Past, main polysilicon and the Al (aluminium) of adopting was as the electrode and the wiring material that are formed at the semiconductor integrated circuit on Si (silicon) substrate.Yet, in recent years along with semiconductor device is scaled, attempt to introduce for example refractory metal and new electrode of their silicide conduct and wiring materials such as W (tungsten), Ti (titanium), cobalt, because the resistance ratio silicon of these metals and metallic compound is low, electromigration resisting property is than Al height.
By the target of sputter sintering refractory metal (silicide) powder preparation in argon, on semiconductor wafer, form refractory metal (silicide) film as electrode and wiring material.
Japanese Patent Laid discloses 192974/1994,192979/1994,3486/1995 and discloses the technology of utilizing electrolytic purification technology to make high-purity Co, reduced its impurity content particularly Ni (nickel) and Fe (iron) content, made Co have the purity that surpasses 99.999% (5N).This high-purity Co is applied to make the Co target that forms as the Co film of the electrode of semiconductor device and wiring (electrode, grid, wiring unit, diaphragm etc.).
Japanese Patent Laid discloses 1370/1993 and has introduced the method that a kind of manufacturing is used for the refractory metal silicide target of sputter, can limit to cause the particle of electrode and wiring electric leakage and short circuit to form in other cases.In the document illustration W, Mo (molybdenum), Ta (tantalum), Ti, Co and Cr (chromium) as refractory metal.
Except that the said method that adopts the refractory metal silicide target, the refractory metal silicide film can form by refractory metal and pasc reaction.
Japanese Patent Laid discloses 321069/1995 and has introduced a kind of so-called " Salicide technology ", may further comprise the steps: the composition metal target that adopts the permanent magnetic materials such as for example Ti by ferromagnetic material such as for example Co of 20 atom % and 80 atom % to constitute, utilize magnetron sputtering technique, be formed with thereon and form the Co-Ti film on the whole surface of Semiconductor substrate of MOSFET (mos field effect transistor); Then, heat-treat, in polysilicon gate and source and leakage, to form Co silicide-Ti silicide mixed layer; Remove the non-reacted parts of mixed layer by corrosion; Heat-treat again, thereby reduce the resistance of mixed layer.
For high operation speed, high-performance and the low-power consumption of the large-scale semiconductive device realizing making according to the deep-submicron design rule that for example is not more than 0.25 micron, the delay in reducing wiring, the also essential high speed operation of realizing discrete MOSFET.For example, when MOSFET was scaled, the source of MOSFET/ohmic leakage increased, and this increase of resistance is the key factor that influences the transistor high operation speed.Specifically, under the situation with 2V or the lower transistorized low energy-consumption electronic device of low voltage drive, the raising of the operating rate of discrete MOSFET is a key issue.
With 2V or lower low voltage drive MOSFET the time, becoming is difficult to control threshold voltage (Vth) in the buried channel type structure, and grid is made of n type polysilicon in this structure, the same with the situation of the p channel mosfet of prior art.Therefore, how to control threshold voltage and become another problem.
The present inventor has verified the problem that is introduced in the Salicide technology that forms low-resistance high-melting-point disilicide layer in polysilicon gate and source and the leakage for the high operation speed problem that solves MOSFET.The inventor has selected to provide the Co of low resistance silicide of about 15 little Ω cm as refractory metal material.On the other hand, in order to control the threshold voltage of MOSFET, the inventor has attempted introducing dual gate CMOS structure, wherein by p type polysilicon the grid of p channel mosfet is constituted the surface channel type, by n type polysilicon the grid of n channel mosfet is constituted the surface channel type.In order to introduce this dual gate CMOS structure, the p type polysilicon bar has become problem with the method for attachment of n type polysilicon bar, but this problem can be solved by this structure is combined with the Salicide technology that forms silicide layer on polysilicon gate.
Be on the polysilicon gate of MOSFET and source below and the technology of leaking formation Co silicide layer.
At first, adopt the Co target, utilize sputtering technology, be formed with deposit Co film on the Semiconductor substrate of MOSFET thereon, heat-treat then so that Co and Si react each other, thereby on the surface of grid, source and leakage formation Co silicide layer (first heat treatment).The Co silicide that obtain this moment is the single silicide (CoSi) with high electrical resistance of the little Ω cm of 50-60, after wet etching removes unreacted Co film, carries out a heat treatment again, thereby carries out single silicide to the disilicide (CoSi with low-resistance
2) phase transformation (second heat treatment).
