JPH09223788A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid-state image pickup device with a reduced number of manufacturing processes. SOLUTION: This device includes a horizontal charge transfer part an unnecessary change discharge part, and a potential barrier part all located under a horizontal charge transfer electrode, and a channel region of the horizontal charge transfer part and the unnecessary charge discharge part are formed in the same impurity profile. The horizontal charge transfer part becomes a depleted state owing to a potential VD applied to a diffusion layer disposed an one end thereof, and the unnecessary charge discharge part becomes a non- depleted state owing to a potential VD1 applied to a diffusion layer disposed at one end or both ends thereof.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to a solid-state image pickup device having a charge discharging portion formed adjacent to a horizontal charge transfer portion.

[0001]

2. Description of the Related Art A solid-state image pickup device which has been conventionally used as an input device of a camera-integrated VTR has been developed in recent years to have a higher number of pixels, and instead of exposing a film, optical information is converted into an electric signal to be a storage medium. It has been started to be used as an input device of an electronic still camera that is stored in a hard copy or viewed on a monitor screen.

In such a solid-state image pickup device, unnecessary signals exist in the photoelectric conversion section and the vertical and horizontal charge transfer sections. When used as an input device for a camera-integrated VTR, such unnecessary signal charges settle to a level that does not cause a problem after displaying several screens, so it is not a big problem, but as an input device for an electronic still camera. When used, there is a time delay until the shutter is actually opened and closed after being triggered by the shutter button, and there is a risk of losing the shutter chance.

Therefore, a solid-state image pickup device used as an input device of an electronic still camera is a camera-integrated VTR.
Unlike the case of being used for the above, it is necessary to remove all unnecessary signal charges existing in the photoelectric conversion part and the vertical and horizontal charge transfer parts at the same time when the trigger is applied by the shutter button.

As means for removing such unnecessary charges, the unnecessary charges existing in the photoelectric conversion portion are removed by forming a P-type semiconductor region having a low concentration directly under the N-type semiconductor region forming the photoelectric conversion portion. Then, by applying a reverse bias voltage to the N-type semiconductor substrate, blooming control is performed to remove the excess charge to the N-type semiconductor substrate, and the signal charge is removed to the N-type semiconductor substrate by depleting the N-type semiconductor region itself. This has been achieved by forming a vertical overflow drain structure that conforms to the standards (Journal of the Television Society, Vol 37. No 10).
(1983) pp782-787).

Further, since unnecessary charges existing in the horizontal charge transfer section can be operated at a high speed in the horizontal charge transfer section, they are dealt with by removing them in the reset drain provided at the end of the horizontal charge transfer section by a normal operation. Has been done.

On the other hand, in order to remove the unnecessary charges existing in the vertical charge transfer section, it is necessary to transfer at least one to several screens.

As a method of removing unnecessary charges existing in such a vertical charge transfer unit, a still camera is provided with a drain for removing unnecessary charges at the end of the vertical charge transfer unit opposite to the horizontal charge transfer unit. A first method for removing unnecessary charges by setting the buried channel of the vertical charge transfer portion and the substrate in the reverse bias even when it is not in use (Japanese Patent Laid-Open No. 6-58242).
No. 8-31671), a drain for removing unnecessary charges is arranged at the end of the vertical charge transfer unit opposite to the horizontal charge transfer unit, and the unnecessary charges in the vertical charge transfer unit are removed by reverse transfer. And a third method (Japanese Patent Laid-Open No. 58-31672) for removing unnecessary charges by arranging a drain at the connection between the horizontal charge transfer section and the vertical charge transfer section and controlling the reset gate. Proposed.

However, according to the first method, the vertical charge transfer electrode is always in a depleted state, that is, in a high resistance state.
There is a drawback in that the time for removing unnecessary charges in the vertical charge transfer section is very long, and that a reverse bias power supply must always be applied. In the second method, unnecessary charges in the vertical charge transfer unit are removed by being transferred in the reverse direction, so that a defect occurs due to local signal loss due to a difference from the normal signal charge transfer direction. However, there is a drawback that the driving method of the solid-state imaging device becomes complicated in order to compensate for this drawback. In the third method, the control gate and the unnecessary charge discharging drain have to be formed in a small area by miniaturization, which is difficult to manufacture, and a pulse for controlling the control gate is required, which drives the solid-state imaging device. Has the drawback of being complicated.

For this reason, recently, an unnecessary charge discharging region is generally formed adjacent to the horizontal charge transfer unit, and the unnecessary charges of a plurality of vertical charge transfer units are simultaneously transferred in the forward direction, whereby the unnecessary charges are discharged. A method for removing it has been proposed (JP-A-2-205359, JP-A-62-154881).

