JPH03119758A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce a smear by a method wherein a photodetecting region and a charge transfer region which are composed of a single-crystal semiconductor layer are structured so as to be surrounded by an insulating film. CONSTITUTION:A photodetecting region 3 whose depth is d1 and which is composed of single-crystal Si is formed in an Si oxide film 2 on an Si substrate 1. A p-type impurity region 5 and an n-type impurity region 6 from the bottom part are formed in the region 3. On the other hand, a charge transfer region 4 which is united to the region 3, whose depth is d2 and which is composed of single-crystal Si is formed on the surface of the film 2. A register part 7 composed of an n-type impurity region and a readout part 8 composed of a p-type impurity region are formed in the region 4. A signal charge generated in the photodetecting region 3 is read out by the register 7 via the readout part 8 and is transferred. An oxide film 9 is formed on the whole surface; a transfer electrode 10 composed of an Si layer is formed on it; an oxide film 11 as an interlayer insulating film wrapping the electrode 10 is formed. A light- shielding film 12 which is opened on the region 3 is formed. Thereby, even when light is incident from an oblique direction, almost all of the light reaches the substrate 1; it is possible to restrain electrons causing an erroneous signal from being generated and to reduce a smear.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides 5ol (silicon-on-insulator)
The present invention relates to a solid-state imaging device and a method for manufacturing the same, in which smear is reduced by employing the above technology.

[Summary of the invention]

The present invention provides a solid-state imaging device in which a light-receiving region separated for each cell and a charge transfer region extending along the light-receiving region are formed in a single crystal semiconductor layer at different depths on the surface of an insulating substrate, and a solid-state imaging device thereof. In the manufacturing method, the light receiving region is formed in a single crystal semiconductor layer of a first depth, the charge transfer region is formed in a single crystal semiconductor layer of a second depth that is integrated with the light receiving region, and By forming a transfer electrode on the charge transfer region via an insulating film and forming a light shielding film except on the light receiving region, smear can be reduced.

[Conventional technology]

Interline transfer type CCDs are widely known as solid-state imaging devices for color images. In this interline transfer type CCD, the light receiving section is usually a photodiode, and incident light is converted by the photodiode into an electric charge proportional to the intensity of the light. A vertical resistor is then arranged along the photodiode. The charge temporarily accumulated in the photodiode is read out and transferred to the vertical register via the readout section.

In such an interline type COD imager, in the conventional technology, as shown in FIG. 3, a readout section 103. A vertical register 104 and a channel stopper section 105 are respectively formed. The readout section 103 and the channel stopper section 105 are p-type impurity regions, and the vertical register 104 is an n-type impurity region fiJ.
It is considered to be in the r region. Then, an oxide film 106 is formed on the entire surface of the well region 102, and the readout portion 103. A polysilicon layer 107 functioning as a transfer electrode of a charge transfer section is formed on the oxide film 106 above the vertical register 104 and the channel stopper section 105. polysilicon layer 10
On the surface of the well region 102 in the opening surrounded by
A type impurity region is formed to form a photodiode 108.

Also, in a pattern opening above the photodiode 108, oxide II! Light-shielding F! via 109! 110 is formed.

[Problem to be solved by the invention]

However, the light incident from the open pattern of the light shielding film 110 is not limited to the light incident perpendicularly to the main surface of the semiconductor substrate 101;
Some light passes through the polysilicon layer 107 and the oxide film 106 without reaching the vertical resistor 104 and enters the vertical register 104 obliquely. This causes an erroneous signal to occur inside the vertical register 104, and reduction of such smear components is required in order to improve the performance of solid-state imaging devices.

Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and an object of the present invention is to provide a solid-state imaging device that can prevent smearing.

