JPH0455028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the sensitivity of a solid-state imaging device.

In general, solid-state imaging devices have a photoelectric conversion section and a signal readout section on the main surface of the semiconductor substrate, so 100%
The area cannot be used as a photoelectric conversion section. As a means to solve this drawback, there is a CCD frame transfer method in which the photoelectric conversion section and the signal readout section are separated. This method has a problem in that the chip size becomes large. In addition, we form a photoconductive film on CCD interline transfer type and MOS type image sensors.
Configurations that improve photoelectric conversion efficiency have been proposed. This method is not consistent with conventional silicon integrated circuit manufacturing technology, and also has many new problems, such as afterimages and burn-in phenomena peculiar to photoconductive films.

An object of the present invention is to provide a method for manufacturing a highly sensitive solid-state imaging device that eliminates the above-mentioned drawbacks.

According to the present invention, photoelectric conversion element groups are arranged in a mosaic pattern on the same semiconductor substrate, and a plurality of light-shielded signal readout groups for reading signal charges provided between adjacent photoelectric conversion elements are formed. After coating the first photosensitive resin on the semiconductor wafer, the first photosensitive resin is removed in areas other than the photoelectric conversion area by photolithography.
means for removing the photosensitive resin; means for treating the first photosensitive resin at a temperature equal to or higher than the softening temperature of the resin;
means for applying a second photosensitive resin on the photosensitive resin and removing a part of the second photosensitive resin other than the photoelectric conversion element by photolithography; the resin at a temperature equal to or higher than the softening temperature of the second resin,
In addition, a method for manufacturing a solid-state imaging device is obtained, which includes means for causing fluidization at a temperature lower than the heat treatment of the first photosensitive resin.

Next, the present invention will be explained using the drawings. FIG. 1 is a diagram for explaining one embodiment of the present invention,
A conceptual plan view of an interline transfer CCD imaging device is shown.

11 is a photoelectric conversion region made of, for example, a photodiode, and 12 is a vertical CCD register for reading out the signal photoelectrically converted in the photoelectric conversion region 11. Although not shown, signal charge is transferred between the photodiode and the vertical CCD register 12. A transfer gate is placed to control the Reference numeral 13 denotes a horizontal CCD register that reads signals from the vertical CCD registers transferred in parallel to the output section 14 line by line. FIG. 2 is a partially enlarged view of FIG. 1. 11
is a photodiode, 12 is a vertical CCD register,
15 is a transfer gate region, and 16 and 17 are transfer electrodes of a vertical CCD register, which are usually made of polycrystalline silicon. Transfer electrodes 16 and 17 are 1
A 1/2 stage CCD is formed corresponding to the two photoelectric conversion elements 11, and although not shown, each transfer electrode is vertical.
The CCD12 part has two different potentials.
The two-layer gate structure or impurity control of the substrate semiconductor is performed. Furthermore, the transfer electrodes 16 and 17 are connected to adjacent vertical CCDs through the vertical separation section 18 of the photoelectric conversion element 11. Furthermore, the transfer gate section and the vertical CCD register section 12 are made of Aluminum, for example.
The light is blocked by a layer 19 that does not allow light to pass through.
In this way, the actual aperture ratio of the photoelectric conversion element 11 is 20~
Limited to 40%.

FIGS. 3 to 7 are diagrams for explaining an embodiment of the method for manufacturing a solid-state imaging device according to the present invention, which is an example applied to the interline transfer CCD imaging device shown in FIG.

FIG. 3 schematically shows a cross section taken along the - line in FIG. 2. The same parts as in FIG. 2 are designated by the same symbols. The interline transfer CCD image sensor has a vertical structure formed on the main surface of a substrate semiconductor 10, which includes, for example, a photodiode section 11 having a conductivity type opposite to that of the substrate impurity, a transfer gate region 15 whose threshold voltage is controlled by the impurity, and a buried channel. CCD
A register 12 is formed. Transfer electrodes 16 are arranged on the surface of the substrate with an insulating film 20 interposed therebetween. Furthermore, the vertical CCD is connected via the phosphorus glass layer 21.
An aluminum layer 19 is arranged to shield light from light on the transfer gate section 12 and the transfer gate section 15.

