JP2002184968A - Solid state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CCD type solid state image sensor in which the driving voltage and power consumption are reduced without increasing the ineffective region. SOLUTION: A vertical charge transfer channel 20 is formed continuously such that parts 20A and 20B intruding and not intruding, respectively, between respective photoelectric conversion elements in photoelectric conversion element arrays disposed on the opposite sides are arranged alternately and extends in the vertical direction while snaking between photodiodes 14 arranged in honeycomb. Transfer electrodes 32 extending in the horizontal direction and being driven with difference phases are single layer electrodes formed on the same plane through a narrow gap 34. Peripheral region of the photodiode 14 is used as the vertical charge transfer channel 20 except a channel stop 28 and no ineffective region is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly, to a photoelectric conversion element array in which a plurality of photoelectric conversion elements are arranged at predetermined intervals in a predetermined direction, and a plurality of photoelectric conversion elements arranged at the predetermined intervals. A CCD type solid-state image pickup device comprising a plurality of sets of element arrays each of which is arranged in a predetermined direction and is shifted by a predetermined amount in the predetermined direction with respect to the photoelectric conversion element rows. (CCD with honeycomb array)
About.

[0002]

2. Description of the Related Art Conventionally, a solid-state imaging device has been developed for use in a system that displays a captured image on a television or the like as a moving image, that is, a system conforming to a standard television system such as the so-called NTSC. In this standard television system,
In order to display a moving image without flicker, an interlaced scanning (interlaced scanning) method is adopted. For this reason, CCD-type solid-state imaging devices used in video camcorders and the like (often referred to as interline-type CCDs (Charge Coupled Devices)) are generally equipped with an interlaced scanning method for pixels. Reading is being performed.

In recent years, the market for electronic still cameras has been rapidly expanding with the increase in resolution and cost of CCD type solid-state imaging devices, the development of the Internet environment, and the spread of personal computers. An electronic still camera is required to have a function similar to that of a conventional film camera that can record a high-definition still image and obtain a high-resolution print image equivalent to that of a conventional silver halide photograph.
However, when an electronic still camera captures a still image by an interlaced scanning method, one screen of a still image is formed in two fields in a pseudo manner, and a difference occurs in the pixel signal reading time between the two fields. If the subject moves during this time, there is a problem that an image shift occurs depending on the field.

In order to solve this problem, in an electronic still camera, a mechanical shutter that performs a precise operation is used together to mechanically control the exposure time to a CCD solid-state image pickup device, and pixels are read out by a mechanical shutter. This is performed after the image is closed, thereby preventing the image from shifting.

Further, for the purpose of recording a still image, a progressive-scan CCD solid-state imaging device for simultaneously reading out all pixels has been developed. In this CCD type solid-state imaging device, since all pixels are read simultaneously, a high-precision mechanical shutter is not required. Here, the configuration of a conventional progressive scanning interline CCD will be described with reference to FIGS. As shown in FIG. 9A, this interline type CCD has photodiodes 10 separated from each other by a channel stop 108.
6, vertical charge transfer path 100, this vertical charge transfer path 100
Charge transfer electrodes 102a disposed above and parallel to each other so as to extend in the horizontal direction while avoiding the photodiode 106;
102b and 102c. In order to perform progressive scanning, the charge transfer electrodes 102a, 102b,
Reference numeral 102c denotes three-phase driving in which one transfer stage 102 is constituted by three. When the three-phase driving is performed in this way, as shown in FIG. 9B, the charge transfer electrodes 102a, 102b, and 102c arranged in parallel between the vertical pixels.
Is formed through an insulating film 104 such as a polysilicon oxide film.
Layered in layers. Also, as shown in FIG.
Even on the vertical charge transfer path 100, the charge transfer electrodes 10
2a, 102b, and 102c are partially overlapped with an insulating film 104 interposed therebetween.

