JP2009064797A - Manufacturing method of solid-state image pickup element, solid-state image pickup element and image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid-state image pickup element, which meets the requirements of a film thickness of both a pixel portion and a peripheral circuit portion of a solid-state image pickup element, and achieves high-speed operation while eliminating F-value dependency with high sensitivity and low smear. <P>SOLUTION: The solid-state image pickup element 100 has a semiconductor substrate provided with: a pixel portion 1 where a plurality of photodiodes are arranged; and a peripheral circuit portion 5 for executing reading driving of signal charges generated by each of the photodiodes and signal processing of the signal charges. The manufacturing method of the element 100 includes: a first step of forming a first interlayer insulating film by a common process for both the pixel portion 1 and the peripheral circuit portion 5 having a gate electrode formed thereon; a second step of selectively removing the first interlayer insulating film only for the pixel portion 1; and a third step of forming a second interlayer insulating film thinner than the first interlayer insulating film by a common process for both the pixel portion 1 and the peripheral circuit portion 5. The interlayer insulating film for the pixel portion 1 has a thickness thinner than that of the interlayer insulating film formed on the gate electrode of the peripheral circuit portion 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a solid comprising a pixel portion having a photoelectric conversion element that generates a signal charge corresponding to incident light on a semiconductor substrate, and a peripheral circuit portion for performing signal processing such as reading drive of the generated signal charge. The present invention relates to an image pickup device manufacturing method, a solid-state image pickup device, and an image pickup apparatus.

  In recent years, CCD-type and CMOS-type solid-state imaging devices are used in imaging apparatuses such as video cameras and electronic cameras that are widely used. The solid-state imaging device has a pixel portion configured by two-dimensionally arranging a large number of pixels on one semiconductor chip, and a peripheral circuit portion disposed outside the pixel portion. The pixel unit is provided with a photodiode (photoelectric conversion element) that photoelectrically converts incident light to generate a signal charge, and the peripheral circuit unit performs predetermined signal processing such as CDS (correlation) on the pixel signal from the pixel unit. A signal processing circuit that performs double sampling), gain control, A / D conversion, and the like, and a drive control circuit that drives each pixel of the pixel portion to control the output of the pixel signal are provided.

By the way, in the solid-state imaging device, in the pixel portion, it is desirable to make the intermediate layer (interlayer insulating film) on the gate electrode and the light shielding film thin in order to improve optical characteristics. This is because if the intermediate layer is thick, the incident light attenuates in the middle of the optical path to the photodiode, and the longer the optical path length, the stronger the tendency for the incident light to deviate from the light receiving position of the photodiode.
On the other hand, in the peripheral circuit portion, if the thickness of the interlayer insulating film between the gate electrode and the metal wiring or between the metal wirings is thin, the parasitic capacitance component increases, causing a problem in high-speed driving. Part of the metal wiring or the like is easily exposed during the etch-back process when forming the inner lens of the part. When the metal wiring is exposed, the wiring is corroded due to moisture absorption, electrical characteristics are changed, and reliability is deteriorated.
Since these interlayer insulating films are formed at the same time in a common process, in device design, the two are in a trade-off relationship, and the thickness of the interlayer insulating film is set by properly negotiating both. It was.

FIGS. 6 and 7 show the state of the interlayer insulating film. FIG. 6A shows a peripheral circuit portion when the interlayer insulating film is thin in a CCD type solid-state imaging device, FIG. 6B shows a horizontal charge transfer portion (HCCD portion), and FIG. 6C shows a pixel portion. FIG. 7 shows (a) a peripheral circuit portion, (b) a horizontal charge transfer portion (HCCD portion), and (c) a pixel portion when the interlayer insulating film is thick in the solid-state imaging device.
If an interlayer insulating film 500A thickness _{t 3} of the shown in FIG. 6 (c) thin, as shown in FIG. 6 (a), (b) , the gate electrode 501a, 501b and the metal wires 503a, between 503b The distances t ₁ and t ₂ are shortened, resulting in an increase in parasitic capacitance and a problem of partial expression. On the other hand, when the thicknesses t ₁ and t _{2 of the} interlayer insulating film 500B shown in FIGS. 7A and 7B are thick, the optical path length t ₃ to the photodiode 505 is as shown in FIG. 7C. It becomes longer, resulting in lower sensitivity and vignetting from the light receiving position.

  For this reason, for example, Patent Document 1 proposes a method of forming an interlayer insulating film on a gate electrode using SiN or polysilicon as a stopper film, etching only the pixel portion, and then forming a light shielding film. Yes. That is, the wiring conductive film and the light-shielding conductive film are formed as separate layers, and a layer serving as an etching stopper is provided between the interlayer insulating films, and the interlayer insulating film is removed in the pixel region, while the interlayer insulating film is removed in the peripheral circuit region. By increasing the thickness while leaving the film, smear suppression is achieved while realizing low parasitic capacitance of the peripheral circuit and highly reliable wiring formation.