Yet, be Co film that 99.9% Co target forms when carrying out first heat treatment the inventor to utilizing purity, the thickness of the single silicide of gained Co (CoSi) shows the high dependency that heat treatment temperature is changed.Say that more specifically observe high more heat treatment temperature and cause big more thickness, low more heat treatment temperature causes the phenomenon of more little thickness.Thereby, can not stably control thickness.Perhaps, this change of thickness mainly be since in the Co target silication of contained a part of impurity transition metal such as for example Fe and Ni etc. cause.
Above-mentioned achievement in research suggestion, in order to obtain having the Co silicide layer of low-resistance, must be very high by the first heat treated temperature is set to, the mono-silicide layer of the quite big thickness of preparation.Yet when the thickness of mono-silicide layer became big, the junction leakage that source-leakage p-n junction is shallower than in 0.30 micron the 0.25 micro MOS device increased.Suppose that the Co and the Si that enter in the substrate react gathering of lattice silicon and growth in form excessive, thereby caused this increase of junction leakage.
If the first heat treated temperature raises, undesirable silicification reaction easily takes place in source-drain terminal portion, and easily causes so-called " creep ", or silicide layer extends up to field insulating membrane and grid side wall insulating film.As a result, in very undersized MOSFET, between the grid and source of adjacent mos FET, can be short-circuited between between grid and leakage and source and source.Particularly, when dual gate CMOS is carried out first heat treatment, easily be diffused in the gate oxidation films as the B (boron) of the impurity in the p type polysilicon of the grid that constitutes the p channel mosfet, the transistorized electrical characteristics of result easily fluctuate.
On the other hand,, reduce the thickness of mono-silicide layer, thereby when avoiding junction leakage to increase, it is big that the resistance of silicide layer becomes by setting first heat treatment temperature very low.When heat treatment temperature was low, the silicification reaction progress was also slack-off, so that the resistance of silicide layer further increases.In addition, when its thickness diminished, the thermal resistance of Co silicide layer descended.Thereby; Technology for Heating Processing after forming MOSFET (for example; deposit contains the silicon oxide film of doped P (phosphorus) on MOSFET; at high temperature carry out sintering then; thereby absorb for example technology of Na metals such as (sodium)) during; Co silicide crystal grain can condense, thereby, resistance can take place to be increased undesiredly.
The purpose of this invention is to provide a kind of Salicide technology, can form Co disilicide layer with low resistance and little junction leakage.
For this reason, the method for semiconductor collector body constructed in accordance may further comprise the steps:
(a) on the silicon face of first first type surface of a wafer, form an isolated groove, thereby this silicon face is divided into first area and these two zones of second area;
(b) form first silicon oxide insulating film above silicon face and in the isolated groove by chemical vapor deposition method;
(c) remove first dielectric film of isolated groove outside with chemical mechanical polishing method, make the silicon face planarization that is coated with first dielectric film;
(d) form N type grid and these two grids of P type grid respectively above first and second zones, each described grid all has the silicon fiml for the polysilicon conducting film;
(e) form N type source region and drain region in the first area, described N type source region and drain region constitute first isolated-gate field effect transistor (IGFET) with this N type grid;
(f) form P type source region and drain region in second area, described P type source region and drain region constitute second isolated-gate field effect transistor (IGFET) with this P type grid that is doped with boron;
(g) from a Co sputtering target by on the silicon face that sputters at described N type and P type source region, drain region top and respectively by deposit Co film on the upper surface of the described N type of insulative sidewall and described N type and P type source region, drain region isolation and P type grid, the purity of described Co sputtering target is at least 99.99% by weight under the situation of not considering carbon and oxygen impurities, wherein Fe and Ni sum are not more than 50ppm by weight in the Co sputtering target, wherein carry out sputter according to the component of the Co film of institute's deposit and the essentially identical mode of component of Co sputtering target;
(h) under first temperature first first type surface that is coated with the Co film is carried out first rapid thermal annealing, thereby form monocrystalline silicon membrane on this silicon face and this upper surface, wherein first temperature is to make the low temperature that creep does not take place substantially along sidewall;
(i) remove the Co film that remains in first first type surface top with wet etch method;
(j) afterwards, first first type surface is carried out second rapid thermal annealing, thereby on this silicon face and this upper surface, form cobalt disilicide film with second temperature that is higher than first temperature in step (i).