The reason why the charge transfer electrodes are multi-layered is as follows. That is, by electrically separating the electrodes from each other by the insulating film 104 such as a polysilicon oxide film,
The electrodes can be brought close to each other via a “narrow gap” of the thickness of the insulating film 104, and the charges can be smoothly moved in the charge transfer path. Further, as shown in FIGS. 9A and 9B, the photodiode 1 is located between the photodiodes 106 adjacent in the vertical direction (between the vertical pixels).
It is an element isolation region that is neither the 06 nor the vertical charge transfer path 100, and is a so-called ineffective region that is simply used for wiring the transfer electrodes. However, by making the charge transfer electrodes multilayer, the ineffective region is reduced. Therefore, the area of the vertical charge transfer path 100 is not pressed by the invalid region.

[0007]

However, CCDs
The driving voltage of a solid-state imaging device of a type is higher than that of another solid-state imaging device such as a solid-state imaging device of a MOS type, and a driving voltage of 5 volt or more is required to drive a solid-state imaging device of a CCD type. In addition, it has been pointed out that power consumption increases because a plurality of transfer electrodes having a large capacitance component are driven at high speed. In the CCD type solid-state imaging device, each transfer electrode is formed by patterning by plasma etching, but the gate oxide film exposed by plasma etching is damaged. In particular, in the case of a multi-layer electrode structure, this plasma etching step needs to be performed twice for a two-layer electrode and three times for a three-layer electrode, and the gate oxide film is greatly damaged. In order to reduce the damage to the gate oxide film, a CCD type solid-state imaging device has a thickness of 300 to 700 mm.
Å and a thicker gate oxide film than an ordinary IC etc. are formed. In order to control the charge transfer in the substrate through the thick gate oxide film, the driving voltage is higher than that of the MOS type solid-state imaging device. Must. This is the reason why the driving voltage of the CCD solid-state imaging device is higher than that of another solid-state imaging device such as a MOS solid-state imaging device.

On the other hand, when the plurality of charge transfer electrodes have a “single-layer electrode structure”, an insulating film provided between layers in the multilayer electrode structure is unnecessary, the capacitance component can be reduced, and the thickness of the gate oxide film can be reduced. Therefore, the driving voltage of the CCD solid-state imaging device can be reduced and power consumption can be reduced, as compared with the case where a multilayer electrode structure is used. Also, in the case of a single-layer electrode structure, it is necessary to form a “narrow gap” between the electrodes with high precision. However, in recent years, a combination of anisotropic etching technology and lithography technology has reduced A gap of about 1 μm to 0.3 μm can be accurately formed.

However, when the single-layer electrode structure is employed, there is a problem that an increase in the number of electrodes per pixel increases an ineffective area occupying one pixel, thereby sacrificing light sensitivity and dynamic range. . For example, in a progressive-scan CCD solid-state imaging device equipped with a three-phase drive VCCD, when the charge transfer electrode has a single-layer electrode structure, the width of [electrode width × 3 + gap width × 2] is set between pixels. Therefore, the area of the light receiving section is significantly compressed. Therefore, it is extremely difficult to make the charge transfer electrodes have a single-layer electrode structure in a progressive-scan CCD solid-state imaging device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to reduce a driving voltage and a power consumption of a CCD without increasing an invalid area.
It is an object of the present invention to provide a solid-state imaging device of the type.

[0011]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, there is provided a photoelectric conversion element array in which a plurality of photoelectric conversion elements are arranged at predetermined intervals in a predetermined direction; Elements are arranged in the predetermined direction at the predetermined interval,
A plurality of pairs of element arrays each including a plurality of photoelectric conversion element rows arranged in the predetermined direction with respect to the photoelectric conversion element rows. A solid-state imaging device in which transfer paths are arranged so as to penetrate between the photoelectric conversion elements of a matching photoelectric conversion element row and do not contact each other, and intersect with the predetermined direction by passing between the photoelectric conversion elements. And a plurality of single-layer electrodes that are arranged at predetermined intervals so as to transfer signal charges generated by the photoelectric conversion elements along the transfer path.

In the solid-state image pickup device according to the first aspect, the transfer path includes:
Each of the photoelectric conversion elements is arranged so as to penetrate between the photoelectric conversion elements adjacent to each other between the photoelectric conversion element rows and not to contact each other. The elements are effectively used as transfer paths. Accordingly, a plurality of single-layer electrodes extending in a direction intersecting the predetermined direction so as to pass between the photoelectric conversion elements are separated by a predetermined distance so that signal charges generated in the photoelectric conversion elements are transferred along the transfer path. Even if they are arranged vertically, no so-called ineffective area occupied only by the electrode wiring does not occur, and the area of the light receiving section is not pressed. In addition, since the transfer electrode is a single-layer electrode, an insulating film provided between layers in the multilayer electrode structure becomes unnecessary, and the driving voltage of the solid-state imaging device is reduced and power consumption is reduced as compared with the case of a multilayer electrode structure. Can be reduced.

