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JP7012349B2 - A scanning microwave microscope and a method for measuring the electrical characteristics of the surface of the object to be measured using the microscope. - Google Patents

A scanning microwave microscope and a method for measuring the electrical characteristics of the surface of the object to be measured using the microscope. Download PDF

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JP7012349B2
JP7012349B2 JP2017222752A JP2017222752A JP7012349B2 JP 7012349 B2 JP7012349 B2 JP 7012349B2 JP 2017222752 A JP2017222752 A JP 2017222752A JP 2017222752 A JP2017222752 A JP 2017222752A JP 7012349 B2 JP7012349 B2 JP 7012349B2
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雅弘 堀部
育 平野
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National Institute of Advanced Industrial Science and Technology AIST
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Description

本発明は、走査型マイクロ波顕微鏡に関し、より具体的には、位相可変型の共振回路を含む走査型マイクロ波顕微鏡、及びこれを用いた被測定物の表面の電気特性の測定方法に関する。 The present invention relates to a scanning microwave microscope, and more specifically, to a scanning microscope including a phase-variable resonance circuit, and a method for measuring electrical characteristics of the surface of an object to be measured using the scanning microscope.

走査型マイクロ波顕微鏡(SMM、以下単にSMMとも呼ぶ)は、原子間力顕微鏡(AFM、以下単にAFMとも呼ぶ)をベースとした電磁波を用いた材料表面の電気特性評価装置である。SMMでは、電磁波信号をAFMプローブの先端の針先(探針)から試料に照射し、その反射信号を検出して、試料表面のインピーダンスに伴う反射特性を測定する。また、AFMと同様の機能として表面を走査しながら測定することが可能であるため、試料表面の導電率、誘電率、あるいは透磁率などの電気特性の分布を測定することができる。これにより、試料である複合材における材料の分布や半導体などのキャリア濃度の分布を観察・解析することができる。 A scanning microwave microscope (SMM, hereinafter also simply referred to as SMM) is an electric property evaluation device for a material surface using an electromagnetic wave based on an atomic force microscope (AFM, hereinafter also simply referred to as AFM). In SMM, an electromagnetic wave signal is irradiated to a sample from the needle tip (needle) at the tip of the AFM probe, the reflected signal is detected, and the reflection characteristic accompanying the impedance of the sample surface is measured. Further, since it is possible to measure while scanning the surface as a function similar to that of AFM, it is possible to measure the distribution of electrical characteristics such as conductivity, permittivity, and magnetic permeability of the sample surface. This makes it possible to observe and analyze the distribution of materials and the distribution of carrier concentrations of semiconductors and the like in the composite material as a sample.

このため、材料表面からの電磁波信号を高精度で安定に測定する手法が必要である。しかし、SMMでは電磁波信号の測定にベクトルネットワークアナライザを用いるため、ただ繋ぐだけでは低インピーダンスおよび高インピーダンスの領域での微小な変化に対して十分な検出感度を得ることができない。また、装置自体は除振台に搭載する必要があり、スペースや重量に制限があるため、部品点数が少ない簡素な検出回路が必要となる。 Therefore, there is a need for a method for measuring electromagnetic wave signals from the surface of materials with high accuracy and stability. However, since the SMM uses a vector network analyzer to measure the electromagnetic wave signal, it is not possible to obtain sufficient detection sensitivity for minute changes in the low impedance and high impedance regions simply by connecting them. Further, since the device itself needs to be mounted on the vibration isolation table and the space and weight are limited, a simple detection circuit with a small number of parts is required.

従来技術としてこれまでに複数の検出回路が提案されてきた。例えば、比較的簡素な回路構造を含むSMMとして、非特許文献1は、半波長共振器と並列接続された50Ω抵抗による共振回路を含む反射型のSMMを開示する。また、非特許文献2は、インピーダンス調整器と位相調整器による共振回路(干渉計)を含む反射型のSMMを開示する。しかし、これらの従来のSMMでは、十分な検出感度を得ることができていない。 As a prior art, a plurality of detection circuits have been proposed so far. For example, as an SMM including a relatively simple circuit structure, Non-Patent Document 1 discloses a reflection type SMM including a resonance circuit with a 50Ω resistor connected in parallel with a half-wavelength resonator. Further, Non-Patent Document 2 discloses a reflection type SMM including a resonance circuit (interferometer) by an impedance adjuster and a phase adjuster. However, these conventional SMMs have not been able to obtain sufficient detection sensitivity.

