KR20070070538A - Vertical-type cmos image sensor and method for manufacturing the same - Google Patents

Abstract

A vertical CMOS image sensor and its manufacturing method are provided to define a gettering part without masking process by forming a pattern for defining the gettering part except an alignment pattern to a zero-mask required for alignment without using an additional mask, so that the productivity can be improved by implementing the gettering part through a simplified process. A pixel array region and a dummy area are formed on a silicon substrate(101). A first and a second epi layer(104,107) are formed sequentially on the entire surface of the silicon substrate. A first photodiode(103) is formed on the pixel array area of the silicon substrate. A second and a third photo diodes(106,108) are formed on the first and the second epi layer respectively by overlapping with a region of the first photodiode formation region. A first gettering part(102) is formed on a lower portion of a groove. A second gettering part(105) is formed on the first epi region corresponding to the around of the groove. A third gettering part(109) is formed on the second epi region corresponding to the upper portion of the groove.

Description

Vertical CMOS image sensor and method for manufacturing the same

1 is a plan view showing a typical vertical CMOS image sensor

FIG. 2 is a structural cross-sectional view taken along line II ′ of FIG. 1. FIG.

3 is a plan view showing a vertical CMOS image sensor of the present invention

4 is a structural cross-sectional view taken along line II-II 'of FIG.

5A and 5B show patterns of first and second zero masks used in the vertical CMOS image sensor of the present invention.

6 is a cross-sectional view illustrating a dummy region and a photodiode region of the vertical CMOS image sensor according to the present invention.

* Description of the symbols for the main parts of the drawings *

100: image sensor 101: silicon substrate

102: first gettering unit 103: first photodiode

104: first epitaxial layer 105: second gettering portion

106: second photodiode 107: second epi layer

108: third photodiode 109: third gettering portion

110: pixel array unit 120: dummy area

130: Peripheral region 135: Pattern matching portion of the zero mask

135a: first zero mask pattern 135b: second zero mask pattern

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to CMOS image sensors, and more particularly, to a vertical CMOS image sensor efficiently forming a gettering region for metal ion gettering and a method of manufacturing the same.

In general, CMOS image sensors are semiconductor devices that convert an optical image into an electrical signal. Among them, a charge coupled device (CCD) includes an individual metal-oxide silicon (MOS) capacitor. A device in which charge carriers are stored and transported in a capacitor while being in close proximity to one another.

CMOS image sensors, on the other hand, use CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to create as many photodiodes as the number of pixels and transistors connected to them to open and close channels. The transistors sequentially detect red, green, and blue optical signals using the transistors and output the same by a switching method.

Such CMOS image sensor has many advantages such as low power consumption, low process cost and high level of integration. In particular, with recent technological advances, CMOS image sensors have been spotlighted as an alternative to charge-coupled devices (CCDs) in many applications.

Such CMOS image sensors are classified into 3T type, 4T type, and 5T type according to the number of transistors. The 3T type consists of one photodiode and three transistors, and the 4T type consists of one photodiode and four transistors.

The unit pixel of a general 3T CMOS image sensor is composed of one photodiode (PD) and three nMOS transistors (T1, T2, T3). The cathode of the photodiode PD is connected to the drain of the first nMOS transistor T1 and the gate of the second nMOS transistor T2.

The sources of the first and second nMOS transistors T1 and T2 are all connected to a power supply line supplied with a reference voltage VR, and the gate of the first nMOS transistor T1 has a reset signal RST. It is connected to the reset line supplied.

Further, the source of the third nMOS transistor T3 is connected to the drain of the second nMOS transistor, the drain of the third nMOS transistor T3 is connected to a read circuit (not shown in the drawing) via a signal line, The gate of the third nMOS transistor T3 is connected to a column select line to which a selection signal SLCT is supplied.

Accordingly, the first nMOS transistor T1 is referred to as a reset transistor Rx, the second nMOS transistor T2 is referred to as a drive transistor Dx, and the third nMOS transistor T3 is referred to as a selection transistor Sx.

In this case, in the case of a general CMOS image sensor, transistors for driving and the like are formed horizontally, including a photo diode, and the unit pixel uses color filters of red (R), green (G), and blue (B). Will detect the light of the corresponding color.

In this case, in a general CMOS image sensor, one unit pixel must include all of the red (R), green (G), and blue (B) color filters formed in a planar shape, so that the size of the unit is large. Thus, in the case of such a general CMOS image sensor, the pixel integration degree is lowered.

As such, a vertical image sensor has been proposed to improve the problem of lowering the density of a general image sensor.

