JP4984377B2 - Solid-state imaging device and method for manufacturing solid-state imaging device - Google Patents

Solid-state imaging device and method for manufacturing solid-state imaging device Download PDF

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JP4984377B2
JP4984377B2 JP2004140798A JP2004140798A JP4984377B2 JP 4984377 B2 JP4984377 B2 JP 4984377B2 JP 2004140798 A JP2004140798 A JP 2004140798A JP 2004140798 A JP2004140798 A JP 2004140798A JP 4984377 B2 JP4984377 B2 JP 4984377B2
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勇三 福崎
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Sony Corp
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本発明は、半導体基板に形成された受光部の上方に光導波路領域が形成されている固体撮像装置および固体撮像装置の製造方法に関する。   The present invention relates to a solid-state imaging device in which an optical waveguide region is formed above a light receiving portion formed on a semiconductor substrate, and a method for manufacturing the solid-state imaging device.

固体撮像素子は画質の向上への要請から、画素数を増やして解像度を高くすることが必要である。コストを増加させずに画素数を増やすためには画素サイズを縮小する必要があるが、画素サイズを縮小すると一つの画素に入力できる光量は減少し、感度が低くなってしまう。一方、感度を高くするために遮光膜の開口部を大きくすると、隣接画素への光の混入が発生してしまう。   In order to improve the image quality of a solid-state image sensor, it is necessary to increase the number of pixels and increase the resolution. In order to increase the number of pixels without increasing the cost, it is necessary to reduce the pixel size. However, when the pixel size is reduced, the amount of light that can be input to one pixel is reduced and the sensitivity is lowered. On the other hand, if the opening of the light shielding film is enlarged in order to increase the sensitivity, light is mixed into adjacent pixels.

そこで、画素の感度の向上と光の混入の防止を達成するために、半導体装置表面にオンチップレンズを設けることが行われている。また、微細化による隣接画素への光の混入が防げない状態になってきているため、オンチップレンズと受光部との間に設けられた絶縁膜内に光透過材料の膜で構成される光導波路を設ける構造も考えられている。光導波路は、隣接受光部への光の混入を防ぎ、目的の受光部への光を誘導するものである（例えば、特許文献１、特許文献２参照。）。   Therefore, in order to achieve an improvement in pixel sensitivity and prevention of light contamination, an on-chip lens is provided on the surface of the semiconductor device. In addition, since it is not possible to prevent light from being mixed into adjacent pixels due to miniaturization, an optical film composed of a light transmitting material film is formed in an insulating film provided between the on-chip lens and the light receiving unit. A structure in which a waveguide is provided is also considered. The optical waveguide prevents light from being mixed into the adjacent light receiving section and guides light to the target light receiving section (see, for example, Patent Document 1 and Patent Document 2).

特開２００２−１１８２４５号公報JP 2002-118245 A 特開２００３−６０１７９号公報JP 2003-60179 A

しかしながら、受光部への導波路の形成には、光導波路形成用穴を開口する必要がある。光導波路は従来、受光部まで達しているために、前記光導波路形成用穴を加工する際に受光部がエッチングダメージを受けてしまい、感度特性の劣化をきたす。また、光導波路側面に反射用材料を形成するためには、一旦反射用材料を一律に形成したのち、異方性エッチングを行う必要があり、その際にも受光部はエッチングストップのための材料となり、ダメージを受けてしまう。このエッチングダメージに対する感度低下は、微細化が進む程に相対的に影響が大きくなる。   However, in order to form a waveguide in the light receiving portion, it is necessary to open an optical waveguide forming hole. Conventionally, since the optical waveguide has reached the light receiving portion, the light receiving portion is subjected to etching damage when the optical waveguide forming hole is processed, resulting in deterioration of sensitivity characteristics. In addition, in order to form the reflective material on the side surface of the optical waveguide, it is necessary to form the reflective material once and then perform anisotropic etching. And take damage. This decrease in sensitivity to etching damage has a relatively large effect as the miniaturization progresses.

本発明はこのような課題を解決するために成されたものである。すなわち、本発明は、半導体基板上に設けられる受光部と、半導体基板上を覆う絶縁膜と、絶縁膜の受光部上方に対応する位置に設けられる光導波路領域とを備える固体撮像装置において、光導波路領域は、受光部側の端部から反対側の端部に徐々に開口が広げられ、光導波路領域における受光部側の端部と受光部の受光面との間に、当該光道波路領域の底部から前記絶縁膜を等方的にエッチングした部分を光道波路となる材料で埋め込んだ部分を含む所定の間隔が設けられているものである。 The present invention has been made to solve such problems. That is, the present invention provides a solid-state imaging device including a light receiving portion provided on a semiconductor substrate, an insulating film covering the semiconductor substrate, and an optical waveguide region provided at a position corresponding to the light receiving portion above the insulating film. waveguide region, gradually opening is widened in the end opposite from the end portion of the light receiving portion side, between the light receiving surface of the light receiving portion and the end portion of the light receiving unit side of the optical waveguide region, the optical path waveguide region A predetermined interval including a portion in which the portion where the insulating film is isotropically etched from the bottom portion is embedded with a material which becomes an optical path waveguide is provided.

