WO1999064855A1 - Process for monitoring the concentration of metallic impurities in a wafer cleaning solution - Google Patents
Process for monitoring the concentration of metallic impurities in a wafer cleaning solution Download PDFInfo
- Publication number
- WO1999064855A1 WO1999064855A1 PCT/US1999/012529 US9912529W WO9964855A1 WO 1999064855 A1 WO1999064855 A1 WO 1999064855A1 US 9912529 W US9912529 W US 9912529W WO 9964855 A1 WO9964855 A1 WO 9964855A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- solution
- concentration
- sample
- cleaning
- impurities
- Prior art date
Links
- 238000004140 cleaning Methods 0.000 title claims abstract description 125
- 239000012535 impurity Substances 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 76
- 230000008569 process Effects 0.000 title claims abstract description 65
- 238000012544 monitoring process Methods 0.000 title description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 20
- 239000010703 silicon Substances 0.000 claims abstract description 20
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 13
- 239000003513 alkali Substances 0.000 claims abstract description 12
- 150000001342 alkaline earth metals Chemical class 0.000 claims abstract description 12
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 11
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 11
- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 11
- 150000003624 transition metals Chemical class 0.000 claims abstract description 11
- 238000004458 analytical method Methods 0.000 claims description 32
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 22
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 13
- 229910052708 sodium Inorganic materials 0.000 claims description 13
- 239000011734 sodium Substances 0.000 claims description 13
- 229910052759 nickel Inorganic materials 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- 239000011575 calcium Substances 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 239000011572 manganese Substances 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 239000011733 molybdenum Substances 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- 239000010936 titanium Substances 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 239000011701 zinc Substances 0.000 claims description 3
- 229910052725 zinc Inorganic materials 0.000 claims description 3
- 239000000243 solution Substances 0.000 description 146
- 235000012431 wafers Nutrition 0.000 description 85
- 238000005070 sampling Methods 0.000 description 24
- 239000002699 waste material Substances 0.000 description 20
- 239000000356 contaminant Substances 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 14
- 239000002184 metal Substances 0.000 description 14
- 239000007788 liquid Substances 0.000 description 12
- 238000011109 contamination Methods 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 11
- 150000002739 metals Chemical class 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 239000002253 acid Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 238000007796 conventional method Methods 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 239000004809 Teflon Substances 0.000 description 3
- 229920006362 Teflon® Polymers 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000009616 inductively coupled plasma Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- -1 polytetrafluoro-ethylene Polymers 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 241000283153 Cetacea Species 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000003929 acidic solution Substances 0.000 description 2
- 238000005251 capillar electrophoresis Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000284 extract Substances 0.000 description 2
- 238000004255 ion exchange chromatography Methods 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229940058401 polytetrafluoroethylene Drugs 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010223 real-time analysis Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67242—Apparatus for monitoring, sorting or marking
- H01L21/67253—Process monitoring, e.g. flow or thickness monitoring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/508—Containers for the purpose of retaining a material to be analysed, e.g. test tubes rigid containers not provided for above
- B01L3/5085—Containers for the purpose of retaining a material to be analysed, e.g. test tubes rigid containers not provided for above for multiple samples, e.g. microtitration plates
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/10—Devices for withdrawing samples in the liquid or fluent state
- G01N1/20—Devices for withdrawing samples in the liquid or fluent state for flowing or falling materials
- G01N1/2035—Devices for withdrawing samples in the liquid or fluent state for flowing or falling materials by deviating part of a fluid stream, e.g. by drawing-off or tapping
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/18—Water
- G01N33/1813—Specific cations in water, e.g. heavy metals
-
- 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
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67017—Apparatus for fluid treatment
- H01L21/67028—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like
- H01L21/6704—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing
- H01L21/67057—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing with the semiconductor substrates being dipped in baths or vessels
Definitions
- the process of the present invention relates generally to the cleaning of silicon wafers. More particularly, the present invention relates to a process for continuously sampling and analyzing a silicon wafer cleaning bath solution in order to determine the concentration of trace alkali, alkaline earth and transition metals contained therein.
- Semiconductor wafers suitable for the fabrication of integrated circuits are produced by slicing thin wafers from a single crystal silicon ingot. After slicing, the wafers undergo a lapping process to give them a somewhat uniform thickness. The wafers are then etched to remove damage and produce a smooth surface . The next step in a conventional wafer shaping process is a polishing step to produce a highly reflective and damage-free surface on at least one face of the wafer. It is upon this polished face that electrical device fabrication takes place.