[Means to solve the problem]

In order to achieve the above object, the solid-state imaging device of the present invention includes a light-receiving region formed of a single crystal semiconductor region separated for each cell and having a first depth shallower than the first depth on an insulating substrate. a charge transfer region formed of a single crystal semiconductor region having a second depth on the surface of the insulating substrate and integral with the light receiving region; and a transfer electrode formed on the charge transfer region via an insulating film. and a light-shielding film having an opening above the light-receiving region.

Further, the present invention etches the surface of a single-crystal semiconductor substrate to form island-like regions separated into planar cells for each cell and having a first height, and adjacent to the island-like regions and between the island-like regions. forming a band-like region having a second height and a groove adjacent to the band-like region along the direction in which the band-like region extends; and forming an insulating layer on the entire surface of the single crystal semiconductor substrate. , a step of shaving the single crystal semiconductor substrate from the back surface to at least the bottom of the groove, a step of forming a transfer electrode on the band-like region via an insulating film, and a step of forming a light-shielding film except on the island-like region. It is characterized by having the step of forming.

Note that before the step of cutting the single crystal semiconductor substrate from the back surface to at least the bottom of the groove, the substrates may be bonded together.

[Effect]

Since the light-receiving region is a single crystal semiconductor layer surrounded by an insulating base and separated from each other for each cell, even if light is incident obliquely, most of it reaches the insulating base. Therefore,
Since the generation of electrons that cause erroneous signals is suppressed, smear is reduced.

The charge transfer region is formed in a semiconductor layer shallower than the depth of the single crystal semiconductor layer on the surface of the insulating substrate, so that even when light is incident from an oblique direction, most of it enters the insulating film below the charge transfer region. Therefore, smear can be reduced.

Further, in the method for manufacturing a solid-state imaging device of the present invention, the surface of the single crystal semiconductor substrate is processed in advance into an island-like region having a first height and a band-like region having a second height. Here, the island-like region is used as a light-receiving region, and the strip-like region is used as a charge transfer region. Next, an insulating film is formed over the entire surface of the single crystal semiconductor substrate whose surface has been processed in this manner. This insulating film makes it possible to separate each cell and to bond substrates together.

Then, in the step of cutting from the back surface to the groove portion, the cells are separated by the insulating film.

〔Example〕

Preferred embodiments of the present invention will be described with reference to the drawings.

In this embodiment, a light receiving region is formed in a single crystal silicon layer separated for each cell of a silicon oxide film, and a charge is formed in a single crystal silicon layer integral with the single crystal silicon layer and having different depths. This is an example of a solid-state imaging device having a transfer area.

First, the structure of the solid-state imaging device of this embodiment will be explained. 1st
As shown in the figure, a silicon oxide film 2 on a silicon substrate 1
A light-receiving region 3 made of a single-crystal silicon layer and having a depth d separated from each other for each cell is provided. This light receiving area 3
A p-type impurity region 5 and an n-type impurity region 6 are sequentially formed from the bottom. In this n-type impurity region 6, photoelectrically converted signal charges are accumulated. The depth dl of the light receiving region 3 is designed in consideration of the wavelength of the incident light, that is, the depth at which the incident light reaches and generates electrons. Note that in this example, 3
It is preferable to set it to 5 micrometers.

On the other hand, on the surface of the silicon oxide film 2, a charge transfer region 4 is formed which is integrated with the light receiving region 3 and has a depth at. ! The load transfer region 4 is made of a single crystal silicon layer. A register section 7 and a readout section 8 are formed in such a charge transfer region 4. A readout section 8 made of a p-type impurity region is formed adjacent to the light receiving region. A resistor section 7 made of an n-type impurity region is formed on the side opposite to the light-receiving region with respect to the readout section 8 . Therefore, the signal charges generated in the light receiving region 3 are successively outputted and transferred to the register section 7 via the reading section 8. Note that the depth d of the charge transfer region 4
2 is preferably 1000 to 3000 people, and 3
By making the thickness shallower to 000 Å or less, charges generated in a deep part of the substrate will not flow into the charge transfer region 4, and smear can be reduced.

