JP3124413B2 - Semiconductor wafer minority carrier lifetime measurement system - Google Patents
Semiconductor wafer minority carrier lifetime measurement systemInfo
- Publication number
- JP3124413B2 JP3124413B2 JP05145869A JP14586993A JP3124413B2 JP 3124413 B2 JP3124413 B2 JP 3124413B2 JP 05145869 A JP05145869 A JP 05145869A JP 14586993 A JP14586993 A JP 14586993A JP 3124413 B2 JP3124413 B2 JP 3124413B2
- Authority
- JP
- Japan
- Prior art keywords
- microwave
- semiconductor wafer
- minority carrier
- sample
- waveguide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
- Testing Or Measuring Of Semiconductors Or The Like (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は,半導体ウエハの少数キ
ャリアのライフタイム測定装置に係り,詳しくは半導体
ウエハの品質管理に用いられる半導体ウエハの少数キャ
リアのライフタイム測定装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a minority carrier lifetime of a semiconductor wafer, and more particularly to an apparatus for measuring a minority carrier lifetime of a semiconductor wafer used for quality control of the semiconductor wafer.
【0002】[0002]
【従来の技術】近年の超LSIに代表される半導体デバ
イスの超精密化傾向に伴い,そこに使用される半導体ウ
エハはより厳しい品質管理が要求されるようになった。
この管理のためには半導体ウエハの汚染や損傷の恐れの
ない非接触式の評価方法が望ましく,その一例としてマ
イクロ波による半導体ウエハの少数キャリアのライフタ
イム測定装置が公知である(特公昭61−60576
号)。図4は従来の半導体ウエハの少数キャリアのライ
フタイム測定装置の一例A01における概略回路構成を
示す模式図である。図4に示す如く従来の半導体ウエハ
の少数キャリアのライフタイム測定装置A01は,試料
保持台兼搬送機構51と,試料保持台兼搬送機構51に
支持搬送される試料52(半導体ウエハ)の表面に光パ
ルスを照射する光パルス発生器53と,試料52の表面
に放射するマイクロ波を発生させるガン発振器54と,
ガン発振器54から放射されるマイクロ波を調整するイ
ンピーダンス整合器55,E−Hチューナ56,57,
マジックT58及び無反射終端59からなる調整機構6
0と,調整機構60で調整されたマイクロ波を導波管6
1及び調整機構60を再び経過させて検出する検波器6
2と,検波器62により検出されたマイクロ波の変化を
表示するシンクロスコープ63とから構成されている。
以下,測定原理を説明する。試料52に光パルス発生器
53から照射された光パルスにより自由電子−正孔対で
あるキャリアが励起される。このキャリアは試料52の
熱平衡状態でのキャリア濃度よりも過剰なものであり,
キャリア濃度を上昇させる。そして,光の照射が中断さ
れる光パルスと光パルスとの間に過剰なキャリアが再結
合してしだいに消滅し,キャリア濃度を低下させる。こ
のようなキャリア濃度の変化は少数キャリア側において
著しく,その変化により試料52の電気伝導度(比抵
抗)を変化させる。このため,試料52に入射されたマ
イクロ波はレベル変化などを生じる。変化を生じたマイ
クロ波は反射波となって導波管61及び調整機構60を
通り検波器62に伝達される。ここで検出されたマイク
ロ波の反射波はシンクロスコープ63により減衰曲線と
して表示される。この減衰曲線から試料52の物性を表
す少数キャリアのライフタイムを測定することができ
る。2. Description of the Related Art With the recent trend toward ultra-precise semiconductor devices typified by VLSI, stricter quality control has been required for semiconductor wafers used therein.
For this control, a non-contact type evaluation method that does not cause contamination or damage to the semiconductor wafer is desirable. As an example, a device for measuring the minority carrier lifetime of a semiconductor wafer by microwave is known (Japanese Patent Publication No. 61-1986). 60576
issue). FIG. 4 is a schematic diagram showing a schematic circuit configuration of an example A01 of a conventional minority carrier lifetime measuring device for a semiconductor wafer. As shown in FIG. 4, a conventional semiconductor wafer minority carrier lifetime measuring apparatus A01 includes a sample holder / transport mechanism 51 and a sample 52 (semiconductor wafer) supported and transported by the sample holder / transport mechanism 51. An optical pulse generator 53 for irradiating an optical pulse, a gun oscillator 54 for generating a microwave radiating on the surface of the sample 52,
Impedance matching device 55 for adjusting microwaves radiated from gun oscillator 54, EH tuners 56, 57,
Adjustment mechanism 6 including magic T58 and anti-reflection end 59
0 and the microwave adjusted by the adjustment mechanism 60
1 and a detector 6 for detecting by making the adjusting mechanism 60 pass again
2 and a synchroscope 63 for displaying a change in the microwave detected by the detector 62.
Hereinafter, the measurement principle will be described. The carrier, which is a free electron-hole pair, is excited by the light pulse applied to the sample 52 from the light pulse generator 53. This carrier is in excess of the carrier concentration of the sample 52 in the thermal equilibrium state,
Increase the carrier concentration. Then, the excess carriers are recombined between the light pulses at which light irradiation is interrupted and disappear as soon as possible, thereby lowering the carrier concentration. Such a change in the carrier concentration is remarkable on the minority carrier side, and the change changes the electric conductivity (specific resistance) of the sample 52. Therefore, the level of the microwave incident on the sample 52 changes. The changed microwave is reflected and transmitted to the detector 62 through the waveguide 61 and the adjusting mechanism 60. The microwave reflected wave detected here is displayed as an attenuation curve by the synchroscope 63. From this attenuation curve, the lifetime of the minority carrier representing the physical properties of the sample 52 can be measured.
