HK1014894A - On-site manufacture of ultra-high-purity hydrochloric acid for semiconductor processing - Google Patents

Description

In situ preparation of ultra-high purity hydrochloric acid for semiconductor processing

no marking

Background and summary of the invention

The present invention relates to systems and methods for providing ultra-high purity hydrochloric acid for semiconductor manufacturing.

Contamination is often a top priority in integrated circuit fabrication. Most of the steps in modern integrated circuit fabrication are these or those cleaning steps; these cleaning steps may require removal of organic contaminants, metal contaminants, photo-etchants (or inorganic residues thereof), by-products of etching, native oxides, and the like.

According to 1995 data, the cost of a set of pre-fabrication facilities (integrated circuit wafer fabrication plants) is typically greater than $ 10 billion, most of which are used for particle control, cleaning, and contamination control measures.

One important source of contamination is impurities in the process chemicals. Because cleaning is so frequent and important, contamination due to cleaning chemistry is highly undesirable.

One of the process variations that have long occurred in semiconductor processing is the variation (and attempted variation) between dry processing and wet processing. In dry processing, only gaseous or plasma phase reactants are in contact with the wafer. In wet processing, various liquid reagents are used for different purposes, such as etching silicon dioxide or removing native oxide layers, removing organic substances or traces of organic contaminants, removing metals or traces of organic contaminants, etching silicon nitride, etching silicon.

Plasma etching, while having many attractive capabilities, is not suitable for cleaning. There are no readily available chemical methods for removing certain of the least desirable impurities, such as gold. Therefore, wet cleaning is important for modern semiconductor processing; and may still be so in the foreseeable future.

Plasma etching is performed by using a photoresist in place, which cannot be followed directly by a high temperature step. Otherwise the etchant is stripped and must be cleaned.

The substances that must be removed for cleaning may include: photo-etchant residues (organic polymers); sodium; alkaline earth metals (such as calcium or magnesium); and heavy metals (e.g., gold). Many of these species do not form volatile halides and therefore plasma etching cannot carry them away. Cleaning by wet chemistry is desirable.

As a result, the purity of the process chemistry during plasma etching is less critical because there is always a cleaning step after the plasma etching step before the high temperature step is performed, which can remove these harmful contaminants from the surface before the high temperature step acts on them. However, the purity of the liquid chemistry is much more important because the collision rate on the semiconductor surface is typically millions of times higher than in plasma etching, and because the liquid cleaning step is directly followed by a high temperature step.

But instead of the other end of the tubeWet processing has one major disadvantage, namely ionic contamination. Integrated circuit structures use only a few dopant species (boron, arsenic, phosphorus and sometimes antimony) to form the desired P-type and N-type doped regions. However, many other species are also electronically active dopants, which are highly undesirable contaminants. Many of these contaminants may have deleterious effects, for example at concentrations below 10¹³Per cm³High junction leakage currents are generated and some less desirable contaminants are leached into the silicon; that is, where the silicon is contacted with an aqueous solution, the equilibrium concentration of contaminants in the silicon is higher than in the solution. Moreover, some of the less desirable contaminants have a high diffusion coefficient, such that the introduction of such dopants into any portion of the silicon wafer tends to diffuse these contaminants throughout the wafer, including the semiconductor junctions where these contaminants would cause electrical leakage.

Therefore, all metal ions in all liquid solutions used on semiconductor wafers are preferably present in very low levels. Preferably, the combined concentration of all metals should be less than 300ppt (parts per trillion); for any metal, the concentration should be less than 10ppt, and as small as possible. Furthermore, contamination by both anions and cations must be controlled. (some anions may have a deleterious effect, e.g., complexing metal ions may decrease the mobility of metal atoms or ions in the silicon lattice.)

The precursor manufacturing facilities typically include an on-site purification system that produces high purity water (referred to as "DI" water, i.e., deionized water). However, it is more difficult to obtain process chemicals of the desired purity.

The parent application discloses a method for producing ultra-high purity ammonia in an in-situ system at a semiconductor wafer production site: withdrawing ammonia vapor from the liquid ammonia reservoir; passing the ammonia vapor through a microfilter; and washing the filtered vapor with high pH purified water, preferably deionized water, which has been equilibrated with the ammonia stream. This discovery allows commercial grade ammonia to be converted to ammonia of sufficiently high purity for high precision manufacturing without the need for conventional distillation columns. The withdrawal of ammonia vapor from the feed reservoir itself is used as a single stage distillation to remove non-volatile impurities and 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. Reactive volatile impurities previously thought to be found in commercial grade ammonia, such as certain transition metal halides, group III metal hydrides and halides, certain group IV metal hydrides and halides, and halogens, require distillation removal, and it has now been found that they can be removed by scrubbing to a degree suitable for use in high precision operations. This is a very unusual finding, since scrubbing processes are traditionally used to remove the major impurities, not the minor impurities.

The extremely pure contents required for semiconductor manufacturing are rare or unique in various industrial processes. At such very pure levels, treatment of the chemicals is inherently undesirable (although, of course, this cannot be completely avoided). It is necessary to minimize exposure of the ultrapure chemicals to air (particularly also in the environment in which workers are present). Such exposure risks the introduction of particulate matter, thereby creating contamination. Shipment of ultrapure chemicals in closed containers is also undesirable because of the high risk of contamination inherent in either the manufacturer or the user. Moreover, undetected contaminants can damage a large number of expensive wafers.

