JPH09176843A - Titanium target for magnetron sputtering - Google Patents

Titanium target for magnetron sputtering

Info

Publication number
JPH09176843A
JPH09176843A JP33478495A JP33478495A JPH09176843A JP H09176843 A JPH09176843 A JP H09176843A JP 33478495 A JP33478495 A JP 33478495A JP 33478495 A JP33478495 A JP 33478495A JP H09176843 A JPH09176843 A JP H09176843A
Authority
JP
Japan
Prior art keywords
target
film
sputtering
blast
magnetron sputtering
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.)
Granted
Application number
JP33478495A
Other languages
Japanese (ja)
Other versions
JP3407518B2 (en
Inventor
Shuji Miki
修司 三木
Munetaka Mashima
宗位 真嶋
Terushi Mishima
昭史 三島
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Materials Corp
Original Assignee
Mitsubishi Materials Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mitsubishi Materials Corp filed Critical Mitsubishi Materials Corp
Priority to JP33478495A priority Critical patent/JP3407518B2/en
Publication of JPH09176843A publication Critical patent/JPH09176843A/en
Application granted granted Critical
Publication of JP3407518B2 publication Critical patent/JP3407518B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Landscapes

  • Physical Vapour Deposition (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a Ti target for magnetron sputtering capable of forming a film small in particles over a long period. SOLUTION: A film in a state in which blast material grains are driven into a wedged shape so as to expose the heads of the blast material grains is formed on the nonerosion part in the sputtered face of a Ti target. Furthermore, a film in a state in which blast material grains are driven into a wedged shape so as to expose the heads of the blast material grains is formed on the nonerosion part in the sputtered face of the Ti target and on the side of the sputtered face of a backing plate.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【発明の属する技術分野】この発明は、長期に亘ってパ
ーティクルの少ない成膜形成が可能なマグネトロンスパ
ッタリング用Tiターゲットに関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ti target for magnetron sputtering capable of forming a film with few particles for a long period of time.

【0002】[0002]

【従来の技術】一般に、雰囲気ガスとしてN2 やO2
どの反応性ガスを用いてプラズマを発生させ、マグネッ
トによりTiターゲットの表面に垂直方向の磁界を印加
しながら、前記Tiターゲット表面をスパッタして基体
の表面にTiN膜などのスパッタ膜を形成するマグネト
ロンスパッタリング法が知られている。このTiターゲ
ットを用いてマグネトロンスパッタリングを行うと、T
iターゲットのスパッタ面は中央部および外周縁部を除
くリング部分が溶融し、中央部および外周縁部は溶融さ
れない。Tiターゲットのスパッタ面の溶融されない中
央部および外周縁部を、通常、非エロージョン部と称
し、Tiターゲットのスパッタ面の中央部と外周縁部で
挟まれた溶融する部分を、通常、エロージョン部と称し
ている。マグネトロンスパッタリング中に前記非エロー
ジョン部は溶融しないため、その部分にTiNなどのス
パッタ膜が形成され、非エロージョン部に形成されたス
パッタ膜が剥離脱落してシリコンウエハなどの基板上に
直径:0.3μm以上の粗大なパーティクルが生ずると
言われている。
In general, plasma is generated using a reactive gas such as N 2 or O 2 as an atmosphere gas, while applying a magnetic field in the direction perpendicular to the surface of the Ti target by the magnet, sputtering the Ti target surface Then, a magnetron sputtering method is known in which a sputtered film such as a TiN film is formed on the surface of the substrate. When magnetron sputtering is performed using this Ti target, T
On the sputter surface of the i target, the ring portion except the central portion and the outer peripheral edge portion is melted, and the central portion and the outer peripheral edge portion are not melted. The unmelted central portion and outer peripheral edge portion of the sputtering surface of the Ti target are usually referred to as non-erosion portions, and the molten portion sandwiched between the central portion and outer peripheral edge portion of the Ti target sputtering surface is usually referred to as an erosion portion. I am calling it. Since the non-erosion portion does not melt during magnetron sputtering, a sputtered film of TiN or the like is formed on the non-erosion portion, and the sputtered film formed on the non-erosion portion is peeled off and dropped onto a substrate such as a silicon wafer with a diameter of 0. It is said that coarse particles of 3 μm or more are generated.

