JPH03283571A - Production of solid-state image pick up device - Google Patents

Abstract

PURPOSE:To allow high sensitivity and improve production yield by accumulating lens material on a solid-state image pick up element chip, then, selectively irradiating the lens material with such energy beams as light beams and forming a lens by using the expansion or the contraction of the lens material. CONSTITUTION:A convex lens is formed at a photoelectric transfer part for collecting light by accumulating a dielectric film 20 such as PLZT on a solid- state image pick up element chip, then, selectively irradiating the film with laser beams according to the photoelectric transfer part. The sensitivity is improved without increasing the chip area by the operation of the convex lens. The method is different from a method which bonds a previously formed convex lens on the solid-state image pick up element chip using an adhesive, etc., it does not cause positioning deviation nor the loss by the adhesive nor pixel defect caused by a bubble and the production yield can be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a solid-state imaging device in which a lens is provided for each pixel, and in particular to a solid-state imaging device in which a lens forming means is improved. The present invention relates to a method for manufacturing a device.

(Prior Art) In recent years, solid-state imaging devices have been attracting attention as imaging units used in television cameras, video cameras, and the like. Although this solid-state imaging device has many advantages over conventionally used imaging tubes, it also has problems that need to be improved.

A typical example of this problem is low sensitivity.

In image pickup tubes, the electron beam scans the image pickup surface with charges corresponding to the incident light, effectively utilizing the entire image pickup surface, but in solid-state imaging devices, the photoelectric conversion element and the charge readout mechanism are the same. This is because since it is installed on a flat surface, it is not possible to effectively utilize incident light.

Figure 4 shows CCD (Charge Coupled D
FIG. 3 is a plan view showing a pixel configuration of a conventional solid-state imaging device using a semiconductor device (device). The pixels of this device are constructed on a p-type semiconductor substrate, and the area surrounded by a broken line 1 in the figure corresponds to one pixel. Reference numeral 2 indicates a p-type diffusion layer for mutual insulation between pixels, 3 indicates a photoelectric conversion element, 4 indicates a charge transfer section using a CCD, and 5 indicates an AI shield. Note that, in this figure, the gate of the charge transfer section 4 and the transfer gate that sends charges from the photoelectric conversion element 3 to the charge transfer section 4 are omitted.

FIG. 5 is a cross-sectional view taken along the line AA' in FIG. 2. In the same figure, the numbers indicating the components in the figure correspond to the numbers shown in FIG. 2, 6 is the semiconductor substrate, 7 is the gate insulating film,
Reference numeral 8 indicates a transfer electrode, and reference numeral 9 indicates a transfer gate.

In this example, the effective photoelectric conversion portion of the photoelectric conversion element is approximately 30% of the pixel area. In other words, the remaining approximately 70% of the light is ineffective.

In order to improve the sensitivity of a solid-state imaging device, it is sufficient to increase the area of the photoelectric conversion element, but this increases the chip area of the solid-state imaging device and causes a decrease in resolution.

As a method of increasing the area of the photoelectric conversion element without increasing the chip area, a photoelectric conversion element part, a charge readout mechanism, and two
A structure has been proposed in which a photoelectric conversion film (photoelectric conversion element) is formed in the upper layer, and a function for reading out the charge of the photoelectric conversion element is formed in the lower layer, that is, the surface of the semiconductor substrate. However, such a configuration has a complicated structure, and problems include manufacturing difficulties and reliability.

In addition, as another method, as disclosed in Japanese Patent Application Laid-open No. 57-9180, there is a photoelectric conversion method in which the light that has been ineffective in the photoelectric conversion section of a solid-state imaging device is collected into each photoelectric conversion element. It has been proposed to increase the amount of solid-state imaging devices with high sensitivity. As disclosed in this proposal, by using a material that acts as a convex lens as a means for collecting light and installing it in line with the photoelectric conversion section, incident light can be collected efficiently without increasing the chip area. It becomes possible to emit light.

