JP6972068B2 - Photoelectric converter - Google Patents

Description

The present invention relates to a photoelectric conversion device.

Some photoelectric conversion devices used for automatic focus detection of cameras, automatic exposure adjustment of cameras, radiation detection, etc. have large-area photodiodes with a diameter of several tens of microns to several hundreds of microns. There is something. It is desired that such a large-area photodiode has a large amount of saturated charge and can be read out at high speed. Patent Document 1 discloses a technique for realizing high sensitivity and high-speed readout by devising a potential distribution in a photodiode.

Japanese Unexamined Patent Publication No. 2016-076647

In order to further increase the sensitivity of the photoelectric conversion device, it is desired to further increase the saturated charge amount of the photodiode while suppressing the noise superimposed on the output signal.

An object of the present invention is to provide a highly sensitive photoelectric conversion device having a photoelectric conversion unit having a large amount of saturated charge.

According to one aspect of the present invention, a photoelectric conversion unit that generates a signal charge of the first polarity by incident light, a charge conversion circuit that converts the signal charge into a signal voltage, and a charge conversion circuit from the photoelectric conversion unit. The first conductive type, which has a transfer transistor for transferring the signal charge, is provided on the surface portion of the semiconductor substrate, and has a large number of carriers of the first polarity. A second conductive type first, which is provided on the semiconductor region and the surface portion of the semiconductor substrate apart from the first semiconductor region and has a large number of carriers having a second polarity different from the first polarity. The second semiconductor region and the third semiconductor region , the first conductive type fourth semiconductor region provided at a first depth deeper than the depth provided with the second semiconductor region, and the first. 4 of the semiconductor region is provided on the second depth greater than the depth provided a fifth semiconductor region of the second conductivity type overlaps with said second semiconductor region in a plan view, the fifth semiconductor It has a sixth semiconductor region of the first conductive type provided at a third depth deeper than the depth at which the region is provided , and the first semiconductor region electrically connects to the transfer transistor. The first semiconductor region is connected, and the first semiconductor region is arranged between the second semiconductor region and the third semiconductor region, and the first semiconductor region, the fourth semiconductor region, and the third semiconductor region are connected. The sixth semiconductor region is electrically connected in the depth direction, and the fourth semiconductor region and the sixth semiconductor region are the first semiconductor region and the second semiconductor region in a plan view. , A photoelectric conversion device that overlaps the third semiconductor region and the fifth semiconductor region. The photoelectric conversion device is provided.

According to the present invention, it is possible to realize a highly sensitive photoelectric conversion device having a photoelectric conversion unit having a large amount of saturated charge.

It is a circuit diagram which shows the schematic structure of the photoelectric conversion apparatus according to 1st Embodiment of this invention. It is a top view which shows the photoelectric conversion part of the photoelectric conversion apparatus according to 1st Embodiment of this invention. It is a schematic sectional drawing which shows the photoelectric conversion part of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is a potential figure of the photoelectric conversion part of the photoelectric conversion apparatus according to 1st Embodiment of this invention. It is schematic cross-sectional view which shows the photoelectric conversion part of the photoelectric conversion apparatus by the modification of 1st Embodiment of this invention. It is a top view which shows the photoelectric conversion part of the photoelectric conversion apparatus according to 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the photoelectric conversion part of the photoelectric conversion apparatus by 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the image pickup system according to 3rd Embodiment of this invention. It is a figure which shows the structural example of the image pickup system and the moving body according to 4th Embodiment of this invention. It is a figure which shows the radiation imaging system by 5th Embodiment of this invention.

[First Embodiment]
The photoelectric conversion device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a circuit diagram showing a schematic configuration of a photoelectric conversion device according to the present embodiment. FIG. 2 is a plan view showing the structure of the photoelectric conversion unit of the photoelectric conversion device according to the present embodiment. FIG. 3 is a schematic cross-sectional view showing the structure of the photoelectric conversion unit of the photoelectric conversion device according to the present embodiment. FIG. 4 is a potential diagram of the photoelectric conversion unit of the photoelectric conversion device according to the present embodiment.

First, the structure of the photoelectric conversion device according to the present embodiment will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, the photoelectric conversion device 100 according to the present embodiment has a plurality of pixels 10, a scanning circuit 20, an operational amplifier 30, and an integral capacity 40.

Each of the plurality of pixels 10 has a photoelectric conversion unit PD and a transfer transistor M1. The photoelectric conversion unit PD is, for example, a photodiode, the anode is connected to the ground node, and the cathode is connected to the source of the transfer transistor M1. The gate of the transfer transistor M1 is connected to the scanning circuit 20. The drain of the transfer transistor M1 is connected to a signal output line 12 common to a plurality of pixels 10.

The signal output line 12 is connected to the inverting input terminal (−) of the operational amplifier 30. A voltage Vref is supplied to the non-inverting input terminal (+) of the operational amplifier 30. The output terminal of the operational amplifier 30 is connected to the sensor output line 32. An integral capacitance 40 is connected between the inverting input terminal (−) of the operational amplifier 30 and the output terminal.

In FIG. 1, for simplification, three pixels 10 connected to one signal output line 12 are shown, but the number of pixels 10 connected to one signal output line 12 is particularly limited. is not it. The number of pixels 10 connected to one signal output line 12 may be 2 or less, or 4 or more. Further, a plurality of pixels 10 may be connected to each of the plurality of signal output lines 12 to form a two-dimensional pixel array.

The photoelectric conversion unit PD converts the incident light into an amount of electric charge corresponding to the amount of light (photoelectric conversion), and accumulates the generated electric charge. When the transfer transistor M1 is turned on, the electric charge held by the photoelectric conversion unit PD is output to the signal output line 12. By sequentially supplying the readout pulse to each pixel 10 from the scanning circuit 20, the electric charge generated in the photoelectric conversion unit PD of each pixel 10 can be sequentially output to the signal output line 12.