Used term " wafer " is meant sheet-like workpiece in this specification, and mainly after forming the above-mentioned technology of semiconductor device on its first type surface zone, its part comprises a monocrystalline or a plurality of single-crystal region (mainly being silicon among the present invention) at least at least.Here used term " semiconductor device " is not only finger-type and is formed in those of common single-chip, but also finger-type is formed on other substrate such as TFT liquid crystal for example those.
From the introduction and accompanying drawing of following specification, it is clearer that these and other objects of the present invention and new feature will become.
Introduce the present invention in detail below in conjunction with accompanying drawing.In the following description, identical reference number is used to represent to have the member of identical function, so will omit the introduction that repeats to them.
This embodiment represents that the present invention is applied to the example according to the dual gate CMOS technology of 0.25 micron design rule, and wherein working power voltage is 2V.Yet, need not, the invention is not restricted to this embodiment.
Make CMOSFET in the following manner with double-gate structure.At first, thermal oxidation is by p
-The surface that monocrystalline silicon constitutes and has the Semiconductor substrate 1 of about 10 Ω cm resistivity forms the thick silicon oxide film 2 of 10nm.The thick silicon nitride film 3 of CVD technology deposit 100nm on this silicon oxide film 2 as shown in Figure 1, then, is made mask with photoresist then, and this silicon nitride film 3 of dry etching composition is with the silicon nitride film 3 that removes device isolation region.
Then, as shown in Figure 2, make mask with silicon nitride film 3, corrosion oxidation silicon fiml 2 and Semiconductor substrate 1, thus in the Semiconductor substrate 1 of device isolation region, form the dark groove 4a of 350nm.
As shown in Figure 3, CVD technology utilizes CMP technology to polish the surface of this silicon oxide film 5 behind deposit silicon dioxide film 5 on the Semiconductor substrate 1, makes it flat-satin, to keep silicon oxide film 5 in groove 4a, so form device isolation groove 4.Then, heat-treat at 1000 ℃, make silicon oxide film 5 densifications in the device isolation groove 4, utilize hot phosphoric acid then, wet etching removes silicon nitride film 3.
Then, in Semiconductor substrate 1, form n trap 6n and p trap 6p, as shown in Figure 4.At first, make mask with the photoresist that has with p channel mosfet formation district corresponding opening, ion is infused in the impurity that forms the n trap in the Semiconductor substrate 1, and then, ion injects the impurity of the threshold voltage of regulating the p channel mosfet.The impurity that forms the n trap for example is P (phosphorus), and ion is infused in the energy and 1.5 * 10 of 360keV
13/ cm
2Dosage under carry out.The impurity of regulating threshold voltage for example is P, and this ion is infused in the energy and 2 * 10 of 40keV
12/ cm
2Dosage under carry out.After removing photoresist, usefulness has corresponding to the photoresist of the opening of n channel mosfet makes mask, and ion is infused in the impurity that forms the p trap in the Semiconductor substrate 1, and ion injects the impurity of the threshold voltage of regulating the n channel mosfet again.The impurity that forms the p trap for example is B (boron), and ion is infused in the energy and 1.0 * 10 of 200keV
13/ cm
2Dosage under carry out.The impurity of regulating threshold voltage is boron fluoride (BF
2), this ion is infused in the energy and 2 * 10 of 40keV
12/ cm
2Dosage under carry out.After this, Semiconductor substrate 1 is carried out heat treatment in 1 minute at 950 ℃, activator impurity, thus form n trap 6n and p trap 6p.
Then, thermal oxidation Semiconductor substrate 1 forms the thick gate oxidation films 7 of 4nm on the surfaces of active regions of n trap and p trap 6n and 6p, as shown in Figure 5, and on Semiconductor substrate 1 the thick polysilicon 8 of CVD deposit 250nm.In addition, CVD silicon oxide deposition film 9 on polysilicon film 8.There are not n type and p type doping impurity in polysilicon film 8.
