CN105448693A - Forming method of tungsten electrode - Google Patents
Forming method of tungsten electrode Download PDFInfo
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- CN105448693A CN105448693A CN201410521989.0A CN201410521989A CN105448693A CN 105448693 A CN105448693 A CN 105448693A CN 201410521989 A CN201410521989 A CN 201410521989A CN 105448693 A CN105448693 A CN 105448693A
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- formation method
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- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 title claims abstract description 269
- 229910052721 tungsten Inorganic materials 0.000 title claims abstract description 268
- 239000010937 tungsten Substances 0.000 title claims abstract description 268
- 238000000034 method Methods 0.000 title claims abstract description 91
- 239000004065 semiconductor Substances 0.000 claims abstract description 86
- 239000000758 substrate Substances 0.000 claims abstract description 55
- 230000015572 biosynthetic process Effects 0.000 claims description 66
- 238000005530 etching Methods 0.000 claims description 27
- 238000002230 thermal chemical vapour deposition Methods 0.000 claims description 27
- 238000009792 diffusion process Methods 0.000 claims description 18
- 238000001312 dry etching Methods 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 12
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical group [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 5
- 239000010410 layer Substances 0.000 abstract description 190
- 239000012495 reaction gas Substances 0.000 abstract description 3
- 239000012792 core layer Substances 0.000 abstract 2
- 239000007789 gas Substances 0.000 description 46
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 5
- 238000010276 construction Methods 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 229910052731 fluorine Inorganic materials 0.000 description 5
- 239000011737 fluorine Substances 0.000 description 5
- 238000003786 synthesis reaction Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000011229 interlayer Substances 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 239000003989 dielectric material Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000000231 atomic layer deposition Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QKCGXXHCELUCKW-UHFFFAOYSA-N n-[4-[4-(dinaphthalen-2-ylamino)phenyl]phenyl]-n-naphthalen-2-ylnaphthalen-2-amine Chemical compound C1=CC=CC2=CC(N(C=3C=CC(=CC=3)C=3C=CC(=CC=3)N(C=3C=C4C=CC=CC4=CC=3)C=3C=C4C=CC=CC4=CC=3)C3=CC4=CC=CC=C4C=C3)=CC=C21 QKCGXXHCELUCKW-UHFFFAOYSA-N 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 description 1
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- Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
- Electrodes Of Semiconductors (AREA)
Abstract
The invention provides a forming method of a tungsten electrode. The method comprises the steps of: forming a first opening in a semiconductor substrate, forming a tungsten layer respectively on the side wall and the bottom part of the first opening and the surface of the semiconductor substrate, then removing the tungsten layer on the surface of the semiconductor substrate, and at least reserving a part of tungsten layer on the bottom part of the first opening; and then using the residual tungsten layer in the first opening as a core layer, and continuously forming tungsten to fill the first opening. After tungsten on the surface of the first opening is removed, tungsten cannot be formed on the surface of the semiconductor surface in the tungsten forming process with the residual tungsten layer in the first opening used as the core layer, so that the first opening is prevented from being blocked by tungsten on the surface of the semiconductor substrate, and the problem that reaction gas fails to enter the first opening is solved, the number and size of gaps in tungsten formed in the opening are further reduced, and the performance of the tungsten electrode is improved.
Description
Technical field
The present invention relates to field of semiconductor manufacture, especially relate to a kind of formation method of tungsten electrode.
Background technology
Along with the develop rapidly of integrated circuit (being called for short IC) manufacturing technology, the process node of traditional integrated circuit reduces gradually, the size of integrated circuit (IC)-components constantly reduces, in a wafer, the quantity of semiconductor element constantly increases, and integrated circuit preparation technology constantly reforms the performance improving integrated circuit (IC)-components for this reason.
As the requirement in order to meet semiconductor element increasing number, a wafer often comprises the semiconductor element of sandwich construction, and the semiconductor element of adjacent layer realizes electrical connection by metal interconnect structure, thus semiconductor element quantity is increased on the chip of particular area, improve the integrated level of semiconductor device.
Preparation process with reference to the semiconductor device of the existing sandwich construction of figure 1 comprises:
After forming transistor 11 over the semiconductor substrate 10, at the coated dielectric layer 13 of transistor 11 periphery; In dielectric layer 13, offer the through hole of turn-on transistor 11 source-drain area 12, and in through hole, fill tungsten to form tungsten electrode 14.Afterwards, described transistor 11 and dielectric layer 13 form interlayer dielectric layer 15, and offer the grid of transistor 11 described in conducting and the through hole of metal plug 14 in interlayer dielectric layer 15 after, the material such as filling aluminum and tungsten forms connector 16 and 17 in this through hole; The semiconductor element be connected with described connector 16 and 17 is formed afterwards again on described interlayer dielectric layer 15 ... repeat according to this, thus form the semiconductor element of sandwich construction on the same semiconductor substrate.
