CN110223927A - The metallic pollution analysis method of silicon wafer - Google Patents
The metallic pollution analysis method of silicon wafer Download PDFInfo
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- CN110223927A CN110223927A CN201810173218.5A CN201810173218A CN110223927A CN 110223927 A CN110223927 A CN 110223927A CN 201810173218 A CN201810173218 A CN 201810173218A CN 110223927 A CN110223927 A CN 110223927A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
Abstract
The present invention provides a kind of metallic pollution analysis method of silicon wafer, comprising: is contacted by making the silicon wafer as analysis object with the mixed gas of hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas, is etched to the surface region of the silicon wafer；To the silicon wafer heating after the etching, the surface exposed by etching is heated to 180 DEG C or more of temperature；Silicon wafer surface after the heating is exposed under fluoric acid steam；Metal component on silicon wafer surface after the exposure is trapped in recycling aqueous solution；The recycling is analyzed with the metal component in aqueous solution.
Description
Technical field
The present invention relates to a kind of metallic pollution analysis method of silicon wafer, more specifically to one kind can rapidly and
The metallic pollution analysis method of the silicon wafer of the metallic pollution of silicon wafer surface region is analyzed in high sensitivity.
Background technique
In field of semiconductor manufacture, along with the microminiaturization of semiconductor device, highly integrated, report has and is made as substrate
The trace meter impurity of silicon wafer surface impacts the characteristic of device, for example, leak electricity bad, oxidation film is not withstand pressure,
Service life is low etc..In addition, not only the metal impurity pollution on silicon wafer surface impacts the characteristic of device, device is being formed
The trace meter impurity of the silicon wafer surface region of construction pollutes the shadow such as shallow ridges and source, electric leakage caused by equipment energy characteristic
Sound is also gradually considered as problem.
In the past, the metal impurity evaluation method as silicon wafer surface and surface section, the method used are as follows: use acid solution
Silicon wafer surface section is dissolved, then the acid solution is diluted or is concentrated, with Atomic Absorption Spectrometer (AAS) or inductive coupling etc. from
Daughter mass spectrograph (ICP-MS) carries out quantitative analysis (hereinafter referred to as " liquid etching method ").However, in liquid etching method, in order to
To silicon wafer surface layer uniform etching, a large amount of acid solution is needed.Therefore, because metal impurity concentration is dilute by a large amount of acid solutions
It releases, so sensitivity is insufficient, it is low that the rising of analysis background caused by the pollution that acid solution itself is brought into will lead to sensitivity,
In the field of semiconductor manufacture for asking ultramicron metal impurity to evaluate, high-sensitivity analysis is interfered.
Therefore, in recent years, proposing that a kind of method (referring to Japanese Unexamined Patent Publication 2008-130696 bulletin) is used as replaces liquid phase
The measure of etching method, that is, it is decomposed by gas phase with acid vapour (etching gas) to silicon wafer surface section, recycles its residue decomposition,
Utilize the method (hereinafter also referred to as gas phase etching method) of AAS or ICP-MS quantitative analysis.
Summary of the invention
Compared with liquid etching method, the quantity for the acid solution that gas phase etching method is used in etching is few, acid solution itself band
The contaminant capacity entered is also considerably less, is studied using above-mentioned advantage.However, gas phase etching method, compared with liquid etching method, acid is (sour
Steam) and the reaction speed of silicon wafer it is very slow.Prolonged gas-phase decomposition reaction is carried out, may be easy to increase etch quantity, but
It is that analysis takes a long time, especially when analyzing subject area becomes broadness, will lead to productivity and be remarkably decreased.
Moreover, in the metallic pollution analysis of the silicon wafer used as semiconductor substrate, although pursuing highly sensitive
Ultramicron metal component is analyzed on ground, but as documented in Japanese Unexamined Patent Publication 2008-130696 bulletin, in gas phase etching
In method, the Si compound (Si level of residue) generated on analysis object silicon wafer in gas-phase decomposition reaction will become ICP-MS etc.
Obstructive substance in analysis instrument when quantitative assessment.Particularly, if analysis subject area becomes broad, in silicon wafer, benefit
The quantity that the silicon of removing is decomposed with gas-phase decomposition also becomes more, and the generation quantity of Si residue also becomes more therewith, so Si residue pair
The influence of sensitivity for analysis bring increases to the degree that cannot be ignored.
As described above, pursuit being capable of rapid and Gao Ling in the metallic pollution analysis of the silicon wafer using gas phase etching method
The analysis of sensitivity, especially analysis subject area become broader, which becomes stronger.
Therefore, the purpose of the present invention is to provide a kind of measures, in the metallic pollution for carrying out silicon wafer using gas phase etching method
When analysis, for shortening gas-phase decomposition reaction required time and improving sensitivity for analysis.
The present inventor is hardy studied to achieve the goals above, obtains following neodoxies.
In existing gas phase etching method, as documented in Japanese Unexamined Patent Publication 2008-130696 bulletin, by hydrogen fluorine
The mixed acid of acid and nitric acid gasifies resulting acid vapour (the namely mixed gas of hydrogen fluoride gas and nitric acid gas) as erosion
Gas is carved to use.In contrast, the present inventor is by (being hereafter also recorded into " NO for oxides of nitrogen gasxGas ") it is mixed
It closes in above-mentioned mixed gas, the reaction screening degree of gas-phase decomposition reaction can be increased substantially.Thus, even if in analysis target area
Domain is wide, using existing gas phase etching method and etching work procedure become the time it is very long in the case where, compared with existing gas phase etching method,
Also the time required to can be shortened etching work procedure.The present inventor speculates its reason as following.
