US3627278A

US3627278A - Vibratory treatment apparatus

Info

Publication number: US3627278A
Application number: US527A
Authority: US
Inventors: Paul L Dee Syracuse; Richard L Edwards; Harold R Lee
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-01-05
Filing date: 1970-01-05
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

This invention relates to an ultrasonic vibratory treatment apparatus which is particularly useful in ultrasonically cleaning or etching semiconductor bodies comprising the following elements: an etchant-resistant receptacle having a plurality of retaining walls; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer having a vibrationtransferring portion and an anchoring portion between the receptacle and the transducer; and a heat-transfer element which is imbedded in the adhesive layer. The vibration-transferring portion is directly adhered to both the bottom surface of the transducer and one of the retaining walls. The anchoring portion surrounds the vibration-transferring portion and part of the transducer thereby securing the transducer to one of the walls of the receptacle. The receptacle, the transducer, the epoxyadhesive layer and the heat-transfer element are all correlated to produce a standing-wave system in a liquid having a known cavitation threshold in the receptacle responsive to a particular power input to the transducer.

Description

United States Patent 3,480,258 11/1969 Massa ABSTRACT: This invention relates to an ultrasonic vibratory treatment apparatus which is particularly useful in ultrasonically cleaning or etching semiconductor bodies comprising the following elements: an etchant-resistant receptacle having a plurality of retaining walls; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer having a vibration-transferring portion and an anchoring portion between the receptacle and the transducer; and a heattransfer element which is imbedded in the adhesive layer. The vibration-transferring portion is directly adhered to both the bottom surface of the transducer and one of the retaining walls. The anchoring portion surrounds the vibration-transferring portion and part of the transducer thereby securing the transducer to one of the walls of the receptacle. The receptacle, the transducer, the epoxy-adhesive layer and the heattransfer element are all correlated to produce a standing-wave system in a liquid having a known cavitation threshold in the receptacle responsive to a particular power input to the transducer.

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PAUL L. DEE, I 2 RICHARD L.EDWARDS,

Hmong. LEE, BYfiwL k THEI ATTORNE VlllBRATGlRY TREATMENT APPARATUS This invention relates to an ultrasonic vibratory treatment apparatus capable of producing a standing-wave system in a body of liquid contained therein and is particularly useful in the etching and cleaning operations used in the manufacturing of semiconductor devices.

in order to produce a standing-wave system (i.e., a continuous, periodically varying sinusoidal wave) in a body of liquid held in a receptacle, a number of factors must be considered including the cavitation threshold of the liquid, the frequency of the ultrasonic transducer, the input power to the transducer and the thickness of the receptacle directly below the area where the transducer is attached to the receptacle. When all the above factors are properly correlated, they produce a standing-wave system which in turn generates a cavitation cycle. Cavitation is defined as the continuous forming and collapsing of millions of tiny bubbles in a body of liquid while under the influence of a standing-wave system; the magnitude of the cavitation determines the speed of the cleaning action.

The ultrasonic transducer converts the predetermined electrical input received from a generator into vibratory mechanical or acoustic energy of sufficient intensity to induce cavitation and cleaning. Generally, the transducer is attached to the bottom of the receptacle to develop uniform cavitation fields along the entire bottom surface of the receptacle. To increase the distance the cavitation is effectively produced from this bottom surface, the power input is increased. In addition, the thickness of the bottom wall of the receptacle is matched with the frequency of the transducer to minimize any dampening effects, i.e., as the thickness of the bottom wall increases the dampening effect increases. This is because sound intensity diminishes in accordance with the universally applicable inverse square law.

To illustrate the effect of the above factors in a practical example let us consider the following situation. Ultrasonic energy propagating at about 1,400 meters per second through fresh deionized water at a frequency of 20 kilohertz has a wavelength of about 7 centimeters. If the vibratory surface of the 20-kilohertz transducer is attached to the bottom surface of a receptacle, it is possible to establish a standing-wave system in a vertical direction. The periodic energy travels up to the surface of the liquid and is reflected back down again to the bottom of the receptacle. A standing wave thus automatically establishes itself in water if the liquid level is an even multiple of the wavelength dimension away from the source, divided by two. Thus at levels of 3.5, 7, 10.5 centimeters and so on, a standing-wave system is established. If the level of the fresh water was lowered to l centimeter, it would be necessary to retune the generator by a sufficient amount-up to 28 kilohertz-to reestablish the standing wave.