But, along with the process node of integrated circuit constantly reduces, the depth-to-width ratio being opened in the through hole in dielectric layer increases, thus, with reference to figure 2, as when filling tungsten 141 in the through hole in dielectric layer 13, space 18 can be formed at the tungsten layer of dielectric layer through hole, thus affecting the performance of the tungsten electrode of follow-up formation.
In order to overcome above-mentioned defect, in conjunction with reference to figure 3, fill tungsten in the through hole to described dielectric layer 13 after, etching technics can be adopted to reopen described through hole to remove via hollow gap 18, in the new opening 19 formed, filling tungsten 142 more afterwards.
Obviously can reduce finally to be formed at conduction by above-mentioned technique and form the voidage being filled with part tungsten, improve the performance of the tungsten electrode of follow-up formation.But in practical operation, with reference to figure 4, because the depth-to-width ratio of opening 19 is still comparatively large, when filling tungsten 142 in described opening 19, still can form space 181, the tungsten electrode performance thus formed still cannot meet the semiconductor device development requirement improved constantly.
For this reason, the performance how improving tungsten electrode is further the problem that those skilled in the art need solution badly.
Summary of the invention
The problem that the present invention solves is to provide a kind of formation method of tungsten electrode, to improve the performance of tungsten electrode.
For solving the problem, the formation method of a kind of tungsten electrode of the present invention, comprising:
Semiconductor base is provided, in described semiconductor base, forms the first opening;
Tungsten layer is formed in the sidewall of described first opening and bottom and described semiconductor substrate surface;
Remove the tungsten layer of described semiconductor substrate surface, at least retain the tungsten layer being positioned at the segment thickness of described first open bottom;
In described first opening, remaining tungsten layer continue to form tungsten as nucleating layer, to filling full described first opening, forming tungsten electrode.
Alternatively, comprise at the sidewall of described first opening and the step of bottom and described semiconductor substrate surface formation tungsten layer:
Described tungsten layer fills described first opening;
Remove the tungsten layer of described semiconductor substrate surface, at least retain the step being positioned at the tungsten layer of the segment thickness of described first open bottom and comprise:
Adopt dry etching to remove the tungsten layer of described semiconductor substrate surface, and form the second opening in the tungsten layer of described first opening.
Alternatively, the depth-to-width ratio of described second opening is less than the depth-to-width ratio of described first opening.
Alternatively, the top end opening size of described second opening is greater than bottom opening size.
Alternatively, the step removing the tungsten layer of described semiconductor substrate surface is: adopt dry etching to remove the tungsten layer of described semiconductor substrate surface.
Alternatively, the etching gas flow of described dry etching is 3 ~ 40sccm.
Alternatively, the temperature of described dry etching is 30 ~ 100 DEG C, and power is 300 ~ 900W, and air pressure is 0.1 ~ 1torr.
Alternatively, the etching gas of described dry etching comprises NF
3.
Alternatively, in described first opening, remain tungsten layer continue to form the step of tungsten as nucleating layer and comprise: adopt thermal chemical vapor deposition method, in described first opening, remain tungsten layer continue to form tungsten as nucleating layer.
Alternatively, the technique of described thermal chemical vapor deposition method comprises:
With H
2and WF
6as reacting gas, air pressure is 20 ~ 60torr, and temperature is 350 ~ 450 DEG C.
Alternatively, described H
2with WF
6flow-rate ratio be 10:1 ~ 30:1.
Alternatively, described H
2flow be 5000 ~ 15000sccm, WF
6flow be 200 ~ 600sccm.
Alternatively, the step forming tungsten layer in the sidewall of described first opening and bottom and described semiconductor substrate surface comprises: be formed into stratum nucleare in the sidewall of described first opening and bottom and described semiconductor substrate surface; Afterwards, the basis of described nucleating layer is continued form tungsten, to form described tungsten layer.
Alternatively, the formation method of described nucleating layer is thermal chemical vapor deposition method, and described thermal chemical vapor deposition method comprises with B
2h
6and WF
6as reacting gas.
Alternatively, the technological parameter forming the thermal chemical vapor deposition method of described nucleating layer comprises: air pressure is 20 ~ 60torr, and temperature is 250 ~ 350 DEG C, B
2h
6flow be 200 ~ 500sccm, WF
6flow be 150 ~ 350sccm.
Alternatively, described B
2h
6with WF
6flow-rate ratio be 1:1 ~ 2:1.
Alternatively, described reacting gas also comprises H
2.