感度を向上するために、他の従来技術として、各種の共振回路(干渉計)を含む複数の透過型のSMMが提案されている。しかし、それらの従来のSMMでは、その回路構成には電源を必要とするアンプ(アクティブ素子)を必要とし、さらには多くの部品を使用するなど、複雑な回路構成であり、回路のサイズも大きい。一般的には、高周波精密計測においてアクティブ素子の利用や回路の複雑さは、周辺温度の変化や振動などで安定性を低下させるなどの要因となる。結果として、感度と測定/検出回路の実現の容易性について両立した方法が確立されていない。 In order to improve the sensitivity, as another conventional technique, a plurality of transmissive SMMs including various resonance circuits (interferometers) have been proposed. However, these conventional SMMs require an amplifier (active element) that requires a power supply for their circuit configuration, and also use many parts, resulting in a complicated circuit configuration and a large circuit size. .. In general, in high-frequency precision measurement, the use of active elements and the complexity of circuits are factors such as deterioration of stability due to changes in ambient temperature and vibration. As a result, a method that achieves both sensitivity and ease of realization of the measurement / detection circuit has not been established.

H. Tanbakuchi, et al., Semiconductor Material and Device Characterization via Scanning Microwave Microscopy, “IEEE Compound Semiconductor Integrated Circuit Symposium (CSICS), Pages: 1-5, 2013.H. Tanbakuchi, et al., Semiconductor Material and Device TEXT via Scanning Microwave Microscopy, “IEEE Compound Semiconductor Integrated Circuit Symposium (CSICS), Pages: 1-5, 2013. A. Lewandowski, et al., “Wideband measurement of extreme impedances with a multistate reflectometer,”72nd ARFTG Microwave Measurement Symposium, Pages:45-49, 2008.A. Lewandowski, et al., “Wideband measurement of extreme impedances with a multistate reflectometer,” 72nd ARFTG Microwave Measurement Symposium, Pages: 45-49, 2008.

本発明の目的は、アクティブ素子を利用せず部品点数を減らした共振回路(干渉計)を用いた走査型マイクロ波顕微鏡の感度向上を図ることである。 An object of the present invention is to improve the sensitivity of a scanning microwave microscope using a resonance circuit (interferometer) that does not use an active element and reduces the number of parts.

本発明の一態様の走査型マイクロ波顕微鏡は、被測定物の表面を走査能なAFMプローブと、第1端がAFMプローブに接続するT分岐と、T分岐の第2端に接続する位相可変短絡器と、T分岐の第3端を介してAFMプローブと位相可変短絡器に接続するベクトルネットワークアナライザと、を備える。AFMプローブと位相可変短絡器は1つの共振回路を構成し、位相可変短絡器は、ベクトルネットワークアナライザがAFMプローブを介して被測定物の表面に照射した電磁波の反射波信号の共振周波数の位相を調整する。 The scanning microwave microscope according to one aspect of the present invention has an AFM probe capable of scanning the surface of an object to be measured, a T-branch having a first end connected to the AFM probe, and a variable phase microscope connecting the second end of the T-branch. It comprises a short circuit and a vector network analyzer connected to the AFM probe and the phase variable short circuit via the third end of the T-branch. The AFM probe and the phase variable short circuit block form one resonance circuit, and the phase variable short circuit controller determines the phase of the resonance frequency of the reflected wave signal of the electromagnetic wave that the vector network analyzer irradiates the surface of the object to be measured via the AFM probe. adjust.

本発明の一態様の走査型マイクロ波顕微鏡を用いた被測定物の表面の電気特性の測定方法は、(a)AFMプローブを介して被測定物の表面に所定範囲の周波数の電磁波を照射するステップと、(b)被測定物の表面からの反射電磁波をAFMプローブを介してベクトルネットワークアナライザにより検出するステップと、(c)位相可変短絡器を用いて、反射電磁波の共振周波数の位相を調整するステップと、(d)ベクトルネットワークアナライザにより、位相調整後の選択された共振周波数での反射電磁波の振幅変化または位相変化から、被測定物の表面の電気特性を求めるステップと、を含む。 The method for measuring the electrical characteristics of the surface of the object to be measured using the scanning microwave microscope according to one aspect of the present invention is as follows: (a) The surface of the object to be measured is irradiated with an electromagnetic wave having a frequency within a predetermined range via an AFM probe. The phase of the resonance frequency of the reflected electromagnetic wave is adjusted by using the steps, (b) the step of detecting the reflected electromagnetic wave from the surface of the object to be measured by the vector network analyzer via the AFM probe, and (c) the phase variable short circuit. This includes (d) determining the electrical characteristics of the surface of the object to be measured from the amplitude change or phase change of the reflected electromagnetic wave at the selected resonance frequency after the phase adjustment by the vector network analyzer.

本発明によれば、アクティブ素子を利用せず部品点数を減らした共振回路(干渉計)を用いた走査型マイクロ波顕微鏡の感度向上を図ることができる。さらに、共振回路(干渉計)の構成要素として位相可変型短絡素子を用いることで、観測する共振(干渉)周波数を自由に選択することができる。これにより、被測定物の表面状態や材料の性質等に応じた高感度/高精度で安定した測定を実現することができる。 According to the present invention, it is possible to improve the sensitivity of a scanning microwave microscope using a resonance circuit (interferometer) that reduces the number of parts without using an active element. Further, by using a phase variable short-circuit element as a component of the resonance circuit (interferometer), the resonance (interference) frequency to be observed can be freely selected. This makes it possible to realize highly sensitive / highly accurate and stable measurement according to the surface condition of the object to be measured, the properties of the material, and the like.

