JP2001308308A - Solid-state image pickup device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a thin transfer electrode and a gate insulating film below the transfer electrode are etched, and metal wiring and a substrate may be short-circuited when the selectivity between an interlayer insulation film and the transfer electrode is low in a dry etching process of lining method for connecting the metal wiring to the transfer electrode to solve the problem that the resistance of the electrode is increased when the transfer electrode of a vertical registor is thinned to increase sensitivity to blue light in a full frame transfer system CCD image sensor. SOLUTION: The film thickness of at least one portion of the transfer electrode of a specific pixel containing a blue pixel 62 is set thinner than that of the transfer electrode of another pixel 63, thus increasing the sensitivity to the blue light, preventing the film thickness of the electrode in other regions from being thinned, hence preventing decrease in the amount of transfer charge caused by increase of resistance of the electrode and the deterioration in transfer efficiency, and preventing the metal wiring and substrate from being short- circuited.

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 full-frame transfer type or frame transfer type CCD type solid-state imaging device and a method of manufacturing the same.

[0002]

2. Description of the Related Art A full frame transfer type CCD image sensor has a higher aperture ratio than an interline transfer type CCD image sensor, and thus does not require a microlens. Characteristics, such as no transfer charge amount. For this reason, in single-lens reflex digital still cameras that require various interchangeable lenses and require a wide range of gradation reproducibility, full-frame transfer type CCD image sensors with a large chip area of 2 to 6 million pixels are widely used. I have.

FIG. 14 shows a general full frame transfer system C.
1 shows a configuration of a CD image sensor. A vertical register 301, a horizontal register 302, and an output amplifier 303, which also serve as a light receiving unit and a vertical charge transfer unit, are provided.

FIG. 15 shows a plan configuration of a pixel. A vertical register 301 is provided on the entire area between the channel stoppers 311.
Are formed. In this example, a four-phase drive register is assumed, and a unit pixel 362 surrounded by a dashed line
Four electrodes (half of the first layer transfer electrode 315, the second layer transfer electrode 316, the first layer transfer electrode 317, the second layer transfer electrode 31
8, half of the first layer transfer electrode 319). These transfer electrodes usually have pulses φV1 to
φV4 is supplied.

FIGS. 16 (a) and 16 (b) respectively show H- of FIG.
The cross section along H ′ and II ′ is shown. A channel stopper 311 of a high-concentration P layer and an N layer 312 constituting a transfer channel of a vertical register are formed on a P-type silicon substrate 310, and a silicon oxide film (hereinafter simply referred to as an oxide film) is formed on the P-type silicon substrate 310. ) Or first layer transfer electrodes 315 and 31 made of polycrystalline silicon or amorphous silicon with a gate insulating film 313 having a laminated structure of an oxide film and a silicon nitride film (hereinafter simply referred to as a nitride film) interposed therebetween.
7, 319, and second layer transfer electrodes 314, 316, 3
18, 320 are formed. The film thickness of these transfer electrodes is short-wavelength light whose absorption length in silicon is short,
3 so as to transmit blue light whose main component is 00 nm or less.
Interline transfer CCD with about 0-100nm
200 to 60 commonly used in image sensors
It is thinner than 0 nm.

On the transfer electrode, an oxide film, a nitride film, a film having a composition between both, and an interlayer film 321 made of an organic film such as a resist are formed. In the case of a CCD image sensor used for a single-chip color camera, a color filter is formed on the interlayer film, but is omitted here.

Next, the operation will be briefly described. In a full frame transfer type CCD image sensor, a mechanical shutter is essential in order to perform light reception and charge transfer by a vertical register. By setting φV1 to low level and φV2 to φV4 to high level while the mechanical shutter is open, signal charges (electrons in this example) corresponding to the amount of incident light are accumulated. After the mechanical shutter is closed, the electric charges transferred downward in the vertical register are transferred to the horizontal register line by line, transferred to the horizontal register, converted into a voltage by the output amplifier, and taken out as a signal to the outside.

FIG. 17 is a plan view of a pixel of another conventional full frame transfer type CCD image sensor, and FIG. 18 is a sectional view taken along the line JJ 'of FIG. In this example, metal wirings 323 and 333 such as aluminum and tungsten are arranged on the channel stopper 311 and connected to the second-layer transfer electrode 318 and the first-layer transfer electrode 315 via the contacts 322 and 332, respectively. A drive pulse is supplied from a metal wiring. (December 1991, IEDM Technical Digest,
167-170). As in the example of FIG. 15, the drive pulse may be supplied from both ends of the transfer electrode.

FIG. 19A shows a cross section along the transfer direction of a horizontal register of a conventional full frame transfer type CCD image sensor. Here, a two-phase drive register is assumed, and charges are transferred from right to left in the figure. The difference from the cross section of the vertical register shown in FIG. 16B is that a low-concentration N layer 353 is formed under the second layer transfer electrode 352 of the horizontal register, and the first layer of the adjacent horizontal register is different. The point is that a common drive pulse φH1 or φH2 is applied to the transfer electrode 351 and the second layer transfer electrode 352. The low-concentration N layer 353 is formed so that when the same voltage is applied to the first-layer transfer electrodes 351 and 352, the charge is accumulated and the charge is not returned in the opposite direction to the transfer. This is because it is necessary to make a difference in channel potential. The low-concentration N layer 353 is generally formed by patterning a first-layer transfer electrode and then implanting boron in a self-aligned manner using this electrode as a mask.

FIG. 19B is a cross-sectional view of a MOS transistor used for an output amplifier, of which a surface type is exemplified here. The high-concentration N layers of the source region 354 and the drain region 355 are usually formed by ion-implanting phosphorus or arsenic in a self-aligned manner using the gate electrode 356 as a mask.

