JPH0542820B2 - - Google Patents
Info
- Publication number
- JPH0542820B2 JPH0542820B2 JP56201247A JP20124781A JPH0542820B2 JP H0542820 B2 JPH0542820 B2 JP H0542820B2 JP 56201247 A JP56201247 A JP 56201247A JP 20124781 A JP20124781 A JP 20124781A JP H0542820 B2 JPH0542820 B2 JP H0542820B2
- Authority
- JP
- Japan
- Prior art keywords
- crystal
- crystallinity
- infrared light
- impurities
- light
- 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
- 239000013078 crystal Substances 0.000 claims description 30
- 239000004065 semiconductor Substances 0.000 claims description 15
- 239000000969 carrier Substances 0.000 claims description 9
- 230000001678 irradiating effect Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 claims description 2
- 239000012535 impurity Substances 0.000 description 17
- 238000005259 measurement Methods 0.000 description 9
- 238000011156 evaluation Methods 0.000 description 8
- 230000005284 excitation Effects 0.000 description 8
- 230000007547 defect Effects 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000006798 recombination Effects 0.000 description 3
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- 239000000370 acceptor Substances 0.000 description 2
- 230000001066 destructive effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910001385 heavy metal Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000005355 Hall effect Effects 0.000 description 1
- 238000000149 argon plasma sintering Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000003574 free electron Substances 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
Landscapes
- Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Testing Of Individual Semiconductor Devices (AREA)
- Testing Or Measuring Of Semiconductors Or The Like (AREA)
Description
【発明の詳細な説明】
本発明は半導体結晶の結晶評価法に係り、特に
レーザ光と赤外光を併用することにより、非接
触、非破壊の測定を行うことができる結晶評価法
に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal evaluation method for semiconductor crystals, and more particularly to a crystal evaluation method that allows non-contact, non-destructive measurement by using a combination of laser light and infrared light.
従来の非接触、非破壊の半導体評価法としては
(1)フオトルミネツセンス、(2)光吸収、(3)マイクロ
波を用いたライフタイム、(4)光散乱、(5)うず電流
を用いたホール効果、等の測定を行うことによつ
てなされるもの等が挙げられる。 As a conventional non-contact, non-destructive semiconductor evaluation method,
By measuring (1) photoluminescence, (2) light absorption, (3) lifetime using microwaves, (4) light scattering, (5) Hall effect using eddy current, etc. Examples include things that are carried out.
これらの測定法においてはＡ：エピタキシヤル
層だけの情報を得ることができない（(2)、(5)）。
Ｂ：特に高価な装置が必要かそれでなければ測定
に時間がかかる（(1)、(3)，(4)）。Ｃ：測定場所の
位置分解能が悪い（(5)）。などの欠点がある。 In these measurement methods, A: Information on only the epitaxial layer cannot be obtained ((2), (5)).
B: Especially expensive equipment is required or measurement takes time ((1), (3), (4)). C: The positional resolution of the measurement location is poor ((5)). There are drawbacks such as.
本発明は上述の点に鑑みなされたもので、簡便
な、位置分解能の良い、エピ層の評価もできる結
晶評価法を提供するにある。 The present invention has been made in view of the above points, and it is an object of the present invention to provide a crystal evaluation method that is simple, has good positional resolution, and can also evaluate epitaxial layers.
本発明の目的は、キヤリア励起のためのレーザ
光とキヤリア密度測定のための赤外光を併用する
ことによつて、半導体結晶中に存在するキヤリア
トラツプ（発行中心、非発光中心）の量を推定す
ることを可能にするもので、半導体結晶にレーザ
光を照射することにより結晶内キヤリアを励起
し、そのキヤリア密度を赤外光の反射で測定する
ことにより半導体中の発光、非発光中心となる不
純物や欠陥の量を推定する結晶評価法により達成
される。 The purpose of the present invention is to estimate the amount of carrier traps (emitting centers, non-emitting centers) present in a semiconductor crystal by using a combination of laser light for carrier excitation and infrared light for measuring carrier density. By irradiating a semiconductor crystal with laser light, carriers within the crystal are excited, and by measuring the carrier density by reflection of infrared light, it is possible to identify the luminescent and non-luminous centers in the semiconductor. This is achieved using crystal evaluation methods that estimate the amount of impurities and defects.
