阅读说明：本技术 具有金属填充的深源极触点的功率mosfet (The power MOSFET of deep source contact with metal filling ) 是由 林福任 F·贝奥奇 Y·刘 L·刘 T·吕 P·林 H·林 于 2016-01-18 设计创作，主要内容包括：本申请公开了一种平面栅功率MOSFET(100),所述平面栅功率MOSFET包括：衬底(105),其具有以第一导电类型掺杂的半导体表面(108)；多个晶体管单元(单元),其包括各自具有在本体区(113)上方的栅极堆叠(111a/112、111b/112)的第一单元(110a)和至少第二单元(110b)。沟槽具有＞3的纵横比,在所述栅极堆叠之间从所述半导体表面的顶侧向下延伸,从而提供从以第二导电类型掺杂的源极(127)到所述衬底的源极触点(SCT)(120)。场板(FP)(128)位于所述栅极堆叠上方,其提供用于所述沟槽的内衬。所述沟槽具有位于其内部的难熔金属或铂族金属(PGM)金属填料(122)。以所述第二导电类型掺杂的漏极(132)位于与所述沟槽相对的所述栅极堆叠侧面上的所述半导体表面中。(This application discloses a kind of planar gate power MOSFET (100), the planar gate power MOSFET includes: substrate (105), has the semiconductor surface (108) adulterated with the first conduction type；Multiple transistor units (unit) comprising the respective first unit (110a) with the gate stack (111a/112,111b/112) above body zone (113) and at least second unit (110b).Groove has the aspect ratio of > 3, it is extended downwardly between the gate stack from the top side of the semiconductor surface, to provide from the source contact (SCT) (120) of the second conduction type impure source (127) to the substrate.Field plate (FP) (128) is located above the gate stack, provides the liner for being used for the groove.The groove has refractory metal on its interior or platinum group metal (PGM) metal packing (122).It is located in the semiconductor surface on the gate stack side opposite with the groove with the drain electrode (132) that second conduction type adulterates.)

1. a kind of manufacture planar gate power metal oxide semiconductor field-effect transistor, that is, planar gate power MOSFET method, Comprising:

Planar gate power MOSFET tube core is provided, the planar gate power MOSFET tube core includes that multiple transistor units are i.e. multiple Unit, the multiple transistor unit include being formed on the substrate with the semiconductor surface adulterated with the first conduction type First unit and at least second unit, the first unit is stacked with first grid and the second unit has second gate Pole stacks, and each gate stack includes: gate electrode, is located on the gate-dielectric above body zone；Groove has At least 3 aspect ratio, from the top of the semiconductor surface between the first grid stacks and the second grid stacks Side extends downwardly, to provide from the substrate to source contact, that is, SCT of the second conduction type impure source；Field plate is FP extends above the gate stack to provide the liner for the groove, and the groove has on its interior Refractory metal or platinum group metal, that is, PGM metal packing, that is, metal packing；And the drain electrode adulterated with second conduction type, It is located in the semiconductor surface on the gate stack side opposite with the groove；

First etching is carried out to the metal packing, for removing the gold along the side wall of the FP above the drain electrode Belong to filler and removes a part of the metal packing in the groove；

Deposit the metal packing, including to fill the groove, and

Second etching is carried out to the metal packing.

2. according to the method described in claim 1, wherein the metal packing includes tungsten (W).

3. according to the method described in claim 1, wherein the metal packing includes Ta, Pt or Pd.

4. according to the method described in claim 1, wherein the gate electrode includes the metal silicide (WSi on polysilicon₂)。

5. according to the method described in claim 1, wherein the substrate includes p+ substrate, and the semiconductor surface includes p Epitaxial layer, and wherein the power MOSFET includes NMOS.

6. according to the method described in claim 1, wherein the substrate includes n+ substrate, and the semiconductor surface includes n Epitaxial layer, and wherein the power MOSFET includes PMOS.

7. according to the method described in claim 1, wherein first etching and second etching all include that plasma loses It carves.

