CN101076879A - Plasma doping method - Google Patents
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Abstract
To realize a plasma doping method which can control a dosage precisely to improve an in-plane homogeneity of the dosage. The plasma doping method is based on such a discovery, while noting the result, that the dosage of boron is substantially constant for a time period, if a silicon substrate is irradiated with a B2H6/He plasma and is biased, and that the saturation time period is longer and stabler than that, for which the repetitions of an apparatus control can be retained. When the plasma irradiation is started, the dosage increases at first, but then continues to be substantially constant independently of the time change. The dosage then decreases if the time is elongated. If this time period, for which the dosage is substantially constant independently of the time change, is employed as a process window, the dosage can be precisely controlled.
Description
Technical field
The present invention relates to a kind of plasma doping, relate in particular to impurity is incorporated into plasma doping in the surface of the solid sample of semiconductor substrate for example.
Background technology
As the technology in the surface of impurity being mixed solid sample, be well known that make impurity ionization and with ionization impurity with low-yield plasma doping (PD) method of mixing in the solid.(for example, seeing patent documentation 1)
On the other hand, in the doping method, the most extensive employing at present be ion injection method.In non-patent literature 1 and non-patent literature 2, plasma doping is described to the daughter ion injection technique.Plasma doping is different from ion injection method.And ITRS is the document of the extensive reference of engineer in the semi-conductor industry.Now illustrate in greater detail the technological disparity between ion injection and the plasma doping.
In the ion injection method, adopt a kind of device, it comprise from gas produce plasma ion source, carry out mass separation so as the ion that takes out from ion source, to select the expectation ion the analysis magnet, quicken the electrode of expectation ion and the expectation ion that will speed up injects the process chamber of silicon substrate.Ion injects, and is shallow for impurity is injected, and preferably sets from the taking-up energy of ion source taking-up ion little with the acceleration energy that is used to quicken.Yet when taking out energy settings hour, the amount of ions that is removed reduces.In addition, set hour when acceleration energy, during ion beam was delivered to wafer from ion source, the repulsive force of interionic charge generation was widened beam diameter.As a result, ion beam may collide the inwall of bunch (beam line), and may lose a large amount of ions.For this reason, injecting the output of handling reduces.For example, when injecting the B+ ion, if acceleration energy is 2kev or littler, output begins to descend, if acceleration energy is 0.5kev or littler, bundle is carried the difficulty that self becomes.In addition, even acceleration energy is reduced to 0.5kev, the B ion also can inject the degree of depth of about 20nm.That is, under the situation that forms thickness thin extension electrode than the degree of depth, productivity ratio may sharply descend.
Contrast, in plasma doping, use a kind of device, it comprises that induced plasma enters plasma generation source in the cylindric vacuum chamber that wherein is provided with silicon substrate, the bias electrode of silicon substrate and regulate the bias supply of the current potential of bias electrode is set thereon.The difference that the formation of this device and ion inject the formation of the device that adopts is not provide analysis magnet and accelerating electrode.Bias electrode as plasma source and wafer chuck is provided in vacuum chamber.Then, the electromotive force that produced between plasma and the wafer of ion quickens and imports.Utilize this formation, owing to can directly adopt low energy plasma, compare ion and inject, a large amount of low energy ions can shine on the wafer.That is to say that dose rate is very high.For this reason, inject, can keep high yield at low-yield B ion.
By using plasma doping, the inventor has developed to form has very shallow thickness and the low-resistance source electrode technology to the drain electrode extension electrode.The paper of this novel technique was adopted by the VLSI discussion of one of the most authoritative international conference in June, 2004.This new technology is known as the technology (non-patent literature 3) with special-effect.
In this method, from dopant material gas, for example B of gas introduction port importing
2H
6Come plasmaization by plasma generation unit with microwave waveguide and electromagnet.Then, the boron ion in the plasma is supplied to sample surfaces by high frequency electric source.
Along with size of semiconductor device reduces and high integrated, it is extremely important that impurity mixes the characteristic in district.In these characteristics, dosage (doping) decision low resistance, low resistance are one of important elements of decision element characteristic.Therefore, control dosage is extremely important.
If the use plasma doping can see forming to have very shallow thickness and low-resistance source electrode to the drain electrode extension electrode.Yet, also do not develop the dosage control method of control element characteristic.At present, tested the method that changes dosage by the mode that changes the plasma doping time, but the method does not obtain sufficient control precision, therefore practicability not.
In this situation, as by as much as possible diluting to the dangerous high poisonous B of human body
2H
6And the method that can improve fail safe, stablize generation and keep plasma and not reduce doping efficiency and carry out dopant dosage control easily, the inventor proposes following method.In this method, utilize He gas dilution as the B that comprises the material that is impregnated in impurity with little ionization energy
2H
6So gas is initial stage generation He plasma, B subsequently
2H
6Discharge (patent documentation 2).This method proposes B
2H
6The concentration of gas is preferably less than 0.05%.
When concentration is low, for example about 0.05%, although reported easy control dosage, put down in writing when gas concentration remains unchanged and changed dosage by the change time.That is, work as B
2H
6When the concentration of gas was hanged down, the time dependent change of dosage was little, so control dosage easily.Here, on increasing, the dosage control precision gets along with.Yet this has only improved by changing the known method that the plasma doping time changes dosage.Wherein, do not study relation between DM and the gas concentration.