As use hydrogen fluoride gas (HF) and nitric acid gas (HNO3) mixed gas as etching gas to silicon wafer
When surface region etches, while carrying out below by HNO3The oxidation (1) of Si caused by gas and as caused by HF gas
The removing (2) of SiO2.
Si+4HNO3↑→SiO2+8NO↑+2H2O …(1)
SiO2+4HF↑→SiF4+2H2O …(2)
Generated NO gas is just reacted with oxygen after rigid reaction as shown in following (3) in the reaction.
2NO↑+O2→2NO2↑ …(3)
It is paid in reaction vessel inner face and after becoming fine droplet in the vapor that formula (1), formula (2) generate, such as formula (4) institute
Show that SiF4 gas is reacted with the drop, generates gelatinous orthosilicic acid (H like that4SiO4).Moreover, the orthosilicic acid generated herein
(H4SiO4) distillation can be decomposed within the shorter time.
SiF4A+4H2O→H4SiO4↓+4HF↑ …(4)
Utilize the NO generated respectively in formula (3), formula (4)2Above-mentioned formula (1), formula (2) is repeated in gas and HF gas
Reaction, Si are decomposed distillation.Here, if by NOxGas (preferably NO gas and/or NO2Gas) it imported into reaction system
It is interior, the reaction of (1)~(4) can be promoted, it is believed that the reaction speed (etching speed) of gas-phase decomposition can be greatlyd improve.
Moreover, it was found by the inventors of the present invention that in the mixing using hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas
After gas carries out gas-phase decomposition reaction, the silicon wafer surface exposed due to by reacting because being decomposed by gas phase is heated to 180 DEG C or more,
The Si level of residue for reducing sensitivity for analysis can be greatly reduced.The present inventor speculates its reason as following.
As above description, the present inventor speculates, if using hydrogen fluoride gas (HF) and nitric acid gas is included
Body (HNO3) mixed gas be etched as surface region of the etching gas to silicon wafer, then simultaneously carry out it is above-mentioned by HNO3
The oxidation (1) of Si caused by gas and the SiO as caused by HF gas2Removing (2).Generated NO gas is as above in the reaction
It states shown in (3) like that, is just reacted with oxygen after rigid reaction.Yu Fanying is paid in the vapor that above-mentioned formula (1), formula (2) generate to hold
Device inner face and after becoming small water droplet, as shown in above-mentioned formula (4), SiF4Gas is reacted with the drop, is generated gelatinous
Orthosilicic acid (H4SiO4).As above description, if by NOxGas is imported into reaction system, can promote (1)~(4)
Reaction, so the reaction speed (etching speed) of gas-phase decomposition can be greatlyd improve.But only according to this point, it is difficult to reduce
Si level of residue after gas-phase decomposition reaction.Although this is because utilizing HF and HNO3, usual 97% or more Si decomposes and generates
SiF4, but the Si of other remainings generates difficult the ammonium hexafluorosilicate ((NH decomposed4)2SiF6)。
In contrast, it was found by the inventors of the present invention that the silicon exposed after by by above-mentioned mixed gas gas phase etching
Wafer surface is heated to 180 DEG C or more, can make (NH4)2SiF6Distillation is decomposed, therefore can significantly drop bottom Si level of residue.And
And it although is disclosed in paragraph [0030], in above-mentioned Japanese Unexamined Patent Publication 2008-130696 bulletin after gas-phase decomposition, by silicon
Chip heats in the heating plate for being heated to 100~150 DEG C, but here, since the set temperature of heating plate is up to 150
DEG C, so cannot be reached by being placed the surface temperature of silicon wafer on hot plate by 180 DEG C.Here, even if by making to be easy to divide
The H4SiO of solution4(product of above-mentioned formula (4)) decomposes distillation and can reduce Si level of residue, but makes the difficult (NH decomposed4)2SiF6It is extremely difficult to decompose distillation.Although in the embodiment 2 of Japanese Unexamined Patent Publication 2008-130696 bulletin, by by gas
Silicon wafer after phase decomposition reaction heats 30 minutes in the heating plate for be set as 120 DEG C, the silicon fluoride of about 90 mass % or more
Compound evaporation, it is believed that in the embodiment 2 of Japanese Unexamined Patent Publication 2008-130696 bulletin, due to only 02 μm of etch quantity, institute
With (NH4)2SiF6Generation quantity it is few, most of fluorinated silicon compound is easily decomposed H4SiO4.In contrast, due to etching
Measure (the NH more, hardly possible is decomposed4)2SiF6Generation quantity it is more, so utilize Japanese Unexamined Patent Publication 2008-130696 bulletin record
Method, it is difficult to prevent sensitivity for analysis from reducing because of Si level of residue.
As described above, the following situations of the present inventor's new discovery, that is, by by hydrogen fluoride gas, nitric acid gas
It uses with the mixed gas of oxides of nitrogen gas as etching gas, the time required to gas-phase decomposition reaction can be shortened, and passes through
Silicon wafer surface after gas-phase decomposition reaction is heated to 180 DEG C or more, Si level of residue can be greatly reduced.Moreover, this hair
Bright inventor completes the present invention according to above-mentioned opinion, further investigation.
