SEMICONDUCTOR COMPONENT INCLUDING BACK SIDE INPUT/OUTPUT SIGNAL ROUTING
20230170297 · 2023-06-01
Inventors
Cpc classification
H01L27/0292
ELECTRICITY
H01L23/5226
ELECTRICITY
H01L24/02
ELECTRICITY
H01L23/535
ELECTRICITY
H01L23/481
ELECTRICITY
International classification
H01L23/522
ELECTRICITY
H01L23/60
ELECTRICITY
H01L27/02
ELECTRICITY
Abstract
A semiconductor component, for example an integrated circuit chip, including a semiconductor substrate having active devices at the front side thereof and I/O terminals at the back side of the component, is provided. In one aspect, the terminals are connected to the active devices through TSV connections and buried rails in an area of the substrate that is separate from the area in which the active devices are located. The I/O TSV connections are located in a floating well of the substrate that is separated from the rest of the substrate by a second well formed of material of the opposite conductivity type compared to the material of the floating well. The second well includes at least one contact configured to be coupled to a voltage that is suitable for reverse-biasing the junction between the floating well and the second well. A small capacitance is placed in series with the large parasitic capacitance generated by a thin dielectric liner that isolates the I/O TSVs and I/O rails from the substrate, thereby mitigating the negative effect of the large parasitic capacitance. Additional contacts and conductors can be provided which are configured to create an ESD protection circuit for protecting the I/O TSVs and the I/O rails from electrostatic discharges.
Claims
1. A semiconductor component comprising a semiconductor substrate having a front side and a back side, and comprising a first area and a second area not overlapping the first area, the areas extending from the front side of the substrate to the back side through a complete thickness of the substrate, the semiconductor component comprising: a device layer at the front side of the substrate, comprising a plurality of active devices located in the first area, wherein the active devices are configured to receive input signals and to send output signals (I/O signals); a plurality of buried interconnect rails (I/O rails) at least partially buried in the substrate, at the front side thereof, and located in the second area; a plurality of through substrate via (TSV) connections (I/O TSVs) located in the second area, passing through the substrate from the I/O rails to the back side of the substrate, each I/O TSV and each I/O rail being isolated from the substrate by a dielectric liner; a front side redistribution layer on the device layer, configured to route the I/O signals between the active devices in the first area and the I/O rails in the second area; input/output terminals (I/O terminals) at the back side of the component; a back side redistribution layer at the back side of the substrate configured to route the I/O signals between the I/O terminals on the back side of the component and a back end of the I/O TSVs; and a plurality of power supply terminals (V.sub.SS, V.sub.DD) and conductors connected thereto, configured to supply power to the active devices, the power supply terminals being coupled to either a reference voltage Vss or a power voltage V.sub.DD, wherein: the plurality of I/O TSVs and the plurality of I/O rails are located in a first well of the substrate, the first well being formed of semiconductor material of a first conductivity type, the first well extending from the front side of the substrate to the back side of the substrate, through the complete thickness of the substrate, the first well is a floating well that is not provided with contacts for applying a bias voltage to the first well, the substrate comprises a second well in the second area, the second well extending from the front side of the substrate to the back side of the substrate through the complete thickness of the substrate, wherein the second well separates the first well from the rest of the substrate, the second well being of a second conductivity type opposite the first conductivity type, so that a junction is formed between the first well and the second well, and the second well includes at least one contact, configured to enable an application of a bias voltage to the second well, so as to reverse bias at least part of the junction between the first well and the second well.
2. The component according to claim 1, further comprising buried power rails and power TSV connections in the first area, coupled to Vss and V.sub.DD terminals at the back side of the component and coupled to the active devices in the device layer at the front side of the substrate for supplying power thereto.
3. The component according to claim 1, wherein the at least one contact of the second well is coupled to V.sub.DD.
4. The component according to claim 1, further comprising additional contacts, junctions, and conductors which implement an ESD protection circuit for protecting the I/O rails and the I/O TSVs from ESD pulses.
5. The component according to claim 4, wherein: the substrate is formed of semiconductor material of the first conductivity type, the at least one contact of the second well comprises a first contact coupled to V.sub.DD and comprising a region of the second conductivity type; the substrate comprises a second contact coupled to Vss, wherein the second contact comprises a region of the first conductivity type, located adjacent the second well; the second well comprises a third contact opposite the first contact, at the other side of the substrate compared to the first contact, the third contact comprising a region of the first conductivity type; the substrate comprises a fourth contact opposite the second contact, the fourth contact comprising a region of the second conductivity type; and the third and fourth contacts are coupled to the I/O rails, so that the ESD circuit is a double diode circuit formed by two diodes formed respectively by at least part of the junction between the substrate and the region of the fourth contact and by at least part of the junction between the second well and the region of the third contact.
