JP2008182042A - Solid-state imaging device and manufacturing method thereof - Google Patents

Abstract

A solid-state imaging device capable of preventing the occurrence of dark current due to an interface state generated at an interface between a semiconductor substrate and an insulating film without narrowing a photoelectric conversion region by impurity implantation and a method for manufacturing the same provide.
A photoelectric conversion region is formed near a main surface of a silicon substrate in a portion where external light is incident, and an external light incident side of the photoelectric conversion region is covered with a light-transmitting insulating film. In this solid-state imaging device, a surface recombination layer 106 having a composition of main elements and a band gap different from those of the photoelectric conversion region is formed between the photoelectric conversion region and the insulating film 102.
[Selection] Figure 2

Description

  The present invention relates to a solid-state imaging device, and more particularly to a technique for preventing dark current from being generated due to an interface state generated at an interface between a semiconductor substrate and an insulating film.

Solid-state imaging devices are used in video cameras, digital cameras, and the like, but in recent years, their sensitivity has increased and imaging with low illuminance is possible.
At low illuminance, the influence of the dark current due to the interface state generated at the interface between the insulating film of the solid-state imaging device and the semiconductor substrate (for example, a silicon substrate) becomes large, and video noise is likely to occur.
Therefore, a p-type impurity high concentration layer is formed in the silicon substrate in order to suppress the generation of dark current. FIG. 14 is a cross-sectional view around the unit pixel of the conventional solid-state imaging device 10 disclosed in Patent Document 1. The solid-state imaging device 10 includes a silicon substrate 11, an insulating film 15, a gate electrode 19, an interlayer insulating film 20, and a light shielding film 21.

In the silicon substrate 11, a p-type well layer 12, an n-type light receiving portion 13 constituting a photoelectric conversion region, a p-type impurity high concentration layer 14, a p-type element isolation portion 16, a p-type region 17, and an n-type charge transfer portion 18 is formed.
The p-type impurity high concentration layer 14 is formed on the upper surface side of the silicon substrate 11 and, as shown in FIG. 15, p electrons generated due to the interface state at the interface between the silicon substrate 11 and the insulating film 15 Generation of dark current due to the electrons is prevented by recombination with holes formed in the high concentration impurity layer 14.

15 indicates the level of electron energy, the thick line indicated by reference numeral 152 indicates the energy band at the lower end of the conduction band, and the dotted line indicated by reference numeral 153 indicates the energy band at the upper end of the valence band.
Thereby, generation | occurrence | production of a video noise can be prevented and favorable image quality can be implement | achieved also at low illumination intensity.
Japanese Patent Laid-Open No. 8-28896

  However, since boron (B) ion-implanted as a p-type impurity in order to form a p-type impurity high-concentration layer has a characteristic of being easily thermally diffused by heat treatment after ion implantation, the implanted boron (B) diffuses deep inside the silicon substrate 11 and reaches the photoelectric conversion region, which causes a problem of narrowing the photoelectric conversion region and reducing the maximum accumulated charge amount.

  In view of the above problems, the present invention provides a solid that can prevent the generation of dark current due to interface states generated at the interface between a semiconductor substrate and an insulating film without narrowing the photoelectric conversion region by impurity implantation. It is an object of the present invention to provide an imaging device and a manufacturing method thereof.

  In order to achieve the above object, according to the present invention, a photoelectric conversion region is formed in a portion near one main surface of a semiconductor substrate where external light is incident, and the external light incident side in the photoelectric conversion region is light transmissive. A solid-state imaging device covered with an insulating film, wherein a discontinuous band region in which a composition and a band gap of main elements are different from the photoelectric conversion region is formed between the photoelectric conversion region and the insulating film. ing.

The band gap in the band discontinuous region can be smaller than the band gap in the photoelectric conversion region.
The main element constituting the photoelectric conversion region can be silicon, and the main element constituting the band discontinuous region can be silicon, germanium, or carbon.
The main element constituting the photoelectric conversion region may be silicon, and the band discontinuous region may be composed of an intrinsic semiconductor layer containing at least silicon and germanium as main elements.

  Manufacture of a solid-state imaging device in which a photoelectric conversion region is formed in a portion near one main surface of a semiconductor substrate where external light is incident, and an external light incident side in the photoelectric conversion region is covered with a light-transmissive insulating film A recombination layer that forms a surface recombination layer having a band discontinuous region in which a composition and a band gap of main elements are different from those of the photoelectric conversion region between the photoelectric conversion region and the insulating film. A forming step may be included.

  The recombination layer forming step includes a deposition step of depositing the surface recombination layer on the semiconductor substrate by an epitaxial method, and a portion near one main surface of the semiconductor substrate where external light is incident, A forming step for forming a photoelectric conversion region and a covering step for covering the surface recombination layer deposited on the semiconductor substrate with an insulating film can be included.

The recombination layer forming step includes a first forming step in which the photoelectric conversion region is formed by doping an impurity in a portion near one main surface of the semiconductor substrate where external light is incident. A second forming step of forming the surface recombination layer by ion implantation of an element different from the main component into the photoelectric conversion region can be included.
The main elements constituting the surface recombination layer can be silicon, germanium, or carbon.

  A photoelectric conversion region is formed in the vicinity of one main surface of the semiconductor substrate where external light is incident, and a charge serving as a transfer destination of electrons generated in the photoelectric conversion region is located near the photoelectric conversion region. A solid-state imaging device in which a transfer region is formed, and an external light incident side and the charge transfer region in the photoelectric conversion region are covered with a single light-transmitting insulating film, wherein the charge transfer region and the insulation A band discontinuous region having a composition of a main element and a band gap different from that of the charge transfer region may be formed between the film and the film.

  The band gap in the band discontinuous region may be smaller than the band gap in the charge transfer region.

  By providing the above configuration, the present invention forms a band discontinuous region having a smaller band gap than the photoelectric conversion region or the charge transfer region in a region sandwiched between the insulating film and the photoelectric conversion region or the charge transfer region. Therefore, an electron energy barrier is formed between the band discontinuous region and the photoelectric conversion region or the charge transfer region, and the electron energy barrier is generated due to an interface state generated between the semiconductor substrate and the insulating film. Electrons can be prevented from flowing into the photoelectric conversion region or the charge transfer region from the band discontinuous region.

Therefore, generation of dark current due to the interface state can be suppressed without forming a p-type impurity layer on the surface layer of the photoelectric conversion region, and the photoelectric conversion region is narrowed as the p-type impurity layer is formed. The image quality of the solid-state imaging device is not deteriorated.
Here, in the semiconductor substrate, a charge transfer region that is covered with the insulating film and serves as a transfer destination of electrons generated in the photoelectric conversion region is formed at a position close to the photoelectric conversion region, and the charge transfer region A second band discontinuous region having a band gap smaller than that of the charge transfer region may be formed between the insulating layer and the insulating film.

The main element constituting the charge transfer region may be silicon, and the main element constituting the band discontinuous region may be silicon, germanium, or carbon.
Further, a charge transfer region that is covered with the insulating film and serves as a transfer destination of electrons generated in the photoelectric conversion region is formed at a position close to the photoelectric conversion region in the semiconductor substrate, and the recombination layer is formed. In the step, the second element further includes a second band discontinuous region between the charge transfer region and the insulating film, the main element being different in composition from the charge transfer region and having a band gap smaller than the charge transfer region. A two-surface recombination layer can be formed.

