JP2004139944A - Ion implantation device and ion implantation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion implantation device and an ion implantation method for keeping a current amount of an ion beam in a high level and attaining a sufficient through-put, and to provide a manufacturing method of an SOI wafer. <P>SOLUTION: The ion implantation device comprises an ion source, a drawing-out electrode, and a mass spectrometer. A plurality of slits through which ion is drawn out are arranged on the ion source in parallel with each other along a direction of the short axis of the slits, and a plurality of slits corresponding to respective slits of the ion source are arranged to the drawing-out electrode in parallel with each other along the direction of the short axis of the slit. <P>COPYRIGHT: (C)2004,JPO

Description

【００５７】
［式（２）中、ω_ｅは電子サイクロトロン周波数を表し、ｍ_ｅは電子の質量を表し、ｅは電子の電荷を表し、Ｂは磁場の強さを表す。］
で表される電子サイクロトロン周波数（磁束線に沿って旋回する電子の周波数）と一致させることによって、電子サイクロトロン共鳴吸収過程で電子を選択的に励起し、その励起電子と水素分子とを衝突させてプラズマを生成させるものである。しかしながら、ＥＣＲモードでプラズマ生成を行うと、水素原子イオン（Ｈ^＋）が生成しやすく、水素イオンビームの電流密度が不十分となりやすい。
【００５８】
一方、非ＥＣＲモードとは、ＥＣＲ条件を満たさないように、すなわちマイクロ波の周波数及び磁場の強さが下記式（３）又は（４）：
【００５９】
【数２】

【００６０】
【数３】

【００６１】
［式（３）、（４）中、ωはマイクロ波の周波数を表し、ｍ_ｅは電子の質量を表し、ｅは電子の電荷を表し、Ｂは磁場の強さを表す］
で表される条件を満たすように設定してプラズマ生成を行うものである。なお、非ＥＣＲモード設定の際には、マイクロ波の周波数を固定して磁場の強さを調節してもよく、また、磁場の強さを固定してマイクロ波の周波数を調節してもよい。
【００６２】
非ＥＣＲモードにおいては、マイクロ波の周波数ωが電子サイクロトロン周波数ω_ｅよりも１０〜５０％（より好ましくは２０〜４０％）だけ高く（又は低く）なるように、マイクロ波の周波数及び磁場の強さを設定することが好ましい。従って、例えば２．４５ＧＨｚのマイクロ波を用いる場合、磁場の強さは９６〜１３１ｍＴ又は４４〜７９ｍＴ（より好ましくは１０５〜１２３ｍＴ又は５３〜７０ｍＴ）であることが好ましい。また、１４．５ＧＨｚのマイクロ波を用いる場合、磁場の強さは５７０〜７７７ｍＴ又は２５９〜４６６ｍＴであることが好ましい。
【００６３】
また、プラズマ生成領域３７に水素ガスが導入されてから水素イオンビームＩＢが引き出されるまでの水素分子の平均滞留時間は、５×１０^−４〜５×１０^−３秒であることが好ましく、７×１０^−４〜３×１０^−３秒であることがより好ましい。平均滞留時間が前記上限値を超えると水素分子イオンの割合が低下する傾向にあり、また、前記下限値未満であるとプラズマの生成効率が低下する傾向にある。当該平均滞留時間の設定は、プラズマチャンバ２９の形状及びサイズ、水素ガスの供給量、水素イオンビームＩＢの引き出し量等の調節により行うことができる。
【００６４】
なお、アーク放電型イオン源やＲＦイオン源等を用いた従来法では、水素分子イオンよりも水素原子イオンの方が生成しやすいため、イオン注入の際には専ら水素原子イオンが利用されていた。これに対して本発明のイオン注入方法では、マイクロ波を利用してプラズマ生成を行い、イオンの引出方向に沿って磁場を形成してイオンを引き出すことで、従来法に比べてプラズマ中の水素分子イオンの割合を飛躍的に増大させ、さらにはその水素分子イオンを低い引出エネルギーで且つ高いビーム電流で利用することができる。従って、従来では達成が困難であった高水準のスループットを容易に実現することができる。
【００６５】
例えば、本発明者は、マイクロ波の周波数が２．４５ＧＨｚ、マイクロ波の出力が７００Ｗ、磁場の強さが７０ｍＴである非ＥＣＲモードにおいて、水素分子の平均滞留時間を８．９×１０^−４秒としてプラズマを生成させたとき、Ｈ^＋イオンが１３．５％、Ｈ_２ ^＋イオンが７８．１％、Ｈ_３ ^＋イオンが８．４％というイオン組成が達成されたことを確認している。これに対して、従来型のアーク放電型イオン源により生成したプラズマ中のイオン組成は、Ｈ^＋イオンが６０．２％、Ｈ_２ ^＋イオンが２２．９％、Ｈ_３ ^＋イオンが１６．９％であった。
【００６６】
本発明のイオン注入装置及びイオン注入方法は、上述のように高水準のスループットの達成が可能なものであり、高ドーズのイオン注入を要するトランジスターの接合部形成やＳＯＩウェハのイオン注入層形成等の工程において非常に有用である。
【００６７】
ここで、ＳＯＩウェハの製造方法について、Ｓｉ層／ＳｉＯ_２層／Ｓｉ基板の積層構造を有するＳＯＩウェハを製造する場合を例にとって詳述する。
【００６８】
図９（ａ）〜（ｄ）はそれぞれ各工程におけるウエハの積層構造を模式的に示す断面図である。
【００６９】
イオン注入工程においては、ターゲット基板として、Ｓｉ基板（Ｓｉ−ｄｏｎｏｒ　ｗａｆｅｒ）９１の一方面上にＳｉＯ_２層９２が形成されたものを用いる。ＳｉＯ_２層９２は、例えばＳｉ基板の表面を酸化させることにより形成可能であり、その厚さは例えば０．０１〜１．０μｍである。
【００７０】