To improve this, a vertical image sensor was developed. The vertical image sensor has a red / green / blue photodiode for detecting red (R), green (G), and blue (B) signals per unit pixel. It has a vertical structure.

Hereinafter, a conventional vertical CMOS image sensor will be described with reference to the accompanying drawings.

FIG. 1 is a plan view illustrating a general vertical CMOS image sensor, and FIG. 2 is a structural cross-sectional view taken along line II ′ of FIG. 1.

1 and 2, the conventional vertical image sensor 10 is a vertical image sensor 10, the photodiode is formed in a well shape formed by doping the n + type, it is possible to detect all the signals per unit pixel The red (R), green (G), and blue (B) photodiodes (3, 6, 8) have a vertical structure.

Here, the conventional vertical image sensor 10 has a large area, a pixel area 20 in which a plurality of unit pixels are formed, elements (not shown) formed in the pixel area 20, and each photodiode. A peripheral region 40 including predetermined terminals and grounding terminals (not shown) for applying a signal to (3, 6, 8) is formed. The conventional vertical image sensor 10 is used as a grounding (GND) terminal by applying a P + type source / drain implant process to the peripheral area 40 for grounding. In particular, the dummy region 30 of the P + type present in the unit pixel (including R, G, and B photo diodes one by one) is not only a grounding role but also a first or second constituting the vertical image sensor 10. It was added to increase the gettering effect of the metal impurity generated during the formation process of the epitaxial layers 4 and 7. That is, the P + boron implant can be applied to the dummy moat regions 9, 19, and 29 (e.g., Fe-B bond) to getter the metal ions (M +) remaining in the epi layer. Thus, metal ion contamination can be eliminated.

The conventional vertical CMOS image sensor includes a silicon substrate 1, a first photodiode 3 for sensing red light formed at a predetermined portion of the silicon substrate 1, and the silicon substrate 1 on the silicon substrate 1; A first epitaxial layer 4 formed, a second photodiode 6 formed on the first epitaxial layer 4 overlapping with the first photodiode 3, and the first epitaxial layer 4. A second epitaxial layer 7 formed on (4), a third photodiode 8 formed on the second epitaxial layer 7 overlapping with the second photodiode 6, and the second epitaxial layer; P + type ions are implanted into a predetermined portion on the layer 6, and the first to third dummy moieties are formed at portions separated from corresponding silicon diodes and corresponding photodiodes of the first and second epitaxial layers ( dummy moat) (9, 19, 29).

The conventional vertical-type CMOS image sensor 10 requires three epilayers in the same manner because three photodiodes of red, green, and blue are formed vertically. At this time, an unwanted leakage current is increased due to metal ion contamination such as Fe, Ni, Cu, etc. generated during the epi layer deposition process, resulting in poor image sensor quality. In this case, one method of removing metal ions is to apply P + ion implantation (B) to the dummy region 30 of the image sensor circuit. This is called gettering in a narrow sense. For example, Fe ions can be decontaminated with Fe-B bonds.

In the conventional vertical CMOS image sensor, P + type ions are implanted into the dummy region 30 to the substrate and each epitaxial layer, thereby forming dummy moiety regions 9, 19 and 29, respectively. The metal ions gettered in the dummy mount region. That is, in the formation process of each pixel array unit, a predetermined mask for implanting P + type impurities is provided, and P + ion implantation is performed after growth of three substrates of the dummy region 30 and first and second epitaxial layers, respectively. In this case, dummy moats 9, 19, and 29 are added to predetermined portions of the dummy area 30.

As described above, the conventional vertical CMOS image sensor forms dummy moieties 9 and 19 on the silicon substrate 1 and the first epitaxial layer 4 in addition to the second epitaxial layer 7 on the top. To this end, an impurity implantation process using a mask is further involved, and thus the formation process is complicated, which causes problems in terms of time, productivity, and resources.

Here, reference numeral 25, which has not been described, is a pattern used as a mark for aligning the element or the like on the silicon substrate 1 and the first epitaxial layer 4. The alignment pattern 25 is an alignment pattern 25 that is initially defined when the silicon substrate 1 or the first epitaxial layer 4 is formed, and is formed to correspond to the peripheral region 4 that is not actually displayed. .

However, the conventional CMOS image sensor as described above has the following problems.

In the conventional vertical CMOS image sensor, since the dummy epitaxial region is formed on the silicon substrate and the first epitaxial layer together with the top epitaxial layer, an impurity implantation process using a mask is further involved. As it becomes complex, it has problems in terms of time, productivity, and resources.

An object of the present invention is to provide a vertical CMOS image sensor and a method for manufacturing the same, which efficiently form a gettering region for metal ion gettering. .

