JP4751753B2 - Lens array manufacturing method, lens array, and solid-state imaging device - Google Patents

Description

  The present invention relates to a method of manufacturing a lens array in which a large number of condenser lenses are arranged.

  In recent years, in solid-state imaging devices, the number of imaging pixels has been increasing to more than gigapixels, and miniaturization of the devices is also increasing. Under such circumstances, improvement in sensitivity is required, and the sensitivity cannot be improved only by the uppermost on-chip lens formed on the color filter, and a lens is further provided between the on-chip lens and the sensor unit. There has been proposed a technique for forming a (intralayer lens) to enhance a light collecting function. As an example of the intra-layer lens, there is an intra-layer upward convex lens that forms a lens having a convex surface on the light incident side on a surface flattened by filling a step due to a transfer electrode or the like.

  As an example of the manufacturing method of the in-layer upward convex lens, there is a method of dry etching the laminated film of the lens material film and the resist of the in-layer upward convex lens. This is a method of depositing a lens material film, patterning a resist on the lens material thereon, and then transferring the lens shape of the resist to the lens material film by dry etching.

  There has also been proposed a method for increasing the sensitivity by adjusting the focal length of the lens to a desired distance over a wide range (see Patent Document 1). In this method, a lens-shaped resist mask is formed on the layer of the upper convex lens material in the layer, and the lens shape of the resist mask is transferred to the layer of the upper convex lens material in the layer by an etch back method to form the upper convex lens in the layer. The focal length is adjusted by the etch back amount.

  Thus, by providing the upper convex lens in the layer under the on-chip lens by the microlens, the incident light can be condensed in two stages, and more light can be incident on the light receiving unit. The sensitivity of the solid-state imaging device can be improved as compared with the case where only the film is formed.

JP 2000-164837 A

  An object of this invention is to provide the manufacturing method of the lens array which can manufacture easily the lens array which arranged many condensing lenses represented by the in-layer convex lens.

The method of manufacturing a lens array according to the present invention is a method of manufacturing a lens array in which a large number of condensing lenses are arranged on a flat surface, and a lens pattern forming step of forming an inorganic lens material film pattern on the flat surface And by changing the pattern of the inorganic lens material film by sputter etching using a gas obtained by adding a CxHyFz-based reactive gas (x> 0, y ≧ 0, z> 0) to an inert gas, the reaction product of the reactive gas and the inorganic lens material is deposited between the pattern seen including a lens forming step of forming the plurality of condensing lenses, the lens material of the inorganic oxide or silicon nitride The inert gas is argon gas, and the reactive gases are CF ₄ and CHF ₃ .

  The lens array of the present invention is manufactured by the above manufacturing method.

  The solid-state imaging device of the present invention includes the lens array.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the lens array which can manufacture easily the lens array which arranged many condensing lenses represented by the in-layer convex lens can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial cross-sectional schematic view of a solid-state image sensor for explaining a method of forming an upward convex lens that is an intra-layer lens of a CCD type solid-state image sensor according to an embodiment of the present invention.
For example, the upward convex lens is formed on the planarized insulating film after the step formed by the charge transfer electrode and the light shielding film formed on the silicon substrate is filled with the insulating film and planarized. A film indicated by reference numeral 15 in FIG. 1 is a flattened insulating film (hereinafter referred to as a flattened film 15) that constitutes the formation surface of the upward convex lens.

  First, an inorganic lens material film 16 serving as a material for an upwardly convex lens such as silicon oxide or silicon nitride is formed on the planarizing film 15, and is patterned by photolithography and etching to form a pattern of the lens material film 16. (FIG. 1A). In FIG. 1A, the lens material film 16 is viewed as a flat film having a thickness between the surface of the planarization film 15 and the surface farthest from the surface of the planarization film 15 of the lens material film 16. The lens material film 16 has a hole k between the patterns. The pattern of the lens material film 16 is a pattern corresponding to the photodiode below it.

