JPH098262A - Image pickup device and its manufacture - Google Patents

Abstract

PURPOSE: To provide an image pickup device whose smear characteristic is further improved without lowering the sensitivity and a method for manufacturing the device. CONSTITUTION: An image pickup device 20 is provided with a light receiving section 3, a channel stopper 21 provided on one side of the section 3, a charge transfer section 6 provided on the outside of the channel stopper 21 and a read- out section 5, transfer electrodes 22a and 22b provided nearly immediately above the transfer section 6, low-reflection film 23 which is formed in such a state that the film 23 can cover the electrode 22a and 22b and at least part of the film 23 is opened immediately above the light receiving section 3, and a light shielding film 24 formed on the film 23. The channel stopper 21 side edge of the transfer electrode 22a on the channel stopper 21 side is positioned immediately above the channel stopper 21. A method for manufacturing this image pickup device is also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device having a light receiving portion for photoelectric conversion, and more particularly to an image pickup device having improved smear characteristics and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, CCD (Charge-Coupled Device)
As a type) image pickup device, for example, one having a structure shown in FIG. 5 is known. In FIG. 5, reference numeral 1 is an image pickup device. The image pickup device 1 has an overflow barrier (not shown) formed on a surface layer of a silicon substrate 2, a light receiving unit 3 formed on the overflow barrier, and the light receiving unit 3 further. The hole accumulating portion 4 is formed on the above. A charge transfer section 6 is arranged on one side of the light receiving section 3 via a reading section 5. A channel stop 7 is arranged on the other side of the light receiving section 3, another charge transfer section 6 is arranged on the side of the channel stop, and further on the side of the charge transfer section 6. A reading section (not shown) and a light receiving section (not shown) are sequentially arranged.

An insulating film 8 is formed on the surface of the silicon substrate 2, and a transfer electrode 9 is formed on the insulating film 8 so as to cover a position directly above the charge transfer portion 6. Here, the edge of the transfer electrode 9 on the channel stop 7 side of the transfer electrodes 9 on the channel stop 7 side is formed to extend beyond the position directly above the channel stop 7 to the position directly above the light receiving unit 3. It has been arranged. An insulating film 10 is formed on the insulating film 8 so as to cover the transfer electrodes 9. A low reflection film 11 is formed on the insulating film 10 so as to cover the transfer electrode 9 and open a part of a position directly above the light receiving portion 3, and the low reflection film 11 is covered with the low reflection film 11. The light shielding film 12 is formed. Further, a transparent layer (not shown) is formed on the silicon substrate 2 so as to cover the light shielding film 12 and the like.

[0004] With such a configuration, the image pickup device 1
Receives the incident light that has passed through the transparent layer in the light receiving unit 3 and performs photoelectric conversion to generate electric charges. Then, the obtained charges are sent to the charge transfer unit 6 via the readout unit 5, further moved in the charge transfer unit 6 by driving the transfer electrode 9, and output as a signal via the horizontal transfer unit (not shown). . Further, due to the aperture value of the lens of the optical camera in which the image pickup device 1 is mounted, light is obliquely incident on the image pickup device 1, and this incident light is shielded from the surface of the silicon substrate 2 as indicated by an arrow A in FIG. If the incident light enters between the film 12 and the low-reflection film 1 formed below the surface of the silicon substrate 2 and the light-shielding film 12.
The incident light is reflected several times between the portion 1 and the portion (protruding portion 11a) protruding outside the transfer electrode 9, and the incident light is attenuated particularly when reflected by the low reflection film 11. Therefore, the image sensor 1 has a structure for attenuating such obliquely incident light, so that the obliquely incident light can be prevented from being emitted by the channel stop 7.
May reach the charge transfer unit 6 or the vicinity thereof, and a part of the charges generated by photoelectric conversion here may be taken into the charge transfer unit 6 and become smear signal charges to deteriorate the smear characteristic. It is prevented.

