JP2003229556A - Solid-state imaging device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent dark current noise of a photodiode which is generated by the effect of titanium contained in barrier material of a solid-state imaging device. <P>SOLUTION: High melting point metal, e.g. tungsten which does not contain titanium is used as an anti-reflection film 122. As a barrier layer 134 and an adhesive layer 136, e.g. silicon nitride or silicon oxide which do not contain titanium is used. Titanium is not used in other elements, so that titanium is not arranged entirely in a peripheral part of the photodiode 112. As a result, hydrogen (H) component distributed in a peripheral region of the photodiode 112 is not absorbed in titanium based material, an interfacial level of the photodiode 112 can be reduced effectively, and the dark current noise can be prevented. <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 a CC for picking up images of various subjects using a photoelectric conversion element such as a photodiode.
The present invention relates to a solid-state image sensor such as a D-type image sensor or a CMOS-type image sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a solid-state image pickup device of this kind, photodiodes and various gate devices forming a unit pixel are formed by subjecting a semiconductor substrate to steps such as impurity addition and thermal diffusion. A gate electrode, a light-shielding film, a wiring layer, and the like are formed on this semiconductor substrate, and an on-chip filter and an on-chip microlens are positioned and arranged on the upper layer. That is, such a solid-state imaging device is manufactured by using a general method for manufacturing various semiconductor devices. Particularly, in the CMOS type image sensor, titanium () is formed above and below the wiring layer and around the plug layer. An alloy material containing Ti) or titanium is used.

FIG. 3 is a sectional view showing a structure of a photodiode peripheral portion of a CMOS type image sensor which is such a conventional solid-state image pickup device. First, the silicon substrate 10
In the upper layer region, a photodiode 12, an FD (floating diffusion) portion 14, a logic transistor 16 and the like are arranged via an element isolation layer 18, respectively. The photodiode 12 is composed of a P region formed on the surface of the silicon substrate 10 and an N region formed below the P region, and converts the light incident from above into a signal charge and accumulates it in the lower depletion layer. Is. The FD (floating diffusion) unit 14 accumulates the signal charges generated by the photodiode 12 in synchronization with the reset signal. Logic transistor 16
Is a part of a gate circuit for outputting the voltage (current) signal corresponding to the potential fluctuation of the FD section 14 to the output signal line at a predetermined timing.

An insulating layer 20 functioning as a flattening film or a protective film is provided on the silicon substrate 10, and various gate electrodes 30 are arranged at predetermined positions. Further, the photodiode 1 is provided on the insulating layer 20.
The anti-reflection film 22 and various wiring layers 24 and 26 for preventing re-incident light reflected on the second layer 2 and improving the fidelity to the mask pattern for wiring processing are formed via the interlayer insulating layer 28. On-chip filter 40 is provided on the upper layer
An on-chip microlens 42 is arranged. Then, these antireflection film 22, wiring layers 24 and 26, FD
Contact holes are formed at predetermined positions in the insulating layers 20 and 28 between the portion 14 and the logic transistor 16, and the antireflection film 22 and the wiring layer 2 are formed by the contact plugs 32 embedded in the contact holes.
4, 26, and the FD section 14 and the logic transistor 1
Each part of 6 is electrically connected.

A barrier layer 34 is arranged at the connection between the contact plug 32 and the upper and lower wirings, and an adhesion layer 36 is formed between the contact plug 32 and the contact hole. In the CMOS type image sensor having such a configuration, aluminum or a refractory metal is used as a material for the upper wiring layers 24 and 26 and the contact plug 32, but a titanium material and a barrier material are used for the barrier layer 34 and the adhesion layer 36. An alloy material of titanium is used, and the antireflection film 22 is used.
Similarly, a titanium material or a titanium alloy material is used.

[0006]

However, in the conventional solid-state imaging device as described above, when a titanium-based material is used in the peripheral region of the photodiode, the hydrogen (H) component distributed in the periphery is The absorption by the titanium-based material causes a problem that the interface order of the photodiode cannot be reduced and dark current noise increases. Therefore, in such a solid-state imaging device, there is a problem that effective effects cannot be obtained even if hydrogen annealing or hydrogen plasma treatment for reducing dark current noise is performed. In particular, the recent miniaturization of solid-state imaging devices is progressing, and, for example, those having a design rule with a minimum line width of 1.0 μm or less are required. In the solid-state imaging device having such a miniaturized wiring structure, The effect of the titanium-based material described above cannot be ignored.

