JP2555893B2 - Method of manufacturing solid-state imaging device - Google Patents

Description

The present invention relates to a solid-state imaging device, and more particularly to a method for manufacturing a solid-state imaging device having a light collector on its surface.

[Conventional technology]

In a solid-state imaging device, high sensitivity is an important point in terms of characteristics, but there is a limit to improvement in sensitivity due to improvement of a conventional semiconductor structure as the device has a higher pixel density. Therefore, in recent years, a method of forming a convex light collector on the surface of the device and collecting the incident light on the photoelectric conversion unit to improve the sensitivity has been put into practical use.

FIG. 2 is a cross-sectional view of a conventional solid-state imaging device having a light collector formed on its surface. A light receiving portion 202, a charge transfer portion (not shown), and a light shielding film 203 are sequentially formed on the surface of the semiconductor substrate 201.
Next, the transparent flattening layer 204 is provided inside the color filter layer 206.
Then, the light collector 205 is formed on the surface of the transparent flattening layer 204.

The light collector 205 is made of a material having a relatively low softening temperature such as a novolac photoresist, and after patterning,
For example, a convex condensing body is formed corresponding to each light receiving part by melting (reflowing) at a temperature of 150 ° C.

[Problems to be Solved by the Invention]

The light collector 205 having such a conventional structure has the following problems. That is, when the light collector 205 is formed by using a heat-deformable resin having a low softening temperature such as photoresist, the temperature of the light collector 205 is sufficiently controlled so that the light collector 205 is uniform in the same chip.
Even when the light-collecting body 205 is formed, the photoresist may be melted again in the heat step after the light-collecting body 205 is formed, and the shape of the light-collecting body 205 may change. For example, in the assembly process, bonding, chip attachment, and encapsulation in a container, the temperature may range from approximately 150 ° C to approximately 180 ° C.
Each time the heat of ℃ is applied, the shape of the light collector 205 is deformed.

Therefore, there is a problem in that the shape of the light collector 205 varies within the same chip, resulting in variation in sensitivity of the device, or inability to obtain desired sensitivity.

As a countermeasure for this, a method of forming the light collector 205 in advance with a material having a high softening temperature (about 200 ° C) is possible.
When a temperature of not less than 0 ° C. is applied to the semiconductor substrate during the formation of the light collector 205, the color filter layer 206 formed under the light collector 205, for example, which stains the chromosome subject made of casein or gelatin, is decolorized, and the color is removed. There was a problem that defects such as unevenness occurred.

[Means for solving the problem]

According to the present invention, a plurality of light receiving portions and charge transfer portions are formed on one main surface of a semiconductor substrate, and a transparent flattening layer having a color filter layer therein is formed on the light receiving portions, and then the transparent flattening layer is formed. Patterning a photoresist having a softening temperature lower than the decolorization temperature of the color filter layer, and heat-treating the photoresist at a temperature lower than the decolorization temperature of the color filter layer to form a convex light collector, After that, the solution containing a silane coupling agent which is a curing agent for the light collector is used to cure the light collector by a dip method, and then an assembly process is performed at a temperature lower than the decolorization temperature of the color filter layer. It is a thing.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor chip according to one embodiment of the present invention. A light receiving section 102, a charge transfer section (not shown), and a transparent film 103 are sequentially formed on the surface of the semiconductor substrate 101. Next, the transparent flattening layer 104 is applied to PGMA (polyglycidyl metalate) or PMMA.
Approximately by spin coating method such as (polymethylmethacrylate)
Form a thickness of 3.0 μm. At this time, the color filter layer 108 is embedded in the transparent flattening layer 104.

Next, for example, a positive type photoresist is patterned by a normal lithography technique, and after irradiating the entire surface with light to have a transmittance of 95% or more in a visible light region, heat treatment is performed at about 150 ° C. to form light on each light receiving unit 102. Correspondingly, the first light collector transparent layer 105 is formed.

Next, after forming the first light-collecting body transparent layer 105,
By hardening the surface of the first light-collecting body transparent layer 105, a hardened layer 106 having a thickness of about 2000Å to 3000Å can be formed as a second light-collecting body transparent layer. The cured layer 106 can prevent the reflow of the first light-collecting body transparent layer 105 due to heat in a later step. Such curing treatment is
For example, it is suitable to treat the semiconductor substrate on which the first light-collecting body transparent layer 105 is formed with a solution containing a silane coupling agent by a dip method.

Next, one reference example of the present invention will be described. After forming the first light-collecting body transparent layer 105, the softening temperature is higher than that of the first light-collecting body transparent layer 105 (about 200 ° C.), for example, PGMA, PMMA, or deep UV whose light absorption wavelength is 400 nm or less. The first condensing body transparent layer having a thickness of about 1000-2000Å
The second light-collecting body transparent layer 106 is deposited on the layer 105 to form a solid-state imaging device.

This second light-collecting body transparent layer 106 is the first light-collecting body transparent layer 105.
Since the first light-collecting layer 105 is on the surface, the first light-collecting layer 105 is pressed down by the second light-collecting layer 106 even if heat is applied in the step after the light-collecting body is formed. There is nothing to do.

〔The invention's effect〕

As described above, according to the present invention, by curing the surface of the first light collector transparent layer made of a photoresist film or the like having a low softening temperature, for example, by the heat applied in the assembly process after the light collector is formed. This has the effect of preventing the first light-collecting body transparent layer from being remelted and deformed. This makes it possible to stably form a high-sensitivity solid-state imaging device.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view for explaining a conventional structure. 101,201 …… Semiconductor substrate, 102,202 …… Light receiving part, 103,203
...... Light shielding film, 104,204 …… Transparent flattening layer, 105,106,107,2
05 …… Light collector.

Claims (1)

(57) [Claims] 1. A transparent flattening layer after forming a plurality of light receiving portions and charge transfer portions on one main surface of a semiconductor substrate and a transparent flattening layer having a color filter layer therein on the light receiving portions. A photoresist having a softening temperature lower than the decolorization temperature of the color filter layer is patterned on the layer, and the photoresist is heat-treated at a temperature lower than the decolorization temperature of the color filter layer to form a convex light collector. Then, the condensing body is cured by a dip method using a solution containing a silane coupling agent which is a curing agent for the condensing body, and then assembled at a temperature lower than the decolorization temperature of the color filter layer. A method for manufacturing a solid-state imaging device, comprising: