CN220543254U - Device for spin coating - Google Patents

Abstract

An apparatus for spin coating. The device includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The inner wall surrounds the axis of rotation of the chuck. The chuck is adapted to rotate the wafer during a coating operation. The partition wall surrounds the inner wall. The dividing wall at least partially divides the interior of the device into a liquid chamber and a gas chamber. The outer wall surrounds the dividing wall. The device includes a divider cover coupled to the inner wall but not to the divider wall. The divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

Description

Device for spin coating

Technical Field

Embodiments presented in this disclosure relate to the field of semiconductor devices. More particularly, embodiments disclosed herein relate to techniques for spin coating during fabrication of semiconductor devices.

Background

Semiconductor devices are widely used in the control of electrical power, ranging from dimmer electric motor speed control to high voltage dc power transmission. For example, thyristors are used in alternating current (alternating current, AC) power control applications. The thyristor may operate as an electrical power switch in that the thyristor is characterized by being capable of switching rapidly from a non-conductive state to a conductive state. In operation, the thyristor is turned on, switching from a high impedance state to a low impedance state. This is achieved by applying a voltage between the gate and the cathode and allowing current to travel from the gate to the cathode.

Disclosure of Invention

One embodiment presented in the present disclosure provides an apparatus for spin coating. The device includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The apparatus also includes an inner wall that substantially surrounds the axis of rotation of the chuck (chuck). The chuck is adapted to hold and rotate a wafer during a coating operation wherein a coating material is dispensed onto the wafer. The device further includes a dividing wall that substantially surrounds the inner wall. The dividing wall at least partially divides the interior of the device into a liquid chamber and a gas chamber. The device further includes an outer wall substantially surrounding the dividing wall.

The device further includes a divider cover coupled to the inner wall but not to the divider wall. The divider cover substantially surrounds the axis of rotation of the chuck. The divider cover has a top surface and a bottom surface. The top surface is at least partially convex and the bottom surface is at least partially concave. The divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

Another embodiment provides a spin coater. The spin coater includes a chuck adapted to hold and rotate a wafer during a coating operation, wherein a coating material is dispensed onto the wafer. The spin coater also includes a motor adapted to rotate the chuck at a specified rotational speed during a coating operation. The spin coater also includes a dispenser adapted to dispense coating material onto the wafer during a coating operation. The dispenser is disposed above the chuck. The spin coater also includes a sump (catchbasin) having an outer cover and containing a separate cover. The separating cover is adapted to isolate the liquid and the gas from each other in the sump. The divider cover is at least partially concave-convex.

Drawings

Fig. 1 depicts an apparatus for spin coating in semiconductor fabrication according to one embodiment presented in this disclosure.

Fig. 2A-2B depict cross-sectional views of a semiconductor device on a wafer during different stages of a fabrication process according to one embodiment presented in the present disclosure.

Fig. 3A-3B depict cross-sectional views of a semiconductor device during a lithographic (photolithography) operation in a manufacturing process, according to one embodiment presented in the present disclosure.

Fig. 4 is a flow chart depicting a method of fabricating a semiconductor device according to one embodiment presented in the present disclosure.

FIG. 5 is a flow chart depicting a method for photolithography according to one embodiment presented in the present disclosure.

Fig. 6 is a flow chart depicting a method of applying a coating material to a wafer according to one embodiment presented in the present disclosure.

Detailed Description

Embodiments presented in the present disclosure provide techniques for spin coating using a device. Depending on the embodiment, the device itself may be a component of, or constitute, a spin coater. The device includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The apparatus includes an inner wall that substantially surrounds the axis of rotation of the chuck. The chuck is adapted to hold and rotate the wafer during a coating operation in which coating material is dispensed onto the wafer. The coating operation may be part of a process to form semiconductor devices, such as thyristors or diodes, on the wafer.

In one embodiment, the device includes a dividing wall that substantially surrounds the inner wall. The dividing wall at least partially divides the interior of the device into a liquid chamber and a gas chamber. The device further includes an outer wall substantially surrounding the dividing wall. The device further includes a divider cover coupled to the inner wall but not to the divider wall. The divider cover substantially surrounds the axis of rotation of the chuck.

The divider cover has a top surface and a bottom surface. The top surface is at least partially convex and the bottom surface is at least partially concave. The divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

In some embodiments, the thickness measure of the divider cover is reduced by increasing the concavity measure of the bottom surface of the divider cover. This increases the measure of relief of the divider cover while reducing the measure of plano-convexity of the divider cover. Depending on the embodiment, the convexity measure of the top surface of the partition cover is reduced or remains unchanged.

With reference to measures of the type described herein, such as relief-concentration (relief), plano-concentration (concavity), and the like, each such type of measure may represent the extent to which a divider cap or portion thereof approximates a reference volume or shape or portion thereof corresponding to the type of measure. Depending on the embodiment, the proximity may be determined based on the volume, cross-sectional area, or surface area of the divider cover and/or the reference volume or shape.

For a given type of measure, the reference volume or shape may have any arbitrary measure that is greater than the corresponding measure of the separating cover both before and after the thickness of the separating cover is reduced. Alternatively, for a given type of measure, the reference volume or shape may have any arbitrary measure that is smaller than the corresponding measure of the separating cover both before and after the thickness of the separating cover is reduced.

