US20010019872A1 - Transistor and method - Google Patents
Transistor and method Download PDFInfo
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- US20010019872A1 US20010019872A1 US09/821,602 US82160201A US2001019872A1 US 20010019872 A1 US20010019872 A1 US 20010019872A1 US 82160201 A US82160201 A US 82160201A US 2001019872 A1 US2001019872 A1 US 2001019872A1
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- 238000000034 method Methods 0.000 title claims description 14
- 125000006850 spacer group Chemical group 0.000 claims abstract description 41
- 239000000758 substrate Substances 0.000 claims abstract description 36
- 239000004020 conductor Substances 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 239000004065 semiconductor Substances 0.000 claims abstract description 6
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 41
- 229920005591 polysilicon Polymers 0.000 claims description 41
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 17
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 17
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 17
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 17
- 238000002513 implantation Methods 0.000 claims description 4
- 239000007943 implant Substances 0.000 claims description 3
- 230000005669 field effect Effects 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 description 13
- 239000002184 metal Substances 0.000 description 13
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 10
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 6
- 230000003071 parasitic effect Effects 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 239000010936 titanium Substances 0.000 description 6
- 229910052719 titanium Inorganic materials 0.000 description 6
- 229910052721 tungsten Inorganic materials 0.000 description 6
- 239000010937 tungsten Substances 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 229910017052 cobalt Inorganic materials 0.000 description 4
- 239000010941 cobalt Substances 0.000 description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 239000002019 doping agent Substances 0.000 description 4
- 229910021341 titanium silicide Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 239000003989 dielectric material Substances 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910018999 CoSi2 Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 description 1
- 229960001231 choline Drugs 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
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- 239000010409 thin film Substances 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66234—Bipolar junction transistors [BJT]
- H01L29/66272—Silicon vertical transistors
- H01L29/66287—Silicon vertical transistors with a single crystalline emitter, collector or base including extrinsic, link or graft base formed on the silicon substrate, e.g. by epitaxy, recrystallisation, after insulating device isolation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/08—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions with semiconductor regions connected to an electrode carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
- H01L29/0821—Collector regions of bipolar transistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/10—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions with semiconductor regions connected to an electrode not carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
- H01L29/1004—Base region of bipolar transistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/70—Bipolar devices
- H01L29/72—Transistor-type devices, i.e. able to continuously respond to applied control signals
- H01L29/73—Bipolar junction transistors
- H01L29/732—Vertical transistors
- H01L29/7322—Vertical transistors having emitter-base and base-collector junctions leaving at the same surface of the body, e.g. planar transistor
Definitions
- the invention relates to electronic semiconductor devices and integrated circuits, and more particularly to fabrication methods of MOS and bipolar transistors in integrated circuits.
- Such parasitic capacitances arise whenever there are two charge carrying locations in the device or between the device and an external location separated by a dielectric. With the continued miniaturization of semiconductor devices, the distances between these charge carrying locations decreases and the thicknesses of the dielectrics also decreases, thereby increasing the parasitic capacitnace within the device being fabricated. Also, the doping levels have been increasing, this also leading to an increase in capacitance.
- the present invention provides small contacts by use of sidewall removals to form the contact openings.
- FIGS. 1 a - c show process steps for a MOS trnasistor.
- FIG. 2 shows a bipolar transistor
- FIGS. 3 a - b show a salicide version of the MOS transistor.
- FIG. 4 shows a metal gate version of the MOS transistor.
- the preferred embodiments provide small contacts to substrate regions by selectively removing the outer one of two sidewall dielectric layers and refilling the resultant opening with a conductor to make contact to the underlying substrate.
- the contact opening size is controlled by the thickness of the sidewall dielectric layer thickness, and this contact opening can be used for introduction of dopants to form a source/drain or an extrinsic base.
- this second sidewall dielectric removal permits the length of the contact openings to the source and drain to be narrower than half the gate length and thus be of sublithographic size. Also, the heavily doped source and drain may be formed by dopant introduction through these contact openings and thus provide small regions with consequent decreased parasitic capacitance.