【0003】しかし,装置A01の導波管61の開口端
と試料52との間での多重反射波などの不要な反射波が
存在し,その量は試料52の比抵抗に依存して変化す
る。従って,上記装置A01では広範囲な比抵抗を有す
る半導体ウエハの少数キャリアのライフタイムを測定す
ることが困難である。このため,本発明者らは,上記不
要な反射波を除去するべく以下のような装置A02を開
発した(特願平4−121838号)。図5はこの従来
装置A02を示すものであって,前述の装置A01にお
ける導波管61を2分割すると共に(61a,61
b),ガン発振器54により放射されたマイクロ波をマ
ジックT58′により二分割する。この二分割されたマ
イクロ波を上記二分割された導波管61a,61bを介
して試料52にそれぞれ放射し,ここでの反射光を再び
導波管61a,61bを経由させてマジックT58′に
導き,ここで干渉させる。導波管61a側にはレーザ5
3によりレーザパルス光を照射する。この時のマジック
T58′により干渉させたマイクロ波の変化に対応する
出力RFをアンプ65により増幅して検波器62に入力
する。一方,ガン発振器54により発生したマイクロ波
の一部を分波器67により取り出して基準信号LOとし
て検波器62に入力し,ここで出力RFと混合検波す
る。検波器62からの出力信号IFは波形処理回路66
により処理され,ライフタイム表示装置63′により表
示される。又,導波管61a,61bの開口側にはアン
テナ64a,64bがそれぞれ設けられている。この従
来装置A02では,上記二分割された導波管61a,6
1b内を通過させたマイクロ波の反射波は導波管61
a,61bの実効長を等しくすることにより同位相のも
のとなる。ただし,励起光の照射側のみにレベル変化を
生じている為,導波管61a,61bをそれぞれ経由し
てきたマイクロ波の反射波同士を干渉させることにより
マイクロ波の反射波のレベル変化のみが検出されること
になる。このようにして,不要な波を除去することによ
り,半導体ウエハの比抵抗が広範囲なものであっても少
数キャリアのライフタイムを正確に測定することができ
た。However, unnecessary reflected waves such as multiple reflected waves exist between the open end of the waveguide 61 of the apparatus A01 and the sample 52, and the amount of the reflected waves varies depending on the specific resistance of the sample 52. . Therefore, it is difficult for the apparatus A01 to measure the lifetime of minority carriers of a semiconductor wafer having a wide specific resistance. For this reason, the present inventors have developed the following device A02 to remove the above unnecessary reflected waves (Japanese Patent Application No. 4-121838). FIG. 5 shows this conventional device A02, in which the waveguide 61 in the device A01 is divided into two parts (61a, 61a).
b) The microwave radiated by the gun oscillator 54 is divided into two by the magic T58 '. The two divided microwaves are radiated to the sample 52 via the two divided waveguides 61a and 61b, respectively, and the reflected light is again transmitted to the magic T58 'via the waveguides 61a and 61b. Guide and interfere here. The laser 5 is provided on the waveguide 61a side.
3 irradiates laser pulse light. The output RF corresponding to the change of the microwave interfered by the magic T58 'at this time is amplified by the amplifier 65 and input to the detector 62. On the other hand, a part of the microwave generated by the gun oscillator 54 is taken out by the splitter 67 and input to the detector 62 as the reference signal LO, where it is mixed and detected with the output RF. An output signal IF from the detector 62 is output to a waveform processing circuit 66.
And displayed by the lifetime display device 63 '. Antennas 64a and 64b are provided on the opening sides of the waveguides 61a and 61b, respectively. In the conventional device A02, the two divided waveguides 61a, 61
1b passes through the waveguide 61.
By making the effective lengths of a and 61b equal, they have the same phase. However, since the level change occurs only on the irradiation side of the excitation light, only the level change of the reflected wave of the microwave is detected by causing the reflected waves of the microwaves passing through the waveguides 61a and 61b to interfere with each other. Will be done. By removing unnecessary waves in this way, it was possible to accurately measure the minority carrier lifetime even when the specific resistance of the semiconductor wafer was wide.
【0004】[0004]
【発明が解決しようとする課題】上記したような従来の
測定装置A02では,半導体ウエハ52や支持台51の
平面度が充分に出ていない場合においては,マイクロ波
回路にアンバランスが生じることがある。即ち,2個の
アンテナ64a,64bと半導体ウエハ52との間隔が
異なる場合,マジックT58′で反射波同士を干渉させ
る際に,位相差を生じる。この為,励起光の照射がない
場合でも干渉波の電力が完全にゼロとはならず,アンプ
65や検波器62などのマイクロ波回路部品が飽和する
ほどの電力を生じる場合があった。しかし,このように
マイクロ波回路部品を飽和させて使用すると,信号レベ
ルが低減したり,部品を故障させる原因となりやすい。
又,一枚の半導体ウエハ内のライフタイム分布を調べる
場合には,半導体ウエハを機械的に移動させて測定する
ので,半導体ウエハ52や支持台51の平面度が充分で
ない場合には,ライフタイム分布測定結果に影響を及ぼ
すおそれもあった。本発明は,このような従来の技術に
おける課題を解決する為に,半導体ウエハの少数キャリ
アのライフタイム測定装置を改良し,半導体ウエハ又は
/及びその支持台の平面度のいかんに拘わらず常に高精
度測定を行うことができる半導体ウエハの少数キャリア
のライフタイム測定装置を提供することを目的とするも
のである。In the conventional measuring apparatus A02 as described above, when the flatness of the semiconductor wafer 52 and the support table 51 is not sufficient, an imbalance may occur in the microwave circuit. is there. That is, when the distance between the two antennas 64a and 64b and the semiconductor wafer 52 is different, a phase difference occurs when the reflected waves interfere with each other in the magic T58 '. For this reason, even when the excitation light is not irradiated, the power of the interference wave does not become completely zero, and there is a case where the microwave circuit components such as the amplifier 65 and the detector 62 generate enough power to saturate. However, when the microwave circuit components are used in such a saturated state, the signal level is likely to be reduced or the components may be damaged.
