KR19990022226A - Ultra-pure buffered HF on-site generation system for semiconductor process - Google Patents

Abstract

The present application relates to an on-site manufacturing system and method of ultrapure hydrogen peroxide in an integrated circuit fabrication front end facility. The starting point is high purity aqueous H ₂ O ₂ (eg, 30% H ₂ O ₂ ). The incoming aqueous H ₂ O ₂ is further purified in an on-site purification unit before being used for binding with other reagents.

Description

Ultra-pure buffered HF on-site generation system for semiconductor process

The present invention relates to conventional semiconductor processes, and more particularly to the preparation of ultrapure liquid reagents.

Background: Contaminant Control in IC Manufacturing

Contaminants are of great importance in integrated circuit fabrication. The majority of modern integrated circuit fabrication steps are one cleaning step or another cleaning step; This washing step may be required to remove organic contaminants, metal contaminants, photoresists (or inorganic residues thereof), etch byproducts, natural oxides, and the like.

In 1995, the cost of producing a new front end (integrated circuit wafer fabrication facility) was typically over $ 1 billion ($ 1,000,000,000), most of which was to evaluate particulate control, cleaning, and contaminant control.

An important source of contaminants is impurities in process chemicals. Since cleaning is done very often and is important, contaminants due to cleaning chemistry are very undesirable.

Many corrosive and / or toxic chemicals are often used in semiconductor processing, and reagent supplies are usually away from the location of the foremost operator. Pipe connection configuration and management for ultra-pure gaseous and liquids is well known in the semiconductor industry, so most gaseous and liquids can be transported from any location in the same structure (or at the same site) to a wafer fabrication station. have.

The present application discloses an on-site manufacturing system and method of ultrapure chemicals in a semiconductor manufacturing facility, so that it can be piped directly to the destination. Since the disclosed system is a compact unit that can be installed as a front end in the same structure (or in an adjacent structure), processing is avoided.

Background: Wet vs. Dry Process

One technological implementation that has long been used in semiconductor processes is the change (and attempts to change) between dry and wet processes. In the dry process, only gaseous or plasma phase reactants are in contact with the wafer. In wet processes, various liquid reagents are used for applications such as etching silicon dioxide or removing natural oxide layers, removing traces of organic or organic contaminants, removing traces of metal or organic contaminants, etching silicon nitride, etching silicon, and the like.

Plasma etching has many attractive properties but is not suitable for cleaning. This is because there is no chemical treatment available to remove some of the most undesirable impurities such as gold. Therefore, the cleaning process is essential for the current semiconductor process and is expected to continue in the future.

Plasma etching is performed using a suitable photoresist and is not immediately following the high temperature step. Instead of stripping the resist, it needs to be cleaned.

Materials removed by washing include photoresist residues (organic polymers), sodium, alkaline earths (eg calcium or magnesium), and heavy metals (eg gold). Most of these do not form volatile halides, so plasma etching cannot remove them. Therefore, there is a need to wash using wet chemical treatment.

As a result, the purity of the chemical in the plasma etching process is not so important because these steps are always followed by a cleaning step before the high temperature step is performed, and the cleaning step is performed on the surface before the high temperature step is performed on these contaminants. Hazardous pollutants can be removed from However, the purity of the liquid chemical becomes more important because the impact rate on the semiconductor surface is typically one million times higher than the impact rate upon plasma etching, and the liquid cleaning step immediately follows the high temperature treatment step.

However, the wet process has a significant defect called so-called ionic contaminants. Integrated circuit structures use only a few dopants (boron, arsenic, phosphorus, and sometimes antimony) to form the desired p- and n-type doped regions. However, many other kinds of dopants are electrically active dopants and are very undesirable contaminants. Many such contaminants may have adverse effects, such as increased binding leakage, at concentrations well below 10 ¹³ cm ⁻³ . In addition, some of the very undesirable contaminants are separated into silicon in contact with the aqueous solution, where the equilibrium concentration of the contaminant is higher in silicon than in solution. In addition, some of the very undesirable contaminants have very high diffusion coefficients, so if these dopants are injected into any part of the silicon wafer, these contaminants can diffuse through the site containing the junction causing the leak. .