FIG. 14 is a schematic diagram of the structure of a conventional solid-state image pickup device having a charge discharging unit adjacent to a horizontal charge transfer unit. The photoelectric conversion unit 1101, the vertical charge transfer unit 1102, the horizontal charge transfer unit 1103, and the output. The N ⁺⁺ type semiconductor region 11 provided at one end of the circuit portion 1104, the unnecessary charge discharging portion 1105, and the unnecessary charge discharging portion 1105 and connected to the power supply voltage
It is composed of 06.

FIG. 15 is a plan view of a region having an unnecessary charge discharging unit 1105 adjacent to the conventional horizontal charge transfer unit 1103 of FIG. 14, which is a vertical charge transfer channel 1201, a horizontal charge transfer channel 1202, and a potential barrier region. 120
3, the unnecessary charge discharging area 1204, the first horizontal charge transfer electrode 1205, the second horizontal charge transfer section 1206, and the final vertical charge transfer electrode 1207.

FIG. 16 is a cross-sectional view of the conventional solid-state image pickup device of FIGS. 14 and 15 taken along the line II 'and a drawing showing the potential potential. The conventional solid-state imaging device has an N ^-- type semiconductor substrate 1301 with an impurity concentration of about 2.0 × 10 ¹⁴ cm ^-3.
And the P-type well layer 1302 having an impurity concentration of about 1.0 × 10 ¹⁶ cm ⁻³ , and the impurity concentration of the buried channels of the vertical charge transfer section, the horizontal charge transfer section and the potential barrier section being 1.
The N-type semiconductor region 1303 of about 0 × 10 ¹⁷ cm ⁻³ and the impurity concentration of the unnecessary charge discharging portion of 1.0 × 10 ¹⁸ cm ^−3.
The extent of N ⁺ -type semiconductor region 1305, a P ⁺ -type semiconductor regions 1307 impurity concentration of about 1.0 × 10 ¹⁸ cm ^-3 constituting the element isolation portion, a made of polycrystalline silicon 1308 of the first layer 1 Horizontal charge transfer electrode 1205 and the final vertical charge transfer electrode 1 made of the second layer polycrystalline silicon 1309.
207. Here, the vertical charge transfer section, the vertical horizontal connection section, and the N-type semiconductor region 13 immediately below the potential barrier section.
03 is formed with a width narrower than that of the N-type semiconductor region 1303 directly below the horizontal charge transfer portion so as to obtain a narrow channel effect. In addition, the N ⁺ type semiconductor region 1305 forming the unnecessary charge discharging part is an N ⁺⁺ type semiconductor region 1106 having an impurity concentration of about 1.0 × 10 ²⁰ cm ⁻³ provided at one end of the unnecessary charge discharging part. Through the power supply voltage V _{D of} about 15V
Is applied to the N ⁺ -type semiconductor region 130 of the unnecessary charge discharging portion.
No. 5 is in a non-depleted state. On the other hand, the channel of the horizontal charge transfer portion is in a depleted state because the impurity concentration and the power supply voltage are applied. That is, in the unnecessary charge discharging portion, holes supplied from the N ⁺⁺ type semiconductor region 1106 exist in the entire unnecessary charge discharging portion, and as soon as charges are injected into the unnecessary charge discharging portion, they are recombined with the holes and the holes are recombined. The electric charge is in a state of disappearing. Further, the potential potential ΨB of the potential barrier portion is formed to be deeper than the potential potential ΨV _H formed in the vertical horizontal connection portion so as not to return to the vertical charge transfer portion 1102.

FIG. 17 shows a conventional solid-state image pickup device II-II '.
It is a figure which shows the cross-sectional view of a surface, and a potential. The solid-state imaging device includes an N ^-- type semiconductor substrate 1301 and a P well layer 1
302, and an N-type semiconductor region 130 forming buried channels of the vertical charge transfer unit, the horizontal charge transfer unit, and the charge barrier unit.
3, an N ⁻ -type semiconductor region 1304 having an impurity concentration of about 7.0 × 10 ¹⁶ cm ^−3, which constitutes a buried channel in the potential barrier region of the horizontal charge transfer portion, a floating diffusion layer portion and a reset drain portion. N ⁺⁺ type semiconductor regions 1306, 1311
A first horizontal charge transfer electrode 1205 composed of a P ⁺ -type semiconductor region 1307 and a first-layer polycrystalline silicon 1308, which form an element isolation portion, and a second-layer polycrystalline silicon 130.
It is composed of a second horizontal charge transfer electrode 1206 composed of nine. Here, the power supply voltage V _{D of} about 15 V is normally applied to the N ⁺⁺ type semiconductor region 1306 which constitutes the reset drain of the signal charge.