It is, above-mentioned purpose is realized by following measures.
[1] the metallic pollution analysis method of a kind of silicon wafer, comprising:
By the gaseous mixture for making silicon wafer and hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas as analysis object
Body contact etches the surface region of the silicon wafer；
To the silicon wafer heating after above-mentioned etching, the surface exposed by etching is made to be heated to 180 DEG C or more of temperature；
Silicon wafer surface after above-mentioned heating is exposed under fluoric acid steam；
The metal component on silicon wafer surface after trapping above-mentioned exposure in recycling aqueous solution；
Above-mentioned recycling is analyzed with the metal component in aqueous solution.
[2] in the metallic pollution analysis method for the silicon wafer that [1] is recorded, above-mentioned surface region is from analysis object silicon wafer
The region that the surface of piece is 3 μm or more to depth.
[3] in the metallic pollution analysis method for the silicon wafer that [1] or [2] is recorded, the silicon wafer after above-mentioned etching is added
Heat makes the surface exposed by etching be heated to 180 DEG C or more and 250 DEG C of temperature below.
[4] above-mentioned as analysis in the metallic pollution analysis method for the silicon wafer that any one of [1]~[3] are recorded
The silicon wafer of object is the chip for grasp engineering pollution.
Effect of the invention
It according to the present invention, also can be right in high sensitivity in a short time even if in the case where analyzing the wide situation of subject area
The metallic pollution of the silicon wafer of baneful influence is brought to be evaluated to equipment energy characteristic.By that will be used to carry out to grasp engineering pollution
Silicon wafer of the silicon wafer as evaluation object will appreciate that engineering pollutes, it is thus possible to provide the silicon wafer of high quality.
Specific embodiment
The metallic pollution analysis method (hereinafter referred to as " analysis method ") of silicon wafer of the invention includes: by making conduct
The silicon wafer of analysis object is contacted with the mixed gas of hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas, to the silicon wafer
Surface region etching；To the silicon wafer heating after above-mentioned etching, the surface exposed by etching is made to be heated to 180 DEG C or more
Temperature；Silicon wafer surface after above-mentioned heating is exposed under fluoric acid steam；After trapping above-mentioned exposure in recycling aqueous solution
Silicon wafer surface on metal component；Above-mentioned recycling is analyzed with the metal component in aqueous solution.
As described above, can be shortened needed for gas-phase decomposition reaction by being used using above-mentioned mixed gas as etching gas
Si level of residue can be greatly reduced by the way that the silicon wafer surface after gas-phase decomposition reaction is heated to 180 DEG C or more in time.
But since the silicon wafer surface after heating becomes the hydrophilic surface for being formed with oxidation film, so if sharp in the case
Metal component is recycled with recycling aqueous solution, since recycling aqueous solution on silicon wafer surface be unfolded by large area, it is difficult to
It is comprehensively scanned in whole surface, and, it is also difficult to recycling aqueous solution is accurately recycled from silicon wafer surface.It is thus impossible to
Metal component is trapped from silicon wafer surface with high-recovery, causes sensitivity for analysis low.Therefore in the present invention, will heat
Silicon wafer surface afterwards is exposed under fluoric acid steam.Thus, due to silicon wafer surface hydrophobization, so recycling is easy with aqueous solution
It is rolled on silicon wafer surface with drop state, can then entire Surface scan is easy to recycle drop from silicon wafer surface.Cause
And metal component can be trapped from silicon wafer surface with high-recovery.
Hereafter analysis method of the invention is described in detail.
In analysis method of the invention, by making silicon wafer and hydrogen fluoride gas, nitric acid gas as analysis object
It contacts with the mixed gas (etching gas) of oxides of nitrogen gas, is reacted using gas-phase decomposition, silicon wafer surface region is carried out
Etching.For example, can be made by importeding into above-mentioned etching gas in the chamber (dead-air space) configured with analysis object silicon wafer
Etching gas is contacted with silicon wafer.
Hydrogen fluoride gas, nitric acid gas and the NO used as etching gasxThe mixed gas of gas passes through arbitrarily to compare
Example can obtain above-mentioned 3 kinds of gas mixings.For example, by making carrier gas in the nitric acid and hydrofluoric acid impregnated of silicon wafer
Mixed acid (hereinafter referred to as " mixed acid A ") the interior bubbling of (fluoric acid) and generate nitric acid gas and NOxThe mixed gas of gas, passes through
So that carrier gas is generated hydrogen fluoride gas in mixed acid (hereinafter referred to as " mixed acid B ") the interior bubbling of hydrofluoric acid and sulfuric acid, leads to
It crosses above-mentioned nitric acid gas and NOxThe mixed gas of gas is mixed with above-mentioned hydrogen fluoride gas, can obtain above-mentioned mixed gas.
