KR20230118973A - Plasma density control system and method - Google Patents

Abstract

The present application discloses a plasma density control system and method, including an ion source, a reaction chamber, a baffle mechanism and a Faraday cup set, the Faraday cup set being installed on the reaction chamber wall corresponding to the screen grid, a Faraday cup mounting frame and at least N Faraday cups, the N Faraday cups corresponding to the positions of the N sets of screen grid annular holes on the screen grid, the baffle mechanism including a drive controller and at least two sets of baffle assemblies, each set of baffle assemblies includes a plurality of baffles and a baffle drive device, the plurality of baffles are uniformly arranged along the circumferential direction of the distal end of the discharge chamber, and each baffle is rotated and inserted into the discharge chamber to block plasma entering the annular hole of the screen grid; , the baffles between the baffle assemblies are alternately arranged, and the baffle shapes between the baffle assemblies are different. The present application measures the density of an ion beam extracted from an ion source and controls the plasma density in real time to effectively solve the problem of non-uniformity in etching due to a change in process conditions, thereby reducing production costs.

Description

Plasma density control system and method

This application claims priority based on Chinese Patent Application No. 202110002170.3, filed with the Patent Office of China on January 4, 2021, entitled “Plasma Density Control System and Method”, the entire contents of which are incorporated herein by reference. is used

This application relates to the field of ion beam etching, and more particularly to a plasma density control system and method.

Ion beam etching can be used for etching and processing of various metals (Ni, Cu, Au, Al, Pb, Pt, Ti, etc.) and their alloys, non-metals, oxides, nitrides, carbides, semiconductors, polymers, ceramics, infrared and superconducting materials. can In principle, by using the glow discharge principle, argon gas is decomposed into argon ions, and the argon ions are accelerated by an anode electric field to give a physical impact to the sample surface, thereby achieving an etching effect. In the etching process, the ion source discharge chamber is filled with Ar gas to ionize it to form plasma, and then the ions are drawn out in the form of a beam by the grid and accelerated. is fired to impact the solid surface atoms, causing the sputtering of material atoms to achieve the purpose of etching, and belongs to pure physical etching. Since ions are not generated by glow discharge, and an independent ion source fires inert gas ions, which are accelerated through an electric field and then introduced into the vacuum chamber where the sample is placed, the vacuum levels of the ion beam source and the sample chamber are each in their respective optimum states. can be reached, and the purity of the membrane is very high.

An ion source is a device that extracts an ion beam by ionizing neutral atoms or molecules. Conventional ion sources are mainly Kaufman ion sources, radio frequency ion sources, electron cyclotron resonance (ECR) ion sources, and end hole (End Hall) ion sources. Hall) ion source, wherein in a vacuum environment, the gas filled in the vacuum chamber is ionized by the interaction of the electric field and the magnetic field, and emits ions through the action of the electric field and the magnetic field, and the radio frequency induction It has advantages such as generating plasma, electrostatic acceleration of ions, electrodeless discharge, stable long-term operation, large uniform area, accurate control of ion beam density, and less contamination. widely applied in the process.

In the ion beam etching, the ion source is in a working state, and due to different process conditions, the etching result has a relatively large difference. In the excited state of the radio frequency power source, the plasma density in the discharge chamber is medium to high, and at the edge To ensure the uniformity of etching, the size of the small holes on the screen grid gradually increases from the middle towards the edge to ensure that the ion flux through the edge region is large (Figure 2 and Figure 2). 3), the extracted ion beam density is uniformly distributed, but if the process conditions are changed, the ion beam current density extracted from the ion source may increase in the edge region (Fig. 4), thereby reducing the non-uniformity of the wafer surface etching. (see Figs. 5a-5b), affecting the etching effect. In Fig. 3, the abscissa is the radial distance, and the ordinate is the grid hole diameter size, that is, the screen grid annular hole size.

Each exemplary embodiment of the present application provides a plasma density control system, wherein the plasma density control system and method can measure the density of an ion beam drawn from an ion source, control the plasma density in real time, and control process conditions. It is possible to effectively solve the etching non-uniformity problem caused by the change, thereby reducing the production cost.