このような本発明では、受光部の上方に光導波領域が設けられる固体撮像装置において、受光部の受光面と光導波領域の受光部側の端部との間に所定の間隔が設けられているため、光導波領域をエッチングによって構成する際、受光部へのエッチングダメージを回避できるようになる。   In the present invention, in the solid-state imaging device in which the optical waveguide region is provided above the light receiving unit, a predetermined interval is provided between the light receiving surface of the light receiving unit and the end of the optical waveguide region on the light receiving unit side. Therefore, when the optical waveguide region is formed by etching, etching damage to the light receiving portion can be avoided.

また、本発明は、半導体基板上に受光部を形成し、その受光部の上に所定の厚さの第１絶縁膜を介してストッパメタル層を形成し、このストッパメタル層の上に第２絶縁膜を形成する工程と、受光部と対応する位置の第２絶縁膜をストッパメタル層までエッチングし、このエッチングによってストッパメタル層から上方に向けて徐々に開口が広がる孔を形成する工程と、孔の内壁に光反射材もしくは第２絶縁膜と屈折率の異なる材料から成る薄膜を形成する工程と、孔を介してストッパメタル層をエッチングするとともに、そのエッチング部分から第１絶縁膜を等方性エッチングする工程と、孔および第１絶縁膜を等方性エッチングした部分に光導波路となる材料を埋め込む工程とを備える固体撮像装置の製造方法である。   According to the present invention, a light receiving portion is formed on a semiconductor substrate, a stopper metal layer is formed on the light receiving portion via a first insulating film having a predetermined thickness, and a second metal is formed on the stopper metal layer. A step of forming an insulating film, a step of etching the second insulating film at a position corresponding to the light receiving portion to the stopper metal layer, and forming a hole in which the opening gradually widens upward from the stopper metal layer by this etching; Forming a thin film made of a material having a refractive index different from that of the light reflecting material or the second insulating film on the inner wall of the hole, etching the stopper metal layer through the hole, and isolating the first insulating film from the etched portion; And a step of embedding a material to be an optical waveguide in a portion where the hole and the first insulating film are isotropically etched.

このような本発明では、受光部の上にストッパメタル層を形成し、このストッパメタル層まで第２絶縁膜をエッチングして光導波領域を構成する孔を形成し、その後、孔を介してストッパメタル層をエッチングするとともに、そのエッチング部分から第１絶縁膜を等方性エッチングすることで、受光部の上に所定の間隔を開けた状態で光導波領域の端部を配置できるようになる。   In the present invention, a stopper metal layer is formed on the light receiving portion, the second insulating film is etched to the stopper metal layer to form a hole constituting the optical waveguide region, and then the stopper is formed through the hole. By etching the metal layer and isotropically etching the first insulating film from the etched portion, the end portion of the optical waveguide region can be disposed on the light receiving portion at a predetermined interval.

したがって、本発明によれば、受光部の上に設けられる光導波領域の受光部側の端部を受光面から所定間隔離した状態で設けることができ、光導波領域形成を形成する際のエッチングで、受光部がダメージを受けることがなくなり、受光部の特性劣化を防止することが可能となる。これにより、光導波領域を備える固体撮像装置の微細化および感度向上を図ることが可能となる。   Therefore, according to the present invention, the end portion on the light receiving portion side of the optical waveguide region provided on the light receiving portion can be provided in a state of being separated from the light receiving surface by a predetermined distance, and etching when forming the optical waveguide region formation Thus, the light receiving portion is not damaged, and it is possible to prevent deterioration of the characteristics of the light receiving portion. As a result, it is possible to reduce the size and improve the sensitivity of the solid-state imaging device including the optical waveguide region.

以下、本発明の実施の形態を図に基づき説明する。図１は、第１実施形態に係る固体撮像装置を説明する模式断面図である。すなわち、この固体撮像装置は、半導体基板１に設けられる受光部２と、半導体基板１の受光部２側を覆う絶縁膜３と、絶縁膜３の受光部２の上方に対応する位置に設けられる光導波領域４とを備えているもので、この光導波領域４における受光部２側の端部と受光部２の表面（受光面２ａ）との間に所定の間隔が設けられている点に特徴がある。   Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating the solid-state imaging device according to the first embodiment. That is, the solid-state imaging device is provided at a position corresponding to the light receiving portion 2 provided on the semiconductor substrate 1, the insulating film 3 covering the light receiving portion 2 side of the semiconductor substrate 1, and the light receiving portion 2 of the insulating film 3. The optical waveguide region 4 is provided, and a predetermined interval is provided between the end of the optical waveguide region 4 on the light receiving unit 2 side and the surface of the light receiving unit 2 (light receiving surface 2a). There are features.

光導波領域４は、この内側に入射した光を受光部２の受光面２ａまで導くためのもので、本実施形態では光導波領域４の内壁となる光反射面４ａの角度が徐々に変化して光を受光部２の中央部分へ集められるようになっている。つまり、図１に示す一点鎖線矢印のように、光導波領域４の光反射面４ａに反射しないで直接受光部２へ到達する光のほか、光反射面４ａで反射を繰り返して受光部２へ到達する光もあり、集光力を向上できることになる。   The optical waveguide region 4 is for guiding the light incident on the inside to the light receiving surface 2a of the light receiving unit 2. In the present embodiment, the angle of the light reflecting surface 4a that is the inner wall of the optical waveguide region 4 is gradually changed. Thus, the light can be collected at the central portion of the light receiving unit 2. That is, as indicated by the one-dot chain line arrow shown in FIG. 1, in addition to the light that directly reaches the light receiving unit 2 without being reflected by the light reflecting surface 4a of the optical waveguide region 4, the light reflecting surface 4a repeatedly reflects to the light receiving unit 2. There is also light that reaches, and the light collecting power can be improved.

