JPH0945886A - Amplifying semiconductor image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a gate electrode and others thick enough so as to prevent an amplifying semiconductor image pickup device from deteriorating in smear characteristics by a method wherein light rays are made to enter the rear of a substrate, and the substrate is made small in thickness. SOLUTION: In an amplifying semiconductor image pickup device, the rear of a silicon substrate 1 is made to serve as a light incident plane 1a, so that light rays enters the rear of the silicon substrate 1. Provided that a distance between the rear-side end of a depletion layer induced by a PN junction formed between the P-type silicon substrate 1 and an N<-> -type well layer 2 and the light incident plane 1a is represented by d1 , and a depth of light penetration to the wavelength of light rays entering the light incident plane 1a is represented by d2 , the thickness W of the silicon substrate 1 is so set as to satisfy a formula, d1 <=d2 . Therefore, a gate electrode 7 can be formed of thick film of polysilicon or metal, so that a gate electrode line can be lessened in sheet resistance and improved in drive frequency. An amplifying semiconductor image pickup device of this constitution can be prevented from deteriorating in smear characteristics due to the diffusion of photoelectric conversion carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMD type amplification type semiconductor image pickup device.

[0002]

2. Description of the Related Art Conventionally, CCD [C
harge Coupled Device] and MOS [Metal Oxide Semicond
[uctor] type semiconductor image pickup devices are generally used. However, in all of these, the accumulated photoelectric conversion carriers are directly output as signal charges by destructive reading, so that the sensitivity is lowered and the S / N ratio of the signal is deteriorated due to the miniaturization and increase in the number of pixels of the solid-state imaging device. There was a flaw.

Therefore, CMD [C which can obtain high sensitivity and high S / N ratio even when the size of the solid-state image sensor is increased and the number of pixels is increased.
[Harge Modulating Device] type amplification type semiconductor imaging device has been proposed in the past (for example, 1986 National Conference of the Television Society "Gate storage type MOS phototransistor image sensor" Nakamura Riki et al.). FIG. 18 shows an example of such a conventional amplification type semiconductor imaging device. In this amplification type semiconductor imaging device, an n ⁻ type well layer 2 is formed as a buried channel on a p type silicon substrate 1, and a high concentration n ⁺ type source region 3 is formed on the surface layer portion of the well layer 2. A concentric drain region 4 surrounding the source region 3 is formed. In addition, these source regions 3
S on the surface of the gate region 5 between the drain region 4 and the drain region 4.
A gate electrode 7 is formed in a ring shape via an insulating film 6 of iO ₂ , and a source electrode 8 and a drain electrode 9 are formed on the surfaces of the source region 3 and the drain region 4 through an opening of the insulating film 6. Has been formed.

In the amplification type semiconductor image pickup device, the source electrode 8 is grounded, the drain electrode 9 is positively biased, and the silicon substrate 1 is negatively biased. Then, when light is irradiated from the surface side of the silicon substrate 1 with the gate electrode 7 as a negative bias, the light is emitted from the gate electrode 7 and the insulating film 6.
Through to reach the depletion layer formed by the pn junction between the p-type silicon substrate 1 and the n-type well layer 2, and photoelectric conversion carriers are generated there. The electrons of the photoelectric conversion carriers flow out to the source region 3 or the drain region 4 depending on the generation position thereof, but the holes are charged at the interface between the gate region 5 below the gate electrode 7 and the insulating film 6. Source region 3 and drain region 4 since they are accumulated as an inversion layer.
The potential barrier between and decreases.
Therefore, this amplification type semiconductor imaging device can modulate and amplify the source current flowing between the source region 3 and the drain region 4 according to the amount of incident light and output the source current.
By keeping the gate potential of the gate electrode 7 at the hole accumulation potential, nondestructive read-out of signals becomes possible, so that high sensitivity and high S / N ratio can be obtained.

[0005]

However, when the light is irradiated from the front surface side of the silicon substrate 1 as in the conventional amplification type semiconductor image pickup device, the gate electrode 7 and the insulating film 6 are formed.
In order to increase the light transmittance of the above, it is necessary to form these films thin, and in particular, the gate electrode 7 must be formed extremely thin (about 0.1 μm or less). When the film thickness of the gate electrode 7 is thin as described above, the sheet resistance of the gate electrode line is increased and the time constant is increased, so that the distortion of the drive pulse waveform is increased and the gate electrode 7 is controlled at high speed. Therefore, the conventional amplification type semiconductor imaging device has a problem that the improvement of the driving frequency is limited.

In an amplification type semiconductor image pickup device, generally, each pixel formed in a two-dimensional matrix is scanned by an XY address so that signals are sequentially read out. Therefore, the number of pixels is increased to increase the number of pixels. And the drive frequency is several MHz
It is necessary to raise to a certain degree. Therefore, in the conventional amplification type semiconductor image pickup device, the gate region 5 through which the incident light is transmitted is transmitted.
Only the upper gate electrode 7 is formed to be extremely thin and the other gate electrode lines are formed to be thick, or the sheet resistance is formed by using a complicated manufacturing process such as contact bonding of another electrode line. And the drive frequency was improved.

Further, since the light applied to the amplification type semiconductor image pickup device passes through the gate electrode 7 and the insulating film 6 for each pixel, the spectroscopic optics for each pixel such as the gate electrode 7 and the insulating film 6 is transmitted. It becomes necessary to make the characteristics uniform. However, since the spectroscopic optical characteristics fluctuate greatly due to variations in optical properties such as the refractive index and absorption coefficient of the electrode material and the insulating film material and the nonuniform film thickness, the conventional amplification type semiconductor The image pickup device also has a problem that it is necessary to control the film thickness and the like with high precision by using a precise manufacturing process. Moreover, since the gate electrode 7, the insulating film 6 and the like have irregularities due to the pattern formation, there is a problem that when the irradiation light is transmitted, light is scattered on these irregularities and light loss is increased.

Further, as shown in FIG. 19, a microlens 15 is formed on the gate electrode 7 so that the irradiation light is condensed and made incident, or as shown in FIG. Spectral filter 2 to cover the entire area
In the case of achieving color compatibility by forming 0, there is a problem that it becomes difficult to uniformly form the optical characteristics of the microlens 15 and the spectral filter 20 due to the uneven surface of the gate electrode 7 and the like. It was

Further, in some CCD type semiconductor image pickup devices, in order to avoid the above problem, light is incident from the back surface side of the substrate while avoiding the front surface side on which electrodes and the like are formed. However, the CCD type semiconductor image pickup device has a photodiode section which is a light receiving section and a CCD section which is a charge transfer section.
It is necessary to optically separate the CCD unit and the CCD unit from light. Since a light-shielding film is formed on the back surface side of the substrate to shield the CCD portion, unevenness of the light-shielding film should form uniform optical characteristics when the microlens 15 and the spectral filter 20 are provided. The problem that it becomes difficult has not been solved yet.

