System and method for dispensing liquid spin-on glass (SOG) onto semiconductor wafers

A device and method for dispensing liquid spin-on glass (SOG) onto semiconductor wafers. The method includes dispensing liquid SOG through a dispenser nozzle, detecting liquid SOG outside of the dispenser nozzle, indicating the presence of liquid SOG in an abnormal length relative to the dispenser nozzle and adjusting a suck back (SB) valve to withdraw liquid SOG from the abnormal length.

BACKGROUND

Spin on glass (SOG) has a number of practical applications and benefits in semiconductor device fabrication. For example, SOG is used as an inter-layer dielectric (ILD) capable of filling sub-micron gaps between metal interconnects on a semiconductor device and being planarized. SOG can also function as a passivation layer or a photoresist layer for lithographic circuitry definition. In semiconductor device fabrication, SOG is deposited in liquid drop form onto an upper surface of a semiconductor wafer, then the entire wafer is rotated to produce a relatively uniform coating. The SOG fills gaps in the semiconductor wafer, and once hardened (cured) with an appropriate application of heat, SOG enables planarization of the surface. Planarization may be by etch-back, chemical mechanical polishing (CMP), or other suitable methods. Cured SOG has similar insulating electrical properties to silicon dioxide, which is often replaced by SOG, although SOG provides a benefit of an even lower dielectric constant. Deposition of SOG replaces a process step that may have used physical vapor deposition (sputtering), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) or the like, to deposit silicon dioxide or other similar materials. However, uniformity of deposition of SOG has proven to be difficult, particularly when the SOG used is not a perfectly pure and uniform material.

DETAILED DESCRIPTION

The making and using of various embodiments are discussed in detail below. It should be appreciated; however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are examples of specific ways to make and use, and do not limit the scope of the disclosure.

FIG. 1Ais a side view of a liquid spin-on glass (SOG) dispenser system100. The SOG dispenser system100includes a SOG dispenser102with a dispenser nozzle104for dispensing liquid SOG106onto a semiconductor wafer108. The liquid SOG106includes a type of liquid SOG such as methylsiloxane, methylsilsesquioxane, phenylsiloxane, phenylsilsesquioxane, methylphenylsiloxane, methylphenylsilsesquioxane, silicate polymers, etc. The wafer108is supported by a rotatable platter110rotated by a physically coupled electric motor (as shown inFIG. 3). In this example, the liquid SOG106includes particles112. The particles112are undesirable impurities or SOG crystals in the liquid SOG that are initially dispensed in a random pattern but form a spiral pattern after spinning.

FIG. 1Bis a top view of the semiconductor wafer108fromFIG. 1Awith a deposited liquid SOG layer106after spinning. A spiral pattern of particles112is illustrated. A center portion of the wafer108contains fewer particles112due to their higher density, while away from the center portion some areas have high numbers of particles112in the spiral pattern due to clumping. SOG106and particles112are present but not shown in the unused fringe areas114of the wafer108.

FIG. 2Ais a side view of the liquid spin-on glass (SOG) dispenser system200. The SOG dispenser system200includes a SOG dispenser202with a dispenser nozzle204for dispensing liquid SOG206onto a semiconductor wafer208. The liquid SOG204includes a type of liquid SOG such as methylsiloxane, methylsilsesquioxane, phenylsiloxane, phenylsilsesquioxane, methylphenylsiloxane, methylphenylsilsesquioxane, silicate polymers, etc. The wafer208is supported by a rotatable platter210rotated by a physically coupled electric motor. In this example, the liquid SOG106includes SOG clumps216. The clumps216are undesirable additional amounts of SOG that are dispensed in a random pattern.

FIG. 2Bis a top view of the semiconductor wafer208fromFIG. 2Awith a deposited liquid SOG layer206after spinning. A bi-polar-resembling pattern of SOG clumps216is illustrated inFIG. 2B. A center portion of the wafer208contains fewer clumps216, while away from the center portion two areas in particular have high numbers of clumps216in the bi-polar-resembling pattern. SOG206and clumps216are not shown in the unused fringe areas214of the wafer208.

FIG. 3is a schematic block diagram of a SOG dispensing system300according to some embodiments. The SOG dispensing system300includes a SOG dispenser302with a dispenser nozzle304for dispensing liquid SOG306onto a semiconductor wafer308. Note that SOG306includes particles112from SOG106and/or clumps216from SOG206, as described herein. The wafer308is supported by a rotatable platter310rotated by a physically coupled electric motor318. In some embodiments, the SOG dispenser302is movable above a semiconductor wafer308for dispensing liquid SOG306through the SOG dispenser nozzle304.

The SOG dispenser302receives liquid SOG306from a SOG supply reservoir320. The SOG supply reservoir320contains enough liquid SOG306for SOG deposition onto multiple wafers308, in some embodiments. SOG306from the SOG supply reservoir320is received by a suck back valve (“SB valve”)322and carried from the SB valve322through a connecting pipe323to the SOG dispenser302. The SB valve322has a switch valve324and an adjustment valve326. The switch valve324corresponds to roughly the upper half of the SB valve322and the adjustment valve326corresponds to roughly the lower half of the SB valve322. In some embodiments, the switch valve324is not spring loaded. In some embodiments, the adjustment valve324is not spring loaded.