Alternatively, after formation first opening, before forming described tungsten layer, the formation method of described tungsten electrode also comprises:
At sidewall and the bottom formation diffusion impervious layer of described first opening.
Alternatively, the material of described diffusion impervious layer is titanium nitride.
Alternatively, the depth-to-width ratio of described first opening is more than or equal to 15:1.
Compared with prior art, technical scheme of the present invention has the following advantages:
The sidewall of the first opening in described semiconductor base and bottom, and after semiconductor substrate surface formation tungsten layer, remove the tungsten layer of described semiconductor substrate surface, at least retain the tungsten layer being positioned at the segment thickness of described first open bottom; Afterwards, in described first opening, remaining tungsten layer continue to form tungsten as nucleating layer, to filling full described first opening, forming tungsten electrode.Because semiconductor substrate surface loses the basis continuing to form tungsten, in described first opening, remain tungsten layer continue to be formed in tungsten process as nucleating layer, tungsten cannot be formed again at semiconductor substrate surface, thus solution the first opening is positioned at the tungsten shutoff of described substrate surface formation, cause reacting gas cannot enter problem in described first opening, reduce quantity and the volume in the space in being formed in opening tungsten, and then improve the performance of tungsten electrode of follow-up formation.
Further alternatively, when adopting dry etch process removal to be formed at semiconductor substrate surface tungsten layer, by reducing etching gas flow (flow of etching gas is only 2 ~ 40sccm particularly), when making to etch described tungsten layer, etching gas consumes larger when etching is positioned at semiconductor substrate surface and be positioned at the tungsten layer of the first open upper end, and the etching gas entering open lower end is less, when guaranteeing to remove the tungsten layer being positioned at described semiconductor substrate surface, at least retain the part tungsten layer being positioned at described open bottom, thus for follow-up only by the tungsten layer basis remaining in open bottom being continued forms the described opening tungsten of filling, avoid continuing formation on a semiconductor substrate to prepare,
And consume larger during the tungsten layer of etching semiconductor substrate surface and the first open upper end, and the etching gas entering open lower end is less, effectively can expand the opening size of the second opening in the tungsten layer that is formed in described first opening, thus when follow-up employing thermal chemical vapor deposition method continues to form tungsten using remaining tungsten layer in described first opening as nucleating layer, reacting gas of being more convenient for enters in described second opening, improve the synthesis speed that second opens the tungsten of bottom, the opening solving the second opening closes too early; And reduce to cause reacting gas cannot enter in the second opening based on the second opening is closed too early, and result from quantity and the volume in the space in tungsten electrode, improve the performance of the tungsten electrode of follow-up formation.
Accompanying drawing explanation
Fig. 1 and Fig. 4 is the structural representation of the semiconductor device of existing sandwich construction;
Fig. 5 to Figure 15 is the schematic diagram of formation method one embodiment of tungsten electrode of the present invention.
Embodiment
As described in the background art, along with the development of semiconductor device, the required precision of corresponding semiconductor device improves constantly, but when existing technique is formed and has the semiconductor device of sandwich construction, be arranged in dielectric layer, for connect transistor and other layer of semiconductor element tungsten electrode in can form space, thus reduce tungsten electrode performance, and then affect the performance of semiconductor device.Especially along with the development of semiconductor device, the depth-to-width ratio for the formation of the opening of tungsten electrode constantly increases, and in tungsten electrode, interstitial defect is obvious all the more, and the impact of the semiconductor device day by day improved for required precision is larger.
Analyze its reason, along with semiconductor technology evolves, the depth-to-width ratio for the formation of tungsten electrode through hole increases gradually, and thus the thermal chemical vapor deposition method that adopts forms tungsten electrode more.When forming tungsten electrode, needing first to form one deck nucleating layer at the sidewall of dielectric layer and through hole and bottom, thermal chemical vapor deposition method continued growth tungsten metal level could be adopted afterwards on the basis of nucleating layer, to fill up the through hole of described dielectric layer.
Wherein, when forming described nucleating layer, dielectric layer surface and through-hole side wall upper end more easily form described nucleating layer, make at the nucleating layer of dielectric layer surface and through-hole side wall upper end thicker.In addition when the technique such as follow-up employing thermal chemical vapor deposition method continues to form tungsten on described nucleating layer basis, reacting gas through dielectric layer surface and through-hole side wall upper end is more than the reacting gas entering through hole depths, thus follow-up on nucleating layer basis continue formed tungsten layer time, the tungsten synthesis speed of dielectric layer surface and through hole upper end is faster, thus causes the through hole of dielectric layer to close; Although in existing technique, can after the certain thickness tungsten layer of formation, etching removes the tungsten being positioned at through-hole surfaces, open described through hole to remove the space be formed in through hole in tungsten layer, and continue to form tungsten layer, but limit based on the depth-to-width ratio that through hole is larger, reacting gas through dielectric layer surface and through-hole side wall upper end is more than the reacting gas entering through hole depths, thus through hole closes again very soon, in the tungsten of through hole, form new space, thus the final electrode performance formed of impact.
