Classifications

• • 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
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/3105—After-treatment
  • H01L21/311—Etching the insulating layers by chemical or physical means
  • H01L21/31105—Etching inorganic layers
  • H01L21/31111—Etching inorganic layers by chemical means
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
  • C01C1/02—Preparation, purification or separation of ammonia
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/04—Processes using organic exchangers
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/01—Hydrogen peroxide
  • C01B15/013—Separation; Purification; Concentration
  • C01B15/0135—Purification by solid ion-exchangers or solid chelating agents
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/19—Fluorine; Hydrogen fluoride
  • C01B7/191—Hydrogen fluoride
  • C01B7/195—Separation; Purification
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/19—Fluorine; Hydrogen fluoride
  • C01B7/191—Hydrogen fluoride
  • C01B7/195—Separation; Purification
  • C01B7/197—Separation; Purification by adsorption
  • C01B7/198—Separation; Purification by adsorption by solid ion-exchangers
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
  • C01C1/02—Preparation, purification or separation of ammonia
  • C01C1/024—Purification
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
  • C01C1/16—Halides of ammonium
  • C01C1/162—Ammonium fluoride
• • 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
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
  • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
  • H01L21/30604—Chemical etching
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• This invention lies in the field of the manufacture of high-precision electronic components, and relates to the preparation and handling of the ammonia used as a treatment agent in the manufacture of such components.
• a major concern at every stage in the manufacture of electronic components is contamination. Control of contamination is critical to product quality, and an extremely high level of cleanliness and purity in the manufacturing environment is needed for obtaining acceptable product yield and maintaining profitability. These requirements are particularly acute in the manufacture of very high density circuitry as well as in ultra- precision bearings, recording heads and LCD displays.
• Sources of contamination include the manufacturing facility, personnel and processing equipment. In many cases, contamination can be lowered to acceptable levels by the use of "clean room” techniques such as isolation, air filtration, special equipment and special clothing and body coverings to avoid contact between the operator and the manufacturing materials. With ultra-high precision manufacturing, however, the highest levels at which defects can be tolerated are particularly low and control over sources of contamination is even more critical. Ammonia presents particular difficulties, since liquid ammonia contains both solid and volatile impurities, many of which are damaging to electronic components if present during the manufacturing process. The impurities level and content may vary widely depending on the source as well as the handling method, and all such impurities must be removed before the ammonia can be used in electronic component production lines.
• Ammonium hydroxide are shipped at concentrations no higher than 30%.
• ammonia can be supplied to a production line for high-precision electronic devices in ultra-high purity form by use of an on-site system which draws ammonia vapor from a liquid ammonia reservoir, passes the ammonia vapor through a microfiltration filter, and scrubs the filtered vapor with high-pH purified water in a liquid-vapor contact unit such as a scrubbing tower or a bubbler unit.
• a liquid-vapor contact unit such as a scrubbing tower or a bubbler unit.
• the drawing of the ammonia vapor from the supply reservoir serves by itself as a single-stage distillation, eliminating non-volatiles or high-boiling impurities, such as alkali and alkaline earth metal oxides, carbonates and hydrides, transition metal halides and hydrides, and high-boiling hydrocarbons and halocarbons.
• the reactive volatile impurities that could be found in commercial grade ammonia, such as certain transition metal halides, Group III metal hydrides and halides, certain Group IV hydrides and halides, and halogens, previously thought to require distillation for removal, are now discovered to be capable of removal by scrubbing to a degree which is adequate for high- precision operations.
• the liquid-vapor contact unit lowers the levels of impurities which are damaging to semiconductor wafer manufacture to less than 1 ppb per element or less than 30 ppb total.
• distillation may also be performed subsequent to the scrubbing.
• An advantage of the invention is that if distillation is included, the liquid-vapor contact unit considerably lessens the burden on, and design requirements for, the distillation column, enhancing the product purity even further.
• FIG. 1 is an engineering flow diagram of one example of a unit for the production of ultrapure ammonia in accordance with the present invention.
• FIG. 2 is a block diagram of a semiconductor fabrication line in which the ammonia purification of FIG. 1 may be incorporated, thereby serving as one example of an implementation of the present invention.
• ammonia vapor is first drawn from the vapor space in a liquid ammonia supply reservoir. Drawing vapor in this manner serves as a single-stage distillation, leaving certain solid and high-boiling impurities behind in the liquid phase.
