CN111769030B

CN111769030B - Device and method for measuring density distribution of beam in vertical direction

Info

Publication number: CN111769030B
Application number: CN201910258890.9A
Authority: CN
Inventors: 李更兰; 田龙; 张丛
Original assignee: Beijing Zhongkexin Electronic Equipment Co Ltd
Current assignee: Beijing Zhongkexin Electronic Equipment Co Ltd
Priority date: 2019-04-02
Filing date: 2019-04-02
Publication date: 2024-10-01
Anticipated expiration: 2039-04-02
Also published as: CN111769030A

Abstract

The invention discloses a device and a method for measuring beam current density in the vertical direction, relates to an ion implanter, and belongs to the field of semiconductor manufacturing. The device comprises: faraday cup (1), beam baffle (3), transmission (10), controller (12). The method comprises the following steps: setting measurement precision, wherein the precision determines how much distance (6) the beam baffle moves per time, and the Faraday cup acquires a value; recording the acquisition value of the Faraday cup according to the position value of the bottom edge (4) of the beam baffle to obtain an acquisition value array; when the position of the top edge (2) of the beam baffle is lower than the bottom edge (7) of the Faraday cup slot, one-time measurement is finished; and substituting the acquisition value array elements into a beam current density iteration formula in the specification in sequence to obtain a beam current average density array.

Description

Device and method for measuring density distribution of beam in vertical direction

Technical Field

The invention relates to a device and a method for measuring beam current density in an ion implanter, relates to the ion implanter, and belongs to the field of semiconductor equipment manufacturing.

Background

With the rapid development of integrated circuit manufacturing technology, there is an increasing demand for semiconductor processing equipment, and in order to meet the needs of new technology, an ion implanter, which is one of the key devices of a semiconductor ion doping process line, needs to be continuously improved and improved in terms of beam current index, beam energy purity, implantation depth control, implantation uniformity, productivity and the like. Uniformity of implantation, beam leveling, implantation angle, and ion implantation accuracy are key performance parameters of an ion implanter during implantation. These parameters need to be monitored by beam current measurements.

Ion implanters employ a variety of beam current measurement techniques. For example, a one-dimensional moving Faraday cup, used to measure the profile and beam uniformity of the beam; the moving Faraday array is composed of multiple Faraday cups, and is fixed on the bottom and can move together for measuring the two-dimensional section and uniformity of beam current.

The above measurement techniques all have certain drawbacks. For example, a one-dimensional moving Faraday can only measure the beam profile in the horizontal direction, but cannot measure the beam profile in the vertical direction. While the moving faraday array can measure the beam profile in the vertical direction, the number of faraday cups is too large, and the complexity of mechanical and signal reading is greatly increased.

Therefore, there is a need to apply new beam current density measurement techniques in ion implanters. The invention provides a measuring technology of density distribution of beam in the vertical direction.

Disclosure of Invention

The present invention relates to a system and method for beam current density measurement in an ion implantation system. The controller controls the beam baffle to move in the vertical direction of the beam profile, and collects a group of measured values, and the measured values are subjected to iterative algorithm processing in the processor to obtain a beam density curve of the beam on the vertical profile. Different from the conventional beam profile measurement technology, the scheme has adjustable measurement precision, simpler structure and flexible application. Such as the ability to be applied to a conventional one-dimensional moving faraday to form a two-dimensional beam profile.

One aspect of the invention provides a system for beam current density measurement in an ion implantation system. The system is coordinated by the controller, and the controller has four functions, namely, controlling the movement of the beam baffle, processing collected data, controlling the beam flow generating device and interacting with the upper computer.

Another aspect of the invention provides a method for beam current density measurement in an ion implantation system. The beam baffle moves in the vertical direction of the beam, and the controller periodically collects the beam value according to the position of the baffle. The core of the method is an iterative algorithm, wherein the first step is to determine a starting point and an ending point, the second step is to take a value of 0 before the starting point, and the third step is to use a beam current density iterative formula. The collecting beam value is processed by an iterative algorithm to obtain the beam density distribution.

Drawings

The invention is further described below with reference to the drawings and specific examples, which are not intended to limit the scope of the invention.

Figure 1a is a schematic view of the beam stop and faraday cup configuration of the present invention.

FIG. 1b is a schematic diagram of a beam current density measurement system according to the present invention

FIG. 2a is the position of the acquisition point relative to the beam stop when the measurement accuracy is W

FIG. 2b shows the density of the cross-sectional beam obtained when the measurement accuracy is W (Gaussian beam)

FIG. 3a position of acquisition point relative to beam baffle when measurement accuracy is W/2

FIG. 3b shows the density of the cross-sectional beam obtained when the measurement accuracy is W/2 (Gaussian distribution beam)

FIG. 4a position of acquisition point relative to beam baffle for W/4 measurement accuracy

FIG. 4b shows the density of the cross-sectional beam obtained when the measurement accuracy is W/4 (Gaussian distribution beam)

Detailed Description

The invention is further described below with reference to the accompanying drawings, which are not intended to be limiting.