For this reason, the invention provides a kind of formation method of tungsten electrode.Comprise: in semiconductor base, form the first opening, and after tungsten layer is formed on the sidewall of described first opening and bottom and described semiconductor substrate surface, remove the tungsten layer of described semiconductor substrate surface, at least retain the tungsten layer being positioned at the segment thickness of described first open bottom; In described first opening, remain tungsten layer afterwards continue to form tungsten, to fill completely described first opening as nucleating layer.Because eliminated the tungsten of described semiconductor substrate surface, semiconductor substrate surface loses the basis continuing to form tungsten, so remain in described first opening tungsten layer as nucleating layer continue formed tungsten process in, the opening of the first opening can be avoided to be positioned at the tungsten shutoff of described semiconductor substrate surface formation, cause reacting gas cannot enter problem in described first opening, and then reduce quantity and the volume in the space in being formed in opening tungsten, improve the performance of tungsten electrode.
For enabling above-mentioned purpose of the present invention, feature and advantage more become apparent, below in conjunction with accompanying drawing, to be described in detail specific embodiments of the invention.
The structural representation of an embodiment of the formation method of tungsten electrode of Fig. 5 ~ Figure 15 for providing.
The formation method of the present embodiment tungsten electrode specifically comprises:
Shown in figure 5, provide semiconductor base.
Described semiconductor base can comprise Semiconductor substrate.Or, comprise Semiconductor substrate, be positioned in Semiconductor substrate and inject the semiconductor element such as transistor arrangement and interconnection structure, and be positioned at the structures such as dielectric layer in described Semiconductor substrate.
In the present embodiment, described semiconductor base comprises: Semiconductor substrate 20, is positioned at the transistor arrangement 21 in described Semiconductor substrate, and to be positioned at above described Semiconductor substrate 20 and to cover the dielectric layer 30 of described transistor arrangement 21.
Described Semiconductor substrate 20 is silicon substrate, but in other embodiments, described Semiconductor substrate 20 also can be germanium, germanium silicon, gallium arsenide substrate or silicon-on-insulator substrate, common Semiconductor substrate all can be used as the Semiconductor substrate in the present embodiment, and the materials and structures of the present invention to described Semiconductor substrate does not limit.
In the present embodiment, described dielectric layer 30 adopts dielectric material, further alternatively, the material of described dielectric layer 30 is low-K dielectric material (K value is less than or equal to 3.0), as the silica of loose structure and the silica etc. of carbon dope, thus effectively reduce the parasitic capacitance between the follow-up electrode be formed in described dielectric layer 30.
In the present embodiment, the material of described dielectric layer 30 is silica, but the material of the present invention to described dielectric layer 30 does not limit.
Then with reference to figure 6, in described semiconductor base, the first opening 31 is formed, follow-up for the formation of tungsten electrode.
In the present embodiment, the step forming the first opening 31 in described semiconductor base comprises, in described dielectric layer 30, form the first opening 31, and described first opening 31 exposes the source electrode (or drain electrode) 22 of described transistor arrangement 21.
Alternatively, in the present embodiment, the depth-to-width ratio of described first opening 31 is more than or equal to 15:1.
Described first opening 31 has larger depth-to-width ratio, contributes to the characteristic size of the semiconductor device reducing follow-up formation.But the depth-to-width ratio of described first opening 31 is not limited in above-mentioned scope, the size of the present invention to described first opening 31 is not specifically limited.
In the present embodiment, while described dielectric layer 30 forms the first opening 31, in described dielectric layer 30, form the 3rd opening 32.The depth-to-width ratio of described 3rd opening 32 is less than the depth-to-width ratio of described first opening 31.
Then with reference to figure 7, on the surface of described dielectric layer 30, the sidewall of described first opening 31 and the 3rd opening 32 and bottom, and diffusion impervious layer 33 is formed.
The material of described diffusion impervious layer 33 comprises titanium nitride (TiN), tantalum (Ta) and tantalum nitride (TaN), and formation process is chemical vapour deposition technique, atomic layer deposition method etc.
In the present embodiment, the material of described diffusion impervious layer 33 is titanium nitride.But the material of the present invention to described diffusion impervious layer does not limit.
Described diffusion impervious layer 33 after formation electrode, effectively can suppress the atom in electrode material to spread in described dielectric layer, thus improve the performance of semiconductor device of follow-up formation follow-up in the first opening 31 and the 3rd opening 32; In addition, titanium nitride is adopted also effectively can to improve the cohesive force between the electrode of follow-up formation and dielectric layer 33 as diffusion impervious layer.