• the supply reservoir can be any conventional supply tank or other reservoir suitable for containing ammonia, and the ammonia can be in anhydrous form or an aqueous solution.
• the reservoir can be maintained at atmospheric pressure or at a pressure above atmospheric if desired to enhance the flow of the ammonia through the system.
• the reservoir is preferably heat controlled, so that the temperature is within the range of from about 10°C to about 50°C, preferably from about 15°C to about 35°C, and most preferably from about 20°C to about 25°C.
• Impurities that will be removed as a result of drawing the ammonia from the vapor phase include metals of Groups I and II of the Periodic Table, as well as aminated forms of these metals which form as a result of the contact with ammonia. Also included will be oxides and carbonates of these metals, as well as hydrides such as beryllium hydride and magnesium hydride. Further included will be Group III elements and their oxides, as well as ammonium adducts of hydrides and halides of these elements. Still further are transition metal hydrides. Heavy hydrocarbons and halocarbons such as pump oil will also be included.
• the ammonia drawn from the reservoir is passed through a filtration unit to remove any solid matter entrained with the vapor.
• Microfiltration and ultrafiltration units and membranes are commercially available and can be used.
• the grade and type of filter will be selected according to need. Preferred filters are those which eliminate panicles of 0.005 micron or greater in size, and further preferred are those which filter down to 0.003 micron particle size.
• the filtered vapor is then contacted with high-pH purified (preferably deionized) water.
• the high-pH water is preferably an aqueous ammonia solution, and the contact between this solution and the filtered vapor can be achieved in various conventional untis designed to achieve liquid-vapor contact.
• the vapor can be bubbled through a reservoir of the solution.
• the contact can be achieved in a scrubber, preferably one with recycling of the solution through the scrubber to raise the concentration to saturation.
• the scrubber may be conveniently operated as a conventional scrubbing column in countercurrent fashion.
• the column is preferably run at a temperature ranging from about 10°C to about 50°C, preferably from about 15 °C to about 35 °C.
• the operating pressure is not critical, although preferred operation will be at a pressure of from about atmospheric pressure to about 30 psi above atmospheric.
• the column will typically contain a conventional column packing to provide for a high degree of contact between liquid and gas, and preferably a mist removal section as well.
• a scrubber column is used with a packed height of approximately 3 feet (0.9 meter) and an internal diameter of approximately 7 inches (18 cm), to achieve a packing volume of 0.84 cubic feet (24 liters), and is operated at a pressure drop of about 0.3 inches of water (0.075 kPa) and less than 10% flood, with a recirculation flow of about 2.5 gallons per minute (0.16 liter per second) nominal or 5 gallons per minute (0.32 liter per second) at 20% flood, with the gas inlet below the packing, and the liquid inlet above the packing but below the mist removal section.
• Preferred packing materials for a column of this description are those which have a nominal dimension of less than one-eighth of the column diameter.
• the mist removal section of the column will have a more dense packing, and is otherwise conventional in construction. It should be understood that all descriptions and dimensions in this paragraph are examples only. Each of the system parameters may be varied.
• startup is achieved by first saturating deionized water with ammonia to form a solution for use as the starting scrubbing medium.
• a small amount of liquid in the column sump is drained periodically to remove accumulated impurities.
• impurities that will be removed by the scrubber include reactive volatiles such as silane (SiH 4 ) and arsine (AsH 3 ), halides and hydrides of phosphorus, arsenic and antimony, transition metal halides in general, and Group III and Group VI metal halides and hydrides.
• reactive volatiles such as silane (SiH 4 ) and arsine (AsH 3 ), halides and hydrides of phosphorus, arsenic and antimony, transition metal halides in general, and Group III and Group VI metal halides and hydrides.
• the high-pH purified water can further contain one or more additives to decompose or otherwise eliminate specific types of impurities which were not removed by the single-stage distillation in the liquid ammonia supply reservoir.
• One such possible additive is hydrogen peroxide, which is useful in decomposing organic contaminants.
• Other possible additives are various types of catalysts for decomposing specific contaminants.
• the units described up to this point may be operated in either batchwise, continuous or semi-continuous manner. Continuous or semi-continuous operation is preferred.
• the volumetric processing rate of the ammonia purification system is not critical and may vary widely. In most operations for which the present invention is contemplated for use, however, the flow rate of ammonia through the system will be within the range of about 200 cc/h to about 500,000 L/h.