Moreover, when light is incident from the back side of the silicon substrate 1 in the conventional amplification type semiconductor image pickup device, the incident light is p because the layer thickness of the silicon substrate 1 is large.
Since photoelectric conversion is performed in the neutralization region before reaching the depletion layer of the n-junction, photoelectric conversion carriers diffuse before being accumulated in the gate region 5 and affect adjacent pixels to improve smear characteristics. The problem of exacerbation occurs. Further, when the layer thickness of the silicon substrate 1 is large as described above, there is a problem that the sensitivity of light in a short wavelength region where the depth of light penetration into the silicon substrate 1 is shallow is lowered.

The present invention solves the above-mentioned problems of the prior art. The gate electrode and the like can be formed sufficiently thick by making the irradiation light incident from the back surface side of the substrate and forming the layer thickness of the substrate thin. An object of the present invention is to provide an amplification type semiconductor imaging device capable of preventing deterioration of smear characteristics.

[0012]

In the amplification type semiconductor imaging device of the present invention, a semiconductor well layer of a second conductivity type semiconductor layer is formed on a semiconductor substrate of a first conductivity type, and a surface layer of the semiconductor well layer. -Type semiconductor image pickup in which a source region and a drain region of the high-concentration first conductivity type semiconductor layer are formed in the respective regions, and a gate electrode is formed on the surface of the gate region between the source region and the drain region via an insulating film In the device, the back surface of the semiconductor substrate is used as a light incident surface, and the layer thickness of the semiconductor substrate is such that a back surface side end of a depletion layer generated by a pn junction between the semiconductor substrate and the semiconductor well layer and the semiconductor substrate. When the distance from the back surface is d1 and the light penetration depth with respect to the wavelength of the light incident on the light entrance surface is d2, the thickness is formed to satisfy the condition of d1≤d2. The above purpose is achieved Be done.

Preferably, the semiconductor well layer of the second conductivity type semiconductor layer is formed on the first conductivity type semiconductor substrate, and the high-concentration first conductivity type semiconductor layer is formed on the surface layer portion of the semiconductor well layer. In an amplification type semiconductor imaging device in which a source region and a drain region are respectively formed, and a gate electrode is formed on the surface of the gate region between the source region and the drain region via an insulating film, light is incident on the back surface of the semiconductor substrate. The surface of the semiconductor substrate is formed so that the depletion layer formed by the pn junction with the semiconductor well layer reaches the back surface of the semiconductor substrate.

Further, preferably, the amplification type semiconductor imaging device in the amplification type semiconductor imaging device of the present invention is such that the semiconductor well layer of the second conductivity type semiconductor layer is formed on the first conductivity type semiconductor substrate, and A source region and a drain region of the high-concentration first conductivity type semiconductor layer are respectively formed in the surface layer portion of the semiconductor well layer, and a first gate is formed on the surface of the semiconductor well layer between the source region and the drain region via an insulating film. An electrode and a second gate electrode are formed adjacent to each other, and the first gate electrode is in a region covered by the second gate electrode in the surface layer portion of the semiconductor well layer or through the second gate electrode. The reset drain region of the high-concentration second conductivity type semiconductor layer is formed in the region on the opposite side.

Further, preferably, the layer thickness of the semiconductor substrate in the amplification type semiconductor image pickup device of the present invention is formed to have a predetermined thickness at least in a range corresponding to the gate region or the gate region below the first gate electrode. To be done.

Further, preferably, in the amplification type semiconductor image pickup device of the present invention, on the light incident surface of the back surface of the semiconductor substrate, a dielectric antireflection film for suppressing reflection with respect to the wavelength of light incident on the light incident surface. Is formed.

Further, preferably, in the amplification type semiconductor image pickup device of the present invention, a dielectric bandpass filter for transmitting only a specific wavelength region of the light incident on the light incident surface to the light incident surface on the back surface of the semiconductor substrate. Alternatively, an organic color filter is formed.

Further, preferably, in the amplification type semiconductor image pickup device of the present invention, a microlens array having a condensing effect on the wavelength of the light incident on the light incident surface is provided on the light incident surface on the back surface of the semiconductor substrate. It is formed.

Further, preferably, a Fresnel lens array having a condensing effect on the wavelength of light incident on the light incident surface is provided on the light incident surface on the back surface of the semiconductor substrate in the amplification type semiconductor image pickup device of the present invention. It is formed.

Further, preferably, in the amplification type semiconductor image pickup device of the present invention, the electrode or the insulating film on the front surface side of the semiconductor substrate is higher than the wavelength of light incident on the light incident surface on the back surface of the semiconductor substrate. It is formed of a metal reflection film or a dielectric reflection film having a reflectance.

Further, preferably, a reinforcing protective layer for reinforcing the semiconductor substrate is formed on the insulating film and the electrode on the surface side of the semiconductor substrate in the amplification type semiconductor image pickup device of the present invention.

Further, preferably, another substrate for reinforcing the semiconductor substrate is attached to the upper layer of the insulating film and the electrode on the front surface side of the semiconductor substrate in the amplification type semiconductor image pickup device of the present invention.

Further, preferably, the semiconductor substrate in the amplification type semiconductor image pickup device of the present invention is thinned from the back surface side so that the semiconductor substrate is formed to have a predetermined layer thickness.

The operation will be described below.

With the above structure, since the irradiation light is incident from the back surface of the semiconductor substrate, the incident light does not pass through the gate electrode or the like. Therefore, not only does it become unnecessary to reduce the film thickness of the gate electrode in order to improve the light transmittance, or to precisely control the uniformity of the film thickness in order to make the light transmittance of each pixel constant, The unevenness of the gate electrode or the like prevents the light from scattering and increasing the light loss.

Moreover, the light incident from the back surface of the semiconductor substrate can penetrate at least to the light penetration depth d2 and is longer than the distance d1 between the back surface side end of the depletion layer and the back surface of the semiconductor substrate. Since the light penetrates the distance, this incident light can be surely photoelectrically converted in the depletion layer. Therefore, the incidence of light from the rear surface side of the semiconductor substrate eliminates the possibility that the sensitivity in the short wavelength region will decrease and that the smear characteristics will deteriorate due to the diffusion of photoelectric conversion carriers.

Further, according to the above structure, the layer thickness of the semiconductor substrate is further reduced until the depletion layer reaches the back surface of the semiconductor substrate, so that the smear characteristic deterioration due to the diffusion of photoelectric conversion carriers can be prevented more reliably. You will be able to.

Further, with the above structure, the accumulated carriers accumulated in the lower layer of the first gate electrode can be discharged to the reset drain region by controlling the second gate electrode.

Further, with the above structure, only the layer thickness of the light incident portion is thinned, so that the reduction in strength due to the thinning of the semiconductor substrate can be suppressed to some extent.

Further, according to the above structure, since the dielectric antireflection film is formed on the light incident surface, the irradiation light can be incident on the semiconductor substrate without waste.

Further, with the above structure, since the dielectric bandpass filter or the organic color filter can be formed on the flat light incident surface on the back surface of the semiconductor substrate, it becomes easy to make the optical characteristics uniform.

Further, with the above structure, since the microlens array can be formed on the flat light incident surface on the back surface of the semiconductor substrate, it becomes easy to make the optical characteristics uniform.

