KR20100045609A - Image sensor and method for manufacturing thereof - Google Patents

Abstract

PURPOSE: An image sensor and a method for manufacturing the same are provided to reduce the resistance of a signal line by forming a plurality of contact plugs on a wiring. CONSTITUTION: A readout circuitry(120) is formed on a first substrate(100). An interlayer insulation layer(160) is formed on the fist substrate. A wiring is formed on the interlayer insulation layer to be electrically connected to the readout circuitry. A plurality of contract plugs(154) is formed on the wiring. An image sensor(210) is formed on the contact plugs. An electric junction region is electrically connected to the readout circuitry.

Description

Image sensor and method for manufacturing

Embodiments relate to an image sensor and a manufacturing method thereof.

An image sensor is a semiconductor device that converts an optical image into an electrical signal, and is classified into a charge coupled device (CCD) image sensor and a CMOS image sensor (CIS). .

In the prior art, a photodiode is formed on a substrate by ion implantation. However, as the size of the photodiode gradually decreases for the purpose of increasing the number of pixels without increasing the chip size, the image quality decreases due to the reduction of the area of the light receiver.

In addition, since the stack height is not reduced as much as the area of the light receiving unit is reduced, the number of photons incident on the light receiving unit is also decreased due to diffraction of light called an airy disk.

One alternative to overcome this is to deposit photodiodes with amorphous Si, or read-out circuitry using wafer-to-wafer bonding such as silicon substrates. And photodiodes are formed on the lead-out circuit (hereinafter referred to as "three-dimensional image sensor"). The photodiode and lead-out circuit are connected via a metal line.

Meanwhile, according to the related art, a signal line forming process is required on a wafer on which two wafers are bonded and a photodiode on the top is formed. To this end, a contact is formed on a logic wafer, and later, a wafer on which a photodiode is formed is bonded, leaving only the photodiode region and removing other wafers Si. At this time, the contact resistance is high, there is a problem that greatly affects the sensitivity of the image sensor. That is, the sensitivity reduction caused by the high resistance in the conventional structure is a problem.

In addition, according to the related art, since both the source and the drain of the both ends of the transfer transistor are doped with a high concentration of N-type, charge sharing occurs. When charge sharing occurs, the sensitivity of the output image is lowered and image errors may occur.

In addition, according to the related art, a dark current is generated between the photodiode and the lead-out circuit and the photocharge is not smoothly moved, and saturation and sensitivity are decreased.

In addition, the embodiment is to provide an image sensor and a method of manufacturing the same that can reduce the resistance of the contact plug to the photodiode.

In addition, the embodiment is to provide an image sensor and a method of manufacturing the same that can increase the charge factor (Charge Sharing) does not occur.

In addition, the embodiment of the present invention provides an image sensor capable of minimizing dark current sources and preventing saturation and degradation of sensitivity by creating a smooth movement path of photo charge between the photodiode and the lead-out circuit. To provide a manufacturing method.

The image sensor according to the embodiment includes a readout circuitry formed on the first substrate; An interlayer insulating layer formed on the first substrate; A wiring formed in the interlayer insulating layer to be electrically connected to the lead-out circuit; A plurality of contact plugs formed on the wiring; And an image sensing unit formed on the contact plug.

In addition, the manufacturing method of the image sensor according to the embodiment comprises the steps of forming a readout circuitry (Readout Circuitry) on the first substrate; Forming an interlayer dielectric layer on the first substrate, and forming a wire in the interlayer dielectric layer that is electrically connected to the readout circuit; Forming a plurality of contact plugs on the wiring; And forming an image sensing unit on the contact plug.

According to the image sensor and the method of manufacturing the same according to the embodiment, the resistance of the signal line can be reduced by forming a plurality of contact plugs for the image sensing unit.

In addition, according to the embodiment, the device may be designed such that there is a potential difference between the source and the drain across the transfer transistor Tx, thereby enabling full dumping of the photo charge.

In addition, according to the embodiment, the charge connection region is formed between the photodiode and the lead-out circuit to create a smooth movement path of the photo charge, thereby minimizing the dark current source, and reducing saturation and sensitivity. You can prevent it.

Hereinafter, an image sensor and a method of manufacturing the same according to an embodiment will be described in detail with reference to the accompanying drawings.

In the description of the embodiments, where it is described as being formed "on / under" of each layer, it is understood that the phase is formed directly or indirectly through another layer. It includes everything.

The present invention is not limited to the CMOS image sensor, and may be applied to an image sensor requiring a photodiode.

(First embodiment)

1 is a cross-sectional view of an image sensor according to a first embodiment.

The image sensor according to the first embodiment includes a readout circuitry 120 formed on the first substrate 100; An interlayer insulating layer 160 formed on the first substrate 100; A wiring 150 formed in the interlayer insulating layer 160 to be electrically connected to the lead-out circuit 120; A plurality of contact plugs 154 formed on the wiring 150; And an image sensing unit 210 formed on the contact plug 154.