- the wafer is subjected to a cleaning process in order to remove various contaminants, such as organics and other particulate contaminants, which are present on the surface of the wafer. Removal of these contaminants is typically achieved by immersing the wafer for several minutes in a series of chemical baths which act to dissolve the particulate.
- this standard cleaning method is generally successful in removing surface particulate, it also acts to contaminate the wafer surface with metallic impurities that are present in the cleaning baths.
- silicon wafers typically have a very low surface concentration of metallic impurities. For example, wafers may have surface concentrations which are as low as about 0.1 x 10 10 atoms/cm 2 .
- the surface concentrations of many of the metallic impurities may have increased to as high as about 2 to about 2.5 x 10 10 atoms/cm 2 .
- This re-contamination of the wafer surface is a result of the fact that, prior to the wafer being immersed in the cleaning bath solutions, the concentration of metallic impurities in such solutions is much higher than the concentration of these impurities on the wafer surface.
- the presence of metallic impurities on the wafer surface can act to greatly diminish the quality and performance of integrated circuits fabricated from the wafer. As a result, integrated circuit manufacturers continues to place increasingly more stringent limitations on the surface concentrations of these impurities.
- wafer cleaning solutions must be prepared to have far lower concentrations of such metals than exist presently.
- the sources of these impurities must be identified and eliminated. This means that each reagent used in the preparation of a particular cleaning solution must be analyzed and the concentration of these metals determined.
- successfully identifying the source of a metallic impurity is dependent upon the accuracy and reliability of the analytical data that is obtained.
- the sensitivity of the analytical method is also critical.
- this off-line method is prone to the introduction of additional contaminants from outside sources.
- human contact with the sample often leads to the introduction of metallic contaminants such as aluminum, iron, calcium, and sodium.
- the vial or container which holds the collected sample, as well as the pipette or other sampling device used to collect the sample typically cannot be sufficiently cleaned such that the introduction of outside contaminants into the sample is avoided.
- this off-line method also lack the sensitivity needed in order to accurately detect metal concentrations of less than about 100 ppt. Since this conventional method lacks the ability to detect the presence of metals at such low concentrations, the wafer may still be contaminated by metallic impurities even though, based on the results obtained from such a conventional analysis, the solution appears to be
- the provision of a process which allows for continuous sampling of the cleaning bath solution ; the provision of such a process which efficiently determines the concentration of metallic contaminants in the cleaning solution in near real time; the provision of such a process which enables the efficient detection of wafers having unacceptable surface concentrations of metallic contaminants by means of analyzing the cleaning solutions in which the wafers have been treated; and, the provision of such a process which maximizes the useful life of a cleaning bath solution by efficiently determining the concentration of metallic contaminants contained therein.
- the present invention is directed to a process for determining the concentration of metallic impurities in a silicon wafer cleaning solution, the solution being maintained in continuous flow through a bath.
- the process comprises continuously delivering from said flow a portion of the cleaning bath solution to and through a sample cell.
- a sample of the solution is then withdrawn a from the sample cell and analyzed in order to determine the concentration of trace alkali, alkaline earth or transition metal impurities in the cleaning bath solution.
- the present invention is further directed to a process for determining whether the concentration of metallic impurities on a surface of a silicon wafer exceeds an acceptable limit.
- the process comprises immersing the silicon wafer in a cleaning solution which is maintained in continuous flow through a bath.
- a portion of this flow of solution is continuously delivered to and through a sample cell.
- a sample of the solution is then withdrawn from the sample cell and analyzed to determine the concentration of trace alkali, alkaline earth or transition metal impurities in the cleaning bath solution.
- a comparison is then made between the concentration of impurities in the cleaning solution and an empirically determined correlation in order to determine if the concentration of impurities on the silicon wafer surface exceeds about 1 x 10 10 atoms/cm 2 .
- FIG. 1 is a schematic view of an on-line wafer cleaning system, including on-line sample collector and analytical instrumentation, in accordance with the process of the present invention.
- FIG. 2 is a perspective view of a preferred embodiment of a sample collector, or cell.
- FIG. 3 is a sectional view taken along the plane of line 3-3 of FIG. 2.