Each exemplary embodiment of the present application provides a plasma density control system, including a reaction chamber, an ion source, a Faraday cup set, and a baffle mechanism, wherein the ion source includes an ion source chamber and a discharge chamber coaxially installed from the outside to the inside. ; and a screen grid installed at an end of the ion source chamber, wherein N sets of screen grid annular holes are installed along a radial direction, where N is an integer and is greater than or equal to 1, wherein the Faraday cup set corresponds to the screen grid. a Faraday cup mounting frame installed on the chamber wall; and at least N Faraday cups corresponding to positions of the N sets of annular holes in the screen grid, wherein the baffle mechanism includes a driver controller and at least two sets of baffle assemblies. Each set of baffle assemblies all include a plurality of baffles and baffle drives. A plurality of baffles are uniformly arranged along the circumferential direction of the discharge chamber end. Each baffle can be rotated and inserted into the discharge chamber by driving the baffle driving device to block plasma entering the corresponding annular hole of the screen grid. The baffles between the baffle assemblies are alternately arranged, and the baffle shapes between the baffle assemblies are different. All baffle drives and all Faraday cups are interconnected with drive controllers. In one embodiment, the Faraday cup mounting frame is a strip-shaped frame, and the number of Faraday cups is N+1. One of the Faraday cups is located on the central axis of the reaction chamber, and the other N Faraday cups are mounted on the same line on the strip frame, corresponding to the positions of the N annular holes in the screen grid.

In one embodiment, the Faraday cup mounting frame has an L-shaped frame, and the corners of the L-shaped frame are located on the central axis of the reaction chamber. One Faraday cup is mounted on a corner of the L-shaped frame, and N Faraday cups are mounted on two right angle sides of the L-shaped frame, respectively. The 2N Faraday cups are located at different radial positions of the screen grid, and correspond to the positions of the N annular holes of the screen grid, respectively.

In one embodiment, the baffle mechanism includes two sets of baffle assemblies, each a first baffle assembly and a second baffle assembly. The first baffle assembly includes a plurality of first baffles and a first baffle driving device. The second baffle assembly includes a plurality of second baffles and a second baffle driving device. A cross section of each first baffle has a structure of an inverted cone or an inverted trapezoid with a wide center and a narrow edge. The cross section of each second baffle has a conical or trapezoidal structure with a wide edge and a narrow center.

In one embodiment, the discharge chamber is mounted to the ion source chamber of the ion source via a discharge chamber support base. Edge ends of each first baffle and each second baffle are both rotationally mounted on the end face of the discharge chamber support base.

In one embodiment, the length of each first baffle and each second baffle is the same, and both are 1/4r to 1/2r, where r is the screen grid radius.

In one embodiment, the baffle drive is a rotating cylinder or motor.

Each exemplary embodiment of the present application further provides a plasma density control method including the steps below.

Step 1, plasma signal detection: before etching, the ion source is turned on, the plasma located in the discharge chamber passes through the screen grid annular hole of the screen grid, and then is focused to form an ion beam, each set of Faraday cups has its own radial direction Detect the plasma signal of the location. The detected plasma signal is converted into a current signal and fed back to the driving device controller.

Step 2, Determination of Plasma Density Uniformity: The driver controller reads the maximum current and the minimum current according to all current information received, compares the maximum current and the minimum current, and determines the difference between the maximum current and the minimum current as the set value. If less than , it is determined that the plasma density in the reaction chamber is uniform. Otherwise, it is determined that the plasma density is non-uniform.

Step 3: Control the plasma density, specifically including the following steps.

Step 31, Determination of Shutdown Time: If it is determined in step 2 that the plasma density is non-uniform, the driving device controller reads the position of the Faraday cup corresponding to the maximum current.

Step 32, cut off: the driver controller determines the baffle assembly to be operated according to the position of the Faraday cup corresponding to the maximum current, and rotates the baffle of the baffle assembly under the control of the baffle driver to open a region with high plasma density. block it When the baffle rotates radially, the width corresponding to the maximum current Faraday cup is maximum.

Step 33, re-detection of plasma density: at the same time that the baffle stops rotating, the Faraday cup detects the plasma density in real time, and the driver controller judges the uniformity of the plasma density according to step 2 until the plasma density becomes uniform; , the baffle stops rotating.

In step 32, the blocking step,

Step 32A, when the Faraday cup corresponding to the maximum current is positioned at the edge, the driver controller controls the second baffle driver to move the second baffle to cut off.

In step 32, when the Faraday cup corresponding to the maximum current is close to the inner center, the driver controller controls the first baffle driver to move the first baffle to shut off.

In step 33, after the second baffle driving device rotates by 90°, if it is determined that the edge plasma density is still maximum and the uniformity of the plasma density is non-uniform, the driving device controller controls the first baffle driving device to move; Block more edge plasma until the plasma density is uniform.

The present application measures the density of an ion beam drawn from an ion source using a Faraday cup set, and controls the plasma density in real time through rotation of a baffle among baffle mechanisms, effectively solving the problem of non-uniform etching due to changes in process conditions. So, reduce the production cost.

1 shows a schematic diagram of plasma density distribution in a prior art discharge chamber.
2 shows a structural schematic diagram of a prior art screen grid.
3 shows a schematic diagram of the radial distribution position of annular holes in a screen grid in the prior art.
4 shows a schematic diagram of the density distribution of an ion beam in a reaction chamber of the prior art.
5A and 5B show two effect diagrams of wafer surface etch non-uniformity in the prior art.
6 shows a structural schematic diagram of a plasma density control system in an embodiment of the present application.
7 shows a schematic view of a mounting position of a baffle assembly in a plasma density control system according to an embodiment of the present application.
8 shows a structural schematic diagram in which the Faraday cup mounting frame of an embodiment of the present application is a strip-shaped frame.
9 shows a structural schematic diagram in which the Faraday cup mounting frame of an embodiment of the present application is an L-shaped frame.
10 shows a distribution schematic diagram of baffles in an embodiment of the present application.
11 shows a structural schematic diagram when a first baffle rotation is blocked according to an embodiment of the present application.
12 shows a structural schematic diagram when the rotation of the second baffle is blocked according to an embodiment of the present application.
13 is a structural schematic diagram when the second baffle mainly blocks and the first baffle provides auxiliary block in an embodiment of the present application.

Hereinafter, the technical solutions of the embodiments of the present application will be clearly and completely described by combining the drawings of the embodiments of the present application. In the following description, the drawings are just some embodiments of the present application, and those skilled in the art can further obtain other drawings according to these drawings without creative labor. The embodiments described below are some embodiments of the present application, but not all embodiments. Based on the embodiments in this application, all other embodiments obtained by a person skilled in the art without creative labor fall within the protection scope of this application.

It should be understood that the terms "comprehensive" and "comprising" as used in the description and claims of this application mean the presence of the described features, wholes, steps, operations, elements and/or components, but not one or more other features. , does not exclude the presence or addition of wholes, steps, operations, elements, components and/or collections thereof.

In the description of the present application, it should be understood that the direction or positional relationship indicated by the terms “left”, “right”, “upper”, “lower”, etc. is based on the direction or positional relationship shown in the drawings, It is only intended to be easy to explain and to simplify the explanation, and does not indicate or imply that the device or element to be indicated must have a specific direction, be configured and operated in a specific direction, and "first", "second", etc. It does not indicate the importance of the component and should not be construed as limiting this application. The specific size used in this embodiment is only for exemplifying the technical solution, and does not limit the protection scope of the present application.

At present, there are two ways to obtain conventional good beam density uniformity, one is to adjust the parameters and design structure of the ion source, and the other is to build a heterogeneous physical shielding mechanism between the ion source etched samples. , By continuously adjusting the geometry of the physical shielding mechanism to compensate for the ion beam density characteristics, after designing the shielding device each time, they should all be tested for uniformity; if the correction effect is not reached, the geometry of the physical shielding device is It is processing the shape as an object, but the test cycle is long and the production cost is high. Therefore, it is very important to measure the density of an ion beam extracted from an ion source and to control the plasma density in real time. The present application presents a plasma density control system, which effectively solves the etching non-uniformity problem caused by the above-described process condition change, and can reduce production cost.

Hereinafter, the present application will be described in detail in combination with drawings and specific preferred embodiments.

As shown in FIG. 6, the plasma density control system includes an ion source (1), a reaction chamber (2), a baffle mechanism, a baffle (6) and a set of Faraday cups (3).

The ion source 1 is coaxially installed on one side of the reaction chamber 2, and the ion source 1 includes an ion source controller 14 and an ion source chamber and discharge chamber 11 coaxially installed from the outside to the inside. do.

The ion source controller 14 is for controlling process parameters of the ion source.

In one embodiment, the discharge chamber 11 is mounted on the inner wall surface of the ion source chamber through the discharge chamber support base 9 .

A grid assembly is installed at an end of the ion source chamber, and the grid assembly includes a screen grid 12 and an acceleration grid 13 .

