Increasing development and yield and reducing process time

due to competition to reﬁne semiconductor processes are fac-

tors that maximize productivity and proﬁts of semiconductor

companies, and the key solution for this is MI process. Among

MI processes, thin-ﬁlm metrology is a measurement equipment

that is used primarily in major semiconductor processes. Thin-

Film Metrology in the exposure process is one of the very

important element technologies because if the Wafer vision

alignment is poor, numerous defective Wafer can be produced

due to incorrect measurement.

Semiconductors are currently upgrading their technology

through pattern reﬁnement using equipment that can draw

circuit widths ﬁnely at the nano level through EUV technology,

so it is necessary to upgrade their technology to review product

production during product production. The Ellipsometer is a

measuring device that measures the change in polarization

state after light reﬂection or transmission, and the change in

polarization state is corrected according to the characteristics

of the measured sample and can have a resolution of up to

angstroms. Several companies are identifying ﬁne patterns,

recognizing problems during the process, and maximizing pro-

ductivity through process improvement activities by applying

the Ellipsometer production process, and a Wafer inspection

system is essential for this.

Thin ﬁlm thickness measuring equipment is an important

measuring instrument that is often used in each process.

Therefore, it is possible to expect an increase in semiconductor

production efﬁciency by introducing the Ellipsometer System

into the production process to reduce time in the process

by identifying defects during the actual factory production

process.

In this paper, we propose an inspection system design using

Ellipsometer for the MI process during the semiconductor

process.

Measure the area where the Wafer is inspected for defects

using an Ellipsometer. Existing Ellipsometer equipment is not

equipped with equipment to align Wafer, so Wafer cannot be

aligned when Wafer is inspected using Ellipsometer. Combin-

ing CCD Aligner with Ellipsometer helps Wafer measurements

be made more accurately and quickly.

By combining the WTR to transfer Wafer to the CCD

Aligner and the Ellipsometer measurement equipment, rapid

and accurate input and recovery of the Wafer is possible.

Combining Wafer’s auto-alignable CCD Aligner, WTR

Design and Implementation of an Ellipsometer Inspection System that

Conforms to the Wafer’s MI Process in the Production Process

1JAE-SUNG KIM, 1JONGPIL JEONG, 1CHAE-GYU LEE, 1TAE-YONG KIM, 2YONGJU NA,

2SE-HYEON RYU

1Department of Smart Factory Convergence, SungKyunKwan University, Suwon-si, REPUBLIC OF KOREA

2AI Research Lab, AIM Hanam-si, REPUBLIC OF KOREA

Abstract: Due to the recent semiconductor yield issue, the proportion of the MI (Measurement, Inspection)

process in the semiconductor industry is rapidly growing. Mass production of one wafer takes enormous cost

and time, and due to the nature of wafers, defective wafers cannot be reused, which causes enormous losses. In

this study, we propose an inspection method system using an ellipsometer for the wafer MI process. It is

expected that cost reduction in semiconductor production can be achieved by making wafer defect inspection

more efficient.

Keywords: Semiconductor Process, MI, Ellipsometer,Wafer Align, CCD Aligner

Received: April 19, 2022. Revised: May 29, 2023. Accepted: June 21, 2023. Published: August 1, 2023.

1. Introduction

DESIGN, CONSTRUCTION, MAINTENANCE

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Yongju Na, Se-Hyeon Ryu

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takes Wafer from the Wafer slot, puts Wafer into CCD

Aligner, collects Wafer aligned after Wafer alignment, mea-

sures Wafer’s thin ﬁlm thickness using Ellipsometer, and

proposes Wafer’s Examine system.

There are several processes in the semiconductor Wafer

process, and several studies are underway to manufacture

Wafers more efﬁciently for each process. [1] [2] [3]

To make as many normal chips as possible in one Wafer,

each process must be fully controlled, and accurate mea-

surement is essential for complete control. Metrology is the

exact measurement of the Wafer process as intended, and

Inspection is the inspection of whether the Wafer is defective

or the particle is separated, and the combination of these

two is called the MI (Measurement, Inspection) process. The

semiconductor process consists of a total of eight steps, and as

the measurement is carried out at the end of each process, the

MI process in the semiconductor process is very important.