- FIG. 4 is a sectional view taken along the plane of line 4-4 of FIG. 2.
- FIG. 5 is a plot showing a correlation between the log of the concentration of sodium in a SC-2 cleaning bath solution and the log of the concentration of sodium, minus 10, on the surface of a number of silicon wafers.
- FIG. 6 is a plot showing a correlation between the log of the concentration of nickel in a SC-2 cleaning bath solution and the log of the concentration of nickel, minus 10, on the surface of a number of silicon wafers.
- the concentration of metallic impurities in a cleaning bath solution is determined by an on-line process which allows for the sampling and analysis of the cleaning solution in a substantially metal-free environment.
- on-line shall refer to a process wherein solution sampling and analysis occurs as a single, integrated process in conjunction with wafer cleaning.
- online shall refer to a process wherein a sample may be removed from a wafer cleaning solution and analyzed without being exposed to direct, or intimate, contact with a human operator or other outside source of metallic impurities.
- the phrase "substantially metal-free environment,” as well as variations thereof, shall refer to a process wherein solution sampling and analysis may be performed such that an accurate and reproducible detection limit for alkali, alkaline earth and transition metals of less than about 100 parts per trillion (ppt) , and as low as about 1 ppt, may be achieved.
- this phrase shall refer to a process wherein solution sampling and analysis may be performed in such a way that the sample is not exposed to outside sources of metallic impurities, such as sample collection containers or human operators, thus allowing for concentrations of metallic impurities as low as about 1 ppt to be accurately and reproducibly detected.
- automated shall refer to a process which is capable of being substantially performed without the aid of human operators.
- automated shall refer to a process for sampling and analyzing a cleaning bath solution which generally requires the involvement of a human operator only to routinely calibrate the instrumentation.
- the present process may be used to test reagents directly, prior to their use in the cleaning solutions, thus aiding in the preparation of solutions which are substantially metal-free (i.e., solutions having metal concentrations which are less than about 100 ppt, preferably less than about 50 ppt, more preferably less than about 25 ppt, still more preferably less than about 10 ppt, and most preferably less than about 1 ppt) .
- the process of the present invention affords the means by which to continually monitor each of the cleaning solutions in use to more consistently and efficiently determine the concentration of metallic impurities, such as alkali, alkaline earth or transition metals. In this way the use of a particular cleaning solution, once it becomes unacceptably contaminated, can be halted before wafers are contaminated by the solution and further processed.
- the process of the present invention involves the use of on-line instrumentation for sampling and analysis. This process affords more accurate and reliable results because it significantly reduces the potential for contamination of the sample to be analyzed from outside sources, such as through direct human contact or through the use of sampling devices or containers which are contaminated. This process also allows for a significant reduction on the time required to sample and analyze a cleaning solution, as compared to existing "off-line" methods wherein the sample is collected and transported to another locate, often a site not proximate to the wafer production area, in order for the analysis to be performed.
- a wafer is immersed in a series of cleaning bath solutions.
- cleaning solutions include SC-1 (a solution comprising ammonium hydroxide, hydrogen peroxide and water, typically in a 1:1:5 ratio), SC-2 (a solution comprising water, hydrogen peroxide and hydrochloric acid, or citric acid, in a 5:1:1 ratio), as well as other acidic solutions (including solution of hydrogen fluoride, nitric acid, sulfuric acid, and phosphoric acid) , ozonated water, as well as deionized water for rinsing.
- SC-1 a solution comprising ammonium hydroxide, hydrogen peroxide and water, typically in a 1:1:5 ratio
- SC-2 a solution comprising water, hydrogen peroxide and hydrochloric acid, or citric acid, in a 5:1:1 ratio
- other acidic solutions including solution of hydrogen fluoride, nitric acid, sulfuric acid, and phosphoric acid
- ozonated water as well as deionized water for
- Each cleaning bath solution in a series is typically recirculated continuously, by means of a recirculation line, filter and pump, while a wafer, or cassette of wafers, is immersed in the solution.
- Recirculation through a filter aids in the removal of organic and other particulate contaminants from the solution and helps prevent such contaminants from being redeposited on the wafer surface.
- a sampling cell or collector indicated generally at 1, an analytical instrumentation 4, and a cleaning bath 8; the sampling cell, analytical instrument and cleaning bath each being proximate to the others.
- the collector 1 is connected to a recirculation line 6 of the cleaning bath 8 by a suitable bleed line 12.