The operational amplifier 30 constitutes a charge integration type charge conversion circuit together with an integral capacity 40 connected between the inverting input terminal and the output terminal. As a result, the signal charge output from the photoelectric conversion unit PD to the signal output line 12 is integrated with the integration capacity 40, and the signal voltage corresponding to the amount of the charge is output to the sensor output line 32. The potential on the cathode side of the photoelectric conversion unit PD becomes a potential corresponding to the voltage Vref after the electric charge is output to the signal output line 12, that is, when the photoelectric conversion unit PD is reset.

The integrated capacitance 40 is composed of a capacitive element having no voltage dependence, such as a MIM type capacitor. This is to ensure the linearity of the signal vs. output. As will be described later, the PN junction capacitance of the photodiode constituting the photoelectric conversion unit PD has a large voltage dependence. However, by constructing the charge integration circuit using the integrated capacity 40 having no potential dependence, it is proportional to the amount of charge output from the photoelectric conversion unit PD regardless of the potential dependence of the PN junction capacitance of the photodiode. The output voltage can be output to the sensor output line 32. This makes it possible to ensure signal-to-output linearity.

Next, the structure of the photoelectric conversion unit PD of the photoelectric conversion device according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a plan layout view showing a configuration example of the photoelectric conversion unit PD. FIG. 3 is a cross-sectional view taken along the line AA'of FIG. In the present specification, the plan view represents a state in which each component of the photoelectric conversion unit PD is projected onto a plane parallel to the surface of the semiconductor substrate, and corresponds to the plan layout diagram of FIG.

In the present embodiment, the case where the carrier of the first polarity, which is the signal charge, is an electron will be described as an example. In this case, the semiconductor region having a large number of carriers (electrons) of the first polarity is the N-type semiconductor region, and the semiconductor region having a large number of carriers (holes) of the second polarity different from the first polarity is. This is a P-type semiconductor region. The signal charge (electrons) generated in the photoelectric conversion unit PD is accumulated in the N-type semiconductor region. The signal charge does not necessarily have to be an electron, but may be a hole. In this case, the conductive type of each region described later is a reverse conductive type.

The photoelectric conversion unit PD of the photoelectric conversion device according to the present embodiment is a photodiode composed of a PN junction provided on the semiconductor substrate 110. The semiconductor substrate 110 is, for example, a low impurity concentration N-type ^- a (N type) silicon substrate. As shown in FIG. 2, the photoelectric conversion unit PD is provided in the photoelectric conversion unit forming region 112 of the semiconductor substrate 110.

^{As shown in FIG. 3, an N-type (N +} type) semiconductor region 120 and a P-type semiconductor region 122 are provided on the surface portion of the semiconductor substrate 110 on the main surface 160 side. The N-type semiconductor region 124 and the P-type semiconductor region 126 are provided at the first depth 162 of the semiconductor substrate 110 deeper than the region where the N-type semiconductor region 120 and the P-type semiconductor region 122 are provided. There is. The P-type semiconductor region 128 is provided at the second depth 164 of the semiconductor substrate 110, which is deeper than the region where the N-type semiconductor region 124 and the P-type semiconductor region 126 are provided. An N-type semiconductor region 130 and a P-type semiconductor region 132 are provided at a third depth 166 of the semiconductor substrate 110, which is deeper than the region provided with the P-type semiconductor region 128. The P-type semiconductor region 134 is provided at the fourth depth 168 of the semiconductor substrate 110, which is deeper than the region where the P-type semiconductor region 132 is provided. A P-type semiconductor region 136 is provided at a fifth depth 170 of the semiconductor substrate 110, which is deeper than the region where the P-type semiconductor region 134 is provided.

P-type semiconductor region 136, N-type region shallower than the fifth depth 170 of the semiconductor substrate 110 (N ^- -type) semiconductor region 138, N of a region deeper than the fifth depth 170 of the semiconductor substrate 110 having a ^- (type N) serve to electrically separate the semiconductor region 140 type. In other words, the P-type semiconductor region 136 defines the depth at which the photoelectric conversion unit PD generates a signal charge by photoelectric conversion. Charges (electrons) generated in a region shallower than the P-type semiconductor region 136 are collected in the N-type semiconductor region 120 to become signal charges.

As shown in FIG. 2, the P-type semiconductor regions 126, 132, and 134 are provided in an annular shape along the inner circumference of the photoelectric conversion portion forming region 112 in a plan view. In the arrangement region of the P-type semiconductor regions 126, 132, 134 in a plan view, the P-type semiconductor regions 122, 126, 128, 132, 134, 136 are electrically connected in the depth direction. That is, the P-type semiconductor regions 126, 132, and 134 have a role as a separation layer for separating the elements together with the P-type semiconductor region 136.

As shown in FIG. 2, the N-type semiconductor region 120 has an elongated rectangular pattern extending in a first direction (Y direction in FIG. 2) parallel to the surface of the semiconductor substrate 110. The N-type semiconductor region 120 has a length close to the diameter in the Y direction of the photoelectric conversion portion forming region 112. In FIG. 2, two N-type semiconductor regions 120 are arranged in the photoelectric conversion portion forming region 112, but the number of N-type semiconductor regions 120 arranged in the photoelectric conversion portion forming region 112 is not particularly limited, and the photoelectric conversion portion is not particularly limited. It can be appropriately set according to the size and shape of the conversion portion forming region 112. That is, the number of the N-type semiconductor regions 120 may be one or three or more.

The P-type semiconductor region 122 is provided apart from the N-type semiconductor region 120. More specifically, the P-type semiconductor region 122 is provided on the entire surface of the photoelectric conversion portion forming region 112 excluding the region provided with the N-type semiconductor region 120 and a certain range around the N-type semiconductor region 120. Has been. The P-type semiconductor region 128 is provided in a region that overlaps with the P-type semiconductor region 122 in a plan view.

The N-type semiconductor regions 124 and 130 are provided corresponding to each of the two N-type semiconductor regions 120, respectively. Each of the N-type semiconductor regions 124 and 130 overlaps the corresponding N-type semiconductor region 120, the P-type semiconductor region 122, and the P-type semiconductor region 128 in a plan view. Specifically, each of the N-type semiconductor regions 124 and 130 is provided in a trunk portion provided in a region overlapping the N-type semiconductor region 120 in a plan view and in a region overlapping the P-type semiconductor regions 122 and 128 in a plan view. It has a plurality of branch portions 142 and. The plurality of branch portions 142 extend in a comb-teeth shape in both directions parallel to the second direction (X direction in FIG. 2) intersecting the first direction from the trunk portion. The width of the branch 142 becomes narrower as it goes away from the trunk. In the arrangement region of the N-type semiconductor region 120 in a plan view, the N-type semiconductor regions 120, 124, 130 are electrically connected in the depth direction.