The image sensing unit 210 may be a photodiode, but is not limited thereto and may be a photogate, a combination of a photodiode and a photogate, and the like. On the other hand, the embodiment is an example in which the photodiode is formed in the crystalline semiconductor layer, but is not limited thereto, and includes the one formed in the amorphous semiconductor layer.

Unexplained reference numerals among the reference numerals of FIG. 1 will be described in the following manufacturing method.

Hereinafter, a manufacturing method of an image sensor according to an exemplary embodiment will be described with reference to FIGS. 2 to 7.

First, as shown in FIG. 2, the first substrate 100 having the wiring 150 and the readout circuit 120 is prepared. For example, the isolation layer 110 is formed on the second conductive first substrate 100 to define an active region, and a readout circuit 120 including a transistor is formed in the active region. For example, the readout circuit 120 may include a transfer transistor (Tx) 121, a reset transistor (Rx) 123, a drive transistor (Dx) 125, and a select transistor (Sx) 127. Can be formed. Thereafter, an ion implantation region 130 including a floating diffusion region (FD) 131 and source / drain regions 133, 135, and 137 for each transistor may be formed. In addition, according to the embodiment, the noise can be improved by adding a noise removing circuit (not shown).

The forming of the lead-out circuit 120 on the first substrate 100 may include forming an electrical junction region 140 on the first substrate 100 and forming an interconnection on the electrical junction region 140. And forming a first conductivity type connection region 147 connected to 150.

For example, the electrical junction region 140 may be a PN junction 140, but is not limited thereto. For example, the electrical junction region 140 may include a first conductive ion implantation layer 143 and a first conductive ion implantation layer (143) formed on the second conductive well 141 or the second conductive epitaxial layer. 143 may include a second conductivity type ion implantation layer 145. For example, the PN junction 140 may be a P0 145 / N- 143 / P-141 junction as shown in FIG. 2, but is not limited thereto. The first substrate 100 may be conductive in a second conductivity type, but is not limited thereto.

According to the embodiment, the device can be designed such that there is a voltage difference between the source / drain across the transfer transistor Tx, thereby enabling full dumping of the photo charge. Accordingly, as the photo charge generated in the photodiode is dumped into the floating diffusion region, the output image sensitivity may be increased.

That is, the embodiment forms the electrical junction region 140 on the first substrate 100 on which the readout circuit 120 is formed as shown in FIG. 2 so that there is a voltage difference between the source / drain across the transfer transistor (Tx) 121. This allows full dumping of the photocharge.

Hereinafter, the dumping structure of the photocharge of the embodiment will be described in detail.

Unlike the floating diffusion (FD) 131 node, which is an N + function in the embodiment, the P / N / P section 140, which is an electrical junction region 140, does not transmit all of the applied voltage and pinches at a constant voltage. It is off (Pinch-off). This voltage is called a pinning voltage and the pinning voltage depends on the P0 145 and N- (143) doping concentrations.

Specifically, the electrons generated by the photodiode 210 are moved to the PNP caption 140 and are transferred to the FD 131 node when the transfer transistor (Tx) 121 is turned on to be converted into a voltage.

Since the maximum voltage value of the P0 / N- / P- caption 140 becomes pinning voltage and the maximum voltage value of the FD (131) node becomes Vdd-Rx Vth, the charge sharing is performed due to the potential difference between both ends of the Tx (131). Electrons generated from the photodiode 210 above the chip may be fully dumped to the FD 131 node.

That is, in the embodiment, the reason why the P0 / N- / P-well junction, not the N + / P-well junction, is formed in the silicon sub, which is the first substrate 100, is P0 during the 4-Tr APS Reset operation. In / N- / P-well junction, + voltage is applied to N- (143) and ground voltage is applied to P0 (145) and P-well (141), so P0 / N- / P-well Double above a certain voltage Junction is Pinch-Off as in BJT structure. This is called pinning voltage. Therefore, a voltage difference is generated in the source / drain at both ends of the Tx 121, and thus the photocharge is completely dumped from the N-well to the FD through the Tx at the Tx On / Off operation to prevent the charge sharing phenomenon.

Therefore, unlike the case where the photodiode is simply connected by N + junction as in the prior art, the embodiment can avoid problems such as degradation of saturation and degradation of sensitivity.

Next, according to the embodiment, the first conductive connection region 147 is formed between the photodiode and the lead-out circuit to make a smooth movement path of the photo charge, thereby minimizing the dark current source and saturation ( Saturation) can be prevented and degradation of sensitivity.