FIG. 18 shows a conventional solid-state image pickup device III-II.
3 is a cross-sectional view of the I ′ plane and a drawing showing a potential potential. The semiconductor device includes a ^N-over type semiconductor substrate 1301, a P-type well layer 1302, required an N ⁺ -type semiconductor region 1305 that constitutes the charge discharging section, unnecessary charge discharging unit N ⁺⁺ type semiconductor which is provided at one end of the Region 1306, P ⁺ semiconductor region 1307 forming the element isolation portion, and first-layer polycrystalline silicon 1
It is composed of a first horizontal charge transfer electrode 1205 made of 308 and a second horizontal charge transfer electrode 1206 made of second layer polycrystalline silicon 1309. Here, the N ⁺ -type semiconductor region 1305 that constitutes the unnecessary charge discharging section, the power supply voltage V _D of usually about 15V through the N ^{+ +} -type semiconductor region 1306 is provided at one end of the unnecessary charge discharging unit is applied Has been done. The power supply voltage V _D which is applied to the N ⁺ -type semiconductor region 1306 in FIG. 18, the same power supply and the power supply voltage V _D which is applied to the N ⁺⁺ type semiconductor region 1306 in FIG. 17.

The operation of the conventional semiconductor device having such a structure will be described with reference to FIG.

During the unnecessary charge discharging period, as described above, the unnecessary charge removal depending on the photoelectric conversion unit 1101 is performed.
A P ^- type semiconductor region having a low concentration is formed immediately below the N-type semiconductor region that constitutes the photoelectric conversion unit, and a reverse bias voltage is applied to the N-type semiconductor substrate 1301 to deplete the N-type semiconductor region itself, thereby depleting the signal charge. Are all N-type semiconductor substrates 130
Remove to 1.

In addition to the above operation, the vertical charge transfer section 1102
Unnecessary charges existing in the horizontal charge transfer section 1103 are simultaneously transferred to the horizontal charge transfer section 1103 by clock pulses of four layers, for example. The horizontal charge transfer electrodes 1205 and 1206 are shown in FIG.
The high level voltage V _H to .phi.H ₁ shown is, the low level voltage V _L are applied to .phi.H _2, the horizontal charge transfer portion 110
The excess charge overflowing at 3 does not return to the vertical charge transfer portion 1102, and the potential potential ΨB of the potential barrier portion is
Beyond the N ⁺ semiconductor region 13 of the unnecessary charge discharging portion 1105
It is absorbed and removed in 05.

The unnecessary charges remaining in the horizontal charge transfer section 1103 are reset at the end of the horizontal charge transfer section 1103 by the normal high-speed operation of the horizontal charge transfer section by a two-phase clock pulse as shown in FIG. It is absorbed and removed in the N ⁺⁺ type semiconductor region 1306 of the drain.

Then, when shifting to the signal charge transfer period,
The vertical charge transfer unit 1102 corresponds to the signal charge accumulated in the photoelectric conversion unit 1101 according to the amount of light incident at a predetermined time.
After being read out to each of the vertical charge transfer units 1102, each horizontal line transferred vertically in the vertical charge transfer units 1102 is sent to the horizontal charge transfer unit 1103, and is horizontally transferred in the horizontal charge transfer units 1103 and vertically. It is output via the circuit unit 1104.

As described above, even when the signal charge having a transfer capacity higher than that of the horizontal charge transfer section is transferred from the vertical charge transfer section, the excess charge does not flow back to the vertical charge transfer section.
It can be made to flow to the unnecessary charge removal region. Therefore, it is possible to prevent adverse effects such as a white crushed phenomenon on the monitor screen.

[0021]

However, in the solid-state image pickup device having the unnecessary charge discharging section adjacent to the horizontal charge transfer section as described above, in order to remove the unnecessary charge overflowing in the horizontal charge transfer section, The horizontal charge transfer channel 1202, the potential barrier region 1203, and the unnecessary charge discharging region 1204 must be formed under the charge transfer electrode 1205. At this time, the conventional solid-state imaging device has a drawback that the number of manufacturing steps increases because it is necessary to form the N-type semiconductor region 1303 and the N ⁺ -type semiconductor region 1305 having different impurity concentrations under the horizontal charge transfer electrode. It was

Further, since the N ⁺ type semiconductor region 1305 which becomes an unnecessary charge transfer portion having a relatively high impurity concentration is formed below the horizontal charge transfer portion, when the gate insulating film below the horizontal charge transfer electrode is formed in a later step. , N ⁺ -type semiconductor region 1305, by outward diffusion of impurities,
There is also a drawback that an abnormal diffusion layer is formed in the N ⁻ type semiconductor region 1304 and the potential potential fluctuates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid-state image pickup device having a small number of manufacturing steps.

