JP7271127B2 - Photoelectric conversion device - Google Patents

Description

The present invention relates to a photoelectric conversion device.

2. Description of the Related Art Conventionally, a photoelectric conversion device is known that includes a filter that transmits infrared light (hereinafter also referred to as “IR light”) and a filter that transmits visible light. For example, Patent Literature 1 discloses a photoelectric conversion device that includes a filter that transmits IR light and a filter that transmits visible light.

On the other hand, a photoelectric conversion device is known in which a plurality of photoelectric conversion units share one microlens. For example, Patent Literature 2 discloses a configuration in which a plurality of photoelectric conversion units share one microlens, and filters that transmit visible light are arranged corresponding to the plurality of photoelectric conversion units. . Patent Document 2 discloses that each photoelectric conversion unit includes a plurality of N-type semiconductor regions for collecting signal charges, and a P-type semiconductor region for isolation is arranged between the N-type semiconductor regions. there is

U.S. Patent Application Publication No. 2018/219040 JP 2014-204043 A

Patent Documents 1 and 2 have room for improving the characteristics of a photoelectric conversion device that includes a filter that transmits IR light and a filter that transmits visible light.

An object of the present invention is to improve the characteristics of a photoelectric conversion device that includes a filter that transmits IR light and a filter that transmits visible light.

A photoelectric conversion device according to one aspect of the present invention includes a semiconductor substrate including a plurality of photoelectric conversion units, first and second microlenses, and a first filter having a higher transmittance for infrared light than for visible light. and a second filter having a higher transmittance for visible light than for infrared light, wherein the plurality of photoelectric conversion units overlap the first microlens and the first filter in plan view. at least one photoelectric conversion unit disposed; and a plurality of photoelectric conversion units disposed so as to overlap the second microlens and the second filter in plan view; At least one photoelectric conversion unit that overlaps in view and each of the plurality of photoelectric conversion units that overlaps the second filter in plan view is a first semiconductor of a first conductivity type that accumulates signal charges. and a second conductivity type opposite to the first conductivity type, arranged on the side opposite to the first filter side of the first semiconductor region, and in plan view from the first semiconductor region and a second semiconductor region forming a PN junction with the first semiconductor region, the impurity concentration of at least a portion of the second semiconductor region of the at least one photoelectric conversion unit being the same as that of the plurality of photoelectric conversion units. The impurity concentration is lower than that of a portion of the second semiconductor region of the conversion portion that is arranged at the same depth as the at least one portion.

A photoelectric conversion device according to one aspect of the present invention includes a semiconductor substrate including a plurality of photoelectric conversion units, first and third filters having a higher transmittance for infrared light than for visible light, and second and fourth filters having high light transmittance, wherein the photoelectric conversion unit is arranged to overlap the first filter in plan view; and the photoelectric conversion unit is arranged to overlap the third filter in plan view. a photoelectric conversion unit overlapping the second filter in plan view, and a photoelectric conversion unit overlapping the fourth filter in plan view, arranged adjacent to each other in one direction. A photoelectric conversion unit arranged to overlap the first filter in plan view has a first conductivity type first semiconductor region for accumulating signal charges, The photoelectric conversion section arranged to overlap has the second semiconductor region of the first conductivity type, and the photoelectric conversion section arranged to overlap the third filter in a plan view has the second semiconductor region of the first conductivity type. The photoelectric conversion section, which has three semiconductor regions and is arranged to overlap the fourth filter in plan view, has the fourth semiconductor region of the first conductivity type, the second semiconductor region and the third semiconductor. A fifth semiconductor region of a second conductivity type opposite to the first conductivity type is disposed between the first semiconductor region and the second semiconductor region. A second conductivity type sixth semiconductor region is provided, a second conductivity type seventh semiconductor region is provided between the third semiconductor region and the fourth semiconductor region, the fifth semiconductor region, the Each of the sixth semiconductor region and the seventh semiconductor region has at least one impurity concentration peak, and among the peaks of the sixth semiconductor region, the impurity concentration is the highest from the surface of the semiconductor substrate on the first filter side. The position of the farthest peak is farther from the first filter of the semiconductor substrate than the position of the peak farthest from the surface of the semiconductor substrate on the first filter side among the peaks of the seventh semiconductor region. The position of the peak farthest from the first filter side surface of the semiconductor substrate among the peaks of the fifth semiconductor region is the peak position of the sixth semiconductor region. It is further away from the surface of the semiconductor substrate on the first filter side than the position of the peak farthest from the surface of the semiconductor substrate on the first filter side.

According to the present invention, it is possible to improve the characteristics of a photoelectric conversion device that includes a filter that transmits IR light and a filter that transmits visible light.

1 is a block diagram of a photoelectric conversion device according to a first embodiment; FIG. 4 is a diagram showing the arrangement of color filters in part of the pixel area of the first embodiment; FIG. 3 is a cross-sectional view corresponding to III-III' in FIG. 2; FIG. 4 is a plan view of the substrate of FIG. 3; FIG. FIG. 5 is a cross-sectional view of part of a pixel region according to a modification of the first embodiment; FIG. 5 is a cross-sectional view of part of a pixel region according to a modification of the first embodiment; It is a figure which shows the variation of arrangement|positioning of a color filter. FIG. 8 is a cross-sectional view of part of a pixel region according to the second embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to a modification of the second embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to a modification of the second embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to the third embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to a fourth embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to a fifth embodiment; FIG. 11 is a cross-sectional view of part of a pixel region according to a sixth embodiment; FIG. 11 is a schematic perspective view of a photoelectric conversion device according to a seventh embodiment; FIG. 16 is a cross-sectional view taken along line AA' of FIG. 15; It is a schematic diagram of a photoelectric conversion system according to an eighth embodiment. FIG. 21 is a schematic diagram of a moving body according to a ninth embodiment; 4 is a graph showing the transmittance of color filters. 4 is a graph showing the transmittance of each color when no IR cut filter is provided; 3 is a spectroscopic diagram of a photoelectric conversion device; FIG.

