US20060207631A1 - Apparatus and method of cleaning a sustrate - Google Patents

Abstract

A cleaning apparatus is provided with a processing bath to be filled with a cleaning chemical, an ultrasonic oscillator, and a retainer for holding a substrate to be immersed into a cleaning chemical. The front surface of the substrate is cleaned while ultrasonic waves are radiated from the ultrasonic oscillator onto the back surface of the substrate.

Description

• This application is a Divisional Application of U.S. Ser. No. 11/078,728, filed on Mar. 14, 2005, which is in turn a Divisional Application of U.S. Ser. No. 10/050,161, filed on Jan. 18, 2002, which claims priority from Japanese Patent Applications 2001-016964, filed on Jan. 25, 2001. The entire contents of each of the aforementioned applications are incorporated herein by reference
FIELD OF THE INVENTION
• The present invention relates to a method and apparatus for cleaning a substrate, such as a semiconductor substrate.
BACKGROUND ART
• When an interconnection pattern is formed on a semiconductor substrate during the course of manufacture of a semiconductor device, a resist pattern is formed on a metal film; e.g., Al or Cu. The semiconductor substrate is subjected to plasma etching via the resist pattern, thus forming an interconnection pattern.
• In association with an increase in the packing density of a device, a sidewall protection film for protecting sidewalls of a pattern during plasma etching is formed thickly, thus improving a geometry into which the metal film is to be etched. In this case, an altered resist layer resulting from plasma etching of a pattern, such as an Al or Cu interconnection, tends to become more difficult to remove during a removal process subsequent to the plasma etching process.
• FIG. 7 is a conceptual drawing of a cross section of a pattern for describing the tendency. Aresist layer73 adhering to the side surfaces of analuminum interconnection pattern72 on asubstrate71 acts as a sidewall protection film. Concurrently, an alteredresist layer75 adheres also to the sidewalls of aresist pattern74.
• In order to eliminate the resist after etching, the alteredresist layer75 has hitherto been removed by means of a wet etching method. However, there still remain residues of the altered layer that cannot be removed by the solubility of the resist in a chemical.
• Alternatively, a single wafer processing cleaner has hitherto been employed.FIG. 8 is a conceptual drawing of an example of such a processing cleaner. In the cleaner, asubstrate82 to be cleaned is placed on top of arotary stage81, and chemicals are dropped from a chemical drop nozzle83 onto thesubstrate82. In the case of such a rotary method, structural limitations are imposed on introduction of ultrasonic cleaner for improving the removal.
• The present invention has been conceived to solve the drawbacks of the related-art cleaning technology as described above. To this end, there is adopted a dipping method of introducing a chemical into a processing bath. A substrate to be cleaned is immersed in the chemical and exposed to ultrasonic waves, thereby improving a cleaning effect and promoting removal of an altered resist layer adhering to the substrate.
SUMMARY OF THE INVENTION
• According to one aspect of the present invention, a substrate cleaning apparatus comprises: a processing bath to be filled with a cleaning chemical, an ultrasonic oscillator disposed in the processing bath and immersed in the cleaning chemical, and a retainer for retaining a substrate to be immersed in the cleaning chemical such that ultrasonic waves originating from the ultrasonic oscillator are radiated onto a back surface of the substrate.
• In another aspect, the ultrasonic oscillator has a plurality of oscillation sources disposed in a dispersed manner.
• In another aspect, the substrate cleaning apparatus further comprises a rotary mechanism for rotating the substrate retained by the retainer.
• In another aspect, the substrate cleaning apparatus further comprises propagation control apparatus for scattering or damping ultrasonic waves originating from the ultrasonic oscillator.
• In another aspect, in the substrate cleaning apparatus, the propagation control apparatus is constituted by means of placing, in a propagation path of ultrasonic waves, a plate-like member having a plurality of openings selectively formed therein.
• In another aspect, the propagation control apparatus includes jet nozzles for squirting a chemical in the propagation path of ultrasonic waves, thus circulating a flow of chemical.