In order to manufacture the image pickup device 1 having such a structure, first, as shown in FIG. 6, a p-type impurity is implanted into a predetermined position of the surface layer portion of the silicon substrate 2 to read out the read portion 5 and the channel stop 7. Are formed at predetermined intervals, and separately from this, an n-type impurity is implanted into the outside of each of the channel stop 7 and the reading section 5 to form the charge transfer section 6.

Next, an insulating film 8 is formed on the surface of the silicon substrate 2 by a thermal oxidation method, and then a polysilicon film (not shown) is formed on the insulating film 8. Then, this polysilicon film is patterned by a known lithography technique and etching technique to form a transfer electrode 9 made of polysilicon at a position substantially directly above the charge transfer portion 6 as shown in FIG. At this time, regarding the patterning of the transfer electrode 9, the end of the transfer electrode 9 located on the side of the channel stop 7 on the side of the channel stop 7 is located near the end of the channel stop 7 on the side of the readout section 5 as shown in FIG. It is formed by extending it to the position directly above.

Then, by self-alignment using the formed transfer electrode 9 as a mask, an n-type impurity is implanted at a relatively deep position in the surface layer portion of the silicon substrate 2 to form the read portion 5 and the channel stop 7 as shown in FIG. The light receiving portion 3 is formed between them. Further, similarly, using the transfer electrode 9 as a mask, a p-type impurity is implanted at a relatively shallow position in the surface layer portion of the silicon substrate 2 to form the hole accumulating portion 4 immediately above the light receiving portion 3.
Subsequently, an insulating film 10 is formed on the insulating film 8 by a CVD method or the like so as to cover the formed transfer electrode 9.

Next, the insulating film 1 is formed so as to cover the transfer electrode 9.
0, a low reflection layer (not shown) and a light shielding layer (not shown) are sequentially formed, and a resist layer (not shown) is further formed on each of these layers, and the resist layer is patterned by a known lithography technique or etching technique. Forming a resist pattern (not shown). Then, the low reflection layer and the light shielding layer were simultaneously etched by using the obtained resist pattern as a mask to cover the transfer electrode 9 and to open a part of the position directly above the light receiving portion 3 as shown in FIG. Low reflective film 1
First, the light shielding film 12 is formed. After that, a transparent layer made of a silicon nitride layer or the like is formed on the silicon substrate 2 so as to cover the light shielding film 12, and the image pickup device 1 shown in FIG. 5 is obtained.

[0009]

However, the image pickup device 1 having the above structure has the following disadvantages. In this image pickup device 1, as described above, light obliquely enters the light receiving unit 3, and smear characteristics are deteriorated due to the incident light. Particularly, the low reflection film 11 is located outside the transfer electrode 9. It is prevented by the overhanging part. Therefore, the light receiving unit 3
As the length of the low-reflection film 11 protruding upward is longer, the number of reflections of the obliquely incident light on the low-reflection film 11 is increased, so that the intensity is more attenuated and the smear characteristic is further improved. You will be able to do that. However, if the protruding portion 11a of the low-reflection film 11 is simply lengthened, the protruding portion of the light-shielding film 12 thereon is naturally lengthened, and the effective aperture area of the light-receiving portion 3 is reduced, which lowers the sensitivity. I will leave.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image pickup device in which the smear characteristic is further improved without lowering the sensitivity, and a manufacturing method thereof.

[0011]

According to the image pickup device of the present invention,
A light receiving section provided on the surface layer of the base body for performing photoelectric conversion, a channel stop provided on one side of the light receiving section, a reading section provided on the other side of the light receiving section, the channel stop, and A charge transfer section respectively provided on the side of the reading section opposite to the light receiving section, and on the base,
A transfer electrode provided substantially directly above the charge transfer portion,
A low reflection film is provided on the transfer electrode so as to cover the transfer electrode, and at least a part of the position directly above the light receiving portion is opened, and a light shielding film provided on the low reflection film. In the imaging device, the transfer electrode located on the channel stop side of the transfer electrodes has a channel stop side end edge located immediately above the channel stop, which is a means for solving the problems. .