The wiring 150 is connected to the N-type semiconductor region 120 via a connection electrode 152 such as a contact plug. The wiring 150 is a wiring for connecting the cathode of the photoelectric conversion unit PD and the source of the transfer transistor M1.

In this way, the photoelectric conversion unit PD is configured by the PN junction between the N-type semiconductor regions 120, 124, 130, 138 and the P-type semiconductor regions 122, 128. The N-type semiconductor regions 124 and 130 have a role as a charge storage layer for accumulating the signal charges generated in the photoelectric conversion unit PD. The N-type semiconductor region 120 has a higher impurity concentration than the N-type semiconductor regions 124 and 130 from the viewpoint of reducing the contact resistance with the connection electrode 152 and the connection resistance with the N-type semiconductor regions 124 and 130. Is preferable.

Although not shown in FIGS. 2 and 3, a fixed voltage is supplied to the P-type semiconductor region 122. As a result, the same fixed voltage as the fixed voltage supplied to the P-type semiconductor region 122 is also supplied to the P-type semiconductor regions 126, 128, 132, 134, 136 electrically connected to the P-type semiconductor region 122. .. In the following description, this fixed voltage will be described as a reference voltage (0V) for the sake of simplicity, but the present invention is not limited to the reference voltage.

Next, the operation of the photoelectric conversion unit PD will be described with reference to FIGS. 2 to 4. FIG. 4 is a potential diagram along the X direction at the first depth 162 in which the N-type semiconductor region 124 and the P-type semiconductor region 126 at the time of resetting the photoelectric conversion unit PD are provided.

When the transfer transistor M1 is turned on and the electric charge accumulated in the photoelectric conversion unit PD is output to the signal output line 12, the potential on the cathode side of the photoelectric conversion unit PD becomes a potential corresponding to the voltage Vref, and the photoelectric conversion unit becomes available. PD is reset.

The voltage Vref, which is the reset voltage of the photoelectric conversion unit PD, is a positive potential with respect to the reference voltage supplied to the P-type semiconductor region 122, and the maximum voltage Vref at the PN junction of the photoelectric conversion unit PD is set at the time of reset. A magnitude reverse bias voltage is applied. At this time, the N-type semiconductor region 120 is a neutral region having a high impurity concentration, and depletion does not occur so much. Therefore, the N-type semiconductor region 120 has substantially the same voltage (voltage Vref) at any portion. On the other hand, since the impurity concentrations of the N-type semiconductor regions 124 and 130 are low, almost the entire region thereof, particularly the portion overlapping the P-type semiconductor regions 122 and 128 in plan view, is depleted at the time of reset. That is, the depletion voltage in this overlapping portion is smaller than the voltage Vref.

As shown in FIG. 4, the potential of the depleted N-type semiconductor region 124 is not constant and has a gradient. This is because the width of the branch portion 142 of the N-type semiconductor region 124 in the plan view becomes narrower so as to be farther from the portion (trunk portion) overlapping the N-type semiconductor region 120 in the plan view. That is, since the depletion of the N-type semiconductor region 124 progresses not only from the surface parallel to the surface of the semiconductor substrate 110 but also from the side surface, the portion farther from the trunk and the width of the branch portion 142 is narrower, the more the N-type semiconductor region 124 is depleted. The depletion voltage becomes smaller. As a result, a potential gradient as shown in FIG. 4 is generated in the N-type semiconductor region 124.

The N-type semiconductor region 130 also has a trunk portion and a branch portion 142 similar to the N-type semiconductor region 124, and has a potential gradient similar to that of the N-type semiconductor region 124. However, in the region where the N-type semiconductor region 124 and the N-type semiconductor region 130 overlap with the N-type semiconductor region 120 in plan view, the potential of the N-type semiconductor region 130 is shallower than the potential of the N-type semiconductor region 124. , Impure concentration, etc. are set appropriately.

The P-type semiconductor region 128 may be hardly depleted, but at least the vicinity of the N-type semiconductor region 120 is depleted when the photoelectric conversion unit PD is reset. The P-type semiconductor region 122 has a role of suppressing a dark current generated on the surface portion of the semiconductor substrate 110, and is set to a high impurity concentration so that depletion does not occur so much during the operation of the photoelectric conversion unit PD. NS.

By configuring the photoelectric conversion unit PD in this way, most of the capacity at the time of resetting the photoelectric conversion unit PD is the PN junction capacity between the N-type semiconductor region 120 and the P-type semiconductor region 122. However, the N-type semiconductor region 120 occupies only a small part of the total area of the photoelectric conversion unit PD, and the PN junction capacity between the N-type semiconductor region 120 and the P-type semiconductor region 122 is very large. small.

In general, the noise at the time of reading the charge is dominated by the noise at the time of resetting the photoelectric conversion unit PD, that is, the so-called kTC noise. The kTC noise is proportional to the 1/2 power of the capacitance at the time of resetting the photoelectric conversion unit PD. In the photoelectric conversion device according to the present embodiment, as described above, since the capacitance of the photoelectric conversion unit PD at reset is small, kTC noise and thus noise at charge readout can be suppressed.

When the transfer transistor M1 is turned off and the signal reading from the photoelectric conversion unit PD to the signal output line 12 (reset of the photoelectric conversion unit) is completed, the photoelectric conversion unit PD starts accumulating the signal charge generated by the incident light, and the photoelectric conversion unit PD starts to accumulate the signal charge. The potential of the cathode of the conversion unit PD gradually decreases.