JP-A-5-29598

However, in the method of Patent Document 1, after forming an interlayer insulating film using SiN or polysilicon as a stopper film on the gate electrode, only the pixel portion is etched, and then a light shielding film is formed. In this method, the pixel portion is formed. A method of shielding light with a metal silicide (intermetallic compound), which is a functional material, in the immediate vicinity of the gate electrode cannot be used, and the interlayer insulating film cannot be used as the lower shape of the intralayer lens. A bug was left.
That is, in the configuration of Patent Document 1, the etching stopper film is always disposed below the light shielding film, and the light shielding film is disposed directly above the gate electrode as shown in FIGS. This is different from the structure in which an insulating film is formed and a step is formed after the formation. When forming an optical path that forms a convex in-layer lens on the lower side, the gate electrode in the vicinity of the optical path needs to be shielded from light. However, a metal silicide material generally has BPSG reflow in terms of heat resistance. Therefore, it is impossible to form a convex shape on the lower side by reflow.

  In addition, the incident light to the solid-state image sensor has a component that is incident not only vertically but also obliquely on the semiconductor substrate. The obliquely incident light includes a light shielding film that covers the vertical CCD, the surface of the silicon substrate, And proceeding with multiple reflections, directly reaching the buried layer serving as the transfer channel of the vertical CCD. For this reason, when the interlayer insulating film in the pixel portion is thick, the light incident obliquely increases, and the charge generated by such light causes the smear to increase.

  Furthermore, in addition to the so-called on-chip lens structure in which a microlens is formed on the upper part of the solid-state imaging device due to the miniaturization of the element, an in-layer lens having a condensing characteristic between the microlens and the light receiving unit. To improve the sensitivity of the light receiving unit. However, in a solid-state imaging device having an in-layer lens, light of various incident angles is incident depending on the aperture value (F value) of the lens system in the imaging apparatus. For example, when the F value is large, the incident light is reduced. On the other hand, when the F value is small, when the F value is small, the incident light is expanded and the oblique component increases, and the F value of the camera changes, so that the amount of the oblique component changes and the sensitivity is different. There was F value dependency. Even in this case, when the interlayer insulating film in the pixel portion is thick, there is a problem that the amount of the oblique component increases and the F value dependency becomes remarkable.

  The present invention has been made in view of the above situation, and enables the formation of a light-shielding film by metal silicide and the use of the lower shape of the inner lens by an interlayer insulating film, while the pixel portion and the peripheral circuit portion of the solid-state image sensor. The solid-state imaging device manufacturing method and the solid-state imaging device capable of satisfying the requirements for the film thickness of the interlayer insulating film, having high sensitivity, low smear, no F-number dependency, and capable of realizing high-speed operation. An object is to provide an imaging apparatus.

The above object of the present invention is achieved by the following configuration.
(1) A solid-state imaging device comprising: a pixel unit in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit unit that performs reading drive of signal charges generated by the photodiodes and signal processing of the signal charges. A method for manufacturing an element, comprising:
(A-1) forming a first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion on which the gate electrode is formed;
(A-2) selectively removing the first interlayer insulating film only with respect to the pixel portion;
(A-3) forming a second interlayer insulating film thinner than the first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion;
Including
A method for manufacturing a solid-state imaging device, wherein an interlayer insulating film formed in the pixel portion is thinner than an interlayer insulating film formed on the gate electrode of the peripheral circuit portion.

  According to this method for manufacturing a solid-state imaging device, unlike the conventional configuration in which the interlayer insulating film is formed before the light shielding film is formed and partially removed, the pixel is compared with the interlayer insulating film formed after the light shielding film of the pixel portion is formed. Since the film thickness is different between the pixel portion and the peripheral circuit portion, the F value dependency is reduced by thinning the interlayer insulating film in the pixel portion, and the improvement in smear characteristics by thinning the interlayer insulating film in the pixel portion is the original. As a result, it is possible to form an intralayer lens with the surface of the interlayer insulating film as the bottom surface, and it is possible to reduce leakage light accompanying an increase in tilted light and increase the light collection rate and increase the sensitivity. In addition to this, by making the interlayer insulating film thickness in the peripheral circuit part including the HCCD part thick and flat, the parasitic capacitance with the wiring layer formed in the upper layer is reduced, enabling high-speed operation and wiring. The probability of disconnection during layer processing can be reduced.

(2) A method for producing a solid-state imaging device according to (1),
After the step (A-3), at least for the pixel portion, a high refraction index higher than that of the second interlayer insulating film is provided on the reflow-treated surface obtained by reflowing the second interlayer insulating film. A method for manufacturing a solid-state imaging device for forming a refractive index layer.

