JP3842859B2 - Low dielectric constant material, interlayer insulation film and IC substrate - Google Patents
Low dielectric constant material, interlayer insulation film and IC substrate Download PDFInfo
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- JP3842859B2 JP3842859B2 JP00870597A JP870597A JP3842859B2 JP 3842859 B2 JP3842859 B2 JP 3842859B2 JP 00870597 A JP00870597 A JP 00870597A JP 870597 A JP870597 A JP 870597A JP 3842859 B2 JP3842859 B2 JP 3842859B2
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Description
【0001】
【発明の属する技術分野】
本発明は、LSI素子の層間などに用いられる絶縁膜、電気回路部品として用いられるIC基板など低誘電率材料に関するものである。
【0002】
【従来の技術】
LSI素子の高速化、高集積化が進むにつれ、配線間ならびに層間の容量に起因する信号の遅延が問題になりつつある。これを解決するためには、層間絶縁膜の誘電率を下げることが有効な手段である。
従来、層間絶縁膜としてはテトラエトキシシラン加水分解して作製したゾルをスピンオングラス(SOG)法によって成膜する方法が知られている。しかし、このようにして作製した材料の分子構造は、≡Si−O−Si≡の三次元網目構造で空隙を全く有さないものであり、誘電率は4.0と高かった。誘電率を下げるための方法の1つとして、材料を低密度化することが考えられる。低密度化の方法として、多孔質化する方法と、分子構造を疎にする方法がある。
【0003】
多孔質化した場合、孔の量に応じて誘電率は4.7から2.3まで下げられる[青井、第43回応用物理学会講演予稿集、26p−N−5(1996)]。しかし、多孔質膜は吸湿性などに問題があるため、通常の半導体素子や電気回路部品に使うことが難しい。一方、分子構造を疎にできる材料として、HO−[Si(CH3)2 −O]n −H(nは平均40)で表される骨格を有するシロキサンポリマーを各種金属アルコキシドを用いて架橋させたものがある[山田ら、日本セラミックス協会秋季シンポジウム講演予稿集、p1(1996)]。この材料は、有機成分としてメチル基を多量に含む上、1つの網目を構成する要素がMO−[Si(CH3)2 −O]n −Mという直鎖状ポリマーであり、網目の間に大きな空隙をもつ分子構造になるため、低密度化が実現すると考えられる。しかしながら、このようにして作製した材料の誘電率は3.2〜3.7で低誘電率化はまだ不十分なものであった。
【0004】
【発明が解決しようとする課題】
本発明は、誘電率が低く、半導体素子、電気回路部品などに適用可能な低誘電率材料を提供するものである。
【0005】
【課題を解決するための手段】
前記課題は、
[1] (A)一般式
MO−[SiR1R2−O]8−50−M(R1,R2は水素または有機基、MはB,Al,Si,Ti,Ge,Y,Zr,Nb,Taの中から選ばれた少なくとも1種類の元素)で表される分子構造、ならびに
(B)一般式
MO−[SiR3R4−O]1−7−M(R3,R4は水素または有機基、MはB,Al,Si,Ti,Ge,Y,Zr,Nb,Taの中から選ばれた少なくとも1種類の元素)で表される分子構造、
とを含み、
そのモル比(A)/(B)が0.1以上2.0以下であることを特徴とする低誘電率材料、
[2] 前記1記載の低誘電率材料から成る層間絶縁膜、
[3] 前記1記載の低誘電率材料から成るIC基板、
により達成される。
【0006】
【発明の実施の形態】
本発明の分子構造(A)に示される−[SiR1 R2 −O]8-50−はSi−Oの結合が8〜50個つながった構造を、分子構造(B)に示される−[SiR3 R4 −O]1-7 −はSi−Oの結合が1〜7個つながった構造を指すものである。本発明の低誘電率材料は、金属Mにより−[SiR1 R2 −O]8-50−および−[SiR3 R4 −O]1-7 −が架橋されることにより、分子構造(A)および(B)から3次元的な網目構造が形成されて得られる材料である。
【0007】
本発明によれば、HO−[Si(CH3)2 −O]n −H(nは平均40)を架橋させた材料と同程度の密度を有していながら、それよりも低誘電率化することができる。その理由について詳しく述べる。