In the present embodiment, the N-type semiconductor regions 120, 124, 130 constituting the charge storage layer of the photoelectric conversion unit PD, particularly the branch portions 142 of the N-type semiconductor regions 124, 130, are the light receiving surfaces of the photoelectric conversion unit PD in a plan view. It is densely formed inside. Therefore, the signal charge generated outside the charge storage layer also quickly reaches the charge storage layer by diffusion and is accumulated. Therefore, for example, it is not necessary to form a potential step in a region away from the charge storage layer to promote charge transfer as described in Patent Document 1, and the masking process at the time of manufacturing is reduced to reduce the manufacturing cost and the product price. Can be suppressed.

While the amount of charge stored in the charge storage layer is small, the signal charge is stored only in the N-type semiconductor region 120 and its vicinity. When the amount of charge accumulated in the charge storage layer exceeds a certain amount, the signal charge is also accumulated in the portion where the N-type semiconductor regions 124 and 130 and the P-type semiconductor regions 122 and 128 overlap in a plane. ..

When the amount of charge in the charge storage layer reaches the saturated amount of charge, the signal charge is accumulated in the entire area where the N-type semiconductor regions 124 and 130 and the P-type semiconductor regions 122 and 128 overlap in a plane. The capacitance of the photoelectric conversion unit PD at this time includes the N-type semiconductor regions 124 and 130 and the P-type semiconductor regions 122 and 128 with respect to the PN junction capacitance between the N-type semiconductor region 120 and the P-type semiconductor region 122. The PN junction capacitance between is added. Since the N-type semiconductor regions 124 and 130 and the P-type semiconductor regions 122 and 128 are close to each other as shown in FIG. 3, the capacity per unit area is large. Further, since the N-type semiconductor region 120 has a length close to the diameter of the photoelectric conversion unit PD, the N-type semiconductor regions 124 and 130 are formed inside the semiconductor substrate 110 by connecting to the N-type semiconductor region 120. , A wide PN junction area can be secured. In addition, the charge storage layer has a two-tiered structure composed of N-type semiconductor regions 124 and 130 in the depth direction. Therefore, the capacity of the photoelectric conversion unit PD at the time of saturation becomes a value significantly larger than the capacity of the photoelectric conversion unit PD at the time of reset, and a sufficient amount of saturation signal can be obtained.

The signal read from the photoelectric conversion unit PD is performed by turning on the transfer transistor M1. When the transfer transistor M1 is turned on, the potential of the N-type semiconductor region 120 approaches the voltage Vref through the signal output line 12. At the same time, the signal charge accumulated in the charge storage layer flows out toward the N-type semiconductor region 120.

At this time, since the N-type semiconductor region 120 includes a neutral region and has a low resistance, the signal reading speed from the photoelectric conversion unit PD is mainly rate-determined by the reading speed of the signal charges stored in the N-type semiconductor regions 124 and 130. Will be done. However, in the present embodiment, the signal charges in the N-type semiconductor regions 124 and 130 located away from the N-type semiconductor region 120 can be quickly read out by the drift motion due to the potential gradient shown in FIG. Further, as shown in FIG. 2, the N-type semiconductor regions 124 and 130 have a length of only about 1/4 of the diameter of the photoelectric conversion unit PD from the N-type semiconductor region 120. Therefore, according to the configuration of the present embodiment, the signal reading speed from the photoelectric conversion unit PD can be improved.

FIG. 5 is a schematic cross-sectional view showing the structure of the photoelectric conversion unit of the photoelectric conversion device according to the modified example of the present embodiment. The structure shown in FIG. 5 is a structure in which the N-type semiconductor region 130 in FIG. 3 is not provided and the lower portion of the P-type semiconductor region 128 is the N-type semiconductor region 138.

In FIG. 5, the N-type semiconductor region 138 is an N-type semiconductor layer having a lower impurity concentration than the N-type semiconductor region 124. Typically, the N-type semiconductor region 138 has the same impurity concentration as the N-type semiconductor region 140. Therefore, the N-type semiconductor region 138 is less likely to accumulate signal charges than the N-type semiconductor region 124, and is more likely to be depleted. Therefore, the PN junction capacitance of the portion of the N-type semiconductor region 138 is smaller than the PN junction capacitance of the portion of the N-type semiconductor region 130 in FIG. Therefore, in the form of FIG. 5, the PN junction capacitance of the photoelectric conversion unit PD can be reduced as compared with the case where the N-type semiconductor region 130 is provided in the lower part of the P-type semiconductor region 128 as in the form of FIG. Therefore, although the amount of saturation signal of the photoelectric conversion unit PD is reduced, the noise can be made smaller.

As described above, according to the present embodiment, it is possible to realize a highly sensitive photoelectric conversion device having a photoelectric conversion unit having a small noise and a large saturation charge amount.

[Second Embodiment]
The photoelectric conversion device according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG. 6 is a plan view showing the structure of the photoelectric conversion unit of the photoelectric conversion device according to the present embodiment. FIG. 7 is a schematic cross-sectional view showing the structure of the photoelectric conversion unit of the photoelectric conversion device according to the present embodiment. The same components as those of the photoelectric conversion device according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The photoelectric conversion device according to the present embodiment is the same as the photoelectric conversion device according to the first embodiment, except that the structure of the photoelectric conversion unit PD is different. The photoelectric conversion unit PD of the photoelectric conversion device according to the present embodiment is provided with an N-type semiconductor region 144 instead of the N-type semiconductor regions 124 and 130, and the layout of the P-type semiconductor regions 126, 132 and 134 in a plan view. Is different from the first embodiment.

That is, as shown in FIG. 7, the photoelectric conversion unit PD of the photoelectric conversion device according to the present embodiment has a first depth 162 to a third depth of the semiconductor substrate 110 instead of the N-type semiconductor regions 124 and 130. It has an N-type semiconductor region 144 provided in the region up to 166. The N-type semiconductor region 144 has the same planar layout as the N-type semiconductor regions 124 and 130 in the first embodiment at the first depth 162 and the third depth 166. That is, the N-type semiconductor region 144 is parallel to the first depth 162 and the third depth 166 in the second direction (X direction in FIG. 6) from the region overlapping the N-type semiconductor region 120 in a plan view. It has a plurality of branch portions 142 extending in a comb-teeth shape in both directions. The branch portion 142 has a tapered shape whose width becomes wider as it approaches a region overlapping the N-type semiconductor region 120.