Further, with the above structure, since the Fresnel lens array can be formed on the flat light incident surface on the back surface of the semiconductor substrate, it becomes easy to make the optical characteristics uniform.

Further, according to the above structure, since the electrodes and the insulating film are formed by the metal reflection film or the dielectric reflection film, the light incident from the light incident surface on the back surface of the semiconductor substrate is reflected on the front surface side and again the semiconductor substrate. The light can be made incident inside, and the photoelectric conversion efficiency can be improved.

Further, with the above structure, a reinforcing protective layer can be formed on the surface side of the semiconductor substrate to reinforce the thinned semiconductor substrate.

Further, with the above structure, another substrate can be formed on the front surface side of the semiconductor substrate to reinforce the thinned semiconductor substrate.

Further, with the above structure, the semiconductor substrate is thinned from the back surface side, so that the layer thickness of this semiconductor substrate can be easily made thin.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

1 to 7 show a first embodiment of the present invention. FIG. 1 is a vertical sectional view schematically showing the structure of an amplification type semiconductor image pickup device, and FIG. 2 is a view of the amplification type semiconductor image pickup device. 3 is a vertical cross-sectional view for explaining the manufacturing process, FIG. 3 is a vertical cross-sectional view when a supporting substrate is attached to the amplification type semiconductor image pickup device of FIG. 2, and FIG. 4 is a thin film of the silicon substrate of the amplification type semiconductor image pickup device of FIG. FIG. 5 is a vertical cross-sectional view when the visible light transmitting glass plate is adhered to the amplification type semiconductor imaging device of FIG. 4, and FIG. 6 is a support substrate from the amplification type semiconductor imaging device of FIG. FIG. 7 is a vertical cross-sectional view when removed, and FIG. 7 is a potential distribution diagram of the amplification type semiconductor imaging device. In addition, FIG.
Components having the same functions as those of the conventional example shown in FIG. 20 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. The amplification type semiconductor imaging device, carrier concentration of about 1.0 × 10 ¹⁴ / cm p-type carrier concentration on the silicon substrate 1 of ³ approximately 1.0 × 10 ¹⁶ /
A cm ³ n ⁻ type well layer 2 is formed. The well layer 2 is formed to a thickness of about 0.5 μm to 3 μm by epitaxial growth or ion implantation. In the surface layer portion of the well layer 2, a high-concentration p ⁺ type source region 3 and a concentric drain region 4 surrounding the source region 3 are formed. The source region 3 and the drain region 4 have a junction depth of 0.3 by an ion implantation method with an interval of the gate region 5 having a gate length of about 2.5 μm.
It is formed to a thickness of about μm. Also, on the surface of the well layer 2,
An insulating film 6 of SiO ₂ is formed with a thickness of about 35 nm. On the insulating film 6 covering the gate region 5 between the source region 3 and the drain region 4, a gate electrode 7 made of a polysilicon film or an aluminum metal film is annularly formed to a thickness of about 0.1 μm to 0.5 μm. Is formed. Further, the insulating film 6 covering the source region 3 and the drain region 4 is partially formed with an opening, and a source electrode 8 and a drain electrode 9 are formed.

In the amplification type semiconductor image pickup device, the back surface of the silicon substrate 1 is used as a light incident surface 1a, and light is incident from the back surface side. In addition, the layer thickness W of the silicon substrate 1 is set such that the edge of the depletion layer on the back surface side (p-type side) formed by the pn junction between the p-type silicon substrate 1 and the n ⁻ type well layer 2 and the light incident surface 1 a. When the distance between them is d1 and the light penetration depth with respect to the wavelength of the light incident on the light incident surface 1a is d2, the thickness is formed to satisfy the condition of d1≤d2. The thickness of the depletion layer formed on both sides of the pn junction is determined by the carrier concentration of each of the silicon substrate 1 and the well layer 2, the gate voltage, and various semiconductor constants. In the case of the amplification type semiconductor imaging device shown here, If the voltage is set to 5V (the reference voltage is set to 0V, the same applies below), about 11.
5 μm. The light penetration depth d2 is determined by the wavelength λ of the incident light and the absorption coefficient α of the silicon substrate 1. In the case of the amplification type semiconductor image pickup device in the visible light region shown here, the wavelength λ is set to 0.8 μm and absorption is performed. Coefficient α is 1.0 × 10
^{When it is 3} cm ^-1 , it becomes about 10 μm. Therefore, the distance d1 must be less than the light penetration depth d2.
The layer thickness W of the silicon substrate 1 is about 1 of this light penetration depth d2.
It is set to about 21.5 μm or less, which is the sum of 0 μm and the depletion layer thickness of about 11.5 μm.

The layer thickness W of the silicon substrate 1 may be formed so that the depletion layer reaches the back surface of the silicon substrate 1. Therefore, the layer thickness W of the silicon substrate 1 in this case is about 11.5 μm or less, which is the thickness of the depletion layer.

A method of manufacturing an amplification type semiconductor image pickup device for reducing the thickness W of the silicon substrate 1 to about 21.5 μm or less or about 11.5 μm or less as described above will be described.
First, as shown in FIG. 2, a well layer 2, a source region 3 and a drain region 4 are formed on a silicon substrate 1, and an insulating film 6, a gate electrode 7, a source electrode 8 and a drain electrode 9 are formed. However, the layer thickness W0 of the silicon substrate 1 at this time has a sufficient thickness of the silicon wafer itself. As shown in FIG. 3, this amplification type semiconductor imaging device has electrodes 6 to 8 on the front surface side of the silicon substrate 1 and the like.
The support substrate 11 is bonded to the resist 10 via the resist 10. The support substrate 11 is a substrate having a sufficient layer thickness such as another silicon substrate or a glass substrate.

As shown in FIG. 4, the amplification type semiconductor image pickup device in which the support substrate 11 is adhered is a thin film from the back surface side until the layer thickness W of the silicon substrate 1 becomes about 21.5 μm or less or about 11.5 μm or less. Turn into. This thinning is possible by grinding the back surface of the silicon substrate 1 with an abrasive. For example, SiO of 100 angstrom diameter
_{By using 2} as a polishing agent in which ₂ is suspended in an aqueous solution of sodium hydroxide in a colloidal form, the back surface of the silicon substrate 1 can be mirror-polished to form the light incident surface 1a. Further, a diamond slurry or an abrasive such as Al ₂ O ₃ or SiC can be used. Further, this thinning may be performed by etching the back surface of the silicon substrate 1 by a reactive ion etching technique. In the reactive ion etching technique, a halogen-based gas (Br, F, Cl ₂ or the like) is used as a reaction gas, whereby the back surface of the silicon substrate 1 can be uniformly removed by etching to form a thin film. Even with the current substrate thinning technology, the layer thickness W of the silicon substrate 1 is about 1
It is possible to reduce the film thickness to about 0 μm.
A film thickness of 1.5 μm or less or about 11.5 μm or less can be sufficiently achieved, but in the future, due to improvement in accuracy, 2 μm
It is also possible to reduce the thickness to about 3 to 3 μm.

