US20060292799A1 - Memory embedded semiconductor device and method for fabricating the same - Google Patents
Memory embedded semiconductor device and method for fabricating the same Download PDFInfo
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- US20060292799A1 US20060292799A1 US11/511,441 US51144106A US2006292799A1 US 20060292799 A1 US20060292799 A1 US 20060292799A1 US 51144106 A US51144106 A US 51144106A US 2006292799 A1 US2006292799 A1 US 2006292799A1
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 86
- 238000000034 method Methods 0.000 title claims description 58
- 229910021332 silicide Inorganic materials 0.000 claims abstract description 123
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims abstract description 123
- 238000009792 diffusion process Methods 0.000 claims abstract description 69
- 239000000758 substrate Substances 0.000 claims abstract description 43
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 56
- 229920005591 polysilicon Polymers 0.000 claims description 56
- 238000006243 chemical reaction Methods 0.000 claims description 26
- 150000002500 ions Chemical class 0.000 claims description 23
- 239000012535 impurity Substances 0.000 claims description 18
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 9
- 229910052710 silicon Inorganic materials 0.000 claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 7
- 229910052785 arsenic Inorganic materials 0.000 claims description 7
- 239000010703 silicon Substances 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 239000007943 implant Substances 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 229910052732 germanium Inorganic materials 0.000 claims description 4
- 229910052754 neon Inorganic materials 0.000 claims description 4
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims description 3
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 3
- 238000000151 deposition Methods 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 71
- 229910017052 cobalt Inorganic materials 0.000 description 19
- 239000010941 cobalt Substances 0.000 description 19
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 19
- -1 boron ions Chemical class 0.000 description 10
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- 239000011229 interlayer Substances 0.000 description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000000593 degrading effect Effects 0.000 description 3
- 238000005468 ion implantation Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 238000007669 thermal treatment Methods 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B12/00—Dynamic random access memory [DRAM] devices
- H10B12/01—Manufacture or treatment
- H10B12/02—Manufacture or treatment for one transistor one-capacitor [1T-1C] memory cells
- H10B12/05—Making the transistor
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B12/00—Dynamic random access memory [DRAM] devices
- H10B12/01—Manufacture or treatment
- H10B12/09—Manufacture or treatment with simultaneous manufacture of the peripheral circuit region and memory cells
Definitions
- the present invention relates to a memory embedded semiconductor device comprising a memory such as a DRAM or a ROM and a high-speed CMOS logic circuit.
- a DRAM embedded LSI is an LSI having a memory region and a logic region each provided in a common substrate and suitable for processing a large amount of data at a high speed due to the structural feature thereof which allows a wider data bus to be provided between the memory and logic regions.
- the DRAM embedded LSI need not use wiring provided on a printed circuit board or the like which is located outside of the LSI package. This achieves a reduction in the power consumption of a system and renders the DRAM embedded LSI extremely effective as a system LSI.
- FIG. 3 shows a cross-sectional structure of a memory embedded semiconductor device (DRAM embedded LSI) according to a first conventional embodiment disclosed in Japanese Laid-Open Patent Publication No. 2000-332220 (Abstract).
- DRAM embedded LSI memory embedded semiconductor device
- a memory embedded semiconductor device has a logic region Rlogc comprising logic transistors and a DRAM region Rdram comprising the transistors of DRAM memory cells (memory transistors) disposed in a common semiconductor substrate 100 .
- the logic transistors include a p-channel transistor and an n-channel transistor, the drawing shows only the n-channel transistor. The drawing also shows the structure in which n-channel transistors are used as the memory transistors.
- the logic transistor comprises: a gate insulating film 102 and a gate electrode 103 each provided on an active region surrounded by isolations (trench isolations) 101 ; source/drain diffusion layers 104 formed in the regions of the semiconductor substrate 100 located sidewise of the gate electrode 103 ; and sidewalls 105 covering the side surfaces of the gate electrode 103 .
- the gate electrode 103 is composed of a lower electrode 103 a made of polysilicon containing an n-type impurity and an upper electrode 103 b made of silicide.
- the upper electrode 103 b is formed simultaneously with source/drain silicide layers 106 formed on the source/drain diffusion layers 104 by a common salicide process step.
- Each of the memory transistors comprises: a gate insulating film 112 and a gate electrode 113 each provided on an active region surrounded by the isolations (trench isolations) 101 ; source/drain diffusion layers 114 formed in the regions of the semiconductor substrate 100 located sidewise of the gate electrode 113 ; and sidewalls 115 covering the side surfaces of the gate electrode 113 .
- the gate electrode 113 is composed of a lower electrode 113 a made of polysilicon containing an n-type impurity and an upper electrode 113 b made of silicide. It is to be noted that source/drain silicide layers are not provided in the memory transistor.
- FIG. 4 shows a cross-sectional structure of a memory embedded semiconductor device according to a second conventional embodiment disclosed in Japanese Laid-Open Patent Publication No. 2001-127270 (Abstract), which allows the higher-speed operation of the memory transistors.
- the memory embedded semiconductor device has a logic region Rlogc and a DRAM region Rdram disposed in a common semiconductor substrate 200 in the same manner as in the first conventional embodiment.
- a logic transistor comprises: a gate insulating film 202 and a gate electrode 203 each provided on an active region surrounded by isolations (trench isolations) 201 ; source/drain diffusion layers 204 formed in the regions of the semiconductor substrate 200 located sidewise of the gate electrode 203 ; and sidewalls 205 covering the side surfaces of the gate electrode 203 .
- the gate electrode 203 is composed of a lower electrode 203 a made of polysilicon containing an n-type impurity and an upper electrode 203 b made of silicide.
- the upper electrode 203 b is formed simultaneously with source/drain silicide layers 206 formed on the source/drain diffusion layers 204 by a common salicide process step.
- a memory transistor comprises: a gate insulating film 212 and a gate electrode 213 each provided on an active region surrounded by the isolations (trench isolations) 201 , source/drain diffusion layers 214 formed in the regions of the semiconductor substrate 200 located sidewise of the gate electrode 213 ; and sidewalls 215 covering the side surfaces of the gate electrode 213 .
- the gate electrode 213 is composed of a lower electrode 213 a made of polysilicon containing an n-type impurity and an upper electrode 213 b made of silicide.
- the upper electrode 213 b is formed simultaneously with source/drain silicide layers 216 formed on the source/drain diffusion layers 214 by a common salicide process step.
- a junction leakage can be reduced and an impurity concentration in each of the source/drain diffusion layers 114 can be reduced because the silicide layer is not formed on either of the source/drain diffusion layers 114 of the memory transistor.
- This provides a memory transistor with an excellent short-channel effect (with a reduced off leakage). As a result, it becomes possible to implant a logic transistor operable at a high speed, while suppressing a reduction in pause time.
- the silicide layer 216 is formed on each of the source/drain diffusion layers 214 of the memory transistor in the memory embedded semiconductor device according to the second conventional embodiment.
- the arrangement has achieved an impurity concentration equal to that in the logic transistor in each of the source/drain diffusion layers 214 .
- a resulting reduction in parasitic resistance due to the silicide allows the higher-speed operation of the memory transistor and thereby implements a high-speed memory operation.
- the memory transistor is allowed to have only a leakage characteristic as low as that of the logic transistor so that the pause time is shortened, though the memory operation is performed. Accordingly, it becomes necessary to increase the number of times data refreshing is performed so that power consumption is increased. As a result, the problem is encountered that it is difficult to embed a DRAM having a memory capacity over 10 Mbits in terms of power consumption, though the embedding of a DRAM having a memory capacity of about 1 to 2 Mbits presents no serious problem.
- a memory embedded semiconductor device has a silicide film provided on each of the source/drain diffusion layers of a memory transistor which is thinner than a silicide film provided on each of the source/drain diffusion layers of a logic transistor.
- a first memory embedded semiconductor device comprises: a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, wherein the logic transistor comprises: a gate electrode formed on the semiconductor substrate; and source/drain diffusion layers each formed in the semiconductor substrate and having a silicide film formed thereon and the memory transistor comprises: a gate electrode formed on the semiconductor substrate; and source/drain diffusion layers each formed in the semiconductor substrate and having a silicide film formed thereon to be thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- the memory embedded semiconductor device achieves reductions in a leakage to the substrate and a parasitic resistance in the memory transistor without degrading the performance of the logic transistor and thereby prevents a reduction in pause time. As a result, it becomes possible to implement a low-power and large-capacity memory embedded semiconductor device operable at a high speed.