【0003】このマグネトロンスパッタリング法を実施
するためのマグネトロンスパッタリング装置は、近年、
ますます大型化および高性能化し、これに伴ないスパッ
タ条件は一段と苛酷さを増す状況にあるが、上記の従来
Tiターゲットを一段と苛酷な条件下でスパッタを行う
と、一層短時間の操業で成膜中に直径:0.3μm以上
の粗大なパーティクルが多数発生し、このため、Tiタ
ーゲットの頻繁な交換を必要とするところから、スパッ
タリングの操業効率はかえって低下することがあった。
A magnetron sputtering apparatus for carrying out this magnetron sputtering method has recently been used.
Although the size and performance of the sputtering equipment are becoming larger and larger, the sputter conditions are becoming more and more severe, but if the conventional Ti target is sputtered under the more severe conditions, the operation will be completed in a shorter time. A large number of coarse particles having a diameter of 0.3 μm or more were generated in the film, which required frequent replacement of the Ti target, which sometimes rather reduced the operating efficiency of sputtering.

【0004】これを改善するために、スパッタ面の平面
リング状のエロージョン部の表面粗さを0.1〜1μm
Ra(中心線平均粗さ)とし、残りのスパッタ面の中央
部および外周縁部で構成された非エロージョン部の表面
粗さをエロージョン部の表面粗さよりも粗い2〜5μm
Raにしたマグネトロンスパッタリング用Tiターゲッ
トが提案されている。すなわち、Tiターゲットの非エ
ロージョン部の表面粗さを通常よりも粗い2〜5μmR
aに加工して、非エロージョン部に付着したTiNなど
の被膜が剥離脱落しないようにしっかりと付着させ、粗
大パーティクルが発生するのを抑制したのである。そし
て上記非エロージョン部における外周縁部の角部をR加
工面とすることにより粗大パーティクルの発生がさらに
防止されるとしている(特開平6−306592公報参
照)
In order to improve this, the surface roughness of the flat ring-shaped erosion portion of the sputter surface is 0.1 to 1 μm.
Ra (center line average roughness), and the surface roughness of the non-erosion portion constituted by the central portion and the outer peripheral edge portion of the remaining sputtering surface is 2 to 5 μm which is rougher than the surface roughness of the erosion portion.
Ra-based Ti targets for magnetron sputtering have been proposed. That is, the surface roughness of the non-erosion portion of the Ti target is 2 to 5 μm, which is rougher than usual.
By processing into a, the coating such as TiN adhered to the non-erosion portion was firmly adhered so as not to peel off and fall off, and the generation of coarse particles was suppressed. Further, it is said that the generation of coarse particles is further prevented by making the corner portion of the outer peripheral edge portion of the non-erosion portion into the R processed surface (see Japanese Patent Laid-Open No. 6-306592).

【0005】[0005]

【発明が解決しようとする課題】上記特開平6−306
592公報記載のマグネトロンスパッタリング用Tiタ
ーゲットは、確かに粗大パーティクルの発生が少なく、
優れたTiターゲットであるが、出力:10KWを越え
る高出力スパッタリングに対しては、スパッタ中の加熱
冷却の熱サイクルが激しく、そのためにターゲットの非
エロージョン部に堆積した付着膜が剥離し脱落すること
による粗大パーティクルの発生は避けられず、これが原
因で使用寿命に至るのが現状であった。
DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The Ti target for magnetron sputtering described in the 592 publication does not generate much coarse particles,
It is an excellent Ti target, but the output: High-power sputtering exceeding 10 KW requires a vigorous thermal cycle of heating and cooling during the sputtering, and as a result, the deposited film deposited on the non-erosion part of the target peels off and falls off. Occurrence of coarse particles due to unavoidable is inevitable, and it is the current situation that this leads to the end of service life.

