JP2002009266A - Solid-state image pickup element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup element in which an optical resin protection film having a function of preventing adhesion of dust or the like to its microlenses is formed. SOLUTION: In this manufacturing method, by applying a coating material consisting of solution of an organic solvent, polymethyl methacrylate, using a rotary coating method, microlenses 12 and wirings are buried under a protection film 13 composed of polymethyl methacrylate, and simultaneously the surface of the protection film 13 is finished flatly. In this solid-state image pickup element, (1) dust seldom adheres to the surface of the microlenses, (2) even if dust adheres to the surface of a chip 21, dust can easily be removed by air blow A without gwing any damages to the surface of the chip, (3) even if scratched are given to the surface of the chip, wirings will not be damaged anymore, and (4) since the refractive index of the protection film 13 is very small, intended functions of the solid-state image pickup element can be secured.

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 pickup device having a microlens and a method of manufacturing the same, and more particularly, to a function of preventing dust from adhering to a microlens, a production process and quality control caused by scratches. The present invention relates to a CCD chip in which a protective film made of an optical resin also serving as a protection function for preventing troubles is formed on the chip surface, and a method for manufacturing the CCD chip.

[0002]

2. Description of the Related Art Heretofore, as a solid-state imaging device, a device in which a solid-state imaging device structure, an organic flat film and a microlens are provided in this order on a semiconductor substrate is well known. FIG.
Is a CCD (Charge Coupled Device)
FIG. 3 is a block diagram showing a configuration of a solid-state imaging device using the device.

In FIG. 6, reference numeral 51 denotes an image pickup unit, and reference numeral 5 denotes
Reference numeral 2 denotes a horizontal transfer unit (horizontal CCD) that transfers a charge signal from the imaging unit 51 in the horizontal direction, and reference numeral 53 denotes an output unit that outputs signal charges transferred by the horizontal transfer unit 52. Also,
Reference numeral 54 denotes a light receiving unit (sensor unit) that generates a signal charge corresponding to the amount of received light by performing photoelectric conversion. Reference numeral 55 denotes a read gate for reading a charge signal from the light receiving unit 54, and reference numeral 56 denotes a read gate 55.
Denotes a vertical transfer unit (vertical CCD) for transferring the read signal charges in the vertical direction, and reference numeral 57 denotes a unit pixel (unit cell). A unit pixel 57 is configured by the light receiving unit 54, the readout gate 55, and the vertical transfer unit 56. By arranging the plurality of unit pixels 57 in a planar matrix, the imaging unit 5
1 is configured. Note that a silicon substrate (silicon wafer) is usually used as the semiconductor substrate.

FIG. 7 is a sectional view taken along the line BB of FIG. 6 and shows the structure of the unit pixel 57. In this figure, reference numeral 58 denotes a microlens (OCL: On Chip Len).
s), symbol 59 is an on-chip color filter, symbol 60
Is a flattening film, 61 is a photoelectric conversion unit (sensor),
Reference numeral 62 indicates the optical path region of the color filter, and reference numeral 63 indicates the thickness of the filter layer. In FIG. 7, the received light is condensed by a microlens 58, passes through an on-chip color filter 59, and is photoelectrically converted by a photoelectric conversion unit 61.

As described above, in the conventional solid-state image pickup device, CC
In order to secure or improve the performance (sensitivity, brightness, light-collecting property) of D, the uneven surface of the microlens (OCL) is exposed.

[0006]

However, in the assembling process after the microlenses are formed in the wafer process, it is inevitable that some dust is present in the atmosphere. As shown in FIG. 7, a concave portion 58a is formed between the adjacent microlenses 58, 58, and the width of the concave portion 58a is extremely small.

Therefore, there are the following problems (1) and (2). (1) When dust adheres to the surface of a microlens when processing a wafer in the above assembling process or when assembling a CCD, it is not easy to remove the dust. In particular, as apparent from FIG. 8, when the dust D enters the concave portion 58a, it is difficult to reliably remove the dust D even by using the dicing water flow W or the air blow A. In recent technology, even if the diameter of the dust adhering to the surface of the microlens is as large as about 1 μm, it causes the solid-state imaging device to be defective. For this reason, development of a technique for preventing dust from adhering or easily removing dust even if adhering has been awaited.