- the gate electrode of the logic transistor preferably has a polysilicon film and a silicide film formed on the polysilicon film and the gate electrode of the memory transistor preferably has a polysilicon film and a silicide film formed on the polysilicon film to be thinner than the silicide film formed on the polysilicon film of the logic transistor.
- the arrangement achieves a reduction in the parasitic resistance of the gate electrode not only in the logic transistor but also in the memory transistor so that it becomes possible to implement a memory embedded semiconductor device operating at a higher speed.
- an impurity selected from nitrogen, argon, neon, arsenic, silicon, and germanium has preferably been implanted in each of the source/drain diffusion layers of the memory transistor.
- the arrangement allows reliable adjustment of the thickness of the silicide film formed in the memory transistor to be smaller than the thickness of the silicide film formed in the logic transistor.
- the memory region is preferably a DRAM or a ROM.
- a first method for fabricating a memory embedded semiconductor device is a method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of: (a) forming source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate; (b) implanting ions of an impurity for suppressing a silicide reaction at least into each of the source/drain diffusion layers of the memory transistor by using an implant mask covering the logic region; and (c) forming a silicide film on each of the source/drain diffusion layers of each of the logic transistor and the memory transistor with the implant mask having been removed, wherein the silicide film formed on each of the source/drain diffusion layers of the memory transistor is thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- the first method for fabricating a memory embedded semiconductor device can suppress a silicide reaction in each of the source/drain diffusion layers of the memory transistor. Accordingly, the thickness of the silicide film formed on each of the source/drain diffusion layers of the memory transistor can be adjusted to be smaller than the thickness of the silicide film formed on each of the source/drain diffusion layers of the logic transistor. As a result, it becomes possible to fabricate a lower-power memory transistor operating at a high speed and having a reduced leakage to the substrate and a reduced parasitic resistance without degrading the performance of the logic transistor.
- the step (a) preferably includes further forming, on the semiconductor substrate, polysilicon films having exposed upper surfaces and forming the respective gate electrodes of the memory transistor and the logic transistor
- the step (b) preferably includes implanting the ions of the impurity for suppressing a silicide reaction also in the polysilicon film forming the gate electrode of the memory transistor
- the step (c) preferably includes forming a silicide film also on each of the polysilicon films forming the respective gate electrodes of the logic transistor and the memory transistor
- the silicide film formed on the polysilicon film forming the gate electrode of the memory transistor is preferably thinner than the silicide film formed on the polysilicon film forming the gate electrode of the logic transistor.
- the arrangement allows the silicidation of the gate electrode not only in the logic transistor but also in the memory transistor so that the parasitic resistance is reduced reliably. As a result, it becomes possible to fabricate a higher-speed memory embedded semiconductor device.
- the ions of the impurity for suppressing a silicide reaction are preferably ions of an impurity selected from nitrogen, argon, neon, arsenic, silicon, and germanium.
- the arrangement can reliably suppress silicidation in the memory region and allows the adjustment of the thickness of the silicide film formed in the memory region to be smaller than the thickness of the silicide film formed in the logic region.
- a second method for fabricating a memory embedded semiconductor device is a method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of: (a) forming source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate; (b) forming an insulating film for suppressing a silicide reaction covering at least each of the source/drain diffusion layers of the memory transistor and having an opening over the logic region; and (c) depositing a metal film over each of the logic region and the memory region with the insulating film for suppressing a silicide reaction being formed to form a silicide film through silicidation on each of the source/drain diffusion layers of each of the logic transistor and the memory transistor, wherein the silicide film formed on each of the source/drain diffusion layers of the memory transistor is thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- the second method for fabricating a memory embedded semiconductor device can suppress a silicide reaction in the memory region. Accordingly, the thickness of the silicide film formed on each of the source/drain diffusion layers of the memory transistor can be adjusted to be smaller than the thickness of the silicide film formed on each of the source/drain diffusion layers of the logic transistor. As a result, it becomes possible to fabricate a memory embedded semiconductor device comprising a lower-power memory transistor operating at a high speed and having a reduced leakage to the substrate and a reduced parasitic resistance without degrading the performance of the logic transistor.
- the step (a) preferably includes further forming, on the semiconductor substrate; polysilicon films having exposed upper surfaces and forming the respective gate electrodes of the memory transistor and the logic transistor, the step (b) preferably includes forming the insulating film for suppressing a silicide reaction also on the polysilicon film forming the gate electrode of the memory transistor, the step (c) preferably includes forming a silicide film also on each of the polysilicon films forming the respective gate electrodes of the logic transistor and the memory transistor, and the silicide film formed on the polysilicon film forming the gate electrode of the memory transistor is preferably thinner than the silicide film formed on the polysilicon film forming the gate electrode of the logic transistor.
- the arrangement allows the silicidation of the gate electrode not only in the logic transistor but also in the memory transistor so that the parasitic resistance is reduced reliably. As a result, it becomes possible to fabricate a higher-speed memory embedded semiconductor device.
- the insulating film for suppressing a silicide reaction is preferably an oxide film.
- the arrangement can reliably suppress silicidation in the memory region and allows the adjustment of the thickness of the silicide film formed in the memory region to be smaller than the thickness of the silicide film formed in the logic region.
- the memory embedded semiconductor device and the fabrication method therefor allows a reduction in leakage in the memory transistor and the higher-speed operation thereof, while retaining the performance of the logic transistor and implements a high-speed, large-capacity, and low-power memory embedded semiconductor device and a fabrication method therefor.
- FIGS. 1A to 1 D are cross-sectional views illustrating the process steps of fabricating a memory embedded semiconductor device according to a first embodiment of the present invention
- FIGS. 2A to 2 D are cross-sectional views illustrating the process steps of fabricating a memory embedded semiconductor device according to a second embodiment of the present invention
- FIG. 3 is a cross-sectional view showing a structure of a memory embedded semiconductor device according to a first conventional embodiment
- FIG. 4 is a cross-sectional view showing a structure of a memory embedded semiconductor device according to a second conventional embodiment.
- FIGS. 1A to 1 D show the cross-sectional states of a DRAM embedded semiconductor device according to a first embodiment of the present invention in the individual process steps of a fabrication method therefor.
- the memory embedded semiconductor device according to the first embodiment has a logic region Rlogc comprising logic transistors and a memory region Rdram comprising transistors (memory transistors) each as a part of a DRAM memory cell, which are disposed in a common semiconductor substrate 1 .
- the drawings show a structure in which both a p-channel transistor (pMISFET) and an n-channel transistor (nMISFET) are used as the logic transistors and n-channel transistors are used as the memory transistors.
- pMISFET p-channel transistor
- nMISFET n-channel transistor
- isolation regions 7 each defining an active region are formed in the surface regions of the semiconductor substrate 1 doped with a p-type impurity. Then, a p-type well region 2 , an n-type well region 3 , a triple p-type well region 4 , and an n-type buried diffusion region 5 are formed at predetermined positions by a well-known method. It is to be noted that the n-type buried diffusion region 5 need not necessarily be formed.
- a gate insulating film 14 composed of a thermal oxide film is formed on the active region of the semiconductor substrate and then a polysilicon film is deposited on the gate insulating film 14 .
- the polysilicon film is patterned to form a polysilicon film 15 forming the lower electrode of the pMISFET in the logic region Rlogc, a polysilicon film 16 forming the lower electrode of each of the nMISFETs in the logic region Rlogc, and the polysilicon film 26 forming the lower electrode of the nMISFET in the memory region Rdram.
- boron ions (B + ) are implanted at an acceleration voltage of 3 keV and a dose of 1 ⁇ 10 14 cm ⁇ 2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the nMISFET and the memory region Rdram, thereby forming the extension region of the pMISFET of the logic region Rlogc in the n-type well region 3 .
- arsenic ions are implanted at an acceleration voltage of 5 keV and a dose of 1 ⁇ 10 14 cm ⁇ 2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the pMISFET and the memory region Rdram, thereby forming the extension region of the nMISFET of the logic region Rlogc in the p-type well region 2 .
- phosphorus ions are implanted at an acceleration voltage of 5 keV and a dose of 5 ⁇ 10 13 cm ⁇ 2 by using a resist film (not shown) covering the logic region Rlogc, thereby forming LDD (Lightly Doped Drain) regions for the memory transistors (nMISFETs) in the triple p-type well region 4 .