First, as shown in FIG. 4, a transparent and photosensitive resin layer 22 is formed on the main surface of the conventional interline transfer CCD shown in FIG. Photosensitive resin 2
2 eliminates unevenness on the main surface of the CCD imaging device, and
It also serves to adjust the focal length of the lens, which will be formed later, so that the focal point is on the photoelectric conversion element. The thickness of the transparent photosensitive resin layer 22 is determined by the curvature of the lens, the refractive index of the lens material, and the aperture ratio of the photoelectric conversion element. When using resin as a condensing lens as in this invention, the refractive index is 1.5, the radius of curvature of the lens is the pitch of the photoelectric conversion element, and the aperture ratio of the photoelectric conversion element is 50%, at least the thickness of the photosensitive resin. is required to be more than 1/2 of the pitch of the photoelectric conversion element.

After the photosensitive resin 22 is deposited, the photosensitive resin 22 on the bonding pad portion of the imaging device and on the scribe line is removed using the photoresist action of the resin itself. Thereafter, heat treatment is performed at a temperature higher than the softening temperature of the resin 22 in order to harden the photosensitive resin. Next, a second lens array is formed on the photosensitive resin 22 to form a lens array.
A photosensitive resin layer 23 is applied. Thereafter, a part of the second photosensitive resin 23 on the light shielding part 19 and a part on the photoelectric conversion element 11 separated in the vertical direction are removed by a photoresist process of exposure and development. FIG. 5 is a schematic plan view of the second photosensitive resin 23 after the phenomenon occurs, and the resin 23 is formed in a mosaic shape corresponding to the photoelectric conversion element 11.

Thereafter, the photosensitive resin 23 is heat-treated at a temperature higher than the softening temperature of the resin and lower than the temperature at which the first photosensitive resin 22 was heat-treated, so that the resin 23 forms a lens shape by thermal flow. FIG. 7 is a sectional view of the resin 23 after heat treatment.

Depending on the radius of curvature of the resin 23 and the thickness of the resin 22, the incident light passes through the light shielding part 19 and the vertical separation part 1 of the photoelectric conversion element.
The light irradiated onto the photoelectric conversion element 11 can also be completely focused on the photoelectric conversion element 11 .

The present invention can be applied not only to interline transfer CCD imaging devices but also to all solid-state imaging devices such as MOS imaging devices. It can also be applied to concentrating light irradiated onto an electrode part of a photodiode, solar cell, etc. onto a photoelectric conversion section.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of an interline transfer type CCD imaging device for explaining an embodiment of the present invention.
FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a sectional view along the line shown in FIG. 2, and FIGS. The figure shows. 10 is a substrate semiconductor, 11 is a photoelectric conversion element, 12
is a signal readout area, 16 and 17 are transfer electrodes, 1
9 is a light shielding layer, 22 is a first photosensitive resin layer, and 23 is a second photosensitive resin layer.

Claims (1)

[Claims] 1. In manufacturing a solid-state imaging device comprising a group of photoelectric conversion elements arranged in a mosaic pattern on the same semiconductor substrate and a light-shielded signal readout group provided between adjacent photoelectric conversion elements to read signal charges, the solid-state imaging device After forming the first photosensitive resin, the first photosensitive resin is applied to the main surface of the solid-state imaging device, and the first photosensitive resin other than the photoelectric conversion area including the photoelectric conversion element and the signal readout group is a step of heat-treating the first photosensitive resin at a softening temperature or higher; and a step of heat-treating the first photosensitive resin at a softening temperature or higher;
a step of applying a second photosensitive resin on the photosensitive resin; a step of leaving the second photosensitive resin so as to correspond to the photoelectric conversion element group by photopolymerization of the second photosensitive resin; The remaining second photosensitive resin is subjected to heat treatment at a temperature higher than the softening temperature of the second photosensitive resin and lower than the heat treatment temperature of the first photosensitive resin, thereby causing the second photosensitive resin to flow. A method of manufacturing a solid-state imaging device, characterized in that: