WO2001006553A1 - Polishing mixture and process for reducing the incorporation of copper into silicon wafers - Google Patents
Polishing mixture and process for reducing the incorporation of copper into silicon wafers Download PDFInfo
- Publication number
- WO2001006553A1 WO2001006553A1 PCT/US2000/019872 US0019872W WO0106553A1 WO 2001006553 A1 WO2001006553 A1 WO 2001006553A1 US 0019872 W US0019872 W US 0019872W WO 0106553 A1 WO0106553 A1 WO 0106553A1
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- WIPO (PCT)
- Prior art keywords
- copper
- polishing
- polishing mixture
- set forth
- mixture
- Prior art date
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Classifications
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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
- H01L21/02002—Preparing wafers
- H01L21/02005—Preparing bulk and homogeneous wafers
- H01L21/02008—Multistep processes
- H01L21/0201—Specific process step
- H01L21/02024—Mirror polishing
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09G—POLISHING COMPOSITIONS; SKI WAXES
- C09G1/00—Polishing compositions
- C09G1/02—Polishing compositions containing abrasives or grinding agents
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K3/00—Materials not provided for elsewhere
- C09K3/14—Anti-slip materials; Abrasives
- C09K3/1454—Abrasive powders, suspensions and pastes for polishing
Definitions
- This invention relates generally to a polishing mixture and process for reducing the incorporation of copper into silicon wafers and, more particularly, to such a polishing mixture and process for reducing the amount of copper that enters silicon wafers during polishing without affecting polishing performance adversely.
- polishing mixtures contain an inorganic base and colloidal silica. Such mixtures and other polishing chemicals present in the mixture contain trace metal impurities. Of these, copper presents a particular problem because it is incorporated into wafers during surface polishing. It is important to reduce such copper contamination because a large fraction of random semiconductor device and gate-oxide failures can be traced to copper suicide precipitates. Furthermore, high concentrations of copper contamination cause an undesired resistivity increase and promotes a degradation of the wafer surface known as chemical haze.
- the concentration of copper on the surface of a silicon wafer be no more than lxlO 10 atoms/cm 2 to lxl 0 n atoms/cm 2 , as determined by methods standard in the art. It is foreseeable that this requirement will be decreased to a value of lxl 0 9 atoms/cm 2 to 5x10 9 atoms/cm 2 , or less.
- copper incorporation into silicon wafers during surface polishing may be reduced by the addition to the polishing mixture of certain chemicals which form copper-complexes with a certain coordination arrangement or geometry.
- a favorable geometry is any that differs sufficiently from the square planar arrangement, a tetrahedral geometry or arrangement being preferred.
- Ligands that form such favorable complexes with copper are identified as alcohols and hydroxycarboxylic acids, for example, ethylene glycol and tartaric acid, respectively.
- the above- noted prior art teaches controlling copper contamination by adding the complexing ligands in an amount 6-7 orders of magnitude greater than the copper present in the polishing mixture. Such addition is not only inefficient, but may shift the pH and other conditions of the polishing mixture away from the optimum required by the polishing process.
- the present invention is directed to a process for reducing the incorporation of copper into a semiconductor single-crystal silicon wafer during polishing which comprises the steps of: a) adding a copper-controlling additive to a polishing mixture containing copper, the copper-controlling additive reacting with the copper in the polishing mixture to form a copper compound having a solubility product (K ⁇ ) less than about 10 "20 ; and b) thereafter contacting a surface of the wafer with a polishing material and the polishing mixture as the wafer moves relative to the polishing material to polish the surface of the wafer.
- K ⁇ solubility product
- the present invention is directed to a polishing mixture for use in polishing a single-crystal silicon wafer and reducing the incorporation of copper in the wafer during polishing, the polishing mixture comprising an inorganic base, colloidal silica, and a copper compound having a solubility product (K ⁇ ) less than about 10 "20 formed by reacting a copper-controlling additive added to the polishing mixture with copper present in the polishing mixture.
- the polishing mixture comprising an inorganic base, colloidal silica, and a copper compound having a solubility product (K ⁇ ) less than about 10 "20 formed by reacting a copper-controlling additive added to the polishing mixture with copper present in the polishing mixture.