The reduced thickness of the separating cover enlarges the air passage between the liquid chamber and the gas chamber. This reduces the speed at which gas is allowed to flow from the liquid chamber to the gas chamber as it is pumped through the device via the pump during the coating operation. The reduced rate of allowing gas flow also reduces the rate at which excess coating material is allowed to flow in the liquid chamber. This in turn increases the rate of chemical interaction between the excess coating material and the solvent. The increased rate of chemical interaction reduces the rate of deposition of excess coating material within the device. Advantageously, the frequency with which the device needs to be cleaned and/or replaced is reduced. As a result, the measure of operational durability of the apparatus for spin coating is increased.

Although embodiments are described herein with reference to specific examples of semiconductor devices for the purpose of illustration and explanation, this is not intended to limit the scope of the disclosed embodiments. The specific example constitutes a thyristor, a known device based on four different semiconductor layers arranged in electrical series and typically formed in a monocrystalline substrate such as silicon. The thyristor comprises four layers of alternating polarity type (positive, P) or negative (N) material, wherein each layer is arranged between an anode and a cathode. Those skilled in the art will recognize that, more generally, other types of power switching devices and semiconductor devices may be fabricated using the techniques disclosed herein. For example, a diode such as a transient-voltage-suppression (TVS) diode may be fabricated.

Fig. 1 includes an exterior view 102, the exterior view 102 depicting an apparatus 101 for spin coating in semiconductor fabrication according to one embodiment. In some embodiments, and as depicted in the interior view 104, the apparatus 101 includes a sump 108 and a platform disposed at or substantially near a center of the sump 108.

Depending on the embodiment, some or all of the sump and/or device may be made of plastic and may constitute a replaceable component of the spin-coater. In addition, the spin coater may support one or more different types of film delivery methods such as arm drives and belt drives. Additionally or alternatively, the spin coater may support different types of control methods such as single chip microcomputer control and industrial computer control.

The platform is also referred to as a chuck 112 and is in view 110 ₁ Is shown in (a). The wafer 116 may be placed on the chuck 112 such that the bottom surface of the wafer 116 is substantially in contact with the face of the chuck 112. Vacuum may be applied to the bottom surface of the wafer 116 to secure the wafer 116 to the cardOn the disk 112, although the chuck 112 rotates during the spin-coating process.

In some embodiments, the diameter of the chuck 112 may be smaller than the diameter of the wafer 116. The chuck 112 is rotatable via a shaft 114 operatively connected to the chuck 112, and the shaft 114 is in turn rotatable by operation of an electric motor (not shown).

View 110 _2-4 A series of steps during spin coating is shown. At the from view 110 ₂ At a first step shown, a coating material 118 is applied over the wafer 116. More specifically, a specified amount of coating material 118 may be applied at or substantially near the center of the upper face of the wafer 116 via a dispenser (not shown). The specified amount of coating material 118 may be adjusted by controlling the flow rate through the dispenser, and the flow rate may be controlled via the pressure in the reservoir for coating material.

In at least some embodiments, the coating material 118 is a photoresist (photoresist) material, and the photoresist material is a liquid. The photoresist material may contain one or more components including resins that provide physical properties, sensitizers with photoactive compounds, and/or solvents that help maintain the liquid form of the photoresist material. The first step is also referred to as deposition.

In one embodiment, the coating material 118 may be applied to the wafer 1116 as a first step of a photolithographic process. The coating material 118 is coated so that the image can be developed on the substrate of the wafer 116. The coating material 118 may be applied while the wafer 116 is stationary or rotated by the chuck 112 at a relatively low speed.

At the from view 110 ₃ At the second step shown, the rotational speed of the chuck 112 is increased, causing the coating material 118 to spread from the center of the upper face of the wafer 116 toward the circumference of the wafer 116 via centrifugal force. This is done so that the upper side of the wafer 116 is substantially coated with a relatively thin layer of coating material 118. The relatively high rotational speed at the second step may promote thickness uniformity of the layer over the top of the wafer 116. The second step is also known as spin-up (spin-up).

At the from view 110 ₄ At the third step shown, the rotational speed of the chuck 112 is maintained substantially for a specified duration. The third step is also known as spin-off. During the second and/or third step, excess coating material is spun off the wafer. In some embodiments, the wafer is thereby spin-dried.

During the first, second, and/or third steps, some or all of the solvent component of the coating material 118 evaporates, causing the coating material to cure on top of the wafer 116. Certain parameters of spin coating may be adjusted in order to obtain a desired level of layer thickness. Examples of such parameters include, but are not limited to, the amount of coating material 118, the rotational speed of the chuck 112, and/or the specified duration.

Other steps are also widely contemplated. For example, in some embodiments, baking (baking) may be adapted to promote evaporation. Additionally or alternatively, the rinsing (ring) of the wafer may also be performed via a spraying (spray) operation using a solvent. The rinse may rinse off coating material deposited at or near a designated area of the wafer, such as the circumference of the wafer. In some embodiments, such a solvent is a separate solvent that is not confused with the solvent composition of the coating material 118.