Because there are typically many corrosive and/or toxic chemicals used in semiconductor processing, the supply of reagents is typically separate from the site of the predecessor. The construction and maintenance of piping systems for ultra-high purity gases and liquids is well understood in the semiconductor industry so that most gases and liquids can be transported from anywhere in the same building (or even the same site) to the wafer fabrication site.

Systems and methods for preparing ultrapure chemicals on-site at a semiconductor manufacturing facility such that they can be directly piped to a point of use are disclosed. The disclosed systems are very compact devices that can be in the same building as the previous fabrication (or in an adjacent building) so that disposal can be avoided.

Hydrochloric acid

One important class of semiconductor processing chemicals is HCl in gaseous and aqueous forms. Liquid hydrochloric acid is also widely used in the acid cleaning portion of standard RCA cleaning.

As noted above, the parent application discloses methods and systems for producing ultra-high purity ammonia. It has now been found that improvements in these processes and systems can be used to prepare ultra-high purity HCl.

The starting material was commercial grade anhydrous HCl. The first purification step is provided by simple vaporization. (HCl vapor pressure of 613 lb/in at 70 ℃ F.)²And 1185 lbs/inch at 124.5 ° F²This vapour pressure therefore always provides sufficient delivery pressure for withdrawal from the large tank. ) Preferably, the HCl vapor is withdrawn directly from the storage tank. (in another embodiment, liquid HCl is transferred from a bulk storage tank in batches and vaporized in a vaporization chamber at controlled temperature and pressure.)

Preparation of hydrochloric acid

The purified gaseous HCl can now be dissolved in water to produce concentrated hydrochloric acid.

In situ preparation of ultra pure mixed cleaning solutions

The present application discloses methods of preparing mixed cleaning solutions, such as RCA acid cleaning solutions and RCA base cleaning solutions, from individual components that have themselves been ultra-purified at the same site, on-site at a wafer fabrication facility.

The RCA cleaning method comprises the following steps: 1) solvent washing to remove all organics-with tetrachloroethylene or similar solvents; 2) alkaline cleaning of-NH₄OH+H₂O₂+H₂O; and 3) acid cleaning of-HCl + H₂O₂+H₂And O. See w.runyan and k.bean, semiconductor integrated circuit processing (1990), incorporated herein by reference. For semiconductor manufacturing, such cleaning agents are typically purchased as packages. However, this means that some handling of the solutions in these packages is required at the manufacturer's plant and place of use. Such asAs mentioned above, such treatment of ultra-high purity chemicals is always undesirable.

Various other cleaning chemistries have been proposed. For example, the Shiraki clean is a corrosive pre-epi (pre-epitaxy) clean that adds a nitric acid step to the cleaning sequence, using slightly higher temperatures and concentrations. See Ishizaki and Shiraki, "Low temperature surface cleaning of silicon and its use in silicon MBE", 133, journal of the society of electronic chemistry (J.ELECTROCROCHEM. Soc.)666(1986), incorporated herein by reference.

RCA acid cleaning solution is usually HCl + H₂O₂+H₂O, in a ratio of 1: 6 or 1: 2: 8. According to one of the innovations disclosed herein, an RCA acid cleaning solution (or similar cleaning solution) is prepared in-situ at a wafer fabrication facility by mixing in-situ purified ultra-pure HCl with in-situ purified ultra-pure hydrogen peroxide. The purity is thereby increased, while the risk of undetected adventitious contamination is reduced.

Brief Description of Drawings

The disclosed invention will now be described with reference to the accompanying drawings, which illustrate important exemplary embodiments of the invention and are therefore incorporated herein by reference, wherein:

figure 1 is a process flow diagram of one embodiment of an apparatus for producing ultrapure hydrochloric acid.

Fig. 2 is a block diagram of a semiconductor manufacturing line that may include the purification apparatus of fig. 1.

FIG. 3 is a block diagram of a semiconductor cleaning section in a wafer fabrication facility, which may include hydrochloric acid purification of FIG. 1.

Detailed description of the preferred embodiments

The numerous innovative teachings of the present application will be described with particular reference to the presently preferred embodiments (which are intended to be illustrative of the invention and not limiting), in which:

purification of HCl

According to the invention, HCl vapor is first withdrawn from the vapor space of the liquid HCl supply reservoir. The vapor withdrawn in this way is used as a single stage distillation to leave some solid impurities and high boiling impurities in the liquid phase. The feed reservoir may be any conventional feed tank or other reservoir suitable for holding HCl, which may be in anhydrous form or in aqueous solution (preferably anhydrous form). The reservoir can be maintained at atmospheric pressure or, if necessary, at a pressure greater than atmospheric pressure to increase the flow rate of HCl through the system. The reservoir is preferably temperature controlled so that the temperature is maintained in the range of about 10 to about 50 c, preferably about 15 to about 35 c, most preferably about 20 to about 25 c.

Impurities that may be removed by withdrawing HCl vapor from the vapor phase include metals of groups I and II of the periodic table, as well as impurities in the form of complexes formed as a result of their contact with HCl. Oxides and carbonates of these metals, and hydrides such as beryllium hydride and magnesium hydride; group III elements and oxides thereof, and adducts of hydrides and halides of these elements; a transition metal hydride; and heavy hydrocarbons and halocarbons such as pump oils.