- FIG. 1 c is a cross sectional elevation view of a first preferred embodiment MOS transistor with polysilicon gate 9 of length 130 nm, gate oxide 7 of thickness 2 nm, oxide sidewall spacers 13 of thickness 30 nm, polysilicon source/drain contacts 19 with length 30 nm at the source/drain, shallow trench isolation oxide 5 , and electrodes 19 .
- the ratio of the contact length to the gate length thus is much less than one half, and the source/drains formed by dopant introduction through the contact opening may also have length of less than half the gate length. Indeed, the contact opening is roughly one quarter of the gate length in FIG. 1 c.
- a preferred embodiment fabrication process for formation of a MOS transistor commences in standard manner as shown in FIG. 1 a with a silicon substrate 1 having an active device region which is isolated on the chip by a shallow trench isolation (STI) oxide 5 which surrounds the active device region and is formed in standard manner such as etch trenches, grow interface oxide, deposit oxide in a high density plasma to fill trenches, and planarize.
- STI shallow trench isolation
- a first layer of 2 nm thick gate oxide 7 is grown or deposited over the active device region 3 and extends to and becomes a part of the trench oxide 5 .
- a polysilicon gate 9 is then formed over the portion of the first layer of gate oxide 7 as well as over the active device region 3 with a hard mask 11 which is disposed on the upper surface of the gate 9 .
- the hard mask 11 is sufficiently thick or selective to the subsequent etch used in forming the gate sidewall spacers 13 to remain after sidewall spacer formation. If the hard mask 11 and sidewall spacer 13 are made of silicon nitrides, then the second dielectric layer 15 discussed below will be an oxide, and vice versa to insure selective etchability as discussed herein.
- the hard mask 11 can be patterned over a first 300 nm thick layer of polysilicon with subsequent etching of the first layer of polysilicon to provide the gate 9 with the hard mask thereon.
- a lightly doped drain implant through the exposed gate oxide 7 follows the gate formation.
- the sidewall spacer 13 which can be an oxide or nitride as discussed above and which will be assumed to be an oxide for this embodiment, is then formed on the sidewalls of gate 9 as well as on the sidewalls of the hard mask 11 by standard deposition of a 30 nm thick film followed by anisotropic etchback. The etchback may remove the exposed portion of oxide 7 .
- a second 30 nm thick dielectric layer 15 which can be silicon oxide or nitride but which must be selectively etchable to the sidewall spacers 13 , is then conformally deposited over the entire structure to provide some offset and to provide the region which will eventually be used to form the contact opening to the source/drain.
- This is followed by a similar second deposition of polysilicon 17 to which the source/drain will be ultimately connected.
- the second polysilicon 17 is planarized (e.g., by chemical mechanical polishing) and then the polysilicon is etched back to expose dielectric 15 on hard mask 11 as illustrated by the broken line in FIG. 1 b.
- polysilicon 17 could be replaced with another conductor such as tungsten on a titanium nitride barrier layer.
- the second polysilicon layer 17 is then patterned in standard manner, premetal level dielectric formed, metal interconnects, intermetal level dielectrics, and passivation steps complete an integrated circuit.
- FIG. 2 illustrates in cross sectional elevation view a preferred embodiment bipolar transistor using the selective removal of the second dielectric.
- the primary difference over the foregoing discussed fabrication of a MOS device includes substrate doping: providing p-type substrate 21 which has an n + -type subcollector 23 implanted therein.
- An n-type epitaxial layer 25 is formed over the subcollector 23 with a p-type base 27 thereover, and an n + -type emitter 29 is formed in the base, all in standard manner as shown.
- the oxide layer 31 is formed over the base and the polysilicon emitter 33 is formed after removal of a portion of the oxide layer 31 to allow diffusion of the n + dopant into the base and to make contact between the polysilicon emitter 33 and the emitter region 29 .
