JP3153925B2 - Solid-state imaging device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device in which a micro-condensing lens is formed on a light-receiving portion composed of, for example, a pn photodiode, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a solid-state image pickup device, for example, a CCD solid-state image pickup device, when the relationship between the signal charge and noise in the CCD and the illuminance on the image surface is viewed, on the low illuminance side, noise due to fluctuation of the signal charge (shot noise) is generated. It is known that the influence of dark noise increases.

The shot noise can be reduced by increasing the aperture ratio of the light receiving portion. However, with the recent trend toward miniaturization, there is a limit to the increase in the aperture ratio. Therefore, a structure in which a micro condenser lens is formed on a light receiving unit has been proposed. In the case of the structure in which the micro condenser lens is formed, the light utilization rate increases, the sensitivity in the light receiving section can be improved, and this is effective in reducing the shot noise (the formation of the micro condenser lens). The method is described in, for example, JP-A-60-53073 and
-10666 publication).

In a conventional CCD solid-state imaging device, as shown in FIG. 6, a transfer electrode 23 made of a polycrystalline silicon layer is selectively formed on a silicon substrate 21 via a gate insulating film 22 made of SiO ₂ or the like. An Al light-shielding film 25 is selectively formed on these transfer electrodes 23 via an interlayer insulating film 24, and a planarizing interlayer film 26 is further laminated on the entire surface including the Al light-shielding film 25. A micro condenser lens 27 is formed on the interlayer film 26. Here, a portion where the transfer electrode 23 is not formed is a light receiving portion 28, the Al light shielding film 25 is removed on the light receiving portion 28, and a micro condenser lens corresponding to the light receiving portion 28. 27 are formed.

[0005]

By the way, the conventional CC
In the D solid-state imaging device, the micro condenser lens 2
As a material of No. 7, a photoresist generally used for semiconductor processing is used. This has an advantage that when a photoresist is used, the micro condenser lens 27 can be easily formed in a small area on the light receiving section 28 by, for example, a reflow process by forming a resist pattern and baking.

However, since the refractive index of the photoresist is not so high as 1.6 to 1.7, the light condensing property is low, and it becomes difficult to secure an effective aperture ratio in finer pixels. It is getting. That is, considering the central portion of the image portion in which a large number of pixels are arranged in a matrix, light Lo incident on the top of the micro condenser lens 27 and the vicinity thereof is collected by the micro condenser lens 27 and received. The light Le that is incident on the portion 28 but is incident near the periphery of the micro condenser lens 27 is blocked by the shoulder portion 25a of the Al light shielding film 25, or is dispersed outside the light receiving portion 28. Problem.

As described above, the conventional micro condenser lens 2
In the case of 7, there is a disadvantage that a light component that does not enter the light receiving unit 28 is generated, and the sensitivity improvement effect, which is an original effect of the micro condenser lens, is impaired. This phenomenon appears particularly in the periphery of the image area where light is obliquely incident,
The peripheral dimming after passing through the lens of the camera becomes very conspicuous, and there is a disadvantage that the size of the CCD solid-state imaging device and the improvement of image quality are limited.

Further, the above-mentioned photoresist generally has a large amount of a material having a relatively high absorption in a visible region close to an ultraviolet region, so that there is a problem that the gradation accuracy of a reproduced image taken is deteriorated, that is, the reproducibility of natural colors is poor. .

In the case of photoresist, reflow processing by baking is indispensable. However, the diameter of the micro condenser lens 27 becomes larger than a design value by the reflow processing, and the density of the micro condenser lens 27 is increased. However, there is a disadvantage that the integration of pixels is limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the light-collecting performance of a condenser lens, to improve the effective aperture ratio, It is another object of the present invention to provide a solid-state imaging device capable of improving the gray scale accuracy of a reproduction screen and promoting high integration of pixels.

Further, the present invention can enhance the light-collecting performance of the condenser lens, improve the effective aperture ratio, and promote the improvement of the gradation accuracy of the reproduction screen and the high integration of pixels. It is an object of the present invention to provide a method of manufacturing a solid-state imaging device that can easily manufacture a solid-state imaging device that can be made to operate.

[0012]

According to the present invention, in a solid-state imaging device in which a condenser lens 8 is formed on a light receiving section 2, the condenser lens 8 is formed of diamond.