8. according to the method described in claim 1, wherein the FP includes at least one high melting metal layer.

9. according to the method described in claim 1, wherein the groove by the autoregistration that the gate stack provides using being passed through Etching process is formed.

10. according to the method described in claim 1, it further includes the shape at the bottom of the SCT after forming the groove At substrate contact region, the substrate contact region is doped with first conduction type.

11. a kind of plane gate metal oxide semiconductor field effect transistor, that is, power MOSFET comprising:

Substrate has the semiconductor surface adulterated with the first conduction type；

Multiple transistor units, that is, multiple units comprising the first unit formed on the semiconductor surface and at least second Unit, the first unit is stacked with first grid and the second unit is stacked with second grid；

Each gate stack includes: gate electrode, is located on the gate-dielectric above body zone；Groove has extremely It is less 3 aspect ratio, from the top side of the semiconductor surface between the first grid stacks and the second grid stacks It extends downwardly, to provide from the substrate to source contact, that is, SCT of the second conduction type impure source；And field plate That is FP extends above the gate stack to provide the liner for the groove；

The groove has the refractory metal being located in the groove or platinum group metal, that is, PGM filler, that is, metal packing, and

With the drain electrode that second conduction type adulterates, the institute being located on the gate stack side opposite with the groove It states in semiconductor surface.

12. power MOSFET according to claim 11, wherein the metal packing includes tungsten (W).

13. power MOSFET according to claim 11, wherein the metal packing include Ta, Pt or Pd or the Ta, The refractiveness metal silicide of Pt or Pd.

14. power MOSFET according to claim 11, wherein the gate electrode includes the metal silicide on polysilicon (WSi₂)。

15. power MOSFET according to claim 11, wherein the FP includes at least one high melting metal layer.

16. power MOSFET according to claim 11, wherein the substrate includes p+ substrate, and the semiconductor table Face includes p epitaxial layer, and wherein the power MOSFET includes NMOS.

17. power MOSFET according to claim 11, wherein the substrate includes n+ substrate, and the semiconductor table Face includes n epitaxial layer, and wherein the power MOSFET includes PMOS.

18. power MOSFET according to claim 11, wherein the FP includes at least one high melting metal layer.

19. power MOSFET according to claim 11 further includes the substrate contact region at the bottom of the SCT, Wherein the substrate contact region is doped with first conduction type.

20. a kind of plane gate metal oxide semiconductor field effect transistor, that is, power MOSFET comprising:

Substrate has the semiconductor surface adulterated with the first conduction type；

Multiple transistor units, that is, multiple units comprising the first unit formed on the semiconductor surface and at least second Unit, the first unit is stacked with first grid and the second unit is stacked with second grid；

Each gate stack includes: gate electrode, is located on the gate-dielectric above body zone；Groove has extremely It is less 3 aspect ratio, from the top side of the semiconductor surface between the first grid stacks and the second grid stacks It extends downwardly, to provide from the substrate to source contact, that is, SCT of the second conduction type impure source；And field plate That is FP extends above the gate stack to provide the liner for the groove；

The groove has the tungsten being located in the groove or the filler including tungsten, and

With the drain electrode that second conduction type adulterates, the institute being located on the gate stack side opposite with the groove It states in semiconductor surface.

Technical field

Disclosed embodiment is related to planar gate power semiconductor arrangement.

Background technique

For power field effect transistor (FET), lower specific on-resistance (RSP) usually improvement performance (including Improve power conversion efficiency) trend.Power device as a kind of is planar gate groove metal oxide semiconductor FET, all Such as the NEXFET of Texas Instrument^TM。

NEXFET^TMFrom the structure for being similar to lateral diffusion metal oxide semiconductor (LDMOS) transistor, horizontal proliferation Metal-oxide semiconductor (MOS) (LDMOS) transistor can be used for being up to about the amplification of the RF signal in the frequency range of 2GHz.In LDMOS In device, drain electrode is allowed electric current lateral flow by lateral arrangement, and drift region is plugged between channel and drain electrode to provide High Drain-Source breakdown voltage.

