Spin-on film processing using acoustic radiation pressure

An apparatus and process operate to impose sonic pressure upon a spin-on film liquid mass that exhibits a liquid topography and in a solvent vapor overpressure to alter the liquid topography. Other apparatus and processes are disclosed.

BACKGROUND

During semiconductor device fabrication processes, spin-on films are formed upon semiconductive wafers. Film thickness and uniformity are process variables.

DETAILED DESCRIPTION

The embodiments of a device, an apparatus, or an article described herein can be manufactured, used, or shipped in a number of positions and orientations. Some will be shown below, and numerous others will be understood by those of ordinary skill in the art upon reading the following disclosure.

FIG. 1shows a top plan view of a plurality of acoustic radiation pressure (ARP) broadcast sources disposed in an array100according to an embodiment. The array100includes a mounting substrate110and a plurality of ARP broadcast sources, one of which is designated with numeral112. The array100may have a substantially circular form factor with a diameter that is large enough to approximate the size of a semiconductive wafer during wafer processing.

FIG. 2ashows a cross-section elevation200of a semiconductive wafer214during spin-on processing that uses acoustic radiation pressure on a spin-on mass216according to an embodiment. For illustrative purposes, a device and metallization layer215is depicted below a spin-on mass216. The spin-on mass216is depicted with an exaggerated irregular upper surface for illustrative purposes. The spin-on mass216tends to form depressions above depressions in the device and metallization layer215and it tends to from prominences above prominences in the device and metallization layer215. A measurement between the bottom of a depression and the top of an adjacent prominence is referred to as a step height.

A plurality of ARP broadcast sources are disposed in a first array201. The first array201includes a mounting substrate210and a plurality of ARP broadcast sources, one of which is designated with reference numeral212.

The semiconductive wafer214is disposed upon a spinner218. A second array202of ARP broadcast sources are disposed on a mounting substrate211, and one of the sources is designated with reference numeral213.

As depicted, the spin-on mass216on the semiconductive wafer214exhibits a spin-on film liquid topography. The liquid topography is shown with an arbitrary shape and size for illustrative purposes. The arbitrary shape and size is exhibited in the “head space” between the top of the spin-on mass216and the ARP broadcast sources212. Because of the small geometries of the thickness of the spin-on mass, the entirety of the spin-on mass216may be affected by boundary layer effects.

In an embodiment, the spin-on mass216is a glass material. In an embodiment, the spin-on mass216is a masking material. In an embodiment, the spin-on mass216is an interlayer dielectric material.

FIG. 2aalso depicts acoustic radiation pressure as emanating waves220and222being sourced from the respective arrays201and202. In a process embodiment, the spin-on mass216is dispensed onto the semiconductive wafer214while the spinner218is being rotated. Both the first array201and the second array202of acoustic radiation pressure broadcast sources212,213are active to alter the liquid topography of the spin-on mass216. In an embodiment, only one of the first array201or the second array202of ARP broadcast sources212,213is used to assist in altering the liquid topography of the spin-on mass216.

In an embodiment, the first array201is used to alter the liquid topography of the spin-on mass216, in addition to use of the spinner218. In an embodiment, the first array201provides ultrasonic acoustic radiation, defined as a frequency up to about 900 kHz. In an embodiment, the first array201emanates megasonic acoustic radiation, defined as a frequency above about 900 kHz, to about 2 MHz. Modulating of the ARP may include changing either of the frequency or of the amplitude thereof. Modulating of the ARP may include changing the uniformity of the ARP from a uniform pulse to an asymmetrical pulse.

In an embodiment, the first array201is spaced apart and above the spin-on mass216by a spacing distance224that is related to the diameter of a given ARP broadcast source212. In an embodiment, a 13-inch wafer214is processed with about 52 ARP broadcast sources that may be arranged similarly to the array100depicted inFIG. 1.FIG. 1depicts about 36 ARP broadcast sources212.

In an embodiment, the spin-on mass216is processed within a closed tool and the tool is flooded with solvent vapors that are indigenous to the spin-on mass216. Consequently, solvent within the spin-on mass216has a lowered driving force because of a lower solvent concentration gradient between the spin-on-mass and the environment. Consequently the solvent may be hindered in the process of escaping the spin-on mass216into the environment within the tool because of the overpressure placed on the solvent in the spin-on mass216.

FIG. 2bshows a cross-section elevation201of the semiconductive wafer214during spin-on processing after further processing according to an embodiment. The spin-on mass216has been flattened such that the step height has been virtually eliminated. In this disclosure the term “virtually eliminated” with respect to step height in the spin-on mass means no discernable difference in unevenness can be determined between a region of no topography on a wafer surface and a region of device and metallization layer215topography where device and metallization exhibits topography steps.