なお、図１に示す例では、光導波領域４の光反射面４ａが多角形状に段階的に変化しているが、曲面状に連続的に変化するようにしてもよい。このような角度変化によって、光導波領域４の光入射端では広く光を集め、光出射端では集めた光を受光部２へ集中させることが可能となる。ここで、光反射面４ａの角度変化は、入射側から出射側にかけて受光面２ａに対して４５度から９０度まで変化するように設定するのが望ましい。   In the example shown in FIG. 1, the light reflecting surface 4 a of the optical waveguide region 4 is gradually changed to a polygonal shape, but may be continuously changed to a curved shape. By such an angle change, it is possible to collect light widely at the light incident end of the optical waveguide region 4 and concentrate the collected light on the light receiving unit 2 at the light emitting end. Here, it is desirable that the angle change of the light reflecting surface 4a is set so as to change from 45 degrees to 90 degrees with respect to the light receiving surface 2a from the incident side to the emission side.

また、光導波路領域４における受光部２側の端部の口径は、受光部２が受光面２ａにおける口径よりも小さくなっている。これは、光導波領域４の受光部２側の端部が受光部２の受光面２ａと間隔を開けて設けている関係から、この隙間から光が受光部２の外側へ逃げてしまうことが考えられ、これを防止する観点から、光導波領域４の受光部２側の端部の口径を受光部２の受光面２ａにおける口径よりも小さく設けて、端部から広がる光を確実に受光面２ａに当てるようにするためである。   Further, the diameter of the end portion on the light receiving portion 2 side in the optical waveguide region 4 is smaller than the diameter of the light receiving portion 2 in the light receiving surface 2a. This is because the end of the optical waveguide region 4 on the side of the light receiving unit 2 is provided at a distance from the light receiving surface 2a of the light receiving unit 2, and light may escape to the outside of the light receiving unit 2 from this gap. In order to prevent this problem, the diameter of the end of the optical waveguide region 4 on the side of the light receiving unit 2 is set smaller than the diameter of the light receiving surface 2a of the light receiving unit 2 so that light spreading from the end can be reliably received. This is to make it hit 2a.

また、光導波路領域４の受光部２とは反対側の端部（光入射端）の口径は、受光部２の受光面２ａの口径よりも大きくなっている。光入射端の口径が受光面２ａの口径よりも大きいことで、受光面２ａの微細化が進んでも多くの光を集めて受光できるようになる。   In addition, the diameter of the end portion (light incident end) of the optical waveguide region 4 opposite to the light receiving portion 2 is larger than the diameter of the light receiving surface 2 a of the light receiving portion 2. Since the aperture of the light incident end is larger than the aperture of the light receiving surface 2a, a large amount of light can be collected and received even if the light receiving surface 2a is miniaturized.

さらに、光導波路領域４の内壁である光反射面４ａの光反射効率を高めるため、光反射面４ａに絶縁膜３よりも高反射率の薄膜を形成したり、光導波領域４の内部に埋め込まれる材料よりも低屈折率の薄膜を形成しておく。   Further, in order to increase the light reflection efficiency of the light reflection surface 4a which is the inner wall of the optical waveguide region 4, a thin film having a higher reflectance than the insulating film 3 is formed on the light reflection surface 4a or embedded in the light waveguide region 4. A thin film having a refractive index lower than that of the material to be formed is formed.

次に、第１実施形態に係る固体撮像装置の製造方法を図２〜図７の模式断面図に沿って説明する。先ず、図２に示すように半導体基板１に受光部２を形成し、この受光部２の上に絶縁膜３を介してストッパメタル層Ｍを形成する。ストッパメタル層Ｍの材質としては、他の配線としても使用できるアルミニウムやタングステンが好適である。ここで、タングステンは過酸化水素水で選択的にエッチングされ、酸化シリコン系から成る絶縁膜３のへのダメージが最小である。ストッパメタル層Ｍの厚さは５０ｎｍ〜３００ｎｍの間で適宜選択する。   Next, the manufacturing method of the solid-state imaging device according to the first embodiment will be described along schematic sectional views of FIGS. First, as shown in FIG. 2, the light receiving portion 2 is formed on the semiconductor substrate 1, and the stopper metal layer M is formed on the light receiving portion 2 via the insulating film 3. As the material of the stopper metal layer M, aluminum or tungsten which can be used as other wiring is preferable. Here, tungsten is selectively etched with hydrogen peroxide, and damage to the insulating film 3 made of silicon oxide is minimal. The thickness of the stopper metal layer M is appropriately selected between 50 nm and 300 nm.

