JP2006222270A - Solid-state image sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a lowering in embedding of a core member in an optical waveguide provided in a solid-state image sensor to improve an incidence efficiency. <P>SOLUTION: The core member of the optical waveguide 10 efficiently guides the light formed in a light receiving part 21 direction through a plurality of interlayer insulating films 3, 4, 5, 8 and a protective film 9 formed on the light receiving part 21 formed on a semiconductor substrate 1 and entering from an on-chip lens 13 to the light receiving part 21. Using a TiO distributed polyimide resin having a high refraction factor of 1.8 to 1.9 due to the TiO distribution as the core member prevents the lowering in embedding of the core member in the optical waveguide 10 and can improve the incidence efficiency to the light receiving part 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device such as a CMOS image sensor that performs photoelectric change by forming an image of a subject on a light receiving unit using a lens, and a manufacturing method thereof.

  In a conventional CMOS image sensor, a sensor part having a light receiving part is formed on a semiconductor substrate, and a plurality of interlayer insulating films including a wiring part for transmitting a signal generated by the light receiving part are formed on the sensor part. An on-chip lens is formed on it. Incident light is condensed on the light receiving portion by the on-chip lens and subjected to photoelectric conversion.

However, due to the miniaturization of the solid-state imaging device such as the CMOS image sensor described above, there is a problem that the area of the light receiving surface is reduced, the incident light rate is lowered, and the sensitivity characteristic is deteriorated. As a countermeasure to solve this, there is a method of improving the sensitivity characteristic by increasing the incident light rate by arranging an optical waveguide on the light receiving surface (see Patent Document 1). The optical waveguide on the light receiving surface is composed of a clad portion and a core portion. The clad portion is a silicon oxide film (SiO2), and the core portion is formed of a high refractive index inorganic film (Si3N4, DLC (Diamond Like Corbon) or polyimide resin). Has been.
JP 2003-224249 A (page 4-5, FIG. 1)

  By the way, when the high refractive index inorganic film forming the core portion of the optical waveguide is Si3N4 or DLC, there is a problem that it is difficult to completely embed Si3N4 or DLC in the optical waveguide. In order to solve this, there is one using a polyimide resin having a good embedding property in an optical waveguide as a core member. However, polyimide resin has good embeddability in the optical waveguide, but its refractive index is low (1.6 to 1.7), and the critical angle when incident light is totally reflected at the interface between the core and cladding is small. As a result, there is a problem that the reflection efficiency of light incident obliquely is lowered, and therefore the incidence efficiency is lowered.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device including an optical waveguide that can improve the incident efficiency without reducing the embeddability of the core member, and the same It is to provide a manufacturing method.

  In order to achieve the above object, the present invention provides a semiconductor substrate having a photoelectric conversion portion formed thereon, and a signal transmission wiring portion formed on the photoelectric conversion portion and electrically connected to the photoelectric conversion portion. A plurality of interlayer insulating films each including an optical waveguide provided in the surface direction of the photoelectric conversion unit from the uppermost layer of the plurality of interlayer insulating films through the interlayer insulating film thereunder and guiding light to the photoelectric conversion unit The core member of the optical waveguide is a TiO-dispersed polyimide resin.

  The present invention also provides a semiconductor substrate having a photoelectric conversion portion formed thereon, a plurality of interlayer insulating films formed on the photoelectric conversion portion and including a signal transmission wiring portion therein, and the plurality of interlayer insulations A solid-state imaging device manufacturing method comprising: an optical waveguide provided in a surface direction of the photoelectric conversion unit from an uppermost layer of the film through an interlayer insulating film thereunder, and guiding light to the photoelectric conversion unit. And TiO dispersion type polyimide resin is poured into the substrate.

  As described above, in the present invention, TiO is used as a core member of an optical waveguide formed in the direction of the photoelectric conversion section through a plurality of interlayer insulating films (silicon oxide) formed on the photoelectric conversion section formed on the semiconductor substrate. By using the dispersion type polyimide resin, the TiO dispersion type polyimide resin can be easily embedded in the optical waveguide, and the TiO dispersion type polyimide resin has a high refractive index of 1.8 to 1.9 due to TiO dispersion. Because of the high refractive index inorganic film, the incidence efficiency is high, and the sensitivity characteristics of the solid-state imaging device of this embodiment can be improved.