Therefore, all liquid solutions used in semiconductor wafers preferably have extremely low levels of total metal ions. It is preferable that the density | concentration of all the metals to be bonded is 300ppt (one-trillion) or less, and it is 10ppt or less with respect to arbitrary metals, and it is more preferable if it is below. Contaminants can also be controlled by both anions and cations. That is, some anions, such as alloy ions, may have the adverse effect of reducing mobile metal atoms or ions in the silicon lattice.

Front end equipment typically includes an on-site purification system for producing high purity water (deionized water, ie DI). However, it is more difficult to obtain process chemicals of the required purity.

On-site refining process

The present invention relates to a method for producing ultra-purity ammonia in an on-site system installed at a semiconductor wafer production site. Drawing ammonia vapor from the liquid ammonia reservoir, passing the ammonia vapor through a microfiltration filter, and filtered with high pH purified water (preferably ultrapure deionized water equilibrated with ammonia stream). It is produced by scrubbing the steam. The present invention enables the conversion of commercial ammonia to high purity ammonia sufficient for high precision production without the use of conventional distillation tubes. The ammonia vapors extracted from the feed reservoir act on their own as a single stage distillation process, providing non-volatile and nonvolatile properties such as alkali and alkaline earth metal oxides, carbonates and hydrides, transition metal halides and hydrides and high boiling point hydrocarbons and halide carbons. Eliminate high boiling point impurities. Reactive volatile impurities that can be found in commercial ammonia, such as certain transition metal halides, group III metal hydrides and halides, group IV hydrides and halides, and halogens, which were previously thought to be removed only by distillation, It has been found that it can be removed by an ultra-purifying process that is suitable for high precision operation. This is a surprising finding since cleaning techniques are commonly used to remove large scale impurities rather than microscale.

Hydrogen peroxide

Hydrogen peroxide (H ₂ 0 ₂ ) is an important treatment chemical in the semiconductor manufacturing process and is commonly used as a cleaning solution. For example, a widely used piranha wash solution typically uses H ₂ O ₂ + H ₂ SO ₄ in a ratio of 30:70, and a widely used RCA wash is a 3-stage using hydrogen peroxide in two stages. Stage wash.

Therefore, ultrapure hydrogen peroxide water is a major component in integrated circuit processing. However, hydrogen peroxide is not an easy chemical to purify because decomposition is promoted by various metals and contaminants and has exothermic and temperature sensitivity. H ₂ O ₂ is also known as a strong oxidant. Substantial work has been done in this area. For example, it is reported in the literature that an anionic exchange resin for purifying hydrogen peroxide is preferably charged with bicarbonate (HCO ₃ ⁻ ) ions. This is because other commonly used anions (eg, OH ⁻ , Cl ⁻ ) promote the decomposition of H ₂ O ₂ under any circumstances.

Removal of organic acid constituents contained in H ₂ O ₂ is described in the literature. For example, French Patent No. 1,539,843 (using nonfunctionalized resin and neutralized hydrochloric acid), US Patent No. 3,294,488 (basic resin [HCO ₃ ] + CO ₂ ); Japanese Patent No. 6,725,845 (1967) (nonfunctionalized resin); US Patent No. 3,297,404 (1967) (basic resins [HC ₃ ] and CO); U.S. Patent No. 3,305,314 (the basic [HC _3] and a CO _2/3 ^-); See US Pat. No. 4,792,403 (1988) (halogenated resin).

H ₂ O ₂ purification of cationic and anionic resins is described, for example, in French Patent Application No. 10,431 (1953) using sulfone group resins; Polish Patent No. 50,982 (1961) (cationic + anionic resin); Polish Patent 55,378 (1968); Spanish Patent No. 328,719 (1961) (sulfone group resins, acrylics, strong bases and strong acids [gel form]); US Patent No. 3,297,404 (1967) (hybrid resin cations and anions [HCO ₃ ]); And U.S. Patent No. 4,999,179 is described in claim (sulfonic resin + anionic resin _{[HCO 3], CO 2/} 3 + brominated). For various purification methods, for example, French Patent No. 2,677,010 (1992) (strong cationic resin + medium strength gel-type resin + unfunctionalized resin); French Patent 2,677,011 (1992) (medium strength anion resin); PCT Application No. 92/06918 (1992) (cationic and anionic resin, description of fluidized bed technology method).

