TWI892731B - Method for increasing dipole moment of high dielectric constant film - Google Patents

Abstract

A method for increasing the dipole moment of a high dielectric constant film, used to increase the dipole moment of the high dielectric constant film formed on sidewalls of a deep trench isolation structure of a CMOS sensor. The method comprises: providing a substrate into a processing chamber, wherein the substrate comprises a deep trench isolation structure with a high dielectric constant film formed on sidewalls of the deep trench isolation structure; and providing and maintaining a supercritical fluid into the processing chamber such that the supercritical fluid reacts with the high dielectric constant film to increase the dipole moment of the high dielectric constant film. By this method, the accumulation of electric holes in sidewalls of the deep trench isolation structure can be induced, thereby achieving a reduction in dark current in CMOS sensors.

Description

Method for increasing dipole moment of high dielectric constant film

The present invention relates to a method for increasing the dipole moment of a high-dielectric-constant film, and more particularly to a method for increasing the dipole moment of a high-dielectric-constant film using a supercritical fluid.

A CMOS image sensor (CIS) is a photosensitive element that converts light signals into electrical signals. In recent years, CMOS image sensors have been widely used in mobile phone cameras, backup camera systems, and even have a growing application value in the medical field.

During the CMOS image sensor manufacturing process, metal contamination and damage to the silicon substrate caused by plasma etching can cause defects in the CMOS image sensor, leading to sensor leakage (i.e., dark current) and increased noise.

Currently, it is known that a backside deep trench isolation (BDTI) structure is formed on a semiconductor substrate, such as a silicon substrate, to isolate the pixels of a CMOS image sensor. Simultaneously, a high-k dielectric film is deposited on the surface of the BDTI structure to passivate the surface. The high-k dielectric film's dipole moment can be utilized to cause holes to accumulate on the sidewalls of the BDTI structure. This allows electrons generated in the dark state to combine with these holes, thereby reducing dark current. However, after the BDTI structure is formed, it enters the semiconductor back-end of line (BEOL) process and is not suitable for high-temperature processing (e.g., above 400°C). Therefore, further increasing the dipole moment of high-k films will be limited by the process temperature.

In view of this, it is necessary to develop a method for increasing the dipole moment of high-k films that can effectively increase the dipole moment of high-k films at temperatures suitable for semiconductor back-end processes.

To address the above-mentioned problems, the main purpose of the present invention is to provide a method for increasing the dipole moment of a high-k dielectric film, which can effectively increase the dipole moment of the high-k dielectric film at temperatures suitable for semiconductor back-end processing.

Throughout this disclosure, directional terms or similar terms, such as "front," "rear," "left," "right," "upper (top)," "lower (bottom)," "inner," "outer," and "side," are primarily used with reference to the accompanying drawings. These directional terms or similar terms are intended solely to facilitate description and understanding of the various embodiments of the present invention and are not intended to limit the present invention.

The use of the quantifiers "a" or "an" in the elements and components described throughout this invention is merely for convenience and to provide a general understanding of the scope of the invention. They should be interpreted in this invention to include one or at least one, and the singular concept also includes the plural, unless it is obvious that it means otherwise.

The method of increasing the dipole moment of a high-k dielectric film of the present invention comprises: providing a substrate in a processing chamber, the substrate comprising at least one deep trench isolation structure, and forming a high-k dielectric film on at least a portion of the sidewalls of the deep trench isolation structure; and providing and maintaining a supercritical fluid in the processing chamber, such that the supercritical fluid reacts with the high-k dielectric film to increase the dipole moment of the high-k dielectric film, thereby promoting more hole accumulation on the sidewalls of the deep trench isolation structure and reducing defects at the interface between the high-k dielectric film and the deep trench isolation structure.

Accordingly, the present invention's method for increasing the dipole moment of a high-k film utilizes the high permeability and reactivity of supercritical fluids to reduce defects at the interface between the high-k film and the deep trench isolation structure. Furthermore, the high-k film's dipole moment is increased, encouraging more holes to accumulate on the sidewalls of the deep trench isolation structure, thereby reducing the generation of dark current. This is the purpose of the present invention.

