JP2012247593A - Method and apparatus for forming thin film - Google Patents
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本発明は、酸化シリコンや酸窒化シリコンなどのシリコンの化合物からなる薄膜を円形基板の上に形成する薄膜形成方法および装置に関するものである。 The present invention relates to a thin film forming method and apparatus for forming a thin film made of a silicon compound such as silicon oxide or silicon oxynitride on a circular substrate.
今日の光通信ネットワークにおいて、導波路型光デバイスは重要な役割を担っている。ここで使われている光導波路のコアおよびクラッドは、石英系膜（シリコン酸化膜など）で形成されている。これらの膜は、熱ＣＶＤ法の一種である火炎堆積法により形成（成膜）されている。この火炎堆積法は、１０００℃以上の高温で成膜を行う必要があるが、コアおよびクラッドとする膜の屈折率を高い精度で制御でき、ウエハ（円形基板）面内の膜厚、屈折率の均一性が非常に高いという優れた成膜法である。火炎堆積法が開発されたことで、光通信ネットワークを支える高性能の光デバイスが提供されるようになった。 In today's optical communication networks, waveguide-type optical devices play an important role. The core and clad of the optical waveguide used here are formed of a quartz-based film (silicon oxide film or the like). These films are formed (film formation) by a flame deposition method which is a kind of thermal CVD method. In this flame deposition method, it is necessary to perform film formation at a high temperature of 1000 ° C. or higher. However, the refractive index of the film used as the core and the clad can be controlled with high accuracy, and the film thickness and refractive index within the wafer (circular substrate) plane This is an excellent film forming method with extremely high uniformity. The development of flame deposition has provided high performance optical devices that support optical communication networks.
近年では、通信のさらなる大容量化、高速化に対応するため、石英系導波路光デバイスを、シリコン導波路光デバイスあるいはシリコン電気デバイスとともに、シリコンプラットフォーム上にモノリシック集積し、通信デバイスのさらなる高機能化、低消費電力化を目指す研究開発が盛んになってきている。シリコン光デバイス、シリコン電気デバイスに石英系導波路光回路をモノリシック集積するためには、シリコンデバイスに損傷を与えない低温で石英系膜を成膜することが必要である。このために、火炎堆積法に変わり、低温で成膜可能なプラズマＣＶＤ法による導波路膜の形成が検討されてきている（特許文献１参照）。 In recent years, silica-based waveguide optical devices have been monolithically integrated on a silicon platform together with silicon waveguide optical devices or silicon electrical devices in order to cope with further increase in capacity and speed of communication. Research and development aimed at reducing power consumption and power consumption has become popular. In order to monolithically integrate a silica-based waveguide optical circuit in a silicon optical device or a silicon electric device, it is necessary to form a silica-based film at a low temperature that does not damage the silicon device. Therefore, in place of the flame deposition method, the formation of a waveguide film by a plasma CVD method capable of forming a film at a low temperature has been studied (see Patent Document 1).
プラズマＣＶＤ法による導波路用の薄膜形成の一例として、電子サイクロトロン共鳴（ＥＣＲ）によるプラズマを用いたＣＶＤ法がある。このＥＣＲプラズマＣＶＤ法では、例えば、図９に例示するＥＣＲプラズマＣＶＤ装置が用いられている。この装置を用いた成膜では、まず、成膜ガスとマイクロ波をプラズマ源９０１に導入してプラズマ９１０を生成する。次に、生成したプラズマ９１０を成膜室９０２に引き出し、成膜室９０２に配置したシリコンもしくは石英からなる円形の基板９０９に照射し、基板９０９の上に、数μｍから十数μｍの導波路膜を形成する。 As an example of forming a thin film for a waveguide by a plasma CVD method, there is a CVD method using plasma by electron cyclotron resonance (ECR). In this ECR plasma CVD method, for example, an ECR plasma CVD apparatus illustrated in FIG. 9 is used. In film formation using this apparatus, first, a film formation gas and a microwave are introduced into the plasma source 901 to generate plasma 910. Next, the generated plasma 910 is drawn out to the film formation chamber 902 and irradiated to a circular substrate 909 made of silicon or quartz disposed in the film formation chamber 902, and a waveguide of several μm to several tens μm is formed on the substrate 909. A film is formed.
しかしながら、プラズマは、装置の形状やガスの流れなどの影響を受けて円形基板の全域で均一に生成することが難しいため、プラズマＣＶＤ法による成膜は、円形基板内で膜の厚みや屈折率に分布が発生しやすい。電子デバイスとは異なり、光デバイスでは、膜厚だけでなく膜の屈折率に少し違いがでただけでもデバイス特性に大きな影響が発生する。このため、プラズマＣＶＤ法により形成した導波路膜を用いた導波路デバイスでは、円形基板内で特性にばらつきが出てしまうという問題があった。 However, since it is difficult to generate plasma uniformly over the entire area of the circular substrate due to the influence of the shape of the apparatus and the gas flow, film formation by plasma CVD is performed within the circular substrate. The distribution tends to occur. Unlike an electronic device, an optical device has a great influence on device characteristics even if the refractive index of the film is slightly different as well as the film thickness. For this reason, in the waveguide device using the waveguide film formed by the plasma CVD method, there is a problem that the characteristics vary within the circular substrate.
