JP2013131613A - Manufacturing method of color solid-state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve removal of resin of a synthetic resin layer deposited on a pad and the bottom of scribing, and peeling of an antireflection layer by resist patterning of only once, and to employ a silica film as an antireflection layer in place of a fluoride based antireflection layer in the manufacturing process.SOLUTION: The manufacturing method of a color solid-state image sensor including at least a planarization layer, a color separation filter, a microlens, and an antireflection layer on a solid-state image sensor includes a step for providing an SiOlayer, as an antireflection layer, on the microlens, applying a resist, providing an aperture in the resist at a part not requiring the SiOlayer by photolithography, and removing the exposed SiOlayer by a dry etching method using a fluorine-based gas.

Description

  The present invention relates to rationalization and simplification of a manufacturing method of a color solid-state imaging device including a microlens array coated with an antireflection film on a color filter, and particularly relates to a technology for cleaning connection pads and the like.

  Digital cameras and mobile phone cameras are mainly composed of charge coupled (CCD) or complementary oxide semiconductor (CMOS) solid-state image sensors, and color filters and microlens arrays are combined on the solid-state image sensors. The camera module which modularizes the color solid-state image sensor provided with the on-image sensor color filter is mounted.

  The solid-state imaging device itself is manufactured by a semiconductor process using a silicon wafer having a diameter of 20 to 30 cm. Although the on-image sensor color filter is similar, it is processed in a separate process, and finally cut in a dicing process and then packaged into one camera module. In the case of a camera attached to a mobile phone, if the size of the solid-state imaging device is only about 3 mm square, about 1500 to 2800 pieces can be taken from one wafer having a diameter of 20 cm.

  By the way, the light receiving unit corresponding to the pixel of the solid-state imaging device is a photoelectric conversion device that generates an electric signal by reacting the device when receiving light. However, since the light receiving element as a photoelectric conversion element is an element that simply reacts to the brightness of light, a color image cannot be obtained as it is. Therefore, a color separation filter consisting of red, blue, green or cyan, magenta, yellow, and green is regularly formed in front of each light receiving element, and the light from the subject is separated into three or four colors and then photoelectrically separated. It has been converted.

  Furthermore, when the number of pixels of the camera reaches 10 million and the light receiving portion is miniaturized, the area of the light receiving element is reduced, and the amount of wasted light incident between the pixels is relative to the amount of light incident on the light receiving portion. Will increase. Therefore, the gap between the pixel and the lens is narrowed (about 0.05 μm or less), and at the same time, the microlens for refracting the light incident between the light receiving parts and guiding it to the light receiving part is provided for each pixel such as red, blue, and green. The sensitivity of the photoelectric conversion element is increased by laying on the top.

  However, a microlens made of a transparent resin such as an acrylic resin has a surface reflection of about 4.5% to 5.5% and is required to be improved. Therefore, in order to reduce surface reflection, the lens surface is covered with an inorganic insulating film having a refractive index smaller than that of the lens material, and the reflectance is suppressed to about 3.5%.

  On a wafer substrate on which a large number of solid-state image sensors are multifaceted, various processes for colorization as described above are performed collectively on the entire wafer surface to form a color solid-state image sensor substrate. This substrate is cut and used for each image sensor, and the outer periphery of the image sensor 1 is connected to a metal terminal for connection to the outside as shown in FIGS. 1 (a) and 1 (f). 6 (hereinafter, simply referred to as a pad) and a scribe (not shown) for partitioning the imaging elements, and an organic film and an inorganic film applied during the processing are equally laminated thereon. May remain.

The individual solid-state imaging device 1 is finally mounted on a resin substrate or a lead frame, and the connection terminal is connected to a predetermined terminal of the substrate by wire bonding or flip imaging device connection. It is necessary to peel off and remove the material laminated in the processing process from the terminal 6 for use, scribe, etc., and to return the surface to the original clean state.

JP 2000-150843 A JP 2002-214436 A

  FIG. 1F shows the structure of the color solid-state imaging device 1 in a cross-sectional view. The portion below the broken line is a solid-state image pickup device portion of CCD or CMOS, and the details of the structure are omitted, but on this, the planarization layer 4, the color separation filter 3, the lens array 2 and the like are photolithography. Patterned by the method.