However, this type of solid-state imaging device has the following problems. That is, placing a substance that acts as a convex lens in alignment with the photoelectric conversion section on the pixel requires a fine positioning technique and also requires bonding using an adhesive or the like. It is an extremely difficult task to accurately align and bond a solid-state image sensor chip with a photoelectric conversion section and a signal charge readout section on a substrate, and a convex lens that has been formed in advance to match the arrangement of the photoelectric conversion section. It is.

Furthermore, when the solid-state image sensor chip and the convex lens are bonded using an adhesive, there is a loss due to diffuse reflection of light at the respective interfaces. Furthermore, bubbles generated in the adhesive cause pixel defects, leading to a decrease in the manufacturing yield of solid-state imaging devices.

(Problems to be Solved by the Invention) As described above, conventional solid-state imaging devices equipped with a condensing lens for each pixel can improve sensitivity without increasing the area of the photoelectric conversion section. When bonding the element chip and the condensing lens, misalignment may occur.
There were problems such as air bubbles forming in the adhesive and causing pixel defects.

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to be able to form a condenser lens accurately aligned with a photoelectric conversion section without causing pixel defects; It is an object of the present invention to provide a method for manufacturing a solid-state imaging device with high sensitivity and high manufacturing yield.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is not to bond a pre-formed condensing lens to a solid-state image sensor chip, but to form a material formed on a solid-state image sensor chip into a lens shape. It lies in the processing on top.

That is, the present invention provides a solid-state image sensor chip having a plurality of photoelectric conversion units and signal charge readout units provided on a semiconductor substrate.
In the method for manufacturing a solid-state imaging device produced by forming a condensing lens that focuses light incident on the chip onto a photoelectric conversion section, a lens material is deposited on the solid-state imaging element chip, and then the lens material is deposited on the solid-state imaging element chip. In this method, the lens is formed by selectively irradiating the lens with an energy beam such as light and utilizing the expansion or contraction of the lens material.

(Function) According to the present invention, by appropriately selecting the lens material deposited on the solid-state image sensor chip and its composition, this material is expanded or contracted by applying some kind of energy from the outside, and the energy is supplied. The changed state can be maintained without continuing. Utilizing this phenomenon, by partially expanding or contracting the lens material and changing its shape to keep the mechanical stress parallel to the surroundings, it is possible to form a condensing lens, for example, a convex lens. . The lens formed in this way is
Since the area can be made larger than the photoelectric conversion section of the solid-state image sensor chip, the light from the entire surface of the lens can be efficiently focused on the photoelectric conversion section by the effect of the condensing lens. Therefore, it is possible to equivalently increase the area of the photoelectric conversion section and realize a solid-state imaging device with higher sensitivity.

Further, unlike the case where an adhesive is used, there is less risk of misalignment and no pixel defects due to bubbles or the like occur, making it possible to improve manufacturing yield.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention. This device has a convex lens added to the conventional device shown in FIG. 5 above.

In FIG. 1, numeral 10 is a p-type Si substrate, on the surface of which is an n-type diffusion layer 11 that becomes a photoelectric conversion section, and a CCD channel 12 that serves as a charge transfer section, which sends the charges of the photoelectric conversion section to the charge transfer section. A transfer gate 13 is formed.

A transfer electrode 1 is provided on the substrate 10 via a gate insulating film 15.
6 is formed. Then, a flattening insulating film 17 is deposited on these, and an AN thin film 18 is formed in this insulating film 17 so as to cover areas other than the photoelectric conversion areas.

The configuration of the solid-state image sensor chip up to this point is the same as that of the conventional device, but in this embodiment, in addition to this, a transparent electrode 21 is provided on the chip. A dielectric film 20 and a transparent electrode 22 are laminated, and a convex lens is formed from an antiferroelectric portion 20a and a ferroelectric portion 20b of the dielectric film 20. By the action of this convex lens, the light incident on the dielectric film 20 is focused on the photoelectric conversion section.

Next, a method of manufacturing the apparatus of this embodiment having the above structure will be explained with reference to FIG.

