Radiation emitter and measurement system

Abstract

To provide a radiation emitter and a measurement system.SOLUTION: A radiation emitter 100A includes a first light source 102 that emits a first light beam L1 that transmits along a first optical path, a polarizer 104 arranged on the first optical path of the first light beam, and at least one mirror 106 arranged on the first optical path of the first light beam, and the first light beam is reflected by a first mirror of the at least one mirror and leaves the radiation emitter.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a radiation emitter and a measurement system.

Background Art

[0002] Terahertz radiation is widely used in non-contact measurements such as semiconductor wafer inspection. In conventional terahertz detection systems, it is difficult to align the terahertz radiation emitted by a terahertz light source such as a photoconductive antenna with the optical axis, so that the focus of the terahertz radiation cannot be properly adjusted on the sample, resulting in a decrease in measurement quality.

Summary of the Invention

Problems to be Solved by the Invention

[0003] To generate terahertz radiation emitted by a terahertz light source with better terahertz radiation alignment.

Means for Solving the Problems

[0004] Based on one embodiment of the present invention, a radiation emitter is provided. The radiation emitter includes a first light source that emits a first light beam transmitted along a first optical path, a polarizer disposed on the first optical path of the first light beam, and at least one mirror disposed on the first optical path of the first light beam. The first light beam is reflected by the first mirror of the at least one mirror and leaves the radiation emitter.

[0005] Based on another embodiment of the present invention, a measurement system is provided. The measurement system includes a laser source that emits a laser beam, a beam splitter that splits the laser beam into a first portion of the laser beam and a second portion of the laser beam, a sample stage configured to hold a sample, a radiator that receives the first portion of the laser beam, and a radiation detector that receives the second portion of the laser beam. The radiator includes a first light source that emits a first light beam based on the first portion of the laser beam, transmits the first light beam to the sample along a first optical path, and generates a first reflected light beam, a polarizer disposed on the first optical path of the first light beam, and at least one mirror disposed on the first optical path of the first light beam. The first light beam is reflected by the first mirror of the at least one mirror and reaches the sample away from the radiator. The radiation detector includes at least one receiver that receives a portion of the first reflected light beam, and a lock-in amplifier amplifier that is connected to the radiation detector and receives a detection signal from the radiation detector.

Effects of the Invention

[0006] The off-axis arrangement of the optical path of terahertz radiation can compensate for the deviation of the optical axis of terahertz radiation. Additional visible light provides another way to compensate for the deviation of the optical axis of terahertz radiation. By measuring the terahertz radiation reflected by the sample with a radiation detector, the reflected terahertz radiation can be measured simultaneously in two different polarization directions.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

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Figure 6

Figure 7A

Figure 7B

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described in detail in combination with the accompanying drawings. However, the provided embodiments are not used to limit the scope of the present invention. Also, the sizes of the components in the drawings are drawn for convenience of explanation and do not represent the actual sizes of the components. Furthermore, in the text, terms such as "first" and "second" are used to describe different components and / or film layers, but these components and / or film layers should not be limited to these terms. Rather, these terms are only used to distinguish one component or film layer from another. Therefore, the first component or film layer discussed below may also be referred to as the second component or film layer without departing from the teachings of the embodiment. For ease of understanding, in the following description, similar components are described using the same reference numerals.

[0009] In the description of embodiments of the present invention, reference signs and / or words that repeat in different examples can be used. These repeating signs or words are for the purpose of simplification and clarification, and are not used to limit the relationship and / or appearance structure between various embodiments. Further, in the disclosure of the following specification, when it is described that a first feature is formed above or on a second feature, embodiments in which the formed first feature and the second feature are in direct contact are included, and embodiments in which additional features are formed between the first feature and the second feature are also included. Therefore, there may be cases where the first feature and the second feature are not in direct contact. For ease of understanding, in the following description, similar components are described using the same signs.

[0010] FIG. 1 is a schematic diagram of a measurement system according to one embodiment of the present invention.

[0011] Referring to FIG. 1, the measurement system 10 includes a laser source 12, a beam splitter 14, a sample stage 18, a radiation emitter 100, a radiation detector 200, and a lock-in amplifier 24.

[0012] The laser source 12 emits a laser beam L. The laser beam L is transmitted to the beam splitter 14 via an optical fiber. In some embodiments, the laser source 12 is a femto - second laser source, and the laser beam L is a femto - second laser beam.