Ellipsometry is a technology that uses interference or phase

difference between reﬂected light on a thin ﬁlm surface and

reﬂected light from an interface under the thin ﬁlm, and

changes due to the inﬂuence of the medium as light passes

through the medium. The change uses a property in which the

degree is proportional to the refractive index and thickness

of the thin ﬁlm. The device for measuring this is referred to

as an Ellipsometer, and various methods for measuring thin

ﬁlm thickness using the Ellipsometer are being studied. [4]

[5] [6] Ellipsometer measurement law is a non-destructive

test, and the advantage of measuring time is relatively short

to measure the sample, and it is relatively easy to measure

semiconductors. [7] Ellipsometry measures the polarization

variation of incident light and reﬂected light to determine the

thickness of the thin ﬁlm and the complex refractive index,

and the thickness of the thin ﬁlm can be measured from

the lowest number of angstroms to hundreds of micrometers.

These Ellipsometer technologies are currently being applied

in various ﬁelds, ranging from basic research such as physics,

electronics, and biology to industrial applications, and can be

applied to semiconductor measurement processes. Fig. 1 shows

a schematic diagram for measuring wafers using Ellipsometer.

Fig. 1. Schematic of Ellipsometer.

Fig. 2 is an overall conﬁguration diagram of the CCD

Aligner. The CCD Aligner is operated using a vision system.

The method of measuring [8] using Vision Aligner for Wafer

allows the controller to rotate the chuck once when the wafer

is placed on the chuck of the aligner, at which point the

image proﬁle of the wafer can be obtained from the CCD

circuit. After one turn, the chuck motor stops, and in this

case, the controller may obtain image data of the wafer from

the CCD circuit. Using these values, the eccentric amount of

the wafer and the direction of the fret or notch are calculated.

Thereafter, after going through an eccentric correction process

of matching the center of the chuck and the wafer, the direction

of the fret or notch is aligned in a predetermined direction.

As a result, the position of the visual marking marked on

the wafer is analyzed using a camera to check whether the

eccentricity of the wafer and the direction of the ﬂat or notch

are accurately aligned. The amount of error is calculated based

on the measurement of the initial alignment result. Repeating

accuracy may be obtained by repeating such an operation more

than 2,000 times.

Fig. 2. CCD Aligner.

A thin ﬁlm thickness measuring device using Ellipsometer,

which can be used in the MI process of semiconductor Wafer,

was designed.

By interlocking the WTR(Wafer Transfer Robot) and CCD

Aligner with the existing Ellipsometer equipment, WTR scans

the Wafer to be inspected in the Wafer slot and puts it into the

CCD Aligner. The injected Wafer is aligned by CCD aligner

by Wafer Aligner. The aligned Wafer is recovered by the WTR

again and the recovered Wafer is put into the Ellipsometer. The

injected Wafer has a structure in which the thickness of a thin

ﬁlm is measured using an Ellipsometer.

Fig. 3 shows the overall structure of the proposed system.

The WTR is located between the Wafer case and the Wafer

Aligner, and the Ellipsometer System is located in the center,

combined with each other, and interlocked.

Fig. 4 shows the overall ﬂow of the Ellipsometer system.

Determine whether to place the Wafer on the Wafer Stage

2. Related Work

2.1 M, (Measurement, Inspection)

2.2 Ellipsometer

2.3 CCD Aligner

3. Align Inspection System for Ellipsometer

3.1 System Design

3.2 Operation Procedures of Ellipsometer Inspection

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.12

Jae-Sung Kim, Jongpil Jeong,

Chae-Gyu Lee, Tae-Yong Kim,

Yongju Na, Se-Hyeon Ryu

E-ISSN: 2732-9984

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Fig. 3. Proposed System Structure.