To this end, the first embodiment may form an n + doped region as the first conductive connection region 147 for ohmic contact on the surface of the P0 / N− / P− junction 140. The N + region 147 may be formed to contact the N− 143 through the P0 145.

Meanwhile, in order to minimize the first conductive connection region 147 from becoming a leakage source, the width of the first conductive connection region 147 may be minimized. To this end, the embodiment may proceed with a plug implant after etching the first metal contact 151a, but is not limited thereto. For example, as another example, an ion implantation pattern (not shown) may be formed and the first conductive connection region 147 may be formed using the ion implantation mask as an ion implantation mask.

That is, as in the first embodiment, the reason for locally N + doping only to the contact forming part is to facilitate the formation of ohmic contact while minimizing the dark signal. As in the prior art, when N + Doping the entire Tx Source part, the dark signal may increase due to the substrate surface dangling bond.

Next, the interlayer insulating layer 160 may be formed on the first substrate 100, and the wiring 150 may be formed. The wiring 150 may include a first metal contact 151a, a first metal 151, a second metal 152, and a third metal 153, but is not limited thereto.

Subsequently, an embodiment may form a plurality of contact plugs 154 on the wiring 150. For example, a plurality of contact plugs 154 including a first contact plug 154a, a second contact plug 154b, and a third contact plug 154c may be formed on the third metal 153. However, it is not limited thereto.

An embodiment is to reduce the contact resistance by forming a plurality of contact plugs, which are signal lines. To this end, a contact plug connected to the image sensing unit may be formed as much as possible over the entire area of the image sensing unit.

The maximum number of contact plugs is determined by the size of the contact plug and the distance between the contact plugs. For example, if the size of the contact plug is defined as a and the distance between the contact plugs is defined as b, and the size of the image sensing unit is c, the number of contact plugs is c / (a + b).

For example, if the size c of the image sensing unit is 2 m, the size a of the contact plug is 0.16 m, and the distance b between the contact plugs is 0.18 m, the maximum number of contact plugs is 16. Meanwhile, even if the size c of the image sensing unit is 1.4 μm, at least nine contact plugs may be formed.

According to the image sensor and the method of manufacturing the same according to the embodiment, the resistance of the signal line can be reduced by forming a plurality of contact plugs for the image sensing unit.

Next, as shown in FIG. 3, a crystalline semiconductor layer 210a is formed on the second substrate 200. In the first embodiment, the photodiode 210 is formed on a crystalline semiconductor layer. Thus, according to the first embodiment, the image sensing unit adopts a three-dimensional image sensor positioned above the readout circuit to increase the fill factor while forming the image sensing unit in the crystalline semiconductor layer to prevent defects in the image sensing unit. Can be.

For example, the crystalline semiconductor layer 210a is formed on the second substrate 200 by epitaxial. Thereafter, hydrogen ions are implanted into the boundary region of the second substrate 200 and the crystalline semiconductor layer 210a to form the hydrogen ion implantation layer 207a. The implantation of the hydrogen ions may be performed after ion implantation for forming the photodiode 210.

Next, as shown in FIG. 4, the photodiode 210 is formed by ion implantation into the crystalline semiconductor layer 210a. For example, a second conductivity type conductive layer 216 is formed under the crystalline semiconductor layer 210a. For example, a high concentration P-type conductive layer 216 may be formed by implanting ions into the entire surface of the second substrate 200 with a blanket under the crystalline semiconductor layer 210a without a mask. For example, the second conductivity type conductive layer 216 may be formed with a junction depth within about 0.5 μm.

Thereafter, a first conductivity type conductive layer 214 is formed on the second conductivity type conductive layer 216. For example, the low concentration N-type conductive layer 214 may be formed by implanting ions onto the entire surface of the second substrate 200 without a mask on the second conductive conductive layer 216. For example, the low concentration first conductivity type conductive layer 214 may be formed with a junction depth of about 1.0-2.0 μm.

According to the embodiment, the thickness of the first conductivity type conductive layer 214 is formed to be thicker than the thickness of the second conductivity type conductive layer 216, thereby increasing the charge storage capacity. That is, by forming the N-layer 214 thicker to expand the area, it is possible to improve the capacity (capacity) that may contain the optoelectronic.

Thereafter, the first embodiment may further include forming a high concentration of the first conductivity type conductive layer 212 on the first conductivity type conductive layer 214. For example, the high concentration first conductive type layer 212 may be formed with a junction depth of about 0.05 to 0.2 μm. For example, an ion implantation may be performed on the entire surface of the second substrate 200 without a mask on the first conductive type conductive layer 214 to form a high concentration N + type conductive layer 212, thereby contributing to ohmic contact.