The HCl withdrawn from the reservoir is passed through a filtration device to remove any solid material entrained with the vapor. Microfiltration and ultrafiltration units and membranes are commercially available and used. The brand and type of filter may be selected as desired. The presently preferred embodiment uses a coarse filter followed by a 0.1 micron filter before the ion purifier without further filtration after the ion purifier.

The filtered vapor is then passed through a scrubber where the vapor is washed with low pH pure water, preferably deionized water. The low pH water is preferably an aqueous HCl solution, which is circulated through a scrubber to raise the concentration to saturation. The scrubber is easily operated as a conventional countercurrent scrubbing tower. Although the operating temperature is not critical, the scrubbing tower is preferably operated at about 10 to about 50 deg.C, preferably about 15 to about 35 deg.C. Again, the operating pressure is not critical, although it is preferably from about atmospheric to about 30 pounds per inch above atmospheric²Operating at a pressure of (1). Scrubber tower tubeConventional column packing is often provided to provide adequate contact between the liquid and gas, and a demisting stage is preferred.

In a presently preferred embodiment, the column has packing of about 3 feet (0.9 meters) in height and an internal diameter of about 7 inches (18 centimeters) 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 kilopascals) and less than 10% flooding, with a circulation flow rate of about 2.5 gallons per minute (0.16 liters per second) at normal conditions and 5 gallons per minute (0.32 liters per second) at 20% flooding, with the gas inlet below the packing, the liquid inlet above the packing, but below the demisting stage. For the column of this specification, the preferred packing is one having a nominal size of less than one eighth of the column diameter. The demisting section of the tower has similar or denser packing, and additionally has a conventional construction. It should be understood that all descriptions and dimensions in this paragraph are examples only. Each system parameter is variable.

In a typical operation, deionized water is first saturated with HCl to produce the wash medium used as the start. During operation of the scrubber, small amounts of liquid are periodically withdrawn from the column tank to remove accumulated impurities.

Examples of impurities removed with scrubbers include reactive volatile species such as metal halides; halides and hydrides of phosphorus, arsenic and antimony; a transition metal halide; and halides and hydrides of group III and VI metals.

The apparatus described herein may be operated in batch, continuous or semi-continuous mode. Continuous or semi-continuous operation is preferred. The volumetric processing rate of the HCl purification system is not critical and can vary over a wide range. However, in most operations used in the present invention, the flow rate of HCl through the system is in the range of about 200 mL/hr to several thousand L/hr.

Optionally, the HCl leaving the scrubber may be further purified prior to use, depending on the particular type of manufacturing process in which the HCl is purified for use. For example, in some cases it may be advantageous to have a dehydration unit and a distillation unit in the system. The distillation column can also be operated in a batch mode,Continuous mode or semi-continuous mode operation. In batch operation, a typical operating pressure is 300 pounds per inch²Absolute pressure (2068 kpa) and batch size of 100 lbs (45.4 kg). In this example, the column has a diameter of 8 inches (20 cm), a height of 72 inches (183 cm), and operates at 30% flooding with a vapor velocity of 0.00221 feet/second (0.00067 m/s), corresponding to a theoretical plate height of 1.5 inches (3.8 cm), 48 theoretical plates. In this example, the reboiler (boiler) size was about 18 inches (45.7 cm) in diameter and 27 inches (68.6 cm) long, with a reflux ratio of 0.5, a recirculating cooling water inlet temperature of 60 ° F (15.6 ℃) and an outlet temperature of 90 ° F (32.2 ℃). Again, this is only an example and distillation columns with wide variations in structure and operating parameters may be used.

Depending on its use, purified HCl can be used as a purified gas or as an aqueous solution, whether with or without a distillation step, in which case the purified HCl is dissolved in pure water (preferably deionized water). The proportions and methods of mixing are conventional.

A flow diagram depicting one example of an HCl purification device according to the present invention is shown in fig. 1. Liquid HCl is stored in reservoir 11. HCl vapor 12 is drawn from the vapor space of the reservoir and then through a shut-off valve 13, a filter 14. The flow rate of the filtered HCl vapor 15 is controlled by a pressure regulator 16, and the vapor 15 is then sent to a scrubber 17 equipped with a packing section 18 and a defogging pack 19. Saturated aqueous HCl20 flows downward and HCl vapor flows upward, the liquid is circulated by circulation pump 21, and the level is controlled by level sensor 22. Waste liquid 23 is periodically withdrawn from the residual liquid at the bottom of the scrubber. Deionized water 24 is fed to scrubber 17 and maintained at high pressure by pump 25. The washed HCl26 was sent to one of three alternative schemes. They are: (1) distillation column 27, where HCl is further purified. The resulting distilled HCl28 was then sent to the point of use. (2) Dissolving unit 29 where HCl is mixed with deionized water 30 to produce an aqueous solution 31 which is sent to the point of use. For plant operations with multiple points of use, the aqueous solution may be collected in a storage tank from which the HCl is withdrawn to the various lines of the same plant at the multiple points of use. (3) Line 32 is sent, line 32 sending HCl in gaseous form to the point of use.

Of these alternative schemes, the second scheme and the third scheme, which do not use distillation column 27, are suitable for producing HCl with less than 100ppt of any metal impurities. However, for some applications, it is preferred to have a distillation column 27. In this case, the distillation column will remove non-condensable gases, such as oxygen and nitrogen, which may interfere with the purge. Furthermore, since the HCl leaving the scrubber 17 is saturated with water, a dehydration unit can be added to the system between the scrubber 17 and the distillation column 27, as an alternative, depending on the characteristics and efficiency of the distillation column.

