KR20210103198A - Inductively coupled plasma source - Google Patents

Abstract

The present invention relates to an inductively coupled plasma source for increasing uniformity and efficiency of plasma used in a semiconductor manufacturing process, etc. According to the present invention, the inductively coupled plasma source comprises an antenna coil to which RF power is applied to generate an RF magnetic field. The antenna coil (111) is a conductive strip having a rectangular cross section with a height (h) and a thickness (t) and is spirally wound. The antenna coil (111) satisfies (t + d) < r / N and 1 < h / t, wherein d is a spacing between adjacent strips, N is the number of turns, and r is the design radius of the antenna coil.

Description

Inductively coupled plasma source

The present invention relates to an inductively coupled plasma source for improving the uniformity and efficiency of plasma used in a semiconductor manufacturing process or the like.

Plasma is a fourth material, not a solid, liquid, or gas, in which a part of the gas is ionized, and is composed of neutral particles, ions, and electrons. However, it is not defined as a plasma simply because ions and electrons are gathered. In order to become a plasma state, first, a sufficient number of “ion-electron” pairs must exist in a given system for statistical processing, and secondly, the entire system must be macroscopically processed. It should be electrically neutral when viewed as a , and therefore plasma also has a collective behavior as seen in a general neutral gas system.

Such plasma is used in the manufacture of various devices such as semiconductor integrated circuits and flat panel display manufacturing processes, physical vapor deposition (PVD), plasma enhanced chemical vapor deposition (PECVD: Plasma Enhanced Chemical Vapor Deposition), It is used in various surface treatment processes such as dry etching, sputtering, in-situ chamber cleaning, and plasma immersion ion implantation.

As a plasma generating method for plasma treatment, various methods such as inductively coupled plasma (ICP), electron cyclotron resonance (ECR), and surface wave plasma (SWP) are being developed.

On the other hand, the size of wafers for semiconductor devices or substrates for flat panel display devices is becoming larger in order to reduce costs and improve productivity. Therefore, plasma equipment for semiconductor processes can also secure high plasma density and uniformity to increase the processing area. A plasma device is required.

As such a plasma device, an inductively coupled plasma (ICP) generator has the advantage of easily obtaining high-density plasma, and has a simple structure, so it is in the spotlight as a next-generation equipment for manufacturing large-area wafers.

A general inductively coupled plasma generator consists of a plasma source that generates an induced electric field for generating plasma, and a chamber in which the actual process is performed through the interaction of ions in plasma and reactive gas, and the plasma source and chamber are made of an insulating plate are separated

An inductively coupled plasma source is an antenna (also referred to as "ICP antenna") that has a single-wire spiral structure and generates an electromagnetic field by applied RF power, and is manufactured by spirally winding a coil having a circular or square cross section.

In such an ICP antenna, when an electromagnetic field having a non-uniform density is generated, a plasma having a non-uniform density distribution is generated inside the chamber, and when the plasma density is non-uniform, it is difficult to accurately control the wafer, making it difficult to precisely process the wafer. In particular, this problem becomes a more serious problem in a large area wafer.

Laid-open Patent Publication No. 10-2007-0097232 (published on October 4, 2007)

An object of the present invention is to provide an inductively coupled plasma source capable of improving plasma efficiency (density) and uniformity.

An inductively coupled plasma source according to an aspect of the present invention for achieving this object is an inductively coupled plasma source comprising an antenna coil to which RF power is applied to generate an RF magnetic field, wherein the antenna coil has a height A conductive strip having a rectangular cross section having (h) and a thickness (t) and spirally wound, satisfying the following equation.

[Equation]

Here, d is the distance between adjacent strips, N is the number of turns, and r is the design radius of the antenna coil.

Preferably, the thickness t is 0.5 mm ≤ t ≤ 10 mm, 2 ≤ h/t ≤ 100, more preferably, the thickness t is 1 mm and the height h is 20 mm, or the thickness t is 0.5 mm and the height h is 50 mm.

The inductively coupled plasma source of the present invention is an inductively coupled plasma source including an antenna coil to which RF power is applied to generate an RF magnetic field, wherein the antenna coil is a square having a height (h) and a thickness (t). As a conductive strip having a cross section of

[Equation]

d is the spacing between adjacent strips, N is the number of turns, and r is the design radius of the antenna coil.