次に本発明の原理を説明する。 Next, the principle of the present invention will be explained.
(1) 自由電子または正孔によつて赤外光が反射さ
れるのは、プラズマ反射としてよく知られてい
る。反射の起る赤外光の臨界波長λminはキヤ
リア（電子、正孔）の密度をｎとすれば
λminα1／√の関係がある。(1) The reflection of infrared light by free electrons or holes is well known as plasma reflection. The critical wavelength λmin of infrared light at which reflection occurs has the relationship λminα1/√, where n is the density of carriers (electrons, holes).
従つて、λminを測定することにより、ｎを
推定することができる。 Therefore, n can be estimated by measuring λmin.
(2) 半導体にそのバンドキヤツプより大きなエネ
ルギーを持つ光を照射すると、価電子帯から伝
導帯に電子が励起され、電子−正孔対が形成さ
れる。これらの電子、正孔はある時間（life
time）の後に再結合をして消滅する。再結合
を行う場合、伝導帯の電子と価電子帯の正孔が
直接結合する場合もあるが、バンドギヤツプ内
に存在する再結合中心を介在して結合する場合
もある。(2) When a semiconductor is irradiated with light with energy greater than its bandcap, electrons are excited from the valence band to the conduction band, forming electron-hole pairs. These electrons and holes have a certain period of time (life
time) and then recombine and disappear. When recombining, electrons in the conduction band and holes in the valence band may combine directly, but they may also combine via a recombination center that exists within the band gap.
この再結合中心は結晶中の不純物や結晶欠陥が
原因となつて形成されるため、結晶性の悪い試料
においては再結合中心が多数あり、従つて電子−
正孔対が消滅する機会が非常に多くなる。すなわ
ち同一強度の光で励起した場合、結晶性の悪い試
料ほど電子−正孔対が見出される確率が小さくな
る。電子−正孔対数は励起光強度が十分大きけれ
ば結晶中のキヤリア数に対応するからキヤリア数
の測定により結晶性を評価することができる。 These recombination centers are formed due to impurities or crystal defects in the crystal, so in samples with poor crystallinity, there are many recombination centers, and therefore electrons
There are many opportunities for hole pairs to disappear. That is, when excited with light of the same intensity, the probability that electron-hole pairs will be found decreases in a sample with poorer crystallinity. Since the electron-hole pair number corresponds to the number of carriers in the crystal if the excitation light intensity is sufficiently large, crystallinity can be evaluated by measuring the number of carriers.
もし、レーザ光による励起を行わずに、プラズ
マ反射という現象のみで不純物や欠陥の量を調べ
ようとすると以下のような問題がある。 If one attempts to examine the amount of impurities and defects using only the phenomenon of plasma reflection without excitation with laser light, the following problems arise.
現実に存在する結晶は、ドナ・アクセプタ・重
金属類・結晶欠陥など多くの性質の異なる不純物
を含有している。通常のドナ・アクセプタは浅い
不純物としての性質を備え、結晶内のキヤリア生
成に寄与している。重金属類や結晶欠陥などは深
い不純物の性質を備えることが多く、結晶内のキ
ヤリアを減少させるキヤリアキラー、すなわちト
ラツプとして働く。結晶の良否は広義には全不純
物の量が基準となるが、結晶性といつた場合、狭
義に後者の深い不純物の量を基準とする。それ
は、半導体レーザなどを作製する時発光効率を問
題とするが、この量が深い不純物の量に大きく依
存するからである。 Really existing crystals contain many impurities with different properties, such as donors, acceptors, heavy metals, and crystal defects. Normal donor acceptors have the properties of shallow impurities and contribute to carrier formation within the crystal. Heavy metals and crystal defects often have deep impurity properties and act as carrier killers, or traps, that reduce carriers within the crystal. In a broad sense, the quality of a crystal is determined by the amount of all impurities, but when it comes to crystallinity, in a narrower sense, the standard is the amount of deep impurities. This is because luminous efficiency is an issue when manufacturing semiconductor lasers and the like, and this amount largely depends on the amount of deep impurities.