  According to the present invention, an inorganic material having a high refractive index as a core member of an optical waveguide formed in the direction of a photoelectric conversion section through a plurality of interlayer insulating films (silicon oxide) formed on a photoelectric conversion section formed on a semiconductor substrate. By using a TiO-dispersed polyimide resin that is a film, it is possible to improve the incident efficiency to the photoelectric conversion portion without reducing the embedding property of the core member in the optical waveguide, and therefore the core member of the optical waveguide. As compared with the conventional example using a polyimide resin, the sensitivity characteristics of the solid-state imaging device can be improved.

  A plurality of components formed on the photoelectric conversion unit formed on the semiconductor substrate for the purpose of improving the incident efficiency without reducing the embeddability of the core member in the optical waveguide provided in the solid-state imaging device. This was easily realized by using a TiO-dispersed polyimide resin as the core member of the optical waveguide formed in the direction of the photoelectric conversion portion through the interlayer insulating film.

  FIG. 1 is a partial cross-sectional view illustrating a configuration of a solid-state imaging device according to an embodiment of the present invention. In a CMOS image sensor, which is a solid-state imaging device, a light receiving portion 21 that photoelectrically converts light and a sensor portion 2 having a silicon oxide film (SiO 2) covering the light receiving portion 21 are formed on a semiconductor substrate 1. First, second, and third interlayer insulating films 3, 4, and 5 made of an oxide film are formed. A first wiring D1, a second wiring D2, and a third wiring D3 made of copper are formed in each of the first, second, and third interlayer insulating films, and each wiring is electrically connected by contact plugs V2 and V3. The first wiring D1 is electrically connected to the light receiving unit 21 by a contact plug V1. Further, silicon carbide (SiC) films 6 and 7 are formed between the first, second and third interlayer insulating films 3, 4 and 5 to form the second wiring D 2 and the third wiring D 3. Prevents copper diffusion. The light receiving portion 21 is formed of a silicon oxide film 211, polysilicon 212, and three silicon nitride layers 213, 214, and 215 having different film qualities. Further, the wirings D1, D2, and D3 are made of copper, the contact plug V1 is made of tungsten, and the contact plugs V2 and V3 are made of copper.

  On the third interlayer insulating film 5, an interlayer insulating film 8 of a silicon oxide film and a protective film 9 of an overcap are formed via a silicon nitride (SiN) film 15 as an isolation film. A plurality of first, second, and third interlayer insulating films 3, 4, 5, 8, and a protective film 9 immediately above the light receiving portion 21, a silicon nitride film 15 between these interlayer insulating films, and silicon carbide The optical waveguide 10 is formed through the films 6 and 7, and the core portion 101 is formed of TiO-dispersed polyimide. On the TiO-dispersed polyimide, a color filter 12 is formed via an acrylic thermosetting resin 11 that improves adhesion, and an on-chip lens that is an optical element that condenses incident light 100 on the color filter 12. 13 is formed.

  In the CMOS image sensor configured as described above, the incident light 100 is collected by the on-chip lens 13, and is irradiated to the light receiving unit 21 through the core unit 101 made of TiO-dispersed polyimide of the optical waveguide 10. Is photoelectrically converted.

  Next, the manufacturing method of the solid-state image sensor of this invention is demonstrated. First, as shown in FIG. 2, a sensor unit 2 having a light receiving unit 21 and a silicon oxide film 22 covering the light receiving unit 21 is formed on a semiconductor substrate 1, and a first wiring D <b> 1 and a second wiring are formed on the sensor unit 2. First, second, and third interlayer insulating films 3, 4, and 5 having D2 and third wiring D3 are formed through silicon carbide films 6 and 7, and further on third interlayer insulating film 5 An interlayer insulating film 8 and a protective film 9 are formed through the silicon nitride film 15.

  Thereafter, an optical waveguide 10 as shown in FIG. 3 is formed. The optical waveguide 10 is formed by lithography so that a resist 14 becomes an optical waveguide pattern, and the silicon oxide film forming the protective film 9 and the interlayer insulating films 8, 5, 4, 3 is etched by dry etching using the resist 14 as a mask. To form.

