Method and system of coating polymer solution on surface of a substrate

A method and system of coating a polymer solution on a substrate such as a semiconductor wafer. The method includes providing a substrate. Dispensing a polymer solution onto the surface of the substrate using a pump. The pump is connected in-line with a buffer tank and a polymer solution source such that the pump draws the polymer solution from the polymer solution source and the buffer tank in a continuous fluid path to dispense the polymer solution. The polymer solution source is connected to a pressure source capable of causing a transfer of the polymer solution from the polymer solution source into the buffer tank. The buffer tank to maintain a relatively constant level of polymer solution.

BACKGROUND

Aspects of this disclosure pertain to a method and system of coating a polymer solution such as a photoresist polymer solution over a surface of a substrate such as silicon substrate.

2. Discussion of Related Art

The manufacture of integrated circuits involves the transfer of geometric shapes on a mask to the surface of a semiconductor wafer. Thereafter the semiconductor wafer corresponding to the geometric shapes or corresponding to the areas between the geometric shapes is etched away. The transfer of the shapes from the mask to the semiconductor wafer typically involves a lithographic process. This includes applying a photosensitive pre-polymer solution to the semiconductor wafer. The solvent in the pre-polymer solution is removed by evaporation, and the resulting polymer film is then baked. The film is exposed to radiation, for example ultraviolet light, through a photomask supporting the desired geometric patterns. The images in the photosensitive material are then developed by soaking the wafer in a developing solution. The exposed or unexposed areas are removed in the developing process, depending on the nature of the photosensitive material. Thereafter the wafer is placed in an etching solution which etches away the areas not protected by the photosensitive material. Due to their resistance to the etching process, the photosensitive materials are also known as photoresists. These may for instance be sensitive to ultraviolet light, electron beams, x-rays, or ion beams.

Systems and methods have been developed for the dispensing the photoresist solutions on a substrate. Typically, the system includes a pump connected to a reservoir containing a photoresist solution. The reservoir may be filled with the photoresist solution from a photoresist solution source. A vacuum source can typically be used to transfer the photoresist solution from the source into the reservoir. One problem with the current systems and methods is the non-uniformity in the photoresist film of photoresist coated on the substrate. For instance, when the photoresist solution source is low and required changing, micro bubbles and air may get into the system causing non-uniformity in the photoresist film. Additionally, when the vacuum is used to transfer the photoresist solution, splattering tends to occur in the reservoir causing the viscosity of the polymer solution to change or increase over time and inhibiting the leveling of the resulting film. This produces thickness non-uniformities in the photoresist film.

The high cost of the photoresist solutions (or other polymer solutions) makes it desirable to devise methods of improving the efficiency of the coating process so as to minimize the polymer solution's consumption. Furthermore, thickness uniformity of the photoresist layer is an important criterion in the manufacture of integrated circuits. It ensures satisfactory reproduction of the geometric patterns on the semiconductor wafer.

The features of the described embodiments are specifically set forth in the appended claims. The embodiments are best understood by referring to the following description and accompanying drawings, in which similar parts are identified by like reference numerals.

SUMMARY

In one aspect of the invention, an embodiment includes a method of coating a surface of a substrate with a polymer solution in which a substrate is provided. A polymer solution is dispensed onto the surface of the substrate using a coating system having a pump connected in-line with a buffer tank and a polymer solution source such that the pump draws the polymer solution from the polymer solution source and the buffer tank in a continuous fluid path to dispense the polymer solution. The polymer solution source is connected to a pressure source capable of causing a transfer of the polymer solution from the polymer solution source into the buffer tank. The buffer tank to maintain a relatively constant level of polymer solution to prevent the pump from drawing air to dispense on the surface of the substrate. The buffer tank to maintain a relatively constant level of polymer solution in that the buffer tank is filled to a predetermined level and when the pump draws the polymer solution, it draws the polymer solution in a continuous fluid path from the polymer solution source. Thus, the polymer solution in the buffer tank is maintained at a relatively constant level.