• Ammonia leaving the scrubber can be further purified by distillation prior to use, depending on the particular type of manufacturing process for which the ammonia is being purified.
• the ammonia is intended for use in chemical vapor deposition, for example, the inclusion of a dehydration unit and a distillation unit in the system will be beneficial.
• the distillation column may also be operated in either batchwise, continuous or semi-continuous manner. In a batch operation, a typical operating pressure might be 300 pounds per square inch absolute (2,068 kPa), with a batch size of 100 pounds (45.4 kg).
• the column in this example has a diameter of 8 inches (20 cm), a height of 72 inches (183 cm), operating at 30% of flood, with a vapor velocity of 0.00221 feet per second (0.00067 meter per second), a height equivalent to a theoretical plate of 1.5 inches (3.8 cm), and 48 equivalent plates.
• the boiler size in this example is about 18 inches (45.7 cm) in diameter and 27 inches (68.6 cm) in length, with a reflux ratio of 0.5, and recirculating chilled water enters at 60°F (15.6°C) and leaves at 90°F (32.2°C). Again, this is merely an example; distillation columns varying widely in construction and operational parameters can be used.
• the purified ammonia may be used as a purified gas or as an aqueous solution, in which case the purified ammonia is dissolved in purified (preferably deionized) water.
• the proportions and the means of mixing are conventional.
• a flow chart depicting one example of an ammonia purification unit in accordance with this invention is shown in FIG. 1.
• Liquid ammonia is stored in a reservoir 11.
• Ammonia vapor 12 is drawn from the vapor space in the reservoir, is then passed through a shutoff valve 13, then through a filter 14.
• Saturated aqueous ammonia 20 flows downward as the ammonia vapor flows upward, the liquid being circulated by a circulation pump 21, and the liquid level controlled by a level sensor 22.
• Waste 23 is drawn off periodically from the retained liquid in the bottom of the scrubber.
• Deionized water 24 is supplied to the scrubber 17, with elevated pressure maintained by a pump 25.
• the scrubbed ammonia 26 is directed to one of three alternate routes. These are:
• a distillation column 27 where the ammonia is purified further. The resulting distilled ammonia 28 is then directed to the point of use.
• a dissolving unit 29 where the ammonia is combined with deionized water 30 to form an aqueous solution 31, which is directed to the point of use.
• the aqueous solution can be collected in a holding tank from which the ammonia is drawn into individual lines for a multitude of point-of-use destinations at the same plant.
• a transfer line 32 which carries the ammonia in gaseous form to the point of use.
• the inclusion of the distillation column 27 is preferred.
• Examples are furnace or chemical vapor deposition (CVD) uses of the ammonia. If the ammonia is used for CVD, for example, the distillation column would remove non-condensables such as oxygen and nitrogen, that might interfere with CVD.
• CVD chemical vapor deposition
• the distillation column would remove non-condensables such as oxygen and nitrogen, that might interfere with CVD.
• a dehydration unit may be incorporated into the system between the scrubber 17 and the distillation column 27, as an option, depending on the characteristics and efficiency of the distillation column.
• the resulting stream be it gaseous ammonia or an aqueous solution, may be divided into two or more branch streams, each directed to a different use station, the purification unit thereby supplying purified ammonia to a number of use stations simultaneously.
• FIG. 2 A conventional cleaning line for semiconductor fabrication is depicted in FIG. 2.
• the first unit in the cleaning line is a resist stripping station 41 where aqueous hydrogen peroxide 42 and sulfuric acid 43 are combined and applied to the semiconductor surface to strip off the resist.
• a rinse station 44 where deionized water is applied to rinse off the stripping solution.
• a cleaning station 45 Immediately downstream of the rinse station 44 is a cleaning station 45 where an aqueous solution of ammonia and hydrogen peroxide are applied.
• This solution is supplied in one of two ways. In the first, aqueous ammonia 31 from the dissolving unit 29 shown in FIG. 1 is combined with aqueous hydrogen peroxide 46, and resulting the mixture 47 is directed to the cleaning station 45.
• the wafer or wafer batch 61 will be held on a wafer support 52, and conveyed from one workstation to the next by a robot 63 or some other conventional means of achieving sequential treatment.
• the means of conveyance may be totally automated, partially automated or not automated at all.