As acid solution used in the manufacture in mixed acid A and mixed acid B, for example, capableing of the hydrogen of 40~50 mass % of exemplary concentration
Sulfuric acid (the H of fluoric acid (HF), 50~98 mass % of concentration2SO4), the nitric acid (HNO of 50~70 mass % of concentration3).In mixed acid A
In nitric acid and the mixing ratio of hydrofluoric acid can be for example, nitric acid: hydrofluoric acid (volume reference)=10~20: 1~3.It is mixing
The mixing ratio of sulfuric acid and hydrofluoric acid in sour B can be for example, hydrofluoric acid: sulfuric acid (volume reference)=3~6: 1~3.Moreover,
As the carrier gas used in bubbling, it is preferable to use the inert gases such as nitrogen.Once wanting bubbling, it is preferably able to supply always
Constant gas, although bubbling quantity is not specifically limited, it is preferred that for example, 0.1~2L/min.Although above-mentioned mixed gas
Mixing ratio be not specifically limited, for example, being adjusted according to the flow of the carrier gas used for bubbling.
Alternatively, instead of mixed acid B, can also using the hydrofluoric acid after heating as hydrogen fluoride gas occurring source come using.?
This, is the gas-phase decomposition reaction speed in order to improve wafer surface to the reasons why hydrofluoric acid heating.If do not heated to hydrofluoric acid,
Then compared with to hydrofluoric acid heating, since the occurrence quantity of hydrogen fluoride gas in the unit time is few, so the etching speed of wafer surface
Degree is lower.From the angle of etching speed, hydrofluoric acid is preferably heated to 30 DEG C of liquid temperature or more.Inventor according to the present invention
Research, 40 DEG C of hydrofluoric acid liquid temperature be optimum condition, temperature control be also easier.The present inventor thinks, using by
It is heated to hydrogen fluoride gas caused by 40 DEG C of hydrofluoric acid to be in predefined conditions etched wafer surface, then etching speed
For 10 μm/hr or so, using the hydrogen fluoride gas as caused by discontented 30 DEG C of hydrofluoric acid under the same conditions to wafer surface
It is etched, then etching speed is less than half the case where being heated to 40 DEG C.Therefore, using hydrofluoric acid as hydrogen fluoride gas
In the case where occurring source, 30 DEG C of liquid temperature or more are preferably heated to, is most preferably heated to 40 DEG C of liquid temperature or so.Although the heating of hydrofluoric acid
Temperature is higher, and the occurrence quantity of the hydrogen fluoride gas in the unit time more increases, but the research of inventor according to the present invention, even if
Hydrofluoric acid is heated to above 50 DEG C of liquid temperature increase the occurrence quantity of the hydrogen fluoride gas of unit time, and used hydrogen fluorine
Acid is heated to 40 DEG C and the etching speed in the case where the hydrogen fluoride gas of generation is compared, and the etching speed of wafer surface does not mention
It is high.Inventor think the reason is that, wafer surface gas-phase decomposition reaction be determine speed element.Moreover, because if hydrogen fluorine
The liquid temperature of acid is more than 50 DEG C, and the occurrence quantity of the hydrogen fluoride of unit time increases, so the replacement frequency of hydrofluoric acid increases.Therefore,
The heating temperature of industrial hydrofluoric acid is preferably 50 DEG C or less.For example, using heating facilities such as electric heaters to being introduced into container
Interior hydrofluoric acid heating, and temperature sensor is set to control the output of heater, maintain desired temperature (as described above,
It is preferred that 30~50 DEG C) in the state of, make the nitrogen bubbling as carrier gas, hydrogen fluoride gas can be made from the hydrogen fluorine after heating
It is generated in acid.
In order to generate the NO of predetermined quantity always or periodically from mixed acid AxGas, preferably by carrier gas make impregnated of
The mixed acid bubbling of the nitric acid and hydrofluoric acid of silicon wafer, and quantitative hydrofluoric acid is added always or periodically.As silicon as used herein
Piece generates in the reaction system due to the decomposition of silicon wafer pollute the silicon wafer, it is preferable to use high-purity in order to prevent.As this height
The silicon wafer of purity can enumerate silicon wafer, preferably to the silicon wafer in silicon substrate board manufacturing process after finally cleaning into
Row is punched and the silicon wafer of acquisition.Although the usage quantity of silicon wafer is not specially limited, as long as can generate the desired number of
Gas, for example, the mixed acid of 68 mass % aqueous solution of nitric acid 80g and 50 mass % aqueous fluorine acid solution 6g, leaching can be directed to
The fluoric acid of 50 mass % is added in the mixed acid by the silicon wafer of 3~5g of stain or so with the quantity of 0.1~1.0g/min.
It can also collaborate and mix in the reaction chamber configured with silicon wafer in the gas that different occurring sources generate, it can also be with
It mixes in the container being arranged on before reaction chamber, is imported into reaction chamber with the state of mixed gas.In order to improve gaseous mixture
The uniformity of body, it is preferred to use later approach.
The time for contacting silicon wafer with etching gas is according to the etching gas quantity that is directed to reaction chamber and desired
Etch quantity setting, be not specially limited.Moreover, by being heated or cooled to when being decomposed by gas phase and reacting to silicon wafer
Promote gas-phase decomposition reaction, also can further shorten etching period.