In another aspect of the invention, an embodiment includes a polymer solution coating system. The polymer solution coating system comprises a substrate station to support a substrate. The substrate station may be rotatable. A pump to dispense a polymer solution over a surface of the substrate is included. A buffer tank and a polymer solution source connected in-line with the pump wherein the buffer tank is connected between the polymer solution source and the pump. The pump is configured to channel or draw the polymer solution from the polymer solution source and the buffer tank in a continuous fluid path. The buffer tank to maintain a relatively constant level of polymer solution to prevent the pump from drawing air to dispense on the surface of the substrate. A momentary valve is coupled to the polymer solution. The momentary valve to allow a controlled supply of pressure of gas into the polymer solution source to fill the buffer tank upon demand. The momentary valve also can be used to prevent the supply of gas to be continuously supplied into the polymer solution source in the event that the operator forgets to move the gas source. As pressure is applied to the polymer solution source, some polymer solution is transferred to fill the buffer tank to a predetermined level.

In another aspect of the invention, an embodiment includes a method of coating a polymer solution over a surface of a substrate. The method comprises securing a substrate on a rotable substrate station. A polymer solution is dispensed onto the surface of the substrate using a coating system having a pump connected in-line with a buffer tank and a polymer solution source. The pump draws the polymer solution from the polymer solution source and the buffer tank in a continuous fluid path to dispense the polymer solution on the surface of the substrate. The polymer solution level in the buffer tank is maintained at a constant level to prevent the pump from drawing air to dispensed over substrate. The substrate is spun or rotated while the polymer solution is being dispensed over the surface.

DETAILED DESCRIPTION

Exemplary embodiments are described with reference to specific configurations and techniques. Those of ordinary skill in the art will appreciate the various changes and modifications to be made while remaining within the scope of the appended claims. Additionally, well known elements, pumps, sensors, tubes, process steps and the like are not set forth in detail. The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention.

The embodiments of the present invention direct to methods and systems of coating a surface of a substrate such as a semiconductor wafer with a polymer solution such as a photoresist solution. In addition, the embodiments pertain to methods and systems of improving the thickness uniformity of coatings formed when depositing polymer solutions on substrates and reducing the wastage of such solutions. In particular, the methods and systems will be described with more reference to semiconductor wafers used in the manufacture of integrated circuits and the application of photoresist pre-polymer solutions to a surface of a semiconductor wafer. It will be appreciated that films or coatings used in integrated circuit manufacture are not limited to photoresist layers and could, for example, include materials such as organic planarization films, anti-reflection films, siloxane spin-on-glass films, polyimide films, and polimide siloxane films.

In one embodiment, a polymer solution such as a photoresist solution has a solute content ranging from about 10% to about 50% by weight. In one embodiment, the photoresist solution is a deep-ultraviolet photoresist polymer.

FIG. 1illustrates a polymer solution coating system100that can be used to coat a polymer layer such as a photoresist on a substrate such as a semiconductor wafer120. In one embodiment, the polymer solution coating system100includes pump102, an enable valve104, a buffer tank106, a polymer solution source108, a pressure source110, and a momentary valve112. The pump102, the polymer solution source108, and the buffer tank106are connected in-line such that when the pump102channels or draws the polymer solution, it draws the solution in a continuous fluid path from the polymer solution source108through the buffer tank106to dispense the polymer solution onto the surface of the wafer120. In one embodiment, a dispensing line114from the pump102is provided to dispense the polymer solution over the wafer102. The dispensing line114may include a dispensing head (not shown) as is known in the art to distribute the polymer solution over the wafer120. A fluid line130(e.g., tubing) connects the polymer solution source108to the buffer tank106. A fluid line128(e.g., tubing) connects the buffer tank106to the pump102. The fluid line130is always open to allow a continuous fluid path from the polymer solution source108to the pump102. The fluid line130and128, and the dispensing line114are in communication with each other.