FIG. 3is a detail of a portion of an acoustic radiation pressure source during spin-on processing according to an embodiment. The detail is taken fromFIG. 2at the section3. In an embodiment, the mounting substrate210is moved in an oscillatory motion relative to the spin-on material (not shown).FIG. 3illustrates a lateral oscillatory motion in the X-Y plane. Each ARP broadcast source212is illustrated with a symmetry line228. A dashed circular motion line230illustrates oscillatory motion. In an embodiment, the oscillatory motion is eccentric oscillatory. In an embodiment, the symmetry line228of a given ARP broadcast source212moves with an oscillatory motion such that an oscillatory radius232is achieved. In an embodiment, the oscillatory radius234is less than one half the characteristic diameter, D, of the given ARP broadcast source212. In an embodiment, the oscillatory radius232is substantially equal to the characteristic diameter of the given ARP broadcast source212. In an embodiment, the oscillatory radius232is greater than one half the characteristic diameter of the given ARP broadcast source212.

In an embodiment, the oscillatory radius232is greater than one half the characteristic diameter of the given ARP broadcast source212and is large enough that the oscillatory motion of the ARP broadcast source212causes the symmetry line228of an ARP broadcast source212to intersect the dashed circular motion line226of a neighboring ARP broadcast source212. The degree of intersection therebetween may be quantified by the intersection dimension234. In an embodiment, the intersection dimension234is less than half the oscillatory radius228.

FIG. 4shows a top plan view of a plurality of ARP broadcast sources disposed in an array400according to an embodiment. The array400includes a mounting substrate410and a plurality of ARP broadcast sources, one of which is designated with numeral412. The array400may have a substantially circular form factor with a diameter that is large enough to approximate the size of a semiconductive wafer during wafer processing. As depicted, the array400has about 52 ARP broadcast sources412that are spaced apart upon the mounting substrate410.

Reference is made to eitherFIG. 1orFIG. 4. In a process embodiment, the array includes a plurality of ARP broadcast sources. During the formation of spin-on liquid, the plurality of ARP broadcast sources is activated in the ultrasonic range to alter the liquid topography of the spin-on liquid.

In an embodiment, the array100is activated such that the broadcast source enumerated with numeral1is first activated and remains activated, followed by the broadcast sources enumerated with numerals2, which surround the broadcast source enumerated with numeral1. Next, the broadcast sources enumerated with numerals3are activated and remain activated. Finally the broadcast sources enumerated with numeral4are activated such that all broadcast sources are activated. Consequently, a center-to-edge radial smoothing force is imposed upon the spin-on liquid under conditions to alter the topography of the spin-on liquid.

In an embodiment, the aforementioned center-to-edge radial smoothing force is imposed upon the spin-on liquid at a first ultrasonic frequency, followed by a second center-to-edge radial smoothing force at a second ultrasonic frequency that is different than the first ultrasonic frequency. In an embodiment, the first ultrasonic frequency is lower than the second ultrasonic frequency.

In an embodiment, the entire array100is activated substantially simultaneously. In an embodiment, the entire array100is activated substantially simultaneously, at a first ultrasonic frequency, followed by altering the first ultrasonic frequency to a second frequency that is different from the first frequency. In an embodiment, the first ultrasonic frequency is lower than the second ultrasonic frequency.

In an embodiment, the array is activated at a sub-sonic frequency. The center-to-edge radial smoothing force is then applied. In an embodiment, the array is activated at an ultrasonic frequency, and the center-to-edge radial smoothing force is then applied.

In an embodiment, the array400is activated such that the broadcast sources enumerated with numerals1are first activated, followed by the broadcast sources enumerated with numerals2, which surround the broadcast sources enumerated with numeral1. Next, the broadcast sources enumerated with numerals3are activated. Finally the broadcast sources enumerated with numeral4are activated. Consequently, a center-to-edge radial smoothing force is imposed upon the spin-on liquid under conditions to alter the topography of the spin-on liquid.

In an embodiment, the entire array400is activated substantially simultaneously. In an embodiment, the entire array400is activated substantially simultaneously, at a first ultrasonic frequency, followed by altering the first ultrasonic frequency to a second frequency that is different from the first frequency. In an embodiment, the first ultrasonic frequency is lower than the second ultrasonic frequency.

In an embodiment, the entire array400is activated at a sub-sonic frequency. The center-to-edge radial smoothing force is then applied. In an embodiment, the entire array400is activated at an ultrasonic frequency, and the center-to-edge radial smoothing force is then applied.

In can now be appreciated that other smoothing schemes may be used, such as a traverse smoothing process that begins at one region of an ARP broadcast source array. For example, some of the ARP broadcast sources on the right-hand side of the array400may be activated, and then activation may traverse the face of the array400in a right-to-left fashion, instead of a center to edge fashion, as described previously. The traverse smoothing process may be repeated with different frequencies. It can also be appreciated that all disclosed embodiments may be carried out at megasonic frequencies.

