JP2001177086A - Image pickup element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform the gettering of precious metals affecting a photo sensor part. SOLUTION: A first getter layer 120 is provided at the deep layer part of a substrate 110 of a CCD solid image pickup element 100, and a first epitaxial growth layer 130 is provided on the upper layer. Also, a second getter layer 140 is provided at a region ranging from an element separation region 100B on the upper layer to a substrate scissioning part 100C. Further, a second epitaxial growth layer 150 is provided on the upper layer of the first epitaxial growth layer 130 and the second getter layer 140. The getter layer 140 is arranged closer to the photo sensor part of an image pickup region, and is provided at a region without affecting the element structure of the image pickup region, thus easily performing the gettering of precious metals affecting the photo sensor part and effectively suppressing the generation of white blemisk by the precious metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup device having a getter structure capable of effectively gettering a heavy metal which has a bad influence on a photosensor portion, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, heavy metals (Fe, Cu, N
If i, Ca, Zn, Mo, etc.) are present in the vicinity of the photosensor portion that performs photoelectric exchange of the imaging portion, it causes white flaws on the imaging screen. These heavy metals are diffused by heat applied during the manufacturing process of the imaging device. Therefore, conventionally, for example, as shown in FIG. 4, a getter layer 12 is provided inside an epitaxial growth substrate (a substrate on which Si is epitaxially grown) 10 on which an imaging device is formed in order to eliminate the influence of heavy metals on the photosensor portion. I have to.

[0003] The getter layer 12 is formed by ion implantation of C ions, N ions, or the like, is formed in a step prior to epitaxial growth, and is formed deeper than the epitaxial growth layer 14 (near the back surface of the substrate 10). Is formed over the entire surface. In FIG. 4, a photosensor unit and a CCD transfer unit (both not shown) constituting an image sensor are formed in an upper layer portion of the epitaxial growth substrate 10. In addition, on the surface of the epitaxial growth substrate 10, an upper film forming layer 1 on which wiring electrodes, light shielding films, and microlenses are disposed.
6 are provided. Such an imaging device is divided into a central imaging region 18A and a peripheral device isolation region 18B. The imaging region 18A includes a light-receiving film and a light-shielding film for each photosensor unit, a microlens, and a CCD vertical. A transfer section and the like are arranged, and the element isolation region 18B has a CC
A D horizontal transfer unit, an output amplifier, a reset gate, an element protection transistor and the like are arranged.

[0004]

However, since the getter layer as described above is usually formed before the epitaxial growth, if the thickness of the epitaxial growth is large, the position of the getter layer is farther from the surface of the imaging device. . On the other hand, there is a certain limit to the heat history due to the heat process, and unlimited heating cannot be performed, so the diffusion distance of heavy metals has a certain limit, and the effective range taken into the getter layer is relatively narrow. Will be. At the same time, with the recent miniaturization and high-density of the image pickup device, a low-temperature process in the heat process is progressing, and there is a tendency to suppress thermal diffusion. Therefore, the effective range taken into the getter layer is further narrowed. In addition, during epitaxial growth, heavy metals generally tend to easily enter the substrate. As a result, particularly heavy metals easily affect the sensor region, resulting in defects such as white spots.

The present invention has been made in view of the above circumstances, and an object of the present invention is to easily perform gettering of heavy metals affecting the photosensor portion, and to reduce white scratches caused by heavy metals. It is an object of the present invention to provide an image pickup device having a getter structure capable of effectively suppressing generation thereof and a method of manufacturing the same.

[0006]

According to the present invention, in order to achieve the above object, an image pickup area comprising a plurality of image pickup pixels and an element isolation region provided around the image pickup area are formed on an epitaxial growth substrate. In addition, in the imaging device provided with a getter layer for performing heavy metal gettering on the epitaxial growth substrate, the imaging device has a plurality of epitaxial growth layers in the epitaxial growth substrate, and has a getter layer between the plurality of epitaxial growth layers. The getter layer is formed in a peripheral area of the imaging area.

Further, according to the present invention, an imaging region composed of a plurality of imaging pixels and an element isolation region provided around the imaging region are formed on an epitaxial growth substrate, and gettering of heavy metal is performed on the epitaxial growth substrate. A method for manufacturing an imaging device provided with a getter layer for performing a first epitaxial growth step of forming a first epitaxial growth layer in the epitaxial growth substrate, and a second epitaxial growth layer above the first epitaxial growth layer in the epitaxial growth substrate. And a getter layer forming step of forming a getter layer between the first epitaxial growth layer and the second epitaxial growth layer after the first epitaxial growth step and before the second epitaxial growth step. And The serial getter layer is characterized in that so as to form a peripheral area of the imaging region.

In the image sensor according to the present invention as described above,
Since the epitaxial growth substrate has a plurality of epitaxial growth layers and a getter layer between the epitaxial growth layers, the getter layer is arranged at a position near the photosensor portion in the imaging region. Further, since the getter layer is formed in the peripheral region of the imaging region, the getter layer can be provided without affecting the element structure of the imaging region. Therefore, gettering of heavy metals affecting the photosensor portion can be easily performed, and generation of white spots due to heavy metals can be effectively suppressed.