As shown in FIG. 5, the amplification type semiconductor image pickup device has a visible light transmissive glass plate on the light incident surface 1a on the back surface of the thinned silicon substrate 1 via a visible light transmissive epoxy resin 12. Glue 13 The visible light transmissive glass plate 13 is a glass plate that transmits light in the visible light region imaged by this amplification type semiconductor imaging device, and protects the light incident surface 1a on which light is incident, and also a thinned silicon substrate. Bonded to reinforce 1. The visible light transmissive epoxy resin 12 is a translucent thermosetting adhesive that transmits light in the visible light region. The amplification type semiconductor imaging device to which the visible light transmitting glass plate 13 is adhered is divided into each element by chip dicing, and then the resist mover is dissolved by the registry mover, and the supporting substrate 11 is removed as shown in FIG. remove. Then, each of the divided elements is mounted and packaged by performing mounting and wire bonding in the same manner as in the related art to form a solid-state imaging element.
However, contrary to the conventional case, the light incident surface 1a on the back surface of the silicon substrate 1 is mounted toward the window portion of the package.

In the amplification type semiconductor image pickup device having the above structure, when light is incident from the light incident surface 1a on the back surface of the silicon substrate 1 with a high voltage of about 5 V applied to the gate electrode 7, p
Photoelectric conversion carriers are generated in the depletion layer of the n-junction and are accumulated in the gate region 5 as signal charges (electrons). Therefore,
As shown in FIG. 7, the potential distribution of the gate region 5 rises from the state due to the accumulation of signal charges. Further, in this figure, the silicon substrate 1 is located at 21.1 from the boundary between the well layer 2 and the insulating film 6.
μm or less, that is, a depth of 10 μm or less from the end of the depletion layer, or 11.5 μm from the boundary between the well layer 2 and the insulating film 6.
The following, that is, the end of the depletion layer is thinned.

In the amplification type semiconductor image pickup device, since the irradiation light is incident from the light incident surface 1a on the back surface of the silicon substrate 1,
There is no need to form the gate electrode 7 on the front surface thin.
Therefore, a thick polysilicon film or a metal film can be used as the gate electrode 7, so that the sheet resistance of the gate electrode line can be reduced and the drive frequency can be improved. . Moreover, in order to keep the light transmittance of the gate electrode 7 and the insulating film 6 constant for each pixel, it is not necessary to make the film thickness control in the manufacturing process more accurate than necessary. Furthermore, light is not scattered due to the unevenness of the pattern of the gate electrode 7 and the insulating film 6 and the light loss can be reduced.

Further, since the layer thickness W of the silicon substrate 1 is made thin, incident light can be surely photoelectrically converted in the depletion layer of the pn junction. Therefore, it is possible to eliminate the defect that the sensitivity is lowered in the short wavelength region, which has been conventionally caused when light is incident from the light incident surface 1a on the back surface of the silicon substrate 1.
Moreover, when the layer thickness W is reduced, the smear characteristic hardly deteriorates due to the diffusion of the photoelectric conversion carriers until the incident light is photoelectrically converted and accumulated. In particular, when the layer thickness W is reduced to about 11.5 μm or less so that the depletion layer reaches the back surface of the silicon substrate 1, deterioration of smear characteristics due to the diffusion of incident light can be reliably prevented.

The light incident surface 1 on the back surface of the silicon substrate 1
The smear characteristics and blooming can be further improved by patterning a light-shielding film such as WSi on a. Moreover, since the light incident surface 1a is a flat surface on which the gate electrode 7 and the like are not formed, it is possible to easily form the light shielding film in a precise pattern.

8 and 9 show a second embodiment of the present invention. FIG. 8 is a vertical cross-sectional view schematically showing the structure of an amplification type semiconductor image pickup device, and FIG. 9 shows an amplification type semiconductor image pickup device. It is a longitudinal section showing other composition typically. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. This amplification type semiconductor image pickup device has a well layer 2, a source region 3 and a drain region 4 on a silicon substrate 1 as in the first embodiment shown in FIG.
And the insulating film 6, the gate electrode 7, the source electrode 8 and the drain electrode 9 are formed. However, the carrier concentration of the silicon substrate 1 is about 5.0 × 10.
And ¹³ / cm ³ of p-type silicon, well layer 2, n of the carrier concentration of about 1.0 × 10 ¹³ / cm ^{3 -} was formed to a thickness of about 0.5μm~3μm by type epitaxial silicon layer I shall. The gate electrode 7 is formed by forming a polysilicon film to a thickness of about 0.1 μm to 0.5 μm. As in the case of the first embodiment shown in FIG. 1, the source region 3 and the drain region 4 are formed as gate regions 5 with a gate length of about 2.5 μm and a junction depth of 0. The insulating film 6 of SiO2 is formed to have a thickness of about 3 .mu.m, and has a thickness of about 35 nm. Therefore, the thickness of the depletion layer formed on both sides of the pn junction between the silicon substrate 1 and the well layer 2 is about 11.5 μm when the gate voltage is 5V.

The above-mentioned amplification type semiconductor image pickup device also receives light from the back side of the silicon substrate 1. However, the total layer thickness W1 of the silicon substrate 1 is sufficiently thick, and only the back surface corresponding to the gate region 5 below the gate electrode 7 is thinned as the light incident surface 1a. The layer thickness W of the light incident surface 1a is the same as in the case of the first embodiment.
The depth is equal to or less than the sum of the depth of light penetration and the thickness of the depletion layer or less than the thickness of the depletion layer. That is, since the depth of light penetration and the thickness of the depletion layer are the same as in the first embodiment, they are set to about 21.5 μm or less or about 11.5 μm or less. Such thinning is performed by first forming the layer thickness W by the polishing process described in the first embodiment.
The back surface of the silicon substrate 1 is ground until 1 becomes about 50 μm, then a resist mask having a thickness of about 5 μm is formed on the back surface in a predetermined pattern, and the reactive ion etching technique using a halogen-based gas is used. By performing selective etching, only the layer thickness W of the light incident surface 1a is further reduced to about 21.5 μm or less or about 11.
It becomes possible by setting it to 5 μm or less.

In addition to the same effects as in the first embodiment, the above-mentioned amplification type semiconductor image pickup device has an advantage that the strength of the silicon substrate 1 can be maintained to some extent, so that the handling becomes easy. Further, since it is possible to eliminate the incidence of light from the portion other than the light incident surface 1a corresponding to the gate region 5, blooming and smear characteristics caused by the generation of unnecessary photoelectric conversion carriers can be surely reduced.

In the amplification type semiconductor imaging device shown in FIG. 9, the light incident surface 1a on the back surface of the silicon substrate 1 is spread over the entire pixel region, and the layer thickness W of this entire region is about 21.5 μm.
The thickness is reduced to below or about 11.5 μm. Such thinning can be easily realized by changing the pattern of the resist mask. Then, this amplification type semiconductor image pickup device can also obtain the same effect as that shown in FIG.