In some embodiments, excess coating material spun off of the wafer 116 during spin coating is drained from the sump 108 via the liquid outlet 120 of the sump 108. However, at least some of the excess coating material may deposit on the inner surfaces of the sump, forming a solidified residue. The build-up of such deposits over time may begin to adversely affect subsequent use of the apparatus for spin coating. In some instances, the liquid outlet may be partially or completely blocked by such deposits. Further, attempts to clean such deposits from sump 108 and/or unblock the liquid outlet may prove difficult. In some instances, the sump 108 or device 101 or components thereof may even need to be replaced.

Thus, in one embodiment, and as shown in the interior view 104, the device has a base 124 of the sump 108, wherein the base 124 is coupled to each of the inner wall 126, the divider wall 128, and the outer wall 130. The inner wall 126 substantially surrounds the axis of rotation of the chuck 112. The dividing wall 128 substantially surrounds the inner wall 126. Furthermore, the dividing wall 128 at least partially divides the interior of the device into a liquid chamber 132 and a gas chamber 134. The outer wall 130 substantially surrounds the dividing wall 128.

The device also includes a divider cover 138. The divider cover 138 is coupled to the inner wall 126 but not to the divider wall 128. The divider cover 138 substantially surrounds the axis of rotation of the chuck 112. The divider cover 138 has a top surface and a bottom surface. According to some embodiments, the top surface is at least partially convex and the bottom surface is at least partially concave. The divider cover 138 is adapted to divert excess coating material to flow over the divider wall 128 and into the liquid chamber 132. The divider cover 138 and divider wall 128 are adapted to maintain the gas chamber 134 substantially free of excess coating material during a coating operation.

Factors that influence the measure of drainage efficiency in sump 108 include, but are not limited to, the shape of sump 108, the flow rate of the solvent, the spray time of the solvent, the volume of air drawn through apparatus 101, and a measure of the effectiveness of sump 108 in separating gas and liquid. Of these factors, all but the first and last factors are easily adjustable, at least in some embodiments.

In some embodiments, even a partial or a large portion of the optimal setting of the adjustable factor results in the gas outlet 122 being at least partially blocked by the build-up of residue within the sump 108 after about three thousand coating operations have been performed using the apparatus. Such blockage drastically reduces the rate of air flow through the device 101 and the gas outlet 122. In practice, the sump 108 and/or the apparatus 101 need to be replaced after only about two thousand five hundred coating operations have been performed.

Clogging is typically accompanied by a build-up of residue on both the base of the liquid chamber 132 and the base of the gas chamber 134, with a greater amount of residue typically being built up on the former. During a coating operation, excess coating material may be deposited on the bottom of the divider cover 138 and/or the top of the divider wall 128 as it is drawn near and/or through the airway between the bottom of the divider cover 138 and the top of the divider wall 128. As residues accumulate, the height of the divider wall 128 increases and the size of the airway also decreases. Eventually, the gas outlet 122 and/or the liquid outlet 120 is partially or mostly blocked by the residue.

As shown in the close-up view 106 relative to the interior view 104, the thickness measure of the divider cover 138 is reduced, represented in the form of a reduction amount 144. The scraping operation may be adapted to reduce the thickness measure. Doing so increases the rate of air flow through the device 101 by expanding the ventilation path through the device 101. In some embodiments, a portion of the bottom surface of the divider cover 138 is shaved, as described further below.

In at least some embodiments, the outer cover 136 has a diameter of about 288.5 millimeters and/or a perimeter of about 906.5 millimeters, and the divider cover 138 has a diameter of about 238 millimeters and/or a perimeter of about 747.5 millimeters. In addition, the device 101 has a height of about 111 millimeters, while the divider cover 138 has a height of about 54.5 millimeters. In at least such embodiments, prior to scraping, a portion of the bottom surface of the divider cover 138 (depending on the embodiment) is flat or substantially aligned in one or more dimensions with at least a portion of the outer surface of a sphere having a radius of about 120 millimeters. This portion is shown in close-up view 106 as bottom surface 140 prior to reducing the thickness of divider cover 138.

On the other hand, after scraping a portion of the bottom surface to reduce its width to about 3.56 millimeters, the portion is substantially aligned in one or more dimensions with at least a portion of the outer surface of a sphere having a radius now reduced to about 60 millimeters. In close-up view 106, this portion is shown as bottom surface 142 after the thickness of divider cover 138 is reduced. Other measurements and dimensions are widely contemplated without departing from the scope of the present disclosure.

In some embodiments, the thickness measure is reduced by increasing a concavity measure of at least a portion of the bottom surface of the divider cover. Doing so may increase the measure of relief of the divider cover 138 while decreasing the measure of plano-convexity of the divider cover 138. Depending on the embodiment, the measure of plano-convexity of at least a portion of the top surface of the divider cover 138 may be reduced or may remain unchanged.

As shown in the interior view 104, the reduced amount 144 of the thickness of at least a portion of the divider cover expands the air path 146 between the liquid chamber 132 and the gas chamber 134. Doing so reduces the rate at which gas flows from the liquid chamber 132 to the gas chamber 134 as gas is pumped through the apparatus 101 via the pump during a coating operation.

In some embodiments, the reduced velocity of the gas flow also reduces the velocity of the excess coating material flowing in the liquid chamber 132. This in turn increases the rate of chemical interaction between the excess coating material and the solvent. Depending on the embodiment, the solvent may be a solvent component of the excess coating material and/or a separate solvent. The separate solvent may be a developer solvent and/or a cleaning solvent.

Advantageously, the increased rate of chemical interaction has the effect of reducing the rate of deposition of excess coating material within the apparatus 101. The operational durability measure of the device is thereby increased. This increase may be due to a reduced frequency of cleaning and/or replacement of the device. In a particular embodiment, the excess coating material is unexposed photoresist and the solvent is xylene.

By using the techniques described herein, at least in some embodiments, at least four thousand coating operations may be performed without having to replace the sump 108 and/or the apparatus 101, as opposed to the sump 108 and/or the apparatus 101 having to be replaced after only about two thousand five hundred coating operations have been performed. This corresponds to a sixty percent improvement in the operational durability of device 101. For example, it has been observed in practice that residue build-up is still at an acceptable level even after three thousand coating operations have been performed with the apparatus described herein.

In some embodiments, and as shown in the interior view 104, the device 101 includes an outer cover 136 that is a cover of at least the liquid chamber 132. The outer cover 136 substantially surrounds the axis of rotation of the chuck 112. The outer cover 136 is disposed over the liquid chamber 132 and the partition wall 128. A divider cover 138 is at least partially disposed over the liquid chamber 132. On the other hand, the outer cover 136 is at least partially disposed over the gas chamber 134. In addition, the outer cover 136 is at least partially disposed over the divider cover 138.

According to one embodiment, the base 124 defines the liquid outlet 120 for the liquid chamber 132 and also defines the gas outlet 122 for the gas chamber 134. The outer cover 136 may define one or more inlets, and each inlet may be a liquid inlet and/or a gas inlet. In one embodiment, the gas outlet 122 is operatively connected to a pump (not shown). The pump is adapted to cause air to be drawn into the device 101 via the inlet and to be drawn out of the device 101 via the gas outlet 122. In a particular embodiment, the air is clean room air and is drawn into an exhaust system (not shown). Excess coating material and/or solvent is at least substantially discharged from the device 101 via the liquid outlet 120.

In some embodiments, the apparatus 101 further comprises a motor adapted to rotate the chuck at a specified rotational speed during the coating operation. Additionally or alternatively, the apparatus 101 includes a dispenser disposed above the chuck 112. The dispenser is adapted to dispense coating material onto the wafer 116 during a coating operation.

Fig. 2A-2B depict cross-sectional views of a semiconductor device on a wafer during different stages of a fabrication process, according to one embodiment. The cross-sectional view corresponds to a vertical cross-section of the wafer, i.e., a cross-section perpendicular to the wafer face.

As shown in fig. 2A, at a first stage 210 of the fabrication process, wafer 202 includes a substrate layer 212, wherein substrate layer 212 includes silicon. Both the top and bottom surfaces of the substrate layer 212 are doped using dopants 216 and a doping mask 214. As used herein, a top surface is also referred to as an upper or front surface, while a bottom surface is also referred to as a lower or rear surface. According to one embodiment, the doping mask 214 comprises an oxide.

At the substrate layer 212 is N ^- In the case of a substrate layer, the dopant 216 used is a P-dopant. An example of a P dopant is boron and an example of an N dopant is phosphorus. As used herein with reference to dopants, the symbols or absence of symbols in the superscript indicate relative doping concentrations, where The plus sign indicates a higher relative doping concentration, the minus sign indicates a lower relative doping concentration, and the no symbol indicates a medium relative doping concentration. Even if a symbol is not in the superscript, the symbol herein may be used interchangeably with the same symbol in the superscript. Multiple plus or minus signs in a row may be used to represent successively higher or lower relative doping concentrations.

According to one embodiment, the substrate layer 212 of the wafer 202 is doped with dopants 216, resulting in the wafer 202 in a second stage 220 of the fabrication process. As shown, the wafer 202 of the second stage 220 includes isolation structures 222, which isolation structures 222 laterally isolate the semiconductor devices from one another in the wafer. In the case of using P dopants, the isolation structure is a P isolation structure. Generally, the isolation structures 222 are formed once dopants 216 diffused from the top and bottom surfaces of the wafer 202 meet. In other words, to form isolation structures 222, each of the top and bottom surfaces of substrate layer 212 are doped with dopants 216 until dopants diffused from the top surface encounter dopants diffused from the bottom surface. The point at which the diffused dopants meet may be generally adjacent to the vertical center of the wafer 202 in terms of the thickness of the wafer 202.

In one embodiment, both the top and bottom surfaces of the substrate layer 212 of the wafer 202 may be further doped with dopants 216 to produce the wafer 202 at the third stage 230 of the fabrication process. As shown, the wafer 202 of the third stage 230 includes a lower base layer 232 and an upper base layer 234. In the case of using P dopants, the lower base layer 232 is a P lower base layer and the upper base layer 234 is a P upper base layer. The upper base layer 234 may then be doped with a different dopant. Doping the upper base layer 234 produces a top layer 236. At N ^- In the case of a substrate layer, this dopant is N ⁺ Dopant, and top layer 236 is N ⁺ And (5) a top layer.

In at least some embodiments, the top layer 236 is smaller in area than the upper base layer 234 from a plan view of the face of the wafer 202, exposing at least a portion of the upper base layer 234. Additionally or alternatively, the substrate layer 212 is greater in thickness than each of the lower base layer 232, the upper base layer 234, and the top layer 236, and the isolation structures 222.

After the top layer 236 is created, a deep trench (moat) 238 is formed for each semiconductor device in the wafer 202. Based on the plan view of wafer 202, deep trench 238 is characterized as being formed around upper base layer 234 of each semiconductor device. As such, based on a plan view of the wafer 202, the deep trench 238 surrounds the upper base layer 234. The deep trench 238 may be formed via an etching process, such as a silicon etching process.

Further, the deep trench 238 partially exposes each of the substrate layer 212, the upper base layer 234, the top layer 236, and the isolation structures 222. Furthermore, the substrate layer 212 is exposed only through the deep trench 238. On the other hand, in at least some embodiments, the deep trench 238 does not expose any of the lower base layer 232. Because the deep trench 238 has a cylindrical shape in the wafer 202, according to one embodiment, the deep trench 238 has a semicircular shape based on a cross-sectional view of the wafer 202. However, depending on the type of semiconductor device to be fabricated in wafer 202, upper base layer 234 need not necessarily be exposed by deep trench 238. In certain alternative embodiments, the upper base layer 234 is not exposed at all via the deep trench 238. The formation of deep trench 238 is further described below in conjunction with fig. 3A-3B.

After forming deep trench 238, a glass deposit (represented as glass 239) is formed atop one or more electroplated regions on the top surface of wafer 202. The one or more plated regions may include a respective one or more plated regions of each semiconductor device in wafer 202. In particular embodiments, the respective one or more plating regions include the deep trench 238 itself, as well as one or more additional ones of the regions surrounded by the deep trench 238 based on a planar view of the wafer 202. According to one embodiment, glass deposition forms a respective plating atop each of the plated areas, the respective plating comprising electrical glass.

As shown in fig. 2B, a cross-sectional view of wafer 202 during a fifth stage 250 of the fabrication process shows that the semiconductor devices in wafer 202 are thyristors 252. In an alternative embodiment, the semiconductor device is a TVS diode. According to one embodiment, the thyristor 252 has terminals including an anode 254, a cathode 256, and a gate 258. An anode 254 is formed on the lower base layer 232, a cathode 256 is formed on the top layer 236, and a gate 258 is formed on the upper base layer 234.

In one embodiment, each of the lower base layer 232 and the top layer 236 constitute a respective emitter layer (emitter layer) of the thyristor 252. The lower base layer 232 constitutes an emitter layer that may be the case for certain types of thyristors, such as silicon controlled rectifiers (silicon controlled rectifiers, SCRs). For some other types of thyristors, such as TRIACs, the lower base layer does not constitute any emitter layer.

In addition, the thyristor 252 has a P-N junction (P-Njunctions) including a first junction J1260, a second junction J2262, and a third junction J3264. A first junction J1260 is disposed between the lower base layer 232 and the substrate layer 212. A second junction J2262 is disposed between the substrate layer 212 and the upper base layer 234. A third junction J3264 is disposed between the upper base layer 234 and the top layer 236.

Although reference is made herein to N for the purpose of illustration and description ^- The substrate layer describes embodiments, but this is not intended to limit the scope of the disclosed embodiments. For example, by reversing the respective polarities of each of the dopants disclosed herein, the techniques disclosed herein are applicable to P ^- Alternative examples of substrate layers.

Fig. 3A-3B depict cross-sectional views of a semiconductor device on a wafer during different stages of a fabrication process, according to one embodiment. Each stage may correspond to a respective, same or different lithographic operation. In a particular embodiment, the stages of FIGS. 3A-3B correspond to a single lithographic operation to form the deep trench 238 of FIG. 2A. The lithographic operation is of the type that operates on silicon. In other embodiments, lithographic operations operating on metal are supported.

As shown in fig. 3A, a substrate layer 312 is provided at a first stage 310 of the fabrication process. The substrate layer 312 may correspond to any one or more elements of the wafer 202 of the third stage 230 of fig. 2A. In one embodiment, substrate layer 312 corresponds to the entirety of wafer 202 of fig. 2A, including upper base layer 234, substrate layer 212, and isolation structure 222. In this embodiment, the substrate layer 312 may be understood in terms of processing as corresponding to the substrate layer 212 from the first stage 210 but in the third stage 230 of fig. 2A.

In the first stage 310, silicon deposition is optionally performed on a substrate layer 312, which substrate layer 312 itself may comprise silicon. The deposition of silicon at the second stage 320 of the fabrication process results in a silicon layer 322 atop the substrate layer 312.

