JP2003209230A - Solid-state imaging device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device with which sensitivity can be improved by increasing the condensing rate, and a method of manufacturing the same. <P>SOLUTION: When a second microlens 52 of which refractive index is higher than that of a first microlens 51 is formed on the first microlens 51, it is sufficient that the second microlens 52 in the top layer has only a function of condensing to the first microlens 51. Accordingly, a microlens with a short focal distance and a small radius of curvature can be obtained. Since oblique incident light L2 can also be guided to a photosensor 2 efficiently, variation in light focus corresponding to changes in F values of a camera lens can be minimized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a solid-state image pickup device having an on-chip microlens for improving light collection efficiency and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the recent development of portable personal computers and small video cameras, solid-state image pickup devices with lower power consumption have become indispensable. In particular, a CCD solid-state image pickup device is mainly used for a device handling image processing, but it is very difficult to reduce power consumption because of its operation characteristics. To drive the CCD solid-state image sensor,
A voltage of at least 5V or higher is required. In recent years, the research and development of 1.5V for digital LSIs for mobile devices has become the mainstream. However, in order to reduce the power consumption of these mobile devices, CC
The use of the D solid-state image sensor causes a serious problem in that it consumes a lot of power.

Therefore, in recent years, CMOs have been used as image input devices.
An S-type solid-state image sensor (CMOS image sensor) has been receiving attention. Since this solid-state image sensor uses CMOS technology, it can be driven at a low voltage, and it is considered to be a very effective solid-state image sensor particularly in combination with a recent mobile terminal from the viewpoint of low power consumption.

FIG. 13 is a diagram showing an example of a cross section of a CMOS image sensor. In the CMOS image sensor shown in FIG. 13, the photo sensor 20 is formed on the substrate 10, and the wirings 131, 132, 133 are embedded in the insulating film.
Is formed, a PSG film or a silicon nitride film is formed after the final wiring step, and the flattening film 140 is formed by flattening by CMP or the like. On the upper layer of the flattening film 140, a color filter 150 and an on-chip microlens 151 are formed by a method well known in the method of manufacturing a CCD image sensor.

With reference to FIG. 14, a manufacturing process after forming a planarizing film in the conventional technique will be described. Here, the wiring and the like formed under the planarization film 140 are not shown. First, as shown in FIG.
0, for example, a colored resin having photosensitivity is formed into a color filter pattern by a lithographic method.
The color filter 150 is formed. Specifically, a coloring resin having photosensitivity and dispersed with a pigment is applied, and a hot plate at a temperature of 90 ° C. to 100 ° C. is applied for 90 seconds to 120 seconds.
After baking for 2 seconds, exposure is performed using an i-line stepper, development is performed with an alkali developing solution such as TMAH (tetramethyldisilazane) aqueous solution, and after 90 seconds on a hot plate at a temperature of 100 ° C to 120 ° C. It is formed by repeating curing for 120 seconds as many times as necessary. For example, a primary color type image sensor repeats red, blue and green three times, and a complementary color type image sensor repeats cyan, magenta, yellow and green four times.

Next, as shown in FIG. 14B, a transparent photosensitive resin such as polystyrene resin is applied to form a transparent organic film 151 '. This transparent organic film 1
51 'is a lens material.

Next, as shown in FIG. 14 (c), after coating the photosensitive resin, a microlens-shaped photosensitive resin R is formed by a photolithography technique and thermal reflow. Thermal reflow is performed for 120 seconds to 2 seconds at a temperature of, for example, 150 ° C to 180 ° C to obtain an optimum lens shape.
It takes place in 40 seconds.

Finally, by anisotropic plasma dry etching using oxygen plasma, the microlens shape of the photosensitive resin R formed in FIG. 14C is transferred to the transparent organic film 151 'which is a lens material. As a result, the on-chip microlens 151 is formed, and the structure of FIG. 14D is obtained.

In the conventional example shown in FIG. 13, the distance L1 from the lower end of the color filter 150 and the upper surface of the flattening film 140 to the lower end of the on-chip microlens 151 is 2.
It is from 5 μm to 3 μm. This distance L1 has almost no difference between the CMOS image sensor and the CCD image sensor.

However, since the CMOS image sensor has several transistors for one photosensor, it is necessary to form the multi-layered wirings 131, 132, 133 on the photosensor 20. From the lower end of the color filter 150, the flattening film 14
0 The distance L2 to the upper surface becomes long.

In the CCD image sensor, the distance L2
Is 2.3 μm, but 5 for CMOS image sensors
More than μm. As a result, the distance from the photosensor 20 to the on-chip microlens 151, that is, the so-called layer thickness L3 becomes large. Similar to the CCD image sensor, it is easily expected that the pixel size of the CMOS image sensor will decrease in the future, but the CMOS image sensor manufactured by utilizing the MOS memory process has a complicated wiring structure as the process progresses. Therefore, it is not easy to reduce the layer thickness L3.