The third depth 166 does not necessarily have to be deeper than the deepest portion of the P-type semiconductor region 128 in this embodiment. The third depth 166 can be changed based on the amount of saturated charge obtained from the photoelectric conversion unit PD.

At the first depth 162, the outer edge of the N-type semiconductor region 144 in plan view is defined by the junction with the P-type semiconductor region 126. At the second depth 164, the outer edge of the N-type semiconductor region 144 in plan view is defined by the junction with the P-type semiconductor region 128. At a third depth of 166, the outer edge of the N-type semiconductor region 144 in plan view is defined by a junction with the P-type semiconductor region 132. In FIG. 6, the layouts of the P-type semiconductor regions 126, 132, and 134 in the plan view are the same, but the layout of the P-type semiconductor regions 134 may be the same as in the case of the first embodiment.

In FIG. 6, the P-type semiconductor regions 126, 132, 134 are formed outside the alternate long and short dash line indicated by the P-type semiconductor regions 126, 132, 134. This is different from the formation of the N-type semiconductor regions 124 and 130 inside the dotted lines indicated by the N-type semiconductor regions 124 and 130 in FIG.

The N-type impurity for forming the N-type semiconductor region 144 can be introduced into the entire photoelectric conversion portion forming region 112 in a plan view, similarly to the P-type impurity for forming the P-type semiconductor region 136. In this case, the concentration of the N-type impurities constituting the N-type semiconductor region 144 is set to be lower than the concentration of the P-type impurities constituting the P-type semiconductor regions 126, 128, 132. With this configuration, the region other than the region where the P-type semiconductor regions 126, 128, 132 are formed becomes the N-type semiconductor region 144.

In the present embodiment as well, as in the case of the first embodiment, when the photoelectric conversion unit PD is in the reset state, the N-type semiconductor region 144 is depleted in most of the regions overlapping the P-type semiconductor regions 122 and 128 in a plan view. do. Then, a potential gradient is formed in the N-type semiconductor region 144 in both the plane direction and the depth direction so that the potential becomes deeper as the N-type semiconductor region 120 approaches. That is, the photoelectric conversion unit PD according to the present embodiment is the same as the first embodiment in that the capacitance at reset is small, that is, the noise is low, and a large amount of saturation signal can be secured.

In addition, in the photoelectric conversion unit PD of the present embodiment, as described below, the signal reading speed can be improved as compared with the case of the photoelectric conversion unit PD of the first embodiment.

When the signal charge is read out, as the signal charge (electrons in this embodiment) in the charge storage layer moves, the holes in the P-type semiconductor regions 122, 128, 136 also move. In general, when the voltage between two electrodes forming a capacitance changes, the charge stored in both electrodes moves by the same amount. Here, the P-type semiconductor region 122 generally has a high concentration and a low resistance. On the other hand, it is difficult to increase the concentration of the P-type semiconductor region 128 because the N-type semiconductor region 144 is less likely to be formed when the concentration is increased. Further, although the P-type semiconductor region 136 is formed in a deep region by using high-energy ion implantation, it is generally difficult to increase the amount of high-energy ion implantation. Therefore, the P-type semiconductor regions 128 and 136 have a relatively low concentration and high resistance as compared with the P-type semiconductor region 122. Therefore, in the first embodiment, the moving speed of the holes in the P-type semiconductor regions 128 and 136 is not always sufficient, which causes the signal reading speed to slow down.

On the other hand, in the present embodiment, as shown in FIGS. 6 and 7, the P-type semiconductor region 128 is electrically with the P-type semiconductor regions 126 and 132 in most of the photoelectric conversion portion forming region 112. It is conducting. Further, the P-type semiconductor region 136 is electrically conductive with the P-type semiconductor region 134 in most of the regions of the photoelectric conversion portion forming region 112. Therefore, the holes in the P-type semiconductor region 128 rapidly move to the P-type semiconductor region 122 through the P-type semiconductor region 126 and are discharged from the P-type semiconductor region 122. Further, the holes in the P-type semiconductor region 136 rapidly move to the P-type semiconductor region 122 through the P-type semiconductor regions 134, 132, 126, and are discharged from the P-type semiconductor region 122.

Therefore, in the photoelectric conversion unit PD of the present embodiment, the signal reading speed can be improved as compared with the case of the first embodiment.

Further, in the photoelectric conversion unit PD of the present embodiment, as described below, it is possible to reduce the masking process at the time of manufacturing as compared with the case of the photoelectric conversion unit PD of the first embodiment, and the manufacturing cost can be reduced. As a result, it is possible to reduce the cost of the photoelectric conversion device.

That is, in the photoelectric conversion unit PD of the first embodiment, as shown in FIGS. 2 and 3, the N-type semiconductor regions 124 and 130 and the P-type semiconductor region 136 have different planar layouts. That is, in manufacturing the photoelectric conversion unit PD, a masking step for forming the N-type semiconductor regions 124 and 130 and a masking step for forming the P-type semiconductor region 136 are required, respectively.

On the other hand, in the photoelectric conversion unit PD of the present embodiment, as described above, the N-type impurities constituting the N-type semiconductor region 144 can be introduced into the entire photoelectric conversion unit forming region 112 in a plan view. .. That is, the same mask can be used as the mask used when forming the N-type semiconductor region 144 and the mask used when forming the P-type semiconductor region 136. Therefore, in manufacturing the photoelectric conversion unit PD, the N-type semiconductor region 144 and the P-type semiconductor region 136 can be formed in one masking step, and the masking step is 1 as compared with the case of the first embodiment. The number of processes can be reduced.

Therefore, in the present embodiment, the manufacturing cost can be reduced as compared with the case of the first embodiment, and the cost of the photoelectric conversion device can be reduced.

As described above, according to the present embodiment, it is possible to realize a highly sensitive photoelectric conversion device having a photoelectric conversion unit having a small noise and a large saturation charge amount.

[Third Embodiment]
The image pickup system according to the third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a block diagram showing a schematic configuration of an imaging system according to the present embodiment.