[0011]

As described above, in the full frame transfer type CCD image sensor, the transfer electrode of the vertical register is thinned for the purpose of improving the sensitivity to blue light, so that the resistance of the electrode is increased. In an image sensor having a large light receiving area, the driving pulse is supplied from the left and right ends of the electrodes, and in the examples shown in FIGS. 15 and 16, the pulse becomes dull near the center, the transfer charge amount decreases, and the transfer efficiency decreases. A problem of deterioration occurs.

Although not shown here, in the case of a frame transfer type CCD image sensor having a similar pixel structure and having a memory area between a pixel area and a horizontal register, charges generated by photoelectric conversion are stored in the memory. When data is transferred to an area at high speed, pulse dulling occurs again, and the high-speed transfer speed is restricted, so that a false signal called smear increases and image quality deteriorates.

In order to suppress such dulling of the pulse,
As shown in FIGS. 17 and 18, a technique of connecting a metal wiring disposed on a channel stopper and a transfer electrode to supply a pulse is used. However, in this case, the metal wiring 323 and the second-layer transfer electrode 3
In the dry etching step of opening the contact 322 connecting the first and second transfer electrodes 18 and 18, if the selectivity between the interlayer film 321 and the second-layer transfer electrode 318 is low, the thin second-layer transfer electrode 318
Is etched, and the gate insulating film 313 thereunder is further etched.
Is also etched, and the metal wiring 323 and the P-type silicon substrate 310 may be short-circuited at the channel stopper 311.

The transfer electrode of the horizontal register and the gate electrode of the transistor of the output amplifier are generally formed in the same process as the transfer electrode of the vertical register. Since the horizontal register is driven at a high frequency of 1 MHz to 100 MHz, the resistance of the transfer electrode becomes a problem as in the case of the vertical register, causing a reduction in the amount of transfer charge and a deterioration in transfer efficiency.

Further, in FIG. 19A, in the step of implanting boron ions for forming the low concentration N layer 353 using the first layer transfer electrode 351 of the horizontal register as a mask, when the transfer electrode is thin, it functions as a mask. The gate insulating film 31 under the first-layer transfer electrode 351 of the horizontal register.
Boron ions may also be implanted into the third and N layers 312, causing a problem that the channel potential fluctuates.

In FIG. 19B, using the gate electrode 356 of the transistor as a mask, the gate electrode 356 is also formed in the step of ion-implanting phosphorus or arsenic to form a high concentration N layer of the source region 354 and the drain region 355.
If it is thin, it will not function as a mask, and the threshold voltage and the like will fluctuate from the design value.

An object of the present invention is to reduce the thickness of at least a part of a transfer electrode of a specific pixel including a pixel on which a color filter transmitting blue is formed, so as to be thinner than that of another pixel. While reducing the transfer charge of the vertical and horizontal registers and preventing the transfer efficiency from deteriorating, preventing the occurrence of short circuits between the metal wiring and the substrate in the backing structure, and improving the transfer electrodes and amplifiers of the horizontal registers. An object of the present invention is to realize a solid-state imaging device and a method of manufacturing the same, which enable self-aligned ion implantation using a gate electrode of a transistor as a mask.

[0018]

According to the present invention, there is provided a solid-state imaging device comprising: a vertical register having a function of generating an electric charge in accordance with the intensity of light passing through an electrode and transferring the electric charge in one direction; A color register that transfers a charge in a direction orthogonal to the one direction; and an output amplifier connected to one end of the horizontal register. A color filter that transmits light of a predetermined wavelength is provided above an electrode of the vertical register. Is provided, wherein an electrode of a vertical register corresponding to a specific color in the color filter includes a thin-film electrode region having a smaller thickness than electrodes of other vertical registers.

In the solid-state imaging device according to a first application form of the solid-state imaging device, the vertical register is configured such that a plurality of vertical registers are arranged in parallel with each other and connected to the horizontal register. Corresponding to one different color filter constituting the color filter for each column, the electrode of the vertical register drives the vertical register above the vertical register and is orthogonal to the transfer direction of the vertical register. A first electrode and a second electrode having two different layers that scan each other, and the second electrode has both ends overlapping above the first electrode,
At least a second electrode among the electrodes constituting the electrodes of the vertical register corresponding to the specific color is formed of the thin-film electrode region.

Further, in the solid-state imaging device according to a second application form of the solid-state imaging device, the color filter is green.
The vertical register includes three color filters of a filter, a red (Red) filter, and a blue (Blue) filter, and the vertical register has a configuration in which a plurality of vertical registers are arranged in parallel with each other and connected to the horizontal register. The registers are
When the entire vertical register is viewed in a plan view, the green filters are arranged in a checkered pattern.When the vertical registers are viewed column by column, the green filters arranged in a checkered pattern in one column of vertical registers. And a blue filter is sandwiched between the green filters arranged in a checkered pattern in a vertical register adjacent to the vertical register in the one column.

Further, in the solid-state imaging device according to a third application form of the solid-state imaging device, the color filter is green.
The color filter includes four color filters of a filter, a magenta filter, a cyan filter, and a yellow filter, and the vertical registers are connected to the horizontal registers by a plurality of vertical registers being arranged in parallel rows. The vertical register is configured such that, when the entire vertical register is viewed in the row direction, cyan filters and yellow filters are alternately arranged in one row, and green in upper and lower rows adjacent to the one row. The filters and the magenta filters are alternately arranged, and the green filters and the magenta filters in the upper and lower rows are shifted from each other by one column in the row direction.

Further, in the first application form of the solid-state imaging device, the specific color is blue, and in the solid-state imaging device of the second application form of the solid-state imaging device, the specific colors are blue and red. Alternatively, the specific colors are magenta and cyan in the third application form of the solid-state imaging device, wherein blue and green are the rows where the red filters are arranged when the vertical registers are viewed row by row. That is.