  Briefly, the surface of the CMOS has irregularities, and forming the color separation filter 3 directly causes color unevenness. Therefore, there is a flattening layer 4 of about 1 μm for smoothing the wafer surface.

  On the flattening layer 4, a color separation filter 3 composed of red, green, and blue pixels having a thickness of approximately 1.0 to 2.0 μm is formed by a regular photolithography method. An antireflection layer may be formed between the flattening layer 4 and the color separation filter 3 (not shown in the figure). The planarization layer 4 may also serve as an antireflection layer.

  In addition, there is a step between the red, blue, and green pixels of the color separation filter 3 and a protection that also serves as a flattening layer on the color separation filter in order to prevent the color components from diffusing to the surroundings due to heat or the like. A layer may be formed (not shown).

  On the color separation filter 3 or the protective layer, a dome-shaped microlens 2 having a predetermined height in the range of 1.0 to 3.5 μm is formed for each pixel (light receiving portion). Further, an antireflection layer 7 made of an inorganic insulating film such as fluoride or silica is formed on the surface.

  Therefore, a coating layer that has not been removed by the patterning process is left on the electrode pad 6 or the bottom of the scribe (not shown, cutting groove) on which an object should not be placed. ing. At least the antireflection layer 7 made of an inorganic material and the synthetic resin layer composing the microlens 2 are laminated. In some cases, the planarizing layer 4 and the synthetic resin layer of the filter 3 may remain.

  Therefore, only the connection pad 6 and the scribe portion are exposed, and the other portions are covered with a resist, and then dry etching that dissolves an extra synthetic resin layer in a solvent from the upper layer or plasma irradiation or ion irradiation is used. They are removed sequentially by either etching.

  An example is shown below. Further, to clean the scribe portion (not shown) on the pad 6 is referred to as “resin removal”, and the objects to be resin-removed are collectively referred to as synthetic resin.

When the microlens 2 is not covered with the antireflection layer 7, the microlens 2 is an acrylic or novolac synthetic resin, and these on the pad are removed by dry etching of O ₂ gas.

A peeling technique including resin removal when a fluoride-based antireflection film is formed is disclosed in Patent Document 1. In this technique, resin removal of a synthetic resin such as a microlens composition is performed by O ₂ dry etching as usual, as shown in FIGS. 1 (a) to 1 (f), and the removal of the antireflection film on the pad is performed. The lift-off method using a resist layer is used.

  Specifically, the synthetic resin layers such as the planarizing layer 4 and the microlens 2 are laminated on the pad 6, but before the antireflection layer 7 is formed on the entire surface of the wafer, the first lift-off layer is formed on the pad. The resist pattern 5 is formed (FIG. 1A). Then, after the formation of the antireflection layer ((b) in the same figure), the first resist pattern 5 is dissolved and removed. At this time, the antireflection layer 7 on the resist is also washed away and does not remain on the pad 6. (FIG. (C)).

Thereafter, the antireflection layer 7 on the microlens 2 is protected from damage caused by subsequent dry etching, and the pad 6 is an opening for dry etching the synthetic resin deposited thereon. The second resist pattern 9 is formed, and the synthetic resin layer 2 is removed by O ₂ dry etching. Finally, the second resist 9 is peeled off.

  The above resin removal method requires two resist patterning steps for lift-off and dry etching, and the process is long, leading to a reduction in productivity and a good product yield.

  Therefore, in view of the above problems, the present invention realizes the resin removal of the synthetic resin layer deposited on the pad and the bottom of the scribe and the removal of the antireflection layer by only one resist patterning, and the antireflection of the fluoride system. Instead of the film, it was an object to make a process capable of adopting a silica film as an antireflection film.

The invention according to claim 1 for achieving the above object is a method for manufacturing a color solid-state image pickup device comprising at least a flattening layer, a color separation filter, a microlens, and an antireflection layer on the solid-state image pickup device. After providing a SiO ₂ layer on the microlens as a prevention film, a resist is applied, an opening is provided in the resist where the SiO ₂ layer is unnecessary by photolithography, and a fluorine-based gas is used for the exposed SiO ₂ layer The present invention provides a method for manufacturing a color solid-state imaging device, including a step of removing by a dry etching method.