FIG. 5is a cross-section elevation of a spin-on mass applicator500that uses acoustic radiation pressure during dispensing according to an embodiment. The spin-on mass applicator500includes a transducer512that comprises an ARP broadcast source. A spin-on mass516forms as a droplet at the end of a syringe513that is affixed to the transducer512. The spin-on mass516depicts acoustic radiation pressure as waves520emanating from the transducer512source. As the spin-on mass516leaves the syringe513, it has been set into internal motion by virtue of acoustic waves generated by the transducer512.

In an embodiment, the spin-on mass applicator500may be positioned above a semiconductive wafer that is being spun. The spin-on mass applicator500induces internal mixing motion within the spin-on mass516that alters the final topography of the spin-on mass as it spins onto the semiconductive wafer.

In an embodiment, the spin-on mass applicator500may be positioned at approximately the center of a mounting substrate such as the mounting substrate110, the mounting substrate210, or the mounting substrate410. Accordingly, a space is made for the spin-on mass applicator500. In an embodiment, a substantially centrally located ARP broadcast source is removed to allow a penetrating location for the spin-on mass applicator500. In an embodiment, a plurality of spin-on mass applicators500may be positioned above the semiconductive wafer that is being processed.

In an embodiment, the spin-on mass applicator500and an array of ARP broadcast sources are used substantially simultaneously. Consequently, the spin-on mass516is first perturbed by the transducer512, and second perturbed by at least one ARP broadcast sources, such as at least one of ARP broadcast sources112,212,412mounted upon one of the mounting substrate110, the mounting substrate210, or the mounting substrate410.

In an embodiment, spin-on mass viscosity may be combined with spin rate and/or sonic frequency from the ARP broadcast source as variables. Further, saturation of a tool with a solvent that is soluble in the spin-on mass may be combined with spin rate and/or sonic frequency from the ARP broadcast source as variables.

FIG. 6is a process flow diagram according to an embodiment.

At block610, the process600includes forming a spin-on film liquid topography upon a semiconductive substrate. Forming the spin-on film liquid topography can be carried out in a tool, wherein the spin-on film comprises a spin-on solder paste, and wherein the imposing a solvent vapor at an overpressure includes flushing the tool with a solvent vapor prior to forming the spin-on film. Forming the spin-on film liquid topography can be carried out in a tool, wherein the spin-on film comprises a spin-on photoresist, and wherein the imposing a solvent vapor positive pressure includes flushing the tool with a solvent vapor prior to forming the spin-on film. The semiconductive substrate can be moved laterally and the source can be moved eccentrically.

At620, the process600includes imposing ultrasonic radiation pressure onto the spin-on film liquid topography under conditions to alter the liquid topography. Imposing sonic radiation pressure on the liquid topography can include broadcasting from the source while vertically oscillating the source relative to the liquid topography.

At630, the process600includes imposing the ultrasonic radiation pressure from at least one of above and below the spin-on film liquid. The directions “above” and “below” are given with respect toFIG. 3where the broadcast source212is above the spin-on film liquid that is in a gravity field, and the broadcast source213is below the spin-on film liquid that is also in the gravity field.

At640, the process600includes altering the frequency from a first frequency to a second frequency, wherein the second frequency is different from the first frequency.

It should be noted that the methods and processes described herein do not have to be executed in the order described, or in any particular order. Thus, various activities described with respect to the methods identified herein can be executed in repetitive, simultaneous, serial, or parallel fashion.

This Detailed Description refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments. Other embodiments may be used and structural, logical, and electrical changes may be made without departing from the scope of the present disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

The Detailed Description is, therefore, not to be taken in a limiting sense, and the scope of this disclosure is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

The terms “wafer” and “substrate” used in the description include any structure having an exposed surface with which to form an electronic device or device component such as a component of an integrated circuit (IC). The term substrate is understood to include semiconductor wafers. The term substrate is also used to refer to semiconductor structures during processing and may include other layers such as silicon-on-insulator (SOI), etc. that have been fabricated thereupon. Both wafer and substrate include doped and undoped semiconductors, epitaxial semiconductor layers supported by a base semiconductor or insulator, as well as other semiconductor structures well known to one skilled in the art.

The term “conductor” is understood to include semiconductors, and the term “insulator” or “dielectric” is defined to include any material that is less electrically conductive than the materials referred to as conductors.

The term “horizontal” as used in this application is defined as a plane parallel to the conventional plane or surface of a wafer or substrate, regardless of the orientation of the wafer or substrate. The term “vertical” refers to a direction perpendicular to the horizontal as defined above. Prepositions, such as “on,” “side” (as in “sidewall”), “higher,” “lower,” “over,” and “under” are defined with respect to the conventional plane or surface being on the top surface of the wafer or substrate, regardless of the orientation of the wafer or substrate.