US-12628602-B2 - Substrate processing method and substrate processing apparatus

US12628602B2US 12628602 B2US12628602 B2US 12628602B2US-12628602-B2

Abstract

This invention relates to a substrate processing technique for performing a pressure increasing step, a pressure keeping step and a pressure reducing step in this order in a processing container. A flow rate of a processing fluid in a processing space is suppressed to a second flow rate lower than a first flow rate while maintaining the processing space at a first pressure between the pressure increasing step and the pressure keeping step or in an initial stage of the pressure keeping step. In this way, the mutual diffusion between the processing fluid and a liquid in the processing space is promoted. After this diffusion proceeds, the substrate is dried by the discharge of the processing fluid from the processing space.

Inventors

Zhida WANG
Koji Ando
Noritake SUMI
Chiaki MORIYA
Daiki UEHARA

Assignees

SCREEN Holdings Co., Ltd.

Dates

Publication Date: 20260512
Application Date: 20220823
Priority Date: 20210902

Claims (9)

1 . A substrate processing method for drying a substrate using a processing fluid in a supercritical state while accommodating the substrate having a liquid adhered to a surface formed with a pattern in a processing space of a processing container, the method comprising: (a) increasing a pressure in the processing space to a first pressure by supplying the processing fluid fed from a fluid supplier to the processing space, the supercritical state being reached at the first pressure; (b) flowing the processing fluid to the processing space at a first flow rate while maintaining the processing space at the first pressure by supplying the processing fluid to the processing space and discharging the processing fluid from the processing space, the processing space having been increased to the first pressure by the increasing the pressure in the processing space; (c) reducing the pressure in the processing space by discharging the processing fluid from the processing space, following the flowing the processing fluid to the processing space; and (d) performing mutual diffusion between the liquid and the processing fluid in the processing space by suppressing a flow rate of the processing fluid in the processing space to a second flow rate lower than the first flow rate while maintaining the processing space at the first pressure between the increasing the pressure in the processing space and the flowing the processing fluid to the processing space or in an initial stage of the flowing the processing fluid to the processing space.
2 . The substrate processing method according to claim 1 , wherein: the flow rate of the processing fluid in the processing space is maintained at the second flow rate in the performing mutual diffusion.
3 . The substrate processing method according to claim 1 , wherein: a flow rate switching operation of switching the flow rate of the processing fluid in the processing space between the first flow rate and the second flow rate is repeated in the performing mutual diffusion.
4 . The substrate processing method according to claim 1 , wherein: the second flow rate is zeroed by discharging all of the processing fluid fed from the fluid supplier by way of a bypass pipe separated from the processing container in the performing mutual diffusion.
5 . The substrate processing method according to claim 1 , wherein: the second flow rate is set to a value higher than zero and lower than the first flow rate by feeding part of the processing fluid fed from the fluid supplier to the processing space and, discharging a remainder of the processing fluid by way of a bypass pipe separated from the processing container and discharging the processing fluid from the processing space in the performing mutual diffusion.
6 . The substrate processing method according to claim 1 , wherein: an execution time of the performing mutual diffusion is in a range of 30 seconds or more and 45 seconds or less.
7 . The substrate processing method according to claim 1 , wherein: the processing fluid is carbon dioxide.
8 . A substrate processing apparatus, comprising: a processing unit having a processing container and configured to dry a substrate using a processing fluid in a supercritical state while accommodating the substrate having a liquid adhered to a surface formed with a pattern in a processing space of the processing container: a fluid supplier configured to supply a processing fluid for a supercritical treatment to the processing space having the substrate accommodated therein; a fluid discharger configured to discharge the processing fluid from the processing space having the substrate accommodated therein; a fluid flow adjuster configured to adjust the supply of the processing fluid from the fluid supplier to the processing space and the discharge of the processing fluid from the processing space to the fluid discharger; and a controller configured to control the fluid flow adjuster to perform: a pressure increasing operation of increasing a pressure in the processing space to a first pressure by supplying the processing fluid to the processing space, the supercritical state being reached at the first pressure; a pressure keeping operation of causing the processing fluid to flow to the processing space at a first flow rate while maintaining the processing space at the first pressure by supplying the processing fluid to the processing space, the pressure of the processing space being increased to the first pressure, and discharging the processing fluid from the processing space; a pressure reducing operation of reducing the pressure in the processing space by discharging the processing fluid from the processing space, following the pressure keeping operation; and a diffusion operation of causing the liquid and the processing fluid to be mutually diffused in the processing space by suppressing a flow rate of the processing fluid in the processing space to a second flow rate lower than the first flow rate while maintaining the processing space at the first pressure between the pressure increasing operation and the pressure keeping operation or in an initial stage of the pressure keeping operation.
9 . The substrate processing apparatus according to claim 8 , comprising a bypass pipe separated from the processing container and configured to directly feed the processing fluid supplied from the fluid supplier to the fluid discharger, wherein: the controller is configured to adjust the flow rate of the processing fluid in the processing space by feeding all or part of the processing fluid supplied from the fluid supplier to the fluid discharger via the bypass pipe in the diffusion operation.