  According to this method for manufacturing a solid-state imaging device, the second layer insulating film is formed into a concave curved surface corresponding to the photodiode by the reflow process, so that the second refractive index layer is formed. An inter-layer lens in which the boundary surface between the interlayer insulating film and the high refractive index layer, that is, the bottom surface of the high refractive index layer becomes a convex curved surface is formed, and the light condensing rate for the photodiode is increased and the sensitivity is improved. .

(3) A solid-state imaging device comprising: a pixel portion in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit portion that performs reading drive of signal charges generated by the photodiodes and signal processing of the signal charges. A method for manufacturing an element, comprising:
(B-1) forming a first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion on which the gate electrode is formed;
(B-2) forming an etching stopper film on the first interlayer insulating film;
(B-3) forming a second interlayer insulating film thicker than the first interlayer insulating film on the etching stopper film;
(B-4) selectively removing the second interlayer insulating film only with respect to the pixel portion using the etching stopper film;
Including
A method for manufacturing a solid-state imaging device, wherein an interlayer insulating film formed in the pixel portion is thinner than an interlayer insulating film formed on the gate electrode of the peripheral circuit portion.

  According to this method for manufacturing a solid-state imaging device, in addition to the same operation as the basic operation (1), an etching stopper film is formed on the first interlayer insulating film formed in the pixel portion and the peripheral circuit portion. After the second interlayer insulating film is formed on the etching stopper film, the second interlayer insulating film is selectively removed only for the pixel portion. The film can be covered with a film, and when the second interlayer insulating film is removed, the influence on the exposed upper layer electrode and the like can be eliminated, and the change in the upper layer characteristic can be suppressed.

(4) A method for producing a solid-state imaging device according to (3),
After the step (B-1), at least the pixel portion is subjected to a reflow process on the first interlayer insulating film,
After the step (B-4), manufacturing a solid-state imaging device in which a high refractive index layer having a higher refractive index than that of the first interlayer insulating film is formed on the etching stopper film at least for the pixel portion Method.

  According to this method for manufacturing a solid-state imaging device, an etching stopper film is formed on a portion of the first interlayer insulating film that has a concave curved surface corresponding to the photodiode by reflow processing, and high refractive index is formed on the etching stopper film. By forming the refractive index layer, an interface lens between the etching stopper film and the high refractive index layer, that is, an in-layer lens in which the bottom surface of the high refractive index layer is a convex curved surface is formed, and the light collection rate with respect to the photodiode is increased. This increases the sensitivity.

(5) The method for manufacturing a solid-state imaging device according to any one of (1) to (4),
A method for manufacturing a solid-state imaging device, wherein the first interlayer insulating film and the second interlayer insulating film are made of a material containing silicon oxide.

  According to this method for manufacturing a solid-state imaging device, efficient removal of the intermediate layer and removal using the silicon nitride film as an etching stopper film can be facilitated.

(6) A solid-state imaging device comprising: a pixel unit in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit unit that performs read drive of signal charges generated by the photodiodes and signal processing of the signal charges. An element,
(1) to (5) are manufactured using the method for manufacturing a solid-state imaging device according to any one of the above, and the thickness of the interlayer insulating film formed above the photodiode of the pixel portion is set to the gate of the peripheral circuit portion. A solid-state imaging device thinner than an interlayer insulating film formed on an electrode.

  According to this solid-state imaging device, the F-value dependency is reduced and the smear characteristic is improved by reducing the thickness of the interlayer insulating film in the pixel portion. In addition, it is possible to form an intralayer lens with the surface of the interlayer insulating film as the bottom surface, and the leakage light accompanying the increase of the inclined light is reduced, and the light collection rate is increased to increase the sensitivity. In addition to this, the interlayer insulating film thickness in the peripheral circuit portion including the HCCD portion becomes thick and flat, the parasitic capacitance between the upper wiring layer and the wiring layer formed on the upper layer is reduced, and high-speed operation is possible. The disconnection probability is reduced.

(7) The solid-state imaging device according to (6),
An optical system for forming an optical image on the solid-state imaging device;
An imaging apparatus comprising:

  According to this imaging apparatus, since the solid-state imaging device according to claim 6 and the optical system that forms an optical image on the solid-state imaging device are provided, there is little difference in sensitivity even if the F value is changed, and smear The influence can also be suppressed, high sensitivity can be obtained, and a good image without noise can be acquired at high speed.

  According to the method for manufacturing a solid-state imaging device and the solid-state imaging device according to the present invention, it is possible to reduce the F value dependency and improve the smear characteristics by thinning the interlayer insulating film of the pixel portion. By forming the inner lens with the surface as the bottom surface of the inner lens, the light collection rate can be increased and the sensitivity can be increased, while the interlayer insulating film thickness in the peripheral circuit part including the HCCD part is made thick and flat. As a result, the parasitic capacitance with the wiring layer formed in the upper layer can be reduced, high-speed operation can be performed, and the probability of disconnection during processing of the wiring layer can be reduced. As a result, a solid-state imaging device with high sensitivity, low smear, high speed operation, high reliability, and stable yield can be realized.