1 is a perspective configuration diagram of an inductively coupled plasma source according to an embodiment of the present invention;
2 is a cross-sectional configuration diagram of an inductively coupled plasma source according to an embodiment of the present invention;
3 is a graph showing the relationship between plasma density (np) and RF power (wp);
4 is a configuration diagram of a plasma device used in the simulation;
5 (a) (b) is a configuration diagram of the plasma source of the comparative example and this embodiment used in the simulation, respectively,
6 (a) (b) is a distribution diagram of power flow according to the simulation results of the comparative example and the present embodiment, respectively.

Specific structural or functional descriptions presented in the embodiments of the present invention are only exemplified for the purpose of describing embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention may be implemented in various forms. In addition, it should not be construed as being limited to the embodiments described herein, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Meanwhile, in the present invention, terms such as first and/or second may be used to describe various components, but the components are not limited to the above terms. The above terms are used only for the purpose of distinguishing one component from other components, for example, within the scope of not departing from the scope of rights according to the concept of the present invention, the first component may be named as the second component, Similarly, the second component may also be referred to as a first component.

When a component is referred to as being “connected” or “connected” to another component, it should be understood that it may be directly connected or connected to the other component, but other components may exist in between. something to do. On the other hand, when an element is referred to as being “directly connected” or “in direct contact with” another element, it should be understood that no other element is present in the middle. Other expressions for describing the relationship between elements, that is, expressions such as "between" and "immediately between" or "adjacent to" and "directly adjacent to", should be interpreted similarly.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. As used herein, terms such as "comprises" or "have" are intended to designate the presence of an embodied feature, number, step, action, component, part, or combination thereof, one or more other features or numbers, It should be understood that the possibility of the presence or addition of steps, operations, components, parts or combinations thereof is not precluded in advance.

1 is a perspective configuration diagram of an inductively coupled plasma source according to an embodiment of the present invention, and FIG. 2 is a cross-sectional configuration diagram of an inductively coupled plasma source according to an embodiment of the present invention.

1 and 2, the inductively coupled plasma source 100 of this embodiment includes an antenna coil 111 having a single-wire spiral structure, and the antenna coil 111 has a height (h) and a thickness (t). ) is a strip with a rectangular cross-section.

The antenna coil 111 is provided with terminals 111a and 111b respectively connected to the ground and RF power at both ends. Reference numeral 1 denotes a dielectric dome that divides the plasma source and the chamber.

The antenna coil 111 is a helical conductive strip having a rectangular cross section with a certain thickness t and a height h and a certain number of turns N within a certain radius r, preferably, the thickness t ) is greater than the height (h) (t<h). The radius r of the antenna coil 111 may be determined by the size of a chamber in which plasma is generated.

When RF power is applied to the antenna coil 111 and an RF current flows, a magnetic field is formed along the antenna coil 111 and the generated magnetic field forms an induced electric field in the chamber to generate plasma.

The density of the plasma generated within the chamber is closely dependent on the RF power and the geometry of the antenna coil.

3 is a graph showing the relationship between plasma density (n _p ) and RF power (w _{p ).}

The plasma density (n _p ) may be expressed as in the following [Equation 1].

[Equation 1]

a _c is the coupling parameter, n _L is the maximum plasma density, and α is the undefined parameter.

_{Plasma density (n p} ) for the case where the RF power applied in [Equation 1] is low and large is the same as in [Equation 2].

[Equation 2]

In a typical commercial plasma generating apparatus, it is used in the middle area (hatch area in FIG. 3 ).

Therefore, as the RF power increases, the plasma density (n _p ) increases proportionally, and the proportional coefficient is determined by the _{coupling parameter (a c ).}

In general, the coupling parameter (a _c ) has a characteristic that is proportional to the number of turns (N) of the antenna coil and inversely proportional to the impedance (Z) as shown in Equation (3).

[Equation 3]

In general, the impedance (Z) of the antenna coil is proportional to the surface area (S) of the antenna coil as shown in Equation 4 and is inversely proportional to the number of turns (N).

[Equation 4]

t and h are the thickness and height of the antenna coil, respectively.

Therefore, it can be seen that an efficient antenna coil maximizes the number of turns (N) within the allowed radius (r) and increases the surface area (S) as the optimal design condition. It can be expressed as the following [Equation 5].

[Equation 5]

d is the spacing between the spirally wound antenna coils (see FIG. 2 ).

As described above, the radius r of the antenna coil corresponds to the design radius determined by the size of the chamber of the plasma generating device.