Therefore, an object of the present invention is to provide a solid-state image sensor capable of suppressing dark current noise due to the influence of titanium and a method for manufacturing the same.

[0008]

In order to achieve the above object, the present invention reads a plurality of photoelectric conversion elements that generate and store signal charges according to the amount of received light, and read out the signal charges stored in the photoelectric conversion elements. And a gate element for outputting the light are provided on the semiconductor substrate, the incidence of scattered light on the photoelectric conversion element is suppressed through the insulating film on the semiconductor substrate, and the fidelity to the mask pattern for wiring processing is improved. In the solid-state imaging device in which an antireflection film to be improved and a plurality of wiring layers for supplying a signal to the gate element are laminated via an insulating film, and the wiring layer and the gate element are connected by a contact plug, A material in which the antireflection film is made of a material containing no titanium, and the barrier layer and the adhesion layer for the wiring layer and the contact plug do not contain titanium. Thus it is formed, characterized in that is.

Further, according to the present invention, a plurality of photoelectric conversion elements for generating and accumulating signal charges according to the amount of received light and a gate element for reading and outputting the signal charges accumulated in the photoelectric conversion elements are provided on a semiconductor substrate. Together with the gate element, an antireflection film that suppresses the incidence of scattered light on the photoelectric conversion element through an insulating film on the upper part of the semiconductor substrate and that improves the fidelity to a mask pattern for wiring processing, In the method for manufacturing a solid-state imaging device, wherein a plurality of wiring layers for supplying a signal are laminated via an insulating film, and the wiring layers and the gate element are connected by a contact plug, the antireflection film does not contain titanium. Formed by material,
The barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of a material containing no titanium.

In the solid-state image sensor according to the present invention, the antireflection film for suppressing the incidence of scattered light on the photoelectric conversion element and improving the fidelity to the mask pattern for wiring processing is formed of a material containing no titanium. In addition, since the barrier layer and the adhesion layer for the wiring layer and the contact plug are made of a material that does not contain titanium, it is possible to eliminate the titanium-based material from the peripheral region of the photoelectric conversion element. It is possible to eliminate the increase of dark current noise due to the influence of.

In the method of manufacturing a solid-state image pickup device according to the present invention, the antireflection film for suppressing the incidence of scattered light on the photoelectric conversion device and improving the fidelity to the mask pattern for wiring processing is made of a material not containing titanium. Since the barrier layer and the adhesion layer for the wiring layer and the contact plug are made of a material not containing titanium, it is possible to eliminate the titanium-based material from the peripheral region of the photoelectric conversion element. It is possible to eliminate the increase of dark current noise due to the influence of.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a solid-state image sensor and a method of manufacturing the same according to the present invention will be described below.
The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments. In the present embodiment, the present invention is a CM.
An example applied to the OS type image sensor and its manufacturing method will be described.

FIG. 1 is a sectional view showing a structure of a photodiode peripheral portion of a CMOS type image sensor according to a first embodiment of the present invention. The CMOS image sensor of this example has a basic structure similar to that of the conventional example shown in FIG.
Photodiode 112, FD section 114, logic transistor 116, element isolation layer 118, insulating layer 120, 1
28, the gate electrode 130, the contact plug 132, the wiring layers 124 and 126, the on-chip filter 140, and the on-chip microlens 142 are the silicon substrate 10, the photodiode 12, the FD portion 14, the logic transistor 16, and the element isolation shown in FIG. Layer 18, insulating layers 20, 2
8, gate electrode 30, contact plug 32, wiring layer 2
4, 26, the on-chip filter 40, and the on-chip microlens 42, which are common elements.

The difference between this embodiment and the conventional example is that the materials of the antireflection film 122, the barrier layer 134 and the adhesion layer 136 shown in FIG. 1 are the same as those of the antireflection film 22 shown in FIG.
This is different from the materials of the barrier layer 34 and the adhesion layer 36. That is, the conventional antireflection film 22 is made of a titanium material or its alloy material, but the antireflection film 122 in the present embodiment is made of a refractory metal such as tungsten which does not contain titanium. . Further, the conventional barrier layer 34 and the adhesion layer 36 are made of a material containing titanium, but the barrier layer 134 and the adhesion layer 136 in the present embodiment do not contain titanium, for example, silicon nitride or Silicon oxide is used. In the CMOS image sensor according to this embodiment, the antireflection film 122 and the barrier layer 13 are provided.
No titanium is used for the elements other than No. 4 and the adhesion layer 136, so that no titanium is arranged in the peripheral portion of the photodiode 112.