Further, according to the present invention, in a method for manufacturing a solid-state imaging device in which a condensing lens 8 is formed on a light receiving portion 2, after forming the light receiving portion 2 on the semiconductor substrate 1, the insulating film 7 is formed on the semiconductor substrate 1. Then, a diamond film 11 is formed, and then an oxide film 12 is formed on the diamond film 11. Thereafter, after forming a resist film 13 on the oxide film 12, the resist film 13 is patterned, and using the resist film 13 as a mask, the oxide film 12 is selectively etched and removed. Leave. Thereafter, using the remaining oxide film 12 as a mask, the diamond film 11 is selectively removed by etching to form the diamond film 11 into a lens shape.

[0014]

According to the structure of the present invention described above, the condensing lens 8 is formed of diamond having a high refractive index of 2.4, so that the condensing rate of the condensing lens 8 is increased, The light Le that has entered near the periphery of the lens 8 can be focused on the light receiving unit 2 side. As a result, the effective aperture ratio of the light receiving unit 2 is improved, and the miniaturization of the pixel area can be promoted, and the deterioration of image quality (peripheral dimming) in the peripheral part of the image part can be suppressed.

Also, unlike conventional photoresists, diamond has no absorption in the visible region, so that the incident light L
Can be efficiently condensed on the light receiving unit 2, and the gradation accuracy of the reproduced image captured and the reproducibility of natural colors can be improved.

Since the reflow process by baking is not required, the diameter of the condenser lens 8 can be reduced according to the design value. As a result, the arrangement pitch and the aperture width of the light receiving sections 2 can be reduced, leading to high integration of the solid-state imaging device.

Further, according to the manufacturing method of the present invention, the condenser lens 8 can be easily formed of diamond. That is, a solid-state imaging device capable of improving the light-collecting property of the condenser lens 8, improving the effective aperture ratio, and improving the gradation accuracy of the reproduction screen and increasing the integration of pixels. The element can be easily manufactured.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram illustrating a main part of a CCD solid-state imaging device according to the present embodiment.

In this CCD solid-state image pickup device, light receiving sections 2 composed of pn photodiodes are selectively arranged in a matrix on a silicon substrate 1, and a gate insulating film made of SiO ₂ or the like is formed on the silicon substrate 1. A transfer electrode 4 made of a polycrystalline silicon layer is selectively formed via the gate electrode 3. The transfer electrode 4 is formed avoiding the light receiving section 3.

An Al light-shielding film 6 is selectively formed on these transfer electrodes 4 with an interlayer insulating film 5 interposed therebetween.
An interlayer film 7 for planarization is laminated on the entire surface including the light shielding film 6,
Further, a micro condenser lens 8 is formed on the interlayer film 7 to constitute a CCD solid-state imaging device. The light receiving unit 3
Other impurity diffusion regions, such as vertical registers and channel stopper regions, are omitted.

In this embodiment, the micro condenser lens 8 is formed by forming diamond.

Next, a method for manufacturing the CCD solid-state imaging device according to the present embodiment will be described with reference to FIGS. The components corresponding to those in FIG. 1 are denoted by the same reference numerals.

First, as shown in FIG. 2A, after a gate insulating film 3 made of SiO ₂ is formed on a silicon substrate 1,
A transfer electrode 4 made of a polycrystalline silicon layer is selectively formed on the gate insulating film 3, and a light receiving section 2 made of a pn photodiode is formed on the surface of the silicon substrate 1 where the transfer electrode 4 is not formed. Form selectively.

Thereafter, after an interlayer insulating film 5 is formed on the entire surface, an Al light-shielding film 6 is selectively formed on a portion of the interlayer insulating film 5 corresponding to the transfer electrode 4. Then, after an interlayer film 7 for planarization is formed on the entire surface, a diamond film 11 is stacked on the entire surface of the interlayer film 7 by a CVD method, and subsequently, an SiO ₂ film 12 used as a mask for etching is stacked.

Next, as shown in FIG. 2B, after forming a photoresist film on the entire surface, exposure and development are performed to form a resist pattern 13 for forming a micro condenser lens.
Then, using the resist pattern 13 as a mask,
The O ₂ film 12 is etched to leave the SiO ₂ film 12 in the lens forming portion (the portion corresponding to the light receiving portion 2).

Next, as shown in FIG. 3A, after removing the resist pattern 13, the remaining SiO ₂
Using the film 12 as a mask, the lower diamond film 11 is etched with an oxygen-based gas. At this time, by appropriately combining anisotropic etching and isotropic etching, the diamond film 11 is processed into a convex lens shape having a tapered cross-sectional shape, and the micro condenser lens 8 made of diamond is formed.

Next, as shown in FIG. 3B, the remaining upper SiO ₂ film 12 is removed with a hydrofluoric acid solution to obtain the CCD solid-state imaging device according to the present embodiment. Here, when an SiO ₂ -based film is used as the interlayer film 7, the interlayer film 7 is removed at the same time when the upper SiO ₂ film 12 is removed. Before forming the diamond film 11 on the interlayer film 7, FIG.
As shown in FIG. 6, an SiN film 14 having a different etching rate from that of the SiO ₂ film 12 is formed on the interlayer film 7 in advance.