Silicon wafer surface after above-mentioned etching, the metal remained in the surface region after being comprised in etching are impure
Object.Therefore, by that can seek being comprised in the table after etching from the silicon wafer surface recycling metal component after etching and quantitatively
Metal impurity concentration in layer region, can seek the metallic pollution amount of surface region.However as described above, if losing
Silicon wafer surface after quarter, it is a large amount of to remain orthosilicic acid and ammonium hexafluorosilicate, these Si compounds (Si residue) with as analysis pair
The metal impurity of elephant is recovered together, and is directed to analysis instrument, this can become the low reason of sensitivity for analysis.It is specific and
Speech, in Atomic Absorption Spectrometer (AAS), in analysis, background is got higher, and the peak shape of sample is abnormal.In inductively coupled plasma
In constitution spectrometer (ICP-MS), anomaly peak when analysis as interference molecules peak is detected.Thus while in Japanese Unexamined Patent Publication
It is proposed in 2008-130696 bulletin, by being heated after the etching to silicon wafer, to remove Si residue, but one kind of Si residue,
That is ammonium hexafluorosilicate ((NH4)2SiF6) it is hard-decomposed substance, it is recorded using Japanese Unexamined Patent Publication 2008-130696 bulletin such
Heat treatment be difficult to be removed.In view of this, in the present invention, for the silicon wafer after etching, by what is exposed by etching
Surface is heated to 180 DEG C or more of temperature.Thus, make the ammonium hexafluorosilicate being present on the surface decompose distillation, can greatly every
Degree reduces the Si level of residue being recovered together with the metal impurity of analysis object, so analysis precision can be improved.
The surface temperature of silicon wafer when above-mentioned heating is 180 DEG C or more, preferably 180 DEG C or more and 250 DEG C hereinafter, most
Good is 180 DEG C or more and 220 DEG C or less.This is because if the surface temperature of silicon wafer is high, the metal in batches of silicon wafers at
Divide (Cu etc.) that there is a possibility that spreading to wafer surface.Metal when generating this diffusion, outside analysis subject area
Ingredient become trapped in recovered liquid, impacts to analysis result, so as surface temperature as described above, the heating of silicon wafer
Temperature is preferably 250 DEG C hereinafter, more preferably 220 DEG C or less.
Above-mentioned heating can be configured the silicon wafer after etching facing towards vertical upper power by make to expose by etching
It is carried out in the heating plate for be heated to predetermined temperature.It, preferably will heating from the angle for preventing the pollution from heating plate
After plate cleaning, then on hot plate by silicon wafer configuration.In order to further prevent the pollution from heating plate, preferably with silicon wafer
The mode being not directly contacted with heating plate configures the silicon wafer for sufficiently cleaning and improving clean degree between heating plate and silicon wafer
Piece (false piece).
The ammonium hexafluorosilicate that the time of above-mentioned heating is configured to silicon wafer surface can sufficiently decompose distillation.Once six
Ammonium fluosilicate decomposes distillation, just generates white cigarette, so by until being heated to not generate white cigarette, it can be abundant from silicon wafer surface
Remove ammonium hexafluorosilicate.Such as in the case where being etched to the silicon wafer of diameter 200mm away from 10 μm of case depth or so, pass through
Heating 10 minutes or more, the ammonium hexafluorosilicate quantity of silicon wafer surface can be reduced to the degree of not impact analysis sensitivity.
Although usually remaining moisture that etching gas included, because reaction is produced moreover, silicon wafer surface after the etching
Raw moisture and easy decomposability substance orthosilicic acid, but these substances can be removed by heating.
It, can by scanning recycling aqueous solution in the silicon wafer surface by the low Si level of residue of above-mentioned heating sun
The metal impurity that object silicon wafer surface region is included will be analyzed to be captured in recovered liquid.In the present invention, make to recycle
With aqueous solution before silicon wafer surface scanning, silicon wafer surface is exposed under fluoric acid steam.As described above, pass through progress
The processing can make silicon wafer surface hydrophobization, so recycling is easy to roll on silicon wafer surface with drop state with aqueous solution
It is dynamic, entire surface can be scanned, is then easy to recycle drop from silicon wafer surface.By making carrier gas bubbling in hydrofluoric acid,
Above-mentioned fluoric acid steam can be generated.As carrier gas, the inert gases such as nitrogen are suitable.
As above-mentioned recycling aqueous solution, HF/H can be used2O2、HF/HCl/H2O2、HNO3/HF、HNO3/ HF/HCl etc.
Mixed acid aqueous solution.From the angle of recovery efficiency, the acid concentration in mixed acid aqueous solution as used herein is preferably 10 matter
Measure % or more.50~250 μ L of yield for supplying and scanning to silicon wafer surface is suitable.
As the method for scanning recycling aqueous solution in silicon wafer surface, can be used rotates wafer inclination to drip
The method of the solution impregnation entire surface of silicon wafer surface is arrived down.In the present invention, it is steamed since silicon wafer surface is exposed on fluoric acid
Hydrophobization under gas, so recycling aqueous solution not sprawl by large area on silicon wafer surface, but with the rolling of the state of drop
It is dynamic.Thus, recycling generally can comprehensively be scanned with aqueous solution in the entire surface of silicon wafer surface.Then, such as by making silicon
Chip tilts on container, and the drop (recycling aqueous solution) on surface is made to drip into container, can by recycling aqueous solution from
Silicon wafer surface recycling.Here, if recycling aqueous solution largely remains on silicon wafer surface, the rate of recovery of metal component
Low, sensitivity for analysis is lower.In contrast, in the present invention, since silicon wafer surface is hydrophobic, so recycling can be made to use
Aqueous solution does not remain in the recycling of silicon wafer surface Shangdi largely.Moreover, aforesaid operations can be manual, can also carry out automatically.