Then, an oxide film 9 is formed by thermal oxidation of the entire surface. A transfer electrode 10 made of a polysilicon layer is formed on the oxide film 9 in an area other than the light receiving area. This transfer electrode 10
By applying a required driving pulse to the transfer electrode 10
The charges read out to the register section 7 below are sequentially transferred.

An oxide film 11 functioning as an interlayer insulating film is formed on the entire surface including the transfer electrode 10. Then, a light shielding film 12 having an opening above the light-receiving kl region 3 is formed on the oxide film 11.

This light shielding film 12 is made of aluminum or the like, and an oxide film 13 is formed on the entire surface including the light shielding film 12.

As described above, in the solid-state imaging device of this embodiment, the light receiving region 3 is formed in the single crystal silicon layer separated from each other for every two cells of the silicon oxide WJ. Therefore, even if light is incident from an oblique direction, most of it will reach the insulating base. Therefore, since the generation of electrons that cause erroneous signals is suppressed, smear is reduced. In addition, the light receiving area 3
By forming the charge transfer region 4 in a single crystal silicon layer shallower than the depth of the charge transfer region 4, even if light is incident from an angle, most of it will enter the insulating film below the charge transfer region, reducing smear. .

Next, a method of manufacturing the solid-state one-image device of this embodiment will be explained.

First, as shown in FIG. 2(a), a silicon oxide film 2a is formed on a single crystal silicon substrate 21, and then a resist film 22 is applied to the entire surface. Then, the resist film 22 in areas corresponding to the patterns of the light receiving areas arranged in a matrix is selectively exposed.

develop. Etching is performed by RIE using this resist film 22 as a mask. As a result, silicon substrate 2
Island-like regions 23 having a height hl and separated from each other for each cell are left on the surface of the substrate 1 .

Then, as shown in FIG. 2(b), a resist film 24 is applied to cover the entire surface while leaving the resist film 22. Then, a resist film 2 is formed using a mask pattern in which grooves 26 for forming element isolation regions are provided.
Selectively expose 4. The pattern of the resist film 24 consists of a portion extending in a strip shape along the island region 23 and a portion covering at least a part of the island region 23, and a portion extending in the vertical direction of the region extending in the strip shape. between at least the island-like regions 23 in the direction of the vertical rows
1 is exposed. Using such a resist film 24, the silicon substrate 21 is etched by RrE method or the like. By this etching, a band-like region 2 adjacent to the island-like region 23 and having a height hz (d2) connecting the island-like regions 23 is formed.
5 will remain. Further, along the band-shaped region 25, a groove portion 26 is provided.
The grooves 26 are also formed between the island-shaped regions 23 in the vertical column direction according to the exposed pattern of the silicon substrate 21.

After ashing the resist films 22 and 24, as shown in FIG. 2(c), a silicon oxide film 2a is formed on the band-shaped region 25 and the groove 26 using CVD or the like to the extent that the surface is approximately flat. let

Subsequently, as shown in FIG. 2(d), a base body B having a silicon oxide film 2b formed on a single-crystal silicon substrate 1;
The base A on which the island-like regions 23 and the like are formed as described above is joined by bringing the surfaces of the silicon oxide JII 2a and 2b into abutment. Then, the etch bank is started from the back side of the silicon substrate 21 of the substrate A, and the etching is finished when the silicon oxide film 2a, that is, the bottom of the groove 26 is first exposed.

As shown in FIG. 2(e), an oxide film 9 functioning as a gate oxide film is formed over the entire surface. Note that the island-like region 23
The single-crystal silicon layer becomes the light-receiving region 3, and the band-shaped region 25
becomes the charge transfer region 4.

Subsequently, a polysilicon layer is formed over the entire surface. Then, as shown in FIG. 2(f), the polysilicon layer is patterned to form a transfer electrode 0 on the charge transfer region 4 and the oxide film 9 on the silicon oxide film 2 parallel thereto. . The transfer electrode 10 has a pattern in which a second polysilicon layer is formed between first polysilicon layers arranged at a predetermined interval in the signal charge readout direction.