after automatic alignment using the WTR or after manual

alignment for Ellipsometer measurement. If Wafer measure-

ment is performed manually without using WTR, the user

can use the Ellipsometer System after arbitrarily aligning the

Wafer position. If Wafer is automatically measured, detect the

Wafer cassette of the WTR inspection target, recognize the

slot in which Wafer is inserted, wait for the Wafer transfer,

and check if the CCD Aligner is empty. If the CCD Aligner

is empty, transfer from the Wafer in the slot at the bottom

of the Wafer cassette to the CCD Aligner. The transferred

Wafer is aligned from the CCD Aligner and is prepared to

be transferred to the Stage of the Ellipsometer System. If

the stage is found to be empty, the WTR takes the aligned

wafer from the CCD Aligner and sends it to the Ellipsometer

Stage for Ellipsometer measurement. The transferred Wafer is

completed by measuring the Ellipsometer, and the measured

Wafer is moved to the completed cassette and received. After

that, if Wafer remains in the cassette to be inspected, repeat

the process until Wafer does not remain in the cassette to be

inspected, and if it does not remain, the measurement system

is terminated.

Fig. 4. Whole System Flowchart.

STD-LP2 was used for the Load Port of this study. The

WTR robot used STD-WTR128. The CCD Aligner used

AL128. The Ellipsometer device used M-2000 [9].

Fig. 5 is a diagram that designs hardware based on the LM

Bearing and the precision control motor for the implementa-

tion of the precision Wafer Stage. In addition, a sensor network

and a data collection analysis system were established to

measure this. Thereafter, a computing system for motor control

and laser sensor interworking was established. Considering

the combination of the Ellipsometer System and WTR, the

Wafer holder and Y-axis conﬁguration can be transferred and

returned. In the case of the Wafer holder, the Wafer is adsorbed

using a vacuum, so that the Wafer movement does not occur

when moving to the stage. 6-in, 8-in, and 12-in wafers may be

mounted by giving a step to the holder so that wafers having

various speciﬁcations may be mounted.

Fig. 5. Combination of Ellipsometer System and WTR.

Fig. 6 shows the entire software for the system. Using

motion control and sensor data collection modules, an Edge

precision control module that can analyze and utilize data was

studied and implemented as software. It was developed to

facilitate code exchange between developers and maximize the

efﬁciency of writing by developing an algorithm by API/DLL

so that it can be developed as a publicized model rather

than applied to a speciﬁc type of application. Looking at the

S/W conﬁguration, WTR is controlled in the JMT Control

area. The Stage sends the Wafer’s insertion and injection

signals, the number of Wafer slots, and errors in WTR to

the Ellipsometer System area, which manages measurement

points and results. Based on the signals received earlier in

the Ellipsometer System area, Ellipsometer’s operating instruc-

tions and Ellipsometer’s measurement instructions are sent

to CompleteEASE, a software dedicated to Ellipsometer that

4. Implemenation and Results

4.1 Motor Control and Laser Sensor Linkage

4.2 Edge Precision Control Module for

Data Analysis and Utilization

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.12

Jae-Sung Kim, Jongpil Jeong,

Chae-Gyu Lee, Tae-Yong Kim,

Yongju Na, Se-Hyeon Ryu

E-ISSN: 2732-9984

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processes measurement and raw data. After measurement, soft-

ware communication is conﬁgured in the form of transmitting

the status and measurement results of the Ellipsometer back

to the Ellipsometer System, sending Stage’s Wafer detection

signal, Wafer measurement completed, and JMT Control.

Fig. 6. All Software.

Fig. 7 is an image of WTR. The WTR performed normal

operation according to the order conﬁgured in the system

ﬂowchart. The WTR recognized the Wafer slot in the Wafer

case and extracted the Wafer from the bottom. In the WTR,

the extracted Wafer is located in the opposite direction. It was

transferred to the CCD Aligner at Fig. 8 and the CCD Aligner

recognized and aligned the Wafer transferred to the WTR.

Fig. 7. WTR.

Fig. 8. CCD Aligner.

Wafer, whose alignment was completed in CCD Aligner,

was recovered by WTR again and shown in Fig. 9 Transferred

to Ellipsometer Stage.

Fig. 9. Ellipsometer Stage.

The transferred Wafer was measured by Ellipsometer, and

the measurement was shown in CompleteEAS, the Ellipsome-

ter software. It is displayed in a shape such as Fig. 10 and can

be checked. Fig. 10 is a result photo using a wafer position

recognition system [10] using a radial calibrator. The black

dot in Fig. 10 indicates the radius and angle, and the color

indicates Wafer’s ﬁlm thickness. The unit of thickness is nm,

red indicates thickness, and blue indicates thinness.