The reaction pressure between the supercritical fluid and the high-k dielectric film can be between 1 and 220 atm. This allows the viscosity, density, and diffusion coefficient of the supercritical fluid within the processing chamber to be fine-tuned, allowing the supercritical fluid's properties to be tailored to actual needs.

The reaction temperature between the supercritical fluid and the high-k dielectric film can be between room temperature and 400°C. Thus, the method of increasing the dipole moment of a high-k dielectric film of the present invention can achieve the effect of effectively increasing the dipole moment of a high-k dielectric film at temperatures suitable for semiconductor back-end processing, or even at room temperature.

The reaction time between the supercritical fluid and the high-k dielectric film can be between 1 and 180 minutes. Thus, by performing the method of increasing the dipole moment of the high-k dielectric film of the present invention for the aforementioned time, a more effective increase in the dipole moment of the high-k dielectric film can be achieved.

The supercritical fluid can be selected from at least one of the group consisting of carbon dioxide, carbon tetrafluoride, nitrogen, argon, hydrogen, and water in a supercritical state. By selecting such a supercritical fluid, the dipole moment of the high-k dielectric film can be more effectively increased.

The material of the high-k dielectric film can be at least one selected from the group consisting of aluminum oxide, einsteinium oxide, zirconium oxide, titanium oxide, silicon dioxide, germanium oxide, tantalum oxide, and yttrium oxide. By selecting the aforementioned high-k dielectric film materials, a better interaction with the supercritical fluid can be achieved, effectively increasing the dipole moment of the high-k dielectric film.

1:Substrate

11: Deep trench isolation structure

11a: Sidewall

11b: Bottom

12: High dielectric constant film

2: Processing chamber

21: Base

3: Supercritical fluid source

S: Supercritical fluid

[Figure 1] Schematic diagram of the method for increasing the dipole moment of a high-k film according to the present invention.

To make the above and other purposes, features, and advantages of the present invention more clearly understood, the following specifically provides a preferred embodiment of the present invention and provides a detailed description with reference to the accompanying drawings.

The term "supercritical fluid" as used herein refers to a fluid in a state above its critical temperature and critical pressure. For example, if the supercritical fluid is carbon dioxide in a supercritical state, this means the ambient pressure is above approximately 72.9 atm and the ambient temperature is above approximately 31.3°C. The same applies to other fluids. Furthermore, the present invention does not limit the method for forming a supercritical fluid.

Please refer to FIG. 1 , which is a schematic diagram illustrating an embodiment of the method for increasing the dipole moment of a high-k dielectric film using a supercritical fluid according to the present invention. In FIG. 1 , a substrate 1 is provided on a base 21 within a processing chamber 2. The substrate 1 may be a semiconductor substrate, such as a silicon substrate. The substrate 1 has at least one deep trench isolation (DTI) structure 11, each deep trench isolation structure 11 including a sidewall 11 a and a bottom surface 11 b. The deep trench isolation structure 11 may be formed by any suitable method known to a person of ordinary skill in the art, and the present invention is not limited thereto. A high-k dielectric film 12 is formed on at least a portion of the sidewall 11a of the deep trench isolation structure 11. The high-k dielectric film 12 may completely cover the sidewall 11a or the sidewall 11a and the bottom surface 11b. The material of the high-k dielectric film 12 may be aluminum oxide, einsteinium oxide, zirconium oxide, titanium oxide, silicon dioxide, germanium oxide, pyrite oxide, or a combination thereof. The high-k dielectric film 12 may be formed on the surface of the deep trench isolation structure 11 by, for example, chemical deposition or atomic layer deposition, but is not limited thereto.

Continuing with FIG. 1 , a supercritical fluid S can be provided from a supercritical fluid source 3 into the processing chamber 2. The supercritical fluid S can be carbon dioxide, carbon tetrafluoride, nitrogen, argon, hydrogen, water, or any combination thereof, all in a supercritical state. In one embodiment, supercritical carbon dioxide is used as the supercritical fluid S. It should be noted that the pressure and temperature of the processing chamber 2 vary depending on the composition of the supercritical fluid used, thereby ensuring that the supercritical fluid S remains in a supercritical state after entering the processing chamber 2. The supercritical fluid S and the high dielectric constant film 12 can react under a pressure of 1 to 220 atm and at a temperature between room temperature and 400°C, 100 to 350°C, or 150 to 250°C. Furthermore, the reaction time between the supercritical fluid S and the high dielectric constant film 12 can be between 1 and 180 minutes. In this way, the supercritical fluid S can modify the high-k dielectric film 12 at a temperature suitable for back-end processing (e.g., below 400°C), thereby increasing the dipole moment of the high-k dielectric film 12 and promoting the accumulation of more holes on the sidewalls 11a of the deep trench isolation structure 11, thereby reducing the generation of dark current.