結晶内では、これら性質の異なる多数の不純物
と、結晶自身の持つ状態すなわち伝導帯と価電子
帯とにその結晶がおかれた温度に対応して電子が
分布し、いわゆる熱平衡状態が実現している。 Inside the crystal, electrons are distributed between these many impurities with different properties and the states of the crystal itself, that is, the conduction band and valence band, depending on the temperature at which the crystal is placed, and a so-called thermal equilibrium state is achieved. There is.
そして、この状態で反射赤外光を測定すると、
得られる情報としてはキヤリア密度（ｎ型半導体
では伝導帯の電子密度）が得られる事になるが、
上述したように、これは結晶性をそのまま表した
ものとはなつていない。それは、伝導帯の電子密
度が浅い不純物と深い不純物の相関関係によつて
いるからである。さらに、反射赤外光の測定によ
つてキヤリア密度の測定が行える条件として、プ
ラズマ反射が生じる赤外光を用いなければならな
いが、通常用いられる50μｍ以下の波長での測定
を可能とするためにはキヤリア密度1017cm-3台の
キヤリアの存在が必要である。 Then, when measuring the reflected infrared light in this state,
The information that can be obtained is the carrier density (electron density in the conduction band for n-type semiconductors).
As mentioned above, this does not directly represent crystallinity. This is because the electron density in the conduction band depends on the correlation between shallow impurities and deep impurities. Furthermore, in order to be able to measure carrier density by measuring reflected infrared light, it is necessary to use infrared light that causes plasma reflection, but in order to enable measurement at wavelengths of 50 μm or less, which are commonly used, requires the presence of three carriers with a carrier density of 10 17 cm -.
これらの事情から、単に反射赤外光によつて不
純物密度を測定し、結晶性の良否を判断すること
は原理的・技術的に困難である。 Due to these circumstances, it is theoretically and technically difficult to determine the quality of crystallinity by simply measuring the impurity density using reflected infrared light.
一方本願発明では、まずレーザ光によつて価電
子帯から多量の電子を伝導帯に励起する。励起さ
れた電子は熱平衡状態と比べて過剰となるのでエ
ネルギーの低い状態へ緩和しようとする。その終
状態は、禁制帯内の不純物レベルもしくは価電子
帯である。緩和した電子は、再びレーザ光により
励起され、また緩和するというプロセスを繰り返
し、ある定常状態を形成する。この定常状態にお
いて伝導帯の電子密度は禁制帯内の不純物密度と
レーザ光強度に依存するが、レーザ光強度をある
一定の大きさ以上にすると、浅い不純物から生じ
る電子量が無視できるほど電子を価電子帯から励
起できるようになる。この状態では、レーザ光強
度と深い不純物すなわち結晶性が、伝導帯上の電
子密度を決定する。すなわち、結晶性が悪くなる
ほど、励起光強度が大きくなるほど電子密度は大
きくなる。従つて、励起光強度を一定にしておい
て異なる二つの試料を比較すれば、結晶性が悪い
試料の方が電子密度が小さくなることから結晶性
を評価できるわけである。また、結晶性が悪い試
料は、電子密度が小さいために反射赤外光の測定
が困難だが、レーザ光強度を大きくすることによ
り電子密度を増加させ、プラズマ反射の起きる波
長を測定可能領域まで持つてくることが可能とな
る。 On the other hand, in the present invention, a large amount of electrons are first excited from the valence band to the conduction band using laser light. Since the excited electrons are in excess compared to the thermal equilibrium state, they try to relax to a lower energy state. The end state is an impurity level within the forbidden band or valence band. The relaxed electrons are excited by the laser beam again and the process of relaxation is repeated to form a certain steady state. In this steady state, the electron density in the conduction band depends on the impurity density in the forbidden band and the laser light intensity, but when the laser light intensity is increased above a certain level, the electron density is reduced to such an extent that the amount of electrons generated from shallow impurities can be ignored. It becomes possible to excite from the valence band. In this state, laser light intensity and deep impurities, or crystallinity, determine the electron density on the conduction band. That is, as the crystallinity worsens and the excitation light intensity increases, the electron density increases. Therefore, by comparing two different samples while keeping the excitation light intensity constant, the crystallinity can be evaluated because the sample with poor crystallinity has a lower electron density. In addition, it is difficult to measure reflected infrared light for samples with poor crystallinity due to their low electron density, but by increasing the laser light intensity, the electron density can be increased to bring the wavelength at which plasma reflection occurs into the measurable range. It becomes possible to come.
