JPH05145813A - Manufacture of micro lens for solid-state image pickup element - Google Patents

Abstract

PURPOSE:To provide the micro lens for the solid-state image pickup element in which an inter-lens gap is eliminated to enhance the light collection rate. CONSTITUTION:A transparent resin material is applied onto a solid-state image pickup element 1 through rotation to form a flat layer 2, a transparent resin material layer of thermoplastic type is formed onto the flat layer 2 as a lens layer through rotary coating, patterning is implemented by the photolithogoraphy to form a transparent resin layer pattern onto a light receiving section. Then a drooping is caused to a circumferential part of the resin layer pattern through heat treatment to form a background micro lens 3. Then a transparent film 4 is depositted till an inter-lens gap G is eliminated isotropically at a temperature below the softening point of the background micro lens 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a microlens formed on a solid-state image pickup device.

[0002]

2. Description of the Related Art Generally, a solid-state image pickup device such as a CCD has a photoelectric conversion portion and a signal reading portion on a main surface of a semiconductor. Therefore, the area actually contributing to photoelectric conversion depends on the element size. Limited to ~ 50%. As a means for solving this drawback, a method has conventionally been proposed in which a solid-state imaging device is combined with a condensing microlens array to condense incident light on a photoelectric conversion unit. A method for forming such a microlens is described in, for example, Japanese Patent Publication No. 60-597.
No. 52, Japanese Patent Application No. 3-74441, Japanese Patent Application No. 3-1571
No. 0 etc. have been proposed.

FIG. 4 is a sectional view showing a structural example of a conventional solid-state image pickup device having a microlens. In the figure,
Reference numeral 101 is a substrate made of p-type silicon, and 102 is an n ⁺ -type diffusion region, which corresponds to the photoelectric conversion light receiving portion. 103 is an Al wiring for signal detection, and a passivation film 104 is formed on the entire surface including the Al wiring 103. Then, on the passivation film 104, microlenses 105 are arranged corresponding to the photoelectric conversion light receiving portions.

The microlens 105 is usually formed by the following process. That is, first, as shown in FIG. 5A, a material that is optically colorless and has a high light transmittance, such as a resin such as PMMA (polymethylmethacrylate), is formed on the semiconductor substrate 101 including the light receiving portion 102 and the transfer portion. Is applied by a spin coating method to form a flat layer 105a. Subsequently, as shown in FIG. 5B, a transparent layer is formed by applying a material that is also optically colorless and has a heat softening property by a spin coating method to form a transparent layer, and a microlens forming portion of the transparent layer. The edges of the transparent layer pattern 105b are removed by photolithography to form a transparent layer pattern 105b. Then, heat treatment at a temperature equal to or higher than the thermal softening point causes sagging in the peripheral portion of each transparent layer pattern 105b to form the microlens 105.

[0005]

As described above, the condensing ability can be obtained by forming the microlens 105 on the solid-state image pickup device. To increase the condensing rate by the microlens, as shown in FIG. It is necessary to make the gap G between the respective lenses shown smaller. However, the gap G is required to be about 0.8 μm even if the gap G is small due to the restriction in forming the transparent layer pattern for forming the microlens by the photolithography technique. That is 0.8 μm
In the gaps below, it is difficult to form a space stably in the light-transmitting layer that is the lens material due to the resolution during photolithography, and the sag around the pattern due to the subsequent heat treatment above the thermal softening point. This is because there is a problem that it is very difficult to control the shape at the time of causing the phenomenon.

The present invention has been made in order to solve the above-mentioned problems in the conventional method for manufacturing a microlens, and manufactures a microlens for a solid-state image pickup device in which a gap between lenses is eliminated to increase the light collection rate. The purpose is to provide a method.