The number of transducers needed to establish a standing wave in a given receptacle varies depending on desired results. To answer the question how many transducers and how much ultrasonic power is required, one must first examine the values of the cavitation threshold for various liquids. These vary from roughly 0.3 watt per square centimeter of transducer vibrating area for fresh water at frequencies up to about 10 kilohertz, to values 10 times higher for more viscous liquids and solvents. Above 10 kilohertz increasingly higher sonic threshold intensity are required. For example, roughly 10 watts per square centimeter is required for water at 200 kilohertz. The magnitude for each application depends on the degree of impurities encountered, desired cleaning time, equipment cost, and the sophistication of the equipment. Therefore, once sufficient sound intensity is generated in the liquid to overcome the cavitation threshold, cavitation will occur.

In the prior art of etching and cleaning semiconductor materials it has been very difficult to automate this process when metallic ultrasonic tanks are used because the etchants and solvents oftentimes attacked the metal tanks containing the etchant or solvent. To date the use of an ultrasonic tank made of a suitable chemical and etchant-resistant plastic which would eliminate this problem was thought to be impractical because no one had yet found a way to mount a vibratory transducer to this type of plastic material. Furthermore, it had been assumed that a plastic material would have a dampening effect on the transducers ability to change electrical to mechanical energy thereby making it an unsuitable material for forming ultrasonic tanks.

Accordingly, it is an object of this invention to provide an ultrasonic vibratory treatment apparatus which is particularly useful for agitation of a body of liquid to promote accelerated and enhanced action of the liquid, such as cleaning or etching action, on objects immersed therein.

It is another object of this invention to provide an ultrasonic vibratory treatment apparatus which will minimize any dampening effects during the conversion of electrical to mechanical energy while at the same time providing a standing-wave system.

It is still another object of this invention to provide an ultrasonic vibratory treatment apparatus which is suitable for use in a process system consisting of a plurality of units of such apparatus each being capable of modifications in structure wherein such modifications are primarily predetermined by the type of liquid solution contained in each apparatus and the use to which the solution will be put.

These and other objects of this invention will be apparent from the following description and the accompanying drawing, wherein:

FIG. 1 is a frontal view of a preferred embodiment of this invention.

FIG. 2 is an enlarged cross-sectional view of a portion of the apparatus shown in FIG. ll.

Briefly, this invention relates to an ultrasonic vibratory treatment apparatus which is capable of ultrasonically cleaning or etching semiconductor devices. The apparatus comprises an etchant-resistant receptacle, at least one vibrationgenerating transducer, a vibration-transferring epoxy-adhesive layer attaching the transducer to the receptacle and a heat-transfer member embedded in the epoxy adhesive layer. The above elements of the apparatus are all adapted so that in combination, they generate a standing-wave system in a liquid having a known cavitation threshold in the receptacle responsive to a particular power input to the transducer.

Referring to FIGS. 1 and 2 there is shown one preferred embodiment of our ultrasonic vibratory treatment apparatus ll. The apparatus ll includes a chemicaland etchant-resistant receptacle 2 for containing a body of liquid, having a bead 7 around its bottom surface, a plurality of retaining walls 3 and a top lip 5 having an opening 6 therethrough, one or more vibration-generating transducers 110, a heat-conductive epoxy layer llll interposed between the receptacle 2 and the transducers 10 not visible in FIG. l but shown in H0. 2 and a heat-transfer element 4 embedded in the epoxy layer llll. H6. 2 shows the vibration-transferring epoxy layer 1111 including a vibrationtransferring portion 19 which directly adheres to the bottom surface of the transducers l0 and the bottom wall of the receptacle 2, and an anchoring portion 18 which surrounds the vibration-transferring portion and a part of the transducers 10 thereby securing the transducers to the receptacle 2. Although FlGS. l and 2 show the vibratory apparatus l with the opening 6 of the receptacle 2 facing down in actual use the opening would be facing upward.