[0012]

Therefore, the aspect ratio between the pixel size and the layer thickness is only increasing. As a result, when the oblique incident light L2 to the image sensor is increased as in the case where the F-number of the camera lens is small, FIG.
As shown in, a situation occurs in which light is not condensed on the photo sensor 20.

In addition, the CMOS image sensor has a low aperture ratio of the photosensor 20 to the unit cell area, and in many cases, the wiring is close to the opening C to the uppermost layer as shown in FIG. The incident light L1 collected by the microlens 151 is the wiring 133.
Will be blocked by.

In order to prevent the light condensed at this time from being blocked by the wiring, it is conceivable to form an on-chip microlens 151a at a position further away from the photosensor 20 as shown in FIG. As in the case described above, when the aspect ratio between the pixel size and the layer thickness is further increased and the oblique incident light L2 to the image sensor is increased, as in the case where the F value of the camera lens is small, the photo sensor 20 has A situation occurs where light is not collected.

In order to focus incident light on the photosensor 20 regardless of the F value of the camera lens, it is preferable that the radius of curvature of the on-chip microlens 151 is small. The distance to 151 needs to be short. However, in the CMOS image sensor, due to the presence of the multilayer wiring formed in the upper layer around the photo sensor 20,
The photo sensor 20 without the incident light being blocked by the wiring
There is a limit to lowering the position of the on-chip microlens 151 while maintaining the state of condensing light on the.

As described above, in the CMOS image sensor, it is difficult to collect all the incident light on the photo sensor, and as a result, the device sensitivity is lowered. Therefore, a device structure and a manufacturing method thereof that efficiently guide the incident light to the photosensor are desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state image pickup device capable of improving the light collection rate and the sensitivity, and a manufacturing method thereof. .

[0018]

In order to achieve the above-mentioned object, a solid-state image pickup device of the present invention is formed on a substrate and formed on a light receiving portion for generating electric charges according to the amount of incident light and on an upper layer of the light receiving portion. A first lens having a curved surface on the light incident side so that incident light having a first refractive index can be condensed on the light receiving portion; and the first lens formed on the first lens. A second lens having a second refractive index larger than the refractive index of 1 to collect incident light to the first lens.

The second lens is formed to have a curvature for condensing incident light on the first lens.

The second lens has a filter function of transmitting light in a predetermined wavelength range. Alternatively, the first
The lens has a filter function of transmitting light in a predetermined wavelength range. Alternatively, it has a color filter formed under the first lens and transmitting light in a predetermined wavelength range.

In the above solid-state image pickup device of the present invention, when incident light is incident on the second lens, the incident light is condensed on the first lens. Since the refractive index of the first lens is smaller than that of the second lens, the incident light condensed by the second lens at the curved surface of the first lens, that is, the interface with the second lens. The incident light path is changed so that the light is refracted toward the longer focal length and is condensed on the light receiving portion, so that the incident light is condensed on the light receiving portion. In this way, the second lens collects the incident light on the first lens,
Since the second lens only needs to have the function of condensing the first lens by condensing the incident light to the light receiving section by the lens of, the lens having a short focal length, that is, It is formed of a lens having a small radius of curvature.

Further, in order to achieve the above object, in the method for manufacturing a solid-state image pickup device of the present invention, a step of forming a light receiving portion on a substrate, and an incident light having a first refractive index on the upper layer of the light receiving portion. Forming a first lens having a curved surface on the incident side of the light so that the light can be condensed on the light receiving section; and a second refraction having a refractive index larger than the first refractive index on the first lens. Forming a second lens having a refractive index and capable of condensing incident light to the first lens.

In the step of forming the second lens, a colored resin in which a pigment is dispersed is patterned into a lens shape to be formed. Alternatively, in the step of forming the first lens, a colored resin in which a pigment is dispersed is patterned into a lens shape to be formed. Alternatively, after the step of forming the light receiving portion and before the step of forming the first lens, the method further includes the step of forming a color filter that transmits light in a predetermined wavelength region.

In the above-described method for manufacturing a solid-state image pickup device of the present invention, a curved surface is provided on the light-incident side of the light-receiving portion so that the light having the first refractive index and incident on the light-receiving portion can be condensed. First
And forming a second lens on the first lens, the second lens having a second refractive index higher than the first refractive index and capable of condensing incident light to the first lens. Then, the solid-state imaging device having the above-described operation is manufactured, and the second lens having a short focal length, that is, a small radius of curvature is formed.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a solid-state image pickup device and a method of manufacturing the same according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows an example of the configuration of a CMOS type solid-state imaging device according to this embodiment. A solid-state image pickup device 1 shown in FIG. 1 includes a photodiode (that is, a pn junction type photosensor) 2 that performs photoelectric conversion, a vertical selection switch element 4 that includes, for example, a MOS transistor that selects a pixel, and an MO transistor, for example.
A unit pixel 5 composed of an S-transistor read-out switching element 3 is arranged in a matrix, and an imaging region and a control electrode (gate electrode) of the vertical selection switching element 4 are commonly provided for each row. A vertical scanning pulse φV (φV1, ...
.Phi.Vm, ... .phi.Vm + k, ...), A vertical signal line VL to which the main electrode of the read switch element 3 is commonly connected for each column, and a vertical signal line for each column The read pulse line RL connected to the main electrode of the selection switch element 4, the horizontal switch element 7 formed of, for example, a MOS transistor having main electrodes connected to the vertical signal line VL and the horizontal signal line HL, and the horizontal switch element 7 A horizontal scanning circuit 8 connected to the control electrode and the read pulse line RL;
The amplifier 9 is connected to the horizontal signal line HL.