- a hard mask is on the top of the polysilicon emitter 33 ; a dielectric spacer 35 is formed over the top and sidewalls of the emitter 33 , and the process proceeds with a second dielectric in the same manner as in the fabrication of the MOS device to provide a polysilicon coupling 37 to the p + -type extrinsic base 39 and to the layer of polysilicon 41 disposed over the oxide region 43 .
- the diffusion from the polysilicon 37 is nominally p-type to form the extrinsic base or base contact.
- a self-aligned silicide (salicide) process can be used with the MOS preferred embodiment as follows. After the contact openings have been filled with polysilicon 19 as in FIG. 1 c, pattern the polysilicon, deposit dielectric, planarize with chemical mechanical polishing to remove dielectric, the hard mask 11 , and polysilicon to reduce the polysilicon thickness to about 150-200 nm. See FIG. 3 a which also shows lightly doped source/drains 31 and heavily doped source/drains 33 .
- a metal gate and metal contact preferred embodiment may be derived from the foregoing polysilicon MOS preferred embodiment (FIGS. 1 a - 1 c ) simply by using metal (such as tungsten on a titanium nitride barrier) in place of polysilicon.
- Another metal gate and metal contact preferred embodiment can be derived as follows. Starting with the structure of FIG. 3 a, remove all of the polysilicon with a choline etch, this is a timed etch to limit the amount of substrate silicon also removed. Then deposit a 10-20 nm thick layer of titanium and react the titanium contacting the silicon substrate at the source/drains in a nitrogen atmosphere with rapid thermal processing. This forms titanium silicide at the source/drains and titanium nitride elsewhere including a thin film of titanium nitride on top of the titanium silicide. Then deposit tungsten and apply chemical mechanical polishing to reduce the metal thickness to reveal the dielectric 13 which thereby separates the metal gate and to about 200-300 nm. See FIG. 4 showing titanium nitride 41 and tungsten 49 form the metal gate and titanium silicide 43 on heavily doped source/drains 33 , plus titanium nitride 45 and tungsten 47 forming the metal contacts.
- the preferred embodiments may be varied in many ways while retaining one or more of their features of a contact derived from the removal of a sidewall dielectric.
- the dimensions of the components in the preferred embodiments can be varied such as the gate length could be any of the expected standard lengths of 250 nm, 180 nm, 130 nm, 100 nm, et cetera, and the corresponding contact opening size and sidewall dielectric thicknesses similarly varied.
- the sidewall dielectrics could be formed as two or more sublayers, the materials may be varied such as the inner dielectric could be nitride on oxide and the removed dielectric could be oxide or nitride on oxide for use with two step removal.
- the dielectric layers may be of differing thicknesses, so the contact opening and the sidewall spacer may have differing sizes.
- the gate material may differ from the contact material which itself may include multiple materials such as in FIG. 1 c the material 17 could differ from the contact opening fill material 19 .
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Abstract
A method of fabricating a semiconductor device and the device. The device is fabricated by providing a substrate having a region thereover of electrically conductive material, and a dielectric first sidewall spacer on the region of electrically conductive material. A second sidewall spacer is formed over the first sidewall spacer extending to the substrate from a material which is selectively removal relative to the first sidewall spacer. An electrically conductive region is formed contacting the second sidewall spacer and spaced from the substrate. The second sidewall spacer is selectively removable to form an opening between the substrate and the electrically conductive region. The opening is filled with electrically conductive material to electrically couple the electrically conductive material to the substrate.
Description
- The invention relates to electronic semiconductor devices and integrated circuits, and more particularly to fabrication methods of MOS and bipolar transistors in integrated circuits.
- In the fabrication of semiconductor devices, it is well known that parasitic capacitances tend to decrease the operating speed of the devices. Accordingly, the industry is constantly attempting to decrease parasitic capacitance to obtain the concomitant increase in device operating speed.