  According to the imaging apparatus of the present invention, since the solid-state imaging device and the optical system that forms an optical image on the solid-state imaging device are provided, there is little difference in sensitivity even if the F value is changed, and smear The influence can also be suppressed, high sensitivity can be obtained, and a good image without noise can be acquired at high speed.

Preferred embodiments of a method for manufacturing a solid-state imaging device, a solid-state imaging device, and an imaging apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a plan view conceptually showing the positional relationship among a pixel portion, a horizontal charge transfer portion, and a peripheral circuit portion of a solid-state imaging device according to the present invention.
The solid-state imaging device 100 according to the present embodiment receives a pixel unit 1 including a plurality of vertical transfer paths (VCCD) for transferring signal charges from a plurality of photoelectric conversion elements, and a signal charge transferred from the plurality of vertical transfer paths. And a peripheral circuit section 5 such as a signal processing circuit for performing signal processing in accordance with the transferred signal charges.

  In the method for manufacturing the solid-state imaging device 100 according to the present invention, the pixel portion 1 in which a plurality of photodiodes are arranged on a semiconductor substrate, the signal charge read drive generated by each photodiode, and the signal charge signal processing are performed. In the solid-state imaging device 100 including the peripheral circuit unit 5, a first step of forming a first interlayer insulating film by a process common to both the pixel unit 1 and the peripheral circuit unit 5 on which the gate electrode is formed ( A-1), the second step (A-2) for selectively removing the first interlayer insulating film only for the pixel portion 1, and common to both the pixel portion 1 and the peripheral circuit portion 5 And the third step (A-3) of forming a second interlayer insulating film thinner than the first interlayer insulating film by the above process, the thickness of the interlayer insulating film formed in the pixel portion 1 is set to a peripheral circuit. Thinner than the interlayer insulating film formed on the gate electrode To do.

This manufacturing method will be described more specifically.
2 divides the manufacturing method according to the first embodiment into the main parts of the peripheral circuit part, the horizontal charge transfer part, and the pixel part as shown by arrows AB in FIG. 1 (a) to (f). It is explanatory drawing shown roughly in the order of these processes.
As shown in FIG. 2A, a laminated film (silicon oxide film (SiO ₂ ) / silicon nitride film (SiN) / silicon oxide film (SiO ₂ ) on a semiconductor substrate 7 that has been subjected to necessary processing in advance. An insulating film 9 made of ONO film or the like is formed. In the peripheral circuit portion 5, a signal wiring 11 made of polysilicon or metal, a gate electrode, and the like are formed on the gate insulating film. In the horizontal transfer path 3, a charge transfer electrode (gate electrode) 13 made of polysilicon is formed on the gate insulating film. In the pixel portion 1, a charge readout electrode 15 and a charge transfer electrode (vertical charge transfer portion) 17 made of polysilicon are formed on a gate insulating film, and a light shielding film 19 made of tungsten or the like is formed thereon.

Next, as shown in FIG. 2B, the first step is performed by a process common to the peripheral circuit unit 5 and the horizontal transfer path 3 in which the pixel unit 1 and the gate electrode are formed. As the interlayer insulating film 21, SiO ₂ or BPSG (Boron Phosphorus Silicon Glass) is formed thick by CVD.

  Next, as shown in FIG. 2C, the first interlayer insulating film 21 is selectively removed only to the pixel portion 1 by etching in the second step described above. This etching process is performed until the lower insulating film 9 and the light shielding film 19 are exposed in the pixel portion 1, that is, the insulating film 9 and the light shielding film 19 are used as stopper layers, or the upper portions of the insulating film 9 and the light shielding film 19 are covered. The interlayer film which is different in etching resistance from the one interlayer film and functions as a stopper is used as a stopper layer. Alternatively, in order not to expose the insulating film 9 and the light shielding film 19, the first interlayer film on the pixel portion is left with a predetermined thickness by controlling the etching.

Next, as shown in FIG. 2D, the second process, which is thinner than the first interlayer insulating film 21, is performed by a process common to both the pixel unit 1 and the peripheral circuit unit 5 by the third process described above. An interlayer insulating film 23 is formed. As in the above, the second interlayer insulating film 23 is formed by thinly forming SiO ₂ or BPSG by CVD.

Next, as shown in FIG. 2E, the second interlayer insulating film 23 made of the SiO ₂ or BPSG layer of the pixel portion 1 is formed into a smooth wavy uneven surface by reflow processing. The downward convex reflow processing surface formed by this reflow processing becomes the bottom surface of an interlayer lens described later.