In order to make NEXFET^TMHigher dynamic property is realized, by making gate electrode on lightly doped drain extension (LDD) The overlapping of side remains to minimum value and Miller capacitance is reduced to single micromicrofarad.Additionally, NEXFET^TMWith a kind of topology knot Structure, wherein source metal wraps up gate electrode and creates field plate element above LDD region, thus gate terminal and leakage in device Effective electrostatic screen is generated between extreme son.Electric field along the surface LDD has also been stretched out by the field plate that source metal creates Distribution.The field plate feature reduces the height of the peak electric field of the drain electrode corner of gate electrode.By doing so, avoiding in routine The hot carrier's effect of integrity problem is generated in LDMOS device.

Summary of the invention

There is provided the content of present invention and be hereafter will be (including provided attached in specific embodiment in order to introduce in simplified form Figure) in the brief selection of public concept that further describes.The content of present invention is not intended to be limited to the model of theme claimed It encloses.

Disclosed embodiment is from above-mentioned NEXFET^TMPlanar gate power field effect transistor (FET) design start and It modifies to it, including by the way that aluminium-silicone tip of the source contact from source electrode surface to be changed into the extension (epi) on substrate The deep source contact (deep SCT) of metal (for example, W) filling in layer or in substrate itself.Deep SCT Ohmic contact device simultaneously Source electrode and substrate, the source electrode and substrate are doped with reciprocal type.Recognize the depth of metal (for example, W) filling The SCT dead resistance and area normalization on state resistance (RSP) of SCT reduction power fet.Deep SCT usually has high aspect ratio (AR), the opening for being 0.4 μm with critical dimension (CD) between self aligned gate stack is such as being provided for source electrode, and deep Degree is at least 1.2 μm (including gate stacks) so that the AR of depth SCT is big for 3:1 or more.The CD of deep SCT can be about 0.3 μm Or it is smaller, and total depth is about 1.5 μm (gate stack thickness including about 0.5 μm), is about 5:1 so as to cause groove AR.

Disclosed embodiment carrys out autoregistration using gate stack to form deep SCT so as to improve performance, and recognizes Make it difficult to be formed in extension (epi) layer (or substrate) needed for obtaining SCT on substrate to this is electrically isolated simultaneously with drain electrode With low-resistance taper SCT profile.After trench formation, field plate (FP) is formed above gate stack, passes through liner The FP material (for example, refractory metal liner (liner)) of SCT is electrically coupled to deep SCT.

Herein, it is understood that the groove AR of at least 3:1 (being such as in one particular embodiment about 5:1) is to Dan Jin Belong to (for example, W) depth SCT filling and etching process causes significant challenge.The challenge includes metal filling and etch back process, is used Not having any metal residue above FP in formation depth SCT, (metal residue may cause source electrode (because it is connected To the leakage or short circuit between FP) and drain contact), and avoid also connecing the metal that dead resistance is added to RSP in SCT It stitches (interstice coverage).

Disclosed embodiment includes manufacture power planes gate groove metal-oxide semiconductor (MOS) FET (power MOSFET) Method, the method includes providing at least one MOSFET tube core, the MOSFET tube core includes that multiple transistor units are (single Member), the multiple transistor unit includes in the lining with the semiconductor surface (for example, epi) adulterated with the first conduction type The first unit formed on bottom (for example, on chip) and at least second unit.The first unit is stacked with first grid And the second unit is stacked with second grid.Each gate stack includes: gate electrode, the grid being located above body zone On the dielectric of pole；Groove, have be at least 3 AR, the first grid stack and the second grid stack between from The top side of the semiconductor surface extends downwardly.

FP extends above each gate stack to provide the liner for the groove；The groove has position in the inner The metal packing including refractory metal in portion.The drain electrode with second conduction type doping in the semiconductor surface is located at On the gate stack side opposite with the groove.Institute is removed along the side wall of the FP to the first etching of the metal packing It states the metal packing of drain electrode top and removes a part of the metal packing in the groove.Metal packing deposition filling The groove, and depth SCT is completed to the second etching of the metal packing.