A mode for carrying out the present invention will be described below with reference to the drawings. However, the embodiments shown below are for embodying the technical idea of the present invention, and do not limit the present invention. Note that the sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation.

In the following description, the first polarity is assumed to be negative and the second polarity is assumed to be positive. However, similar effects can be obtained even when the first polarity is positive and the second polarity is negative. . For convenience of explanation, the light-receiving surface side of the semiconductor substrate 100 (hereinafter also referred to as "substrate 100") is defined as the upper side, and the surface of the substrate 100 facing the light-receiving surface is defined as the lower side.

In the following embodiments, an example in which electrons are used as signal charges will be described. In the following embodiments, the semiconductor region of the first conductivity type having carriers of the first polarity as majority carriers is a P-type semiconductor region, and the semiconductor region of the second conductivity type having carriers of the second polarity as majority carriers is a P-type semiconductor region. The regions are N-type semiconductor regions. However, the present invention is valid even when holes are used as signal charges. In this case, N-type and P-type are reversed.

<First Embodiment>
A photoelectric conversion device 10 according to the present embodiment will be described with reference to FIGS. 1 to 4. FIG. FIG. 1 is a block diagram of a photoelectric conversion device 10. As shown in FIG. FIG. 2 is a diagram showing the arrangement of color filters in part of the pixel area included in the photoelectric conversion device 10. As shown in FIG. FIG. 3 is a cross-sectional view taken along line III-III' of FIG. FIG. 4 is a plan view of the substrate 100. FIG.

As shown in FIG. 1, the photoelectric conversion device 10 includes a pixel region 21 in which a plurality of pixels 20 are continuously arranged in row and column directions. In this specification, a region in which a plurality of pixels 20 are continuously arranged is called a pixel region 21, and the other region is called a peripheral circuit region.

First, the pixel area 21 in FIG. 1 will be described. FIG. 2 shows an example of the arrangement of color filters included in the pixel area 21. As shown in FIG. The color filters 103 and 104 are made of dyes or pigments, for example.

FIG. 19A shows the transmittance of the color filters. In FIG. 19, the IR line indicates the transmittance of the color filter 103, and the BL, GR, and RE lines indicate the transmittance of the color filter 104. In FIG. In FIG. 19A, color filter 104 includes an IR cut filter and color filter 103 does not include an IR cut filter. FIG. 19B shows the transmittance of the filter before the IR cut filter is arranged. In the state of FIG. 19B, the transmittance of the BL line, the GR line, and the RE line is high even in the infrared region (wavelength λ≧650 nm). On the other hand, by arranging an IR cut filter, it is possible to reduce the incidence of IR light on color filter 104 as shown in FIG. An IR cut filter is, for example, a filter that reflects or absorbs light with a wavelength λ≧670 nm. FIG. 20 shows a spectroscopic diagram of a photoelectric conversion device.

The color filter 103 is a filter having a higher transmittance for infrared light than for visible light. Light passing through the color filter 103 and incident on the photoelectric conversion portion has a peak wavelength in the infrared region (wavelength λ≧650 nm).

Also, the color filter 104 is a filter having a higher transmittance for visible light than for infrared light. Light that passes through the color filter 104 and enters the photoelectric conversion portion has a peak wavelength in the visible region (wavelength λ<650 nm). The color filter 104 is, for example, a color filter that transmits blue light, red light, or green light. Also, the color filter 104 may be a color filter that transmits at least one of cyan light, magenta light, and yellow light.

FIG. 3 shows a cross-sectional view of the pixel region 21 taken along line III-III' of FIG. In FIG. 2, only the photoelectric conversion units arranged in the regions overlapping the three color filters 103 and 104 in plan view are indicated by dashed lines, but the photoelectric conversion units are similarly arranged also in the regions overlapping the other color filters. there is

The substrate 100 is, for example, a silicon substrate. As shown in FIG. 2, the substrate 100 includes a plurality of photoelectric conversion units 106a and 106b that photoelectrically convert IR light in regions overlapping the color filters 103 in plan view. The substrate 100 also includes a plurality of photoelectric conversion units 106c and 106d that photoelectrically convert visible light in regions overlapping the color filters 104 in plan view. The photoelectric conversion units 106a, 106b, 106c, and 106d are arranged adjacent to each other in one direction. In this specification, the axis along the direction in which the two photoelectric conversion units 106c and 106d are arranged is defined as the X axis, and the axis perpendicular to the X axis in the plane parallel to the surface of the substrate 100 on which the filter is arranged is defined as the Y axis. axis. An axis perpendicular to the X-axis and the Y-axis is defined as the Z-axis. Light is incident from the surface of the microlens 107 opposite to the side on which the filter is arranged. In the following description, subscripts such as a, b, c, and d are omitted when the description is common.