- Such parasitic capacitances arise whenever there are two charge carrying locations in the device or between the device and an external location separated by a dielectric. With the continued miniaturization of semiconductor devices, the distances between these charge carrying locations decreases and the thicknesses of the dielectrics also decreases, thereby increasing the parasitic capacitnace within the device being fabricated. Also, the doping levels have been increasing, this also leading to an increase in capacitance.
- The present invention provides small contacts by use of sidewall removals to form the contact openings.
- This has the advantage of permitting small source/drains in MOS and small extrinsic bases in bipolar transistors with consequent small junction capacitance.
- The drawings are schematic for clarity.
- FIGS. 1a-c show process steps for a MOS trnasistor.
- FIG. 2 shows a bipolar transistor.
- FIGS. 3a-b show a salicide version of the MOS transistor.
- FIG. 4 shows a metal gate version of the MOS transistor.
- Overview
- The preferred embodiments provide small contacts to substrate regions by selectively removing the outer one of two sidewall dielectric layers and refilling the resultant opening with a conductor to make contact to the underlying substrate. Thus the contact opening size is controlled by the thickness of the sidewall dielectric layer thickness, and this contact opening can be used for introduction of dopants to form a source/drain or an extrinsic base.
- For MOS transistors (as illustrated in cross sectional elevation view in FIGS. 1c, 3 b, and 4), this second sidewall dielectric removal permits the length of the contact openings to the source and drain to be narrower than half the gate length and thus be of sublithographic size. Also, the heavily doped source and drain may be formed by dopant introduction through these contact openings and thus provide small regions with consequent decreased parasitic capacitance.
- For bipolar transistors (illustrated in FIG. 2), this permits the size of the extrinsic base to be small and separated from the emitter only by the first dielectric sidewall spacer on the polysilicion emitter. This reduces parasitic capacitance.
- MOS Transistor
- FIG. 1c is a cross sectional elevation view of a first preferred embodiment MOS transistor with
polysilicon gate 9 of length 130 nm,gate oxide 7 of thickness 2 nm,oxide sidewall spacers 13 of thickness 30 nm, polysilicon source/drain contacts 19 with length 30 nm at the source/drain, shallowtrench isolation oxide 5, andelectrodes 19. The ratio of the contact length to the gate length thus is much less than one half, and the source/drains formed by dopant introduction through the contact opening may also have length of less than half the gate length. Indeed, the contact opening is roughly one quarter of the gate length in FIG. 1c. - Fabrication Method
- A preferred embodiment fabrication process for formation of a MOS transistor commences in standard manner as shown in FIG. 1a with a
silicon substrate 1 having an active device region which is isolated on the chip by a shallow trench isolation (STI)oxide 5 which surrounds the active device region and is formed in standard manner such as etch trenches, grow interface oxide, deposit oxide in a high density plasma to fill trenches, and planarize. - A first layer of 2 nm
thick gate oxide 7 is grown or deposited over theactive device region 3 and extends to and becomes a part of thetrench oxide 5. Apolysilicon gate 9 is then formed over the portion of the first layer ofgate oxide 7 as well as over theactive device region 3 with ahard mask 11 which is disposed on the upper surface of thegate 9. Thehard mask 11 is sufficiently thick or selective to the subsequent etch used in forming thegate sidewall spacers 13 to remain after sidewall spacer formation. If thehard mask 11 andsidewall spacer 13 are made of silicon nitrides, then the seconddielectric layer 15 discussed below will be an oxide, and vice versa to insure selective etchability as discussed herein. Thehard mask 11 can be patterned over a first 300 nm thick layer of polysilicon with subsequent etching of the first layer of polysilicon to provide thegate 9 with the hard mask thereon. A lightly doped drain implant through the exposedgate oxide 7 follows the gate formation. - The
sidewall spacer 13, which can be an oxide or nitride as discussed above and which will be assumed to be an oxide for this embodiment, is then formed on the sidewalls ofgate 9 as well as on the sidewalls of thehard mask 11 by standard deposition of a 30 nm thick film followed by anisotropic etchback. The etchback may remove the exposed portion ofoxide 7. - A second 30 nm thick