Both the screen grid 12 and the acceleration grid 13 are provided with N sets of screen grid annular holes along the radial direction. To ensure the uniformity of etching, the radial height of the annular holes in the N sets of screen grids gradually increases from the middle to the edge to ensure that the ion flux through the edge area is large, as shown in FIG. 8 . In Fig. 8, N = 6, and the radial heights of the annular holes of the 6 sets of screen grids are 2.35 mm, 2.47 mm, 2.63 mm, 2.72 mm, 2.91 mm and 3.13 mm from the middle to the edge, respectively. Plasma is focused by applying positive electricity to the screen grid 12, and negative electricity is applied to the accelerating grid 13 to extract and accelerate ions in the form of a beam, thereby extracting the plasma in the form of an ion beam.

The baffle 6 is mounted on the head of the reaction chamber located downstream of the grid assembly, blocking the annular holes of the N-set screen grid. A lower electrode 4 for placing a wafer 5 in the reaction chamber 2 is installed.

The baffle mechanism includes a drive controller 7 and at least two sets of baffle assemblies.

Each set of baffle assemblies all include a plurality of baffles and baffle drives. All of the plurality of baffles are uniformly arranged along the circumferential direction at the end of the discharge chamber. Each baffle can be rotated and inserted into the discharge chamber 11 by driving the baffle driving device to block plasma entering the annular hole of the screen grid. The baffles between the baffle assemblies are alternately arranged, and the baffle shapes between the baffle assemblies are different.

In one embodiment, there are preferably two sets of baffle assemblies, each a first baffle assembly and a second baffle assembly.

The first baffle assembly includes a plurality of first baffles 81 and a first baffle driving device 71 .

As shown in FIG. 10, the cross section of each first baffle 81 preferably has a structure of an inverted cone or an inverted trapezoid with a wide center and narrow edges.

As shown in FIG. 7, the edge end of the first baffle 81 is preferably rotatably mounted to the end of the discharge chamber support base via a hinge shaft.

As shown in FIG. 12, each of the first baffles 81 can rotate by driving the first baffle driving device 71, and the number of first baffle driving devices 71 can be one or two. That is, the first baffle 81 may be driven independently, or one or a plurality of first baffle driving devices 71 may be synchronously driven.

The second baffle assembly includes a plurality of second baffles 82 and a second baffle driving device 72 . As shown in FIG. 10, the cross section of each second baffle 82 has a conical or trapezoidal structure with a wide edge and a narrow center. The edge end of the second baffle 82 is preferably rotatably mounted to the end of the discharge chamber support base 9 via a hinge shaft.

The first baffles 81 and the second baffles 82 are alternately disposed along the circumferential direction at the end of the discharge chamber support base 9, and may be uniform or non-uniform.

The length of each first baffle 81 and each second baffle 82 is the same, and both are 1/4r to 1/2r, more preferably 1/3r, where r is the screen grid radius.

The axial distance L between each baffle and the screen grid 12 is such that the baffle is located within the sheath of the screen grid 12 to prevent damage to the ion source 1 device, and at the same time the distance is large. , preferably 1 mm to 10 mm to prevent plasma from spreading.

As shown in FIG. 11, each second baffle 82 can rotate by driving the second baffle driving device 72, and the number of second baffle driving devices 72 can be one or two. That is, the second baffle 82 may be driven independently, or one or a plurality of second baffle driving devices 72 may be synchronously driven.

Alternatively, baffle assemblies may be three sets, four sets, and the like.

Preferably, the baffle driving device is a rotating cylinder or a motor.

The Faraday cup set includes a Faraday cup mounting frame and at least N Faraday cups (31).

The Faraday cup mounting frame is installed on the reaction chamber wall corresponding to the screen grid. The N Faraday cups correspond to the positions of N sets of screen grid annular holes.

In this application, the Faraday cup mounting frame has the following two preferred embodiments.

Embodiment 1 A frame with a Faraday cup, which is a strip type frame

The Faraday cup mounting frame is a strip type frame, and the number of Faraday cups 31 is N+1. In this embodiment, since there are 6 sets of annular holes in the screen grid, that is, N=6, the number of Faraday cups is 7, and as shown in FIG. 8, Faraday cups 1 and 2 from the center to the outside, respectively. ), Faraday cup (3), Faraday cup (4), Faraday cup (5), Faraday cup (6) and Faraday cup (7).