Another object of the present invention is to provide a solid-state imaging device in which the potential potential does not fluctuate due to the abnormal diffusion layer. The solid-state imaging device of the present invention includes a photoelectric conversion unit, a vertical charge transfer unit disposed adjacent to the photoelectric conversion unit, and an adjacent vertical charge transfer unit disposed adjacent to one end of the vertical charge transfer unit. A horizontal charge transfer section for accumulating electric charges and an unnecessary charge discharging section for receiving charges overflowing the horizontal charge transfer section, and the channel region of the horizontal charge transferring section and the unnecessary charge discharging section have the same impurity profile. , The channel region of the horizontal charge transfer portion is in a depleted state due to the application of the first potential, and the unnecessary charge discharging portion has the second potential different from the first potential.
The solid-state imaging device is characterized in that it is in a non-depleted state due to the application of the electric potential.

Further, another solid-state image pickup device of the present invention has a shift register for transferring charges and a reset transistor connected to the shift register for converting the charges into a voltage and having a region to which a reset voltage is applied. It is characterized by having an output circuit and an overflow drain which receives a charge overflowing in the shift register and to which a drain voltage different from the reset voltage is applied.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to clarify the above and other objects, features, and effects of the present invention, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view of the configuration of a solid-state image pickup device having a charge discharging unit adjacent to the horizontal charge transfer unit according to the first embodiment of the present invention.
And a vertical charge transfer unit or CCD shift register 102
And a horizontal charge transfer unit or CCD shift register 103
The output circuit section 104, the unnecessary charge discharging section or the overflow drain 105, and the N ⁺⁺ type semiconductor region 10 provided at one end of the unnecessary charge discharging section and connected to the constant voltage V _D1.
6. φ1 to 4 are vertical charge transfer units 1
This is a drive signal for driving 02.

FIG. 2 is an enlarged plan view of the solid-state image pickup device according to the first embodiment of the present invention shown in FIG. 1 in the vicinity of the line II ′. This solid-state imaging device includes a vertical charge transfer channel 201, a horizontal charge transfer channel 202, a potential barrier region 203,
Unnecessary charge discharging area or overflow drain area 204
A first horizontal charge transfer electrode 205 made of polycrystalline silicon for the first layer, and a second horizontal charge transfer electrode 205 made of polycrystalline silicon for the second layer.
The horizontal charge transfer electrode 206, the final vertical charge transfer electrode 207, and the vertical horizontal connection region 208. The vertical charge transfer channel 201, the horizontal charge transfer channel 202, the unnecessary charge discharge region 204, and the vertical horizontal connection region 208 are formed by being surrounded by a P-type semiconductor region, which is provided outside the dotted line and serves as an element isolation portion. The horizontal charge transfer signal φH ₁ is applied to the first and second horizontal charge transfer electrodes 205 and 206. A horizontal charge transfer signal φH ₁ is applied to the first and second horizontal charge transfer electrodes provided adjacent to the first and second horizontal charge transfer electrodes 205 and 206.
, And a horizontal charge transfer signal φH ₂ complementary thereto is applied. A final vertical charge transfer signal φ is applied to the final vertical charge transfer electrode.
VLAST is applied.

FIG. 3 is a cross-sectional view of the solid-state image pickup device according to the first embodiment of the present invention shown in FIGS. 1 and 2 and a drawing showing a potential potential. This solid-state imaging device has an N ^-- type semiconductor substrate 301 with an impurity concentration of about 2.0 × 10 ¹⁴ cm ^-3.
And a P-type well layer 302 having an impurity concentration of about 1.0 × 10 ¹⁶ cm ⁻³ , a vertical charge transfer section, a horizontal vertical connection section, a buried channel of a horizontal charge transfer section and a potential barrier section, and an unnecessary charge discharging section. impurity concentration constituting the is 1.0 × 10 ¹⁷ cm ^-3 of about N-type semiconductor region 303, the impurity concentration is 1.0 × 10 ¹⁸ cm ^-3 of P ⁺ -type semiconductor region 3 forming the device isolation region
07, the first-layer polycrystalline silicon 308 as the first horizontal charge transfer electrode 205, and the final vertical charge transfer electrode 2
The second layer 07 is made of polycrystalline silicon 309. Unlike the conventional solid-state imaging device, the embedded channel of the horizontal charge transfer unit and the unnecessary charge discharging unit are formed of semiconductor regions having the same impurity profile.