First, as shown in FIG. 2(a), various diffusion layers 11 to 14 are formed on a Si substrate 10, and a transfer electrode 16 is formed with a gate insulating film 15 interposed therebetween. Furthermore, an interlayer insulating film 17 and an AI thin film 18 are formed. The steps up to this point are the same as the conventional method.

In addition, in FIG. 2, the substrate 10. Diffusion layer 11. Portions other than the insulating film 17 and the AI electrode 18 are omitted.

On such a solid-state image sensor chip, a transparent electrode 21 is deposited for about 70 ns, a transparent antiferroelectric film 20 is deposited to a thickness of several tens of μm,
Further, a transparent electrode 22 is formed with a thickness of about 70 nm. Here, the transparent electrodes 21 and 22 are ITO (Ind
ium Tin Oxide) or the like by sputtering or the like. The dielectric film 20 is made of PLZT [(Pb1-3(Lax)(
Zry Tl1-Y)o, ] x -0,076, y-
A film having a composition of 0.0.7 (generally indicated as 7.6/70/30) is used to form a film by sputtering.

Next, as shown in FIG. 2(b), transparent electrodes 21, 22
During this period, an electric field of about 80 to 90% of the electric field that causes the dielectric film 20 to change its phase from the antiferroelectric phase to the ferroelectric phase is applied, and the wavelength is changed so that the photoelectric conversion part of the solid-state image sensor chip is centered. 633
Selectively irradiate with nm laser light. By using this electric field and the energy of the laser beam, it is possible to change the phase of a transparent antiferroelectric material into a ferroelectric material only in the necessary portions. At this time, since the ferroelectric region expands in volume, it is deformed by the stress between it and the antiferroelectric region, thereby forming a convex lens as shown in FIG. 2(C).

Thus, according to the method of this embodiment, after depositing the dielectric film 20 such as PLZT on the solid-state image sensor chip, by selectively irradiating the laser beam in accordance with the photoelectric conversion part,
A convex lens for focusing light on the photoelectric conversion section can be formed. Due to the effect of this convex lens, sensitivity can be increased without increasing the chip area. Also, unlike the method of bonding a pre-formed convex lens onto a solid-state image sensor chip using an adhesive, misalignment does not occur, and furthermore, there is no risk of loss due to the adhesive or pixel defects due to air bubbles. Therefore, it is possible to improve the manufacturing yield. In addition, since a ferroelectric film generally has a higher refractive index than an antiferroelectric film, it is possible to efficiently focus incident light on the photoelectric conversion section with a lens made of the dielectric film 20.

In this example, when forming a convex lens, the volume expansion and the formation of regions with different refractive indexes are utilized when a phase change occurs from an antiferroelectric phase to a ferroelectric phase using an antiferroelectric film. Although the incident light is equivalently increased by doing this, it is also possible to form a convex lens in the following manner instead.

For example, an antiferroelectric film formed on a solid-state image sensor chip is turned into a ferroelectric phase over the entire surface by applying an electric field, then a bias voltage is applied, and the necessary areas are irradiated with laser light. A convex lens can also be formed by returning to the dielectric phase.

Another method is to use a structure in which one transparent electrode 21 on the solid-state image sensor chip is omitted, and a shielding Ag film 18 is used instead of the transparent electrode. In this case, it is also possible to use the typical antiferroelectric materials mentioned above, but
Since the All film 18 is formed outside the photoelectric conversion section, the L-nones formation process can be further simplified by using a material that exhibits a ferroelectric phase after film formation and becomes an antiferroelectric phase when external energy is applied. .

In addition, in order to improve the light transmittance, the transparent electrode 22
It is desirable to remove the transparent electrode 22, and removal of the transparent electrode 22 is easily possible by using an appropriate etching material. Also, depending on the size of the photoelectric conversion section of the solid-state image sensor chip and the pixel pitch, the distance between the photoelectric conversion section and the lens may be insufficient depending on the lens material and the shape of the formed lens. Incident light may not be sufficiently focused. In this case, the problem can be solved by forming two layers of transparent antiferroelectric material on the solid-state image sensor chip.