• purified HC1 for the acid cleaning station 54 may be prepared and supplied on site in a manner similar to that of the ammonia purification system of FIG. 1.
• FIG. 2 is one example of a cleaning line for semiconductor fabrication.
• cleaning lines for high-precision manufacture can vary widely from that shown in FIG. 2, either eliminating one or more of the units shown or adding or substituting units not shown.
• the concept of the on-site preparation of high-purity aqueous ammonia however in accordance with this invention is applicable to all such systems.
• ammonia and hydrogen peroxide as a semiconductor cleaning medium at workstations such as the cleaning station 45 shown in FIG. 2 is well known throughout the industry. While the proportions vary, a nominal system would consist of deionized water, 29% ammonium hydroxide (weight basis) and 30% hydrogen peroxide (weight basis), combined in a volume ratio of 6:1:1. This cleaning agent is used to remove organic residues, and, in conjunction with ultrasonic agitation at frequencies of approximately 1 MHz, removes particles down to the submicron size range.
• the ammonia purification system will be positioned in close proximity to the point of use of the ammonia in the production line leaving only a short distance of travel between the purification unit and the production line.
• the ammonia from the purification unit may pass through an intermediate holding tank before reaching the points of use. Each point of use will then be fed by an individual outlet line from the holding tank.
• the ammonia can therefore be directly applied to the semiconductor substrate without packaging or transport and without storage other than a small in-line reservoir, and thus without contact with the potential sources of contamination normally encountered when chemicals are manufactured and prepared for use at locations external to the manufacturing facility.
• the distance between the point at which the ammonia leaves the purification system and its point of use on the production line will generally be less than about one foot (30 cm). This distance will be greater when the purification system is a central plant-wide system for piping to two or more use stations, in which case the distance may be two thousand feet (6,100 m) or greater. Transfer can be achieved through an ultra-clean transfer line of a material which does not introduce contamination. In most applications. stainless steel or polymers such as high density polyethylene or fluorinated polymers can be used successfully.
• the water used in the unit can be purified in accordance with semiconductor manufacturing standards. These standards are commonly used in the semiconductor industry and well known among those skilled in the art and experienced in the industry practices and standards. Methods of purifying water in accordance with these standards include ion exchange and reverse osmosis.
• Ion exchange methods typically include most or all of the following units: chemical treatment such as chlorination to kill organisms; sand filtration for particle removal; activated charcoal filtration to remove chlorine and traces of organic matter; diatomaceous earth filtration; anion exchange to remove strongly ionized acids; mixed bed polishing, containing both cation and anion exchange resins, to remove further ions; sterilization, involving chlorination or ultraviolet light; and filtration through a filter of 0.45 micron or less.
• Reverse osmosis methods will involve, in place of one or more of the units in the ion exchange process, the passage of the water under pressure through a selectively permeable membrane which does not pass many of the dissolved or suspended substances.
• Typical standards for the purity of the water resulting from these processes are a resistivity of at least about 15 megohm-cm at 25 °C (typically 18 megohm-cm at 25 °C), less than about 25ppb of electrolytes, a paniculate content of less than about 150/cm 3 and a particle size of less than 0.2 micron, a microorganism content of less than about 10/cm 3 , and total organic carbon of less than lOOppb.

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• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Physics & Mathematics (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
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• Separation Using Semi-Permeable Membranes (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1995
  • 1995-06-05 JP JP9500388A patent/JPH11506411A/ja active Pending
  • 1995-06-05 EP EP95923915A patent/EP0830316A1/de not_active Withdrawn
  • 1995-06-05 KR KR1019970708760A patent/KR19990022281A/ko active IP Right Grant
  • 1995-06-05 AU AU28624/95A patent/AU2862495A/en not_active Abandoned
  • 1995-06-05 WO PCT/US1995/007649 patent/WO1996039358A1/en active IP Right Grant
• 1996
  • 1996-06-05 EP EP96918226A patent/EP0835168A4/de not_active Withdrawn
  • 1996-06-05 WO PCT/US1996/009215 patent/WO1996039263A1/en active IP Right Grant
  • 1996-06-05 KR KR1019970708704A patent/KR19990022225A/ko active IP Right Grant
  • 1996-06-05 AU AU60934/96A patent/AU6093496A/en not_active Abandoned
  • 1996-06-05 JP JP9501593A patent/JPH11507004A/ja active Pending

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