FIG. 10 shows a third embodiment of the present invention and is a vertical cross-sectional view schematically showing the structure of an amplification type semiconductor image pickup device. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

FIG. 10 shows the structure of one pixel of the amplification type semiconductor image pickup device of this embodiment. This amplification type semiconductor image pickup device has a well layer 2, a source region 3 and a drain region 4 on a silicon substrate 1 as in the second embodiment shown in FIG.
And the insulating film 6, the gate electrode 7, the source electrode 8 and the drain electrode 9 are formed. However, the well layer 2 has a carrier concentration of about 1.0 × 10 ¹³ /
It is assumed that an n ⁻ -type silicon layer of cm ³ is formed by epitaxial growth or an ion implantation method to a thickness of about 0.5 μm to 5.0 μm, and the gate electrode 7 is a polysilicon film having a thickness of about 50 nm to 70 nm. It is assumed to have been formed. Note that, as in the second embodiment shown in FIG. 8, the silicon substrate 1 has a carrier concentration of about 5.0 × 10 ¹³ / cm ^3.
Source region 3 and drain region 4
Are formed as gate regions 5 with a gate length of about 2.5 μm and a junction depth of 0.3 by ion implantation.
The insulating film 6 made of SiO _{2 has} a thickness of 35 nm.
It is formed to a thickness of about. Therefore, the silicon substrate 1
The thickness of the depletion layer formed on both sides of the pn junction of the well layer 2 is about 11.5 μm when the gate voltage is 5V.

As in the case of the first embodiment shown in FIG. 1, the amplification type semiconductor image pickup device of the present embodiment allows the entire layer thickness W of the silicon substrate 1 to optically penetrate by the polishing process and the reactive ion etching technique. The depth is less than or equal to the sum of the thickness of the depletion layer or less than or equal to the thickness of the depletion layer. That is, since the depth of light penetration and the thickness of the depletion layer are the same as in the first embodiment, they are set to about 21.5 μm or less or about 11.5 μm or less. Further, in this amplification type semiconductor imaging device, the back surface of the thinned silicon substrate 1 is used as the light incident surface 1a, and the antireflection film 14 is formed on the light incident surface 1a. Antireflection film 1
4 is a multi-layer coating of dielectric thin films such as SiO ₂ , ZnO and TiO ₂ . For example, when the design wavelength λ is set to 550 nm, the dielectric thin films shown in Table 1 are sequentially formed into multiple layers by the electron beam evaporation method,

[0058]

[Table 1]

The antireflection film 14 having a reflectance of 0.2% or less in the visible light region can be formed, and the light reflection on the light incident surface 1a of the irradiated light can be almost completely eliminated. Like It should be noted that such an antireflection film 14 is insoluble in an organic solvent such as a registry mover.
Since it does not react with the epoxy resin such as the visible light transmissive epoxy resin 12 shown in FIG. 1, the silicon substrate 1 is thinned using the support substrate 11 or the light incident surface 1a is formed by using the support substrate 11 as in the first embodiment. It is also possible to adhere the visible light transmitting glass plate 13.

In the amplification type semiconductor image pickup device, in addition to the effect similar to that of the first embodiment, almost 100% of the light irradiated to the light incident surface 1a can be made incident through the antireflection film 14. Therefore, the light loss due to reflection can be made extremely small and the photoelectric conversion efficiency can be improved. Further, since such an antireflection film 14 is formed on the flat light incident surface 1a on the back surface of the silicon substrate 1, it is possible to easily form a film having uniform optical characteristics.

In the color type amplification type semiconductor image pickup device, a bandpass filter for a necessary color component is formed in place of the antireflection film 14 for each pixel area shown in FIG. The bandpass filter is a filter that transmits light only in the wavelength region of the required color component, and corresponds to each color of the RGB signal and the MCYG complementary color signal, for example. The bandpass filter is composed of a dielectric bandpass filter or an organic color filter. Such a bandpass filter is formed on the flat light incident surface 1a on the back surface of the silicon substrate 1 unlike the conventional surface side of the silicon substrate 1 on which the gate electrode 7 and the like are formed. It becomes possible to easily form a film having uniform physical properties.

FIG. 11 shows a fourth embodiment of the present invention and is a vertical cross-sectional view schematically showing the structure of an amplification type semiconductor image pickup device. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. In this amplification type semiconductor image pickup device, the well layer 2, the source region 3 and the drain region 4 are formed on the silicon substrate 1 as well as the insulating film 6 and the gate electrode 7 as in the third embodiment shown in FIG. A source electrode 8 and a drain electrode 9 are formed. The silicon substrate 1 has a carrier concentration of about 5.0 × 10 5.
¹³ / cm ³ of a p-type silicon, well layer 2, n of the carrier concentration of about 1.0 × 10 ¹³ / cm ^{3 -} -type silicon layer by epitaxial growth or ion implantation 0.5
It is assumed that the source region 3 and the drain region 4 are formed as a gate region 5 with a gate length of about 2.5 μm and a junction depth of 0. The thickness is about 3 μm. The SiO ₂ insulating film 6 is formed to a thickness of about 35 nm, and the gate electrode 7 is a polysilicon film of 50 nm to 7 nm.
It is assumed that it is formed to a thickness of about 0 nm. Therefore,
The thickness of the depletion layer formed on both sides of the pn junction between the silicon substrate 1 and the well layer 2 is about 11.5 when the gate voltage is 5V.
μm.

As in the case of the first embodiment shown in FIG. 1, the amplification type semiconductor image pickup device of this embodiment uses the polishing step and the reactive ion etching technique to optically penetrate the entire layer thickness W of the silicon substrate 1. The depth is less than or equal to the sum of the thickness of the depletion layer or less than or equal to the thickness of the depletion layer. That is, since the depth of light penetration and the thickness of the depletion layer are the same as in the first embodiment, they are set to about 21.5 μm or less or about 11.5 μm or less. Further, in this amplification type semiconductor imaging device, the back surface of the thinned silicon substrate 1 is used as a light incident surface 1a, and a large number of microlenses 15 are formed as a microlens array on the light incident surface 1a. In the case of the first embodiment, the microlens 15 is made of a material that is insoluble in an organic solvent such as a registry mover and does not react with an epoxy resin such as the visible light transmitting epoxy resin 12 shown in FIG. Similarly, it is preferable that the support substrate 11 is used for thinning or the visible light transmitting glass plate 13 can be bonded to the light incident surface 1a. The microlens array can be formed using a mode index lens or a geodesic lens. As a typical example of the mode index lens, a complex conical surface aperture mask or a shadow mask in which a plurality of circular aperture plate masks are combined is formed on the light incident surface 1a on the back surface of the silicon substrate 1, and the refractive index n = 1.6. Al ₂ O ₃ or refractive index n = 2.
There is one in which TiO ₂ of No. 4 is deposited as a lens layer having a predetermined film thickness distribution by a sputtering method or an evaporation method.