In the solid-state imaging device, an insulating film is formed between the electrode and the color filter, and the insulating film is provided with a contact penetrating the insulating film.
Wiring electrically connected to the electrode through the contact is formed above the insulating film, and a portion of the electrode of the vertical register corresponding to the specific color where the contact is located is the other vertical register. When the electrode has the same thickness as the electrode of the register, or when the vertical register is cut along a plane perpendicular to the transfer direction, the thin film electrode region corresponds to the specific color rather than the portion where the contact is located. The vertical register corresponding to the specific color and the vertical register adjacent to the specific color are separated by a channel stopper layer formed on a semiconductor substrate, and the contact is formed on the channel stopper layer. Located above and inside, in this case, when the vertical register is cut along a plane perpendicular to the transfer direction, the thin film electrode area Than the channel stopper layer in the middle portion of the vertical register corresponding to the specific color, is that.

In the solid-state imaging device, an electrode above the horizontal register and driving the horizontal register is an electrode having the same thickness as an electrode of the other vertical register, and constitutes the output amplifier. The output gate electrode to be formed is an electrode having the same thickness as the electrode of the other vertical register, and the electrode may be made of a polycrystalline silicon film or an amorphous silicon film.

Next, the method for manufacturing a solid-state imaging device according to the present invention comprises the steps of: generating a charge in accordance with the intensity of incident light; and transferring the charge in one direction in accordance with a signal voltage; A semiconductor substrate having a channel stopper layer for separating transfer channels from each other is prepared, a gate insulating film is formed on the surface of the semiconductor substrate, and a silicon film, an oxide film, and an oxidation-resistant film are sequentially deposited on the gate insulating film. Then, the oxidation resistant film and the oxide film are selectively removed using the same mask pattern as a mask to form a silicon film exposed region where a part of the surface of the silicon film is exposed, and the silicon film exposed region is selected. The silicon film is partially oxidized to form a part of the silicon film exposed region as an oxide film, the oxide film on the silicon film is removed, and the silicon film is formed as a thin film electrode region of the silicon film exposed region. A method of manufacturing a solid-state imaging device including a manufacturing method of partitioning an electrode region other than the silicon film exposed region, wherein the thin-film electrode region corresponds to a specific color among color filters constituting the solid-state imaging device. A more specific solid-state imaging device manufacturing method is characterized by being formed in an electrode of a vertical transfer channel, and generates a charge in accordance with the intensity of incident light, and transfers the charge in one direction according to a signal voltage. Preparing a semiconductor substrate having a vertical transfer channel for transferring data to the semiconductor substrate and a channel stopper layer for separating the vertical transfer channel from each other; forming a first gate insulating film on the surface of the semiconductor substrate; A first silicon film, a first oxide film, and a first oxidation-resistant film in this order, and selectively removing the first oxidation-resistant film and the first oxide film using the same mask pattern as a mask. Forming a first silicon film exposed region where a part of the surface of the first silicon film is exposed, and selectively oxidizing the first silicon film exposed region to remove a part of the first silicon film exposed region. After removing the oxide film on the first silicon film as an oxide film, the first silicon film is divided to be orthogonal to the charge transfer direction of the vertical transfer channel and to the first silicon film exposed region. Forming a first electrode including a first thin film electrode region and a first electrode region other than the first silicon film exposed region;
After removing the first gate insulating film between the electrodes, the first oxidation-resistant film on the first electrode, and the first oxide film, a heat treatment is performed to form a second gate insulating film on the surface of the semiconductor substrate between the first electrodes. Forming an interlayer insulating film on the side and surface of the first electrode, and sequentially depositing a second silicon film, a second oxide film, and a second oxidation resistant film on the surface of the semiconductor substrate including the first electrode. Then, the second oxidation resistant film and the second oxide film are selectively removed using the same mask pattern as a mask to form a second silicon film exposed region where a part of the surface of the second silicon film is exposed. Selectively oxidizing the second silicon film exposed region to form a part of the second silicon film exposed region as an oxide film, removing the oxide film on the second silicon film, and dividing the second silicon film. Then, the space between the first electrodes is filled so that both ends are in contact with the first electrodes. Superimposed in parallel with said first electrode,
A method of manufacturing a solid-state imaging device for forming a second electrode including a second thin film electrode region of the second silicon film exposed region and a second electrode region other than the second silicon film exposed region; The first thin film electrode region and the second thin film electrode region are formed in electrodes of a vertical transfer channel corresponding to a specific color among color filters constituting the solid-state imaging device. .

In the above specific method of manufacturing a solid-state imaging device, horizontal transfer for transferring charges transferred from the vertical transfer channel to the semiconductor substrate in a direction orthogonal to the one direction in addition to the vertical transfer channel. A channel and an output amplifier connected to one end of the horizontal transfer channel. A horizontal transfer electrode for driving the horizontal transfer channel is formed simultaneously with the first electrode region and the second electrode region. An output gate electrode for driving the amplifier is formed simultaneously with the first electrode region or the second electrode region.

In the method for manufacturing a solid-state imaging device and the specific method for manufacturing a solid-state imaging device, the specific color is blue, or blue and red, or magenta and cyan. is there.

Further, in the above specific method for manufacturing a solid-state imaging device, the first thin film electrode region is arranged such that, when the vertical transfer channel is cut along a plane perpendicular to the transfer direction, the first thin film electrode region is located at a position closer to the center of the channel stopper layer. Also, the first silicon film and the second silicon film are formed at the center portion side of the vertical transfer channel corresponding to the specific color, and the first silicon film and the second silicon film are doped with impurities when the silicon film is deposited or immediately after the silicon film is deposited. Alternatively, the first silicon film and the second silicon film are each formed by depositing a non-doped silicon film, and an oxide film on the first silicon film and an oxide film on the second silicon film, respectively. Is removed, impurities are introduced into the non-doped silicon film, and the first oxidation-resistant film and the second oxidation-resistant film are nitride films. It is a function.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an example of the configuration of a full frame transfer type CCD image sensor according to the present invention. The basic configuration is the same as that of FIG. 14, and includes a vertical register 1, a horizontal register 2, and an output amplifier 3 which also serve as a light receiving section and a vertical charge transfer section. In addition, a green stripe on the pixel
(G), blue (B), and red (R) color filters are formed in column units.

