TWI803098B - Ion source device - Google Patents

Abstract

The application discloses an ion source device, comprising a discharge cavity, a spiral coil and an ion source cavity which are arranged coaxially from the inside to the outside in sequence; the outer wall of the discharge cavity is provided with a metal foil, which can shield the intensity of the edge magnetic field in the discharge cavity neutralizes the high plasma density caused by the skin effect, so that the plasma density distribution in the discharge cavity is uniform. The width W of the metal foil ranges from 1 to 20 mm, and the thickness T of the metal foil ranges from 0.1 mm to t, wherein t is the skin depth. According to the difference between the edge plasma density in the discharge cavity and the plasma density in the center area, the thickness T and surface area of the metal foil are selected. By adding a Faraday structure outside the discharge cavity, and performing power distribution on the Faraday structure, the plasma density is adjusted for different working conditions, thereby effectively improving the etching uniformity.

Description

Ion source device

The invention relates to the field of ion beam etching, and in particular to an ion source device with adjustable plasma density.

related application

This application claims the priority of the Chinese patent application with the application number 2021100021686 and the application title "An Ion Source Device with Adjustable Plasma Density" filed with the China Patent Office on January 4, 2021, the entire contents of which are incorporated herein by reference Applying.

Ion beam etching can be used for etching various metals (Ni, Cu, Au, Al, Pb, Pt, Ti, etc.) and their alloys, as well as non-metals, oxides, nitrides, carbides, semiconductors, polymers, ceramics, Infrared and superconducting materials. The principle is to use the principle of glow discharge to decompose argon gas into argon ions, and the argon ions are accelerated by the anode electric field to physically bombard the surface of the sample to achieve the effect of etching. The etching process is to fill the Ar gas into the discharge chamber of the ion source and ionize it to form a plasma, and then the grid will draw out the ions in a beam shape and accelerate them. The ion beam with a certain energy enters the working chamber and shoots to the solid surface to bombard the solid surface. Atoms, so that material atoms sputtering, to achieve the purpose of etching Yes, it is purely physical etching. Since the ions are not generated by glow discharge, but are emitted by an independent ion source, the inert gas ions are accelerated by an electric field and then enter the vacuum chamber where the sample is placed. The vacuum degrees of the ion beam source and the sample chamber can reach their respective optimal levels. State, the purity of the membrane is very high.

The ion source is a device that ionizes neutral atoms or molecules and extracts the ion beam from it. The quality of the ion source directly affects the etching performance. The existing ion sources mainly include Kaufman ion source, radio frequency ion source, microwave electron cyclotron resonance (ECR ) ion source and Hall ion source (End Hall), among them, radio frequency ion source is widely used in the fields of ion beam etching, material surface modification and thin film processing due to its advantages of high density, no pollution, easy maintenance and long life , the principle is that the working principle is: when a certain radio frequency current flows into the radio frequency coil placed on the dielectric window, an induced radio frequency electric field is induced in the discharge chamber, and the induced electric field will accelerate the movement of electrons, making them continuously collide with neutral gas molecules Ionization, whereby RF energy from the induction coil is coupled into the ionized gas to maintain a plasma discharge. Most of the ions generated by radio frequency discharge are drawn out by the grid system to form an ion beam. The radio frequency ion source has the characteristics of electrodeless discharge, stable operation for a long time, large uniform area, precise control of ion beam density, and low pollution. In the ion beam etching process been widely used in.

When the existing ion source is in use, when the coil is energized, the plasma density is the highest in the skin layer, and the plasma density gradually decays in the area outside the skin layer. Under low pressure conditions, the plasma density in the discharge chamber is high The distribution is parabolic. With the increase of current, the edge skin effect is enhanced. The plasma density distribution in the discharge chamber generally presents a saddle-shaped distribution, and the plasma density center and edge distribution in the discharge chamber is uneven, as shown in Figure 1 and Figure 2. The existing method is to solve this problem by opening apertures of different specifications on the screen grid, but it can only be improved for certain working conditions, and multi-working conditions cannot be adjusted, which affects the uniformity of etching.

Each exemplary embodiment of the present application provides an ion source device with adjustable plasma density. The ion source device with adjustable plasma density adds a Faraday structure outside the discharge chamber and distributes power to the Faraday structure. The plasma density is adjusted to effectively improve the etching uniformity.