Then, in described first opening 31 and the 3rd opening 32, tungsten (W) is filled, to form tungsten electrode.
In the present embodiment, the process forming tungsten electrode in described first opening 31 and the 3rd opening 32 comprises:
With reference to figure 8, first on dielectric layer 30 surface, the sidewall of described first opening 31 and the 3rd opening 32 and bottom be formed into stratum nucleare 41; Afterwards with reference to figure 9, the basis of described nucleating layer 41 is continued form tungsten 42, the tungsten 42 above described nucleating layer 41 and nucleating layer 41 forms tungsten layer 40.Tungsten in described nucleating layer 41 is as the follow-up growing point continuing the tungsten 42 formed.
In the present embodiment, the formation process of described nucleating layer 41 is thermal chemical vapor deposition method (ThermalChemicalVaporDeposition).
In the present embodiment, form the thermal chemical vapor deposition method of described nucleating layer 41 with B
2h
6and WF
6as reacting gas.
Wherein, in the thermal chemical vapor deposition method being formed into stratum nucleare 41, if temperature is too small, flow velocity is excessively slow, can hinder tungsten metal synthesis speed, be lowered into the thickness evenness of stratum nucleare; If but temperature is too high, reacting gas flow velocity is too fast, reaction process can be affected equally, cause and cannot be formed into stratum nucleare smoothly, and the reaction gas of too fast flow velocity knows from experience the adhesion reducing tungsten and described diffusion impervious layer, and local thickness's difference of the nucleating layer 41 covering described dielectric layer 30 surface and described first opening 31 sidewall can be increased equally, follow-up on nucleating layer basis continue formed tungsten time, described first opening 31 may be caused closed ahead of time, in the first opening 31, form larger space.
In the present embodiment, the technological parameter of described thermal chemical vapor deposition method comprises: air pressure is 20 ~ 60torr, and temperature is 250 ~ 350 DEG C, B
2h
6flow be 200 ~ 500sccm, WF
6flow be 150 ~ 350sccm.Thus on described diffusion impervious layer 41, cover the uniform nucleating layer 41 of a layer thickness lentamente.
Alternatively, described B
2h
6with WF
6flow-rate ratio be 1:1 ~ 2:1, to improve tungsten convert metals rate, make simultaneously formed tungsten metal stick to diffusion impervious layer surface better.
Further alternatively, described reacting gas also can comprise H
2, thus increase tungsten convert metals rate further, reduce the WF in reacting gas simultaneously
6ratio can improve the thickness evenness of described nucleating layer 41.
Continue with reference to figure 8, if described nucleating layer 41 thickness is excessive, easily cause described first opening 31 blocked; If thickness is too small, be unfavorable for that follow-up continuation on the basis of nucleating layer 41 forms tungsten.
In the present embodiment, the thickness of described nucleating layer 41 is
In conjunction with reference to figure 9, in the present embodiment, after the described nucleating layer 41 of formation, adopt thermal chemical vapor deposition method on the basis of described nucleating layer 41, using the tungsten in nucleating layer 41 as growing point, continue to form tungsten.And be formed into stratum nucleare 41 compared on described diffusion impervious layer 41, described nucleating layer 41 continues form tungsten relatively easy.
In the present embodiment, employing thermal chemical vapor deposition method nucleating layer 41 continuing formed tungsten adopts H
2with WF
6as reacting gas.Adopt H
2with WF
6the conversion rate of tungsten can be significantly improved as reacting gas.But reaction temperature and gas velocity must be controlled simultaneously, prevent described first opening 31 from closing too early.The technique that described nucleating layer 41 continues the thermal chemical vapor deposition method forming tungsten specifically comprises:
Control air pressure is 20 ~ 60torr, and temperature is 350 ~ 450 DEG C, H
2flow be 5000 ~ 15000sccm, WF
6flow be 200 ~ 600sccm.
Alternatively, H
2with WF
6flow-rate ratio be 10:1 ~ 30:1.To improve conversion ratio and the synthesis speed of tungsten.
Continue with reference to shown in figure 8 and Fig. 9, in the present embodiment, after forming described tungsten layer 40, described tungsten layer 40 covers described diffusion impervious layer 33 surface, and described tungsten layer 40 fills described first opening 31 and the 3rd opening 32.But based on process technology limit, and the depth-to-width ratio restriction that described first opening 31 is larger, the opening part of described first opening 31 comparatively fast closes, thus there is in the tungsten layer formed in described first opening 31 space 50 of larger volume, described space 50 can have a strong impact on the tungsten electrode performance in follow-up formation and described first opening 31.And based on described 3rd opening 32, there is less depth-to-width ratio, space 51 small volume formed in the tungsten layer 40 in described 3rd opening in 32, less for the follow-up tungsten electrode impact be formed in described 3rd opening 32.