このターゲット基板に対して、ウェハのＳｉＯ_２層９２側から水素分子イオンを照射することによって、Ｓｉ基板９２中の所定深さに水素イオン注入層９３が形成され、これに伴いＳｉＯ_２層９２と水素イオン注入層９３との間に薄いＳｉ層が形成される（図９（ａ））。
【００７１】
イオン注入工程において、マイクロ波イオン源を用いる場合は、非ＥＣＲモードによるプラズマ生成を行うことが好ましい。これにより、水素分子イオンの生成が促進されるため、非常に高いスループットが実現可能となり、その結果、ＳＯＩウェハの製造効率を飛躍的に向上させることができる。
【００７２】
イオン注入工程におけるイオン注入量は１×１０^１６ｉｏｎｓ／ｃｍ^２以上であることが好ましい。また、水素イオン注入層９３は、例えばＳｉ層９４とＳｉＯ_２層８２との界面からの深さ０．００５〜１．５μｍの位置に形成される。
【００７３】
次に、ターゲット基板のＳｉＯ_２層９２上にＳｉ基板（Ｓｉ−ｈａｎｄｌｅ　ｗａｆｅｒ）９５を貼り合わせる（図９（ｂ））。なお、ＳｉＯ_２層が形成されていないＳｉ基板を用いて上記と同様のイオン注入工程を行い、その一方で表面にＳｉＯ_２層が形成されたＳｉ基板を用意して、積層工程において両者を貼り合わせることによっても目的の積層体を得ることができる。
【００７４】
この積層体を水素イオン注入層９３で分断する（図９（ｃ））。水素イオン注入層９３はシリコン原子同士の共有結合が切断された脆弱な層であるため、水素イオン注入層９３の側面に乾燥空気等のガスを吹き付けたり、機械的に剪断を加えたりすることによって容易に分断することができる。
【００７５】
このようにして、Ｓｉ基板９５上にＳｉＯ_２層９２及びＳｉ層９４がこの順で積層されたＳＯＩウェハが得られる（図９（ｃ））。なお、分断工程後のＳｉ層９４の表面に水素イオン注入層９３の一部が残存する場合があるが、研磨処理等を行うことでその残さを容易に除去することができる。また、Ｓｉ層９４を更に研磨することにより、Ｓｉ層９４の厚みを調整することができる。
【００７６】
【発明の効果】
以上説明した通り、本発明のイオン注入装置及びイオン注入方法によれば、イオン源中のプラズマ密度をほとんど変化させずに、また、引出電極によるイオンビームの収束効果を損なわずに、イオンの有効引出面積を増大させることができるので、低エネルギーのイオンを引き出す場合であってもビーム電流が高められ、高水準のスループットが実現可能となる。
【００７７】
また、本発明のＳＯＩウェハの製造方法によれば、イオン注入工程の際に上記本発明のイオン注入方法を適用することで高水準のスループットが実現可能となり、高集積化等の点で優れたＳＯＩウェハを効率よく且つ確実に製造することができる。
【図面の簡単な説明】
【図１】本発明のイオン注入装置の一例を示す概略構成図である。
【図２】図１に示したイオン注入装置が備えるイオン引出アセンブリ１００の概略構成を示す断面図である。
【図３】（ａ）、（ｂ）はそれぞれイオンビームが形成されるときのイオン源及び引出電極の位置関係、並びに各イオンビームの光路を示す概念図であり、（ａ）は斜視図、（ｂ）は上面図である。
【図４】ソレノイドコイルにより形成される磁場の方向とイオンの引出方向との関係を示す概念図である。
【図５】永久磁石により形成される磁場の方向とイオンの引出方向との関係を示す概念図である。
【図６】電磁石により形成される磁場の方向とイオンの引出方向との関係を示す概念図である。
【図７】マイクロ波イオン源の一例を示す概略構成図である。
【図８】図７に示したマイクロ波イオン源のソースヘッドをマイクロ波の導入路を含む平面で切断したときの断面図である。
【図９】（ａ）〜（ｄ）はそれぞれ各工程におけるウエハの積層構造を模式的に示す断面図である。
【符号の説明】
１００…イオン引出アセンブリ、１３０…イオン質量セレクタ、１３１…質量選択スリット、１３２…磁気セクタ質量分析器、１４０…ターゲット基板、１４１…ターゲット基板ホルダ、３…ソースチャンバ、４…ターボポンプ、５…イオン源、６…ソレノイドコイル、７…引出電極系、８…主電極、９…接地電極、１２、１４…電極本体、１０ａ、１０ｂ、１２ａ、１２ｂ、１４ａ、１４ｂ…スリット、１５…取付プレート、１７…ボンベ、２１…マグネトロン、２２…マグネトロンマウント、２３…サーキュレータ、２４…ダミーロード、２５…パワーモニタ、２６…スタブチューナ、２７…インターフェースチューブ、２８…ソースヘッド、２９…プラズマチャンバ、３１…ソースチャンバ、３２…ソースブッシング、３３…マグネットヨーク、３４…出口側プレート、３５…マグネットポール、３６…導波管、３７…プラズマ生成領域、３８…ソレノイドコイル、５０…永久磁石、６０…電磁石、６１…心材、６２…ソレノイドコイル、９１、９５…Ｓｉ基板、９２…ＳｉＯ_２層、９３…水素イオン注入層、９４…Ｓｉ層、ＩＢ…イオンビーム、ＭＷ…マイクロ波。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ion implantation apparatus and method.
[0002]
[Prior art]
Conventionally, an ion implantation process has been used as a method of embedding a dopant in an IC device.
[0003]
In addition, the ion implantation process is also used in the smart cut method, which is one of the methods for manufacturing an SOI wafer (Silicon @ on @ Insulator). The smart cut method refers to an insulating layer (SiO 2) formed on the surface of a Si substrate.₂In this method, an SOI wafer is manufactured by implanting hydrogen ions into a Si substrate through a layer or the like, bonding the substrate to another Si substrate, and then dividing the substrate at a hydrogen ion implanted layer.