Still withFIG. 1, the polymer solution source108stores the polymer solution (e.g., a photoresist solution) to be coated over the wafer120. The buffer tank106also stores the polymer solution to be coated over the wafer120. The buffer tank106acts as a buffer zone for the polymer solution to ensure that the pump102will always channel or draw in the polymer solution and not air, for example as when the polymer solution source108is low or substantially empty. In one embodiment, the buffer tank106is configured to have a volume ranging between 0–500 cc. Other suitable volume is possible. Low or substantially empty refers to a level in the polymer solution source108that will cause the pump102to draw in air due to insufficient liquid level in the polymer solution source108. The buffer tank106provides a uniform flow of the polymer solution since without the buffer tank106, replacing the polymer solution source when it is low or substantially empty would disrupt the flow and cause contamination and/or non-uniformity in the coated film on the wafer120. For example, when the polymer solution source108is low or substantially empty, the buffer tank106allows for more time for the replacement of the polymer solution source108. The buffer tank106provides a constant flow for the polymer solution. The buffer tank106also maintains a relatively constant level of polymer solution predetermined to be sufficient to prevent the pump102from having to draw air into the dispensing line114. Because fluid is channeled or drawn from the polymer source108through the buffer tank106in a continuous fluid path, the polymer solution level in the buffer tank106remains relatively constant. In addition, without the buffer tank106, the wafer120needs to be pre-treated or pre-wet with a polymer solution. The presence of the buffer tank106eliminates the need to pre-treat the wafer120. Thus, less polymer solution is needed to coat the wafer120allowing for cost cutting especially when the polymer solution is a photoresist solution.

Still withFIG. 1, in one embodiment, a fluid sensor118is installed into a vent line122that leads out from the buffer tank106. The fluid sensor118detects the fluid level within the buffer tank106and/or the vent line122to provide an indication of bubbles or micro bubbles that may be present in the buffer tank106. The fluid sensor118is configured to be in communication with a release valve124such that when bubbles or micro bubbles are detected in the buffer tank106, the release valve124is open to allow for the elimination of the bubbles. The bubble or micro bubble elimination process is often desired when a new polymer solution source108is installed or when the polymer solution needs to be out-gassed. The release valve124may be a manual release valve that requires an operator to open to release the bubbles. Alternatively, the release valve124may be configured to be automatically triggered to be opened when bubbles are detected or configured to be opened upon demand the as a result of the fluid sensor118sensing the presence of the bubbles.

Still withFIG. 1, the enable valve104is connected between the buffer tank106and the pump102. The enable valve104is placed in a fluid line128that acts as a conduit for the polymer solution between the buffer tank106and the pump102. The enable valve104may be incorporated into an outlet leading out from the buffer tank106. When the enable valve104is opened, the pump102is able to draw the polymer solution in a continuous fluid path from the buffer tank106and the polymer solution source108to dispense polymer solution on the wafer120. In addition, the enable valve104is configured to be able to shut off when the coating system100indicates that the polymer solution source108is low or substantially empty. The enable valve104may be configured to automatically shut off in the event the system100indicates that the polymer solution source108is low or substantially empty. Substantially low indicates that the polymer solution in the polymer solution source108is so low that air may be drawn into the lines if the pump102is allowed to continue to draw from the polymer solution source108.

Still withFIG. 1, in one embodiment, a fluid sensor126is connected to the polymer solution source108. The fluid sensor126is configured to detect the fluid level in the polymer solution source108. The fluid sensor126is also configured to convey the detection to a controller (not shown) to cause the enable valve104to shut down to prevent the pump102from drawing the polymer solution.

In one embodiment, the system100includes a temperature control116in communication with the dispensing line114. The temperature control116allows for the monitoring of the dispensing temperature of the polymer solution. In one embodiment, the polymer solution is dispensed at a temperature between about 10° C. and 30° C.

In one embodiment, the system100includes a dispensing valve132placed in line with the pump102. In one embodiment, the dispensing valve132is configured to control the dispensing rate of the polymer solution onto the wafer120. The dispensing valve132may cooperate with the pump102to control the dispensing rate of the polymer solution. The dispensing valve132may also be configured to shut off the dispensing of the polymer solution. In addition, the dispensing valve132may also be configured to have a suck-back function such that when the dispensing process is complete or otherwise halted, the polymer solution may be sucked back within the dispensing line114to prevent excess or undesirable drip on the wafer120.

Still withFIG. 1, the pressure source110is provided to apply a small amount of pressure into the polymer solution source108to the transfer of the polymer solution to the buffer tank106. In one embodiment, an inert gas such as nitrogen (N2) is flown into the polymer solution source108to create a small pressure (e.g., about less than 10 psi) within the polymer solution source108which in turn causes the polymer solution to be pushed or transferred to the buffer tank106. In one embodiment, the inert gas (e.g., N2) is flown at a rate of about 1–5 sccm. The flow of the inert gas into the polymer solution source108to bring about the transfer of the polymer solution may create micro bubbles in the buffer tank106. The bubbles may be vented through the release valve124as previously described.