In the above-mentioned solid-state image pickup device, the plurality of single-layer electrodes are arranged such that the distance between the single-layer electrodes on the transfer path is determined by the distance between the single-layer electrodes on the element isolation region for electrically separating adjacent transfer paths. By making the width narrower, the flow of charges in the transfer path becomes smooth. In addition, the plurality of single-layer electrodes are formed such that the distance between the single-layer electrodes on the transfer path is formed linearly from one side edge to the other side edge of the transfer path, so that the flow of charges is smoother. become.

Further, since the insulating film is not required as described above, the range of choice of electrode material is widened, and the single-layer electrode can be made of a metal other than polysilicon such as aluminum or copper. In this case, the reflectance of the electrode surface is lower than the surface reflectance of the metal aluminum itself (for example, 50% or less of the surface reflectance of the metal aluminum itself).
For this purpose, it is preferable to add a surface treatment. The electrode material can be selected from the group consisting of low resistance polysilicon, tungsten, molybdenum, tungsten silicide, molybdenum silicide, titanium silicide, tantalum silicide, and copper silicide.

Note that a single-layer electrode means a single electrode with respect to a multilayer electrode in which a plurality of electrodes are stacked, and a single-layer electrode may be formed by stacking a plurality of electrode materials. Well, for example, low-resistance polysilicon, tungsten, molybdenum, tungsten silicide, molybdenum silicide, titanium silicide, tantalum silicide,
And a multilayer structure formed by laminating two or more kinds of electrode materials selected from the group consisting of copper silicide and copper silicide.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) In a CCD image sensor according to a first embodiment of the present invention, as shown in FIG. 1, a photodiode 14 as a photoelectric conversion element is formed on a semiconductor substrate (not shown). A plurality of first photoelectric conversion element rows 16 arranged in a vertical direction at a predetermined interval (vertical pixel pitch VP), and a plurality of photodiodes 14 arranged in the vertical direction at the same interval as the first photoelectric conversion element rows 16; 1 for the vertical pixel pitch VP in the vertical direction with respect to the first photoelectric conversion element row 16.
/ 2, a second photoelectric conversion element row 18 arranged at a shift
Are arranged in the horizontal direction.

The adjacent first photoelectric conversion element rows 16 and the adjacent second photoelectric conversion element rows 18 are arranged at the same interval as the vertical pixel pitch (horizontal pixel pitch HP). The photoelectric conversion element row constituted by the photodiodes 14 included in the second photoelectric conversion element column 18 has a horizontal pixel pitch H
It is arranged to be shifted by 1/2 from P. That is, the photodiodes 14 are arranged in a so-called honeycomb shape.

Between the first photoelectric conversion element row 16 and the second photoelectric conversion element row 18 arranged close to each other, signal charges generated in the photodiode 14 are read out and transferred in the vertical direction. A vertical charge transfer channel 20 is provided for each. The vertical charge transfer channels 20 are continuously formed such that the invading portions 20A and the non-invading portions 20B invading between the photodiodes of the photoelectric conversion element rows located on both sides are alternately arranged, and are arranged in a honeycomb shape. It extends vertically while meandering between the photodiodes 14.
In addition, a channel stop 28 described later is provided between the adjacent intruding portions 20A, so that the vertical charge transfer channels 20 are not in contact with each other. This allows
Except for the channel stop 28, the entire peripheral region of the photodiode 14 is used as the vertical charge transfer channel 20, and an "ineffective region" used only for the transfer electrode wiring does not occur. In this point, it is significantly different from the conventional interline CCD, and the peripheral area of the photodiode 14 is used more effectively than the conventional interline CCD.