Patent documentation 1: No. the 4912065th, United States Patent (USP)
Patent documentation 2: TOHKEMY 2004-179592 communique
The Front EndProcess of the Figure 30 of the Shallow Junction Ion Doping of non-patent literature 1:International Technology Roadmap for Semiconductors 2001Edition (ITRS2001)
Non-patent literature 2:International Technology Roadmap for Semiconductors 2003Edition (ITRS2003)
Non-patent literature 3: " people such as Y.Sasaki, Symp.on VLSI Tech.P180 (2004) "
Summary of the invention
＜technical problem to be solved by this invention 〉
As mentioned above, form that impurity mixes the district or control dosage is important.Certainly, inner evenness also is very important for forming element.Especially, though up-to-date progress is arranged, the extremely difficult uniform dose that obtains in the surface on the major diameter wafer.
Consider above problem finished the present invention and the purpose of this invention is to provide a kind of can High Accuracy Control dosage and can form the plasma doping that shallow impurity mixes the district.
Another object of the present invention provides high and the plasma doping that can High Accuracy Control dosage of a kind of inner evenness that can realize dosage.
＜the means of dealing with problems 〉
According to an aspect of of the present present invention, provide a kind of plasma that will comprise the gas of foreign ion to supply on the sample with the lasting scheduled time of predetermined concentration and mix the plasma doping in district so that form impurity in sample surfaces, described plasma doping comprises that the concentration of the plasma of the gas of setting doping time and comprising impurity makes dosage keep necessarily and not having the step of time dependent behavior.
The inventor has repeated various tests and discovery, if by irradiation B
2H
6/ He plasma applies bias voltage to silicon substrate, then exist to make the dosage of boron keep the basic moment uniformly.In addition, as can be seen, compare the time of the repeatability that can guarantee device control, saturation time is than length and be easy to stable the use.That is, if plasma irradiating begins, then dosage increases at first, but makes dosage substantially evenly and with the time that the time variation has nothing to do continue.In addition, if the time further increases, dosage reduces.The inventor also finds the process window by the time, can accurately control dosage, makes dosage evenly basic and irrelevant with the time variation in this time.Focus on that this result has finished the present invention.
According to another aspect of the present invention, provide a kind of plasma that will comprise the gas of foreign ion to supply on the sample and mix the plasma doping in district so that in sample surfaces, form impurity with the lasting scheduled time of predetermined concentration.Thereby described plasma doping is included in and wherein makes dosage evenly and not have in the time range of time dependent behavior, so be set in the doping time of the plasma of the gas that comprises foreign ion and concentration and make dosage evenly and not have the step of carrying out plasma doping under the state of time dependent behavior.
Constitute according to this, make dosage evenly and not have the interior concentration of setting the plasma of the gas that comprises foreign ion of time range of time dependent behavior therein.Therefore, can accurately control dosage.That is, although the time change a little because dosage is almost constant, can the stability control agent amount.Contrast, in the known method according to time control dosage, even the time changes a little, dosage also can acutely change.
Result as duplicate test works as B
2H
6When the relative predetermined bias of/He concentration changes, can obtain the almost constant and saturated time range of dosage.In addition, the inventor finds, in above time range, exist annealing back sheet resistance (Rs) inner evenness, be the very satisfied time range of inner evenness of dosage.Finished the present invention based on this result.Therefore, when plasma doping can practical application, the solution problem relevant in the lump with dosage control and inner evenness.
In according to the present invention's plasma doping on the other hand, can set the doping time and the concentration of the plasma of the gas that comprises impurity, the impurity sputter that the feasible impurity that enters in the substrate surface mixed and left substrate surface is saturated.
The inventor has repeated various tests and discovery, if by irradiation B
2H
6/ He plasma applies bias voltage to silicon substrate, exist by irradiation ion, group, gas and the doping of boron and from time of substrate surface sputter saturated (balance) in plasma.In addition, as can be seen, compare with the time of the repeatability that can guarantee device control, saturation time is than length and be easy to stable the use.
In according to the present invention's plasma doping on the other hand, doping time is set at the degree that the dosage that makes the part that dosage is little in the substrate surface is followed the dosage of the saturated part of dosage.
Constitute according to this, make dosage evenly and not have the interior concentration of setting the plasma that comprises foreign ion of time range of time dependent behavior therein.In addition, doping time is set at the degree that the dosage that makes the part that dosage is little in the substrate surface is followed the dosage of the saturated part of dosage.Therefore, in order to increase inner evenness, can accurately control dosage.In the reality, the saturation time scope at each point place and the doping terminal point is set at latest time in the initial point of tested time range in the surface measurements.Therefore, the dosage of the part that dosage is little in the substrate surface is followed the dosage of the saturated part of dosage.Therefore, can obtain satisfied inner evenness.
In according to the present invention's plasma doping on the other hand, the level that does not have the uniform dose of time dependent behavior can change along with the concentration of the plasma of the gas that comprises foreign ion and change.
Utilize this to constitute, set the concentration of gaseous plasma, the sputter that the feasible foreign ion that enters in the substrate surface mixed and left substrate surface is saturated.Therefore, can change the level of uniform dose.So, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
In according to the present invention's plasma doping on the other hand, the concentration of plasma of gas that comprises foreign ion is along with the change of the concentration of the gas that comprises foreign atom and pressure and power and change.
Utilize this to constitute, the concentration of gaseous plasma can be set in the expected range.
Especially, when the concentration of the gas that comprises foreign atom changes, can be simply and the concentration of plasma that accurately change comprises the gas of foreign ion.As concrete unit, comprise that the gas of foreign atom and diluent gas can mix to be used, can change gas flow speed by mass flow controller, make the mixing ratio of gas change.Therefore, can be simply and accurately change the concentration of the plasma of the gas that comprises foreign ion.