さらに、電子デバイスで使われている８インチ、１２インチと径が大きい円形基板に対応するため、生成するプラズマの領域をより広くすると、均一性の問題がより顕著になり、光デバイスと電子デバイスをモノリシック融合する上での大きな妨げになっていた。 Furthermore, in order to cope with a circular substrate having a large diameter of 8 inches or 12 inches used in electronic devices, the problem of uniformity becomes more conspicuous if the region of the plasma to be generated is widened. It was a great hindrance to monolithic fusion.
本発明は、以上のような問題点を解消するためになされたものであり、より低温で実用レベルの膜厚と屈折率の均一な導波路膜を、径の大きい円形基板においても形成できるようにすることを目的とする。 The present invention has been made to solve the above-described problems, and can form a waveguide film having a uniform film thickness and a refractive index at a lower temperature at a practical temperature even on a circular substrate having a large diameter. The purpose is to.
本発明に係る薄膜形成方法は、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短いプラズマ照射領域で原料ガスのプラズマを照射している状態で、プラズマ照射領域に対して相対的に第２方向に円形基板を移動させる第１工程と、プラズマの照射により円形基板の上にシリコンの化合物からなる薄膜を形成する第２工程とを少なくとも備える。 In the thin film forming method according to the present invention, a raw material is formed in a plasma irradiation region in which the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction orthogonal to the first direction is shorter than the diameter of the circular substrate. A first step of moving the circular substrate in a second direction relative to the plasma irradiation region in a state where the gas plasma is irradiated; and a thin film made of a silicon compound on the circular substrate by the plasma irradiation. And a second step to be formed.
上記薄膜形成方法において、プラズマ照射領域以外にまで円形基板を移動させる往復移動を第２方向に行うことで、円形基板にプラズマを照射し、円形基板の上に薄膜を形成すればよい。また、往復移動の回数および移動速度により薄膜の厚さを制御することができる。 In the above thin film forming method, the circular substrate may be irradiated to the circular substrate by reciprocating in the second direction to move the circular substrate to a region other than the plasma irradiation region, and the thin film may be formed on the circular substrate. Further, the thickness of the thin film can be controlled by the number of reciprocating movements and the moving speed.
上記薄膜形成方法において、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短い領域でプラズマを生成することで、プラズマ照射領域におけるプラズマの照射を行えばよい。また、生成されたプラズマを、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短い領域の引き出し部から引き出すことで、プラズマ照射領域におけるプラズマの照射を行うようにしてもよい。 In the thin film forming method, plasma is generated in a region where the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction perpendicular to the first direction is shorter than the diameter of the circular substrate. The plasma irradiation in the plasma irradiation region may be performed. Further, the generated plasma is drawn out from a lead-out portion in a region where the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction perpendicular to the first direction is shorter than the diameter of the circular substrate. Thus, plasma irradiation in the plasma irradiation region may be performed.
また、本発明に係る薄膜形成装置は、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短いプラズマ照射領域で原料ガスのプラズマを照射するプラズマ照射手段と、プラズマ照射領域に対して相対的に第２方向に、プラズマ照射領域以外にまで円形基板を往復移動させる照射領域移動手段とを少なくとも備える。 In the thin film forming apparatus according to the present invention, the width of the first direction is longer than the diameter of the circular substrate to be formed, and the length of the second direction orthogonal to the first direction is shorter than the diameter of the circular substrate. And at least irradiation region moving means for reciprocally moving the circular substrate to other than the plasma irradiation region in the second direction relative to the plasma irradiation region.
以上説明した本発明によれば、より低温で実用レベルの膜厚と屈折率の均一な導波路膜を、径の大きい円形基板においても形成できるようになるという優れた効果が得られる。 According to the present invention described above, an excellent effect can be obtained that a waveguide film having a practical film thickness and a uniform refractive index can be formed even on a circular substrate having a large diameter at a lower temperature.
以下、本発明の実施の形態について図を参照して説明する。図１は、本発明の実施の形態における薄膜形成方法を説明するためのフローチャートである。まず、ステップＳ１０１で、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短いプラズマ照射領域で原料ガスのプラズマを照射している状態で、プラズマ照射領域に対して相対的に第２方向に円形基板を移動させる。原料ガスは、例えば、シラン、酸素、窒素などである。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining a thin film forming method according to an embodiment of the present invention. First, in step S101, the source gas plasma is generated in a plasma irradiation region in which the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction perpendicular to the first direction is shorter than the diameter of the circular substrate. In this state, the circular substrate is moved in the second direction relative to the plasma irradiation region. The source gas is, for example, silane, oxygen, nitrogen or the like.
次に、ステップＳ１０２で、上述した状態のプラズマの照射により円形基板の上にシリコンの化合物からなる薄膜を形成する。原料ガスとして、シランを用いることで、シリコンの薄膜が形成できる。原料ガスとして、シランおよび酸素を用いることで、酸化シリコンの薄膜が形成できる。原料ガスとして、シランおよび窒素を用いることで、窒化シリコンの薄膜が形成できる。また、原料ガスとして、シラン、酸素、および窒素を用いることで、酸窒化シリコンの薄膜が形成できる。また、酸化シリコン、窒化シリコン、酸窒化シリコンの薄膜形成では、各原料の供給比などにより、形成される薄膜の屈折率が制御できる。 Next, in step S102, a thin film made of a silicon compound is formed on the circular substrate by plasma irradiation in the state described above. By using silane as the source gas, a silicon thin film can be formed. By using silane and oxygen as source gases, a silicon oxide thin film can be formed. By using silane and nitrogen as source gases, a silicon nitride thin film can be formed. Further, by using silane, oxygen, and nitrogen as source gases, a silicon oxynitride thin film can be formed. In addition, in forming a thin film of silicon oxide, silicon nitride, or silicon oxynitride, the refractive index of the formed thin film can be controlled by the supply ratio of each raw material.
例えば、プラズマ照射領域以外にまで円形基板を移動させる往復移動を第２方向に行うことで、円形基板にプラズマを照射することで、円形基板の上に薄膜を形成すればよい。このような往復移動の回数、および往復移動における移動速度により、円形基板の上に形成する薄膜の厚さが制御できる。 For example, a thin film may be formed on the circular substrate by irradiating the circular substrate with plasma by performing a reciprocating movement in which the circular substrate is moved outside the plasma irradiation region in the second direction. The thickness of the thin film formed on the circular substrate can be controlled by the number of such reciprocations and the moving speed in the reciprocation.
ここで、プラズマ照射領域について説明すると、例えば、図２の斜視図に示すように、矩形形状のプラズマ源２０１に成膜ガスを供給して矩形状プラズマ２０２を生成すればよい。試料台（不図示）に固定された円形基板２０３に、矩形状プラズマ２０２を照射し、プラズマ誘起ＣＶＤ（Plasma Enhanced CVD）法により、シリコン酸化膜（ＳｉＯ2またはＳｉＯx）、あるいはシリコン酸窒化膜（ＳｉＯＮ）、あるいはシリコン窒化膜（ＳｉＮ）を形成すればよい。 Here, the plasma irradiation region will be described. For example, as shown in a perspective view of FIG. 2, a rectangular plasma 202 may be generated by supplying a film forming gas to a rectangular plasma source 201. A circular substrate 203 fixed on a sample stage (not shown) is irradiated with a rectangular plasma 202, and a silicon oxide film (SiO 2 or SiO x ) or a silicon oxynitride film is formed by plasma induced CVD (Plasma Enhanced CVD). (SiON) or a silicon nitride film (SiN) may be formed.
矩形状プラズマ２０２は、プラズマの照射面の形状が、例えば、移動方向（第２方向）に６ｃｍ、移動方向に直交する幅方向（第１方向）の長さ（幅）が、４０〜６０ｃｍ程度とすればよい。円形基板２０３の径が４〜１２インチ程度であれば、幅が成膜対象の円形基板の直径より長く、移動方向の長さが円形基板の直径より短いプラズマ照射領域となる。プラズマ発生方式は、誘導結合、電子サイクロトロン共鳴、表面波など一般的なプラズマ生成法を用いればよい。 In the rectangular plasma 202, the shape of the plasma irradiation surface is, for example, 6 cm in the moving direction (second direction), and the length (width) in the width direction (first direction) orthogonal to the moving direction is about 40 to 60 cm. And it is sufficient. When the diameter of the circular substrate 203 is about 4 to 12 inches, the plasma irradiation region has a width that is longer than the diameter of the circular substrate to be deposited and whose moving direction is shorter than the diameter of the circular substrate. As a plasma generation method, a general plasma generation method such as inductive coupling, electron cyclotron resonance, or surface wave may be used.
また、円形基板２０３を載置する試料台は、上面の法線方向が矩形状プラズマ２０２の照射法方向とされ、上述した移動方向に移動可能とする移動機構（照射領域移動手段）を備えている。この試料台を動作させ、矩形状プラズマ２０２の照射領域以外にまで円形基板２０３を移動させる往復移動を移動方向に行うことで、円形基板２０３に矩形状プラズマ２０２を照射し、円形基板２０３の上に薄膜を形成すればよい。 Further, the sample stage on which the circular substrate 203 is placed includes a moving mechanism (irradiation region moving means) that allows the normal direction of the upper surface to be the irradiation method direction of the rectangular plasma 202 and is movable in the moving direction described above. Yes. By operating the sample stage and performing a reciprocating movement in the moving direction to move the circular substrate 203 to a region other than the irradiation region of the rectangular plasma 202, the circular substrate 203 is irradiated with the rectangular plasma 202, A thin film may be formed on the substrate.
大きな径の大面積の円形基板の全域に対応させて、プラズマを均一に発生させるのは容易ではない。これに対し、上述したように、プラズマ照射領域を、一方の長さが６ｃｍ程度と短い矩形状とすることで、他方の長さが大きくても均一性のよいプラズマが比較的容易に生成できる。さらに、移動方向に直交する幅方向は、例えば、円形基板の径に対して１．５倍と円形基板より大きくすることで、プラズマの中心付近の均一性の良い領域を、円形基板に対して照射することが可能となる。 It is not easy to generate plasma uniformly corresponding to the entire area of a large-diameter large-area circular substrate. On the other hand, as described above, by forming the plasma irradiation region into a rectangular shape having a short length of about 6 cm, plasma with good uniformity can be generated relatively easily even if the other length is large. . Furthermore, the width direction orthogonal to the moving direction is, for example, 1.5 times the diameter of the circular substrate and larger than the circular substrate, so that a region with good uniformity near the center of the plasma can be obtained with respect to the circular substrate. Irradiation is possible.