dielectric layer 15, which can be silicon oxide or nitride but which must be selectively etchable to thesidewall spacers 13, is then conformally deposited over the entire structure to provide some offset and to provide the region which will eventually be used to form the contact opening to the source/drain. This is followed by a similar second deposition ofpolysilicon 17 to which the source/drain will be ultimately connected. Thesecond polysilicon 17 is planarized (e.g., by chemical mechanical polishing) and then the polysilicon is etched back to expose dielectric 15 onhard mask 11 as illustrated by the broken line in FIG. 1b. Of course,polysilicon 17 could be replaced with another conductor such as tungsten on a titanium nitride barrier layer. - Selectively etch away the sidewall portion of dielectric15 to leave a 30 nm thick slot-like opening with
sidewall spacer 13 on one side andpolysilicon 17 on the other and the substrate (or anyoxide 7 still present) on the bottom. An anisotropic etch insures that lateral etching of dielectric 15 underpolysilicon 17 is limited. Then etch away any exposedoxide 7 if necessary. Theactive area 3 is sxposed at the bottom of the opening, and the heavily doped source/drain regions may now be formed in the substrate by implantation, plasma implantation, or gas phase doping; or by diffusion out of theconductor 19 which is deposited to fill the opening in the next step. - Fill the opening created by the removal of dielectric15 (and exposed gate oxide 7) with a conductor such as doped polysilicon or a metal like titanium or titanium followed by titanium nitride via a conformal deposition. Then etch back the conductor to achieve the device of FIG. 1c which shows polysilicon. For titanium fill, the titanium may be reacted with the source/drain silicon to form titanium silicide; similarly if tungsten, cobalt, nickel, platinum, et cetera had used to fill the opening. This fill material thus provides a contact between the
second polysilicon layer 17 and the source/drains in the silicon substrate. - The
second polysilicon layer 17 is then patterned in standard manner, premetal level dielectric formed, metal interconnects, intermetal level dielectrics, and passivation steps complete an integrated circuit. - Bipolar Transistor
- FIG. 2 illustrates in cross sectional elevation view a preferred embodiment bipolar transistor using the selective removal of the second dielectric. In particular, in the fabrication of a bipolar device the primary difference over the foregoing discussed fabrication of a MOS device includes substrate doping: providing p-
type substrate 21 which has an n+-type subcollector 23 implanted therein. An n-typeepitaxial layer 25 is formed over thesubcollector 23 with a p-type base 27 thereover, and an n+-type emitter 29 is formed in the base, all in standard manner as shown. Theoxide layer 31 is formed over the base and thepolysilicon emitter 33 is formed after removal of a portion of theoxide layer 31 to allow diffusion of the n+ dopant into the base and to make contact between thepolysilicon emitter 33 and theemitter region 29. A hard mask is on the top of thepolysilicon emitter 33; adielectric spacer 35 is formed over the top and sidewalls of theemitter 33, and the process proceeds with a second dielectric in the same manner as in the fabrication of the MOS device to provide apolysilicon coupling 37 to the p+-typeextrinsic base 39 and to the layer ofpolysilicon 41 disposed over theoxide region 43. The diffusion from thepolysilicon 37 is nominally p-type to form the extrinsic base or base contact. - Salicided MOS Transistor
- A self-aligned silicide (salicide) process can be used with the MOS preferred embodiment as follows. After the contact openings have been filled with
polysilicon 19 as in FIG. 1c, pattern the polysilicon, deposit dielectric, planarize with chemical mechanical polishing to remove dielectric, thehard mask 11, and polysilicon to reduce the polysilicon thickness to about 150-200 nm. See FIG. 3a which also shows lightly doped source/drains 31 and heavily doped source/drains 33. - Next, deposit a 50 nm thick layer of cobalt, and react the cobalt with the underlying polysilicon (both the
polysilicon gate 9 and the polysilicon 17-19) to form CoSi2. The silicidation reaction may be in one or two steps at differing or the same temperatures. Lastly, remove the unreacted cobalt which was on dielectric. The silicidation consumes about 50 nm of polysilicon to form about 100 nm thick CoSi2 layers 35 ongate - Metal Gate MOS
- A metal gate and metal contact preferred embodiment may be derived from the foregoing polysilicon MOS preferred embodiment (FIGS. 1a-1 c) simply by using metal (such as tungsten on a titanium nitride barrier) in place of polysilicon.