One of the Faraday cups 31 (that is, the Faraday cup 1) is located on the central axis of the reaction chamber 2, and the other N Faraday cups 31 are mounted on the same line to the strip frame. and corresponds to the positions of the N screen grid annular holes.

That is, the Faraday cup (2), Faraday cup (3), Faraday cup (4), Faraday cup (5), Faraday cup (6), and Faraday cup (7) are 2.35 mm, 2.47 mm, 2.63 mm, and 2.72 mm, respectively. , corresponding to the screen grid annular holes of 2.91 mm and 3.13 mm, it is ensured that the plasma density of regions where different hole diameters are located on the screen grid 12 can be effectively measured.

Example 2

As shown in Fig. 9, the Faraday cup mounting frame has an L-shaped frame (which may be a cross frame), and the corner of the L-shaped frame is located on the central axis of the reaction chamber. The number of Faraday cups is preferably 2N+1.

One of the Faraday cups 31 (that is, the Faraday cup 1) is mounted on a corner of the L-shaped frame, and N number of Faraday cups 31 are mounted on the two right angles of the L-shaped frame, respectively .

The N number of Faraday cups 31 on one of the right angle sides are Faraday cups 2, Faraday cups 3, Faraday cups 4, Faraday cups 5, Faraday cups 6, and Faraday cups ( 7) is.

N Faraday cups 31 on the other right angle side are Faraday cups 8, Faraday cups 9, Faraday cups 10, Faraday cups 11, Faraday cups 12, and Faraday cups 13, respectively. am.

The 2N Faraday cups 31 are located at different radial positions of the screen grid 12, and correspond to the positions of the N annular holes in the screen grid, respectively. That is, the Faraday cup 2 and the Faraday cup 8 correspond to the annular hole of the screen grid of 2.35 mm, the Faraday cup 3 and the Faraday cup 9 correspond to the annular hole of the screen grid of 2.47 mm, and the Faraday cup (4) and the Faraday cup 10 correspond to the annular hole of the screen grid of 2.63 mm, the Faraday cup 5 and the Faraday cup 11 correspond to the annular hole of the screen grid of 2.72 mm, and the Faraday cup 6 and The Faraday cup 12 corresponds to the screen grid annular hole of 2.91 mm, and the Faraday cup 7 and Faraday cup 13 correspond to the screen grid annular hole of 3.13 mm. In this embodiment, multi-sampling measurement may be performed so that the uniformity adjustment is more accurate.

All the baffle drives and all Faraday cups 31 are connected to the drive controller.

The plasma density control method includes the following steps.

Step 1, Plasma Signal Detection:

Before etching, the baffle 6 leaves the screen grid annular hole by driving the baffle driving device 61.

The ion source 1 is turned on through the ion source controller 14, and by the action of the ion source controller 14, the Ar filled in the discharge chamber 2 is ionized to form plasma, and the screen grid 12 forms a positive charge. is applied to focus the plasma, negative electricity is applied to the accelerating grid 13 to draw and accelerate ions in the form of a beam, the plasma is drawn out in the form of an ion beam, and is incident on the Faraday cup set 3, and the Faraday cup set A plurality of Faraday cups 31 are distributed in (3), and the Faraday cups 31 convert the injected ion beam quantity into a current signal and feed it back to the drive controller 7.

Step 2, Judging Plasma Density Uniformity:

When the Faraday cup set 3 feeds back the current signal to the driving device controller 7, the driving device controller 7 compares the current signal, and the plasma density in the area where the current is high is high and the plasma density in the area where the current is low is high. Density is low.

The driver controller 7 selects and compares the maximum current and the minimum current, and if the difference between the maximum current and the minimum current is less than the set value, it means that the extracted ion beam density is uniform, and in this state, the wafer 5 ) can be ensured to have excellent uniformity when etching, and by the action of the baffle driving device 61, the baffle 6 blocks the ion beam, and the wafer is placed on the lower electrode 4 to be etched. When rotated, the baffle 6 drops, and the ion beam proceeds to etch the wafer 5 .

If the difference between the maximum current and the minimum current is greater than the set value, it means that the extracted ion beam density distribution is non-uniform.

Step 3, control the plasma density, specifically including the following steps:

Step 31, Determination of cut-off timing: When it is determined that the plasma density is non-uniform in step 2, the driving device controller 7 reads the position of the Faraday cup 31 corresponding to the maximum current.