このように、照射領域内ではより均一な状態としたプラズマの照射を、円形基板に対して相対的に移動させて行うことで、膜厚および屈折率が均一な状態の膜を円形基板の全域に形成できる。 In this way, by performing the plasma irradiation in a more uniform state within the irradiation region by moving the plasma relative to the circular substrate, a film having a uniform film thickness and refractive index can be obtained over the entire area of the circular substrate. Can be formed.
次に、ＥＣＲプラズマによる薄膜形成装置について、図３を用いて説明する。図３は、本発明の実施の形態における薄膜形成装置の構成例を示す構成図である。図３では、装置の断面を模式的に示している。 Next, a thin film forming apparatus using ECR plasma will be described with reference to FIG. FIG. 3 is a configuration diagram showing a configuration example of the thin film forming apparatus in the embodiment of the present invention. FIG. 3 schematically shows a cross section of the apparatus.
この装置は、プラズマ生成室３０１の周囲に磁気コイル３０２を配置し、プラズマ生成室３０１内の適当な領域でＥＣＲ条件を満たす磁界（８７５ガウス）を発生させる。また、ガス導入管３０５によりアルゴンガスとともに酸素ガスや窒素ガスなどを導入し、ガス導入管３０８によりシランガスを導入し、図示しないマイクロ波発生源で生成した２．４５ＧＨｚのマイクロ波を、導波管３０３およびマイクロ波導入口３０４を介して導入し、プラズマ生成室３０１でプラズマを発生させる。また、発生させたプラズマを、反応室３０６に引き出し、円形基板３０７に照射して成膜を行う。これらの構成は、よく知られているＥＣＲプラズマ装置と同様である。 In this apparatus, a magnetic coil 302 is arranged around the plasma generation chamber 301 and a magnetic field (875 gauss) that satisfies the ECR condition is generated in an appropriate region in the plasma generation chamber 301. Further, oxygen gas, nitrogen gas, or the like is introduced together with argon gas through the gas introduction tube 305, silane gas is introduced through the gas introduction tube 308, and 2.45 GHz microwave generated by a microwave generation source (not shown) is guided into the waveguide. Introduced through 303 and the microwave inlet 304, plasma is generated in the plasma generation chamber 301. Further, the generated plasma is drawn out to the reaction chamber 306 and irradiated onto the circular substrate 307 to perform film formation. These structures are the same as the well-known ECR plasma apparatus.
この装置では、円形基板３０７は、試料トレイ３０９の上に固定され、試料トレイ３０９は、移動機構３１２により移動可能とされている。また、プラズマが引き出される引き出し方向を法線とする平面におけるプラズマ生成室３０１の断面形状が、試料トレイ３０９の移動方向（第２方向）の長さが円形基板３０７の直径より短く、移動方向に直交する方向（第１方向）の長さが円形基板３０７の直径より長い、長方形とされている。従って、円形基板３０７が固定される平面に対する上記プラズマの照射領域も、移動方向の長さが円形基板３０７の直径より短く、移動方向に直交する方向の長さが円形基板３０７の直径より長い、長方形となる。なお、移動方向は、図２の紙面左右方向であり、移動方向に直交する方向は、図２の紙面手前から奥の方向となる。 In this apparatus, the circular substrate 307 is fixed on the sample tray 309, and the sample tray 309 can be moved by the moving mechanism 312. In addition, the cross-sectional shape of the plasma generation chamber 301 in a plane whose normal is the extraction direction of plasma is such that the length of the sample tray 309 in the moving direction (second direction) is shorter than the diameter of the circular substrate 307. The length in the orthogonal direction (first direction) is a rectangle longer than the diameter of the circular substrate 307. Accordingly, the plasma irradiation region with respect to the plane on which the circular substrate 307 is fixed also has a length in the moving direction shorter than the diameter of the circular substrate 307 and a length in the direction orthogonal to the moving direction is longer than the diameter of the circular substrate 307. It becomes a rectangle. The moving direction is the left-right direction in FIG. 2, and the direction orthogonal to the moving direction is the direction from the front to the back in FIG.