In the case of any of these alternative schemes, the gaseous HCl or aqueous solution stream produced may be divided into two or more sub-streams, each of which is sent to a different point of use, so that the purification unit sends purified HCl to many points of use simultaneously.

Experiment summary

Two separate HCl cylinders from Matheson Gas Products were used in this study. Note the difference in impurity composition between the two cylinders, which may reflect changes in the typical HCl source. The objective of this study was to develop a purification process for virtually any feed, rather than optimizing the process for a particular batch.

The entire experimental procedure was carried out in a fume hood with ventilation and no control of the room atmosphere. The floor is untreated concrete and therefore it is likely that the results for Ca, K and Na are higher than those obtained in an environmentally controlled point-of-use system.

The sampling device made by CGA had an 1/4 inch tube fitting and a bellows-sealed valve with a 1/4 inch tube connector, both made of stainless steel. The outlet of the valve was connected to an 1/4 inch tetrafluoroethylene stub so that liquid or vapor could enter the sample vial directly. In this way, an aqueous HCl sample can be prepared directly in the sample vial without the need for liquid transfer in an uncontrolled environment.

The sample bottles were prepared by thoroughly rinsing and emptying 4 times with DI before adding approximately 100 ml of DI and capping the bottles. Samples were prepared by bubbling HCl from the selected source and method into DI pre-added to the sample vial. In most cases, the addition of HCl was continued until the solution in the sample bottle was saturated, as evidenced by HCl passing through the solution and venting to the fume hood exhaust. Upon saturation, the sample solution felt hot to the hand, and after being capped and cooled, the sample bottle was partially dented.

An analog ion purifier ("IP") system was made from 1 inch teflon tubing. One end of the connecting tube was welded to the capped portion of the tube, which was about 1 foot high. The other portion of the tube was capped with a cap having two 1/4 inch holes in the cap. 1/4 inch Teflon tubing was inserted through the two tight fitting holes, one tubing extending down the bottom of the device and the other tubing passing through the top only. The 4 inch lower section of the module was fitted with raschig rings cut from 1/4 inch thin walled teflon tubing. This simulated IP was loaded with about 100 ml of DI during the experiment. HCl gas is introduced through the bottom tube to obtain a gas/liquid interface. While this assembly is far less effective than the well-designed IP with packed columns, the worst-case IP performance can be estimated. This IP bottom sample requires added processing in order to transfer the bottom sample into a sample vial for laboratory experiments. For this reason, the IP bottom sample may measure higher due to environmental contamination.

The HCl liquid sample was taken from each cylinder by inverting the cylinder and draining the liquid into a pre-prepared sample container. The impurities measured are the real worst case because such liquid sampling techniques often also leave the sample more particulate, and the additional handling exposes the sample to room air for a longer period of time. The ICP results for the liquids taken from the two cylinders are shown in Table 1. These results have been normalized to 37.25% HCl, which is the nominal specification for aqueous HCl obtained from the HCl point-of-use system. The significant excess of Fe and other contaminants makes the more sensitive ICP/MS test unnecessary; thus, the actual content of less important contaminants is not known. However, the exact amount is only technically meaningful as long as these impurities can be reduced to acceptable levels in the product. Fortunately, all of these impurities can be removed by distillation and/or IP techniques.

The following elements were found in one or both cylinders analyzed: al, B, Ba, Cr, Cu, Fe, K and Na. The contaminant concentration and removal techniques will be discussed in the following sections.

Numerous experiments have been performed in order to demonstrate this basic principle of purification for HCl. For simplicity and clarity, similar experiments are described in groups.

Measurement of liquid anhydrous HCl

Anhydrous liquid HCl was measured by inverting the cylinder and absorbing the anhydrous liquid HCl directly into water. This represents a worst case scenario, as solid impurities may also enter the solvent. The sample was then sent for ICP analysis of the metal. (Steel cylinder 1: sample No. 062993602, steel cylinder 2: sample No. 062993605).

Measurement of vaporous anhydrous HCl

In these experiments, the cylinder was supported with a top outlet line. Anhydrous HCl vapor was distilled from the liquid and dissolved in a small volume of ultrapure water sample through a spray tube. This process represents a conventional single stage distillation. These data were compared to the purifier experiments. (Steel cylinder 1: sample No. 071293601, steel cylinder 2: sample No. 062993603).

Ion purifier measurement

These laboratory scale experiments were carried out using the equipment described previously. After loading the simulated purifier with ultrapure water and connecting the outlet of the purifier to another portion of ultrapure water, HCl gas was slowly fed to the experimental set-up. As HCl is absorbed into the first stage purifier there is a considerable exotherm and the temperature and concentration in the purifier increases before the boiling point of the system is reached. Upon reaching the boiling point of the system, the HCl gas is no longer absorbed in the purifier, but instead is bubbled through the liquid along the tortuous path provided by the raschig ring packing. In this way, the steam is scrubbed with the aqueous medium. Metal impurities having a greater affinity for aqueous solutions than in the vapor state will remain in the liquid phase. The purified gas is then absorbed in the next stage to form hydrochloric acid. The liquid remaining in the purifier ("bottom" sample) and the "washed" product sample ("product") were then both sent for analysis by ICP/MS. Both cylinders were used for several experiments and are listed in the remainder of table 1.