Next, as shown in FIG. 2F, in the peripheral circuit portion 5, a contact hole H is formed, a metal conductor layer M is embedded in the hole H, and the signal wiring 25 is formed on the surface of SiO _2. Form. In the horizontal transfer path 3 as well, the signal wiring 27 is formed on the surface of SiO ₂ .

Here, the pixel unit 1 will be described separately with reference to FIG.
FIG. 3 is an explanatory view schematically showing the manufacturing method for the pixel portion in the order of steps (a) to (e).
In the present embodiment, after the third step described above, at least for the pixel portion 1, the second interlayer insulating film 23 is refracted more than the second interlayer insulating film 23 on the reflow processed surface. A high refractive index material layer 29 having a high refractive index is formed. That is, in the pixel unit 1, first, as shown in FIG. 3A, SiN, which is a high refractive index material, is formed by plasma CVD. Next, as shown in FIG. 3B, planarization is performed to a predetermined thickness by resist etchback, CMP (Chemical Mechanical Polishing), or the like. Thus, a downwardly convex inner lens 31a is completed.

  Next, as shown in FIG. 3C, SiN is further formed by plasma CVD. As shown in FIG. 3D, after forming the resist 30 by patterning, as shown in FIG. 3E, the pattern of the resist 30 is transferred to the SiN layer by etch back. Thereby, an upward convex in-layer lens 31 made of SiN of the high refractive index material layer 29 is completed. FIG. 2 (f) shows the result. Simultaneously with the processing of the pixel unit 1, a protective film is formed on the peripheral circuit unit 5 and the metal wiring of the horizontal transfer path 3. On the inner lens 31, although not shown, a flattening layer, red (R), green (G), and blue (B) color filters, and a microlens are formed. Light incident from above is detected by the photodiode PD.

  By the above reflow process, the high refractive index material layer 29 is formed in the portion of the second interlayer insulating film 23 that has a concave curved surface corresponding to the photodiode, so that the second interlayer insulating film 23 and An in-layer lens 31 having a convex curved surface at the boundary surface with the high refractive index material layer 29, that is, the bottom surface of the high refractive index material layer 29 is formed, and the light condensing rate with respect to the photodiode is increased, thereby improving the sensitivity. It is done.

  In the present embodiment, the thick first interlayer insulating film 21 is first formed in the peripheral circuit portion 5 and the horizontal transfer path 3, and the distance from the gate electrode and the other conductor portion of the signal wiring is increased, and the parasitic capacitance is increased. Capacitance is reduced and the electrodes and wiring are reliably protected. In the pixel portion 1, the thick first interlayer insulating film 21 is once removed to return to the initial state, and a thin second interlayer insulating film 23 is formed again. The second interlayer insulating film 23 becomes smooth by the reflow process, and the base of the downward convex lens is formed. And the top part (lower end) of the downward convex inner lens 31 is formed in the height position near a photodiode by forming SiN of a high refractive material on it.

  Therefore, unlike the conventional configuration in which the interlayer insulating film is formed before the light shielding film is formed and partially removed, the pixel portion 1 and the first interlayer insulating film 21 formed after the light shielding film 19 of the pixel portion 1 is formed. Since the film thickness differs between the peripheral circuit portion 5 and the interlayer insulating film of the pixel portion 1 is made thin, the F value dependency is reduced, and the smear characteristic is improved by making the interlayer insulating film of the pixel portion 1 thin. From the beginning, it is possible to form the intralayer lens 31 with the surface of the interlayer insulating film as the bottom surface, and it is possible to reduce the leakage light accompanying the increase of the inclined light and to increase the light collection rate and increase the sensitivity. In addition to this, by making the interlayer insulating film thickness in the peripheral circuit section 5 including the horizontal transfer path (HCCD section) 3 thick and flat, the parasitic capacitance between the wiring layer formed in the upper layer is reduced and high speed operation is performed. And the risk of disconnection when processing the wiring layer can be reduced.

  Further, when the interlayer insulating film of the peripheral circuit portion or the horizontal charge transfer portion is thin at the same level as the pixel portion, the metal wiring formed thereon has a shape that undulates so as to trace the base shape. For this reason, in a high temperature process (around 400 ° C.) such as a sintering process performed later in the manufacturing process, the metal of the wiring material expands, stress concentration occurs in the upper silicon nitride film, and the film is torn, Although an extruding phenomenon in which the lower metal material blows out from the silicon nitride film may occur, according to the configuration of the present embodiment, a sufficiently thick silicon nitride film is formed on the metal signal wirings 25 and 27. Since (SiN) is formed and the metal wiring becomes less susceptible to the influence of the underlying step, the element structure is stabilized without causing an extrusion phenomenon.