Detailed description of the invention

With reference to the drawings, the attached drawing is not necessarily drawn to scale, in which:

Fig. 1 is the exemplary power MOSFET for showing the deep SCT with metal filling according to exemplary implementation scheme The sectional view of a part.

Fig. 2 is the exemplary bimetallic for showing the deep SCT for being used to form power MOSFET according to exemplary implementation scheme The flow chart of step in filler deposition/etch back process.

The enhancement type scanning that Fig. 3 A- Fig. 3 C shows the section of 2 gate stacks is described, and has between the gate stack It is connected to the deep SCT of FP, the FP is located above gate stack, such as from the scanning electricity of a part of disclosed power MOSFET What sub- microscope (SEM) image obtained, this demonstrate that the FP side-walls in drain region successfully remove W residue and in depth W seam is not formed in the area SCT.

Fig. 4 shows the yield tendency chart of power MOSFET device yield, it was demonstrated that be used to form power MOSFET's Other equivalent monometallic filler deposition/etch back process (being illustrated as " the first process ") of deep SCT are compared, and disclosed use is being used Yield when forming bimetallic filler deposition/etch back process (being illustrated as " the second process ") of deep SCT of power MOSFET mentions It is high.

Specific embodiment

Exemplary implementation scheme is described with reference to the drawings, wherein similar reference number is for referring to similar or equivalent member Part.The shown sequence of behavior or event should not be considered as limiting, because some behaviors or event may be with different Sequence occurs and/or occurs simultaneously with other behaviors or event.In addition, realizing can not need according to disclosed method The behavior or event shown.

In addition, the used herein and term " being coupled to (coupled to) " that does not further limit or " with ... couple (couples with) " (s) is intended to describe directly or indirectly to be electrically connected.Therefore, if first device is " coupled " to the second dress Set, then the connection can be by wherein access there is only parasitics it is direct electrical connection or by via include other The indirect electrical connection that device and the insert of connection carry out.For INDIRECT COUPLING, insert does not modify the information of signal usually, but Its adjustable current level, voltage level and/or power level.

Fig. 1 is the exemplary planar grid function for showing the deep SCT 120 with metal filling according to exemplary implementation scheme The sectional view of a part of rate MOSFET (power MOSFET) 100, the power MOSFET are described as having tungsten (as infusibility Metal) or platinum group metal (PGM) filler (metal packing 122) n-channel MOSFET.As known in material science, infusibility gold The identification feature of category is its heat resistance, wherein five kinds of industrial refractory metal (molybdenum (Mo), niobium (Nb), rhenium (Re), tantalum (Ta) and tungsten (W)) all there is the fusing point more than 2000 DEG C, wherein the fusing point of tungsten is 3422 DEG C.PGM include iridium (Ir), osmium (Os), palladium (Pd), Platinum (Pt) and rhodium (Rh).The fusing point of Pt and Pd is respectively 1,769 DEG C and 1,554 DEG C.Such fusing point (can not be difficult with aluminium (Al) Molten metal or PGM) it is compared, the fusing point of aluminium is only 660 DEG C and is therefore not suitable as filling for disclosed metal Deep SCT 120 metal.

Disclosed MOSFET has the form similar to LDMOS device.As it is used herein, LDMOS device and expansion Dispersed metallic oxide semiconductor (DMOS) device is synonymous.Other than tungsten (W), metal packing 122 can also include other infusibilities The metal alloy (including Ti-W) of metal (such as Ta) or PGM (such as Pt or Pd), its metal silicide or this metalloid.