Also, when examining the lifetime distribution in one semiconductor wafer, the measurement is performed by mechanically moving the semiconductor wafer. If the flatness of the semiconductor wafer 52 or the support table 51 is not sufficient, the lifetime is measured. There was also a risk of affecting the distribution measurement results. In order to solve the problems in the prior art, the present invention has improved an apparatus for measuring the lifetime of a minority carrier of a semiconductor wafer, and has always improved the flatness of the semiconductor wafer and / or its support. It is an object of the present invention to provide an apparatus for measuring the lifetime of a minority carrier of a semiconductor wafer capable of performing accuracy measurement.
【0005】[0005]
【課題を解決するための手段】上記目的を達成する為に
本発明は,半導体ウエハに励起光を照射する照射手段
と,上記照射手段により励起光が断続的に照射される上
記半導体ウエハに放射するマイクロ波を発生させるマイ
クロ波発生手段と,上記マイクロ波発生手段により発生
したマイクロ波を二分割するマイロ波分割手段と,上記
マイクロ波分割手段により二分割した一方のマイクロ波
を上記半導体ウエハの上記励起光の照射部分に導く第1
の導波手段と,他方のマイクロ波を上記半導体ウエハの
上記励起光の非照射部分に導く第2の導波手段と,上記
第1,第2の導波手段にそれぞれ入射されるマイクロ波
の反射波又は透過波同士の干渉波を検出する検波手段と
を具備し,上記検波手段により検出された上記干渉波の
変化に基づいて上記半導体ウエハの少数キャリアのライ
フタイムを測定する装置において,上記第2の導波手段
を上記第1の導波手段とはマイクロ波の片道で略半波長
の整数倍だけ異なる実効長を有するものとすると共に,
上記照射手段により励起光を照射しない時に,上記検波
手段により検出される上記干渉波が少くなるように上記
マイクロ波発生手段により発生する上記マイクロ波の周
波数を調整するマイクロ波周波数調整手段を設けてなる
ことを特徴とする半導体ウエハの少数キャリアのライフ
タイム測定装置として構成されている。SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an irradiating means for irradiating a semiconductor wafer with excitation light, and irradiating the semiconductor wafer to which the excitation light is intermittently irradiated by the irradiating means. A microwave generating means for generating a microwave to be generated, a myro wave dividing means for dividing the microwave generated by the microwave generating means into two, and a microwave divided by the microwave dividing means into one of the semiconductor wafers. The first guide to the irradiated part of the excitation light
A second waveguide for guiding the other microwave to the non-irradiation portion of the semiconductor wafer with the excitation light, and a second waveguide for guiding the microwaves incident on the first and second waveguides, respectively. A detecting means for detecting an interference wave between reflected waves or transmitted waves, wherein the apparatus measures the lifetime of the minority carrier of the semiconductor wafer based on a change in the interference wave detected by the detecting means. The second waveguide means has an effective length different from the first waveguide means by an integral multiple of substantially a half wavelength in one way of microwaves,
Microwave frequency adjusting means for adjusting the frequency of the microwave generated by the microwave generating means so that the interference wave detected by the detecting means is reduced when the exciting means is not irradiated with the excitation light; The apparatus is configured as an apparatus for measuring a minority carrier lifetime of a semiconductor wafer.
【0006】[0006]
【作用】本発明によれば,半導体ウエハに励起光が照射
手段により照射される。上記照射手段により励起光が断
続的に照射される上記半導体ウエハに放射するマイクロ
波がマイクロ波発生手段により発生させられる。上記マ
イクロ波発生手段により発生させられたマイクロ波がマ
イクロ波分割手段により二分割される。上記マイクロ波
分割手段により二分割された一方のマイクロ波が,上記
半導体ウエハの上記励起光の照射部分に第1の導波手段
により導かれる。他方のマイクロ波が上記半導体ウエハ
の上記励起光の非照射部分に第2の導波手段により導か
れる。上記第1,第2の導波手段にそれぞれ入射される
マイクロ波の反射波又は透過波同士の干渉波が検波手段
により検出される。上記検波手段により検出された上記
干渉波の変化に基づいて上記半導体ウエハの少数キャリ
アのライフタイムが測定される。この際,上記第2の導
波手段が上記第1の導波手段とはマイクロ波の片道で略
半波長の整数倍だけ異なる実効長を有するものとされる
と共に,上記照射手段により励起光が照射されない時
に,上記検波手段により検出される上記干渉波が少くな
るように上記マイクロ波発生手段により発生させられる
上記マイクロ波の周波数がマイクロ波周波数調整手段に
より調整される。このように,マイクロ波の波長を変え
て第1,第2の導波手段間の実効長差を調整することに
より,半導体ウエハ又は/及びその支持台の平面度の誤
差に起因する反射波又は透過波同士の干渉波の位相差を
吸収させることができる。その結果,半導体ウエハ又は
/及びその支持台の平面度のいかんに拘わらず常に高精
度測定を実現し得る半導体ウエハの少数キャリアのライ
フタイム測定装置を得ることができる。According to the present invention, the semiconductor wafer is irradiated with the excitation light by the irradiation means. Microwaves radiated to the semiconductor wafer to which the excitation light is intermittently irradiated by the irradiation means are generated by the microwave generation means. The microwave generated by the microwave generating means is split into two by the microwave splitting means. One of the two microwaves divided by the microwave dividing means is guided to a portion of the semiconductor wafer irradiated with the excitation light by the first waveguide means. The other microwave is guided to the non-irradiated part of the semiconductor wafer by the second waveguide. An interference wave between reflected waves or transmitted waves of the microwaves respectively incident on the first and second waveguide means is detected by the detection means. A minority carrier lifetime of the semiconductor wafer is measured based on a change in the interference wave detected by the detection means. In this case, the second waveguide means has an effective length different from the first waveguide means by an integral multiple of substantially half a wavelength in one way of the microwave, and the irradiating means emits the excitation light. When not irradiated, the frequency of the microwave generated by the microwave generation means is adjusted by the microwave frequency adjustment means so that the interference wave detected by the detection means is reduced. As described above, by adjusting the effective length difference between the first and second waveguide means by changing the wavelength of the microwave, the reflected wave or the reflected wave caused by the error in the flatness of the semiconductor wafer and / or its support base is adjusted. The phase difference between the interference waves of the transmitted waves can be absorbed. As a result, it is possible to obtain an apparatus for measuring the minority carrier lifetime of a semiconductor wafer that can always achieve high-accuracy measurement regardless of the flatness of the semiconductor wafer and / or its support.