- an insulating film for sidewalls is deposited on the substrate and subjected to anisotropic etching, thereby forming sidewalls 18 on the respective side surfaces of the polysilicon films 15 and 16 , while forming sidewalls 28 on the side surfaces of the polysilicon film 26 .
- boron ions (B + ) are implanted at an acceleration voltage of 5 keV and a dose of 4 ⁇ 10 15 cm ⁇ 2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the nMISFET and the memory region Rdram, thereby forming the heavily doped source/drain regions of the pMISFET in the logic region Rlogc.
- arsenic ions are implanted at an acceleration voltage of 10 keV and a dose of 4 ⁇ 10 15 cm ⁇ 2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the pMISFET and the memory region Rdram, thereby forming the heavily doped source/drain regions of the nMISFET in the logic region Rlogc.
- arsenic ions (As + ) are implanted at an acceleration voltage of 10 keV and a dose of 4 ⁇ 10 14 cm ⁇ 2 by using a resist film (not shown) covering the logic region Rlogc, thereby amorphizing the surface portion of the triple p-type well region 4 for the prevention of channeling.
- phosphorus ions (P + ) are implanted at an acceleration voltage of 10 keV and a dose of 4 ⁇ 10 15 cm ⁇ 2 , thereby forming the heavily doped source/drain regions of the memory transistors (nMISFETs).
- a thermal treatment (Rapid Thermal Annealing: RTA) is performed at a temperature of 1050° C. for 10 seconds to activate the impurities implanted in the individual ion implantation steps, thereby forming the respective source/drain diffusion layers 17 , 19 , and 27 of the individual MISFETs and changing the polysilicon film 15 into the p-type gate electrode, while changing the polysilicon films 16 and 26 into the respective n-type gate electrodes.
- RTA Rapid Thermal Annealing
- the present embodiment has performed the implantation of the ions in each of the nMISFETs in the logic region and the memory region under different ion implantation conditions by using the different resist masks, the simultaneous process may also be performed under the same implant conditions by using the same resist mask.
- nitrogen molecular ions (N 2 + ) for suppressing a silicide reaction are implanted selectively only in the memory region Rdram at an acceleration voltage of 10 keV and a dose of 1 ⁇ 10 15 cm ⁇ 2 by using the resist film Re 1 covering the logic region Rlogc, thereby forming respective ion implanted regions 27 x and 26 x each as an amorphous layer in the source/drain diffusion layers 27 and 26 .
- the depth from the upper surface of each of the source/drain diffusion layers 27 and the polysilicon film 26 to the upper surface of each of the ion implanted regions 27 x and 26 x is adjusted to about 20 nm.
- the same effects are obtainable if ions of Ar, Ne, As, Si, Ge, or the like are implanted instead of the nitrogen molecular ions (N 2 + ).
- the proper ranges of the ion implantation conditions are such that the acceleration voltage is 5 keV to 30 keV and the dose is 5 ⁇ 10 14 cm ⁇ 2 to 5 ⁇ 10 15 cm ⁇ 2 .
- a cobalt film 31 with a thickness of 10 nm is deposited on the substrate.
- a thermal process is performed at a temperature of 600° C. for about 30 minutes, thereby causing a reaction between silicon and cobalt and forming a silicide film.
- unreacted cobalt is removed by using a solution mixture (SPM) of a sulfuric acid and an aqueous hydrogen peroxide.
- SPM solution mixture
- a thermal treatment is performed at a temperature of 750° C. for about 30 minutes, thereby forming a cobalt silicide film forming the upper electrode of the gate electrode of each of the MISFETs and a part of each of the source/drain regions thereof.
- the gate electrode 10 of the pMISFET is therefore composed of the p-type polysilicon film 15 as the lower electrode and the silicide film 13 as the upper electrode, while the gate electrode 11 of the nMISFET is composed of the n-type polysilicon film 16 as the lower electrode and the silicide film 13 as the upper electrode.
- the source/drain regions of the pMISFET are composed of the p-type source/drain diffusion layers 19 and the silicide films 12
- the source/drain regions of the nMISFET are composed of the n-type source/drain diffusion layers 17 and the silicide films 12 .
- the gate electrode 21 of each of the memory transistors is composed of the n-type polysilicon film 26 including the ion implanted region 26 x as the lower electrode and the silicide film 23 as the upper electrode.
- the source/drain regions of the memory transistor are composed of the n-type source/drain diffusion layers 27 including the ion implanted region 27 x and the silicide film 22 .
- the steps of forming an interlayer insulating film on the substrate, forming respective plugs reaching the source/drain regions, forming a DRAM capacitor on the interlayer insulating film in the memory region Rdram, and forming a multilevel wiring layer insulated by the interlayer insulating film are subsequently performed, though the depiction thereof is omitted, whereby the memory embedded semiconductor device is formed.
- the present embodiment has formed the DRAM as the memory region, it is also possible to form a ROM or the like instead of the DRAM.
- the ion implanted regions 27 x and 26 x each composed of an amorphous layer formed in the step shown in FIG. 1B inhibit the diffusion of cobalt in each of the gate electrode and source/drain diffusion layers of the memory transistor so that a silicide reaction is suppressed.
- each of the ion implanted regions 27 x and 26 x formed in the present embodiment is positioned at a depth of about 20 nm, a relatively thick cobalt silicide film with a thickness of about 30 nm can be formed on each of the source/drain diffusion layers 17 and 19 of the logic transistors and a relatively thin cobalt silicide film with a limited thickness of about 20 nm can be formed on each of the source/drain diffusion layers 27 of the memory transistors.
- the junction is substantially deepened in each of the memory transistors so that a junction leakage to the substrate is suppressed in the memory transistor.
- cobalt silicide spike resulting from an abnormal reaction can be suppressed in the logic region Rlogc.
- the fabrication method according to the present embodiment has implanted nitrogen molecular ions for suppressing a silicide reaction or the like only in the memory transistors to form the amorphized ion implanted regions in the regions each at a predetermined depth from the surface and then performed silicidation in each of the memory region Rdram and the logic region Rlogc by using a salicide technology. Since the ion implanted regions suppress a silicide reaction in the source/drain diffusion layers of the memory transistors, it becomes possible to reduce the thickness of the silicide film of each of the memory transistors, while increasing the thickness of the silicide film of each of the logic transistors. This allows a reduction in junction leakage in the memory transistors and the higher-speed operation thereof, while retaining the conventional performance of the logic transistors in the memory embedded semiconductor device.
- the silicide film on the boundary region between the n-type polysilicon layer and the p-type polysilicon layer is abnormally thinned at the gate electrode portion so that there are concerns about the agglomeration of crystal grains which occurs in the silicide film when a thermal process is performed.
- the present embodiment has thinned the silicide film only in each of the transistors in the memory region composed of DRAM memory cells or ROM memory cells each using a gate electrode of one conductivity type (which is normally an n-type). Accordingly, there is no boundary region between the n-type polysilicon layer and the p-type polysilicon layer so that the abnormal thinning of the silicide film does not occur. This allows the higher-speed operation of the memory embedded semiconductor device without affecting the reliability thereof.
- FIGS. 2A to 2 D show the cross-sectional states of a DRAM embedded semiconductor device according to a second embodiment of the present invention in the individual process steps of a fabrication method therefor.
- the memory embedded semiconductor device according to the second embodiment has a logic region Rlogc comprising logic transistors and a DRAM region Rdram comprising transistors (memory transistors) each as a part of a DRAM memory cell, which are disposed in a common semiconductor substrate 1 in the same manner as in the first embodiment.
- the drawings show a structure in which both a p-channel transistor (pMISFET) and an n-channel transistor (nMISFET) are used as the logic transistors and n-channel transistors are used as the memory transistors.
- pMISFET p-channel transistor
- nMISFET n-channel transistor
- isolation regions 7 STIs
- a p-type well region 2 a p-type well region 2 , an n-type well region 3 , a triple p-type well region 4 , an n-type buried diffusion region 5 , a gate insulating film 14 , the respective polysilicon films 15 , 16 , and 26 of the individual MISFETs, the respective sidewalls 18 and 28 of the individual MISFETs, and the respective source/drain diffusion layers 17 , 19 , and 27 of the individual MISFETs are formed, as shown in FIG. 2A .