また、ストッパメタル層Ｍの上に絶縁膜３を設ける。ここで、実際には絶縁膜３は多層となるが、説明の便宜上、受光部２とストッパメタル層Ｍとの間の絶縁膜３を第１絶縁膜３ａ、その上の絶縁膜３を第２絶縁膜３ｂと言うものとする。   An insulating film 3 is provided on the stopper metal layer M. Here, although the insulating film 3 is actually a multilayer, for convenience of explanation, the insulating film 3 between the light receiving portion 2 and the stopper metal layer M is the first insulating film 3a, and the insulating film 3 thereon is the second. It shall be called the insulating film 3b.

次に、図３に示すように、第２絶縁膜３ｂの上にレジストＲを塗布し、受光部２の受光面２ａの位置に対応して受光面２ａより大きな開口を開けた状態で、例えばＲＩＥ（Reactive Ion Etching）法によって第２絶縁膜３ｂを異方的にエッチングする。これにより、上方が広がっている孔がストッパメタル層Ｍまで形成される。この孔は光導波路領域となるため、孔の内面の角度が光導波路領域の光反射面の角度となる。したがって、ＲＩＥ法による異方性エッチングの条件を制御することで、孔の内面の角度を調整する。また、孔の下端部の口径はストッパメタル層Ｍよりも片側１００ｎｍ程度小さくしておく。ストッパメタル層Ｍによって確実にエッチングを止めるためである。   Next, as shown in FIG. 3, a resist R is applied on the second insulating film 3 b, and an opening larger than the light receiving surface 2 a corresponding to the position of the light receiving surface 2 a of the light receiving unit 2 is opened, for example, The second insulating film 3b is anisotropically etched by RIE (Reactive Ion Etching). As a result, a hole extending upward is formed up to the stopper metal layer M. Since this hole becomes an optical waveguide region, the angle of the inner surface of the hole becomes the angle of the light reflecting surface of the optical waveguide region. Therefore, the angle of the inner surface of the hole is adjusted by controlling the conditions of anisotropic etching by the RIE method. Further, the diameter of the lower end portion of the hole is made smaller than the stopper metal layer M by about 100 nm on one side. This is because etching is surely stopped by the stopper metal layer M.

ＲＩＥ法のエッチング条件としては、例えば、ＣxＦy、Ａｒ、Ｏ2、ＣＨＦz系のガス種を使用し、２ステップ以上のマルチステップとし、後のステップでＣＨＦz流量比を下げ、Ｏ2流量比を上げるようにする。ここでｘ,ｙ,ｚは数字であり、ＣxＦyは具体的にはＣ4Ｆ8、ＣＨＦzはＣＨＦ3である。 The etching conditions for the RIE method, for example, C x F y, using Ar, the O 2, CHF z based gas species, a more multi-step two-step, lowering the CHF z flow ratio in a later step, O 2 Increase the flow rate ratio. Here, x, y, z are numbers, C x F y is specifically C 4 F 8 , and CHF z is CHF 3 .

次に、図４に示すように、第２絶縁膜３ｂに設けた孔の内壁に金属材料を一部もしくは全部使用した光反射のための薄膜４ｂ、もしくは孔に埋め込まれる材料よりも屈曲率の低い材料から成る薄膜４ｃを形成する。その後、ストッパメタル層Ｍの上に被着している薄膜４ｂ（４ｃ）をＲＩＥ法によってエッチング除去し、図５に示すようにストッパメタル層Ｍが露出する状態にする。   Next, as shown in FIG. 4, the light reflection thin film 4b using a metal material partially or entirely on the inner wall of the hole provided in the second insulating film 3b, or a bending rate higher than that of the material embedded in the hole. A thin film 4c made of a low material is formed. Thereafter, the thin film 4b (4c) deposited on the stopper metal layer M is removed by etching by the RIE method so that the stopper metal layer M is exposed as shown in FIG.

次に、この孔を介してウェットエッチングを行い、ストッパメタル層Ｍを除去し、続いてストッパメタル層Ｍが除去された部分から第１絶縁膜３ａをウェットエッチングして等法的に除去する。このエッチング後の状態が図６に示される。第１絶縁膜３ａの等法性エッチングによって、孔の下端における口径が広がる状態となる。この際、受光部２の受光面２ａから約５００ｎｍほど上の部分までしかエッチングが行われないことから、受光面２ａに対するエッチングダメージを防止できる。その後、図７に示すように、孔の内部に光導波路材となる材料を埋め込む。これにより、孔の部分に光導波路領域４が構成される。   Next, wet etching is performed through the hole to remove the stopper metal layer M, and then the first insulating film 3a is wet-etched from the portion from which the stopper metal layer M has been removed by isotropic removal. The state after this etching is shown in FIG. By the isotropic etching of the first insulating film 3a, the diameter at the lower end of the hole is expanded. At this time, since etching is performed only up to about 500 nm above the light receiving surface 2a of the light receiving portion 2, etching damage to the light receiving surface 2a can be prevented. Thereafter, as shown in FIG. 7, a material to be an optical waveguide material is embedded in the hole. Thereby, the optical waveguide region 4 is formed in the hole portion.