In the amplification type semiconductor image pickup device, in addition to the effect similar to that of the first embodiment, the light irradiated to the light incident surface 1a is condensed on the gate region 5 by each microlens 15, so that stray light is generated. And the photoelectric conversion efficiency can be improved. Further, since the microlens array of the microlens 15 is formed on the flat light incident surface 1a on the back surface of the silicon substrate 1, the microlens array is affected by the unevenness of the gate electrode 7 and the like like the front surface side of the silicon substrate 1. It is possible to form a uniform product having uniform optical characteristics easily and with good yield.

FIG. 12 shows a fifth embodiment of the present invention and is a vertical cross-sectional view schematically showing the structure of an amplification type semiconductor image pickup device. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. This amplification type semiconductor imaging device is similar to the third embodiment shown in FIG. 10 and the fourth embodiment shown in FIG.
Similar to the embodiment, the well layer 2, the source region 3 and the drain region 4 are formed on the silicon substrate 1, and
An insulating film 6, a gate electrode 7, a source electrode 8 and a drain electrode 9 are formed. However, as the well layer 2, an n ⁻ -type silicon layer having a carrier concentration of about 1.0 × 10 ¹³ / cm ³ was formed by epitaxial growth or ion implantation.
It is formed to have a thickness of about 5 μm to 3.0 μm. The silicon substrate 1 has a carrier concentration of about 5.0 × 10 5.
And ¹³ / cm ³ of p-type silicon, the source region 3 and the drain region 4, an interval of about a gate length 2.5μm as a gate region 5, is formed in each junction depth 0.3μm about by ion implantation It The insulating film 6 of SiO ₂ is formed to have a thickness of about 35 nm. Therefore, the thickness of the depletion layer formed on both sides of the pn junction between the silicon substrate 1 and the well layer 2 is about 1 when the gate voltage is 5V.
It becomes 1.5 μm.

Further, in the amplification type semiconductor image pickup device of this embodiment, the gate electrode 7 is formed of a highly reflective metal film such as an aluminum metal film having a high reflectance with respect to visible light, instead of the polysilicon film. ing. Then, as in the case of the first embodiment shown in FIG. 1, the total layer thickness W of the silicon substrate 1 is less than or equal to the sum of the light penetration depth and the thickness of the depletion layer or depleted by the polishing process or the reactive ion etching technique. It should be less than the layer thickness. That is, since the depth of light penetration and the thickness of the depletion layer are the same as in the first embodiment, about 2
The thickness is 1.5 μm or less or about 11.5 μm or less.

The amplification type semiconductor image pickup device has the light incident surface 1
When the light incident from a reaches the gate electrode 7 on the front surface side of the silicon substrate 1 without being photoelectrically converted even if it passes through the gate region 5, it is reflected by the highly reflective metal film of the gate electrode 7 and gated again. Since it returns to the region 5, the photoelectric conversion efficiency can be further improved in addition to the effect similar to that of the first embodiment. Further, since the incident light reciprocates in the gate region 5 as described above, if the photoelectric conversion efficiency is the same, the layer thickness W of the silicon substrate 1 can be further reduced, and the light penetration depth is half the light penetration wavelength. It is possible to make the layer thickness W thin. Further, as the layer thickness W of the silicon substrate 1 becomes thinner, the thickness of the well layer 2 can also be made thinner, so that the layer thickness formed by epitaxial growth can be made thinner to facilitate the control of crystallinity and the ion implantation method. The impurity implantation depth can be made shallower to facilitate the control of the impurity concentration distribution, and the yield of the manufacturing process can be improved.

FIG. 13 shows a sixth embodiment of the present invention and is a vertical cross-sectional view schematically showing the structure of an amplification type semiconductor image pickup device. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. This amplification type semiconductor imaging device is similar to the third embodiment shown in FIG. 10 and the fourth embodiment shown in FIG.
Similar to the embodiment, the well layer 2, the source region 3 and the drain region 4 are formed on the silicon substrate 1, and
An insulating film 6, a gate electrode 7, a source electrode 8 and a drain electrode 9 are formed. However, as the gate electrode 7, a polysilicon film or an aluminum metal film is formed in a thickness of 50 nm to 7 nm.
It is assumed that it is formed to a thickness of about 0 nm. The silicon substrate 1 has a carrier concentration of about 5.0 × 10 ¹³ / cm ^3.
The well layer 2 is made of n ^- type silicon layer having a carrier concentration of about 1.0 × 10 ¹³ / cm ³ by epitaxial growth or ion implantation, and the well layer 2 has a thickness of 0.5 μm to 5.
The source region 3 and the drain region 4 are formed as a gate region 5 with a gate length of 2.5.
A junction depth of about 0.3 μm is formed by ion implantation with an interval of about μm. In addition, SiO ₂
The insulating film 6 is formed with a thickness of about 35 nm. Therefore, the thickness of the depletion layer formed on both sides of the pn junction between the silicon substrate 1 and the well layer 2 is about 11.5 μm when the gate voltage is 5V.

As in the case of the first embodiment shown in FIG. 1, the amplification type semiconductor image pickup device of this embodiment uses the polishing step and the reactive ion etching technique to optically penetrate the entire layer thickness W of the silicon substrate 1. The depth is less than or equal to the sum of the thickness of the depletion layer or less than or equal to the thickness of the depletion layer. That is, since the depth of light penetration and the thickness of the depletion layer are the same as in the first embodiment, they are set to about 21.5 μm or less or about 11.5 μm or less. Further, in this amplification type semiconductor imaging device, the back surface of the thinned silicon substrate 1 is used as a light incident surface 1a, and a large number of Fresnel lenses 16 are formed as a Fresnel lens array on this light incident surface 1a. As the Fresnel lens 16,
The phase difference on the x-axis (semiconductor substrate plane) between the parallel light propagating in the z direction in the two-dimensional waveguide (x, z plane) and the light converging at the point (0, f) is Φ (x) = k ₀ · n · {f−√ (x ² + f ² )} Here, since k ₀ = 2π / λ n: effective refractive index, an element that gives phase modulation of Φ (x) on the x-axis Is a lens having a focal length f. Here, if the thickness of the Fresnel lens is L and the difference between the effective refractive index of the lens region and that of the surrounding region is Δn, the phase shift when L is thin is the product of L and Δn. Is the thickness distribution L (x) = L _max [Φ (x) / (2π + 1)] Δn = const or the refractive index distribution is Δn (x) = Δn _max [Φ (x) / ( 2π + 1)] L = const.

In the Fresnel lens array including the Fresnel lens 16 as described above, a resist film is formed on the light incident surface 1a on the back surface of the silicon substrate 1, and the resist film is formed by an electron beam method or a photolithography method. By forming an exposure dose distribution according to the Fresnel lens shape of the formula, each Fresnel lens 16 is formed in this resist film and transferred to the light incident surface 1a of the silicon substrate 1 by the ion beam etching method.