• According to another aspect of the present invention, in a substrate cleaning method, a substrate whose surface has been processed is immersed in a cleaning chemical filled in a processing bath, and ultrasonic waves are radiated onto a back surface of the substrate, thereby cleaning a front surface of the substrate.
• Other and further objects, features and advantages of the invention will appear more fully from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a cross-sectional view schematically showing a configuration of a substrate cleaning apparatus according to a first embodiment of the present invention.
• FIG. 2 depicts a preferred example of the ultrasonic oscillator, showing an example layout in which the radiators are arranged on the surface of the ultrasonic oscillator.
• FIG. 3 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a second embodiment of the present invention.
• FIG. 4 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a third embodiment of the present invention.
• FIG. 5 is a plan view showing a preferred example of the shield plate adapted in the third embodiment.
• FIG. 6 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a fourth embodiment of the present invention.
• FIG. 7 is a conceptual drawing of a cross section of a pattern for describing an etching process.
• FIG. 8 is a conceptual drawing of an example of a conventional processing cleaner.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Embodiments of the present invention will be described hereinbelow by reference to the accompanying drawings. Throughout the drawings, like or corresponding elements are assigned identical reference numerals, and their repeated explanations are simplified or omitted.
First Embodiment
• FIG. 1 is a cross-sectional view schematically showing a configuration of a substrate cleaning apparatus according to a first embodiment of the present invention.
• In the cleaning apparatus shown inFIG. 1, a processing bath1 (or a chemical bath1) is filled with acleaning chemical2. Anultrasonic oscillator3 is disposed so as to be immersed in the cleaningchemical2 within theprocessing bath1. Preferably, theultrasonic oscillator3 is disposed in the vicinity of an interior bottom of theprocessing bath1. Aretainer5 for holding asubstrate4 to be cleaned is disposed, preferably, in the vicinity of an interior upper portion of theprocessing bath1 such that thesubstrate4 is immersed and held in thecleaning chemical2.
• Radiators31 (or oscillators31), which serve as radiation sources for emitting ultrasonic waves, are provided on the surface of theultrasonic oscillator3. The surface of each of theradiators31 is oriented toward thesubstrate4. Theradiators31 are dispersed at appropriate intervals on the surface of theultrasonic oscillator3. Theultrasonic oscillator3 is constituted by means of housing theultrasonic radiators31 into, e.g., a chemical-resistant box.
• FIG. 2 depicts a preferred example of theultrasonic oscillator3, showing an example layout in which theradiators31 are arranged on the surface of theultrasonic oscillator3. Each of theradiators31 has a diameter of, e.g., about 1.5 cm, and theradiators31 are affixed to asurface plate32 in a uniformly-dispersed manner at an interval of about 5 cm.
• Ultrasonic waves are emitted from theradiators31 by means of activation of theultrasonic oscillator3. The ultrasonic waves propagate through thechemical2 and are irradiated onto the back surface of thesubstrate4. As a result, removal of an altered resist layer adhering to the front surface of thesubstrate4 is promoted. For this reason, as shown inFIG. 2, a plurality ofradiators31 are preferably arranged at small intervals in a dispersed manner, thereby improving the consistency of radiated ultrasonic waves within a plane. On the contrary, if oneradiator31 or only a small number ofradiators31 would be provided, an undesirable difference will arise between one area of thesubstrate4 located immediately above theradiators31 and the other area surrounding the one area of thesubstrate4, in terms of intensity of ultrasonic waves radiated onto the back surface of thesubstrate4.
• As has been described above, in the present embodiment, theprocessing bath1 filled with a cleaning chemical is provided with theultrasonic oscillator3 and theretainer5 for holding thesubstrate4 to be immersed into the cleaningchemical2 for cleaning purpose. Ultrasonic waves originating from theultrasonic oscillator3 are radiated onto the back surface of thesubstrate4, thereby cleaning the front surface of thesubstrate4.