In according to the present invention's plasma doping on the other hand, can set the concentration of ion, group and the gas of the concentration of gaseous plasma and gaseous plasma, make foreign ion enter the doping of substrate surface and the sputter of leaving substrate surface increases saturated in time.
Utilize this to constitute, set the concentration of gaseous plasma, the sputter that the feasible foreign ion that enters in the substrate surface mixed and left substrate surface is saturated.Therefore, dosage can accurately be controlled and the time that do not rely on changes.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
In according to the present invention's plasma doping on the other hand, the plasma that comprises the gas of foreign ion can be the molecule (B with boron atom and hydrogen atom
nH
m) mixed gas plasma.
The inventor has repeated various tests and discovery, works as B
nH
mThe concentration of gas hour exists to make that dosage is evenly basic and change irrelevant district with the time.So, set B
nH
mThe concentration of gas, the sputter that the feasible boron that enters in the substrate surface mixed and left substrate surface is saturated.Therefore, dosage can accurately be controlled and the time that do not rely on changes.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
In according to the present invention's plasma doping on the other hand, the plasma that comprises the gas of foreign ion can be B
2H
6Mixed gas plasma with He.
The inventor has repeated various tests and discovery, is using B
2H
6Under the situation of the mixed gas plasma of He, work as B
2H
6The concentration of gas hour exists to make that dosage is evenly basic and change irrelevant district with the time.Pay attention to this fact and finished the present invention.So, set B
2H
6The concentration of gas, the sputter that the feasible boron that enters in the substrate surface mixed and left substrate surface is saturated.Therefore, dosage can accurately be controlled and the time that do not rely on changes.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
In according to the present invention's plasma doping on the other hand, B
2H
6With the B in the mixed gas plasma of He
2H
6Gas concentration can be in 0.01% to 1% scope.Under less than 0.01% situation, when changing B
2H
6Concentration the time, the saturated time dependent change of boron dosage is too small.Therefore, be difficult to by changing B
2H
6Concentration change the saturated boron dosage of control according to the time.In addition, under 1.0% the situation of surpassing, when changing B
2H
6Concentration the time, the saturated time dependent change of boron dosage is excessive.Therefore, in this case, the controllability deterioration.By the same token, B
2H
6Concentration more preferably in 0.025% to 0.6% scope.
Find from result of the test, work as B
2H
6With the B in the mixed gas plasma of He
2H
6Concentration is about 0.1% o'clock, exists to make dosage substantially evenly change irrelevant district with the time.
In according to the present invention's plasma doping on the other hand, bias voltage V
DCCan be 60V or littler.
Find from result of the test, as bias voltage V
DCBe 60V or more hour, exist to make that dosage is evenly basic and change irrelevant district with the time.
In according to the present invention's plasma doping on the other hand, power can be about 1500W.
Find from result of the test, when power is about 1500W, exist to make dosage substantially evenly change irrelevant district with the time.
In according to the present invention's plasma doping on the other hand, the plasma that comprises the gas of foreign ion can be BF
3Mixed gas plasma with He.
From result of the test, using BF
3Under the situation of the mixed gas plasma of He, be similar to and use B
2H
6With the situation of the mixed gas plasma of He, the same discovery worked as BF
3The concentration of gas hour exists to make that dosage is evenly basic and change irrelevant district with the time.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
In according to the present invention's plasma doping on the other hand, sample can be a silicon substrate.
From result of the test, during in silicon substrate, mixing, use B
2H
6Under the situation of the mixed gas plasma of He, have been found that and work as B
2H
6The concentration of gas hour exists to make that dosage is evenly basic and change irrelevant district with the time.When using B
nH
mDuring with the mixed gas plasma of He, can obtain same effect.
So, in the present invention, set doping time and comprise the concentration of the gaseous plasma of boron, make to enter that boron in the substrate surface mixes and to leave the sputter of substrate surface saturated.
In according to the present invention's plasma doping on the other hand, can carry out plasma doping making dosage evenly and not have in the time range of time dependent behavior.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.
Utilize this to constitute,, can accurately control dosage by making dosage evenly change irrelevant time process window with the time.
Preferably, activation step can comprise the step of irradiating laser.
Because laser has high-energy-density, can carry out the high efficiency activation.
Activation step can comprise the step of the radiant light of illumination flash lamp.
Photoflash lamp is cheap, so can realize low cost.
Activation step can comprise the step of the radiant light that shines tungsten halogen lamp.
All use the heat treatment of tungsten halogen lamp to enter practicability, so can good reliability activate.
In according to the present invention's plasma doping on the other hand, can carry out plasma doping under the state substantially uniformly in the feasible temperature that contacts the reaction chamber wall of plasma.
In according to the present invention's plasma doping on the other hand, can under the heated state of reaction chamber wall of contact plasma, carry out plasma doping.
In according to the present invention's plasma doping on the other hand, carry out plasma doping under the state that can be cooled at the reaction chamber wall of contact plasma.
In according to the present invention's plasma doping on the other hand, can reduce the concentration of the gas that comprises foreign atom during the processing.
＜invention effect 〉
As mentioned above, according to plasma doping of the present invention, can accurately control the impurity incorporation.In addition, can form dosage wherein by the impurity range of the stable control of high accuracy.
In addition, can form impurity range with excellent inner evenness.