Experiment summary

Comparison of the liquid obtained from each cylinder with the vapour distilled from the liquid illustrates the purifications obtainable by simple distillation (cylinder 1 liquid with cylinder 1 vapour, cylinder 2 liquid with cylinder 2 vapour) and shows good purifications with a separation factor of 10-5000. However, many species still exceed 1 ppb. Increasing the sequential or multistage distillation capacity, while further improving purity, adds significant expense and complexity. However, the impurity content of the outlet product of the purifier is significantly reduced compared to the simple distillation scheme. Furthermore, the bottom sample of any one experiment was much higher than the product stream for any particular element, demonstrating the separation effect of this technique. The purifier is much simpler and more economical to manufacture and operate than a multi-stage distillation system.

2IP simulation-I of steel cylinder

Experimental work: the tank valve is opened without leakage. The sample valve was opened and a large amount of bubbling and liquid was carried out to waste. The sample valve was closed and there was some back suction. Reopen at the appropriate rate. Some of the HCl gas was discarded a few seconds before injection into the DI. The DI sample remained clear and the IP bottom became very yellow. The sample injection tube was removed and capped with a sample of the HClS product. The sample tube sent to the IP was removed from the sample valve and the sample valve was closed. Pour IP bottom sample into sample container.

Sample number: IP base 063093501, HClS product 063093502.

1IP simulation of steel cylinder

Experimental work: opening the valve gives a good flow of HCl gas to the IP. When saturated, HCl gas passes over IP. After reaching line clean in a few seconds, the product line was introduced into the sample vial. The product line was removed when the sample was saturated. It was observed that leakage from the bleed port in the valve, premature suck back and water washing had to corrode the hole in the bellows seal. Samples were recovered from IP tanks.

Sample number: IP product 071293603, IP bottom sample 071293602

Cylinder-2 IP test

Experimental work: same apparatus and procedure as in the previous experiment, but without (NH)₄)₂S。

Sample number: IP bottom sample 071493603, IP product 071493604

Sample analysis meter

The following three tables illustrate the results of the tests involving the above-mentioned samples:

HCl lab scale test results:

sample number	062993602	062993603	062993605	063093601	063093602
						Id：	93-7239	93-07240	93-07242	93-07338	93-07339
Sample (I)	Steel cylinder 1 liquid	Cylinder 2 vapor	Steel cylinder 2 liquid	Steel cylinder 2IP	Steel cylinder 2IP
										Bottom sample	Product(s)
Analysis of	6.10	17.31	6.80	34.55	15.34
						Ag		＜2.15
Al	＜136.18	16.89	164.34	191.91	＜54.15
						Au		＜2.15		＜24.04	＜54.15
B	2070.12	4.41	745.00	410.77	＜27.20
						Ba	36.64	＜2.15	＜12.60	＜2.48	＜5.59
Be	＜1.83	＜0.65	＜1.64	＜0.32	＜0.73
						Bi	＜678.44	＜2.15	＜608.60	＜	＜269.78
Ca	＜7.33	＜2.58	8.44	＜1.29	＜
						Cd	＜14.05	＜2.15	＜12.60	＜	＜5.59
Co	＜136.18	＜2.15	＜122.16	＜	＜54.15

Sample number	062993602	062993603	062993605	063093601	063093602
						Id：	93-7239	93-07240	93-07242	93-07338	93-07339
Sample (I)	Steel cylinder 1 liquid	Cylinder 2 vapor	Steel cylinder 2 liquid	Steel cylinder 2IP	Steel cylinder 2IP
										Bottom sample	Product(s)
Cr	775.53	＜24.10	＜61.35	27276.06	＜27.20
						Cu	1337.34	2.71	＜61.35	354.71	＜27.20
Fe	144225	29.22	129696	84865.31	＜27.20
						Ga	＜678.44	＜239.08	＜608.60		＜269.78
Ge	＜678.44	＜239.08	＜608.60	＜119.78
						In		＜2.15
K	＜1801.43	2.39	3.62
						La		＜2.15
Li	＜14.05	＜2.15	＜12.60	＜2.48	＜5.59
						Mg	＜1.83	＜0.65	＜1.64	＜0.32	＜0.73
Mn	＜14.05	＜4.95	＜12.60	2043.09	＜5.59
						Mo	＜183.20	2.71	＜61.35	414.01	＜27.20
Na	293.11	0.97	＜0.55	＜47.98	＜108.06
						Ni	＜271.74	＜95.76	＜243.77	14402.97	＜108.06
P	＜136.18	＜47.99	＜122.16	＜24.04	＜54.15
						Pb		＜2.15
Pd	＜678.44	＜2.15	＜608.60	＜119.78	＜269.78
						Pt	＜678.44	＜2.15	＜608.60	＜119.78	＜269.78
Sb	＜678.44	＜2.15	＜608.60	＜119.78	＜269.78
						Sn	＜339.52	＜2.15	＜304.57	＜59.95	＜135.01
Sr	＜68.39	＜2.15	＜61.35	＜12.08	＜27.20