FIG. 3 is a process sectional view for explaining another embodiment of the method of the present invention. Note that the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in that a polymeric material having a transparent cis-trans transition photosensitive group was used as the lens material instead of an antiferroelectric material. Specifically, polymers with azobenzene in their side chains (
aspartic acid benzyl ester), spirobenzopyran-containing polymers, polymers made by dyeing nylon fabric with azo dyes, polymer gels made from azostilbene dyes, aromatic polyamides with stilbene groups or azobenzene groups in the main chain skeleton It is a thin film layer such as

In this example, as shown in FIG. 3(a), a spirobenzopyran group-containing monomer (
A polymer material film) 30 is applied and dried. The film thickness of this polymeric material film 30 is determined so that a desired convex lens can be obtained.
The optimal film thickness was determined from the refractive index of the polymer material, the shrinkage rate after processing, and the pixel size of the solid-state image sensor chip.

Next, as shown in FIG. 3(b), a portion of the light shielding Al film 18, which is an ineffective area of the solid-state image sensor chip, was irradiated with ultraviolet rays having a wavelength of 254 nm. Although this ultraviolet irradiation was selectively performed using a photomask, the light irradiation may be selectively performed by scanning an ultraviolet beam. Such irradiation with ultraviolet rays causes the polymer material film 30 on the AJ film 18 to contract, thereby forming a convex lens on the photoelectric conversion section on the opposite principle to that of the previous embodiment. . FIG. 3(C) shows the state in which this convex lens is formed.

As described above, by forming a convex lens made of a polymer material on a solid-state image sensor chip, as in the previous embodiment, compared to a normal solid-state image sensor, light utilization efficiency is improved and sensitivity is increased. achieved.

Further, unlike the previous embodiment, there is no need to provide a transparent electrode, so the process can be further simplified.

Note that the present invention is not limited to the embodiments described above. In the examples, a dielectric material or a polymer material was used as the lens material, but instead of these materials, materials that are transparent to the light detected by the photoelectric conversion unit and whose volume expands or contracts when irradiated with an energy beam may be used. can be used. In addition, energy beams are not limited to light;
Any material that promotes volumetric expansion or contraction of the lens material may be used.

Further, since a lens can be formed for each pixel of a solid-state image sensor chip, it is also possible to correct light loss due to the color filter of a solid-state image sensor chip equipped with a color filter. For example, forming the lens of the present invention only in the photoelectric conversion section of a pixel corresponding to blue, which has relatively low sensitivity, is an effective means for current solid-state imaging devices. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, after forming a lens material on a solid-state image sensor chip in advance, a condensing lens is formed by selective irradiation with an energy beam.
A condensing lens can be formed with accurate alignment to the photoelectric conversion section without causing pixel defects. Therefore,
A solid-state imaging device with high sensitivity and high manufacturing yield can be realized.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a sectional view showing the manufacturing process of the solid-state imaging device, and FIG. 3 is another embodiment of the invention. 4 is a plan view showing a schematic configuration of a conventional solid-state imaging device; FIG. 5 is a cross-sectional view of the process for explaining the method; FIG. 5 is a view taken along arrow A-A in FIG. 4;
FIG. 10...p-type Si substrate, 11...n-type diffusion layer (photoelectric conversion section), 12...CC
D channel, 13... Transfer gate, 16... Transfer electrode, 17... Insulating film for flattening, 18... l thin film, 20... Dielectric film (lens material), 20a... Antiferroelectric part, 20b... Ferroelectric part, 21.22... Transparent electrode,

Claims (1)

[Scope of Claims] A condenser lens is formed on a solid-state image sensor chip, which is formed by providing a plurality of photoelectric conversion units and a signal charge readout unit on a semiconductor substrate, to condense light incident on the chip onto the photoelectric conversion unit. In doing so, after depositing a lens material on the solid-state image sensor chip, this lens material is selectively irradiated with an energy beam, and the lens is formed using expansion or contraction of the lens material. A method for manufacturing a solid-state imaging device.