- recirculation pump 10 continuously circulates the cleaning solution through the cleaning bath, a small portion of the cleaning solution in the cleaning bath is bled off into the bleed line 12 for delivery to the collector 1.
- the sample may be obtained either directly from the cleaning bath (i.e., the bleed line 12 may be directly plumbed from the bath 8 to the analytical instrument 4, with suitable valving in order to control flow as necessary) , or from any position along the recirculation line 6 (i.e., the bleed line 12 may be connected at any position to the recirculation line 6) .
- the bath which contains the cleaning solution, the recirculation and bleed lines, as well as all the parts of the pump 10, collector 1 and analytical instrument 4 which contact the solution are preferably constructed, lined or coated with a material which, after thorough cleaning, will not leach metallic impurities into the solution and, therefore, cause inaccurate and inconsistent results to be obtained upon analysis of the solution.
- the bath is typically constructed of quartz, while the bleed line 12 is preferably constructed from Teflon (i.e., polytetrafluoro-ethylene) .
- the bleed line may be constructed from poly (vinylidene fluoride) or other comparable materials, depending upon the composition of the cleaning solution being sampled and analyzed.
- high purity polypropylene has been found to be suitable for use with acidic solutions in which hydrochloric acid is the acidic component.
- the cleaning solution may be diverted through the bleed line 12 either continuously or intermittently. If the solution is to be diverted intermittently, a valve (not shown) may be inserted between the recirculation line 6 and the bleed line 12. Preferably, however, the solution is diverted continuously in order to ensure that at all times the solution being fed to the collector 1 is representative of the solution within the bath 8.
- This continuous flow of solution enables near real time analysis of the cleaning solution of interest; that is, the continuous flow ensures that the sample will, at the moment of collection and analysis, be representative of the solution in the cleaning bath itself. Furthermore, such a continuous flow acts to minimize or prevent contamination of the solution itself as a result of leaching of metallic impurities from the bleed line 12 or collector 1, which may occur if the solution is allowed to become stagnant .
- the diameter of the bleed line is preferably as small as the system configuration and process conditions will allow.
- the diameter of the bleed line is less than about one-quarter inch in diameter, preferably about one-eighth inch in diameter, and more preferably about one-sixteenth inch in diameter.
- the collector 1 comprises a generally rectangular block 25 constructed from, as noted above, a material which will not leach metallic impurities into the solution after having been thoroughly cleaned.
- the block 25 of the illustrated embodiment is preferably constructed from Teflon. It is to be noted, however, that materials having similar properties may also be used without departing from the scope of this invention.
- the block 25 has a central waste trough 11 extending longitudinally within the upper surface of the block and multiple receptacle overflow spillways or troughs 7 extending laterally within the upper surface of the block in communication with the central waste trough.
- the waste trough 11 and spillways 7 are designated generally by their reference numbers.
- the receptacle spillways 7 each have a floor 27, an outer end 29 disposed generally adjacent a lateral edge margin of the upper surface of the block and an inner end 31 opening into the central waste trough 11.
- each receptacle spillway 7 slopes downward from the outer end 29 to the inner end 31 of the receptacle trough for delivering liquid in the receptacle trough to the central waste trough 11 (Fig. 3) .
- Vertically oriented receptacle 3 are formed in the block at the laterally outer end 29 of each spillway 7.
- the receptacles 3 open at their upper ends into the spillways 7 to allow overflow liquid from the receptacles to drain to the central waste trough 11.
- the diameter of each receptacle is sized to permit a sample collector 41 of the automated analytical instrumentation 4 (Fig. 1) to be dipped down into the receptacle 3 for collecting a sample to be analyzed.
- Each receptacle 3 also has an inlet 17 generally adjacent the bottom of the receptacle for receiving fluid into the receptacle (Fig. 3) .
- the inlet 17 communicates with a respective inlet port 9 in a side wall of the block.
- the diameter of the inlet 17 is substantially reduced at an inner portion adjacent the receptacle for controlling the flow rate of liquid into the receptacle.
- the inlet port 9 communicates with the cleaning bath 8 (Fig. 1) by the bleed line 12 for receiving the liquid into the collector 1 to analyze the liquid.
- the central waste trough 11 slopes downward from a rear end of the block 25 toward a front end of the block to direct liquid in the waste trough 11 to a waste drain 13.