- Fig. 1 is a graph showing the effect of adding potassium monohydrogen phosphate to a polishing mixture in reducing the incorporation of copper into semiconductor single-crystal silicon wafers;
- Fig. 2 is a graph showing the effect of adding hydrogen sulfide to a polishing mixture in reducing the incorporation of copper into semiconductor single-crystal silicon wafers.
- polishing mixtures conventionally employed in polishing semiconductor single-crystal silicon wafers typically contain colloidal silica, commercially available as silica-slurry, and an inorganic base (e.g., alkali metal hydroxide) as the principal ingredients.
- the copper impurity is typically present in concentrations on the order of 1 to 10 ppb by mass, and rarely up to 100 ppb by mass, depending upon the purity grade of the silica and other ingredients of the polishing mixture.
- the copper-controlling additive is any compound which reacts with the copper impurity in the polishing mixture to form a copper compound having a solubility product (K ⁇ ) less than about 10 "20 .
- the copper-containing additive preferably comprises an anion selected from the group consisting of phosphate, sulfide, selenide and arsenate and is chemically stable in alkaline aqueous media having a pH in the range usual for the polishing mixture.
- the additive may be dissociated in solution prior to being added to the polishing mixture.
- the amount of copper-controlling additive added to the polishing mixture is preferably at least stoichiometrically equivalent to the copper content of the polishing mixture, more preferably, at least about 100 times the stoichiometric equivalent of the copper content of the polishing mixture, still more preferably about 100 to about 10,000 times the stoichiometric equivalent of the copper content of the polishing mixture.
- Examples of compounds which may be employed in the practice of the invention include potassium monohydrogen phosphate, potassium phosphate, hydrogen sulfide, ammonium sulfide, and potassium selenide.
- any compound which reacts with the copper impurity to form a precipitate with a very low solubility i.e. a precipitate having a solubility product (K ⁇ ) of less than about 10 "20 , is effective for use in controlling copper contamination.
- K ⁇ solubility product
- the threshold maximum solubility product (K sp ) of less than about 10 " 20 was determined quantitatively using a simplified single phase solution model — a liquid solution comprising an inorganic base and copper impurity.
- the hydroxide ions are present in a high concentration and, therefore, copper(II)-hydroxide, Cu(OH) 2 , is formed before the addition of any copper-controlling additive.
- copper(II)-hydroxide is a stable compound with a K ⁇ of about 10 "20 , and because undesirable copper contamination of wafers takes place when polishing with the standard polishing mixture, this value of K sp is not low enough.
- an effective copper-controlling additive should form a copper compound with a K_. p value less than about 10 "20 .
- the copper-controlling additive forms a copper compound with a K. p value less than about 10 "23 , more preferably less than about 10 "26 , still more preferably less than about 10 "29 , yet more preferably less than about 10 "32 , and even more preferably less than about 10 '35 .
- the amount of copper-controlling additive added to the polishing mixture should be sufficient to potentially precipitate all the copper impurity, i.e. the amount of the copper- controlling additive should at least be equal to the stoichiometric equivalent of the copper content of the polishing mixture.
- the molar concentration of copper is denoted by [Cu]
- hydrogen sulfide when hydrogen sulfide is used as the additive, its molar concentration, denoted by [H 2 S], should be at least equal to [Cu] because the precipitate formed is CuS.
- the amount of copper- controlling additive added to the polishing mixture is preferably in excess of the stoichiometric amount. Since typical values of [Cu] are extremely small (usually on the order of 10 "7 M), the preferable amount of additive, 100 to 10,000 times the copper content of the polishing mixture, is still low enough not to shift the pH of the mixture and adversely affect polishing performance.
- the process of the present invention is useful in any polishing operation in which silicon is removed from the surface of a wafer by contacting the wafer with a polishing material and the polishing mixture as the wafer moves relative to the polishing material to polish the surface of the wafer and encompasses all types of silicon polishers such as, for example, but not limited to single-side polishers, double-side polishers and edge-polishers.