以上のように本発明は、レーザ光により伝導帯
の電子の密度を制御するという構成を導入するこ
とにより、反射赤外光を用いた結晶性の評価が可
能となるものである。 As described above, the present invention makes it possible to evaluate crystallinity using reflected infrared light by introducing a configuration in which the electron density in the conduction band is controlled by laser light.
以下本発明の半導体結晶評価法を図を参照して
説明する。 The semiconductor crystal evaluation method of the present invention will be explained below with reference to the drawings.
第１図に本発明の一実施例として、GaAsエピ
タキシヤル結晶の評価装置に応用したときのブロ
ツク図を示す。 FIG. 1 shows a block diagram of one embodiment of the present invention when it is applied to an evaluation apparatus for GaAs epitaxial crystals.
測定試料１にレーザ２から励起光を照射する。
このとき、レーザ光のパワーをモニタするために
ハーフミラー３と光パワーメータ４が必要であ
る。レーザ光により励起されたキヤリアの密度を
測定するため、赤外光光源５より赤外分光器６を
通して単一波長光を試料１に当て、その反射光を
赤外デイクタ７によつて受光する。光電変換され
た信号は増幅器８を通つてレコーダ９に送られ
る。レコーダには分光器６から、波長を示す参照
信号も送られる。 A measurement sample 1 is irradiated with excitation light from a laser 2.
At this time, a half mirror 3 and an optical power meter 4 are required to monitor the power of the laser beam. In order to measure the density of carriers excited by the laser beam, single wavelength light is applied to the sample 1 from an infrared light source 5 through an infrared spectrometer 6, and the reflected light is received by an infrared detector 7. The photoelectrically converted signal is sent to a recorder 9 through an amplifier 8. A reference signal indicating the wavelength is also sent to the recorder from the spectrometer 6.
第２図、第３図に本装置を用いて得た縦軸に赤
外反射率（％）、横軸に波長でプロツトした赤外
反射スペクトルを示す。 FIGS. 2 and 3 show infrared reflection spectra obtained using this apparatus, plotted with the vertical axis representing the infrared reflectance (%) and the horizontal axis representing the wavelength.
第２図はレーザの出力を変えたときの反射スペ
クトルの変化であり、強励起条件（実線）では弱
励起条件（点線）に比べ反射スペクトルが極小を
示す点λminが短波長側にずれ、自由キヤリアが
増加することを示している。 Figure 2 shows the change in the reflection spectrum when the laser output is changed. Under strong excitation conditions (solid line), compared to weak excitation conditions (dotted line), the point λmin where the reflection spectrum shows a minimum shifts to the short wavelength side, and the free This indicates that carriers will increase.
第３図は、レーザの出力を一定として、異なる
二つの試料の反射スペクトルを示したもので、試
料Ａのλminは試料Ｂのλminより短波長側にあ
り、試料Ａの方が試料Ｂに比べ結晶性が良いこと
を示している。 Figure 3 shows the reflection spectra of two different samples with the laser output constant. The λmin of sample A is on the shorter wavelength side than the λmin of sample B, and sample A is shorter than sample B. This indicates good crystallinity.
このように本発明の実施例によれば、レーザ光
の出力を変化させることにより測定波長領域を自
由に選び、最適化できるため、結晶性の良否に広
い範囲を持つGaAs結晶においても１台の装置に
よつて十分対応できるという効果がある。 In this way, according to the embodiments of the present invention, the measurement wavelength range can be freely selected and optimized by changing the output of the laser beam, so even GaAs crystals with a wide range of crystallinity can be measured with a single device. This has the effect of being fully compatible with the equipment.