Potential potential φB of the potential barrier section 203
Are formed to be deeper than the potential potential ΨV _H formed in the vertical / horizontal connection portion 208 so as not to return to the vertical charge transfer portion 102. For more information,
As shown in FIG. 2, the width of the N-type semiconductor region 303 of the potential barrier unit 203 is the N-type semiconductor region 30 of the horizontal charge transfer unit.
The width of 3 is formed narrow, and the potential of ΨB is set by the narrow channel effect. Also, the vertical and horizontal connection portion 208
The potential potential Ψ V _{H of is} also set by the narrow channel effect.

FIG. 4 is a cross-sectional view of the solid-state image pickup device of FIG. 1 according to the first embodiment of the present invention taken along the line II-II ′ and a drawing showing a potential. This solid-state imaging device includes an N ^-- type semiconductor substrate 301, a P well layer 302, and an N-type semiconductor region 30.
3, and an N ⁻ type semiconductor region 304 having an impurity concentration of about 7.0 × 10 ¹⁶ cm ^−3, which serves as a charge barrier region of the horizontal charge transfer portion,
N ^{+ +} type semiconductor region 31 constituting a floating diffusion region and a reset drain part or a reset transistor, respectively.
1, 306, a P ⁺ type semiconductor region 307 forming an element isolation portion, a first layer of polycrystalline silicon 308 forming a first horizontal charge transfer electrode 205, and a second horizontal charge transfer electrode 206. And a second layer of polycrystalline silicon 309. A power supply voltage V ^{D of} about 15 V is normally applied to the N ⁺⁺ type semiconductor region 306 which constitutes the reset drain of the signal charge. Therefore, the channel region under the horizontal charge transfer portion is in a depleted state. By applying complementary horizontal charge transfer signals φH ₁ and φH ₂ to the horizontal charge transfer electrodes, the potential potential changes as shown in the figure. V _OG is a constant voltage signal applied to the final horizontal charge transfer electrode. The charge information accumulated in the floating diffusion region 311 is transmitted to the output circuit unit 312 as illustrated. φR is a reset pulse.

FIG. 5 is a cross-sectional view of the solid-state image pickup device of FIG. 1 according to the first embodiment of the present invention taken along line III-III ′ and a drawing showing a potential. The solid-state imaging device includes a ^N-over type semiconductor substrate 301, a P-type well layer 302, an N-type semiconductor region 306 constituting the unnecessary charge discharging unit, a P ⁺ -type semiconductor region 307 constituting the element isolation portion, a A first layer of polycrystalline silicon 308 forming one horizontal charge transfer region 307;
The second horizontal charge transfer region 206 is composed of a second layer of polycrystalline silicon 309. Electric potential of the N-type semiconductor region 303 below the horizontal charge transfer electrodes horizontal charge transfer signal .phi.H ₂ of low level is applied, the horizontal potential PusaiH _L, and the horizontal charge transfer signal .phi.H _H of a high level is applied charge N-type semiconductor region 3 under the transfer electrode
The potential potential of 03 is ΨH _H. Unnecessary charge discharging section, N type semiconductor electric potential of the region 303 so that the non-depleted even when ΨH _L, unnecessary charge discharging unit N ⁺⁺ type semiconductor region 306 which is provided at one end of the
A constant voltage V _D1 is applied via the. That is, when the first horizontal charge transfer electrode 205 is at a low level, the N ⁺⁺ type semiconductor region 106, which is provided at one end of the unnecessary charge discharging part, is formed in the N type semiconductor region 303 forming the unnecessary charge discharging part. Three
First shallower than electric potentials PusaiH _L formed in the N-type semiconductor region 303 of the lower horizontal charge transfer electrodes 205 via the 06, the constant voltage V _D1 as deeper than the potential potential ΨB potential barrier section is applied (See Figure 3). In this case, between the constant voltage V _D1 and electric potential PusaiH _L, the difference between the constant voltage V _D1 and electric potential ΨB it may be desirable respectively than 0.5V. That is, when the constant potential V _D1 is shallower than the potential potential ΨB, there arises a problem that the charges flow back from the unnecessary charge discharging portion to the horizontal charge transfer portion. On the other hand, the constant potential V _D1 is the potential potential Ψ.
When it is deeper than H _L, the unnecessary charge discharging portion immediately below where the low level is applied to the horizontal charge transfer electrode is in a depleted state. Then, since the unnecessary charge discharging portion has a high resistance, the supply of holes from the N ⁺⁺ type semiconductor region 306 is delayed,
There is a problem that the unnecessary electric charge discharging section delays absorption and removal of unnecessary electric charges. Therefore, the constant voltage V _D1 must be provided between the potential potentials ΨH _{L and} ΨB, and considering the operation margin, the range described above is desirable.