  As a result, a second band discontinuous region having a band gap smaller than that of the charge transfer region is formed in a region sandwiched between the insulating film and the charge transfer region, and therefore, between the second band discontinuous region and the charge transfer region. An electron energy barrier is formed on the substrate, and the electron energy barrier can prevent electrons generated due to an interface state generated between the semiconductor substrate and the insulating film from flowing into the charge transfer region.

Here, the composition of the main element in the band discontinuous region may be composed of a composition ratio that lattice matches with the semiconductor substrate.
As a result, the band discontinuous region can be lattice-matched to the semiconductor substrate, so that the crystal structure is distorted between the band discontinuous region and the other region in the semiconductor substrate, and the crystal defect is generated in the semiconductor substrate. It is possible to prevent the occurrence of image quality deterioration of the solid-state imaging device.

Here, the composition ratio Ge / C of germanium and carbon in the band discontinuous region can be 6.4 or more and 11.1 or less.
Further, the composition ratio Ge / C between germanium and carbon in the elemental composition of the main element can be 6.4 or more and 11.1 or less.
As a result, a high-quality crystal structure free from lattice defects due to strain can be formed on the semiconductor substrate in which the band discontinuous region is formed, and image quality deterioration due to crystal defects occurring in the solid-state imaging device can be prevented. .

Here, the band discontinuous region may be composed of a plurality of layers having different elemental compositions of silicon, germanium, and carbon.
In the deposition step, a plurality of layers having different elemental compositions of the main element may be laminated to form the surface recombination layer on the semiconductor substrate.
Accordingly, a superlattice for relaxing the distortion of the crystal structure can be formed between layers having different element compositions, so that it is possible to prevent crystal defects from occurring in the band discontinuous region.

Here, the band discontinuous region may further include an impurity having a conductivity type different from that of the photoelectric conversion region.
The main element constituting the photoelectric conversion region is silicon, the band discontinuous region is composed of two layers, and one of the two layers located on the insulating film side is mainly composed of silicon. The other layer included as an element and located on the photoelectric conversion region side includes at least silicon and germanium as main elements, and the two layers further include impurities of a conductivity type different from the conductivity type of the photoelectric conversion region. Can be.

  The main element constituting the photoelectric conversion region is silicon, the band discontinuous region is composed of two layers, and one of the two layers located on the insulating film side is mainly composed of silicon. Intrinsic semiconductor which contains an impurity of a conductivity type different from that of the photoelectric conversion region and the other one layer located on the photoelectric conversion region side contains at least silicon and germanium as main elements It can be a layer.

The conductivity type of the photoelectric conversion region may be n-type, and the conductivity type different from the conductivity type may be p-type.
As a result, an impurity layer having a conductivity type different from that of the photoelectric conversion region is formed in the band discontinuous region. For example, when the conductivity type of the photoelectric conversion region is n-type, a p-type impurity layer is formed in the band discontinuous region. Thus, when electrons generated due to interface states generated at the interface between the insulating film and the semiconductor substrate move to the p-type impurity layer, they can be combined with holes and disappear.

Therefore, the generation of dark current due to the interface state is effectively suppressed by the synergistic effect of the effect of the electron energy barrier generated between the band discontinuous region and the photoelectric conversion region and the effect of the p-type impurity layer. Can do.
Here, the composition of the main element in the second band discontinuous region may be composed of a composition ratio that lattice matches with the semiconductor substrate.

As a result, the second band discontinuous region can be lattice-matched with the semiconductor substrate, so that the crystal structure is distorted between the second band discontinuous region and the other region in the semiconductor substrate. Crystal defects can be prevented and image quality deterioration of the solid-state imaging device can be prevented.
Here, the composition ratio Ge / C between germanium and carbon in the second band discontinuous region may be 6.4 or more and 11.1 or less.

As a result, a high-quality crystal structure free from lattice defects due to strain can be formed on the semiconductor substrate in which the second band discontinuous region is formed, and image quality deterioration due to crystal defects occurring in the solid-state imaging device can be prevented. Can do.
Here, the second band discontinuous region may be composed of a plurality of layers having different elemental compositions of silicon, germanium, and carbon.

Thereby, a superlattice for relaxing the distortion of the crystal structure can be formed between layers having different elemental compositions, so that a crystal defect can be prevented from occurring in the second band discontinuous region.
Here, the second band discontinuous region may further include an impurity having a conductivity type different from that of the photoelectric conversion region.

The conductivity type of the photoelectric conversion region may be n-type, and the conductivity type different from the conductivity type may be p-type.
As a result, an impurity layer having a conductivity type different from that of the photoelectric conversion region is formed in the second band discontinuous region. For example, when the conductivity type of the photoelectric conversion region is n-type, p is formed in the second band discontinuous region. Since the type impurity layer is formed, when electrons generated due to the interface state generated at the interface between the insulating film and the semiconductor substrate move to the p-type impurity layer, they can be combined with holes and disappear. it can.

Therefore, the synergistic effect of the effect of the electron energy barrier generated between the second band discontinuous region and the charge transfer region and the effect of the p-type impurity layer effectively suppresses the generation of dark current due to the interface state. can do.
Here, in the second forming step, the crystal structure of the photoelectric conversion region is made amorphous by ion-implanting an element different from the main component element of the photoelectric conversion region by a predetermined dose or more, thereby forming the recombination layer. The step further includes a third formation step of forming an impurity region in the surface recombination layer by ion-implanting an impurity having a conductivity type different from that of the photoelectric conversion region into the amorphous photoelectric conversion region. Can be.

The predetermined dose may be 5 × 10 ¹³ pieces / cm ² .
As a result, since the impurity for forming the impurity region is ion-implanted into the photoelectric conversion region in a state where the photoelectric conversion region is amorphized, the collision between the implanted impurity and the main element constituting the photoelectric conversion region is prevented. It becomes easy to occur, and it is possible to prevent the collision from occurring frequently in the process of diffusing the impurity and the impurity reaching the deep region of the photoelectric conversion region.

Therefore, generation of dark current due to the interface state between the semiconductor substrate and the insulating film can be prevented while suppressing narrowing of the photoelectric conversion region due to impurities.
Here, the main component element is silicon, the different element is germanium, and the recombination layer forming step further includes conducting the photoelectric conversion region to the photoelectric conversion region having an amorphized structure. A carbon implantation step of ion-implanting carbon may be included before the impurity having a conductivity type different from the type is ion-implanted.

  As a result, the main element (so-called interstitial atoms) in the photoelectric conversion region, which is generated by ion implantation and promotes the diffusion of impurities and moved from the lattice point to the lattice, is trapped by the carbon atoms implanted in advance. Impurities can be prevented from reaching a deep region of the photoelectric conversion region.

Hereinafter, embodiments of the present invention will be described.
(Embodiment 1)
<Configuration>
FIG. 1 is a diagram illustrating an outline of the configuration of the solid-state imaging device 100.
As shown in FIG. 1, the solid-state imaging device 100 according to the present embodiment includes a plurality of photodiodes 1 arranged in two horizontal and vertical directions and a photodiode 1 arranged in the vertical direction on a semiconductor substrate plane. The vertical CCD (Charge Coupled Device) 2, the horizontal CCD 4, and the output amplifier 3 are arranged so as to be adjacent to each column.