[0013] The beam splitter 14 divides the laser beam L into a first portion of a laser beam LA and a second portion of a laser beam LB. The first portion of the laser beam LA is transmitted to the radiation emitter 100 by an optical fiber. The second portion of the laser beam LB is transmitted to the radiation detector 200 via a delay line 20 and an optical fiber.

[0014] In some embodiments, the ratio of the intensity of the first portion of the laser beam LA to the intensity of the second portion of the laser beam LB is between 30:70 and 70:30, and preferably, it is 50:50.

[0015] The radiation emitter 100 receives the first portion of the laser beam LA and emits the first light beam L1 to the sample 16. The detailed structure of the radiation emitter 100 will be described in a later paragraph.

[0016] The sample 16 is held by the sample stage 18. In some embodiments, the sample 16 is a semiconductor wafer. In some embodiments, the sample 16 may be a wafer with a diameter between 4 inches and 8 inches. However, the wafer may be a larger or smaller wafer, and the present invention is not limited thereto.

[0017] In some embodiments, the sample stage 18 is an XY table that moves the sample 16 along the X and Y directions. In some embodiments, the sample stage 18 rotates the sample 16. By moving and rotating the sample 16, the sample 16 can be scanned entirely with the first light beam L1.

[0018] The first light beam L1 is directed towards the sample 16 and is reflected by the sample 16 as the first reflected light beam L1'. Therefore, the first reflected light beam L1' carries information of the sample 16. A part of the first reflected light beam L1' is received by the radiation detector 200.

[0019] The radiation detector 200 receives a part of the first reflected light beam L1' from the sample. The radiation detector 200 also receives the second portion of the laser beam LB from the beam splitter 14. The radiation detector 200 transmits a detection signal to a pre - amplifier 22 based on the first reflected light beam L1' and the second portion of the laser beam LB, and amplifies the detection signal.

[0020] The lock-in amplifier 24 is connected to the radiation detector 200 and receives the detection signal from the radiation detector 200. The lock-in amplifier 24 compares the detection signal from the radiation detector 200 with the reference signal and extracts the signal corresponding to the characteristics of the sample 16.

[0021] The signal extracted by the lock-in amplifier 24 is transmitted to the data acquisition and control unit 26. The signal is then processed and transmitted to the computer 28 for further analysis.

[0022] The following is a detailed description of the radiation emitter 100 and the radiation detector 200.

[0023] FIG. 2 is a schematic diagram of the radiation emitter of the measurement system according to one embodiment of the present invention.

[0024] The radiation emitter 100A is an embodiment of the radiation emitter 100 shown in FIG. 1. The radiation emitter 100A includes a first light source 102, a polarizer 104, and at least one mirror (mirrors 106 and 108).

[0025] The first light source 102 emits a first light beam L1 that travels along a first optical path to the sample 16 and generates a first reflected light beam L1'. The first light beam L1 is terahertz radiation. In some embodiments, the frequency range of the first light beam L1 is between 0.1 and several hundred terahertz. In some embodiments, the first light source 102 is a photoconductive antenna or an array of photoconductive antennas excited by a first portion of the laser beam LA as shown in FIG. 1.

[0026] The polarizer 104 is disposed on the first optical path of the first light beam L1. In some embodiments, the polarizer 104 is a linear polarizer. The polarizer 104 may be an S-type polarizer or a P-type polarizer according to the desired polarization direction of the first light beam L1. Here, the S-type polarization refers to the electric field of the light beam being perpendicular to the incident plane. The P-type polarization refers to the electric field of the light beam being parallel to the incident plane.

[0027] In some embodiments, the polarizer 104 may be disposed at other desired positions along the first optical path. In some embodiments, the polarizer 104 may be disposed between the mirror 108 and the sample 16.

[0028] At least one mirror is disposed on the first optical path of the first light beam L1 and reaches the sample 16 away from the radiation emitter 100A. In this embodiment, the number of mirrors is two. However, the number of mirrors and the positions where the mirrors are disposed are due to the desired characteristics and design of the radiation emitter 100A, and the present invention is not limited thereto.

[0029] In some embodiments, the mirrors 106 and 108 are off-axis parabolic (OAP) mirrors. The off-axis parabolic mirror has the ability to focus collimated light without introducing spherical aberration. The first light beam L1 incident on the OAP mirrors 106 and 108 is focused. The first light beam L1 is then reflected by the mirror 112 and reaches the sample 16 away from the radiation emitter 100A.