Although being generally described NMOS transistor herein, those of ordinary skill in the art, which should be understood that, to be made PMOS transistor is formed also by n doped region is replaced with p doped region with the information disclosed herein and vice versa, it is in office In a kind of situation, structure is similar.For example, the deep trench that the metal in semiconductor (for example, silicon) is filled will be deep SCT, and And metal filling plug (being typically connected to Met1) in dielectric stack will be drain contact (DCT).Disclosed PMOS function The difference of rate MOSFET device and NMOS power MOSFET device is the doping using opposite types, for example, for NMOS's P/p+ substrate becomes the n/n+ substrate for PMOS, and S/D becomes the p-type doping for PMOS from the n-type doping for NMOS, and And body zone becomes the N-shaped for PMOS from the p-type for NMOS.Therefore, it is disclosed by refractory metal (for example, W) or The method that PGM filler forms deep SCT can be applied to both PMOS and NMOS.

Power MOSFET 100 includes the semiconductor surface for being illustrated as epi layer 108 on substrate 105.Substrate 105 and/ Or epi layer 108 may include silicon, SiGe or other semiconductor materials.However, MOSFET100 can be directly (all in substrate 105 Such as include the substrate with the body silicon of appropriate doping concentration) on formed.One embodiment includes being lightly doped and having to be set The epi layer 108 for increasing the epi thickness degree of device breakdown voltage is counted into, is contacted more positioned at by adjusting SCT trench depth In heavy doping substrate 105.

Power MOSFET 100 includes the drain electrode 132 with drain contact (DCT) 130.DCT 130 includes metal plug 130a and barrier metal liner 130b (for example, Ti/TiN).The source electrode 127 usually formed by ion implanting is surrounded and is coupled Low resistance contact is provided to the source electrode 127 to deep SCT 120, the depth SCT 120.Deep SCT 120 passes through in deep SCT 120 High doped substrate contact region 139 (being doping p+ for p-substrate) at bottom is (alternately through the thin of epi layer 108 Area) source electrode 127 is connected to epi floor 108 or substrate 105, so that electric current can during the operation that power MOSFET 100 is connected With the smallest resistance vertical downflow and the back side of substrate 105 (tube core) can be flowed out.

For external circuit, the back side of substrate 105 is usually source lead, and topside metal (its will be located at one or Drain contact is extended on the top of more dielectric layers 138 and by dielectric layer 138 to drain electrode 132) it is that drain electrode is drawn Foot.The FP 128 of deep SCT 120 carries out Ohmic contact with source electrode 127 at the top corner of the groove of deep SCT 120.Recognize Know, such as the deep SCT groove of polysilicon filling would not allow for 100 proper function of power MOSFET, because in source electrode 127 Semi-conductor diode junction will be will form between substrate 105, this is because they are doped with opposite types (for example, n+ mixes Miscellaneous source electrode 127 and p+ doping substrate 105 and epi layers 108).Therefore, refractory metal or the SCT 120 of PGM filling are with low The area n+ is allowed power MOSFET 100 normally to rise by resistance ohmic connection together with the area p+ (opposite types) constraint (strap) Effect.

As described above, substrate contact region 139 is located at the bottom of depth SCT 120, the substrate contact region 139 usually exists The injection region formed after the etching of groove for deep SCT 120, is doped to type identical with epi layer 108.Substrate The boron doping level of contact zone 139 can be about 1 × 10²⁰cm^-3(for example, 5 × 10¹⁹cm^-3To 1 × 10²¹cm^-3) in order to provide with The low resistance Ohmic contact of substrate 105.Invention shows two transistor units for being used as power MOSFET device building block 110a and 110b is respectively defined as from the midpoint of deep SCT 120 to the midpoint of DCT 130.However, actual power MOSFET device is considered 2D transistor array because there may be cable address in parallel connect (hook) together hundreds of or Thousands of independent active crystal pipe units.In circuit design, it is used to form the 2D transistor array of power MOSFET device Usually constructed by the repetition mirror image of unit cell 110a, 110b.

Although not shown in FIG. 1, the corresponding gate electrode 111a and 111b (quilt of active crystal pipe unit 110a, 110b It is shown as that there is optional silicide layer 117 thereon) it is electrically connected by another metal or doped polycrystalline element (not shown) Together, the metal or doped polycrystalline element are typically connected to the gate electrode terminal of device encapsulation.Since transistor array is logical It is often constructed by the repetition mirror image of the unit cell, therefore a DCT 130 shares two grids on either side, as one A depth SCT 120 shares two grids on either side.