本発明の一実施形態の走査型マイクロ波顕微鏡の構成を示す図である。It is a figure which shows the structure of the scanning microwave microscope of one Embodiment of this invention. 本発明の一実施形態の測定方法のフローを示す図である。It is a figure which shows the flow of the measuring method of one Embodiment of this invention. 本発明の一実施形態の共振周波数の位相調整前の状態を説明する図である。It is a figure explaining the state before the phase adjustment of the resonance frequency of one Embodiment of this invention. 本発明の一実施形態の共振周波数の位相調整後の状態を説明する図である。It is a figure explaining the state after the phase adjustment of the resonance frequency of one Embodiment of this invention. 本発明の一実施例の測定結果(振幅変化による断面SMM像)を示す図である。It is a figure which shows the measurement result (cross-sectional SMM image by the amplitude change) of one Example of this invention. 本発明の一実施例の測定結果(位相変化による断面SMM像)を示す図である。It is a figure which shows the measurement result (cross-sectional SMM image by a phase change) of one Example of this invention. 本発明の一実施例の測定結果(振幅変化)を示す図である。It is a figure which shows the measurement result (amplitude change) of one Example of this invention. 本発明の一実施例の測定結果(位相変化)を示す図である。It is a figure which shows the measurement result (phase change) of one Example of this invention.

図面を参照しながら本発明の実施の形態を説明する。図1は、本発明の一実施形態の走査型マイクロ波顕微鏡(SMM)の構成を示す図である。SMM100は、AFMプローブ1と、T分岐(回路)3、位相可変型短絡素子(Sliding short)7と、ベクトルネットワークアナライザ(VNA)9を備える。さらに、SMM100の一部として、あるいは外部装置(機構)として、被測定物12を載置しXYZ方向で移動するための駆動機構(図示なし)を有するステージ11を備える。 Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a scanning microwave microscope (SMM) according to an embodiment of the present invention. The SMM 100 includes an AFM probe 1, a T-branch (circuit) 3, a phase variable short circuit element (Sliding short) 7, and a vector network analyzer (VNA) 9. Further, as a part of the SMM 100 or as an external device (mechanism), a stage 11 having a drive mechanism (not shown) for mounting the object 12 to be measured and moving in the XYZ direction is provided.

AFMプローブ1は、一般にカンチレバーとも呼ばれ、先端の探針2を有し、半導体や金属等で形成されている。AFMプローブ1の自らの上下移動により、あるいはステージ11の上下移動により、AFMプローブの先端の探針2が被測定物12の表面13に接触あるいはその近傍に非接触で位置するように調整される。T分岐3の第1端4は同軸ケーブルを介してAFMプローブ1に接続し、第2端5は同軸ケーブルを介して位相可変型短絡素子7に接続し、第3端6は同軸ケーブルを介してVNA9の1つの入出力ポート(PORT1)に接続する。AFMプローブ1と位相可変型短絡素子7は、T分岐3を介してVNA9の入出力ポートに対して並列接続し、両者で1つの共振(共鳴、干渉)回路、言い換えればインピーダンス調整回路を構成する。 The AFM probe 1 is also generally called a cantilever, has a probe 2 at the tip, and is made of a semiconductor, a metal, or the like. By moving the AFM probe 1 up and down or by moving the stage 11 up and down, the probe 2 at the tip of the AFM probe is adjusted to be in contact with or in the vicinity of the surface 13 of the object 12 in a non-contact manner. .. The first end 4 of the T-branch 3 is connected to the AFM probe 1 via a coaxial cable, the second end 5 is connected to the phase variable short-circuit element 7 via a coaxial cable, and the third end 6 is connected via a coaxial cable. Connect to one input / output port (PORT1) of VNA9. The AFM probe 1 and the phase variable short-circuit element 7 are connected in parallel to the input / output port of the VNA 9 via the T branch 3, and both form one resonance (resonance, interference) circuit, in other words, an impedance adjustment circuit. ..