Description of drawings
Fig. 1 is the cross section view that the impurity that uses in the first embodiment of the invention mixes device;
Fig. 2 is the cross section view that the impurity that uses in the second embodiment of the invention mixes device;
Fig. 3 is illustrated in according to dosage in the method for example 1 of the present invention and the figure that concerns between the time;
Fig. 4 is illustrated in the figure that concerns between dosage and the gas concentration according in the method for example 1 of the present invention;
Fig. 5 is the figure that the Rs of the sample that obtains in the method that is illustrated in according to example 1 of the present invention distributes;
Fig. 6 is the figure that the Rs of the sample that obtains in the method that is illustrated in according to example 1 of the present invention distributes;
Fig. 7 is illustrated in according to dosage in the method for example 2 of the present invention and the figure that concerns between the time;
Fig. 8 is the figure that is illustrated in according to the inner evenness of dosage in the method for example 2 of the present invention;
Fig. 9 is illustrated in the figure that distributes according to sheet resistance on the Y-axis in the method for example 2 of the present invention; And
Figure 10 is the figure that is illustrated in according to the sheet resistance standard value distribution of Y-axis in the method for example 2 of the present invention.
Description of reference numerals
1 high frequency electric source
2 matching boxes
3 coils
4 mass flow controllers
5 mass flow controllers
6 turbomolecular pumps
7 pressure regulating valves
8 dry pump
9 cooling agent feed units
10 V
DCWatch-dog
11 matching boxes
12 high frequency electric sources
13 samples (processed substrate)
14 bottom electrodes
15 reative cells
21 high frequency electric sources
23 coils
24 mass flow controllers
25 mass flow controllers
33 samples
34 sample stage
35 reative cells
Embodiment
Hereinafter, embodiments of the invention are described with reference to the accompanying drawings.
(first embodiment)
Describe the first embodiment of the present invention in detail below with reference to accompanying drawing.
Device shown in Fig. 1 is called plasma doping apparatus A (PD device A).
Among this embodiment, when impurity mixes, set the concentration comprise the gaseous plasma that is impregnated in foreign ion, make foreign ion mix and the sputter on silicon substrate (silicon wafer) surface saturated.According to like this, can accurately control dosage and change irrelevant with the time.Therefore, can form impurity concentration wherein by the impurity range of the stable control of high accuracy.In addition, can form impurity range with excellent inner evenness.
Here, set the concentration of gaseous plasma, make that mixing with the sputter of substrate surface of foreign ion is saturated.According to like this, can accurately control dosage and change irrelevant with the time.Therefore, can form impurity dose wherein by the impurity range of the stable control of high accuracy.
This can followingly represent.When mixing with the sputter of substrate surface when saturated of foreign ion, making dosage evenly and the time changes in the irrelevant time range and carries out plasma doping.
In order to obtain inner evenness, the saturation time scope at each point place and the doping terminal point is made as latest time in the initial point of tested time range in the measurement face.Therefore, the dosage in the part that dosage is few in the substrate surface is followed the dosage in the saturated part of dosage, thereby obtains inner evenness.
Fig. 1 is the cross section view that the impurity that uses in the first embodiment of the invention mixes device.
Impurity mix device established technology chamber comprise reative cell 15, as the turbomolecular pump 6 of the exhaust apparatus of reative cell 15 exhausts, as the pressure regulating valve 7 of the pressure control device of pressure in the control reative cell 15, be arranged in the face of near the dielectric window of bottom electrode 14 as the coil of plasma source and antenna 3, supply with the high frequency electric source 12 of 13.56MHz High frequency power and as high frequency electric source 1 to the voltage source of bottom electrode 14 service voltages to coil and antenna 3.Processed substrate (substrate) 13 is arranged on the bottom electrode 14 of double as sample stage and carries out plasma irradiating on substrate 13.
Here, via the matching box 2 of high frequency electric source 1 that produces plasma and adjustment discharge, from coil and antenna 3 supply high frequency rates.Desired gas is supplied with via mass flow controller (MFC) 4 and 5.Control vacuum degree in the reative cell 15 by mass flow controller 4 and 5, turbomolecular pump 6, pressure regulating valve 7 and dry pump 8.Electric power is supplied to reative cell 15 from high frequency electric source 12 via matching box 11.The processed substrate 13 that is arranged in the reative cell 15 is placed on the sample stage 14, then supply capability.
Next, plasma doping technology is described.
Predetermined gas is discharged and carry out gas by the turbomolecular pump 6 as exhaust apparatus from the reative cell 15 of gas supply device via mass flow controller 4 and introducing technology chambers 5.In addition, by pressure regulating valve 7 reative cell 15 is remained on predetermined pressure as pressure control device.Then, the High frequency power of supplying with 13.56MHz from high frequency electric source 1 is to the coil 3 as plasma source, thereby produces inductively coupled plasma in reative cell 5.Under this state, by high frequency electric source 12 supply high frequency electric power, the feasible silicon substrate (processed substrate) 13 as sample of current potential that can control bottom electrode 14 then has the negative potential of relative plasma.
Although use coil to produce inductively coupled plasma in the present embodiment, can use antenna to replace coil.Perhaps, can produce spiral plasma, surface wave plasma, Ecr plasma etc.
After on silicon substrate 13 is placed on as the sample stage 14 of bottom electrode, when reative cell 15 exhausts, by mass flow controller 4 helium being supplied to reative cell 15 neutralizations will be as the diborane (B of dopant material gas by mass flow controller 5
2H
6) gas supplies in the reative cell 15.At this moment, control pressure regulating valve 7 makes the pressure of reative cell 15 remain on 0.9Pa.Then, High frequency power 1500W is supplied to the coil 3 as plasma source, to produce plasma in reative cell 15.In addition, High frequency power 200W is supplied to bottom electrode 14, makes boron inject the near surface of silicon substrate 13.Here, the plasma that is exposed to silicon substrate 13 is B
2H
6Mixed gas plasma (B with He
2H
6/ He plasma).And, by changing He gas and the B that flows in the mass flow controller 4 and 5
2H
6The flow-rate ratio of gas can change B
2H
6Mixing ratio with He.
