Electrolyte for Forming Anodic Oxide Film, Method of Forming Anodic Oxide Film, and Anodic Oxide Film and Member for Semiconductor Device Manufactured Thereby

The present application claims priority to Korean Patent Application No. 10-2024-0081462, filed Jun. 21, 2024, the entire contents of which is incorporated herein for all purposes by this reference.

The present disclosure relates to an electrolyte for forming an anodic oxide film, a method of forming an anodic oxide film, and an anodic oxide film and a member for a semiconductor device manufactured thereby. More specifically, the present disclosure relates to an electrolyte capable of improving the corrosion resistance of an anodic oxide film, a method of forming an anodic oxide film, and an anodic oxide film and a member for a semiconductor device manufactured thereby.

Vacuum plasma devices are widely used to manufacture semiconductor devices. However, vacuum plasma devices involve the use of high-temperature plasma and highly corrosive reactive gases, so problems with damage to parts or members within semiconductor manufacturing devices may occur.

Among such semiconductor manufacturing devices, showerhead members made of aluminum are being used, for example, in chemical vapor deposition (CVD) devices. A showerhead member, a part constituting CVD devices, dry etching devices, and the like, is mounted on the upper or lower portion of a semiconductor wafer in a process chamber to manufacture semiconductors and serves to spray reactive gases for deposition and etching and control process temperature.

is a diagram illustrating a typical showerhead.

A showerheadis a structure installed in a process chamber to spray a reactive gas onto a semiconductor wafer so that the reactive gas can make even contact with the wafer. To spray the reactive gas, a plurality of spray nozzlesin fine hole form is formed in the showerhead.

In CVD processes, a corrosive gas containing a fluorine (F)-based halogen element serves as a reactive gas. Accordingly, such formed showerheads made of aluminum react with reactive gases, leading to corrosion. In other words, the reaction between aluminum and fluorine may result in the formation of an AlFlayer, which may cause changes in the concentration of the reactive gas in a process chamber, leading to deterioration in initial process stabilization and a decrease in process efficiency. The long-term use of such corroded members causes the AlFlayer to peel off from the member, generating particulate impurities in the process chamber. The cost of replacing expensive showerheads also results in increased process costs.

To prevent the members of semiconductor manufacturing devices from being corroded by reactive gases, the surface of such members is coated with an oxide film using methods such as anodic oxidation treatment, electroplating, vapor phase growth, and the like. The showerheadhas a complex structure in which a plurality of fine holes is formed, so a coating is typically formed by chemical methods. Among all chemical coating methods, CVD or atomic layer deposition (ALD) are high-cost processes, so anodic oxidation (anodizing), a relatively low-cost chemical immersion method, is preferred.

Examples of anodic oxidation include methods using sulfuric acid, oxalic acid, a mixture of sulfuric acid and chromic acid, and the like. In the case of forming an anodic oxide film using such anodic oxidation, deviations in the hole size of each spray nozzleof the showerhead may occur when the thickness of the anodic oxide film is increased to protect aluminum members. In addition, due to the high-temperature process, cracks may occur in the anodic oxide film.

When the thickness of an anodic oxide film is reduced to 1 μm or smaller to address these problems, corrosion resistance may deteriorate due to the structural characteristics of the anodic oxide film containing a porous layer. This is because, when forming an existing anodic oxide film to have a thickness of 500 nm or greater, a porous layer containing pores is formed in the anodic oxide film.

Ammonium borate, an alkaline component, and tartaric acid or malic acid, which are organic acids, can be used to form an anodic oxide film without a porous layer. However, defects occur inside a coating layer when forming the oxide film to have a thickness of 200 nm or greater with the use of ammonium borate. In addition, when the thickness of the oxide film becomes 300 nm or greater with the use of tartaric acid or malic acid, not only a porous layer is formed, but also an oxide film having a thickness of 500 nm or greater fails to be formed, which is problematic.

In the case of using ammonium borate in the related art, an anodic oxide film has been formed using 4 to 15 wt % of ammonium borate under the following conditions: a supplied current in the range of 0.1 to 0.5 A/dmand an electrolyte temperature in the range of 20° C. to 60° C. In this case, a barrier layer having a thickness of 200 nm can be formed. However, when the thickness of the anodic oxide film becomes 200 nm or greater, there have been problems with multiple defects occurring within the film. In the case of using an electrolyte by mixing tartaric acid and malic acid, an anodic oxide film has been formed using 4 to 15 wt % of tartaric acid and malic acid under the following conditions: a supplied current in the range of 0.1 to 0.5 A/dmand an electrolyte temperature in the range of 20° C. to 60° C. In this case, when the thickness of the barrier layer becomes 300 nm or greater, a porous layer is formed, and a barrier layer having a thickness of 500 nm or greater fails to be formed, which has been problematic.