FIG. 2 shows a plan configuration near the pixels of the blue filter row. As in FIG. 15, the vertical register 1 is formed over the entire area between the channel stoppers 11. Also in this example, a four-phase driving register is assumed, and a unit pixel surrounded by a dashed line has four electrodes (half of the first layer transfer electrode 15, the second layer transfer electrode 16, the first layer transfer electrode 17). , Second
Layer transfer electrode 18 and half of the first layer transfer electrode 19). Pulses φV1 to φV4 are usually supplied to both ends of these transfer electrodes.

FIGS. 3 (a), 3 (b) and 3 (c) show a first example of the first embodiment.
The cross section along A ', BB', and CC 'is shown. FIG.
As in (a) and (b), a channel stopper 11 of a high-concentration P layer and an N layer 12 forming a transfer channel of a vertical register are formed on a P-type silicon substrate 10. A first-layer transfer electrode 15 made of polycrystalline silicon or amorphous silicon, with a gate insulating film 13 having an oxide film or a stacked structure of an oxide film and a nitride film interposed therebetween;
17, 19, and the second layer transfer electrodes 14, 16, 18,
20 are formed. On the transfer electrode, an interlayer film 21 made of an oxide film, a nitride film, a film having a composition between them, or an organic film such as a resist is formed. Further, in each pixel column, a green filter 41, a blue filter 42, and a red filter 43 are formed on the interlayer film 21, respectively.

This embodiment is different from the conventional example shown in FIGS. 13 to 15 in that the first layer transfer electrode and the second layer transfer electrode in the pixels of the blue filter row are replaced with the pixels of the green filter row and the red filter row. This is to make it thinner than the transfer electrode. Of the transfer electrodes of the blue filter row, the film thickness on the entire channel width of the vertical
As in the conventional example, it is made as thin as about 30 to 100 nm so as to transmit short-wavelength light whose absorption length in silicon is short, particularly blue light whose main component is 500 nm or less (FIG. 3).
(A))).

On the other hand, the film thickness of the transfer electrodes of the pixels in the green filter row and the red filter row is determined by the interline transfer method CC.
200 to 6 commonly used in D image sensors
It is about 00 nm. In this embodiment, the transfer electrodes of the pixels in the blue filter row are made thinner as in the conventional example,
The sensitivity to blue light can be improved.

On the other hand, the transfer electrodes of the pixels in the green filter row and the red filter row have the same thickness as that of the interline transfer CCD image sensor, thereby preventing an increase in the electrode resistance and suppressing the dulling of the pulse. Conventional problems such as a decrease in transfer charge amount and a decrease in transfer efficiency can be solved. For example, assuming that the thickness of the transfer electrode of the blue filter pixel is 50 nm and the thickness of the transfer electrode of the pixels of the green filter row and the red filter row is 300 nm, the resistance from the end to the center of the transfer electrode is equal to that of all the pixels. Is reduced to の or less as compared with the conventional case where the thickness of the transfer electrode is 50 nm.

When the backing structure shown in FIGS. 17 and 18 is applied, the second-layer transfer electrode 18 on the channel stopper 11 of the present embodiment has a large thickness.
Metal wiring 323 and second layer transfer electrode 31 in 7 and 18
In the dry etching step of opening the contact 322 connecting the second layer transfer electrode 8 and the gate insulating film 313 thereunder, the metal wiring 3
There is also an effect that there is no possibility of short-circuit between the channel stopper 311 and the P-type silicon substrate 310.

FIG. 4 shows a cross section along the transfer direction of the horizontal register corresponding to FIG. 19 of the conventional example and a cross section of a MOS transistor used for an output amplifier.

The difference from the conventional example is that the first horizontal register
Thickness of the layer transfer electrode 51, the second layer transfer electrode 52 of the horizontal register, and the gate electrode 5 of the output amplifier MOS transistor.
6 is about 200 to 600 nm, which is the same as the transfer electrodes of the pixels in the green and red filter rows.

For example, the same 300 as the above-described vertical register
If it is set to nm, the resistance of the transfer electrode of the horizontal register is reduced to 1/6 of the conventional one, so that the transfer charge amount does not decrease and the transfer efficiency does not deteriorate. In forming the low-concentration N layer 53 of FIG. 4A, after patterning the first-layer transfer electrode 51 of the horizontal register, boron is generally implanted in a self-aligned manner using this electrode as a mask. For example, the thickness of the polycrystalline silicon transfer electrode is set to 50 n
m, when the thickness of the gate insulating film of the oxide film is 60 nm, if boron is ion-implanted with an energy of 40 keV, the peak position of the implantation penetrates the transfer electrode and the gate oxide film and enters the inside of the silicon substrate. That is, about 50% of the injection amount is equal to the transfer resistance of the first layer
As a result, the channel potential is modulated, so that the transfer charge amount is reduced and the transfer efficiency is deteriorated.

On the other hand, if the thickness of the first layer transfer electrode 51 of the horizontal register is 300 nm, the electrode serves as a mask, and almost all boron ions stop in the electrode.

Similarly, when the high-concentration N layers of the source region 54 and the drain region 55 in FIG. 4B are ion-implanted in a self-aligned manner using the gate electrode 56 as a mask, for example, the thickness of the polycrystalline silicon transfer electrode is reduced. When the thickness of the gate insulating film of the oxide film is 50 nm and the thickness of the oxide film is 60 nm, the phosphorous is 80 keV.
When ions are implanted at the energy of about 15%, about 15% of the implanted amount penetrates the injection transfer electrode and the gate oxide film and enters the inside of the silicon substrate. As a result, the threshold voltage greatly deviates from the design value, and a desired operation cannot be obtained. On the other hand, if the thickness of the gate electrode 56 is 300 nm, the electrode serves as a mask and almost all of the phosphorus ions stop in the electrode.