In the above-described method of manufacturing an imaging device according to the present invention, after the first epitaxial growth step and before the second epitaxial growth step, the first epitaxial growth layer and the second epitaxial growth layer are formed by the getter layer forming step. Since the getter layer is formed in the peripheral region of the imaging region in the middle, this getter layer is arranged at a position near the photosensor portion in the imaging region. Further, since the getter layer is formed in the peripheral region of the imaging region, the getter layer can be provided without affecting the element structure of the imaging region. Therefore, gettering of heavy metals affecting the photosensor portion can be easily performed, and generation of white spots due to heavy metals can be effectively suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an image pickup device and a method of manufacturing the same according to the present invention will be described in detail. The image pickup device according to the present embodiment is intended to suppress white spots by forming a getter layer by ion implantation during two-stage epitaxial growth of an image pickup device using an epitaxially grown substrate. Here, a case where the present invention is applied to a CCD image sensor will be described as a specific example. FIG. 1 is a sectional view showing a layer structure of an image sensor according to an embodiment of the present invention, and FIG.
FIG. 2 is a plan view illustrating a shape of an imaging region of the imaging device illustrated in FIG. 1. FIG. 3 is a cross-sectional view showing a manufacturing process when the imaging device shown in FIG. 1 is manufactured.

First, referring to FIG. 1 and FIG.
The structure of the CD solid-state imaging device will be described. As shown in FIG. 2, the CCD solid-state imaging device 100 has a rectangular imaging region 100A, and an element isolation region 100B, which is a non-imaging region, is provided around the imaging region 100A. Also, CC
The outer peripheral edge of the D solid-state imaging device 100 is a substrate dividing portion 100C that divides the plurality of CCD solid-state imaging devices 100 from a common semiconductor substrate. That is, in the CCD solid-state imaging device 100, in the forming process, a large number of imaging devices are formed on a semiconductor wafer which is a common substrate, and a scribe line for dividing the device is provided on the semiconductor wafer. Are manufactured as individual CCD solid-state imaging devices 100 by dividing the CCD. In the imaging region 100A of the CCD solid-state imaging device 100, a light receiving film and a light shielding film for each photo sensor unit, a micro lens, a CCD vertical transfer unit, and the like are arranged. An amplifier, a reset gate, an element protection transistor, and the like are provided.

Next, as shown in FIG. 1, inside the CCD solid-state imaging device 100, a first getter layer 120 is provided on the entire surface of the substrate 110 at a deep portion of the substrate 110, and the first getter layer 120 is provided on the upper layer of the first getter layer 120. First epitaxial growth layer 130
Is provided over the entire surface of the substrate. In addition, this first
A second getter layer 140 is provided in a region above the epitaxial growth layer 130 and extending from the element isolation region 100B to the substrate cutting part 100C. Further, a second epitaxial growth layer 150 is provided above the first epitaxial growth layer 130 and the second getter layer 140.

In such a CCD image pickup device 100, the second getter layer 140 is provided between the first and second epitaxial growth layers 130 and 150 in the epitaxial growth substrate 110.
Therefore, the second getter layer 140 is disposed at a position near the photosensor portion in the imaging region. Further, since the second getter layer 140 is formed in the peripheral region of the imaging region 100A, that is, from the element isolation region 100B to the substrate dividing portion 100C, the second getter layer 140 is not affected and the second getter layer 140 is not affected. A layer 140 can be provided. Therefore, gettering of heavy metals affecting the photosensor portion can be easily performed, and generation of white spots due to heavy metals can be effectively suppressed. Note that the gettering operation of the first getter layer 120 is the same as that of the related art.

The substrate 11 having such a layer structure
In the first and second epitaxial growth layers 130 and 150, a photo sensor unit and a CCD transfer unit (both not shown) constituting an image sensor are formed. Also, the substrate 11
An upper film formation layer 160 on which a wiring electrode, a light-shielding film, a microlens, and the like are further disposed is provided on the surface of No. 0.

Next, a method of manufacturing the CCD solid-state imaging device 100 according to the present embodiment will be described with reference to FIG. In addition,
FIG. 3 shows one image sensor independently, but each step shown in FIG. 3 is performed for a plurality of image sensors before division provided on the semiconductor wafer as described above. First, in FIG. 3A, ions are implanted into the silicon substrate 110 before the epitaxial growth, and the first getter layer 1 is formed.
20 is formed. In this ion implantation step, for example, carbon (C), nitrogen (N), phosphorus (P), or the like is used as the getter element. Thus, the first getter layer 120 is formed over the entire surface of the semiconductor wafer.

Next, in FIG. 3B, a first epitaxial growth layer 130 is formed by a first epitaxial growth step. Thereby, the first epitaxial growth layer 130 is formed over the entire surface of the semiconductor wafer. Next, in FIG. 3C, the first epitaxial growth layer 130 is formed.
From the upper element isolation region 100B to the substrate dividing portion 100C.
Is ion-implanted into the region over the second getter layer 140.
To form In this ion implantation step, for example, carbon (C), nitrogen (N), phosphorus (P), or the like is used as the getter element. Thereby, the imaging area 1
A second getter layer 140 is formed in the peripheral region of 00A.