[0030] When a typical terahertz radiation source such as a photoconductive antenna emits typical terahertz radiation, the emitted photoconductive antenna often deviates from the optical axis of the terahertz radiation source. Therefore, when the emitted terahertz radiation is reflected by a mirror, the terahertz radiation encounters a serious problem of misalignment of the reflecting surface.

[0031] However, in the arrangement shown in FIG. 2, due to the off-axis arrangement of the mirrors 106 and 108, the optical axis of the first light beam L1 can be adjusted, so that an unexpected misalignment of the optical axis from the first light source 102 can be compensated. The circular spot formed on the sample 16 by the first light beam L1 can also be adjusted.

[0032] Furthermore, in the arrangement shown in FIG. 2, the radiation emitter 100A does not have a lens within the optical setup. The first optical beam L1 is transmitted between the OAP mirrors by reflection. Therefore, when the first optical beam L1 needs to be transmitted through a lens-shaped optical component, since there is no material absorption, the aberration and loss of the first optical beam L1 are reduced.

[0033] To provide better alignment of terahertz radiation, another visible light source may be provided to assist with the alignment.

[0034] FIG. 3 is a schematic diagram of a radiation emitter of a measurement system according to one embodiment of the present invention.

[0035] The arrangement in FIG. 3 is similar to the arrangement in FIG. 2. The difference is that the first light source 102 is replaced with a second light source 112.

[0036] The second light source 112 emits a second optical beam L2 that is transmitted along a second optical path. In some embodiments, the second optical beam L2 is visible light. The second light source 112 is a visible light source.

[0037] As shown in FIG. 3, the mirrors 106 and 108 are reflective not only with respect to the first terahertz optical beam L1 but also with respect to the visible light L2.

[0038] As shown in FIG. 3, the second optical path of the second optical beam L2 is the same as that of the first optical beam L1. Therefore, the second optical beam L2 can be used to calibrate the first optical path of the invisible first terahertz optical beam L1. Specifically, when the second optical beam L2 is irradiated onto the sample, an optical spot may be formed by the second optical beam L2. By comparing the positions of the optical spots generated by the first optical beam L1, it can be determined whether the deviation of the optical axis of the first optical beam L1 has been compensated. When the deviation of the optical axis of the first optical beam L1 is completely compensated, the first optical spot of the first optical beam L1 formed on the sample 16 and the second optical spot of the second optical beam L2 formed on the sample 16 overlap.

[0039] In the arrangements of FIGS. 2 and 3, in order to calibrate the optical axis of the first optical beam L1 (FIG. 2), it is necessary to replace the first light source 102 with the second light source 112. Therefore, it is also called the off-line alignment of the first optical beam L1.

[0040] FIG. 4 is a schematic diagram of a radiation emitter of a measurement system according to an embodiment of the present invention.

[0041] The radiation emitter 100B is an embodiment of the radiation emitter 100 shown in FIG. 1 and is similar to the radiation emitter 100A shown in FIG. 2. The difference is that, as shown in FIG. 4, the first optical path of the first optical beam L1 is here directed towards the sample 16 by four mirrors 120, 122, 124, and 126. More specifically, the mirrors 120 and 126 are OAP mirrors, and the mirrors 122 and 124 are plane mirrors.

[0042] The presence of more mirrors along the first optical path of the terahertz first optical beam L1 makes it easier to compensate for the deviation of the optical axis of the first optical beam L1.

[0043] FIG. 5 is a schematic diagram of a radiation emitter of a measurement system according to an embodiment of the present invention.

[0044] The radiation emitter 100C is an embodiment of the radiation emitter 100 shown in FIG. 1 and is similar to the radiation emitter 100B shown in FIG. 4. The difference is that, as shown in FIG. 5, the second light source 112 is arranged at a position different from that of the first light source 102. The second optical beam L2 emitted by the second light source 112 is transmitted through the mirror 122 and reflected by the mirrors 124 and 126 to reach the sample 16.

[0045] As shown in FIG. 5, the mirror 122 reflects the first light beam L1 which is terahertz radiation and transmits the second light beam L2 which is visible light. Starting from the mirror 122, the optical paths of the first light beam L1 and the second light beam L2 overlap with each other. That is, the optical paths of the first light beam L1 and the second light beam L2 partially overlap.