- STIs isolation regions 7
- a p-type well region 2 a p-type well region 2
- an n-type well region 3 a triple p-type well region 4
- an oxide film 32 with a thickness of about 1 nm is formed on the silicon layer exposed on the substrate by an oxidation process using an oxygen plasma.
- an oxygen plasma instead of the oxidation process using the oxygen plasma, it is also possible to use a normal thermal oxidation process, a native-oxide-film formation process subsequent to a wet process, a CVD process, or the like to form the oxide film 32 .
- the portion of the oxide film 32 located in the region other than the memory region Rdram is selectively removed by wet etching using a resist film Re 2 covering the memory region Rdram.
- a cobalt film 31 with a thickness of 10 nm is deposited to cover the surface of the substrate exposed in the logic region Rlogc and cover the oxide film 32 in the memory region Rdram.
- a thermal process is performed at a temperature of 600° C. for about 30 minutes, thereby causing a reaction between silicon and cobalt and forming a silicide film.
- unreacted cobalt is removed by using a solution mixture (SPM) of a sulfuric acid and an aqueous hydrogen peroxide.
- SPM solution mixture
- a thermal treatment is performed at a temperature of 750° C. for about 30 seconds, thereby forming a cobalt silicide film serving as the gate electrode of each of the MISFETs and a part of each of the source/drain regions thereof. Since the thin oxide film 32 is interposed between the cobalt film 31 and the silicon layer in the memory region Rdram, a silicide reaction is suppressed so that a thin silicide film is formed therein.
- the gate electrode 10 of the pMISFET is therefore composed of the p-type polysilicon film 15 as the lower electrode and the silicide film 13 as the upper electrode and the gate electrode 11 of the nMISFET is composed of the n-type polysilicon film 16 as the lower electrode and the silicide film 13 as the upper electrode.
- the source/drain regions of the pMISFET are composed of the p-type source/drain diffusion layers 19 and the silicide films 12
- the source/drain regions of the nMISFET are composed of the n-type source/drain diffusion layers 17 and the silicide films 12 .
- the gate electrode 26 of each of the memory transistors is composed of the n-type polysilicon film 16 as the lower electrode and the relatively thin silicide film 23 as the upper electrode.
- the source/drain regions of the memory transistor are composed of the n-type source/drain diffusion layers 27 and the relatively thin silicide films 22 .
- the steps of forming an interlayer insulating film on the substrate, forming respective plugs reaching the source/drain regions, forming a DRAM capacitor on the interlayer insulating film in the memory region Rdram, and forming multilayer wiring insulated by the interlayer insulating film are subsequently performed, though the depiction thereof is omitted, whereby the memory embedded semiconductor device is formed.
- the present embodiment has formed the DRAM as the memory region, it is also possible to form a ROM or the like instead of the DRAM.
- the diffusion of cobalt in the step illustrated in FIG. 2C is suppressed in the memory region Rdram by the oxide film 32 formed in the step illustrated in FIG. 2B so that a silicide reaction above the polysilicon film 26 and source/drain diffusion layers 27 of the memory transistor is suppressed.
- a relatively thick cobalt silicide film with a thickness of about 30 nm can be formed on each of the logic/drain diffusion layers 17 and 19 in the logic region Rlogc and a relatively thin cobalt silicide film with a limited thickness of about 20 nm can be formed on each of the source/drain diffusion layers 27 in the memory region Rlogc.
- the junction can substantially be deepened in each of the memory transistors so that a junction leakage to the substrate is suppressed in each of the memory transistors.
- the present embodiment allows the thickness of the silicide film 22 formed on each of the source/drain diffusion layers 27 of the memory transistors to be set as required by adjusting the thickness of the oxide film 32 .
- the fabrication method according to the present embodiment has performed silicidation with respect to each of the memory region Rdram and the logic region Rlogc by using a salicide technology with the memory region Rdram being covered with the oxide film. Since the oxide film suppresses the silicidation in the source/drain diffusion layers of the memory transistors, it becomes possible to reduce the thickness of the silicide film of each of the memory transistors, while increasing the thickness of the silicide film of each of the logic transistors. This allows a reduction in junction leakage in the memory transistor and the higher-speed operation thereof, while retaining the conventional performance of the logic transistors in the memory embedded semiconductor device.
- the cobalt silicide film as the upper electrode of the gate electrode is also reduced in thickness so that there are concerns about the breakage of the silicide film at the gate electrode due to agglomeration.
- the present embodiment has suppressed the thickness of the cobalt silicide film only in each of the transistors in the memory region composed of DRAM memory cells or ROM memory cells each using only the gate electrode of one conductivity type (which is normally an n-type) and hence there is no boundary region between the n-type polysilicon and the p-type polysilicon so that a problem does not occur.
- each of the first and second embodiments has provided the cobalt silicide film even over the polysilicon film included in the gate electrode
- the present invention is not limited to such embodiments.
- the same effects as achieved in the foregoing individual embodiments are achievable by applying the present invention even to the case where the gate electrode of each of the MIS transistors is a polymetal gate, a metal gate, a polysilicon gate, or the like.
- an insulating film for suppressing a silicide reaction or the like may be provided appropriately in the uppermost layer of the gate electrode in the state shown in FIGS. 1A and 2A .
- the memory embedded semiconductor device according to the present invention allows a reduction in leakage in each of the memory transistors and the higher-speed operation thereof, while retaining the performance of the logic transistors, and thereby implements a high-speed, large-capacity, and low-power memory embedded semiconductor device and a fabrication method therefor.
- the memory embedded semiconductor device according to the present invention is useful as a memory embedded semiconductor device comprising a memory such as a DRAM or a ROM and a high-speed CMOS logic circuit or the like.
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Abstract
A memory embedded semiconductor device according to the present invention has a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate. The logic transistor has a gate electrode provided on the semiconductor substrate and source/drain diffusion layers formed in the semiconductor substrate each having a silicide film formed thereon. On the other hand, the memory transistor has a gate electrode provided on the semiconductor substrate and source/drain diffusion layers formed in the semiconductor substrate each having a silicide film formed thereon to be thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
Description
- This application claims priority under 35 U.S.C. § 119 on Patent Application No. 2003-378407 filed in Japan on Nov. 7, 2003, the entire contents of which are hereby incorporated by reference.
- The present invention relates to a memory embedded semiconductor device comprising a memory such as a DRAM or a ROM and a high-speed CMOS logic circuit.
- A DRAM embedded LSI is an LSI having a memory region and a logic region each provided in a common substrate and suitable for processing a large amount of data at a high speed due to the structural feature thereof which allows a wider data bus to be provided between the memory and logic regions. In addition, the DRAM embedded LSI need not use wiring provided on a printed circuit board or the like which is located outside of the LSI package. This achieves a reduction in the power consumption of a system and renders the DRAM embedded LSI extremely effective as a system LSI.
- To enhance the performance of a transistor (logic transistor) in the logic region of the DRAM embedded LSI, it is necessary to reduce the parasitic resistance of the transistor by using a salicide technology. However, since a shallow junction is used in each of the source/drain regions of a transistor (memory transistor) provided in the memory region with the view to suppressing a short channel effect, a leakage current to the substrate increases when a silicide layer is formed on each of the source/drain regions of the memory transistor so that a charge retention time (pause time) is shortened. A description will be given herein below to the structures of conventional DRAM embedded LSIs and fabrication methods therefor with reference to the drawings.