  According to the manufacturing method of the solid-state imaging device 100 and the solid-state imaging device 100 according to the present embodiment, it is possible to reduce the F value dependency and improve the smear characteristics by thinning the interlayer insulating film of the pixel unit 1. By forming the inner lens 31 with the interlayer insulating film surface as the lens bottom surface, the light collection rate can be increased and the sensitivity can be increased, while the interlayer insulating film thickness in the peripheral circuit portion 5 including the horizontal transfer path 3 is increased. By making it thick and flat, it is possible to reduce the parasitic capacitance between the upper wiring layer and the wiring layer, to enable high-speed operation, and to reduce the risk of disconnection when processing the wiring layer. As a result, the solid-state imaging device 100 with high sensitivity, low smear, high speed operation, high reliability, and stable yield can be realized.

Next, a second embodiment of the method for manufacturing a solid-state imaging device according to the present invention will be described.
In the method for manufacturing a solid-state imaging device according to the present embodiment, a pixel unit 1 in which a plurality of photodiodes are arranged on a semiconductor substrate, signal charge reading drive generated by each photodiode, and signal processing of the signal charges are performed. In the solid-state imaging device including the peripheral circuit unit 5, a step of forming a first interlayer insulating film by a process common to both the pixel unit 1 and the peripheral circuit unit 5 on which the gate electrode is formed (B- 1), forming an etching stopper film on the first interlayer insulating film (B-2), and forming a second interlayer insulating film thicker than the first interlayer insulating film on the etching stopper film Including the step (B-3) and the step (B-4) of selectively removing the second interlayer insulating film only with respect to the pixel portion 1 using the etching stopper film. The thickness of the interlayer insulating film formed on the peripheral circuit portion 5 Thinner than the interlayer insulating film formed on the over gate electrode.

This manufacturing method will be described more specifically.
4A and 4F divide the manufacturing method according to the second embodiment into the main parts of the peripheral circuit part, the horizontal charge transfer part, and the pixel part as shown by arrows AB in FIG. It is explanatory drawing shown roughly in the order of these processes.
As shown in FIG. 4A, the manufacturing method of the solid-state imaging device according to the present embodiment has a silicon oxide film (SiO ₂ ) / silicon nitride film (SiN) on a semiconductor substrate 7 that has been subjected to necessary processing in advance. ) / The insulating film 9 is formed of a silicon oxide film (SiO ₂ ) laminated film (ONO film) or the like. In the peripheral circuit portion 5, a signal wiring 11 and a gate electrode made of polysilicon or metal are formed on the gate insulating film. In the horizontal transfer path 3, a charge transfer electrode (gate electrode) 13 made of polysilicon is formed on the gate insulating film 9. In the pixel portion 1, a charge readout electrode 15 and a charge transfer electrode (vertical charge transfer portion) 17 made of polysilicon are formed on the gate insulating film 9, and a light shielding film 19 made of tungsten is formed thereon.

Next, as shown in FIG. 4B, in the first step, the first interlayer insulating film 33 is formed by a process common to both the pixel portion 1 and the peripheral circuit portion 5 on which the gate electrode is formed. Form. The first interlayer insulating film 33 is obtained by forming a thin SiO ₂ or BPSG interlayer insulating film. The first interlayer insulating film 33 made of the SiO ₂ or BPSG layer of the pixel portion 1 is made into a smooth wavy uneven surface by reflow processing.

  Next, as shown in FIG. 4C, in the second step, SiN that functions as an etching stopper film 35 is formed on the first interlayer insulating film 33 in the subsequent etch back.

Next, as shown in FIG. 4D, in the third step, a second interlayer insulating film 37 thicker than the first interlayer insulating film 33 is formed on the etching stopper film 35. The second interlayer insulating film 37 is obtained by forming thick SiO ₂ or BPSG. As a result, a thick film is formed in the peripheral circuit section 5 and the horizontal transfer path 3.

Next, as shown in FIG. 4E, in the fourth step, the second interlayer insulating film 37 is selectively removed only with respect to the pixel portion 1 using the etching stopper film 35. That is, only the pixel portion 1 is removed by etching SiO ₂ or BPSG. In this etching, the SiN layer functions as an etching stopper layer. Therefore, in the pixel portion 1, only a thin SiO ₂ layer or BPSG layer and the etching stopper film 35 remain, whereby the interlayer insulating film formed in the pixel portion 1 is formed on the gate electrode of the peripheral circuit portion 5. It is thinner than the interlayer insulating film.

  Also in the present embodiment, after the second step, the first interlayer insulating film 33 is reflowed at least for the pixel portion 1 and after the fourth step, at least the pixel portion 1 is etched. A high refractive index material layer 29 having a refractive index higher than that of the one interlayer insulating film 33 is formed on the stopper film 35. That is, the SiN layer of the high refractive index material is formed to form the downwardly convex inner lens 31. Even in this case, the top of the in-layer lens 31 is formed at a height close to the photodiode.