- the present invention thus overcomes the shortcomings of the prior art and provides an effective means for reducing copper incorporation into silicon wafers during polishing.
- the improved process and polishing mixture of the present invention are effective in the presence of ammonia or amines and permit the use of such low concentrations of the additive compound that the chemical composition of the final polishing mixture is not substantially changed and the polishing rate is unaffected.
- wafers of a Czochralski-grown boron-doped p-type silicon, 200 mm diameter, (100) crystallographic orientation and resistivity between 0.071 and 0.084 ⁇ » cm were used.
- potassium monohydrogen phosphate was added to a conventional polishing mixture in concentration of 10 "4 mole/L as fed to the polishing pad.
- hydrogen sulfide was added to a conventional polishing mixture in concentration of 1.5 X 10 "3 mole/L as fed to the polishing pad.
- the standard ingredients of the polishing mixture were colloidal silica stabilized by an alkali hydroxide, and an amine.
- the two resulting polishing mixtures were used to polish the wafers for 245 seconds with an applied pressure of 7 psig and a pH of 12.6.
- the results are shown in Figs. 1 and 2.
- the dependent variable was surface concentration of copper measured on wafers after heat- treating at 120° C for 90 minutes.
- the heat-treatment step allows the copper incorporated into the wafer bulk to diffuse back onto the wafer surface (see, Prigge et al., Journal of the Electrochemical Society, vol. 138, (1991), pp. 1385-1389).
- the measurement method consisted of acid drop extraction of the surface and analysis of the extract for trace copper by ICP-MS (inductively coupled plasma/mass spectroscopy).
- Example 2 In the following tests, wafers of a Czochralski-grown boron-doped p-type silicon, 200 mm diameter, (100) crystallographic orientation and resistivity between 0.071 and 0.084 ⁇ *cm were polished to measure the effectiveness of various additives at reducing the copper incorporation into the wafers. Other conditions were as described in Example 1.
- each test was dedicated to determining the effectiveness of a single polishing additive; the first six additives listed in Table 1 , infra, are known in the art as copper- complexing additives, the remaining additives are believed to control copper by forming a copper compound/precipitate.
- Each test consisted of: a) polishing 7 or 8 wafers using a polishing mixture containing the additive being tested; b) polishing 7 or 8 wafers in the same polishing mixture without the additive; c) heat treating all the foregoing polished wafers, as well as 5 to 8 unpolished wafers; d) extracting copper from the surface of the heat treated wafers by the acid drop method and analyzing the extract for trace copper by the ICP-MS method (inductively coupled plasma/mass spectroscopy) and converting the result into surface copper concentration expressed in number of atoms per square centimeter of the wafer surface.
- the heat-treatment step allows the copper incorporated into the wafer bulk to diffuse back onto the wafer surface (see, Prigge et al., Journal of the Electrochemical Society, vol. 138, (1991), pp. 1385-1389).
- the numerical result of the tests depend on the characteristics of the wafers used and on the regime of heat- treatment, however, a quantity of identical wafers sufficient for all the tests could not be obtained. Despite the variability manifested in the test wafers and the heat- treatment procedures between the different tests, a common basis for comparison of numerical results was obtained by: a) using randomized wafers that had been cut from the same crystal section, and b) introducing a special measure of surface copper concentration change due to the additive. This quantity is denoted by ⁇ ⁇ Cu ⁇ and is defined by the following formula:
- Equation (1) defines ⁇ Cu ⁇ as the difference in surface copper concentration to be expected between wafers polished with and without the additive, and expressed in percent of the change due to polishing that would be observed when polishing without the additive.
- ⁇ Cu ⁇ The isolation of ⁇ Cu ⁇ from the variability manifested in the test wafers and the heat-treatment procedures between the different tests is based on the following assumptions: a) the rate of copper incorporation during polishing is independent of the average surface concentration of copper before polishing, ⁇ Cu ⁇ u ⁇ p , and b) the copper incorporated in the wafer during the polishing process completely diffuses out of the wafer during the heat-treatment.
- a negative value of ⁇ Cu ⁇ indicates that a decrease of copper contamination during polishing was achieved by using the additive, and a positive value indicates an increase.