• Use of such a method promotes removal of an altered resist layer or resist residues adhering to the front surface of thesubstrate4; for example, an altered resist layer or resist residues resulting from plasma etching of a pattern, such as an Al pattern or a Cu pattern.
Second Embodiment
• FIG. 3 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a second embodiment of the present invention.
• In this embodiment, in addition to the structure of a cleaning apparatus shown inFIG. 1, the cleaning apparatus shown inFIG. 3 is further provided with arotary mechanism6 for rotating theretainer5 that holds thesubstrate4. For instance, therotary mechanism6 rotates theretainer5 at a constant speed in a circumferential direction while supporting theretainer5 from below. As a result, thesubstrate4 can be rotated in the circumferential direction while remaining within the chemical.
• As a result, the surface of thesubstrate4 is cleaned with the chemical, thereby improving a cleaning effect. Further, even if inconsistency exists in the intensity profile of ultrasonic waves radiated onto thesubstrate4, oscillation exerted within the plane of thesubstrate4 can be made consistent by means of rotating thesubstrate4. Thus, the effect of ultrasonic waves can be averaged, thereby improving a cleaning effect.
Third Embodiment
• FIG. 4 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a third embodiment of the present invention.
• In addition to the structure of the cleaning apparatus shown inFIG. 1, the cleaning apparatus shown inFIG. 4 is further provided with ashield plate7 disposed between theultrasonic oscillator3 and thesubstrate4 within theprocessing bath1; in short, in a path along which ultrasonic waves propagate. Theshield plate7 can scatter or attenuate ultrasonic waves. Specifically, theshield plate7 is an example of a propagation control member for controlling a propagation characteristic of ultrasonic waves. For example, a member of mesh structure is utilized as theshield plate7.
• As has already been mentioned, utilization of ultrasonic waves for cleaning thesubstrate4 promotes removal of an altered resist layer adhering to thesubstrate4. There may be a case where there is a necessity of controlling the intensity of ultrasonic waves so as not to impose damage (e.g., exfoliation or corrosion) to Al or Cu, which serves a material of the interconnection, formed on thesubstrate4. In this case, there is selected ashield plate7 having an appropriate shielding effect, and the thus-selectedshield plate7 is disposed, thereby controlling influence of ultrasonic waves.
• When the profile of consistency of ultrasonic waves radiated onto thesubstrate4 is not necessarily sufficient, a shield plate is interposed between theultrasonic oscillator3 and thesubstrate4, thereby optimizing the ultrasonic waves through scattering and attenuation.
• FIG. 5 is a plan view showing a preferred example of theshield plate7. Theshield plate7 is formed, by means of forming in a plate member71 a plurality ofslits72 of appropriate width at predetermined intervals. For instance, a stainless plate or another metal plate possessing chemical resistance can be utilized as theplate member71. Preferably, a material that does not absorb ultrasonic waves is used. The width of theslit72 is set to, e.g., 1 to 2 cm. Ultrasonic waves passing through theslits72 can be controlled by means of adjusting an area ratio of theslits72 to theshield plate7. Thus, the intensity of ultrasonic waves propagating through theshield plate7 can be controlled.
• As another example of theshield plate7,shield plates7 shown inFIG. 5 are stacked into a double layer, and the positions of theshield plates7 are displaced from each other through adjustment. As a result, the area ratio of theslits72 to the stackedshield plates7 can be variably adjusted.
• Theshield plate7 possesses chemical resistance, and is made of material which does not absorb ultrasonic waves. By means of variably changing the area ratio of theslits72 to the shield plate orplates7, required action of ultrasonic waves can be selected for eachsubstrate4.
Fourth Embodiment
• FIG. 6 is a cross-sectional view schematically showing a construction of a substrate cleaning apparatus according to a fourth embodiment of the present invention.