Next, the operation of the solid-state image pickup device according to the first embodiment of the present invention will be described with reference to FIGS. 6 is a drawing corresponding to the potential potential diagram of FIG. 3, FIG.
8 is a drawing corresponding to the potential potential diagram of FIG.
FIG. 6 is a timing waveform chart showing an unnecessary charge discharging period and a signal charge transfer period.

During the unnecessary charge discharging period, unnecessary charges existing in the photoelectric conversion unit 101, the vertical charge transfer unit 102, and the horizontal charge transfer unit 103 are removed. The method of removing unnecessary charges existing in the photoelectric conversion unit 101 is the same as in the conventional N
A P ⁻ type semiconductor region having a low concentration is formed immediately below the type semiconductor region, and a reverse bias voltage is applied to the N type semiconductor substrate 301 to deplete the N type semiconductor region itself and all the signal charges to the N type semiconductor substrate 301. To remove.

With the above operation, the unnecessary charges existing in the vertical charge transfer unit 102 are simultaneously transferred to the horizontal charge transfer unit 103 by four-phase clock pulses, for example.
At this time, the first and second horizontal charge transfer electrodes 205, 20
6, a high level voltage V _H is applied to the first horizontal charge transfer signal φH ₁ and a low level voltage V _L is applied to the second horizontal charge transfer signal φH ₂ . Therefore, as shown in FIG. 6A, charges are accumulated in the channel region of the horizontal charge transfer unit 103. After that, the excess charge that further accumulates and overflows the channel region of the horizontal charge transfer unit 103 crosses the potential barrier unit 203 and reaches the N-type semiconductor region 303 of the unnecessary charge discharging unit 105 as illustrated in FIG. 6B. Are absorbed and removed.

Thereafter, the unnecessary charges remaining in the horizontal charge transfer unit 103 are provided at the end of the horizontal charge transfer unit 103 by the normal high-speed operation of the horizontal charge transfer unit by the two-phase clock pulse shown in FIG. It is absorbed and removed by the N ^{+ +} type semiconductor region 306 of the reset drain. At this time, when the first and second horizontal charge transfer signals are inverted, as shown in FIG. 6C, the potential potential of the channel region of the horizontal charge transfer unit becomes shallow, and the charges overflow in the horizontal charge transfer unit. However, the overflowed charges are removed by being transferred in the horizontal direction of the horizontal charge transfer unit.

Then, in the signal charge transfer period, after the signal charges accumulated in the photoelectric conversion unit 101 are read out to the corresponding vertical charge transfer units 102 by the amount of light incident at a predetermined time, each vertical charge is transferred. Each horizontal line transferred in the charge transfer unit 102 in the vertical direction is sent to the horizontal charge transfer unit 103. In the horizontal charge transfer unit 103, since the horizontal transfer signals are sequentially switched, as shown in FIG.
The signal charge is transferred in the horizontal direction, and the floating charge region 311
To stay in. The signal charge is output via the output circuit 104. Then, as shown in FIG. 7C, a reset pulse φe is applied to reset the potential potential of the floating charge region 311.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 9 is a schematic view of the configuration of a solid-state image pickup device having a charge discharging unit adjacent to the horizontal charge transfer unit according to the second embodiment of the present invention, and that of the first embodiment of the present invention. The difference is that the constant voltage V _D2 is applied to the N ⁺⁺ type semiconductor region 106 provided at one end of the unnecessary charge discharging portion.

FIG. 10 is a cross-sectional view of the II ′ plane of the solid-state imaging device according to the second embodiment of the present invention in FIG. 9 and a drawing showing the potential potential, and FIG. 11 is the present invention in FIG. 3A is a cross-sectional view taken along line III-III ′ of the solid-state imaging device according to the second embodiment and FIG. The difference from the first embodiment of the present invention is that when the horizontal charge transfer signals φH ₁ and φH ₂ applied to the horizontal charge transfer electrodes are both high level signals, the N-type which constitutes the unnecessary charge discharging portion is formed. Semiconductor region 3
03 through the N ⁺⁺ type semiconductor regions 106 and 306,
N-type semiconductor region 30 under the first horizontal charge transfer electrode 205
A voltage V _{D2 that} is shallower than the potential potential ΨH _H formed in 3 and deeper than the potential potential ΨB of the potential barrier portion is applied. In this case, it is desirable that the difference between the constant voltage V _D2 and the potential potential ΨH _H and the difference between the constant voltage VD ₂ and the potential potential ΨB be 0.5 V or more.