この装置において、移動機構３１２を動作させることで、試料トレイ３０９を移動方向に往復させれば、上述した長方形のプラズマ照射領域に対して相対的に、移動方向に円形基板３０７を移動させることができる。このように相対的に移動している状態で、反応室３０６に設けたガス導入管３０５を通して酸素ガス，窒素ガスおよびアルゴンガスをプラズマ生成室３０１に導入し、ガス導入管３０８によりシランガスを成膜室３０２の円形基板３０７の近傍に供給し、円形基板３０７の表面近傍で、シランガスを酸素プラズマ，窒素プラズマと反応させることで、円形基板３０７の表面に、ＳｉＯ2，ＳｉＯx，ＳｉＯＮなど石英系の導波路膜を形成できる。 In this apparatus, if the sample tray 309 is reciprocated in the moving direction by operating the moving mechanism 312, the circular substrate 307 can be moved in the moving direction relative to the rectangular plasma irradiation region described above. it can. In this state of relative movement, oxygen gas, nitrogen gas, and argon gas are introduced into the plasma generation chamber 301 through the gas introduction tube 305 provided in the reaction chamber 306, and silane gas is formed through the gas introduction tube 308. By supplying silane gas to oxygen plasma and nitrogen plasma in the vicinity of the surface of the circular substrate 307 in the vicinity of the circular substrate 307 in the chamber 302, a quartz system such as SiO 2 , SiO x , or SiON is formed on the surface of the circular substrate 307. The waveguide film can be formed.
上述したような薄膜形成の手順としては、まず、ロードロック室３２２を介し、円形基板３０７が固定された試料トレイ３０９を、反応室３０６に搬入し、移動機構３１２の上にセットする。この後、反応室３０６内を密閉状態とし、排気ポンプ３２１を動作させてプラズマ生成室３０１および反応室３０６の中を、所定の圧力にまで排気する。次に、ガス導入管３０５およびガス導入管３０８により各ガスを導入する。次いで、前述したようにＥＣＲ条件としてプラズマを生成させる。 As a procedure for forming a thin film as described above, first, the sample tray 309 on which the circular substrate 307 is fixed is loaded into the reaction chamber 306 via the load lock chamber 322 and set on the moving mechanism 312. Thereafter, the inside of the reaction chamber 306 is sealed, and the exhaust pump 321 is operated to exhaust the plasma generation chamber 301 and the reaction chamber 306 to a predetermined pressure. Next, each gas is introduced through the gas introduction pipe 305 and the gas introduction pipe 308. Next, as described above, plasma is generated as an ECR condition.
上述したようにプラズマを生成させている状態で、移動機構３１２を動作させて試料トレイ３０９を移動方向に往復移動させれば、円形基板３０７が長方形のプラズマ照射領域を横切るように移動する。これにより、円形基板３０７の上に、薄膜が形成できる。 When the moving mechanism 312 is operated and the sample tray 309 is reciprocated in the moving direction while the plasma is generated as described above, the circular substrate 307 moves across the rectangular plasma irradiation region. Thereby, a thin film can be formed on the circular substrate 307.
上述した装置によれば、移動方向の長さが短い矩形のプラズマ照射領域で原料ガスのプラズマを照射している状態で、プラズマ照射領域に対して相対的に移動方向に円形基板を移動させることができる。このように、照射領域内ではより均一な状態としたプラズマの照射を、円形基板に対して相対的に移動させて行えるので、本装置によれば、膜厚および屈折率が均一な状態の膜を円形基板の全域に形成できる。 According to the apparatus described above, the circular substrate is moved in the moving direction relative to the plasma irradiation region in the state where the plasma of the source gas is irradiated in the rectangular plasma irradiation region whose length in the moving direction is short. Can do. As described above, since the plasma irradiation in a more uniform state in the irradiation region can be performed by moving the plasma relative to the circular substrate, according to the present apparatus, the film having a uniform film thickness and refractive index can be obtained. Can be formed over the entire area of the circular substrate.
なお、上述したように、プラズマ生成室３０１の断面形状を長方形にしている場合、一般的には、プラズマ生成室３０１内で均一なプラズマが生成しにくい。これに対し、この装置では、各ガスを反応室３０６の側よりプラズマ生成室３０１に導く構成としているので、プラズマ生成室３０１内のガスの分布をより均一にでき、この結果、均一な状態でプラズマが生成できる。 Note that, as described above, when the cross-sectional shape of the plasma generation chamber 301 is rectangular, it is generally difficult to generate uniform plasma in the plasma generation chamber 301. In contrast, in this apparatus, since each gas is guided to the plasma generation chamber 301 from the reaction chamber 306 side, the gas distribution in the plasma generation chamber 301 can be made more uniform, and as a result, in a uniform state. Plasma can be generated.
次に、上述した相対的な往復移動と、得られる薄膜における膜厚および屈折率の状態について説明する。図４は、円形基板がプラズマ照射領域を１回通過するように移動したとき（黒四角）、および２回通過するように移動（往復移動）したとき（黒丸）での、膜厚の分布を比較した結果を示す特性図である。また、図５は、円形基板がプラズマ照射領域を１回通過するように移動したとき（黒四角）、および２回通過するように移動（往復移動）したとき（黒丸）での、屈折率の分布を比較した結果を示す特性図である。 Next, the above-described relative reciprocation and the state of the film thickness and refractive index of the obtained thin film will be described. FIG. 4 shows the film thickness distribution when the circular substrate moves so as to pass once through the plasma irradiation region (black square) and when it moves so as to pass twice (reciprocating movement) (black circle). It is a characteristic view which shows the result of the comparison. FIG. 5 shows the refractive index when the circular substrate moves so as to pass once through the plasma irradiation region (black square) and when it moves so as to pass twice (reciprocating movement) (black circle). It is a characteristic view which shows the result of having compared distribution.