In the second stage 320, a photoresist coating is applied to the silicon layer 322. Alternatively, if no silicon deposition is performed, a photoresist coating is applied to the substrate layer 312. Applying a photoresist coating at the third stage 330 of the fabrication process results in a photoresist layer 332 over the silicon layer 322 and/or the substrate layer 312.

In the third stage 330, ultraviolet (UV) light 336 is applied to the photoresist layer 332 via pattern exposure using a photomask 334. In some embodiments, one or more alignment keys (alignment keys) on the wafer are used to align the photomask with the wafer. More specifically, the photomask may be aligned with the wafer by aligning a reticle (reticle) of an objective lens of the aligner with one or more alignment keys. Depending on the embodiment, the aligner may be a contact aligner, a proximity aligner, and/or a projection aligner. Application of UV light to photoresist layer 332 produces photoresist layer 332 with exposed areas 342 in a fourth stage 340 of the fabrication process.

In a fourth stage 340, a developer solvent 344 is applied to the photoresist layer 332 having exposed areas 342. To this end, the developer solvent 344 is of the positive photoresist type in order to remove the exposed areas 342. In an alternative embodiment, the developer solvent 344 may be a negative photoresist type to remove the unexposed areas of the photoresist layer 332, provided that a different photomask is used at the third stage 330 that constitutes the inversion of the photomask 334. Application of the developer solvent 344 to the photoresist layer 332 produces a photoresist layer 332 with the exposed areas removed at a fifth stage 350 of the fabrication process.

In a fifth stage 350, a chemical etch is performed on the silicon layer 322 based on the photoresist layer 332 having the exposed areas removed. Performing the chemical etch causes silicon layer 322 to be etched in a sixth stage 360 of the fabrication process.

In a sixth stage 360, photoresist removal is performed on the wafer. Performing photoresist removal results in etched silicon layer 322 with the photoresist layer removed in a seventh stage 370 of the fabrication process.

In a seventh stage 370, an insulator is added to the wafer. In some embodiments, the insulator may be silicon dioxide. Adding insulator to the wafer produces etched silicon layer 322 with insulator regions 382 at the eighth stage 380 of the fabrication process.

If any additional photolithographic layers remain to be processed, the eighth stage 380 reverts to the first stage 310 to repeat the stage for the next photolithographic layer to be processed. If no additional photolithographic layers remain to be processed, no processing is performed in the eighth stage 380 and processing may be considered to have been completed after the seventh stage 370. By performing various stages of the fabrication process according to fig. 3A-3B, deep trenches 238 are formed on the wafer 202 of fig. 2A.

Fig. 4 is a flow chart depicting a method 400 of fabricating a semiconductor device according to one embodiment. As shown, the method 400 begins at step 410, where a substrate layer of a wafer is provided. At step 420, isolation structures of the wafer are formed by doping a first portion of the substrate layer. At step 430, a lower base layer of the wafer is formed by doping a second portion of the substrate layer. At step 440, the upper base layer of the wafer is formed by doping the third portion of the substrate layer. At step 450, the top layer is formed by doping only a portion of the upper base layer.

At step 460, one or more photolithographic operations are used to form a respective deep trench around the upper base layer of each semiconductor device to be fabricated on the wafer. Step 460 is further described below in conjunction with fig. 5. At step 470, a respective electroplated glass deposit is formed atop each electroplated region of each semiconductor device. After step 470, the method 400 terminates.

FIG. 5 is a flow chart depicting a method 500 for photolithography, in accordance with one embodiment. As shown, the method 500 begins at step 510, where a wafer is provided for fabricating a semiconductor device. The wafer includes isolation structures that laterally isolate the semiconductor devices from one another in the wafer. At step 520, a lithographic operation is performed on the wafer. The lithographic operation includes applying a coating material to the wafer using a spin coater.

In one embodiment, the spin coater includes a sump. The sump has an outer cover and carries a dividing cover adapted to isolate liquid and gas in the individual chambers in the sump. The divider cover is at least partially concave-convex to reduce the deposition rate of excess coating material in the sump. This rate is reduced at least with respect to the divider cap which is less concave-convex and more plano-convex with respect to the aforementioned divider cap. Step 520 is further described below in conjunction with fig. 6. After step 520, the method 500 terminates.

Fig. 6 is a flow chart depicting a method 600 for applying a coating material to a wafer, in accordance with one embodiment. Method 600 corresponds to some or all of step 520 of fig. 5. As shown in fig. 6, the method 600 begins at step 610, where a deposition operation is performed by dispensing a coating material onto a wafer. The wafer is held by a chuck of a spin coater, and the spin coater includes a sump.

In one embodiment, the sump has an outer cover and contains a dividing cover adapted to isolate liquid and gas in the individual chambers in the sump. The divider cover is at least partially concave-convex to reduce the deposition rate of excess coating material in the sump. The deposition rate is reduced at least with respect to the second divider cap, which is less concave-convex and more plano-convex with respect to the (first) divider cap. At step 620, a spin-up operation is performed using the motor to increase the rotational speed of the chuck.