Next, in FIG. 3D, a second epitaxial growth layer 150 is formed by a second epitaxial growth step. Thereby, the second epitaxial growth layer 150 is formed over the entire surface of the semiconductor wafer. Thereafter, a step of forming a photosensor portion or the like of an image sensor on each of the epitaxial growth layers 130 and 150 is performed.
Through the step of forming the upper film formation layer 160 on the substrate 100, the imaging device 100 shown in FIG. 1 can be obtained.
In the above example, the second getter layer 140 is provided in the region extending from the element isolation region 100B to the substrate dividing portion 100C. However, the second getter layer 140 may be provided only in the element isolating region 100B or only in the substrate dividing portion 100C. Good.

[0018]

As described above, the imaging device of the present invention has a plurality of epitaxial growth layers in an epitaxial growth substrate and a getter layer between the epitaxial growth layers. The getter layer can be provided at a position close to the photosensor portion and without affecting the element structure of the imaging region. Therefore, gettering of heavy metals affecting the photosensor portion can be easily performed, and there is an effect that generation of white spots due to heavy metals can be effectively suppressed.

Further, in the method of manufacturing an image pickup device according to the present invention, after the first epitaxial growth step and before the second epitaxial growth step, the imaging region is formed between the first epitaxial growth layer and the second epitaxial growth layer by the getter layer forming step. Since the getter layer is formed in the peripheral area of the imaging area, the getter layer is arranged at a position near the photosensor portion of the imaging area, and the getter layer can be provided without affecting the element structure of the imaging area. it can. Therefore, gettering of heavy metals affecting the photosensor portion can be easily performed, and there is an effect that generation of white spots due to heavy metals can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a layer structure of an image sensor according to an embodiment of the present invention.

FIG. 2 is a plan view showing a shape of an imaging area of the imaging device shown in FIG.

FIG. 3 is a cross-sectional view illustrating a manufacturing process when the imaging device illustrated in FIG. 1 is manufactured.

FIG. 4 is a cross-sectional view illustrating a layer structure of a conventional image sensor.

[Explanation of symbols]

100: CCD imaging device, 100A: imaging area, 1
00B: element isolation region, 100C: substrate cutting part, 1
10 substrate, 120 first getter layer, 130 first epitaxial growth layer, 140 second getter layer, 1
50: second epitaxial growth layer, 160: upper film formation layer.

Claims (12)

[Claims] 1. An imaging region comprising a plurality of imaging pixels and an element isolation region provided around the imaging region are formed on an epitaxial growth substrate, and gettering of a heavy metal is performed on the epitaxial growth substrate. An image pickup device provided with a getter layer, comprising: a plurality of epitaxial growth layers in the epitaxial growth substrate; and a getter layer between the plurality of epitaxial growth layers; wherein the getter layer is formed in a peripheral region of the imaging region. An imaging device, characterized in that: 2. The device according to claim 1, wherein the getter layer is formed in an element isolation region around the imaging region.
An imaging device according to any one of the preceding claims. 3. The imaging device according to claim 1, wherein the getter layer is formed in a substrate dividing portion around the imaging region. 4. The imaging device according to claim 1, wherein the getter layer is formed from a device isolation region around the imaging region to a substrate dividing portion. 5. An epitaxial growth substrate for forming an imaging region composed of a plurality of imaging pixels and an element isolation region provided around the imaging region, and performing heavy metal gettering on the epitaxial growth substrate. In the method for manufacturing an imaging device provided with a getter layer, a first epitaxial growth step of forming a first epitaxial growth layer in the epitaxial growth substrate; and forming a second epitaxial growth layer above the first epitaxial growth layer in the epitaxial growth substrate. A second epitaxial growth step; and a getter layer forming step of forming a getter layer between the first epitaxial growth layer and the second epitaxial growth layer after the first epitaxial growth step and before the second epitaxial growth step. And the getter Manufacturing method of an image pickup element characterized by the, possible to form the peripheral region of the imaging region. 6. The device according to claim 5, wherein the getter layer is formed in an element isolation region around the imaging region.
A manufacturing method of the imaging device according to the above. 7. The method according to claim 7, further comprising the step of separating each of the imaging elements by forming the plurality of imaging elements on a common substrate and then dividing the common substrate, wherein the getter layer divides the substrate around the imaging area. The method for manufacturing an image sensor according to claim 5, wherein the method is formed in a portion. 8. After forming a plurality of image sensors on a common substrate, the method further includes a step of separating the image sensors by dividing the common substrate, wherein the getter layer is used to separate elements around the image pickup area. 6. The method according to claim 5, wherein the substrate is formed from the region to the substrate dividing portion. 9. The method according to claim 5, wherein the getter layer is formed by ion implantation of a getter element. 10. The method according to claim 8, wherein the getter element is carbon. 11. The method according to claim 8, wherein the getter element is nitrogen. 12. The method according to claim 8, wherein the getter element is phosphorus.