JP7547984B2 - Etching composition, etching method, method for manufacturing semiconductor device, and method for manufacturing gate-all-around transistor - Google Patents

Description

The present invention relates to an etching composition, an etching method, a method for manufacturing a semiconductor device, and a method for manufacturing a gate-all-around transistor.

In accordance with Moore's Law, integrated circuits are becoming increasingly miniaturized.
In recent years, in addition to reducing the size of conventional planar transistors, studies have been conducted to improve performance by changing the structure, such as in fin transistors (fin FETs) and gate-all-around transistors (GAA FETs), while also promoting further miniaturization and integration.

In FinFETs, by forming fins perpendicular to the silicon substrate, not only does it increase the number of transistors per unit area, but it also exhibits excellent performance in ON/OFF control at low voltages. However, in order to further improve performance, it is necessary to devise ways to increase the aspect ratio of the fins, but if the aspect ratio is too large, there are issues such as the fins collapsing during the cleaning and drying processes used to form the fins.

On the other hand, in a GAA FET, the nanosheet or nanowire that forms the channel is covered with a gate electrode, increasing the contact area between the channel and gate electrode, thereby improving the transistor performance per unit area.

To form a GAA FET, an etching composition is required to selectively etch silicon germanium from a structure in which silicon and silicon germanium are alternately stacked. As such an etching composition, Patent Document 1 discloses a composition containing acetic acid. Patent Document 2 discloses a composition containing hydrogen peroxide.

JP 2005-303305 A JP 2019-050365 A

However, the etching composition disclosed in Patent Document 1 has a low content of acetic acid, and the selective solubility of silicon germanium relative to silicon is not sufficient.
Moreover, the etching composition containing hydrogen peroxide disclosed in Patent Document 2 also does not have sufficient selective solubility of silicon germanium relative to silicon.

As in Patent Documents 1 and 2, etching compositions containing various components have been investigated in the past, but none of them have been found to have sufficient selective solubility of silicon germanium relative to silicon.

The present invention has been made in view of these problems, and an object of the present invention is to provide an etching composition that suppresses the dissolution of silicon, promotes the dissolution of silicon germanium, and has excellent selective solubility of silicon germanium relative to silicon. Another object of the present invention is to provide an etching method using this etching composition, a method for manufacturing a semiconductor device, and a method for manufacturing a gate-all-around transistor.

As a result of extensive research, the inventors have discovered that the etching composition of the present invention described below inhibits the dissolution of silicon, promotes the dissolution of silicon germanium, and has excellent selective solubility of silicon germanium relative to silicon.

That is, the gist of the present invention is as follows.
[1] An etching composition that selectively dissolves silicon germanium relative to silicon, comprising an oxidizing agent (A) and an organic acid (B), wherein the oxidizing agent (A) contains nitric acid, and the content of the organic acid (B) is 50 mass% or more in 100 mass% of the etching composition.
[2] The etching composition according to [1], wherein the organic acid (B) contains at least one compound selected from the group consisting of acetic acid, propionic acid, oxalic acid, and citric acid.
[3] The etching composition according to [1] or [2], further comprising a fluorine-containing compound (C).
[4] The etching composition according to [3], wherein the fluorine-containing compound (C) contains at least one compound selected from the group consisting of hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid.
[5] The etching composition according to [3] or [4], wherein the content of the fluorine-containing compound (C) is 5 mass% or less in 100 mass% of the etching composition.
[6] The etching composition according to any one of [1] to [5], further comprising water (D).
[7] The etching composition according to [6], wherein the content of water (D) is 20 mass% or less in 100 mass% of the etching composition.
[8] An etching method for etching a structure containing silicon and silicon germanium using the etching composition according to any one of [1] to [7].
[9] A method for manufacturing a semiconductor device, comprising a step of etching a structure containing silicon and silicon germanium using the etching composition according to any one of [1] to [7].
[10] A method for manufacturing a gate-all-around transistor, comprising a step of etching a structure containing silicon and silicon germanium using the etching composition according to any one of [1] to [7].