Sulfone and for the H ₂ O ₂ tablets of pyridine resin, for example, switch Patent No. 1,643,452 (1991) (cationic resin +2.5 methyl basic resin-vinyl pyridine [HCO ₃ ^-]); Japanese Patent No. 62,187,103 (1966) (cationic resin + pyridine anion structure).

For H ₂ O ₂ purification of resins and pyridine resins, for example, French Patent No. 2,624,500 (1988) (adding a carboxyl group or a phosphorus chelating agent to the basic resin); German Patent No. 3,822,248 (1990) (EDTA added to basic resin); EP 502,466 (1992) (chelating agent added to H ₂ O ₂ and passed through an unfunctionalized resin); U.S. Patent No. 5,200,166 (stabilized addition of acid and a basic resin in the ^{_{H 2 O 2 [HCO 3 -}} , CO 2/3 -] and reaction); It is described in ^- (/ ⁺ C + Al and Fe chelator chelating resin including phosphate 0.1ppm A) EP 626 342 (1994).

Several patents have also been reported that have succeeded in achieving purity below 1 ppb. For example, French Patent No. 624,500 of TOKKAI (using resins and complexing agents); WO90 / 11967 from INTEROX (using SnO ₂ + ultrafiltration); See NEC French Patent No. 3,045,504 (using silica treatment). All of the above cited documents are described by reference in the specification.

On-Site Preparation of Ultra-Purity Hydrogen Peroxide

The present application relates to an on-site manufacturing system and method of ultrapure hydrogen peroxide in an integrated circuit fabrication front end facility. The starting point is high purity aqueous H ₂ O ₂ (eg, 30% H ₂ O ₂ ). The incoming aqueous H ₂ O ₂ is further purified in an on-site purification unit before it can be combined with other reagents. In a preferred embodiment of the present invention, an on-site purification unit consisting of an anion and a cation exchange bed with one or more particulate filters was used.

The present application also relates to a system and method for producing ultrapure on-site mixed wash solutions in an integrated circuit fabrication front end facility by on-site ultra-purified hydrogen peroxide bonds using on-site ultra-purified acids or bases. .

On-Site Preparation of Ultra-Purity Mixed Wash Solution

The present application relates to the preparation of mixed cleaning solutions, such as RCA acidic washes and RCA basic washes, from super-purified materials at a wafer fabrication facility site.

The RCA wash comprises a solvent wash step using tetrachloroethylene or a similar solvent to remove total organics; A basic washing step using NH ₄ OH + H ₂ O ₂ + H ₂ O; It is made with an acidic wash step using a _{HCl + H 2 O 2 + H} 2 0. See W.Runyan and K.Bean, SEMICONDUCTOR INTEGRATED CIRCUIT PROCESSING TECHNOLOGY (1990), incorporated herein by reference. In semiconductor manufacturing, these cleaning reagents are usually purchased in packaged containers. However, these reagents require some treatment of the solution in the vessel on both the production plant and the user side.

Several different cleaning chemicals have been proposed. Shiraki washing, for example, is an erosive pre-epitaxial wash, the step of adding nitric acid to the washing sequence and is used at rather high temperatures and concentrations. See Low Temperature Surface Cleaning of Silicon and its application to Silicon MBE by Ishizaki and Shiraki of 133 J. ELECTROCHEM. Soc. 666 (1986), disclosed herein by reference.

The RCA basic washing solution is usually a mixture of NH ₄ OH + H ₂ O ₂ + H ₂ O in a ratio of 1: 1: 5 or 1: 2: 7. According to the innovative features disclosed herein, RCA basic wash solutions (or similar wash solutions) are generated at the site of a wafer fabrication plant by combining on-site purified ultra-purity ammonia with on-site purified ultra-purity hydrogen peroxide. Therefore, purity increases and the risk of undetected incidental contaminants is reduced.

The RCA acidic wash solution is usually a mixture of HCl + H ₂ O ₂ + H ₂ 0 at a ratio of 1: 1: 6 or 1: 2: 8. In accordance with the innovative features disclosed herein, RCA acidic washes (or similar wash solutions) are generated at the site of a wafer fabrication plant by combining onsite purified ultrapure HCl with onsite purified ultrapure hydrogen peroxide. Therefore, purity increases and the risk of undetected incidental contaminants is reduced.