Next, in order to minimize the impedance (Z) of the antenna coil at the determined number of turns (N), it is preferable to design the maximum height (h) of the strip having a rectangular cross section, and therefore the height (h) of the strip is equal to the thickness (t) ) is preferably greater than (1 < h/t)

The antenna coil having the above-described rectangular cross-section and consisting of a spirally wound strip can be manufactured to satisfy these conditions, thereby increasing efficiency and plasma density.

For example, when the antenna coil of this embodiment (refer to FIG. 1) has 5 turns and a design radius of 150 mm, the condition of [Equation 6] must be satisfied.

[Equation 6]

If the thickness (t) and the spacing (d) of the antenna coil are designed to be the same (t = d), the thickness (t) of the antenna coil is 15 mm or less and the height (h) is preferably 15 mm or more. .

Considering the practicality of manufacturing the antenna coil, the thickness (t) is preferably 0.5 mm ≤ t ≤ 10 mm, and it is preferable to determine the height (h) within the range of 2 ≤ h/t ≤ 100 .

The antenna coil of this embodiment has a thickness (t) of 1 mm and a height (h) of 20 mm (h/t=20). Meanwhile, when the thickness t is 0.5 mm and the height h is 50 mm (h/t=100), it can be used as an appropriate antenna coil.

Meanwhile, even when the thickness t is 2 mm and the height h is 20 mm (h/t=10), it can be used as an appropriate antenna coil.

4 is a block diagram of a plasma apparatus used for simulation. The antenna coil 220 is positioned on the insulating dome 211 in the chamber 210 , and RF power is applied to the antenna coil 220 to obtain an electromagnetic field. A power flow (arrow direction) is generated by The simulation is a measurement of power flow in the horizontal plane VP below a predetermined interval (6 mm) in the insulating dome 211, and the simulation results are shown in FIG. 6(a)(b). Reference numeral 212 denotes a chuck on which a plasma-treated object is placed.

5 (a) (b) is a configuration diagram of a plasma source of a comparative example and this embodiment used for simulation, respectively, (a) shows an antenna coil having a rectangular cross section (12 × 12 mm) as a comparative example and (b) shows an antenna coil having a thin cross-section (1×20 mm) as this embodiment. The conditions for the shape (number of turns, etc.) except for the size of the cross section in the comparative example and this example were designed to be the same.

By applying the plasma source of the comparative example and the present embodiment to the plasma apparatus of FIG. 4 , respectively, simulations of power flow under the same conditions were made.

6 (a) (b) is a power flow distribution according to the simulation results of the comparative example and this example, respectively, and specifically, [Table 1] and [Table 2] are specific positions for the comparative example and this example, respectively The quantitative data values of the simulation results for the power (VA) of (#1-#9) are shown.

[Table 1]

From the simulation results, the average power flow of the comparative example is 2.28 (VA/m 2 ).

[Table 2]

From the simulation results, it can be seen that the average power flow of this example is 5.43 (VA/m 2 ), and the power efficiency is about 2.38 times higher than that of the comparative example.

The present invention described above is not limited by the above-described embodiments and the accompanying drawings, and it is common in the technical field to which the present invention pertains that various substitutions, modifications, and changes are possible without departing from the technical spirit of the present invention. It will be clear to those who have the knowledge of

111: antenna coil

Claims (6)

In an inductively coupled plasma source comprising an antenna coil to which RF power is applied to generate an RF magnetic field,
The antenna coil is
A conductive strip having a rectangular cross section having a height (h) and a thickness (t) and spirally wound, an inductively coupled plasma source satisfying the following equation.
[Equation]

d is the spacing between adjacent strips, N is the number of turns, and r is the design radius of the antenna coil. The inductively coupled plasma source according to claim 1, wherein the thickness (t) is in the range of 0.5 mm ≤ t ≤ 10 mm, and 2 ≤ h/t ≤ 100. 3. The inductively coupled plasma source of claim 2, wherein the thickness (t) is 1 mm and the height (h) is 20 mm. 3. The inductively coupled plasma source according to claim 2, characterized in that the thickness (t) is 0.5 mm and the height (h) is 50 mm. 3. The inductively coupled plasma source according to claim 2, wherein the thickness (t) is 2 mm and the height (h) is 20 mm. A plasma generating apparatus comprising the inductively coupled plasma source according to claim 1 .

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