このような第１実施形態に係る固体撮像装置では、光導波路領域４の受光部２とは反対側の端部（光入射端）の口径が受光部２の受光面２ａの口径より大きいため、より多くの光を光導波路領域４内に導くことができる。また、光導波路領域４の形成時に受光部２をエッチストップに使用しないので、受光面２ａへのエッチングダメージを発生させずに済む。このため、光導波路領域４の下端は受光部２と一定の間隔で離れているが、光導波路領域４の受光部２側の端部の口径は受光部２の受光面２の口径よりも小さいので、導波路内に導入した光を無駄なく、有効に受光部２へ当てることが可能となる。   In the solid-state imaging device according to the first embodiment, since the diameter of the end portion (light incident end) of the optical waveguide region 4 opposite to the light receiving portion 2 is larger than the diameter of the light receiving surface 2a of the light receiving portion 2, More light can be guided into the optical waveguide region 4. Further, since the light receiving portion 2 is not used for etching stop when the optical waveguide region 4 is formed, etching damage to the light receiving surface 2a can be avoided. For this reason, the lower end of the optical waveguide region 4 is separated from the light receiving unit 2 at a constant interval, but the diameter of the end of the optical waveguide region 4 on the light receiving unit 2 side is smaller than the diameter of the light receiving surface 2 of the light receiving unit 2. Therefore, the light introduced into the waveguide can be effectively applied to the light receiving unit 2 without waste.

次に、第２実施形態に係る固体撮像装置を説明する。図８は、第２実施形態に係る固体撮像装置を説明する模式断面図である。すなわち、この固体撮像装置は、半導体基板１に設けられる受光部２、半導体基板１の受光部２側を覆う絶縁膜３、絶縁膜３の受光部２の上方に対応する位置に設けられる光導波領域４を備え、この光導波領域４における受光部２側の端部と受光部２の表面（受光面２ａ）との間に所定の間隔が設けられている点、先に説明した第１実施形態と同様であるが、光導波路領域４の受光部２側の端部にレンズＬが設けられている点で相違する。   Next, a solid-state imaging device according to the second embodiment will be described. FIG. 8 is a schematic cross-sectional view illustrating a solid-state imaging device according to the second embodiment. That is, this solid-state imaging device includes a light receiving portion 2 provided on the semiconductor substrate 1, an insulating film 3 covering the light receiving portion 2 side of the semiconductor substrate 1, and an optical waveguide provided at a position corresponding to the upper side of the light receiving portion 2 of the insulating film 3. The first embodiment described above is provided with a region 4, and a predetermined interval is provided between the end of the optical waveguide region 4 on the light receiving unit 2 side and the surface of the light receiving unit 2 (light receiving surface 2 a). Although it is the same as that of a form, it differs in the point by which the lens L is provided in the edge part by the side of the light-receiving part 2 of the optical waveguide area | region 4. FIG.

つまり、光導波路領域４を形成する際、ストッパメタル層の形状を変えることでストッパメタル層の除去後の形状から絶縁膜３を等法性エッチングすることでレンズ形状を構成している。また、このレンズＬに光学的な特性を持たせるため、光導波路領域４の内部に埋め込む材料４０の屈折率を絶縁膜３の屈折率より大きくすることで、レンズＬによる集光力を高めるようにしている。このようなレンズＬを設けることで、光導波路領域４に導かれた光（図中一点鎖線矢印参照）は、直接受光部２へ到達するもののほか、光反射面４ａで反射を繰り返していくとともに、レンズＬで集光して受光部２へ確実に到達できるようになる。   That is, when the optical waveguide region 4 is formed, the shape of the stopper metal layer is changed to form a lens shape by isotropically etching the insulating film 3 from the shape after the stopper metal layer is removed. Further, in order to give this lens L optical characteristics, the light condensing power by the lens L is increased by making the refractive index of the material 40 embedded in the optical waveguide region 4 larger than the refractive index of the insulating film 3. I have to. By providing such a lens L, the light guided to the optical waveguide region 4 (see the dashed line arrow in the figure) reaches the light receiving part 2 directly and is repeatedly reflected by the light reflecting surface 4a. The light is condensed by the lens L and can be surely reached the light receiving unit 2.

光導波路領域４の光反射面４ａの角度は第１実施形態と同様に、光入射側から光出射側にかけて受光面２ａに対して４５度から９０度まで変化するように設定するのが望ましい。また、光導波路領域４の光入射側の端部の開口は受光面２の開口より大きく、光出射側の端部の開口は受光面２の開口より小さくなっている。さらに、光導波路領域４の内壁である光反射面４ａの光反射効率を高めるため、光反射面４ａに絶縁膜３よりも高反射率の薄膜を形成したり、光導波領域４の内部に埋め込まれる材料４０よりも低屈折率の薄膜を形成しておく。   As in the first embodiment, the angle of the light reflecting surface 4a of the optical waveguide region 4 is desirably set so as to change from 45 degrees to 90 degrees with respect to the light receiving surface 2a from the light incident side to the light emitting side. The opening at the light incident side end of the optical waveguide region 4 is larger than the opening at the light receiving surface 2, and the opening at the light emitting side end is smaller than the opening at the light receiving surface 2. Further, in order to increase the light reflection efficiency of the light reflection surface 4a which is the inner wall of the optical waveguide region 4, a thin film having a higher reflectance than the insulating film 3 is formed on the light reflection surface 4a or embedded in the light waveguide region 4. A thin film having a refractive index lower than that of the material 40 to be formed is formed.