【0006】[0006]

【課題を解決するための手段】そこで、本発明者等は、
上述のような観点から、出力:10KWを越える高出力
スパッタリングを行っても成膜中の粗大パーティクルの
発生が少ないマグネトロンスパッタリング用Tiターゲ
ットを開発すべく研究を行なった結果、(a)Tiター
ゲットのスパッタ面の非エロージョン部、すなわちスパ
ッタ面の中央部および外周縁部にブラスト材粒子が打ち
込まれた状態の膜(以下、ブラスト打ち込み膜という)
を形成すると、非エロージョン部に堆積した堆積物がス
パッタ中に前記非エロージョン部から剥離しにくくなっ
て、スパッタ中の粗大パーティクルの混入が防止され
る、(b)ブラスト打ち込み膜は、TiC、SiC、T
iO2 、SiO2 、Ta23 、Al2 3 の内のいず
れかのブラスト材粒子が打ち込まれた状態の膜であるこ
とが好ましい、(c)これらブラスト打ち込み膜はTi
ターゲットのスパッタ面の非エロージョン部だけでな
く、Tiターゲットのバッキングプレートのスパッタ面
側にも形成すると、成膜中の粗大パーティクルの形成が
一層抑制されるようになる、などの研究結果を得たので
ある。
Means for Solving the Problems Accordingly, the present inventors have
From the viewpoints described above, as a result of conducting research to develop a Ti target for magnetron sputtering in which coarse particles are less likely to be generated during film formation even when high-power sputtering exceeding output: 10 KW is performed, A film in which blast material particles have been implanted into the non-erosion portion of the sputter surface, that is, the central portion and outer peripheral edge portion of the sputter surface (hereinafter referred to as the blast implantation film).
The formation of the layer makes it difficult for the deposits deposited on the non-erosion portion to separate from the non-erosion portion during sputtering, and prevents coarse particles from being mixed in during sputtering. (B) The blast-implanted film is made of TiC or SiC. , T
iO 2, SiO 2, Ta 2 O 3, it is preferable either blast material particles of the Al 2 O 3 is film in the state they were implanted, (c) These blasting implants films Ti
We have obtained research results such that formation of coarse particles during film formation can be further suppressed by forming not only on the non-erosion part of the sputtering surface of the target but also on the sputtering surface side of the backing plate of the Ti target. Of.

【0007】この発明は、上記の研究結果にもとづいて
なされたものであって、(1)Tiターゲットのスパッ
タ面中央部および外周縁部の非エロージョン部にブラス
ト打ち込み膜が形成されているマグネトロンスパッタリ
ング用Tiターゲット、(2)Tiターゲットのスパッ
タ面の非エロージョン部およびTiターゲットをバック
アップするバッキングプレートのスパッタ面の側にブラ
スト打ち込み膜が形成されているマグネトロンスパッタ
リング用Tiターゲット、に特徴を有するものである。
The present invention has been made on the basis of the above-mentioned research results. (1) Magnetron sputtering in which a blast-implanted film is formed on the non-erosion portion of the sputtering target center portion and outer peripheral edge portion of a Ti target. Ti target for sputtering, (2) Ti target for magnetron sputtering in which a blast-implanted film is formed on the non-erosion part of the sputtering surface of the Ti target and on the sputtering surface side of the backing plate that backs up the Ti target. is there.