In each unit pixel 5, one main electrode of the read switch element 3 is connected to the photo sensor 2, and the other main electrode is connected to the vertical signal line VL. Also,
One main electrode of the vertical selection switch element 4 is connected to the control electrode of the read switch element 3, the other main electrode is connected to the read pulse line RL, and the control electrode thereof is connected to the vertical select line SVL. ing.

From the horizontal scanning circuit 8 to each horizontal switching element 7
Horizontal scanning pulse φH (φH1, ... φH
n, ... φHn + 1, ...) is supplied, and a horizontal read pulse φH is supplied to each read pulse line RL.
^R (φH ^R 1, ... φH ^R n, ... φH ^R n + 1,
...) is supplied.

The basic operation of the solid-state image pickup device 1 is as follows. Vertical scanning pulse φVm from vertical scanning circuit 6
And the vertical selection switch element 4 which has received the read pulse φH ^R n from the horizontal scanning circuit 8 receives those pulses φV.
A pulse of the product of m and φH ^R n is generated, and the control electrode of the read switch element 3 is controlled by this pulse of the product to read the signal charge photoelectrically converted by the photosensor 2 to the vertical signal line VL. This signal charge is output to the horizontal signal line HL through the horizontal switch element 7 controlled by the horizontal scanning pulse φH from the horizontal scanning circuit 8 during the horizontal video period,
The signal is converted into a signal voltage by the amplifier 9 connected to this and output.

In the above example, an example in which two transistors are included in the unit pixel has been described. However, the present invention is not limited to this, and there are various types such as one having five transistors in the unit pixel. .

FIG. 2 is a sectional view showing the photosensor 2 and its upper layer structure. As shown in FIG. 2, n is formed in the active region of the p-type semiconductor substrate 10 which is pixel-separated by the element isolation insulating film 11 made of, for example, silicon oxide.
An n-type semiconductor region 12 containing a type impurity is formed, and a photosensor 2 is formed by forming a pn junction between the n-type semiconductor region 12 and the p-type semiconductor substrate 10.

An n-type semiconductor region 12 'formed at the same time as the n-type semiconductor region 12 of the photosensor 2 is formed in another portion of the semiconductor substrate 10 in which pixels are separated,
On the semiconductor substrate 10 between the n-type semiconductor regions 12 and 12 ', a read switch element composed of an nMOS transistor configured by laminating and forming a gate insulating film made of silicon oxide or the like and a gate electrode made of polysilicon or the like. 3 is formed. Note that other transistors and the like are formed in a region (not shown).

An insulating film 13 made of silicon oxide or the like is formed to cover the photosensor 2 and the read switch element 3.
And a light shielding film 14 made of titanium or the like having an opening above the photosensor 2 is formed on the insulating film 13. A first interlayer insulating film 21 made of silicon oxide or the like is formed so as to cover the light shielding film 14 and the insulating film 13, and in the same manner, a second interlayer insulating film 22 made of silicon oxide or the like is formed. .

On the second interlayer insulating film 22, a first wiring 31 composed of an aluminum wiring 31a containing copper or silicon sandwiched between barrier metals 31b composed of titanium or titanium nitride is formed. .

Second interlayer insulating film 22 and first wiring 3
A third interlayer insulating film 23 and a fourth interlayer insulating film 24, which are made of silicon oxide or the like, are formed on the entire surface of the first interlayer insulating film 24 by covering the first interlayer insulating film 24 with titanium or titanium nitride. A second wiring 32 made of an aluminum wiring 32a containing copper or silicon and sandwiched between barrier metals 32b made of, for example, is formed.

Fourth interlayer insulating film 24 and second wiring 3
A fifth interlayer insulating film 25 and a sixth interlayer insulating film 26 made of silicon oxide or the like are formed on the entire surface by covering the second interlayer insulating film 26, and titanium or titanium nitride is formed on the sixth interlayer insulating film 26. A third wiring 33 made of an aluminum wiring 33a containing copper or silicon and sandwiched between barrier metals 33b made of, for example, is formed.

In this way, multilayer wiring is formed on the photosensor 2, the read switch element 3, and the other transistors formed on the semiconductor substrate 10. The wirings 31, 32, and 33 are electrically connected to each other through a contact hole formed in the interlayer insulating film, if necessary. In the present embodiment, as an example, the first wiring 31, the second wiring 32, and the third wiring 3
Although the example of the three-layer wiring of No. 3 is shown, the present invention is not limited to this.