In the method of manufacturing an image pickup device according to the present invention, impurities are injected into the surface layer portion of the substrate to form a channel stop and a reading section at predetermined intervals, and the channel stop and the reading section are formed outside the channel stop and the reading section, respectively. Forming a charge transfer part, and forming a transfer electrode on the substrate at a position substantially directly above the charge transfer part, and forming a channel stop of the transfer electrode located on the channel stop side of the transfer electrode. A side edge extending to a position directly above the channel stop, and a state of covering at least a part of the transfer electrode on the substrate and not covering the space between the channel stop and the reading section. A step of forming a resist pattern, and using the resist pattern and the transfer electrode as a mask, impurities are implanted into the surface layer of the base to form the base. Forming a light receiving portion in the layer unit,
A step of forming an insulating film on the base to cover the transfer electrode, and a low reflection film and a light shielding film on the insulating film in a state of covering the transfer electrode and opening a part of a position directly above the light receiving portion. And a step of forming the resist pattern in the step of forming the resist pattern, wherein the step of forming the resist pattern is performed by extending the transfer electrode located on the channel stop side of the transfer electrodes outside the edge on the channel stop side of the transfer electrode. Forming a resist pattern so as to directly cover the upper part was a means for solving the above problems.

[0013]

According to the image pickup device of the present invention, the edge of the transfer electrode located on the channel stop side on the channel stop side has been extended to just above the light receiving portion in the past, but to just above the channel stop. Since it is set back, it is possible to widen the distance between the transfer electrodes that are arranged with the light receiving portion interposed therebetween. Therefore, without reducing the effective opening area of the light receiving portion, the transfer electrode of the low reflection film can be removed. It is possible to lengthen the portion protruding to the light receiving portion side.

According to the method of manufacturing an image pickup device of the present invention, the transfer electrode is used as it is as a mask to implant impurities to form a light receiving portion, and the resist pattern is used as a mask on the channel stop side of the light receiving portion. Thus, the position of the edge of the light receiving portion is determined. Therefore, since the position of the edge on the channel stop side does not contribute to the formation arrangement of the light receiving portion, the edge of the transfer electrode on the channel stop side may be formed so as to recede to the charge transfer portion side. it can. Therefore, in the image pickup device thus obtained, the end edge of the transfer electrode located on the channel stop side on the channel stop side is set back to just above the channel stop.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 1 is a diagram showing an embodiment of an image pickup device of the present invention. In FIG. 1, reference numeral 20 is an image pickup device. In addition, in the image sensor 1 shown in FIG. 1, the image sensor 1 shown in FIG.
Constituent elements that are the same as the above are given the same reference numerals and description thereof is omitted. The image pickup device 20 shown in FIG. 1 is different from the image pickup device 1 shown in FIG. 5 mainly in the position of the transfer electrode 22a on the channel stop 21 side and the transfer electrode 22a.
It is the length of the projecting portion 23a of the low reflection film 23 and the light shielding film 24 formed on 22b.

That is, in the image pickup device 20 of this embodiment,
An end edge of the transfer electrode on the side of the channel stop 21 on the side of the channel stop 21 is located immediately above the channel stop 21. On the other hand, the width of the light receiving unit 3 (width between the reading unit 5 and the channel stop 21) is formed to be the same as that of the image pickup device 1 shown in FIG. 5, and therefore, in the image pickup device 21 of the present embodiment. The distance between the transfer electrodes 22a and 22b arranged with the light receiving portion 3 interposed therebetween is wider than that of the conventional image sensor 1 shown in FIG.