Each exemplary embodiment of the present application provides an ion source device with adjustable plasma density, which includes a discharge chamber, a helical coil, and an ion source chamber arranged coaxially from the inside to the outside; a metal foil is arranged on the outer wall of the discharge chamber, and the metal The foil can shield the magnetic field strength at the inner edge of the discharge chamber, neutralize the high plasma density caused by the skin effect, and make the plasma density distribution in the discharge chamber uniform.

In one embodiment, the width W of the metal foil ranges from 1 to 20 mm, and the thickness T of the metal foil ranges from 0.1 mm to t, where t is the skin depth of the helical coil. The thickness T and surface area of the metal foil are selected according to the difference between the edge plasma density in the discharge chamber and the plasma density in the central region.

In one embodiment, when the edge plasma density is higher than the central region by more than 3%, the thickness T or surface area of the metal foil should be increased to increase the shielding effectiveness of the metal foil and reduce the edge plasma density; when the edge plasma density is high If the plasma density in the central area is 3% or less, the thickness or surface area of the metal foil will be reduced, the shielding effectiveness will be reduced, and the edge The plasma density in the edge region is lower than that in the central region.

In one embodiment, the metal foil is annular and arranged axially on the outer wall of the discharge chamber.

In one embodiment, the metal foil is strip-shaped and spirally wound on the outer wall of the discharge chamber.

In one embodiment, the metal foil is a vertical strip and is arranged on the outer wall of the discharge chamber along the circumferential direction.

In one embodiment, the material of the metal foil is aluminum, gold or copper, which has a Faraday shielding effect and shields current.

In one embodiment, a grid (Grid) assembly is arranged at the tail end of the discharge chamber; the Grid assembly includes a screen grid and an acceleration grid arranged in sequence from the inside to the outside, and the screen grid is used to focus the plasma in the discharge chamber to form ion beam; the accelerator grid is used to accelerate the formed ion beam.

In an embodiment, the Grid assembly further includes a deceleration grid disposed outside the acceleration grid. Wherein, the screen grid and the acceleration grid are respectively connected to the filtered direct current (DC) power supply, and the deceleration grid is grounded to reduce the divergence of the ion beam.

The helical coil is connected with a radio frequency power supply through a radio frequency matcher.

The application has the following beneficial effects.

1. The metal foil described in this application forms a Faraday structure outside the discharge chamber. By distributing power to the Faraday structure, the plasma density is adjusted according to different working conditions, thereby effectively improving the etching uniformity.

2. The metal foil described in this application can shield the inner edge of the discharge cavity from a strong magnetic field To neutralize the high plasma density caused by the skin effect, so that the plasma density distribution in the discharge chamber is uniform.

3. The ion source device with adjustable plasma density described in this application can select the thickness T and surface area of the metal foil according to the difference between the edge plasma density in the discharge chamber and the plasma density in the central region.

4. The material of the metal foil described in this application is a conductor such as aluminum, gold, copper, etc., so that it can well achieve the Faraday shielding effect and form a shielding effect on the current.

10: Ion source cavity

20: discharge cavity

21: discharge cavity support

30: spiral coil

31: helical coil fixed

40: RF power supply

41: RF matcher

42: RF column

43: RF column

50: metal foil

60: Grid component

61: screen grid

62: Acceleration grid

63: Speed reduction grid

70:Intake pipe

611: DC power supply

612: filter

613: RF column

621: DC power supply

622: filter

623: RF column

Fig. 1 shows a schematic diagram of the distribution of plasma density in a discharge chamber in the prior art.

FIG. 2 shows distribution diagrams of ion beam current density in the reaction chamber under high-energy working conditions and low-energy working conditions in the prior art.

FIG. 3 is a schematic structural diagram of an ion source device with adjustable plasma density according to an embodiment of the present application.

Fig. 4 is a schematic diagram of the layout of the metal foil on the outer wall of the discharge chamber when the metal foil is ring-shaped in an embodiment of the present application.

Fig. 5 is a schematic diagram of the layout of the metal foil on the outer wall of the discharge chamber when the metal foil is in the first spiral shape in an embodiment of the present application.

Fig. 6 is a schematic diagram of the layout of the metal foil on the outer wall of the discharge chamber when the metal foil is in the second spiral shape in an embodiment of the present application.

Fig. 7 shows the outer wall of the discharge chamber when the metal foil is a vertical strip in an embodiment of the present application The layout diagram above.

The present application will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

The meaning of "and/or" in this application means that each exists alone or both exist simultaneously.