- the waste drain 13 has an outlet 23 generally adjacent the bottom of the waste drain for discharging liquid from the waste drain.
- the outlet 23 extends to an outlet port 15 in the front end of the block 25 for discharging liquid from the collector 1 to a suitable drainage system (not shown) or sewer (not shown) of the type well known to those of ordinary skill in the art.
- Instrumentation common in the art for detecting trace amounts of metallic impurities.
- instrumentation includes atomic absorption, inductively- coupled plasma mass spectrometry (ICP/MS) , capillary electrophoresis, and ion chromatography, among others.
- Common metallic impurities of particular interest include alkali, alkaline earth and transition metals, such as sodium, nickel, iron, copper, aluminum, zinc, and calcium, as well as titanium, potassium, cobalt, chromium, molybdenum and manganese.
- the precise instrument selected is in part a function of the sensitivity of the instrument for the particular metallic impurity, or impurities, for which a cleaning solution is being monitored.
- a rinse bath containing only deionized water
- Such a bath may be connected to a capillary electrophoresis or an ion chromatography instrument in order to monitor the concentration of, among other things, chloride, fluoride or ammonium ions, as well as sulfates or nitrates.
- the analytical instrument 4 (Fig. 1) is automated, possessing a sample collecting device 40 and a syringe, or other suitable sampling device, 41 which may be inserted into the receptacle 3 through its opening 5 by a robotic arm or similar automated mechanism. Again through automation, the syringe extracts a sample of the cleaning solution from the receptacle.
- Common automated instrumentation which are acceptable for use as the collecting device 40 include an autosampler designed for ICP/MS instrumentation (e.g., Cetac 500, commercially available from Cetac of Omaha; Gilson 222, commercially available from Gilson of England) .
- Common analytical instrumentation 4 include a HP4500 ICP/MS (commercially available from Hewlitt Packard; Sunnyvale, CA) , and a Varian 400 AA (commercially available from Varian; Sunnyvale, CA) .
- An automated analytical instrumentation is preferred because it allows for the more frequent analysis of a given cleaning bath solution. For example, using a conventional sampling and analysis method in a typical wafer production facility, it is not uncommon for a cleaning solution to be sampled and analyzed only about once over the course of a standard eight hour production shift, if at all. In contrast, the process of the present invention allows for such a solution to be sampled and analyzed on a much more frequent basis. For example, using a preferred embodiment of the collector 1 generally allows for essentially continuous sampling of a cleaning bath solution. Likewise, through means of automation, analysis of the solution may be performed as frequently as the analytical instrumentation of choice, and the design or configuration of the system, will allow.
- the collector 1 comprises more than one receptacle so that a plurality of cleaning baths and/or cleaning lines can be connected to the collector at the same time. As shown in Fig. 2, the collector 1 has two sets of ten receptacles 3, one set being on each side of the central waste trough 11.
- the receptacles 3 of each set are arranged in series, which in the illustrated embodiment is a line of equally spaced receptacles, to permit the instrumentation 4 to progressively dip into the receptacles one after another in a predetermined order.
- Each receptacle 3 would be connected to its own bleed line (not shown) in order to received liquid from a different cleaning bath (not shown) . It is understood, however, that the arrangement and number of receptacles 3 in the collector 1 may vary without departing from the scope of this invention.
- the recirculation pump 10 draws cleaning bath solution from the cleaning bath 8 and pumps the solution through the recirculation line 6.
- the recirculation pump 10 creates sufficient pressure in the recirculation line 6 such that a small portion of the cleaning solution is continuously diverted from the recirculation line, through the bleed line 12 for delivery to the collector 1.
- the solution then flows through the inlet port 9 of the block 25 into the inlet 17.
- the inlet 17 meters the solution into the receptacle 3. Since the solution diverted through the inlet 17 is typically not returned to the cleaning bath 8, the diameter of the inlet is preferable minimized to prevent excessive depletion of the cleaning solution from the bath.
- the inlet 17 of the illustrated embodiment is preferably less than about one-quarter inch in diameter, and more preferably less than about one- eighth inch in diameter.