In addition, the invention according to claim 2 includes a step of subsequently removing the synthetic resin layer exposed to the opening and below the resin layer composing the microlens by a dry etching method using O ₂ gas. The method of manufacturing a color solid-state imaging device according to claim 1.

The invention according to claim 3 is the method for producing a color solid-state imaging device according to claim 1 or 2, wherein the fluorine-based gas is a C ₃ F ₈ gas. .

According to the present invention, the fluorine-based gas C ₃ F ₈ was used for dry etching, so that the SiO ₂ layer could be adopted as the antireflection film of the microlens by the plasma CVD method with high wafer process compatibility. This is superior in chemical stability to low-temperature film formation as compared with fluoride-based films.

According to the present invention, by continuously using a resist pattern formed in a single resist patterning process, it is possible to remove the material used for forming the SiO ₂ layer and the microlens, and a significant streamlining of the process is achieved. It was.

The resist pattern surface hardened by dry etching using C ₃ F ₈ gas is O
As a result of the removal in the dry etching step ₂ , there was a secondary effect that the resist in the final step can be easily removed.

It is a figure of the cross-sectional view explaining the peeling method of the antireflection layer by a prior art. (A) ~ a synthetic resin layer (e) SiO ₂ anti-reflection film is a cross-sectional view showing the portion of the resin vent to process. (F) ~ and a synthetic resin layer (j) SiO ₂ anti-reflection film is a cross-sectional view showing the portion of the resin vent to process. (A)-(e) It is process drawing of the cross sectional view explaining the resin removal method which becomes this invention.

  As shown in FIG. 2, the color solid-state imaging device according to the present invention is manufactured according to the following procedure with the solid-state imaging device 1 as a given one. However, the planarization layer 4 and the color separation filter 3 are predetermined. These are manufactured by a conventional photolithography method using a colored or transparent photosensitive pigment resist, and details thereof are omitted.

  The microlens 2 in this example was formed on the color separation filter 3 by using a novolac resin by heat flow or by a transfer method using an acrylic resin. In the heat flow method, a novolac resin to which a naphthoquinone diazide having a predetermined thickness was added was divided by a photolithography method so as to correspond to each light receiving part. When the divided resin portion is heated and liquefied by thermoplasticity, the resin portion is spontaneously deformed into a dome shape, and then the shape is spontaneously fixed by thermosetting. The height of the microlens 2 was set to a predetermined value in a range of approximately 1.3 to 3.5 μm.

  In the transfer method, a lens matrix is formed on a transparent acrylic resin layer, which is a microlens material, using a resist material that has alkali solubility, photosensitivity, and heat flow, by photolithography and thermal reflow, and is then dry etched. The shape of the lens matrix was transferred to the underlying acrylic transparent resin layer by the method.

The SiO ₂ layer serving as the antireflection layer 7 is an image sensor substrate on which a microlens is formed with a thickness of about 90 nm by a plasma CVD method using a mixed gas of TEOS, O ₂ and He under a low temperature condition of 150 ° C. or less. To form a film.

However, O ₂ gas can decompose and remove synthetic resin, but cannot remove the outermost SiO ₂ film. Therefore, in the present invention, the SiO ₂ film was removed by reactive dry etching using a perfluorocarbon-based C ₃ F ₈ gas. In this case, prior to etching, hexamethyldisilazane (HMDS) is applied in advance to the SiO ₂ film surface by spin coating and dried at 90 ° C. for about 30 seconds to improve the surface and improve the adhesion of the resist. (Not shown).

  Next, a novolac positive resist is applied to the first resist layer 5 so that the finish is about 5.5 μm (FIG. 2B), and then the pad and the scribe portion are formed by a regular exposure / development process. The resist was dissolved to provide an opening 11 (FIG. 2C).

Next, the SiO 2 film 7 exposed at the opening was removed by dry etching of C ₃ F ₈ under a predetermined condition (flow rate 35 sccm, gas pressure 6.0 Pa, using Unity Me85d manufactured by Tokyo Electron Ltd.). At the same time, the surface of the resist 5 is made into a hardened layer 12 by C ₃ F ₈ gas, so that it is difficult to dissolve and remove the resist layer with the stripping solution, and it is necessary to repeat washing with the stripping solution many times (FIG. 2 (d)). As the stripping solution, a mixed solution of 60% by weight of dimethyl sulfoxide and 40% by weight of N-methyl-2-pyrrolidone was used.