The end of each vertical charge transfer channel 20 on the downstream side in the transfer direction is connected to a horizontal charge transfer device (H) for transferring the signal charges transferred from the vertical charge transfer channel 20 in the horizontal direction.
The transfer electrode of the HCCD 22 has a single-layer electrode structure, similarly to a vertical charge transfer device 33 described later. An end of the HCCD 22 on the downstream side in the transfer direction is connected to an output unit 24 that outputs a voltage corresponding to the amount of signal charges.

FIG. 2 is a partially enlarged view showing the configuration of the imaging section of the CCD image sensor according to the present embodiment.
FIG. 5 is a sectional view taken along line V1-V2 of FIG. As shown in FIGS. 2 and 3, the semiconductor substrate 12 is roughly divided into an n-type semiconductor substrate 12a such as silicon and a p-type impurity-added region (p-type).
(Well) 12b.

The photodiode 14 is formed as a buried photodiode in the p-type impurity-added region 12b, and as described above, the n-type impurity-added region 14a functioning as a charge storage region and the n-type impurity-added region. Area 1
4a is formed of ap ⁺ -type impurity-added region 14b formed on the substrate 4a.

The vertical charge transfer channel 20 is formed as an n-type impurity added region in the p-type impurity added region 12b. A read gate channel 26 formed of a p-type impurity-doped region is provided between the vertical charge transfer channel 20 and the photodiode 14 on the side from which signal charges are read from the vertical charge transfer channel 20. On the surface of the semiconductor substrate 12, the n-type impurity-added region 14a is formed along the read gate channel 26.
Is exposed. Then, the signal charges generated in the photodiode 14 are temporarily stored in the n-type impurity added region 14a, and then read out, for example, in the direction of arrow A via the readout gate channel 26.

On the other hand, the vertical charge transfer channel 20 and other
Between the photodiode 14 and p ⁺Type impurity doped region
Is provided. This switch
The channel stop 28 makes the photodiode 14 perpendicular to the photodiode 14.
When the direct charge transfer channel 20 is electrically separated from the
Also, the vertical charge transfer channels 20 do not contact each other.
Separated.

A transfer electrode 32 extending in the horizontal direction is formed on the surface of the semiconductor substrate 12 with a gate oxide film 30 interposed between the photodiodes. Also,
The transfer electrode 32 is formed so as to cover the read gate channel 26, expose the n-type impurity added region 14a, and expose a part of the channel stop 28.
The signal charges are transferred from the read gate channel 26 below the electrode to which the read signal is applied among the transfer electrodes 32.

The transfer electrode 32 is connected to the vertical charge transfer channel 2
0, a vertical charge transfer device (VCCD) 33 for transferring signal charges generated by the photodiode 14 in the vertical direction.
Is composed. The VCCD 33 is driven by four phases (φ1 to φ
4), the signal charges generated in the photodiodes 14 are transferred in the vertical direction by the four transfer electrodes 32 driven at different phases with respect to each photodiode 14. Each of the transfer electrodes 32 driven in different phases is formed of a single-layer electrode formed on the same plane with a narrow gap (interval in the arrangement direction of the transfer electrodes) 34 interposed therebetween. in this way,
By forming the transfer electrode with a single-layer electrode, an insulating film provided between layers in the multi-layer electrode structure becomes unnecessary, and the capacitance component can be reduced as compared with the multi-layer electrode structure. Power is reduced. Also,
As described above, the area around the photodiode 14 is:
Since it is used as the vertical charge transfer channel 20 and no "ineffective region" is generated except for the channel stop 28, even if the transfer electrode 32 has a single-layer electrode structure, the area of the light receiving portion will not be squeezed.

The gap 34 is formed by connecting a horizontal gap portion extending in the horizontal direction and a skew gap portion disposed between the horizontal gap portions and extending in an oblique direction. The distance between the transfer electrodes 32 is the same in all parts, and is preferably about 0.3 μm or less in order to make the flow of electric charges smooth.
It is particularly preferred that it is between 1 μm and about 0.2 μm.

The transfer electrode 32 can be formed using an electrode material generally used in a semiconductor manufacturing process or a solid-state device. Since the transfer electrode 32 has a single-layer electrode structure, an insulating film (high-resistance silicon oxide film) for insulating between electrode layers is not required, and the range of electrode materials can be selected widely. In addition, the electrode shape such as the electrode width and the electrode thickness has a wider design range according to the electrode material.