Then, by being analyzed with the metal component in aqueous solution the recycling after being scanned on silicon wafer surface, energy
Enough metal components for being included to the silicon wafer surface region for being etched removing carry out qualitative analysis and quantitative analysis.Metal component
Analysis can be using can be to the progress of known method that the metal component in solution is analyzed.It, can example as such method
Lift atomic absorption spectroscopy (AAS) and inductivity coupled plasma mass spectrometry analysis (ICP-MS).Since AAS and ICP-MS can
High-sensitivity analysis is carried out to trace meter ingredient, it is advantageous to use AAS and ICP-MS.It, can as the metal that can be analyzed
To enumerate the various metals such as Ag, Cu, Li, Na, Mg, Al, K, Ca, Cr, Fe, Ni, Zn.
It is sensitive due to ICP-MS although AAS and ICP-MS are the analytical equipments for being able to carry out high-sensitivity analysis
Du Genggao, so in order to further increase sensitivity for analysis, it is preferable to use ICP-MS.Although ICP-MS is greatly classified into quadrupole rod
Type ICP-MS and double focusing type fly ICP-MS, but compared with quadrupole rod-type ICP-MS, double focusing type fly ICP-MS has high-resolution, from
Resolution angle sets out, it is preferable to use double focusing type fly ICP-MS.
In the various heat treatments such as oxidation, diffusion in silicon wafer manufacturing process, metal impurity is easy to substrate surface layer
Portion's diffusion worries that this can cause precipitate, dislocation, oxidation induction stacking fault (OSF:Oxidation-induced
Stacking Fault) etc. crystal defects, the service life of minority carrier are short, leakage current increases, the insulation breakdown of oxidation film electricity
Pressure deterioration etc..Therefore, it in order to reduce the metallic pollution in the manufacturing processes such as heat treatment procedure, is usually heat-treated to product
Before, in-service evaluation carries out test evaluation with process contaminant capacity of the substrate to heating furnace to be used.Improved according to the evaluation of estimate dirty
After dye, formal product heat treatment is carried out.Moreover, in order to grasp daily engineering pollution, such as with every batch of 1,1 daily
Or 1 evaluation is used substrate as sample by 1 mode weekly, is evaluated engineering pollution.Metallic pollution of the invention is commented
Valence method can as it is as described above for carry out engineering pollution grasp chip evaluation method come using.For metal
Contamination analysis and the surface region etched refers to the region from silicon wafer surface towards depth direction, although according to the use of silicon wafer
Way and the physical characteristic pursued, it should which the depth (etch quantity) of etching is different, but for the silicon wafer used in device manufacturing
Piece, the metallic pollution for the surface section that 3 μm away from case depth~30 μm or so of Optimization Analysis, more preferably analysis is away from 10 μm of case depth
The metallic pollution of~30 μm or so of surface section.Particularly, the extension of 3 μm or more and 10 μm of etch quantities below to epitaxial wafer
Metal impurity evaluation in layer is highly effective.Moreover, 10 μm or more of etch quantity comments the metal impurity of silicon wafer interior
Valence is highly effective.In order to analyze wider region like this, etch quantity increases, along with this, the difficult Si level of residue decomposed
Increase, but according to the present invention, even in this case, can also be etched in a short time, and due to that can prevent because of Si
The decline of sensitivity for analysis caused by level of residue, so being able to carry out rapid and highly sensitive analysis.
Using the present invention, the analyzed silicon wafer of the metallic pollution of surface region can be p-type semiconductor substrate, can also be with
It is n-type semiconductor substrate.Its thickness is, for example, 600~1000 μm, and however, it is not limited to this.Analysis method of the invention is suitable for
The chip of diameter 200mm, 300mm, in addition, also can be suitably used for the chip of the bore like that such as diameter 450mm.
In analysis method of the invention explained above, above-mentioned each process is carried out in same device, i.e. gas phase is lost
It carves process, chip heating process, surface-hydrophobicized process caused by fluoric acid steam and metal impurity and traps process, by with soft
Part, which controls each process, can also realize automation.
[embodiment]
Hereafter, illustrate the present invention using embodiment.But the invention is not limited to mode shown in embodiment, hereafter remember
" % " carried indicates quality %.
[embodiment 1]
(1) etching of silicon wafer surface region caused by being reacted because of gas-phase decomposition
Surface and back part are polished after processing, diameter 200mm p-type silicon chip (resistivity: 10 Ω cm) to match
It sets in reaction chamber.
The mixed gas of hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas is imported into and is configured with above-mentioned silicon wafer
In reaction chamber, etched 1 hour using surface region of the gas-phase decomposition reaction to silicon wafer.The region being etched is away from silicon wafer table
The surface region of face depth to 11 μm.
Above-mentioned mixed gas is manufactured using following methods and is imported into reaction chamber.
After weighing the fluoric acid of the concentration 50% of 200g and putting it into the container of the first fluorine resin manufacture, added using electricity
Hot device makes liquid temperature become 40 DEG C to heating in container, then monitors liquid temperature with temperature sensor, liquid temperature is maintained 40 DEG C.