Next, the novolak resin (heat flow) used for forming the microlens 2 and deposited on the pad 6 was removed. The procedure is the same as the removal of the SiO ₂ film. First, HMDS is spin-coated on the entire surface, and then the second resist 13 is applied (FIG. 3 (g)), and an opening is formed in the pad and the scribe portion by a regular photolithography method. The part 11 was provided (FIG.3 (h)).

Whether the microlens material was an acrylic resin or a novolac resin, it could be removed by dry etching using O ₂ gas (flow rate 150 cssm, gas pressure 3.0 Pa, manufactured by Tokyo Electron Ltd., Unity Me85d). Finally, the resist film was dissolved and removed with a peeling image solution, and then washed with pure water after IPA substitution (FIG. 3 (j)).

  The synthetic resin that is the target of resin removal is usually the synthetic resin that composes the microlens 2, but includes layers that were applied in the process but did not have a peeling process, or layers that were peeled but left behind May be.

As described above, it was found that the removal of the SiO ₂ film 7 from the pad 6 and the scribe can be performed by dry etching using C ₃ F ₈ gas. Resin can also be removed by simply changing the etching gas to O ₂ .
However, resist patterning for dry etching needs to be performed twice, and the problem that peeling of the first resist film after removal of the SiO ₂ film is troublesome due to the hardened layer remains.

Therefore, the present inventor made extensive studies and found that the second resist formation is unnecessary. That is, the first resist layer 12 whose surface is hardened is not peeled off with a mixed solution of dimethyl sulfoxide and N-methyl-2-pyrrolidone, but is changed to dry etching of O ₂ while leaving the resin. It was found that it can be removed.

As shown in FIGS. 4A to 4E, after the SiO ₂ film is removed by dry etching (flow rate is 35 sccm) using C ₃ F ₈ gas under a predetermined condition, the synthetic resin exposed to the opening is exposed. The remaining layer was removed by dry etching of O ₂ (flow rate was 150 sccm) (FIG. 4C). It was also found that by this dry etching, the hardened layer 12 on the resist surface generated by the C ₃ F ₈ gas irradiation was also scraped off. Therefore, since the resist layer that has been difficult to peel is also free of the hardened layer 12, the stripping solution can be easily stripped in 19 seconds, IPA replacement in 15 seconds, and pure water cleaning in about 40 seconds. (FIG. 4 (e)).

In the present invention, the resist patterning is performed once, and is commonly used in dry etching using C ₃ F ₈ gas and O ₂ gas. At the same time, the resist can be easily peeled off and the process can be greatly shortened and rationalized. It was.

C ₃ F ₈ gas is preferable, but C ₄ F ₈ or C _a F _b X _c (where X is one of H, Cl and Br, a = 1 to 5, b = 2a + 2-c, c = 0 , 1) can also be used.

1. Solid-state image sensor (substrate)
2, micro lens 3, color separation filter 4, flattening layer 5, first resist layer 6, pad (scribe)
7. Antireflection film (SiO ₂ )
8, plasma 11, opening 12, hardened layer 13, second resist layer

Claims (3)

In a method for manufacturing a color solid-state image pickup device including at least a flattening layer, a color separation filter, a microlens, and an antireflection layer on a solid-state image pickup device, an SiO ₂ layer is provided on the microlens as an antireflection film, and then a resist And a step of providing an opening in a resist where a SiO ₂ layer is unnecessary by photolithography, and removing the exposed SiO ₂ layer by dry etching using a fluorine-based gas. Manufacturing method of imaging device. _{2. The} method according to claim 1, further comprising a step of removing a synthetic resin layer exposed below the resin layer composing the microlens and exposed to the opening by a dry etching method using O ₂ gas. Manufacturing method of a color solid-state imaging device. The method for manufacturing a color solid-state imaging device according to claim 1, wherein the fluorine-based gas is a C ₃ F ₈ gas.