【0007】[0007]
【実施例】以下,添付図面を参照して本発明を具体化し
た実施例につき説明し,本発明の理解に供する。尚,以
下の実施例は本発明の具体化した一例であって本発明の
技術的範囲を限定する性格のものではない。ここに,図
1は本発明の一実施例に係る半導体ウエハの少数キャリ
アのライフタイム測定装置A1の概略回路構成を示す模
式図,図2はマイクロ波発振周波数の制御特性を示す説
明図,図3は本発明の他の実施例に係る半導体ウエハの
少数キャリアのライフタイム測定装置A2の概略回路構
成を示す模式図である。図1に示す如く,本実施例に係
る半導体ウエハの少数キャリアのライフタイム測定装置
A1は,主として試料1(半導体ウエハ)の表面にレー
ザパルス光を照射するレーザ2(照射手段に相当)と,
レーザ2によりレーザパルス光が断続的に照射される試
料1に放射するマイクロ波を発生させるマイクロ波発振
器3(マイクロ波発生手段に相当)と,マイクロ波発振
器3により発生したマイクロ波を二分割するマジックT
5(マイクロ波分割手段に相当)と,マジックT5によ
り二分割した一方のマイクロ波を試料1のレーザパルス
光の照射部分に導く導波管6a(第1の導波手段に相
当)と,他方のマイクロ波を試料1のレーザパルス光の
非照射部分に導く導波管6b(第2の導波手段に相当)
と,両導波管6a,6bにそれぞれ入射されるマイクロ
波の反射波又は透過波同士の干渉波を検出するミキサ9
(検波手段に相当)とを具備し,ミキサ9により検出さ
れた干渉波の変化に基づいて試料1の少数キャリアのラ
イフタイムを測定する点で従来例(従来装置A02)と
同様である。しかし,本実施例では,導波管6bを導波
管6aとはマイクロ波の片道で略半波長の整数倍だけ異
なる電気長(実効長)を有するものとすると共に,レー
ザ2によりレーザパルス光を照射しない時に,ミキサ9
により検出される干渉波が少くなるようにマイクロ波発
振器3により発生するマイクロ波の周波数を調整するマ
イクロ波周波数調整器10′(マイクロ波周波数調整手
段に相当)を設けている点で従来例と異なる。Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are embodied examples of the present invention and do not limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing a schematic circuit configuration of a device A1 for measuring the minority carrier lifetime of a semiconductor wafer according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing control characteristics of a microwave oscillation frequency. FIG. 3 is a schematic diagram showing a schematic circuit configuration of a minority carrier lifetime measurement apparatus A2 of a semiconductor wafer according to another embodiment of the present invention. As shown in FIG. 1, a device A1 for measuring the minority carrier of a semiconductor wafer according to the present embodiment mainly includes a laser 2 (corresponding to an irradiating unit) for irradiating a laser pulse light onto a surface of a sample 1 (semiconductor wafer).
A microwave oscillator 3 (corresponding to microwave generating means) for generating a microwave radiating to a sample 1 to which a laser pulse light is intermittently irradiated by a laser 2 and a microwave generated by the microwave oscillator 3 are divided into two. Magic T
5 (corresponding to microwave dividing means), a waveguide 6a (corresponding to first waveguide means) for guiding one of the two microwaves divided by the magic T5 to a portion of the sample 1 irradiated with the laser pulse light, and the other. 6b (corresponding to the second waveguide means) for guiding the microwave to the portion of the sample 1 not irradiated with the laser pulse light.
And a mixer 9 for detecting a reflected wave of a microwave or an interference wave between transmitted waves which are incident on the waveguides 6a and 6b, respectively.
(Corresponding to a detecting means), and is similar to the conventional example (conventional apparatus A02) in that the lifetime of the minority carrier of the sample 1 is measured based on the change of the interference wave detected by the mixer 9. However, in this embodiment, the waveguide 6b has an electric length (effective length) that is different from the waveguide 6a by an integral multiple of substantially a half wavelength in one direction of the microwave, and the laser 2 emits a laser pulse light. Mixer 9 when not irradiating
In that a microwave frequency adjuster 10 '(corresponding to microwave frequency adjusting means) for adjusting the frequency of the microwave generated by the microwave oscillator 3 is provided so that the interference wave detected by the microwave is reduced. different.