If by irradiation B
2H
6Mixed gas plasma (B with He
2H
6/ He plasma) to silicon substrate, applies bias voltage, then have the time with sputter saturated (balance) of mixing of boron.In addition, in this embodiment, can see that saturation time is long and be easy to stable the use.That is to say that if plasma irradiating begins, then dosage increases at first, but make dosage substantially evenly continue with the time that the time variation has nothing to do.In addition, if the time further increases, dosage reduces.Therefore, by making dosage substantially evenly change irrelevant time process window, can accurately control dosage with the time.In addition, make the uniform time of dosage in the silicon substrate surface and set doping time, can obtain inner evenness according to late start time by measuring in advance.
(second embodiment)
Followingly the second embodiment of the present invention is described with reference to Fig. 2.
Device shown in Fig. 2 is called plasma doping apparatus B (PD device B).
Fig. 2 is the floor map that the impurity that uses in the second embodiment of the invention mixes device.Among Fig. 2, impurity mixes device and uses the spiral plasma device, so in this device, supply with B via mass flow controller 24 and 25
2H
6/ He gas and He gas.
Here, impurity also mixes in the silicon substrate (sample) 33 on the sample stage 34 that is placed in the reative cell 35., follow to coil 23 supply high frequency rates by high frequency electric source 21 via mass flow controller 24 and 25 B that supply with
2H
6/ He gas and He gas are by plasmaization.
This device in, High Accuracy Control mass flow controller 24 and 25 and control B
2H
6The mixing ratio of/He.Therefore, concentration that can the control gaseous plasma makes dosage evenly not have time dependent behavior.
＜example 1 〉
Use changes the dosage and the plasma doping time of boron simultaneously with reference to the PD device B that figure 2 illustrates in a second embodiment, carries out plasma doping on the 200mm substrate.
Fig. 3 shows the dosage of boron this moment and the measurement result that plasma doping concerned between the time.The longitudinal axis represents that dosage and transverse axis represent the plasma doping time.
If by irradiation B
2H
6Mixed gas plasma (B with He
2H
6/ He plasma) to silicon substrate, applies bias voltage, then have the time with sputter saturated (balance) of mixing of boron.In addition, in this embodiment, can see that saturation time is long and be easy to stable the use.That is to say that if plasma irradiating begins, then dosage increases at first, but make dosage substantially evenly continue with the time that the time variation has nothing to do.In addition, if the time further increases, dosage reduces.Therefore, evenly change time process window when irrelevant, can accurately control dosage with the time by making that dosage is basic.In addition, can obtain inner evenness.
Utilize this phenomenon, for example, confirm that the dosage of boron can be set at 2.62E15cm
-2, precision is in 1 σ=1%.If utilize 0.2%/99.8%B
2H
6/ He gas concentration is at V
DCCarry out plasma doping under 60V, power 1500W and the pressure 0.9Pa, because 45 seconds dosage is 2.62E15cm
-2With 60 seconds dosage be 2.63E15cm
-2, are negligible 0.01E15cm from 45 seconds to 60 seconds DMs
-2, shown in the curve b of Fig. 3.At this moment, the dosage time per unit increases with little increment.Speed is very slow, that is, and and (2.63E15-2.62E15)/(60-45)=6.7E11cm
-2/ second.That is, dosage is stable with respect to the time variation.
Seek 2.62E15cm
-2The time, make that difference (± 3 σ) is 2.52-2.68E15cm between acceptable dose that condition 1 σ=1% sets up minimum and maximum
-2, that is, and about 1.5E14cm
-2During the doping time between 45 seconds to 60 seconds, dosage is only with 6.7E11cm
-2The slow rate of/second changes.Therefore, can to carry out target be 2.62E15cm in expection
-2The dosage control of 1 σ=1%.This is because be that 100 milliseconds of magnitudes and doping time were offset maximum 1 second by the control of the doping time of device decision.
Here, infer dosage from sheet resistance after annealing 3 minutes, and the difference between the sheet resistance of sample during the doping time between 45 seconds to 60 seconds is that can to ignore ground 107.4 to 107.0ohm/sq be 0.4ohm/sq at 1100 ℃.The long-time little change of dosage down in 15 seconds is significant discovery.Although as mentioned above, with regard to device control, it is hundreds of at the most microseconds that plasma doping repeats 50 seconds time migration.Because for the concern of about 50 seconds ± 0.5 second skew is enough, so the dosage control method is highly stable and have a high controllability.
As can be seen from Figure 3, work as B
2H
6/ He gas concentration is 0.025%/99.975% o'clock, has the doping and the sputter balance time scope of boron near 60 seconds.Work as B
2H
6/ He gas concentration is 0.1%/99.9% o'clock, has this time range near 60 seconds.Work as B
2H
6/ He gas concentration is 0.2%/99.8% o'clock, has this time range near 45 to 60 seconds.Work as B
2H
6/ He gas concentration is 0.5%/99.5% o'clock, has this time range near 60 to 70 seconds.In addition, work as B
2H
6/ He gas concentration is 0.6%/99.4% o'clock, has this time range near 60 to 100 seconds.In near these, with regard to device control, the time dependent change of dosage is very little, and can control dosage accurately.This can pass through B
2H
6/ He gas concentration is that the identity logic under 0.2%/99.8% situation is explained.