One aspect of the present disclosure aims to improve the corrosion resistance of an anodic oxide film.

Another aspect of the present disclosure aims to provide an anodic oxide film without forming a porous layer.

One embodiment of the present disclosure provides an electrolyte for forming an anodic oxide film, the electrolyte including citric acid and an additive, wherein the citric acid accounts for 3.0 wt % or more and 6.0 wt % or less based on 100 wt % of the electrolyte, the additive includes one or more selected from among tartaric acid, sulfuric acid, and sodium acetate, and the additive accounts for 0.5 wt % or more and 4.0 wt % or less based on 100 wt % of the electrolyte.

One embodiment of the present disclosure provides the electrolyte for forming the anodic oxide film, wherein the electrolyte includes 1.5 wt % or more and 2.5 wt % or less of one or more selected from among the tartaric acid, the sulfuric acid, and the sodium acetate.

One embodiment of the present disclosure provides the electrolyte for forming the anodic oxide film, wherein the electrolyte includes: about 6.0 wt % of the citric acid, about 1.0 wt % of the tartaric acid, 0 wt % or more and about 0.5 wt % or less of the sulfuric acid, and 0 wt % or more and about 0.5 wt % or less of the sodium acetate.

One embodiment of the present disclosure provides the electrolyte for forming the anodic oxide film, wherein the electrolyte includes: about 6.0 wt % of the citric acid, about 0.5 wt % of the sulfuric acid, and 0 wt % or more and about 0.5 wt % or less of the sodium acetate.

One embodiment of the present disclosure provides a method of forming an anodic oxide film, the method including the following steps: preparing an electrolyte including 3.0 wt % or more and 6.0 wt % or less of citric acid and 0.5 wt % or more and 4.0 wt % or less of an additive, based on 100 wt % of the electrolyte; and forming an anodic oxide film on a metal member by immersing the metal member in the electrolyte, wherein the additive includes one or more selected from among tartaric acid, sulfuric acid, and sodium acetate.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the electrolyte includes 1.5 wt % or more and 2.5 wt % or less of one or more selected from among the tartaric acid, the sulfuric acid, and the sodium acetate.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the electrolyte includes: about 6.0 wt % of the citric acid, about 1.0 wt % of the tartaric acid, 0 wt % or more and about 0.5 wt % or less of the sulfuric acid, and 0 wt % or more and about 0.5 wt % or less of the sodium acetate.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein when forming the anodic oxide film, a current to be supplied to the electrolyte is 0.1 A/dmor more and 1.0 A/dmor less.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein when forming the anodic oxide film, the electrolyte has a temperature of 20° C. or higher and 30° C. or lower.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the time required for forming the anodic oxide film is 100 minutes or more and 150 minutes or less.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the anodic oxide film is formed to have a thickness of 500 nm or greater and 900 nm or smaller.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the metal member is formed of aluminum or an aluminum alloy.

One embodiment of the present disclosure provides the method of forming the anodic oxide film, wherein the metal member is a showerhead.

One embodiment of the present disclosure provides an anodic oxide film manufactured by the method described above.

One embodiment of the present disclosure provides the anodic oxide film, wherein the anodic oxide film includes a barrier layer without a porous layer, and the anodic oxide film has a thickness of 500 nm or greater and 900 nm or smaller.

One embodiment of the present disclosure provides a member for a semiconductor device, the member being manufactured by the method described above.

According to embodiments of the present disclosure, an anodic oxide film without forming a porous layer can be provided, thereby improving the corrosion resistance of a member for a semiconductor manufacturing device.

In addition, according to embodiments of the present disclosure, an anodic oxide film with improved corrosion resistance can be formed without increasing the thickness.

Hereinafter, although embodiments disclosed herein will be described in detail with reference to the attached drawings, the same reference numerals will be assigned to refer to the same components regardless of numerals in the drawings, and redundant descriptions thereof will be omitted. Hereinafter, in the following description of the embodiments according to the present disclosure, when each layer (film), region, pattern, or structure is described as being formed “on” or “under” another substrate, layer (film), area, pad, or pattern, it can be “directly” formed “on” or “under” another substrate, layer (film), region, pad, or pattern or can be “indirectly” formed with other intervening layers being present. In addition, the criteria for determining whether each layer is on or under another are based on the drawings. In the drawings, the thickness and size of each layer are exaggerated, omitted, or schematically illustrated for convenience and clarity of explanation. In addition, the size of each component does not utterly reflect the actual size.

In this description, terms such as “including,” “having,” or “comprising” are used to specify the presence of certain features, integers, steps, operations, elements, or some or combinations thereof but should not be construed as precluding the presence or possibilities of one or more other features, integers, steps, operations, elements, or some or combinations thereof in addition to the foregoing.

Although terms such as first or second may be used to describe various components, such components are not limited by these terms, and these terms are used only to distinguish one component from another.