【0008】以下,この装置A1の動作について略述す
る。まず,マイクロ波発振器3により,レーザパルス光
が照射される試料1の表面に放射するマイクロ波を発振
する。マイクロ波発振器3より発振したマイクロ波は分
波器4により,一部をローカル信号(LO)として用い
る。残りの部分は,マジックT5に伝送され,そのH面
T分岐により二分割される。二分割されたマイクロ波
は,2つの導波管6a,6bを介してアンテナ7a,7
bにそれぞれ伝送される。ここで導波管6a,6bの長
さ(マジックT5とアンテナ7a,7bまでの電気長)
を等しくせず,マイクロ波の片道で略半波長のN倍(N
は1以上の整数)の電気長差(=L1+L2)を設けて
いる。アンテナ7a,7bは試料1の上方に配置され,
マイクロ波を試料1の測定領域に送信し,試料1で反射
した反射波を同一のアンテナにて受信する。試料1の表
面からの2つの反射波は,再びマジックT5に伝送さ
れ,ここで干渉させられる。通常は,二つの反射波は,
同振幅で且つ同位相であるので,相殺されてゼロ出力と
なり,アンプ8を経由してミキサ9のRF端子へ入力さ
れる。レーザパルス光を照射していない時は,このRF
信号の振幅はゼロである。ここで,ローカル信号LOは
移相器12を介してミキサ9に伝送され,RF信号と混
合検波される。ミキサ9の出力波信号IFにより,RF
信号の振幅の時間変化を測定し,演算器10でライフタ
イムの値を求め,表示器11により表示する。次に,レ
ーザ2によりレーザパルス光を照射する。照射直後の試
料1の表面には,レーザパルス光により励起した過剰キ
ャリアが発生し,表面の比抵抗が低下する。その為,試
料1表面のマイクロ波反射率が高まり,マイクロ波の反
射量が増える。この時は,二つのアンテナ7a,7bか
らのマイクロ波の反射波がマジックT5にて相殺されず
に,その変化量がアンプ8により増幅されて,ミキサ9
に入力される。そして,ローカル信号LOと混合検波さ
れる。ここで,移相器12を用いて,ミキサ9の出力ピ
ーク電圧が最大になるように調整し,ミキサ9で得られ
たIF信号を演算器10に伝送する。Hereinafter, the operation of the device A1 will be briefly described. First, the microwave oscillator 3 oscillates a microwave radiated to the surface of the sample 1 to be irradiated with the laser pulse light. A part of the microwave oscillated by the microwave oscillator 3 is used as a local signal (LO) by the splitter 4. The remaining part is transmitted to the magic T5, and is divided into two by its H-plane T-branch. The split microwaves are transmitted through two waveguides 6a and 6b to antennas 7a and 7b.
b. Here, the length of the waveguides 6a and 6b (electrical length between the magic T5 and the antennas 7a and 7b)
Are not equal, and one-way of microwaves is N times (N
Is an integer greater than or equal to 1) (= L1 + L2). The antennas 7a and 7b are arranged above the sample 1,
The microwave is transmitted to the measurement area of the sample 1, and the reflected wave reflected by the sample 1 is received by the same antenna. The two reflected waves from the surface of the sample 1 are transmitted again to the magic T5, where they are interfered. Usually, the two reflected waves are
Since they have the same amplitude and the same phase, they are canceled and become zero output, and input to the RF terminal of the mixer 9 via the amplifier 8. When not irradiating laser pulse light, this RF
The amplitude of the signal is zero. Here, the local signal LO is transmitted to the mixer 9 via the phase shifter 12, and mixed and detected with the RF signal. The output wave signal IF of the mixer 9 causes RF
The time change of the amplitude of the signal is measured, and the value of the lifetime is obtained by the arithmetic unit 10 and displayed by the display unit 11. Next, laser pulse light is irradiated by the laser 2. Excess carriers excited by the laser pulse light are generated on the surface of the sample 1 immediately after the irradiation, and the specific resistance of the surface decreases. Therefore, the microwave reflectivity on the surface of the sample 1 increases, and the amount of microwave reflection increases. At this time, the reflected waves of the microwaves from the two antennas 7a and 7b are not canceled out by the magic T5, but the amount of change is amplified by the amplifier 8 and the mixer 9
Is input to Then, mixed detection with the local signal LO is performed. Here, the phase shifter 12 is used to adjust the output peak voltage of the mixer 9 to be maximum, and the IF signal obtained by the mixer 9 is transmitted to the arithmetic unit 10.
【0009】ここで,試料1自体又は支持台13の平面
度の誤差により試料1が反り返っている場合を考える。
二つのアンテナ7a,7bの各先端部と試料1との間隔
が異なる場合が生じる。試料1の表面からの2つの反射
波は,それぞれマジックT5に伝送されてそのE面T分
岐回路により干渉させられる時に,二つの反射波はその
位相差がゼロではなくなる。この場合には,反射波が完
全に相殺されずにマジックT5の出力電力が発生する。
この電力(オフセット電力)がアンプ8を経由し,ミキ
サ9のRF端子に入力される。このままでは,従来例と
同様の問題が発生する為に,本発明では,マジックT5
の出口側に方向性結合器14を設けてオフセット電力を
取り出し,更に検波器15を設けてこの取り出されたオ
フセット電力の内のレーザパルス光照射前の値を測定す
る。この値をゼロに近づける為にマイクロ波周波数調整
器10′を用いてマイクロ波発振器3の発振周波数を変
化させる。このマイクロ波周波数調整器10′は図に示
す如く演算器10と一体のものとしても,さらには個別
に設けてもよい。このようにして,マイクロ波の波長を
変化させることにより上記電気長差(L1+L2)を調
整して,マジックT5に伝送されるマイクロ波の反射波
の位相差をゼロに近づけるように調整することができ
る。このゼロ調整により,試料1または支持台13の平
面度の誤差を吸収させることができる。このことは,平
面度が充分に出ていない試料1も測定が可能となり,ま
た支持台13の要求製作精度を緩和することができるこ
とを意味する。また,アンプ8やミキサ9などのマイク
ロ波回路部品を飽和させて使用することがなくなるた
め,これらの部品の故障を防止することができる。更
に,試料1を移動させてライフタイム分布を測定する場
合でも,試料1又は支持台13の平面度の誤差を吸収し
て同一のS/N比での測定とすることができる。図2は
マイクロ波の発振周波数を変化させた時のオフセット電
力の変化をプロットしたものである。即ち,二つのアン
テナ7a,7bの各先端部と試料1との間隔のずれ量を
μm単位で横軸に取り,縦軸には,各ずれ量に対してオ
フセット電力がゼロとなるような基準の発振周波数(2
4GHz)からの周波数偏移量をMHz単位で示してい
る。導波管6a,6b間の電気長差(L1+L2)を半
波長の1倍,2倍,3倍とした場合をそれぞれプロット
した。図より,ずれ量と変位量とはほぼ線形な比例関係
にあることがわかる。この関係を用いて最大ずれ量と発
振器の電気同調範囲とから半波長のN倍のNを適当に選
択する。Here, a case where the sample 1 is warped due to an error in the flatness of the sample 1 itself or the support 13 is considered.