There are one or more dielectric layers 138 above FP 128, such as including one or more deposited oxides Silicon layer (for example, derived from tetraethyl orthosilicate (TEOS), TEOS (BPTEOS)/TEOS of boron and phosphorus doping)) dielectric heap It is folded.Dielectric layer 138 can be the result of standard interlayer dielectric processing (deposition/etching).

There are hard mask materials (for example, oxidation derived from silicon nitride or TEOS (at FP 128) on silicide layer 117 Silicon layer), it is located on gate electrode 111a and 111b, wherein silicide layer 117 reduces grid resistance (Rg), and can also help In disclosed deep SCT etching process.The remaining dielectric substance (being illustrated as dielectric layer 138) of gate stack above and around It can be the dielectric layer of deposition, silicon oxide layer derived from such as TEOS.Gate stack is shown as including optional sidewall spacers Object 143.

FP 128 is arranged to include extending above gate stack and on LDD 129, to provide the LDD to grid The control of Electric field shielding effect around 129 sides.FP 128 may include refractory metal material layer or refractory metal material layer heap Folded (such as TiN/Ti).Refractory metal material exists at the bottom of deep SCT 120.In the presence of can TiN/Ti deposition after Rapid thermal annealing (RTA) step of execution causes to form titanium silicide in the interface Ti/Si for silicon epitaxy layer 108.In addition to Suitably except (sufficiently high) doping concentration, this is for the good Europe between deep SCT 120 and epitaxial layer 108 (or substrate 105) Nurse contact is important.

As described above, being also required to contact with the good ohmic of the source electrode 127 of power MOSFET 100 at top silicon surface. For being described as the power MOSFET 100 of NMOS, the deep SCT 120 of the groove as metal filling provides 127 (its of source electrode It is that n is adulterated) it is connect with the low resistance between epi layer 108 or substrate 105 (it is all that p is adulterated).As described previously for PMOS transistor will use opposite doping, but the part of device is still source side.

For device robustness, it is also necessary to reduce the resistance between the body region p 113 and substrate 105 or epi layer 108. This is the purpose for tilting infusion, and the inclination infusion enters trench side wall area to form doping liner as shown in Figure 1 136.Inclined groove infusion uses the first conduction type, is p-type for power MOSFET 100, because of the power MOSFET 100 is NMOS device.The typical infusion parameter for tilting infusion includes: from 1 × 10¹⁴cm^-2To 5 × 10¹⁵cm^-2's Boron dosage range, the energy range from 20keV to 60keV and the angular range from 5 degree to 25 degree.100 quilt of power MOSFET It is shown as including that the lightly doped drain (LDD) 129 of the drain electrode extension side of grid is provided.

It is considered the deep SCT 120 that a unique feature for disclosed power MOSFET is metal filling, It is extended downwardly to provide the low resistance contact with epi layer 108 or substrate 105 and with source electrode 127.Another specific characteristic quilt The boundary layer being considered between corresponding metal packing (for example, tungsten (W)) layer, such as since chemical vapor deposition (CVD) tungsten is heavy Precursor step during product, the precursor step make pure silane (SiH₄) flowing continues for some time to prepare for CVD tungsten The surface of process.Therefore, boundary layer generally includes tungsten silicide (WSi₂) thin layer (for example, a few nm).

Fig. 2 is shown according to exemplary implementation scheme for manufacturing power MOSFET (power such as shown in FIG. 1 MOSFET 100) exemplary bimetallic filler deposition/etch back process 200 in step flow chart.Step 201 includes providing Power MOSFET tube core, the power MOSFET tube core include multiple transistor units (unit), and the transistor unit includes The first unit 110a and at least second unit 110b formed on substrate 105 (for example, on chip), the substrate 105 have There is semiconductor surface (the epi layer 108 such as adulterated with the first conduction type).There is first unit first grid to stack and the Unit two are stacked with second grid, wherein each gate stack includes on gate-dielectric 112 above body zone 113 Gate electrode 111a, 111b.