In conjunction with reference to Figure 10 and Figure 11, after forming the tungsten layer 40 of filling described first opening 31 and the 3rd opening 32, remove the tungsten layer being positioned at described dielectric layer 30 surface, at least retain the tungsten layer being positioned at the segment thickness of described first open bottom.
The follow-up tungsten layer that can remain in described first opening continues to form tungsten as nucleating layer, continue to form tungsten, to when filling full described first opening for the formation of tungsten electrode, tungsten on described dielectric layer 30 is removed, the surface of described dielectric layer 30 has lost the basis continuing to form tungsten, thus tungsten cannot directly be formed described dielectric layer 30 surface (being diffusion impervious layer 33 surface in the present embodiment), thus avoid forming tungsten on described dielectric layer 30 surface thus causing the upper end open of the first opening again to close too early, cause reacting gas cannot enter in the second opening 52, thus in the tungsten of the first opening, form the defect in the space of larger submission.
In the present embodiment, dry etching is adopted to remove the tungsten layer 40 being positioned at described dielectric layer 30 surface.
Particularly, adopt the gas containing fluorine base gas as dry etching agent, etching removes the tungsten layer 40 be positioned on described dielectric layer 30.
In the present embodiment, described fluorine base gas is Nitrogen trifluoride (NF
3).In other embodiments, described fluorine base gas also can be other fluorine base gass, or the mist of multiple fluorine base gas, or is the gas of other etching tungsten, and the present invention does not limit for described etching gas.
Alternatively, in the present embodiment, control the flow of etching gas, guaranteeing the tungsten layer removing described dielectric layer 30 surface while, reduce etching gas flow, etching gas is consumed larger when etching is positioned at semiconductor substrate surface and be positioned at the tungsten layer of the first open upper end, and the etching gas entering the first opening depths is less, and then behind the space 50 of removing in described first opening 31 in tungsten material, increase the etching proportional difference of the tungsten of described first opening 31 sidewall upper and lower end, the etch rate of the first opening 31 sidewall upper portion tungsten is made to be greater than the etch rate of described first opening 31 sidewall hypomere part tungsten, and then effectively expand the opening size being formed at described second opening 52.
In the present embodiment, the flow controlling etching gas is 3 ~ 40sccm.
In the present embodiment, after dry etch process, the top end opening size of the second opening 52 formed is greater than bottom opening size, make the second opening 52 larger-size horn-like in upper end open, thus suppress follow-up when continuing to form tungsten material in described second opening 52, the defect that the tungsten that the both sides of described second opening 52 upper end sidewall are formed closes too early.
In addition, in the etch process, temperature controllable, air pressure and power, thus guarantee to remove the tungsten on dielectric layer 33, and remove space 50 in the first opening 31 simultaneously, avoid reaction pressure and tungsten to react too fast, thus accelerate tungsten etch rate, make to be positioned at remaining tungsten bottom described first opening 31 and cross thin and affect subsequent technique and carry out.
In the present embodiment, the reference of described dry etch process comprises: temperature is 30 ~ 100 DEG C, and power is 300 ~ 900W, and air pressure is 0.1 ~ 1torr.
It should be noted that in the present embodiment, fill described first opening 31 at described tungsten layer 40.Remove the tungsten layer on described dielectric layer 30 surface afterwards again, and form the second opening in the tungsten layer of described first opening 31, to remove the space 50 of the tungsten layer 40 being originally arranged in the first opening 31, and the reserve part tungsten bottom the first opening 31.
In other embodiments of the invention, can only filling part tungsten in described first opening 31, namely described tungsten layer does not fill completely described first opening, when described first opening is not closed, carry out above-mentioned dry etch process, to remove the tungsten layer being positioned at described dielectric layer 30 surface, the opening size of first opening of not filling full tungsten can be expanded simultaneously, the opening size making bottom and sidewall be coated with described first open top end of segment thickness tungsten is greater than bottom opening size, the last tungsten only needing reserve part bottom described first opening 31; Or be, when dry etching, remove the tungsten on described first opening 31 sidewall, only need the tungsten of reserve part bottom described first opening 31, above-mentioned simple change is all in protection scope of the present invention simultaneously.The parameter of above-mentioned dry etch process is described above, does not repeat them here.
With reference to Figure 12, after removing the tungsten layer 40 be positioned on described dielectric layer 30, in described first opening, remain tungsten layer (being also the tungsten in described second opening 52) continue to form tungsten as nucleating layer, to filling full described second opening 52, thus form electrode 43 in described first opening 31.Described electrode 43 comprises the tungsten being originally positioned at described first opening 31, and the tungsten of follow-up formation.