Description

CROSS REFERENCE TO RELATED APPLICATION The disclosure of Japanese Patent Application No. 2021-142952 filed on Sep. 2, 2021 including specification, drawings and claims is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a substrate processing technique for processing a substrate by a processing fluid in a supercritical state in a processing space of a processing container. 2. Description of the Related Art A processing process of various substrates such as semiconductor substrates and glass substrates for display device includes processing the surface of the substrate by various processing fluids. Processes using liquids such as chemical liquids and rinse liquids as the processing fluids have been conventionally widely performed. In recent years, processes using supercritical fluids have been also put to practice. Particularly, in a process of a substrate having a fine pattern formed on a surface, a supercritical fluid having a lower surface tension than a liquid enters deep into clearances of the pattern. Thus, the process can be efficiently performed and an occurrence risk of pattern collapse due to a surface tension during drying can be reduced. For example, a substrate processing apparatus for drying a substrate using a supercritical fluid is described in JP 2018-082043A. In this apparatus, a wafer (substrate) placed on a holding plate in the form of a thin plate is carried into the inside (processing space) of the apparatus from one end part of the processing container, and carbon dioxide in a supercritical state is introduced into the processing container from another end part. Further, a fluid discharge header is provided in the processing container. A discharge port is connected to this fluid discharge header, and the supercritical fluid is discharged from the processing space to the outside of the processing container via the fluid discharge header and the discharge port. SUMMARY OF INVENTION Although not described in detail in JP 2018-082043A, after a substrate having a liquid adhering to a surface formed with a pattern is carried into the processing space of the processing container, a pressure increasing step, a pressure keeping step and a pressure reducing step are performed (described later with reference to FIG. 3). That is, CO2 (carbon dioxide) serving as a processing fluid is supplied into the processing space, and a pressure of the processing fluid in the processing space is increased to a pressure at which a supercritical state can be maintained (pressure increasing step). By supplying the processing fluid into the processing space and discharging the processing fluid from the processing container via the fluid discharge header, a laminar flow of the processing fluid flowing substantially in parallel to the surface of the substrate is formed while the above pressure is maintained (pressure keeping step). After this pressure keeping step, a pressure reducing step is performed. By this series of steps, the substrate is dried. However, in the prior art, the processing fluid and the liquid could not be sufficiently diffused with each other in the pressure keeping step, and a two-phase state of the processing fluid and the liquid remained between pattern elements as shown in field (a) of FIG. 5 in some cases. As a result, it has been difficult to effectively prevent a pattern collapse. This invention was developed in view of the above problem and aims to provide a substrate processing method and a substrate processing apparatus capable of satisfactorily drying a substrate while effectively suppressing the collapse of a pattern formed on a surface of the substrate. One aspect of the invention is a substrate processing method for drying a substrate using a processing fluid in a supercritical state while accommodating the substrate having a liquid adhered to a surface formed with a pattern in a processing space of a processing container, includes: (a) increasing a pressure in the processing space to a first pressure by supplying the processing fluid fed from a fluid supplier to the processing space, the supercritical state being reached at the first pressure; (b) flowing the processing fluid to the processing space at a first flow rate while maintaining the processing space at the first pressure by supplying the processing fluid to the processing space and discharging the processing fluid from the processing space, the processing space having been increased to the first pressure by the operation (a); (c) reducing the pressure in the processing space by discharging the processing fluid from the processing space, following the operation (b); and (d) performing mutual diffusion between the liquid and the processing fluid in the processing space by suppressing a flow rate of the processing fluid in the processing space to a second flow rate lower than the first flow rate while maintaining the processing space at the firs