As shown inFIG. 1, the momentary valve112is placed between the pressure source110and the polymer solution source108. The momentary valve112functions to prevent excess inert gas to be flown into the polymer solution source108. For example, an operator may turn on a valve to apply pressure into the polymer solution source108and inadvertently neglect to turn off the valve after the transfer is complete. Continuous flow of the inert gas into the polymer solution source108may cause micro bubbles to be generated which then can travel into the buffer tank106and cause contamination and non-uniformity in the solution. In one embodiment, the momentary valve112is a manually operated valve that requires the operator to manually press down on the valve112to allow the flow of the inert gas into the polymer solution source108. In one embodiment, the operator presses down on the valve112for a few seconds (e.g., 5 seconds) to generate sufficient pressure in the polymer solution source108to transfer the polymer solution into the buffer tank106. In another embodiment, the momentary valve112is configured so that it will turn on only for a predetermined amount of time (e.g., about 5 seconds) so that no excess inert gas is flown into the polymer solution source108.

Applying pressure to transfer the polymer solution into the buffer tank106prevents non-uniform concentration of the polymer solution in the buffer tank106. For instances when a vacuum source (not shown) is used to cause the transfer of the polymer solution into the buffer tank106, too high of a vacuum level may cause splashing of the polymer solution onto the wall of the buffer tank. Dried solution may later on cause a change in the solution concentration.

In one embodiment, a controller (e.g., a processor or microprocessor operated on a computer) (not shown) is included in the coating system10to control the operation of the components of the system100. For example, the controller may control the flow of the polymer solution, the functions of the pump102, the dispensing valve132, the enable valve102, and the momentary valve112. The controller may also control the shut down of the valve104when the sensor126indicates that the level in the polymer solution source108is insufficient for drawing or channeling polymer solution. The controller may also control the momentary valve112, e.g., to keep the momentary valve112open for a predetermined amount of time (e.g., 1–7 seconds) to allow a flow of inert gas into the polymer solution source108to transfer the polymer solution into the buffer bank106. The controller may also control the venting of the buffer tank106, the temperature of the dispensing line114, the dispensing valve132, and the like of the coating system100. The controller may be housed in a computer or similar machine. The controller may also be ran by a set of instructions programmed to carry out the coating and/or operation of the coating system100.

In one embodiment, the polymer solution coating system100is modified for coating multiple wafers. As shown inFIG. 2, a polymer solution coating system200is configured to accommodate for the coating of multiple wafers. In one embodiment, only the polymer solution source108is provided. The polymer solution coating system200is similar to the polymer solution coating system100in all aspects except that the pump102is configured to draw the polymer solution for the coating of two wafers, wafer120and wafer140. As illustrated in this figure, the pump102is connected to two dispensing valves132and133, which dispense the polymer solution into the dispensing lines114and115, respectively. The dispensing line114dispenses the polymer solution to coat the surface of the wafer120as previously discussed, and the dispensing line115dispenses the polymer solution to coat the surface of the wafer140in similar fashion. The temperature control116monitors the dispensing temperature for the dispensing line114and temperature control117monitors the dispensing temperature for the dispensing line115.

In one embodiment, the polymer solution coating system100is modified for coating multiple wafers using multiple pumps. As shown inFIG. 3, a polymer solution coating system300is configured to accommodate for the coating of multiple wafers using one polymer solution source108and multiple pumps (pumps102and103). In one embodiment, each pump is used to control the dispensing for one wafer. The polymer solution coating system300is similar to the polymer solution coating system100in all aspects except that in addition to the pump102, a pump103is included to accommodate for the coating of a wafer140using a separate pump. This configuration differs from the coating system200in that each of the dispensing lines114and115can dispense the polymer solution at a different rate and different time. Thus, the coating system300allows for more freedom in coating multiple wafers. The coating system300includes all the components of the coating system100and in addition, the coating system300includes the pump103connected to a dispensing valve133, which dispenses the polymer solution into the dispensing line and115. The dispensing line115dispenses the polymer solution to coat the surface of the wafer140. The temperature control117monitors the dispensing temperature for the dispensing line115.