[0004]
As an ion implantation apparatus used for this ion implantation process, there is known an ion implantation apparatus provided with an ion source for generating plasma containing predetermined ions in a plasma chamber by arc discharge or microwave excitation (for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-9-283074
[0006]
[Problems to be solved by the invention]
By the way, with the recent miniaturization and high performance of IC devices, the energy of implanted ions is decreasing at an accelerating rate. For example, when boron (B) is implanted, it is required that the energy of ions be less than 1 keV.
[0007]
However, in the case of the above-described conventional ion implantation apparatus, when trying to implant low-energy ions, the beam current of the ions decreases. Therefore, in a process such as formation of a junction of a transistor which requires high dose ion implantation or formation of an ion implantation layer of an SOI wafer, ion implantation cannot be performed with a reasonable throughput.
[0008]
The present invention has been made in view of the above-mentioned problems of the related art, and when performing low-energy ion implantation, an ion implantation apparatus capable of maintaining a current amount of an ion beam at a high level and achieving a sufficient throughput. And a method, and a method for manufacturing an SOI wafer.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the ion implantation apparatus of the present invention is an ion source that excites a predetermined gas to generate plasma containing predetermined ions, and an extraction electrode that extracts ions from the ion source to generate an ion beam, A mass analyzer that introduces an ion beam into a predetermined magnetic field and selects ions to be implanted into the semiconductor substrate from the ion beam.In the ion implantation apparatus, the ion source has a plurality of slits from which ions are extracted. The slits are formed so as to be parallel to each other along the short axis direction, and a plurality of slits corresponding to each slit of the ion source are formed in the extraction electrode so as to be parallel to each other. .
[0010]
Thus, the plurality of slits are formed in the ion source so as to be parallel to each other along the short axis direction, and the plurality of slits corresponding to each slit of the ion source are formed in the extraction electrode so as to be parallel to each other. The effective extraction area of the ions can be increased without substantially changing the plasma density in the ion source and without impairing the convergence effect (optical lens effect) of the ion beam by the extraction electrode. Therefore, even when extracting low-energy ions, the beam current can be increased. Further, the ion beam generated in this manner has a good beam shape corresponding to the shape of the slit (rectangular or substantially rectangular with rounded corners), so that the desired ion is It can be effectively selected from ion beams. Therefore, in the process of forming a junction of a transistor requiring high dose ion implantation or forming an ion implantation layer of an SOI wafer by the ion implantation device of the present invention, a high level of ion implantation which has been difficult to achieve with the conventional ion implantation device is used. Throughput becomes feasible.
[0011]
According to the study of the present inventor, in a conventional ion implantation apparatus in which one slit is formed in the ion source and the extraction electrode, the size of the ion beam extracted from the ion source is simply increased by increasing the size of the slit itself. It is possible to increase the amount of current. However, in such a method, the convergence effect (optical lens effect) of the ions by the extraction electrode is reduced, the ion beam diverges, and the current amount of the beam that can reach the wafer is reduced. It is very difficult to get.
[0012]
Further, as means for increasing the effective extraction area of ions, shower-like ions may be extracted by forming a plurality of circular holes in the ion source and the extraction electrode instead of the plurality of slits according to the present invention. In this case, the total width of the ion beam becomes large. Even if an attempt is made to select desired ions from such an ion beam, a sufficient resolution (for example, 50 to 100 M / ΔM) cannot be obtained in the mass analyzer, and the above-described effect of improving the throughput cannot be achieved.
[0013]
The ion implantation apparatus of the present invention may be characterized in that the major axes of the plurality of slits of the ion source and the extraction electrode are perpendicular to the deflection surface of the mass analyzer. Thus, a desired ion can be efficiently selected from the ion beam with high resolution in the mass analyzer.
[0014]
Further, the ion implantation apparatus of the present invention may be characterized in that the extraction electrode includes a main electrode and a ground electrode which are arranged to face each other, and a plurality of slits are formed in the main electrode.
[0015]
Further, the ion implantation apparatus of the present invention may be characterized in that the extraction electrode extracts ions at an extraction energy of 10 keV or less. According to the ion implantation apparatus of the present invention, a high level of throughput can be achieved even when such low energy ions are extracted.
[0016]
In addition, the ion implantation apparatus of the present invention may further include a magnet that forms a magnetic field along a direction in which ions are extracted. By forming a magnetic field along the direction in which ions are extracted, ion generation can be promoted. Further, since the magnetic field does not affect the traveling direction of the extracted ions, the traveling direction of the ions is substantially the same as the extraction direction of the ions (that is, the direction of the magnetic field), and the extracted ions are bent by the magnetic field. The phenomenon in which the ions collide with the extraction electrode or the like does not occur. Therefore, even if the ions are low energy ions or ions having a smaller mass number, the extracted ions are subjected to ion implantation while the beam current is maintained at a high level, so that the throughput can be further increased. .
[0017]
In addition, the ion implantation method of the present invention includes the steps of: exciting a predetermined gas in an ion source to generate plasma containing predetermined ions; extracting ions from the ion source by an extraction electrode to generate an ion beam; Selecting an ion to be implanted into the semiconductor substrate from the ion beam by introducing an ion beam to a predetermined magnetic field in a vessel, wherein a plurality of slits are provided along the minor axis direction of the slit as an ion source. A plurality of slits corresponding to the respective slits of the ion source were used as extraction electrodes, each of which was formed so as to be parallel to each other. The ion beam generated from each slit passes through the slit corresponding to each slit of the ion source formed on the extraction electrode. And introducing into the mass spectrometer. As a result, the beam current can be increased even when extracting low-energy ions, and the ion beam introduced into the mass spectrometer can be maintained in a good shape. A high level of throughput can be achieved in processes such as formation of a portion and formation of an ion implantation layer of an SOI wafer.
