JP-7854738-B2 - Supercritical wafer cleaning/drying medium recovery method and system

JP7854738B2JP 7854738 B2JP7854738 B2JP 7854738B2JP-7854738-B2

Inventors

肖剛
肖昊瑾
劉亞飛

Assignees

浙江大学

Dates

Publication Date: 20260507
Application Date: 20241213
Priority Date: 20231214

Claims (10)

A method for cleaning/drying a supercritical wafer and recovering the medium, A cleaning/drying step in which an organic solvent adhering to a wafer is dissolved and removed using a supercritical cleaning/drying medium to obtain a mixed medium supporting the organic solvent, After the washing/drying step, a depressurization step is performed to reduce the pressure of the mixed medium to a first pressure, After the vacuum step, the vacuum-reduced mixed medium is heated to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium comes into contact with an organic solvent adsorbent in an adsorbent, the organic solvent in the mixed medium is adsorbed and concentrated by the organic solvent adsorbent, and separated from the washing/drying medium in an adsorption step, A method for recovering a supercritical wafer cleaning/drying medium, characterized by including the following:
An adsorbent switching step is performed to determine whether the organic solvent adsorbent in the first adsorbent has reached an adsorption threshold, and if it has, to switch the adsorbent in the adsorption step from the first adsorbent to the second adsorbent, After the adsorbent switching step, the organic solvent adsorbent in the first adsorbent is heated to a second temperature, and after the organic solvent is desorbed from the organic solvent adsorbent in the first adsorbent, it is discharged from the first adsorbent and flows into the organic solvent collection port in a desorption step. The supercritical wafer cleaning/drying medium recovery method according to claim 1, further comprising the above.
The supercritical wafer cleaning/drying medium recovery method according to claim 1, further comprising a purification step of removing organic solvent adsorbent pellets in the cleaning/drying medium separated in the adsorption step.
The supercritical wafer cleaning/drying medium recovery method according to claim 2, characterized in that the organic solvent adsorbent is an activated carbon adsorbent or a molecular sieve adsorbent with a pore size in the range of 0.7 nm to 0.9 nm, and the cleaning/drying medium is carbon dioxide.
The supercritical wafer cleaning/drying medium recovery method according to claim 4, characterized in that the first pressure is 3-9 MPa, the first temperature is 30-90°C, and the second temperature is 150-300°C.
A gas supply step provides a gas that supplies the cleaning/drying medium used in the cleaning/drying step by pressurizing and heating the gaseous cleaning/drying medium separated in the adsorption step and/or an external medium supplied from an external gas source to obtain the cleaning/drying medium in a supercritical state, A pressure adjustment step is performed to pressurize and transport the gaseous cleaning/drying medium obtained in the adsorption step, and to adjust the pressure of the pressurized cleaning/drying medium to be the same as the pressure of the external medium before the gas supply step. The supercritical wafer cleaning/drying medium recovery method according to claim 1, further comprising the above.
A supercritical wafer cleaning/drying medium recovery system, A cleaning/drying apparatus that contains a wafer and uses a supercritical cleaning/drying medium to dissolve and remove organic solvents adhering to the wafer, thereby obtaining a mixed medium supporting the organic solvent, A first pressure reducing valve is connected to the outlet of the washing/drying equipment and reduces the pressure of the mixed medium to a first pressure, A supercritical wafer cleaning/drying medium recovery system comprising: an adsorption/desorption unit having an organic solvent adsorbent built in and communicating with the outlet of a first pressure reducing valve, the adsorption/desorption unit having a first heating device for heating the mixed medium that has entered the adsorption/desorption unit to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium coming into contact with the organic solvent adsorbent, the organic solvent in the mixed medium being adsorbed and concentrated by the organic solvent adsorbent, and separated from the cleaning/drying medium; and
The adsorption/desorption unit comprises a plurality of adsorbents, each containing the organic solvent adsorbent, and the first heating device. The supercritical wafer cleaning/drying medium recovery system according to claim 7, characterized in that a plurality of adsorbents are provided in parallel, the inlets of the plurality of adsorbents are connected to the outlets of the first pressure reducing valve, the solvent outlets of the plurality of adsorbents are connected to organic solvent collection ports, and the first heating device is provided around the plurality of adsorbents and is used to control the temperature of the plurality of adsorbents to a first temperature or a second temperature higher than the first temperature.
The supercritical wafer cleaning/drying medium recovery system according to claim 8, further comprising a purifier communicating with the medium outlets of multiple adsorbents for removing organic solvent adsorbent pellets from the cleaning/drying medium.
A gas supply unit is connected to the media outlet of the adsorption/desorption unit and the inlet of the washing/drying equipment, and includes a pressure boosting pump and a second heating device. An external gas source whose outlet is connected to the inlet of the gas supply unit, A pressure regulating device having a compressor and a second pressure reducing valve, which are in communication with the medium outlet of the adsorption/desorption unit and the inlet of the external gas source, and which are in sequential communication along the direction of fluid flow, The supercritical wafer cleaning/drying medium recovery system according to claim 9, further comprising the above.