Further, the low reflection film 23 and the light shielding film 24 formed on the transfer electrodes 22a and 22b with the insulating film 10 interposed therebetween.
Is a projecting portion 23 formed by projecting to the light receiving portion 3 side.
The lengths of a and 24a are longer than that of the image sensor 1 of FIG. That is, as described above, in the image pickup device 20, since the distance between the transfer electrodes 22a and 22b is wide, if the effective aperture area of the light receiving portion 3 is made the same as that of the image pickup device 1, the projecting portions 23a and 24a are inevitably formed. The overhang length of the is increased. Here, the low reflection film 23 is made of TiO 2.
The light shielding film 24 is formed of a material having a low reflectance such as N or WSi, and the light shielding film 24 is formed of a material such as Al.

Next, an embodiment of the manufacturing method of the present invention will be described based on the manufacturing method of the image pickup device 20. First, in the same manner as in the prior art, as shown in FIG. 2, p-type impurities are implanted at predetermined positions on the surface layer portion of the silicon substrate (base) 2 to form the read-out portion 5 and the channel stop 7 at predetermined intervals. Separately from this, an n-type impurity is injected into the outside of each of the channel stop 7 and the read section 5 to form the charge transfer section 6.

Next, an insulating film 8 is formed on the surface of the silicon substrate 2 by a thermal oxidation method, and then a polysilicon film (not shown) is formed on the insulating film 8. Then, this polysilicon film is patterned by a well-known lithography technique and etching technique to form transfer electrodes 22a and 22b made of polysilicon at positions substantially directly above the charge transfer portion 6 as shown in FIG. At this time, the patterning of the transfer electrode 22a on the channel stop 21 side is different from that of the example shown in FIG.
As shown in FIG. 2, the edge on the 1 side is connected to the channel stop 2
It is formed so as to extend to a position directly above the position of 1 on the side of the charge transfer portion 6 from the central portion. That is, in this embodiment, as compared with the conventional example shown in FIG. 6, the edge position of the transfer electrode 22a is formed so as to recede toward the charge transfer portion 6 side.

Next, a resist layer (not shown) is formed on the silicon substrate 2 so as to cover the transfer electrodes 22a and 22b, and this is patterned by a known lithography technique and etching technique to form resist patterns 25a and 25b. With respect to these resist patterns 25a and 25b, almost the entire surfaces of the transfer electrodes 22a and 22b are covered, and the channel stop 21 and the reading section 5 formed previously are formed.
It is formed so that the space between and is not covered. In particular, on the transfer electrode 22a side, the end edge of the resist pattern 25a is formed to extend beyond the end edge of the transfer electrode 22a on the channel stop 21 side, so that the transfer electrode 22a at a position directly above the channel stop 21 is covered. Almost the entire surface of the non-existing portion is directly covered with the resist pattern 25a through the insulating film 8. That is, the position of the edge of the resist pattern 25a is made to substantially coincide with the position of the edge of the transfer electrode 9 on the channel stop 7 side of the conventional image sensor 1 shown in FIG. On the transfer electrode 22b side, the end surface of the registration pattern 25b on the read-out portion 5 side is set to the transfer electrode 22b.
It is not necessary to form the resist pattern 25b so as to extend from the end surface of b, and therefore, it is not necessary to form the resist pattern 25b on the reading section 5 side so as to cover the entire upper surface of the transfer electrode 22b.

Next, the formed resist pattern 25
a and 25b and the transfer electrodes 22a and 22b are used as masks to implant an n-type impurity into a relatively deep position of the surface layer of the silicon substrate 2, and as shown in FIG. The light receiving part 3 is formed. Here, the implantation concentration of the n-type impurity for forming the light receiving portion 3 is set sufficiently higher than the implantation concentration of the p-type impurity when the channel stop 21 was first formed. Then, the channel stop 21 is formed by such n-type impurity implantation.
2 retreats the edge position of the channel stop 21 in the state shown in FIG. 2 toward the charge transfer section 6 side as shown in FIG.