- Another metal gate and metal contact preferred embodiment can be derived as follows. Starting with the structure of FIG. 3a, remove all of the polysilicon with a choline etch, this is a timed etch to limit the amount of substrate silicon also removed. Then deposit a 10-20 nm thick layer of titanium and react the titanium contacting the silicon substrate at the source/drains in a nitrogen atmosphere with rapid thermal processing. This forms titanium silicide at the source/drains and titanium nitride elsewhere including a thin film of titanium nitride on top of the titanium silicide. Then deposit tungsten and apply chemical mechanical polishing to reduce the metal thickness to reveal the dielectric 13 which thereby separates the metal gate and to about 200-300 nm. See FIG. 4
showing titanium nitride 41 andtungsten 49 form the metal gate andtitanium silicide 43 on heavily doped source/drains 33, plustitanium nitride 45 andtungsten 47 forming the metal contacts. - Modifications
- The preferred embodiments may be varied in many ways while retaining one or more of their features of a contact derived from the removal of a sidewall dielectric.
- In particular, the dimensions of the components in the preferred embodiments can be varied such as the gate length could be any of the expected standard lengths of 250 nm, 180 nm, 130 nm, 100 nm, et cetera, and the corresponding contact opening size and sidewall dielectric thicknesses similarly varied. Indeed, the sidewall dielectrics could be formed as two or more sublayers, the materials may be varied such as the inner dielectric could be nitride on oxide and the removed dielectric could be oxide or nitride on oxide for use with two step removal. Of course, the dielectric layers may be of differing thicknesses, so the contact opening and the sidewall spacer may have differing sizes. Further, the gate material may differ from the contact material which itself may include multiple materials such as in FIG. 1c the
material 17 could differ from the contactopening fill material 19.
Claims (17)
1. A method of fabricating a semiconductor device which comprises the steps of:
(a) providing a substrate having a first region thereover of electrically conductive material, a dielectric first sidewall spacer on said first region of electrically conductive material;
(b) forming a second sidewall spacer over said first sidewall spacer extending to said substrate from a material which is selectively removable relative to said first sidewall spacer;
(c) forming a second electrically conductive region contacting said second sidewall spacer and spaced from said substrate;
(d) selectively removing said second sidewall spacer relative to said first sidewall spacer to form an opening extending between said substrate and said second electrically conductive region; and
(e) filling said opening with electrically conductive material to electrically couple said second electrically conductive region to said substrate.
2. The method of further including the step of providing in step (a) a dielectric layer between said first region of electrically conductive material and said substrate.
claim 1
3. The method of further including the step of implantation source/drain regions into said substrate prior to step (e) using said first sidewall spacer as a portion of the implant mask.
claim 1
4. The method of further including the step of implantation source/drain regions into said substrate prior to step (e) using said first sidewall spacer as a portion of the implant mask.
claim 2
5. The method of wherein said first region of electrically conductive material is polysilicon, said first sidwall spacer is one of silicon oxide or silicon nitride and said second sidewall spacer is the other of silicon oxide or silicon nitride.
claim 1
6. The method of wherein said first region of electrically conductive material is polysilicon, said first sidwall spacer is one of silicon oxide or silicon nitride and said second sidewall spacer is the other of silicon oxide or silicon nitride.
claim 2
7. The method of wherein said first region of electrically conductive material is polysilicon, said first sidwall spacer is one of silicon oxide or silicon nitride and said second sidewall spacer is the other of silicon oxide or silicon nitride.
claim 3
8. The method of wherein said first region of electrically conductive material is polysilicon, said first sidwall spacer is one of silicon oxide or silicon nitride and said second sidewall spacer is the other of silicon oxide or silicon nitride.
claim 4
9. A semiconductor device which comprises:
(a) a substrate;
(b) a region of electrically conductive material over said substrate;
(c) a dielectric sidewall spacer on said region of electrically conductive material;
(d) a second electrically conductive material extending along said sidewall spacer to said substrate; and
(e) a second electrically conductive region contacting said second electrically conductive material and spaced from said substrate.