Fig. 4 illustrates for time of Fig. 3 result of the test and changes, and changes dosage B and B when saturated when the time
2H
6The rank results that concerns between/He the gas concentration.The longitudinal axis is represented Sa, and transverse axis is represented B
2H
6/ He gas concentration.As a result, B
2H
6/ He gas concentration and Sa have relation one to one.From top explanation, below can be proved.At first, work as B
2H
6When/He gas concentration changes, wherein make the basic dosage level uniformly of DM that changes with respect to the time to be changed.In addition, adjust B
2H
6/ He gas concentration makes and wherein makes the basic dosage level uniformly of DM that changes with respect to the time become desired amount.In addition, the plasma doping time is adjusted into the feasible basic time zone uniformly of DM that changes with respect to the time, and dosage accurately can be controlled at desired value thus.
Contrast, only by adjusting B
2H
6/ He gas concentration then lacks the stability at time migration.In addition, making the basic time zone uniformly of the DM zone in addition that changes with respect to the time, only, lack stability at time migration by adjusting the plasma doping time.In addition, make the basic time zone uniformly of DM that changes with respect to the time pass through B
2H
6/ He gas concentration changes.Therefore, need be according to each B
2H
6Gas concentration is adjusted time zone.When carrying out this adjustment, in particular B
2H
6In the time of can accurately adjusting dosage under the gas concentration, may lack different B
2H
6Under the gas concentration at the stability of time migration.
Fig. 5 and 6 shows after the using dosage control method is carried out plasma doping 1075 ℃ of results that substrate was annealed 20 seconds.81 position measurement sheet resistances in the surface of the end 5mm that removes the 200mm substrate.It has and is characterised in that to have used and makes the dosage relative time change uniform plasma doping time and B
2H
6/ He gas concentration.Here, provide simple declaration with reference to Fig. 3 and 4.If B
2H
6The relative predetermined bias of/He gas concentration is suitably set, and as shown in Figure 3, the change that can form the relative plasma doping time of B dosage changes and saturated time range hardly.When changing B
2H
6Can change saturated B dosage during/He gas concentration, as shown in Figure 4.That is, but the dosage Be Controlled.Here, the plasma doping condition of using among Fig. 5 and 6 is the plasma doping condition by arrow a and b indication in Fig. 3 and 8.Symbol a presentation graphs 5 and symbol b presentation graphs 6.
Fig. 5 shows the using dosage control method, by setting B
2H
6/ He gas concentration 0.1%/99.9% and plasma doping time 60 seconds, B dosage is adjusted to 1.63E15cm
-2The time the Rs uniformity.Rs's on average is that 194.0ohm/sq and uniformity are 2.25% 1 σ.Under the situation of the sample of unsaturated time of dosage preparation, uniformity is about 5% to 10% 1 σ, so do not form layer uniformly.This is an effect of selecting according to the saturation time of dosage.
Fig. 6 illustrates the using dosage control method, by setting B
2H
6/ He gas concentration 0.2%/99.8% and plasma doping time 45 seconds, B dosage is adjusted to 2.62E15cm
-2The time gas concentration and the measurement result that concerns between the time figure.Rs's on average is that 147.9ohm/sq and uniformity are 2.42% 1 σ.So, be different under the dosage situation of Fig. 5, can reproducing 2.5% or littler excellent homogeneity.
Generally speaking, about uniformity, the value of 1 σ is more little, and improving inhomogeneity technical difficulty increases fast.That is, uniformity is being brought up to 5% difficulty and uniformity is brought up to 2.5% the difficulty from 5% from 10%, back one situation is also more difficult.5% or above uniformity about not using when of the present invention are used the present invention and are obtained 2.5% or littler uniformity easily.This has showed validity of the present invention.
＜example 2 〉
Next,, use the PD device A shown in Fig. 1, change the dosage and the plasma doping time of boron simultaneously, on the 300mm substrate, carry out plasma doping as example 2 of the present invention.
Fig. 7 shows the measurement result of the dosage and the inner evenness of plasma doping time and boron.As can be seen the dosage relative time of boron change located at about 30 seconds to begin to become saturated.In addition, the dosage of boron and inner evenness through 30 seconds the time, the plasma doping time shows good value when arriving 60 seconds.
Fig. 8 shows and by plasma doping boron is being mixed in the 300mm substrate shown in Figure 7 and then distributing in the face of 1075 ℃ of sheet resistances after 20 seconds of annealing.121 position measurement sheet resistances in the surface of the end 3mm that removes the 300mm substrate.Distribution by sheet resistance on the longitudinal axis of substrate center during Fig. 9 shows and distributes in the face of Fig. 8.In addition, Figure 10 corresponding diagram 9 is tables that the standardized value of the sheet resistance that sheet resistance obtains divided by mean value in each surface of substrate is shown.
So, dosage does not change with the change of plasma doping time, in the near future, has improved inner evenness yet.This can be that in the near future, the dosage in the part that dosage is little in the substrate surface is followed the dosage in the saturated part of dosage because dosage does not change with the change of plasma doping time.
Simultaneously, be the plasma doping time if follow the time set of dosage after not changing closely with the change of plasma doping time, the dosage in the part that dosage is little in the substrate surface is not followed the dosage in the saturated part of dosage.In this case, inner evenness is insufficient.
That is,,, need to optimize more the plasma doping time of setting in order to ensure inner evenness even dosage control is fully.