Subsequently, resist patterns 25a and 25b
Are removed by an appropriate method, and in that state, the transfer electrode 22
Using the masks a and 22b as masks, p-type impurities are implanted at a relatively shallow position of the surface layer of the silicon substrate 2 to form the hole accumulating portion 26 from directly above the light receiving portion 3 to the channel stop 21 side as shown in FIG. Further, the insulating film 10 is formed on the insulating film 8 by the CVD method or the like so as to cover the formed transfer electrodes 22a and 22b.

Next, a low reflection layer (not shown) made of a low reflectance material and a light shielding layer (not shown) made of Al or the like are sequentially formed on the insulating film 10 so as to cover the transfer electrodes 22a and 22b. A resist layer (not shown) is formed on each layer and patterned by a known lithography technique or etching technique to form a resist pattern (not shown).
To form Then, the low reflection layer and the light shielding layer are simultaneously etched using the obtained resist pattern as a mask,
As shown in FIG. 1, covering the transfer electrodes 22a and 22b,
Further, the low reflection film 23 and the light shielding film 24 are formed in a state where a part of the position directly above the light receiving portion 3 is opened.

Here, when patterning the low reflection layer and the light shielding layer by etching, the resist pattern used as a mask is the same as the resist pattern used for patterning the low reflection layer and the light shielding layer in the conventional manufacturing of the image pickup device 1. A shape is formed. That is, etching is performed without changing the shape and size of the opening surface that opens on the light receiving portion 3 as compared with the image pickup device 1 shown in FIG. Then, since the space between the transfer electrodes 22a and 22b is wider than the space between the transfer electrodes 9 and 9 in the image pickup device 1 shown in FIG. 5, the overhang portions 23a and 24a formed on the low reflection film 23 and the light shielding film 24 are formed as shown in FIG. It is longer than each of the projecting portions in the image pickup device 1 shown in FIG. After that, the light shielding film 2
4, a transparent layer made of a silicon nitride layer or the like is formed on the silicon substrate 2 to obtain the image pickup device 20 shown in FIG.

In the image pickup device 20 thus obtained, the low reflection film 23 is projected from the transfer electrode 22a to the light receiving part 3 side without reducing the effective opening area of the light receiving part 3. Since the overhanging portion 23a is longer than the overhanging portion 11a of the conventional image pickup device 1, light is obliquely incident on the image pickup device 20, and this incident light is reflected by the silicon substrate 2 as indicated by an arrow B in FIG. When entering between the surface and the light shielding film 24, the obliquely incident light is reflected and attenuated several times between the surface of the silicon substrate 2 and the protruding portion 23a of the low reflection film 23. Therefore, in the image pickup device 20 of the present embodiment, as described above, the projecting portion 2 of the low reflection film 23 is formed.
The length of 3a is the protruding portion 11 of the image pickup device 1 shown in FIG.
Since the oblique incident light is formed longer than the length a, the number of times the obliquely incident light is reflected by the projecting portion 23a of the low reflection film 23 increases, and the degree of the attenuation increases. Therefore, in this image pickup device 20, the smear characteristic is further improved as compared with the image pickup device 1 shown in FIG.

Further, in the method of manufacturing the image pickup device 20 as described above, the light receiving portion 3 is not formed by implanting impurities by using the transfer electrodes 22a and 22b as they are as masks.
On the channel stop 21 side of the light receiving portion 3, the position of the edge of the light receiving portion 3 is determined by using the resist pattern 25a as a mask. Therefore, the transfer electrode 22a on the channel stop 21 side of the channel stop 21 side is determined. Can be formed by retreating the edge thereof to just above the channel stop 21, so that the image pickup device 1 can be easily formed.

[0027]

As described above, according to the image pickup device of the present invention, the channel stop side edge of the transfer electrode located on the channel stop side is extended to just above the light receiving portion in the related art. Since it is set back to the position just above, the distance between the transfer electrodes arranged across the light receiving part becomes wider, and the effective opening area of the light receiving part does not decrease, and The portion protruding from the electrode toward the light receiving portion becomes long. Therefore, for example, when light is obliquely incident between the substrate surface and the projecting portion, this obliquely incident light can be largely attenuated at the projecting portion of the low reflection film, whereby the smear characteristic is greatly improved. It becomes a thing.