Next, as illustrated in FIG. 5, the first substrate 100 and the second substrate 200 are bonded to each other so that the photodiode 210 and the wiring 150 contact each other. In this case, the bonding may be performed by increasing the surface energy of the surface bonded by activation by plasma before bonding the first substrate 100 and the second substrate 200. Meanwhile, in order to improve the bonding force, bonding may be performed through an insulating layer, a metal layer, and the like on the bonding interface.

Thereafter, as illustrated in FIG. 6, the hydrogen ion injection layer 207a may be changed into a hydrogen gas layer (not shown) through heat treatment on the second substrate 200. Subsequently, the photodiode 210 may be exposed by leaving a photodiode 210 based on the hydrogen gas layer and removing a portion of the second substrate 200 using a blade or the like.

Subsequently, an etching process of separating the photodiode 210 for each pixel may be performed to fill an etched portion between pixels with an inter-pixel insulating layer (not shown) to separate the pixels for each pixel.

Next, as shown in FIG. 7, a process such as an upper electrode 240 and a color filter (not shown) may be performed.

(2nd Example)

8 is a cross-sectional view of the image sensor according to the second embodiment, which is a detailed view of the first substrate on which the wiring 150 is formed.

The second embodiment can employ the technical features of the first embodiment.

Meanwhile, unlike the first embodiment, the second embodiment is an example in which the first conductive connection region 148 is formed on one side of the electrical bonding region 140.

According to an embodiment, an N + connection region 148 for ohmic contacts may be formed in the P0 / N− / P− junction 140, in which case the N + connection region 148 and the M1C contact 151a are formed in the process. A source may occur. This is because the electric field EF may be generated on the Si surface of the substrate because the reverse bias is applied to the P0 / N− / P− junction 140. The crystal defects generated during the contact forming process in the electric field become a liquid source.

In addition, when the N + connection region 148 is formed on the surface of the P0 / N- / P- junction 140, an E-field by the N + / P0 junction 148/145 is added, which may also be a leakage source. .

Accordingly, in the second embodiment, the first contact plug 151a is formed in an active region formed of the N + connection region 148 without being doped with a P0 layer, and a layout for connecting the first contact plug 151a with the N-junction 143 is provided. present.

According to the second embodiment, the E-Field of the Si surface does not occur, which may contribute to the reduction of dark current of the 3-D integrated CIS.

The present invention is not limited to the described embodiments and drawings, and various other embodiments are possible within the scope of the claims.

1 is a sectional view of an image sensor according to a first embodiment;

2 to 7 are process cross-sectional views of a method of manufacturing the image sensor according to the first embodiment.

8 is a sectional view of an image sensor according to a second embodiment;

Claims (16)

A readout circuitry formed on the first substrate; An interlayer insulating layer formed on the first substrate; A wiring formed in the interlayer insulating layer to be electrically connected to the lead-out circuit; A plurality of contact plugs formed on the wiring; And And an image sensing unit formed on the contact plug. According to claim 1, And an electrical junction region formed on the first substrate to be electrically connected to the lead-out circuit. The method of claim 2, The electrical junction region is A first conductivity type ion implantation region formed on the first substrate; And And a second conductivity type ion implantation region formed on the first conductivity type ion implantation region. The method of claim 2, The readout circuit includes a transistor, And a potential difference between the source and the drain of both sides of the transistor. The method of claim 4, wherein The transistor is a transfer transistor, And an ion implantation concentration of the transistor source is lower than an ion implantation concentration of a floating diffusion region which is a drain. The method of claim 2, And a first conductivity type connection region formed between the electrical junction region and the wiring. The method according to claim 6, The first conductivity type connection region And a first conductivity type connection region formed on the electrical junction region and electrically connected to the wiring. The method according to claim 6, The first conductivity type connection region And a first conductivity type connection region formed on one side of the electrical junction region to be electrically connected to the wiring. Forming a readout circuitry on the first substrate; Forming an interlayer dielectric layer on the first substrate, and forming a wire in the interlayer dielectric layer that is electrically connected to the readout circuit; Forming a plurality of contact plugs on the wiring; And And forming an image sensing unit on the contact plug. The method of claim 9, And forming an electrical junction region electrically connected to the lead-out circuit on the first substrate. The method of claim 10, Forming the electrical junction region is Forming a first conductivity type ion implantation region in the first substrate; And And forming a second conductivity type ion implantation region on the first conductivity type ion implantation region. The method of claim 10, The readout circuit includes a transistor, And a potential difference between the source and the drain of both sides of the transistor. The method of claim 12, The transistor is a transfer transistor, And an ion implantation concentration of the transistor source is lower than an ion implantation concentration of the floating diffusion region, the drain. The method of claim 10, And forming a first conductive connection region between the electrical junction region and the wiring. The method of claim 14, The first conductivity type connection region And an electrical connection with the wirings formed on the electrical junction region. The method of claim 14, The first conductivity type connection region And an electrical connection with the wiring on one side of the electrical bonding region.

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