FIG. 5 shows a second example of the first embodiment, and is a cross section along AA 'in FIG. This embodiment differs from FIG. 3A in that the range in which the film thickness of the second-layer transfer electrode 18 is reduced is set to a width narrower than the channel of the vertical register. This has no effect of improving the sensitivity to blue light at both ends of the vertical register.
Unlike the channel stopper 11, the film thickness is large on the channel stopper 11,
When the backing structure shown in FIG. 18 is employed, the metal wiring corresponding to the metal wiring 323 in FIG.
The contact 322 of FIG.
In the photolithography process of forming a contact similar to that in this embodiment, the contact is applied to a thin portion due to misalignment of the mask, and in the subsequent dry etching process, the second layer transfer electrode 18 and the gate The disadvantage that the insulating film 13 is also etched and the metal wiring and the P-type silicon substrate 10 are short-circuited at the channel stopper 11 can be removed.

FIG. 6 shows a third example of the first embodiment, and is a cross section taken along line BB 'of FIG. This embodiment differs from FIG. 3B in that the thickness of the first layer transfer electrodes 15, 17, and 19 in the pixels in the blue column is the same as the thickness of the other pixels. Thereby, the sensitivity to blue light is not improved as much as in FIG. 3, but there is an advantage that the process is not required because the film is not thinned, and the construction period is shortened. FIG. 6 can be combined with FIG.

Next, a second embodiment of the present invention will be described with reference to FIGS.
Explanation will be made using 0.

FIG. 7 shows an example of the configuration of a full-frame transfer type CCD image sensor for explaining the second embodiment. The basic configuration is the same as that shown in FIG. 14, and a vertical register 10 which also serves as a light receiving section and a vertical charge transfer section.
1, a horizontal register 102, and an output amplifier 103. Further, on each pixel, a green filter (G) is formed in a checkered pattern, and a blue filter (B) and a red filter (R) are formed between the green filters every other row.

FIG. 8 shows a plan configuration of four pixels which are a repeating unit of the array. 9 (a), 9 (b) and 10 (a),
(b) shows DD ′, EE ′, and F− in FIG.
The cross section along F ′, GG ′ is shown.

This embodiment differs from FIG. 3 in that not only the transfer electrodes on the blue filter pixels but also the transfer electrodes on the red filter pixels are formed thin. The reason for this is that if only the transfer electrode of the blue filter pixel is thinned, the resistance of the transfer electrode differs between the row of blue filter pixels and the row of the red filter pixel, and the degree of pulse blunting can be different. When transferring in the vertical register from the row of blue filter pixels to the row of red filter pixels, or from the row of red filter pixels to the row of blue filter pixels, charge transfer failure may occur. is there.

For example, the thickness of the thicker transfer electrode is set to 300
If the thinner film thickness is 50 nm, the resistance of the transfer electrode in the row of blue filter pixels increases to 3.5 times the resistance of the row of red filter pixels. Therefore, by making the transfer electrode of the red filter pixel thin, the resistance of the transfer electrode in the row of the blue filter pixel matches the resistance of the transfer electrode in the row of the red filter pixel.
It is possible to avoid the above-described problems.

Although the example in which the transfer electrode of the red filter pixel is made thinner is shown here, the same effect can be obtained by making the transfer electrode of the green filter pixel in the row of the red filter pixel thinner.

Also, in FIG. 10A, the first layer transfer electrodes 115, 119 and 123 at the boundary between the unit pixel 162 of the blue filter and the unit pixel 161 of the green filter, and in FIG. First layer transfer electrodes 115, 119, and 12 at the boundary between pixel 163 and unit pixel 161 of the green filter.
3 is thinned over approximately half the width, but the same effect can be obtained even if the thickness of these electrodes is reduced over the entire thickness or remains large.

FIG. 11 shows an example of the configuration of a full frame transfer type CCD image sensor for explaining the third embodiment of the present invention. Green filter (G), magenta filter (Mg), cyan filter (Cy) every other row on each pixel
And yellow filters (Ye) are formed alternately. In the present embodiment, since the essential structure is the same as that of FIGS. 8 to 10 except for the filter arrangement, the cross-sectional view is omitted, but the film of the transfer electrode of the magenta filter pixel and the cyan filter pixel that transmits light of the blue wavelength is omitted. By reducing the thickness, it is possible to obtain the same effects as in the first and second embodiments.

Next, a basic manufacturing method for obtaining the structure of the embodiment of the present invention will be described with reference to FIGS. 12 and 13 using the method of manufacturing the full-frame transfer type CCD image sensor of the first embodiment as an example. Will be explained.

FIG. 12 shows the manufacturing process in the same cross section as FIG. 3 (c), that is, a cross section along the line CC 'in FIG.

After a channel stopper 11 of a high-concentration P layer and an N layer 12 forming a transfer channel of a vertical register are formed on a P-type silicon substrate 10, the P-type silicon substrate 1
A gate insulating film 13 having an oxide film or a stacked structure of an oxide film and a nitride film is formed on the gate insulating film 13. Thereafter, a silicon film 24 of polycrystalline silicon or amorphous silicon having a thickness of about 200 to 600 nm to be the first layer transfer electrode of the vertical register is deposited on the entire surface. After this, if necessary, phosphorus is diffused or phosphorus or arsenic is ion-implanted to reduce the resistance. An oxide film 25 having a thickness of about 20 to 50 nm is directly grown thereon, and a nitride film 26 having a thickness of about 20 to 100 nm is grown thereon. Next, using a photolithography technique, the photoresist 27 is patterned so as to cover portions other than the transfer electrode portion to be thinned (FIG. 1).
2 (a)). FIG. 13 shows a plane pattern of the photoresist at this time.