(2) Conventionally, in a process of assembling a predetermined solid-state imaging device using a solid-state imaging device, a predetermined surface is formed on a surface of the solid-state imaging device (hereinafter, referred to as a chip or a CCD chip after a dicing process), that is, a chip surface. There is a step of performing the processing by directly contacting the processing members. In this step, as shown in FIG. 9, the wiring 72 provided on the surface of the chip 71 may be damaged for some reason. FIG.
Reference numeral 73 denotes a scratch. In that case, serious troubles occur, such as the production line being stopped for a long time or the product having to be collected from the user. Therefore, there has been a demand for a means for preventing the occurrence of the above-mentioned flaw or preventing the flaw from affecting the wiring 72 or the like (the flaw does not reach the wiring 72 or the like).

The present invention has been made in view of the above problems, and has as its object to provide a function of preventing dust from adhering to microlenses and a function of protecting a production process and quality control caused by scratches. An object of the present invention is to provide a solid-state imaging device having a protective film made of an optical resin, which also serves as a protective film.

[0010]

According to the present invention, there is provided a solid-state imaging device having a solid-state imaging device structure, an organic flat film, and a microlens provided in this order on a semiconductor substrate. Is covered with a protective film made of a colorless and transparent optical resin to bury the uneven surface of the microlens and the wiring under the protective film and finish the surface of the protective film to a flat surface.

In the solid-state imaging device according to the present invention, the surface and the wiring of the microlens are covered with the protective film made of a colorless and transparent optical resin, and the surface of the protective film is finished to a flat surface. . (1) Even if dust adheres to the chip surface,
No dust adheres to the microlens surface. (2) Even if dust adheres to the chip surface,
This can be easily removed without damaging the chip surface by dicing water flow or air blow (spraying of pressurized air) (simplification of cleaning). (3) Even if the chip surface is scratched for some reason, wiring and the like are not damaged. (4) Since the refractive index of the protective film is very small and close to that of air, the protective film does not lower the function of the solid-state imaging device (chip).

The most preferred optical resin is polymethyl methacrylate (PMMA). The reason is that, among the optical resins, polymethyl methacrylate has the lowest refractive index and extremely high transparency.

Further, according to the present invention, there is provided a method for manufacturing a solid-state imaging device, comprising a solid-state imaging device structure, an organic flat film and a microlens provided on a semiconductor substrate in this order. The surface of the microlens is coated with a protective film made of a colorless and transparent optical resin, by applying a coating solution made of a solvent solution of an optical resin by a spin coating method, and then evaporating the solvent to cover the surface and the wiring of the microlens with a protective film made of a colorless transparent optical resin. While burying the uneven surface of the microlens and the wiring under the protective film,
The surface of the protective film is finished to a flat surface.

In this manufacturing method, since a predetermined paint is applied by a spin coating method, a colorless and transparent resin protective film having a flat surface can be formed simply and reliably.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a method of forming a protective film (made of resin) by applying a coating material made of an acrylic resin on the surface of a microlens by a spin coating method. FIG. 2 is a sectional view showing the microlens before forming the protective film. FIG. 3 is a cross-sectional view showing a microlens having a protective film formed thereon. FIG. 4 is an explanatory view showing an action of preventing dust adhesion by the protective film, and FIG. 5 is an explanatory view showing an action of preventing wiring damage by the protective film.

On the surface of the wafer 11 shown in FIG. 2 on which the microlenses 12 have been formed in the wafer process, as shown in FIG. 1, a coating 13a made of polymethyl methacrylate (a solution in which the resin is dissolved in an organic solvent) is spin-coated. After application by the method, the organic solvent contained in the paint is removed by evaporation. As a result, as shown in FIG. 3, the surface of the wafer 11 is covered with a protective film 13 made of a colorless and transparent resin having a flat surface, so that the uneven surface and the wiring (not shown) of the microlens 12 are protected.
3 buried underneath. Thereafter, the wafer is sent to an assembling process.

In the spin coating, while the wafer 11 is rotated at a low speed, the paint 13a is dropped on the center of the wafer 11, and the wafer 11 is rotated at a high speed.
a is spread over the entire surface of the wafer (including the entire surface of the microlenses 12 and the entire area above the wiring (not shown)) to a uniform thickness. Then paint 13
By evaporating and removing the organic solvent in a, the coating film is cured to form the protective film 13.

In the solid-state imaging device of the present invention, it is preferable to use an acrylic resin as the optical resin, and among the acrylic resins, polymethyl methacrylate (wavelength: 5) is used.
The refractive index of light having a wavelength of 89 nm is particularly preferably 1.49). In addition, polystyrene (the refractive index is 1.
60), polydiethylene glycol bisallyl or
Carbonet (CR-39: the refractive index is 1.50) can also be used.

In the method for manufacturing a solid-state imaging device of the present invention, an aqueous or non-aqueous emulsion is prepared by using an optical resin monomer such as polymethyl methacrylate instead of the above-mentioned organic solvent solution of polymethyl methacrylate. After applying these to the wafer surface by a spin coating method, a method of polymerizing the monomer by an appropriate means may be adopted.