At step 630, a spin-off operation is performed by maintaining the rotational speed of the chuck for a specified duration to spin excess coating material from the wafer and evaporate solvent components of the coating material. Excess coating material is directed by the divider cover to flow into the liquid chamber of the sump. The excess coating material is substantially discharged from the liquid chamber via a liquid outlet for the liquid chamber. After step 630, the method 600 terminates.

Further embodiments are described below. One embodiment provides an apparatus for spin coating. The device includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The apparatus further includes an inner wall that substantially surrounds the axis of rotation of the chuck. The chuck is adapted to hold and rotate the wafer during a coating operation in which coating material is dispensed onto the wafer. The device further includes a dividing wall that substantially surrounds the inner wall. The dividing wall at least partially divides the interior of the device into a liquid chamber and a gas chamber. The device further includes an outer wall substantially surrounding the dividing wall.

The device further includes a divider cover coupled to the inner wall but not to the divider wall. The divider cover substantially surrounds the axis of rotation of the chuck. The divider cover has a top surface and a bottom surface. The top surface is at least partially convex and the bottom surface is at least partially concave. The divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

In some embodiments, the thickness measure of the separation lid is reduced by increasing the concavity measure of the bottom surface of the separation lid. This increases the measure of relief of the divider cover while reducing the measure of plano-convexity of the divider cover. The convexity measure of the top surface of the divider cover is reduced or maintained.

In certain embodiments, the reduced thickness of the divider cover enlarges the gas path between the liquid chamber and the gas chamber. This reduces the speed at which gas flows from the liquid chamber to the gas chamber as gas is pumped through the device via the pump during the coating operation. The reduced velocity of the gas flow also reduces the velocity of the excess coating material flowing in the liquid chamber. This in turn increases the rate of chemical interaction between the excess coating material and the solvent.

Advantageously, the deposition rate is thus reduced in terms of excess coating material within the device. The measure of the operational durability of the device is increased as the frequency with which the device needs to be cleaned or replaced is reduced. In some embodiments, the excess coating material is a polymer, wherein the polymer may be unexposed photoresist and the solvent may be xylene.

In some embodiments, the device further comprises an outer cover, the outer cover being a cover of the liquid chamber. The outer cover substantially surrounds the axis of rotation of the chuck. Further, an outer cover is provided above the liquid chamber and the partition wall. The divider cover is at least partially disposed over the liquid chamber. In another aspect, the cover is at least partially disposed over the gas chamber. Furthermore, the outer cover is at least partially arranged above the separating cover.

In certain embodiments, the base defines a liquid outlet for the liquid chamber and also defines a gas outlet for the gas chamber. The outer cover defines an inlet including a liquid inlet or a gas inlet. The gas outlet is operatively connected to a pump adapted to cause air to be drawn into the device via the inlet and to be drawn out of the device via the gas outlet. The air may be clean room air and the air may be drawn into the exhaust system. Each of the excess coating material and the solvent for the excess coating material may be at least substantially discharged from the device via the liquid outlet.

In some embodiments, the spin-coating apparatus is a sump, and the sump forms part of the spin-coater. The apparatus further includes one or more of a motor and a dispenser. The motor is adapted to rotate the chuck at a specified rotational speed during a coating operation. The dispenser is adapted to dispense coating material onto the wafer during a coating operation. The dispenser may be disposed above the chuck. The coating operation is part of the process used to form semiconductor devices on the wafer. The semiconductor device may comprise a thyristor or a diode. The diode may be a TVS diode.

Another embodiment provides a spin coater. The spin coater includes a chuck adapted to hold and rotate a wafer during a coating operation, wherein a coating material is dispensed onto the wafer. The spin coater also includes a motor adapted to rotate the chuck at a specified rotational speed during a coating operation. The spin coater also includes a dispenser adapted to dispense coating material onto the wafer during a coating operation. The spin coater also includes a sump having an outer cover and containing a divider cover. The separation cap is adapted to isolate the liquid and gas from each other in the sump. The divider cover is at least partially concave-convex.

In some embodiments, the divider cap is a first divider cap that is at least partially concave-convex to reduce the deposition rate of excess coating material in the sump. The velocity is reduced at least relative to an at least partially plano-convex second divider cap. The second divider cover is less concave-convex and more plano-convex than the first divider cover.

In certain embodiments, the sump includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The sump further includes an inner wall that substantially surrounds the axis of rotation of the chuck. The sump further includes a dividing wall that substantially surrounds the inner wall. The dividing wall at least partially divides the interior of the sump into a liquid chamber and a gas chamber. The sump further includes an outer wall substantially surrounding the dividing wall.

In some embodiments, the divider cover is coupled to the inner wall but not to the divider wall. The divider cover substantially surrounds the axis of rotation of the chuck. The partition cover may have a top surface and a bottom surface. The top surface is at least partially convex and the bottom surface is at least partially concave.

In some embodiments, the divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

Yet another embodiment provides a spin-on method. The method includes providing a wafer in which a plurality of semiconductor devices are to be fabricated. The wafer includes isolation structures that laterally isolate the semiconductor devices from one another in the wafer. The method also includes performing one or more lithographic operations on the wafer. One or more lithographic operations include applying a coating material to a wafer using a spin coater. The spin coater includes a sump having an outer cover and containing a divider cover. The sump is adapted to isolate the liquid and the gas from each other in the sump, and the separating cover is at least partially concave-convex.