  An etching stopper film 35 is formed on the portion of the first interlayer insulating film 33 that has a concave curved surface corresponding to the photodiode by the reflow process, and the high refractive index material layer 29 is formed on the etching stopper film 35. Thus, an in-layer lens 31 in which the boundary surface between the etching stopper film 35 and the high refractive index material layer 29, that is, the bottom surface of the high refractive index material layer 29 is a convex curved surface is formed, and the light condensing rate with respect to the photodiode is increased. This increases the sensitivity.

In the peripheral circuit portion 5 shown in FIG. 4F, a contact hole H is formed, a metal conductor layer M is buried in the hole H, and a signal wiring 25 is formed on the surface of SiO ₂ . In the horizontal transfer path 3 as well, the signal wiring 27 is formed on the surface of SiO ₂ .

  According to the method for manufacturing a solid-state imaging device according to this embodiment, the same effects as the basic action of the first embodiment can be obtained, and the first interlayer formed in the pixel portion 1 and the peripheral circuit portion 5 can be obtained. An etching stopper film 35 is formed on the insulating film 33, a second interlayer insulating film 37 is formed on the etching stopper film 35, and then the second interlayer insulating film 37 is applied only to the pixel portion 1. Since the pixel portion 1 is first covered with the etching stopper film 35 and the second interlayer insulating film 37 is removed, there is no influence on the exposed upper layer electrode and the like, and the upper layer characteristics are removed. Changes can be suppressed.

Note that the first and second interlayer insulating films 21, 23, 33, and 37 are made of a material containing silicon oxide. This makes it possible to facilitate efficient removal of the intermediate layer and removal using the silicon nitride film as an etching stopper film.
Therefore, according to this configuration, it is possible to form a light-shielding film by metal silicide or use the lower shape of the inner lens by an interlayer insulating film when forming an optical path that forms a lower-layer inner lens. It becomes.

Next, a digital camera that is an image pickup apparatus including the solid-state image pickup device according to the above-described embodiment will be described.
FIG. 5 is a block diagram of a digital camera equipped with a solid-state imaging device according to the present invention.
The digital camera shown in the figure includes a photographic lens 41, the above-described solid-state imaging device 100, a diaphragm 43 provided therebetween, an infrared cut filter 45, and an optical low-pass filter 47. A CPU 49 that performs overall control of the entire digital camera controls the flash light emitting unit 51 and the light receiving unit 53, controls the lens driving unit 55 to adjust the position of the photographing lens 41 to the focus position, and controls the aperture via the aperture driving unit 57. The amount of opening 43 is controlled to adjust the exposure amount.

  Further, the CPU 49 drives the solid-state image sensor 100 via the image sensor driving unit 59 and outputs the subject image captured through the photographing lens 41 as a color signal. An instruction signal from the user is input to the CPU 49 through the operation unit 61, and the CPU 49 performs various controls according to the instruction.

  The electric control system of the digital camera includes an analog signal processing unit 67 connected to the output of the solid-state imaging device 100, and an A / D conversion circuit that converts RGB color signals output from the analog signal processing unit 67 into digital signals. 69, and these are controlled by the CPU 49.

  Further, the electric control system of the digital camera includes a memory control unit 73 connected to a main memory (frame memory) 71 and digital signal processing for performing image processing such as gamma correction calculation, RGB / YC conversion processing, and image synthesis processing. Unit 75, a compression / decompression processing unit 77 that compresses the captured image into a JPEG image or expands the compressed image, an integration unit 79 that integrates photometric data and obtains the gain of white balance correction performed by digital signal processing unit 75 , An external memory control unit 83 to which a detachable recording medium 81 is connected, and a display control unit 87 to which a liquid crystal display unit 85 mounted on the rear surface of the camera is connected. These include a control bus 89 and a data bus. 91 are connected to each other and controlled by a command from the CPU 49.

  When a subject image is picked up by the digital camera according to the present embodiment, each pixel 1 shown in FIG. 1 accumulates signal charges corresponding to the amount of received light, and the signal charges are first read out to the vertical charge transfer path. Are transferred in the direction of the horizontal charge transfer path 3.

  At the timing immediately before each signal charge is read out to the vertical charge transfer path, each vertical charge transfer path and horizontal charge transfer path 3 are emptied by the sweeping operation. After the readout processing of the injected predetermined charge amount, the signal charge corresponding to the received light amount of each pixel is read from the solid-state imaging device 100, and the digital signal processing unit 75 generates subject image data.

  According to this digital camera, since the solid-state imaging device 100 and the optical system for forming an optical image on the solid-state imaging device 100 are provided, there is little difference in sensitivity even when the F value is changed, and the influence of smear is also suppressed. It is possible to obtain high-sensitivity and good images without noise at high speed. Further, the output signal difference can be corrected with high accuracy using a uniform reference signal, and a good image can be obtained.