The etching composition of the present invention inhibits dissolution of silicon, promotes dissolution of silicon germanium, and has excellent selective solubility of silicon germanium relative to silicon.
Furthermore, the etching method of the present invention using such an etching composition of the present invention, the manufacturing method of a semiconductor device of the present invention, and the manufacturing method of a gate-all-around transistor of the present invention suppress the dissolution of silicon and promote the dissolution of silicon germanium in the etching step, and due to the excellent selective solubility of silicon germanium relative to silicon, it is possible to perform highly accurate etching and manufacture desired products with good yields.

The present invention is described in detail below, but is not limited to the following embodiments and can be modified and implemented in various ways within the scope of the gist. In this specification, when the expression "~" is used, it is used as an expression including the numerical values or physical property values before and after it.

The etching composition of the present invention contains an oxidizing agent (A) (hereinafter sometimes referred to as "component (A)") and an organic acid (B) (hereinafter sometimes referred to as "component (B)"), and since the oxidizing agent (A) contains nitric acid and the content of the organic acid (B) is 50 mass% or more in 100 mass% of the etching composition, silicon germanium can be selectively dissolved relative to silicon.

<Component (A)>
The component (A) is an oxidizing agent. By including an oxidizing agent in the etching composition, the effect of oxidizing the surface of silicon or silicon germanium is exhibited.

Examples of the oxidizing agent include nitric acid, hydrogen peroxide, permanganic acid, periodic acid, and perchloric acid. These oxidizing agents may be used alone or in combination of two or more. Among these oxidizing agents, nitric acid and hydrogen peroxide are preferred because they can remove metals that are a source of contamination, and nitric acid is more preferred because it has excellent selective oxidation properties for silicon germanium.
Therefore, the etching composition of the present invention is characterized by containing at least nitric acid as the oxidizing agent of component (A).

The content of the component (A) is preferably 5 mass % or more, and more preferably 10 mass % or more, in 100 mass % of the etching composition, because the component (A) has an excellent selective oxidation property for silicon germanium.
The content of component (A) is preferably 50 mass % or less, and more preferably 40 mass % or less, in 100 mass % of the etching composition, because this is excellent in suppressing etching of silicon.

When an oxidizing agent other than nitric acid is used in combination as component (A), in order to effectively obtain the effect of selective oxidation of silicon germanium by using nitric acid, the content of nitric acid in 100% by mass of component (A) is preferably 50% by mass or more, and more preferably 80 to 100% by mass.

<Component (B)>
The component (B) is an organic acid. By including an organic acid in the etching composition, the effect of protecting silicon and an oxide film is exhibited.

Examples of organic acids include acetic acid, propionic acid, oxalic acid, and citric acid. These organic acids may be used alone or in combination of two or more. Among these organic acids, acetic acid, propionic acid, oxalic acid, and citric acid are preferred because they are excellent at inhibiting silicon etching, and acetic acid is more preferred.

The content of component (B) is 50 mass% or more, preferably 55 mass% or more, and more preferably 60 mass% or more, in 100 mass% of the etching composition, because component (B) has excellent silicon etching inhibition properties and excellent penetration into narrow spaces.
The content of component (B) is preferably 95 mass % or less, more preferably 90 mass % or less, and even more preferably 75 mass % or less, in 100 mass % of the etching composition, because the component (B) has excellent selective oxidation property for silicon germanium.

<Component (C)>
The etching composition of the present invention preferably contains a fluorine-containing compound (C) (hereinafter sometimes referred to as "component (C)") in addition to the components (A) and (B).

The etching composition contains the fluorine-containing compound of component (C), which exerts the effect of etching the surface of oxidized silicon or silicon germanium.

Examples of fluorine-containing compounds include hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid. These fluorine-containing compounds may be used alone or in combination of two or more. Among these fluorine-containing compounds, hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid are preferred, with hydrofluoric acid being more preferred, because they have excellent selective solubility for silicon germanium.