次に、第２実施形態に係る固体撮像装置の製造方法を図９〜図１４の模式断面図に沿って説明する。先ず、図９に示すように半導体基板１に受光部２を形成し、この受光部２の上に絶縁膜３を介してストッパメタル層Ｍを形成する。また、ストッパメタル層Ｍの上に絶縁膜３を設ける。ここで、実際には絶縁膜３は多層となるが、説明の便宜上、受光部２とストッパメタル層Ｍとの間の絶縁膜３を第１絶縁膜３ａ、その上の絶縁膜３を第２絶縁膜３ｂと言うものとする。   Next, a manufacturing method of the solid-state imaging device according to the second embodiment will be described along schematic sectional views of FIGS. First, as shown in FIG. 9, the light receiving portion 2 is formed on the semiconductor substrate 1, and the stopper metal layer M is formed on the light receiving portion 2 via the insulating film 3. An insulating film 3 is provided on the stopper metal layer M. Here, although the insulating film 3 is actually a multilayer, for convenience of explanation, the insulating film 3 between the light receiving portion 2 and the stopper metal layer M is the first insulating film 3a, and the insulating film 3 thereon is the second. It shall be called the insulating film 3b.

第２実施形態では、このストッパメタル層Ｍの形状として、受光面２ａ側の周縁にトレンチ形状を設けておく。トレンチ形状を形成するには、第１絶縁膜３ａを形成した後にトレンチ部分に対応した溝を形成し、その溝にストッパメタル層Ｍと同じ金属材料を埋め込み平坦化する。その後、トレンチ部分と一体となるようストッパメタル層Ｍを形成する。   In the second embodiment, as the shape of the stopper metal layer M, a trench shape is provided at the periphery on the light receiving surface 2a side. In order to form the trench shape, after forming the first insulating film 3a, a groove corresponding to the trench portion is formed, and the same metal material as that of the stopper metal layer M is buried and planarized. Thereafter, a stopper metal layer M is formed so as to be integrated with the trench portion.

トレンチ部分の溝の形成は、エッチング・ガスの調整によって行う。条件は、例えば、ＣxＦy、Ａｒ、Ｏ2、ＣＨＦz系のガス種を使用し、所望の深さが得られたのち、トレンチ部分の形成ステップとして、ガス比を以下のように変更する。すなわちＣＨＦz流量比を上げ、Ｏ2流量比を下げる。ＣxＦyは具体的にはＣ4Ｆ8、ＣＨＦzはＣＨＦ3である。 The formation of the trench in the trench portion is performed by adjusting the etching gas. The conditions are, for example, using C x F y , Ar, O 2 , and CHF z gas species, and after the desired depth is obtained, the gas ratio is changed as follows as a trench formation step To do. That is, the CHF z flow rate ratio is increased and the O 2 flow rate ratio is decreased. C x F y is specifically C 4 F 8 and CHF z is CHF 3 .

次に、図１０に示すように、第２絶縁膜３ｂの上にレジストＲを塗布し、受光部２の受光面２ａの位置に対応して受光面２ａより大きな開口を開けた状態で、例えばＲＩＥ法によって第２絶縁膜３ｂを異方的にエッチングする。これにより、上方が広がっている孔がストッパメタル層Ｍまで形成される。この孔は光導波路領域となるため、孔の内面の角度が光導波路領域の光反射面の角度となる。したがって、ＲＩＥ法による異方性エッチングの条件を制御することで、孔の内面の角度を調整する。また、孔の下端部の口径はストッパメタル層Ｍよりも片側１００ｎｍ程度小さくしておく。ストッパメタル層Ｍによって確実にエッチングを止めるためである。ＲＩＥ法のエッチング条件は、例えば第１実施形態と同様である。   Next, as shown in FIG. 10, a resist R is applied on the second insulating film 3 b, and a larger opening than the light receiving surface 2 a is opened corresponding to the position of the light receiving surface 2 a of the light receiving unit 2. The second insulating film 3b is anisotropically etched by the RIE method. As a result, a hole extending upward is formed up to the stopper metal layer M. Since this hole becomes an optical waveguide region, the angle of the inner surface of the hole becomes the angle of the light reflecting surface of the optical waveguide region. Therefore, the angle of the inner surface of the hole is adjusted by controlling the conditions of anisotropic etching by the RIE method. Further, the diameter of the lower end portion of the hole is made smaller than the stopper metal layer M by about 100 nm on one side. This is because etching is surely stopped by the stopper metal layer M. The etching conditions of the RIE method are the same as those in the first embodiment, for example.

次に、図１１に示すように、第２絶縁膜３ｂに設けた孔の内壁に金属材料を一部もしくは全部使用した光反射のための薄膜４ｂ、もしくは孔に埋め込まれる材料よりも屈曲率の低い材料から成る薄膜４ｃを形成する。その後、ストッパメタル層Ｍの上に被着している薄膜４ｂ（４ｃ）をＲＩＥ法によってエッチング除去し、図１２に示すようにストッパメタル層Ｍが露出する状態にする。   Next, as shown in FIG. 11, the light reflection thin film 4b using a metal material partially or entirely on the inner wall of the hole provided in the second insulating film 3b, or a bending rate higher than that of the material embedded in the hole. A thin film 4c made of a low material is formed. Thereafter, the thin film 4b (4c) deposited on the stopper metal layer M is removed by etching by the RIE method so that the stopper metal layer M is exposed as shown in FIG.