The operation is almost the same as that of the first embodiment, except that the horizontal charge transfer signal applied to the horizontal charge transfer electrodes 205 and 206 in the unnecessary charge discharging period is different as shown in FIG. That is, when φH ₁ and H ₂ are both at a high level, charges are transferred to the channel region below the horizontal charge transfer unit and the unnecessary charge discharging unit.

According to the second embodiment, the first aspect of the present invention
Are possible embodiment of the solid-state imaging device and the same operation, and the constant voltage V _D2 is the horizontal charge transfer signal .phi.H ₁ is not required to set the constant voltage V _D2 thinking when a low level There is an advantage that the constant voltage setting margin of the constant voltage V _D1 of the first embodiment is further expanded.

FIG. 13 is a drawing showing a third embodiment of the present invention. The present embodiment is different from the first and second embodiments in that an N ⁺⁺ type impurity region 106 to which the constant voltage V _D1 or the constant voltage V _D2 is applied is arranged at both ends of the unnecessary charge discharging portion 105. It is that.

Therefore, N ^{++ is} generated from the unnecessary charge discharging portion 105.
This has the advantage that the distance of the type semiconductor region 106 is shortened and the ability to remove unnecessary charges is improved.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified as long as the scope of the invention does not change.

For example, in the above-described embodiment of the present invention, the charge transfer device in which the potential barrier section is formed by the narrow channel effect of the charge transfer channel has been described. Even in the charge transfer region where the potential barrier portion is formed by introducing impurities of opposite conductivity type, a dedicated electrode is arranged, and a desired potential is applied to the electrode to form the potential barrier portion. It goes without saying that the same can be applied to the device.

In the above-described embodiment of the present invention,
The N ⁺⁺ type semiconductor region, which serves as a reset drain to which a constant voltage is applied only to one end of the horizontal charge transfer region, and the output circuit section are arranged, but the N ⁺⁺ type serves as a reset drain at both ends of the horizontal charge transfer section. It goes without saying that the same can be applied to a solid-state imaging device in which a semiconductor region and an output circuit section are arranged.

Further, in the above-described embodiment of the present invention, an example in which it is applied to a buried type two-phase drive charge transfer device has been described.
It goes without saying that the same can be applied to a charge transfer device of a four-phase or four-phase drive.

[0048]

As described above, according to the present invention, the semiconductor region formed with the same impurity profile is used as the N-type semiconductor region used as the unnecessary charge discharging portion in the non-depleted state, so that the conventional solid state can be obtained. The same operation as that of the image pickup device can be performed, and the N-type semiconductor region of the unnecessary charge discharging portion can be formed with the same impurity profile as that of the N-type semiconductor region of the charge transfer channel of the horizontal charge transfer portion. There is an effect that the number of manufacturing steps can be reduced as compared with the device.

Further, since it is not necessary to form the N ⁺ type impurity region serving as an unnecessary charge discharging portion having a relatively high impurity concentration below the horizontal charge transfer electrode, a gate insulating film below the horizontal charge transfer electrode is formed in a later step. In this case, the out-diffusion of impurities from the N + -type semiconductor region causes abnormal diffusion in the N-type semiconductor region serving as the channel region or the potential barrier portion, resulting in fluctuation of the potential potential. There is an effect that the disadvantage of can be solved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a solid-state imaging device having an unnecessary charge discharging unit adjacent to a horizontal charge transfer unit according to a first embodiment of the present invention.

FIG. 2 is a plan view of a region having an unnecessary charge discharging unit adjacent to the horizontal charge transfer unit according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an I- of the solid-state imaging device according to the first embodiment of the present invention.
3 is a cross-sectional view of the I ′ plane and a drawing showing a potential potential.

FIG. 4 is a II of the solid-state imaging device according to the first embodiment of the present invention.
3 is a cross-sectional view of the -II 'plane and a drawing showing a potential potential.

FIG. 5: II of the solid-state imaging device according to the first embodiment of the present invention
3 is a cross-sectional view of the I-III ′ plane and a drawing showing a potential.

FIG. 6 shows an I- of the solid-state imaging device according to the first embodiment of the present invention.
It is a timing waveform diagram of the potential of the I'plane.

FIG. 7 is a II of the solid-state imaging device according to the first embodiment of the present invention.
It is a timing waveform diagram of the potential potential of the -II 'plane.