  The present invention is a CCD-type or CMOS-type solid-state image pickup device, and in particular, a solid-state image pickup device formed by multilayer wiring by a pixel portion, a peripheral circuit portion, a horizontal transfer path, etc. Since the requirements for different film thicknesses of the insulating film can be compatible, high sensitivity, low smear, no dependence on F value, and high-speed operation can be realized. For example, electronic cameras, video cameras, portable terminals, etc. It is effective for use.

3 is a plan view conceptually showing a positional relationship among a pixel portion, a horizontal charge transfer portion, and a peripheral circuit portion of the solid-state imaging device according to the present invention. The manufacturing method according to the first embodiment is divided into the main parts of the peripheral circuit part, the horizontal charge transfer part, and the pixel part as shown by arrows A-B in FIG. 1, and the order of steps (a) to (f). It is explanatory drawing shown roughly by. It is explanatory drawing which showed schematically the manufacturing method about a pixel part in order of the process of (a)-(e). The manufacturing method according to the second embodiment is divided into the main parts of the peripheral circuit part, the horizontal charge transfer part, and the pixel part as shown by arrows A-B in FIG. 1, and the order of steps (a) to (f). It is explanatory drawing shown roughly by. 1 is a block diagram of a digital camera that is an imaging apparatus equipped with a solid-state imaging device according to the present invention. FIG. 6 is a cross-sectional view showing a peripheral circuit portion in a conventional CCD solid-state image pickup device when the interlayer insulating film is thin, (a) a horizontal charge transfer portion (HCCD portion), and (c) a pixel portion. FIG. 6 is a cross-sectional view showing a peripheral circuit portion (a), a horizontal charge transfer portion (HCCD portion) (b), and a pixel portion (c) when the interlayer insulating film is thick in the conventional solid-state imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pixel part 5 Peripheral circuit part 7 Semiconductor substrate 21 1st interlayer insulation film 23 2nd interlayer insulation film 29 High refractive index material layer 33 1st interlayer insulation film 35 Etching stopper film 37 2nd interlayer insulation film 100 Solid Image sensor PD photodiode

Claims (7)

Manufacturing a solid-state imaging device comprising: a pixel portion in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit portion that performs reading drive of signal charges generated by the photodiodes and signal processing of the signal charges. A method,
(A-1) forming a first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion on which the gate electrode is formed;
(A-2) selectively removing the first interlayer insulating film only with respect to the pixel portion;
(A-3) forming a second interlayer insulating film thinner than the first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion;
Including
A method for manufacturing a solid-state imaging device, wherein an interlayer insulating film formed in the pixel portion is thinner than an interlayer insulating film formed on the gate electrode of the peripheral circuit portion. It is a manufacturing method of the solid-state image sensing device according to claim 1,
After the step (A-3), at least for the pixel portion, a high refraction index higher than that of the second interlayer insulating film is provided on the reflow-treated surface obtained by reflowing the second interlayer insulating film. A method for manufacturing a solid-state imaging device for forming a refractive index layer. Manufacturing a solid-state imaging device comprising: a pixel portion in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit portion that performs reading drive of signal charges generated by the photodiodes and signal processing of the signal charges. A method,
(B-1) forming a first interlayer insulating film by a process common to both the pixel portion and the peripheral circuit portion on which the gate electrode is formed;
(B-2) forming an etching stopper film on the first interlayer insulating film;
(B-3) forming a second interlayer insulating film thicker than the first interlayer insulating film on the etching stopper film;
(B-4) selectively removing the second interlayer insulating film only with respect to the pixel portion using the etching stopper film;
Including
A method for manufacturing a solid-state imaging device, wherein an interlayer insulating film formed in the pixel portion is thinner than an interlayer insulating film formed on the gate electrode of the peripheral circuit portion. It is a manufacturing method of the solid-state image sensing device according to claim 3,
After the step (B-1), at least the pixel portion is subjected to a reflow process on the first interlayer insulating film,
After the step (B-4), manufacturing a solid-state imaging device in which a high refractive index layer having a higher refractive index than that of the first interlayer insulating film is formed on the etching stopper film at least for the pixel portion Method. It is a manufacturing method of the solid-state image sensing device according to any one of claims 1 to 4,
A method for manufacturing a solid-state imaging device, wherein the first interlayer insulating film and the second interlayer insulating film are made of a material containing silicon oxide. A solid-state imaging device comprising: a pixel portion in which a plurality of photodiodes are arranged on a semiconductor substrate; and a peripheral circuit portion that performs reading drive of signal charges generated by each photodiode and signal processing of the signal charges. And
An interlayer insulating film formed using the solid-state imaging device manufacturing method according to claim 1 and formed above the photodiode of the pixel portion has a thickness of the gate of the peripheral circuit portion. A solid-state imaging device thinner than an interlayer insulating film formed on an electrode. A solid-state imaging device according to claim 6;
An optical system for forming an optical image on the solid-state imaging device;
An imaging apparatus comprising:

Images