Therefore, the hydrogen (H) component distributed in the peripheral region of the photodiode 112 is not absorbed by the titanium-based material, and the photodiode 112 is not absorbed.
It is possible to effectively reduce the order of the interfaces and suppress dark current noise. Further, by this, hydrogen annealing or hydrogen plasma treatment for reducing dark current noise can be effectively applied, and for example, a CMOS type image having a fine wiring structure according to a design rule with a minimum line width of 1.0 μm or less. Also in the sensor, dark current noise can be effectively suppressed. Further, since the nitride of silicon or the oxide of silicon is used for the barrier layer 134, the contact resistance does not increase even when the subsequent process includes heat treatment. Therefore, the contact resistance between the wirings can be reduced and the propagation delay can be reduced as compared with the related art, and there is also an advantage that it is possible to realize high-speed driving and a large area of the image sensor.

FIG. 2 is a sectional view showing the structure of the peripheral portion of the photodiode of the CMOS type image sensor according to the second embodiment of the present invention. In FIG. 2, the same components as those of the CMOS image sensor shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The CMOS image sensor according to the present embodiment includes a flattening film 120A in which the upper film of the insulating layer 120 is flattened by a reflow process. This reflow process is 800 °
By heating at a high temperature of C or higher for 5 minutes or longer, the upper surface of the flattening film 120A is melted and flattened. Note that this heat treatment is performed before the formation of the aluminum wiring layer included in the upper wiring. Then, by performing high-temperature heating associated with such a reflow treatment, it is possible to further improve the dark current suppressing action in addition to eliminating the titanium-based material described above. Note that such high-temperature heat treatment is not limited to the reflow treatment for forming the planarization film, and other heat treatments can be combined. Further, other configurations are the same as those shown in FIG.

In the above embodiments, the present invention is applied to the CMOS type image sensor, but the present invention can also be widely applied to solid-state image pickup devices having a photodiode such as a CCD type image sensor. It is a thing. That is, in the CMOS type image sensor,
Photodiode, FD section and various MOS for each unit pixel
A transistor is provided, and the signal charge from the photodiode is converted into an electric signal by the FD section and the MOS transistor and output to the output signal line. Charge-voltage (current) conversion is performed for each unit pixel to the outside. It is what is output.

On the other hand, in the CCD image sensor, the signal charge from each photodiode is transferred by the CCD vertical transfer register and the CCD horizontal transfer register, and converted into an electric signal by the FD section and the MOS transistor provided in the final output stage. Although converted and output, the solid-state image sensor and the manufacturing method according to the above-described embodiments can be applied to such a CCD image sensor. In the case of a CCD image sensor, the transfer gate and read gate of each transfer register correspond to the gate element of the present invention.

Further, the photoelectric conversion element is not limited to the photodiode, but may be a solid-state image pickup element using another element. The configurations of the antireflection film, various wirings, and contact plugs described above are not limited to the above examples. Further, in the above-described embodiments, the nitride or oxide of silicon is used as the barrier material forming the barrier layer 134 and the adhesion layer 136, but other refractory metal-based materials (refractory metal It is also possible to use a nitride or an oxide).

[0020]

As described above, according to the solid-state image pickup device of the present invention, the antireflection film for suppressing the incident of scattered light on the photoelectric conversion device and improving the fidelity to the mask pattern for wiring processing. Is formed of a material containing no titanium, and the barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of a material containing no titanium. Can be eliminated, and the increase in dark current noise due to the influence of titanium can be eliminated.

According to the method for manufacturing a solid-state image sensor according to the present invention, the incidence of scattered light on the photoelectric conversion element is suppressed, and
An antireflection film that improves the fidelity to the mask pattern for wiring processing is formed of a material not containing titanium,
Since the barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of a material not containing titanium, it becomes possible to eliminate the titanium-based material from the peripheral region of the photoelectric conversion element, and it is possible to eliminate the darkness due to the influence of titanium. It is possible to eliminate the increase in current noise.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a photodiode peripheral portion of a CMOS type image sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a photodiode peripheral portion of a CMOS type image sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a photodiode peripheral portion of a CMOS type image sensor according to a conventional example.