Sample number	062993602	062993603	062993605	063093601	063093602
						Id：	93-7239	93-07240	93-07242	93-07338	93-07339
Sample (I)	Steel cylinder 1 liquid	Cylinder 2 vapor	Steel cylinder 2 liquid	Steel cylinder 2IP	Steel cylinder 2IP
										Bottom sample	Product(s)
Ta	＜678.44	＜2.15	＜608.60	＜119.78
						Ti	＜136.18	＜47.99	＜122.16	＜24.04	＜54.15
Tl		＜2.15
						V	＜68.39	＜24.10	＜61.35	＜12.08	＜27.20
W		＜2.15
						Zn	＜68.39	＜24.10	＜61.35	152.02	＜27.20
Zr	＜189.30	＜2.15	＜122.16	＜24.04	＜54.15

Sample number	070193601	070193602	071293601
				Id	93-07388	93-07389	93-07890
Sample (I)	Steel cylinder 2IP	Steel cylinder 2IP	Cylinder 1 vapor
					Bottom sample	Product(s)
Analysis of	33.92	14.42	18.49
				Ag	0.00	＜2.58	＜44.93
Al	＜24.49	2.40
				Au	0.00	＜2.58
B	＜12.30	3.93	＜22.56
				Ba	＜2.53	＜2.58	8.06
Be	＜0.33	＜2.58	＜0.60
				Bi	＜122.01	＜2.58	＜223.82
Ca	0.00	＜3.10	＜2.42

Sample number	070193601	070193602	071293601
				Id	93-07388	93-07389	93-07890
Sample (I)	Steel cylinder 2IP	Steel cylinder 2IP	Cylinder 1 vapor
					Bottom sample	Product(s)
Cd	＜2.53	＜2.58	＜2.62
				Co	＜24.49	＜2.58	＜44.93
Cr	＜12.30	＜2.58	＜22.56
				Cu	＜12.30	＜2.58	＜22.56
Fe	124.09	3.69	＜22.56
				Ga	＜122.01	＜0.00	＜223.82
Ge	0.00	＜0.00	＜223.82
				In	0.00	＜2.58
K	0.00	7.17
				La	0.00	＜2.58
Li	＜2.53	＜2.58	＜4.63
				Mg	＜0.33	＜2.58	＜0.60
Mn	91.15	0.00	＜4.63
				Mo	＜12.30	＜2.58	＜22.56
Na	＜48.87	11.47	＜89.65
				Ni	＜48.87	0.00	＜89.65
P	＜24.49	0.00	＜44.93
				Pb	0.00	＜2.58
Pd	＜122.01	＜2.58	＜223.82
				Pt	＜122.01	＜2.58	＜223.82
Sb	＜122.01	＜2.58	＜223.82

Sample number	070193601	070193602	071293601
				Id	93-07388	93-07389	93-07890
Sample (I)	Steel cylinder 2IP	Steel cylinder 2IP	Cylinder 1 vapor
					Bottom sample	Product(s)
Sn	＜61.06	＜2.58	＜112.01
				Sr	＜12.30	＜2.58	＜22.56
Ta	0.00	＜2.58	＜223.82
				Ti	＜24.49	0.00	＜44.93
Tl	0.00	＜2.58
				V	＜12.30	0.00	＜22.56
W	0.00	＜2.58
				Zn	＜12.30	0.00	＜22.56
Zr	＜24.49	＜2.58	＜44.93

Sample number	071293602	071293603	071493603	071493604
					Id	93-07891	93-07892	93-07974	93-07975
Sample (I)	Steel cylinder 1IP	Steel cylinder 1IP	Steel cylinder 1IP	Steel cylinder 1IP
						Bottom sample	Product(s)	Bottom sample	Product(s)
Analysis of	33.33	16.67	35.08	14.49
					Ag	＜24.92	＜49.83	7.33	＜2.57
A1	0.00	0.00	3.57	0.67
					Au	0.00	0.00	＜1.06	＜2.57
B	＜12.52	＜25.03	19.64	＜2.57
					Ba	5.59	＜5.14	＜1.06	＜2.57
Be	＜0.34	＜0.67	＜1.06	＜2.57
					Bi	＜124.17	＜248.26	＜1.06	＜2.57
Ca	＜1.34	＜2.68	19.76	1.90
					Cd	＜1.45	＜2.90	＜1.06	＜2.57
Co	＜24.92	＜49.83	2.34	＜2.57
					Cr	＜12.52	＜25.03	0.00	0 00
Cu	＜12.52	＜25.03	21.02	＜2.57
					Fe	62.59	＜25.03	0.00	1.75
Ga	＜124.17	＜248.26	0.00	0.00
					Ge	＜124.17	＜248.26	0.00	0.00
In	0.00	0.00	＜1.06	＜2.57
					K	0.00	0.00	0.00	2.08
La	0.00	0.00	＜1.06	＜2.57
					Li	＜2.57	＜5.14	＜1.06	＜2.57
Mg	＜0.34	＜0.67	11.79	＜2.57