[0007]

In order to solve the above problems, the present invention provides a method for manufacturing a microlens for a solid-state image pickup device, wherein a microlens is directly formed on the solid-state image pickup device. A step of forming a heat-softening type transparent resin layer on the entire light receiving side, a step of patterning the transparent resin layer so as to be located in each light receiving portion of the solid-state imaging device, and a step of heating and melting the transparent resin layer pattern The process for forming the transparent resin layer pattern on the convex lens and the process for depositing and forming a transparent film on the entire surface of the convex lens at a temperature lower than the melting temperature of the transparent resin layer so as to eliminate the gap between the convex lenses A lens is manufactured.

As described above, the transparent film is formed on the entire surface of the convex lens having a gap between the lenses formed by heating and melting the transparent resin layer pattern provided corresponding to the light receiving portion of the solid-state image pickup device at low temperature. By depositing and forming so as to eliminate the gap between them, a microlens having a high light collection rate without a gap portion can be obtained.

[0009]

EXAMPLES Next, examples will be described. FIG. 1 is a manufacturing process diagram for explaining a first embodiment of a method for manufacturing a microlens for a solid-state image sensor according to the present invention. As shown in FIG. 1A, first, an optically transparent resin material such as P is formed on a solid-state image sensor 1 including a light receiving portion, a transfer portion, and the like.
GMA (polyglycidyl methacrylate) or the like is applied by spin coating to form the flat layer 2 with a desired thickness. Next, an optically transparent and heat-softening type resin material layer is similarly formed as a lens layer on the flat layer 2 by spin coating, and then patterning is performed corresponding to the light receiving portion by an ordinary photolithography technique to receive light. A transparent resin layer pattern is formed on the part. Next, heat treatment at a temperature equal to or higher than the thermal softening point causes sagging in the peripheral portion of the transparent resin layer pattern,
A base microlens 3 having a convex lens shape is formed. At this time, the inter-lens gap G is set to about 1.0 μm, which corresponds to the blank space at the time of photolithography of the transparent resin layer pattern to be the lens and which can easily obtain the resolution.

Next, as shown in FIG. 1B, an optically transparent film 4 isotropically formed by forming an optically transparent film 4 that can be formed at a temperature equal to or lower than the thermal softening point of the transparent resin material forming the underlying microlens 3. Deposition is performed until the gap G between the lenses 3 disappears, that is, about 0.5 μm thick. For example, photo CVD and plasma CVD used when forming an oxide film of a semiconductor.
According to the method described above, an isotropic transparent oxide film can be formed within a temperature range from room temperature to about 120 ° C. which does not exceed the softening point of the lens resin material. There is no fear that the base microlens 3 will be deformed.

When the transparent film 4 isotropically formed on the base microlens 3 in this manner, an ideal lens shape having no inter-lens gap can be obtained, as shown in FIG. 1B. Note that the isotropic transparent film 4 formed on the underlying microlens 3 is not limited to the CVD method, and any method can be used as long as it is a method capable of forming an isotropic film below the thermal softening point of the lens constituent material. Is. Further, the optically transparent film 4 is not particularly limited to an oxide film, and can be similarly used as long as it is transparent and can be isotropically formed at a low temperature.

Next, a second embodiment will be described with reference to FIG. First, the base microlens 3 is formed as shown in FIG. 1A by the same method as in the first embodiment. At this time, the inter-lens gap G is similarly set to about 1.0 μm. Subsequently, as shown in FIG. 2, spin coating using spin-on-glass (SOG), which is used for flattening the interlayer insulating film of the semiconductor, is performed and sintered at a temperature lower than the thermal softening point of the lens resin material. The oxide film 5 is obtained. FIG. 2 shows the lens shape after the oxide film 5 of SOG is deposited and formed on the base microlens 3 as described above. According to this method, the gap portion that has been generated conventionally is almost eliminated, and a microlens having a high light collection rate can be easily formed.