In FIG. 3, one microlens 107 is shared by the photoelectric conversion units 106a and 106b. Also, one microlens 107 is shared by the photoelectric conversion units 106c and 106d. Hereinafter, a plurality of photoelectric conversion units sharing one microlens 107 may be collectively referred to as a “photoelectric conversion unit”.

Each photoelectric conversion unit 106 is formed by implanting impurities into the substrate 100 from the upper surface side of the substrate 100 . Each photoelectric conversion unit 106 has an N-type semiconductor region 202 (first semiconductor region), which is a semiconductor region of the first conductivity type that accumulates at least signal charges. In FIG. 3, each photoelectric conversion unit 106 further has a second conductivity type P-type semiconductor region 203 (second semiconductor region) that is of the opposite conductivity type to the first conductivity type. The P-type semiconductor region 203 is arranged on the side opposite to the color filter side of the N-type semiconductor region 202 and forms a PN junction with the N-type semiconductor region 202 .

As shown in FIG. 3, it is preferable that the P-type semiconductor region 201 is arranged on the surface of the N-type semiconductor region 202 on the color filter side. Thereby, a dark current component generated near the upper surface of the substrate 100 can be suppressed.

A P-type semiconductor region 110 is arranged between the N-type semiconductor region 202 of the photoelectric conversion portion 106b and the N-type semiconductor region 202 of the photoelectric conversion portion 106c. A P-type semiconductor region 112 is arranged between the N-type semiconductor region 202 of the photoelectric conversion portion 106a and the N-type semiconductor region 202 of the photoelectric conversion portion 106b. A P-type semiconductor region 111 is arranged between the N-type semiconductor region 202 of the photoelectric conversion portion 106c and the N-type semiconductor region 202 of the photoelectric conversion portion 106d. The impurity concentrations of the P-type semiconductor regions 110, 111 and 112 are higher than the impurity concentrations of the P-type semiconductor regions 203 and 205, respectively. The P-type semiconductor regions 110, 111, and 112 each function as an isolation section for isolating signals accumulated in the N-type semiconductor regions.

Each of the P-type semiconductor regions 110, 111, 112 has at least one impurity concentration peak. Among the peaks of the P-type semiconductor region 112 , the position of the peak of the impurity concentration farthest from the top surface of the substrate 100 is the farthest from the top surface of the substrate 100 among the peaks of the P-type semiconductor region 111 . It is lower than the position of the impurity concentration peak at the position. Among the peaks of the P-type semiconductor region 110, the position of the peak of the impurity concentration farthest from the top surface of the substrate 100 is the farthest from the top surface of the substrate 100 among the peaks of the P-type semiconductor region 112. It is lower than the position of the impurity concentration peak at the position. As a result, deterioration in pixel performance can be reduced. Details are given below.

Charges generated by IR light have a higher specific gravity generated at deeper positions in the substrate 100 than those generated by visible light. When setting the depths of the P-type semiconductor regions 111 and 112, the depths of the P-type semiconductor regions 111 and 112 are assumed to be the same. For example, the depth of the P-type semiconductor region arranged between a plurality of photoelectric conversion units for photoelectrically converting IR light is defined as the depth of the P-type semiconductor region arranged between a plurality of photoelectric conversion units for photoelectrically converting visible light. be the same as In this case, charges are mixed without being separated between a plurality of photoelectric conversion units that photoelectrically convert IR light. On the other hand, the depth of the P-type semiconductor region arranged between the plurality of photoelectric conversion units for photoelectrically converting visible light is the depth of the P-type semiconductor region arranged between the plurality of photoelectric conversion units for photoelectrically converting IR light. Make it the same as the depth. In this case, the plurality of photoelectric conversion units that photoelectrically convert visible light may deteriorate in knee characteristics and degrade pixel performance.

Here, the worsening of the knee characteristic means that when a graph is drawn where the horizontal axis is the amount of light incident on the pixel and the vertical axis is the number of saturated electrons in the pixel, the line of the graph is bent in the middle. If the knee characteristic deteriorates, the input/output characteristic deteriorates. Deterioration of the knee characteristic is caused by, for example, the charge saturated in the photoelectric conversion unit 106a leaking not only to the photoelectric conversion unit 106b but also to the photoelectric conversion unit 106c. Deterioration of the knee characteristics can be prevented by allowing the charges saturated in the photoelectric conversion units 106a and 106b to flow to the photoelectric conversion units 106a and 106b in the same pixel.

According to this embodiment, since the depth of the P-type semiconductor region is changed according to the characteristics of the photoelectric conversion portion, it is possible to perform highly accurate focus detection while preventing deterioration of knee characteristics in each pixel. .

As shown in FIG. 4, on the upper surface of the substrate 100, there are a gate electrode 130a of a transfer transistor for transferring the charge of the photoelectric conversion unit 106a and a gate electrode 130b of the transfer transistor for transferring the charge of the photoelectric conversion unit 106b. are distributed. Charges are transferred to floating diffusions (FD) 131a and 131b by each transfer transistor.

As shown in FIG. 3, the color filters 103 and 104 and the microlens 107 are arranged on the upper surface of the substrate 100 via the wiring layer 150 including the insulating film 109 and the wiring 113 .