Next, the pattern of the lens material film 16 is deformed by sputter etching using a gas obtained by adding a CxHyFz-based reactive gas (x> 0, y ≧ 0, z> 0) to an inert gas such as argon. The reaction product of the added reactive gas and the lens material film 16 is deposited between the patterns of the lens material film 16 (FIG. 1B). For example, when the lens material film 16 is a silicon nitride film, sputter etching is performed using a gas obtained by adding CHF ₃ to argon gas at 5% or more of the total flow rate and setting the RF frequency to a low frequency (1 MHz or less). Thus, both deformation of the pattern of the lens material film 16 and deposition of the reaction product can be realized. This is because, when the RF frequency is set to a low frequency in the sputtering apparatus, depending on the type of CxHyFz-based reactive gas added to the inert gas, the reaction product of the reactive gas and the lens material film 16 is generated during sputter etching. This is because it can be deposited in the hole k.

  When the sputter etching is finished, an insulating film 17 is formed to protect the upper convex lens (FIG. 1C). By such a method, the pattern of the etched lens material film 16 becomes an upward convex lens convex toward the light incident side. This upward convex lens becomes a condensing lens having a function of condensing light on a photodiode below the convex lens.

  If sputter etching is performed from the state of FIG. 1A without adding a reactive gas, the upper end portions of the pattern of the lens material film 16 are brought into contact with each other by deposits, and voids are generated between the upper convex lenses. As a result, the light collection efficiency is reduced, leading to a reduction in sensitivity. In addition, it is difficult to obtain a beautiful lens shape. On the other hand, according to the method of the present embodiment, the occurrence of this void can be suppressed, so that the light collection efficiency can be increased and the sensitivity of the solid-state imaging device can be improved. In addition, since the reaction product can be deposited in the hole k by adjusting the RF frequency, the shape control of the upward convex lens is facilitated. Further, since the reaction product can be deposited in the hole k, a large number of completed upward convex lenses can be made gapless, and the light collection efficiency can be further increased.

  Further, according to the method of the present embodiment, after forming the pattern of the lens material film 16, it is possible to form an upward convex lens only by performing sputter etching. Can be reduced.

Example 1
In FIG. 1A, the material of the planarizing film 15 is silicon nitride, the material of the lens material film 16 is silicon nitride, the film thickness of the lens material film 16 is 0.4 μm, and the distance between patterns is 0.3 μm. Then, an upward convex lens was manufactured by performing sputter etching under the following conditions. As a result, generation of voids between the patterns of the lens material film 16 could be suppressed. Further, reactive organisms could be deposited on the bottom of the hole k, and a gapless upward convex lens could be formed.
<Sputter etching conditions>
Gas composition: Ar (750 sccm), CF ₄ (25 sccm), CHF ₃ (50 sccm)
Pressure: 500mTorr
RF power: 900W
RF frequency: 0.38 MHz
Susceptor temperature: 0 ° C

(Example 2)
In FIG. 1A, the material of the planarizing film 15 is silicon oxide, the material of the lens material film 16 is silicon oxide, the film thickness of the lens material film 16 is 0.6 μm, and the distance between patterns is 0.3 μm. Then, an upward convex lens was manufactured by performing sputter etching under the following conditions. As a result, generation of voids between the patterns of the lens material film 16 could be suppressed. Further, reactive organisms could be deposited on the bottom of the hole k, and a gapless upward convex lens could be formed.
<Sputter etching conditions>
Gas composition: Ar (300 sccm), CHF ₃ (40 sccm), CF ₄ (20 sccm)
Pressure: 500mTorr
RF power: 900W
RF frequency: 0.38 MHz
Susceptor temperature: -10 ° C

The partial cross section schematic diagram of the solid-state image sensor for demonstrating the formation method of the upward convex lens which is the inner lens of the CCD type solid-state image sensor which is embodiment of this invention

Explanation of symbols

15 Planarizing film 16 Lens material film 17 Insulating film k Hole

Claims (3)

A method of manufacturing a lens array in which a large number of condenser lenses are arranged on a flat surface,
A lens pattern forming step of forming a pattern of an inorganic lens material film on the flat surface;
The pattern of the inorganic lens material film is deformed by sputter etching using a gas obtained by adding a CxHyFz-based reactive gas (x> 0, y ≧ 0, z> 0) to an inert gas, and the reactivity the reaction product of the lens material of the inorganic gas is deposited between the pattern seen including a lens forming step of forming the plurality of condensing lenses,
The inorganic lens material is silicon oxide or silicon nitride;
The inert gas is argon gas;
Production method of the reactive gas, the lens array is a CF ₄ and CHF _3. A lens array manufactured by the manufacturing method according to claim 1 . A solid-state imaging device comprising the lens array according to claim 2 .

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