The disclosed invention will be described with reference to the accompanying drawings, which are incorporated herein by reference and represent important sample embodiments.

1 is an on-site purification system of hydrogen peroxide water in a semiconductor facility.

2 is a block diagram of a semiconductor cleaning station in a wafer fabrication facility in which the ammonia purification system of FIG. 1 may be incorporated.

3 shows on-site generation of an RCA cleaning solution using two on-site ultra-purified components (added to ultrapure water) in a wafer fabrication facility.

Numerous innovative features of the present application will be described (by way of example and not by way of limitation) with reference to the preferred embodiments presented.

The target purity of aqueous H ₂ O ₂ is

Cationic concentration <1.0 ppb

-Anion concentration <20 ppb

Total organic contaminants <20 ppm.

Overview of Processes and Systems

The vessel and pipe connections used in the superpurifying system are preferably selected from materials that are inert to H ₂ O ₂ and non-catalytic, and inert fluorine because most metals promote at least some degree of H ₂ O ₂ degradation. Polymers are preferred.

1 shows an on-site system for the purification of hydrogen peroxide water in a semiconductor facility. Hydrogen peroxide (preferably of high purity) coming from such a system is further purified into sub-ppb by the on-site ultrapure system.

In a preferred embodiment of the present invention, the on-site ultrapurifier system uses an anion exchange distillation tube in combination with a cation exchange distillation tube. However, other conventional sub-ppb polishing techniques may be used.

As shown in FIG. 1, the filter stage is preferably disposed in a subsection of the exchange resin distillation tube to remove particulates that may be injected by the distillation tube.

Anion exchange distillation tube

Such distillation tubes are preferably initially charged with bicarbonate ions (bicarbonate preconditioning is described in US Pat. Nos. 3,294,488 or 3,305,314, disclosed herein by reference). The concentrated bicarbonate preconditioning step can preferably be carried out using a concentrated NH ₄ HCO ₃ solution (a possible alternative is to use alkaline bicarbonates that need to remove alkali metal ions, or unsaturated CO ₂ due to low solubility CO ₂₎ . Can be).

In an embodiment of the invention, the anionic resin is IRA 958 from Rohm and Hass. However, other suitable anionic resins may optionally be used.

Cation exchange distillation tube

This distillation tube is preferably initially charged with acid. This process can be done, for example, by washing in 10% H ₂ SO ₄ solution, for example.

In an embodiment of the invention, the cationic resin is A-35 from Rohm and Hass. However, other suitable cationic resins may optionally be used.

Generation of Mixed Wash Solutions

FIG. 3 shows on-site generation of RCA cleaning solutions using two on-site ultra-purified components (added to ultrapure water) in a wafer fabrication facility.

Wafer cleaning

Several washing stations in a conventional semiconductor manufacturing line are shown in FIG. The first unit in the cleaning line is a resist removal station 41 where hydrogen peroxide 42 and sulfuric acid 43 are combined and applied to the semiconductor surface to strip the resist. The resist removal station proceeds to a rinse station 44 which adds deionized water for the rinse solution rinse. The on-site downstream stream of the rinse station 44 becomes a washing station 45 to which ammonia and hydrogen peroxide aqueous solutions are applied. This solution is supplied in one of two ways. First, the mixture 47 produced by combining the aqueous ammonia 31 and the aqueous hydrogen peroxide 46 is fed to the washing station 45. Second, a pure gaseous ammonia 32 bubbled aqueous hydrogen peroxide solution 48 produces a similar mixture 49 and is likewise fed to the washing station 45. The semiconductor once washed with the ammonia / hydrogen peroxide combination is sent to a second rinse station 50 where deionized water is added to remove the cleaning solution. The next station is an additional wash station 54 which further washes by combining hydrochloric acid 55 aqueous solution and hydrogen peroxide 56 and applying it to the semiconductor surface. This station is involved in the last rinse station 57 which adds deionized water to remove HCl and H ₂ O ₂ . Dilute buffered HF at the deglaze station 59 is applied to the wafer to remove the native oxide or other oxides. Diluted buffered hydrofluoric acid is fed directly to the generator 70 through a sealed pipe. As described above, the reservoir 72 stores anhydrous HF from which a stream of gaseous HF is supplied to the generator 70 through the ion purifier 71. Gaseous ammonia is bubbled to the generator 70 to produce a buffered solution, and ultrapure deionized water is added to obtain the desired diluent. This station is accompanied by a rinse in ultrapure deionized water (station 60) and dried in station 58. The wafer or wafer batch 61 is retained on the wafer support 52 and transported from one workstation to the next, by the robot 63 or other conventional sequential processing means. The transport means can be all fully automatic, partially automatic or fully non-automatic transport means. It should be appreciated that purified HCl for acidic wash station 54 may be manufactured and supplied in an on-site manner similar to that of the ammonia purification system of FIG. 1.