The plurality of photodiodes 1 and the vertical CCD 2 constitute a pixel region. The vertical CCD 2 transfers signal electrons generated by photoelectric conversion in the photodiode 1 in the vertical direction, and the horizontal CCD 4 transfers signal electrons transferred from the vertical CCD 2. Is transferred in the horizontal direction, and the output amplifier 3 converts the signal electrons transferred from the horizontal CCD 4 into a voltage and outputs the voltage.
FIG. 2 is a cross-sectional view of the solid-state imaging device 100 taken along the line aa ′.

The region shown in the cross-sectional view of the solid-state imaging device 100 includes a silicon substrate 101, an insulating film 102, a gate electrode 103, an interlayer insulating film 104, a light shielding film 105, and a surface recombination layer 106.
In the silicon substrate 101, a p-type well layer 107, an n-type light receiving unit 108, a p-type element isolation unit 109, an n-type charge transfer unit 110, and a p-type region 111 are formed.
(P-type well layer 107)
This is a layer containing a p-type impurity (for example, boron (B)) formed inside the silicon substrate 101.

(N-type light receiving unit 108)
This is a region containing n-type impurities (for example, arsenic (As)) formed inside the silicon substrate 101, and forms a photoelectric conversion region.
(P-type element isolation unit 109)
This is a region formed between the n-type light receiving unit 108 and the n-type charge transfer unit 110 and contains p-type impurities, and prevents electrons from flowing into the n-type charge transfer unit 110 from the n-type light receiving unit 108. .

(N-type charge transfer unit 110)
Near the surface of the silicon substrate 101, an n-type charge transfer unit 110 is formed, and signal electrons generated by photoelectric conversion in the n-type light receiving unit 108 are transferred.
(P-type region 111)
This is a region containing p-type impurities (for example, boron (B)) formed inside the silicon substrate 101, and is formed under the n-type charge transfer unit 110.

(Surface recombination layer 106)
FIG. 3 is a view showing the structure of the surface recombination layer 106. As shown in FIG. 3, the surface recombination layer 106 includes a silicon layer 1061 made of silicon (Si) and a discontinuous layer (SiGe layer) 1062 made of a mixed crystal (SiGe layer) of silicon (Si) and germanium (Ge). An intrinsic semiconductor layer that does not contain p-type impurities.

The composition ratio (Si / Ge) of silicon (Si) and germanium (Ge) in the discontinuous layer 1062 is desirably 1.0 to 19.0 in terms of atomic ratio in order to obtain a high-quality crystal structure without crystal defects.
Further, the discontinuous layer 1062 may be a mixed crystal (SiGeC layer) of silicon (Si), germanium (Ge), and carbon (C). The lattice constant (5.65 （) of germanium (Ge) is larger than the (Si) lattice constant (5.43Å) of silicon, whereas the lattice constant (3.57Å) of carbon (C) is larger than that of silicon (Si). Therefore, by including both elements in the discontinuous layer 1062, strain due to lattice mismatch can be reduced.

In particular, by making the composition ratio (Ge / C) of germanium (Ge) and carbon (C) so that the atomic ratio is about 8.2, the lattice constant is matched with the lattice constant of the silicon substrate 101. When lattice-matched with the silicon substrate 101, the strain can be extremely reduced.
Here, “lattice matching” means that the lattice constant of the discontinuous layer 1062 is 99.81 to 100.08% of the lattice constant of the silicon substrate 101.

In order to form a high-quality crystal free from lattice defects due to strain, it is desirable that the composition ratio (Ge / C) in the discontinuous layer 1062 be in the range of 6.4 to 11.1.
The content of carbon (C) in the mixed crystal of silicon (Si), germanium (Ge), and carbon (C) is preferably 2% to 5% in terms of the number of atoms, The germanium (Ge) content in the mixed crystal is preferably 5% to 50% in terms of the number of atoms.

Thereby, it is possible to prevent crystal defects from occurring in the mixed crystal.
FIG. 4 shows the energy band structure around the surface recombination layer 106. 4 indicates the level of electron energy, the thick line indicated by reference numeral 42 indicates the energy band at the lower end of the conduction band, and the dotted line indicated by reference numeral 43 indicates the energy band at the upper end of the valence band.
Since silicon (Si) has a larger band gap than germanium (Ge), the band gap in the discontinuous layer 1062 which is a mixed crystal of silicon (Si) and germanium (Ge) is the silicon layer 1061 and the n-type light receiving portion 108. As shown in FIG. 4, the heterointerface between the silicon layer 1061 and the discontinuous layer 1062 and the heterointerface between the discontinuous layer 1062 and the n-type light-receiving portion 108 are formed as shown in FIG. Band discontinuities occur in the conduction band and valence band.

Accordingly, electrons generated due to the interface state generated at the interface between the insulating film 102 and the silicon substrate 101 are confined in the discontinuous layer 1062, and the electrons are prevented from flowing into the n-type light receiving unit 108. Therefore, unlike the conventional solid-state imaging device 10, it is possible to prevent the generation of dark current due to the interface state without forming the p-type impurity high concentration layer 14.
(Insulating film 102)
It consists of a light transmissive silicon oxide film (SiO ₂ film) and covers the surface of the silicon substrate 101.

(Gate electrode 103)
This is an electrode for transferring the signal electrons generated by the n-type light receiving unit 108 to the n-type charge transfer unit 110, which is composed of a polysilicon film or the like and is disposed on the surface of the insulating film 102.
(Interlayer insulating film 104)
It is composed of a silicon oxide film (SiO ₂ film). The gate electrode 103 is covered.

(Light shielding film 105)
It is made of a tungsten (W) film, an aluminum (Al) film, or the like, and covers the interlayer insulating film 104.
<Manufacturing method>
(Step of forming surface recombination layer 106)
FIG. 5 is a diagram showing each process for forming the surface recombination layer 106.

A discontinuous layer 1062 is formed on the silicon substrate 101 shown in FIG. 5A by an epitaxial growth method as shown in FIG. 5B, and the discontinuous layer 1062 further formed is shown in FIG. 5C. In this manner, the surface recombination layer 106 is formed by forming the silicon layer 1061 by an epitaxial growth method.
As the epitaxial growth method, a chemical vapor deposition method (CVD method), a molecular beam epitaxy method (MBE method), or the like can be used.

As the CVD method, for example, an ultra-high vacuum CVD (UHV / CVD) method in which crystal growth is performed in a low-pressure molecular flow region can be used. In the UHV / CVD method, since epitaxial growth is performed at a low temperature, a highly reactive gas is used as a raw material.
Specifically, disilane (Si ₂ H ₆ ) germane (GeH ₄ ) is used as a raw material for forming the SiGe layer.

Further, in the case of forming the SiGeC layer, monomethylsilane (CH ₃ SiH ₃ ), dimethylsilane ((CH ₃ ) ₂ SiH ₂ ), trimethylsilane ((CH ₃ ) ₃ SiH) are further used as the C source gas. , Methane, ethylene, acetylene, etc. are used.
The germanium (Ge) composition ratio and carbon (C) composition ratio in the discontinuous layer 1062 can be controlled by adjusting the supply amount of the gas.