As shown in Figure 6, make mask with photoresist, corrosion oxidation silicon fiml 9 and polysilicon film 8 so that form the grid 8n of n channel mosfet on p trap 6p, form the grid 8p of p channel mosfet on n trap 6n.It is long that these grids 8n and 8p are processed into 0.25 micron grid.
Then, make mask with grid 8p with photoresist, with the energy and 7.0 * 10 of 20keV
13/ cm
2Dosage, inject p type impurity (BF at n trap 6n intermediate ion
2), make mask with grid 8n with photoresist, with the energy and 3.0 * 10 of 20keV
14/ cm
2Dosage, inject n type impurity (arsenic (As)) at p trap 6p intermediate ion.Then, under 1000 ℃, Semiconductor substrate 1 is carried out heat treatment in 10 seconds, activator impurity, and form p among the n trap 6n on grid 8p both sides
-Semiconductor region 10 forms n among the p trap 6p on grid 8n both sides
-Semiconductor region 11.
As shown in Figure 7, be 0.1 micron side wall spacers 12 being formed on thickness on the grid length direction on the sidewall of grid 8n and 8p.Side wall spacers 12 is to form to Semiconductor substrate 1 by the silicon oxide film anisotropic etch of reaction corrosion with the CVD deposit.When carrying out this corrosion, also corrode the silicon oxide film 9 on grid 8n and the 8p simultaneously, the surface of exposing grid 8n and 8p.
Then, make mask with photoresist, with the energy and 1.0 * 10 of 20keV
14/ cm
2Dosage, in n trap 6n and grid 7p, inject p type impurity (B), with the energy and 2.0 * 10 of 5keV
15/ cm
2Dosage, ion injects p type impurity (B) again.Then, make mask, with the energy and 2.0 * 10 of 40keV with this photoresist
14/ cm
2Dosage, inject n type impurity (P) to p trap 6p and grid 8n intermediate ion, after this, with the energy and 3.0 * 10 of 60keV
15/ cm
2Dosage inject n type impurity (As).Then, under 1000 ℃, Semiconductor substrate 1 is carried out heat treatment in 10 seconds, activator impurity, thus in n trap 6n, form p
+Semiconductor region 13, and the conduction type of grid 8p is transformed into the p type.In addition, shape n in p trap 6p
+Semiconductor region 14, and transfer into the conduction type of grid 8n to the n type.p
+Semiconductor region 13 and n
+The junction depth that semiconductor region 14 forms is the 0.2-0.1 micron.
Incidentally, preceding in the heat treatment (1000 ℃, 10 seconds) that activates said n type and p type impurity, at 750 ℃ Semiconductor substrate 1 is carried out heat treatment in 30 minutes, n
+(the n in N-type semiconductor N district 14
+/ p) junction leakage can reduce, as shown in Figure 8.This is because ion is incorporated into the cause that the point defect of Semiconductor substrate 1 is repaired by this heat treatment when injecting.Although estimate p
+Semiconductor region 13 also has similar effects in this case, but p
+The impurity of semiconductor region 13 (B) has high diffusivity, and diffusion to a certain degree takes place in the heat treatment meeting of this temperature.In order to prevent this diffusion, n can formed
+After the ion of semiconductor region 14 injects,, forming p then at first immediately 750 ℃ of heat treatments of carrying out 30 minutes
+The ion of semiconductor region 13 carries out heat treatment in 10 seconds at 1000 ℃ after injecting.
Removed p with hydrofluoric acid (HF) wet etching
+Semiconductor region 13 and n
+Behind the semiconductor region 14 lip-deep gate oxidation films 7, with the sputter of Co target, the Co film 16 that deposit 15nm is thick on Semiconductor substrate 1, in addition, the oxygen-proof film 17 that deposit 10-15nm is thick on Co film 16.For example the TiN film of sputtering deposit is as oxygen-proof film 17, as shown in Figure 9.The thickness of Co film 16 is preferably 18-60nm.If thickness is not more than 18nm, the sheet resistance that is difficult to the Co silicide layer that then can become is reduced to 10 Ω cm/ or lower, if thickness surpasses 60nm, then source one drain junction current leakage will increase.