The insulating film 109 included in the wiring layer 150 has a light-transmitting property. The insulating film 109 may be a single layer or a multilayer film in which a plurality of layers made of different materials are laminated. A single layer is made of silicon oxide (SiO ₂ ), for example. Moreover, in the case of a multilayer film, for example, a layer made of any one of resin, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and silicon carbide (SiC) is included. The material of the microlens 107 is resin, for example.

The peripheral circuit area will be described with reference to FIG. As shown in FIG. 1, the peripheral circuit area includes a vertical scanning circuit 22, a readout circuit 23, a horizontal scanning circuit 24, and an output amplifier 25. FIG.

The vertical scanning circuit 22 is connected to multiple pixels 20 arranged in the pixel region 21 . The multiple pixels 20 are, for example, multiple pixels 20 arranged in the column direction. The vertical scanning circuit 22 selects and scans rows that output signals obtained from the pixels 20 .

A plurality of pixels 20 arranged in a pixel region 21 are connected to a readout circuit 23 via vertical signal lines. The readout circuit 23 includes, for example, column amplifiers, correlated double sampling (CDS) circuits, and adder circuits. The readout circuit 23 reads out signals from the plurality of pixels 20 selected by the vertical scanning circuit 22 . The multiple pixels 20 are, for example, multiple pixels 20 arranged in the row direction.

The horizontal scanning circuit 24 is connected to the readout circuit 23 . The horizontal scanning circuit 24 generates a signal for sequentially reading signals based on pixel signals from the reading circuit 23 .

The output amplifier 25 is connected to the readout circuit 23 and amplifies and outputs a plurality of signals selected by the horizontal scanning circuit 24 . The multiple signals selected by the horizontal scanning circuit 24 are, for example, the signals of the multiple pixels 20 arranged in the column direction.

The configuration of the photoelectric conversion device 10 according to this embodiment is not limited to the configuration described above. For example, a modified example of the photoelectric conversion device 10 according to this embodiment is shown below.

In FIG. 3, one photoelectric conversion unit 101, 102 has two photoelectric conversion units 106a, 106b, but one photoelectric conversion unit may include three or more photoelectric conversion units. In this case, three or more photoelectric conversion units are arranged in a region overlapping one microlens in plan view. Further, the photoelectric conversion device may include a photoelectric conversion unit having only one photoelectric conversion section. In this case, one photoelectric conversion unit is arranged in a region overlapping one microlens in plan view.

In FIG. 3, a plurality of photoelectric conversion units share one microlens, but as shown in FIG. good. Even in this case, the generated charges are less likely to be mixed between the photoelectric conversion units, and it is possible to prevent the charges generated based on light of different colors from being mixed.

As shown in FIG. 6, the N-type semiconductor region may include an N-type semiconductor region 202A and an N-type semiconductor region 202B having a lower impurity concentration than the N-type semiconductor region 202A. The N-type semiconductor region 202B is arranged between the N-type semiconductor region 202A and the P-type semiconductor region 203 . In this case, the depth of the P-type semiconductor regions 110 and 112 may be deeper than the PN junction surface. As a result, the rate of electric charges generated in the P-type semiconductor region 203 leaking to the photoelectric conversion units that photoelectrically convert light of different colors can be reduced.

In this specification, the term "concentration of added impurities" means the concentration of impurities actually added. The measurement of the additive impurity concentration described above can be performed by, for example, the SIMS method or the SCM method. According to these methods, it is possible to verify how much the impurity exists per unit volume.

On the other hand, in this specification, the term "impurity concentration" simply means the net impurity concentration in which the added impurity concentration is compensated by the opposite conductivity type impurity. For example, in a given region, if the N-type impurity concentration is higher than the P-type impurity concentration, the region becomes an N-type semiconductor region. In addition, if the P-type impurity concentration in a predetermined region is higher than the N-type impurity concentration, the region becomes a P-type semiconductor region.

Note that in FIG. 6, the depth of the PN junction surface of the photoelectric conversion unit that overlaps the color filter 103 in plan view is the same as the depth of the PN junction surface of the photoelectric conversion unit that overlaps the color filter 104 in plan view. It may be lower than the depth.

Variations of the arrangement of the color filters are shown in FIGS. 7(a) to 7(c). As shown in FIGS. 3 and 6, it is preferable that photoelectric conversion units having the same configuration are arranged at both ends of the photoelectric conversion unit 101 . In other words, it is preferable that the photoelectric conversion unit 101 is arranged between two photoelectric conversion units 101 or that the photoelectric conversion unit 101 is arranged between two photoelectric conversion units 102 . As a result, it is possible to reduce the asymmetry of the amount of charge that moves, and the focus detection performance is less likely to deteriorate.

The color filter is not limited to 4 or 5 colors, and may be a multiband of 6 or more colors. By using multiband, it is possible to obtain detailed information about the subject's school.

<Second embodiment>
FIG. 8 shows a cross-sectional view of part of the pixel region 21 of the photoelectric conversion device according to this embodiment. In the photoelectric conversion device according to this embodiment, the P-type semiconductor region overlapping the color filter 104 in plan view has a lower impurity concentration than the P-type semiconductor region overlapping the color filter 103 in plan view. It is different from the photoelectric conversion device according to the first embodiment in that it includes a portion. Below, description of the same configuration as that of the photoelectric conversion device according to the first embodiment is omitted.