The pressure during epitaxial growth is desirably about 1 Pa or less in order to perform uniform epitaxial growth.
The growth temperature for epitaxial growth is preferably 500 ° C. to 650 ° C. in order to prevent the crystallinity of the epitaxial growth layer from deteriorating.
(Pixel area formation process)
FIG. 6 is a diagram illustrating each process for forming a pixel region of the solid-state imaging device 100. As shown in FIG. 6A, a silicon oxide film (SiO ₂ ) 51 serving as a protective film is formed on the surface of the silicon substrate 101 on which the surface recombination layer 106 is formed, and the silicon oxide film 51 is interposed therebetween. The p-type impurity boron (B) is ion-implanted to form the p-type well layer 107, a resist pattern corresponding to the formation region of the n-type light-receiving portion 108 is formed, and arsenic (As) is ion-implanted. After the n-type light-receiving portion 108 is formed, the resist pattern is removed and annealing (RTA (Rapid Thermal Annealing) is performed in a nitrogen atmosphere.

Here, annealing is performed at a temperature of 900 ° C. to 1100 ° C. for 30 seconds to 60 seconds, for example.
Arsenic (As) ion implantation can be performed, for example, at an acceleration energy of 550 KeV and a dose of 2.6 × 10 ¹² ions / cm ² .
Next, as shown in FIG. 6B, a resist pattern corresponding to the n-type charge transfer unit 110 and the p-type region 111 is formed, and boron (B) and arsenic (As) are sequentially ion-implanted,
After the p-type region 111 and the n-type charge transfer unit 110 are formed, the resist pattern is removed.

Next, as shown in FIG. 6C, after the silicon oxide film 51 is peeled off, a silicon oxide film (SiO ₂ film) having a thickness of about 30 nm is formed on the surface layer of the surface recombination layer 106 by thermal oxidation. After forming the insulating film 102 to be formed, a resist pattern corresponding to the p-type element isolation portion 109 is formed, boron (B) is ion-implanted to form the p-type element isolation portion 109, and then the resist pattern is removed. .

Next, as shown in FIG. 6D, a polysilicon film having a thickness of about 250 nm is grown on the formed insulating film 102 by the CVD method, a resist pattern corresponding to the gate electrode is formed, and dry etching is performed. Then, the gate electrode 103 is formed.
Next, as shown in FIG. 6E, the formed gate electrode 103 is covered with an interlayer insulating film 104 made of a silicon oxide film (SiO ₂ film) by thermal oxidation.

Next, as shown in FIG. 6F, a tungsten (W) film having a thickness of about 200 nm is formed by sputtering, and dry etching is performed so that an opening is formed above the n-type light-receiving portion 108. Then, a part of the formed tungsten (W) film is removed, and the light shielding film 105 is formed.
(Solid-state imaging device formation process)
In addition to the above steps, the solid-state imaging device 100 is completed by forming the horizontal CCD 4, the output amplifier 3, and the like other than the pixel region shown in FIG.

(Embodiment 2)
In the first embodiment, the p-type impurity layer is not formed in the surface recombination layer 105. However, in the solid-state imaging device according to the present embodiment, the p-type impurity layer is formed in the surface recombination layer. This is different from the first embodiment.

By providing the above configuration, it is possible to enhance the dark current suppression effect.
<Configuration>
The configuration of the solid-state imaging device 200 according to Embodiment 2 is the same as the configuration of the solid-state imaging device 100 shown in FIG.
FIG. 7 is a cross-sectional view corresponding to the cross-sectional view along the line aa ′ in FIG.

The region shown in the cross-sectional view of the solid-state imaging device 200 includes a silicon substrate 101, an insulating film 102, a gate electrode 103, an interlayer insulating film 104, a light shielding film 105, and a p-type impurity discontinuous layer 206.
About each said component, the same number is attached | subjected about the same component as the solid-state imaging device 100 which concerns on Embodiment 1. FIG. Hereinafter, the p-type impurity discontinuous layer 206 having different components will be described, and description of the same components will be omitted.
(P-type impurity discontinuous layer 206)
The p-type impurity discontinuous layer 206 is formed by doping a mixed crystal layer of silicon (Si) and germanium (Ge) with p-type impurity boron (B).

  Since silicon (Si) has a larger band gap than germanium (Ge), the band gap in the p-type impurity discontinuous layer 206 can be made narrower than the band gap in the n-type light-receiving portion 108, and the p-type impurity discontinuity can be reduced. At the heterointerface between the layer 206 and the n-type light-receiving portion 108, band discontinuity occurs in the conduction band and the valence band, as in FIG.

As a result, an energy barrier against the movement of electrons occurs between the p-type impurity discontinuous layer 206 and the n-type light-receiving portion 108 formed thereunder, so that an interface generated at the interface between the insulating film 102 and the silicon substrate 101 is generated. Electrons generated due to the level can be confined inside the p-type impurity discontinuous layer 206, and can be prevented from flowing into the n-type light receiving unit 108.
In addition, since holes are formed in the p-type impurity discontinuous layer 206 by doping boron (B), electrons generated due to the interface states generated at the interface between the insulating film 102 and the silicon substrate 101 are When moving into the p-type impurity discontinuous layer 206, electrons can be annihilated by combining with holes.

As described above, in the p-type impurity discontinuous layer 206, the movement of electrons generated due to the interface states into the n-type light receiving portion 108 can be synergistically suppressed.
<Manufacturing method>
FIG. 8 is a diagram illustrating each process for forming a pixel region of the solid-state imaging device 200. As shown in FIG. 8A, a silicon oxide film (SiO ₂ ) 51 serving as a protective film is formed on the surface of the silicon substrate 101, and boron (B) as a p-type impurity is ionized through the silicon oxide film 51. Implantation is performed to form a p-type well layer 107, a resist pattern corresponding to the formation region of the n-type light-receiving portion 108 is formed, and arsenic (As) is ion-implanted to form the n-type light-receiving portion 108. Then, the resist pattern is removed and annealing is performed in a nitrogen atmosphere.

Here, the annealing is performed, for example, at a temperature of 900 ° C. to 1100 ° C. for a time of 30 seconds to 60 seconds.
Arsenic (As) ion implantation can be performed, for example, at an acceleration energy of 550 KeV and a dose of 2.6 × 10 ¹² ions / cm ² .
Next, as shown in FIG. 8B, a resist pattern corresponding to the n-type charge transfer unit 110 and the p-type region 111 is formed, and boron (B) and arsenic (As) are sequentially ion-implanted,
After the n-type charge transfer unit 110 and the p-type region 111 are formed, the resist pattern is removed.

Next, as shown in FIG. 8C, after the silicon oxide film 51 is peeled off, an insulating layer made of a silicon oxide film (SiO ₂ film) having a thickness of about 30 nm is formed on the surface layer of the silicon substrate 101 by a thermal oxidation method. The film 102 is formed, a resist pattern corresponding to the p-type element isolation portion 109 is formed, boron (B) is ion-implanted to form the p-type element isolation portion 109, and then the resist pattern is removed.

Next, as shown in FIG. 8D, a polysilicon film having a thickness of about 250 nm is grown on the formed insulating film 102 by CVD, a resist pattern corresponding to the gate electrode is formed, and dry etching is performed. Then, the gate electrode 103 is formed.
Next, as shown in FIG. 8E, germanium (Ge) ion implantation is performed using the gate electrode 103 as a mask to make the surface layer of the n-type light receiving portion 108 amorphous. The ion implantation is performed with an acceleration energy of 50 keV and a dose amount of 5 × 10 ¹³ ions / cm ² or more.