6. The component according to claim 5, wherein the second well further comprises a fifth contact, comprising a region of the first conductivity type, and located adjacent the fourth contact and at the same side of the substrate as the fourth contact, wherein the fifth contact is coupled to the I/O rails, so that the ESD circuit additionally comprises a bipolar transistor formed by: at least part of the junction between the region of the fifth contact and the second well, and at least part of the junction between the floating well and the second well.
7. The component according to claim 4, wherein: the substrate is formed of semiconductor material of the first conductivity type, the at least one contact of the second well comprises a first contact coupled to V.sub.DD and comprises a region of the second conductivity type, the substrate comprises a second contact coupled to Vss, the second contact comprising a region of the first conductivity type, located adjacent the second well, the second well comprises a third contact opposite the first contact, the third contact comprising a region of the first conductivity type, the second well comprises a fourth contact also opposite the first contact and adjacent the third contact, the fourth contact comprising a region of the second conductivity type, the second well comprises a fifth contact on the same side of the substrate as the third and fourth contacts but on the opposite side of the floating well, the fifth contact comprising a region of the second conductivity type, the substrate comprises a sixth contact adjacent the fifth contact and opposite the second contact, the sixth contact comprising a region of the second conductivity type, the substrate comprises a seventh contact adjacent the sixth contact and also opposite the second contact, the seventh contact comprising a region of the first conductivity type, the third contact and the sixth contact are coupled to the I/O rails, the fourth contact and the fifth contact are coupled to V.sub.DD, and the seventh contact is coupled to V.sub.SS, so that the ESD circuit is a double diode circuit comprising: a first set of two diodes formed respectively by a first portion of the junction between the substrate and the region of the sixth contact and by a first portion of the junction between the second well and the region of the third contact, a second set of two diodes formed respectively by a second portion of the junction between the substrate and the region of the sixth contact and by a second portion of the junction between the second well and the region of the third contact, and a bipolar transistor formed by: at least part of the junction between the region of the sixth contact and the substrate, and at least part of the junction between the floating well and the second well.
8. The component according to claim 4, wherein one or more of the additional contacts comprise regions which form guard rings around the floating well.
9. The component according to claim 1, wherein the substrate is a p or n doped silicon substrate.
10. The component according to claim 1, wherein the component is an integrated circuit chip.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION OF CERTAIN ILLUSTRATIVE EMBODIMENTS
[0067] With reference to
[0068] As seen in
[0069] Throughout the description of disclosed technology, the terms “front side” and “back side” are used in relation to the substrate as well as to the component (for example, the IC) as a whole. For example, when it is stated that a layer is located “at the front side” of the substrate, this may refer to a layer that is on top of the substrate, possibly with other layers between the front surface of the substrate and the layer in question, or it may refer to a top layer of the substrate as such. Likewise, “terminals” located “at the back of the component” may include terminals directly on the back surface of the component or fully or partially embedded in the back surface. A dividing line 8 is drawn between a first area 4 and second area 5 of the substrate 1. The areas 4 and 5 are non-overlapping and extend from the front side 2 to the back side 3 of the substrate 1, through the full thickness of the substrate 1. At the front side of the substrate 1, the IC includes a device layer 6, including a plurality of active devices. The device layer 6 is a top layer of the substrate 1 as such, from the dotted line 2′ upwards.
[0070] In some ICs, the devices in layer 6 can include a large number of nano-scaled transistors such as finFETs or nano-sheet based transistors, processed according to a given layout. Without showing details of the devices as such, the rectangle 7 in
[0071] With reference again to
[0072] In the first area 4 of the IC illustrated in
[0073] The back side redistribution layer 17 is similar to the front side redistribution layer 9, that is, it is a multilevel interconnect structure including several layers of conductors running parallel to the substrate 1 and interconnected by via connections. The back side redistribution layer 17 together with the power TSVs 16a are part of the back side power delivery network PDN, configured to deliver power to the active devices in the first area (and other “first areas” of the IC). Power supply voltage levels are conventionally noted as a power voltage V.sub.DD supplied with respect to a reference (usually ground) voltage Vss. Power terminals are provided at the back of the IC which are configured to be coupled to an external power source. In
[0074] The second area 5 is now described in more detail. This second area 5 includes an array of nanoTSVs 16b, hereafter referred to as “I/O TSVs,” dedicated to the transmission of I/O signals between the front side and the back side of the substrate 1. To this aim, the IC further includes a number of I/O terminals 19 on its back side which are connected to the I/O TSVs 16b through conductors of the back side redistribution layer 17, symbolized by the dotted lines 20. The I/O TSVs 16b are connected at their front side to a further set of buried rails 15b, hereafter referred to as “I/O rails,” which are coupled to the front side redistribution layer 9 through conductors symbolized by the connections 21 which may be via connections or a combination of vias and conductors in the M0level.