[0046] In the radiation emitter 100C, the first light source 102 and the second light source 112 coexist, and the first light beam L1 and the second light beam L2 can be emitted simultaneously. Therefore, the second light beam L2 can be used to calibrate the deviation of the optical axis of the first light beam L1 in real time, which is different from the radiation emitter 100A shown in FIGS. 2 and 3. Therefore, the radiation emitter 100C can more efficiently calibrate the deviation of the optical axis of the first light beam L1.

[0047] FIG. 6 is a schematic diagram of a radiation emitter and a radiation detector of a measurement system according to an embodiment of the present invention.

[0048] As shown in FIG. 6, in this embodiment, the radiation emitter 100C shown in FIG. 5 is used. However, here, the radiation emitter 100A shown in FIGS. 2 and 3 or the radiation emitter 100B shown in FIG. 4 can also be used, so the present invention is not limited thereto.

[0049] The radiation detector 200A is an embodiment of the radiation detector 200 shown in FIG. 1.

[0050] The radiation detector 200A includes at least one receiver and receives a part of the first reflected light beam L1' from the sample 16. As shown in FIG. 6, the radiation detector 200A includes a first receiver 210 and a second receiver 216, which will be described later.

[0051] As shown in FIG. 6, the radiation detector 200A further includes a beam splitter 204 disposed on the third optical path of the first reflected light beam L1'. The first reflected light beam L1' enters the beam splitter 204 along the third optical path, which includes being reflected by the mirror 202. The beam splitter 204 splits the first reflected light beam L1' into a first portion of the first reflected light beam L3 and a second portion of the first reflected light beam L4.

[0052] The radiation detector 200A further includes a first polarizer 206 and a second polarizer 212. The first polarizer 206 is disposed between the beam splitter 204 and the first receiver 210. The second polarizer 212 is disposed between the beam splitter 204 and the second receiver 216.

[0053] The first portion of the first reflected light beam L3 is transmitted to the first receiver 210 through the first polarizer 206 and is polarized in the first polarization direction. The second portion of the first reflected light beam L4 is transmitted to the second receiver 216 through the second polarizer 212 and is polarized in a second polarization direction different from the first polarization direction.

[0054] In some embodiments, the first polarizer 206 is either an S-type polarizer or a P-type polarizer, and the second polarizer 212 is the other of the S-type polarizer and the P-type polarizer.

[0055] As a result, the radiation detector 200A can simultaneously measure the first reflected light beam in two different polarization directions, namely, the S-type and the P-type, thus providing more information about the sample 16.

[0056] FIGS. 7A and 7B are examples of measurement results of a measurement system according to one embodiment of the present invention.

[0057] One of the characteristic parameters of the wafer measurable by the measurement system (shown in the above embodiment) is the resistivity of the wafer. As described above, the sample 16 is placed on the sample stage 18 and is movable along the X and Y directions and is also rotatable. Therefore, it becomes possible to measure the resistivity of the wafer at a specific position or scan the resistivity distribution of the wafer.

[0058] FIG. 7A shows the measurement of the resistivity of the wafer at a plurality of different positions on the wafer. The measurement results are compatible with the results measured by other methods such as the Eddy current method.

[0059] FIG. 7B shows the measurement of the resistivity distribution of the wafer at a plurality of different positions on the wafer. The measurement results are compatible with the results measured by other methods such as the Eddy current method.

[0060] As described above, a non-destructive measurement system based on terahertz radiation is provided. The off-axis arrangement of the optical path of the terahertz radiation can compensate for the deviation of the optical axis of the terahertz radiation. The additional visible light provides another method for compensating the deviation of the optical axis of the terahertz radiation. By measuring the terahertz radiation reflected by the sample with a radiation detector, the reflected terahertz radiation can be measured simultaneously in two different polarization directions.

[0061] As will be apparent to those skilled in the art, various modifications and changes can be made to the disclosed embodiments without departing from the scope or spirit of the present invention. In view of this, the present invention is intended to cover modifications and changes within the scope of the following claims and their equivalents.

Industrial Applicability

[0062] The radiation emitter and the measurement system of the present invention can be applied to various terahertz radiation emitters and measurement systems.