The content of the component (C) is preferably 0.01 mass % or more, and more preferably 0.1 mass % or more, in 100 mass % of the etching composition, because the component (C) has excellent solubility for silicon germanium.
From the viewpoint of reducing damage to silicon, the content of the component (C) is preferably 5 mass % or less, and more preferably 3 mass % or less, in 100 mass % of the etching composition.

<Component (D)>
The etching composition of the present invention preferably contains water (D) (hereinafter sometimes referred to as “component (D)”) in addition to the components (A), (B), and (C).

The etching composition contains water (component (D)), which exerts the effect of inhibiting etching of silicon.

The content of the component (D) is preferably 5% by mass or more, and more preferably 10% by mass or more, in 100% by mass of the etching composition, because the etching composition is easily produced.
The content of the component (D) is preferably 30 mass % or less, and more preferably 20 mass % or less, in 100 mass % of the etching composition, because the etch rate can be improved.

<Other Ingredients>
The etching composition of the present invention may contain other components in addition to the component (A), the component (B), the component (C), and the component (D).

<Mass ratio of each component>
The mass ratio of the component (B) to the component (A) in the etching composition of the present invention (mass of component (B)/mass of component (A), hereinafter referred to as "(B)/(A)") is preferably 1 to 10, and more preferably 2 to 5, because this provides an excellent balance between the effect of oxidizing the surface of silicon or silicon germanium and the effect of protecting silicon or an oxide film.

The mass ratio of component (C) to component (A) in the etching composition of the present invention (mass of component (C)/mass of component (A), hereinafter referred to as "(C)/(A)") is preferably 0.005 to 0.1, and more preferably 0.01 to 0.05, since this provides an excellent balance between the effect of oxidizing the surface of silicon or silicon germanium and the effect of etching the surface of oxidized silicon or silicon germanium.

The mass ratio of component (C) to component (B) in the etching composition of the present invention (mass of component (C)/mass of component (B), hereinafter referred to as "(C)/(B)") is preferably 0.001 to 0.05, and more preferably 0.002 to 0.025, since this provides an excellent balance between the effect of protecting silicon or an oxide film and the effect of etching the surface of oxidized silicon or silicon germanium.

<Method of manufacturing the etching composition>
The method for producing the etching composition of the present invention is not particularly limited, and the composition can be produced by mixing the component (A) and the component (B), and, if necessary, the component (C), the component (D), and other components.
The order of mixing is not particularly limited, and all of the components may be mixed at once, or some of the components may be mixed in advance and then the remaining components may be mixed.

<Physical Properties of Etching Composition>
The etching rate ER _Si of silicon of the etching composition of the present invention is preferably 1.0 nm/min or less, more preferably 0.5 nm/min or less, and even more preferably 0.3 nm/min or less, because the etching composition has excellent selective solubility of silicon germanium in silicon.

The etching rate ER _SiGe of silicon germanium of the etching composition of the present invention is preferably 0.5 nm/min or more, more preferably 1.0 nm/min or more, and even more preferably 2.0 nm/min or more, because the etching composition has excellent selective solubility of silicon germanium in silicon.

The etching composition of the present invention has a dissolution selectivity ratio DSR (ER _SiGe /ER _Si ) of silicon to silicon germanium of preferably 10 or more, more preferably 15 or more, since the etching composition has excellent selective solubility of silicon germanium relative to silicon.

Since silicon oxide may be exposed in a structure containing silicon and silicon germanium, it is preferable to suppress dissolution of the silicon oxide.
The etching rate ER _SiOx of silicon oxide of the etching composition of the present invention is preferably 50 nm/min or less, more preferably 40 nm/min or less, and even more preferably 30 nm/min or less.

The etch rate ER _Si , the etch rate ER _SiGe , the dissolution selectivity DSR, and the etch rate ER _SiOx are measured and calculated by the method described in the Examples section below.

<Target to be etched by etching composition>
The etching composition of the present invention suppresses dissolution of silicon, promotes dissolution of silicon germanium, and has excellent selective solubility of silicon germanium relative to silicon. Therefore, the etching composition of the present invention is suitable for etching structures containing silicon and silicon germanium, such as semiconductor devices, and is particularly suitable for structures in which silicon and silicon germanium are alternately stacked, which are necessary for forming a GAA type FET.