In addition, in the following description of the embodiments disclosed herein, when a detailed description of related known technology is deemed to obscure the gist of the embodiments disclosed herein, such a detailed description will be omitted.

The attached drawings are provided only to help the understanding of the embodiments disclosed herein. Furthermore, the technical idea disclosed herein is not limited by the attached drawings and should be construed as covering all changes, modifications, equivalents, or alternatives that fall within the spirit and technical scope of the present disclosure.

Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings.

is a diagram schematically illustrating a typical anodic oxide film being formed on the surface of an aluminum member.

Anodic oxidation, a method of forming a metal film, forms a film by primarily anodizing aluminum or an aluminum alloy and can be applied to magnesium, zinc, titanium, and the like. The description of the anodic oxidation will be based on a member formed of aluminum or an aluminum alloy (hereinafter referred to as “aluminum member”) as one example.

Water molecules in electrolyte solutions made of sulfuric acid, oxalic acid, chromic acid, and the like are electrolyzed into hydrogen ions (H) and hydroxyl group (OH) by electrolysis. The resulting hydrogen ions move to a cathode, combine with electrons between the electrolyte solution and the surface of the cathode, and are released as hydrogen gas. When an aluminum memberon which an anodic oxide film is to be formed is used as an anode and subjected to electrolysis, an anodic oxide film (AlO) is formed on the surface of the aluminum member.

Referring to, when immersing the aluminum memberin an electrolyteand supplying current, a barrier layerwithout poresis formed. The electrolytemay be made of sulfuric acid, oxalic acid, chromic acid, or a mixture thereof. When continuously supplying current to the aluminum memberon which the barrier layeris formed, a porous layercontaining poresgrows. In this case, depending on the composition, temperature, and supplied current of the electrolyte, a structure made of poresand cellsis formed between the uppermost interfaceof the porous layer, being in contact with the electrolyte, and the barrier layer.

As described above, when the anodic oxide film contains pores, the corrosion resistance of the anodic oxide film deteriorates when the thickness of the anodic oxide film is reduced. Thus, to address problems of pore formation in the case of existing methods using sulfuric acid, oxalic acid, and a mixture of sulfuric acid and chromic acid, one embodiment of the present disclosure provides a method of forming an anodic oxide film for forming the barrier layerhaving a thickness of 500 nm or greater without forming a porous layer in the anodic oxide film. In one embodiment of the present disclosure, an electrolyte in which a predetermined additive is mixed in citric acid is used.

is a flowchart illustrating a method of forming an anodic oxide film according to one embodiment of the present disclosure.

According to one embodiment of the present disclosure, a member for a semiconductor device, on which the anodic oxide film is to be formed, is a member formed of a metal and may be an aluminum member, that is, a member formed of aluminum or an aluminum alloy. For example, the member for the semiconductor device may be a showerhead formed of aluminum or an aluminum alloy.

To form the anodic oxide film, according to one embodiment of the present disclosure, an electrolyte in which citric acid and an additive are mixed in deionized water is prepared (S). Based on 100 wt % of the electrolyte, 3 wt % or more and 6 wt % or less of citric acid is mixed. When citric acid accounts for less than 3 wt %, an anodic oxide film having a great thickness may be challenging to form under low current conditions. When citric acid accounts for more than 6 wt %, surface defects and cross-sectional defects are highly likely to occur, making control over the thickness of the anodic oxide film challenging.

Citric acid has the chemical formula CHO, and the structural formula thereof is shown below.

As the additive, tartaric acid, sulfuric acid, or sodium acetate may be used. Alternatively, a mixture of two or more of the foregoing may be used. Based on 100 wt % of the electrolyte, 0.5 wt % or more and 4.0 wt % or less, preferably 1.5 wt % or more and 2.5 wt % or less, and more preferably 1.5 wt % or more and 2.0 wt % or less of the additive including one or more selected from among tartaric acid, sulfuric acid, or sodium acetate is mixed. When the additive accounts for less than 0.5 wt %, a barrier layer having a thickness of 500 nm or greater may be challenging to form. When the additive accounts for more than 4.0 wt %, the characteristics of the barrier layer of the anodic oxide layer may deteriorate, leading to deterioration in the corrosion resistance of the film.

The prepared electrolyte is supplied to an electrolysis tank, and a metal member, such as a showerhead formed of aluminum or an aluminum alloy, is immersed in the electrolyte, followed by forming an anodic oxide film (S). In one embodiment of the present disclosure, a current of 0.1 A/dmor more and 1.0 A/dmor less may be supplied to form the anodic oxide film. When the supplied current is less than 0.1 A/dm, an anodic oxide film having a thickness of 500 nm or greater may be challenging to form. When the supplied current exceeds 1.0 A/dm, the reaction between aluminum and acid increases, so the growth rate of the anodic oxide film may increase, leading to defects.