After germanium (Ge) is ion-implanted, boron (B) is further ion-implanted into the n-type light-receiving portion 108 to form a p-type impurity discontinuous layer 206 on the surface layer.
The ion implantation of boron (B) is performed at an acceleration energy of 10 keV and a dose amount of 5 × 10 ¹³ ions / cm ² or more.
Since the ion implantation of boron (B) is performed in a state where the surface layer of the n-type light receiving portion 108 is amorphized, the implanted boron (B) collides with the element (Si) present at the lattice point, The diffusion of boron (B) is suppressed as compared with the case where boron (B) is ion-implanted when the surface layer of the n-type light receiving unit 108 is not in an amorphous state.

  FIG. 9 shows that when boron (B) is ion-implanted in a state where the n-type light receiving portion 108 is not amorphized (having a crystal structure), boron (B) diffuses into the n-type light receiving portion 108. FIG. 10 is a conceptual diagram showing the state in which boron (B) diffuses into the n-type light receiving unit 108 when boron (B) is ion-implanted in a state where the n-type light receiving unit 108 is amorphized. It is an image figure which shows a mode that it does.

  As shown in FIG. 9, when boron (B) is ion-implanted in a non-amorphous state, the main components constituting the n-type light receiving unit 108, which is regularly arranged at lattice points and indicated by reference numeral 90, is shown. Boron (B) indicated by reference numeral 92 diffuses deeply into the n-type light receiving portion 108 through a lattice space indicated by reference numeral 91 existing between elements (Si or Ge), as shown in FIG. When boron (B) is ion-implanted in an amorphous state, the lattice structure is distorted. Therefore, boron (B) indicated by reference numeral 92 is indicated by reference numeral 90 arranged at the lattice points. Then, while colliding with the main element (Si or Ge) of the n-type light-receiving unit 108, it proceeds inside the n-type light-receiving unit 108, and boron (B) is prevented from diffusing deep inside the n-type light-receiving unit 108. be able to.

Note that reference numeral 93 in FIGS. 9 and 10 indicates a hole in which no element is arranged at the lattice point. When boron (B) is arranged in the hole, the hole is bonded to the surrounding Si element to form a hole. Is formed.
Next, after boron (B) is ion-implanted as described above, the resist pattern is removed, and annealing is performed in a nitrogen atmosphere.
Here, annealing is performed at a temperature of 900 ° C. to 1100 ° C. for 30 seconds to 60 seconds, for example.

Next, as shown in FIG. 8E, the formed gate electrode 103 is covered with an interlayer insulating film 104 made of a silicon oxide film (SiO ₂ film) by thermal oxidation.
Next, as shown in FIG. 8F, a tungsten (W) film having a thickness of about 200 nm is formed by sputtering, and dry etching is performed so that an opening is formed above the n-type light-receiving portion 108. Then, a part of the formed tungsten (W) film is removed, and the light shielding film 105 is formed.

In addition to the above steps, the solid-state imaging device 200 is completed by forming the horizontal CCD 4, the output amplifier 3, and the like other than the pixel region shown in FIG.
(Example)
In FIG. 16, according to the manufacturing method according to the second embodiment, p-type impurities (boron (B)) are ion-implanted in a state where the n-type light receiving portion is amorphized, and the p-type impurity discontinuous layer 206 is formed. Comparison of the concentration distribution of the p-type impurity in the solid-state imaging device with the case where the p-type impurity layer is formed by ion implantation of boron (B) without making the n-type light receiving portion amorphous according to the conventional method FIG.

The concentration distribution of the p-type impurity was examined by secondary ion mass spectrometry (SIMS).
FIG. 16 shows the concentration distribution of the p-type impurity in the light receiving region extending from the interface with the insulating film (SiO ₂ ) to the n-type light receiving portion.
The broken line indicated by reference numeral 162 in FIG. 16 indicates the concentration distribution of boron (B) when boron (B) is ion-implanted according to the conventional method, and the solid line indicated by reference numeral 161 in FIG. 16 indicates the second embodiment. 2 shows the boron (B) concentration distribution when the p-type impurity discontinuous layer 206 is formed according to the manufacturing method according to FIG.

As shown in FIG. 16, in the case where the p-type impurity discontinuous layer 206 is formed according to the manufacturing method according to the second embodiment, boron (B), as shown in FIG. The concentration distribution range in the region where the n-type light receiving portion is formed is narrower and more densely distributed. For this reason, according to the second embodiment, the generation of dark current and white scratches caused by interface states and crystal defects due to ion implantation is reduced, and the photoelectric conversion region is narrowed by diffusion of p-type impurities, It can suppress that the saturation charge amount of a photodiode falls. As a result, the solid-state imaging device according to the second embodiment can improve the image quality of the output image as compared with the conventional solid-state imaging device.
(Embodiment 3)
In the second embodiment, the p-type impurity discontinuous layer 206 is formed by making the surface layer of the n-type light-receiving portion amorphous to suppress the diffusion of the p-type impurity. However, in the third embodiment, The second embodiment is different from the second embodiment in that the diffusion of p-type impurities is suppressed by ion-implanting carbon (C) before ion-implanting p-type impurities into the n-type light-receiving portion.
<Configuration>
The configuration of the solid-state imaging device 300 according to Embodiment 3 is the same as the configuration of the solid-state imaging device 100 shown in FIG.

FIG. 11 is a cross-sectional view corresponding to the cross-sectional view along the line aa ′ in FIG.
The region shown in the cross-sectional view of the solid-state imaging device 300 includes a silicon substrate 101, an insulating film 102, a gate electrode 103, an interlayer insulating film 104, a light shielding film 105, and a p-type impurity discontinuous layer 306.

About each said component, the same number is attached | subjected about the same component as the solid-state imaging device 100 which concerns on Embodiment 1. FIG. Hereinafter, the p-type impurity discontinuous layer 306 having different components will be described, and description of the same components will be omitted.
(P-type impurity discontinuous layer 306)
The p-type impurity discontinuous layer 206 is formed by doping a mixed crystal layer of silicon (Si), germanium (Ge), and carbon (C) with boron (B) as a p-type impurity.

  Since silicon (Si) has a larger band gap than germanium (Ge) and a smaller band gap than carbon (C), the p-type impurity discontinuous layer 306 is controlled by controlling the composition ratio of Si, Ge, and C. 3 can be made narrower than the band gap in the n-type light receiving unit 108, and the heterointerface between the p-type impurity discontinuous layer 306 and the n-type light receiving unit 108 is similar to the case of FIG. Band discontinuities occur in the conduction band and valence band.

Further, as described in the first embodiment, by including both Ge and C elements in the p-type impurity discontinuous layer 306, strain due to lattice mismatch can be reduced.
In particular, when the mixing ratio of germanium and carbon (Ge / C) is set to around 8.2 so that the lattice constant coincides with the lattice constant of the silicon substrate 101 and is lattice-matched with the silicon substrate 101, the distortion is extremely small. can do.