If the reflectance of the electrode surface is high, such as an aluminum electrode, halation will adversely affect the photolithography process in the manufacturing process, and the reflected light will become unnecessary stray light between the CCD package and the optical lens system during use. In addition, it is desirable to use an electrode material having a lower reflectance than aluminum because it may degrade the quality of a captured image. By using a light-shielding electrode material such as a light-absorbing material, an effect of blocking unnecessary external incident light can be expected. Further, when a large amount of impurities is contained, the gate oxide film and the silicon substrate may be contaminated and image defects such as white flaws may be induced.
It is desirable to use an electrode material having low resistance and low impurity.

As the electrode material having a lower reflectance than aluminum, low-resistance polysilicon, low-resistance metal, and low-resistance materials such as various silicides are preferable. For example, low-resistance polysilicon, tungsten (W), molybdenum (M
o), tungsten silicide (WSi), molybdenum silicide (MoSi), titanium silicide (TiS)
i), tantalum silicide (TaSi), and copper silicide (CuSi). Among them, tungsten has, for example, a reflectance of 50% or less of aluminum to light having a wavelength of 500 nm. Also,
The transfer electrode 32 may be formed by laminating a plurality of these electrode materials without interposing an insulating film.

Semiconductor substrate 12 on which transfer electrode 32 is formed
Is covered with a surface protection film (flattening film) 36 made of a transparent resin or the like, and a light-shielding film 38 is formed on the surface protection film 36. The light shielding film 38 has, for example, an octagonal opening 40 as a light transmitting portion for transmitting light received by the p ⁺ -type impurity-added region 14b, which is a light receiving portion, for each photodiode 14. The edge of the light-shielding film 38 extends in the center direction of the light-receiving region, and the shape of the opening of the photoelectric conversion element 14 is defined by the light-shielding film 38. The light shielding film 38 is made of, for example, aluminum (Al),
Chrome (Cr), tungsten (W), titanium (T
i), a thin film composed of a metal such as molybdenum (Mo), an alloy thin film composed of two or more of these metals, or a combination of two or more selected from the group including the metal thin film and the alloy thin film. It is formed of a multilayer metal thin film or the like.

Although not shown, the light shielding film 38 is not shown.
A color filter, a micro lens, and the like are formed on the upper side via a protective film and a flattening film as in the case of a normal CCD image sensor.

As described above, C according to the present embodiment
In the CD image sensor, since the transfer electrode has a single-layer electrode structure, the gate oxide film thickness can be made smaller than in the case of the multilayer electrode structure, and an insulating film provided between layers in the multilayer electrode structure is unnecessary. Becomes As a result, the capacitance component can be reduced, so that the driving voltage can be reduced and the power consumption can be reduced as compared with the case of using a multilayer electrode structure.

The vertical charge transfer channel extends vertically in a meandering manner between the photodiodes arranged in a honeycomb shape so as to enter between the photodiodes of the photoelectric conversion element rows provided on both sides. Therefore, the peripheral area of the photodiode (for example, the area between pixels in the horizontal and vertical directions and the area between pixels in the oblique direction of 45 °) is used as a vertical charge transfer channel, and is used only for the wiring of the transfer electrode. No "invalid area" occurs.
Therefore, even if the transfer electrode has a single-layer electrode structure, the area of the light receiving portion is not pressed down, and the progressive scan type CCD that simultaneously reads out all pixels without hindering the increase in the number of pixels and miniaturization of the CCD image sensor is not hindered. The present invention can also be applied to a solid-state image sensor.

In addition, since the transfer electrode has a single-layer electrode structure, unevenness on the surface of the imaging section of the CCD image sensor, particularly, before the microlenses and color filters are laminated, is alleviated, and flattening is facilitated. Light collection efficiency and smear are improved. Further, in the multilayer electrode structure, a decrease in yield due to interlayer leakage current is a problem. However, such a problem does not occur due to the single-layer electrode structure.

Further, in the multi-layer electrode structure, there is a problem that a crystal defect is induced by a high-temperature thermal oxidation process of polysilicon for forming an insulating film. This eliminates the need for a thermal oxidation step, suppresses the occurrence of crystal defects, and reduces white spots and the like on the screen, which are problematic in CCD-type solid-state imaging devices. Furthermore, since the single-layer electrode structure can be formed in fewer steps than the multi-layer electrode structure, there is an advantage that the manufacturing process of the CCD image sensor can be simplified.