Groove has the AR of at least (>=) 3, from semiconductor surface between first grid stacks and second grid stacks Top side extend downwardly, to provide to the deep SCT 120 of the second conduction type impure source, and FP 128 is in grid Top is stacked to extend to provide the liner for groove.Groove includes the metal packing (for example, W) 122 in it.With the second conduction The drain electrode 132 of type doping is located in the semiconductor surface (such as epi layer 108) on the gate stack side opposite with groove.

Step 202 includes that the first etching is carried out to metal packing 122, for removing drain electrode along the side wall of FP 128 The metal packing of 132 tops and a part for removing the metal packing 122 in groove.Plasma etching can be used for following retouch The step 202 and step 204 stated.It is known such as in conductor etching field, what plasma etching was related to contacting with sample The controlled glow discharge (plasma) of appropriate admixture of gas, and wherein plasma source is continuously provided and is removed from sample The reactive etch material of solid material can be (ion) of electrification or (atom and the free radical) of neutrality.

Step 203 includes depositing metal packing 122, including fill groove.CVD or plasma enhanced CVD (PECVD) can For depositing refractory metal (such as tungsten or PGM filler).Step 204 includes that the second etching is carried out to metal packing 122.

Bimetallic filling disclosed herein and etch back process solve the W residue problem of power MOSFET, without appointing What undesirable negative effect.At FP foot filling metal (for example, W) residue elimination is helpful because it increase from The boundary DCT to the boundary FP (it is connected to source electrode) distance and reduce a possibility that FP is bridged to DCT.Disclosed double gold Belong to the combination of filling deposition and etch back process process and the filling of disclosed metal also simultaneously from the high shape on power MOSFET tube core Looks region removes metal packing, and stays in filler metal in deep SCT feature.Institute in embodiment as described below Show, by implementing disclosed double W deposition and etch-back process, discovery power MOSFET multiprobe yield significantly improves simultaneously And become stable (from 50% to about 85% reaches consistent and substantially more than 90%, referring to Fig. 4 described below).

The enhancement type scanning in the section that the slave SEM image that Fig. 3 A- Fig. 3 C shows 2 gate stacks obtains is described, described Have between gate stack and be connected to the deep SCT 120 of FP 128, the FP 128 is above gate stack, it was demonstrated that not only exists Side-walls close to the FP 128 of drain electrode 132 successfully remove 122 residue of W metal packing, and in the metal of deep SCT 120 Also without forming detectable W seam in filler 122.First W is etched back (step 202) and provides taper depth as shown in Figure 3A SCT profile is believed to be helpful in the 2nd W deposition.Instead of, at an angle of 90 degrees, taper offer can be with horizontal surface with horizontal surface At about 87 degree to 89 degree of angle.Because being etched back the taper of the tungsten filler (being illustrated as metal packing 122) provided by the first W, the The preferably filling of two W deposition is without forming seam.This means that the second etch back process can carry out longer time to remove on The morphological regions in face are without removing the material in depth SCT 120.

As shown in Figure 3B, after the deposition (step 203) of the 2nd W metal packing 122, may not be used in deep SCT 120 122 seam of metal packing seen.As shown in Figure 3 C, it is etched back in the 2nd W for corresponding to step 204 (for example, using high temperature formulations (for example, 50 DEG C)) after, the FP side-walls above the LDD 129 close to drain electrode 132 remove 122 residue of W metal packing. As it appears from the above, being portrayed as the resulting structures of power MOSFET 100 in Fig. 1, evidence suggests have W metal to fill out at FP 128 Expect 122 residues, which increase boundary (wherein as described above, the DCT 130 of 132 DCT 130 from formed later to draining Including metal plug 130a and barrier metal liner 130b (for example, Ti/TiN)) to the boundary of FP 128, (wherein FP 128 is connect To source electrode 127) distance, therefore reduce a possibility that FP128 is bridged to 130 DCT by W metal packing 122.