In the solid-state imaging device of the present invention, since a predetermined protective film is formed, even if dust D adheres to the surface of the chip 21 as shown in FIG. And the dust D adhering to the chip surface can be easily removed by the dicing water flow W or the air blow A without damaging the chip surface.

Further, as shown in FIG. 5, even if the surface of the chip 21 may be scratched 23 for some reason, the damage scarcely reaches the wiring 22, so that the damage of the wiring 22 is prevented. The effect increases. Furthermore, since the refractive index of the protective film 13 is very small and close to that of air, it is almost optically equivalent to the absence of the protective film. Can be secured.

[0022]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) According to the solid-state imaging device of the present invention, even if dust adheres to the chip surface, the dust does not adhere to the microlens surface. In addition, even if dust adheres to the chip surface,
The air blow can easily remove the chip without damaging the chip surface. Further, even if the chip surface is scratched for some reason, the wiring is not damaged. For this reason, effects such as improvement of yield, improvement of quality, reduction of line stop time, reduction of man-hours, and reduction of complaints due to dust adhesion can be obtained. Further, since the refractive index of the protective film is very small and close to that of air, the intended function of the solid-state imaging device (chip) can be secured.

(2) In the method of manufacturing a solid-state imaging device according to the present invention, a predetermined coating material is applied by a spin coating method, so that a colorless and transparent optical resin protective film having a flat surface and a colorless and transparent surface can be easily and reliably formed. Thus, a solid-state imaging device having excellent characteristics can be provided.

[Brief description of the drawings]

FIG. 1 relates to an embodiment of the present invention and is an explanatory view showing a method of forming a protective film by applying a coating made of an optical resin to a wafer surface by a spin coating method.

FIG. 2 is a sectional view showing a microlens before a protective film is formed.

FIG. 3 is a cross-sectional view illustrating a microlens having a protective film formed thereon.

FIG. 4 is an explanatory view showing an effect of preventing dust from adhering to microlenses and an effect of simplifying cleaning by a protective film.

FIG. 5 is an explanatory view showing a wiring damage preventing action by a protective film.

FIG. 6 is a block diagram illustrating a configuration of a solid-state imaging device using a CCD.

FIG. 7 is a cross-sectional view taken along the line BB of FIG. 6, illustrating a structure of a unit pixel of the solid-state imaging device.

FIG. 8 relates to a conventional solid-state imaging device, and is a cross-sectional view of a microlens and an explanatory diagram showing problems of the solid-state imaging device.

FIG. 9 relates to a conventional solid-state imaging device and is an explanatory view showing a problem of wiring damage caused by a flaw generated on the surface.

[Explanation of symbols]

11 wafer, 12 micro lens, 13a paint (PMMA solution), 13 protective film (made of optical resin), 21
... Chip, 22. Wiring, 23. Scratches, 51. Imaging unit, 52
... horizontal transfer section (horizontal CCD), 53 ... output section, 54 ... light receiving section (sensor section), 55 ... readout gate, 56 ... vertical transfer section (vertical CCD), 57 ... unit pixel (unit cell), 58 ... micro Lens (OCL), 58a recess, 59 on-chip color filter, 60 flattening film, 61 photoelectric conversion unit (sensor), 62 optical path region of color filter, 63 filter layer thickness, 71 chip 72: wiring, 73: scratch, A: air blow, D: dust, W: water flow of dicing

Claims (4)

[Claims] A solid-state imaging device structure on a semiconductor substrate;
In a solid-state imaging device provided with an organic flat film and a microlens in this order, the surface of the microlens and the wiring are covered with a protective film made of a colorless and transparent optical resin, and the uneven surface of the microlens and the wiring are covered with the protective film. A solid-state imaging device, wherein the solid-state imaging device is buried below and has a flat surface on the surface of the protective film. 2. The solid-state imaging device according to claim 1, wherein the optical resin is polymethyl methacrylate. 3. A solid-state imaging device structure on a semiconductor substrate,
In a method for manufacturing a solid-state imaging device having an organic flat film and a microlens provided in this order, a coating made of a solvent solution of an optical resin is applied to a surface of the microlens and a wiring by a spin coating method, and then the solvent is evaporated. Thereby, the surface and the wiring of the microlens are covered with a protective film made of a colorless and transparent optical resin to bury the uneven surface of the microlens and the wiring under the protective film, and the surface of the protective film is flat. A method for manufacturing a solid-state imaging device, comprising: 4. The method according to claim 3, wherein the optical resin is polymethyl methacrylate.