Trench capacitor device suitable for decoupling applications in high-frequency operation
View Patent ↗A capacitor device, an electronic circuit comprising a capacitor device, an electronic component, and a method of forming a capacitor device are described. In the capacitor device, a current-path region extends from one of two trench capacitor electrodes to a respective contact structure. The current-path region is obtainable by thinning the substrate from an original substrate thickness down to reduced substrate thickness either in a lateral substrate portion containing the capacitor region or over the complete lateral extension of the substrate before forming the first and second contact structures. The capacitor device exhibits a reduced impedance in the current-path region. This reduced impedance implies a low self-inductance and self-resistance that is caused by the current-path region. The low self-inductance provides an improved signal suppression over a broadened spectral range in a circuit configuration that employs the capacitor device as a bypass capacitor between a signal line and ground potential.
1. A capacitor device, comprising:
a substrate, the substrate having a first substrate side and an opposite second substrate side,
a capacitor region embedded in the substrate and comprising at least one layer structure having a first and a second capacitor electrode electrically isolated from each other and having a U-shaped cross-sectional profile in a plane perpendicular to the first and second substrate sides, said first and second capacitor electrode being electrically connected to a first and a second ( 528 ) contact structure respectively, and
a current-path region extending from the first capacitor electrodes to the first contact structure and configured to provide a path for an electrical current, wherein the substrate comprises a recess on the first substrate side in a lateral substrate portion containing the capacitor region, the recess having a bottom face with a contact element that is part of the first contact structure, so that the capacitor region and the current-path region are arranged between the contact element and the second contact structure on the second substrate side.
2. The capacitor device of claim 1 , wherein the first contact structure is provided with at least two signal ports electrically connected with each other, one operating as input and the other as output, while the second contact structure is a ground connection.
3. The capacitor device of claim 2 , wherein the signal ports of the first contact structure are arranged in an unrecessed portion on the first substrate side and connected to the contact element on the bottom face of the recess.
4. The capacitor device of claim 2 , wherein the signal ports of the first contact structure are arranged on the second substrate side and connected to the contact element on the bottom face of the recess through contact lines extending from the first to the second substrate sides.
5. The capacitor device of claim 1 , wherein the recessed lateral substrate portion has a thickness of at most 50 microns.
6. The capacitor device of claim 1 , wherein the side faces of the recess are inclined by an angle of more than 90° with respect to the bottom face of the recess in a first recess section between the contact element and unrecessed portions of the first substrate side, and by an angle of 90° in a second recess section filled with the contact element.
7. The capacitor device of claim 1 , wherein the current-path region is formed by a conductive substrate region that is arranged between the bottom face of the recess on the first substrate side and the capacitor region, and wherein, in the cross-sectional profile, a bottom of the U-shape points towards the bottom face of the recess.
8. The capacitor device of claim 1 , wherein the current-path region is formed by a passivation layer covering the bottom face of the recess and being covered by the contact element.
9. The capacitor device of claim 1 , wherein the current-path region is arranged between the capacitor region and the second contact structure on the second substrate side, and wherein, in the cross-sectional profile, the bottom of the U-shape points towards the second substrate side.
10. The capacitor device of claim 1 , wherein lateral extensions of the current-path region equal lateral extensions of the capacitor region, and wherein the current-path region has a lower electrical resistivity than laterally adjacent areas of the substrate.
11. A broadband system comprising a semiconductor device that processes signals at least one frequency and as a bypass capacitor the capacitor device as claimed in claim 1 .
12. A broadband system as claimed in claim 11 , wherein the capacitor device comprises a plurality of bond pads and interconnect lines and the semiconductor device is assembled to the first side of the substrate.
13. A broadband system as claimed in claim 11 , wherein through-vias extend through the substrate from the first to the second side of the substrate, so that the substrate can be assembled with its second side to a carrier.
14. A broadband system as claimed in claim 11 , wherein the capacitor device is present.
15. An electronic component comprising a carrier substrate and, mounted on the carrier substrate, a capacitor device according to claim 1 .
16. A method for manufacturing a capacitor device, comprising the steps of:
providing a substrate having a first substrate side and an opposite second substrate side,
thinning the substrate from an original substrate thickness down to a reduced substrate thickness in a lateral substrate portion containing the capacitor region,
forming a capacitor region embedded in the predetermined lateral portion of the substrate by producing at least one layer structure having a first and a second capacitor electrodes isolated from each other and having a U-shaped cross-sectional profile in a plane perpendicular to the first and second substrate sides,
forming a first contact structure and forming a second contact structure,
providing a current-path region in the thinned lateral portion of the substrate and thereby electrically coupling a predetermined one of the capacitor electrodes to the respective contact structure.
17. The method of claim 16 ,
wherein the step of thinning the substrate comprises forming a recess on the first substrate side, the recess having a bottom face,
wherein the step of forming the first contact structure comprises connecting its signal ports with each other through a contact element on the bottom face of the recess, and
wherein the step of providing the current-path region comprises providing the current-path region between the contact element on the bottom face of the recess and the second contact structure on the second substrate side.