[0018]
The ion implantation method of the present invention may be characterized in that ions are extracted by an extraction electrode at an extraction energy of 10 keV or less.
[0019]
Further, the ion implantation method of the present invention may be characterized in that a magnetic field is formed along the extraction direction of the ions. By forming such a magnetic field, the throughput can be further increased.
[0020]
Further, the method for manufacturing an SOI wafer according to the present invention includes an ion implantation step of forming a hydrogen ion implantation layer at a predetermined depth of a first wafer having an insulating layer on one surface of a Si substrate, and a second step after the ion implantation step. A method for manufacturing an SOI wafer, comprising: a laminating step of laminating a second wafer made of a Si substrate on an insulating layer of one wafer to obtain a laminated body; and a dividing step of dividing the laminated body by the hydrogen ion implanted layer. In the ion implantation step, a hydrogen ion implantation layer is formed by the above-described ion implantation method of the present invention.
[0021]
In the above manufacturing method, a hydrogen ion implanted layer is formed at a predetermined depth of a first wafer (insulating layer / Si substrate), and a second wafer is stacked on the insulating layer to form a laminate (Si substrate / insulating layer). / Si layer / hydrogen ion implanted layer / Si substrate), and this laminate is divided by the hydrogen ion implanted layer to obtain an SOI wafer (Si layer / insulating layer / Si substrate). At this time, by applying the above-described ion implantation method of the present invention in the ion implantation step, hydrogen ions can be efficiently implanted to a predetermined depth of the Si substrate, thereby dramatically improving the throughput. Therefore, the above manufacturing method is very useful in that an SOI wafer excellent in high integration and the like can be efficiently and reliably manufactured.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions will be denoted by the same reference characters, without redundant description.
[0023]
First, an ion implantation method and an ion implantation apparatus will be described.
[0024]
FIG. 1 is an explanatory view schematically showing one example of the ion implantation apparatus of the present invention. The apparatus shown in FIG. 1 includes an ion source 5 of an arc discharge type, an ion extraction assembly 100 including a cylinder 17 for supplying a predetermined gas to the ion source 5 and a pair of extraction electrodes 8 and 9, an ion mass selector 130, and a target. It has a substrate holder 140.
[0025]
FIG. 2 is a sectional view showing a schematic configuration of the ion extraction assembly 100. In FIG. 1, the ion extraction assembly 100 has a source chamber 3, and the inside of the source chamber 3 is evacuated to a predetermined degree of vacuum by a turbo pump 4. An ion source 5 is accommodated in the source chamber 3.
[0026]
The ion source 5 is of an arc discharge type and discharges a doping gas introduced into a plasma chamber from a gas supply source (not shown) to create a plasma state and ionize a predetermined element (molecule). is there. The gas to be introduced is for generating ions having a mass number of 20 or less, and for example, any one of hydrogen, helium, and boron, or a mixed gas of two or more thereof is suitably used.
[0027]
On the front surface of the ion source 5, two slits 10a and 10b from which ions generated by the ion source 5 are emitted are formed so as to be parallel to each other along the short axis direction of the slits 10a and 10b. . On the front side of the ion source 5, an extraction electrode system 7 for extracting ions from the ion source 5 is arranged. As shown in FIG. 2, the extraction electrode system 7 has a pair of extraction electrodes 8 and 9 (the extraction electrode 8 is a main electrode and the extraction electrode 9 is a ground electrode) arranged to face each other.
[0028]
The main electrode 8 has an electrode body 12 having two slits 12a and 12b, and a disk-shaped mounting plate 13 configured to surround the electrode body 12. The ground electrode 9 has an electrode body 14 having slits 14a and 14b, and a disk-shaped mounting plate 15 configured to surround the electrode body 14. The mounting plate 13 of the slit main electrode 8 is fixed to the source chamber 3 via a support member 16a. The mounting plate 15 of the ground electrode 9 is fixed to the source chamber 3 via a support member 16b.
[0029]
The slits 12a and 12b of the main electrode 8 are formed so as to be parallel to each other along their short axis direction. Similarly, the slits 14a and 14b of the ground electrode 9 are formed so as to be parallel to each other along their short axis direction. The slits 12a and 14a are formed corresponding to the slit 10a of the ion source 5, and the slits 12b and 14b are formed corresponding to the slit 10b.
[0030]
In each of the ion source 5 and the extraction electrodes 8 and 9, the width of the slit forming region in the short axis direction (for example, the long side of the slit 10a far from the slit 10b, the long side of the slit 10b far from the slit 10a, , Is within the range of a width at which a predetermined resolution (preferably 50 to 100 M / ΔM) can be obtained in the mass spectrometer.
[0031]
In the ion extraction assembly 100, when a desired voltage is applied between the ion source 5 and the main electrode 8, ions are extracted from each of the slits 10a and 10b, accelerated, and an ion beam is formed. For example, when extracting positive ions, the ion source 5 is maintained at a positive voltage with respect to the ground electrode 9, and the main electrode 8 is maintained at a negative voltage with respect to the ground electrode 9. At this time, the extraction energy of the ions is obtained by the following equation (1). The extraction energy of the ions in the present invention is preferably 10 keV or less, more preferably 1 keV or less.
[0032]
E = {ZV [eV] = {ZeV [J] (1)
[In the formula (1), E represents the extraction energy of the ions, Z represents the number of charges of the ions, V represents the extraction voltage (the potential difference between the main electrode and the ion source), and e represents the charges of the electrons. FIG. 3 conceptually shows the positional relationship between the ion source 5 and the extraction electrodes 8 and 9 when the ion beam is formed in this way, and the optical path of each ion beam. 3A is a perspective view, and FIG. 3B is a top view. As shown, ions extracted from the slit 10a form an ion beam IB-1, and are guided to the ion mass selector 130 through the slits 12a and 14a. Similarly, ions extracted from the slit 10b form an ion beam IB-2, and are guided to the ion mass selector 130 through the slits 12b and 14b.