The photoelectric conversion device 100 described in the first and second embodiments is applicable to various imaging systems. Examples of applicable imaging systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, in-vehicle cameras, observation satellites and the like. The image pickup system also includes a camera module including an optical system such as a lens and an image pickup device. FIG. 8 illustrates a block diagram of a digital still camera as an example of these.

The image pickup system 200 illustrated in FIG. 8 has an image pickup device 201, a lens 202 for forming an optical image of a subject on the image pickup device 201, a diaphragm 204 for varying the amount of light passing through the lens 202, and a lens 202 for protection. Has a barrier 206 of. The lens 202 and the aperture 204 are optical systems that collect light on the image pickup apparatus 201. The image pickup apparatus 201 is the photoelectric conversion apparatus 100 described in any of the first and second embodiments, and converts the optical image formed by the lens 202 into image data.

The image pickup system 200 also has a signal processing unit 208 that processes an output signal output from the image pickup apparatus 201. The signal processing unit 208 performs AD conversion that converts the analog signal output by the image pickup apparatus 201 into a digital signal. In addition, the signal processing unit 208 also performs various corrections and compressions as necessary to output image data. The AD conversion unit, which is a part of the signal processing unit 208, may be formed on a semiconductor substrate provided with the image pickup device 201, or may be formed on a semiconductor substrate different from the image pickup device 201. Further, the image pickup apparatus 201 and the signal processing unit 208 may be formed on the same semiconductor substrate.

The image pickup system 200 further includes a memory unit 210 for temporarily storing image data, and an external interface unit (external I / F unit) 212 for communicating with an external computer or the like. Further, the imaging system 200 includes a recording medium 214 such as a semiconductor memory for recording or reading imaging data, and a recording medium control interface unit (recording medium control I / F unit) 216 for recording or reading on the recording medium 214. Have. The recording medium 214 may be built in the image pickup system 200 or may be detachable.

Further, the image pickup system 200 has an overall control / calculation unit 218 that controls various calculations and the entire digital still camera, and a timing generation unit 220 that outputs various timing signals to the image pickup device 201 and the signal processing unit 208. Here, a timing signal or the like may be input from the outside, and the image pickup system 200 may have at least an image pickup device 201 and a signal processing unit 208 that processes an output signal output from the image pickup device 201.

The image pickup device 201 outputs an image pickup signal to the signal processing unit 208. The signal processing unit 208 performs predetermined signal processing on the image pickup signal output from the image pickup apparatus 201, and outputs image data. The signal processing unit 208 uses the image pickup signal to generate an image.

As described above, according to the present embodiment, it is possible to realize an image pickup system to which the photoelectric conversion device 100 according to the first and second embodiments is applied.

[Fourth Embodiment]
The image pickup system and the moving body according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram showing a configuration of an imaging system and a moving body according to the present embodiment.

FIG. 9A shows an example of an imaging system related to an in-vehicle camera. The image pickup system 300 includes an image pickup device 310. The image pickup apparatus 310 is the photoelectric conversion apparatus 100 according to any one of the first and second embodiments. The image pickup system 300 has an image processing unit 312 that performs image processing on a plurality of image data acquired by the image pickup device 310, and a parallax (phase difference of the parallax image) from the plurality of image data acquired by the image pickup system 300. It has a parallax acquisition unit 314 that performs calculation. Further, the imaging system 300 has a distance acquisition unit 316 that calculates the distance to the object based on the calculated parallax, and a collision determination unit 318 that determines whether or not there is a possibility of collision based on the calculated distance. And have. Here, the parallax acquisition unit 314 and the distance acquisition unit 316 are examples of distance information acquisition means for acquiring distance information to an object. That is, the distance information is information related to parallax, defocus amount, distance to an object, and the like. The collision determination unit 318 may determine the possibility of collision by using any of these distance information. The distance information acquisition means may be realized by hardware specially designed, or may be realized by a software module. Further, it may be realized by FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like, or may be realized by a combination thereof.

The image pickup system 300 is connected to the vehicle information acquisition device 320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. Further, the image pickup system 300 is connected to a control ECU 330 which 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 unit 318. The image pickup 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 unit 318. For example, when the possibility of a collision is high as the determination result of the collision determination unit 318, the control ECU 330 performs vehicle control to avoid a collision and reduce damage by applying a brake, releasing the accelerator, suppressing engine output, and the like. The alarm device 340 warns the user by sounding an alarm such as a sound, displaying alarm information on the screen of a car navigation system, or giving vibration to the seat belt or steering.

In the present embodiment, the surroundings of the vehicle, for example, the front or the rear, are imaged by the image pickup system 300. FIG. 9B shows an imaging system for imaging the front of the vehicle (imaging range 350). The vehicle information acquisition device 320 sends an instruction to the image pickup system 300 or the image pickup device 310. 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 has been described, but it can also be applied to control for automatically driving following other vehicles and control for automatically driving so as not to go out of the lane. .. Further, the image pickup system can be applied not only to a vehicle such as an own vehicle but also to a moving body (moving device) such as a ship, an aircraft, or an industrial robot. In addition, it can be applied not only to mobile objects but also to devices that widely use object recognition, such as intelligent transportation systems (ITS).

[Fifth Embodiment]
The radiation imaging system according to the fifth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a diagram showing a radiation imaging system according to the present embodiment. In this embodiment, an example in which the photoelectric conversion device described in the first and second embodiments is applied to a radiation imaging system is shown.

As shown in FIG. 10, the radiation imaging system according to the present embodiment includes a radiation imaging device 6040 and an image processor 6070 that processes a signal output from the radiation imaging device 6040. The radiation image pickup device 6040 is configured by configuring the photoelectric conversion device described in each of the above-described embodiments as a device for capturing radiation. The X-ray 6060 generated by the X-ray tube (radioactive source) 6050 passes through the chest 6062 of the patient or the subject 6061 and is incident on the radiation imaging device 6040. This incident X-ray contains information on the inside of the body of the subject 6061. The radiation image pickup device 6040 has a scintillator that converts the wavelength of the incident X-ray. Scintillators typically convert X-rays into light with wavelengths in the visible light range. The radiation imaging device 6040 includes the photoelectric conversion device according to the above-described embodiment, and visible light whose wavelength is converted by a scintillator is incident on the photoelectric conversion device. Therefore, in the photoelectric conversion device 100 of each of the above embodiments, the N-type semiconductor region 120 collects the signal charge corresponding to the visible light incident from the scintillator.