In this embodiment, as in the first embodiment, the N-type semiconductor region 202 is arranged on the side opposite to the color filter 103 side of the N-type semiconductor region 202 and overlaps the N-type semiconductor region 202 in a plan view. and a second semiconductor region (P-type semiconductor region) forming a PN junction. In the present embodiment, the impurity concentration of at least a portion of the P-type semiconductor region of at least one photoelectric conversion unit is arranged at the same depth as that of at least a portion of the P-type semiconductor regions of the plurality of photoelectric conversion units. It is lower than the impurity concentration of the part. Specifically, in FIG. 8, the added impurity concentration of the P-type semiconductor region 203c is higher than the added impurity concentration of the P-type semiconductor region 203 forming a PN junction with the N-type semiconductor region 202 . The P-type semiconductor region 203 c is included in the P-type semiconductor regions of the photoelectric conversion units corresponding to the color filters 104 . In this embodiment, as shown in FIG. 8, at a predetermined depth from the surface of the substrate 100 on the side of the color filters 103 and 104, the added impurity concentration of the P-type semiconductor region 203 of the photoelectric conversion section 106a is higher than that of the photoelectric conversion section 106c. , 106d of the P-type semiconductor region 203c. In other words, the P-type semiconductor region 203c is not arranged in the photoelectric conversion portion corresponding to the color filter 103 at the same depth as the P-type semiconductor region 203c. Therefore, at the same depth as the P-type semiconductor region 203c, the impurity concentration of the P-type semiconductor region 203c overlapping the color filter 104 is higher than the impurity concentration of the P-type semiconductor region 203 overlapping the color filter 104. is also low. The predetermined depth is, for example, at a distance of 2.0 μm or more from the color filter side surface of the substrate 100 . By disposing the P-type semiconductor region 203c at a position separated by 2.0 μm or more, charges generated by red light can be collected in the N-type semiconductor region 202 included in the photoelectric conversion units 106c and 106d.

The P-type semiconductor region 203c functions as a barrier layer against charges photoelectrically converted by IR light. By providing the P-type semiconductor region 203c, even if the light transmitted through the color filter 103 is photoelectrically converted under the P-type semiconductor region 203c, charges are mixed in the photoelectric conversion units 106c and 106d that photoelectrically convert visible light. can be prevented. In addition, the IR light can move charges generated under the P-type semiconductor region 203c to the N-type semiconductor region 202 of the photoelectric conversion unit 106a, thereby improving sensitivity to IR light. In addition, by providing one photoelectric conversion unit arranged in a region that overlaps the color filter 103 in a plan view, the number of FDs can be reduced compared to the first embodiment, so that noise can be reduced. .

The configuration of the photoelectric conversion device according to this embodiment is not limited to the above configuration. For example, modified examples of the photoelectric conversion device according to the present embodiment are shown below.

The P-type semiconductor regions 110, 111, 112 may each be arranged around an insulator.

The P-type semiconductor region 203c may be arranged at a position shallower than 2.0 μm depending on the application. For example, when the color filter 103 is a color filter that transmits blue light or a color filter that transmits green light, the P-type semiconductor region 203c may be arranged at a position shallower than 2.0 μm.

In FIG. 8, each P-type semiconductor region 110 has the same depth. Not limited to this, as shown in FIG. 9, the depth of the P-type semiconductor region 110a arranged around the photoelectric conversion portion for photoelectrically converting IR light is determined by the photoelectric conversion portion for photoelectrically converting IR light and visible light. The depth may be shallower than the depth of the P-type semiconductor region 110b arranged between the photoelectric conversion portion that performs photoelectric conversion. The lower end of the P-type semiconductor region 110b may be arranged at a position farther from the upper surface of the substrate 100 than the lower surface of the P-type semiconductor region 203c. The charges generated under the P-type semiconductor region 203c are diffused. At this time, the presence of the P-type semiconductor region 110b makes it easier for charges to move to the N-type semiconductor region of the photoelectric conversion portion that photoelectrically converts IR light, thereby improving sensitivity to IR light.

As shown in FIG. 10, a P-type semiconductor region 204 parallel to the Z-axis may be arranged under the P-type semiconductor region 203c. The added impurity concentration of the P-type semiconductor region 204 is higher than the added impurity concentration of the P-type semiconductor region 203 . Even in this case, sensitivity to IR light can be improved.

In FIG. 8, one photoelectric conversion unit is arranged to overlap the color filter 103 in plan view, but as shown in FIG. 9, a plurality of photoelectric conversion units are arranged to overlap the color filter 103 in plan view. may

In FIG. 8, the P-type semiconductor region includes a P-type semiconductor region 203 as a third portion and a P-type semiconductor region 203c as a fourth portion, and the third portion and the N-type semiconductor region 202 form a PN junction. be. However, the photoelectric conversion portion may include the N-type semiconductor regions 202a and 202b, and the N-type semiconductor region 202b and the P-type semiconductor region 203c may form a PN junction. In this case, the N-type semiconductor region 202b and the P-type semiconductor region 203 form a PN junction.

<Third Embodiment>
FIG. 11 shows a cross-sectional view of the pixel region 21 of the photoelectric conversion device according to this embodiment. In the photoelectric conversion device according to the second embodiment, the depth of the P-type semiconductor region 203c from the upper surface of the substrate 100 becomes shallower as it approaches the photoelectric conversion unit that photoelectrically converts IR light. different from Below, description of the same configuration as that of the photoelectric conversion device according to the second embodiment is omitted.