When an electrode material having a light-shielding property (such as tungsten) is used for the transfer electrode, the light-shielding electrode material is disposed in a portion near the silicon substrate.
An effect of blocking unnecessary external incident light can also be expected.

(Second Embodiment) A CCD image sensor according to the first embodiment is different from the CCD image sensor according to the second embodiment of the present invention except that the pattern for forming the transfer electrode 32 is different. Therefore, the same portions are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

As shown in FIG. 4, in this CCD image sensor, a gap 3 between adjacent transfer electrodes 32 is provided.
4 is formed so as to be narrow on the vertical charge transfer channel 20 (narrow gap a) and wide on the channel stop 28 (wide gap b). The narrow gap a is preferably about 0.3 μm or less, particularly preferably about 0.1 μm to about 0.2 μm, in order to make the flow of electric charges smooth. The wide gap width b is equal to the transfer electrode 3
2 to prevent electrical contact (short).
The thickness is preferably larger than 3 μm, but is preferably about 0.3 μm to about 0.4 μm so as not to hinder the routing of the electrodes.
It is particularly preferable to set the range of m.

Transfer electrode 3 on vertical charge transfer channel 20
2 is involved in the charge transfer, and by narrowing the gap 34 between the transfer electrodes 32, the flow of charges in the transfer path becomes smooth, and the transfer electrode 3
Since 2 is not involved in charge transfer, widening the gap 34 between the transfer electrodes 32 prevents problems due to electrical contact (short) between the transfer electrodes 32, and reduces the coupling capacitance between the transfer electrodes 32. As a result, noise and power consumption can be reduced.

(Third Embodiment) The CCD image sensor according to the third embodiment of the present invention is the same as the CCD image sensor according to the first embodiment except that the pattern for forming the transfer electrode 32 is different. Therefore, the same portions are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

As shown in FIG. 5, in this CCD image sensor, a gap 3 between adjacent transfer electrodes 32 is provided.
Similarly to the second embodiment, 4 is formed so as to be narrow on the vertical charge transfer channel 20 (narrow gap a) and wide on the channel stop 28 (wide gap b). The channel 20 is formed so as to extend linearly from one side edge to the other side edge. Note that the sizes of the narrow gap a and the wide gap b are the same as in the second embodiment.

By forming the gaps 34 between the transfer electrodes 32 in this manner, the flow of charges in the vertical charge transfer channel 20 is further smoothed, and a problem is caused by electrical contact (short) between the transfer electrodes 32. Generation is prevented, the coupling capacitance between the transfer electrodes 32 is reduced, and noise and power consumption are reduced. In particular, although the gap 34 becomes narrower on the vertical charge transfer channel 20,
When the transfer electrodes 32 are formed so as to extend in a straight line, it is easy to form an accurate gap pattern, and the occurrence of problems due to electrical contact (short circuit) between the transfer electrodes 32 is further prevented.

(Fourth Embodiment) A CCD image sensor according to a fourth embodiment of the present invention is similar to the first embodiment except that the transfer electrode 32 is composed of a plurality of electrode materials. Since it is the same as such a CCD image sensor,
The same portions are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

As shown in FIG. 6, the transfer electrode 32 is
It is composed of a multilayer metal thin film in which a second tungsten silicide (WSi) layer 32b is laminated on a low resistance polysilicon layer 32a. Since the low-resistance polysilicon layer 32a is formed between the WSi layer 32b and the gate oxide film 30, mechanical stress between the WSi layer 32b and the gate oxide film 30 can be reduced, and metal contamination caused by the formation of the WSi layer 32b can be reduced. Problems can be reduced. In addition, low-resistance polysilicon can easily secure an etching selectivity, and can form an accurate gap pattern. In addition, tungsten silicide (WSi) has a lower reflectance than aluminum (Al), and therefore does not adversely affect halation or an imaging optical system.