The silicon content in the silicon germanium to be etched is preferably 10 mass % or more, and more preferably 20 mass % or more, based on 100 mass % of silicon germanium, in order to be suitable for etching with the etching composition of the present invention.
On the other hand, the silicon content in silicon germanium is preferably 95 mass % or less, and more preferably 85 mass % or less, based on 100 mass % of silicon germanium, since this is suitable for etching with the etching composition of the present invention.
Further, the germanium content in silicon germanium is preferably 5 mass % or more, and more preferably 15 mass % or more, based on 100 mass % of silicon germanium, since this is suitable for etching with the etching composition of the present invention.
On the other hand, the germanium content in silicon germanium is preferably 90 mass % or less, and more preferably 80 mass % or less, based on 100 mass % of silicon germanium, since this is suitable for etching with the etching composition of the present invention.

The silicon germanium alloy film can be produced by deposition using known methods, but it is preferable to produce it by deposition using a crystal growth method, as this provides excellent mobility of electrons and holes after transistor formation.

In structures containing silicon and silicon germanium, or structures in which silicon and silicon germanium are alternately stacked, silicon oxide may be exposed.

<Etching Method>
The etching method of the present invention is a method for etching a structure containing silicon and silicon germanium using the etching composition of the present invention.

The etching method can be any known method, such as batch or single wafer.

The temperature during etching is preferably 15° C. or higher, and more preferably 20° C. or higher, since this allows the etching rate to be improved.
The temperature during etching is preferably 100° C. or less, and more preferably 80° C. or less, from the viewpoints of reducing damage to the substrate and ensuring etching stability.
Here, the temperature during etching corresponds to the temperature of the etching composition during etching.

<Applications>
The etching composition and the etching method of the present invention can be suitably used in the manufacture of semiconductor devices, which includes a step of etching a structure containing silicon and silicon germanium, and can be particularly suitably used in the manufacture of GAA type FETs, which includes a step of etching a structure containing silicon and silicon germanium, since the etching composition and the etching method of the present invention suppress the dissolution of silicon, promote the dissolution of silicon germanium, and have excellent selective solubility of silicon germanium relative to silicon.

The present invention will be described in more detail below using examples, but the present invention is not limited to the description of the following examples as long as it does not deviate from the gist of the invention.

<Ingredients>
In the following Examples and Comparative Examples, the following materials were used as raw materials for producing the etching compositions.
Component (A-1): Nitric acid Component (A'-1): Hydrogen peroxide Component (B-1): Acetic acid Component (C-1): Hydrofluoric acid Component (D-1): Water

<Method of measuring silicon etch rate>
A silicon substrate with a thickness of about 0.7 mm cut to a size of 7 cm × 7 cm was immersed in the etching compositions obtained in the Examples and Comparative Examples at 25°C for 60 minutes or more, and the mass of the silicon substrate before and after immersion was measured using a balance. From the change in mass, the silicon etch rate ER _Si [nm/min] was calculated using the following formula (1).
ER _Si [nm/min]=mass change of silicon substrate÷(density of silicon substrate×surface area of silicon substrate×immersion time of silicon substrate) (1)

<Method of Measuring the Etch Rate of Silicon Germanium>
A silicon substrate having a silicon germanium alloy film (thickness: 50 nm) having a germanium content of 25 mass % formed on its surface was immersed in the etching compositions obtained in the Examples and Comparative Examples at 25° C., and the change in film thickness was measured using a spectroscopic ellipsometer (model name: UVISEL ER, manufactured by HORIBA, Ltd.), and the etch rate of silicon germanium ER _SiGe [nm/min] was calculated using the following formula (2).
ER _SiGe [nm/min] = change in thickness of silicon germanium alloy film ÷ immersion time of silicon substrate (2)