Description

This invention relates to the field of wafer processing, and more specifically, to a method and system for recovering a supercritical wafer cleaning/drying medium. Semiconductor wafers are the most important material in the semiconductor industry, and the requirements for their surface cleanliness are quite stringent. In semiconductor wafer processing, cleaning and drying the wafer surface are essential processes for effectively removing solvents and maintaining surface cleanliness. On the other hand, some supercritical media have the characteristic of having zero surface tension, allowing them to penetrate smoothly through the porosity structure of the wafer surface, enabling efficient solvent removal. Conventional cleaning and drying processes using supercritical media typically treat the supercritical cleaning/drying medium as a "disposable" consumable. However, the high consumption of supercritical cleaning/drying medium during the cleaning and drying process results in very high wafer cleaning and drying costs. Furthermore, under certain temperature and/or pressure conditions, the solvent and cleaning/drying medium may become somewhat miscible, making it difficult to separate and recover the cleaning/drying medium using simple separation methods (e.g., gas-liquid separation or liquid-liquid separation). Often, the recovered cleaning/drying medium will contain a significant amount of solvent impurities, potentially resulting in low purity. Therefore, in this field, there is a pressing need for a high-purity supercritical wafer cleaning/drying medium recovery process to reduce the cleaning and drying costs of semiconductor wafers. This is a flowchart of a supercritical wafer cleaning/drying medium recovery method according to an embodiment of the present invention.This is a concentration diagram of the isopropanol organic solvent in a mixed medium adsorbed onto a NaY molecular sieve according to an embodiment of the present invention.This is a schematic diagram of the structure of a supercritical wafer cleaning/drying medium recovery system applied to embodiments of the present invention.This is a flowchart of another supercritical wafer cleaning/drying medium recovery method according to an embodiment of the present invention.This is a schematic diagram of the structure of another supercritical wafer cleaning/drying medium recovery system applied to embodiments of the present invention. The present invention will be described in further detail below with reference to specific embodiments and drawings. The realization of the present invention is not limited to the embodiments described below, and various modifications, substitutions, combinations, and improvements based on the technical concept of the present invention, adopted within the scope of the knowledge of those skilled in the art, are all protected by the present invention. First Embodiment <br/>As shown in Figure 1, the first embodiment of the present invention is a supercritical wafer cleaning/drying medium recovery method, A cleaning/drying step S1 involves dissolving and removing organic solvents adhering to the wafer using a supercritical cleaning/drying medium to obtain a mixed medium supporting the organic solvent, After the washing/drying step S1, a depressurization step S2 is performed to reduce the pressure of the mixed medium to a first pressure, After the depressurization step S2, the depressurized mixed medium is heated to a first temperature to obtain a gaseous mixed medium, the gaseous mixed medium comes into contact with the organic solvent adsorbent in the adsorber, the organic solvent in the mixed medium is adsorbed and concentrated by the organic solvent adsorbent, and separated from the washing/drying medium in the adsorption step S3. The process involves determining whether the organic solvent adsorbent in the first adsorbent has reached the adsorption threshold, and if it has, switching the adsorbent from the first adsorbent to the second adsorbent in the adsorption step S3 in an adsorbent switch step S4. After the adsorbent switching step S4, the organic solvent adsorbent in the first adsorbent is heated to the second temperature, and after the organic solvent is desorbed from the organic solvent adsorbent in the first adsorbent, it is discharged from the first adsorbent and flows into the organic solvent collection port in a desorption step S5. The process includes a purification step S6 to remove organic solvent adsorbent pellets in the washing/drying medium separated in the adsorption step S3. Furthermore, the "organic solvent adsorbent" in this invention may be any adsorbent that highly selectively adsorbs organic solvents. Preferably, an activated carbon adsorbent or a molecular sieve adsorbent with a pore size in the range of 0.7 nm to 0.9 nm may be selected. For example, when the washing/drying medium is carbon dioxide and the organic solvent is isopropanol (IPA), a NaY molecular sieve may be selected as the organic