Radiation emitters and measurement systems

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 technology]

[0002] Terahertz radiation is widely used for non-contact measurements such as semiconductor wafer inspection. Conventional terahertz detection systems face difficulties in aligning the optical axis of the terahertz radiation emitted by a terahertz source such as a photoconductive antenna, resulting in inadequate focusing of the terahertz radiation on the sample, resulting in poor measurement quality. Summary of the Invention [Problem to be solved by the invention]

[0003] The objective is to generate terahertz radiation emitted by a terahertz source with better terahertz radiation alignment. [Means for solving the problem]

[0004] According to one embodiment of the present invention, there is provided a radiation emitter including 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, and at least one mirror disposed on the first optical path of the first light beam, wherein the first light beam is reflected by the first mirror of the at least one mirror and leaves the radiation emitter.

[0005] According to another embodiment of the present invention, there is provided a measurement system including a laser source emitting a laser beam, a beam splitter 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 receiving the first portion of the laser beam, and a radiation detector receiving the second portion of the laser beam. The radiation emitter includes a first light source emitting a first light beam based on the first portion of the laser beam, transmitting the first light beam along a first optical path to the sample, and generating 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, wherein the first light beam is reflected by the first mirror of the at least one mirror, leaves the radiation emitter, and reaches the sample. The radiation detector includes at least one receiver receiving a portion of the first reflected light beam, and a lock-in amplifier connected to the radiation detector and receiving a detection signal from the radiation detector. [Effects of the Invention]

[0006] An off-axis arrangement of the optical path of the terahertz radiation can compensate for the misalignment of the optical axis of the terahertz radiation. Additional visible light provides another way to compensate for the misalignment 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. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a measurement system according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a radiation emitter of a measurement system according to one embodiment of the present invention; [Figure 3] 1 is a schematic diagram of a radiation emitter of a measurement system according to one embodiment of the present invention; [Figure 4]1 is a schematic diagram of a radiation emitter of a measurement system according to one embodiment of the present invention; [Figure 5] 1 is a schematic diagram of a radiation emitter of a measurement system according to one embodiment of the present invention; [Figure 6] 1 is a schematic diagram of a radiation emitter and a radiation detector of a measurement system according to one embodiment of the present invention. [Figure 7A] 10 is an example of a measurement result of a measurement system according to one embodiment of the present invention. [Figure 7B] 10 is an example of a measurement result of a measurement system according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following detailed description will be given in conjunction with the accompanying drawings, but the provided embodiments are not intended to limit the scope of the present invention. The sizes of components in the drawings are for convenience of explanation and do not represent the actual sizes of the components. Furthermore, although terms such as "first" and "second" are used in the present description to describe different components and / or film layers, these components and / or film layers should not be limited by these terms. Rather, these terms are used only to distinguish one component or film layer from another. Therefore, a first component or film layer discussed below may also be referred to as a second component or film layer without departing from the teachings of the embodiments. For ease of understanding, the following description will use the same reference numerals to refer to similar components.

[0009] In describing embodiments of the present invention, repeated reference numerals and / or words may be used in different instances. These repeated numerals or words are for the purposes of brevity and clarity and are not intended to limit the relationship between and / or the external structure of various embodiments. Furthermore, in the following specification disclosure, when a first feature is described as being formed on or above a second feature, this includes embodiments in which the formed first feature and second feature are in direct contact, as well as embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact. For ease of understanding, the following description uses the same numerals to refer to similar components.

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

[0011] Referring to FIG. 1, a 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] Laser source 12 emits a laser beam L. Laser beam L is transmitted via an optical fiber to beam splitter 14. In some embodiments, laser source 12 is a femtosecond laser source and laser beam L is a femtosecond laser.

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

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

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

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

[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 across 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 a first reflected light beam L1'. The first reflected light beam L1' therefore carries information about the sample 16. A portion of the first reflected light beam L1' is received by the radiation detector 200.

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

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

[0021] The signal extracted by the lock-in amplifier 24 is sent to a data acquisition and control unit 26. The signal is then processed and sent to a 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 a radiation emitter of a measurement system according to one embodiment of the present invention.

[0024] Radiation emitter 100A is an embodiment of radiation emitter 100 shown in Figure 1. 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 propagates along a first optical path toward the sample 16, generating 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 that are 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 depending on the desired polarization direction of the first light beam L1. Here, S-type polarization refers to the electric field of the light beam being perpendicular to the plane of incidence. P-type polarization refers to the electric field of the light beam being parallel to the plane of incidence.

[0027] In some embodiments, the polarizer 104 may be positioned at any other desired location along the first optical path. In some embodiments, the polarizer 104 may be positioned 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, which leaves the radiation emitter 100A and reaches the sample 16. In this embodiment, the number of mirrors is two. However, the number of mirrors and the positions at which the mirrors are disposed depend on the desired characteristics and design of the radiation emitter 100A, and therefore the present invention is not limited thereto.

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

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

[0031] 2, however, the off-axis placement of mirrors 106 and 108 allows the optical axis of first light beam L1 to be adjusted to compensate for any unexpected misalignment of the optical axis from first light source 102. The circular spot formed on sample 16 by first light beam L1 also becomes adjustable.

[0032] 2, the radiation emitter 100A does not have a lens in the optical setup. The first light beam L1 is transmitted between the OAP mirrors by reflection. Therefore, if the first light beam L1 has to be transmitted through a lenticular optic, there is less aberration and loss in the first light beam L1 due to the lack of material absorption.