The receptacle 2 is made of a chemical and etchant-resistant material from the group consisting of polyvinyl chloride, polypropylene, polytetrafluoro ethylene and polyethylene. Preferably, polyvinyl chloride is used because of its ability to resist strong etchants and it is easily formed into any desired shape. lf the liquid held in the receptacle is not an etchant (i.e., will not attach metal), the receptacle may, in addition, be made of a suitable metal such as stainless steel, aluminum, nickel and the like. Typical liquids of this type would include deionized water, acetone and methanol alcohol. It is, of course, recognized that the shape of the receptacle 2 may be modified to include cylindrical shapes of the receptacle 2 may be modified to include cylindrical shapes, circular shapes and the like as long as they provide a surface to which the transducer 10 can be attached. Although the transducers are shown mounted to the bottom wall of the receptacle 2 in FIGS. 1 and 2, they may be, if desired, attached to one of the side retaining walls 3 without deviating from the essence of our invention. The purpose of the bead 7 is to facilitate the attachment of the transducers 10 to the receptacle 2 by defining with the bottom wall of the receptacle 2 a cavity. The bead 7 may be formed during or after the fabrication of the original receptacle. An alternate embodiment of this function would be to use a suitable removable mold. Another variable that must be considered in determining the design of the receptacle 2 is the thickness of the retaining wall 3 which is directly below the transducers l and shown in FIG. 2 as A." This thickness is varied depending on the material used for making the receptacle 2 and the frequency of the transducer in order to maximize the efficiency of apparatus 1 to produce a standing-wave system. For example, when the receptacle 2 is made of polyvinyl chloride it has been found that A should be in the range of one-sixteenth-three-eighth inches for transducer frequencies in the range of 25-40 kilocycles.

To assemble the structure shown in FIGS. 1 and 2 the receptacle 2 is placed upside down on a workbench. In this way, the bead 7 and the bottom retaining wall of the receptacle define a cavity. The desired number of transducers 10 to be attached to the receptacle 2 are then provided. This attachment is accomplished using a vibration-transferring epoxy-adhesive layer 11 which consists of a vibration-transferring portion 19 and an anchoring portion 18. A coating of vibration-transferring epoxy adhesive 19 is applied to the chemically clean bottom surface of the transducers l0. Concurrently, a sufficient amount of adhesive 19 is placed in the cavity to facilitate the attachment of the coated surface of the transducers 10 to the receptacle 2. The epoxy adhesive 19 comprises a thixotroping filler and a nondampening epoxy adhesive. The thixotroping filler is made of a filler from the group including talc, calcium carbonate, and colloidal silica. The nondampening epoxy ad hesive is made of a resin from the group consisting of diglycidyl ether of bisphenol-A, cycle-aliphatic, and novalac resins and a curing agent from the group consisting of aliphatic amine, aromatic amine, and acid anhydrides. Preferably, the epoxy adhesive 19 is made of a talc filler in combination with a diglycidyl ether of bisphenol-A resin and an aliphatic amine curing agent because this combination is curable at room temperature. Although layer 19 has sufficient adhesive strength to hold the transducers 10 to the bottom wall of the receptacle 2 by itself, it has an operational lifetime of about hours which in most applications is unacceptable. Therefore, to ensure an operational lifetime of over 1,000 hours, an anchoring portion 18 is used. In this embodiment, it is preferred that layer 19 should be restricted to the area directly below the cross-sectional area of the base surface of the transducers as shown in FIG. 2. In addition, the vibration-transferring portion 19 has a higher modulus of rigidity than the anchoring portion 18. The anchoring layer 18 is then poured into the cavity so as to surround the vibration-transferring portion 19 and a part of the transducers 10. The amount of the anchoring portion 18 used is determined by the requirements of the particular applications of the apparatus 1.

The anchoring portion 18 of the adhesive layer 11 is made of a heat-conductive filler and an epoxy adhesive. The heatconductive filler is made of a material from the group consisting of alumina, zirconium orthosilicate and boron nitride. The epoxy adhesive is made of a resin from the group consisting of diglycidyl ether or bisphenol-A, cycle-aliphatic, and novalac resins which has been previously mixed with a diluent from the group including butyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether and a cross-linking curing agent made from the group including polyamides and polyamines.