If the P-type semiconductor region 203c is arranged parallel to the X-axis, a potential barrier may be formed between the P-type semiconductor region 110 and the P-type semiconductor region 203c. If a potential barrier is formed, it becomes difficult for charges photoelectrically converted under the P-type semiconductor region 203c to move to the photoelectric conversion portion that photoelectrically converts IR light. In contrast, as shown in FIG. 11, by making the P-type semiconductor region 203c shallow, the potential barrier is less likely to occur. Therefore, the charges photoelectrically converted under the P-type semiconductor region 203c can be efficiently transferred to the photoelectric conversion portion that photoelectrically converts IR light, and the sensitivity to infrared light can be improved.

In FIG. 11, one photoelectric conversion unit is arranged in a region overlapping one microlens 107 and color filter 103 in plan view, but a plurality of photoelectric conversion units are arranged in a region overlapping one microlens 107 and color filter 103 in plan view. A photoelectric conversion unit may be arranged.

<Fourth Embodiment>
FIG. 12 shows a cross-sectional view of the pixel region 21 of the photoelectric conversion device according to this embodiment. The photoelectric conversion device according to this embodiment differs from the photoelectric conversion device according to the first embodiment in that it includes a region where the impurity concentration of the P-type semiconductor region 203 increases from the top surface to the bottom surface of the substrate 100 . FIG. 12 shows the impurity concentration profile indicated by the dashed line in FIG. Below, description of the same configuration as that of the photoelectric conversion device according to the first embodiment is omitted.

The substrate 100 according to this embodiment can be formed, for example, by the following method. First, a P-type semiconductor region is formed on the upper surface of a P-type silicon substrate by epitaxial growth. In FIG. 11, the area between the line indicating the lower surface of the substrate 100 and the long chain line is the P-type silicon substrate, and the area between the long chain line and the dashed line is the P-type semiconductor region formed by epitaxial growth. A P-type semiconductor region formed by epitaxial growth has a first portion and a second portion having a higher impurity concentration than the first portion. The second portion is arranged farther from the filter-side surface of the substrate 100 than the first portion. The P-type semiconductor region formed by epitaxial growth is grown so that the impurity concentration is gradually lowered. Next, P-type impurity ions are implanted into the N-type semiconductor region formed by epitaxial growth, and then N-type impurity ions are implanted. In FIG. 11, the area between the one-dot chain line and the line indicating the upper surface of the substrate 100 is the region implanted with P-type impurity ions and N-type impurity ions. When implanting the P-type impurity ions into the N-type semiconductor region, the P-type semiconductor region is implanted so as not to generate a potential barrier at the junction surface between the P-type semiconductor region formed by the epitaxial growth method and the N-type semiconductor region formed by the epitaxial growth method. Impurity ions of the type are implanted. Impurity ions are implanted so that the impurity concentration decreases toward the upper surface of the substrate 100 . As a result, it is possible to collect charges generated at a position distant from the upper surface of the substrate 100, so that sensitivity to IR light can be improved.

In FIG. 11, after the N-type impurity ions are implanted, the P-type impurity ions are further implanted. Thereby, dark current generated in the vicinity of the upper surface of the substrate 100 can be suppressed.

The thickness of the P-type semiconductor region formed by epitaxial growth is, for example, in the range of 1 μm to 50 μm, and the thickness of the N-type semiconductor region formed by epitaxial growth is, for example, in the range of 1 μm to 5 μm. .

<Fifth Embodiment>
FIG. 13 shows a cross-sectional view of the pixel region 21 of the photoelectric conversion device according to this embodiment. The photoelectric conversion device according to this embodiment differs from the photoelectric conversion device according to the second embodiment in that it includes a region where the impurity concentration of the P-type semiconductor region 203 increases from the top surface to the bottom surface of the substrate 100 . FIG. 13 shows the impurity concentration profile indicated by the dashed line in FIG.

The method for manufacturing the substrate 100 according to this embodiment is the same as the method for manufacturing the substrate 100 according to the fourth embodiment except that P-type ions are implanted into the region corresponding to the P-type semiconductor region 203c. Description is omitted.

<Sixth Embodiment>
FIG. 14 shows a cross-sectional view of a photoelectric conversion device according to this embodiment. The photoelectric conversion device according to the present embodiment differs from the photoelectric conversion device according to the first embodiment in that it includes a color filter 402 that transmits light having a wavelength longer than that transmitted by the color filter 103 . Below, description of the same configuration as that of the photoelectric conversion device according to the first embodiment is omitted.

In this embodiment, for example, the color filter 103 is a filter with a transmission peak wavelength of 650 nm≦wavelength λ<700 nm, and the color filter 402 is a filter with a transmission peak wavelength of λ≧700 nm. In the region overlapping the color filter 402 in plan view, the depth of the P-type semiconductor region 403 arranged between the plurality of photoelectric conversion units is deeper than the depth of the P-type semiconductor region 112 and deeper than the P-type semiconductor region 110. shallow. This makes it possible to prevent charge leakage to adjacent pixels while separating charges among the plurality of photoelectric conversion units that photoelectrically convert light transmitted through the color filter 402 .

