KR20020079300A - High Density Plasma Source Apparatus and Method - Google Patents

Abstract

PURPOSE: A high density plasma source and a generating method thereof are provided to form high density plasma by using RF power of higher frequency and distribute uniformly plasma by using RF power of lower frequency. CONSTITUTION: A high density plasma source is formed with power supply sources(10) of n number, matching networks(20) of n number, and a frequency combiner(30). The power supply sources(10) of n number are used for supplying electric power sources with different frequencies(F1,F2,...,Fn) of n number. A frequency combiner(30) is used for combining RF powers of n number. The frequency combiner(30) is formed by frequency filters(31 to 39) of n number. A high pass filter(31) is used for shielding frequencies of the highest frequency and below. A band pass filter(32) is used for passing frequencies between the lowest frequency and the highest filter. A low pass filter(39) is used for shielding frequencies of the lowest frequency or more.

Description

High Density Plasma Source Apparatus and Method

The present invention relates to a high density plasma generating source and method, and more particularly to an apparatus and method for generating a high density plasma in a plasma processing equipment for manufacturing a semiconductor or electronic component.

The present invention provides a high density plasma source and method for applying a power having two or more different frequencies to the antenna to improve the plasma density and density uniformity.

Plasma processing equipment equipped with high density plasma generators can generate high density plasma at lower pressure than conventional capacitive plasma generators and can independently control plasma density and ion bombardment energy. Poetry has many advantages.

Figures 1 through 3 show schematic diagrams of existing high density plasma devices. The high density plasma generators 81, 82, and 83 may include a power supply including a power source 10 and a matcher 20, a reactor 70 including an antenna 40, a dielectric window 50, and a substrate chuck 60. And substrate chuck power supply. In addition, the gas injection part and the vacuum pumping part for plasma generation among the components of the high-density plasma generation source are commonly used parts and are omitted from Fig. 1 to Fig. 3.

High-density plasma sources using antennas have been developed in various ways according to the shape of the antenna, the mounting position and the power application position, and the frequency of the applied power.

Depending on the shape of the antenna, a Helicon Plasma Source using a Helicon Antenna (81, Figure 1) and a Transformer Coupled Plasma Source using a Flat Inductor Coil (82, Fig. 2), Inductivc Coupled Plasma Source (83, Fig. 3) using helical coils or spiral coils.

The antenna is generally mounted outside of the dielectric window 50, but sometimes also inside the dielectric window.

According to the location where the power is applied to the antenna, it is classified into induction coupling and high density plasma generating sources of resonance coupling.

In order to induce a high density plasma by using a high density plasma generating structure by a combination of the shape, the mounting position, and the power application position of the antenna, a sinusoidal wave of a specific frequency is generally applied between 100 kHz and 27.12 MHz. The most used frequency is 13.56MHz, and 2MHz, 1.8MHz, etc. are also widely used. In general, the plasma density increases with increasing frequency while the uniformity of the plasma density decreases.

Therefore, in order to improve the uniformity of the plasma density while maintaining the high plasma density, (a) a method of combining the shape of the antenna, the mounting position, and the power application position; (B) Plasma confinement by mounting magnets near the plasma generating source; (C) a method of appropriately combining the shape, dimensions, and materials of the dielectric window; (D) a method of properly combining the shape, dimensions, and materials of the reactor 70; (ㅁ) A method of controlling the shape, dimensions, and material of the substrate chuck 60 and its relative position with the antenna has been developed.

The present invention provides a high density plasma generating source and method by applying power having two or more different frequencies to an antenna, thereby improving plasma density uniformity.

In general, absorption of high frequency energy in an inductively coupled plasma source is absorbed by the surface layer of the plasma. This is similar to the fact that the high frequency current flowing through the conductor is limited to the skin depth area. In the case of high frequency current flowing through a conductor, the skin depth is inversely proportional to the conductivity of the conductor and inversely proportional to the frequency of the power applied to the conductor.

The high frequency power applied to the antenna in the inductively coupled plasma source is supplied to the plasma mainly by ohmic dissipation of electrons within the skin depth of the plasma. The skin depth at which the ohmic loss of electrons occurs is expressed as

Where δ is the skin depth, ω is the high frequency, μ ₀ is the permeability of the vacuum, and σ _DC is the plasma DC conductivity. For inductively coupled plasma, the skin depth is inversely proportional to the square root of the frequency. The plasma bulk is divided into a plasma generation region and a diffusion region of the skin depth region. In general, the substrate for plasma processing is present in the diffusion region, the plasma density and density distribution of the region where the plasma substrate is present is closely related to the skin depth.

In the present invention, by supplying a high frequency power of two or more frequencies to one antenna to generate a plasma having a different skin depth, to form a high-density plasma by a higher frequency high-frequency power, the plasma density by a lower frequency high-frequency power It is an object of the present invention to provide a high density plasma generating source and method for uniformizing the distribution.

1 is a block diagram of a conventional high density plasma apparatus.