In order to achieve the above object, an image sensor of the present invention includes a silicon substrate having a pixel array region and a dummy region formed thereon, a first epi layer and a second epi layer formed in front on the silicon substrate, and the silicon substrate. A first photodiode formed in a pixel array region of a substrate, second and third photodiodes formed in the first and second epitaxial layers overlapping with the first photodiode forming portion, and the dummy region on the silicon substrate A recess in a predetermined portion of the first gettering portion formed below the recess, a second gettering portion and a second epitaxial layer formed corresponding to the periphery of the recess in the first epitaxial layer, and It is characterized by including a third gettering portion formed correspondingly.

The first to third gettering portions are formed in the dummy region.

After the second gettering part is etched a predetermined depth from the surface on the first epitaxial layer, a dummy poly layer is further formed, and impurities are injected into the dummy poly layer.

The first to third photodiodes are implanted with impurity ions of a first type, and impurity ions of a second type are implanted into the first to third gettering portions. The impurity ions of the first type are n + type, and the impurity ions of the second type are p + type. At this time, the impurity ion of the second type is B (Boron).

In addition, the manufacturing method of the vertical CMOS image sensor of the present invention for achieving the same object comprises the steps of preparing a silicon substrate in which a pixel array region, a dummy region and a peripheral region around the pixel array region is defined, and the first zero Etching a corner of a peripheral region of the silicon substrate and a predetermined portion of the dummy region using a mask to form a first alignment mark and a first gettering portion, and forming a first alignment mark and a first gettering portion; Implanting impurity ions, forming a first photodiode in the pixel array region, forming a first epitaxial layer on the silicon substrate, and using the second zero mask to form the first epitaxial layer Etching a predetermined depth corresponding to an edge of a peripheral area of the edge and an outer portion of the first gettering portion to form a second alignment mark and a second gettering portion; Forming a dummy poly on the second gettering portion, implanting first impurity ions into the dummy poly, and forming a second photodiode on the first epitaxial layer of the pixel array region. Forming a third epitaxial layer by forming a second epitaxial layer on the first epitaxial layer, and implanting first impurity ions into the second epitaxial layer corresponding to the first gettering unit Another feature is that it comprises a step.

Hereinafter, a vertical CMOS image sensor and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a plan view showing a vertical CMOS image sensor of the present invention, Figure 4 is a cross-sectional view of the structure of the line II ~ II 'of FIG.

The vertical image sensor 100 of the present invention is a vertical image sensor 100, the photodiode is formed in a well shape formed by being doped with n + type, red (R), so as to detect all the signals per unit pixel, Green (G) and blue (B) photodiodes have a vertical structure.

As shown in FIG. 3, the vertical image sensor 100 of the present invention has a large area, a pixel array unit 110 in which a plurality of unit pixels are formed, and a dummy region formed around the pixel array unit 110. 120 and a peripheral region 130 formed around the dummy region 120.

Here, the pixel array unit 110 is provided with a plurality of unit pixels, each of the unit pixels, in the vertical direction, R, G, B, photodiodes 103, 106, 108 are formed in a stacked structure. Here, a signal terminal (not shown) and a grounding terminal (not shown) for applying a signal to the elements formed in the pixel region 120 and the photodiode are formed in the peripheral region, and the dummy region 110 First to third gettering units 102, 105, and 109 that perform gettering of the pixel array unit 110 are formed.

The vertical CMOS image sensor of the present invention includes a silicon substrate 101, a first photodiode 103 for sensing red light formed at a predetermined portion of the silicon substrate 101, and an image on the silicon substrate 101. A first epitaxial layer 104 formed on the second epitaxial layer 104, a second photodiode 106 formed on the first epitaxial layer 104 to overlap with the first photodiode 103, and the first epitaxial layer 104. A second epitaxial layer 107 formed on the layer 104, a third photodiode 108 formed on the second epitaxial layer 107 to overlap with the second photodiode 106, and the second P + type ions are implanted into a predetermined portion on the epitaxial layer 106 and are formed in the dummy regions 120 spaced apart from each silicon substrate and the corresponding photodiodes of the first and second epitaxial layers. It comprises three gettering portions (102, 105, 109).

Here, the first to third gettering portions 102, 105, and 109 are formed in the dummy region.

In this case, the first gettering part 102 is defined by injecting a p + type impurity such as B (Boron) to the surface exposed by etching a predetermined depth from the surface of the silicon substrate 101. After the second gettering portion 105 is etched a predetermined depth from the surface on the first epitaxial layer 104, a dummy poly layer 105 is formed, and impurities are injected into the dummy poly layer. Is defined.