10. The device of further including a dielectric layer between said region of electrically conductive material and said substrate.
claim 9
11. The device of further including source/drain regions disposed in said substrate and contacting said electrically conductive material.
claim 9
12. The device of further including source/drain regions disposed in said substrate and contacting said electrically conductive material.
claim 10
13. The device of further including a dielectric layer disposed between said second electrically conductive region and said substrate, said region of electrically conducive material being polysilicon, said sidewall spacer being one of silicon oxide or silicon nitride and said dielectric being the other of silicon oxide or silicon nitride.
claim 9
14. The device of further including a dielectric layer disposed between said second electrically conductive region and said substrate, said region of electrically conducive material being polysilicon, said sidewall spacer being one of silicon oxide or silicon nitride and said dielectric being the other of silicon oxide or silicon nitride.
claim 10
15. The device of further including a dielectric layer disposed between said second electrically conductive region and said substrate, said region of electrically conducive material being polysilicon, said sidewall spacer being one of silicon oxide or silicon nitride and said dielectric being the other of silicon oxide or silicon nitride.
claim 11
16. The device of further including a dielectric layer disposed between said second electrically conductive region and said substrate, said region of electrically conducive material being polysilicon, said sidewall spacer being one of silicon oxide or silicon nitride and said dielectric being the other of silicon oxide or silicon nitride.
claim 12
17. A field effect transistor, comprising:
(a) a gate with a sidewall spacer over a substrate;
(b) a contact to said substrate and adjacent said sidewall spacer, said contact with length less than about one half the length of said gate.
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US09/821,602 US6365451B2 (en) | 1997-12-17 | 2001-03-29 | Transistor and method |
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US6991797P | 1997-12-17 | 1997-12-17 | |
US09/212,136 US6271577B1 (en) | 1997-12-17 | 1998-12-15 | Transistor and method |
US09/821,602 US6365451B2 (en) | 1997-12-17 | 2001-03-29 | Transistor and method |
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US09/821,602 Expired - Lifetime US6365451B2 (en) | 1997-12-17 | 2001-03-29 | Transistor and method |
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US20040137675A1 (en) * | 2002-12-30 | 2004-07-15 | Cheolsoo Park | Methods of manufacturing MOSFETS in semiconductor devices |
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US7303965B2 (en) * | 1998-06-29 | 2007-12-04 | Kabushiki Kaisha Toshiba | MIS transistor and method for producing same |
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US7303965B2 (en) * | 1998-06-29 | 2007-12-04 | Kabushiki Kaisha Toshiba | MIS transistor and method for producing same |
US20040137675A1 (en) * | 2002-12-30 | 2004-07-15 | Cheolsoo Park | Methods of manufacturing MOSFETS in semiconductor devices |
US7118976B2 (en) * | 2002-12-30 | 2006-10-10 | Dongbu Electronics Co., Ltd. | Methods of manufacturing MOSFETs in semiconductor devices |
EP1575094A1 (en) * | 2004-03-12 | 2005-09-14 | Infineon Technologies AG | Bipolar transistor |
US20050205967A1 (en) * | 2004-03-12 | 2005-09-22 | Infineon Technologies Ag | Bipolar transistor |
US7397108B2 (en) | 2004-03-12 | 2008-07-08 | Infineon Technologies Ag | Bipolar transistor |
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US6271577B1 (en) | 2001-08-07 |
US6365451B2 (en) | 2002-04-02 |
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