VNA9は、入出力ポート(PORT1)に接続された同軸ケーブルを介してAFMプローブ1と位相可変型短絡素子7に所定範囲(例えば、1-20GHzの範囲)の周波数の電磁波を送信することができる。AFMプローブの先端の探針2から被測定物12の表面13にその電磁波が照射され、表面13からの反射電磁波がAFMプローブの探針2から受信される。VNA9は、同軸ケーブルを介してAFMプローブ1からの反射電磁波の信号(以下、反射電磁波信号とも呼ぶ)を受信し、その反射電磁波信号を演算処理して被測定物12の表面13の各種電気特性を算出する。その電気特性の測定結果は、VNA9が内蔵する、あるいは外付けの表示部10に表示される。 The VNA 9 can transmit an electromagnetic wave having a frequency within a predetermined range (for example, a range of 1 to 20 GHz) to the AFM probe 1 and the phase variable short-circuit element 7 via a coaxial cable connected to the input / output port (PORT1). .. The electromagnetic wave is irradiated from the probe 2 at the tip of the AFM probe to the surface 13 of the object to be measured 12, and the reflected electromagnetic wave from the surface 13 is received from the probe 2 of the AFM probe. The VNA 9 receives a signal of the reflected electromagnetic wave from the AFM probe 1 (hereinafter, also referred to as a reflected electromagnetic wave signal) via a coaxial cable, processes the reflected electromagnetic wave signal, and performs arithmetic processing on the reflected electromagnetic wave signal to perform various electrical characteristics of the surface 13 of the object 12 to be measured. Is calculated. The measurement result of the electrical characteristics is displayed on the display unit 10 built in or external to the VNA 9.

位相可変型短絡素子7は、例えば円筒型あるいは直方体型の空洞共振器7を備える。空洞共振器7内の可変短絡板8が垂直あるいは水平方向(図1では垂直方向)に移動して空洞の距離Dを変えることにより、空洞共振器7内にT分岐3を介してVNA9から入力される電磁波の共振周波数の位相を調整することができる。空洞共振器7内の可変短絡板8の移動は、手動または付随する駆動機構によって行うことができる。その位相可変型短絡素子7での共振周波数の位相調整によって、詳細は後述するように、共に1つの共振器を形成する並列接続するAFMプローブ1から受信される反射電磁波信号の共振周波数の位相を調整することができる。 The phase-variable short-circuit element 7 includes, for example, a cylindrical or rectangular parallelepiped cavity resonator 7. The variable short-circuit plate 8 in the cavity resonator 7 moves in the vertical or horizontal direction (vertical direction in FIG. 1) to change the cavity distance D, so that the variable short-circuit plate 8 is input from the VNA 9 into the cavity resonator 7 via the T-branch 3. The phase of the resonance frequency of the electromagnetic wave to be generated can be adjusted. The movement of the variable short circuit plate 8 in the cavity resonator 7 can be performed manually or by an accompanying drive mechanism. By adjusting the phase of the resonance frequency in the phase-variable short-circuit element 7, the phase of the resonance frequency of the reflected electromagnetic wave signal received from the AFM probes 1 connected in parallel forming one resonator together is adjusted as described in detail later. Can be adjusted.

図2は、本発明の一実施形態の走査型マイクロ波顕微鏡を用いた被測定物の表面の電気特性の測定方法のフローを示す図である。以下の図2の測定フローの説明は、図1の実施形態のSMM100を用いた場合の例を示すが、この測定フローは本発明の他の実施形態のSMMを用いた場合にも同様に実行可能である。 FIG. 2 is a diagram showing a flow of a method for measuring electrical characteristics of the surface of an object to be measured using the scanning microwave microscope according to the embodiment of the present invention. The following description of the measurement flow of FIG. 2 shows an example when the SMM 100 of the embodiment of FIG. 1 is used, but this measurement flow is similarly executed when the SMM of another embodiment of the present invention is used. It is possible.

図2のステップS1において、ステージ11上に被測定物12をセット(載置)する。被測定物12としては、基本的にAFMプローブ1によってその表面の電気特性が測定可能な任意の材料(半導体、金属、磁性体、誘電体等)からなる基板等を含むことができる。ステップS2において、ステージ11及びAFMプローブ1を移動させることにより、被測定物12の表面13の測定開始ポイント(測定領域のスタート位置)にAFMプローブ1の探針2をセットする。AFMプローブ1の探針2は、被測定物あるいは測定条件等に応じて被測定物12の表面13に接触または非接触にセットされる。 In step S1 of FIG. 2, the object to be measured 12 is set (placed) on the stage 11. The object 12 to be measured can basically include a substrate made of an arbitrary material (semiconductor, metal, magnetic material, dielectric, etc.) whose surface electrical characteristics can be measured by the AFM probe 1. In step S2, by moving the stage 11 and the AFM probe 1, the probe 2 of the AFM probe 1 is set at the measurement start point (start position of the measurement region) on the surface 13 of the object to be measured 12. The probe 2 of the AFM probe 1 is set in contact with or non-contact with the surface 13 of the object to be measured 12 depending on the object to be measured, measurement conditions, and the like.