[0033]
A solenoid coil 6 wound in a predetermined direction is arranged around the ion source 5 in the source chamber 3. By passing a current through the solenoid coil 6, a magnetic field is formed along the direction in which ions are extracted by the extraction electrode system 7. FIG. 4 conceptually shows the relationship between the ion extraction direction at this time and the direction of the magnetic field formed by the solenoid coil 6. As shown in the figure, when a current is passed in a predetermined direction of the solenoid coil 6, the slits 12 a, 14 a (and 12 b) of the extraction electrodes 8 and 9 are drawn along the ion extraction direction, that is, from the slit 10 a (and 10 b) of the ion source 5. , 14b), a magnetic field is formed to promote ion generation. At this time, the traveling direction of the ions extracted from the ion source 5 substantially remains in the extraction direction of the ions (that is, the direction of the magnetic field). Therefore, even if it is an ion of low energy or an ion having a still smaller mass number (for example, an ion of hydrogen, helium, boron or the like having a mass number of 20 or less), the extracted ions are bent by the magnetic field and the ions are extracted. The phenomenon of collision with 7 etc. does not occur, and the ion beam current is maintained at a high level.
[0034]
Returning to FIG. 1, the ion beam IB from the ion extraction assembly 100 is introduced into the ion mass selector 130.
[0035]
The ion mass selector 130 includes a mass selection slit 131 and a magnetic sector mass analyzer 132 that operates with the mass selection slit 131.
[0036]
In the magnetic sector mass analyzer 132, a magnetic field perpendicular to the plane of FIG. 1 is formed. Further, a magnetic field in a plurality of directions may be formed for adjusting the magnetic field. In such a magnetic field, an ion beam containing ions of constant energy having a predetermined mass / charge ratio starts from a point approaching the exit aperture of the arc chamber of the ion source 5 and moves from the entrance aperture of the analyzer 132 to the ion beam. Focus through the exit aperture at the plane of the mass selection slit 131. The slit 131 allows only necessary ions of the ion beam from the magnetic sector mass analyzer 132 to pass therethrough. The desired ions that have passed through the slit 131 are irradiated on the target substrate 141 mounted on the target substrate holder 140. The slit 131 and the magnetic sector mass spectrometer 132 are in the form of being surrounded by a housing or having a tube penetrated in a mechanism, and the inside thereof is evacuated to a predetermined degree of vacuum by a turbo pump (not shown).
[0037]
FIG. 1 schematically shows a state in which an ion beam having a single mass / charge ratio has a single focus on the aperture of the slit 131 and passes through the slit 131 toward the target substrate 14. In practice, the ion beam from ion extraction assembly 100 also includes ions having a different mass / charge ratio than desired for implantation into substrate 141. These unwanted ions have a different radius of curvature than the desired ions and do not pass through the slit. Therefore, the analyzer 132 has a deflection plane (dispersion plane) in the plane of FIG. It is preferable that the major axes of the slits formed in the ion source 5 and the extraction electrodes 8 and 9 are perpendicular to the deflection surface.
[0038]
As described above, in the present embodiment, two slits are formed in each of the ion source 5 and the extraction electrodes 8 and 9 so as to be parallel to each other along the minor axis direction. In addition, the effective extraction area of ions can be doubled as compared with a system in which one slit is formed in each of the extraction electrodes 8 and 9 (hereinafter, referred to as a “single slit system”). In the case of a single slit system, if the size of each slit is increased to increase the effective extraction area of ions, a phenomenon in which the ion beam diverges without obtaining a sufficient convergence effect may occur. When the effective extraction area of the ions is increased by increasing the number without changing the size of the slit, the same convergence effect as in the case of the single slit system of the same size is obtained for each of the ion beams IB-1 and IB-2. Therefore, phenomena such as divergence of the ion beam due to an increase in the effective area of the ions do not occur, and the beam current can be increased even when low-energy ions or ions having a smaller mass number are extracted.
[0039]
In addition, since the ion beam formed in this manner has a good beam shape corresponding to the shape of the slit, the ion beam required for ion implantation is introduced by introducing the ion beam into the ion mass selector 130. Selection can be made efficiently with high resolution. By irradiating the target 141 with the ions selected in this way, it becomes possible to perform ion implantation with a sufficiently high throughput.
[0040]
Further, in the present embodiment, the magnetic field is formed along the direction in which the ions are extracted by the solenoid coil 6 wound around the ion source 5, so that the extracted ions are not bent by the magnetic field. Can be extracted and ion beam current can be maintained at a high level. By arranging the solenoid coil 9 around the arc discharge type ion source 5 to form the above-described magnetic field, it is possible to further improve the throughput without requiring a significant improvement and a large size of the ion source 5 and the like. It is very useful in that the effect can be obtained. Further, with the prevention of the collision of the ions with the extraction electrode due to the formation of the magnetic field, effects such as a longer life of the extraction electrode, reduction of particle contamination, and a longer life of the vacuum pump can be obtained.
[0041]
Note that the present invention is not limited to the above embodiment. For example, FIGS. 3 to 6 show a substantially rectangular slit having an arc-shaped end, but the slit may have a rectangular shape.
[0042]
The ion implantation apparatus shown in FIG. 1 has two slits formed in each of the ion source 5 and the extraction electrodes 8 and 9, but each of the ion source and the extraction electrode has three slits. It may be the above. Even when the number of slits is three or more, the width of the slit forming region in the minor axis direction is within the range where a predetermined resolution (preferably 50 to 100 M / ΔM) can be obtained in the mass analyzer. Is preferred. Further, in the extraction electrode system 7, a plurality of slits corresponding to the slits of the ion source 5 may be formed in the main electrode 8, and the ion beam passing through the slit of the main electrode 8 does not collide with the ground electrode 9. May be provided with one slit.
[0043]
Further, in the ion implantation apparatus shown in FIG. 1, a permanent magnet or an electromagnet, which will be described later, can be used instead of the solenoid coil 9 as a means for forming a magnetic field along the ion extraction direction.