本発明の材料は有機基をモル比でSiの2倍含んでいるため、従来のSiO2 組成の材料に比べて嵩高く低密度である。特に一般式(A)を含むことにより、網目を構成する辺を長くすることができ、大きな空隙を網目構造中に導入できるので、一層の低密度化が図れる。
【0008】
本発明の材料は、1MHz 以上の周波数の高い領域では通常配向性を示さないので、誘電率を支配する要素として電子分極と原子分極が考えられる。電子分極は、構成する元素によってほぼ決まり、分子構造の影響は小さい。一方、原子分極は、材料の固有振動数ωの2乗に反比例する。固有振動数は材料の硬さで決まり、硬いほどωが高くなるので、原子分極が小さく、誘電率が低くなる。Si−O−Siのシロキサン結合は結合角および回転の自由度が大きく、柔軟性に富むので、シロキサン結合の長いポリマーで構成されると柔らかい材料になり、短いオリゴマーまたはモノマーで構成されると硬い材料になる。従って、架橋点間のシロキサン結合が短い一般式(B)で表される分子構造を有することにより材料が硬くなるので誘電率を低くすることができる。
【0009】
本発明の分子構造(A)は、網目をゆるくし、材料を低密度化することに有効に働く。しかし(A)のみでは、架橋点間のシロキサン結合がいずれも長いため、原子分極に起因する誘電率を上げる効果が大きくなってしまう。そのため、原子分極を小さくする効果を持つ本発明の分子構造(B)を同時に含むことが必要となる。とくに(A)/(B)が0.1以上2.0以下のとき、低誘電率化の効果が大きい。
【0010】
一般式(A)で表されるMO−[SiR1 R2 −O]8-50−Mにおいて[SiR1 R2 −O]が50個よりも長い場合、ポリマーを架橋することにより固体が得られないのでふさわしくない。
本発明における、分子構造(A)と(B)を含む低誘電率材料は、(A)と(B)で構成される主骨格の他に、(A),(B)以外の分子構造で表される物質を副次的に含んでもよい。これについて、分子構造(A)と(B)を含む低誘電率材料を、分子量の異なる2種類のシロキサンポリマーα,βおよび金属アルコキシドから合成する場合を例にあげて説明する。ここでαはHO−[SiR1 R2 −O]40−Hで表されるSi−Oの結合を40個含むシロキサンポリマー、βはHO−[SiR3 R4 −O]6 −Hで表されるSi−O結合を6個含むシロキサンポリマーである。α,βおよび金属アルコキシドを溶媒中で加水分解し、熱処理により脱水縮合を行わせると、反応性の高い金属アルコキシドを介してα,βが架橋される。すなわち分子構造(A)は、αの両末端のシラノール基が金属アルコキシドM(OR)n と反応して形成され、分子構造(B)はβの両末端のシラノール基が金属アルコキシドM(OR)n と反応して形成される。α−α,α−β,β−βというシロキサンポリマー間での重合はほとんど起こらないので、分子構造(A),(B)から成る理想的な材料を合成するのに必要な金属アルコキシドの量は化学量論的に計算することができる。しかし、実際に合成する際には、化学量論的に計算された量に対して0.9〜4.0倍の金属アルコキシドを入れてもよい。この場合、金属アルコキシドが化学量論比より少ないときは、分子構造(A),(B)から構成される主骨格の他の架橋されていないフリーなシロキサンポリマーが含まれ、金属アルコキシドが化学量論比より多いときは、金属アルコキシド間での反応により金属−酸素−金属結合を有するクラスター状の無機成分が含まれることになる。
【0011】
また、本発明における低誘電率材料は、分子量の異なる2種類のシロキサンポリマーを使用する代わりに、RO−[SiR1 R2 −O]1-3 −R(Rはアルキル基)で表される単量体、2量体あるいは3量体のような低分子量の原料と金属アルコキシドとから合成することもできる。RO−[SiR1 R2 −O]1-3 −Rは、加水分解後の反応性がシロキサンポリマーに比べると著しく高い。このため、金属アルコキシドに対してモル比で3〜20倍のRO−[SiR1 R2 −O]1-3 −Rを混合し、加水分解を行うと、HO−[SiR1 R2 −O]1-3 −Hと金属アルコキシドの反応に加えて、HO−[SiR1 R2 −O]1-3 −H同士の重合も起こり、結果として最終的な分子構造が(A)と(B)を含むようにすることができる。
【0012】
R1 ,R2 ,R3 ,R4 は水素または有機基であり、R1 ,R2 ,R3 ,R4 で表される有機基はたとえば、アルキル基、フェニル基、−C2 H4 CF3 のようにC,H,Fから構成される有機基である。
本発明の低誘電率材料の作製にアルコキシドを用いる場合、使用するアルコキシドは特に限定しないが、例えばメトキシド、エトキシド、プロポキシド、ブトキシド等があげられる。また、アルコキシ基の一部をβ−ジケトン、β−ケトエステル、アルカノールアミン、アルキルアルカノールアミン、有機酸等で置換したアルコキシド誘導体も使用できる。