ステップS3において、VNA9がAFMプローブ1の探針2から被測定物12の表面13へ所定範囲(例えば、1-20GHzの範囲)で周波数を掃引させながら電磁波を照射する。その際、同時にVNA9からT分岐3の第2端5を介して位相可変型短絡素子7にも同じ周波数範囲の電磁波が入射される。ステップS4において、VNA9がAFMプローブ1の探針2を介して被測定物12の表面13からの反射電磁波信号を受信する。 In step S3, VNA 9 irradiates an electromagnetic wave from the probe 2 of the AFM probe 1 to the surface 13 of the object to be measured 12 while sweeping the frequency within a predetermined range (for example, in the range of 1-20 GHz). At the same time, an electromagnetic wave having the same frequency range is incident on the phase variable short-circuit element 7 from the VNA 9 via the second end 5 of the T branch 3. In step S4, the VNA 9 receives the reflected electromagnetic wave signal from the surface 13 of the object to be measured 12 via the probe 2 of the AFM probe 1.

ステップS5において、位相可変型短絡素子7によってVNA9で測定される反射電磁波信号の共振周波数の位相を調整して、VNA9が電気特性を測定(算出)する反射電磁波信号の周波数を設定する。図3と図4を参照しながらその位相(周波数)調整について説明する。図3(a)と図4(a)は、いずれも被測定物12上のAFMプローブ1、T分岐3、及び位相可変型短絡素子7の等価回路である。被測定物12は、その表面状態に応じて変化するインピーダンス(抵抗R1+容量C2)を有する。VNA9は、そのインピーダンス(の変化)を反射電磁波信号として測定することになる。AFMプローブ1はその材料等に応じて定まるプローブ容量C1を有する。位相可変型短絡素子7は、空洞共振器7内の可変短絡板8の位置(距離D)を変えることにより、等価的なインダクタンスL1を変えて、空洞共振器7内の共振周波数の位相を調整する。 In step S5, the phase of the resonance frequency of the reflected electromagnetic wave signal measured by the VNA 9 is adjusted by the phase variable short-circuit element 7, and the frequency of the reflected electromagnetic wave signal for which the VNA 9 measures (calculates) the electrical characteristics is set. The phase (frequency) adjustment will be described with reference to FIGS. 3 and 4. 3 (a) and 4 (a) are both equivalent circuits of the AFM probe 1, the T-branch 3, and the phase variable short-circuit element 7 on the object 12 to be measured. The object to be measured 12 has an impedance (resistance R1 + capacitance C2) that changes according to its surface state. The VNA 9 measures (changes in) its impedance as a reflected electromagnetic wave signal. The AFM probe 1 has a probe capacity C1 that is determined according to the material and the like. The phase variable short-circuit element 7 adjusts the phase of the resonance frequency in the cavity resonator 7 by changing the equivalent inductance L1 by changing the position (distance D) of the variable short-circuit plate 8 in the cavity resonator 7. do.

図3(b)は、共振周波数の位相調整前の状態を説明する図である。図4(b)は、共振周波数の位相調整後の状態を説明する図である。図3(b)の位相調整前にVNA9で測定された反射電磁波信号の周波数と振幅または反射係数S11パラメータとの関係図では、共振周波数はfに設定されている。電気特性を得るために測定したい共振周波数はfsなので、位相をずらして(遅らせて)fをfsに合せる必要がある。そこで、上述したように、図4(a)の位相可変型短絡素子7の等価的なインダクタンスL1を変えて空洞共振器7内の共振周波数の位相を調整することにより、図4(b)に示すように、VNA9で測定する共振周波数をfsに設定することができる。 FIG. 3B is a diagram illustrating a state before phase adjustment of the resonance frequency. FIG. 4B is a diagram illustrating a state after phase adjustment of the resonance frequency. In the relationship diagram between the frequency and the amplitude or the reflection coefficient S11 parameter of the reflected electromagnetic wave signal measured by VNA9 before the phase adjustment in FIG. 3B, the resonance frequency is set to f0 . Since the resonance frequency to be measured in order to obtain the electrical characteristics is fs, it is necessary to shift (delay) the phase and adjust f0 to fs. Therefore, as described above, by changing the equivalent inductance L1 of the phase variable short-circuit element 7 of FIG. 4A to adjust the phase of the resonance frequency in the cavity resonator 7, FIG. 4B is shown. As shown, the resonance frequency measured by VNA9 can be set to fs.

図2のステップS6において、ステップS5で位相調整された共振周波数での反射電磁波信号の振幅及び位相を測定する。具体的には、VNA9が位相調整後の共振周波数fsでの反射電磁波信号の振幅及び位相を測定(検出)する。その振幅及び位相は、被測定物12の表面13の反射特性、すなわちインピーダンスを反映している。ステップS7において、ステップS6で得られた振幅及び位相から必要に応じて選択的に被測定物12の表面13の電気特性(静電容量、導電率、誘電率、透磁率、不純物レベル等)を算出する。 In step S6 of FIG. 2, the amplitude and phase of the reflected electromagnetic wave signal at the resonance frequency phase-adjusted in step S5 are measured. Specifically, the VNA 9 measures (detects) the amplitude and phase of the reflected electromagnetic wave signal at the resonance frequency fs after the phase adjustment. The amplitude and phase reflect the reflection characteristic, that is, the impedance of the surface 13 of the object to be measured 12. In step S7, the electrical characteristics (capacitance, conductivity, dielectric constant, magnetic permeability, impurity level, etc.) of the surface 13 of the object to be measured 12 are selectively selected from the amplitude and phase obtained in step S6 as necessary. calculate.