<Seventh Embodiment>
FIG. 15 shows a schematic diagram of a photoelectric conversion device according to this embodiment, and FIG. 16 shows a cross-sectional view taken along the line AA' of FIG. The photoelectric conversion device according to the present embodiment is similar to the first embodiment in that it is configured by stacking a base portion 360 including a photoelectric conversion portion and a base portion 370 including at least a part of circuits in the peripheral circuit region. It is different from a photoelectric conversion device. The photoelectric conversion device shown in FIGS. 15 and 16 is a so-called back-illuminated photoelectric conversion device in which a semiconductor substrate 100A including a photoelectric conversion portion is arranged between a wiring layer and a microlens 107. FIG. The sensitivity can be improved by using a back-illuminated photoelectric conversion device.

As shown in FIG. 15, gate electrodes of transistors such as a transfer transistor, a source follower transistor, a reset transistor, and a metal wiring layer are arranged on the lower surface of the first semiconductor substrate 100A including the photoelectric conversion portion. A gate electrode of the transistor is connected to the wiring layer through a plug. The plug can be integrally formed with tungsten as the main component. The plug and wiring 113 are mainly made of copper and can be integrally formed by the dual damascene method.

The base portion 360 includes the first semiconductor substrate 100A and the first wiring layer 150a, and the base portion 370 includes the second semiconductor substrate 100B and the second wiring layer 150b. The base portion 360 and the base portion 370 are bonded together at the joint surface. The joint surface is composed of a metal such as copper and an insulator such as an oxide film. The metal forming the joint surface may constitute wiring that connects elements such as the photoelectric conversion units 106a and 106b arranged on the first semiconductor substrate 100A and the readout circuit 23 arranged on the second semiconductor substrate 100B.

<Eighth embodiment>
A photoelectric conversion system according to this embodiment will be described with reference to FIG. The same reference numerals are assigned to the same components as in the photoelectric conversion device of each embodiment described above, and the description thereof is omitted or simplified. FIG. 17 is a block diagram showing a schematic configuration of a photoelectric conversion system according to this embodiment.

The photoelectric conversion device described in each of the above embodiments can be applied to various photoelectric conversion systems as the photoelectric conversion device of FIG. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, facsimiles, mobile phones, vehicle-mounted cameras, and observation satellites. A camera module including an optical system such as a lens and a photoelectric conversion device is also included in the photoelectric conversion system. FIG. 17 illustrates a block diagram of a digital still camera as an example of these.

The photoelectric conversion system 1 illustrated in FIG. 17 is equipped with a lens as an optical system 11 that forms a subject image. The focus position of the optical system 11 including this lens is controlled by the controller 12 . The photoelectric conversion system 1 includes an aperture 13 for varying the amount of light passing through the lens, and a control unit 14 having an aperture function for adjusting the amount of light by changing the aperture diameter (variable aperture value). have. In the image space of the optical system 11, an imaging plane of a photoelectric conversion device 10 that photoelectrically converts a subject image formed by the optical system 11 is arranged. The photoelectric conversion device 10 is the photoelectric conversion device described in the first to seventh embodiments, and converts an optical image formed by a lens into image data.

The CPU 15 is a controller that controls various operations of the camera. The CPU 15 has an arithmetic unit, a ROM, a RAM, an A/D converter, a D/A converter, a communication interface circuit, and the like. The CPU 15 controls the operation of each part in the camera according to a computer program stored in the ROM, and executes a series of shooting operations such as AF including detection of the focus state of the optical system (focus detection), imaging, image processing and recording. Let The CPU 15 corresponds to computing means.

The control unit 16 controls the operation of the photoelectric conversion device 10 , A/D-converts pixel signals (imaging signals) output from the photoelectric conversion device 10 , and transmits the converted signals to the CPU 15 . Note that the photoelectric conversion device 10 may have an A/D conversion function. The image processing unit 17 performs image processing such as γ conversion and color interpolation on the A/D converted imaging signal to generate an image signal. The display unit 18 is a display unit such as a liquid crystal display (LCD), and displays information regarding the photographing mode of the camera, a preview image before photographing, a confirmation image after photographing, a focus state at the time of focus detection, and the like. Then, the photographed image is recorded by the operation switch 19 and the detachable recording medium 26 .

The camera CPU selects the output value of the pixel with the optimum shape from among a plurality of types of light shielding shapes according to the attached lens and the photographing conditions, and performs focus detection. As a result, it is possible to provide a camera system with higher focus detection accuracy according to various lenses. For example, by using a lens with high transmittance of infrared light, focus detection accuracy for infrared light can be improved.

<Ninth Embodiment>
A photoelectric conversion system and a moving body according to this embodiment will be described with reference to FIG. 18 .

FIG. 18(a) shows an example of a photoelectric conversion system for an in-vehicle camera. A photoelectric conversion system 300 has a photoelectric conversion device 10 . The photoelectric conversion device 10 is the photoelectric conversion device according to any one of the first to seventh embodiments. The photoelectric conversion system 300 includes an image processing unit 312 that performs image processing on a plurality of image data acquired by the photoelectric conversion device 10 , and a parallax (parallax image position) from the plurality of image data acquired by the photoelectric conversion system 300 . phase difference) is provided. The photoelectric conversion system 300 also includes a distance measurement unit 316 that calculates the distance to the object based on the calculated parallax, and a collision determination unit that determines whether there is a possibility of collision based on the calculated distance. 318 and . Here, the parallax calculation unit 314 and the distance measurement unit 316 are examples of distance information acquisition means for acquiring distance information to the target object. That is, the distance information is information related to parallax, defocus amount, distance to the object, and the like. The collision determination unit 318 may use any of these distance information to determine the possibility of collision. The distance information acquisition means may be implemented by specially designed hardware, or may be implemented by a software module. Moreover, it may be implemented by FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like, or by a combination thereof.