Further, in order to form a high-quality crystal free from lattice defects due to strain, it is desirable that the mixing ratio (Ge / C) of Ge and C in the p-type impurity discontinuous layer 306 is in the range of 6.4 to 11.1. .
As a result, the p-type impurity discontinuous layer 306 having a band gap smaller than that of the n-type light receiving portion 108 is formed while reducing the distortion in the mixed crystal layer, so that the p-type impurity discontinuous layer 306 and the lower layer are formed. An energy barrier against the movement of electrons is generated between the n-type light-receiving portion 108 and the p-type impurity discontinuous layer 306, which generates electrons due to the interface state generated at the interface between the insulating film 102 and the silicon substrate 101. And can be prevented from flowing into the n-type light receiving unit 108.

Further, since holes are formed in the p-type impurity discontinuous layer 306 due to boron doping, electrons generated due to interface states generated at the interface between the insulating film 102 and the silicon substrate 101 are converted into p-type impurities. When moving into the discontinuous layer 306, it can be combined with holes and annihilated.
As described above, in the p-type impurity discontinuous layer 306, the movement of electrons generated due to the interface state into the n-type light receiving portion 108 can be synergistically suppressed.

Note that the p-type impurity discontinuous layer 306 may be formed of a mixed crystal of silicon (Si) and carbon (C).
In this case, an energy barrier against electrons generated by the interface state generated at the interface between the insulating film 102 and the silicon substrate 101 is increased, so that the electrons can be prevented from entering the p-type impurity discontinuous layer 306. it can.
<Manufacturing method>
FIG. 12 is a diagram illustrating each process for forming a pixel region of the solid-state imaging device 300. As shown in FIG. 12A, a silicon oxide film (SiO ₂ ) 51 serving as a protective film is formed on the surface of the silicon substrate 101, and p-type impurity boron (B) is added through the silicon oxide film 51. After forming the p-type well layer 107 by ion implantation, forming a resist pattern corresponding to the formation region of the n-type light receiving portion 108, and implanting arsenic (As) to form the n-type light receiving portion 108. Then, the resist pattern is removed and annealing is performed in a nitrogen atmosphere.

Here, annealing is performed at a temperature of 900 ° C. to 1100 ° C. for 30 seconds to 60 seconds, for example.
Arsenic (As) ion implantation can be performed, for example, at an acceleration energy of 550 KeV and a dose of 2.6 × 10 ¹² ions / cm ² .
Next, as shown in FIG. 12B, a resist pattern corresponding to the n-type charge transfer portion 110 and the p-type region 111 is formed, and boron (B) and arsenic (As) are ion-implanted in this order, and the n-type is transferred. After the charge transfer unit 110 and the p-type region 111 are formed, the resist pattern is removed.

Next, as shown in FIG. 12C, after the silicon oxide film 51 is peeled off, an insulating film made of a silicon oxide film (SiO ₂ ) having a thickness of about 30 nm is formed on the surface layer of the silicon substrate 101 by a thermal oxidation method. 102 is formed, a resist pattern corresponding to the p-type element isolation portion 109 is formed, boron (B) is ion-implanted to form the p-type element isolation portion 109, and then the resist pattern is removed.

Next, as shown in FIG. 12D, a polysilicon film having a thickness of about 250 nm is grown on the formed insulating film 102 by CVD, a resist pattern corresponding to the gate electrode is formed, and dry etching is performed. Then, the gate electrode 103 is formed.
Next, as shown in FIG. 12E, germanium (Ge) ions are implanted using the gate electrode 103 as a mask to make the surface layer of the n-type light receiving portion 108 amorphous. The ion implantation is performed with an acceleration energy of 50 keV and a dose amount of 5 × 10 ¹³ ions / cm ² or more.

Next, after carbon (C) is ion-implanted into the n-type light-receiving portion 108, boron (B) is further ion-implanted into the n-type light-receiving portion 108 to form a p-type impurity discontinuous layer 306 on the surface layer. Further, annealing is performed in a nitrogen atmosphere. The annealing is performed at a temperature of 900 ° C. to 1100 ° C. for 30 seconds to 40 minutes, for example.
Here, ion implantation of carbon (C) is performed at an acceleration energy of 10 keV and a dose amount of 5 × 10 ¹³ ions / cm ² or more, and boron (B) ion implantation is performed at an acceleration energy of 10 keV and a dose amount of 5 × 10 5. ^{It is performed at 13} pieces / cm ² or more.

Thereby, in addition to the effect of suppressing the diffusion of boron (B) due to amorphization, the Si atoms moved from the lattice points to the lattice by the ion implantation are trapped by the carbon (C) atoms implanted, so Diffusion of boron (B) atoms diffusing through Si atoms present in the substrate is suppressed.
Therefore, the boron (B) diffusion suppression effect by the amorphousization by Ge ion implantation and the boron (B) diffusion suppression effect by the C ion implantation act synergistically, and the boron (B) n-type light receiving portion. Diffusion into the deep part of 108 can be effectively suppressed.

Next, as shown in FIG. 12E, the formed gate electrode 103 is covered with an interlayer insulating film 104 made of a silicon oxide film (SiO ₂ film) by thermal oxidation.
Next, as shown in FIG. 12 (f), a tungsten (W) film having a thickness of about 200 nm is formed by sputtering, and dry etching is performed so that an opening is formed above the n-type light-receiving portion 108. Then, a part of the formed tungsten (W) film is removed, and the light shielding film 105 is formed.

In addition to the above steps, the solid-state imaging device 300 is completed by forming the horizontal CCD 4, the output amplifier 3, and the like other than the pixel region shown in FIG.
(Example)
(Test method)
A sample of the solid-state imaging device 200 created in accordance with the manufacturing method according to the second embodiment (hereinafter referred to as “control sample”) and a sample of the solid-state imaging device 300 created in accordance with the manufacturing method of the third embodiment (hereinafter referred to as “ About the test sample ", the concentration distribution of the p-type impurity (boron (B)) in the solid-state imaging device was compared.

Specifically, for the control sample, the p-type impurity discontinuous layer 206 is ion-implanted into the silicon substrate 101 with germanium (Ge) at 50 keV and 5 × 10 ¹³ ions / cm ² , and then boron (B) is 10 keV. It is formed by ion implantation at 5 × 10 ¹³ pieces / cm ^2. For the test sample, a p-type impurity discontinuous layer 306 is formed, and germanium (Ge) is 50 keV on the silicon substrate 101, 5 × 10 ¹³ pieces / cm 2. ^Then , carbon (C) is ion-implanted at 10 keV, 5 × 10 ¹³ atoms / cm ² , and boron (B) is ion-implanted at 10 keV, 5 × 10 ¹³ atoms / cm ^2. ,
Formed.

Each prepared sample was annealed (RTA) at 950 ° C. for 30 seconds in a nitrogen atmosphere, and secondary ion mass spectrometry (SIMS) was performed on the region in the vicinity of the n-type light receiving portion in each sample. The impurity concentration distribution was investigated using this method.
(Test results)
FIG. 13 is a diagram comparing the concentration distribution of boron (B) for the measurement samples.

FIG. 13 (a) shows the concentration distribution of boron (B) in the control sample, and FIG. 13 (b) shows the concentration distribution of boron (B) in the test sample.
Reference numeral 131 shown in FIG. 13A indicates the concentration distribution of boron (B) in the control sample before the annealing after ion implantation of boron (B). Reference numeral 132 shown in FIG. Shows the concentration distribution of boron (B) in the control sample after annealing.