Furthermore, because supercritical fluids have properties such as viscosity, density, and diffusion coefficient that lie between those of liquids and gases, they possess both high transparency and high reactivity compared to both gases and liquids. This helps reduce defects at the interface between the high-k dielectric film 12 and the deep trench isolation structure 11, further reducing dark current generation and thus effectively reducing noise in CMOS image sensors.

In one embodiment, the processing chamber 2 may further contain water vapor during the reaction between the supercritical fluid S and the high-k film 12. This further helps reduce defects at the interface between the high-k film 12 and the deep trench isolation structure 11. It should be noted that the pressure and temperature of the processing chamber 2 must not only maintain the supercritical fluid S in a supercritical state, but also the water vapor in a gaseous state. Furthermore, the supercritical fluid S does not contain water in a supercritical state.

In one embodiment, after the supercritical fluid S and the high-k dielectric film 12 have reacted, the pressure and temperature of the processing chamber 2 can be adjusted to normal pressure and temperature, and the reacted substrate 1 can be removed from the processing chamber 2.

In summary, the present invention's method for increasing the high-k dielectric film's dipole moment can reduce defects at the interface between the high-k dielectric film and the deep trench isolation structure by leveraging the high permeability and reactivity of supercritical fluids. Furthermore, the high-k dielectric film's dipole moment can be increased, encouraging more holes to accumulate on the sidewalls of the deep trench isolation structure, thereby reducing the generation of dark current. This is the purpose of the present invention.

Although the present invention has been disclosed using the preferred embodiments described above, they are not intended to limit the present invention. Any person skilled in the art may make various changes and modifications to the above embodiments without departing from the spirit and scope of the present invention. These changes and modifications are still within the technical scope protected by the present invention. Therefore, the scope of protection of the present invention shall include all changes within the meaning and equivalent scope of the appended patent applications.

1:Substrate

11: Deep trench isolation structure

11a: Sidewall

11b: Bottom

12: High dielectric constant film

2: Processing chamber

21: Base

3: Supercritical fluid source

S: Supercritical fluid

Claims (6)

A method for increasing the dipole moment of a high-k dielectric film comprises: providing a substrate in a processing chamber, the substrate comprising at least one deep trench isolation structure, and forming a high-k dielectric film on at least a portion of the sidewalls of the deep trench isolation structure; and providing and maintaining a supercritical fluid in the processing chamber, such that the supercritical fluid reacts with the high-k dielectric film to increase the dipole moment of the high-k dielectric film, thereby promoting more hole accumulation on the sidewalls of the deep trench isolation structure and reducing defects at the interface between the high-k dielectric film and the deep trench isolation structure. The method for increasing the dipole moment of a high dielectric constant film as claimed in claim 1, wherein the reaction pressure between the supercritical fluid and the high dielectric constant film is between 1 and 220 atm. The method for increasing the dipole moment of a high dielectric constant film as claimed in claim 1, wherein the reaction temperature of the supercritical fluid and the high dielectric constant film is between room temperature and 400°C. The method for increasing the dipole moment of a high dielectric constant film as claimed in claim 1, wherein the reaction time between the supercritical fluid and the high dielectric constant film is between 1 and 180 minutes. The method for increasing the dipole moment of a high dielectric constant film as claimed in claim 1, wherein the supercritical fluid is at least one selected from the group consisting of carbon dioxide, carbon tetrafluoride, nitrogen, argon, hydrogen and water in a supercritical state. A method for increasing the dipole moment of a high-k dielectric film as claimed in claim 1, wherein the material of the high-k dielectric film is at least one selected from the group consisting of aluminum oxide, einsteinium oxide, zirconium oxide, titanium oxide, silicon dioxide, germanium oxide, tantalum oxide and yttrium oxide.