In some embodiments, the divider cap is a first divider cap that is at least partially concave-convex to reduce the deposition rate of excess coating material in the sump. The velocity is reduced at least relative to an at least partially plano-convex second divider cap. The second divider cover is less concave-convex and more plano-convex than the first divider cover.

In certain embodiments, the sump includes a base coupled to each of the inner wall, the dividing wall, and the outer wall. The sump further includes an inner wall that substantially surrounds the axis of rotation of the chuck. The sump further includes a dividing wall that substantially surrounds the inner wall. The dividing wall at least partially divides the interior of the sump into a liquid chamber and a gas chamber. The sump further includes an outer wall substantially surrounding the dividing wall.

In some embodiments, the divider cover is coupled to the inner wall but not to the divider wall. The divider cover substantially surrounds the axis of rotation of the chuck. The partition cover may have a top surface and a bottom surface. The top surface is at least partially convex and the bottom surface is at least partially concave. The divider cover is adapted to divert excess coating material to flow past the divider wall and into the liquid chamber. The divider cover and divider wall are adapted to maintain the gas chamber substantially free of excess coating material during a coating operation.

Although the present embodiments have been disclosed with reference to certain embodiments, many modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claims. Accordingly, it is intended that the present embodiment not be limited to the described embodiment, but that it have the full scope defined by the language of the following claims and equivalents thereof.

Claims (11)

1. An apparatus for spin coating, the apparatus comprising:

a base coupled to each of the inner wall, the partition wall, and the outer wall;

an inner wall substantially surrounding an axis of rotation of a chuck adapted to hold and rotate a wafer during a coating operation in which coating material is dispensed onto the wafer;

A dividing wall substantially surrounding the inner wall, the dividing wall at least partially dividing the interior of the device into a liquid chamber and a gas chamber;

an outer wall substantially surrounding the partition wall; and

a divider cover coupled to the inner wall but not to the divider wall, the divider cover substantially surrounding the axis of rotation of the chuck, the divider cover having a top surface and a bottom surface, the top surface being at least partially convex and the bottom surface being at least partially concave, the divider cover being adapted to divert excess coating material to flow through the divider wall and into the liquid chamber, wherein the divider cover and the divider wall are adapted to maintain the gas chamber substantially free of the excess coating material during the coating operation.

2. The apparatus of claim 1, wherein the thickness measure of the divider cover is reduced by increasing the concavity measure of the bottom surface of the divider cover, thereby increasing the convexity measure of the divider cover while reducing the planoconvexity measure of the divider cover, wherein the convexity measure of the top surface of the divider cover is reduced or remains unchanged.

3. The apparatus of claim 2, wherein the reduced thickness measure of the divider cover enlarges an air path between the liquid chamber and the gas chamber, thereby reducing a speed at which gas is allowed to flow from the liquid chamber to the gas chamber as the gas is pumped through the apparatus via a pump during the coating operation.

4. A device according to claim 3, wherein the reduced speed at which the gas is allowed to flow also reduces the speed at which the excess coating material is allowed to flow in the liquid chamber, which in turn increases the rate of chemical interaction between the excess coating material and solvent, which in turn reduces the rate of deposition of the excess coating material within the device, thereby increasing the operational durability measure of the device, and wherein the operational durability measure is increased by reducing the frequency with which the device needs to be cleaned or replaced.

5. The apparatus of claim 4, wherein the excess coating material comprises a polymer comprising unexposed photoresist, and wherein the solvent comprises xylene.

6. The apparatus as recited in claim 4, further comprising:

an outer cover comprising a cover of the liquid chamber, the outer cover substantially surrounding an axis of rotation of the chuck, the outer cover being disposed over the liquid chamber and the dividing wall.

7. The apparatus of claim 6, wherein the divider cap is at least partially disposed above the liquid chamber, wherein the outer cap is at least partially disposed above the gas chamber, and wherein the outer cap is at least partially disposed above the divider cap.

8. The device of claim 6, wherein the base defines a liquid outlet for the liquid chamber and further defines a gas outlet for the gas chamber, wherein the outer cover defines an inlet comprising a liquid inlet or a gas inlet;

wherein the gas outlet is operatively connected to a pump adapted to cause air to be drawn into the apparatus via the inlet and drawn out of the apparatus via the gas outlet, the air comprising clean room air, wherein the air is drawn into an exhaust system;

wherein each of the excess coating material and solvent therefor is at least substantially discharged from the device via the liquid outlet.

9. The apparatus of claim 1, wherein the spin coating apparatus comprises a sump that forms part of a spin coater.

10. The apparatus as recited in claim 1, further comprising:

a motor adapted to rotate the chuck at a specified rotational speed during the coating operation; and

a dispenser adapted to dispense the coating material onto the wafer during the coating operation, the dispenser being disposed above the chuck.

11. The apparatus of claim 1, wherein the coating operation is part of a process to form a plurality of semiconductor devices on the wafer, the plurality of semiconductor devices comprising thyristors or diodes comprising Transient Voltage Suppression (TVS) diodes.