次のステップS8において、AFMプローブ1またはステージ11を走査(移動)させながらステップS3~S7を実行して、被測定物12の表面の測定領域(一部または全体)での反射電磁波信号の振幅及び位相を測定し、さらには必要となる各種電気特性を算出する。なお、代替フローとして、ステップS8をステップS6とS7の間に入れて、ステップS3~S6をAFMプローブ1またはステージ11を走査しながら実行して、先に被測定物12の表面の測定領域(一部または全体)での反射電磁波信号の振幅及び位相を測定するようにしてもよい。 In the next step S8, steps S3 to S7 are executed while scanning (moving) the AFM probe 1 or the stage 11, and the amplitude of the reflected electromagnetic wave signal in the measurement region (part or all) of the surface of the object to be measured 12. And the phase are measured, and various required electrical characteristics are calculated. As an alternative flow, step S8 is inserted between steps S6 and S7, and steps S3 to S6 are executed while scanning the AFM probe 1 or stage 11, and the measurement region on the surface of the object to be measured 12 (1) The amplitude and phase of the reflected electromagnetic wave signal in part or all) may be measured.

ステップS9において、ステップS8で得られた被測定物12の測定領域での電気特性の分布を画像として表示部10に表示する。この画像分布は、被測定物12の測定領域の表面状態を反映したインピーダンスの変化(差異)の分布に相当している。 In step S9, the distribution of the electrical characteristics in the measurement region of the object to be measured 12 obtained in step S8 is displayed on the display unit 10 as an image. This image distribution corresponds to the distribution of impedance changes (differences) that reflect the surface state of the measurement region of the object to be measured 12.

上述した図1に例示されるSMM及び図2に例示される測定方法フローを用いて、実際に被測定物の試料の表面を測定した。下記の測定では、試料としては、不純物としてN型ドーパントが選択された領域にドーピングされたSi層を含むSi基板を用いた。 The surface of the sample of the object to be measured was actually measured by using the SMM exemplified in FIG. 1 and the measurement method flow exemplified in FIG. 2 described above. In the measurements below, a Si substrate containing a Si layer doped in a region where an N-type dopant was selected as an impurity was used as the sample.

図5と図6は、ドーピング濃度が異なるSi層構造の断面のSMM画像である。各画像の横軸はXY方向の距離(μm)で、縦軸はZ(深さ)方向の距離(μm)である。図5は、振幅変化に対応した測定画像であり、図6は位相変化に対応した測定画像である。両図において、(a)は従来の非特許文献1で例示される半波長共振器と50Ω抵抗による共振回路を含む反射型のSMMを用いた測定結果であり、(b)は従来の非特許文献2で例示されるインピーダンス調整器と位相調整器による共振回路(干渉計)を含む反射型のSMMを用いた測定結果であり、(c)は本発明のSMMによる測定結果である。 5 and 6 are SMM images of cross sections of Si layer structures having different doping concentrations. The horizontal axis of each image is the distance (μm) in the XY direction, and the vertical axis is the distance (μm) in the Z (depth) direction. FIG. 5 is a measurement image corresponding to the amplitude change, and FIG. 6 is a measurement image corresponding to the phase change. In both figures, (a) is a measurement result using a reflection type SMM including a half-waver resonator exemplified in the conventional non-patent document 1 and a resonance circuit with a 50Ω resistor, and (b) is a conventional non-patented measurement result. It is the measurement result using the reflection type SMM including the resonance circuit (interferometer) by the impedance regulator and the phase adjuster exemplified in Document 2, and (c) is the measurement result by the SMM of this invention.

各画像において白い部分がドーパント濃度の高い領域を示している。なお、図6(b)の画像は画像処理の関係で白黒が反転しており、黒い部分がドーパント濃度の高い領域を示している。両図において、従来の(a)及び(b)の画像と本発明の(c)の画像を比較することにより、本発明の(c)画像は、従来の(a)及び(b)画像よりもより画像のブレ(ノイズ)が少なくより鮮明にドーパント濃度の高い領域(白領域)が示されており、検出感度(S/N比も)が高いことを示している。 In each image, the white part indicates the region where the dopant concentration is high. In the image of FIG. 6B, black and white are inverted due to image processing, and the black portion indicates a region having a high dopant concentration. In both figures, by comparing the conventional images (a) and (b) with the image of the present invention (c), the image (c) of the present invention is more than the conventional images (a) and (b). The region (white region) where the image blur (noise) is less and the dopant concentration is higher is shown, indicating that the detection sensitivity (S / N ratio is also high) is high.

