MonolithIC 3D ICs
October 2012
MonolithIC 3D Inc. , Patents Pending
MonolithIC 3D Inc. , Patents Pending
1
The Monolithic 3D Innovation

Utilize Ion-Cut (‘Smart-Cut’) to transfer a thin (<100nm) single
crystal layer on top of the bottom (base) wafer
 Form the cut at less than 400ºC *
 Use co-implant
 Use mechanically assisted cleaving
 Form the bonding at less than 400ºC *
* See details at: Low Temperature Cleaving, Low Temperature Wafer
Direct Bonding

Split the transistor processing to two portions
 High temperature process portion (ion implant and activation) to be
done before the Ion-Cut
 Low temperature (<400°C) process portion (etch and deposition) to be
done after layer transfer
See details in the following slides:
Monolithic 3D ICs
Using SmartCut technology - the ion cutting process that
Soitec uses to make SOI wafers for AMD and IBM (millions of
wafers had utilized the process over the last 20 years) - to stack
up consecutive layers of active silicon (bond first and then cut).
Soitec’s Smart Cut Patented* Flow:
*Soitec’s fundamental patent US 5,374,564 expired Sep. 15, 2012
MonolithIC 3D Inc. , Patents Pending
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Monolithic 3D ICs
Ion cutting: the key idea is that if you implant a thin layer
of H+ ions into a single crystal of silicon, the ions will weaken the
bonds between the neighboring silicon atoms, creating a fracture
plane (Figure 3). Judicious force will then precisely break the
wafer at the plane of the H+ implant, allowing you to in-effect
peel off very thin layer. This technique is currently being used to
produce the most advanced transistors (Fully Depleted SOI,
UTBB transistors – Ultra Thin Body and BOX), forming
monocrystalline silicon layers that are less than 10nm thick.
MonolithIC 3D Inc. , Patents Pending
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Figure 3
Using ion-cutting to place a thin layer of monocrystalline silicon
above a processed (transistors and metallization) base wafer
Cleave using <400oC
Hydrogen implant
Oxide
anneal or sideways
Flip top layer and
of top layer
mechanical force. CMP.
bond to bottom layer
p- Si
Top layer
Oxide
p- Si
Oxide
H
p- Si
H
Oxide
Oxide
p- Si
Oxide
Oxide
Bottom layer
Similar process (bulk-to-bulk) used for manufacturing all SOI wafers today
MonolithIC 3D Inc. , Patents Pending
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Chapter 3
Monolithic 3D HKMG
MonolithIC 3D Inc. Patents Pending
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Technology
The monolithic 3D IC technology is applied to produce
monolithically stacked high performance High-k Metal Gate
(HKMG) devices, the world’s most advanced production
transistors.
3D Monolithic State-of-the-Art transistors are formed with ion-cut
applied to a gate-last process, combined with a low
temperature face-up layer transfer, repeating layouts, and an
innovative
inter-layer
via
(ILV)
alignment
scheme.
Monolithic 3D IC provides a path to reduce logic, SOC, and
memory costs without investing in expensive scaling down.
MonolithIC 3D Inc. Patents Pending
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On the donor wafer, fabricate standard dummy
gates with oxide and poly-Si; >900ºC OK
NMOS
Poly
Oxide
PMOS
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Form transistor source/drain
NMOS
Poly
Oxide
PMOS
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Form inter layer dielectric (ILD), S/D implants
and high temp anneals, CMP to transistor tops
S/D Implant
NMOS
ILD
PMOS
CMP to top of
dummy gates
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Implant hydrogen to generate cleave plane
NMOS
PMOS
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Implant hydrogen to generate cleave plane
NMOS
PMOS
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Implant hydrogen to generate cleave plane
NMOS
PMOS
H+
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Bond donor wafer to carrier wafer
~700µm Carrier Wafer
H+
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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Cleave to remove bulk of donor wafer
~700µm Carrier Wafer
Transferred
Donor Layer
Silicon
H+
~700µm Donor Wafer
Silicon
MonolithIC 3D Inc. Patents Pending
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CMP to STI
~700µm
Carrier Wafer
Transferred
Donor Layer
STI
MonolithIC 3D Inc. Patents Pending
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Deposit oxide, ox-ox bond carrier structure to
base wafer that has transistors & circuits
~700µm
Carrier Wafer
Transferred
Donor Layer
STI
Oxide-oxide bond
Base Wafer
NMOS
MonolithIC 3D Inc. Patents Pending
PMOS
17
Remove carrier wafer
~700µm
Carrier Wafer
Transferred
Donor Layer
Oxide-oxide bond
Base Wafer
NMOS
MonolithIC 3D Inc. Patents Pending
PMOS
18
Carrier wafer had been removed
Transferred
Donor Layer
Oxide-oxide bond
Base Wafer
NMOS
MonolithIC 3D Inc. Patents Pending
PMOS
19
Replace dummy gate stacks with Hafnium
Oxide & metal at low temp
Note: Replacing oxide and gate result in oxide and gate that were not damaged by the H+
implant
Transferred
Donor Layer
Oxide-oxide bond
Base Wafer
NMOS
PMOS
MonolithIC 3D Inc. Patents Pending
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Form inter layer via through oxide only (similar
to standard via)
Note: The second mono-crystal layer is very thin (<100nm) and via through it, is similar to other vias in
the metal stack
Transferred
Donor Layer
Oxide-oxide bond
Base Wafer
NMOS
PMOS
MonolithIC 3D Inc. Patents Pending
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Form top layer interconnect and
connect layers with inter layer via
ILV
Transferred
Donor Layer
Oxide-oxide bond
Base Wafer
NMOS
PMOS
MonolithIC 3D Inc. Patents Pending
MonolithIC 3D Inc. Patents Pending
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Novel Alignment Scheme using Repeating Layouts
Oxide
Landing
pad
Bottom
layer
layout
Top
layer
layout
Throughlayer
connection
 Even if misalignment occurs during bonding  repeating layouts allow correct connections.
 Above representation simplistic (high area penalty).
MonolithIC 3D Inc. Patents Pending
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Smart Alignment Scheme
Oxide
Landing
pad
Bottom
layer
layout
Top
layer
layout
MonolithIC 3D Inc. Patents Pending
Throughlayer
connection
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