The meaning of "connection" mentioned in this application may be a direct connection between components or an indirect connection between components through other components. For the sake of brevity, unless otherwise defined, when an element is described as being “connected” to another element in this application, it means that the element is electrically connected to the other element.

In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "left", "right", "upper", "lower" etc. is based on the orientation or positional relationship shown in the drawings, and is only for convenience describe the application and simplify the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and "first", "second", etc. do not indicate the degree of importance of parts , and therefore cannot be construed as limiting the application. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present application.

As shown in FIG. 3 , each exemplary embodiment of the present application proposes an ion source device with adjustable plasma density, which includes a discharge chamber 20 , a helical coil 30 and an ion source chamber 10 arranged coaxially in sequence from inside to outside.

On the inner wall of the ion source cavity 10, there are several helical coils fixed along the circumferential direction. 31 , the helical coil 30 is placed on the helical coil fixation 31 . The positive end of the helical coil is connected to a radio frequency matcher 41 through a radio frequency column 42 provided on the ion source cavity, and the radio frequency matcher is connected to a radio frequency power supply 40 .

The setting of the radio frequency matching device 41 matches the impedance of the load with the impedance of the radio frequency power source 40, so as to reduce the reflected power and ensure the maximum transmission power.

The discharge chamber 20 is installed on the ion source chamber 10 through the discharge chamber support 21 .

An air inlet pipe 70 is provided at the front end of the discharge chamber for introducing Ar and _O2 plasma gas into the discharge chamber.

A Grid component 60 is arranged at the tail end of the discharge cavity; the Grid component 60 can select two grids or three grids.

When the Grid assembly 60 has two grids, it includes a screen grid 61 and an acceleration grid 62 arranged in sequence from the inside to the outside.

The above-mentioned screen grid 61 is sequentially connected to a filter 612 and a DC power supply 611 through a radio frequency column 613 provided on the ion source chamber, and the screen grid 61 can focus the plasma to form an ion beam.

The acceleration grid 62 is sequentially connected to the filter 622 and the DC power supply 621 through the radio frequency column 623 provided on the ion source cavity, and the acceleration grid 62 accelerates the ion beam.

When the grid assembly 60 is three grids, a deceleration grid 64 is added to the two grids for the three grids, and the deceleration grid 63 is arranged outside the acceleration grid, which can effectively reduce the ion beam divergence. Among them, negative electricity is added to the screen grid, positive electricity is added to the acceleration grid, and the deceleration grid is grounded.

Metal foil 50 is preferably pasted on the outer wall of the discharge chamber. The material of the metal foil is preferably a conductor such as aluminum, gold or copper, which has a Faraday shielding effect and forms a screen for the current. shield.

Forms of the above-mentioned metal foil include, but are not limited to, the following forms.

(1) Annular distribution along the axial direction: As shown in Figure 4, the metal foil is annular and arranged axially on the outer wall of the discharge chamber, and its axial distribution can be uniform or uniform.

(2) Spiral distribution preferably includes the following two embodiments.

In an embodiment: as shown in FIG. 5 , the metal foil is in the shape of a strip, and is a whole long strip, which is spirally wound on the outer wall of the discharge chamber, and the winding distance can be uniform or uneven.

In one embodiment: as shown in Figure 6, the metal foil is strip-shaped, and is a plurality of metal foil strips with different lengths, which are spirally wound on the outer wall of the discharge chamber, and the winding distance can be uniform or uneven. .

(3) Vertical strips are distributed along the circumferential direction: as shown in Figure 7, the metal foil is vertical strips, which are arranged on the outer wall of the discharge chamber along the circumferential direction, and the circumferential distribution can be uniform or uniform. In Figure 7 it is evenly laid out.

When etching is required, start the DC power supply 611, 621 and the RF power supply 40, and when the RF power is added to the helical coil 30 through the matching device, there will be a radio frequency current passing through the helical coil 30, thus generating a radio frequency magnetic flux, and in the discharge The interior of the chamber 20 induces a radio frequency electric field along the axial direction of the discharge chamber; Ar and _O2 plasma gas enters the discharge chamber through the intake pipe 70, and under the action of the helical coil, the gas in the discharge chamber is ionized, and the discharge chamber The electrons inside are accelerated by an electric field, producing a dense plasma. After the plasma in the discharge chamber is drawn out by the Grid assembly 60, it bombards the target in the form of ion beams to etch the wafer.