Third wiring 33 and sixth interlayer insulating film 2
6, a seventh interlayer insulating film 27 made of silicon oxide or the like is formed on the entire surface, and the PSG (Phosphosi) having the surface flattened by covering the seventh interlayer insulating film 27 is formed.
A flattening film 40 made of a duplicate glass) film or a silicon nitride film is formed.

A first microlens 51 is formed on the flattening film 40, and on the first microlens 51,
The second microlens 52 is formed. The first microlens 51 is made of a material having a lower refractive index than the second microlens 52, and has a refractive index of 1.5, for example.
It is formed of a BPSG (Borophosphosilicate glass) film. The second microlens 52 is formed of an organic material having a relatively high refractive index, for example, a polyimide resin. The refractive index data of the polyimide resin for light is as shown in FIG. 3, and the refractive index is a normal lens. It is about 1.8, which is higher than about 1.6 of organic materials used as materials. Further, the second microlens 52 is colored by dispersing a pigment, and also has a function of a color filter.

Next, a method of manufacturing the solid-state image pickup device according to this embodiment will be described with reference to FIGS. The example described here is a case where a primary color type CMOS image sensor requires three color filters of red, green and blue.

First, similar to the formation of a general CMOS image sensor, the semiconductor substrate 10 is formed by using CMOS technology.
Various semiconductor regions such as the n-type semiconductor region 12 constituting the photosensor 2 and the source / drain regions of other transistors are formed on the semiconductor substrate 10, and a gate insulating film and a gate electrode are formed on the semiconductor substrate 10 to form a semiconductor substrate. After forming the plurality of transistors, the interlayer insulating film deposition step and the wiring forming step are repeated, whereby the interlayer insulating films 21 to 27 are formed.
Wirings 31, 32 and 33 are formed therein.

Then, as shown in FIG. 4A, after forming the uppermost seventh interlayer insulating film 27, silicon nitride or the like is deposited and flattened by CMP or the like to form the flattening film 4.
Form 0. However, the wiring and the like formed under the flattening film 40 are not shown here. The flattening film 40
For example, a BPSG film having a refractive index of about 1.5 is formed by CVD.
The first microlens layer 510 is formed by depositing about 1 to 2 μm by the method.

Next, as shown in FIG. 4B, after the photosensitive resin is applied on the first microlens layer 510, the microlens-shaped photosensitive resin R1 is formed by a photolithography technique and thermal reflow. To do. Thermal reflow,
To obtain the optimum lens shape, for example, from 150 ℃ to 1
It is carried out at a temperature of 80 ° C. for 120 to 240 seconds.

Next, as shown in FIG. 4C, the microlens shape of the photosensitive resin R1 formed in FIG. 4B by anisotropic plasma dry etching is transferred to the first microlens lens layer 510. Then, the first microlens 51
To form.

Next, as shown in FIG. 5D, for example, a polyimide resin in which a green pigment is dispersed is applied to form a first color filter / lens layer 521. The polyimide resin has a relatively high refractive index of, for example, about 1.8.
FIG. 3 shows an example of the refractive index data with respect to the wavelength of the polyimide resin, but the refractive index can be adjusted by changing the composition of the material.

Next, as shown in FIG. 5E, a positive photoresist R2 having a high plasma dry etching resistance is photolithographically formed on the first color filter / lens layer 521 of the pixel requiring the green color filter. After patterning by using the method described above, anisotropic plasma dry etching is performed using the photoresist R2 as a mask, whereby the first color filter / lens layer 521 is formed.
Is patterned.

Next, as shown in FIG. 5F, the positive photoresist R2 used as the etching mask is replaced with MM.
Remove with a solvent such as P (methyl methoxypropionate).

Next, as shown in FIG.
In the same manner as in (d) to 5 (f), for example, a polyimide resin in which a red pigment is dispersed is applied to form a second color filter / lens layer 522, and the first color of green and the second color of red are formed. The second color filter / lens layer 522 of the pixel that requires a color filter other than the color filter is removed.

Next, as shown in FIG. 6H, a third color filter / lens layer 523 is formed by applying a polyimide resin in which a third color blue pigment is dispersed. Where 4
When a color filter for each color is required, the polyimide resin of the pixel requiring a color filter other than the first, second, and third colors is removed by the same method as in FIGS. Apply polyimide resin.

Next, as shown in FIG. 7I, after the photosensitive resin is applied, a microlens-shaped photosensitive resin R3 is formed by a photolithography technique and thermal reflow. Thermal reflow is performed for 120 seconds to 2 seconds at a temperature of, for example, 150 ° C to 180 ° C to obtain an optimum lens shape.
It takes place in 40 seconds.