In some cases, the distance between the tip of each of the two antennas 7a and 7b and the sample 1 is different. When the two reflected waves from the surface of the sample 1 are transmitted to the magic T5 and interfered by the E-plane T branch circuit, the phase difference between the two reflected waves is not zero. In this case, the output power of the magic T5 is generated without the reflected waves being completely canceled.
This power (offset power) is input to the RF terminal of the mixer 9 via the amplifier 8. In this state, a problem similar to that of the conventional example occurs.
A directional coupler 14 is provided on the exit side of the device to extract offset power, and a detector 15 is further provided to measure a value of the extracted offset power before laser pulse light irradiation. In order to make this value close to zero, the oscillation frequency of the microwave oscillator 3 is changed using the microwave frequency adjuster 10 '. The microwave frequency adjuster 10 'may be integrated with the arithmetic unit 10 as shown in the figure, or may be provided separately. In this way, by adjusting the electrical length difference (L1 + L2) by changing the wavelength of the microwave, the phase difference of the reflected wave of the microwave transmitted to the magic T5 can be adjusted to be close to zero. it can. By this zero adjustment, an error in the flatness of the sample 1 or the support 13 can be absorbed. This means that the measurement of the sample 1 having insufficient flatness can be performed, and the required manufacturing accuracy of the support 13 can be reduced. Further, since microwave circuit components such as the amplifier 8 and the mixer 9 are not used after being saturated, it is possible to prevent failure of these components. Further, even when the lifetime distribution is measured by moving the sample 1, the measurement can be performed at the same S / N ratio by absorbing the flatness error of the sample 1 or the support 13. FIG. 2 is a plot of the change in offset power when the microwave oscillation frequency is changed. That is, the abscissa represents the amount of displacement between the tip of each of the two antennas 7a and 7b and the sample 1 in units of μm, and the ordinate represents a reference such that the offset power becomes zero for each amount of displacement. Oscillation frequency (2
4 GHz) is shown in MHz. The case where the electrical length difference (L1 + L2) between the waveguides 6a and 6b is set to 1, 2 and 3 times the half wavelength is plotted respectively. From the figure, it can be seen that the displacement amount and the displacement amount have a substantially linear proportional relationship. Using this relationship, N times N times a half wavelength is appropriately selected from the maximum deviation amount and the electric tuning range of the oscillator.
【0010】ところで,マイクロ波発振周波数の制御に
必要な情報として,発振周波数を増加させるのか減少さ
せるのかの区別と,周波数の変化量とがある。上記装置
A1では,複数の測定データを基にこれらの情報を間接
的に入手できるが,さらにこれらの情報を直接入手する
為にミキサ9を2つ設けることが考えられる。その実施
例(装置A2)を以下に説明する。図3に示す如く,マ
イクロ波発振器3より発振したマイクロ波は分波器4に
よりその一部をローカル信号LOとして用いる。ローカ
ル信号LOをさらに方向性結合器16などにより二分割
する。二分割されたローカル信号LOはそれぞれミキサ
9a,9bのLO端子に入力される。残りのマイクロ波
はマジックT5に伝送され,ここでさらに二分割され
る。この二分割されたマイクロ波はアンテナ7a,7b
に導波管6a,6bを介してそれぞれ伝送される。アン
テナ7a,7bは試料1の上方に配置される,マイクロ
波を試料1の測定領域に送信し,試料1で反射した反射
波を同一のアンテナ7a,7bにて受信する。試料1表
面からの二つの反射波は再びマジックT5に伝送され,
ここで干渉させられる。二つの反射波の干渉波はアンプ
8を経由するが,途中方向性結合器17などにより二分
割され,それぞれミキサ9a,9bのRF端子に入力さ
れる。上記ローカル信号LOの経路中には移相器12
a,12bが設けられ,ローカル信号LOの経路の電気
長が微調整される。このローカル信号LOと上記RF信
号とがミキサ9a,9bにより混合検波される。ここ
で,ミキサ9aは前述した装置A1のミキサ9と同じく
ライフタイム測定に利用するものである。一方,ミキサ
9bは,試料1や支持台13の傾きとその方向を検出す
るものである。手順としては,基準のマイクロ波周波数
にて反射体(試料1や支持第13)を傾けた時に,ミキ
サ9bのIF出力が正負ともに最大の出力となるように
移相器12bを調整する。試料1或いは支持台13の左
右の傾きはミキサ9bのIF出力の正負によって判別す
ることができる。又,傾き量がミキサ9bの出力量とし
て認識される。このように,装置A2によれば,マイク
ロ波発振周波数の制御に必要な情報を直接入手すること
ができるため,測定時間を装置A1よりも短縮すること
ができる。その他の点については装置A1と同様であ
る。その結果,半導体ウエハ又は/及びその支持台の平
面度のいかんに拘わらず常に高精度測定を実現し得る半
導体ウエハの少数キャリアのライフタイム測定装置を得
ることができた。尚,上記二つの実施例装置A1,A2
においてはいずれもマイクロ波の反射波を用いた測定と
しているが,実使用に際してはマイクロ波の透過波を利
用しても何ら支障はない。尚,上記二つの実施例装置A
1,A2共,半導体ウエハの測定範囲が広い点では,従
来例(装置A02)と同様である。Incidentally, information necessary for controlling the microwave oscillation frequency includes a distinction as to whether the oscillation frequency is to be increased or decreased, and an amount of change in the frequency. In the device A1, the information can be obtained indirectly based on a plurality of measurement data. However, it is conceivable to provide two mixers 9 in order to directly obtain the information. An embodiment (apparatus A2) will be described below. As shown in FIG. 3, a part of the microwave oscillated by the microwave oscillator 3 is used as a local signal LO by the splitter 4. The local signal LO is further divided into two by the directional coupler 16 or the like. The divided local signal LO is input to the LO terminals of the mixers 9a and 9b, respectively. The remaining microwave is transmitted to magic T5, where it is further divided into two. The two divided microwaves are used as antennas 7a and 7b.