In the amplification type semiconductor image pickup device, in addition to the effect similar to that of the first embodiment, the light irradiated to the light incident surface 1a is condensed on the gate region 5 by each Fresnel lens 16, so that stray light is generated. And the photoelectric conversion efficiency can be improved. Further, since the Fresnel lens array of the Fresnel lens 16 is formed on the flat light incident surface 1a on the back surface of the silicon substrate 1, it is affected by the unevenness of the gate electrode 7 etc. like the front surface side of the silicon substrate 1. Disappears. Furthermore, Fresnel lens 16
Since the optical characteristics of the lens are uniquely determined by the mask pattern and the patterning by etching, it is not necessary to obtain the curvature of the lens by the heat treatment step as in the microlens 15 shown in the fourth embodiment, and this heat treatment step is not necessary. The occurrence of variations in optical characteristics due to stability is eliminated. Therefore, compared with the microlens 15, the Fresnel lens 16 can easily form a uniform lens having uniform optical characteristics with high yield.

14 to 17 show a seventh embodiment of the present invention. FIG. 14 is a vertical cross section schematically showing the structure of an amplification type semiconductor image pickup device, and FIG. 15 is a potential at the time of signal charge accumulation. FIG. 16 is a distribution diagram when a signal is read, and FIG. 16 is a potential distribution diagram when a signal charge is discharged. Note that constituent members having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

The structure of one pixel of the amplification type semiconductor image pickup device of this embodiment is shown in FIG. This amplification type semiconductor imaging device has a carrier concentration of about 3.0 × 10 ¹⁶ / on a p-type silicon substrate 1 having a carrier concentration of about 1.0 × 10 ¹⁴ / cm ^3.
A cm ³ n ⁻ type well layer 2 is formed with a thickness of about 0.8. A high-concentration p ⁺ type source region is formed in the surface layer portion of the well layer 2, and an insulating film 6 is formed as a first gate region 5 so as to surround the source region and cover the first gate region. A first gate electrode 19 made of an n ⁺ polysilicon film is annularly formed thereon with a thickness of about 60 nm. Further, a second gate region is formed so as to be in contact with the first gate region, the high-concentration p ⁺ type drain region and the first gate region so as to surround the first gate region. As the second gate region, the high-concentration n ⁺ reset drain region 17 is formed on the surface layer portion of the n ⁻ type well layer 2, and the reset drain region 17 is covered and the first gate region portion and the reset drain region are formed. The width ΔL (ΔL ≧
1.0 μm) is secured, and the second gate electrode 18 made of an n ⁺ polysilicon film is formed on the insulating film 6 with a thickness of about 4500 nm. Therefore, in this embodiment,
The depletion layer formed on both sides of the pn junction between the silicon substrate 1 and the well layer 2 has a thickness of about 8.95 μm.

As in the case of the first embodiment shown in FIG. 1, the amplification type semiconductor image pickup device of the present embodiment allows the entire layer thickness W of the silicon substrate 1 to optically penetrate by the polishing process and the reactive ion etching technique. The depth is less than or equal to the sum of the thickness of the depletion layer or less than or equal to the thickness of the depletion layer. However, the depth of light penetration is about 10 μm as in the first embodiment, but the thickness of the depletion layer is about 8.95 μm, so the layer thickness W is about 18.95 μm or less, which is the sum of these. Alternatively, it is about 8.95 μm or less depending on the thickness of the depletion layer. Further, in this amplification type semiconductor imaging device, the back surface of the thinned silicon substrate 1 is used as the light incident surface 1a.

The above-mentioned amplification type semiconductor image pickup device can be formed regardless of the thickness of the silicon substrate 1. However, since it is difficult to connect the wiring for applying a potential to this substrate especially when the silicon substrate 1 is thin, The structure of this device is excellent in that no special wiring is required.

The operations of the amplification type semiconductor image pickup device at the time of signal charge storage, signal read and signal charge discharge will be described with reference to FIGS.
Details will be described based on the potential distribution in FIG.
15 to 17, the AA cross section of the gate region 5 shown in FIG. 14b is shown on the right side, and the BB cross section of the potential barrier region by the second gate electrode 18 is shown on the left side. .

At the time of accumulating the signal charges, as shown in FIG. 15, a high voltage (about 5 V) voltage V is applied to the first gate electrode 19.
GA (H) is applied to the second gate electrode 18 at a medium voltage (-1
A voltage VGB (M) of about V) is applied. In this state, when light enters from the light incident surface 1a on the back surface of the silicon substrate 1, photoelectric conversion carriers of electron-hole pairs are generated by photoelectric conversion in the depletion layer of the pn junction. The holes among them immediately flow out to the drain region 4, while the electrons are accumulated in the gate region 5 below the first gate electrode 19. Therefore, the potential distribution of the gate region 5 rises from the state due to the accumulation of signal charges (electrons) as shown on the right side of the drawing. However, also in this case, since the bottom potential in the state where the signal charges are accumulated has a potential difference ΔφAB between the bottom potential and the bottom potential under the second gate electrode 18 shown on the left side in the figure, this potential difference ΔφAB is sufficiently large. The signal charge is in the gate region 5 between
Stay in. However, when the accumulation of signal charges becomes excessive and the potential difference ΔφAB becomes small, the signal charges exceed the potential barrier and flow out to the reset drain region 17. Therefore, when the signal charges are excessively accumulated due to the irradiation of strong light, the excess signal charges can be released by overflow, so that blooming can be suppressed.

Next, at the time of reading a signal, as shown in FIG. 16, a low voltage (-3) is applied to the first gate electrode 19 of the selected pixel.
A voltage VGA (L) of about V) is applied. Then, the potential distribution of the gate region 5 shown on the right side of the drawing is raised, and the state becomes when the signal charges are not accumulated, and becomes the state when the photoelectric conversion carriers are accumulated. At this time, the second gate electrode 18
Since the low voltage (about -5 V) VGB (L) is also applied to it, the potential distribution under the second gate electrode 18 shown on the left side of the drawing is also raised, and the bottom potential in the state where the signal charges are accumulated is obtained. A potential barrier having a potential difference ΔφAB is formed between the two, and this signal charge is prevented from flowing out to the reset drain region 17. Then, if the change in the surface potential of the well layer 2 due to the presence or absence of the accumulation of signal charges at this time is read as the change in the potential of the source electrode 8, an output signal according to the amount of incident light can be obtained.

Here, the surface potential of the well layer 2 in the state where the signal charges shown in FIG.
(Sto), the surface potential of the well layer 2 shown in FIG. 16 in the state where the signal charges are not accumulated is ΔφA (De
t), a high-voltage voltage VGA (H) applied to the first gate electrodes 19 of all pixels at the time of signal charge accumulation and non-selected pixels at the time of signal readout, and the first gate of the selected pixel at the time of signal readout. Low voltage VGA applied to electrode 19
(L) is selected as a voltage such that the relationship of ΔφA (Det)> ΔφA (Sto) is always established. Therefore, even if the source electrode 8 shown in FIG. 14 is commonly connected to a plurality of pixels,
The surface potential of the well layer 2 for the selected pixel can be reliably detected from the source electrode 8.

