JPH06232381A - Solid-state image pick-up element and its manufacture - Google Patents

Abstract

PURPOSE:To reduce smear and flare by decreasing transmission and reflection of light in the region where a lens is not formed. CONSTITUTION:The surface of a region 34 between lenses 33 formed on a sensor 15 of each picture element 15 is roughened. When a light 36 enters the region 34, the light which permeates the region 34 and reaches a vertical shift register 21 and the light which is reflected by the region 34 are little. The greater part of the light 36 which has permeated the region 34 is shielded by an Al film 27, and does not enter a sensor 15, so that the light 36 scarcely contributes to the sensitivity of a CCD image pick-up element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image sensor having a lens on a sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional example of a CCD solid-state image pickup device. In this conventional example, an N type Si substrate 11 is used.
P well 12 and P ⁺⁺ type impurity layer 1 in the P well 12
A sensor 15 for one pixel is formed by a photodiode including 3 and the N-type impurity layer 14 under the P ^{+ +} -type impurity layer 13. A vertical shift register 21 is formed by the N-type impurity layer 16 in the P well 12 and the electrode made of the polycrystalline Si film 17 on the Si substrate 11.

Below the N-type impurity layer 16, the P-type impurity layer 2 has a higher concentration of P-type impurities than the P-well 12 and serves as a potential barrier for electrons in the N-type impurity layer 16.
2 is formed. A read gate 23 is provided between the sensor 15 and the vertical shift register 21, and a P ⁺ -type impurity layer 24 on the opposite side of the vertical shift register 21 from the read gate 23 serves as a channel stopper 25. The polycrystalline Si film 17 and the like are covered with an interlayer insulating film 26, and an Al film 27 on the interlayer insulating film 26 forms a light-shielding film having a pattern having an opening on the sensor 15.

The Al film 27 and the like are covered with a passivation film 31, and a flattening layer 32 is formed on the passivation film 31. A lens 33 is formed on the flattening layer 32 and in a region corresponding to each sensor 15, and a region 34 where the lens 33 is not formed is provided between the lenses 33. The region 34 is also made of a transparent material and its surface is smooth.
The above structure is covered with the glass plate 35 of the package.

[0005]

However, most of the light 36 that is incident on the region 34 and transmitted through the region 34 is blocked by the Al film 27 and does not enter the sensor 15. Therefore, the sensitivity of the CCD image pickup device is high. Light 36a not only contributes little to the
Since the diagonal component is strong, it is easy to reach the vertical shift register 21. Therefore, in this conventional example, there is a high probability that smear will occur.

Moreover, when the Al film 27 is also used as a shunt for the polycrystalline Si film 17, the Al film 27 adjacent in the horizontal direction at right angles to the extending direction of the polycrystalline Si film 17.
In order to make contact with the polycrystalline Si film 17 to which different clock pulses should be applied in a state where they are electrically separated from each other, they are cut at the separation portion between pixels in the vertical direction. Therefore, since the separated portion is not covered with the Al film 27 and the separated portion is provided with the region 34 where the lens 33 is not formed, in this case, the probability of smearing is further increased.

Further, since the surface of the area 34 is a smooth surface, the light 36 is easily reflected in this area 34. Therefore, there is a high probability that the reflected light 36b is reflected on the glass plate 35 and flare occurs.

[0008]

According to the solid-state image pickup device of claim 1, in the solid-state image pickup device having the lens 33 on the sensor 15, the surface of the region 34 where the lens 33 is not formed is a rough surface. It has a feature.

According to a second aspect of the present invention, there is provided a method of manufacturing a solid-state image pickup device having a lens 33 on a sensor 15, wherein at least an image pickup region is covered with a flattening layer 32, and the flattening layer 32 is formed. The method includes a step of roughening at least a region 34 of the surface where the lens 33 is not formed, and a step of forming the lens 33 on the flattening layer 32 having the roughened surface.

According to a third aspect of the present invention, in the method for manufacturing a solid-state image pickup device, after forming the lens 33, the flattening layer 32 and the lens 33 are etched back, and the lens 33 is transferred to the flattening layer 32. It further has a step of performing.

[0011]

In the solid-state image pickup device according to the first aspect, even if the light 36 is incident on the region 34 where the lens 33 is not formed, the surface of the region 34 is rough, so that the light passes through the region 34 and becomes vertical. The light 36a reaching the shift register 21 and the light 36b reflected by the area 34 are small.

In the method of manufacturing a solid-state image pickup device according to claim 2,
Since the lens 33 is formed on the flattening layer 32 after roughening the surface of the flattening layer 32, the lens 33
Roughening is easier than the case where roughening is performed after forming. Further, even if the surface of the flattening layer 32 where the lens 33 is formed is roughened,
If the lens 33 is formed in this region, the rough surface of the flattening layer 32 is filled with the material of the lens 33 and is not substantially a rough surface, so that the light collection by the lens 33 is not affected.

In the method for manufacturing a solid-state image pickup device according to claim 3,
Since the lens 33 is formed on the flattening layer 32, the distance from the lens 33 to the inside of the element is shortened, and the light 36a reaching the vertical shift register 21 is further reduced.

[0014]

The first and second embodiments of the present invention will be described below.
This will be described with reference to FIGS. The components corresponding to those of the conventional example shown in FIG. 5 are designated by the same reference numerals.