Sample number	071293602	071293603	071493603	071493604
					Id	93-07891	93-07892	93-07974	93-07975
Sample (I)	Steel cylinder 1IP	Steel cylinder 1IP	Steel cylinder 1IP	Steel cylinder 1IP
						Bottom sample	Product(s)	Bottom sample	Product(s)
Mn	＜2.57	＜5.14	0.00	0.00
					Mo	＜12.52	＜25.03	29.63	＜2.57
Na	＜49.73	＜99.44	1.71	4.19
					Ni	＜49.73	＜99.44	0.00	0.00
P	＜24.92	＜49.83	0.00	0.00
					Pb	0.00	0.00	＜1.06	＜2.57
Pd	＜124.17	＜248.26	＜1.06	＜2.57
					Pt	＜124.17	＜248.26	＜1.06	＜2.57
Sb	＜124.17	＜248.26	＜1.06	＜2.57
					Sn	＜62.14	＜124.24	＜1.06	＜2.57
Sr	＜12.52	＜25.03	＜1.06	＜2.57
					Ta	＜124.17	＜248.26	＜1.06	＜2.57
Ti	＜24.92	＜49.83	0.00	0.00
					Tl	0.00	0.00	＜1.06	＜2.57
V	＜12.52	＜25.03	0.00	0.00
					W	0.00	0.00	＜1.06	＜2.57
Zn	40.23	＜25.03	0.00	0.00
					Zr	＜24.92	＜49.83	＜1.06	＜2.57

Improvements and modifications

As will be recognized by those skilled in the art, the innovative concepts disclosed in the present application can be modified and varied over a wide range of applications, and the scope of protection sought is therefore not limited by the specific illustrative disclosure given.

For example, the disclosed innovative techniques are not strictly limited to the fabrication of integrated circuits, but can also be used to fabricate discrete semiconductor elements, such as optoelectronic devices and power plants.

As another example, the disclosed innovative techniques can also be used in other manufacturing processes that incorporate integrated circuit manufacturing methods, such as thin film magnetic heads and active matrix liquid crystal displays; the primary application is in integrated circuit fabrication and the disclosed techniques have secondary applications in other areas.

As another example, the use of scrubbers for liquid-gas contact is not critical; the scrubber may be replaced by a bubble column (bubbler), although such replacement is less desirable due to the lower efficiency of the gas/liquid contact of the bubble column.

Optionally, other filtration or filtration stages can be used in conjunction with the disclosed purification apparatus.

It should also be noted that additives may be added to the purified water if desired, although this is not done in the presently preferred embodiment.

As mentioned above, the primary embodiment is an in situ purification system. On the other hand, in a less preferred class of embodiments, the disclosed purification systems may also be suitable for use as part of a manufacturing facility that produces ultra-high purity chemicals for shipment; however, this alternative embodiment does not achieve the advantages of in situ purification as discussed above. An inherent risk encountered with such applications is the problem of handling ultra-high purity chemicals as discussed above; the innovative techniques disclosed provide a way to achieve an initial purity that is higher than otherwise achievable for users who need to package chemicals (with concomitant handling). In addition, in such applications, a drying stage may also be used after the ion purifier.

As noted above, the primary embodiment is directed to providing ultra-pure aqueous chemicals that are of paramount importance to semiconductor manufacturing. However, the disclosed system and method embodiments may also be used to provide a purified gas stream. (in many cases, it is appropriate to use a dryer downstream of the purifier).

It should also be noted that the ultrapure chemical piping in semiconductor pre-fabrication facilities may include an in-line or pressurized reservoir. Thus "direct" piping in the claims does not exclude the use of such reservoirs, but they cannot be exposed to an uncontrolled atmosphere.

Claims (38)

1. An on-site subsystem for providing ultra-high purity reagents containing HCl to semiconductor manufacturing operations in a semiconductor device fabrication facility, the subsystem comprising: a vaporization source connected to the source of liquid HCl and providing a stream of HCl vapor therefrom; said HCl vapor stream is connected to pass through an ion purification unit which contacts a high purity water recycle stream containing a high concentration of hydrochloric acid with said HCl vapor stream; and a preparation means connected to receive said stream of HCl vapor from said purification means and to combine said HCl vapor with an aqueous liquid to produce an ultra-pure aqueous solution containing HCl; and a piping system for sending said aqueous solution to various points of use in a semiconductor device manufacturing facility.

2. The system of claim 1, further comprising a particulate filter between said vaporization source and said purification unit.

3. The system of claim 1, wherein said liquid HCl source consists of anhydrous HCl.

4. The system of claim 1, wherein said recycled high purity water is free of any additives.

5. The system of claim 1, wherein said liquid HCl source has only standard commercial-grade purity.

6. The system of claim 1 wherein said vaporizer is a bulk storage tank.

7. The system of claim 1 wherein said vaporizer operates at a controlled temperature and is connected to receive liquid HCl from a bulk storage tank.

8. An on-site subsystem for providing ultra-high purity reagents containing HCl to semiconductor manufacturing operations in a semiconductor device fabrication facility, the subsystem comprising: a vaporization source connected to receive liquid HCl and to provide a stream of HCl vapor therefrom; said HCl vapor stream is connected to pass through an ion purification unit which contacts a high purity water recycle stream containing a high concentration of hydrochloric acid with said HCl vapor stream; and a preparation means connected to receive said stream of HCl vapor from said purification means and to combine said HCl vapor with an aqueous liquid to produce an ultrapure aqueous solution containing HCl; the ultra-pure aqueous solution can thus be used in a semiconductor device manufacturing plant without requiring bulk transport or exposure of the liquid surface to any environment.

9. The system of claim 8 wherein a particulate filter is disposed between said vaporization source and said purification unit.