In addition, weighing 50% fluoric acid of concentration of 12g and 68% nitric acid of concentration of 150g and putting it into the second fluorine-containing tree
After the container of rouge manufacture, 4g silicon wafer is added in the same container.In order to generate NO necessary to etching reactionxGas, to
Machine 5 minutes.
It is standby after five minutes, to the first container, second container medical fluid in respectively with 2L/min (the first container), 0.4L/
The speed of min (second container) is sent into nitrogen, makes medical fluid bubbling.By bubbling, hydrogen fluoride gas is generated from the first container, from the
Two containers generate nitric acid gas and NOxGas.Make the gas generated after the empty container being configured in front of reaction chamber, imported into
In reaction chamber configured with silicon wafer.
(2) heat treatment of silicon wafer
After above-mentioned (1), silicon wafer is taken out out of reaction chamber in such a way that surface is not contaminated, across the silicon cleaned up
Chip (false piece) is configured on implementing the heating plate after cleaning in a manner of being exposed by etching facing towards vertical direction, then
While silicon wafer surface temperature is monitored with contactless thermometer, while heating to the silicon wafer in heating plate.Heating herein refers to,
Heating 10 minutes, makes the surface temperature exposed by etching become 200 DEG C.Due to during heating, being produced from silicon wafer surface
Raw white cigarette, so being able to confirm that, ammonium hexafluorosilicate decomposes distillation by heating.
(3) the surface-hydrophobicized processing as caused by fluoric acid steam
Silicon wafer after above-mentioned heating is configured in reaction chamber, by making nitrogen bubbling in hydrofluoric acid, will thus be produced
Raw fluoric acid steam importing is same intracavitary, is exposed to silicon wafer surface under fluoric acid steam, makes wafer surface hydrophobization.
(4) trapping and analysis of the metal impurity from silicon wafer surface
Silicon wafer after the silicic acid anhydride of above-mentioned (3) is taken out from reaction chamber, by the 10%HF/10%H of 200 μ L2O2's
Mixed acid aqueous solution drips, and after the entire surface for comprehensively scanning the silicon wafer surface after hydrophobization, recycles in container.Use pure water
By the liquid handling after the recovery at 1000 μ L after, import double focusing type fly ICP-MS (your science and technology-Thermo of the silent winged generation of match
Fisher Scientific ELEMENT2).It is 173ppm by silicon concentration of the ICP-MS after quantitative, is not influence double focusing type fly
The concentration of the measurement result of ICP-MS, so can be qualitative in high sensitivity to metal components such as Cu in the liquid being recovered, fixed
Amount analysis.
[comparative example 1]
Other than carrying out the heating of above-mentioned (2) in 30 minutes at 120 DEG C of silicon wafer surface temperature, progress and embodiment
1 identical operation, silicon concentration are 30000ppm (3%), this is dry to the detection sensitivity and macromolecular of double focusing type fly ICP-MS
The concentration impacted is related to, so metal component cannot be analyzed in high sensitivity.
[comparative example 2]
Without the surface-hydrophobicized processing of above-mentioned (3), with above-mentioned (4) in the same manner to have passed through above-mentioned (1) and (2) process
Silicon wafer surface drip mixed acid aqueous solution, liquid is sprawled, cannot function as drop and roll on silicon wafer surface.In the state
Under, it is difficult to trap metal component from silicon wafer surface with high-recovery.
[reference example 1, comparison reference example 1]
Use hydrogen fluoride gas, nitric acid gas and the oxides of nitrogen gas manufactured using method same as Example 1
Mixed gas is all polished after processing, diameter 200mm p-type silicon chip to 3 surfaces and the back side by gas-phase decomposition reaction
The surface region of (resistivity: 10 Ω cm) is etched (reference example 1).
In addition, 50% hydrofluoric acid of concentration of 100g is put into mixed acid B generation container, by 68% nitric acid of concentration of 80g
Be put into mixed acid A generation container, in addition to this, using 3 silicon wafers are etched with the identical method of reference example 1 (compared with join
Examine example 1).
The thickness for measuring center wafer portion respectively afterwards before the etch, measures the etching in reference example 1 and comparison reference example 1
Amount.Result is indicated in table 1.
[table 1]
| Chip 1 | Chip 2 | Chip 3 | |
| Reference example 1 | 10.5 | 10.9 | 10.3 |
| Comparison reference example 1 | 0.0 | 0.0 | 0.0 |
Evaluation result
Comparison reference example 1 be use hydrogen fluoride gas and nitric acid gas as the example of etching gas, but as shown in table 1,
It cannot be etched in etching period identical with reference example 1.In contrast, as shown in table 1, using hydrogen fluoride gas,
The mixed gas of nitric acid gas and oxides of nitrogen gas is as in the reference example 1 of etching gas, identical with comparison reference example 1
In time, silicon wafer surface section can be etched about 10 μm.
It can be seen that by the comparison of above-mentioned reference example 1 and comparison reference example 1 and use hydrogen fluoride gas and nitric acid gas
The existing gas phase etching method of mixed gas compare, by using the mixed of hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas
Gas is closed, the time required to etching can be greatly shortened.