The Faraday cup (1) has a slit (5) for measuring the beam current. The beam baffle (3) is positioned between the slit and the beam current generating device, is close to the slit and is insulated from the Faraday cup. Before starting measurement, the controller (12) moves the beam baffle to the position of the starting point (8) through the driver (11) and the transmission device (10). After the measurement is started, the controller controls the beam baffle to move towards the direction of the end point (7). By means of the coding feedback, the processor obtains the real-time position of the beam baffle. The position of the sampling interval relative to the beam stop is determined by the measurement accuracy m (m is a positive integer, e.g., 1,2,4 …). The processor collects the faraday cup values once every time the position of the beam stop is moved by a distance W/m. When the beam baffle reaches the end point, the measurement is ended, and then the beam baffle is returned. At this time, the controller will obtain a set of measurement data, i.e., a one-dimensional measurement value array { C ₀,C₁,C₂,C₃,......,C_n-2,C_n-1,C_n }, which corresponds to the elements in the array of positions of the beam stop at the time of sampling { S ₀,S₁,S₂,S₃,......,S_n-2,S_n-1,S_n }. The processor will perform an iterative algorithm according to the iterative formula and initial conditions:

B_n＝0(n＜0)

And obtaining a beam average density array { B ₀,B₁,B₂,B₃,......,B_n-2,B_n-1,B_n }, wherein the array corresponds to the elements in the position array one by one to form the distribution of the beam average density in the vertical direction.

In the measurement of the beam density of the vertical section of the primary beam, the acquisition times are determined by m, the larger the value of m is, the more the acquisition times are, the smaller the acquisition interval is, and the more comprehensive the obtained section information is. Fig. 2a-4a show the positions of the acquisition points relative to the beam baffles when m is 1, 2 and 4 respectively, and take gaussian distributed beam as an example, the beam density distribution of 2b-4b is finally obtained. If the measurement accuracy is to be improved continuously, only the m value is required to be increased continuously, and the finally obtained beam current density distribution is more perfect. But the value of m is not infinitely variable, and will have an upper limit for a particular measurement system.

And after obtaining the beam current density distribution, the processor feeds back relevant adjustment parameters to the beam current generating device so as to adjust the beam current and send information to the upper computer.

Specific embodiments of the present patent have been described in detail herein. Any obvious modifications to the present invention, which would be obvious to those skilled in the art without departing from the spirit of the present invention, would constitute an infringement of the present invention and would take on corresponding legal liabilities.

Claims

1. A method for measuring beam current density in a vertical direction in an ion implantation system, the method comprising: determining a beam measurement interval through a value of W/m, wherein W represents the length of the beam baffle in the vertical direction, m is the measurement precision, and m is a positive integer; the beam baffle starts to move from a starting point (8), the controller measures beam values at equal intervals according to the positions of the lower edges of the baffle, when the beam baffle reaches an end point (7), the processor (14) obtains a one-dimensional measured value array, the positions of the lower edges of the beam baffle on a Y axis form a one-dimensional position array, and the measuring array is sequentially subjected to an iterative algorithm to obtain a beam leveling average density array corresponding to the position array one by one;

the iterative algorithm comprises the following steps: the one-dimensional position array is marked as { S ₀,S₁,S₂,S₃,......,S_n-2,S_n-1,S_n };

The one-dimensional measurement array is denoted as { C ₀,C₁,C₂,C₃,......,C_n-2,C_n-1,C_n };

The beam leveling average density array to be solved is marked as { B ₀,B₁,B₂,B₃,......,B_n-2,B_n-1,B_n };

the iterative formula of the beam current density is Substituting corresponding elements of the measurement array and the average density array into the above iterative formula to obtain values of the elements of the beam leveling average density array, wherein the values correspond to positions in the position array one by one, and in the iterative process, when n is less than 0, B _n =0;

Wherein the starting point and the ending point comprise: when the position of the bottom edge (4) of the beam baffle is equal to the top edge (8) of the Faraday cup slot; as a starting point, the beam stop top edge (2) is positioned lower than the faraday cup slit bottom edge (7) and is an ending point.

2. The measurement method of claim 1, wherein determining the beam measurement interval by the value of m comprises: the measurement interval is determined by W/m, wherein W represents the length of the beam baffle in the vertical direction, and m represents a positive integer, and can be selected as 1,2, 4 and the like; the larger the value of m, the smaller the measurement interval, and the more detailed the beam profile information finally obtained.

3. The measurement method of claim 1, wherein the beam average density comprises: the average beam current density refers to the average beam current size over the measurement interval W/m of the Y-axis.

4. A measurement device for vertical beam current density for implementing the measurement method of claim 1, comprising: a Faraday cup (1), a beam baffle (3), a transmission device (10) and a controller (12); the beam baffle can move along the vertical direction of the beam under the drive of the transmission device.