1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing system.
2. Description of the Related Art
In a photolithography process in a fabrication process of, for example, a semiconductor wafer (hereinafter referred to as a xe2x80x9cwaferxe2x80x9d), a resist solution is coated onto a surface of the wafer, and the wafer undergoes a resist coating treatment for forming a resist film, an exposure processing for exposing a pattern to the wafer, a developing treatment for developing the wafer after the exposure and the like, so that a predetermined circuit pattern is formed on the wafer.
As the resist coating treatment, a dominant method today is a spin-coating method which discharges the resist solution to the center of the rotated wafer to diffuse the resist solution over the surface of the wafer.
However, since the wafer is rotated a high speed according to the spin-coating method, high volume of the resist solution scatters from the peripheral edge part of the wafer, and therefore a lot of the resist solution is wasted. Additionally, since the unit is contaminated by the scatter of the resist solution, there are disadvantages that the unit needs to be cleaned frequently and so on.
Hence, instead of the spin-coating method which rotates the wafer, a method of discharging the resist solution onto the wafer while relatively moving the wafer and a resist solution discharge nozzle so that a path of a resist solution discharge part becomes a rectangular wave shape with large amplitude, which results in that the wafer is coated evenly with the resist solution in a plurality of parallel lines, that is, a method of coating of the so-called one continuous writing stroke is conceivable. In this coating method of one continuous writing stroke, there is a possibility that the surface of the resist film after the coating swells along the coating path of the resist solution, and hence it is preferable to use the resist solution having low viscosity which spreads easily over the wafer after the coating, and to flatten the coating film after completion of the coating.
By the way, it is recently demanded to further narrow the so-called xe2x80x9cedge cutting widthxe2x80x9d, which is at the peripheral edge part of the substrate and is not commercialized, and hence a technology for narrowing the edge cutting width needs to be developed in the above-described coating method of the so-called one continuous writing stroke as well. In order to narrow the edge cutting width, it is necessary to increase the viscosity of the resist solution so that the resist solution in the periphery of the wafer does not swell.
However, when the viscosity of the resist solution is increased in the coating method of one continuous writing stroke, the resist solution discharged onto the wafer becomes hard to be spread and to be smoothed in flattening processing after that, and hence film thickness is thickened along the coating path of the resist solution, and an in-plane uniformity of the resist film is decreased. Namely, in the coating method of the so-called one continuous writing stroke, lowering the viscosity of the resist solution in order to narrow the edge-cutting width and maintaining the in-plane uniformity of the resist solution are inconsistent to each other.
The present invention is made in view of the above-described points, and it is an object of the present invention to narrow an edge cutting width while using a coating solution having high viscosity and to maintain an in-plane uniformity of a coating film, even when coating processing of a substrate such as a wafer is performed in the manner of the so-called one continuous writing stroke.
In view of the above object, a processing method of the present invention comprises the steps of coating a coating solution on a surface of the substrate while relatively moving a coating solution discharge nozzle and the substrate and discharging the coating solution onto the substrate from the coating solution discharge nozzle, exposing the substrate to a solvent atmosphere of the coating solution after the step of coating, and reducing pressure inside a container in which the substrate is housed after the step of exposing.
According to another aspect of the present invention, a processing method of the present invention, for processing a substrate, comprises the steps of coating a coating solution on a surface of the substrate while relatively moving a coating solution discharge nozzle and the substrate and discharging the coating solution onto the substrate from the coating solution discharge nozzle, applying pressure inside a container in which the substrate is housed after the step of coating, and reducing pressure inside the container in which the substrate is housed after the step of applying pressure.
According to the present invention, for example, after the coating solution is coated in the manner of the so-called one continuous writing stroke, the substrate is exposed to the solvent atmosphere, whereby the solvent adheres to the surface of the coating solution and the viscosity of the surface of the coating solution can be decreased. Thereafter, by reducing the pressure inside the container in which the substrate is housed and forming airflow inside the container, the surface of the substrate whose viscosity is decreased is smoothed and flattened. At the same time, the solvent is evaporated and the substrate is dried by the airflow. Thereby, even when the coating solution having high viscosity is coated, the in-plane uniformity of the film thickness of the coating film can be maintained. Therefore, even when the coating solution is coated in the manner of the so-called one continuous writing stroke, it is possible to use the coating solution having high viscosity, and to narrow the edge cutting width.
When the pressure is applied inside the container in which the substrate is housed, instead of exposing the substrate to the solvent atmosphere, it is possible to prevent volatilization of the coating solution on the surface of the substrate and to allow the substrate and the coating solution to get to know well each other, thereby improving the flattening during reduced-pressure drying after that.
A processing system of the present invention can perform the above-described processing method efficiently.
Namely, a processing system of the present invention comprises a coating unit for coating the substrate with a coating solution, a solvent atmosphere unit for exposing the substrate to a solvent atmosphere of the coating solution, and a reduced-pressure drying unit for subjecting the substrate to reduced-pressure drying, wherein the coating unit comprises a coating solution discharge nozzle for discharging the coating solution onto the substrate, and a moving mechanism for relatively moving the coating solution discharge nozzle and the substrate, wherein the solvent atmosphere unit comprises a chamber for holding the substrate in a prescribed atmosphere, and a solvent vapor supply mechanism for supplying a solvent vapor of the coating solution of a prescribed concentration into the chamber through a supply pipe, and wherein the reduced-pressure drying unit comprises a pressure reducing mechanism for reducing pressure inside a container in which the substrate is housed. Therefore, it is possible to narrow the edge cutting width while using the coating solution having high viscosity and to maintain the in-plane uniformity of the coating film formed on the substrate.
According to another aspect of the present invention, a processing system of the present invention comprises a coating unit for coating the substrate with a coating solution, and a reduced-pressure drying unit for exposing the substrate to a solvent atmosphere of the coating solution and thereafter subjecting the substrate to reduced-pressure drying, wherein the coating unit comprises a coating solution discharge nozzle for discharging the coating solution onto the substrate, and a moving mechanism for relatively moving the coating solution discharge nozzle and the substrate, and wherein the reduced-pressure drying unit comprises a container for housing the substrate and containing the substrate airtightly, a solvent vapor supply mechanism for supplying a solvent vapor of the coating solution of a prescribed concentration into the container through a supply pipe, and a pressure reducing mechanism for reducing pressure inside the container.
As described above, the processing system of the substrate includes either the coating unit which can perform the coating method of the so-called one continuous writing stroke, the solvent atmosphere unit which can expose the substrate to the solvent atmosphere and the reduced-pressure drying unit which can subject the substrate to the reduced-pressure drying, or the aforesaid coating unit and the reduced-pressure drying unit which can expose the substrate to the solvent atmosphere and subject the substrate to the reduced-pressure drying, and therefore, it can perform the above-described processing method of the present invention preferably. Therefore, it is possible to narrow the xe2x80x9cedge cutting widthxe2x80x9d while using the coating solution having high viscosity and to maintain the in-plane uniformity of the coating film formed on the substrate. Moreover, according to the latter processing system, the processing of exposing the substrate to the solvent atmosphere and the processing of subjecting the substrate to the reduced-pressure drying can be preformed in the same reduced-pressure drying unit, and hence it is possible to save time of carrying the substrate. Furthermore, it is possible to mount larger number of processing units in the processing unit, and hence its processing capacity can be improved.