As described above, when the transfer electrode 32 is formed of a multilayer metal thin film, the first layer of the metal thin film plays a role of relieving stress, preventing impurity contamination, forming an accurate gap pattern, and the like. However, the second metal thin film has a different role in each layer, such as lowering the resistance of the transfer electrode, lowering the reflectivity of the electrode surface, and reducing light penetration into the substrate. , The transfer electrode 32 can have a complex function.

In each of the above-described embodiments, a plurality of sets of element rows composed of the first photoelectric conversion element row 16 and the second photoelectric conversion element row 18 are arranged in a horizontal direction. Although an example in which an even number of photoelectric conversion element rows are provided has been described, an odd number of photoelectric conversion element rows may be provided by further adding or omitting one photoelectric conversion element row.

Next, a method of manufacturing the CCD image sensor according to the fourth embodiment will be described with reference to FIGS.

As shown in FIG. 7A, a p-type impurity-added region (p-well) 12b is formed on a silicon n-type semiconductor substrate 12a, and an n-type impurity-added region 12b is formed at a predetermined position in the p-type impurity-added region 12b. An impurity region 14a is formed.
By forming ap ⁺ -type impurity-doped (high-concentration p-type impurity-doped) region 14b in a part of the type impurity region 14a, the photodiode 14 as a light receiving portion is formed. P-type impurity doped region 1 on the side of each photodiode 14
By adding an n-type impurity to a predetermined portion of 2b, a vertical charge transfer channel 20 composed of, for example, an n-type region having a width of about 0.3 to 0.5 μm is formed. A p-type impurity region is left on one side of the vertical transfer channel 20 (on the side from which charges from the photodiode 14 are read), and the p-type impurity region serves as a read gate channel 26. On the other side of the vertical charge transfer channel 20, a channel stop region 28 with a width of, for example, about 0.5 μm formed by adding ap ⁺ -type impurity to separate the adjacent photodiodes 14 from each other is formed. Form. In each impurity added region, an impurity region having a desired concentration and depth is formed by, for example, an ion implantation method and a subsequent thermal diffusion (annealing) method.

Next, the step of forming a single-layer electrode will be described. First, as shown in FIG. 7B, a gate oxide film 30 is formed on the surface of the semiconductor substrate 12. Next, as shown in FIG. 7C, after polysilicon is deposited on the gate oxide film 30 by a CVD (Chemical Vapor Deposition) method or the like,
The low resistance polysilicon layer 32a is ion-implanted with phosphorus element.
To form Further, a tungsten silicide (WSi) layer 32b is deposited on the low resistance polysilicon layer 32a.

Next, as shown in FIG. 7D, the first C
After depositing the VD film 42, a pattern having a gap of about 0.6 μm is exposed and developed, and the CVD film 42 is patterned by performing an etching process using, for example, a plasma etching method using the remaining resist film as a mask.

Next, as shown in FIG. 8A, the second C
A VD film 44 is deposited. Then, as shown in FIG. 8B, the second CVD film 44 is etched back by, for example, an anisotropic dry etching device, and the first CVD film 42 is etched.
A gap of, for example, about 0.3 μm is formed while leaving the second CVD film 44 attached to the side wall of the first CVD film. The remaining first CVD film 42 and second CVD film 44
Is used as a mask, the low-resistance polysilicon layer 32a and the WS
The i-layer 32b is removed by etching using an anisotropic dry etching apparatus, and a gap 34 of about 0.3 μm is formed between the electrodes. The CVD film includes silicon oxide (SiO ₂ ).
And silicon nitride (Si ₃ N ₄ ) are suitable.

Next, as shown in FIG. 8C, the remaining first CVD film 42 and second CVD film 44 are all removed, and the transfer electrode 32 is formed. Further, boron ions are implanted into the vertical charge transfer channel 20 below the gap 34 to prevent a potential pocket from being generated in the vertical charge transfer channel 20 below the gap 34.

Finally, although not shown, the threshold voltage of the transistor portion is adjusted to form a metal wiring, and after flattening the substrate surface, a color filter and a micro lens are formed to complete a CCD image sensor. .

In the above, the Journal of the Institute of Television Engineers of Japan, Vo
l. 50, No. 2, pp. 234 to 240 (1996), an example in which the transfer electrode is formed with a narrow gap by the anisotropic etching technique while leaving the side wall of the CVD deposited film is described. , The transfer electrode can be formed with a narrow gap.