The system shown in FIG. 2 is just one example of a cleaning line of a semiconductor facility. In general, the washing lines for high precision manufacturing can be drastically changed from those shown in FIG. 2 by removing or adding one or more units of the units shown, or replacing units not shown. However, the concept of on-site preparation of high purity aqueous ammonia according to the present invention is applicable to all such systems.

It is well known in the art to use ammonia and hydrogen peroxide as a semiconductor cleaning medium for workstations such as cleaning station 45 shown in FIG. In varying proportions, the nominal system consists of a combination of deionized water, 29% by weight of ammonium hydroxide and 30% by weight of hydrogen peroxide in a volume ratio of 6: 1: 1. The cleaning agent is used to remove organic residues, and together with ultrasonic agitation at a frequency of about 1 MHz to remove particles to ultrafine size.

On-site systems for the purification of ultrapure H ₂ O ₂ and for generating ultrapure cleaning solutions are connected to destinations in the production line by pipe connections that do not cause exposure to uncontrolled environments. The travel distance between the purification unit and the production line is shortened (if destination mixing equipment is provided) or more preferably the ultrapure cleaning solution generator is connected to multiple destinations via ultra clean pipe connections. For large systems, intermediate storage tanks can be used to adjust the outflow rate to compensate for changing demands, but the wash solution is in no case preserved in ultrapure environments and never exposed to contaminated environments. The risk of contamination due to packaging, transportation, or movement between containers can be avoided thereby. Therefore, the distance between the destination of the generating system where the cleaning solution remains and the destination on the production line is between one foot (30 cm) and 1,000 m or more (if the ultra clean pipe is routed between structures at a single manufacturing site). Non-contaminated material can be transported via ultra clean transport lines. In most applications, stainless steel or polymers such as high density polyethylene or fluorinated polymers can be used well.

Since ultra-pure purification, generation and / or mixing units are in close proximity to the production line, deionized water (purified according to semiconductor manufacturing standards) can be readily used for applications such as concentration adjustment, flushing or dissolution of gas bodies . Such standards commonly used in the semiconductor industry are well known to those skilled in the art. Typical standards of purified water resulting from this process include at least about 15 megohm-cm at 25 ° C. (typically 18 megohm-cm at 25 ° C.), resistivity of up to about 25 ppb, particulate content up to about 150 / cm 3 and up to 0.2 μm. Particle size, fine particle content of about 10 / cm 3 or less, and total organic carbon of 100 ppb or less are taken as the standard.

In the method and system of the present invention, the high precision control for increasing the product concentration and the outflow rate is well maintained by making accurate surveys and measurements using known equipment and instruments. A convenient means of achieving such control uses ultrasonic wave propagation to monitor specific gravity. Other methods will already be understood by those skilled in the art.

Variants and Applications

As will be appreciated by those skilled in the art, the innovative concepts described in the application of the present invention can be applied in a wide variety of variations and modifications, and therefore the scope of the disclosed invention is not limited to the specific embodiments presented.

For example, as will be appreciated by those skilled in the art, the disclosed ideas may be incorporated into semi-continuous or continuous on-site mixing of ultrapure chemicals.

As another example, the disclosed innovations are not strictly limited to the manufacture of integrated circuits, but may be applied to the manufacture of discrete semiconductor devices such as optoelectronics and power devices.

In other embodiments, it is not necessary to use a scrubber to make liquid vapor contact. That is, because gas / liquid contact is relatively less effective, bubbles may be used instead of scrubbers.