次に、この孔を介してウェットエッチングを行い、ストッパメタル層Ｍを除去し、続いてストッパメタル層Ｍが除去された部分から第１絶縁膜３ａをウェットエッチングして等法的に除去する。このエッチング後の状態が図１３に示される。第２実施形態では、ストッパメタル層Ｍにトレンチ形状が設けられていることから、このストッパメタル層Ｍを除去した形状にもトレンチ部分が転写されており、この状態で第１絶縁膜３ａを等法性エッチングすることによって、孔の下端における口径が広がるとともにレンズ形状が構成される。   Next, wet etching is performed through the hole to remove the stopper metal layer M, and then the first insulating film 3a is wet-etched from the portion from which the stopper metal layer M has been removed by isotropic removal. The state after this etching is shown in FIG. In the second embodiment, since the stopper metal layer M is provided with a trench shape, the trench portion is also transferred to the shape in which the stopper metal layer M is removed. By legal etching, the diameter at the lower end of the hole is widened and a lens shape is formed.

また、この際、受光部２の受光面２ａまで達するエッチングは行わないことから、受光面２ａに対するエッチングダメージを防止できる。その後、図１４に示すように、孔の内部に光導波路材となる材料４０を埋め込む。この材料４０は、第１絶縁膜３ａの屈折率の低いものを用いる。これにより、孔の部分に光導波路領域４が構成されるとともに、レンズ形状にエッチングされた部分に材料４０が埋め込まれてレンズＬが形成されることになる。   At this time, the etching reaching the light receiving surface 2a of the light receiving unit 2 is not performed, so that etching damage to the light receiving surface 2a can be prevented. Thereafter, as shown in FIG. 14, a material 40 to be an optical waveguide material is embedded in the hole. As this material 40, a material having a low refractive index of the first insulating film 3a is used. Thereby, the optical waveguide region 4 is formed in the hole portion, and the material L is formed by embedding the material 40 in the portion etched into the lens shape.

このような第２実施形態に係る固体撮像装置では、第１実施形態での効果に加え、光導波路領域４の下端にレンズＬが埋め込まれるため、光導波路領域４内に導入した光を受光部２へ効率良く集光することが可能となる。特に微細化が進んで受光部２の面積がさらに縮小された場合に特に有効である。   In such a solid-state imaging device according to the second embodiment, in addition to the effects of the first embodiment, since the lens L is embedded at the lower end of the optical waveguide region 4, the light introduced into the optical waveguide region 4 is received by the light receiving unit. 2 can be efficiently condensed. This is particularly effective when the area of the light receiving unit 2 is further reduced due to the progress of miniaturization.

なお、いずれの実施形態に係る固体撮像装置でも、光導波路領域４の光入射端側にオンチップレンズを設けるようにして、より一層集光能力を高めるようにしてもよい。   In any of the solid-state imaging devices according to any of the embodiments, an on-chip lens may be provided on the light incident end side of the optical waveguide region 4 to further increase the light collecting ability.

第１実施形態に係る固体撮像装置を説明する模式断面図である。1 is a schematic cross-sectional view illustrating a solid-state imaging device according to a first embodiment. 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その１）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 1). 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その２）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 2). 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その３）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 3). 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その４）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 4). 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その５）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 5). 第１実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その６）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 1st embodiment (the 6). 第２実施形態に係る固体撮像装置を説明する模式断面図である。It is a schematic cross section explaining the solid-state imaging device concerning a 2nd embodiment. 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その１）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 2nd embodiment (the 1). 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その２）である。It is a schematic cross section explaining the manufacturing method of the solid imaging device concerning a 2nd embodiment (the 2). 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その３）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 2nd embodiment (the 3). 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その４）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 2nd embodiment (the 4). 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その５）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 2nd embodiment (the 5). 第２実施形態に係る固体撮像装置の製造方法を説明する模式断面図（その６）である。It is a schematic cross section explaining the manufacturing method of the solid-state imaging device concerning a 2nd embodiment (the 6).

符号の説明Explanation of symbols

１…半導体基板、２…受光部、２ａ…受光面、３…絶縁膜、３ａ…第１絶縁膜、３ｂ…第２絶縁膜、４…光導波路領域、４ａ…光反射面   DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Light-receiving part, 2a ... Light-receiving surface, 3 ... Insulating film, 3a ... 1st insulating film, 3b ... 2nd insulating film, 4 ... Optical waveguide area, 4a ... Light reflection surface

Claims (12)