[0044]
That is, as shown in FIG. 5, the permanent magnet 50 is arranged on the back side of the ion source 5 (the side opposite to the extraction electrode) such that the side near the extraction electrode is the N pole and the side far from the extraction electrode is the S pole. As a result, a magnetic field is formed along the direction in which ions are extracted, so that the same effect as when the solenoid coil 6 is used can be obtained. If a magnetic field is formed along the extraction direction of the ions, the permanent magnets may be arranged such that the S pole is closer to the extraction electrode and the N pole is farther from the extraction electrode.
[0045]
As shown in FIG. 6, a core material 61 made of mild steel or a magnetic material, and a solenoid coil wound around the outer periphery of the core material 61 in a predetermined direction, on the back side of the ion source 5 (the side opposite to the extraction electrode). Also, by arranging the electromagnet 60 provided with 62, a magnetic field is formed along the direction in which ions are extracted, so that the same effect as when the solenoid coil 6 is used can be obtained.
[0046]
In the present invention, a microwave ion source may be used as the ion source as described later. Hereinafter, a case where hydrogen ions are implanted using a microwave ion source will be described as another example of the present invention. Note that the microwave ion source is also applicable to a case where boron or another element is implanted.
[0047]
FIG. 7 is a schematic configuration diagram showing an example of a microwave ion source that can be replaced with the arc discharge ion source 5 in FIG. 7, a magnetron 21, a magnetron mount 22, a circulator 23, a power monitor 25, a stub tuner 26, an interface tube 27, and a source head 28 are connected in this order to form a microwave ion source. A plasma chamber 29 is provided on the front surface of the source head 28. A dummy load 24 is provided on the side of the circulator 23.
[0048]
The magnetron 21 generates a predetermined microwave (e.g., 2.45 GHz), and the microwave is introduced into the source head 28 and used for plasma generation. The circulator 23 diverts the reflected microwave that is going to return to the magnetron 21 to the dummy load 24, and the bypassed microwave is absorbed by the dummy load 24 and converted into heat. The stub tuner 26 adjusts the microwave reflection so that more microwaves are consumed for plasma generation. The power monitor 25 for detecting the output of the microwave, the interface tube 27, and the like are not essential elements and can be omitted as appropriate.
[0049]
FIG. 8 is a cross-sectional view when the source head 28 is cut along a plane including a microwave introduction path. In FIG. 3, a source bushing 32 is formed on the magnetron side (the inlet side of the microwave MW) of the source chamber 31, and the end of the source bushing 32 is bent toward the inside of the source head. A magnet yoke 33 is provided at the tip of the bent portion to provide a space for inserting the source head 28. An outlet plate 34 having an opening is provided on the front surface of the magnet yoke 33, and a concave plasma chamber 29 is arranged in the opening of the plate 34 on the magnetron side. The space 37 in the concave portion of the plasma chamber 29 is a plasma generation region, and a predetermined gas is supplied to this portion.
[0050]
The convex magnet pole 35 is arranged such that the tip of the convex portion is close to the plasma chamber 29 and the bottom side surface is in close contact with the inner wall surface on the side of the magnet yoke 33. A waveguide 36 is arranged on the magnet pole 35 so as to communicate from the center of the bottom to the tip of the projection. The waveguide 36 introduces microwaves into the plasma chamber 29.
[0051]
In a space formed by the inner wall surfaces of the magnet yoke 33 and the plate 34 and the outer wall surfaces of the plasma chamber 29 and the magnet pole 35, a solenoid coil 38 is disposed so as to wind around the convex part of the magnet pole 35. With this configuration, a magnetic field is formed along the direction in which ions extracted from the plasma chamber 29 are extracted.
[0052]
In the microwave ion source having the above configuration, the electrons in the magnetic field rotate along the magnetic flux lines under Lorentz force. At this time, when microwaves are introduced into the waveguide 36 while introducing hydrogen gas into the plasma generation region 37, electrons in the magnetic field are excited by the microwaves, and collision between the excited electrons and the gas in the plasma generation region 37 occurs. As a result, plasma containing hydrogen ions is generated.
[0053]
The ions thus generated are extracted to generate an ion beam, and the target substrate 14 is irradiated with the ions via the ion mass selector 130 as in the case of the arc discharge ion source. Although the slit of the ion source is not shown in FIG. 8, two slits are formed in the plate 34. Thereby, the effective extraction area of the ions increases, and the beam current of the ions can be improved. Further, by forming a magnetic field along the extraction direction of the ions by the solenoid coil 38, it is possible to prevent a phenomenon in which the traveling direction of the ions is bent and collides with the extraction electrode system 7 or the like, and it is possible to prevent low energy ions or even mass numbers. It is possible to achieve a high level of beam current even with ions having a small diameter.
[0054]
In the present invention, plasma generation using a microwave ion source may be performed in any of an ECR mode and a non-ECR mode (Off-ECR mode). However, when a hydrogen gas is used, it is preferably performed in a non-ECR mode. . By performing plasma generation in the non-ECR mode, it is possible to increase the efficiency of generation of hydrogen molecule ions by low-energy electrons and the plasma density, and to improve the current density of the hydrogen ion beam IB and the ratio of hydrogen molecule ions.
[0055]
Note that the ECR (Electron @ Cyclotron @ Resonance) mode here means that the frequency of the microwave is calculated by the following equation (2):
[0056]
(Equation 1)

[0057]
[In equation (2), ω_eRepresents the electron cyclotron frequency and m_eRepresents the mass of the electron, e represents the charge of the electron, and B represents the strength of the magnetic field. ]
By selectively matching the electron cyclotron frequency (frequency of the electron orbiting along the magnetic flux lines) with the electron cyclotron resonance absorption process, the excited electrons collide with hydrogen molecules. This is to generate plasma. However, when plasma is generated in the ECR mode, hydrogen atom ions (H⁺) Is easily generated, and the current density of the hydrogen ion beam tends to be insufficient.