Next, as shown in FIG. 7 (j), the microlens shape of the photosensitive resin R3 formed in FIG. 7 (i) by anisotropic plasma dry etching is applied to color filter / lens layers 521, 522, 523. And the second microlens 52 is formed. In the anisotropic plasma dry etching at this time, conditions such as a gas flow rate are adjusted so that the photosensitive resin R3 and the color filter / lens layers 521, 522, and 523 have the same etching rate. As described above, the solid-state imaging device according to the present embodiment as shown in FIG. 2 is manufactured.

In the solid-state imaging device according to this embodiment described above, the second microlens 5 having the function of a color filter is used.
When the incident light L1 is incident on 2, the incident light L1 is condensed on the first microlens 51. At this time, due to the color filter function of the second microlens 52, only the desired wavelength region of the incident light L1 is transmitted. First
Since the microlens 51 has a smaller refractive index than the second microlens 52, the incident light L1 collected by the second microlens 52 is refracted toward the longer focal length, and the photosensor The incident light path is changed so that the incident light L1 is condensed on the photosensor 2
Will be focused on.

Here, referring to the size of the first microlens 51, in the structure of this embodiment,
Since the incident light from the second microlens 52 has been sufficiently condensed on the microlens 51, it is necessary to form the first microlens 51 to have almost the same size as the pixel as shown in FIG. There is no. It suffices if the size is approximately equal to or larger than the opening C in the upper layer of the photosensor 2 determined by the uppermost layer wiring.

According to the solid-state image pickup device according to the present embodiment having the above-described light condensing action, the second microlens 52 in the uppermost layer has only the function of condensing the first microlens 51. Since it is good, a lens having a short focal length, that is, a microlens having a small radius of curvature can be used, and the photosensor 2 can efficiently perform the oblique incident light L2.
It is possible to reduce the change of the light condensing with respect to the change of the F value of the camera lens. Also, the second
Since the microlens 52 has a relatively high refractive index, the incident light L1 is refracted to a greater extent, and the first microlens 51
The effect is equivalent to that when the radius of curvature of the lens is further reduced.

Further, the use of the colored resin in which the pigment is dispersed in the second microlens 52 has the following effects. That is, the polystyrene-based resin used as the on-chip microlens material has a refractive index of about 1.6 in the related art, but the color filter material generally used has a refractive index of 1.6 to 1.7. Therefore, the refractive indexes of the on-chip microlens and the color filter are not always the same, and reflection and refraction occur at the interface to some extent.
Moreover, the interface between the on-chip microlens and the color filter is not necessarily a plane. This acts as a factor that makes control difficult in the design of the on-chip microlens for efficiently collecting the incident light, and causes variations in the optical path of the incident light. As a result, a state occurs in which the incident light is not completely focused on the photo sensor. On the other hand, in the present embodiment, the second microlens 52 has a color filter function, so that the incident light from the microlens as described above changes its optical path by the color filters having different refractive indexes. It is possible to prevent a decrease in light efficiency.

As described above, in the CMOS type solid-state image pickup device, it is possible to efficiently guide the incident light L1 to the photosensor 2, and since there is little change in the light condensing due to the F value of the camera lens, it is obliquely incident. The light L2 can also be efficiently condensed on the photo sensor 2.

Second Embodiment In the first embodiment, an example in which a polyimide resin containing a dye is used for the second microlens 52 in the uppermost layer and also has the function of a color filter has been described. The colored resin in which the pigment is dispersed is also used for the first microlenses 51, and also has the function of the color filter.

Therefore, in this embodiment, the first microlens uses a colored resin in which a pigment is dispersed in a novolac resin or an acrylic resin having a refractive index of about 1.6, for example. The structure of the layer below the flattening film 40 is similar to that of the first embodiment.

A method of manufacturing the solid-state image pickup device according to this embodiment will be described with reference to FIGS. 8 to 11. The example described here is a case where a CMOS image sensor of a primary color type requires three color filters of red, green, and blue, as in the first embodiment.

First, as in the first embodiment, a general CM
Similar to the formation of the OS image sensor, the CMOS technology is used to form various semiconductor regions such as the n-type semiconductor region 12 forming the photosensor 2 and the source / drain regions of other transistors on the semiconductor substrate 10 to form a semiconductor substrate. By forming a gate insulating film and a gate electrode on 10 to form a plurality of transistors on the semiconductor substrate, by repeating the step of depositing an interlayer insulating film and the step of forming a wiring,
Wirings 31, 32 and 33 are formed in the interlayer insulating films 21 to 27.

Then, as shown in FIG. 8A, after forming the uppermost interlayer insulating film 27, silicon nitride or the like is deposited and flattened by CMP or the like to form a flattening film 40. However, similar to the first embodiment, the wirings and the like formed under the flattening film 40 are not shown. Then, a novolac resin in which, for example, a green pigment is dispersed is applied on the flattening film 40 to form a first color filter / lens layer 51.
1 is formed.