- a negative ⁇ Cu ⁇ value of one hundred would represent complete suppression of copper contamination during polishing, and a value of zero would indicate no effect.
- additives which produce copper compounds that have the same ⁇ Cu ⁇ value when tested under identical conditions should be considered equally effective at reducing the incorporation of copper into a wafer during polishing.
- the first column in Table 1 contains the additive which was tested.
- the overall molar concentration of the additive was 3x10 "4 mole/L in all cases except for K 2 HPO 4 , whose molar concentration was 10 "4 mole/L, and for H 2 S whose molar concentration was 1.5xl0 "3 mole/L.
- the latter concentration was higher to compensate for the low dissociation constant of hydrogen sulfide and ensure a high enough concentration of dissociated sulfide ions in the polishing mixture.
- the overall molar concentration of copper in the polishing mixtures was between 6xl0 "8 and 10 "7 mole/L (3.8 and 6.4 ppb by mass, respectively).
- the second column in Table 1 contains the compound which is believed to be precipitated by the reaction between the copper impurity and the additive, as well as that compound's solubility product, K ⁇ .
- the third column provides the difference in surface copper concentration between wafers that have been polished without and those polished with the additive, expressed by the quantity ⁇ Cu ⁇ , defined in Eq. (1).
- the fourth column indicates whether the difference in surface copper concentration between the wafers polished with the additive and those polished without was significant at a 95% confidence level as determined using the analysis of variance (ANOVA).
- the fifth column contains the/?-value obtained in the ANOVA.
- Each of the tested copper-controlling additives that react with copper to form a copper compound/precipitate produced a statistically significant change in the final concentration of copper for the wafers, whether positive or negative.
- only one of the copper- complexing additives used in the art to reduce copper contamination produced a statistically significant difference in final copper contamination — 1 ,2-benzenediol (o-catechol), and its effect was to increase copper contamination.
- Table 1 shows that hydrogen sulfide, ammonium sulfide, potassium monohydrogen phosphate and ammonium monohydrogen phosphate when added to a polishing mixture produce copper compounds which have a solubility product K_.
- Table 1 also shows, however, that not all tested compounds which satisfy the defined solubility criterion are effective in reducing copper contamination of wafers during polishing. Specifically, two of the additives that were expected to reduce copper contamination, namely potassium carbonate and sodium monohydrogen phosphate, actually caused an increase in wafer contamination by copper.
- the observed negative results are considered to be due to the inability of the assumed single-phase model (i.e., liquid only) to adequately represent the two-phase colloidal suspension of an actual polishing mixture.
- basic copper carbonates may preferentially precipitate on the surface of silica particles where the concentration of OH " ions is significantly higher than the liquid phase.
- silica particles participate in the chemomechanical reaction with silicon during the polishing process (see, Fussstetter, H. et al, "Impact of Chemomechanical Polishing on the Chemical Composition and Morphology of the Silicon Surface," Materials Research Society Symposium Proceedings, vol. 386, (1995), p.
- any form of carbonate will be ineffective at reducing copper contamination from the polishing mixture.
- the undesirable effect of sodium phosphate may be due to the way in which the sodium and the lithium cations interact with colloidal silica particles at pH levels above 11. Namely, unlike all other cations, which have such effect only at pH values below 11, sodium and lithium cause flocculation of silica particles at pH values above 11 (Iler, R., Chemistry of Silica, Wiley, (1979), p. 375).