And described dielectric layer 30 surface (also namely described diffusion impervious layer 33 is surperficial) has not had tungsten (W), lose the basis continuing to form tungsten on described dielectric layer 30 surface, thus cannot continue on described dielectric layer 30 surface to form tungsten, thus the problem that the opening of the second opening 52 upper end is closed can not be caused because of described dielectric layer 30 forms tungsten.
In the present embodiment, adopt on the tungsten of thermal chemical vapor deposition method bottom the second opening 52 and continue to form tungsten.
In the present embodiment, the method continuing to be formed tungsten in described second opening 52 is thermal chemical vapor deposition method, and technique comprises particularly: with H
2and WF
6as reacting gas, the upper continuation of the tungsten (W) bottom described second opening 52 forms tungsten, to filling full described second opening 52.
In the present embodiment, at the etching technics of the etching gas of above-mentioned employing low discharge (flow of etching gas is 3 ~ 40sccm), removing the tungsten on described dielectric layer 30 surface simultaneously, effectively expand the top end opening size of the second formed opening 52, the top end opening size of described second opening 52 is made to be greater than bottom opening size, thus be more conducive to reacting gas and enter in described second opening, tungsten is formed in the bottom of described second opening 52, and the second opening 52 effectively can be suppressed too early closed and cause reacting gas cannot enter defect in the second opening 52, thus avoid causing thus forming larger space in the tungsten in the second opening 52, and then improve the performance of tungsten electrode of follow-up formation.
In the present embodiment, because the top end opening size of the second opening 52 is greater than bottom opening size, the second opening 52 can be suppressed to close too early, and reacting gas of being more convenient for enters in described second opening 52, now can improve reaction temperature and reaction gas flow, reacting gas is more easily entered bottom described second opening 52, improves the synthesis speed of the tungsten bottom the second opening 52, interstitial probability in the tungsten being reduced in described second opening 52.
In the present embodiment, formed in the second opening 52 in the thermal chemical vapor deposition method of tungsten, air pressure is 20 ~ 60torr, and temperature is 350 ~ 450 DEG C, H
2flow be 5000 ~ 15000sccm, WF
6flow be 200 ~ 600sccm.
Alternatively, H
2with WF
6flow-rate ratio be 10:1 ~ 30:1.
Refer again to Figure 12, when adopting dry etching to remove the described tungsten layer 40 on described dielectric layer 30 surface, depth-to-width ratio based on described 3rd opening 32 is less, be convenient to the bottom that etching gas enters described 3rd opening 32, thus removal amount in the tungsten layer 40 in described 3rd opening 32 can be caused comparatively large, remove even completely.
If the tungsten of remainder in described 3rd opening 32, using the residue tungsten in described second opening 52 as nucleating layer continue formed tungsten process in, can continue using the remaining tungsten in the 3rd opening 32 as nucleating layer to form tungsten, to fill described 3rd opening 32 simultaneously.
If the tungsten in described 3rd opening 32 removes (as shown in figure 11) completely in above-mentioned dry etch process, because lost the basis continuing to form tungsten in the 3rd opening 32, as shown in figure 12, while continue to form tungsten using the residue tungsten in described second opening 52 as nucleating layer, tungsten cannot be formed in described 3rd opening 32.For this reason, in conjunction with reference to Figure 13, fill full tungsten in described second opening 52 after, the techniques such as thermal chemical vapor deposition method can be adopted again, again be formed into stratum nucleare 61 on the surface of described tungsten electrode 43, the 3rd opening 32 and dielectric layer 30; Afterwards, with reference to Figure 14, then thermal chemical vapor deposition method is adopted to continue to form tungsten layer 63, to filling described 3rd opening 32 on the basis of described nucleating layer 61.Based on the depth-to-width ratio that described 3rd opening 32 is less, in the tungsten layer 63 in the 3rd opening 32, excessive space can not be formed.
Then with reference to Figure 15, form tungsten layer 63 in described 3rd opening 32 after, the techniques such as cmp (CMP) are adopted to remove unnecessary tungsten and diffusion impervious layer above described dielectric layer 30, expose described dielectric layer 30 surface, in described first opening, form tungsten electrode 71, in described 3rd opening, form tungsten electrode 72.
Although the present invention discloses as above, the present invention is not defined in this.Any those skilled in the art, without departing from the spirit and scope of the present invention, all can make various changes or modifications, and therefore protection scope of the present invention should be as the criterion with claim limited range.