【0008】上記ブラスト打ち込み膜は、TiC、Si
C、TiO2 、SiO2 、Ta2 3 、Al2 3 の内
のいずれかのブラスト材粒子が楔状に打ち込まれた状態
でブラスト材粒子の頭が露出した膜であることが最も好
ましい。
The blast-implanted film is made of TiC, Si.
C, TiOTwo, SiOTwo, TaTwoO Three, AlTwoOThreeWithin
One of the blast material particles is driven into a wedge shape
It is most preferable that the head of the blast material particles is exposed.
Good.

【0009】この発明のTiターゲットにおいて、非エ
ロージョン部にブラスト打ち込み膜を形成すると、出
力:10KWを越える高出力スパッタリングを行っても
成膜中の粗大パーティクルの発生が少なくなる理由とし
て、ブラスト打ち込み膜は表面にブラスト材粒子が楔状
に打ち込まれ、ブラスト材粒子の頭が露出した状態にあ
るために、スパッタ生成堆積物はアンカー状に強固に固
着され、それによってスパッタ中にはスパッタ生成堆積
物がTiターゲットから剥離落下しないことによるもの
と考えられる。
In the Ti target of the present invention, when the blast-implanted film is formed in the non-erosion portion, the reason why the generation of coarse particles during the film formation is reduced even if the high-power sputtering exceeding the output: 10 KW is performed is reduced. Since the blast material particles are struck in a wedge shape on the surface and the heads of the blast material particles are exposed, the sputter-produced deposits are firmly anchored in an anchor-like manner, which causes sputter-produced deposits during spatter. It is considered that this is because the Ti target did not peel off.

【0010】[0010]

【発明の実施の形態】ターゲットスパッタ部として、直
径:250mm×厚さ:10mmの寸法をもった純度:9
9.999%純Ti円板を用意し、さらに冷却用罰金具
プレートとして、直径:350mm×厚さ:15mmの寸法
をもったアルミニウム合金(JIS A5052)製円
板を用意した。この純Ti円板をアルミニウム合金製円
板に拡散接合してターゲット基体を作製し、このターゲ
ット基体の純Ti円板の非エロージョン部およびアルミ
ニウム合金製円板のスパッタ面側に表1に示される組成
のブラスト材粒子をブラスト圧力:6kg/cm2 で打
ち込むことにより、表1に示される被覆率(ブラスト材
粒子が1cm2 に食い込んだ面積)のブラスト打ち込み
膜を形成し、本発明Tiターゲット1〜7を作製した。
BEST MODE FOR CARRYING OUT THE INVENTION As a target sputter part, a purity of 9 with a diameter of 250 mm and a thickness of 10 mm.
A 9.999% pure Ti disk was prepared, and an aluminum alloy (JIS A5052) disk having dimensions of diameter: 350 mm × thickness: 15 mm was prepared as a cooling metal plate. This pure Ti disc is diffusion-bonded to an aluminum alloy disc to prepare a target substrate, and the non-erosion portion of the pure Ti disc of this target substrate and the sputter surface side of the aluminum alloy disc are shown in Table 1. By injecting the blast material particles having the composition at a blast pressure of 6 kg / cm 2 , a blast-implanted film having a coverage rate (area in which the blast material particles dig into 1 cm 2 ) shown in Table 1 is formed, and the Ti target 1 of the present invention 1 ~ 7 were produced.

【0011】比較のために、ターゲット基体の純Ti円
板の非エロージョン部の表面粗さを3.5μmRaとし
た従来Tiターゲットを用意した。
For comparison, a conventional Ti target in which the surface roughness of the non-erosion portion of the pure Ti disk of the target substrate was 3.5 μmRa was prepared.