Explanation of Reference Numerals

[0063] 10 Measurement system 12 Laser source 14, 204 Beam splitter 16 Sample 18 Sample stage 20 Delay line 22 Preamplifier 24 Lock-in amplifier 26 Control unit 28 Computer 100, 100A, 100B, 100C Radiation emitter 102 First light source 104 Polarizer 106, 108, 120, 122, 124, 126, 206 Mirror 112 Second light source 200, 200A Radiation detector 206 First polarizer 210 First receiver 212 Second polarizer 216 Second receiver L1 First light beam L1’, L3, L4 First reflected light beam L2 Second light beam LA, LB Laser light beam

Claims

1. A radiation emitter comprising: a first light source emitting a first light beam that propagates along a first optical path; a polarizer disposed on the first optical path of the first light beam; at least one mirror disposed on the first optical path of the first light beam; Including, The radiation emitter, wherein the first light beam is reflected by a first one of the at least one mirror and leaves the radiation emitter.

2. 2. The radiation emitter of claim 1 wherein the first light source is a photoconductive antenna.

3. 10. The radiation emitter of claim 1, wherein the first light beam is terahertz radiation.

4. 2. The radiation emitter of claim 1, wherein the polarizer is a linear polarizer.

5. 2. The radiation emitter of claim 1, wherein the first mirror of the at least one mirror is an off-axis parabolic mirror.

6. The radiation emitter further comprises: a second light source emitting a second light beam that propagates along a second optical path; the second light beam is visible light; 2. The radiation emitter of claim 1, wherein the second optical path overlaps with the first optical path after the second optical beam is reflected by or transmitted through the first of the at least one mirror.

7. 7. The radiation emitter of claim 6, wherein a first light spot of the first light beam formed on the sample and a second light spot of the second light beam formed on the sample overlap.

8. a laser source emitting a laser beam; a beam splitter for splitting the laser beam into a first portion of the laser beam and a second portion of the laser beam; a sample stage configured to hold a sample; a radiation emitter that receives a first portion of the laser beam; a radiation detector that receives a second portion of the laser beam; In a measurement system comprising: The radiation emitter is a first light source that emits a first light beam based on the first portion of the laser beam, transmits the first light beam along a first optical path to the sample, and generates a first reflected light beam; a polarizer disposed on the first optical path of the first light beam; at least one mirror disposed on the first optical path of the first light beam, the first light beam being reflected by a first mirror of the at least one mirror so as to leave the radiation emitter and reach the sample; Including, The radiation detector comprises: at least one receiver that receives a portion of the first reflected light beam; a lock-in amplifier connected to the radiation detector and receiving a signal detected by the radiation detector; Including, Measurement system.

9. The measurement system of claim 8 , wherein the first light source is a photoconductive antenna.

10. The measurement system of claim 8 , wherein the first light beam is terahertz radiation.

11. The measurement system of claim 8 , wherein the polarizer is a linear polarizer.

12. 9. The measurement system of claim 8, wherein the first mirror of the at least one mirror is an off-axis parabolic mirror.

13. The radiation emitter further comprises: a second light source that emits a second light beam that transmits along a second optical path to the sample and generates a second reflected light beam; the second light beam is visible light; 9. The measurement system of claim 8, wherein after the second light beam is reflected by or transmitted through the first one of the at least one mirror, the second light path overlaps with the first light path and the second light beam is directed toward the sample.

14. 14. The measurement system of claim 13, wherein a first light spot of the first light beam formed on the sample and a second light spot of the second light beam formed on the sample overlap.

15. the at least one receiver includes a first receiver and a second receiver; The radiation detector further comprises: a beam splitter disposed on a third optical path of the first reflected light beam to split the first reflected light beam into a first portion of the first reflected light beam and a second portion of the first reflected light beam; a first polarizer disposed between the beam splitter and the first receiver; a second polarizer disposed between the beam splitter and the second receiver; Including, the first portion of the first reflected light beam is transmitted through the first polarizer to the first receiver and is polarized in a first polarization direction; 9. The measurement system of claim 8, wherein the second portion of the first reflected light beam is transmitted through the second polarizer to the second receiver and is polarized in a second polarization direction different from the first polarization direction.

16. the first polarizer is one of an S-type polarizer and a P-type polarizer, 16. The measurement system of claim 15, wherein the second polarizer is the other of the S-type polarizer and the P-type polarizer.

17. The measurement system of claim 8 , wherein the sample stage is an XY table.

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