The switch valve324of the SB valve322is coupled to the SOG supply reservoir320and switches the SOG flowing through the SB valve322on, if the switch valve324is in an open position, or off, if the switch valve324is in an closed position. The flow of SOG306is digitally controlled by a digital suck back valve controller (digital SBV controller)328that enables a degree of control over the flow of SOG306in gradations between fully on and fully off. The digital SBV controller328controls the switch valve324of the SB valve322through a switch valve control signal330that is transmitted to an electromagnetic actuator in the switch valve324. Similarly, the digital SBV controller328controls the adjustment valve326of the SB valve322through an adjustment valve control signal332that is transmitted to an electromagnetic actuator in the adjustment valve326. Increasing an amount of pressure applied by the actuator in the switch valve324in response to the switch valve control signal330progressively closes the switch valve324, while decreasing the amount of pressure applied by the actuator in the switch valve324progressively opens the switch valve324. SOG passing through the switch valve324of the SB valve322moves past the adjustment valve326of the SB valve322.

In some embodiments, the adjustment valve326of the SB valve322is controlled by the digital SBV controller328to dispense SOG306or withdraw SOG306(“suck back”) from the SOG dispenser302. For example, increasing an amount of pressure applied by the actuator in the adjustment valve326of the SB valve322progressively closes the adjustment valve326, using positive pressure to force SOG306out of the adjustment valve326, while decreasing the amount of pressure progressively opens the adjustment valve326, using negative pressure to cohesively pull SOG306into the adjustment valve326. If the switch valve324is in a closed position and the adjustment valve326is being progressively opened by decreasing pressure applied to the adjustment valve326will withdraw or suck back SOG306from the SOG dispenser302through the connecting pipe323by cohesive forces in the SOG306, thereby preventing or improving the ability to prevent an excessive amount of SOG306from being deposited onto a wafer308, as can occur with unintentional dripping. Withdrawing SOG306that would have been deposited onto the wafer308reduces the amount of particles112and/or clumps216deposited onto the wafer, mitigating problems associated with particles and/or clumps in SOG.

The SOG dispenser302is equipped with an emitter/detector pair334, such as a laser/photodiode pair, to detect the position of the SOG306. The SOG306hanging from the SOG dispenser302takes either a normal SOG length336or an abnormal SOG length338in different circumstances. In the normal SOG length336, the SOG306is held within or nearly within the nozzle304of the SOG dispenser302through capillary forces or the action of the SB valve322, or both. In the abnormal SOG length338, SOG306is in an undesirable SOG position relative to the nozzle304, indicative of potential or actual unintentional dripping of SOG306on the wafer308. The normal SOG length336is interpreted herein as SOG306not being in an undesirable SOG position, for example, in some embodiments, the normal SOG length336is less than the maximum predetermined SOG length338and cannot equal or exceed 2 millimeters SOG hanging from the nozzle304if the nozzle is not actively dispensing SOG306on the wafer308. Note that the maximum predetermined SOG length338is determined based on a variety of factors including SOG306type, viscosity, temperature, pressure, nozzle304type, etc.

In some embodiments, unintentional dripping of SOG306causes an excessive SOG dispensing condition associated with the presence of particles112and/or clumps216in the SOG. SOG306in the abnormal length338will block light in the emitter/detector pair334thereby providing an electronic signal (or lack thereof) indicating the presence of SOG306in the abnormal length338, otherwise the electronic signal from the emitter/detector pair334will correspondingly indicate that the SOG306is in the normal length336. Note that signals indicating SOG306in the abnormal length338during intentional SOG dispensing are ignored. A signal controller340receives a signal from the emitter/detector pair334indicating the normal length336or the abnormal length338of the SOG306with respect to the nozzle304. In some embodiments the signal controller340moves the emitter/detector pair334in an up and down fashion to precisely determine the length of any SOG306hanging from the nozzle A signal analysis circuit342receives one or more signals from the signal controller340derived from the emitter/detector pair334and provides digital input to the digital SBV controller328. In some embodiments the emitter/detector pair334produces an analog signal or signals instead of a digital signal or signals. A fluid data calibration (FDC) sensor344provides a digital indication to the digital SBV controller328regarding the dispensing duration timing and volume of SOG306being dispensed onto the wafer308by the SOG dispensing system300. In some embodiments the fluid data calibration (FDC) sensor344produces an analog signal or signals instead of a digital signal or signals. A tool interlock circuit345provides set operating parameters for the SOG dispenser302to the signal analysis circuit342to determine if the SOG dispenser302is not operating within set operating parameters. For example, if the SOG dispenser302is not operating within set operating parameters, the tool interlock circuit345causes the digital SBV controller328to close the switch valve324of the SB valve322and transmit an alarm signal.