<Dissolution selectivity between silicon and silicon germanium>
The dissolution selectivity ratio DSR of silicon and silicon germanium was calculated using the following formula (3).
DSR=ER _SiGe [nm/min] ÷ ER _Si [nm/min] (3)

<Method of Measuring Silicon Oxide Etch Rate>
A silicon substrate having a silicon oxide film (thickness: 280 nm) formed on its surface was immersed in the etching compositions obtained in the Examples and Comparative Examples at 25° C., and the change in film thickness was measured using a reflection spectroscopic film thickness meter (model name "FE-3000", manufactured by Otsuka Electronics Co., Ltd.), and the etch rate of silicon oxide ER _SiOx [nm/min] was calculated using the following formula (4).
ER _SiOx [nm/min] = change in thickness of silicon oxide film ÷ immersion time of silicon substrate (4)

[Example 1]
The etching composition was obtained by mixing the respective components so that, based on 100 mass% of the etching composition, the component (A-1) was 21.0 mass%, the component (B-1) was 62.5 mass%, the component (C-1) was 1.0 mass%, and the component (D-1) was 15.5 mass%.
The evaluation results of the obtained etching compositions are shown in Table 1.

[Examples 2 to 4, Comparative Examples 1 to 3]
The same procedure as in Example 1 was carried out except that the types and contents of the raw materials were as shown in Table 1, to obtain etching compositions.
The evaluation results of the obtained etching compositions are shown in Table 1.

As can be seen from Table 1, the etching compositions obtained in Examples 1 to 4 suppress the dissolution of silicon, promote the dissolution of silicon germanium, and have excellent selective solubility of silicon germanium relative to silicon.

The etching composition obtained in Comparative Example 1, which contains less component (B) and more component (D), suppressed the dissolution of silicon, but also suppressed the dissolution of silicon germanium, and was inferior in the selective solubility of silicon germanium relative to silicon.

The etching composition obtained in Comparative Example 2, which contains less component (B) and more component (A), promoted the dissolution of silicon germanium, but also promoted the dissolution of silicon, resulting in poor selective solubility of silicon germanium relative to silicon.

The etching composition obtained in Comparative Example 3, which used hydrogen peroxide as component (A), suppressed the dissolution of silicon to some extent and promoted the dissolution of silicon germanium to some extent, but was inferior in the selective solubility of silicon germanium relative to silicon.

The etching composition of the present invention and the etching method of the present invention using this etching composition suppress dissolution of silicon, promote dissolution of silicon germanium, and have excellent selective solubility of silicon germanium relative to silicon, and therefore can be suitably used in the manufacture of semiconductor devices, and in particular, can be suitably used in the manufacture of GAA type FETs.

Claims (8)

An etching composition for selectively dissolving silicon germanium relative to silicon, comprising an oxidizing agent (A) and an organic acid (B), wherein the oxidizing agent (A) contains nitric acid, and the content of the organic acid (B) is 50 mass% or more in 100 mass% of the etching composition;
Further, water (D) is contained,
An etching composition, wherein the content of water (D) is 20 mass% or less (excluding 20 mass%) in 100 mass% of the etching composition . The etching composition according to claim 1, wherein the organic acid (B) contains at least one compound selected from the group consisting of acetic acid, propionic acid, oxalic acid, and citric acid. The etching composition according to claim 1 or 2, further comprising a fluorine-containing compound (C). The etching composition according to claim 3, wherein the fluorine-containing compound (C) comprises at least one compound selected from the group consisting of hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid. The etching composition according to claim 3 or 4, wherein the content of the fluorine-containing compound (C) is 5 mass% or less in 100 mass% of the etching composition. An etching method, comprising etching a structure containing silicon and silicon germanium using the etching composition according to any one of claims 1 to 5 . A method for manufacturing a semiconductor device, comprising the step of etching a structure containing silicon and silicon germanium with the etching composition according to any one of claims 1 to 5 . A method for manufacturing a gate-all-around transistor, comprising the step of etching a structure containing silicon and silicon germanium with the etching composition according to any one of claims 1 to 5 .