Next, as shown in FIG. 8B, a positive photoresist R11 having a high plasma dry etching resistance is photolithographically formed on the first color filter / lens layer 511 of the pixel requiring the green color filter. After patterning using the method described above, anisotropic plasma dry etching is performed using the photoresist R11 as a mask, whereby the first color filter / lens layer 5 is formed.
11 is patterned.

Next, as shown in FIG. 8C, the positive photoresist R11 used as the etching mask is replaced with M
It is removed with a solvent such as MP (methyl methoxypropionate).

Next, as shown in FIG.
In the same manner as in (a) to 8 (c), for example, a novolac resin in which a red pigment is dispersed is applied to form the second color filter / lens layer 512, and the first color green and the second color red are formed. The second color filter / lens layer 512 of the pixel requiring a color filter other than the color filter of No. 1 is removed.

Next, as shown in FIG. 9E, a novolac resin in which a third color blue pigment is dispersed is applied to form a third layer.
A color filter / lens layer 513 is formed. here,
When color filters of four colors are required, the color filter / lens layer of the pixels requiring color filters other than the first, second, and third colors is removed by the same method as in FIGS. 8A to 8C. Later, a color filter / lens layer for the fourth color is formed.

Next, as shown in FIG. 10F, after the photosensitive resin is applied, a microlens-shaped photosensitive resin R12 is formed by a photolithography technique and thermal reflow. The thermal reflow is performed for 120 seconds to 240 seconds at a temperature of, for example, 150 ° C. to 180 ° C. in order to obtain the optimum lens shape.

Next, as shown in FIG. 10G, the microlens shape of the photosensitive resin R12 formed in FIG. 10F by anisotropic plasma dry etching is changed to the color filter / lens layers 511, 512, 513. Transferred to the first
The micro lens 51a is formed. In this anisotropic plasma dry etching, conditions such as a gas flow rate are adjusted so that the photosensitive resin R12 and the color filter / lens layers 511, 512, and 513 have the same etching rate.

Next, as shown in FIG. 10 (h), a colorless and transparent polyimide resin having a refractive index of about 1.8 is applied to the first microlenses 51a by about 1 to 2 μm, and then the second microlenses 51a are formed.
A microlens layer 520 is formed.

Next, as shown in FIG. 11I, after the photosensitive resin is applied on the second microlens layer 520, the microlens-shaped photosensitive resin R13 is formed by the photolithography technique and thermal reflow. To do. The thermal reflow is performed for 120 seconds to 240 seconds at a temperature of, for example, 150 ° C. to 180 ° C. in order to obtain the optimum lens shape.

Next, as shown in FIG. 12 (j), the microlens shape of the photosensitive resin R13 formed in FIG. 12 (i) is transferred to the second microlens layer 520 by anisotropic plasma dry etching. , The second microlens 52
a is formed. As described above, the solid-state imaging device according to this embodiment is manufactured.

The solid-state image pickup device according to this embodiment described above has the same operation as that of the first embodiment except that the first microlens 51a has a color filter function, and is incident on the second microlens 52a. The incident light is
Since the first microlens 51a has a smaller refractive index than the second microlens 52a, the incident light L1 collected by the second microlens 52a is condensed by the first microlens 51a. The incident light L1 is condensed on the photosensor 2 by changing the incident light path so that the light is refracted toward the longer focal length and is condensed on the photosensor 2.

Therefore, also in the solid-state image pickup device according to the present embodiment, for the same reason as in the first embodiment, the uppermost second microlens 52a is the first microlens 51a.
Since a microlens having a short focal length, that is, a small radius of curvature can be provided by only providing a function of condensing light to the photosensor 2, the oblique incident light L2 can be efficiently guided to the photosensor 2. Therefore, it is possible to reduce the change in the light collection with respect to the change in the F value of the camera lens.
Further, since the second microlens 52a has a relatively high refractive index, the incident light is refracted to a greater extent and is condensed on the first microlens 51a, which has the same effect as further reducing the radius of curvature of the lens. can get.

Further, similarly to the first embodiment, by using the colored resin for the first microlenses 51a, the light collection efficiency due to the change of the optical path of the incident light from the microlenses by the color filters having different refractive indexes. Can be prevented.

As described above, also in this embodiment, similarly to the first embodiment, in the CMOS type solid-state image pickup device, it becomes possible to efficiently guide the incident light to the photosensor 2, and the camera can be used. Since there is little change in light collection due to the F value of the lens, it is possible to efficiently collect even obliquely incident light on the photosensor 2.

Third Embodiment FIG. 12 is a sectional view showing the photosensor 2 according to the present embodiment and its upper layer structure. First embodiment and second
In the embodiment, the first microlens or the second microlens
An example of the structure in which one of the microlenses also has a color filter function has been described, but in the present embodiment,
A color filter 5 similar to the conventional one is provided under the micro lens.
Has 0.

That is, in the present embodiment, the flattening film 40
On top of this, there is provided a color filter 50 in which a colored resin having photosensitivity is formed into a color filter pattern by a lithographic method.