[0055]

According to the solid-state imaging device of the present invention, even when the transfer electrode is a single-layer electrode, the transfer path penetrates between each photoelectric conversion element row and between each photoelectric conversion element of adjacent photoelectric conversion element rows. In addition, since the transfer electrodes are arranged so as not to contact each other, the effect that the drive voltage and the power consumption can be reduced can be achieved by using a single-layer electrode as the transfer electrode without increasing the ineffective area.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a CCD image sensor according to a first embodiment.

FIG. 2 is a partially enlarged plan view of an imaging unit of the CCD image sensor according to the first embodiment.

FIG. 3 is a sectional view taken along line V1-V2 of the imaging unit shown in FIG.

FIG. 4 is a partially enlarged plan view of an imaging unit of a CCD image sensor according to a second embodiment.

FIG. 5 is a partially enlarged plan view of an imaging unit of a CCD image sensor according to a third embodiment.

FIG. 6 is a partial cross-sectional view of an imaging unit of a CCD image sensor according to a fourth embodiment.

FIGS. 7A to 7D show C according to a fourth embodiment; FIGS.
It is sectional drawing which shows the manufacturing process of a CD image sensor.

FIGS. 8 (a) to 8 (c) show CCs following the manufacturing process of the CCD image sensor according to the fourth embodiment shown in FIG. 7;
It is sectional drawing which shows the manufacturing process of a D image sensor.

9A is a partially enlarged plan view of an image pickup unit of a conventional progressive scanning interline CCD, and FIG. 9B is a cross-sectional view taken along line A1-A2 of FIG. 9A.
(C) is a sectional view taken along line B1-B2 of (a).

[Explanation of symbols]

 Reference Signs List 12 semiconductor substrate 14 photodiode 16 first photoelectric conversion element row 18 second photoelectric conversion element row 20 vertical charge transfer channel 22 horizontal charge transfer device (HCCD) 24 output section 26 read gate channel 28 channel stop 30 gate oxide film Reference Signs List 32 transfer electrode 33 vertical charge transfer device (VCCD) 34 gap 36 surface protective film (flattening film) 38 light shielding film 40 opening

Continued on front page F-term (reference) 4M118 AA04 AA10 AB01 BA13 CA03 CA04 CA20 DA12 DA18 DA20 DB08 FA07 FA26 FA35 GB03 GB07 GB08 GB11 GB15 GB17 5C024 AX01 CY42 GX03 GY02 GZ01

Claims (6)

[Claims] 1. A photoelectric conversion element array in which a plurality of photoelectric conversion elements are arranged in a predetermined direction at predetermined intervals, and a plurality of photoelectric conversion elements are arranged in the predetermined direction at the predetermined intervals, and And a plurality of pairs of element arrays each including a plurality of photoelectric conversion element rows that are arranged so as to be shifted by a predetermined amount in the predetermined direction, and each of the photoelectric conversion element rows adjacent to each other between the photoelectric conversion element rows. A solid-state imaging device in which transfer paths are arranged so as to penetrate between conversion elements and do not contact each other, wherein the transfer paths extend between the photoelectric conversion elements in a direction crossing the predetermined direction, and the transfer paths A plurality of single-layer electrodes arranged at predetermined intervals so as to transfer signal charges generated by the photoelectric conversion element along the line. 2. The solid-state imaging device according to claim 1, wherein the distance between the single-layer electrodes on the transfer path is smaller than the distance between the single-layer electrodes on the element isolation region that electrically separates adjacent transfer paths. 3. The solid-state imaging device according to claim 1, wherein the distance between the single-layer electrodes on the transfer path is linearly formed from one side edge of the transfer path to the other side edge. 4. The solid-state imaging device according to claim 1, wherein a surface reflectance of said single-layer electrode is lower than a surface reflectance of metal aluminum itself. 5. The single-layer electrode is made of any one electrode material selected from the group consisting of low-resistance polysilicon, tungsten, molybdenum, tungsten silicide, molybdenum silicide, titanium silicide, tantalum silicide, and copper silicide. The solid-state imaging device according to claim 4. 6. The solid-state imaging device according to claim 1, wherein said single-layer electrode is formed by laminating a plurality of electrode materials.