- the receptacle inlet 17 delivers liquid to the receptacle 3 at the bottom of the receptacle so that the liquid flows upward from the bottom of the receptacle. Filling the receptacle 3 from the bottom prevents stagnation of the solution in the receptacle 3. Further, by eliminating stagnation of the cleaning solution, the solution within the receptacle 3 at all times remains representative of the cleaning solution contained within the cleaning bath 8. Moreover, any impurities which might be introduced from the syringe 41 of the sample collector device 40 are prevented from entering the cleaning bath 8.
- a continuing flow of solution into the receptacle 3 causes the solution to overflow the receptacle into the spillway 7.
- the sloped floor 27 of the spillway 7 directs the overflow solution downward, away from the receptacle 3 and into the waste trough 11.
- the waste trough 11 receives the overflow liquid and directs the waste solution to the waste drain 13.
- the overflow solution exits the waste drain through the outlet 23, and is ultimately discharged from the block 25 to a suitable drainage system or sewer via the outlet port 15.
- the syringe 41 or other sampling means of the automated analytical instrumentation 4, is selectively inserted into the upper end of one of the receptacles 3 by a robotic arm 40 or the like.
- the syringe automatically extracts a sample of the cleaning solution from the receptacle and then is withdrawn.
- the contents of the syringe 41 are then injected into the automated analytical instrumentation 4 for analysis.
- the process of the present invention acts to eliminate potential sources of outside contamination.
- Experience to-date has shown that the present process therefore allows for more consistent and reproducible results to be obtained. For example, if a conventional method of sampling and analysis are used, experience has shown that results which indicate the concentration of a given metallic impurity is less than 100 ppt are suspect. Generally speaking, such results from a conventional method would likely prompt one to obtain another sample and perform the analysis again for confirmation.
- the process of the present invention enables one to consistently and reproducible detect metallic impurities at concentration of less than about 100 ppt, preferably less than about 50 ppt, more preferably less than about 25 ppt, still more preferably less than about 10 ppt, and most preferably less than about 1 ppt.
- the reproducibility and consistency of the results obtained from the present process are due to a number of features.
- the equipment is constructed of high purity materials.
- automation allows for the elimination of most common outside sources of contamination.
- the very nature of such a "closed system” allows for in-situ cleaning, which generally enables a more thorough and consistent cleaning of the system before wafer cleaning begins.
- the system may be drained and repeatedly flush with deionized water until the water tests below the desired upper limit.
- a strongly acid solution such as a solution of nitric acid, may be used to clean and flush the system.
- the solution which is used to flush the system is in part a function of the solubility of the metal, or metals, to be removed.
- materials of construction will also factor into determining what type of cleaning solution, as well as the cleaning sequence, is needed. For example, if particular components of the system are fabricated of Teflon, an extremely pure, concentrated acid will need to be heated and recirculated through the system to leach out and remove any metals which are present. This is primarily due to the porous nature of the material . In contrast, quartz is not porous and, therefore, may be much more easily cleaned.
- the present invention In addition to affording a means by which to monitor a cleaning bath solution on a more frequent and efficient basis, and to consistently detect metallic impurities at concentrations not here-to-for attainable by conventional methods of sample collection and analysis, the present invention also affords the means by which to determine whether the concentration of a particular metallic impurity on the surface of a silicon wafer exceeds some predetermined limit. As a result, the acceptability of the wafer may be evaluated.
- the present invention affords an alternative to standard vapor phase decomposition (VPD) or acid drop methods of analysis. (See, e.g., U.S. Pat. Nos . 5,633,172 and 4,990,459.)
- VPD and acid drop methods of analysis involve the application of an acid onto the surface of the silicon wafer in order to dissolve metallic impurities which are present.
- the surface of the wafer is rinsed, and then the rinse water is collected and analyzed by conventional means, in order to identify and determine the concentration of metallic impurities contained therein.
- the resulting metallic impurities present are attributable to the wafer surface.
- the concentration of metallic impurities on the surface of a wafer may be approximated by analyzing the appropriate wafer cleaning solution in which the wafer has been treated.
- a correlation may be made between the concentration of the metallic impurity in the cleaning solution and the concentration of the metallic impurity on the wafer surface.
- this correlation may be empirically determined by first treating a number of silicon wafers in a given cleaning solution. The solution may then be tested using the online process of the present invention, while each wafer may is analyzed using the standard acid drop method.
- a correlation may then be made between the concentration of the metallic impurity in the cleaning solution and the concentration of the same impurity on the wafer surface.