【0013】
本発明における加水分解では、全アルコキシ基に対して2モル倍までの水を添加して加水分解する。この際、無機酸、有機酸あるいはそれらの両方を触媒として使用してもよい。また、アルカリで溶液のpHを調整し、加水分解反応を制御してもよい。添加する水は、アルコール等の有機溶媒で希釈してもよい。2モル倍以上の水を使用すると、すぐにゲル化するために好ましくない。
【0014】
加水分解においては、シロキサンポリマー、アルキルアルコキシシランなどのSi原料およびアルコキシドを均一に分散、溶解できる有機溶媒が使用される。例えば、メタノール、エタノール、プロパノール、ブタノール等の各種アルコール、アセトン、トルエン、キシレン等である。
加水分解後、溶媒、加水分解で生成したアルコール等を常圧あるいは減圧下で留去して塗布してもよい。
【0015】
LSI用層間絶縁膜など膜として用いる場合、基板への塗布は、スプレーコート法、ディップコート法、スピンコート法等で行われる。
低誘電率基板としてバルク体で用いる場合は、鋳型に流し込んで成形し、熱処理する。
塗布膜およびバルク体の熱処理は、70〜500℃で行う。70℃未満であると、溶媒等が十分蒸発せず、固化できない。500℃を越えると、有機成分の分解が始まる。
【0016】
本発明による絶縁膜は、LSI素子用層間絶縁膜、IC基板など各種電子部品に応用することができる。
【0017】
【実施例】
本発明の絶縁膜を以下の実施例によって具体的に説明する。ただし、本発明は、これらの実施例のみに限定されるものではない。
実施例および比較例の材料は、シロキサン骨格を形成するシロキサンポリマー、ジアルキルアルコキシシランなどのSi原料と、金属Mを導入するための金属アルコキシドから合成した。使用したアルコキシドは、MがSiのものはSi(OC2 H5)4 ,AlのものはAl(O−sec−C4 H9)3 ,TaのものはTa(OC2 H5)5 ,TiのものはTi(OC2 H5)4 である。Al,Ta,Tiのアルコキシドはアセト酢酸エチルで化学改質してから用いた。
【0018】
実施例1および2は、分子構造(A)および(B)のMをHで置き換えた形で表される両末端がシラノール基のシロキサンポリマー2種類、および表1に示した金属Mのアルコキシドを原料として作製した。2種類のシロキサンポリマーの混合比は、分子構造(A)を構成するシロキサンポリマー:分子構造(B)を構成するシロキサンポリマーの比で、実施例1は0.17:1、実施例2は1:1とした。金属アルコキシドと2種類のシロキサンポリマーの比は、実施例1では2:1、実施例2では3:2とした。これらをエタノール溶媒中で撹拌し、水のエタノール溶液を添加して加水分解し、ゾルを調整した。得られたゾルをアルミシャーレに流し込み70℃,150℃の2段階で熱処理し、バルク体を作製した。バルク体の両面に電極を付与し、周波数1MHz で誘電率を測定した。このように2種類のシロキサンポリマーを原料にした場合、シロキサンポリマー間の重合は起こらないので、分子構造(A)と(B)の比は原料のシロキサンポリマーの混合比で決まり、表1に示したとおりとなる。
【0019】
実施例3は、分子構造(A)を構成する原料として、分子構造(A)のMをHで置き換えた形で表される両末端がシラノール基のシロキサンポリマーを使用し、分子構造(B)を構成する原料として、低分子量のCH3O−[SiR3R4−O]2−CH3 を原料としている。分子構造(A)を構成する原料と分子構造(B)を構成する原料の比を実施例3で、1:2とし、金属アルコキシドとSi原料の比は、5:2とした。エトキシエタノール溶媒中でこれらの原料を撹拌し、水のエトキシエタノール溶液を添加して加水分解し、ゾルを調整した。得られたゾルをテフロン(登録商標)シャーレに流し込み、実施例3は70℃と200℃の2段階で熱処理し、バルク体を作製した。できあがった材料中の分子構造(A)と(B)の比は、次のようにして計算した。まず、材料を硝酸中に24時間浸漬して溶解させる。その結果、酸によってM−O−Siの結合が切れるのでHO−[SiR1R2−O]n−HおよびHO−[SiR3R4−O]n−Hで表されるシリコーンオイル状のシロキサンポリマーと金属を含む酸性の水溶液になる。分液ロートでオイルと水溶液を分離し、シリコーンオイル状の成分のみを分離する。これを有機溶媒で希釈してゲルパーミエイションクロマトグラフィー(GPS)で分子量分布を測定した。分子量分布は分子構造(A)と(B)に対応する形で2カ所にピークを示した。分子量の高い方のピークが分子構造(A)、分子量の低い方のピークが分子構造(B)に対応する。分子量の低い方のピークからこのシロキサンポリマーに含まれる平均的なSi−O結合の数を計算したものをnavrとして表1の分子構造(B)の欄に示してある。2つのピークの強度比から、分子構造(A)と(B)の比を求めた。電気特性は実施例1および2と同様にして測定した。