In some other embodiments, the emitter/detector pair334is physically moved up and down and/or optically moved up and down, relative to the nozzle304, with moving lenses, moving minors and/or moving standing acoustic waves, thereby scanning the SOG306, to provide a more precise indication of the length and the corresponding volume of SOG306outside the nozzle304. Note that the abnormal length338of the SOG306in these embodiments is a range of positions outside the nozzle304. For example, the presence of SOG306hanging 2 millimeters or more below the nozzle304is considered to be in the abnormal length338.

FIG. 4is a flowchart of a SOG dispensing method according to some embodiments. At operation446, liquid SOG306is dispensed through the dispenser nozzle304to begin the process of depositing a targeted amount of SOG onto the wafer308. In some embodiments, a drop of liquid SOG306is dispensed approximately every 4.5 seconds until 12-13 drops of SOG have been dispensed in approximately 55-60 seconds. In some embodiments, longer or shorter dispensing times and a greater or fewer number of SOG306drops are used depending on wafer size and specified thickness of SOG.

At operation448, liquid SOG306is detected outside of the dispenser nozzle304at a time when the SOG should not be there, i.e., when intentional dispensing is not occurring. In some embodiments, detection is via the emitter/detector pair334or other sensing apparatus. The undesirable presence of a drop of liquid SOG306is detected by SOG extending beyond the nozzle304opening and blocking light from the laser from reaching the photodiode in the emitter/detector pair334. In other embodiments, the emitter/detector pair334is not stationary, but rather moves up and down to scan the presence of liquid SOG306outside the dispenser nozzle304. In still other embodiments, other sensor apparatus detect liquid SOG306outside the dispenser nozzle304, such as detectors or emitter/detector pairs based on detection of changes in sound, ultraviolet light, infrared light, radar, other portions of the electromagnetic spectrum, magnetic fields, electrical fields, etc.

At operation450, the liquid SOG dispensing system300indicates the presence of liquid SOG306in an abnormal length338relative to the dispenser nozzle304. In some embodiments, the system300indicates the abnormal presence of SOG306if the SOG is present at or beyond a certain point relative to the nozzle, such as if the emitter/detector pair334is stationary. In other embodiments, the system300indicates the abnormal presence of SOG306including how great a length, e.g., 2 millimeters below the nozzle304, and/or volume of SOG306is present outside of the nozzle304, such as in those embodiments wherein the emitter/detector pair334is not stationary and moves in a up and down fashion to scan for the presence of SOG306outside of the nozzle304.

In operation452, the signal analysis circuit receives the indication of the presence of liquid SOG306in an abnormal length338relative to the dispenser nozzle304and determines whether the SOG dispensing system300is or is not operating outside set operating parameters. If the SOG dispensing system300is not operating outside set operating parameters, then in step454the digital SBV controller328adjusts the SB valve322to withdraw the liquid SOG306present in the abnormal length338back to a normal length336. If the SOG dispensing system300is operating outside set operating parameters, SOG dispensing is halted. In some embodiments, an alarm signal is transmitted and/or one or more signals from the FDC sensor344are stored in the digital SBV controller328, thereby enabling subsequent failure analysis and preventing or improving the ability to prevent further inappropriate SOG306dispensing and the corresponding potential loss of valuable semiconductor wafers308.

According to some embodiments, a method of depositing spin-on glass (SOG) onto a semiconductor wafer includes dispensing liquid SOG through a dispenser nozzle. The liquid SOG is detected outside of the dispenser nozzle. The presence of liquid SOG in an abnormal length relative to the dispenser nozzle is indicated. Then an SB valve is adjusted to withdraw liquid SOG from the abnormal length.

According to some embodiments, a method of depositing spin-on glass (SOG) onto a semiconductor wafer includes dispensing liquid SOG through a dispenser nozzle. The liquid SOG is detected outside of the dispenser nozzle with an emitter/detector pair that movably scans for the presence of SOG. The presence of liquid SOG in an abnormal length relative to the dispenser nozzle is indicated. Then an SB valve is adjusted to withdraw liquid SOG from the abnormal length.

According to some embodiments, a liquid spin-on glass (SOG) depositing system includes a suck back (SB) valve physically coupled to the SOG supply reservoir for receiving SOG, a SOG dispenser having a nozzle, the SOG dispenser physically coupled to the SB valve for receiving SOG, a sensor positioned to detect SOG outside the nozzle and a digital SB valve controller, the digital SB valve controller coupled to the sensor for receiving signals from the sensor and to the SB valve for controlling operation of the SB valve.

According to some embodiments, a method of manufacturing a semiconductor device includes dispensing liquid SOG through a dispenser nozzle. The liquid SOG is detected outside of the dispenser nozzle. The presence of liquid SOG in an abnormal length relative to the dispenser nozzle is indicated. Then an SB valve is adjusted to withdraw liquid SOG from the abnormal length.

The above method embodiment shows exemplary steps, but they are not necessarily required to be performed in the order shown. Steps may be added, replaced, changed order, and/or eliminated as appropriate, in accordance with the spirit and scope of embodiment of the disclosure. Embodiments that combine different claims and/or different embodiments are within the scope of the disclosure and will be apparent to those skilled in the art after reviewing this disclosure.