FIG. 8 is a diagram showing an example of clock pulses applied to a horizontal charge transfer unit of the solid-state imaging device according to the first embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a solid-state imaging device having an unnecessary charge discharging unit adjacent to a horizontal charge transfer unit according to a second embodiment of the present invention.

FIG. 10 shows a solid-state image pickup device according to a second embodiment of the present invention.
3 is a cross-sectional view of the I-I 'plane and a drawing showing a potential potential.

FIG. 11 shows a solid-state image pickup device according to a second embodiment of the present invention.
3 is a cross-sectional view of the III-III ′ plane and a drawing showing a potential potential.

FIG. 12 is a diagram showing an example of clock pulses applied to the horizontal charge transfer unit of the solid-state imaging device according to the first embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a solid-state imaging device having an unnecessary charge discharging unit adjacent to a horizontal charge transfer unit according to a fourth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a solid-state imaging device having an unnecessary charge discharging unit adjacent to a conventional horizontal charge transfer unit.

FIG. 15 is a plan view of a region having an unnecessary charge discharging unit adjacent to a conventional horizontal charge transfer unit.

FIG. 16 is a cross-sectional view of the conventional solid-state imaging device taken along the line II ′ and a drawing showing a potential potential.

FIG. 17 is a cross-sectional view of the conventional solid-state imaging device taken along the line II-II ′ and a drawing showing a potential potential.

FIG. 18 is a cross-sectional view of a conventional solid-state imaging device taken along the line III-III ′ and a drawing showing a potential potential.

FIG. 19 is a diagram showing an example of clock pulses applied to a horizontal charge transfer unit of a conventional solid-state imaging device.

[Explanation of symbols]

Reference Signs List 101 photoelectric conversion unit 102 vertical charge transfer unit 103 horizontal charge transfer unit 104 output circuit unit 105 unnecessary charge discharging unit 106 N ⁺⁺ type semiconductor region 201 vertical charge transfer channel 202 horizontal charge transfer channel 203 potential barrier region 204 unnecessary charge discharging region 205 first horizontal charge transfer electrodes 206 second horizontal charge transfer electrodes 207 final vertical charge transfer electrodes 208 perpendicular horizontal connection area 301 N ^{over over} type semiconductor region 302 P-type well layer 303 N-type semiconductor region 304 N ^- -type semiconductor region 305 N ⁺ type semiconductor region 306 N ⁺⁺ type semiconductor region 307 P ⁺⁺ type semiconductor region 308 First layer polycrystalline silicon 309 Second layer polycrystalline silicon 310 Insulating film 311 Floating diffusion region

Claims (8)

[Claims] 1. A photoelectric conversion unit, a vertical charge transfer unit disposed adjacent to the photoelectric conversion unit, and a vertical charge transfer unit disposed adjacent to one end of the vertical charge transfer unit and transferred from the vertical charge transfer unit. A horizontal charge transfer part for accumulating electric charges and an unnecessary charge discharging part for receiving charges overflowing the horizontal charge transfer part, and the channel region of the horizontal charge transfer part and the unnecessary charge discharging part have the same impurity profile. And the channel region of the horizontal charge transfer portion is in a depleted state by being applied with a first potential, and the unnecessary charge discharging portion is applied with a second potential different from the first potential. The solid-state imaging device is characterized in that it is in a non-depleted state. 2. The solid-state imaging device according to claim 1, further comprising a diffusion layer disposed at at least one end of the unnecessary charge discharging unit, wherein the second potential is applied to the diffusion layer. 3. The solid-state imaging device according to claim 1, further comprising a diffusion layer disposed at at least one end of the horizontal charge transfer unit, wherein the first potential is applied to the diffusion layer. apparatus. 4. The solid-state imaging device according to claim 1, wherein a high level voltage is applied to all of the horizontal charge transfer electrodes provided in the horizontal charge transfer section. 5. The solid-state image pickup device according to claim 1, wherein the second potential is shallower than the potential potential of the depleted state of the unnecessary charge discharging portion by 0.5 V or more. 6. A shift register for transferring charges, an output circuit having a reset transistor connected to the shift register for converting the charges into a voltage, the reset transistor having a region to which a reset voltage is applied, and the inside of the shift register. And an overflow drain to which a drain voltage different from the reset voltage is applied. 7. The solid-state imaging device according to claim 6, wherein the shift register has a buried channel region having the same impurity concentration as the impurity concentration of the overflow drain. 8. The solid-state imaging device according to claim 6, wherein the drain voltage is a voltage that does not completely deplete the overflow drain.