The first to third photodiodes 103, 106 and 108 are implanted with n + type impurity ions, and the first to third gettering portions are implanted with the same p + type impurity ions.

In the vertical CMOS image sensor, since three photodiodes of red, green, and blue are formed vertically, three epitaxial layers are required. At this time, an unwanted leakage current is increased due to metal ion contamination of Fe, Ni, Cu, etc. generated during each epi layer deposition process, resulting in deterioration of the quality of the image sensor. At this time, one method of removing metal ions is to apply P + ion implantation (B) to the dummy region 120 of the image sensor circuit. This is called gettering in a narrow sense. For example, Fe ions can be decontaminated with Fe-B bonds.

The vertical CMOS image sensor of the present invention, in the conventional CMOS image sensor, complements the gathering method of injecting P + type impurities using a separate mask to initially form an alignment mark for forming an element on a silicon substrate or each epi layer. By applying a dummy pattern to the zero mask used to form a, it is possible to implement a simpler process can bring a significant improvement in terms of time, productivity, and resources.

In addition, the present invention relates to a method of simply generating a conventional zero pattern without additional pattern processing for gathering metal ions in a vertical CMOS image sensor (pattern generation or mask tooling method). The prior art uses two additional P + S / D patterns, making them inefficient due to complex processes. To this end, a new method of manufacturing a zero mask having a same gathering effect and a dummy pattern is added to enable a simpler process.

In FIG. 3, reference numeral 135, which has not been described, is a pattern (alignment mark) used as a mark for aligning the element or the like on the silicon substrate 101 and the first epitaxial layer 104. FIG. The alignment mark 135 is initially defined when the silicon substrate 101 or the first epitaxial layer 104 is formed. The alignment mark 135 is formed to correspond to the peripheral region 130 that does not actually display.

5A and 5B are diagrams showing patterns of first and second zero masks used in the vertical CMOS image sensor of the present invention.

As illustrated in FIG. 5A, the first zero mask (not shown) corresponding to the alignment mark 135 of the silicon substrate 101 having a predetermined opening corresponds to a predetermined portion of the dummy region 120. The first pattern 135a may be further formed. In this case, when the alignment mark is formed on the silicon substrate 101 using the first zero mask (not shown), a portion corresponding to the alignment mark is etched to a predetermined depth. Similarly, the first pattern 135a Like the first gettering portion 102, the portion corresponding to the portion is etched a predetermined depth from the surface of the silicon substrate 101.

Here, the pattern (not shown) corresponding to the pattern 135a or the alignment mark 135 in the first mask is defined as an opening, and a portion of the silicon substrate 101 exposed through the opening has a predetermined depth. Will be removed.

As shown in FIG. 5B, a second zero mask (not shown) corresponding to the alignment mark 135 with respect to the first epitaxial layer 104 and having a predetermined opening may include the first pattern 135a of the first zero mask. The second pattern 135b is provided at a portion corresponding to the outer portion of the. Since the second pattern 135b is formed at the outer portion of the first pattern 135a, the second pattern 135b is formed at different positions, and thus, the same portion is continuously etched, so that the second pattern 135b is relatively at the surface of the epitaxial layers. This can alleviate having a step. In this case, when the alignment mark is formed on the first epitaxial layer 104 using the second zero mask (not shown), a portion corresponding to the alignment mark is etched to a predetermined depth, and likewise, the second pattern ( A portion corresponding to 135b) is also etched to a predetermined depth from the surface of the first epitaxial layer 104, like the second gettering portion 105. In this case, a dummy poly may be further formed in the second gettering portion 105 defined during etching using the second pattern of the second zero mask in order to alleviate the step generation during etching. The dummy poly may be formed together when forming a predetermined element of the pixel array unit.

6 is a cross-sectional view illustrating a dummy region and a photodiode region of the vertical CMOS image sensor of the present invention.

3 to 6, the vertical CMOS image sensor of the present invention includes a silicon substrate 101 having a pixel region 110, a dummy region 120, and a peripheral region 130 formed therein, and A first epitaxial layer 104 and a second epitaxial layer 107 formed on the silicon substrate 101 in turn, a first photodiode 103 formed on the pixel array portion of the silicon substrate 101, and the first epitaxial layer 104. Second and third photodiodes 106 and 108 formed on the first and second epitaxial layers 104 and 107 so as to overlap with the first photodiode 103 forming portion, and the silicon substrate 101 on the A first gettering portion 102 formed in a predetermined portion of the dummy region and formed below the recessed portion, and a second gettering portion 105 formed corresponding to the periphery of the recessed portion in the first epitaxial layer 104. And a third gettering part 109 formed on the second epitaxial layer 107 corresponding to the upper portion of the recess. The.