  Next, as shown in FIG. 4, TiO-dispersed polyimide, which is the material of the core portion 101, is embedded in the optical waveguide 10 formed as described above to complete the optical waveguide structure. Thereafter, as shown in FIG. 1, a color filter 12 is formed on the core portion 101 of TiO-dispersed polyimide via an acrylic thermosetting resin 11, and an on-chip lens 13 is formed on the color filter 12. . Although not shown, a large number of light receiving portions 21 on the semiconductor substrate 1 are arranged in a matrix, and the color filter 12 has a color corresponding to the corresponding light receiving portion 21 (one of the three primary colors). . In this way, the CMOS image sensor of this embodiment is completed. However, in the steps shown in FIGS. 2, 3, 4 and 1, the material embedded in the optical waveguide 10 is different from the conventional one, and the other manufacturing steps are the same as the conventional one. It is.

  According to the present embodiment, the core portion 101 and the optical waveguide are formed by using a TiO-dispersed polyimide having a high refractive index of 1.8 to 1.9 due to TiO dispersion as the material of the core portion 101 constituting the optical waveguide 10. It is possible to increase the critical angle when the incident light is totally reflected at the interface 10, improve the light reflection efficiency when the incident light 100 is incident on the on-chip lens 13 from an oblique direction, and the incident efficiency. Can be improved. Therefore, it is possible to improve the sensitivity characteristics of the solid-state imaging device of the present embodiment.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can implement also with another various form in a concrete structure, a function, an effect | action, and an effect.

It is the fragmentary sectional view showing the composition of the solid-state image sensing device concerning one embodiment of the present invention. It is a fragmentary sectional view explaining the manufacturing method of the solid-state image sensor of this invention. It is a fragmentary sectional view explaining the manufacturing method of the solid-state image sensor of this invention. It is a fragmentary sectional view explaining the manufacturing method of the solid-state image sensor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Sensor part, 3, 4, 5, 8 ... Interlayer insulation film, 6, 7 ... Silicon carbide film, 9 ... Protective film, 10 ... Optical waveguide, 11 ... Acrylic thermosetting resin, 12 ... color filter, 13 ... on-chip lens, 15 ... silicon nitride film, 21 ... light receiving part, 22, 211 ... silicon oxide film, 101 ... core part, 212 ... Polysilicon, 213, 214, 215 ... silicon nitride layer, D1, D2, D3 ... wiring, V1, V2, V3 ... contact plug.

Claims (6)

A semiconductor substrate on which the photoelectric conversion part is formed, and
A plurality of interlayer insulating films each including a signal transmission wiring portion formed on the photoelectric conversion portion and electrically connected to the photoelectric conversion portion;
An optical waveguide provided in the surface direction of the photoelectric conversion unit from the uppermost layer of the plurality of interlayer insulating films through the interlayer insulating film thereunder, and guiding light to the photoelectric conversion unit,
The core member of the optical waveguide is a TiO-dispersed polyimide resin.   The protective film for protecting the uppermost layer of the plurality of interlayer insulating films, and the optical waveguide is formed from the protective film through a lower interlayer insulating film toward the surface of the photoelectric conversion unit. The solid-state imaging device according to 1. A color filter formed on the optical waveguide;
A condensing optical element formed on the color filter;
The solid-state imaging device according to claim 1, further comprising:     The solid-state imaging device according to claim 1, wherein the constituent material of the interlayer insulating film is silicon oxide. A semiconductor substrate on which a photoelectric conversion unit is formed; a plurality of interlayer insulating films formed on the photoelectric conversion unit and including a wiring portion for signal transmission therein; and an uppermost layer of the plurality of interlayer insulating films A method of manufacturing a solid-state imaging device having an optical waveguide provided in a surface direction of the photoelectric conversion unit through a lower interlayer insulating film and guiding light to the photoelectric conversion unit;
A method for producing a solid-state imaging device, comprising a step of pouring a TiO-dispersed polyimide resin into the optical waveguide. 6. The method for manufacturing a solid-state imaging device according to claim 5, further comprising a step of forming a condensing optical element formed on the optical waveguide through a color filter.

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