Are transmitted through the waveguides 6a and 6b, respectively. The antennas 7a and 7b are arranged above the sample 1, transmit microwaves to the measurement area of the sample 1, and receive reflected waves reflected by the sample 1 by the same antennas 7a and 7b. The two reflected waves from the surface of the sample 1 are transmitted again to the magic T5,
It is made to interfere here. The interference wave of the two reflected waves passes through the amplifier 8, but is split into two by the directional coupler 17 and the like, and input to the RF terminals of the mixers 9a and 9b, respectively. A phase shifter 12 is provided in the path of the local signal LO.
a and 12b are provided, and the electrical length of the path of the local signal LO is finely adjusted. The local signal LO and the RF signal are mixed and detected by the mixers 9a and 9b. Here, the mixer 9a is used for lifetime measurement similarly to the mixer 9 of the device A1 described above. On the other hand, the mixer 9b detects the inclination and the direction of the sample 1 and the support 13. As a procedure, the phase shifter 12b is adjusted so that the IF output of the mixer 9b becomes the maximum output in both positive and negative directions when the reflector (the sample 1 or the supporting thirteenth) is tilted at the reference microwave frequency. The left and right inclinations of the sample 1 or the support 13 can be determined by the sign of the IF output of the mixer 9b. Further, the inclination amount is recognized as the output amount of the mixer 9b. As described above, according to the device A2, the information necessary for controlling the microwave oscillation frequency can be directly obtained, so that the measurement time can be shorter than that of the device A1. The other points are the same as those of the device A1. As a result, it was possible to obtain an apparatus for measuring the minority carrier lifetime of a semiconductor wafer, which can always achieve high-accuracy measurement regardless of the flatness of the semiconductor wafer and / or its support. It should be noted that the above two embodiments of the devices A1, A2
In the above, the measurement is performed using the reflected wave of the microwave, but in actual use, the use of the transmitted wave of the microwave does not cause any problem. It should be noted that the above two embodiment apparatuses A
Both 1 and A2 are the same as the conventional example (apparatus A02) in that the measurement range of the semiconductor wafer is wide.
【0011】[0011]
【発明の効果】本発明に係る半導体ウエハの少数キャリ
アのライフタイム測定装置は上記したように構成されて
いる為,マイクロ波の波長を変化させて第1,第2の導
波手段間の実効長差を調整することにより,半導体ウエ
ハ又は/及びその支持台の平面度の誤差に起因する反射
波又は透過波同士の位相差を吸収させることができる。
これにより,平面度が充分に出ていない半導体ウエハの
測定が可能となる。又,半導体ウエハのライフタイム分
布を同一のS/N比で測定できる。更に,半導体ウエハ
を載せる支持台の平面度の要求製作精度を緩和できる。
又,アンプやミキサなどのマイクロ波回路部品の故障を
防止することができる。その結果,半導体ウエハ又は/
及びその支持台の平面度のいかんに拘わらず常に高精度
測定を実現し得る半導体ウエハの少数キャリアのライフ
タイム測定装置を得ることができる。Since the apparatus for measuring the lifetime of minority carriers of a semiconductor wafer according to the present invention is constructed as described above, the effective wavelength between the first and second waveguide means is changed by changing the wavelength of the microwave. By adjusting the length difference, it is possible to absorb the phase difference between reflected waves or transmitted waves due to errors in the flatness of the semiconductor wafer and / or its support.
As a result, it is possible to measure a semiconductor wafer having insufficient flatness. Further, the lifetime distribution of the semiconductor wafer can be measured at the same S / N ratio. Further, the required manufacturing accuracy of the flatness of the support table on which the semiconductor wafer is mounted can be reduced.
Further, it is possible to prevent a failure of a microwave circuit component such as an amplifier and a mixer. As a result, the semiconductor wafer or /
In addition, it is possible to obtain an apparatus for measuring the minority carrier lifetime of a semiconductor wafer, which can always achieve high-accuracy measurement regardless of the flatness of the support.
【図1】 本発明の一実施例に係る半導体ウエハの少数
キャリアのライフタイム測定装置A1の概略回路構成を
示す模式図。FIG. 1 is a schematic diagram showing a schematic circuit configuration of a minority carrier lifetime measurement apparatus A1 of a semiconductor wafer according to one embodiment of the present invention.
【図2】 マイクロ波発振周波数の制御特性を示す説明
図。FIG. 2 is an explanatory diagram showing control characteristics of a microwave oscillation frequency.
【図3】 本発明の他の実施例に係る半導体ウエハの少
数キャリアのライフタイム測定装置A2の概略回路構成
を示す模式図。FIG. 3 is a schematic diagram showing a schematic circuit configuration of a minority carrier lifetime measurement apparatus A2 of a semiconductor wafer according to another embodiment of the present invention.
【図4】 従来の半導体ウエハの少数キャリアのライフ
タイム測定装置の一例A01の概略回路構成を示す模式
図。FIG. 4 is a schematic diagram showing a schematic circuit configuration of an example of a conventional minority carrier lifetime measurement apparatus A01 for a semiconductor wafer.