図7と図8は、ドーピング濃度が異なるSi層構造の1ラインの振幅と位相の測定結果を示すグラフである。図7の各グラフの横軸はXY方向の距離(μm)で、縦軸は振幅(dB)である。図8の各グラフの横軸はXY方向の距離(μm)で、縦軸は位相(deg)である。図7の(a)と(b)のグラフの縦軸のレンジは、-0.004~0.02dBであり、(c)のグラフの縦軸のレンジは、-0.4~2.0dBであって(a)及び(b)のグラフよりも100倍大きい。同様に、図8の(a)と(b)のグラフの縦軸のレンジは、それぞれ-0.01~0.03degと-0.5~0.3であり、(c)のグラフの縦軸のレンジは、-1~4degであって(a)と(b)のグラフよりも100倍または10倍大きい。両図において、(a)は従来の非特許文献1で例示される半波長共振器と50Ω抵抗による共振回路を含む反射型のSMMを用いた測定結果であり、(b)は従来の非特許文献2で例示されるインピーダンス調整器と位相調整器による共振回路(干渉計)を含む反射型のSMMを用いた測定結果であり、(c)は本発明のSMMによる測定結果である。 7 and 8 are graphs showing the measurement results of the amplitude and phase of one line of Si layer structures having different doping concentrations. The horizontal axis of each graph in FIG. 7 is the distance (μm) in the XY direction, and the vertical axis is the amplitude (dB). The horizontal axis of each graph in FIG. 8 is the distance (μm) in the XY direction, and the vertical axis is the phase (deg). The range of the vertical axis of the graphs (a) and (b) in FIG. 7 is −0.004 to 0.02 dB, and the range of the vertical axis of the graph of FIG. 7 (c) is −0.4 to 2.0 dB. It is 100 times larger than the graphs of (a) and (b). Similarly, the range of the vertical axis of the graphs (a) and (b) of FIG. 8 is −0.01 to 0.03 deg and −0.5 to 0.3, respectively, and the vertical axis of the graph of (c) is vertical. The range of the axis is -1 to 4 deg, which is 100 times or 10 times larger than the graphs of (a) and (b). In both figures, (a) is a measurement result using a reflection type SMM including a half-waver resonator exemplified in the conventional non-patent document 1 and a resonance circuit with a 50Ω resistor, and (b) is a conventional non-patented measurement result. It is the measurement result using the reflection type SMM including the resonance circuit (interferometer) by the impedance regulator and the phase adjuster exemplified in Document 2, and (c) is the measurement result by the SMM of this invention.

各グラフにおいて波形の振幅が大きいピーク波形部分がドーパント濃度の高い領域を示している。なお、図8(b)のグラフは画像処理の関係でピーク波形が反転しており、波形の振幅が下側ピークの波形部分がドーパント濃度の高い領域を示している。両図において、従来の(a)及び(b)のグラフと本発明の(c)のグラフを比較することにより、本発明の(c)グラフは、従来の(a)及び(b)グラフよりもより波形の振幅が10倍から100倍程度大きく、かつ波形上のノイズが少なくなっており、ドーパント濃度の高い領域の検出感度(S/N比も)が高いことを示している。 In each graph, the peak waveform portion where the amplitude of the waveform is large indicates the region where the dopant concentration is high. In the graph of FIG. 8B, the peak waveform is inverted due to image processing, and the waveform portion of the lower peak of the waveform shows a region where the dopant concentration is high. In both figures, by comparing the conventional graphs (a) and (b) with the graph of the present invention (c), the graph of the present invention (c) is more than the conventional graphs (a) and (b). The amplitude of the waveform is about 10 to 100 times larger, the noise on the waveform is reduced, and the detection sensitivity (S / N ratio) in the region where the dopant concentration is high is high.

本発明の実施形態について、図を参照しながら説明をした。しかし、本発明はこれらの実施形態に限られるものではない。さらに、本発明はその趣旨を逸脱しない範囲で当業者の知識に基づき種々なる改良、修正、変形を加えた態様で実施できるものである。 An embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to these embodiments. Further, the present invention can be carried out in a mode in which various improvements, modifications and modifications are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

本発明の走査型マイクロ波顕微鏡は、アクティブ素子を利用せず部品点数を減らした共振回路(干渉計)を用いて、被測定物の表面状態や材料の性質等に応じた高感度/高精度で安定した測定を実現することができる走査型マイクロ波顕微鏡として利用することができる。 The scanning microwave microscope of the present invention uses a resonance circuit (interferometer) in which the number of parts is reduced without using an active element, and has high sensitivity / accuracy according to the surface state of the object to be measured, the properties of the material, and the like. It can be used as a scanning microwave microscope that can realize stable measurement.