- concentration of the metallic impurity increases in the solution, eventually a level will be reach which results in the production of a wafer which is contaminated with an unacceptably high surface concentration of the specific metallic impurity of interest.
- an observation may thus be made that when the cleaning solution concentration exceed this particular limit, all wafers subsequently cleaned in the solution will be unacceptably contaminated. Stated another way, the observation may be made that as long as the concentration of the particular metallic impurity of interest in the solution is below the targeted limit, each wafer that is cleaned in the solution will contain an acceptable concentration of that metallic impurity.
- Figs. 5 and 6 such an empirically determined correlation may be shown for sodium and nickel, respectively, in a SC-2 bath which is part of a standard cleaning sequence.
- the bath was configured for continuous recirculation or flow. Multiple samples of the solution were collected and analyzed using the present process. Likewise, multiple samples were taken from the wafers which were processed through this bath and analyzed using a conventional acid drop method. The data collected from these analyses was then used to plot the log of the concentration (in ppt) of sodium and nickel in the rinse bath versus the log of the concentration (in atoms/cm 2 ) , minus 10, of these metals on the surfaces of the wafers (see Figs. 5 and 6) .
- a "best-fit" line may be drawn and used to establish a correlation between the concentration of sodium or nickel in the rinse bath and the concentration of sodium or nickel on the surfaces of the wafers.
- observations may be made about the surface concentration of these metals given a particular solution concentration.
- the concentration of sodium in the solution is about 100 ppt
- the concentration of sodium on the surface of a wafer is about 1.2 x 10 10 atoms/cm 2
- a solution concentration of about 25 ppt correlates to a surface concentration of about 0.3 x 10 10 atoms/cm 2 .
- the concentration of nickel in the solution is about 25 ppt
- the concentration of nickel on the surface of a wafer is about 1 x 10 10 atoms/cm 2
- a solution concentration of about 10 ppt correlates to a surface concentration of about 0.3 x 10 10 atoms/cm 2 .
- the acceptability or unacceptability of a wafer may be determined by sampling and analyzing a given cleaning solution.
- the "acceptability" or "acceptability” of a wafer is dependent upon the specific end application, as well as the limitations imposed by integrated circuit manufactures for a given metallic impurity.
- typical integrated circuit manufacturers have impose limitations which currently require the surface concentration of metals such as aluminum and calcium not exceed about 1 x 10 11 atoms/cm 2 .
- the limitation on most other metals is currently about 1 x 10 10 atoms/cm 2 .
- the concentration of metallic impurities not exceed about 0.75 x 10 10 atoms/cm 2 , more preferably about 0.5 x 10 10 atoms/cm 2 , and still more preferably about 0.25 x 10 10 atoms/cm 2 . Most preferably, it is desirable that the concentration of such impurities not exceed about 0.1 x 10 10 atoms/cm 2 .
- this same empirical process may be employed to determine the maximum concentration of a metallic impurity within a given bath that is acceptable in order to ensure that the concentration of this same impurity on the wafer surface does not exceed the desired limit.
- the present process may also afford the means by which to extend the useful life of a given cleaning solution.
- the useful life a cleaning solution may be extended, once such a correlation is determined, because now the solution may remain in the cleaning bath sequence until, as noted above, it becomes unacceptably contaminated. For example, rather than simply discarding the solution after about 2 to 6 hours, use of the solution may continue for about 8 hours, 10 hours, 12 hours, 14 hours or more.
- a cleaning solution may be monitored using the process of the present invention and allowed to remain in use until the level or concentration of metallic impurities in the solution is found to be in excess of about 100 ppt, preferably about 75 ppt, more preferably about 50 ppt, and still more preferably about 25 ppt.
- the solution is monitored and allowed to remain in use only until the concentration of metallic impurities in solution exceeds about 10 ppt.