During the etching process, as the electrostatic field increases, an obvious skin effect will be caused. At the same time, the charged particles in the plasma move under the action of the electric field force or produce pressure and temperature changes through gas discharge, and at the same time, the particles in the discharge chamber will be affected. The controllable disturbance of the flow field, the inhomogeneity of the flow field distribution, the accumulation of charges and other factors cause the edge plasma density to be high.

In one embodiment, by setting the metal foil 50 outside the discharge chamber 20, it can effectively shield the edge magnetic field strength in the discharge chamber, neutralize the high plasma density caused by the skin effect, and make the plasma density distribution in the discharge chamber uniform.

The width W of the metal foil preferably ranges from 1 to 20 mm, and the thickness T of the metal foil preferably ranges from 0.1 mm to t, where t is the skin depth of the helical coil

The thickness T and surface area of the metal foil are selected according to the difference between the edge plasma density in the discharge chamber and the plasma density in the central region. Specifically: when the edge plasma density is 3% higher than the central area, the thickness T or surface area of the metal foil should be increased to increase the shielding effectiveness of the metal foil and reduce the edge plasma density; when the edge plasma density is higher than the central area If the plasma density is 3% or less, the thickness or surface area of the metal foil will be reduced, the shielding effectiveness will be reduced, and the plasma density in the edge area will be lower than that in the central area.

In addition, the metal foil forms a Faraday structure outside the discharge chamber. By distributing power to the Faraday structure, the plasma density is adjusted for different working conditions, thereby effectively improving the etching uniformity.

The various technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, all possible combinations of the various technical features in the above embodiments are not listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope of this specification.

The above-mentioned embodiments only represent several implementation modes of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the scope of the patent for the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the scope of the attached patent application.

10: Ion source cavity

20: discharge cavity

21: discharge chamber support

30: spiral coil

31: helical coil fixed

40: RF power supply

41: RF matcher

42: RF column

43: RF column

50: metal foil

60: Grid component

61: screen grid

62: Acceleration grid

63: Speed reduction grid

70:Intake pipe

611: DC power supply

612: filter

613: RF column

621: DC power supply

622: filter

623: RF column

Claims (8)

An ion source device, comprising a discharge cavity, a helical coil, and an ion source cavity arranged coaxially from the inside to the outside, wherein, the outer wall of the discharge cavity is provided with a metal foil, and the metal foil can shield the discharge cavity The intensity of the inner edge magnetic field and the relatively high plasma density caused by neutralizing the skin effect make the plasma density distribution in the discharge chamber uniform, wherein: the width W of the metal foil ranges from 1 mm to 20 mm, and the The thickness T of the metal foil ranges from 0.1 mm to t, where t is the skin depth of the spiral coil; according to the difference between the edge plasma density and the central area plasma density in the discharge chamber, the Thickness T and surface area of the metal foil, wherein: when the plasma density at the edge is higher than the plasma density in the central region by more than 3%, then increase the thickness T or the surface area of the metal foil to increase the shielding effectiveness of the metal foil, reducing the plasma density at the edge; and/or reducing the plasma density of the metal foil when the plasma density at the edge is 3% or less of the plasma density in the central region The thickness T or the surface area is used to reduce the shielding effectiveness and prevent the plasma density at the edge from being lower than the plasma density at the central region. The ion source device as claimed in claim 1, wherein the metal foil is annular and arranged axially on the outer wall of the discharge chamber. The ion source device according to claim 1, wherein the metal foil is in the shape of a strip, and is spirally wound on the outer wall of the discharge chamber. The ion source device as claimed in claim 1, wherein the metal foil is a vertical strip arranged on the outer wall of the discharge chamber along a circumferential direction. The ion source device according to claim 1, wherein the metal foil is made of aluminum, gold or copper, which has a Faraday shielding effect and forms a shield against electric current. The ion source device as claimed in claim 1, wherein a grid (Grid) assembly is arranged at the tail end of the discharge chamber; the Grid assembly includes a screen grid and an acceleration grid arranged in sequence from the inside to the outside, and the screen grid It is used to focus the plasma in the discharge chamber to form an ion beam; the acceleration grid is used to accelerate the formed ion beam. The ion source device as described in claim 6, wherein the Grid assembly further includes a deceleration grid arranged outside the acceleration grid; wherein the screen grid and the acceleration grid are respectively connected to the filtered direct current (DC) The power supply is connected, and the deceleration grid is grounded to reduce the divergence of the ion beam. The ion source device according to claim 1, wherein the helical coil is connected to a radio frequency power source through a radio frequency matching device.

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