【0020】
実施例4はSi原料としてC2H5O−[SiR1R2−O]1−C2H5のみを用い、C2H5O−[SiR1R2−O]1−C2H5と金属アルコキシドの比を20:1とした。金属アルコキシドに対してC2H5O−[SiR1R2−O]1−C2H5の比が高いので、加水分解されたHO−[SiR1R2−O]1−H同士の脱水による重合が進んだ。実施例1と同様の方法でゾルを調整し、熱処理によりバルク体を得た。前述した方法でゲルパーミエイションクロマトグラフィー(GPC)によりシロキサンポリマーの分子量分布を調べた結果、Si−O結合が2〜30個でほぼ16個の所に最大値を持つブロードなガウシアン分布を示した。この分布から分子構造(A)と(B)の存在比を計算した。誘電率は、調整した液をSi基板に塗布し、300℃で20分間熱処理した膜について測定した。
【0021】
実施例5は実施例2と同じ方法で合成したが、その際、金属アルコキシドと2種類のシロキサンポリマーの和の比を3:4とし、金属アルコキシドを化学量論比に対して2倍入れたために、分子構造(A),(B)に加えてAl−O−Alのクラスターを含んでいる例である。実施例1〜5はいずれも比誘電率が3.0未満の低い値を示した。
【0022】
比較例6は、n=40のシロキサンポリマーと金属アルコキシドから合成したもので、分子構造(A)のみを含むため、原子分極が大きく誘電率が高い。比較例7は、n=80のシロキサンポリマーを使用したため、熱処理してもゲル化しなかった。比較例8は、C2H5O−[SiR3R4−O]1−C2H5と金属アルコキシドのモル比が2:1で合成をしたため、Tiによる架橋点間のSi−O結合の数が平均2個となり、分子構造(B)のみから構成される。このため比較例8は密度が高く、誘電率も高い材料になった。
【0023】
【発明の効果】
本発明によれば、比誘電率が3.0未満の低誘電率材料が得られる。LSI用層間絶縁膜、IC基板など、半導体素子および電気回路部品へこの低誘電率材料を適用することにより、電気信号の遅延が小さくなるため、デバイスの高速化に対応することができる。
【0024】
【表1】
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low dielectric constant material such as an insulating film used between layers of LSI elements and an IC substrate used as an electric circuit component.
[0002]
[Prior art]
As the speed and integration of LSI elements increase, signal delay due to capacitance between wirings and between layers is becoming a problem. In order to solve this, it is an effective means to lower the dielectric constant of the interlayer insulating film.
Conventionally, as an interlayer insulating film, a method is known in which a sol produced by hydrolyzing tetraethoxysilane is formed by a spin-on-glass (SOG) method. However, the molecular structure of the material thus produced is a three-dimensional network structure of ≡Si—O—Si≡ and has no voids, and has a high dielectric constant of 4.0. One method for reducing the dielectric constant is to reduce the density of the material. As a method of reducing the density, there are a method of making it porous and a method of making the molecular structure sparse.