• In addition to the construction of the cleaning apparatus shown inFIG. 1, the cleaning apparatus shown inFIG. 6 is further provided withjet nozzles8 disposed between theultrasonic oscillator3 and thesubstrate4 beside a path along which ultrasonic waves propagate to thesubstrate4. Thejet nozzles8 squirt thechemical2 toward the propagation path of ultrasonic waves. A plurality ofjet nozzles8 are provided in the vicinity of an interior wall of theprocessing bath1. Thejet nozzles8 are one example of propagation control members for controlling the propagation characteristic of ultrasonic waves.
• Jet flows21 of thechemical2 are induced by thejet nozzles8, thereby stirring or agitating a chemical located in the propagation path of ultrasonic waves, to thereby adjust the flow of chemical within theprocessing bath1. As a result, linear radiation of ultrasonic waves is scattered, and the consistency of radiation of ultrasonic waves due to stirring effect can be improved. Further, the stirring effect can contribute to lessening of damage which arises on the surface of thesubstrate4.
• During manufacture of a semiconductor device, a substrate is cleaned through use of the substrate cleaning method or apparatus described in connection with the previous embodiments, thereby enabling manufacture of a semiconductor device. A cleaning process can be made efficient.
• In each of the embodiments, the present invention has been described by means of taking a semiconductor substrate or a semiconductor device as an example. However, the substrate is not limited to a semiconductor substrate; the present invention can be applied to a substrate of another electronic device in the same manner. Products to be manufactured finally are not limited to semiconductor devices and may be other electronic devices.
• The features and the advantages of the present invention may be summarized as follows.
• Under the substrate cleaning apparatus and method according to the present invention, a substrate is cleaned within a cleaning chemical while being exposed to ultrasonic waves, thus improving an effect of cleaning a substrate.
• Under the substrate apparatus and method according to the present invention, a substrate to be cleaned is cleaned while being rotated within a chemical, thus yielding an effect of rendering a cleaning effect uniform within a plane of the substrate.
• Under the substrate apparatus and method according to the present invention, the intensity of ultrasonic waves to be radiated onto a substrate to be cleaned is adjusted, or a distribution profile of ultrasonic waves is made uniform. As a result, a cleaning effect achieved within a plane of a substrate to be cleaned can be controlled, and the cleaning effects can be made uniform.
• Under the substrate apparatus and method according to the present invention, a substrate is cleaned while being subjected to radiation of ultrasonic waves with a cleaning chemical that is being stirred or agitated. Hence, the consistency of radiation of ultrasonic waves is improved, thereby controlling an effect of cleaning a substrate or rendering the cleansing effect uniform.
• It is further understood that the foregoing descriptions are preferred embodiments of the disclosed apparatus and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
• The entire disclosure of a Japanese Patent Application No. 2001-016964 filed on Jan. 25, 2001 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein by reference in its entirety.

Claims (3)

1. A substrate cleaning method, comprising:

immersing a substrate whose surface has been processed in a cleaning chemical disposed in a processing bath; and

radiating ultrasonic waves onto a back surface of the substrate, thereby cleaning a front surface of the substrate,

wherein the ultrasonic waves are radiated by way of a propagation control member for scattering or damping ultrasonic waves.

2. A substrate cleaning method, comprising:

immersing a substrate whose surface has been processed in a cleaning chemical disposed in a processing bath; and

radiating ultrasonic waves onto a back surface of the substrate, thereby cleaning a front surface of the substrate,

wherein cleaning is effected while the chemical through which ultrasonic waves propagate is stirred or agitated by a means other than the ultrasonic waves, wherein the stirring or agitation is provided between the substrate and an ultrasonic oscillator providing the ultrasonic waves.

3. The substrate cleaning method according toclaim 1, wherein the propagation control member comprises a plate member having a plurality of slits.

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