(a) helicon plasma generator, (b) coupled plasma generator, (c) inductively coupled plasma generator

2 is a block diagram of a high density plasma generating source of the present invention

3 is an embodiment of a high density plasma generating source stably combining two frequencies of the present invention.

10. Power source 80. High density plasma generation source

20. Matcher 81. Helicon plasma generator

30. Coupler 82. Transformer-coupled plasma source

40. Antenna 83. Inductively coupled plasma generator

50. Dielectric Window 90. Substrate Chuck Matcher

60. Substrate Chuck 100. Substrate Chuck Power Source

70. Reactor

A configuration example of the present invention is shown in FIG. Inductively coupled plasma impedance may be equivalently expressed as an inductance, a capacitor, and a reactance component by inductive coupling of an antenna and a plasma. In the consideration of the present invention, in order to more efficiently explain the method and apparatus of power supply, the plasma impedance is replaced with a simple antenna. In order to supply two or more high frequency powers to one antenna, as shown in Fig. 4, n power sources supplying power of _n different frequencies (F ₁ , F ₂ , ...., F _n ) Supply 10, n matching network (20) and one frequency combiner (Combiner) (30). The n high frequency powers coupled in the frequency combiner are superpositioned and applied to the antenna for generating high density plasma. Since the power source and the matching unit are high frequency components commonly used in the field of the present invention, detailed description thereof will be omitted.

The high frequency power from the n power sources is fed to the n matchers through the transmission line, respectively. The n matchers are each automatically matched to provide maximum power to the high density plasma, briefly shown by the antenna. The high frequency power supplied from each matcher is supplied to the antenna through each suitably designed frequency filter and transmission line. n frequency filters form one frequency combiner. The design criteria of the n frequency filters are as follows. As shown in Fig. 4, if the magnitude of each frequency is F ₁ > F ₂ >...> F _n , the filter of the frequency of F _{1 has} a frequency below F ₁ . A high pass filter 31 for blocking; A low pass filter 39 is attached to the lowest frequency F _n , and a band pass filter 32 for passing only respective frequencies in the frequency region between F 1 and F _n. do. All n power sources are electrically decoupled by a frequency combiner consisting of frequency filters. Therefore, the antenna is stably supplied with high frequency power having n frequencies.

By applying power of n frequencies to the antenna, n skin depths are created in the inductively coupled plasma. High-density plasma is induced on the surface of the plasma by the high frequency power having the highest frequency, and n-1 skin depths are formed inside the plasma bulk by the high frequency power having a low frequency. The present invention provides a method of improving the plasma density and density uniformity by penetrating the skin depth to a deeper region of the plasma bulk, thereby providing high frequency energy to the plasma bulk in a more aggressive manner than the formation of the plasma bulk by diffusion.

In order to more accurately convey the spirit of the present invention, an embodiment of stably combining two frequencies is shown in FIG. In this embodiment, one power source uses a frequency of 13.56 MHz and the other power source uses a frequency of 400 kHz. Two frequencies are connected by connecting a high pass filter with a series-connected capacitor to a 13.56 MHz power source and a low pass filter with a capacitor and an inductor connected to the 400 kHz power source. It provides a frequency combiner that combines stably. If the DC conductivity of the plasma is the same for the frequencies of 13.56 MHz and 400 kHz, the ratio of the skin depth of the two high frequency powers is about 6.

Where δ is the skin depth, ω is the high frequency, μ ₀ is the permeability of the vacuum, and σ _DC is the plasma DC conductivity.

Therefore, the application of the frequencies of 13.56 MHz and 400 kHz simultaneously increases the skin depth by about six times compared to the case of applying only the 13.56 MHz frequency, thereby providing the effect of generating high density plasma and improving density uniformity.

The present invention supplies a high frequency power of two or more frequencies to one antenna to generate a plasma having a different skin depth, thereby forming a high density plasma by a higher frequency high frequency power and a plasma density by a lower frequency high frequency power. Provided are a high density plasma generating source and method for uniform distribution. More specifically, as can be easily inferred by the idea described above, there is provided a high density plasma generating source and method that can control the plasma density and density uniformity by appropriately selecting two or more frequencies and supplying power appropriately. do.

Claims (5)

A power supply composed of a power source, a matcher, and a frequency combiner to supply power to the antenna; Reactor composed of antenna, dielectric window, substrate chuck to generate a plasma, Gas supply part for plasma generation, In the high-density plasma generation source consisting of a vacuum pumping portion for maintaining a vacuum in the reactor, The antenna is electrically connected to the frequency combiner, And power having two or more different frequencies through the frequency combiner to the antenna. 2. The high density plasma generating source of claim 1, wherein the frequency combiner is made of a combination of frequency filters. 2. The high density plasma generator of claim 1, wherein the high frequency wave comprises a frequency in the range of 100 kHz to 27.12 MHz. 2. The high density plasma source of claim 1, wherein the low frequency comprises a frequency in the DC to 27.12 MHz range. A high density plasma generating method, comprising applying power having two or more different frequencies to one antenna to control plasma density and density uniformity.