In the method for manufacturing an image pickup device of the present invention, the transfer electrode is used as it is as a mask to implant impurities to form a light receiving portion, and the resist pattern is used as a mask on the channel stop side of the light receiving portion. This is a method of determining the position of the edge of the light receiving portion. Therefore, since the position of the edge on the channel stop side does not contribute to the formation and arrangement of the light receiving portion, the transfer electrode on the channel stop side may be formed by retracting the edge toward the charge transfer portion side. it can. Therefore, according to this manufacturing method,
The image pickup device can be easily formed.

[Brief description of drawings]

FIG. 1 is a side sectional view of an essential part showing a schematic configuration of an embodiment of an image pickup device of the present invention.

FIG. 2 is a side sectional view of a main part for explaining a method for manufacturing the image sensor shown in FIG.

FIG. 3 is a diagram for explaining the manufacturing method for the image sensor shown in FIG. 1, and a cross-sectional side view of essential parts for explaining a step that follows the step shown in FIG. 2.

FIG. 4 is a diagram for explaining the manufacturing method for the image sensor shown in FIG. 1, and a cross-sectional side view of a main portion for explaining a step that follows the step shown in FIG.

FIG. 5 is a side sectional view of an essential part showing an example of a conventional image sensor.

FIG. 6 is a side sectional view of a main part for explaining a method for manufacturing the image pickup device shown in FIG.

FIG. 7 is a diagram for explaining the manufacturing method for the image sensor shown in FIG. 5, and a cross-sectional view of a main part for explaining a step that follows the step shown in FIG. 6.

[Explanation of symbols]

 2 Silicon substrate (base) 3 Light receiving part 5 Readout part 6 Charge transfer part 10 Insulating film 20 Image sensor 21 Channel stop 22a, 22b Transfer electrode 23 Low reflection film 23a Overhanging part 24 Light-shielding film

Claims (2)

[Claims] 1. A light receiving section provided on the surface layer of the base body for performing photoelectric conversion, a channel stop provided on one side of the light receiving section, and a reading section provided on the other side of the light receiving section. A charge transfer section provided on each side of the channel stop and readout section opposite to the light receiving section, a transfer electrode provided on the base substantially directly above the charge transfer section, and the transfer electrode An image pickup device comprising: a low-reflection film provided on the upper surface of the low-reflection film, and a light-shielding film provided on the low-reflection film. 2. The image pickup device according to claim 1, wherein the end of the transfer electrode on the channel stop side of the transfer electrodes on the channel stop side is located directly above the channel stop. 2. A step of injecting an impurity into a surface layer portion of a substrate to form a channel stop and a reading section at predetermined intervals, and forming a charge transfer section outside each of the channel stop and the reading section. A transfer electrode is formed on the substrate at a position substantially directly above the charge transfer portion, and a channel stop side edge of a transfer electrode of the transfer electrodes located on the channel stop side is formed on the channel. Forming a resist pattern in a state of extending to a position directly above a stop, covering at least a part of the transfer electrode on the base, and not covering the channel stop and the reading section; A step of injecting an impurity into the surface layer portion of the substrate by using the resist pattern and the transfer electrode as a mask to form a light receiving portion in the surface layer portion of the substrate; A step of forming an insulating film on the base so as to cover the transfer electrode, and a low reflection film and a light-shielding film on the insulating film with the transfer electrode being covered and a part of a position directly above the light receiving portion being opened. And a step of forming the resist pattern in the step of forming the resist pattern, wherein the step of forming the resist pattern is performed by extending the transfer electrode located on the channel stop side of the transfer electrodes to the outside of the end of the transfer electrode on the channel stop side. A method of manufacturing an image sensor, comprising forming a resist pattern so as to directly cover the surface of the image sensor.