[0058]
On the other hand, the non-ECR mode means that the ECR condition is not satisfied, that is, the frequency of the microwave and the strength of the magnetic field are expressed by the following formula (3) or (4):
[0059]
(Equation 2)

[0060]
(Equation 3)

[0061]
[In the formulas (3) and (4), ω represents the frequency of the microwave, and m_eRepresents the mass of the electron, e represents the charge of the electron, and B represents the strength of the magnetic field.
The plasma generation is performed by setting so as to satisfy the condition represented by. In setting the non-ECR mode, the strength of the magnetic field may be adjusted by fixing the frequency of the microwave, or the frequency of the microwave may be adjusted by fixing the strength of the magnetic field. .
[0062]
In the non-ECR mode, the microwave frequency ω is equal to the electron cyclotron frequency ω_eIt is preferable to set the frequency of the microwave and the strength of the magnetic field so as to be higher (or lower) by 10 to 50% (more preferably 20 to 40%). Therefore, for example, when a microwave of 2.45 GHz is used, the strength of the magnetic field is preferably 96 to 131 mT or 44 to 79 mT (more preferably 105 to 123 mT or 53 to 70 mT). When a microwave of 14.5 GHz is used, the strength of the magnetic field is preferably 570 to 777 mT or 259 to 466 mT.
[0063]
The average residence time of hydrogen molecules from the introduction of hydrogen gas into the plasma generation region 37 to the extraction of the hydrogen ion beam IB is 5 × 10^-4~ 5 × 10^-3Seconds, preferably 7 × 10^-4~ 3 × 10^-3More preferably, it is seconds. If the average residence time exceeds the upper limit, the proportion of hydrogen molecule ions tends to decrease, and if the average residence time is less than the lower limit, the plasma generation efficiency tends to decrease. The setting of the average residence time can be performed by adjusting the shape and size of the plasma chamber 29, the supply amount of hydrogen gas, the extraction amount of the hydrogen ion beam IB, and the like.
[0064]
In the conventional method using an arc discharge type ion source, an RF ion source, and the like, hydrogen atom ions are more easily generated than hydrogen molecule ions, and thus hydrogen ion ions are exclusively used for ion implantation. . On the other hand, in the ion implantation method of the present invention, plasma is generated using microwaves, and a magnetic field is formed along the extraction direction of the ions to extract the ions. The ratio of molecular ions can be greatly increased, and the hydrogen molecular ions can be used with low extraction energy and high beam current. Therefore, it is possible to easily realize a high level of throughput which has been difficult to achieve in the past.
[0065]
For example, in the non-ECR mode in which the microwave frequency is 2.45 GHz, the microwave output is 700 W, and the magnetic field strength is 70 mT, the inventor has set the average residence time of hydrogen molecules at 8.9 × 10 4^-4When a plasma is generated in seconds, H⁺13.5% ion, H₂ ⁺78.1% ion, H₃ ⁺It has been confirmed that an ion composition of 8.4% of ions was achieved. On the other hand, the ion composition in the plasma generated by the conventional arc discharge ion source is H⁺60.2% ion, H₂ ⁺22.9% ion, H₃ ⁺The ion was 16.9%.
[0066]
The ion implantation apparatus and the ion implantation method of the present invention are capable of achieving a high level of throughput as described above, such as formation of a junction portion of a transistor requiring high dose ion implantation and formation of an ion implantation layer of an SOI wafer. It is very useful in the step.
[0067]
Here, regarding the manufacturing method of the SOI wafer, the Si layer / SiO₂The case of manufacturing an SOI wafer having a layered structure of a layer / Si substrate will be described in detail as an example.
[0068]
FIGS. 9A to 9D are cross-sectional views schematically showing the laminated structure of the wafer in each step.
[0069]
In the ion implantation step, as a target substrate, a Si substrate (Si-donor wafer)₂The one on which the layer 92 is formed is used. SiO₂The layer 92 can be formed, for example, by oxidizing the surface of a Si substrate, and has a thickness of, for example, 0.01 to 1.0 μm.
[0070]
For this target substrate, the SiO₂By irradiating hydrogen molecular ions from the layer 92 side, a hydrogen ion implanted layer 93 is formed at a predetermined depth in the Si substrate 92, and accordingly, SiO 2 is implanted.₂A thin Si layer is formed between the layer 92 and the hydrogen ion implanted layer 93 (FIG. 9A).
[0071]
When a microwave ion source is used in the ion implantation step, it is preferable to perform plasma generation in a non-ECR mode. Thereby, the generation of hydrogen molecular ions is promoted, so that a very high throughput can be realized, and as a result, the manufacturing efficiency of the SOI wafer can be drastically improved.
[0072]
The ion implantation amount in the ion implantation step is 1 × 10¹⁶ions / cm²It is preferable that it is above. The hydrogen ion implanted layer 93 is made of, for example, a Si layer 94 and SiO₂It is formed at a depth of 0.005 to 1.5 μm from the interface with the layer 82.
[0073]
Next, the target substrate SiO₂A Si substrate (Si-handle @ wafer) 95 is bonded onto the layer 92 (FIG. 9B). In addition, SiO₂An ion implantation step similar to the above is performed using a Si substrate on which no layer is formed, while a SiO 2₂A target laminated body can also be obtained by preparing an Si substrate on which layers are formed and bonding them together in a laminating step.
[0074]
This stacked body is divided by the hydrogen ion implanted layer 93 (FIG. 9C). Since the hydrogen ion implanted layer 93 is a fragile layer in which covalent bonds between silicon atoms have been broken, a gas such as dry air is blown onto the side surface of the hydrogen ion implanted layer 93, or mechanical shearing is applied. It can be easily divided.
[0075]
Thus, the SiO 2 on the Si substrate 95₂An SOI wafer having the layer 92 and the Si layer 94 stacked in this order is obtained (FIG. 9C). Note that a part of the hydrogen ion implanted layer 93 may remain on the surface of the Si layer 94 after the dividing step, but the residue can be easily removed by performing a polishing treatment or the like. Further, by further polishing the Si layer 94, the thickness of the Si layer 94 can be adjusted.
