim 1 , wherein the forming the TSV includes a two-step etching process with a first etch to etch a substrate portion of the TSV and a second etch to etch an insulator material portion of the TSV.
5. The method of claim 1 , wherein an insulator material cavity formed by the TSV extends to a depth of at least 5 μm in the insulator material from the front surface of the substrate to expose the at least one of the two device terminals to of the device body that is at least partially embedded in the insulator material.
6. A method comprising:
embedding at least one passive device in an insulator material disposed on a front surface of a substrate, the at least one passive device having a device body between two device terminals;
back grinding the substrate to thin a central portion of the substrate to form a support ring on an outer circumference of the substrate;
forming a through-substrate via (TSV) extending from a backside of the substrate toward the front surface of the substrate and extending to a depth in the insulator material disposed on the front surface of the substrate exposing at least one of the two device terminals of the device body that is embedded in the insulator material;
forming a copper layer disposed on the backside of the substrate and in the TSV, the copper layer defining an electrical connection through the TSV to at least one of the two device terminals of the device body embedded in the insulator material,
the TSV being a tapered TSV having a tapered wall sloping in from a wider surface opening of the TSV at the backside of the substrate to a narrower opening at the front surface of the substrate, a substrate portion of the TSV having a width at the front surface of the substrate wider than a width of an insulator material portion of the TSV at the front surface of the substrate; and
removing the support ring on the outer circumference of the substrate after forming the TSV.
7. The method of claim 6 , further comprising:
coupling the substrate to a conductive pad, included on a board, using a conductive epoxy or using a wafer bump solder.
8. The method of claim 6 , wherein an insulator material cavity extends to a depth of at least 5 μm in the insulator material from the front surface of the substrate to expose the at least one of the two device terminals connected to the device body that is at least partially embedded in the insulator material.
9. A method, comprising:
grinding a backside of a semiconductor substrate to reduce a thickness of a central portion of the semiconductor substrate to form a mechanical support ring on an outer portion of the semiconductor substrate;
etching through the semiconductor substrate using a semiconductor dry etch;
etching through a portion of an insulator material layer disposed on a front side of the semiconductor substrate using an insulator etch to form a through-substrate via (TSV) from the backside of the substrate, the TSV defining an interconnect access to at least one passive component embedded in the insulator material layer disposed on a front surface of the semiconductor substrate; and
removing the mechanical support ring on the outer portion of the substrate after using the insulator etch to form the TSV.
10. The method of claim 9 , wherein the at least one passive component includes at least one of an inductor, a resistor, or a capacitor having a terminal embedded in the insulator material layer.
11. The method of claim 9 , wherein the grinding the backside of the substrate includes using a grind process that thins the central portion of the substrate to be at least three-quarters or less of an original thickness.
12. The method of claim 11 , wherein etching through the portion of the insulator material layer exposes a terminal of the at least one passive component embedded in the insulator material layer.
13. The method of claim 11 , further comprising, grinding the mechanical support ring on the outer portion of the substrate to a reduced height.
14. The method of claim 9 , wherein etching through the thickness of the semiconductor substrate and etching through the portion of the insulator material layer includes etching a tapered TSV, the tapered TSV having a tapered wall sloping in from a wider surface opening to a narrower TSV bottom.
15. The method of claim 9 , further comprising:
forming a plated copper layer disposed on the backside of the substrate and in the TSV along a tapered wall of the TSV and over a TSV bottom, the plated copper layer defining an electrical connection to a terminal of the at least one passive component embedded in the insulator material layer.
16. The method of claim 15 , wherein the forming the plated copper layer on the backside of the substrate and in the TSV along the tapered wall and over the TSV bottom includes depositing a titanium-copper (Ti—Cu) barrier and seed layer on the backside of the substrate and in the TSV along the tapered wall.
17. The method of claim 15 , wherein the forming the plated copper layer on the backside of the substrate and in the TSV along the tapered wall and over the TSV bottom includes growing an oxide layer on the backside of the substrate and then the plated copper layer.
18. The method of claim 15 , further comprising, applying an under bump metal (UBM) etch to the plated copper layer.
19. The method of claim 15 , further comprising:
forming a solder resist layer; and
forming a wafer bump or a ball in contact with the plated copper layer.
20. The method of claim 15 , further comprising:
affixing a dicing tape to the substrate;
dicing the substrate into an individual IPD die comprising the at least one passive component embedded in the insulator material layer; and
picking the individual IPD die from the dicing tape.