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FIG. 3 shows a cross-sectional structure of a memory embedded semiconductor device (DRAM embedded LSI) according to a first conventional embodiment disclosed in Japanese Laid-Open Patent Publication No. 2000-332220 (Abstract). - As shown in the drawing, a memory embedded semiconductor device according to the first conventional embodiment has a logic region Rlogc comprising logic transistors and a DRAM region Rdram comprising the transistors of DRAM memory cells (memory transistors) disposed in a
common semiconductor substrate 100. Although the logic transistors include a p-channel transistor and an n-channel transistor, the drawing shows only the n-channel transistor. The drawing also shows the structure in which n-channel transistors are used as the memory transistors. - The logic transistor comprises: a gate
insulating film 102 and agate electrode 103 each provided on an active region surrounded by isolations (trench isolations) 101; source/drain diffusion layers 104 formed in the regions of thesemiconductor substrate 100 located sidewise of thegate electrode 103; andsidewalls 105 covering the side surfaces of thegate electrode 103. Thegate electrode 103 is composed of alower electrode 103 a made of polysilicon containing an n-type impurity and anupper electrode 103 b made of silicide. Theupper electrode 103 b is formed simultaneously with source/drain silicide layers 106 formed on the source/drain diffusion layers 104 by a common salicide process step. - Each of the memory transistors comprises: a gate
insulating film 112 and agate electrode 113 each provided on an active region surrounded by the isolations (trench isolations) 101; source/drain diffusion layers 114 formed in the regions of thesemiconductor substrate 100 located sidewise of thegate electrode 113; andsidewalls 115 covering the side surfaces of thegate electrode 113. Thegate electrode 113 is composed of a lower electrode 113 a made of polysilicon containing an n-type impurity and anupper electrode 113 b made of silicide. It is to be noted that source/drain silicide layers are not provided in the memory transistor. -
FIG. 4 shows a cross-sectional structure of a memory embedded semiconductor device according to a second conventional embodiment disclosed in Japanese Laid-Open Patent Publication No. 2001-127270 (Abstract), which allows the higher-speed operation of the memory transistors. - As shown in the drawing, the memory embedded semiconductor device according to the second conventional embodiment has a logic region Rlogc and a DRAM region Rdram disposed in a
common semiconductor substrate 200 in the same manner as in the first conventional embodiment. - A logic transistor comprises: a gate
insulating film 202 and agate electrode 203 each provided on an active region surrounded by isolations (trench isolations) 201; source/drain diffusion layers 204 formed in the regions of thesemiconductor substrate 200 located sidewise of thegate electrode 203; andsidewalls 205 covering the side surfaces of thegate electrode 203. Thegate electrode 203 is composed of alower electrode 203 a made of polysilicon containing an n-type impurity and anupper electrode 203 b made of silicide. Theupper electrode 203 b is formed simultaneously with source/drain silicide layers 206 formed on the source/drain diffusion layers 204 by a common salicide process step. - On the other hand, a memory transistor comprises: a
gate insulating film 212 and agate electrode 213 each provided on an active region surrounded by the isolations (trench isolations) 201, source/drain diffusion layers 214 formed in the regions of thesemiconductor substrate 200 located sidewise of thegate electrode 213; andsidewalls 215 covering the side surfaces of thegate electrode 213. Thegate electrode 213 is composed of alower electrode 213 a made of polysilicon containing an n-type impurity and anupper electrode 213 b made of silicide. Theupper electrode 213 b is formed simultaneously with source/drain silicide layers 216 formed on the source/drain diffusion layers 214 by a common salicide process step. - In the memory embedded semiconductor device according to the first conventional embodiment, a junction leakage can be reduced and an impurity concentration in each of the source/
drain diffusion layers 114 can be reduced because the silicide layer is not formed on either of the source/drain diffusion layers 114 of the memory transistor. This provides a memory transistor with an excellent short-channel effect (with a reduced off leakage). As a result, it becomes possible to implant a logic transistor operable at a high speed, while suppressing a reduction in pause time. - In recent years, however, an ultra-high-speed operation at about 200 MHz has been requested of a memory as a replacement of an SRAM in the DRAM embedded LSI. In the memory embedded semiconductor device (DRAM embedded LSI) according to the first conventional embodiment, the problem is encountered that it is difficult to allow a high-speed operation because of the high parasitic resistance of each of the source/drain diffusion layers of the memory transistor.
- By contrast, the
silicide layer 216 is formed on each of the source/drain diffusion layers 214 of the memory transistor in the memory embedded semiconductor device according to the second conventional embodiment. The arrangement has achieved an impurity concentration equal to that in the logic transistor in each of the source/drain diffusion layers 214. A resulting reduction in parasitic resistance due to the silicide allows the higher-speed operation of the memory transistor and thereby implements a high-speed memory operation. - In the memory embedded semiconductor device according to the second conventional embodiment, however, the memory transistor is allowed to have only a leakage characteristic as low as that of the logic transistor so that the pause time is shortened, though the memory operation is performed. Accordingly, it becomes necessary to increase the number of times data refreshing is performed so that power consumption is increased. As a result, the problem is encountered that it is difficult to embed a DRAM having a memory capacity over 10 Mbits in terms of power consumption, though the embedding of a DRAM having a memory capacity of about 1 to 2 Mbits presents no serious problem.
- It is therefore an object of the present invention to solve the foregoing conventional problems and implement a high-speed, large-capacity, and low-power memory embedded semiconductor device and a fabrication method therefor by reducing a leakage in a memory transistor and allowing the higher-speed operation thereof, while retaining the performance of a logic transistor.
- To attain the object, a memory embedded semiconductor device according to the present invention has a silicide film provided on each of the source/drain diffusion layers of a memory transistor which is thinner than a silicide film provided on each of the source/drain diffusion layers of a logic transistor.
- Specifically, a first memory embedded semiconductor device according to the present invention comprises: a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, wherein the logic transistor comprises: a gate electrode formed on the semiconductor substrate; and source/drain diffusion layers each formed in the semiconductor substrate and having a silicide film formed thereon and the memory transistor comprises: a gate electrode formed on the semiconductor substrate; and source/drain diffusion layers each formed in the semiconductor substrate and having a silicide film formed thereon to be thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- The memory embedded semiconductor device according to the present invention achieves reductions in a leakage to the substrate and a parasitic resistance in the memory transistor without degrading the performance of the logic transistor and thereby prevents a reduction in pause time. As a result, it becomes possible to implement a low-power and large-capacity memory embedded semiconductor device operable at a high speed.
- In the memory embedded semiconductor device according to the present invention, the gate electrode of the logic transistor preferably has a polysilicon film and a silicide film formed on the polysilicon film and the gate electrode of the memory transistor preferably has a polysilicon film and a silicide film formed on the polysilicon film to be thinner than the silicide film formed on the polysilicon film of the logic transistor. The arrangement achieves a reduction in the parasitic resistance of the gate electrode not only in the logic transistor but also in the memory transistor so that it becomes possible to implement a memory embedded semiconductor device operating at a higher speed.
- In the memory embedded semiconductor device according to the present invention, an impurity selected from nitrogen, argon, neon, arsenic, silicon, and germanium has preferably been implanted in each of the source/drain diffusion layers of the memory transistor. The arrangement allows reliable adjustment of the thickness of the silicide film formed in the memory transistor to be smaller than the thickness of the silicide film formed in the logic transistor.
- In the memory embedded semiconductor device according to the present invention, the memory region is preferably a DRAM or a ROM.
- A first method for fabricating a memory embedded semiconductor device according to the present invention is a method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of: (a) forming source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate; (b) implanting ions of an impurity for suppressing a silicide reaction at least into each of the source/drain diffusion layers of the memory transistor by using an implant mask covering the logic region; and (c) forming a silicide film on each of the source/drain diffusion layers of each of the logic transistor and the memory transistor with the implant mask having been removed, wherein the silicide film formed on each of the source/drain diffusion layers of the memory transistor is thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- The first method for fabricating a memory embedded semiconductor device can suppress a silicide reaction in each of the source/drain diffusion layers of the memory transistor. Accordingly, the thickness of the silicide film formed on each of the source/drain diffusion layers of the memory transistor can be adjusted to be smaller than the thickness of the silicide film formed on each of the source/drain diffusion layers of the logic transistor. As a result, it becomes possible to fabricate a lower-power memory transistor operating at a high speed and having a reduced leakage to the substrate and a reduced parasitic resistance without degrading the performance of the logic transistor.
- In the first method for fabricating a semiconductor device, the step (a) preferably includes further forming, on the semiconductor substrate, polysilicon films having exposed upper surfaces and forming the respective gate electrodes of the memory transistor and the logic transistor, the step (b) preferably includes implanting the ions of the impurity for suppressing a silicide reaction also in the polysilicon film forming the gate electrode of the memory transistor, the step (c) preferably includes forming a silicide film also on each of the polysilicon films forming the respective gate electrodes of the logic transistor and the memory transistor, and the silicide film formed on the polysilicon film forming the gate electrode of the memory transistor is preferably thinner than the silicide film formed on the polysilicon film forming the gate electrode of the logic transistor.
- The arrangement allows the silicidation of the gate electrode not only in the logic transistor but also in the memory transistor so that the parasitic resistance is reduced reliably. As a result, it becomes possible to fabricate a higher-speed memory embedded semiconductor device.