Next, after the nitride film 26 in the portion not covered with the photoresist is removed by dry etching, the oxide film 25 thereunder is removed by wet etching or dry etching (FIG. 12B).

Thereafter, the photoresist 27 is peeled off and the silicon film 24 of polycrystalline silicon or amorphous silicon exposed by thermal oxidation is oxidized until a desired film thickness remains to form an oxide film 28. 12 (c)).

Thereafter, the remaining nitride film 26 is removed.
Further, an oxide film 28 formed by thermally oxidizing the oxide film 25 and the silicon film 24 under the nitride film 26 is removed.

After that, the electrodes are patterned by the same photolithography and dry etching as in the prior art, and an interlayer film of an oxide film is formed by vapor phase growth or thermal oxidation, or a combination of both, and then the second layer transfer electrode is formed. The electrode material of polycrystalline silicon or amorphous silicon is deposited on the entire surface, and the above steps are repeated to reduce the thickness of the transfer electrode on the blue filter pixel.

In the case where the first layer transfer electrode is not thinned as in the example of FIG. 6, the above-mentioned step of thinning the first layer by thermal oxidation can be omitted.

In FIG. 12C, the conditions of the thermal oxidation for thinning are determined as follows. For example, the initial growth thickness of silicon is 200 nm, and finally 50 nm.
It is assumed that the film is thinned. When the silicon film is oxidized, the thickness of the oxide film to be reduced and the thickness of the formed oxide film are approximately 1: 2. Therefore, in the above example, since the thickness of the silicon film is reduced by 150 nm, thermal oxidation may be performed under the condition that an oxide film of 300 nm is formed. However, the first
When the interlayer film between the layer transfer electrode and the second layer transfer electrode is formed by thermally oxidizing the first layer transfer electrode, it is necessary to take into account the reduction in film thickness due to this step.

As an example, the initial growth thickness of silicon is 300 nm, and the final thickness is 50 n for a blue filter pixel.
m, other pixels are 200 nm, oxide film between layers is 200
Assume nm. In this case, the thermal oxidation in FIG. 12C is performed under the condition that an oxide film having a thickness of 300 nm is formed, and the thickness of the thinned portion is set to 150 nm. By setting the subsequent thermal oxidation for forming an interlayer film under the condition that an oxide film of 200 nm is formed, the thinned portion becomes 50 nm and the other portions become 200 nm. As described above, the initial growth film thickness and the thermal oxidation conditions for thinning may be determined according to the film thickness of the final thinned portion and the required film thickness of the interlayer film.

In the above description, an example is shown in which the silicon film is thinned by thermal oxidation after the resistance is reduced.
Conversely, it is also possible to reduce the resistance after thinning by thermal oxidation. Thus, the silicon film in which phosphorus is diffused at a high concentration is subjected to accelerated oxidation in which the oxidation rate is increased as compared with the silicon having a low concentration, so that it is possible to prevent the control of the oxide film thickness from becoming difficult.

The embodiment described above is not limited to this, and various modifications are possible. For example, the present invention is applicable not only to a full frame transfer type CCD image sensor but also to a frame transfer type CC having a similar pixel structure.
It can also be applied to a D image sensor. Also, when the transfer electrode is 2
Although only an example of a single-layer electrode has been described, the present invention can be applied to all or some of the layers even when a single-layer electrode is used, and also when a three- or more-layer electrode is used. Further, the present invention is also effective in a case where the filter arrangement is other than that shown here, or in the case of a vertical register in which an N-layer channel is formed in a P-layer provided on an N-type substrate.

[0064]

According to the present invention, the thickness of at least a part of the transfer electrode of a specific pixel including a pixel on which a color filter transmitting blue wavelength light is formed is changed to the thickness of the transfer electrode of another pixel. When the thickness is smaller than the thickness, sensitivity to blue light can be improved. Since the thickness of the transfer electrodes of other pixels and horizontal registers, and the gate electrodes of transistors of output amplifiers, etc. are not reduced, the transfer resistance of the vertical and horizontal registers is reduced or transferred due to an increase in the resistance of the electrodes. Efficiency degradation can be prevented. Further, it is possible to prevent a short circuit between the metal wiring and the substrate in the backing structure. Further, self-aligned ion implantation using the transfer electrode of the horizontal register and the gate electrode of the transistor of the amplifier as a mask becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a plan configuration diagram of a pixel according to the first embodiment of the present invention.

3 shows a first example of the first embodiment of the present invention, and is a cross-sectional view of a vertical register taken along a section line in a plan view of a pixel in FIG. 2;

FIG. 4 is a sectional view of the horizontal register and the output amplifier transistor of FIG. 1;

5 shows a second example of the first embodiment of the present invention, and is a cross-sectional view of the vertical register taken along line AA ′ of FIG. 2;

6 shows a third example of the first embodiment of the present invention, and is a cross-sectional view of the vertical register taken along line AA ′ of FIG. 2;

FIG. 7 is a configuration diagram of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 8 is a plan configuration diagram of the pixel of FIG. 7;

9 is a cross-sectional view of a vertical register according to a second embodiment of the present invention, taken along a section line in the plan view of the pixel in FIG. 8;

FIG. 10 is a cross-sectional view of a vertical register according to a second embodiment of the present invention, taken along another cutting line in the plan view of the pixel in FIG. 8;

FIG. 11 is a configuration diagram of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 12 is a process chart illustrating a method for manufacturing the solid-state imaging device according to the first embodiment of the present invention.

FIG. 13 is a view showing a photoresist pattern used in the step of FIG.

FIG. 14 is a configuration diagram of a conventional solid-state imaging device.