[0075] Through the front side redistribution layer 9, input and output signals are routed to and from the active devices in the first area 4. The I/O TSVs 16b and the I/O rails 15b and the connections 21 are isolated from the substrate 1 by dielectric liners, which are not shown in detail in the drawings because of the drawing scale but can be suitably implemented. This is a thin layer of a few nm thick, often formed of SiO.sub.2, deposited on the sidewalls of via openings and trenches prior to filling these openings and trenches with an electrically conductive material such as Cu or Ru.
[0076] The elements described so far are known as such, that is, I/O interconnects to the back side through “I/O TSVs” and “I/O buried rails” situated in an area that is remote from the active devices. As stated in the introduction, these configurations can suffer from the high level of parasitic capacitance generated by the I/O TSVs and the I/O buried rails.
[0077] This problem can be solved in the configuration shown in
[0078] The p-well 25 is “floating” in the sense that it is not connected to an external voltage, that is, it does not include a contact configured to be connected to such an external voltage. In particular, the p-well 25 is isolated from the Vss and V.sub.DD power terminals. On the other hand, the surrounding n-well 26 is configured to be biased, that is, placed at a given voltage that can be set at a particular level, in order to cause the depletion of at least part of the p-n junction 27 between the floating well 25 and the surrounding n-well 26. In the embodiment shown, this is realized by producing a contact to the n-well 26 at the front side thereof, in the form of a heavily n-doped region 28 (hereafter referred to as “n+ contact”) that is connected to the lowest level of the front side redistribution layer 9. The connection may take place by a via connection (not shown) between the contact 28 and the lowest level. The representation of a “contact” as a heavily doped region is again a simplification of the reality in order to present merely the concept of the disclosed technology. It will be understood that in reality the contact includes the heavily doped region as well as a contact pad on the heavily doped region, the pad formed of metal or another electrically conductive material.
[0079] Through the front side redistribution layer 9 and the n+ contact 28, the n-well 26 may then be placed at a required voltage, which could, for example, be the supply voltage V.sub.DD, routed to the n+ contact 28 from a V.sub.DD terminal (one of the locations labelled “V.sub.DD” in
[0080] The effect of the reverse-biased p-n junction 27 is to place a small capacitance in series with the large parasitic capacitance generated by the liners of the I/O TSVs 16b and the I/O rails 15b, resulting in a drastic reduction of the overall parasitic capacitance influencing the I/O signal transceiving through the I/O TSVs 16b and rails 15b.
[0081] In an alternative embodiment that is equivalent to the embodiment of
[0082] The embodiment shown in
[0083] According to some embodiments of the disclosed technology, the means for creating a depleted p-n junction in series with the parasitic capacitance of the I/O rails 15b and I/O TSVs 16b is combined with additional contacts and connections which form an ESD protection circuit for the protection of the I/O terminals 19 and thereby the active devices in the first area 4 from electrostatic discharges. A first embodiment of this type is illustrated in
[0084] In this way, a double diode ESD protection circuit is obtained, as depicted in
[0085] The integration of an ESD protection together with the decreased parasitic capacitance can be realized in various ways other than the configuration shown in
[0086] Another embodiment is shown in
[0087] The equivalent circuit of the configuration of
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[0089] The embodiments shown in
[0090] In the embodiments of
[0091] The disclosed technology is not limited to components having supply terminals for Vss and V.sub.DD on the back side, but it is also applicable to components having these supply terminals on the front side, while having I/O terminals on the back side. Such an embodiment is shown in
[0092] Methods that are applicable for producing a component according to the disclosed technology can be suitably implemented and are not described here in detail. Method steps can include dopant implant steps for creating the floating well 25 and/or the second well 26, as well as the doped regions of the various contacts 28, 35, etc. Suitable lithographic masks are to be applied in order to limit the dopant implants to the required areas.
[0093] While the disclosed technology has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the disclosed technology. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.