[embodiment 2~4, comparative example 3]
Other than being heated in such a way that silicon wafer surface temperature becomes 2 temperature displaying functions of table in above-mentioned (2), carry out
Operation same as Example 1.In embodiment 2~4, due to same as Example 1, generated from the silicon chip surface in heating white
Cigarette so being able to confirm that ammonium hexafluorosilicate decomposes distillation because of heating, but in comparative example 3, does not generate white cigarette, so hexafluoro silicon
Sour ammonium decomposition distillation there is no.
The confirmation -1 that heating temperature influences
It is same as Example 1 for embodiment 2~4, comparative example 3, using ICP-MS to the liquid recycled from silicon wafer surface
Silicon concentration in body measures, by measured silicon concentration (Si level of residue) together with the measured value of above-described embodiment 1 under
Stating indicates in table 2.
[table 2]
The confirmation -2 that heating temperature influences
The operation of (1) (etching of silicon wafer surface region caused by being reacted because of gas-phase decomposition) without embodiment 1, into
Capable (2), (3), (4) identical operation with embodiment 1.In the heat treatment of the silicon wafer of above-mentioned (2), with silicon wafer surface
The mode that temperature becomes temperature identical with the silicon wafer surface temperature in Examples 1 to 4, comparative example 3 is heated.Needle
To each silicon wafer, quantifies in above-mentioned (4) from the Cu amount in the metal impurity that silicon wafer surface traps, as a result exist
It is indicated in table 3.The silicon wafer surface heated at temperature identical as Examples 1 to 3, comparative example 1, is not detected
To Cu.The Cu of confirmation inner wafer does not diffuse to the surface pollution.On the other hand, it is carried out at temperature same as Example 4
The silicon wafer of heat treatment only finds that micro Cu, quantity are 1% levels below of internal Cu contaminant capacity.In common product
The silicon wafer of rank, internal Cu contaminant capacity is very low, so even if with 1% or so diffusion pollution, also not to product quality
It makes a big impact.Therefore, as long as the heating temperature of silicon wafer surface be 250 DEG C hereinafter, as long as can be carried out the analysis of high reliability.
In addition in the case where internal Cu contaminant capacity is high concentration, even if 1% diffusion pollution below, Cu also becomes to the diffusing capacity on surface
Height, particularly, in the case where internal Cu contaminant capacity is high, the heating temperature of silicon wafer surface is suitably for 220 DEG C or less.
[table 3]
[embodiment 5]
Prepare 12 same as Example 1, surfaces and the back side is all polished that after processing, the p-type silicon of diameter 200mm is brilliant
Piece (resistivity: 10 Ω cm), as shown in Table 3, other than changing etching period, using identical as (1) of embodiment 1
Method, using gas-phase decomposition reaction surface region is etched.Identical etching period is carried out to 3 silicon wafers every time
Etching.After before the etch, thickness measure is carried out using ADE9900 (manufacture of KLA-Tencor company), according to the thickness of etching front and back
It is poor to spend, and calculates etch quantity, as a result indicates in following table 4.
[table 4] unit μm
As shown in table 4, etch quantity can be controlled using etching period (time being exposed under etching gas).
Processing and analysis same as Example 1 are carried out to each silicon wafer after etching.It is recycled from silicon wafer surface
It is in liquid, unrelated with etch quantity by the silicon concentration of ICP-MS measurement, if it is 1000ppm hereinafter, being exactly not influence double focusing
The concentration of the measurement result of type ICP-MS, so all wafers are directed to, it can be qualitative in high sensitivity to metal components such as Cu, fixed
Amount analysis.
The present invention is useful in the art of semiconductor manufacturing.
Claims (4)
1. a kind of metallic pollution analysis method of silicon wafer, comprising:
By connecing the mixed gas of silicon wafer and hydrogen fluoride gas, nitric acid gas and oxides of nitrogen gas as analysis object
Touching etches the surface region of the silicon wafer；
To the silicon wafer heating after the etching, the surface exposed by etching is heated to 180 DEG C or more of temperature；
Silicon wafer surface after the heating is exposed under fluoric acid steam；
Metal component on silicon wafer surface after the exposure is trapped in recycling aqueous solution；
The recycling is analyzed with the metal component in aqueous solution.
2. the metallic pollution analysis method of silicon wafer according to claim 1, the surface region is span analysis object
The region that the case depth of silicon wafer is 3 μm or more.
3. the metallic pollution analysis method of silicon wafer according to claim 1 or 2, adds the silicon wafer after the etching
The surface exposed by etching is heated to 180 DEG C or more and 250 DEG C of temperature below by heat.
4. the metallic pollution analysis method of silicon wafer according to claim 1 or 2, the silicon wafer as analysis object
It is the chip for grasp engineering pollution.
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| CN111540670A (en) * | 2020-05-11 | 2020-08-14 | 广州粤芯半导体技术有限公司 | Wet cleaning method for wafer and manufacturing method for semiconductor device |
| CN117153713A (en) * | 2023-10-25 | 2023-12-01 | 江苏惠达电子科技有限责任公司 | Method, system and equipment control method for detecting residual pollutants of frequency components |
| WO2024001016A1 (en) * | 2022-06-29 | 2024-01-04 | 江苏鲁汶仪器有限公司 | Enrichment method and analysis method for precious metal elements on surface of wafer |
| CN117393452A (en) * | 2023-12-11 | 2024-01-12 | 合肥晶合集成电路股份有限公司 | Method for collecting metal on surface of wafer |
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