If it is desirable to contact additional heat away from the transducer-retaining wall interface, a heat-transfer member 4 may be embedded in the adhesive layer 11 as shown in FIGS. 1 and 2. In a preferred embodiment 4 has a plurality of spaced 0 vention may be carried out in various ways and may take various forms and embodiments other than the illustrative embodiments heretofore described. Accordingly, it is to be understood that the scope of the invention is not limited by the details of the foregoing description, but will be defined in the following claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A vibratory treatment apparatus comprising:

a chemical and etchant resistant receptacle for containing a body of liquid and having a plurality of retaining walls;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer interposed between one of said walls of said receptacle and said transducer thereby securing said transducer to said one of said walls;

and a heat-transfer member embedded in said vibrationtransferring epoxy layer.

2. A vibratory treatment apparatus as defined in claim 1 wherein said heat-transfer member having a plurality of spaced openings therethrough to allow said epoxy-adhesive layer to flow through and fill in said openings.

3. A vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body of liquid and having a plurality of retaining walls; at least one vibration-generating transducer;

said epoxy layer having a vibration-transferring portion and an anchoring portion;

said vibration-transferring portion being made of a thixotroping filler and a nondampening epoxy adhesive, and said anchoring portion being made of a heat-conductive filler and an epoxy adhesive;

said vibration-transferring portion being directly adhered to the bottom surface of said transducer and to one of said walls of said receptacle;

said anchoring portion surrounding both said vibrationtransferring portion and part of said transducer thereby securing said transducer to said one of said walls;

said vibration-transferring portion having a higher modulus of rigidity than said anchoring portion.

4. A vibratory treatment apparatus as defined in claim 3 wherein said first-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether of bisphenol-A, cylco-aliphatic, and novalac resins and a curing agent from the group consisting of aliphatic amine, aromatic amine, and acid anhydrides; said thixotroping filler is made of a filler from the group including talc, calcium carbonate and colloidal silica; said heat-conductive filler is made of a filler from the group consisting of alumina, silica, zirconium orthosilicate and boron nitride; said second-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether of bisphenol-A, cyclo-aliphatic, and novalac resins which has been previously mixed with a diluent from the group including butyl glycidyl ether, phenyl glycedyl ether, allyl glycidyl ether and a cross-linking curing agent made from the group including polyamides and polyamines.

5. An ultrasonic vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body of liquid and having sidewalls and a bottom wall and a bead formed around the outer edge of its bottom wall and defining with said bottom wall a cavity;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer between said receptacle and said transducer said epoxy-adhesive layer having a vibration-transferring portion and an anchoring portion, said vibration-transferring portion being directly adhered to the bottom surface of said transducer and to said bottom wall of said receptacle, said vibration-transferring portion having a higher modulus of rigidity than said anchoring portion and said anchoring portion surrounding both said vibration-transferring portion and part of said transducer thereby securing said transducer to said bottom wall;

heat-transfer member having a plurality of spaced openings therethrough and embedded in said epoxy-adhesive layer;

said receptacle and said transducer and said epoxy-adhesive layer and said heat-transfer member all being adapted so that a standing-wave system is produced in a liquid having a lcnown cavitation threshold in said receptacle responsive to a particular power input to said transducer.

6. An ultrasonic vibratory treatment apparatus as defined in claim wherein said receptacle is made of polyvinyl chloride, said vibration-transfer portion is made of thixotroping filler and a nondampening adhesive epoxy, and said anchoring portion is made of a heat-conductive filler and an epoxy adhesive.

7. An ultrasonic vibratory treatment apparatus as defined in claim 6 wherein said first-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether of bisphenol-A, cyclo-aliphatic, and novalac resins and a curing agent from the group consisting of aliphatic amine, aromatic amine, and acid anhydrides; said thixotroping filler is made of a filler from the group including talc, calcium carbonate and colloidal silica; said heat-conductive filler is made of a filler from the group consisting of alumina, silica, zirconium orthosilicate and boron nitride; and second-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether or bisphenol-A, cycl c-aliphatic, and novalac resins which has been previously mixed with a diluent from the group including butyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether and a cross-linking curing agent made from the group including polyamides and polyamines.