- In the first method for fabricating a memory embedded semiconductor device according to the present invention, the ions of the impurity for suppressing a silicide reaction are preferably ions of an impurity selected from nitrogen, argon, neon, arsenic, silicon, and germanium. The arrangement can reliably suppress silicidation in the memory region and allows the adjustment of the thickness of the silicide film formed in the memory region to be smaller than the thickness of the silicide film formed in the logic region.
- A second method for fabricating a memory embedded semiconductor device according to the present invention is a method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of: (a) forming source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate; (b) forming an insulating film for suppressing a silicide reaction covering at least each of the source/drain diffusion layers of the memory transistor and having an opening over the logic region; and (c) depositing a metal film over each of the logic region and the memory region with the insulating film for suppressing a silicide reaction being formed to form a silicide film through silicidation on each of the source/drain diffusion layers of each of the logic transistor and the memory transistor, wherein the silicide film formed on each of the source/drain diffusion layers of the memory transistor is thinner than the silicide film formed on each of the source/drain diffusion layers of the logic transistor.
- The second method for fabricating a memory embedded semiconductor device can suppress a silicide reaction in the memory region. Accordingly, the thickness of the silicide film formed on each of the source/drain diffusion layers of the memory transistor can be adjusted to be smaller than the thickness of the silicide film formed on each of the source/drain diffusion layers of the logic transistor. As a result, it becomes possible to fabricate a memory embedded semiconductor device comprising a lower-power memory transistor operating at a high speed and having a reduced leakage to the substrate and a reduced parasitic resistance without degrading the performance of the logic transistor.
- In the second method for fabricating a semiconductor device, the step (a) preferably includes further forming, on the semiconductor substrate; polysilicon films having exposed upper surfaces and forming the respective gate electrodes of the memory transistor and the logic transistor, the step (b) preferably includes forming the insulating film for suppressing a silicide reaction also on the polysilicon film forming the gate electrode of the memory transistor, the step (c) preferably includes forming a silicide film also on each of the polysilicon films forming the respective gate electrodes of the logic transistor and the memory transistor, and the silicide film formed on the polysilicon film forming the gate electrode of the memory transistor is preferably thinner than the silicide film formed on the polysilicon film forming the gate electrode of the logic transistor.
- The arrangement allows the silicidation of the gate electrode not only in the logic transistor but also in the memory transistor so that the parasitic resistance is reduced reliably. As a result, it becomes possible to fabricate a higher-speed memory embedded semiconductor device.
- In the second method for fabricating a memory embedded semiconductor device, the insulating film for suppressing a silicide reaction is preferably an oxide film. The arrangement can reliably suppress silicidation in the memory region and allows the adjustment of the thickness of the silicide film formed in the memory region to be smaller than the thickness of the silicide film formed in the logic region.
- Thus, the memory embedded semiconductor device and the fabrication method therefor according to the present invention allows a reduction in leakage in the memory transistor and the higher-speed operation thereof, while retaining the performance of the logic transistor and implements a high-speed, large-capacity, and low-power memory embedded semiconductor device and a fabrication method therefor.
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FIGS. 1A to 1D are cross-sectional views illustrating the process steps of fabricating a memory embedded semiconductor device according to a first embodiment of the present invention; -
FIGS. 2A to 2D are cross-sectional views illustrating the process steps of fabricating a memory embedded semiconductor device according to a second embodiment of the present invention; -
FIG. 3 is a cross-sectional view showing a structure of a memory embedded semiconductor device according to a first conventional embodiment; and -
FIG. 4 is a cross-sectional view showing a structure of a memory embedded semiconductor device according to a second conventional embodiment. -
FIGS. 1A to 1D show the cross-sectional states of a DRAM embedded semiconductor device according to a first embodiment of the present invention in the individual process steps of a fabrication method therefor. As shown in the drawings, the memory embedded semiconductor device according to the first embodiment has a logic region Rlogc comprising logic transistors and a memory region Rdram comprising transistors (memory transistors) each as a part of a DRAM memory cell, which are disposed in acommon semiconductor substrate 1. The drawings show a structure in which both a p-channel transistor (pMISFET) and an n-channel transistor (nMISFET) are used as the logic transistors and n-channel transistors are used as the memory transistors. - First, in the step shown in
FIG. 1A , isolation regions 7 (STIs) each defining an active region are formed in the surface regions of thesemiconductor substrate 1 doped with a p-type impurity. Then, a p-type well region 2, an n-type well region 3, a triple p-type well region 4, and an n-type burieddiffusion region 5 are formed at predetermined positions by a well-known method. It is to be noted that the n-type burieddiffusion region 5 need not necessarily be formed. - Next, a
gate insulating film 14 composed of a thermal oxide film is formed on the active region of the semiconductor substrate and then a polysilicon film is deposited on thegate insulating film 14. After ions of an n-type impurity (such as phosphorus) are implanted in the regions of the polysilicon film serving as the gate electrodes of nMISFETs, the polysilicon film is patterned to form apolysilicon film 15 forming the lower electrode of the pMISFET in the logic region Rlogc, apolysilicon film 16 forming the lower electrode of each of the nMISFETs in the logic region Rlogc, and thepolysilicon film 26 forming the lower electrode of the nMISFET in the memory region Rdram. - Next, boron ions (B+) are implanted at an acceleration voltage of 3 keV and a dose of 1×1014 cm−2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the nMISFET and the memory region Rdram, thereby forming the extension region of the pMISFET of the logic region Rlogc in the n-
type well region 3. - On the other hand, arsenic ions (As+) are implanted at an acceleration voltage of 5 keV and a dose of 1×1014 cm −2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the pMISFET and the memory region Rdram, thereby forming the extension region of the nMISFET of the logic region Rlogc in the p-
type well region 2. - Additionally, phosphorus ions (P+) are implanted at an acceleration voltage of 5 keV and a dose of 5×1013 cm−2 by using a resist film (not shown) covering the logic region Rlogc, thereby forming LDD (Lightly Doped Drain) regions for the memory transistors (nMISFETs) in the triple p-
type well region 4. Thereafter, an insulating film for sidewalls is deposited on the substrate and subjected to anisotropic etching, thereby formingsidewalls 18 on the respective side surfaces of thepolysilicon films sidewalls 28 on the side surfaces of thepolysilicon film 26. - Next, boron ions (B+) are implanted at an acceleration voltage of 5 keV and a dose of 4×1015 cm−2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the nMISFET and the memory region Rdram, thereby forming the heavily doped source/drain regions of the pMISFET in the logic region Rlogc.
- On the other hand, arsenic ions (As+) are implanted at an acceleration voltage of 10 keV and a dose of 4×1015 cm−2 by using a resist film (not shown) covering the region of the logic region Rlogc to be formed with the pMISFET and the memory region Rdram, thereby forming the heavily doped source/drain regions of the nMISFET in the logic region Rlogc.
- Next, arsenic ions (As+) are implanted at an acceleration voltage of 10 keV and a dose of 4 ×1014 cm−2 by using a resist film (not shown) covering the logic region Rlogc, thereby amorphizing the surface portion of the triple p-
type well region 4 for the prevention of channeling. Then, phosphorus ions (P+) are implanted at an acceleration voltage of 10 keV and a dose of 4×1015 cm−2, thereby forming the heavily doped source/drain regions of the memory transistors (nMISFETs). - Thereafter, a thermal treatment (Rapid Thermal Annealing: RTA) is performed at a temperature of 1050° C. for 10 seconds to activate the impurities implanted in the individual ion implantation steps, thereby forming the respective source/drain diffusion layers 17, 19, and 27 of the individual MISFETs and changing the
polysilicon film 15 into the p-type gate electrode, while changing thepolysilicon films - Although the present embodiment has performed the implantation of the ions in each of the nMISFETs in the logic region and the memory region under different ion implantation conditions by using the different resist masks, the simultaneous process may also be performed under the same implant conditions by using the same resist mask.
- Next, in the step shown in
FIG. 1B , nitrogen molecular ions (N2 +) for suppressing a silicide reaction are implanted selectively only in the memory region Rdram at an acceleration voltage of 10 keV and a dose of 1×1015 cm−2 by using the resist film Re1 covering the logic region Rlogc, thereby forming respective ion implantedregions polysilicon film 26 to the upper surface of each of the ion implantedregions - The same effects are obtainable if ions of Ar, Ne, As, Si, Ge, or the like are implanted instead of the nitrogen molecular ions (N2 +). The proper ranges of the ion implantation conditions are such that the acceleration voltage is 5 keV to 30 keV and the dose is 5×1014 cm−2 to 5×1015 cm−2.