Fig. 10. Measurement Results Displayed on CompleteEASE.

It was developed to enable the introduction of a system in

the production process of the Ellipsometer, which is difﬁcult

to link due to its high development difﬁculty. The actual semi-

conductor production efﬁciency was increased by reducing

the time by measuring defects in the corresponding process

through determination during the semiconductor process. can

secure element technology such as Ellipsometer, micro pattern

analysis, ﬁne Alignment analysis, and precision Alignal. In

future work, we expect to develop a device that enables

more reliable alignment by mounting additional Alignment

devices on Ellipsometer devices, applying a new algorithm

[11] to existing CCD aligners, and mounting Ellipsometer’s

4.3 Result

4.4 Conclusion

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.12

Jae-Sung Kim, Jongpil Jeong,

Chae-Gyu Lee, Tae-Yong Kim,

Yongju Na, Se-Hyeon Ryu

E-ISSN: 2732-9984

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vision camera to increase the accuracy and speed of Wafer

measurement checks with machine vision-based systems [12].

Following are results of a study on the ”Leaders in INdustry-

university Cooperation 3.0” Project, supported by the Ministry

of Education and National Research Foundation of Korea,

Corresponding author. Prof.Jongpil Jeong

[1] Mahandran, Christopher Julian, et al. ”Thermal oxidation improvement

in semiconductor wafer fabrication.” Int J Pow Elec , Dri Syst 10.3

(2019): 1141-1147.

[2] Hong, Sungwon, Younsoo Lee, and Kungsik Lee. ”An optimization

model based on ﬂexible lead times for semiconductor wafer fabrication.”

Proceedings of the Korean Industrial Engineering Society Spring Joint

Academic Conference (2022): 2980-2989.

[3] Saqlain, Muhammad, Bilguun Jargalsaikhan, and Jong Yun Lee. ”A

voting ensemble classiﬁer for wafer map defect patterns identiﬁcation

in semiconductor manufacturing.” IEEE Transactions on Semiconductor

Manufacturing 32.2 (2019): 171-182.

[4] Rothen, Alexander. ”Improved method to measure the thickness of thin

ﬁlms with a photoelectric ellipsometer.” Review of Scientiﬁc Instruments

28.4 (1957): 283-285.

[5] Aspnes, D. E., and A. A. Studna. ”High precision scanning ellipsometer.”

Applied Optics 14.1 (1975): 220-228.

[6] Jae, Geulwon, et al. “Thickness measurement of patterned nano-thin

ﬁlm using Spectroscopic Imaging Ellipsometty.” Journal of the Korean

Society of Precision Engineering 21.6 (2004).

[7] Zollner, Stefan. ”Spectroscopic ellipsometry for inline process control

in the semiconductor industry.” Ellipsometry at the Nanoscale. Berlin,

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[8] Park, Hong-Lae, and Joon Lyou. ”A Wafer Alignment Method and

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systems 8.9 (2002): 812-817.

[9] M-2000 Ellipsometer, https://www.jawoollam.com/products/m-2000-

ellipsometer

[10] Lee, Byung-guk, and Lee,Joon-jae. “Wafer Position Recognition System

Using Radial Calibrator.” Journal of Multimedia Society 14.5 (2011):

632-641.

[11] Jang, Jin-young. “Development of Wafer Aligner Alogrithm Using

CCD Camera.” Domestic master’s thesis Sunmoon University Graduate

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[12] Kim, Jongwon. ”New wafer alignment process using multiple vision

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Acknowledgment

References

Following are results of a study on the ”Leaders in INdustry-

university Cooperation 3.0” Project, supported by the Ministry

of Education and National Research Foundation of Korea,

Corresponding author. Prof.Jongpil Jeong

Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

The authors equally contributed in the present

research, at all stages from the formulation of the

problem to the final findings and solution.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

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_US

DESIGN, CONSTRUCTION, MAINTENANCE

DOI: 10.37394/232022.2023.3.12

Jae-Sung Kim, Jongpil Jeong,

Chae-Gyu Lee, Tae-Yong Kim,

Yongju Na, Se-Hyeon Ryu

E-ISSN: 2732-9984

164

Volume 3, 2023