[0003]
When it is made porous, the dielectric constant is lowered from 4.7 to 2.3 according to the amount of pores [Aoi, 43rd Japan Society of Applied Physics Proceedings, 26p-N-5 (1996)]. However, since the porous film has a problem in hygroscopicity, it is difficult to use it for a normal semiconductor element or electric circuit component. On the other hand, a siloxane polymer having a skeleton represented by HO— [Si (CH 3 ) 2 —O] n —H (n is an average of 40) is cross-linked using various metal alkoxides as a material capable of reducing the molecular structure. [Yamada et al., Proceedings of Autumn Symposium of the Ceramic Society of Japan, p1 (1996)]. This material contains a large amount of methyl groups as organic components, and the element constituting one network is a linear polymer of MO- [Si (CH 3 ) 2 —O] n —M. Since the molecular structure has large voids, it is thought that low density will be realized. However, the dielectric constant of the material produced in this way was 3.2 to 3.7, and the reduction of the dielectric constant was still insufficient.
[0004]
[Problems to be solved by the invention]
The present invention provides a low dielectric constant material that has a low dielectric constant and can be applied to semiconductor elements, electrical circuit components, and the like.
[0005]
[Means for Solving the Problems]
The problem is
[1] (A) General formula MO- [SiR 1 R 2 —O] 8-50 -M (R 1 and R 2 are hydrogen or an organic group, M is B, Al, Si, Ti, Ge, Y, Zr , Nb, Ta), and a molecular structure represented by (B) general formula MO- [SiR 3 R 4 —O] 1-7 -M (R 3 , R 4 Is a hydrogen or organic group, M is a molecular structure represented by at least one element selected from B, Al, Si, Ti, Ge, Y, Zr, Nb, and Ta),
Viewing including the door,
A low dielectric constant material whose molar ratio (A) / (B) is 0.1 or more and 2.0 or less ,
[2] An interlayer insulating film made of the low dielectric constant material as described in 1 above,
[3] An IC substrate made of the low dielectric constant material as described in 1 above,
Is achieved.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
-[SiR 1 R 2 —O] 8-50 — shown in the molecular structure (A) of the present invention is a structure in which 8 to 50 bonds of Si—O are connected, and is shown in the molecular structure (B) — [ [SiR 3 R 4 —O] 1-7 — refers to a structure in which 1 to 7 bonds of Si—O are connected. The low dielectric constant material of the present invention is obtained by crosslinking-[SiR 1 R 2 -O] 8-50-and- [SiR 3 R 4 -O] 1-7-with a metal M to form a molecular structure (A ) And (B) is a material obtained by forming a three-dimensional network structure.
[0007]
According to the present invention, while having a density comparable to that of a material in which HO— [Si (CH 3 ) 2 —O] n —H (n is 40 on average) is crosslinked, the dielectric constant is further reduced. can do. The reason is described in detail.
Since the material of the present invention contains organic groups twice as much as Si in a molar ratio, it is bulky and has a lower density than conventional SiO 2 composition materials. In particular, by including the general formula (A), the sides constituting the mesh can be lengthened and a large gap can be introduced into the network structure, so that the density can be further reduced.
[0008]
Since the material of the present invention does not normally exhibit orientation in a high frequency region of 1 MHz or higher, electronic polarization and atomic polarization can be considered as factors governing the dielectric constant. Electronic polarization is almost determined by the constituent elements, and the influence of the molecular structure is small. On the other hand, atomic polarization is inversely proportional to the square of the natural frequency ω of the material. The natural frequency is determined by the hardness of the material. The harder the material, the higher the ω, so the atomic polarization is small and the dielectric constant is low. The siloxane bond of Si-O-Si has a large bond angle and freedom of rotation and is highly flexible. Therefore, it is soft when composed of a polymer with a long siloxane bond, and hard when composed of a short oligomer or monomer. Become a material. Therefore, since the material is hardened by having the molecular structure represented by the general formula (B) in which the siloxane bond between the crosslinking points is short, the dielectric constant can be lowered.