【図5】 従来の半導体ウエハの少数キャリアのライフ
タイム測定装置の他の例A02の概略回路構成を示す模
式図。FIG. 5 is a schematic diagram showing a schematic circuit configuration of another example A02 of a conventional minority carrier lifetime measurement apparatus for a semiconductor wafer.
A1,A2…半導体ウエハの少数キャリアのライフタイ
ム測定装置 1…試料(半導体ウエハ) 2…レーザ(照射手段に相当) 3…マイクロ波発振器(マイクロ波発生手段に相当) 5…マジックT(マイクロ波分割手段に相当) 6a,6b…導波管(第1,第2の導波手段に相当) 9…ミキサ(検波手段に相当) 10′…マイクロ波周波数調整器(マイクロ波周波数調
整手段に相当)A1, A2: Lifetime measuring device for minority carrier of semiconductor wafer 1: Sample (semiconductor wafer) 2: Laser (corresponding to irradiation means) 3: Microwave oscillator (corresponding to microwave generation means) 5: Magic T (microwave 6a, 6b: waveguides (corresponding to first and second waveguide means) 9: mixer (corresponding to detection means) 10 ': microwave frequency adjuster (corresponding to microwave frequency adjusting means) )
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭54−116176(JP,A) 特開 昭53−118373(JP,A) (58)調査した分野(Int.Cl.7,DB名) G01N 22/00 - 22/04 H01L 21/66 ────────────────────────────────────────────────── (5) References JP-A-54-116176 (JP, A) JP-A-53-118373 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) G01N 22/00-22/04 H01L 21/66
Claims (1)
段と,上記照射手段により励起光が断続的に照射される
上記半導体ウエハに放射するマイクロ波を発生させるマ
イクロ波発生手段と,上記マイクロ波発生手段により発
生したマイクロ波を二分割するマイロ波分割手段と,上
記マイクロ波分割手段により二分割した一方のマイクロ
波を上記半導体ウエハの上記励起光の照射部分に導く第
1の導波手段と,他方のマイクロ波を上記半導体ウエハ
の上記励起光の非照射部分に導く第2の導波手段と,上
記第1,第2の導波手段にそれぞれ入射されるマイクロ
波の反射波又は透過波同士の干渉波を検出する検波手段
とを具備し,上記検波手段により検出された上記干渉波
の変化に基づいて上記半導体ウエハの少数キャリアのラ
イフタイムを測定する装置において,上記第2の導波手
段を上記第1の導波手段とはマイクロ波の片道で略半波
長の整数倍だけ異なる実効長を有するものとすると共
に,上記照射手段により励起光を照射しない時に,上記
検波手段により検出される上記干渉波が少くなるように
上記マイクロ波発生手段により発生する上記マイクロ波
の周波数を調整するマイクロ波周波数調整手段を設けて
なることを特徴とする半導体ウエハの少数キャリアのラ
イフタイム測定装置。An irradiating means for irradiating the semiconductor wafer with excitation light; a microwave generating means for generating a microwave radiating on the semiconductor wafer to which the excitation light is intermittently irradiated by the irradiating means; A myro wave splitting means for splitting the microwave generated by the generating means into two, and a first waveguide means for guiding one of the two microwaves split by the microwave splitting means to a portion of the semiconductor wafer irradiated with the excitation light. A second waveguide for guiding the other microwave to a portion of the semiconductor wafer to which the excitation light is not irradiated, and a reflected wave or transmitted wave of the microwave incident on the first and second waveguides, respectively. Detecting means for detecting an interference wave between each other, and measuring a lifetime of the minority carrier of the semiconductor wafer based on a change in the interference wave detected by the detecting means. In the apparatus, the second waveguide means has an effective length different from the first waveguide means by an integral multiple of substantially a half wavelength in one way of the microwave, and the excitation light is emitted by the irradiation means. A semiconductor device provided with microwave frequency adjusting means for adjusting the frequency of the microwave generated by the microwave generating means so that the interference wave detected by the detecting means is reduced when not irradiating; Equipment for measuring the minority carrier lifetime of wafers.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP05145869A JP3124413B2 (en) | 1993-06-17 | 1993-06-17 | Semiconductor wafer minority carrier lifetime measurement system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP05145869A JP3124413B2 (en) | 1993-06-17 | 1993-06-17 | Semiconductor wafer minority carrier lifetime measurement system |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH075122A JPH075122A (en) | 1995-01-10 |
JP3124413B2 true JP3124413B2 (en) | 2001-01-15 |
Family
ID=15394941
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP05145869A Expired - Lifetime JP3124413B2 (en) | 1993-06-17 | 1993-06-17 | Semiconductor wafer minority carrier lifetime measurement system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP3124413B2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2013195096A (en) * | 2012-03-16 | 2013-09-30 | Kobe Steel Ltd | Device and method for semiconductor crystallinity evaluation |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1242812B1 (en) | 1999-11-19 | 2007-05-09 | Rhino Analytics, Llc | Interferometric microwave sensor |
DE102006051577B4 (en) * | 2006-11-03 | 2011-07-21 | Deutsche Solar AG, 09599 | Apparatus and method for detecting electrical properties of a sample of a stimulable material |
JP2008191123A (en) * | 2007-02-08 | 2008-08-21 | Kobe Steel Ltd | Crystallinity measuring instrument for thin film semiconductor, and method therefor |
JP5242287B2 (en) * | 2008-08-11 | 2013-07-24 | 株式会社神戸製鋼所 | Semiconductor thin film crystallinity evaluation apparatus and crystallinity evaluation method |
-
1993
- 1993-06-17 JP JP05145869A patent/JP3124413B2/en not_active Expired - Lifetime
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2013195096A (en) * | 2012-03-16 | 2013-09-30 | Kobe Steel Ltd | Device and method for semiconductor crystallinity evaluation |
Also Published As
Publication number | Publication date |
---|---|
JPH075122A (en) | 1995-01-10 |
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