8. A vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body of liquid and having sidewalls and a nonmetallic, flexible bottom wall;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer interposed between the bottom wall of said receptacle and the entirety of said transducer and securing said transducer to said bottom wall;

and a body of anchoring adhesive material bonded to the receptacle and the transducer and extended around said vibration-transferring layer;

said vibration-transferring epoxy layer having a higher modulus of rigidity than said body of anchoring adhesive material.

Claims

1. A vibratory treatment apparatus comprising: a chemical and etchant resistant receptacle for containing a body of liquid and having a plurality of retaining walls; at least one vibration-generating transducer; a vibration-transferring epoXy-adhesive layer interposed between one of said walls of said receptacle and said transducer thereby securing said transducer to said one of said walls; and a heat-transfer member embedded in said vibrationtransferring epoxy layer.

3. A vibratory treatment apparatus comprising: a chemical- and etchant-resistant receptacle for containing a body of liquid and having a plurality of retaining walls; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer interposed between one of said walls of said receptacle and said transducer thereby securing said transducer to said one of said walls; said epoxy layer having a vibration-transferring portion and an anchoring portion; said vibration-transferring portion being made of a thixotroping filler and a nondampening epoxy adhesive, and said anchoring portion being made of a heat-conductive filler and an epoxy adhesive; said vibration-transferring portion being directly adhered to the bottom surface of said transducer and to one of said walls of said receptacle; said anchoring portion surrounding both said vibration-transferring portion and part of said transducer thereby securing said transducer to said one of said walls; said vibration-transferring portion having a higher modulus of rigidity than said anchoring portion.

5. An ultrasonic vibratory treatment apparatus comprising: a chemical- and etchant-resistant receptacle for containing a body of liquid and having sidewalls and a bottom wall and a bead formed around the outer edge of its bottom wall and defining with said bottom wall a cavity; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer between said receptacle and said transducer said epoxy-adhesive layer having a vibration-transferring portion and an anchoring portion, said vibration-transferring portion being directly adhered to the bottom surface of said transducer and to said bottom wall of said receptacle, said vibration-transferring portion having a higher modulus of rigidity than said anchoring portion and said anchoring portion surrounding both said vibration-transferring portion and part of said transducer thereby securing said transducer to said bottom wall; a heat-transfer member having a plurality of spaced openings therethrough and embedded in said epoxy-adhesive layer; said receptacle and said transducer and said epoxy-adhesive layer and said heat-transfer member all being adapted so that a standing-wave system is produced in a liquid having a known cavitation threshold in said receptacle responsive to a particular power input to said transducer.

6. An ultrasonic vibratory treatment apparatus as defined in claim 5 wherein said receptacle is made of polyvinyl chloride, said vibration-tRansfer portion is made of thixotroping filler and a nondampening adhesive epoxy, and said anchoring portion is made of a heat-conductive filler and an epoxy adhesive.

7. An ultrasonic vibratory treatment apparatus as defined in claim 6 wherein said first-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether of bisphenol-A, cyclo-aliphatic, and novalac resins and a curing agent from the group consisting of aliphatic amine, aromatic amine, and acid anhydrides; said thixotroping filler is made of a filler from the group including talc, calcium carbonate and colloidal silica; said heat-conductive filler is made of a filler from the group consisting of alumina, silica, zirconium orthosilicate and boron nitride; and second-mentioned epoxy adhesive is made of a resin from the group consisting of diglycidyl ether or bisphenol-A, cyclo-aliphatic, and novalac resins which has been previously mixed with a diluent from the group including butyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether and a cross-linking curing agent made from the group including polyamides and polyamines.

8. A vibratory treatment apparatus comprising: a chemical- and etchant-resistant receptacle for containing a body of liquid and having sidewalls and a nonmetallic, flexible bottom wall; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer interposed between the bottom wall of said receptacle and the entirety of said transducer and securing said transducer to said bottom wall; and a body of anchoring adhesive material bonded to the receptacle and the transducer and extended around said vibration-transferring layer; said vibration-transferring epoxy layer having a higher modulus of rigidity than said body of anchoring adhesive material.