図４から明らかなように、膜厚分布は、１回の移動および往復移動のいずれも同様の結果であり、移動しながら成膜する効果により膜厚が均一に形成されていることがわかる。 As is apparent from FIG. 4, the film thickness distribution is the same for both the single movement and the reciprocating movement, and it can be seen that the film thickness is uniformly formed by the effect of film formation while moving.
一方、図５から明らかなように、屈折率は、１回の移動成膜では大きな偏りが見られ、円形基板の面内で屈折率の値を均一にするためには、２回以上（最低でも１回の往復）の移動が、必要になることを示している。膜の屈折率は、プラズマ照射だけでなく反応室のガス流れにも影響を受けるためと考えられ、屈折率を、上述した相対的な移動により平均化して分布を均一にするには、少なくとも１回の往復移動が必要であることがわかる。光導波路膜のように膜厚だけでなく、屈折率の均一性も要求される膜を成膜する場合には円形基板を１回以上往復移動させて成膜することが重要となる。 On the other hand, as is clear from FIG. 5, the refractive index shows a large deviation in one moving film formation, and in order to make the refractive index value uniform in the plane of the circular substrate, it is at least twice (minimum). But it shows that one round trip) is required. It is considered that the refractive index of the film is influenced not only by the plasma irradiation but also by the gas flow in the reaction chamber. To average the refractive index by the above-described relative movement and make the distribution uniform, at least 1 is required. It can be seen that reciprocal movement is required. When forming a film that requires not only a film thickness but also a refractive index uniformity like an optical waveguide film, it is important to form the film by reciprocating the circular substrate at least once.
ところで、コアあるいはクラッドを形成する導波路膜形成には、導波路設計によって求められる厚さが異なるため、膜厚の制御が必要であるが、上述した薄膜形成方法では、形成する薄膜膜厚は、円形基板の移動速度と移動回数で制御できる。一般に、プラズマＣＶＤで成膜される膜厚は、「膜厚＝成膜速度×プラズマ照射時間」により計算される。円形基板を移動させながら成膜する本方法の場合には、プラズマ照射時間は「プラズマ照射時間＝プラズマ照射領域の幅×移動回数÷移動速度」となる。従って、移動させながらプラズマ照射する薄膜形成による膜厚は、「膜厚＝成膜速度×プラズマ照射領域の幅×移動回数÷移動速度」で求められる。ただし、屈折率を均一にするには前述したように往復移動が必要であるので移動回数は偶数回である必要がある。 By the way, in order to form the waveguide film for forming the core or the clad, the thickness required by the waveguide design is different, so it is necessary to control the film thickness. However, in the thin film forming method described above, the thin film thickness to be formed is It can be controlled by the moving speed and the number of movements of the circular substrate. Generally, the film thickness formed by plasma CVD is calculated by “film thickness = film formation speed × plasma irradiation time”. In the case of this method for forming a film while moving the circular substrate, the plasma irradiation time is “plasma irradiation time = width of plasma irradiation region × number of movements / movement speed”. Therefore, the thickness of the thin film formed by plasma irradiation while being moved can be obtained by “film thickness = deposition rate × plasma irradiation region width × number of movements / movement speed”. However, in order to make the refractive index uniform, reciprocal movement is necessary as described above, and therefore the number of movements needs to be an even number.
プラズマ照射領域の幅は装置よって固定であり、また、成膜速度は同じ屈折率を安定して得るためには固定するのがのぞましい。このため、膜厚は、移動回数と移動速度によって制御すればよいことになる。以下の実施例では、膜厚１μｍのＳｉＯ2膜を形成する場合、移動回数を４回（往復２回）、移動速度４６．８ｍｍ／ｍｉｎとした。また、膜厚１．５μｍのＳｉＯ2膜を形成する場合は、移動回数を４回（往復２回）、移動速度３１．２ｍｍ／ｍｉｎの条件を用いた。 The width of the plasma irradiation region is fixed by the apparatus, and the film formation rate is preferably fixed in order to stably obtain the same refractive index. For this reason, the film thickness may be controlled by the number of movements and the movement speed. In the following examples, when an SiO 2 film having a film thickness of 1 μm was formed, the number of movements was four (two reciprocations) and the movement speed was 46.8 mm / min. Further, in the case of forming a SiO 2 film having a thickness of 1.5 μm, the conditions of a movement speed of 4 times (2 reciprocations) and a movement speed of 31.2 mm / min were used.