FIG. 15 is a plan view of the pixel shown in FIG. 14;

16 is a cross-sectional view of a vertical register taken along a cutting line in the plan configuration diagram of FIG. 15 of the conventional solid-state imaging device.

FIG. 17 is a plan view of a pixel of another conventional solid-state imaging device.

FIG. 18 is a cross-sectional view of a vertical register taken along a cutting line in the plan view of FIG. 17 of another conventional solid-state imaging device.

FIG. 19 is a sectional view of a horizontal register and an output amplifier transistor of a conventional solid-state imaging device.

[Explanation of symbols]

1, 101, 201, 301 Vertical register 2, 102, 202, 302 Horizontal register 3, 103, 203, 303 Output amplifier 10, 110, 310 P-type silicon substrate 11, 111, 311 Channel stopper 12, 112, 312 N layer 13, 113, 313 Gate insulating film 14, 16, 18, 20, 114, 116, 118, 1
20, 122, 124, 314, 316, 318, 32
0 second layer transfer electrodes 15, 17, 19, 115, 117, 119, 121,
123, 315, 317, 319 First layer transfer electrode 21, 121, 321 Interlayer film 24 Silicon film 25, 28 Oxide film 26 Nitride film 27 Photoresist 41, 141, 341 Green filter 42, 142, 342 Blue filter 43, 143 343 Red filter 51, 351 First layer transfer electrode of horizontal register 52, 352 Second layer transfer electrode of horizontal register 53, 353 Low concentration N layer 54, 354 Source region 55, 355 Drain region 56, 356 Gate electrode 62 , 162 unit pixel (B) 63, 163 unit pixel (R) 161 unit pixel (G) 362 unit pixel

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 AA02 AA03 AB01 BA08 BA12 CA08 EA07 EA17 EA20 FA06 FA35 FA40 GC08 5C024 CX41 CY47 EX24 EX52 JX05 JX23 5C065 AA01 BB13 BB30 BB34 DD06 DD11 EE06 EE07 EE08

Claims (23)