- Next, in the step shown in
FIG. 1C , acobalt film 31 with a thickness of 10 nm is deposited on the substrate. - Next, in the step shown in
FIG. 1D , a thermal process is performed at a temperature of 600° C. for about 30 minutes, thereby causing a reaction between silicon and cobalt and forming a silicide film. Then, unreacted cobalt is removed by using a solution mixture (SPM) of a sulfuric acid and an aqueous hydrogen peroxide. Thereafter, a thermal treatment is performed at a temperature of 750° C. for about 30 minutes, thereby forming a cobalt silicide film forming the upper electrode of the gate electrode of each of the MISFETs and a part of each of the source/drain regions thereof. - In the logic region Rlogc, the
gate electrode 10 of the pMISFET is therefore composed of the p-type polysilicon film 15 as the lower electrode and thesilicide film 13 as the upper electrode, while thegate electrode 11 of the nMISFET is composed of the n-type polysilicon film 16 as the lower electrode and thesilicide film 13 as the upper electrode. The source/drain regions of the pMISFET are composed of the p-type source/drain diffusion layers 19 and thesilicide films 12, while the source/drain regions of the nMISFET are composed of the n-type source/drain diffusion layers 17 and thesilicide films 12. - In the memory region Rdram, on the other hand, the
gate electrode 21 of each of the memory transistors is composed of the n-type polysilicon film 26 including the ion implantedregion 26 x as the lower electrode and thesilicide film 23 as the upper electrode. The source/drain regions of the memory transistor are composed of the n-type source/drain diffusion layers 27 including the ion implantedregion 27 x and thesilicide film 22. - Thereafter, the steps of forming an interlayer insulating film on the substrate, forming respective plugs reaching the source/drain regions, forming a DRAM capacitor on the interlayer insulating film in the memory region Rdram, and forming a multilevel wiring layer insulated by the interlayer insulating film are subsequently performed, though the depiction thereof is omitted, whereby the memory embedded semiconductor device is formed. Although the present embodiment has formed the DRAM as the memory region, it is also possible to form a ROM or the like instead of the DRAM.
- In accordance with the method for fabricating a semiconductor device of the present embodiment, the ion implanted
regions FIG. 1B inhibit the diffusion of cobalt in each of the gate electrode and source/drain diffusion layers of the memory transistor so that a silicide reaction is suppressed. - Since each of the ion implanted
regions - Thus, the fabrication method according to the present embodiment has implanted nitrogen molecular ions for suppressing a silicide reaction or the like only in the memory transistors to form the amorphized ion implanted regions in the regions each at a predetermined depth from the surface and then performed silicidation in each of the memory region Rdram and the logic region Rlogc by using a salicide technology. Since the ion implanted regions suppress a silicide reaction in the source/drain diffusion layers of the memory transistors, it becomes possible to reduce the thickness of the silicide film of each of the memory transistors, while increasing the thickness of the silicide film of each of the logic transistors. This allows a reduction in junction leakage in the memory transistors and the higher-speed operation thereof, while retaining the conventional performance of the logic transistors in the memory embedded semiconductor device.
- In the case where the thickness of such a silicide film is suppressed in a transistor having a dual gate electrode composed of an n-type polysilicon layer and a p-type polysilicon layer, such as a logic transistor, the silicide film on the boundary region between the n-type polysilicon layer and the p-type polysilicon layer is abnormally thinned at the gate electrode portion so that there are concerns about the agglomeration of crystal grains which occurs in the silicide film when a thermal process is performed.
- However, the present embodiment has thinned the silicide film only in each of the transistors in the memory region composed of DRAM memory cells or ROM memory cells each using a gate electrode of one conductivity type (which is normally an n-type). Accordingly, there is no boundary region between the n-type polysilicon layer and the p-type polysilicon layer so that the abnormal thinning of the silicide film does not occur. This allows the higher-speed operation of the memory embedded semiconductor device without affecting the reliability thereof.
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FIGS. 2A to 2D show the cross-sectional states of a DRAM embedded semiconductor device according to a second embodiment of the present invention in the individual process steps of a fabrication method therefor. As shown in the drawings, the memory embedded semiconductor device according to the second embodiment has a logic region Rlogc comprising logic transistors and a DRAM region Rdram comprising transistors (memory transistors) each as a part of a DRAM memory cell, which are disposed in acommon semiconductor substrate 1 in the same manner as in the first embodiment. The drawings show a structure in which both a p-channel transistor (pMISFET) and an n-channel transistor (nMISFET) are used as the logic transistors and n-channel transistors are used as the memory transistors. - First, the same process as illustrated in
FIG. 1A is performed in the step shown inFIG. 2A by the procedure described in the first embodiment so that isolation regions 7 (STIs), a p-type well region 2, an n-type well region 3, a triple p-type well region 4, an n-type burieddiffusion region 5, agate insulating film 14, therespective polysilicon films respective sidewalls FIG. 2A . - Next, in the step shown in
FIG. 2B , anoxide film 32 with a thickness of about 1 nm is formed on the silicon layer exposed on the substrate by an oxidation process using an oxygen plasma. Instead of the oxidation process using the oxygen plasma, it is also possible to use a normal thermal oxidation process, a native-oxide-film formation process subsequent to a wet process, a CVD process, or the like to form theoxide film 32. Then, the portion of theoxide film 32 located in the region other than the memory region Rdram is selectively removed by wet etching using a resist film Re2 covering the memory region Rdram. - Next, in the step shown in
FIG. 2C , acobalt film 31 with a thickness of 10 nm is deposited to cover the surface of the substrate exposed in the logic region Rlogc and cover theoxide film 32 in the memory region Rdram. - Next, in the step shown in
FIG. 2D , a thermal process is performed at a temperature of 600° C. for about 30 minutes, thereby causing a reaction between silicon and cobalt and forming a silicide film. Then, unreacted cobalt is removed by using a solution mixture (SPM) of a sulfuric acid and an aqueous hydrogen peroxide. Thereafter, a thermal treatment is performed at a temperature of 750° C. for about 30 seconds, thereby forming a cobalt silicide film serving as the gate electrode of each of the MISFETs and a part of each of the source/drain regions thereof. Since thethin oxide film 32 is interposed between thecobalt film 31 and the silicon layer in the memory region Rdram, a silicide reaction is suppressed so that a thin silicide film is formed therein. - In the logic region Rlogc, the
gate electrode 10 of the pMISFET is therefore composed of the p-type polysilicon film 15 as the lower electrode and thesilicide film 13 as the upper electrode and thegate electrode 11 of the nMISFET is composed of the n-type polysilicon film 16 as the lower electrode and thesilicide film 13 as the upper electrode. The source/drain regions of the pMISFET are composed of the p-type source/drain diffusion layers 19 and thesilicide films 12, while the source/drain regions of the nMISFET are composed of the n-type source/drain diffusion layers 17 and thesilicide films 12. - In the memory region Rdram, on the other hand, the
gate electrode 26 of each of the memory transistors is composed of the n-type polysilicon film 16 as the lower electrode and the relativelythin silicide film 23 as the upper electrode. The source/drain regions of the memory transistor are composed of the n-type source/drain diffusion layers 27 and the relativelythin silicide films 22. - Thereafter, the steps of forming an interlayer insulating film on the substrate, forming respective plugs reaching the source/drain regions, forming a DRAM capacitor on the interlayer insulating film in the memory region Rdram, and forming multilayer wiring insulated by the interlayer insulating film are subsequently performed, though the depiction thereof is omitted, whereby the memory embedded semiconductor device is formed. Although the present embodiment has formed the DRAM as the memory region, it is also possible to form a ROM or the like instead of the DRAM.