[0076]
【The invention's effect】
As described above, according to the ion implantation apparatus and the ion implantation method of the present invention, the effective ion implantation can be performed without substantially changing the plasma density in the ion source and without impairing the convergence effect of the ion beam by the extraction electrode. Since the extraction area can be increased, the beam current can be increased even when extracting low energy ions, and a high level of throughput can be realized.
[0077]
Further, according to the method for manufacturing an SOI wafer of the present invention, a high level of throughput can be realized by applying the above-described ion implantation method of the present invention at the time of the ion implantation step, which is excellent in terms of high integration and the like. SOI wafers can be manufactured efficiently and reliably.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one example of an ion implantation apparatus of the present invention.
FIG. 2 is a sectional view showing a schematic configuration of an ion extraction assembly 100 provided in the ion implantation apparatus shown in FIG.
3A and 3B are conceptual diagrams showing a positional relationship between an ion source and an extraction electrode when an ion beam is formed, and an optical path of each ion beam, respectively. FIG. (B) is a top view.
FIG. 4 is a conceptual diagram showing the relationship between the direction of a magnetic field formed by a solenoid coil and the direction in which ions are extracted.
FIG. 5 is a conceptual diagram showing the relationship between the direction of a magnetic field formed by a permanent magnet and the direction in which ions are extracted.
FIG. 6 is a conceptual diagram showing the relationship between the direction of a magnetic field formed by an electromagnet and the direction in which ions are extracted.
FIG. 7 is a schematic configuration diagram illustrating an example of a microwave ion source.
8 is a cross-sectional view when the source head of the microwave ion source shown in FIG. 7 is cut along a plane including a microwave introduction path.
9 (a) to 9 (d) are cross-sectional views schematically showing a laminated structure of a wafer in each step.
[Explanation of symbols]
Reference Signs List 100 ion extraction assembly, 130 ion mass selector, 131 mass selection slit, 132 magnetic sector mass analyzer, 140 target substrate, 141 target substrate holder, 3 source chamber, 4 turbo pump, 5 ion Source, 6: solenoid coil, 7: extraction electrode system, 8: main electrode, 9: ground electrode, 12, 14: electrode body, 10a, 10b, 12a, 12b, 14a, 14b: slit, 15: mounting plate, 17 ... cylinder, 21 ... magnetron, 22 ... magnetron mount, 23 ... circulator, 24 ... dummy load, 25 ... power monitor, 26 ... stub tuner, 27 ... interface tube, 28 ... source head, 29 ... plasma chamber, 31 ... source chamber , 32 ... Source bushing, 33 ... Magnet Yoke, 34 ... Exit plate, 35 ... Magnet pole, 36 ... Waveguide, 37 ... Plasma generation area, 38 ... Solenoid coil, 50 ... Permanent magnet, 60 ... Electromagnet, 61 ... Core material, 62 ... Solenoid coil, 91, 95: Si substrate, 92: SiO₂Layer 93: hydrogen ion implanted layer, 94: Si layer, IB: ion beam, MW: microwave.

Claims (9)

An ion source that excites a predetermined gas to generate a plasma containing predetermined ions, an extraction electrode that extracts the ions from the ion source to generate an ion beam, and introduces the ion beam into a predetermined magnetic field to generate an ion beam. A mass analyzer for selecting ions to be implanted into the semiconductor substrate;
A plurality of slits from which the ions are extracted are formed in the ion source so as to be parallel to each other along a short axis direction of the slit, and a plurality of slits corresponding to each slit of the ion source are formed in the extraction electrode. Wherein the slits are formed so as to be parallel to each other along the minor axis direction of the slits. 2. The ion implantation apparatus according to claim 1, wherein a major axis direction of the plurality of slits of the ion source and the extraction electrode is perpendicular to a deflection surface of the mass analyzer. 3. 3. The ion implantation apparatus according to claim 1, wherein the extraction electrode includes a main electrode and a ground electrode disposed to face each other, and the main electrode has a plurality of slits. 4. 4. The ion implantation apparatus according to claim 1, wherein the extraction electrode is configured to extract the ions with an extraction energy of 10 keV or less. 5. The ion implantation apparatus according to any one of claims 1 to 4, further comprising a magnet that forms a magnetic field along a direction in which the ions are extracted. Generating a plasma containing predetermined ions by exciting a predetermined gas in the ion source; generating ions by extracting ions from the ion source with an extraction electrode; and converting the ion beam to a predetermined magnetic field in a mass analyzer. Selecting an ion to be implanted into the semiconductor substrate from the ion beam by introducing the ion implantation method,
A plurality of slits as the ion source are formed so as to be parallel to each other along the short axis direction of the slit, and a plurality of slits corresponding to each slit of the ion source are parallel to each other as the extraction electrode. Using each formed so that
An ion implantation method, wherein an ion beam generated from each slit formed in the ion source is introduced into the mass analyzer through a slit corresponding to each slit of the ion source formed in the extraction electrode. The ion implantation method according to claim 6, wherein the extraction electrodes extract the ions at an extraction energy of 10 keV or less. The ion implantation method according to claim 7, wherein a magnetic field is formed along a direction in which the ions are extracted. An ion implantation step of forming a hydrogen ion implantation layer at a predetermined depth of a first wafer having an insulating layer on one surface of a Si substrate; and a step of forming a hydrogen ion implantation layer on the first wafer after the ion implantation step. A method for manufacturing an SOI wafer, comprising: a laminating step of laminating a second wafer made of a substrate to obtain a laminated body; and a dividing step of dividing the laminated body by the hydrogen ion implantation layer.
A method for manufacturing an SOI wafer, comprising forming the hydrogen ion-implanted layer by the ion implantation method according to claim 6 in the ion implantation step.

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