In addition, the manufacturing method of the vertical CMOS image sensor of the present invention is as follows.

First, a silicon substrate 101 having a pixel array portion, a dummy region and a peripheral region defined around the pixel array portion is prepared.

Subsequently, a corner of the peripheral area of the silicon substrate 101 and a predetermined portion of the dummy area 120 are etched by a first depth by using a first zero mask (not shown), so that the first alignment mark 135 and the first 1 Gettering part 102 is formed.

Subsequently, first impurity ions are implanted into the first gettering unit 102.

Subsequently, a first photodiode 103 is formed in the pixel array unit 110.

Subsequently, a first epitaxial layer 104 is formed on the silicon substrate 101.

Subsequently, a second depth is etched by using a second zero mask (not shown) to etch a predetermined portion corresponding to an edge of the peripheral area of the first epitaxial layer 104 and an outer portion of the first gettering part 102. , The second alignment mark 135, and the second gettering portion 105 are formed. In this case, a dummy poly may be formed in the second gettering part 105 to reduce a step between adjacent parts.

Subsequently, first impurity ions are implanted into the second gettering portion 105.

Subsequently, a second photodiode 106 is formed in the first epitaxial layer 104 of the pixel array unit 110.

Subsequently, a second epitaxial layer 107 is formed on the first epitaxial layer 104.

Subsequently, a first gettering unit 109 is formed by implanting first impurity ions into the second epitaxial layer 107 corresponding to the first gettering unit 102.

As described above, in the vertical CMOS image sensor, in the first and second zero masks having no function other than alignment, a predetermined pattern is further added to define an area for gettering. do.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The vertical CMOS image sensor of the present invention and its manufacturing method as described above has the following effects.

The gettering portion formed on the substrate or the epi layers on which each photodiode is formed for gettering is not formed using a separate mask, and a pattern defining the gettering portion in addition to the alignment pattern is further formed on the zero mask required for alignment. This eliminates the need for a mask process and allows the gettering portion to be defined.

In addition, by forming the gettering portion formed on the substrate and the first epitaxial layer at different portions, the step corresponding to the etched portion is removed when defining the gettering portion, thereby reducing the step difference from the surface of the substrate or the other epitaxial layer. Can be. In addition, a dummy poly may be formed to reduce the step difference.

As such, since the dummy mask may be further provided on the zero mask when the gettering portion is formed, the gettering portion may be implemented in a simpler process, thereby bringing a significant improvement in terms of time, productivity, and resources. have.

Claims (7)

A silicon substrate having a pixel array region and a dummy region formed around the pixel array region; A first epi layer and a second epi layer formed on the silicon substrate in front; A first photodiode formed in a pixel array region of the silicon substrate; Second and third photodiodes formed on the first and second epitaxial layers to overlap with the first photodiode forming portions; A first gettering portion provided at a predetermined portion of the dummy region on the silicon substrate and formed under the recessed portion; A second gettering portion formed in the first epitaxial layer corresponding to the periphery of the recess; And And a third gettering part formed on the second epitaxial layer corresponding to the upper portion of the recess. The method of claim 1, And the first to third gettering portions are formed in the dummy region. The method of claim 1, And the second gettering part is etched a predetermined depth from the surface on the first epitaxial layer, and further forms a dummy poly layer, and impurities are injected into the dummy poly layer. The method of claim 1, And the first to third photodiodes are implanted with impurity ions of a first type, and impurity ions of a second type are implanted into the first to third gettering parts. The method of claim 4, wherein The impurity ions of the first type are n + type, and the impurity ions of the second type are p + type. The method of claim 5, The vertical type CMOS image sensor of claim 2, wherein the impurity ions of the second type are B (Boron). Preparing a silicon substrate having a pixel array region, a dummy region around the pixel array region, and a peripheral region defined therein; Forming a first alignment mark and a first gettering part by firstly etching a corner of a peripheral area of the silicon substrate and a predetermined portion of the dummy area by using a first zero mask; Implanting first impurity ions into the first gettering portion; Forming a first photodiode in the pixel array region; Forming a first epitaxial layer on the silicon substrate; A second depth is etched by using a second zero mask to etch a predetermined depth corresponding to an edge of a peripheral area of the first epitaxial layer and an outer portion of the first gettering part to form a second alignment mark and a second gettering part. step; Forming a dummy poly on the second gettering portion; Implanting first impurity ions into the dummy poly; Forming a second photodiode in a first epitaxial layer of the pixel array region; Forming a second epitaxial layer on the first epitaxial layer; And implanting first impurity ions into the second epitaxial layer corresponding to the first gettering part to form a third gettering part.

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