Next, with reference to Fig. 9 and 10 explanations mechanism of the present invention.Among Fig. 9 and 10, show the sheet resistance behind 7 seconds (7sec), 30 seconds (30sec) and 60 seconds (60sec).In the part of mixing a large amount of boron at first (on Fig. 9 and 10 the trunnion axis from 150mm to 0mm part), dosage is along with time lapse is more saturated than more quickly.On the contrary, when plasma doping begins, do not have in the so many part of mixing boron (on Fig. 9 and 10 the trunnion axis from 75mm to 150mm part), before dosage is saturated, used the considerable time.
Yet if dosage begins saturated and time lapse, in the part of mixing a large amount of boron at first, the saturated and boron of dosage no longer is impregnated in.Simultaneously, in not having so many part of mixing boron at first, dosage reaches capacity.Therefore difference diminishes.For this reason, in Fig. 9 and 10, when doping was carried out 60 seconds, the varying width of sheet resistance was little on the longitudinal axis.So, can improve the inner evenness of sheet resistance.According to method of the present invention is the method for inner evenness when effectively guaranteeing plasma doping.Simultaneously, as mentioned above, can control dosage.
And under 1075 ℃, 20 seconds the annealing conditions that uses in example 1 and 2, the distribution of sheet resistance can be thought the distribution of dosage.This is because dosage and sheet resistance have relation one to one.Under the annealing conditions of high temperature and long period, can infer that impurity is by almost electricity activation.This is considered to the reason of one-to-one relationship.
Activation step then is described.This is common for the PD device, does not depend on the PD device.During annealing, on the sample stage of annealing device, place the silicon substrate that has been supplied to foreign ion.Then, be irradiated onto on the silicon substrate surface, make the surface of silicon substrate be heated and activate from the laser of the infrared laser emission and the mirroring that is reflected.
And, in activation step,, can use the photoflash lamp process chamber as the activation processing chamber.The photoflash lamp process chamber comprises chamber, sample stage, window and photoflash lamp.The silicon substrate that has been supplied to foreign ion is placed on the sample stage and the radiating light of photoflash lamp is radiated on the silicon substrate surface, make the surface of silicon substrate be heated and activate.
And among the above embodiment, in activation step, the photoflash lamp process chamber is as the activation processing chamber.Yet, the tungsten halogen lamp that can use the medium quantity batch processing of present semiconductor factory to use.
In the above embodiment of the present invention, in range of application of the present invention, only show some in the various variations of formation, shape and configuration of process chamber.Certainly, can consider except that example, still to drop on various variations in the scope of the invention.
In addition, be the situation of the semiconductor substrate that forms of silicon substrate although sample has been described, when the various different sample of processing, can use the present invention.For example, the present invention can effectively be applied to the silicon substrate and the SOI substrate of staining.This is that described substrate is the same with silicon substrate because of the surface configuration of only considering with regard to plasma.In addition, the present invention can effectively be applied to fin FET (Fin FET).Under the situation of fin FET, usually, structure is 1 μ m or littler magnitude.The coating width of plasma is 1mm or bigger magnitude.Therefore, only consider the surface configuration with regard to plasma, the structure of fin FET is insignificant little.This is the same with silicon substrate.
In addition, be the situation of boron although impurity has been described, when sample be silicon form semiconductor substrate the time, especially, when impurity is arsenic, phosphorus, boron, aluminium or antimony, can effectively use the present invention.This is because can form shallow junction in transistor part.
In addition, when hanging down, the concentration of the gas that comprises impurity can effectively use the present invention.Especially, the present invention can wherein need effectively be applied to the plasma doping of High Accuracy Control dosage.
In addition, illustrated that the gas that is supplied to reative cell in the plasma doping step is the situation that comprises the gas of dopant material.Yet the gas that the present invention can be applied to be supplied to reative cell does not comprise dopant material, and produces the situation of dopant material from solid impurity.That is, the present invention's solid that can effectively be applied to comprise foreign atom be placed in the reative cell, the excitation plasma for example He etc. and foreign atom by the plasmaization and the situation of mixing by plasma doping.
In addition, when carrying out plasma doping, preferably the temperature at the reaction chamber wall that contacts plasma keeps handling under the basic uniform state.This be because, if the inner wall temperature of reative cell changes during handling, the possibility of adhering to of foreign ion changes under inner wall temperature, and the foreign ion quantity that is transmitted into the plasma from the film that comprises the foreign ion that is attached to inwall changes, and this causes the change of unit interval dosage.As keeping the reaction chamber wall method of temperature, can suitably select by the heater heats inwall method or via the method for the circulation cooled inner wall of cold-producing medium.
In addition, when in adjusting reative cell, comprising the concentration of gas of impurity, can use adjust gas delivery volume with the method for direct adjustment self concentration, reduce the temperature of reaction chamber wall and separate out predetermined impurity with the method that reduces impurity concentration, reduce the reative cell temperature inside and suppress the separating out with the method that keeps impurity concentration or the temperature of adjusting reaction chamber wall of predetermined impurity to adjust the method for dosage.In addition, possess feedback function, can carry out concentration control simultaneously in the temperature control of reaction chamber wall.
In addition, when carrying out plasma doping, during handling, can reduce the concentration of the gas that comprises foreign ion.With explanation proper method in this case.
At first, under the high state of the concentration of the gas that comprises foreign atom, carry out plasma doping.The unit interval dosage setting is high when at this moment, handling beginning.
Then, under the low state of the concentration of the gas that comprises foreign atom, carry out plasma doping.Then, handle making dosage evenly and not have to stop plasma doping in the time range of time dependent behavior.Under this mode, the situation that the concentration of comparing the gas that comprises foreign ion is handled under the low state when beginning can shorten total processing time.