FIG. 1 shows a first embodiment. The first embodiment has substantially the same configuration as the conventional example shown in FIG. 5, except that the surface of the region 34 where the lens 33 is not formed is a rough surface. Therefore, this first
In the embodiment, as shown in FIG. 5, the light 36a that passes through the region 34 and reaches the vertical shift register 21 and the light 36b reflected by the region 34 are small, and smear and flare are small.

Also in the manufacture of the first embodiment as described above, the conventionally known steps similar to the conventional example shown in FIG. 5 and the like are executed except for the step of roughening the surface of the region 34. Figure 2
Shows a step of roughening the surface of the region 34 in the manufacturing method of the first embodiment. In this step, a transparent film 37 having a different etching characteristic from that of the material for forming the lens 33 is formed on the passivation film 31 and the like.

After forming the lens 33 on the transparent film 37, only the surface of the transparent film 37 in the region 34 between the lenses 33 is clouded under the condition that the etching selection ratio between the material of the lens 33 and the transparent film 37 is large. Etch into glass. The frosted glass-like etching can be performed by, for example, dry etching by adjusting the gas flow rate ratio, the degree of vacuum, or the like.

FIG. 3 shows the manufacturing method of the first embodiment.
Another process for roughening the surface of the region 34 is shown.
In this step, as shown in FIG. 3A, the SiO ₂ film as the flattening layer 32 is plasma-enhanced in at least the imaging region including the sensor 15, the vertical shift register 21, the horizontal shift register (not shown), and the like. Method. After that, as shown in FIG. 3B, the entire surface of the flattening layer 32 is etched into frosted glass by the same method as the step shown in FIG.

Next, as shown in FIG. 3C, the lens 33
The organic material 41 for forming the is coated or deposited on the planarization layer 32. By this coating or deposition, the rough surface of the flattening layer 32 is filled with the organic material 41 so that it is not substantially rough. After that, as shown in FIG. 3D, the lens 33 is formed of the organic material 41.

Next, under the condition that the etching selection ratio between the organic material 41 and the flattening layer 32 is large, as shown in FIG. 3E, until the flattening layer 32 in the region 34 between the lenses 33 is exposed. Only the organic material 41 is etched back. Since the surface of the flattening layer 32 is roughened in advance, the flattening layer 32 having a rough surface is exposed in the region 34 where the organic material 41 is removed.

After forming the lens 33, the organic material 41 and the flattening layer 32 are etched back under the condition that the etching selection ratio between the organic material 41 and the flattening layer 32 is 1, so that FIG. The lens 33 may be transferred to the flattening layer 32, as indicated by the alternate long and short dash line in (e). By doing this, the distance from the lens 33 to the inside of the element is shortened,
The light 36a reaching the vertical shift register 21 is further reduced, and smear is further reduced.

FIG. 4 shows a second embodiment. In the second embodiment, the lens 33 is not formed on the sensor 15, but the surface of the region 34 of the flattening layer 32 other than the sensor 15 is a rough surface, as shown in FIG. It has substantially the same configuration as the conventional example shown in FIG. Therefore, also in the second embodiment, as shown in FIG. 5, there is little light 36a which passes through the region 34 and reaches the vertical shift register 21 and light 36b which is reflected by the region 34, and smear and flare are little.

Also in the manufacture of the second embodiment as described above, until the formation of the flattening layer 32, the conventionally known steps similar to the conventional example shown in FIG. However, after that, a portion of the surface of the flattening layer 32 on the sensor 15 is covered with a resist 42, and the resist 42 is used as a mask to perform the roughening processing similar to that in the manufacturing of the first embodiment. This is applied to 32 areas 34.

[0024]

According to the solid-state image pickup device of the present invention, even if light is incident on a region where no lens is formed, it is transmitted through this region and reaches the vertical shift register, or is reflected by this region. Less smear and flare due to less light.

In the method of manufacturing a solid-state image pickup device according to claim 2,
Since it is easy to roughen the surface of the region where the lens is not formed, it is possible to easily manufacture a solid-state imaging device with less smear and flare.

In the method for manufacturing a solid-state image pickup device according to claim 3,
Since less light reaches the vertical shift register, a solid-state image sensor with less smear can be manufactured.

[Brief description of drawings]

FIG. 1 is a side sectional view of a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a part of the manufacturing method of the first embodiment.

FIG. 3 is a side sectional view showing a part of another manufacturing method of the first embodiment in the order of steps.

FIG. 4 is a side sectional view of a second embodiment.

FIG. 5 is a side sectional view of a conventional example of the invention of the present application.

[Explanation of Codes] 15 Sensor 32 Flattening Layer 33 Lens 34 Area

Claims (3)

[Claims] 1. A solid-state image sensor having a lens on a sensor, wherein a surface of a region where the lens is not formed is a rough surface. 2. A method of manufacturing a solid-state image sensor having a lens on a sensor, comprising a step of covering at least an imaging region with a flattening layer, and a rough surface at least in a region of the surface of the flattening layer where the lens is not formed. A method of manufacturing a solid-state image sensor, comprising: a step of processing; and a step of forming the lens on the flattening layer subjected to the rough surface processing. 3. The method according to claim 2, further comprising the step of etching back the flattening layer and the lens after forming the lens to transfer the lens to the flattening layer. Manufacturing method of solid-state imaging device.