【0012】これら本発明Tiターゲット1〜7および
従来Tiターゲットを直流マグネトロンスパッタリング
装置に装入し、出力:12KW、雰囲気:Ar/N2
1:1の気流中、スパッタ圧力:8mTorr、スパッ
タ時間:2分/ウエハの条件で、直径:150mmの平面
円形のSiウエハの表面に0.5μmのTiN成膜を形
成する操作を繰り返し行ない、TiN成膜中に存在する
直径:0.2μm以上のパーティクル数をパーティクル
カウンターを用い、レーザー光を当てて観察し、前記成
膜中に前記パーティクルが100個/ウエハを越えるに
至るまでのSiウエハ枚数を測定した。これらの測定結
果を表1に示した。
These Ti targets 1 to 7 of the present invention and the conventional Ti target were loaded into a DC magnetron sputtering apparatus, and output: 12 kW, atmosphere: Ar / N 2 =
An operation of forming a TiN film having a thickness of 0.5 μm on the surface of a flat circular Si wafer having a diameter of 150 mm is repeated under the conditions of a sputtering pressure of 8 mTorr and a sputtering time of 2 minutes / wafer in a 1: 1 air flow. SiN wafer existing during TiN film formation: The number of particles having a diameter of 0.2 μm or more is observed by irradiating a laser beam with a particle counter, and the number of the particles exceeds 100 particles / wafer during the film formation. The number of sheets was measured. Table 1 shows the results of these measurements.

【0013】[0013]

【表1】 [Table 1]

【0014】[0014]

【発明の効果】表1に示される結果から、ターゲット基
体の純Ti円板の非エロージョン部およびアルミニウム
合金製円板のスパッタ面側にブラスト打ち込み膜を形成
した本発明Tiターゲット1〜7は、ブラスト打ち込み
膜を形成しない従来Tiターゲットと比較して、直径:
0.2μm以上のパーティクルが100個/ウエハを越
えるに至るまでのSiウエハ枚数が多く、パーティクル
が発生しにくいことが分かる。したがって、この発明の
Tiターゲットは、10KWを越える苛酷な条件での高
出力スパッタでも成膜中にパーティクルが多発するのを
長期に亘って抑制することができるので、マグネトロン
スパッタリング装置の大型化および高性能化に十分満足
に対応でき、長い使用寿命を示すものである。
From the results shown in Table 1, the Ti targets 1 to 7 of the present invention in which the blast-implanted film is formed on the non-erosion portion of the pure Ti disk of the target substrate and on the sputtering surface side of the aluminum alloy disk are Compared with the conventional Ti target that does not form a blast-implanted film, the diameter:
It can be seen that the number of Si wafers until the number of particles of 0.2 μm or more exceeds 100 / wafer is large, and particles are hard to be generated. Therefore, the Ti target of the present invention can suppress the generation of many particles during film formation for a long period even in high power sputtering under severe conditions exceeding 10 KW, and thus the magnetron sputtering apparatus can be made large and high in size. It has a long service life and can fully satisfy performance improvement.

Claims (3)

【特許請求の範囲】[Claims] 【請求項1】 Tiターゲットのスパッタ面中央部およ
び外周縁部の非エロージョン部にブラスト材粒子が打ち
込まれた状態の膜(以下、ブラスト打ち込み膜という)
が形成されていることを特徴とするマグネトロンスパッ
タリング用Tiターゲット。
1. A film in which blast material particles are implanted into a non-erosion portion of a central portion and an outer peripheral edge portion of a Ti target (hereinafter referred to as a blast implantation film).
A Ti target for magnetron sputtering, wherein:
【請求項2】 Tiターゲットのスパッタ面中央部およ
び外周縁部の非エロージョン部並びにバッキングプレー
トのスパッタ面側にブラスト打ち込み膜が形成されてい
ることを特徴とするマグネトロンスパッタリング用Ti
ターゲット。
2. A Ti for magnetron sputtering, characterized in that a blast-implanted film is formed on the non-erosion part of the center and outer peripheral part of the sputtering target and on the sputtering surface side of the backing plate.
target.
【請求項3】 上記ブラスト打ち込み膜は、TiC、S
iC、TiO2 、SiO2 、Ta2 3 、Al2 3
内のいずれかのブラスト材粒子が打ち込まれた状態の膜
であることを特徴とする請求項1または2記載のマグネ
トロンスパッタリング用Tiターゲット。
3. The blast-implanted film comprises TiC, S
The magnetron sputtering according to claim 1 or 2, which is a film in which blast material particles of any one of iC, TiO 2 , SiO 2 , Ta 2 O 3 , and Al 2 O 3 are implanted. Ti target.
JP33478495A 1995-12-22 1995-12-22 Ti target for magnetron sputtering Expired - Lifetime JP3407518B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP33478495A JP3407518B2 (en) 1995-12-22 1995-12-22 Ti target for magnetron sputtering