Figure 10 is the schematic diagram of process chamber that is used for the sputtering equipment of the above-mentioned Co film 16 of deposit.Process chamber 100 can be evacuated, and Ar gas is introduced this chamber, keeps a few milli torrs when film forms.The Co target 103 that is supported by sputtering electrode 102 is arranged on the support 101 that is used for support semiconductor substrates 1 (wafer), and is relative with Semiconductor substrate 1.When 104 work of the power supply that links to each other with Co target 103, begin constant discharge, because high negative pressure is added on the Co target in the gap between Co target 103 and the Semiconductor substrate 1 generation plasma 105.From this plasma 105 when the Ar ion that Co target 103 quickens is got on the surface of Co target 103, the constituent material of target (Co) is with molecule (atom) scattering, deposit Co film 16 on the surface of Semiconductor substrate 1.
Figure 11 is the schematic diagram of above-mentioned Co target 103.The Co purity of the used Co target 103 of this embodiment is at least 99.99%, Fe or Ni content are no more than 10ppm, or the content of Fe and Ni is not more than 50ppm (in this application, the content of the Co purity of Co sputtering target and each metal impurities refers to the face proportion by subtraction that under the situation of not considering nonmetallic inclusions such as contained carbon and oxygen this kind metal accounts for all metal total weights).Better be that Co purity is at least 99.99%, the content of Fe and Ni is not more than 10ppm, is more preferably, and Co purity is 99.999%.This high-purity target 103 is to make like this, with purification Co raw material powders such as electrolysis process, up to obtaining above-mentioned Co purity, the Co raw material powder that obtains like this is hot pressed into sinter, and this sinter is processed into dish type.
Then, carry out first heat treatment, Co and Si are reacted each other, as shown in figure 12, so that at p
+Semiconductor region 13 and n
+Form CoSi layer 16a on the surface of semiconductor region 14 and grid 8n and 8p.RTA (rapid thermal annealing) equipment is adopted in first heat treatment, carries out in blanket of nitrogen about 30 seconds, and substrate temperature remains on 525 ℃ or following simultaneously.Yet if heat treatment temperature is too low, the process of silicification reaction can be influenced; Therefore, underlayer temperature preferably is set in 475 ℃ at least.
Use NH
4OH+H
2O
2The aqueous solution is HCI+H then
2O
2The aqueous solution carries out wet etching, removed oxygen-proof film 17 and unreacted Co film 16 after, carry out second heat treatment, make CoSi layer 16a change to CoSi mutually
2 Layer 16b, as shown in figure 13.RTA equipment is adopted in second heat treatment, carries out in blanket of nitrogen about 1 minute, is set in 650-800 ℃ with advancing underlayer temperature.
Figure 14 comprises the CoSi that is formed on grid and source and the drain surface
2The n channel mosfet of layer 16b and the amplification diagrammatic sketch of p channel mosfet.Figure 15 shows CoSi
2The curve chart that concerns between the sheet resistance of layer 16b and first heat treatment temperature.With Co purity is that 99.998% high purity product (target B) and Co purity are that 99.9% low-purity product (target A) is made the Co target.Table 1 shows the kind of impurities among target A and the B and their content.
Table 1 (unit: wt ppm)
Element | Target A | Target B |
Fe |
| 50 | 4 |
Ni | 250 | 6 |
Cu | <10 | <1 |
Al | <10 | <1 |
C | <10 | 6 |
O | 6 | 50 |
Na | <1 | <0.05 |
K | <1 | <0.05 |
As shown in the figure, be the CoSi that high-purity target B of 99.998% obtains by purity
216b is low to the first heat treatment temperature dependence of CoSi layer 16b for layer, and this layer has become evenly in fact under the temperature in 500-600 ℃ of scope.Therefore, in this temperature range, can obtain the low sheet resistance of about 4 Ω/.
Even when first heat treatment temperature is set at low temperature, also can obtain having the CoSi of low sheet resistance therefore,
2Layer 16b.Along with the reduction of heat treatment temperature, the speed step-down of silicification reaction can improve the controllability of heat treatment time to thickness.Therefore, can be more easily with CoSi
2The thickness of layer 16b is set in the scope that does not increase junction leakage.In addition, because heat treatment temperature reduces, can prevent CoSi
2Layer 16b creep (creep-up).