A first microlens 51b is formed on the color filter 50, and a second microlens 52b is formed on the first microlens 51b. The first microlens 51b is made of a material having a lower refractive index than the second microlens 52b, and is made of, for example, a novolac resin having a refractive index of about 1.6. The second microlenses 52b are formed of an organic material having a relatively high refractive index, for example, a polyimide resin having a refractive index of about 1.8. The structure of the layer below the flattening film 40 is similar to that of the first embodiment.

In the manufacture of the solid-state image pickup device having the above-mentioned structure, after the flattening film 40 is formed, a coloring resin having photosensitivity and having a pigment dispersed therein is applied in the same manner as in the conventional method, and the temperature of 90 to 100 ° C. 90 seconds to 12 on the temperature hot plate
After baking for 0 seconds, exposure is performed using an i-line stepper, development is performed with an alkali developing solution such as TMAH (tetramethyldisilazane) aqueous solution, and then 90 seconds on a hot plate at a temperature of 100 ° C to 120 ° C. The color filter 50 is formed by repeating the curing for a necessary number of times from 1 to 120 seconds. For example, a primary color type image sensor repeats red, blue and green three times, and a complementary color type image sensor repeats cyan, magenta, yellow and green four times.

Then, similarly to the second embodiment, the first microlenses 51b made of, for example, novolac resin having a refractive index of about 1.6 are formed on the color filter 50 to form the first microlenses 51b. After that, by forming the second microlenses 52b made of, for example, a polyimide resin, the solid-state imaging device according to the present embodiment shown in FIG. 12 is manufactured.

The solid-state imaging device according to the present embodiment described above has the same operation as the first and second embodiments, and
The incident light L1 that has entered the microlens 52b is condensed by the first microlens 51b, and the first microlens 5
Since 1b has a smaller refractive index than the second microlens 52b, the incident light L1 collected by the second microlens 52b is refracted toward the longer focal length thereof to the photosensor 2. The incident light path is changed so as to collect light. Then, by passing through the color filter 50, only the desired wavelength region of the incident light L1 is detected by the photo sensor 2.
Will be focused on.

Therefore, also in the solid-state image pickup device according to the present embodiment, for the same reason as in the first embodiment, the second microlens 52b in the uppermost layer is the first microlens 51b.
Since a microlens having a short focal length, that is, a small radius of curvature can be provided by only providing a function of condensing light to the photosensor 2, the oblique incident light L2 can be efficiently guided to the photosensor 2. Therefore, it is possible to reduce the change in the light collection with respect to the change in the F value of the camera lens.
Further, since the second microlens 52b has a relatively high refractive index, the incident light L1 is refracted to a greater extent and is condensed on the first microlens 51b, which is equivalent to reducing the radius of curvature of the lens. Is obtained.

As described above, also in the present embodiment, in the CMOS type solid-state image pickup device, it is possible to efficiently guide the incident light to the photosensor 2, and the change of the light collection depending on the F value of the camera lens. Therefore, the obliquely incident light can be efficiently condensed on the photosensor 2.

The present invention is not limited to the above description of the embodiments. In the present embodiment, the CMOS image sensor for a single plate color that requires a color filter has been described, but the present invention does not require a color filter.
It is also applicable to a MOS image sensor. For example, to describe the first embodiment, it is possible to use an uncolored colorless transparent polyimide resin in the formation of the second microlens 52, and in the manufacturing method, without patterning the polyimide resin, Figure 7 after applying colorless transparent polyimide resin
The steps (i) to (j) may be performed. Similarly, the present invention can be applied to the second embodiment.

Further, although the embodiments have been described with respect to the application to the CMOS image sensor, the present invention is of course C.
The same application can be applied to a CD image sensor and other image sensors, and the use thereof is not limited. Besides, various modifications can be made without departing from the scope of the present invention.

[0085]

According to the present invention, it is possible to improve the light collection rate and the sensitivity.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of a CMOS type solid-state imaging device according to first to third embodiments.

FIG. 2 is a sectional view showing a photosensor of the solid-state imaging device according to the first embodiment and an upper layer structure thereof.

FIG. 3 is a diagram showing an example of refractive index data with respect to a wavelength of a polyimide resin.

FIG. 4 is a cross-sectional view after the formation of the first microlenses in the manufacturing of the solid-state imaging device according to the first embodiment.

FIG. 5 is a cross-sectional view after the patterning of the first color filter / lens layer in the manufacture of the solid-state imaging device according to the first embodiment.

FIG. 6 is a cross-sectional view after forming a third color filter / lens layer in the manufacture of the solid-state imaging device according to the first embodiment.

FIG. 7 is a cross-sectional view after forming the second microlens in the manufacturing of the solid-state imaging device according to the first embodiment.

FIG. 8 is a cross-sectional view after patterning of the first color filter / lens layer in the manufacture of the solid-state imaging device according to the second embodiment.