[Claims] 1. A vertical register having a function of generating an electric charge according to the intensity of light passing through an electrode and transferring the electric charge in one direction, and transferring the electric charge in a direction orthogonal to the one direction. A solid-state imaging device comprising: a horizontal register; and an output amplifier connected to one end of the horizontal register, wherein a color filter that transmits light of a predetermined wavelength is provided above an electrode of the vertical register. A solid-state imaging device, wherein an electrode of a vertical register corresponding to a specific color in a filter includes a thin-film electrode region having a smaller thickness than electrodes of other vertical registers. 2. The vertical register has a configuration in which a plurality of vertical registers are arranged in parallel with each other in a row and are connected to the horizontal register. The vertical register is one of different ones constituting the color filter for each column. The solid-state imaging device according to claim 1, which corresponds to a color filter. 3. An electrode of the vertical register, which is located above the vertical register, drives the vertical register, and scans two layers of different first and second electrodes orthogonally to a transfer direction of the vertical register. Wherein the second electrode has a configuration in which both end portions are overlapped above the first electrode, and at least the second electrode of the electrodes constituting the electrode of the vertical register corresponding to the specific color is 3. The solid-state imaging device according to claim 2, comprising the thin-film electrode region. 4. The color filter includes three color filters of a green (Green) filter, a red (Red) filter, and a blue (Blue) filter, and the vertical register includes a plurality of vertical registers arranged in parallel with each other. What is connected to the horizontal register, the vertical register, when the entire vertical register is viewed in a plan view, the green filters are arranged in a checkered pattern, when the vertical register is viewed column by column, In one column of vertical registers, a red filter is sandwiched between the green filters arranged in a checkered pattern,
2. The solid-state imaging device according to claim 1, wherein a blue filter is interposed between the green filters arranged in a checkered pattern in a vertical register adjacent to the one column of vertical registers. 3. 5. The color filter includes four color filters of a green (Green) filter, a magenta (Magenta) filter, a cyan (Cyan) filter, and a yellow (Yellow) filter, and the vertical register includes a plurality of vertical registers. Are arranged in parallel with each other and connected to the horizontal register, and the vertical register is configured such that when the entire vertical register is viewed in a row direction, cyan filters and yellow filters are alternately arranged in one row. 2. The solid according to claim 1, wherein green filters and magenta filters are alternately arranged in upper and lower rows adjacent to the one row, and the green filters and magenta filters in the upper and lower rows are shifted from each other by one column in the row direction. Imaging device. 6. The solid-state imaging device according to claim 2, wherein the specific color is blue. 7. The solid-state imaging device according to claim 4, wherein the specific color is blue and red, or green in a row in which a red filter is arranged when blue and the vertical register are viewed row by row. 8. The solid-state imaging device according to claim 5, wherein the specific colors are magenta and cyan. 9. An insulating film is formed between the electrode and the color filter, a contact penetrating the insulating film is provided on the insulating film, and the electrode is electrically connected to the electrode through the contact above the insulating film. And a portion of the electrode of the vertical register corresponding to the specific color where the contact is located is an electrode having the same thickness as the electrode of the other vertical register. 2,
9. The solid-state imaging device according to 3, 4, 5, 6, 7, or 8. 10. When the vertical register is cut along a plane perpendicular to the transfer direction, the thin-film electrode region is closer to the center of the vertical register corresponding to the specific color than the portion where the contact is located. Item 10. The solid-state imaging device according to Item 9. 11. A vertical register corresponding to the specific color and a vertical register adjacent thereto are separated by a channel stopper layer formed on a semiconductor substrate, and the contact is located above the channel stopper layer and
The solid-state imaging device according to claim 9, which is located inside. 12. When the vertical register is cut along a plane perpendicular to the transfer direction, the thin film electrode region is closer to the center of the vertical register corresponding to the specific color than the channel stopper layer. The solid-state imaging device according to claim 1. 13. An electrode above said horizontal register and driving said horizontal register is an electrode having the same thickness as an electrode of said another vertical register.
13. The solid-state imaging device according to 5, 6, 7, 8, 9, 10, 11 or 12. 14. An output gate electrode constituting said output amplifier is an electrode having the same thickness as an electrode of said another vertical register. , 1
The solid-state imaging device according to 0, 11, 12, or 13. 15. The method according to claim 1, wherein said electrode is made of a polycrystalline silicon film or an amorphous silicon film.
5, 6, 7, 8, 9, 10, 11, 12, 13, or 14
The solid-state imaging device according to any one of the preceding claims. 16. A vertical transfer channel for generating charges in accordance with the intensity of incident light and transferring the charges in one direction according to a signal voltage, and a channel stopper layer for separating the vertical transfer channels from each other. A semiconductor substrate is prepared, a gate insulating film is formed on the surface of the semiconductor substrate, a silicon film, an oxide film, and an oxidation resistant film are sequentially deposited on the gate insulating film, and the oxidation resistant film and the oxide film are formed. Using the same mask pattern as a mask, selectively remove the silicon film exposed region by partially removing the silicon film exposed region by exposing a part of the surface of the silicon film, and selectively oxidize the silicon film exposed region. Portion as an oxide film, the oxide film on the silicon film is removed, and the silicon film is exposed to a thin film electrode region of the silicon film exposed region and an electrode region other than the silicon film exposed region. A method of manufacturing a solid-state imaging device having a manufacturing method of partitioning the solid-state imaging device, wherein the thin film electrode region is formed in an electrode of a vertical transfer channel corresponding to a specific color among color filters constituting the solid-state imaging device. A method for manufacturing a solid-state imaging device, comprising: 17. A vertical transfer channel for generating charges in accordance with the intensity of incident light and transferring the charges in one direction according to a signal voltage, and a channel stopper layer for separating the vertical transfer channels from each other. A semiconductor substrate is prepared, a first gate insulating film is formed on a surface of the semiconductor substrate, and a first silicon film and a first silicon film are formed on the first gate insulating film.
Depositing an oxide film and a first oxidation-resistant film in this order, selectively removing the first oxidation-resistant film and the first oxide film using the same mask pattern as a mask, and forming a part of the surface of the first silicon film; Forming a first silicon film exposed region where the first silicon film is exposed, selectively oxidizing the first silicon film exposed region to form a part of the first silicon film exposed region as an oxide film, and oxidizing the first silicon film; After removing the film, the first silicon film is divided so as to be orthogonal to the charge transfer direction of the vertical transfer channel, and the first thin film electrode region of the first silicon film exposed region and the first silicon film exposed region Forming a first electrode including a first electrode region other than the first electrode region, removing the first gate insulating film between the first electrodes, the first oxidation-resistant film on the first electrode, and the first oxide film, and then performing a heat treatment. To form a second gate on the surface of the semiconductor substrate between the first electrodes. Forming an insulating film, forming an interlayer insulating film on the side and surface of the first electrode, and forming a second silicon film, a second oxide film, and a second oxidation-resistant film on the surface of the semiconductor substrate including the first electrode; Are sequentially deposited, and the second oxidation-resistant film and the second oxide film are selectively removed using the same mask pattern as a mask to expose a part of the surface of the second silicon film. Forming the second
Selectively oxidizing a silicon film exposed region to form a part of the second silicon film exposed region as an oxide film, removing the oxide film on the second silicon film, dividing the second silicon film, The second thin film electrode region and the second silicon film exposed region of the second silicon film exposed region are filled in between the first electrodes, and both ends partially overlap the first electrode so as to be parallel to the first electrode. A method of manufacturing a solid-state imaging device for forming a second electrode including a second electrode region other than the first electrode region, wherein the first thin-film electrode region and the second thin-film electrode region are formed of a color filter constituting the solid-state imaging device. A method of manufacturing a solid-state imaging device, wherein the method is formed in an electrode of a vertical transfer channel corresponding to a specific color. 18. The semiconductor substrate, in addition to the vertical transfer channel, is connected to a horizontal transfer channel for transferring charges transferred from the vertical transfer channel in a direction orthogonal to the one direction, and to one end of the horizontal transfer channel. And a horizontal transfer electrode for driving the horizontal transfer channel is formed at the same time as the first electrode region and the second electrode region. An output gate electrode for driving the output amplifier is The method of manufacturing a solid-state imaging device according to claim 17, wherein the method is formed simultaneously with the one electrode region or the second electrode region. 19. The method according to claim 16, wherein the specific color is blue, or blue and red, or magenta and cyan.
19. The method for manufacturing a solid-state imaging device according to 7 or 18. 20. The first thin film electrode region and the second thin film electrode region, when the vertical transfer channel is cut along a plane perpendicular to the transfer direction, the specific color is higher than the position of the center of the channel stopper layer. 20. The method of manufacturing a solid-state imaging device according to claim 17, 18 or 19, wherein the method is formed on a central portion side of a vertical transfer channel corresponding to. 21. The method according to claim 17, wherein the first silicon film and the second silicon film are doped with impurities when depositing a silicon film or immediately after depositing a silicon film.
21. The method for manufacturing a solid-state imaging device according to 19 or 20. 22. The first silicon film and the second silicon film are formed by depositing non-doped silicon films, respectively, and an oxide film on the first silicon film, respectively.
18. An impurity is introduced into the non-doped silicon film after removing the oxide film on the second silicon film.
22. The method for manufacturing a solid-state imaging device according to 18, 19, 20 or 21. 23. The method according to claim 17, wherein the first oxidation-resistant film and the second oxidation-resistant film are nitride films.
23. The method for manufacturing a solid-state imaging device according to 0, 21, or 22.