Step 32, Shutdown: The driver controller 7 determines the baffle assembly to operate according to the position of the Faraday cup 31 corresponding to the maximum current, and rotates the baffle of the baffle assembly under the control of the baffle driver, Block areas with high plasma density. When the baffle rotates radially, the width corresponding to the maximum current Faraday cup is maximum. Here, the width means the width of the baffle blocking the plasma density.

That is, the driving device controller 7 controls the first baffle driving device 71 or the second baffle driving device 72 to move the first baffle 81 or the second baffle 82 to move the plasma density region. By blocking, some plasma density is lowered to achieve the effect that the wafer is uniformly etched.

In this embodiment, the specific preferred blocking method is as follows:

Step 32A, when the Faraday cup 31 corresponding to the maximum current is positioned at the edge, the driver controller 7 controls the second baffle driver 72 to move the second baffle 82 to block.

In step 32B, when the Faraday cup 31 corresponding to the maximum current is close to the inner center, the driver controller 7 controls the first baffle driver 71 to move the first baffle 81 to shut off.

Step 33, re-detection of plasma density: at the same time as the baffle stops rotating, the Faraday cup 31 senses the plasma density in real time, and the driving device controller 7 proceeds according to step 2 until the plasma density becomes uniform. The uniformity of is determined, and the baffle stops rotating.

As shown in FIG. 13, when the Faraday cup 31 corresponding to the maximum current is located at the edge, after the second baffle driving device 72 rotates 90°, the edge plasma density is still maximum and the plasma density is uniform. If it is determined that the plasma is non-uniform, the driver controller 7 controls the first baffle driver to move, blocking more edge plasma until the plasma density becomes uniform.

In terms of theory and process, the etch rate of the wafer 5 is smaller in the middle region than the edge region, the current density within the Faraday cup 2 is the lowest, and the region where the etch rate is fast is generally Faraday cup 3 or Faraday cup. (7) is located within the radial section, and when the Faraday cup set 3 feeds back the current signal to the drive controller 7, the drive controller 7 reads the Faraday cup corresponding to the maximum current, When the Faraday cup 31 corresponding to the maximum current is located at the edge, for example, in the case of the Faraday cup 7, the drive controller 7 operates the second baffle drive 72 until the plasma density becomes uniform. It is controlled to move the second baffle 82 to block it. If the edge plasma density still cannot be lowered after the second baffle drive 72 rotates by 90°, the drive controller 7 sequentially controls the first baffle drive 71 to move, so as to generate more plasma. block it The shape of the second baffle 82 should be wide at the edge and narrow at the center.

When the Faraday cup 31 corresponding to the maximum current is close to the inside, for example in the case of the Faraday cup 3, the driver controller 7 operates the first baffle driver until the maximum current region is not within the corresponding range. 71 is controlled to move the first baffle 81 to block. At this time, as the shape of the first baffle 81, a shape with a wide middle and a narrow edge should be selected. The setting of baffle quantity and size can be designed according to process test results.

Although the preferred embodiment of the present application has been described in detail above, the present application is not limited to the specific contents of the above-described embodiment, and the technical solution of the present application can be equally modified in various ways within the scope of the technical concept of the present application. and all such equivalent modifications fall under the protection scope of the present application.

1: ion source 2: reaction chamber
3: Faraday Cup Set 31: Faraday Cup
4: lower electrode 5: wafer
6: baffle 61: baffle drive
7: drive controller 71: first baffle drive
72: second baffle driving device 81: first baffle
82: second baffle 9: discharge chamber support base
11: discharge chamber 12: screen grid
13: acceleration grid 14: ion source controller

Claims (10)