Further, at the time of discharging the signal charges, as shown in FIG. 17, the same voltage VGA (L) as that of the selected pixel at the time of signal reading is applied to the first gate electrode 19 as a low voltage, and the second gate electrode 18 is applied. High voltage (about 5V) voltage V
Apply GB (H). Then, the bottom potential under the second gate electrode 18 shown on the left side in the figure becomes sufficiently lower than the bottom potential in the state shown in the right side in the figure in which the signal charges in the gate region 5 are not accumulated (potential difference −Δ).
φAB), all the signal charges accumulated in the gate region 5 are discharged to the reset drain region 17 through the region below the second gate electrode 18. That is, since the accumulated signal charge is nondestructively read during signal reading, the image information of each pixel is reset by the operation when discharging the signal charge, so that the signal corresponding to the incident light amount is re-established for each signal charge accumulation period. It becomes possible to accumulate charges. Further, if the operation at the time of discharging the signal charges is executed during the accumulation period of the signal charges, the substantial accumulation period can be shortened, so that a so-called electronic shutter operation can be performed.

In addition to the same effect as in the first embodiment, the amplification type semiconductor image pickup device discharges the signal charge accumulated in the gate region 5 to the reset drain region 17 by controlling the second gate electrode 18. To provide a practical structure for resetting the image information of a pixel.

[0085]

As described above, according to the present invention, since the irradiation light is incident from the back surface of the semiconductor substrate, it becomes easy to form a thick gate electrode on the front surface of the semiconductor substrate to improve the driving frequency. Further, light is not scattered due to unevenness of the gate electrode or the like, and light loss is not increased, and the amount of incident light for each pixel is not uneven. Furthermore, since a microlens, a Fresnel lens, a spectral filter, etc. can be formed on the flat light-incident surface of the back surface of the semiconductor substrate, these optical characteristics can be easily made uniform.

Further, by thinning the semiconductor substrate, deterioration of smear characteristics due to diffusion of photoelectric conversion carriers is prevented, and incident light is surely photoelectrically converted in the depletion layer, whereby sensitivity in the short wavelength region is lowered. There is nothing to do.

[Brief description of drawings]

FIG. 1 shows a first embodiment of the present invention and is a vertical cross-sectional view schematically showing the configuration of an amplification type semiconductor imaging device.

FIG. 2 shows the first embodiment of the present invention and is a vertical cross-sectional view for explaining the manufacturing process of the amplification type semiconductor imaging device.

3 shows the first embodiment of the present invention and is a vertical cross-sectional view when a supporting substrate is attached to the amplification type semiconductor imaging device of FIG.

FIG. 4 is a longitudinal sectional view showing the first embodiment of the present invention when the amplification type semiconductor image pickup device of FIG. 3 is thinned into a silicon substrate.

5 shows the first embodiment of the present invention, and is a vertical cross-sectional view when a visible light transmitting glass plate is bonded to the amplification type semiconductor imaging device of FIG.

6 is a vertical cross-sectional view showing the first embodiment of the present invention when a supporting substrate is removed from the amplification type semiconductor imaging device of FIG. 5. FIG.

FIG. 7 shows the first embodiment of the present invention and is a potential distribution diagram of an amplification type semiconductor imaging device.

FIG. 8 shows a second embodiment of the present invention and is a vertical cross-sectional view schematically showing the configuration of an amplification type semiconductor imaging device.

FIG. 9 shows a second embodiment of the present invention and is a vertical cross-sectional view schematically showing another configuration of the amplification type semiconductor imaging device.

FIG. 10 shows a third embodiment of the present invention,
It is a longitudinal cross-sectional view which shows the structure of an amplification type semiconductor imaging device typically.

FIG. 11 shows a fourth embodiment of the present invention,
It is a longitudinal cross-sectional view which shows the structure of an amplification type semiconductor imaging device typically.

FIG. 12 shows a fifth embodiment of the present invention,
It is a longitudinal cross-sectional view which shows the structure of an amplification type semiconductor imaging device typically.

FIG. 13 shows a sixth embodiment of the present invention,
It is a longitudinal cross-sectional view which shows the structure of an amplification type semiconductor imaging device typically.

FIG. 14 shows a seventh embodiment of the present invention,
a is a plan view schematically showing the configuration of an amplification type semiconductor imaging device, and b is a vertical sectional view taken along the line A'-A '.

FIG. 15 shows a seventh embodiment of the present invention,
It is a potential distribution diagram at the time of signal charge accumulation.

FIG. 16 shows a seventh embodiment of the present invention,
It is a potential distribution diagram at the time of signal reading.

FIG. 17 shows a seventh embodiment of the present invention,
It is a potential distribution diagram at the time of discharging a signal charge.

FIG. 18 is a vertical cross-sectional view showing a conventional example and schematically showing the configuration of an amplification type semiconductor imaging device.

FIG. 19 is a longitudinal sectional view schematically showing a configuration of an amplification type semiconductor imaging device provided with a microlens, showing a conventional example.

FIG. 20 is a vertical cross-sectional view showing a conventional example and schematically showing the configuration of an amplification type semiconductor imaging device provided with a spectral filter.

[Explanation of symbols]

 1 Silicon substrate 1a Light incident surface 2 Well layer 3 Source region 4 Drain region 5 Gate region 6 Insulating film 7 Gate electrode 14 Antireflection film 13 Visible light transmissive glass plate 15 Microlens 16 Fresnel lens 17 Reset drain region 18 Second gate Electrode 19 First gate electrode

Claims (3)

[Claims] 1. A semiconductor well layer of a second conductivity type semiconductor layer is formed on a semiconductor substrate of a first conductivity type, and a source region of a high concentration first conductivity type semiconductor layer is formed on a surface layer portion of the semiconductor well layer. In an amplification type semiconductor imaging device in which a drain region is formed and a gate electrode is formed on an upper surface of a gate region between the source region and the drain region via an insulating film, a back surface of the semiconductor substrate is used as a light incident surface. At the same time, the layer thickness of the semiconductor substrate is such that the distance between the rear surface side end of the depletion layer generated by the pn junction between the semiconductor substrate and the semiconductor well layer and the rear surface of the semiconductor substrate is d1. An amplification type semiconductor imaging device formed to have a thickness satisfying a condition of d1≤d2, where d2 is a light penetration depth with respect to a wavelength of light incident on the. 2. A semiconductor well layer of a second conductivity type semiconductor layer is formed on a semiconductor substrate of the first conductivity type, and a source region of the high-concentration first conductivity type semiconductor layer is formed on a surface layer portion of the semiconductor well layer. In an amplification type semiconductor imaging device in which a drain region is formed and a gate electrode is formed on an upper surface of a gate region between the source region and the drain region via an insulating film, a back surface of the semiconductor substrate is used as a light incident surface. At the same time, the amplification type semiconductor imaging device is formed such that the layer thickness of the semiconductor substrate is such that a depletion layer generated by a pn junction with the semiconductor well layer reaches the back surface of the semiconductor substrate. 3. The metal reflection film or the dielectric reflection film, wherein the electrode or the insulating film on the front surface side of the semiconductor substrate has a high reflectance with respect to the wavelength of light incident on the light incident surface on the back surface of the semiconductor substrate. The amplification type semiconductor image pickup device according to claim 1, which is formed of a film.