In this case, can effectively use by the temperature that improves reaction chamber wall reduce gas concentration, the concentration that increases the gas that comprises impurity to maximum, then reduce the temperature of reaction chamber wall and promote impurity to separate out method subsequently to inwall.
＜industrial applicability 〉
According to this plasma doping method, can realize a kind of can be accurately and economic control impurity mix Amount and the plasma doping that can form shallow impurity diffusion zone. In addition, plasma of the present invention Doping method can be applied to these purposes, and for example semi-conductive impurity mixes in technology or the liquid crystal and uses The manufacturing etc. of thin film transistor (TFT).
Claims (19)
1. the plasma of the gas that will comprise foreign ion continues the scheduled time with predetermined concentration and shines on the sample and mix the plasma doping in district so that form impurity in sample surfaces, and described plasma doping may further comprise the steps:
Make dosage evenly and not have under the state of time dependent behavior in the concentration of plasma of setting doping time and comprising the gas of foreign ion, carry out plasma doping making dosage evenly and not have in the time range of time dependent behavior.
2. according to the plasma doping of claim 1,
Wherein make that in the concentration of plasma of setting doping time and comprising the gas of impurity entering impurity in the substrate surface mixes and leave under the saturated state of the impurity sputter of substrate surface and carry out plasma doping.
3. according to the plasma doping of claim 2,
Wherein doping time is set to have and reaches the length of degree that the dosage that makes the part that dosage is little in the substrate surface is followed the dosage of the saturated part of dosage.
4. according to each plasma doping in the claim 1 to 3,
The level that does not wherein have the uniform dose of time dependent behavior changes and changes along with the concentration of the plasma of the gas that comprises foreign ion.
5. according to each plasma doping in the claim 1 to 4,
The concentration of plasma that wherein comprises the gas of foreign ion changes and changes along with the concentration of the gas that comprises foreign atom.
6. according to each plasma doping in the claim 1 to 4,
The concentration of plasma of gas that wherein comprises foreign ion is along with the change of the concentration of the gas that comprises foreign atom and pressure and power and change.
7. according to each plasma doping in the claim 1 to 5,
The concentration of wherein setting ion, group and the gas of the concentration of gaseous plasma and gaseous plasma makes foreign ion enter the doping of substrate surface and the sputter of leaving substrate surface increases saturated in time.
8. according to each plasma doping in the claim 1 to 7,
The plasma that wherein comprises the gas of foreign ion is the molecule (B with boron atom and hydrogen atom
nH
m) mixed gas plasma.
9. according to the plasma doping of claim 8,
The plasma that wherein comprises the gas of foreign ion is B
2H
6Mixed gas plasma with He.
10. according to the plasma doping of claim 9,
B wherein
2H
6With the B in the mixed gas plasma of He
2H
6Gas concentration is in 0.01% to 1% scope.
11. according to the plasma doping of claim 10,
B wherein
2H
6With the B in the mixed gas plasma of He
2H
6Gas concentration is in 0.025% to 0.6% scope.
12. according to the plasma doping of claim 11,
Bias voltage V wherein
DCBe 60V or littler.
13. according to the plasma doping of claim 8,
The plasma that wherein comprises the gas of foreign ion is BF
3Mixed gas plasma with He.
14. according to the plasma doping of claim 1 to 13,
Wherein sample is a silicon substrate.
15. the plasma of the gas that will comprise foreign ion shines plasma doping on the sample with the predetermined concentration and the lasting scheduled time, described plasma doping comprises step:
Carry out plasma doping making dosage evenly and not have in the time zone of time dependent behavior.
16. according to each plasma doping in the claim 1 to 15,
Wherein make and under the basic uniform state of the temperature of the reaction chamber wall that contacts plasma, carry out plasma doping.
17. according to the plasma doping of claim 16,
Wherein under the heated state of reaction chamber wall of contact plasma, carry out plasma doping.
18. according to the plasma doping of claim 16,
Wherein under the state that the reaction chamber wall that contacts plasma is cooled, carry out plasma doping.
19. according to each plasma doping in the claim 1,2,3,4,5,6,7,8,9,12,13,14,15,16,17 and 18,
Reduce the concentration of the gas that comprises foreign atom during wherein handling.
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| JP2004360122 | 2004-12-13 | ||
| JP360122/2004 | 2004-12-13 | ||
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ID=38977081
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8383496B2 (en) | 2008-08-15 | 2013-02-26 | Kazuhiko Tonari | Plasma doping method and manufacturing method of semiconductor device |
| CN105097437A (en) * | 2014-05-22 | 2015-11-25 | 中芯国际集成电路制造(上海)有限公司 | Method for forming strain silicon layer, manufacturing method for PMOS device and semiconductor device |
-
2005
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8383496B2 (en) | 2008-08-15 | 2013-02-26 | Kazuhiko Tonari | Plasma doping method and manufacturing method of semiconductor device |
| CN102124543B (en) * | 2008-08-15 | 2013-03-13 | 株式会社爱发科 | Plasma doping method and semiconductor device manufacturing method |
| US8440551B2 (en) | 2008-08-15 | 2013-05-14 | Ulvac, Inc. | Plasma doping method and manufacturing method of semiconductor device |
| CN105097437A (en) * | 2014-05-22 | 2015-11-25 | 中芯国际集成电路制造(上海)有限公司 | Method for forming strain silicon layer, manufacturing method for PMOS device and semiconductor device |
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