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Abstract
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2001510909A JP2003505858A (en) | 1999-07-19 | 2000-07-18 | Polishing mixture and method for reducing the incorporation of copper into silicon wafers |
KR1020027000613A KR20020015715A (en) | 1999-07-19 | 2000-07-18 | Polishing mixture and process for reducing the incorporation of copper into silicon wafers |
EP00950499A EP1212789A1 (en) | 1999-07-19 | 2000-07-18 | Polishing mixture and process for reducing incorporation of copper into silicon wafers |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14457599P | 1999-07-19 | 1999-07-19 | |
US60/144,575 | 1999-07-19 | ||
US61027700A | 2000-07-06 | 2000-07-06 | |
US09/610,277 | 2000-07-06 |
Publications (1)
Publication Number | Publication Date |
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WO2001006553A1 true WO2001006553A1 (en) | 2001-01-25 |
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ID=26842130
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US2000/019872 WO2001006553A1 (en) | 1999-07-19 | 2000-07-18 | Polishing mixture and process for reducing the incorporation of copper into silicon wafers |
Country Status (5)
Country | Link |
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EP (1) | EP1212789A1 (en) |
JP (1) | JP2003505858A (en) |
KR (1) | KR20020015715A (en) |
CN (1) | CN1361923A (en) |
WO (1) | WO2001006553A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7833435B2 (en) | 2006-02-24 | 2010-11-16 | Akzo Nobel Chemicals International B.V. | Polishing agent |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN100509980C (en) * | 2002-12-02 | 2009-07-08 | 阿科玛股份有限公司 | Composition and method for copper chemical mechanical planarization |
TWI385226B (en) * | 2005-09-08 | 2013-02-11 | 羅門哈斯電子材料Cmp控股公司 | Polymeric barrier removal polishing slurry |
CN114295457A (en) * | 2021-12-30 | 2022-04-08 | 江苏鼎胜新能源材料股份有限公司 | High-efficiency low-cost metallographic polishing method for aluminum alloy brazing composite material |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4867757A (en) * | 1988-09-09 | 1989-09-19 | Nalco Chemical Company | Lapping slurry compositions with improved lap rate |
JPH04313224A (en) * | 1991-04-11 | 1992-11-05 | Asahi Denka Kogyo Kk | Silicon-wafer abrasives |
WO1998049723A1 (en) * | 1997-04-30 | 1998-11-05 | Minnesota Mining And Manufacturing Company | Method of planarizing the upper surface of a semiconductor wafer |
JPH1180708A (en) * | 1997-09-09 | 1999-03-26 | Fujimi Inkooporeetetsudo:Kk | Composition for polishing |
US5916819A (en) * | 1996-07-17 | 1999-06-29 | Micron Technology, Inc. | Planarization fluid composition chelating agents and planarization method using same |
-
2000
- 2000-07-18 CN CN00810546A patent/CN1361923A/en active Pending
- 2000-07-18 JP JP2001510909A patent/JP2003505858A/en not_active Withdrawn
- 2000-07-18 KR KR1020027000613A patent/KR20020015715A/en not_active Application Discontinuation
- 2000-07-18 EP EP00950499A patent/EP1212789A1/en not_active Withdrawn
- 2000-07-18 WO PCT/US2000/019872 patent/WO2001006553A1/en not_active Application Discontinuation
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4867757A (en) * | 1988-09-09 | 1989-09-19 | Nalco Chemical Company | Lapping slurry compositions with improved lap rate |
JPH04313224A (en) * | 1991-04-11 | 1992-11-05 | Asahi Denka Kogyo Kk | Silicon-wafer abrasives |
US5916819A (en) * | 1996-07-17 | 1999-06-29 | Micron Technology, Inc. | Planarization fluid composition chelating agents and planarization method using same |
WO1998049723A1 (en) * | 1997-04-30 | 1998-11-05 | Minnesota Mining And Manufacturing Company | Method of planarizing the upper surface of a semiconductor wafer |
JPH1180708A (en) * | 1997-09-09 | 1999-03-26 | Fujimi Inkooporeetetsudo:Kk | Composition for polishing |
Non-Patent Citations (2)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 017, no. 148 (E - 1338) 24 March 1993 (1993-03-24) * |
PATENT ABSTRACTS OF JAPAN vol. 1999, no. 08 30 June 1999 (1999-06-30) * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7833435B2 (en) | 2006-02-24 | 2010-11-16 | Akzo Nobel Chemicals International B.V. | Polishing agent |
Also Published As
Publication number | Publication date |
---|---|
EP1212789A1 (en) | 2002-06-12 |
KR20020015715A (en) | 2002-02-28 |
JP2003505858A (en) | 2003-02-12 |
CN1361923A (en) | 2002-07-31 |
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