The image processor (processor) 6070 processes a signal (image) output from the radiation image pickup apparatus 6040, and can display an image on the display 6080 in the control room based on the image signal obtained by the processing, for example.

Further, the image processor 6070 can transfer the signal obtained by the processing to a remote place via the transmission line 6090. As a result, the image can be displayed on a display 6081 arranged in a doctor's room or the like at another place, or the image can be recorded on a recording medium such as an optical disk. The recording medium may be film 6110, in which case the film processor 6100 records an image on film 6110.

The photoelectric conversion device described in the present specification can also be applied to an imaging system that captures an image of visible light. Such an imaging system may include, for example, a photoelectric conversion device and a processor that processes a signal output from the photoelectric conversion device. The processing by the processor may include, for example, at least one of the processing of converting the format of the image, the processing of compressing the image, the processing of resizing the image, and the processing of changing the contrast of the image.

[Modification Embodiment]
The present invention is not limited to the above embodiment and can be modified in various ways.
For example, an example in which a partial configuration of any of the embodiments is added to another embodiment or an example in which a partial configuration of another embodiment is replaced with another embodiment is also an embodiment of the present invention.

Further, in the first and second embodiments, the charge storage layer composed of the N-type semiconductor regions 120, 124, and 130 is divided into two blocks centered on each of the two N-type semiconductor regions 120, and these are divided into two blocks. The blocks are connected by wiring 150. However, the charge storage layer does not necessarily have to be divided, and may be configured to be divided into three or more blocks. The number of blocks constituting the charge storage layer can be appropriately selected according to the size, shape, and the like of the photoelectric conversion portion forming region 112.

Further, when the charge storage layer is divided into a plurality of blocks, a separation portion composed of P-type semiconductor regions 126, 132, and 134 may be arranged between the blocks. With this configuration, the resistance of the P-type semiconductor regions 128 and 136 can be reduced, and the signal reading speed can be improved.

Further, in the first and second embodiments, the branch portions 142 of the charge storage layer are arranged in two stages in the depth direction, but it is not always necessary to arrange them in a plurality of stages, and the branch portions 142 are arranged in three stages in the depth direction. It may be configured to arrange the above.

Further, when the branch portion 142 of the charge storage layer is composed of a plurality of stages, some stages may be the configuration of the first embodiment and the other stages may be the configuration of the second embodiment. Further, when the branch portions 142 of the charge storage layer are configured in a plurality of stages, the planar layout of the branch portions 142 constituting each stage may be the same or different.

Further, in the first and second embodiments, the width of the branch portion 142 in the plan view is continuously changed, but the width of the branch portion 142 does not necessarily have to be continuously changed. The width of the branch portion 142 in the plan view may be widened as it is closer to the region overlapping the N-type semiconductor region 120, and may be configured to change stepwise.

Further, the imaging system shown in the third to fifth embodiments shows an example of an imaging system to which the photoelectric conversion device of the present invention can be applied, and the imaging system to which the photoelectric conversion device of the present invention can be applied is The configuration is not limited to the configuration shown in FIGS. 8 to 10.

It should be noted that the above embodiments are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.

M1 ... Transfer transistor PD ... photoelectric conversion unit 10 ... pixel 30 ... operational amplifier 40 ... integrated capacity 100 ... photoelectric conversion device 110 ... semiconductor substrate 112 ... photoelectric conversion unit forming region 120, 124, 130, 138, 140 ... N-type semiconductor region 122, 126, 128, 132, 134, 136 ... P-type semiconductor region 142 ... Branch

Claims (19)