[0028] Thereafter, in the same manner as mentioned above, after forming a diamond film 11 on the SiN film 14, to form a SiO ₂ film 12 on the diamond film 11, the SiO ₂ film 12
Is patterned to form a SiO ₂ film 12 on the lens forming portion.
(See FIG. 4B). Then, as shown in FIG. 5A,
The exposed diamond film 11 is etched with an oxygen-based gas to form a micro condenser lens 8 made of diamond.
To form Thereafter, as shown in FIG.
The O ₂ film 12 is removed with a hydrofluoric acid-based solution to remove
The D solid-state imaging device is completed. At this time, the lower interlayer film 7
Is protected by the upper SiN film 14, so that the Si
It is not removed at the same time when the O ₂ film 12 is removed.

As described above, according to the present embodiment, the micro condenser lens 8 is formed of diamond having a high refractive index of 2.4, so that as shown in FIG. Is increased, and the incident light L, in particular, the light Le incident near the periphery of the micro-condensing lens 8 can be collected on the light receiving unit 2 side. As a result, the effective aperture ratio of the light receiving unit 2 is improved, and the miniaturization of the pixel area can be promoted, and the deterioration of image quality (peripheral dimming) in the peripheral part of the image part can be suppressed.

Also, unlike conventional photoresists, diamond has no absorption in the visible region, so that the incident light L
Can be efficiently condensed on the light receiving portion, and the gradation accuracy of the reproduced screen captured and the reproducibility of natural colors can be improved.

Since the reflow process by baking is not required, the diameter of the micro condenser lens 8 can be reduced according to the design value. As a result, the light receiving unit 2
Arrangement pitch and opening width can be reduced, and CC
High integration of the D solid-state imaging device can be promoted.

Further, according to the manufacturing method according to the present embodiment shown in FIGS. 2 to 5, the micro condenser lens 8 can be easily formed of diamond. That is, a CCD that can enhance the light-collecting performance of the micro-condensing lens 8, improve the effective aperture ratio, promote the gradation accuracy of the reproduction screen, and promote the high integration of pixels. A solid-state imaging device can be easily manufactured.

[0033]

According to the solid-state imaging device of the present invention, the light-collecting performance of the light-collecting lens can be improved, the effective aperture ratio can be improved, and the gradation accuracy of the reproduction screen can be improved. High integration of pixels can be promoted.

Further, according to the method of manufacturing a solid-state imaging device according to the present invention, it is possible to enhance the light-collecting performance of the light-collecting lens, to improve the effective aperture ratio, and to improve the gradation accuracy of the reproduction screen. It is possible to easily manufacture a solid-state imaging device capable of promoting improvement and high integration of pixels.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a main part of a CCD solid-state imaging device according to an embodiment.

FIG. 2 is a process chart (1) showing one manufacturing method of the CCD solid-state imaging device according to the embodiment.

FIG. 3 is a process chart (2) showing one manufacturing method of the CCD solid-state imaging device according to the embodiment.

FIG. 4 is a process chart (1) showing another method of manufacturing the CCD solid-state imaging device according to the embodiment.

FIG. 5 is a process chart (2) showing another method of manufacturing the CCD solid-state imaging device according to the embodiment.

FIG. 6 is a configuration diagram showing a main part of a CCD solid-state imaging device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Light receiving part 3 Gate insulating film 4 Transfer electrode 5 Interlayer insulating film 6 Al light shielding film 7 Interlayer film 8 Micro condenser lens (diamond)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 27/14-27/148 G02B 3/00 H04N 5/335

Claims (3)

(57) [Claims] 1. A solid-state imaging device in which a condenser lens is formed on a light receiving section, wherein the condenser lens is formed of diamond. 2. A method for manufacturing a solid-state imaging device having a light-collecting lens formed on a light-receiving part, wherein the light-receiving part is formed on a semiconductor substrate, and a diamond film is formed on the semiconductor substrate via an insulating film. A step of forming an oxide film on the diamond film; a step of forming a resist film on the oxide film; and a step of patterning the resist film. A step of leaving the oxide film on the lens forming portion by etching and removing the diamond film selectively using the oxide film as a mask to form the diamond film into a lens shape. A method for producing a solid-state imaging device, comprising: 3. The method according to claim 2, wherein an insulating film having an etching rate different from that of the insulating film is formed on the insulating film before forming the diamond film.