Further, a region denoted by reference numeral 133 shown in FIG. 13A indicates a region where the p-type impurity discontinuous layer 206 is formed, and a region indicated by reference numeral 134 shown in FIG. 13A indicates an n-type light receiving layer. The area | region in which 108 is formed is shown.
Reference numeral 135 shown in FIG. 13B indicates the concentration distribution of boron (B) in the test sample after ion implantation of boron (B) and before annealing, and reference numeral 136 shown in FIG. 13B. Indicates the concentration distribution of boron (B) in the test sample after annealing.

Further, the region indicated by reference numeral 137 shown in FIG. 13B indicates a region where the p-type impurity discontinuous layer 306 is formed, and the region indicated by reference numeral 138 shown in FIG. 13B indicates an n-type light receiving layer. The area | region in which 108 is formed is shown.
As shown in FIG. 13B, the p-type impurity discontinuous layer is made of a mixed crystal (SiGeC) of silicon (Si), germanium (Ge), and carbon (C), so that the structure shown in FIG. Furthermore, compared to the case where the p-type impurity discontinuous layer is a mixed crystal (SiGe) of silicon (Si) and germanium (Ge), the boron (B) undoped layer (Si layer) after annealing (RTA) is used. Is suppressed to about 1/10.
(Supplement)
Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments.
(1) In the first embodiment, the surface recombination layer 106 includes the silicon layer 1061 and the discontinuous layer 1062, but the silicon layer 1061 has a mass number higher than that of p-type impurities such as boron in the silicon layer. It may be formed of a p-type impurity layer doped with a group III element having a large diffusion coefficient and a small diffusion coefficient, for example, indium.

As a result, the generation of dark current due to the interface state is effectively achieved by the synergistic effect of the effect of the electron energy barrier generated between the discontinuous layer 1062 and the n-type light receiving portion 108 and the effect of the p-type impurity layer. Can be suppressed.
Alternatively, both the silicon layer 1061 and the discontinuous layer 1062 may be doped with indium, and both layers may be p-type impurity layers.

In the present embodiment, the surface recombination layer 106 is composed of two layers of the silicon layer 1061 and the discontinuous layer 1062, but the silicon layer 1061 is not provided and the surface recombination layer 106 is composed of only the discontinuous layer 1062. Also good.
(2) In Embodiment 1, the discontinuous layer 1062 is a single layer, but in a mixed crystal of silicon (Si), germanium (Ge) or silicon (Si), germanium (Ge), and carbon (C), By changing the elemental composition ratio, the discontinuous layer 1062 may be composed of a plurality of discontinuous layers having different elemental composition ratios.
(3) In the second embodiment, the surface layer of the n-type light receiving unit 108 is amorphized by germanium (Ge) ion implantation, but may be amorphized by ion implantation of another group IV element.
(4) In the first to third embodiments, an example of a CCD type solid-state imaging device has been described. However, the configuration in each of the above embodiments can also be applied to a MOS (Metal Oxide Semiconductor) type solid-state imaging device. .

  The present invention relates to a solid-state imaging device, and in particular, can be used as a technique for preventing generation of dark current due to an interface state generated at an interface between a silicon substrate and an insulating film.

1 is a diagram illustrating a schematic configuration of a solid-state imaging device 100. FIG. FIG. 4 is a cross-sectional view taken along the line a-a ′ of the solid-state imaging device 100. FIG. 4 is a diagram showing the structure of a surface recombination layer 106. The energy band structure around the surface recombination layer 106 is shown. It is a figure which shows each process for surface recombination layer 106 formation. FIG. 3 is a diagram illustrating each process for forming a pixel region of the solid-state imaging device 100. 2 is a cross-sectional view corresponding to the cross-sectional view taken along line a-a ′ in FIG. 1 of the solid-state imaging device 200. It is a figure which shows each process for pixel area formation of the solid-state imaging device. Shows how boron (B) diffuses into the n-type light receiving portion 108 when boron (B) is ion-implanted when the n-type light receiving portion 108 is not amorphized (having a crystal structure). It is an image figure. FIG. 5 is an image diagram showing how boron (B) diffuses into the n-type light receiving unit 108 when boron (B) is ion-implanted in a state where the n-type light receiving unit 108 is amorphized. 2 is a cross-sectional view corresponding to the cross-sectional view taken along line a-a ′ in FIG. 1 of the solid-state imaging device 300. FIG. 6 is a diagram illustrating each process for forming a pixel region of the solid-state imaging device 300. It is the figure which compared the concentration distribution of boron. A sectional view of a unit pixel of a conventional solid-state imaging device 10 is shown. The energy band structure around the p-type impurity high concentration layer 14 is shown. According to the manufacturing method according to the second embodiment, when the p-type impurity (boron (B)) is ion-implanted in a state where the n-type light receiving portion is amorphized, and the p-type impurity discontinuous layer 206 is formed, FIG. 6 is a diagram comparing the concentration distribution of p-type impurities in a solid-state imaging device with a case where a p-type impurity layer is formed by ion implantation of boron (B) without making an n-type light receiving portion amorphous according to a method. .

Explanation of symbols

1 Photodiode 2 Vertical CCD
3 Output amplifier 4 Horizontal CCD
10, 100, 200, 300 Solid-state imaging device 11, 101 Silicon substrate 12, 107 p-type well layer 13, 108 n-type light receiving portion
14 p-type impurity high-concentration layer 15, 102 insulating film 16, 109 p-type element isolation part 19, 103 gate electrode 20, 104 interlayer insulating film 21, 105 light-shielding film 106 surface recombination layer 18, 110 n-type charge transfer part 17 , 111 p-type region 206, 306 p-type impurity discontinuous layer 1061 silicon layer 1062 discontinuous layer 41, 151 electron energy level 42, 152 energy band at lower end of conduction band 43, 153 energy band at upper end of valence band 51 Silicon oxide film 90 Main element (Si or Ge) constituting n-type light-receiving portion 108
91 Lattice space 92 Boron (B)
93 Porosity 131 Boron (B) concentration distribution 132 in control sample after annealing after boron (B) ion implantation and before annealing 132 concentration distribution 133 p-type impurity in control sample after annealing Region 134 where the discontinuous layer 206 is formed Region 135 where the n-type light-receiving layer 108 is formed Boron (B) concentration distribution in the test sample after ion implantation of boron (B) and before annealing 136 Boron (B) concentration distribution 137 in the test sample after annealing region 138 in which the p-type impurity discontinuous layer 306 is formed region 138 in which the n-type light-receiving layer 108 is formed 161 manufacturing method according to the second embodiment The boron (B) concentration distribution 162 when the p-type impurity discontinuous layer 206 is formed according to the conventional method Thus, the concentration distribution range in the region to which boron (B) is in the case where the ion implantation, the concentration distribution 163 n-type light-receiving portion of boron (B) is formed

Claims (30)