In one embodiment, another polymer solution source is provided for the coating system. Providing the additional polymer solution source provides a back up polymer solution source for the coating system. As illustrated inFIG. 4, a polymer solution coating system400is provided with a polymer solution source109. The polymer solution coating system400is similar to the polymer solution coating system100in all aspects except for the addition of the additional polymer solution source109. The polymer solution source109includes all the associated components similar to the polymer solution source108previously described. An additional buffer tank107is provided for the polymer solution source109. Similar to the polymer solution coating system100, the polymer solution source109, the buffer tank107and the pump102are connected in-line. In addition to the ability to draw the polymer solution from the polymer solution source108in a continuous fluid path as previously described, the pump102can also draw the polymer solution from the polymer solution source109in a continuous fluid path.

In one embodiment, a pressure source111is provided to apply a small amount of pressure into the polymer solution source109to the transfer of the polymer solution to the buffer tank107. In one embodiment, an inert gas such as nitrogen (N2) is flown into the polymer solution source109to create a small pressure (e.g., about less than 10 psi) within the polymer solution source109which in turn causes the polymer solution to be pushed or transferred to the buffer tank107. A momentary valve113is a manual control valve placed between the pressure source111and the polymer solution source109. The momentary valve113functions to prevent excess inert gas to be flown into the polymer solution source109. Continuous flow of the inert gas into the polymer solution source109may cause micro bubbles to be generated which then can travel into the buffer tank107and cause contamination and non-uniformity in the solution. In one embodiment, the momentary valve113is a manually operated valve that requires the operator to manually press down on the valve113to allow the flow of the inert gas into the polymer solution source109. In one embodiment, the operator presses down on the valve113for a few seconds (e.g., 5 seconds) to generate sufficient pressure in the polymer solution source109to transfer the polymer solution into the buffer tank107. In another embodiment, the momentary valve113is configured so that it can be programmed to turn on for only a predetermined amount of time (e.g., about 5 seconds) so that no excess inert gas is flown into the polymer solution source109.

Similar to the polymer solution coating system100, the polymer solution coating system400includes a fluid sensor127for sensing the fluid level in the polymer solution source. The fluid sensor127can cause an enable valve105to close to prevent the pump102from drawing the polymer solution from the polymer solution source109when the polymer solution source109is empty or substantially low. In addition, the polymer solution coating system400also includes a release valve125, which is opened to eliminate the bubbles or micro bubbles that are formed or present in the buffer tank107. The release valve125is activated when the sensor119detects bubbles in the buffer tank107.

In one embodiment, the enable valves104and105are automatic switching valves that will automatically switch off when their associated senor senses a substantially low or empty level of polymer solution in its associated polymer solution source. The sensor126and127are used to sense and indicate the polymer solution level in the polymer solution source108and109. Thus, for example, when the sensor126detects that the polymer solution in the polymer solution source108is substantially low or empty, it will cause the enable valve104to shut off and cause the direction of the pump102to switch to another polymer solution source such as a polymer solution source109. Thus, when the polymer solution source108is substantially low or empty, the pump102draws from the polymer solution source109. The system400minimizes the down time in the coating process as well as ensures that contamination (such as by micro bubbles) is minimized.

In one embodiment, the polymer solution coating system400is modified for coating multiple wafers using multiple pumps. As shown inFIG. 5, a polymer solution coating system500is configured to allow for coating multiple wafers using multiple polymer solution sources (e.g., the polymer solution source108and the polymer solution source109) and multiple pumps (e.g., pumps102and103). In one embodiment, each pump is used to control the dispensing for one wafer. This configuration differs from the coating system400in that each of the dispensing lines114and115can dispense the polymer solution at a different rate and different time. Thus, the coating system500allows for more freedom in coating multiple wafers.

The pump102is connected in-line with the buffer tank106and the polymer solution source108such that a continuous fluid path is drawn from the polymer solution source108by the pump102through the buffer tank106to dispense the polymer solution on the wafer120as in previous embodiments. The pump103is connected in-line with the buffer tank107and the polymer solution source109such that a continuous fluid path is drawn from the polymer solution source109by the pump103through the buffer tank107to dispense the polymer solution on the wafer140. The pump103dispenses the polymer solution onto the wafer140through the dispensing line115. The polymer solution coating system400is similar to the polymer solution coating system100in all aspect except that in addition to the pump102, a pump103is included to allow for the dispensing of the polymer solution for a wafer140. In addition, the pump103is connected to a dispensing valve133, which dispenses the polymer solution into the dispensing line and115. The dispensing line115dispenses the polymer solution to coat the surface of the wafer140. The temperature control117monitors the dispensing temperature for the dispensing line115.