[0009]
The molecular structure (A) of the present invention works effectively to loosen the network and reduce the density of the material. However, only (A) has a long effect of increasing the dielectric constant due to atomic polarization because all of the siloxane bonds between the crosslinking points are long. Therefore, it is necessary to include the molecular structure (B) of the present invention having the effect of reducing atomic polarization at the same time. In particular, when (A) / (B) is 0.1 or more and 2.0 or less, the effect of reducing the dielectric constant is great.
[0010]
In MO- [SiR 1 R 2 —O] 8-50 -M represented by the general formula (A), when [SiR 1 R 2 —O] is longer than 50, a solid is obtained by crosslinking the polymer. It is not suitable because it is not possible.
In the present invention, the low dielectric constant material containing the molecular structures (A) and (B) has a molecular structure other than (A) and (B) in addition to the main skeleton composed of (A) and (B). The substance represented may be included as a secondary. This will be described by taking, as an example, a case where a low dielectric constant material containing molecular structures (A) and (B) is synthesized from two types of siloxane polymers α and β and metal alkoxides having different molecular weights. Here, α is a siloxane polymer containing 40 bonds of Si—O represented by HO— [SiR 1 R 2 —O] 40 —H, and β is represented by HO— [SiR 3 R 4 —O] 6 —H. It is a siloxane polymer containing 6 Si—O bonds. When α, β and metal alkoxide are hydrolyzed in a solvent and subjected to dehydration condensation by heat treatment, α, β is cross-linked through highly reactive metal alkoxide. That is, the molecular structure (A) is formed by reacting the silanol groups at both ends of α with the metal alkoxide M (OR) n, and the molecular structure (B) is formed by reacting the silanol groups at both ends of β with the metal alkoxide M (OR). Formed by reacting with n . Since polymerization between α-α, α-β, and β-β siloxane polymers hardly occurs, the amount of metal alkoxide required to synthesize an ideal material composed of molecular structures (A) and (B) Can be calculated stoichiometrically. However, in the actual synthesis, 0.9 to 4.0 times as much metal alkoxide as the stoichiometrically calculated amount may be added. In this case, when the metal alkoxide is less than the stoichiometric ratio, other uncrosslinked free siloxane polymers of the main skeleton composed of the molecular structures (A) and (B) are included, and the metal alkoxide is in the stoichiometric amount. When the ratio is larger than the stoichiometric ratio, a cluster-like inorganic component having a metal-oxygen-metal bond is contained by a reaction between metal alkoxides.
[0011]
The low dielectric constant material in the present invention is represented by RO— [SiR 1 R 2 —O] 1-3 —R (R is an alkyl group) instead of using two types of siloxane polymers having different molecular weights. It can also be synthesized from a monomer having a low molecular weight such as a dimer or trimer and a metal alkoxide. RO- [SiR 1 R 2 —O] 1-3 -R has a significantly higher reactivity after hydrolysis than siloxane polymers. For this reason, when RO- [SiR 1 R 2 —O] 1-3 —R in a molar ratio of 3 to 20 times with respect to the metal alkoxide is mixed and subjected to hydrolysis, HO— [SiR 1 R 2 —O ] In addition to the reaction of 1-3- H and metal alkoxide, polymerization of HO— [SiR 1 R 2 —O] 1-3 —H occurs, resulting in a final molecular structure of (A) and (B ).
[0012]
R 1 , R 2 , R 3 and R 4 are hydrogen or an organic group, and the organic groups represented by R 1 , R 2 , R 3 and R 4 are, for example, an alkyl group, a phenyl group, —C 2 H 4. It is an organic group composed of C, H and F like CF 3 .
When an alkoxide is used for producing the low dielectric constant material of the present invention, the alkoxide used is not particularly limited, and examples thereof include methoxide, ethoxide, propoxide, butoxide and the like. Moreover, the alkoxide derivative which substituted a part of alkoxy group with (beta) -diketone, (beta) -ketoester, alkanolamine, alkyl alkanolamine, organic acid, etc. can also be used.
[0013]
In the hydrolysis in the present invention, the hydrolysis is carried out by adding up to 2 moles of water with respect to all alkoxy groups. At this time, an inorganic acid, an organic acid, or both of them may be used as a catalyst. Further, the hydrolysis reaction may be controlled by adjusting the pH of the solution with an alkali. The water to be added may be diluted with an organic solvent such as alcohol. Use of 2 moles or more of water is not preferable because it gels quickly.