[0033] To provide better alignment of the terahertz radiation, a separate visible light source may be provided to assist in 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 Figure 3 is similar to that in Figure 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 light beam L2 that propagates along a second optical path. In some embodiments, the second light beam L2 is visible light. The second light source 112 is a visible light source.

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

[0038] As shown in Figure 3, the second optical path of the second light beam L2 is identical to that of the first light beam L1. Therefore, the second light beam L2 can be used to calibrate the first optical path of the invisible terahertz first light beam L1. Specifically, when the second light beam L2 is irradiated onto the sample, a light spot may be formed by the second light beam L2. By comparing the position of the light spot generated by the first light beam L1, it can be determined whether the misalignment of the optical axis of the first light beam L1 has been compensated for. When the misalignment of the optical axis of the first light beam L1 is completely compensated for, the first light spot of the first light beam L1 formed on the sample 16 and the second light spot of the second light beam L2 formed on the sample 16 will overlap.

[0039] 2 and 3, to calibrate the optical axis of the first light beam L1 (FIG. 2), the first light source 102 needs to be replaced with the second light source 112. Therefore, this is also called off-line alignment of the first light beam L1.

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

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

[0042] With more reflecting mirrors along the first optical path of the first terahertz light beam L1, it becomes easier to compensate for misalignment of the optical axis of the first light beam L1.

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

[0044] Radiation emitter 100C is an embodiment of radiation emitter 100 shown in Figure 1 and is similar to radiation emitter 100B shown in Figure 4, except that second light source 112 is located at a different position than first light source 102, as shown in Figure 5. A second light beam L2 emitted by second light source 112 is transmitted through mirror 122 and reflected by mirrors 124 and 126 to reach sample 16.

[0045] 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 each other. That is, the optical paths of the first light beam L1 and the second light beam L2 partially overlap each other.

[0046] In the radiation emitter 100C, the first light source 102 and the second light source 112 are simultaneously present, 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 misalignment of the optical axis of the first light beam L1 in real time, which is different from the radiation emitter 100A shown in Figures 2 and 3. Therefore, the radiation emitter 100C can more efficiently calibrate the misalignment 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 one embodiment of the present invention.

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

[0049] Radiation detector 200A is an embodiment of radiation detector 200 shown in FIG.

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

[0051] 6, the radiation detector 200A further includes a beam splitter 204 disposed on a 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 a mirror 202. The beam splitter 204 splits the first reflected light beam L1' into a first portion of a first reflected light beam L3 and a second portion of a 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] A first portion of the first reflected light beam L3 is transmitted through the first polarizer 206 to the first receiver 210 and is polarized in a first polarization direction. A second portion of the first reflected light beam L4 is transmitted through the second polarizer 212 to the second receiver 216 and is polarized in a second polarization direction different from the first polarization direction.

[0054] In some embodiments, the first polarizer 206 is one of an S-type polarizer and a P-type polarizer, and the second polarizer 212 is the other of an S-type polarizer and a 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 S-type and P-type, thus providing more information about the sample 16.

[0056] 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 a wafer that can be measured 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. This makes it possible to measure the resistivity of the wafer at a specific position or to scan the resistivity distribution of the wafer.

[0058] Figure 7A shows the measurement of resistivity of a wafer at different locations on the wafer. The measurement results are compatible with those measured by other methods, such as the eddy current method.

[0059] Figure 7B shows the resistivity distribution of the wafer measured at different positions on the wafer. The measurement results are compatible with those measured by other methods such as eddy current.

[0060] As described above, a non-destructive measurement system based on terahertz radiation is provided. The off-axis positioning of the optical path of the terahertz radiation can compensate for the offset of the optical axis of the terahertz radiation. The additional visible light provides another way to compensate for the offset 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] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the invention. In view of this, it is intended that the present invention cover modifications and variations that come within the scope of the following claims and their equivalents. [Industrial Applicability]

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

[0063] 10 Measurement System 12 Laser Source 14, 204 Beam splitter 16 samples 18 Sample Stage 20 Delay Line 22 Preamp 24 Lock-in amplifier 26 Control Unit 28 Computer 100, 100A, 100B, 100C Radiation emitters 102 1st light source 104 Polarizer 106, 108, 120, 122, 124, 126, 206 mirrors 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 first light beam is reflected by a first one of the at least one mirror and leaves the radiation emitter; the first light beam is terahertz radiation; The radiation emitter, wherein the first mirror of the at least one mirror is an off-axis parabolic mirror.

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

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

4. 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; 10. 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.

5. 5. The radiation emitter of claim 4, 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.

6. a laser source emitting 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 radiation emitter that receives a first portion of the laser beam; a radiation detector that receives a second portion of the laser beam; a lock-in amplifier connected to the radiation detector and receiving a signal detected by the radiation detector; 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, leaving the radiation emitter and reaching the sample; Including, The radiation detector comprises: at least one receiver that receives a portion of the first reflected light beam; the first light beam is terahertz radiation; the first mirror of the at least one mirror is an off-axis parabolic mirror; Measurement system.

7. The measurement system of claim 6 , wherein the first light source is a photoconductive antenna.

8. The measurement system of claim 6 , wherein the polarizer is a linear polarizer.

9. 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; 7. The measurement system of claim 6, wherein after the second light beam is reflected by or transmitted through the first mirror 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.

10. 10. The measurement system of claim 9, 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.

11. 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, the beam splitter splitting 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; 7. The measurement system of claim 6, 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.

12. the first polarizer is either an S-type polarizer or a P-type polarizer, 12. The measurement system of claim 11, wherein the second polarizer is the other of the S-type polarizer and the P-type polarizer.

13. The measurement system of claim 6 , wherein the sample stage is an XY table.

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