In one embodiment, the polymer solution coating system400is modified for coating multiple wafers using only one pump102. As shown inFIG. 6, a polymer solution coating system600is configured to allow for coating multiple wafers using one polymer solution source108. The polymer solution coating system600is similar to the polymer solution coating system400in all aspects except that the pump102is configured to draw the polymer solution for the coating of two wafers, wafer120and wafer140. As illustrated in this figure, the pump102is connected to two dispensing valves132and133, which dispense the polymer solution into the dispensing line114and115, respectively. The dispensing line114dispenses the polymer solution to coat the surface of the wafer120and the dispensing line115dispenses the polymer solution to coat the surface of the wafer140. The temperature control116monitors the dispensing temperature for the dispensing line114and temperature control117monitors the dispensing temperature for the dispensing line115.

As with any of the modified embodiments, a controller can be included with the coating system for controlling the operation of the coating system as previously discussed.

FIG. 7illustrates an exemplary embodiment of a method700of coating a polymer layer such as a photoresist layer on a surface substrate using one of the exemplary coating systems previous described. At box702, a substrate is provided. In one embodiment, the substrate is a semiconductor wafer used in the manufacture of integrated circuits. The substrate may have patterns and structures formed thereon as is known in the art.

At box704, a polymer solution is dispensed over a surface of the substrate. In one embodiment, the polymer solution is a photoresist solution used in the manufacture of integrated circuits. In other embodiments, the polymer solution includes solutions used to form organic planarization films, anti-reflection films, siloxane spin-on-glass films polyimide films, polimide siloxane films, and other films typically used in the manufacture of integrated circuits.

The polymer solution is dispensed using one of the exemplary embodiments of the coating system of the present invention (e.g., coating system100,200,300,400,500, or600). The coating system includes a pump connected in-line with a buffer tank and a polymer solution source as previously discussed. There is a continuous fluid path from the polymer solution source through the buffer tank and the pump. Thus, when the pump is drawing the polymer solution source to dispense it over the substrate surface, the polymer solution flows from the polymer solution source to the pump in a continuous path.

In one embodiment, the substrate is placed in a housing or a chamber, which allows the atmosphere in the chamber to be at least partially saturated with solvent molecules. This may improve the cast film wetability by establishing a monolayer of coating solvent on the surfaces of the substrate. In addition, thickness uniformity may be improved with a controlled coating environment.

In one embodiment, a spin-cast method is used for the coating of the polymer solution on the substrate. Thus, after the polymer solution is dispensed, the substrate is spun or rotated to spread the solution over the surface of the substrate. The substrate may be placed on a rotable chuck that has a suitable rotating velocity commonly used for spin-cast coating. After the solution has spread over the substrate surface, the solvent is evaporated to leave a layer of solute on the surface of the substrate. In the embodiment where the polymer solution is a photoresist solution, after the evaporation, a photoresist layer is formed over the substrate surface.

In another embodiment, a spray-coat method is used for the coating of the polymer solution on the substrate. The polymer solution may be dispensed onto the substrate surface using a shower head configured to dispense the polymer solution over the substrate surface.

FIG. 8illustrates another exemplary embodiment of a method800of coating a polymer layer such as a photoresist layer on a surface substrate using one of the exemplary coating systems previous described. At box802, a substrate is provided. In one embodiment, the substrate is a semiconductor wafer used in the manufacture of integrated circuits. The substrate may have patterned and structures formed thereon as is known in the art.

At box804, a polymer solution is dispensed over a surface of the substrate. In one embodiment, the polymer solution is a photoresist solution used in the manufacture of integrated circuits. In other embodiments, the polymer solution includes solutions used to form organic planarization films, anti-reflection films, siloxane spin-on-glass films polyimide films, polimide siloxane films, and other films typically used in the manufacture of integrated circuits.

The polymer solution is dispensed using one of the exemplary embodiments of the coating system of the present invention (e.g., coating system100,200,300,400,500, or600). The coating system includes a pump connected in-line with a buffer tank and a polymer solution source as previously discussed. There is a continuous fluid path from the polymer solution source through the buffer tank and the pump. Thus, when the pump is drawing the polymer solution source to dispense it over the substrate surface, the polymer solution flows from the polymer solution source to the pump in a continuous path.