1:AFMプローブ
2:AFMプローブの探針(先端)
3:T分岐(回路)
4:T分岐(回路)の第1端
5:T分岐(回路)の第2端
6:T分岐(回路)の第3端
7:位相可変短絡器(空洞共振器)
8:可動短絡板
9:ベクトルネットワークアナライザ(VNA)
10:表示部
11:ステージ
12:被測定物
100:走査型マイクロ波顕微鏡(SMM)
1: AFM probe 2: AFM probe probe (tip)
3: T branch (circuit)
4: 1st end of T-branch (circuit) 5: 2nd end of T-branch (circuit) 6: 3rd end of T-branch (circuit) 7: Phase variable short circuit (cavity resonator)
8: Movable short circuit plate 9: Vector network analyzer (VNA)
10: Display 11: Stage 12: Object to be measured 100: Scanning microwave microscope (SMM)

Claims (5)

被測定物の表面を走査能なAFMプローブと、
第1端がAFMプローブに接続するT分岐と、
T分岐の第2端に接続する位相可変短絡器と、
T分岐の第3端を介してAFMプローブと位相可変短絡器に接続するベクトルネットワークアナライザと、を備え、
AFMプローブと位相可変短絡器は1つの共振回路を構成し、位相可変短絡器は、ベクトルネットワークアナライザがAFMプローブを介して被測定物の表面に照射した電磁波の反射波信号の共振周波数の位相を調整する、走査型マイクロ波顕微鏡。
With an AFM probe capable of scanning the surface of the object to be measured,
A T-branch whose first end connects to the AFM probe,
A phase variable short circuit connected to the second end of the T-branch,
It comprises an AFM probe and a vector network analyzer connected to the phase variable short circuiter via the third end of the T-branch.
The AFM probe and the phase variable short circuit block form one resonance circuit, and the phase variable short circuit controller determines the phase of the resonance frequency of the reflected wave signal of the electromagnetic wave that the vector network analyzer irradiates the surface of the object to be measured via the AFM probe. A scanning microwave microscope to adjust.
前記ベクトルネットワークアナライザは、前記AFMプローブを介して、前記被測定物の表面に電磁波を照射し、その電磁波の反射波信号を検出し、前記位相可変短絡器による位相調整後の選択された共振周波数での振幅変化または位相変化から、前記被測定物の表面の電気特性を求める、請求項に記載の走査型マイクロ波顕微鏡。 The vector network analyzer irradiates the surface of the object to be measured with an electromagnetic wave via the AFM probe, detects the reflected wave signal of the electromagnetic wave, and selects the resonance frequency after phase adjustment by the phase variable short circuit. The scanning microwave microscope according to claim 1 , wherein the electrical characteristics of the surface of the object to be measured are obtained from the amplitude change or the phase change in the above. 走査型マイクロ波顕微鏡を用いた被測定物の表面の電気特性の測定方法であって、
(a)AFMプローブを介して被測定物の表面に所定範囲の周波数の電磁波を照射するステップと、
(b)被測定物の表面からの反射電磁波をAFMプローブを介してベクトルネットワークアナライザにより検出するステップと、
(c)位相可変短絡器を用いて、反射電磁波の共振周波数の位相を調整するステップと、
(d)ベクトルネットワークアナライザにより、位相調整後の選択された共振周波数での反射電磁波の振幅変化または位相変化から、被測定物の表面の電気特性を求めるステップと、を含む測定方法。
It is a method of measuring the electrical characteristics of the surface of the object to be measured using a scanning microwave microscope.
(A) A step of irradiating the surface of the object to be measured with an electromagnetic wave having a frequency within a predetermined range via an AFM probe.
(B) A step of detecting the reflected electromagnetic wave from the surface of the object to be measured by a vector network analyzer via an AFM probe, and
(C) A step of adjusting the phase of the resonance frequency of the reflected electromagnetic wave using a variable phase short circuit, and
(D) A measurement method including a step of obtaining the electrical characteristics of the surface of an object to be measured from the amplitude change or phase change of the reflected electromagnetic wave at a selected resonance frequency after phase adjustment by a vector network analyzer.
前記AFMプローブと前記位相可変短絡器は、前記ベクトルネットワークアナライザに並列的に接続する、請求項に記載の測定方法。 The measuring method according to claim 3 , wherein the AFM probe and the phase variable short circuit device are connected in parallel to the vector network analyzer. 前記AFMプローブを前記被測定物の表面上を走査しながら前記ステップ(a)~(d)を実行して、前記被測定物の表面の電気特性の分布を得るステップをさらに含む、請求項3または4に記載の測定方法。 3. The third aspect of the present invention further comprises a step of performing the steps (a) to (d) while scanning the surface of the object to be measured with the AFM probe to obtain a distribution of electrical characteristics on the surface of the object to be measured. Or the measuring method according to 4 .
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