半導体基板上に設けられる受光部と、前記半導体基板上を覆う絶縁膜と、前記絶縁膜の前記受光部上方に対応する位置に設けられる光導波路領域とを備える固体撮像装置において、
前記光導波路領域は、前記受光部側の端部から反対側の端部に徐々に開口が広げられ、
前記光導波路領域における前記受光部側の端部と前記受光部の受光面との間に、当該光道波路領域の底部から前記絶縁膜を等方的にエッチングした部分を光道波路となる材料で埋め込んだ部分を含む所定の間隔が設けられている
固体撮像装置。 In a solid-state imaging device, comprising: a light receiving portion provided on a semiconductor substrate; an insulating film covering the semiconductor substrate; and an optical waveguide region provided at a position corresponding to the light receiving portion above the insulating film.
In the optical waveguide region, the opening is gradually widened from the end on the light receiving unit side to the end on the opposite side,
A material that becomes an optical path waveguide by isotropically etching the insulating film from the bottom of the optical waveguide area between the end of the optical waveguide area on the light receiving section side and the light receiving surface of the light receiving section A solid-state image pickup device provided with a predetermined interval including a portion embedded in . 前記光導波路領域における前記受光部側の端部の口径は、前記受光部の受光面における口径よりも小さくなっている
請求項１記載の固体撮像装置。 The solid-state imaging device according to claim 1, wherein a diameter of an end portion on the light receiving unit side in the optical waveguide region is smaller than a diameter of a light receiving surface of the light receiving unit. 前記光導波路領域における前記受光部とは反対側の端部の口径は、前記受光部の受光面における口径よりも大きくなっている
請求項１または２記載の固体撮像装置。 3. The solid-state imaging device according to claim 1, wherein a diameter of an end of the optical waveguide region opposite to the light receiving unit is larger than a diameter of a light receiving surface of the light receiving unit. 前記光導波路領域の内壁には、前記絶縁膜よりも高反射率の薄膜が形成されている
請求項１〜３の何れかに記載の固体撮像装置。 The solid-state imaging device according to claim 1, wherein a thin film having a higher reflectance than the insulating film is formed on an inner wall of the optical waveguide region. 前記光導波路領域の内壁には、前記光導波路領域の内部に埋め込まれる材料よりも低屈折率の薄膜が形成されている
請求項１〜４の何れかに記載の固体撮像装置。 The solid-state imaging device according to claim 1, wherein a thin film having a refractive index lower than that of a material embedded in the optical waveguide region is formed on an inner wall of the optical waveguide region. 前記光導波路領域は、当該光導波路領域の内壁で構成される光反射面と前記受光面とのなす角度が、当該受光面に近いほど垂直に近づくように徐々に変化している
請求項１〜５の何れかに記載の固体撮像装置。 The optical waveguide region is gradually changing so that an angle formed between a light reflection surface formed by an inner wall of the optical waveguide region and the light receiving surface is closer to the light receiving surface. The solid-state imaging device according to any one of 5. 前記光導波路領域における前記受光部とは反対側の端部にはレンズが設けられている
請求項１〜６の何れかに記載の固体撮像装置。 The solid-state imaging device according to claim 1, wherein a lens is provided at an end of the optical waveguide region opposite to the light receiving unit. 前記光導波路領域における前記受光部側の端部にはレンズが設けられている
請求項１〜７の何れかに記載の固体撮像装置。 The solid-state imaging device according to claim 1, wherein a lens is provided at an end portion on the light receiving portion side in the optical waveguide region. 前記レンズの屈折率は、前記レンズの周辺における前記絶縁膜の屈折率よりも大きい
請求項８記載の固体撮像装置。 The solid-state imaging device according to claim 8, wherein a refractive index of the lens is larger than a refractive index of the insulating film around the lens. 半導体基板上に受光部を形成し、その受光部の上に所定の厚さの第１絶縁膜を介してストッパメタル層を形成し、このストッパメタル層の上に第２絶縁膜を形成する工程と、
前記受光部と対応する位置の前記第２絶縁膜を前記ストッパメタル層までエッチングし、このエッチングによって前記ストッパメタル層から上方に向けて徐々に開口が広がる孔を形成する工程と、
前記孔の内壁に光反射材もしくは前記第２絶縁膜と屈折率の異なる材料から成る薄膜を形成する工程と、
前記孔を介して前記ストッパメタル層をエッチングするとともに、そのエッチング部分から前記第１絶縁膜を等方性エッチングする工程と、
前記孔および前記第１絶縁膜を等方性エッチングした部分に光導波路となる材料を埋め込む工程と
を備えることを特徴とする固体撮像装置の製造方法。 Forming a light receiving portion on the semiconductor substrate, forming a stopper metal layer on the light receiving portion via a first insulating film having a predetermined thickness, and forming a second insulating film on the stopper metal layer; When,
Etching the second insulating film at a position corresponding to the light receiving portion to the stopper metal layer, and forming a hole gradually opening upward from the stopper metal layer by this etching;
Forming a light reflecting material or a thin film made of a material having a refractive index different from that of the second insulating film on the inner wall of the hole;
Etching the stopper metal layer through the hole and isotropically etching the first insulating film from the etched portion;
And a step of embedding a material to be an optical waveguide in a portion where the hole and the first insulating film are isotropically etched. 前記孔を形成する工程では、当該孔の内面と前記受光部の受光面とのなす角度が、当該受光面に近いほど垂直に近づくように徐々に変化している
請求項１０記載の固体撮像装置の製造方法。 The solid-state imaging device according to claim 10, wherein in the step of forming the hole, an angle formed between an inner surface of the hole and a light receiving surface of the light receiving unit gradually changes so as to approach the vertical as the light receiving surface is closer. Manufacturing method. 前記ストッパメタル層の前記受光部側の周縁にトレンチ形状を形成する
ことを特徴とする請求項１０または１１記載の固体撮像装置の製造方法。 The method for manufacturing a solid-state imaging device according to claim 10 or 11, wherein a trench shape is formed in a peripheral edge of the stopper metal layer on the light receiving portion side.
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