Optionally, other filtration or filtration stages can be combined with the disclosed purification apparatus.

Although not done in the preferred embodiment of the present invention, it is also possible to inject an additive into purified water if necessary.

As noted above, the main embodiment is an on-site purification system. Optionally, in alternative embodiments, the disclosed purification systems may be grafted to operate as part of a manufacturing unit that produces ultrapure chemicals for transportation. However, this alternative embodiment does not provide the benefits of on-site purification as discussed above. While this application is due to the obvious risk of ultra-pure chemical processing as discussed above, for consumers in need of packaged chemicals (including processing), the disclosed innovations are at least purely obtainable by other techniques. It provides a way to obtain higher initial purity. In other words, in this application, the drying stage may be used after ion purification.

As noted above, the main embodiments are directed to providing ultrapure aqueous chemicals that are most important for semiconductor manufacturing. However, embodiments of the disclosed systems and methods can also be used to supply a purified gas stream (in many cases, using a downstream dryer from a purifier is useful for such a supply).

The ultrapure chemical delivery route to the semiconductor front end includes an inline or pressure reservoir. Thus, the expression direct pipe connection of the claims does not exclude the use of such a reservoir, but excludes exposure to an uncontrolled atmosphere.

Claims (7)

An on-site subsystem in a semiconductor device manufacturing facility that provides a high purity reagent containing H ₂ O ₂ in a semiconductor manufacturing process, A tank connected to receive aqueous H ₂ O ₂ and provide an outflow of H ₂ O ₂ from itself; An anion exchange bed and a cation exchange bed connected to receive the H ₂ O ₂ exiting the tank to produce a purified H ₂ O ₂ outflow with reduced levels of ionic contaminants; The cation exchange bed is preconditioned with an acid and the anion exchange bed is preconditioned with bicarbonate ions; A filter downstream of the anion exchange bed and the cation exchange bed; And a pipe connection to deliver the aqueous H ₂ O ₂ to the route from the filter to a destination in a semiconductor device manufacturing facility without exposing the aqueous H ₂ O ₂ to an uncontrolled environment. An on-site subsystem in a semiconductor device manufacturing facility that provides a high purity reagent containing H ₂ O ₂ in a semiconductor manufacturing process, A tank connected to receive aqueous H ₂ O ₂ and provide an outflow of H ₂ O ₂ from itself; An anion exchange bed and a cation exchange bed connected to receive the H ₂ O ₂ exiting the tank to produce a purified H ₂ O ₂ outflow with reduced levels of ionic contaminants; An ion purification system coupled to pass gaseous reagent precursors through the gaseous / liquid contacting zone to produce ultrapure gaseous reagents; A generation and mixing subsystem coupled to combine the ultrapure gaseous reagents with deionized water and the purified H ₂ O ₂ effluent to produce an ultrapure wash solution; And a pipe connection to deliver the aqueous H ₂ O ₂ to the route from the filter to a destination in a semiconductor device manufacturing facility without exposing the aqueous H ₂ O ₂ to an uncontrolled environment. 3. The on-site subsystem of claim 2, wherein the generation and mixing subsystems are separate. 3. The on-site subsystem of claim 2, wherein the generation and mixing subsystems are combined. The on-site subsystem of claim 2, wherein the gaseous reagent is HCl. The on-site subsystem of claim 2, wherein the gaseous reagent is NH ₃ . In the method for providing a ultra-purity reagent containing H ₂ O ₂ to the semiconductor manufacturing process, Providing an aqueous H ₂ O ₂ effluent from a tank located at the same site as the semiconductor manufacturing process; Passing said H ₂ O ₂ out through an anion exchange bed and a cation exchange bed to produce a purified H ₂ O ₂ effluent with reduced levels of ionic contaminants; The cation exchange bed is preconditioned with an acid and the anion exchange bed is preconditioned with bicarbonate ions; Filtering the purified effluent to produce an effluent of ultrapure aqueous H ₂ O ₂ solution; Delivering the outflow of the ultrapure aqueous H ₂ O ₂ solution to the route through a pipe connection that delivers the aqueous H ₂ O ₂ to the route without exposure to an uncontrolled environment from the filter to a destination in a semiconductor device manufacturing facility. Reagent providing method comprising a.