移動回数と移動速度で膜厚を制御する方法は、成膜中の基板温度の制御にも有効である。移動速度が遅い場合、プラズマ照射領域の通過に時間を要するため、プラズマからの熱が蓄積して基板温度が上昇しやすい。一方、同じ膜厚に形成する場合でも、移動速度を大きくして熱が蓄積する前にプラズマ領域を通過させれば、基板温度の上昇を抑えることができる。例えば、膜厚１μｍのＳｉＯ2膜を形成する場合、移動回数４回、移動速度４６．８ｍｍ／ｍｉｎとすると、基板温度は３００℃程度に上昇する。これに対し、同じ膜厚とするために、移動回数４０回、移動速度４６８ｍｍ／ｍｉｎとすると、基板温度を２００℃以下に抑えられる。この方法によれば、移動速度と移動回数を変えて成膜できるので、熱に弱い有機膜上や電子デバイス上にも対応させることが可能となる。 The method of controlling the film thickness by the number of movements and the movement speed is also effective for controlling the substrate temperature during film formation. When the moving speed is slow, it takes time to pass through the plasma irradiation region, so that heat from the plasma accumulates and the substrate temperature tends to rise. On the other hand, even when they are formed to have the same film thickness, an increase in the substrate temperature can be suppressed if the moving speed is increased and the plasma region is passed before heat is accumulated. For example, when an SiO 2 film having a thickness of 1 μm is formed, the substrate temperature rises to about 300 ° C. when the number of movements is four and the movement speed is 46.8 mm / min. On the other hand, if the number of movements is 40 and the movement speed is 468 mm / min in order to obtain the same film thickness, the substrate temperature can be suppressed to 200 ° C. or lower. According to this method, the film can be formed by changing the moving speed and the number of movements, so that it can be applied to an organic film or an electronic device that is weak against heat.
ここで、前述したように、導波路膜の場合、屈折率の制御も重要である。本発明では屈折率を以下のように制御できる。例えば、ＥＣＲプラズマによるプラズマアシストを用いたＣＶＤ装置において、プラズマ生成室に酸素ガスを導入し、反応室（成膜室）にシランガスを導入して成膜すると、シリコン酸化膜（ＳｉＯ2膜またはＳｉＯx膜）が形成できる。また、酸素ガスに加えて窒素ガスもプラズマ生成室に導入すれば、円形基板上にシリコン酸窒化膜（ＳｉＯＮ）が形成できる。また、プラズマ生成室に窒素ガスを導入、反応室にシランガスを導入すればシリコン窒化膜（Ｓｉ3Ｎ4）が形成できる。 Here, as described above, in the case of a waveguide film, the control of the refractive index is also important. In the present invention, the refractive index can be controlled as follows. For example, in a CVD apparatus using plasma assist by ECR plasma, when an oxygen gas is introduced into a plasma generation chamber and a silane gas is introduced into a reaction chamber (deposition chamber), a silicon oxide film (SiO 2 film or SiO 2 film) is formed. x film) can be formed. If nitrogen gas is introduced into the plasma generation chamber in addition to oxygen gas, a silicon oxynitride film (SiON) can be formed on the circular substrate. Further, if nitrogen gas is introduced into the plasma generation chamber and silane gas is introduced into the reaction chamber, a silicon nitride film (Si 3 N 4 ) can be formed.
図６は、シランガスの流量を固定し、酸素ガスの流量を変化させてシリコン酸化膜を形成したときの、形成されるシリコン酸化膜の屈折率変化を示す特性図である。図６より明らかなように、酸素流量を調節することで、屈折率を１．４６から１．８５で変化させることができることがわかる。 FIG. 6 is a characteristic diagram showing a change in the refractive index of the formed silicon oxide film when the silicon oxide film is formed by changing the flow rate of oxygen gas while fixing the flow rate of silane gas. As is apparent from FIG. 6, it is understood that the refractive index can be changed from 1.46 to 1.85 by adjusting the oxygen flow rate.
また、図７は、シランガスの流量を固定し、酸素ガスと窒素ガスとの流量比を変化させたときの、形成されるＳｉＯＮ膜の屈折率変化を示す特性図である。図７より明らかなように、酸素ガスと窒素ガスの流量比を変化させることで、屈折率１．４６から１．９０までの間で、所望とする屈折率のＳｉＯＮ膜が形成できることがわかる。 FIG. 7 is a characteristic diagram showing the refractive index change of the formed SiON film when the flow rate of silane gas is fixed and the flow rate ratio of oxygen gas and nitrogen gas is changed. As is apparent from FIG. 7, it can be seen that a SiON film having a desired refractive index can be formed between 1.46 and 1.90 by changing the flow ratio of oxygen gas and nitrogen gas.
なお、酸素ガスと窒素ガスの流量比を変化させると、生成されるプラズマの分布が変化し、膜厚と屈折率の円形基板内の面内分布が変化し、均一性が低下する場合がある。このような場合は、酸素、窒素、シランガスに加えてアルゴンガスをプラズマ生成室に導入することで、面内均一性の低下を低減できる。図８は、アルゴンガスの添加流量に対する、膜厚および屈折率の面内分布の変化を示す特性図である。用いた円形基板は、直径４インチである。図８から明らかなように、添加するアルゴンの流量によって面内分布を改善できることがわかる。 Note that when the flow ratio of oxygen gas and nitrogen gas is changed, the distribution of the generated plasma changes, and the in-plane distribution of the film thickness and refractive index in the circular substrate changes, which may reduce the uniformity. . In such a case, in-plane uniformity can be reduced by introducing argon gas into the plasma generation chamber in addition to oxygen, nitrogen, and silane gas. FIG. 8 is a characteristic diagram showing changes in the in-plane distribution of film thickness and refractive index with respect to the addition flow rate of argon gas. The circular substrate used is 4 inches in diameter. As can be seen from FIG. 8, the in-plane distribution can be improved by the flow rate of the added argon.