The entire surface including the transfer electrode IO is oxidized to form an oxide film 11 functioning as an interlayer insulating film. Further, in the light receiving region 3, an n-type impurity region 6 is formed on the p-type impurity region 5. The photoelectrically converted signal charge is accumulated in the n-type impurity region 6. - On the other hand, the charge transfer region 4 has a register section 7 made of an n-type impurity region.
A readout section 8 is formed which includes a p-type impurity region 9.

The readout section 8 is formed adjacent to the n-type impurity region 6, and the register section 7 is provided in a region between the readout section 8 and the adjacent silicon oxide film 2 along the charge transfer region 4. Therefore, the signal charges accumulated in the n-type impurity region 6 are read out and transferred to the register section 7 via the readout section 8.

Finally, a light shielding film 12 is formed on the area excluding the light receiving area 3 with the oxide film 11 interposed therebetween. An oxide film 13 is formed on the surface of this light shielding film 12.

As described above, in the method for manufacturing the solid-state imaging device of this embodiment, the single-crystal silicon substrate 21 is etched to form the island-like regions 23 and the band-like regions 25.

If the silicon oxide film 2a is formed on the silicon substrate 21 after forming the light-receiving region 3 and the charge transfer region 4 in advance by such etching, it is possible to form the silicon oxide film 2a on the silicon substrate 21, as in the second step (e), without the need for complicated steps. Since a base body having a cross-sectional structure is formed, the manufacturing process can be simplified.

〔Effect of the invention〕

As described above, the solid-state imaging device of the present invention has a structure in which the light receiving region and charge transfer region made of a single crystal semiconductor layer are surrounded by an insulating film. The generation of electrons that cause signals is suppressed, smear is reduced, and the image quality of the solid-state imaging device is improved. Also,
Since the charge transfer region is formed in the single crystal semiconductor layer at a shallower depth than the light receiving region on the surface of the insulating substrate, smearing is prevented.

Further, in the method for manufacturing a solid-state imaging device of the present invention, the surface of the single crystal semiconductor substrate can be etched to form regions to be used as light receiving regions and charge transfer regions in advance in a desired pattern. The imaging device can be manufactured through a simplified process.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an example of a solid-state imaging device to which the present invention is applied, and FIGS. 2(a) to 2(f) are steps for explaining the manufacturing process of the above-mentioned example. FIG. The third section is a cross-sectional view showing the structure of an example of a conventional solid-state imaging device. 21...Silicon substrate...Silicon oxide film...Light receiving region...Charge transfer region 6...Impurity opening...Register section...Readout section 11.13...Oxide film...Transfer electrode... ...Light-shielding film 24...Resist film band-shaped region...Groove portion

Claims (2)

[Claims] (1) A light-receiving region consisting of a single crystal semiconductor region separated for each cell and having a first depth on an insulating base, and a second depth shallower than the first depth on the surface of the insulating base. a charge transfer region made of a single crystal semiconductor region integral with the light receiving region; a transfer electrode formed on the charge transfer region via an insulating film; and a light shielding film having an opening above the light receiving region. A solid-state imaging device characterized by: (2) etching the surface of the single-crystal semiconductor substrate to form an island-like region having a first height and separated into cells on a plane;
forming a strip region adjacent to the island region and having a second height by connecting the island regions, and a groove adjacent to the strip region along the direction in which the strip region extends; , forming an insulating layer on the entire surface of the single crystal semiconductor substrate; shaving the single crystal semiconductor substrate from the back side to at least the bottom of the groove; and forming a transfer electrode on the band-shaped region via an insulating film. A method for manufacturing a solid-state imaging device, comprising the steps of: forming a light-shielding film except on the island-like region.