FIG. 9 is a cross-sectional view after formation of a third color filter / lens layer in the manufacture of the solid-state imaging device according to the second embodiment.

FIG. 10 is a cross-sectional view after the formation of the first microlenses in the manufacturing of the solid-state imaging device according to the second embodiment.

FIG. 11 is a cross-sectional view after forming a second microlens in the manufacturing of the solid-state imaging device according to the second embodiment.

FIG. 12 is a cross-sectional view showing a photosensor of a solid-state imaging device according to a third embodiment and an upper layer structure thereof.

FIG. 13 is a cross-sectional view showing a photosensor of a conventional solid-state imaging device and an upper layer structure thereof.

FIG. 14 is a diagram showing a process of forming a color filter and an on-chip microlens of a conventional solid-state imaging device.

FIG. 15 is a diagram for explaining a problem caused by the conventional solid-state imaging device.

FIG. 16 is a diagram for explaining another problem of the conventional solid-state imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Solid-state imaging device, 2, 20 ... Photosensor, 3 ... Readout switch element, 4 ... Vertical selection switch element, 5
Unit pixel, 6 vertical scanning circuit, 7 horizontal switching element, 8 horizontal scanning circuit, 9 amplifier, 10 semiconductor substrate, 11 element isolation insulating film, 12, 12 '... n type semiconductor region, 13 ... Insulating film, 14 ... Shading film, 21 ... First interlayer insulating film, 22 ... Second interlayer insulating film, 23 ... Third interlayer insulating film, 24 ... Fourth interlayer insulating film, 25 ... Fifth interlayer Insulating film, 26 ... Sixth interlayer insulating film, 27 ... Seventh interlayer insulating film, 31 ... First wiring, 31a ... Aluminum wiring, 3
1b ... Barrier metal, 32 ... Second wiring, 32a ... Aluminum wiring, 32b ... Barrier metal, 33 ... Third wiring, 33a ... Aluminum wiring, 33b ... Barrier metal, 40 ... Flattening film, 50 ... Color filter, 51,5
1a, 51b ... 1st micro lens, 52, 52a, 5
2b ... 2nd micro lens, 131, 132, 133 ...
Wiring, 140 ... Planarization film, 150 ... Color filter, 1
51 ... On-chip micro lens, 510 ... First micro lens layer, 511 ... First color filter / lens layer, 512 ... Second color filter / lens layer, 513 ...
Third color filter / lens layer, 520 ... Second microlens layer, 521 ... First color filter / lens layer,
522 ... second color filter / lens layer, 523 ... third
Color filter / lens layer, SVL ... Vertical selection line, VL
... vertical signal line, RL ... read-out pulse line, HL ... horizontal signal line.

Front page continued (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/335 H01L 31/10 AF term (reference) 4M118 AA04 AA10 AB01 BA10 BA14 CA01 CA03 CA40 CB14 FA06 GB11 GC08 GC09 GD04 5C022 AC42 AC54 AC55 5C024 AX01 CX41 CY47 EX24 EX43 EX52 GZ34 5F049 MA02 NA20 NB03 NB05 RA08 TA12

Claims (9)

[Claims] 1. A light-receiving portion formed on a substrate for generating electric charges according to the amount of incident light, and light incident on the light-receiving portion, which has a first refractive index and is condensed on the light-receiving portion. A first lens having a curved surface on the incident side of light so as to obtain, a second refractive index formed on the first lens and higher than the first refractive index, and Solid-state imaging device having a second lens that focuses light onto the lens. 2. The solid-state imaging device according to claim 1, wherein the second lens is formed to have a curvature for condensing incident light to the first lens. 3. The solid-state imaging device according to claim 1, wherein the second lens has a filter function of transmitting light in a predetermined wavelength range. 4. The solid-state image pickup device according to claim 1, wherein the first lens has a filter function of transmitting light in a predetermined wavelength range. 5. The solid-state imaging device according to claim 1, further comprising a color filter formed under the first lens, the color filter transmitting light in a predetermined wavelength range. 6. A step of forming a light-receiving portion on a substrate, and a curved surface on the light-incident side so that light incident with a first refractive index can be condensed on the light-receiving portion above the light-receiving portion. Forming a first lens having a second lens having a second refractive index higher than the first refractive index on the first lens, and capable of condensing incident light to the first lens. 2. A method for manufacturing a solid-state imaging device, the method including the step of forming a second lens. 7. The method for manufacturing a solid-state imaging device according to claim 6, wherein in the step of forming the second lens, a colored resin in which a pigment is dispersed is patterned into a lens shape. 8. The method for manufacturing a solid-state imaging device according to claim 6, wherein in the step of forming the first lens, a colored resin in which a pigment is dispersed is patterned into a lens shape. 9. After the step of forming the light receiving portion, the first
7. The method for manufacturing a solid-state imaging device according to claim 6, further comprising the step of forming a color filter that transmits light in a predetermined wavelength region before the step of forming the lens.