Claims (20)
1. a formation method for tungsten electrode, is characterized in that, comprising:
Semiconductor base is provided, in described semiconductor base, forms the first opening;
Tungsten layer is formed in the sidewall of described first opening and bottom and described semiconductor substrate surface;
Remove the tungsten layer of described semiconductor substrate surface, at least retain the tungsten layer being positioned at the segment thickness of described first open bottom;
In described first opening, remaining tungsten layer continue to form tungsten as nucleating layer, to filling full described first opening, forming tungsten electrode.
2. the formation method of tungsten electrode as claimed in claim 1, is characterized in that, comprises at the sidewall of described first opening and the step of bottom and described semiconductor substrate surface formation tungsten layer:
Described tungsten layer fills described first opening;
Remove the tungsten layer of described semiconductor substrate surface, at least retain the step being positioned at the tungsten layer of the segment thickness of described first open bottom and comprise:
Adopt dry etching to remove the tungsten layer of described semiconductor substrate surface, and form the second opening in the tungsten layer of described first opening.
3. the formation method of tungsten electrode as claimed in claim 2, it is characterized in that, the depth-to-width ratio of described second opening is less than the depth-to-width ratio of described first opening.
4. the formation method of tungsten electrode as claimed in claim 2, it is characterized in that, the top end opening size of described second opening is greater than bottom opening size.
5. the formation method of tungsten electrode as claimed in claim 2, it is characterized in that, the step removing the tungsten layer of described semiconductor substrate surface is: adopt dry etching to remove the tungsten layer of described semiconductor substrate surface.
6. the formation method of tungsten electrode as claimed in claim 5, it is characterized in that, the etching gas flow of described dry etching is 3 ~ 40sccm.
7. the formation method of the tungsten electrode stated as claim 5, it is characterized in that, the temperature of described dry etching is 30 ~ 100 DEG C, and power is 300 ~ 900W, and air pressure is 0.1 ~ 1torr.
8. the formation method of tungsten electrode as claimed in claim 5, it is characterized in that, the etching gas of described dry etching comprises NF
3.
9. the formation method of tungsten electrode as claimed in claim 1, it is characterized in that, in described first opening, remain tungsten layer continue to form the step of tungsten as nucleating layer and comprise: adopt thermal chemical vapor deposition method, in described first opening, remain tungsten layer continue to form tungsten as nucleating layer.
10. the formation method of tungsten electrode as claimed in claim 9, it is characterized in that, the technique of described thermal chemical vapor deposition method comprises:
With H
2and WF
6as reacting gas, air pressure is 20 ~ 60torr, and temperature is 350 ~ 450 DEG C.
The formation method of 11. tungsten electrodes as claimed in claim 10, is characterized in that, described H
2with WF
6flow-rate ratio be 10:1 ~ 30:1.
The formation method of 12. tungsten electrodes as claimed in claim 10, is characterized in that, described H
2flow be 5000 ~ 15000sccm, WF
6flow be 200 ~ 600sccm.
The formation method of 13. tungsten electrodes as claimed in claim 1, it is characterized in that, the step forming tungsten layer in the sidewall of described first opening and bottom and described semiconductor substrate surface comprises: be formed into stratum nucleare in the sidewall of described first opening and bottom and described semiconductor substrate surface; Afterwards, the basis of described nucleating layer is continued form tungsten, to form described tungsten layer.
The formation method of 14. tungsten electrodes as claimed in claim 13, is characterized in that, the formation method of described nucleating layer is thermal chemical vapor deposition method, and described thermal chemical vapor deposition method comprises with B
2h
6and WF
6as reacting gas.
The formation method of 15. tungsten electrodes as claimed in claim 14, it is characterized in that, the technological parameter forming the thermal chemical vapor deposition method of described nucleating layer comprises: air pressure is 20 ~ 60torr, and temperature is 250 ~ 350 DEG C, B
2h
6flow be 200 ~ 500sccm, WF
6flow be 150 ~ 350sccm.
The formation method of 16. tungsten electrodes as claimed in claim 14, is characterized in that, described B
2h
6with WF
6flow-rate ratio be 1:1 ~ 2:1.
The formation method of 17. tungsten electrodes as claimed in claim 14, it is characterized in that, described reacting gas also comprises H
2.
The formation method of 18. tungsten electrodes as claimed in claim 1, is characterized in that, after formation first opening, before forming described tungsten layer, the formation method of described tungsten electrode also comprises:
At sidewall and the bottom formation diffusion impervious layer of described first opening.
The formation method of 19. tungsten electrodes as claimed in claim 18, is characterized in that, the material of described diffusion impervious layer is titanium nitride.
The formation method of 20. tungsten electrodes as claimed in claim 1, it is characterized in that, the depth-to-width ratio of described first opening is more than or equal to 15:1.
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