On the other hand, about by purity being the CoSi that 99.9% target A obtains
2 Layer 16b when the heat treatment temperature step-down, because the Co film thickness diminishes, becomes big so sheet resistance is remarkable.For obtaining equaling resulting CoSi by high-purity target B
2The sheet resistance of layer, the first heat treated temperature must be elevated to 600 ℃.
By the silication Co film of sputtering deposit in a manner described, on the grid of MOSFET and source and drain surface, form CoSi
2During layer, this embodiment of the present invention adopt Co purity be at least 99.99% and Fe and Ni content be not more than high-purity Co target of 10ppm, better be that employing Co purity is high-purity Co target of 99.999%, the 16b of the Co silicide layer with low resistance and low junction leakage can be provided.Therefore, this embodiment can improve the operating rate that grid length is 0.25 micron very little MOSFET, improves its service behaviour, reduces its power consumption.
Then, utilize atmospheric pressure cvd technology, the silicon oxide film 18 that deposit 100nm is thick on Semiconductor substrate 1 utilizes the thick silicon oxide film 19 of plasma CVD deposit 300-500nm again.Then, chemico-mechanical polishing (CMP) polishing silicon oxide film 19, it is smooth that it is had an even surface.Make source gas with monosilane+oxygen+hydrogen phosphide, use CVD technology, after this psg film 20 that deposit 200nm is thick on silicon oxide film 19, under the temperature in 700-800 ℃ scope, heat-treats (sintering), removes the wet steam in the psg film 20.Because this embodiment can fully guarantee CoSi
2The thickness of layer 16b, even when at high temperature carrying out sintering, also can limit CoSi
2 Layer 16b's condenses.Thereby, can prevent CoSi
2The sheet resistance of layer 16b increases, and can improve process margin.
As shown in figure 17, make mask with photoresist, corrosion psg film 20 and silicon oxide film 18 and 19, thereby at p
+And n
+ Form connecting hole 21 on the semiconductor region 13 and 14, on psg film 20, form ground floor wiring 22 then.For forming this ground floor wiring 22, utilize CVD, deposit one deck the one TiN film thinly on psg film 20, and behind the thick W film of deposit on this TiN film, deep etch W film makes it to stay in the connecting hole 21.Behind sputtering deposit Al film on the TiN film and the 2nd TiN film, make mask with photoresist, composition the 2nd TiN film, Al film and a TiN film.
Then, as shown in figure 18, in ground floor wiring 22, form first interlayer dielectric 23.Utilize chemico-mechanical polishing to make having an even surface of this interlayer dielectric 23 and smooth, in first interlayer dielectric 23, form connecting hole 24.Then, on first layer insulation 23, form second layer wiring 25, and be electrically connected to ground floor wiring 22.First interlayer dielectric 23 comprises the silicon oxide film of plasma CVD deposit, and second layer wiring 25 is by constituting with ground floor 22 identical materials that connect up.
Then, in the same manner as described above, in second layer wiring 25, form second interlayer dielectric 26, as shown in figure 19.Make having an even surface of this film 26, and after forming connecting hole 27, on second interlayer dielectric 26, form three-layer routing 28 with smooth.
Then, as shown in figure 20, on three-layer routing 25, form the 3rd interlayer dielectric 29.Make this film 29 have an even surface and smooth and form connecting hole 30 after, on the 3rd interlayer dielectric 29, form the 4th layer of wiring 31, in the 4th layer of wiring 31, form the 4th interlayer dielectric 32 then.Make this film 32 have an even surface and smooth and form connecting hole 33 after, on the 4th interlayer dielectric 32, form layer 5 wiring 34.In fact finished the semiconductor device of this embodiment in this way.
Even now has been introduced the invention that the inventor finishes respectively in conjunction with each embodiment, but the present invention specifically is not limited to these embodiment, but do not break away from the scope of the invention situation under can change or change shape in every way.
For example, adopt the manufacturing of the present invention of high-purity Co target only can be applied to the situation that source and drain surface with MOSFET are transformed into the Co silicide.
As mentioned above, the method that the present invention makes integrated circuit (IC)-components can improve the controllable film thickness of Co silicide layer, can obtain the Co silicide layer of low resistance and low junction leakage.Therefore, this manufacture method can be applicable to adopt the Salicide technology of Co target.