以上に説明したように、本発明によれば、低温で膜厚と屈折率の均一な導波路膜を、大きな直径の円形基板においても形成できるようになるというすぐれた効果が得られる。 As described above, according to the present invention, an excellent effect can be obtained that a waveguide film having a uniform film thickness and refractive index can be formed even on a circular substrate having a large diameter at a low temperature.
なお、本発明は以上に説明した実施の形態に限定されるものではなく、本発明の技術的思想内で、当分野において通常の知識を有する者により、多くの変形および組み合わせが実施可能であることは明白である。例えば、上述した実施の形態では、プラズマ源の照射方向の断面形状を矩形状として矩形プラズマを生成することで、プラズマ照射領域を矩形としたが、これに限るものではない。例えば、生成されたプラズマを、第１方向の幅が成膜対象の円形基板の直径より長く、第１方向に直交する第２方向の長さが円形基板の直径より短い領域の引き出し部（取り出し部）から引き出す（取り出す）ことで、プラズマ照射領域におけるプラズマの照射を行うようにしてもよい。 The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above-described embodiment, the plasma irradiation region is rectangular by generating a rectangular plasma with the cross-sectional shape in the irradiation direction of the plasma source being rectangular, but this is not a limitation. For example, the generated plasma is extracted from a region in which the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction perpendicular to the first direction is shorter than the diameter of the circular substrate. The plasma irradiation in the plasma irradiation region may be performed by pulling out (extracting) from the (part).
また、上述では、円形基板の方を移動させるようにしたが、これに限るものではなく、円形基板は固定しておき、プラズマ照射領域を移動させるようにしてもよい。 In the above description, the circular substrate is moved. However, the present invention is not limited to this, and the circular substrate may be fixed and the plasma irradiation region may be moved.
２０１…プラズマ源、２０２…矩形状プラズマ、２０３…円形基板。 201 ... plasma source, 202 ... rectangular plasma, 203 ... circular substrate.
Claims (6)
前記プラズマの照射により前記円形基板の上にシリコンの化合物からなる薄膜を形成する第２工程と
を少なくとも備えることを特徴とする薄膜形成方法。 The source gas plasma is irradiated in a plasma irradiation region in which the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction orthogonal to the first direction is shorter than the diameter of the circular substrate. A first step of moving the circular substrate in the second direction relative to the plasma irradiation region,
And a second step of forming a thin film made of a silicon compound on the circular substrate by the plasma irradiation.
前記プラズマ照射領域以外にまで前記円形基板を移動させる往復移動を前記第２方向に行うことで、前記円形基板に前記プラズマを照射し、前記円形基板の上に前記薄膜を形成することを特徴とする薄膜形成方法。 The thin film forming method according to claim 1,
The circular substrate is irradiated with the plasma by reciprocating in the second direction to move the circular substrate to a region other than the plasma irradiation region, and the thin film is formed on the circular substrate. Thin film forming method.
前記往復移動の回数および移動速度により前記薄膜の厚さを制御することを特徴とする薄膜形成方法。 In the thin film formation method of Claim 2,
A method of forming a thin film, comprising controlling the thickness of the thin film according to the number of reciprocating movements and the moving speed.
第１方向の幅が成膜対象の円形基板の直径より長く、前記第１方向に直交する第２方向の長さが前記円形基板の直径より短い領域で前記プラズマを生成することで、前記プラズマ照射領域における前記プラズマの照射を行うことを特徴とする薄膜形成方法。 In the thin film formation method of any one of Claims 1-3,
The plasma is generated in a region in which the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction orthogonal to the first direction is shorter than the diameter of the circular substrate. A method of forming a thin film, wherein the plasma irradiation is performed in an irradiation region.
生成された前記プラズマを、第１方向の幅が成膜対象の円形基板の直径より長く、前記第１方向に直交する第２方向の長さが前記円形基板の直径より短い領域の引き出し部から引き出すことで、前記プラズマ照射領域における前記プラズマの照射を行うことを特徴とする薄膜形成方法。 In the thin film formation method of any one of Claims 1-3,
The generated plasma is extracted from a drawing portion in a region where the width in the first direction is longer than the diameter of the circular substrate to be deposited and the length in the second direction perpendicular to the first direction is shorter than the diameter of the circular substrate. A method of forming a thin film, wherein the plasma irradiation is performed in the plasma irradiation region by drawing.
前記プラズマ照射領域に対して相対的に前記第２方向に、前記プラズマ照射領域以外にまで前記円形基板を往復移動させる照射領域移動手段と
を少なくとも備えることを特徴とする薄膜形成装置。 Plasma that irradiates the source gas plasma in a plasma irradiation region having a width in the first direction longer than the diameter of the circular substrate to be deposited and a length in the second direction perpendicular to the first direction shorter than the diameter of the circular substrate. Irradiation means;
A thin film forming apparatus comprising at least irradiation region moving means for reciprocally moving the circular substrate to a position other than the plasma irradiation region in the second direction relative to the plasma irradiation region.
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| JP2019003029A (en) * | 2017-06-15 | 2019-01-10 | 日本電信電話株式会社 | Optical waveguide and method of manufacturing the same |
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