A solid-state imaging device in which a photoelectric conversion region is formed in a portion near one main surface of a semiconductor substrate where external light is incident, and an external light incident side in the photoelectric conversion region is covered with a light-transmissive insulating film. There,
A solid-state imaging device, wherein a band discontinuous region having a composition and a band gap of main elements different from those of the photoelectric conversion region is formed between the photoelectric conversion region and the insulating film. The solid-state imaging device according to claim 1, wherein a band gap in the band discontinuous region is smaller than a band gap in the photoelectric conversion region. A charge transfer region that is covered with the insulating film and serves as a transfer destination of electrons generated in the photoelectric conversion region is formed at a position close to the photoelectric conversion region in the semiconductor substrate.
A second band discontinuous region having a band gap smaller than that of the charge transfer region is formed between the charge transfer region and the insulating film, the composition of a main element being different from that of the charge transfer region. The solid-state imaging device according to claim 2. The solid-state imaging device according to claim 2, wherein a main element constituting the photoelectric conversion region is silicon, and a main element constituting the band discontinuous region is silicon, germanium, or carbon. The solid-state imaging device according to claim 4, wherein the composition of the main element in the band discontinuous region is configured with a composition ratio lattice-matched to the semiconductor substrate. 5. The solid-state imaging device according to claim 4, wherein a composition ratio Ge / C of germanium and carbon in the band discontinuous region is 6.4 or more and 11.1 or less. The solid-state imaging device according to claim 4, wherein the band discontinuous region includes a plurality of layers having different elemental compositions of silicon, germanium, and carbon. The solid-state imaging device according to claim 2, wherein the band discontinuous region further includes an impurity having a conductivity type different from that of the photoelectric conversion region. 4. The solid-state imaging device according to claim 3, wherein a main element constituting the charge transfer region is silicon, and main elements constituting the band discontinuous region are silicon, germanium, and carbon. 10. The solid-state imaging device according to claim 9, wherein a composition of a main element in the second band discontinuous region is configured with a composition ratio lattice-matched to the semiconductor substrate. 10. The solid-state imaging device according to claim 9, wherein a composition ratio Ge / C between germanium and carbon in the second band discontinuous region is 6.4 or more and 11.1 or less. The solid-state imaging device according to claim 9, wherein the second band discontinuous region includes a plurality of layers having different elemental compositions of silicon, germanium, and carbon. The solid-state imaging device according to any one of claims 3 and 9 to 12, wherein the second band discontinuous region further includes an impurity having a conductivity type different from a conductivity type of the photoelectric conversion region. The solid-state imaging device according to claim 8 or 13, wherein a conductivity type of the photoelectric conversion region is an n-type, and a conductivity type different from the conductivity type is a p-type. The main element constituting the photoelectric conversion region is silicon,
The band discontinuous region is composed of two layers,
Of the two layers, one layer located on the insulating film side includes silicon as a main element,
The other layer located on the photoelectric conversion region side contains at least silicon and germanium as main elements,
The solid-state imaging device according to claim 2, wherein the two layers further include an impurity having a conductivity type different from that of the photoelectric conversion region. The main element constituting the photoelectric conversion region is silicon,
The solid-state imaging device according to claim 2, wherein the band discontinuous region is configured by one intrinsic semiconductor layer containing at least silicon and germanium as main elements. The main element constituting the photoelectric conversion region is silicon,
The band discontinuous region is composed of two layers,
Of the two layers, one layer located on the insulating film side includes silicon as a main element, and further includes impurities of a conductivity type different from the conductivity type of the photoelectric conversion region,
3. The solid-state imaging device according to claim 2, wherein the other one layer positioned on the photoelectric conversion region side is an intrinsic semiconductor layer containing at least silicon and germanium as main elements. The solid-state imaging device according to claim 15 or 17, wherein a conductivity type of the photoelectric conversion region is an n-type, and a conductivity type different from the conductivity type is a p-type. Manufacture of a solid-state imaging device in which a photoelectric conversion region is formed in a portion near one main surface of a semiconductor substrate where external light is incident, and an external light incident side in the photoelectric conversion region is covered with a light-transmissive insulating film A method,
A recombination layer forming step of forming a surface recombination layer having a band discontinuous region different from the photoelectric conversion region between the photoelectric conversion region and the insulating film in a composition and a band gap of main elements. A method of manufacturing a solid-state imaging device. The recombination layer forming step includes:
A deposition step of depositing the surface recombination layer on the semiconductor substrate by an epitaxial method;
Forming the photoelectric conversion region in a portion where external light is incident in the vicinity of one main surface of the semiconductor substrate;
The method for manufacturing a solid-state imaging device according to claim 19, further comprising: a covering step of covering the surface recombination layer deposited on the semiconductor substrate with an insulating film. The recombination layer forming step includes:
A first formation step of forming the photoelectric conversion region by doping an impurity in a portion near one main surface of the semiconductor substrate where external light is incident;
The solid formation according to claim 19, further comprising: a second forming step of forming the surface recombination layer by ion implantation of an element different from the main component element into the formed photoelectric conversion region. Manufacturing method of imaging apparatus. The second forming step amorphizes the crystal structure of the photoelectric conversion region by ion-implanting an element different from the main component element of the photoelectric conversion region by a predetermined dose or more,
In the recombination layer forming step, an impurity region is formed in the surface recombination layer by ion-implanting impurities having a conductivity type different from that of the photoelectric conversion region into the amorphous photoelectric conversion region. The method for manufacturing a solid-state imaging device according to claim 21, further comprising: 3 forming step. The main component element is silicon, and the different element is germanium;
The recombination layer forming step further includes a carbon implantation step in which carbon is ion-implanted into the photoelectric conversion region having an amorphized structure before an impurity having a conductivity type different from that of the photoelectric conversion region is ion-implanted. The method for manufacturing a solid-state imaging device according to claim 22, comprising: 24. The method of manufacturing a solid-state imaging device according to claim 22, wherein the predetermined dose is 5 × 10 ¹³ pieces / cm ² . 21. The method of manufacturing a solid-state imaging device according to claim 20, wherein main elements constituting the surface recombination layer are silicon, germanium, and carbon. 26. The solid-state imaging device according to claim 25, wherein in the deposition step, a plurality of layers having different elemental compositions of the main element are stacked to form the surface recombination layer on the semiconductor substrate. Production method. 27. The method of manufacturing a solid-state imaging device according to claim 25 or 26, wherein a composition ratio Ge / C of germanium and carbon in the elemental composition of the main element is 6.4 or more and 11.1 or less. A charge transfer region that is covered with the insulating film and serves as a transfer destination of electrons generated in the photoelectric conversion region is formed at a position close to the photoelectric conversion region in the semiconductor substrate.
In the recombination layer forming step, a second band band gap smaller than that of the charge transfer region and having a band gap smaller than that of the charge transfer region is formed between the charge transfer region and the insulating film. The method of manufacturing a solid-state imaging device according to claim 19, wherein the second surface recombination layer having a continuous region is formed. A photoelectric conversion region is formed in the vicinity of one main surface of the semiconductor substrate where external light is incident, and a charge serving as a transfer destination of electrons generated in the photoelectric conversion region is located near the photoelectric conversion region. A solid-state imaging device in which a transfer region is formed, and the external light incident side and the charge transfer region in the photoelectric conversion region are covered with a single light-transmissive insulating film,
A solid-state imaging device, wherein a band discontinuous region having a composition and a band gap of main elements different from those of the charge transfer region is formed between the charge transfer region and the insulating film. 30. The solid-state imaging device according to claim 29, wherein a band gap in the band discontinuous region is smaller than a band gap in the charge transfer region.

Images