[Explanation of symbols]

110 ... Silicon substrate, 112 ... Photo diode, 114 ... FD section, 116 ... Logic transistor, 118 ... Element isolation layer, 120, 128 ... Insulating layer, 120A ... Planarization film, 122 ... Reflection Prevention film, 1
24, 126 ... Wiring layer, 130 ... Gate electrode, 13
2 ... Contact plug, 134 ... Barrier layer, 136
... Adhesion layer, 140 ... On-chip filter, 142 ...
… On-chip microlens.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M118 AA05 AB01 BA10 BA14 CA02                       DA20 FA28 GC07 GD04 GD07                 5F033 HH17 HH19 KK17 KK19 NN07                       QQ03 QQ74 QQ75 RR04 RR06                       TT07 WW01 WW03 XX00 XX09                       XX27

Claims (12)

[Claims] 1. A semiconductor substrate is provided with a plurality of photoelectric conversion elements for generating and accumulating signal charges according to the amount of received light, and a gate element for reading and outputting the signal charges accumulated in the photoelectric conversion elements. A signal is supplied to the gate element and an antireflection film that suppresses the scattered light from entering the photoelectric conversion element through an insulating film on the upper part of the semiconductor substrate and improves the fidelity to a mask pattern for wiring processing. In the solid-state imaging device in which a plurality of wiring layers for laminating via an insulating film are stacked, and the wiring layer and the gate element are connected by a contact plug, the antireflection film is formed of a material not containing titanium, A solid-state imaging device, characterized in that the barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of a material not containing titanium. Child. 2. The solid-state imaging device according to claim 1, wherein the wiring layer is manufactured by a design rule having a minimum line width of 1.0 μm or less. 3. The solid-state image sensor according to claim 1, which is a CMOS sensor. 4. The solid-state imaging device according to claim 1, wherein the barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of silicon nitride or silicon oxide. 5. A semiconductor substrate is provided with a plurality of photoelectric conversion elements for generating and accumulating signal charges according to the amount of received light, and a gate element for reading and outputting the signal charges accumulated in the photoelectric conversion elements. A signal is supplied to the gate element and an antireflection film that suppresses the scattered light from entering the photoelectric conversion element through an insulating film on the upper part of the semiconductor substrate and improves the fidelity to a mask pattern for wiring processing. In the method for manufacturing a solid-state imaging device, in which a plurality of wiring layers for achieving the above are laminated via an insulating film, and the wiring layer and the gate element are connected by a contact plug, the antireflection film is formed of a material containing no titanium. A barrier layer and an adhesion layer for the wiring layer and the contact plug are formed of a material not containing titanium. Method. 6. The method for manufacturing a solid-state imaging device according to claim 5, wherein the wiring layer is manufactured according to a design rule having a minimum line width of 1.0 μm or less. 7. The method of manufacturing a solid-state imaging device according to claim 5, wherein the barrier layer and the adhesion layer for the wiring layer and the contact plug are formed of silicon nitride or silicon oxide. 8. The barrier layer is formed by forming a film of silicon nitride or silicon oxide on a base and then removing the film leaving a contact region, thereby forming a barrier layer corresponding to the contact region. The method for manufacturing a solid-state image sensor according to claim 7, wherein the solid-state image sensor is formed. 9. The solid-state imaging device according to claim 7, further comprising an upper aluminum wiring layer of the plurality of wiring layers, and performing heat treatment at 800 ° C. or higher before forming the aluminum wiring layer. Manufacturing method. 10. The method according to claim 7, further comprising an upper aluminum wiring layer of the plurality of wiring layers, and having a heat treatment step at a temperature of 800 ° C. or higher before forming the aluminum wiring layer. Manufacturing method of solid-state imaging device. 11. The method for manufacturing a solid-state image sensor according to claim 10, wherein the heat treatment process at a temperature of 800 ° C. or higher is a process of 5 minutes or longer. 12. The method of manufacturing a solid-state image sensor according to claim 5, wherein the solid-state image sensor is a CMOS sensor.