A photoelectric conversion unit that generates a signal charge of the first polarity due to the incident of light,
A charge conversion circuit that converts the signal charge into a signal voltage,
It has a transfer transistor that transfers the signal charge from the photoelectric conversion unit to the charge conversion circuit.
The photoelectric conversion unit is
A first conductive type first semiconductor region provided on the surface of a semiconductor substrate and having a large number of carriers having the first polarity, and
A second conductive type second semiconductor region provided on the surface portion of the semiconductor substrate at a distance from the first semiconductor region and having a large number of carriers having a second polarity different from the first polarity. And the third semiconductor area ,
The fourth semiconductor region of the first conductive type provided at a first depth deeper than the depth at which the second semiconductor region is provided, and
A fifth semiconductor region of the second conductive type, which is provided at a second depth deeper than the depth at which the fourth semiconductor region is provided and overlaps with the second semiconductor region in a plan view.
It has a sixth semiconductor region of the first conductive type provided at a third depth deeper than the depth at which the fifth semiconductor region is provided.
The first semiconductor region is electrically connected to the transfer transistor and is connected to the transfer transistor.
The first semiconductor region is arranged between the second semiconductor region and the third semiconductor region.
The first semiconductor region, the fourth semiconductor region, and the sixth semiconductor region are electrically connected in the depth direction.
The fourth semiconductor region and the sixth semiconductor region overlap with the first semiconductor region, the second semiconductor region , the third semiconductor region, and the fifth semiconductor region in a plan view. A photoelectric conversion device characterized by. The fourth semiconductor region and the sixth semiconductor region extend from the trunk portion that overlaps with the first semiconductor region in a plan view, and the second semiconductor region and the fifth semiconductor region in a plan view. The photoelectric conversion device according to claim 1, further comprising a plurality of branches overlapping the region. The photoelectric conversion device according to claim 2, wherein the width of the branch portion in a plan view becomes narrower as the distance from the trunk portion increases. The first semiconductor region has a rectangular pattern extending in the first direction.
2. The third aspect of the present invention, wherein the plurality of branches of the fourth semiconductor region and the sixth semiconductor region extend in a second direction intersecting the first direction. Photoelectric conversion device. The fourth semiconductor region and the sixth semiconductor region are according to any one of claims 2 to 4, wherein the sixth semiconductor region is electrically connected to the first semiconductor region in the trunk. Photoelectric conversion device. The photoelectric conversion according to any one of claims 1 to 5, wherein the impurity concentration of the fourth semiconductor region and the sixth semiconductor region is lower than the impurity concentration of the first semiconductor region. Device. The portion where the fourth semiconductor region and the sixth semiconductor region overlap with the second semiconductor region and the fifth semiconductor region in a plan view is characterized in that the portion is depleted when the photoelectric conversion unit is reset. The photoelectric conversion device according to any one of claims 1 to 6. The seventh semiconductor region of the second conductive type provided at the first depth, and
It further has an eighth semiconductor region of the second conductive type provided at the third depth.
The outer edge portion of the fourth semiconductor region in a plan view is defined by a junction between the fourth semiconductor region and the seventh semiconductor region.
Any of claims 1 to 7, wherein the outer edge portion of the sixth semiconductor region in a plan view is defined by a junction between the sixth semiconductor region and the eighth semiconductor region. The photoelectric conversion device according to item 1. A photoelectric conversion unit that generates a signal charge of the first polarity due to the incident of light,
A charge conversion circuit that converts the signal charge into a signal voltage,
It has a transfer transistor that transfers the signal charge from the photoelectric conversion unit to the charge conversion circuit.
The photoelectric conversion unit is
A first conductive type first semiconductor region provided on the surface of a semiconductor substrate and having a large number of carriers having the first polarity, and
A second conductive type second semiconductor region provided on the surface portion of the semiconductor substrate at a distance from the first semiconductor region and having a large number of carriers having a second polarity different from the first polarity. And the third semiconductor area ,
The fourth semiconductor region of the first conductive type provided at a first depth deeper than the depth at which the second semiconductor region is provided, and
A fifth semiconductor region of the second conductive type, which is provided at a second depth deeper than the depth at which the fourth semiconductor region is provided and overlaps with the second semiconductor region in a plan view.
It has a sixth semiconductor region of the first conductive type provided at a third depth deeper than the depth at which the fifth semiconductor region is provided.
The first semiconductor region is electrically connected to the transfer transistor and is connected to the transfer transistor.
The first semiconductor region is arranged between the second semiconductor region and the third semiconductor region.
The first semiconductor region, the fourth semiconductor region, and the sixth semiconductor region are electrically connected in the depth direction.
The fourth semiconductor region and the sixth semiconductor region overlap with the first semiconductor region, the second semiconductor region , the third semiconductor region, and the fifth semiconductor region in a plan view.
The seventh semiconductor region of the second conductive type provided at the first depth, and
Before Symbol eighth semiconductor region of the third second conductivity type formed at a depth of, further comprising a,
The outer edge portion of the fourth semiconductor region in a plan view is defined by a junction between the fourth semiconductor region and the seventh semiconductor region.
A photoelectric conversion device characterized in that the outer edge portion of the sixth semiconductor region in a plan view is defined by a junction portion between the sixth semiconductor region and the eighth semiconductor region. The photoelectric conversion device according to claim 8 or 9, wherein the seventh semiconductor region and the eighth semiconductor region constitute a separation layer for separating elements. The fourth semiconductor region and the sixth semiconductor region are a part of the ninth semiconductor region of the first conductive type provided from the first depth to the third depth. ,
One of claims 1 to 10, wherein the concentration of the first conductive type impurity at the second depth is the same in the ninth semiconductor region and the fifth semiconductor region. The photoelectric conversion device according to the section. It is characterized by further having a tenth semiconductor region of the second conductive type, which is provided at a fourth depth deeper than the third depth and overlaps the entire formation region of the photoelectric conversion portion in a plan view. The photoelectric conversion device according to any one of claims 1 to 11. The photoelectric conversion device according to any one of claims 1 to 12, wherein the charge conversion circuit is a charge integration type. A photoelectric conversion unit that generates a signal charge of the first polarity due to the incident of light,
A charge conversion circuit that converts the signal charge into a signal voltage,
It has a transfer transistor that transfers the signal charge from the photoelectric conversion unit to the charge conversion circuit.
The photoelectric conversion unit is
A first conductive type first semiconductor region provided on the surface of a semiconductor substrate and having a large number of carriers having the first polarity, and
A second conductive type second semiconductor region provided on the surface portion of the semiconductor substrate at a distance from the first semiconductor region and having a large number of carriers having a second polarity different from the first polarity. And the third semiconductor area ,
The fourth semiconductor region of the first conductive type provided at a first depth deeper than the depth at which the second semiconductor region is provided, and
It has a fifth semiconductor region of the second conductive type, which is provided at a second depth deeper than the depth at which the fourth semiconductor region is provided and which overlaps with the second semiconductor region in a plan view. ,
The first semiconductor region is electrically connected to the transfer transistor and is connected to the transfer transistor.
The first semiconductor region is arranged between the second semiconductor region and the third semiconductor region.
The first semiconductor region and the fourth semiconductor region are electrically connected in the depth direction.
It said fourth semiconductor region, said first semiconductor region in a plan view, the second semiconductor region, the third semiconductor region and the fifth photoelectric conversion device is characterized in that overlaps the semiconductor region .. The photoelectric conversion unit further has an eleventh semiconductor region of the first conductive type provided on the surface portion of the semiconductor substrate.
The third semiconductor region is arranged between the first semiconductor region and the eleventh semiconductor region so as to be separated from the first semiconductor region and the eleventh semiconductor region.
The photoelectric conversion device according to any one of claims 1 to 14. Further equipped with a scintillator that converts radiation into visible light,
The photoelectric conversion device according to any one of claims 1 to 15 , wherein the photoelectric conversion unit generates the signal charge based on the visible light incident from the scintillator. The photoelectric conversion device according to any one of claims 1 to 15.
An imaging system characterized by having a signal processing unit that processes a signal output from a conversion device using the light. It ’s a mobile body,
The photoelectric conversion device according to any one of claims 1 to 15.
A distance information acquisition means for acquiring distance information to an object from a parallax image based on a signal from the photoelectric conversion device, and
A moving body having a control means for controlling the moving body based on the distance information. The photoelectric conversion device according to claim 16 and
A radiation imaging system comprising a control device for processing an image signal obtained by the photoelectric conversion device.

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