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Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020007013759A KR20010052580A (en) | 1998-06-08 | 1999-06-04 | Process for monitoring the concentration of metallic impurities in a wafer cleaning solution |
EP99926171A EP1084402B1 (en) | 1998-06-08 | 1999-06-04 | Process for monitoring the concentration of metallic impurities in a wafer cleaning solution |
DE69900914T DE69900914T2 (en) | 1998-06-08 | 1999-06-04 | METHOD FOR MONITORING THE CONCENTRATION OF METAL IMPURITIES IN A WAFER CLEANING SOLUTION |
JP2000553799A JP2002517753A (en) | 1998-06-08 | 1999-06-04 | Method for monitoring the concentration of metal impurities in a wafer cleaning solution |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US9343598A | 1998-06-08 | 1998-06-08 | |
US09/093,435 | 1998-06-08 |
Publications (1)
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WO1999064855A1 true WO1999064855A1 (en) | 1999-12-16 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US1999/012529 WO1999064855A1 (en) | 1998-06-08 | 1999-06-04 | Process for monitoring the concentration of metallic impurities in a wafer cleaning solution |
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EP (1) | EP1084402B1 (en) |
JP (1) | JP2002517753A (en) |
KR (1) | KR20010052580A (en) |
CN (1) | CN1305587A (en) |
DE (1) | DE69900914T2 (en) |
TW (1) | TW419769B (en) |
WO (1) | WO1999064855A1 (en) |
Cited By (5)
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EP1239277A1 (en) * | 2001-03-09 | 2002-09-11 | Infineon Technologies AG | Measurement arrangement |
JP2002270568A (en) * | 2001-03-12 | 2002-09-20 | Mimasu Semiconductor Industry Co Ltd | Method of manufacturing semiconductor wafer and metal monitoring device |
WO2011077339A1 (en) * | 2009-12-23 | 2011-06-30 | Memc Electronic Materials, Inc. | Methods for analysis of water and substrates rinsed in water |
WO2015103366A1 (en) * | 2014-01-03 | 2015-07-09 | Hemlock Semiconductor Corporation | Method for determining a concentration of metal impurities contaminating a silicon product |
CN113960155A (en) * | 2021-10-28 | 2022-01-21 | 西安奕斯伟材料科技有限公司 | Method for detecting metal impurities in polishing solution |
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JP4816888B2 (en) * | 2005-08-18 | 2011-11-16 | 栗田工業株式会社 | Sulfuric acid recycling cleaning system |
JP5087839B2 (en) * | 2005-12-19 | 2012-12-05 | 栗田工業株式会社 | Water quality evaluation method, ultrapure water evaluation apparatus and ultrapure water production system using the method |
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US20200094293A1 (en) * | 2018-09-26 | 2020-03-26 | Taiwan Semiconductor Manufacturing Co., Ltd. | Wafer Wet Cleaning System |
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CN114985365B (en) * | 2022-04-18 | 2023-07-14 | 江苏鑫华半导体科技股份有限公司 | Method and system for cleaning and analyzing polycrystalline silicon sample core |
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- 1999-06-04 JP JP2000553799A patent/JP2002517753A/en not_active Withdrawn
- 1999-06-04 CN CN99807175A patent/CN1305587A/en active Pending
- 1999-06-04 KR KR1020007013759A patent/KR20010052580A/en not_active Application Discontinuation
- 1999-06-04 EP EP99926171A patent/EP1084402B1/en not_active Expired - Lifetime
- 1999-06-04 DE DE69900914T patent/DE69900914T2/en not_active Expired - Fee Related
- 1999-06-04 WO PCT/US1999/012529 patent/WO1999064855A1/en not_active Application Discontinuation
- 1999-07-26 TW TW088109481A patent/TW419769B/en not_active IP Right Cessation
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JP2002270568A (en) * | 2001-03-12 | 2002-09-20 | Mimasu Semiconductor Industry Co Ltd | Method of manufacturing semiconductor wafer and metal monitoring device |
WO2011077339A1 (en) * | 2009-12-23 | 2011-06-30 | Memc Electronic Materials, Inc. | Methods for analysis of water and substrates rinsed in water |
WO2015103366A1 (en) * | 2014-01-03 | 2015-07-09 | Hemlock Semiconductor Corporation | Method for determining a concentration of metal impurities contaminating a silicon product |
CN113960155A (en) * | 2021-10-28 | 2022-01-21 | 西安奕斯伟材料科技有限公司 | Method for detecting metal impurities in polishing solution |
Also Published As
Publication number | Publication date |
---|---|
EP1084402A1 (en) | 2001-03-21 |
JP2002517753A (en) | 2002-06-18 |
EP1084402B1 (en) | 2002-02-20 |
DE69900914T2 (en) | 2002-11-28 |
CN1305587A (en) | 2001-07-25 |
KR20010052580A (en) | 2001-06-25 |
DE69900914D1 (en) | 2002-03-28 |
TW419769B (en) | 2001-01-21 |
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