[0014]
In the hydrolysis, an Si solvent such as a siloxane polymer and an alkylalkoxysilane and an organic solvent capable of uniformly dispersing and dissolving the alkoxide are used. For example, various alcohols such as methanol, ethanol, propanol and butanol, acetone, toluene, xylene and the like.
After hydrolysis, the solvent, alcohol produced by hydrolysis, etc. may be distilled off at normal pressure or reduced pressure.
[0015]
When used as a film such as an LSI interlayer insulating film, the substrate is applied by spray coating, dip coating, spin coating, or the like.
In the case of using a bulk material as a low dielectric constant substrate, it is cast into a mold and heat treated.
The heat treatment of the coating film and the bulk body is performed at 70 to 500 ° C. If it is lower than 70 ° C., the solvent and the like are not sufficiently evaporated and cannot be solidified. When the temperature exceeds 500 ° C., decomposition of organic components starts.
[0016]
The insulating film according to the present invention can be applied to various electronic components such as an interlayer insulating film for LSI elements and an IC substrate.
[0017]
【Example】
The insulating film of the present invention will be specifically described by the following examples. However, the present invention is not limited to these examples.
The materials of Examples and Comparative Examples were synthesized from a Si raw material such as a siloxane polymer forming a siloxane skeleton or a dialkylalkoxysilane, and a metal alkoxide for introducing metal M. The alkoxide used is Si (OC 2 H 5 ) 4 for M of Si, Al (O-sec-C 4 H 9 ) 3 for Al, Ta (OC 2 H 5 ) 5 for Ta, The Ti one is Ti (OC 2 H 5 ) 4 . Al, Ta and Ti alkoxides were used after being chemically modified with ethyl acetoacetate.
[0018]
In Examples 1 and 2, two types of siloxane polymers each having a silanol group at both ends represented by replacing M in molecular structures (A) and (B) with H, and alkoxides of metal M shown in Table 1 were used. It was produced as a raw material. The mixing ratio of the two types of siloxane polymers is the ratio of the siloxane polymer constituting the molecular structure (A) to the siloxane polymer constituting the molecular structure (B). Example 1 is 0.17: 1 and Example 2 is 1. : 1. The ratio between the metal alkoxide and the two siloxane polymers was 2: 1 in Example 1 and 3: 2 in Example 2. These were stirred in an ethanol solvent and hydrolyzed by adding an ethanol solution of water to prepare a sol. The obtained sol was poured into an aluminum petri dish and heat-treated at two stages of 70 ° C. and 150 ° C. to prepare a bulk body. Electrodes were applied to both sides of the bulk body, and the dielectric constant was measured at a frequency of 1 MHz. Thus, when two types of siloxane polymers are used as raw materials, polymerization between siloxane polymers does not occur, so the ratio of molecular structures (A) and (B) is determined by the mixing ratio of the raw siloxane polymers and is shown in Table 1. As it is.
[0019]
Example 3, as a material constituting the molecular structure (A), both terminals represented in the form of a M of molecular structure (A) was replaced with H is using the siloxane polymer of the silanol groups, the molecular structure (B ) as a raw material constituting the, and the C H 3 O- [SiR 3 R 4 -O] 2-CH 3 of low molecular weight and raw materials. In Example 3, the ratio of the raw material constituting the molecular structure (A) and the raw material constituting the molecular structure (B) was 1: 2, and the ratio of the metal alkoxide to the Si raw material was 5 : 2. These raw materials were stirred in an ethoxyethanol solvent and hydrolyzed by adding an ethoxyethanol solution of water to prepare a sol. The resulting sol was poured into a Teflon (registered trademark) petri dish, in Example 3 were thermally treated in two stages of 70 ° C. and 200 ° C., to produce a bulk body. The ratio between the molecular structures (A) and (B) in the finished material was calculated as follows. First, the material is dissolved in nitric acid for 24 hours. As a result, since the M—O—Si bond is broken by the acid, the silicone oil-like compounds represented by HO— [SiR 1 R 2 —O] n —H and HO— [SiR 3 R 4 —O] n —H are formed. It becomes an acidic aqueous solution containing a siloxane polymer and a metal. Separate the oil and aqueous solution with a separatory funnel and separate only the silicone oil-like components. This was diluted with an organic solvent, and the molecular weight distribution was measured by gel permeation chromatography (GPS). The molecular weight distribution showed peaks at two locations corresponding to the molecular structures (A) and (B). The peak with the higher molecular weight corresponds to the molecular structure (A), and the peak with the lower molecular weight corresponds to the molecular structure (B). The average number of Si—O bonds contained in the siloxane polymer calculated from the lower molecular weight peak is shown as n avr in the column of molecular structure (B) in Table 1. From the intensity ratio of the two peaks, the ratio between the molecular structures (A) and (B) was determined. The electrical characteristics were measured in the same manner as in Examples 1 and 2.
