CN111769030A

CN111769030A - Device and method for measuring density distribution of beam in vertical direction

Info

Publication number: CN111769030A
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: 2020-10-13

Abstract

The invention discloses a device and a method for measuring beam density in the vertical direction, relates to an ion implanter, and belongs to the field of semiconductor manufacturing. The device includes: the device comprises a Faraday cup (1), a beam current baffle (3), a transmission device (10) and a controller (12). The method comprises the following steps: setting measurement precision, wherein the precision determines the distance (6) of the Faraday cup to collect a primary value when the beam current baffle moves; 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 slit, finishing one measurement; and sequentially substituting the elements of the acquisition value array into a beam density iterative formula in the specification to obtain a beam 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, higher and higher requirements are put forward on semiconductor process equipment, and in order to meet the requirements of new technology, an ion implanter, which is one of key equipment of a semiconductor ion doping process line, needs to be continuously improved in the aspects of beam current index, beam energy purity, implantation depth control, implantation uniformity, productivity and the like. The uniformity of implantation, beam parallelism, implantation angle and ion implantation precision are key performance parameters of the ion implanter in the implantation process. These parameters need to be monitored by beam current measurements.

Ion implanters employ a variety of beam measurement techniques. For example, a one-dimensional moving faraday cup to measure the profile of the beam and beam uniformity; the device comprises a mobile Faraday array, a plurality of Faraday cups and a measurement unit, wherein the mobile Faraday array is composed of a plurality of Faraday cups, and the Faraday cups are fixed on a bottom and can move together to measure the two-dimensional profile and the uniformity of beam current.

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

Therefore, there is a need to apply new beam density measurement techniques in ion implanters. The invention provides a technology for measuring density distribution of beam current 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, a group of measured values are collected, and the measured values are processed in the processor through an iterative algorithm to obtain a beam density curve of the beam on the vertical profile. Different from the conventional beam profile measuring technology, the beam profile measuring method is adjustable in measuring precision, simpler in structure and flexible in application. Such as the ability to form a two-dimensional beam profile when applied to a common one-dimensional moving faraday.

One aspect of the present invention provides a system for beam current density measurement in an ion implantation system. The system is coordinated by a controller, the controller has four functions, one is to control the movement of the beam baffle, the other is to process the acquired data, the third is to control the beam generating device, and the fourth is to interact with an 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 is to determine a starting point and an end point, the second is to take 0 as a value before the starting point, and the third is to take a beam density iterative formula. And the acquired beam current value is processed by an iterative algorithm to obtain beam current density distribution.

Drawings

The invention will be further described with reference to the following drawings and specific examples, but the invention is not limited thereto.

Fig. 1a is a schematic view of the beam baffle and faraday cup configuration of the present invention.

FIG. 1b is a schematic view of a beam density measuring system according to the present invention

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

FIG. 2b is a schematic view of the beam density of a cross section obtained when the measurement accuracy is W (Gaussian beam distribution)

FIG. 3a shows the position of the acquisition point relative to the beam stop at W/2 measurement accuracy

FIG. 3b is a schematic view of the beam density of a cross section obtained when the measurement accuracy is W/2 (Gaussian beam distribution)

FIG. 4a shows the position of the acquisition point relative to the beam stop at W/4 measurement accuracy

FIG. 4b is a schematic view of the beam density of a cross section obtained when the measurement accuracy is W/4 (Gaussian beam distribution)

Detailed Description

The invention will be further described with reference to the accompanying drawings, but the invention is not limited thereto.

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 generating device, and the beam baffle is close to the slit and insulated from the Faraday cup. Before starting measurement, the controller (12) moves the beam current baffle to the position of the starting point (8) through the driver (11) and the transmission device (10). After starting the measurement, the controller controls the beam current baffle to move towards the direction of the end point (7). And the processor obtains the real-time position of the beam baffle through coding feedback. Determined by measuring the accuracy m (m being a positive integer, e.g. 1, 2, 4 …)The position of the sampling interval relative to the beam current baffle is determined. The processor collects a faraday cup value once every time the position of the beam stop moves a distance of 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 array of measurement values { C }₀，C₁，C₂，C₃，......，C_n-2，C_n-1，C_nAnd the position array of the array and the beam baffle during sampling (S)₀，S₁，S₂，S₃，......，S_n-2，S_n-1，S_nThe elements in the Chinese character correspond to one another. The processor will perform an iterative algorithm, based on an iterative formula and initial conditions:

B_n＝0(n＜0)

obtaining a beam average density array { B₀，B₁，B₂，B₃，......，B_n-2，B_n-1，B_nAnd the arrays correspond to elements in the position arrays 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 primary beam vertical section, 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 section information is obtained. Fig. 2a-4a show the beam density distribution of 2b-4b, which is finally obtained by taking the positions of the acquisition points relative to the beam baffle when m is 1, 2 and 4 respectively, taking the beam with gaussian distribution as an example. If the measurement accuracy needs to be improved continuously, only the value m needs to be increased continuously, and finally the obtained beam density distribution is more perfect. However, the value of m is not infinitely large and will have an upper limit for a particular measurement system.

And after the processor obtains the beam density distribution, the processor feeds back related adjusting parameters to the beam generating device so as to adjust the beam and sends information to the upper computer.

The contents of the present patent have been described in detail with reference to specific embodiments thereof. Any obvious modifications to the disclosure herein disclosed which do not depart from the spirit of the disclosure herein will be readily apparent to those skilled in the art as a violation of the disclosure and the pertinent legal responsibility will be afforded thereto.

Claims

1. A vertical beam density measuring device comprises: the device comprises a Faraday cup (1), a beam current 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.

2. A method for vertical beam current density measurement in an ion implantation system, the method comprising: determining beam current measurement intervals by measuring the m value, starting the beam current baffle to move from a starting point (8), measuring the beam current value at equal intervals by the controller according to the position of the lower edge of the baffle, obtaining a one-dimensional measured value array by the processor (14) when the beam current baffle reaches an end point (7), forming a one-dimensional position array by the position of the lower edge of the beam current baffle on the Y axis, and sequentially carrying out an iterative algorithm on the measured arrays to obtain beam current average density arrays in one-to-one correspondence with the position arrays.

3. The method of claim 2, wherein determining the beam current measurement interval by the m value 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, which can be selected from 1, 2, 4 and the like. The larger the value of m is, the smaller the measurement interval is, and the more detailed the finally obtained beam profile information is.

4. The method of claim 2, wherein the iterative algorithm comprises: one-dimensional position array is marked as

{S₀，S₁，S₂，S₃，......，S_n-2，S_n-1，S_n} (position array)

One-dimensional measurement array is recorded as

{C₀，C₁，C₂，C₃，......，C_n-2，C_n-1，C_n} (measurement array)

The average density array of the beam current to be solved is recorded as

{B₀，B₁，B₂，B₃，......，B_n-2，B_n-1，B_n} (array of beam current average density)

The iterative formula of the beam density is

Substituting the corresponding elements of the measurement array and the average density array into the iteration formula to obtain the value of each element of the beam current average density array, wherein the value corresponds to the position in the position array one by one, and when n is less than 0 in the iteration process, B_n＝0。

5. The method of claim 2, wherein the beam current average density comprises: the average beam current density refers to the average value of the beam current magnitude in the measurement interval W/m of the Y axis.

6. The method of claim 2, 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 position of the top edge (8) of the Faraday cup slit, the starting point is, and when the position of the top edge (2) of the beam baffle is lower than the position of the bottom edge (7) of the Faraday cup slit, the ending point is.