A plasma density control system comprising a reaction chamber, an ion source, a set of Faraday cups, and a baffle mechanism, comprising:
The ion source,
an ion source chamber and a discharge chamber coaxially installed from the outside to the inside; and
A screen grid installed at an end of the ion source chamber, wherein N sets of screen grid annular holes are installed along the radial direction, where N is an integer and is equal to or greater than 1;
The Faraday cup set,
a Faraday cup mounting frame installed on a wall surface of the reaction chamber corresponding to the screen grid; and
At least N Faraday cups corresponding to the positions of the N sets of screen grid annular holes;
The baffle mechanism,
drive controller; and
All include a plurality of baffles and a baffle driving device, wherein the plurality of baffles are uniformly arranged along the circumferential direction of the distal end of the discharge chamber, and each baffle is rotatably inserted into the discharge chamber by driving the baffle driving device to produce a corresponding At least two sets of baffle assemblies capable of blocking plasma entering the annular hole of the screen grid;
baffles between the baffle assemblies are alternately arranged, the baffle shapes between the baffle assemblies are different, and all the baffle drivers and all the Faraday cups are all interconnected with the drive controller. According to claim 1,
the Faraday cup mounting frame is a strip frame, and the number of Faraday cups is N+1;
One of the Faraday cups is located on the central axis of the reaction chamber, and the other N Faraday cups are mounted on the same line to the strip frame, corresponding to the positions of the N screen grid annular holes. control system. According to claim 1,
The Faraday cup mounting frame includes an L-shaped frame, a corner of the L-shaped frame is positioned on a central axis of the reaction chamber, one Faraday cup is mounted on a corner of the L-shaped frame, and the L-shaped frame N number of Faraday cups are mounted on two right angles of , and 2N Faraday cups are located at different radial positions of the screen grid, respectively corresponding to the positions of the N number of annular holes in the screen grid, for plasma density control. system. According to claim 1,
the baffle mechanism includes two sets of baffle assemblies, respectively a first baffle assembly and a second baffle assembly, wherein the first baffle assembly includes a plurality of first baffles and a first baffle driving device;
the second baffle assembly includes a plurality of second baffles and a second baffle driving device;
The plasma density control system, wherein a cross section of each of the first baffles has a structure of an inverted cone or an inverted trapezoid with a wide center and a narrow edge, and a structure of a cone or trapezoid with a wide edge and a narrow center, and a cross section of each of the second baffles. . According to claim 4,
the discharge chamber is mounted to the ion source chamber of the ion source via a discharge chamber support base;
The plasma density control system of claim 1 , wherein edges of each of the first baffles and each of the second baffles are rotatably mounted on an end face of the discharge chamber support base. According to claim 5,
The plasma density control system of claim 1 , wherein the lengths of each of the first baffles and each of the second baffles are the same, and are both 1/4r to 1/2r, where r is the screen grid radius. According to claim 1,
The baffle driving device is a rotating cylinder or a motor, the plasma density control system. In the plasma density control method,
Step 1, plasma signal detection: before etching, the ion source is turned on, the plasma located in the discharge chamber passes through the screen grid annular hole of the screen grid, and then is focused to form an ion beam, each set of Faraday cups has its own radial direction detecting a plasma signal at the position, converting the detected plasma signal into a current signal, and feeding back the detected plasma signal to a driving device controller;
Step 2, judging the plasma density uniformity: the drive controller reads the maximum current and the minimum current according to all the received current information, compares the maximum current and the minimum current, and compares the maximum current with the minimum current. If the current difference value is less than a set value, determining that the plasma density in the reaction chamber is uniform, and otherwise, determining that the plasma density is non-uniform;
Step 3: including controlling the plasma density,
Step 31, Determining cut-off timing: If it is determined that the plasma density is non-uniform in step 2, the driving device controller reads the position of the Faraday cup corresponding to the maximum current;
Step 32, cut-off: the driving device controller determines a baffle assembly to operate according to the position of the Faraday cup corresponding to the maximum current, and rotates a baffle of the baffle assembly under the control of the baffle driving device to produce plasma blocking a high-density region, and when the baffle rotates in a radial direction, a width corresponding to the Faraday cup of the maximum current is maximized; and
Step 33, re-detection of the plasma density: at the same time as the baffle stops rotation, the Faraday cup detects the plasma density in real time, and the driving device controller detects the plasma density according to step 2 until the plasma density becomes uniform. Determining the uniformity of the density, and stopping the rotation of the baffle; including, the plasma density control method. According to claim 8,
In step 32, the blocking step,
Step 32A, when the Faraday cup corresponding to the maximum current is positioned at the edge, the driving device controller controls the second baffle driving device to move the second baffle to cut off;
Step 32B, when the Faraday cup corresponding to the maximum current is close to the inner center, the driving device controller controls the first baffle driving device to move the first baffle and block it. According to claim 8,
In step 33, if it is determined that the edge plasma density is still maximum and the uniformity of the plasma density is non-uniform after the second baffle driving device rotates by 90°, the driving device controller controls the first baffle driving device to move. Thus, more of the edge plasma is blocked until the plasma density becomes uniform.