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP33478495A JP3407518B2 (en) 1995-12-22 1995-12-22 Ti target for magnetron sputtering

Publications (2)

Publication Number Publication Date
JPH09176843A true JPH09176843A (en) 1997-07-08
JP3407518B2 JP3407518B2 (en) 2003-05-19

Family

ID=18281202

Family Applications (1)

Application Number Title Priority Date Filing Date
JP33478495A Expired - Lifetime JP3407518B2 (en) 1995-12-22 1995-12-22 Ti target for magnetron sputtering

Country Status (1)

Country Link
JP (1) JP3407518B2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002180243A (en) * 2000-12-11 2002-06-26 Toshiba Corp Titanium sputtering target and manufacturing method therefor
WO2005077677A1 (en) * 2004-02-09 2005-08-25 Honeywell International, Inc. Physical vapor deposition components, and methods of treating components

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002180243A (en) * 2000-12-11 2002-06-26 Toshiba Corp Titanium sputtering target and manufacturing method therefor
WO2005077677A1 (en) * 2004-02-09 2005-08-25 Honeywell International, Inc. Physical vapor deposition components, and methods of treating components

Also Published As

Publication number Publication date
JP3407518B2 (en) 2003-05-19

Similar Documents

Publication Publication Date Title
KR100631275B1 (en) Sputtering target producing few particles or backing plate and sputtering method producing few particles
JP3791829B2 (en) Sputtering target with less generation of particles
EP0630423B1 (en) Method of bonding a sputter target-backing plate assembly
JP4672834B2 (en) Method for joining sputtering target to receiving plate
JP2002527618A (en) Sputter target / back plate assembly and method of manufacturing the same
JP2720755B2 (en) Ti target material for magnetron sputtering
JPH0313570A (en) Device for producing semiconductor and target for the device
JP3407518B2 (en) Ti target for magnetron sputtering
JP2917743B2 (en) Si target material for magnetron sputtering
JPH09143704A (en) Titanium target for sputtering and its production
JPH09209133A (en) Titanium target for magnetron sputtering
JPH09176842A (en) Titanium target for magnetron sputtering
JP2001011617A (en) Sputtering target
JP2917744B2 (en) Si target material for magnetron sputtering
JP2004285445A (en) Sputtering method and apparatus
JP4057287B2 (en) Manufacturing method of erosion profile target
JP2001040471A (en) Sputtering target and sputtering method
JP4851700B2 (en) Components for vacuum film forming apparatus and vacuum film forming apparatus
JPH08325719A (en) Sputtering device
JP2738263B2 (en) Ti target material for magnetron sputtering
JP3275344B2 (en) Ti-W target material and method of manufacturing the same
JP2000239835A (en) Sputtering target
US20180044778A1 (en) Sputtering target having reverse bowng target geometry
JPH09209135A (en) Target for magnetron sputtering
JPH1025569A (en) Sputtering device

Legal Events

Date Code Title Description
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20030212

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20080314

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090314

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090314

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100314

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100314

Year of fee payment: 7

S531 Written request for registration of change of domicile

Free format text: JAPANESE INTERMEDIATE CODE: R313531

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100314

Year of fee payment: 7

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110314

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110314

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120314

Year of fee payment: 9

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130314

Year of fee payment: 10

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140314

Year of fee payment: 11

EXPY Cancellation because of completion of term