本発明によれば半導体結晶の結晶性評価を行う
際、非接触、非破壊で行え、測定場所の位置分解
能を良くでき、測定時間も短縮でき、さらにエピ
タキシヤル層の評価も行うことができるので、非
常に汎用性のある、実用的な測定装置を形成でき
る効果がある。 According to the present invention, when evaluating the crystallinity of a semiconductor crystal, it can be performed non-contact and non-destructively, the positional resolution of the measurement location can be improved, the measurement time can be shortened, and epitaxial layers can also be evaluated. This has the effect of making it possible to form a very versatile and practical measuring device.
第１図は本発明に用いる半導体結晶評価装置の
ブロツク図、第２図、第３図は本発明により得た
赤外反射スペクトルを示す図である。
１は測定試料、２はレーザー、３はハーフミラ
ー、４は光パワーメータ、５は赤外光光源、６は
赤外分光器、７は赤外デイテクタ、８は増幅器、
９はレコーダ。
FIG. 1 is a block diagram of a semiconductor crystal evaluation apparatus used in the present invention, and FIGS. 2 and 3 are diagrams showing infrared reflection spectra obtained by the present invention. 1 is a measurement sample, 2 is a laser, 3 is a half mirror, 4 is an optical power meter, 5 is an infrared light source, 6 is an infrared spectrometer, 7 is an infrared detector, 8 is an amplifier,
9 is a recorder.
Claims (1)
ヤリアを励起する工程と、 該レーザ光照射部に赤外光を照射し、該半導体
結晶からの反射赤外光の臨界波長（λmin）測定
する工程とを有し、 該臨界波長により該半導体結晶の結晶性を判断
することを特徴とする半導体結晶評価方法。[Claims] 1. A step of irradiating a semiconductor crystal with a laser beam to excite carriers in the crystal, and irradiating the laser beam irradiated portion with infrared light to determine the criticality of the reflected infrared light from the semiconductor crystal. A method for evaluating a semiconductor crystal, comprising: measuring a wavelength (λmin), and determining the crystallinity of the semiconductor crystal based on the critical wavelength.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56201247A JPS58102536A (en) | 1981-12-14 | 1981-12-14 | Semiconductor crystal evaluation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56201247A JPS58102536A (en) | 1981-12-14 | 1981-12-14 | Semiconductor crystal evaluation method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58102536A JPS58102536A (en) | 1983-06-18 |
| JPH0542820B2 true JPH0542820B2 (en) | 1993-06-29 |
Family
ID=16437771
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56201247A Granted JPS58102536A (en) | 1981-12-14 | 1981-12-14 | Semiconductor crystal evaluation method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58102536A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4795260A (en) * | 1987-05-15 | 1989-01-03 | Therma-Wave, Inc. | Apparatus for locating and testing areas of interest on a workpiece |
| KR100711301B1 (en) | 2004-05-07 | 2007-04-25 | 가부시키가이샤 리코 | Conveyor belt, sheet feeding device, and image forming apparatus including the sheet feeding device that stably conveys original document |
| JP2007288135A (en) * | 2006-03-20 | 2007-11-01 | Kobe Steel Ltd | Method and device for evaluating crystallinity of silicon semiconductor thin film |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54154265A (en) * | 1978-05-26 | 1979-12-05 | Hitachi Ltd | Impurity doping amount evaluation method for semiconductor |
| JPS56154648A (en) * | 1980-04-30 | 1981-11-30 | Fujitsu Ltd | Measurement of semiconductor impurity concentration |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5487069U (en) * | 1977-12-02 | 1979-06-20 |
-
1981
- 1981-12-14 JP JP56201247A patent/JPS58102536A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54154265A (en) * | 1978-05-26 | 1979-12-05 | Hitachi Ltd | Impurity doping amount evaluation method for semiconductor |
| JPS56154648A (en) * | 1980-04-30 | 1981-11-30 | Fujitsu Ltd | Measurement of semiconductor impurity concentration |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58102536A (en) | 1983-06-18 |
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