10. The system of claim 8, wherein said liquid HCl source consists of anhydrous HCl.

11. The system of claim 8 wherein said recycled high purity water stream is free of any additives.

12. The system of claim 8, wherein said liquid HCl source has only standard commercial-grade purity.

13. The system of claim 8 wherein said vaporizer is a bulk storage tank.

14. The system of claim 8 wherein said vaporizer operates at a controlled temperature and is connected to receive liquid HCl from a bulk storage tank.

15. An on-site subsystem in a semiconductor device fabrication facility for providing ultra-high purity HCl for semiconductor fabrication operations at said facility, comprising: a vaporization source connected to receive liquid HCl and to provide a stream of HCl vapor therefrom; said HCl vapor stream is connected to pass through ion purification means which contacts a high purity water recycle stream containing a high concentration of hydrochloric acid with said HCl vapor stream, and a drier means connected to receive said HCl vapor stream from said purifier and to dry said HCl vapor; and a piping system for sending said aqueous solution to various points of use in a semiconductor device manufacturing facility.

16. The system of claim 15 wherein a particulate filter is disposed between said vaporization source and said purification unit.

17. The system of claim 15, wherein said liquid HCl source consists of anhydrous HCl.

18. The system of claim 15 wherein said high purity water recycle stream is free of any additives.

19. The system of claim 15, wherein the liquid HCl source has only standard commercial-grade purity.

20. The system of claim 15 wherein said vaporizer is a bulk storage tank.

21. The system of claim 15, wherein the vaporizer operates at a controlled temperature and is connected to receive liquid HCl from a bulk storage tank.

22. A system for the preparation of ultra-high purity HCl, said system comprising:

(a) a reservoir of liquid HCl having a vapor space above the stored liquid;

(b) a connecting line for withdrawing HCl-containing vapor from said vapor space;

(c) a filtration membrane for removing particles from the vapor thus withdrawn; and

(d) a gas-liquid interface contact chamber in which the vapor filtered through the filter membrane is contacted with an aqueous HCl solution in deionized water, the vapor so washed being purified HCl gas.

23. The system of claim 22, further comprising a distillation column for distilling vapor from the scrubber.

24. A system for manufacturing high-precision electronic components, said system comprising:

(a) a production line comprising a plurality of stations for performing various steps on a wafer comprising semiconductor material in the manufacture of electronic components, at least one of said stations using gaseous HCl as a gas source for treating said workpiece;

(b) purification support means connected by line to said workstation to provide said ultra-high purity form of HCl, said support means comprising:

(i) a liquid HCl reservoir having a vapor space above the stored liquid HCl;

(ii) a connecting line for withdrawing HCl-containing vapor from said vapor space;

(iii) a filter membrane for removing particles from the vapor thus withdrawn; and

(iv) a scrubber for contacting the vapor filtered through said filter membrane with an aqueous solution of HCl in deionized water, the vapor thus scrubbed being purified HCl gas;

(c) said purification means is connected to said workstation by a line to provide said ultra-high purity form of HCl.

25. The system of claim 24 wherein said ancillary equipment further comprises a distillation column for distilling vapor from said scrubber.

26. The system of claim 24 wherein said auxiliary means further comprises means for combining said purified HCl gas with purified water to form an aqueous HCl solution.

27. The system of claim 24 wherein HCl purified by said ancillary device exits said ancillary device at a location within about 30 cm of said apparatus so that the product of step (b) is applied directly to said workpiece.

28. The system of claim 24, wherein said auxiliary device is sized to produce said purified HCl gas at a rate of from about 2 to about 200 liters/hour.

29. A system according to claim 24, wherein parts (ii), (iii) and (iv) of the auxiliary device are arranged for continuous or semi-continuous flow.

30. A method of providing a high purity HCl reagent to a workstation in a manufacturing line for manufacturing high precision electronic components, the method comprising:

(a) withdrawing HCl gas from the vapor space above the liquid HCl in the HCl-containing reservoir;

(b) passing said HCl gas through a filtration membrane to remove particles greater than 0.005 micron therefrom;

(c) passing said HCl gas so filtered through a scrubber to contact said HCl gas with an aqueous solution of HCl in deionized water; and

(d) recovering said HCl gas from said scrubber and sending said HCl gas to said workstation.

31. The method of claim 30, further comprising dissolving said HCl gas from said scrubber in purified water prior to sending said HCl gas to said workstation.

32. The process according to claim 30, further comprising passing said HCl gas through a distillation column for further purification before passing said HCl gas to said workstation.

33. The method of claim 30, further comprising the step of: (b') passing the HCl gas from the scrubber through a distillation column for further purification and dissolving the HCl gas from the distillation column in pure water before sending the HCl gas to the workstation.

34. The method according to claim 30, wherein step (b) is carried out at a temperature in the range of about 10 to about 50 ℃.

35. The method according to claim 30, wherein step (b) is carried out at a temperature in the range of about 15 to about 35 ℃.

36. The method according to claim 33, wherein steps (b) and (b') are carried out at a temperature in the range of about 15 to about 35 ℃.

37. The method of claim 30, wherein step (b) is performed at a temperature in the range of about 15 to about 35 ℃ and at a pressure in the range of about atmospheric to about 30 lbs/inch above atmospheric²Under pressure of (c).

38. The method of claim 33, wherein steps (b) and (b') are performed at a temperature in the range of about 15 ℃ to about 35 ℃ and at a temperature in the range of about atmospheric to about 30 lbs/inch above atmospheric²Under pressure of (c).