[0020]
Example 4 C 2 H 5 O- [SiR 1 R 2 -O] using only 1 -C 2 H 5 as Si material, C 2 H 5 O- [SiR 1 R 2 -O] 1 -C 2 H The ratio of 5 to metal alkoxide was 20: 1. Due to the high ratio of C 2 H 5 O- [SiR 1 R 2 -O] 1 -C 2 H 5 relative to the metal alkoxide was hydrolyzed HO- [SiR1R2-O] 1- H polymerization by dehydration between Has advanced. A sol was prepared in the same manner as in Example 1, and a bulk body was obtained by heat treatment. As a result of examining the molecular weight distribution of the siloxane polymer by gel permeation chromatography (GPC) by the method described above, it shows a broad Gaussian distribution with 2 to 30 Si—O bonds and a maximum value at approximately 16 locations. It was. The abundance ratio of the molecular structures (A) and (B) was calculated from this distribution. The dielectric constant was measured on a film obtained by applying the adjusted liquid to a Si substrate and heat-treating at 300 ° C. for 20 minutes.
[0021]
Example 5 was synthesized in the same manner as in Example 2, except that the ratio of the sum of the metal alkoxide and the two siloxane polymers was 3: 4, and the metal alkoxide was doubled with respect to the stoichiometric ratio. In addition, in addition to the molecular structures (A) and (B), an Al—O—Al cluster is included. Examples 1 to 5 all showed a low value of relative dielectric constant of less than 3.0.
[0022]
Comparative Example 6 was synthesized from a siloxane polymer of n = 40 and a metal alkoxide. Since it contains only the molecular structure (A), it has a large atomic polarization and a high dielectric constant. Since Comparative Example 7 used a siloxane polymer with n = 80, it did not gel even after heat treatment. Since Comparative Example 8 was synthesized with a molar ratio of C 2 H 5 O— [SiR 3 R 4 —O] 1 -C 2 H 5 and metal alkoxide of 2: 1, Si—O bond between cross-linking points with Ti. The number of is an average of 2 and is composed only of the molecular structure (B). For this reason, Comparative Example 8 was a material having a high density and a high dielectric constant.
[0023]
【The invention's effect】
According to the present invention, a low dielectric constant material having a relative dielectric constant of less than 3.0 can be obtained. By applying this low dielectric constant material to semiconductor elements and electric circuit components such as LSI interlayer insulating films and IC substrates, the delay of the electric signal is reduced, so that the device speed can be increased.
[0024]
[Table 1]
Claims (3)
MO−[SiR1R2−O]8−50−M(R1,R2は水素または有機基、MはB,Al,Si,Ti,Ge,Y,Zr,Nb,Taの中から選ばれた少なくとも1種類の元素)で表される分子構造、ならびに
(B)一般式
MO−[SiR3R4−O]1−7−M(R3,R4は水素または有機基、MはB,Al,Si,Ti,Ge,Y,Zr,Nb,Taの中から選ばれた少なくとも1種類の元素)で表される分子構造、
とを含み、
そのモル比(A)/(B) ) が0.1以上2.0以下であることを特徴とする低誘電率材料。(A) General formula MO- [SiR 1 R 2 —O] 8-50 -M (R 1 and R 2 are hydrogen or organic group, M is B, Al, Si, Ti, Ge, Y, Zr, Nb, A molecular structure represented by (at least one element selected from Ta), and (B) a general formula MO- [SiR 3 R 4 —O] 1-7 -M (where R 3 and R 4 are hydrogen or An organic group, M is a molecular structure represented by at least one element selected from B, Al, Si, Ti, Ge, Y, Zr, Nb, and Ta),
Viewing including the door,
The low dielectric constant material, wherein the molar ratio (A) / (B) 2 ) is 0.1 or more and 2.0 or less .
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