The photoelectric conversion system 300 is connected to a vehicle information acquisition device 320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 300 is also connected to a control ECU 330 that is a control device that outputs a control signal for generating a braking force to the vehicle based on the determination result of the collision determination section 318 . The photoelectric conversion system 300 is also connected to an alarm device 340 that issues an alarm to the driver based on the determination result of the collision determination section 318 . For example, if the collision determination unit 318 determines that there is a high possibility of a collision, the control ECU 330 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, or suppressing the engine output. The alarm device 340 warns the user by sounding an alarm such as sound, displaying alarm information on a screen of a car navigation system, or vibrating a seat belt or steering wheel.

In this embodiment, the photoelectric conversion system 300 captures an image of the surroundings of the vehicle, for example, the front or rear. FIG. 18B shows a photoelectric conversion system for capturing an image in front of the vehicle (imaging range 350). The vehicle information acquisition device 320 sends an instruction to the photoelectric conversion system 300 or photoelectric conversion device 10 to perform a predetermined operation. With such a configuration, the accuracy of distance measurement can be further improved.

In the above, an example of controlling so as not to collide with another vehicle was explained, but it can also be applied to control to automatically drive following another vehicle or control to automatically drive so as not to stray from the lane. . Furthermore, the photoelectric conversion system can be applied not only to vehicles such as own vehicles, but also to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the present invention can be applied not only to mobile objects but also to devices that widely use object recognition, such as intelligent transportation systems (ITS).

[Modified embodiment]
The present invention is not limited to the above embodiment, and various modifications are possible. For example, an example in which a part of the configuration of one of the embodiments is added to another embodiment, or an example in which a part of the configuration of another embodiment is replaced is also an embodiment of the present invention.

It should be noted that the above-described embodiments are merely examples of specific implementations of the present invention, and the technical scope of the present invention should not be construed to be limited by these. That is, the present invention can be embodied in various forms without departing from its technical concept or main features.

Claims (8)

a semiconductor substrate including a plurality of photoelectric conversion units;
first and second microlenses;
a first filter having a higher transmittance for infrared light than for visible light;
a second filter having a higher transmittance for visible light than for infrared light;
The plurality of photoelectric conversion units are
a plurality of first photoelectric conversion units arranged to overlap the first microlens and the first filter in plan view;
a plurality of second photoelectric conversion units arranged to overlap the second microlens and the second filter in plan view;
Each of the first plurality of photoelectric conversion units and the second plurality of photoelectric conversion units
a first conductivity type first semiconductor region for accumulating signal charges;
of a second conductivity type opposite to the first conductivity type, disposed on the opposite side of the first semiconductor region to the first filter side, and overlapping the first semiconductor region in a plan view; and a second semiconductor region forming a PN junction with the first semiconductor region,
a third semiconductor region of the second conductivity type having an impurity concentration higher than that of the second semiconductor region between the first plurality of photoelectric conversion units and the second plurality of photoelectric conversion units;
the plurality of second photoelectric conversion units having a fourth semiconductor region of the second conductivity type provided at a position deeper than the second semiconductor region and having an impurity concentration higher than that of the second semiconductor region;
the second semiconductor regions of the first plurality of photoelectric conversion units are arranged at the same depth as the fourth semiconductor regions ;
a fifth semiconductor region of the second conductivity type having an impurity concentration higher than that of the second semiconductor region is arranged to a first depth between the first plurality of photoelectric conversion units;
a sixth semiconductor region of the second conductivity type having an impurity concentration higher than that of the second semiconductor region is arranged to a second depth between the plurality of second photoelectric conversion units;
the first depth is greater than the second depth
A photoelectric conversion device characterized by: 2. The photoelectric conversion device according to claim 1 , wherein the fourth semiconductor region is located at a distance of 2.0 [mu]m or more from the surface of the semiconductor substrate on the first filter side. The semiconductor substrate includes a first portion of the second conductivity type and the semiconductor substrate further than the first portion at a position away from the surface of the semiconductor substrate on the first filter side relative to the fourth semiconductor region. and a second portion of the second conductivity type having a higher impurity concentration than that of the first portion. 3. The photoelectric conversion device according to . 4. The photoelectric conversion device according to claim 1 , wherein the semiconductor substrate includes a portion formed by epitaxial growth and a portion formed by implanting impurity ions. 5. The photoelectric conversion device according to claim 1, wherein the fourth semiconductor region constitutes a barrier layer against charges generated in the first plurality of photoelectric conversion units. 6. The photoelectric conversion device according to claim 1, wherein said third semiconductor region and said fourth semiconductor region are connected to each other. The fourth semiconductor region located farthest from the first filter-side surface of the semiconductor substrate has an impurity concentration peak at a position farthest from the first filter-side surface of the semiconductor substrate. 7. The photoelectric conversion device according to claim 1, wherein the surface of the semiconductor substrate on the side of the first filter is closer to the peak of the impurity concentration of the third semiconductor region. . The photoelectric conversion device according to any one of claims 1 to 7;
and computing means for processing signals from the photoelectric conversion device .

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