As can be seen from FIG. 2, since the oxide film 5 is formed on the base microlens 3 by spin coating,
The oxide film 5 is not isotropically formed, the thickness T _OX 2 of the oxide film 5 formed in the inter-lens gap portion is large, and the thickness of the oxide film 5 formed on the top of the underlying microlens 3 is large. T _OX 1 has a thin film forming characteristic. As a result, the final curvature of the microlens becomes larger than that of the base microlens 3. Therefore, in consideration of the change in curvature due to the oxide film 5 formed of SOG, the curvature of the base microlens 3 is made smaller than the final design curvature in advance by a method such as thickening the film thickness of the base microlens 3 during coating. I need to leave.

Next, a third embodiment will be described with reference to FIG. Also in this embodiment, first, the base microlens 3 is formed as shown in FIG. 1A by the same method as in the first embodiment. At this time, the inter-lens gap G is similarly set to about 1.0 μm. Next, as shown in FIG. 3, the flat layer 2 and the base microlens 3 are formed by a dry etching method such as reactive ion etching (RIE) generally used in the semiconductor etching process. Etching is performed until the inter-lens gap G disappears under the condition that the selection ratio is 1.

At this time, due to the shape of the base microlens 3, the etching species incident on the lens bottom and the vicinity of the gap are subjected to ion scattering 6 on the lens surface as shown in FIG. 3, and as a result, only the gap is etched. Increase in quantity,
The finally formed microlens 7 has a shape with no gap. Therefore, also by this method, it is possible to easily form the high-condensation microlens in which the gap portion has almost disappeared.

[0016]

As described above on the basis of the embodiments,
According to the present invention, after forming a convex lens by heating and melting, a transparent film is deposited and formed on the convex lens so that the gap between the convex lenses is eliminated, or the surface of the convex lens is removed by etching so that the gap between the convex lenses is eliminated. Since this is done, the gap between the lenses disappears, and it is possible to easily realize a microlens having a higher light collection rate than in the past.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram for explaining a first embodiment of a method for manufacturing a microlens for a solid-state image sensor according to the present invention.

FIG. 2 is a manufacturing process drawing for explaining the second embodiment.

FIG. 3 is a manufacturing process drawing for explaining the third embodiment.

FIG. 4 is a cross-sectional view showing a configuration example of a conventional solid-state imaging device including a microlens.

FIG. 5 is a diagram showing a manufacturing process of a microlens of the solid-state imaging device shown in FIG.

FIG. 6 is a diagram showing a gap between microlenses in a conventional solid-state imaging device.

[Explanation of reference numerals] 1 solid-state imaging device 2 flat layer 3 base microlens 4 transparent film 5 SOG oxide film 6 ion scattering 7 microlens

Claims (3)

[Claims] 1. A method of manufacturing a microlens for a solid-state image pickup device, wherein a microlens is directly formed on the solid-state image pickup device, a step of forming a heat-softening type transparent resin layer on the entire light receiving side of the solid-state image pickup device, Patterning the transparent resin layer so as to be positioned in each light receiving portion of the solid-state imaging device; heating and melting the transparent resin layer pattern to form each transparent resin layer pattern on a convex lens; And a step of depositing a transparent film at a temperature lower than the melting temperature of the transparent resin layer so that the gap between the convex lenses is eliminated. 2. A transparent film formed on the convex lens is C
The method of manufacturing a microlens for a solid-state image pickup device according to claim 1, wherein the microlens is formed by a VD method or a spin-on-glass method. 3. A method of manufacturing a microlens for a solid-state image pickup device, wherein a microlens is directly formed on the solid-state image pickup device, wherein a transparent base transparent film is formed on the entire light-receiving side of the solid-state image pickup device, and then the heat-softening type is formed. Forming a transparent resin layer, patterning the transparent resin layer so as to be positioned in each light receiving portion of the solid-state imaging device, and heating and melting the transparent resin layer pattern to form each transparent resin layer pattern into a convex lens. A solid comprising a step of forming and a step of removing a part of the surface of the convex lens by a dry etching method and a part of the base transparent film to eliminate a gap between the convex lenses. A method for manufacturing a microlens for an image sensor.