- In accordance with the method for fabricating a memory embedded semiconductor device of the present embodiment, the diffusion of cobalt in the step illustrated in
FIG. 2C is suppressed in the memory region Rdram by theoxide film 32 formed in the step illustrated inFIG. 2B so that a silicide reaction above thepolysilicon film 26 and source/drain diffusion layers 27 of the memory transistor is suppressed. As a result, a relatively thick cobalt silicide film with a thickness of about 30 nm can be formed on each of the logic/drain diffusion layers 17 and 19 in the logic region Rlogc and a relatively thin cobalt silicide film with a limited thickness of about 20 nm can be formed on each of the source/drain diffusion layers 27 in the memory region Rlogc. As a result, the junction can substantially be deepened in each of the memory transistors so that a junction leakage to the substrate is suppressed in each of the memory transistors. In addition, the present embodiment allows the thickness of thesilicide film 22 formed on each of the source/drain diffusion layers 27 of the memory transistors to be set as required by adjusting the thickness of theoxide film 32. - Thus, the fabrication method according to the present embodiment has performed silicidation with respect to each of the memory region Rdram and the logic region Rlogc by using a salicide technology with the memory region Rdram being covered with the oxide film. Since the oxide film suppresses the silicidation in the source/drain diffusion layers of the memory transistors, it becomes possible to reduce the thickness of the silicide film of each of the memory transistors, while increasing the thickness of the silicide film of each of the logic transistors. This allows a reduction in junction leakage in the memory transistor and the higher-speed operation thereof, while retaining the conventional performance of the logic transistors in the memory embedded semiconductor device.
- In the case where the thickness of the silicide film is thus suppressed, the cobalt silicide film as the upper electrode of the gate electrode is also reduced in thickness so that there are concerns about the breakage of the silicide film at the gate electrode due to agglomeration. However, the present embodiment has suppressed the thickness of the cobalt silicide film only in each of the transistors in the memory region composed of DRAM memory cells or ROM memory cells each using only the gate electrode of one conductivity type (which is normally an n-type) and hence there is no boundary region between the n-type polysilicon and the p-type polysilicon so that a problem does not occur.
- Although each of the first and second embodiments has provided the cobalt silicide film even over the polysilicon film included in the gate electrode, the present invention is not limited to such embodiments. The same effects as achieved in the foregoing individual embodiments are achievable by applying the present invention even to the case where the gate electrode of each of the MIS transistors is a polymetal gate, a metal gate, a polysilicon gate, or the like. In that case, an insulating film for suppressing a silicide reaction or the like may be provided appropriately in the uppermost layer of the gate electrode in the state shown in
FIGS. 1A and 2A . - Thus, the memory embedded semiconductor device according to the present invention allows a reduction in leakage in each of the memory transistors and the higher-speed operation thereof, while retaining the performance of the logic transistors, and thereby implements a high-speed, large-capacity, and low-power memory embedded semiconductor device and a fabrication method therefor. Hence, the memory embedded semiconductor device according to the present invention is useful as a memory embedded semiconductor device comprising a memory such as a DRAM or a ROM and a high-speed CMOS logic circuit or the like.
Claims (13)
1-10. (canceled)
11. A method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of:
(a) forming gate electrodes and source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate;
(b) implanting ions of an impurity for suppressing a silicide reaction into at least the source/drain diffusion layers of the memory transistor by using an implant mask covering the logic region to form ion implanted regions; and
(c) after step (b), forming a first silicide film on each of the source/drain diffusion layers of the logic transistor and a second silicide film on each of the source/drain diffusion layers of the memory transistor,
wherein in step (c), an under side of a region where the second silicide film is formed on each of the source/drain diffusion layers of the memory transistor has the ion implanted regions, and
an under side of a region where the first silicide film is formed on each of the source/drain diffusion layers of the logic transistor has no ion implanted region.
12. The method of claim 11 , wherein the second silicide film has a thickness thinner than the first silicide film.
13. The method of claim 11 , wherein:
in step (a), polysilicon electrodes having exposed upper surfaces are formed as gate electrodes of each of the memory transistor and the logic transistor,
in step (b), ions of the impurity for suppressing a silicide reaction is also implanted in the polysilicon electrodes of the memory transistor,
in step (c), a third silicide film is formed on each of the polysilicon electrodes of the logic transistor and a fourth silicide film is formed on each of the polysilicon electrodes of the memory transistor.
14. The method of claim 13 , wherein the fourth silicide film has a thickness thinner than the third silicide film.
15. The method of claim 11 , wherein the ions of the impurity for suppressing a silicide reaction are ions of an impurity selected from nitrogen, argon, neon, arsenic, silicon, and germanium.
16. The method of claim 11 , wherein each of the ion implanted regions is an amorphous layer.
17. The method of claim 11 , wherein the memory region is random access memory or read only memory.
18. A method for fabricating a memory embedded semiconductor device comprising a memory region having a memory transistor and a logic region having a logic transistor each provided in a common semiconductor substrate, the method comprising the steps of:
(a) forming gate electrodes and source/drain diffusion layers of each of the memory transistor and the logic transistor in the semiconductor substrate;
(b) forming an insulating film for suppressing a silicide reaction covering the memory region and having an opening over the logic region; and
(c) depositing a metal film over each of the logic region and the memory region with the insulating film for suppressing a silicide reaction being formed to form a first silicide film through silicidation on each of the source/drain diffusion layers of the logic transistor and a second silicide film through silicidation on each of the source/drain diffusion layers of the memory transistor.
19. The method of claim 18 , wherein the second silicide film has a thickness thinner than the first silicide film.
20. The method of claim 18 , wherein:
in step (a), polysilicon electrodes having exposed upper surfaces are formed as gate electrodes of each of the memory transistor and the logic transistor,
in step (b), the insulating film for suppressing a silicide reaction is also formed on each of the polysilicon electrodes of the memory transistor, and
in step (c), a third silicide film is formed on each of the polysilicon electrodes of the logic transistor and a fourth silicide film is formed on each of the polysilicon electrodes of the memory transistor.
21. The method of claim 20 , wherein the fourth silicide film has a thickness thinner than the third silicide film.
22. The method of claim 18 , wherein the insulating film for suppressing a silicide reaction is an oxide film.
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US11/511,441 US20060292799A1 (en) | 2003-11-07 | 2006-08-29 | Memory embedded semiconductor device and method for fabricating the same |
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JP2003378407A JP4308625B2 (en) | 2003-11-07 | 2003-11-07 | Memory-embedded semiconductor device and manufacturing method thereof |
US10/979,222 US7109536B2 (en) | 2003-11-07 | 2004-11-03 | Memory embedded semiconductor device and method for fabricating the same |
US11/511,441 US20060292799A1 (en) | 2003-11-07 | 2006-08-29 | Memory embedded semiconductor device and method for fabricating the same |
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US8044470B2 (en) | 2008-05-23 | 2011-10-25 | Renesas Electronics Corporation | Semiconductor device and method of fabricating the same |
US20130009231A1 (en) * | 2011-07-08 | 2013-01-10 | Broadcom Corporation | Method for Efficiently Fabricating Memory Cells with Logic FETs and Related Structure |
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JP4870908B2 (en) * | 2004-01-23 | 2012-02-08 | エルピーダメモリ株式会社 | Manufacturing method of semiconductor device |
EP1677371A1 (en) * | 2004-12-30 | 2006-07-05 | STMicroelectronics S.r.l. | Dual resistance heater for phase change devices and manufacturing method thereof |
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JP2007019178A (en) * | 2005-07-06 | 2007-01-25 | Toshiba Corp | Semiconductor device and its manufacturing method |
JP4822982B2 (en) * | 2006-08-21 | 2011-11-24 | 株式会社東芝 | Manufacturing method of semiconductor device |
JP2008098504A (en) * | 2006-10-13 | 2008-04-24 | Toshiba Corp | Manufacturing method of semiconductor device |
US7482217B1 (en) * | 2007-12-03 | 2009-01-27 | Spansion Llc | Forming metal-semiconductor films having different thicknesses within different regions of an electronic device |
JP2010135553A (en) * | 2008-12-04 | 2010-06-17 | Renesas Technology Corp | Semiconductor device and method for manufacturing the same |
CN102468162B (en) * | 2010-10-29 | 2014-03-12 | 中芯国际集成电路制造(北京)有限公司 | Production method for n-channel metal oxide semiconductor (NMOS) field effect transistor |
JP5847537B2 (en) * | 2011-10-28 | 2016-01-27 | ルネサスエレクトロニクス株式会社 | Semiconductor device manufacturing method and semiconductor device |
US9876030B1 (en) * | 2016-08-24 | 2018-01-23 | Toshiba Memory Corporation | Semiconductor device and method for manufacturing same |
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Also Published As
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CN100429777C (en) | 2008-10-29 |
US20050101076A1 (en) | 2005-05-12 |
JP4308625B2 (en) | 2009-08-05 |
CN1614785A (en) | 2005-05-11 |
JP2005142422A (en) | 2005-06-02 |
US7109536B2 (en) | 2006-09-19 |
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