In one embodiment, the substrate is placed in a housing or a chamber, which allows the atmosphere in the chamber to be at least partially saturated with solvent molecules. This may improve the cast film wetability by establishing a monolayer of coating solvent on the surfaces of the substrate. In addition, thickness uniformity may be improved with a controlled coating environment.

At box806, the substrate is spun or rotated to spread the solution over the surface of the substrate. The substrate may be rotated after the polymer solution is dispensed or simultaneously with the solution being dispensed over the substrate. The substrate may be placed on a rotable chuck that has a suitable rotating velocity commonly used for spin-cast coating. At box808, the solvent is evaporated after the polymer solution is dispensed on the substrate to leave a layer of solute on the surface of the substrate. In the embodiment where the polymer solution is a photoresist solution, after the evaporation, a photoresist layer is formed over the substrate surface.

FIG. 9illustrates an exemplary embodiment of a method900of coating a polymer layer such as a photoresist layer on a surface substrate using one of the exemplary coating systems previous described. At box902, a substrate is provided. In one embodiment, the substrate is a semiconductor wafer used in the manufacture of integrated circuits. The substrate may have patterned and structures formed thereon as is known in the art.

At box904, a polymer solution is dispensed over a surface of the substrate. In one embodiment, the polymer solution is a photoresist solution used in the manufacture of integrated circuits. In other embodiments, the polymer solution includes solutions used to form organic planarization films, anti-reflection films, siloxane spin-on-glass films polyimide films, polimide siloxane films, and other films typically used in the manufacture of integrated circuits.

The polymer solution is dispensed using one of the exemplary embodiments of the coating system of the present invention (e.g., coating system100,200,300,400,500, or600). The coating system includes a pump connected in-line with a buffer tank and a polymer solution source as previously discussed. There is a continuous fluid path from the polymer solution source through the buffer tank and the pump. Thus, when the pump is drawing the polymer solution source to dispense it over the substrate surface, the polymer solution flows from the polymer solution source to the pump in a continuous path.

At box906pressure is applied to the polymer solution source to get the polymer solution to transfer to the buffer tank. The buffer tank is filled to a predetermined level suitable to prevent the pump from drawing air in the event that the polymer solution source becomes empty or substantially low. In one embodiment, the buffer tank maintains a constant level of polymer solution in it to allow for easy for replacing the polymer solution source when the polymer solution source is low or substantially empty. Low or substantially empty refers to a level in the polymer solution source that will cause the pump to draw in air due to insufficient liquid level in the polymer solution source. In one embodiment, the buffer tank is filled before the dispensing of the polymer solution. The buffer tank may be filled simultaneously with the dispensing if necessary.

In one embodiment, the substrate is placed in a housing or a chamber, which allows the atmosphere in the chamber to be at least partially saturated with solvent molecules. This may improve the cast film wetability by establishing a monolayer of coating solvent on the surfaces of the substrate. In addition, thickness uniformity may be improved with a controlled coating environment.

In one embodiment, a spin-cast method is used for the coating of the polymer solution on the substrate. Thus, after the polymer solution is dispensed, the substrate is spun or rotated to spread the solution over the surface of the substrate. The substrate may be placed on a rotable chuck that has a suitable rotating velocity commonly used for spin-cast coating. After the solution has spread over the substrate surface, the solvent is evaporated to leave a layer of solute on the surface of the substrate. In the embodiment where the polymer solution is a photoresist solution, after the evaporation, a photoresist layer is formed over the substrate surface.

In another embodiment, a spray-coat method is used for the coating of the polymer solution on the substrate. The polymer solution may be dispensed onto the substrate surface using a shower head configured to dispense the polymer solution over the substrate surface.

In any of the methods described, multiple substrates can be coated at the same time or different time using the same coating system. For example, as previously discussed, more dispensing lines can be included to allow for coating multiple substrates (e.g., as in the coating system200). In addition, more polymer solution sources can be included to allow for the switching from an empty or substantially low polymer solution source to a full one. In this way, the empty or substantially low polymer solution source can be replaced without disrupting the coating process.

Having disclosed exemplary embodiments, modifications and variations may be made to the disclosed embodiments while remaining within the spirit and scope of the invention as defined by the appended claims.