JP2018147976A - Solid state image sensor and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state image sensor including electric wiring of a conductive material mainly composed of copper, having a structure capable of suppressing the impact of light interference without complicating the production process, and to provide a manufacturing method the solid state image sensor.SOLUTION: A solid state image sensor has: a semiconductor substrate provided with multiple pixels containing a photoelectric conversion part and a read circuit part for reading; a first insulation film provided on the semiconductor substrate, and on which electric wiring of a conductive material mainly composed of copper is arranged; a second insulation film provided on the first insulation film and the electric wiring, and preventing oxidization of the electric wiring; and a third insulation film provided on the second insulation film, and composed of silicon oxide formed by plasmatizing and reacting deposition gas, containing at least one of alkoxysilane compound and alkoxy siloxane, and at least one oxygen-containing gas selected from a group including O, NO, NO, CO, COand HO.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof.

  In recent years, with the progress of miniaturization of elements, a conductive material mainly composed of copper has been used as a lower resistance wiring material. In a semiconductor device using copper wiring, in order to prevent copper as a constituent material from diffusing into the insulating film, after forming the copper wiring by the damascene method, diffusion for preventing copper diffusion thereon A prevention film was formed. This diffusion prevention film constitutes a part of the interlayer insulating film, and preferably has a function of suppressing copper diffusion and is made of a material having a lower relative dielectric constant. From this point of view, only a part of insulating materials such as SiN, SiC, and SiCN can be used as the material for the diffusion preventing film.

  By the way, when a solid-state imaging device is considered as an example of a semiconductor device, the solid-state imaging device detects light transmitted through an interlayer insulating film with a photodiode and converts signal charges generated by the photodiode into an image signal. At this time, if a diffusion preventing film exists in the interlayer insulating film, it is caused by a difference in refractive index between the above-described material constituting the diffusion preventing film and silicon oxide which is a main constituent material of the interlayer insulating film. Light interference or the like occurs, and light transmitted through the interlayer insulating film decreases.

  From such a viewpoint, in the solid-state imaging device described in Patent Document 1, optical interference is prevented by providing an optical waveguide structure in the interlayer insulating film on the photodiode. Further, in the solid-state imaging device described in Patent Document 2, light interference is prevented by removing the diffusion prevention film existing on the optical path by dry etching.

JP 2003-324189 A JP 2008-199059 A JP 2002-164429 A

  However, the manufacture of the solid-state imaging device described in Patent Document 1 and Patent Document 2 requires a separate process for forming the optical waveguide structure on the optical path and a process for removing the diffusion prevention film on the optical path. As a result, the manufacturing process becomes complicated, and as a result, an increase in manufacturing cost cannot be avoided.

  An object of the present invention is to provide a structure capable of suppressing the influence of optical interference and a method for manufacturing the same in a solid-state imaging device including a wiring made of a conductive material mainly composed of copper without complicating the manufacturing process. is there.

  According to one aspect of the present invention, a semiconductor substrate provided with a plurality of pixels including a photoelectric conversion unit and a readout circuit unit that reads a signal based on charges generated by the photoelectric conversion unit, and the semiconductor substrate A first insulating film provided on the first insulating film; a wiring which is disposed in the first insulating film and made of a conductive material mainly composed of copper; and is provided on the first insulating film and the wiring. A solid-state imaging device having a second insulating film that prevents the wiring from being oxidized and a third insulating film that is provided on the second insulating film and includes a bond of carbon and nitrogen is provided. Is done.

  According to another aspect of the present invention, a step of forming a first insulating film on a semiconductor substrate, and a wiring made of a conductive material mainly composed of copper in the first insulating film Forming a second insulating film on the first insulating film and the wiring to prevent the wiring from being oxidized; and on the second insulating film, There is provided a method for manufacturing a solid-state imaging device including a step of forming a third insulating film including a bond of carbon and nitrogen.

  According to the present invention, in a solid-state imaging device including a wiring made of a conductive material mainly composed of copper, the influence of optical interference can be suppressed without complicating the manufacturing process. Thereby, the utilization efficiency of incident light can be improved and the sensitivity of a solid-state imaging device can be improved.

1 is a block diagram illustrating a schematic configuration of a solid-state imaging device according to a first embodiment of the present invention. It is a schematic sectional drawing which shows the structure of the solid-state imaging device by 1st Embodiment of this invention. It is a graph (the 1) which shows the relationship between the film thickness of the antioxidant film | membrane consisting of a plasma SiN film | membrane, and a reflectance. It is a graph (the 2) which shows the relationship between the film thickness of the antioxidant film | membrane which consists of a plasma SiN film | membrane, and a reflectance. It is process sectional drawing (the 1) which shows the manufacturing method of the solid-state imaging device by 1st Embodiment of this invention. It is process sectional drawing (the 2) which shows the manufacturing method of the solid-state imaging device by 1st Embodiment of this invention. It is the schematic of the film-forming apparatus used for film-forming of a silicon oxide film. It is a graph which shows the result of having measured the behavior of copper in the interface of copper wiring and antioxidant film by the SIMS method. It is a block diagram which shows schematic structure of the imaging system by 2nd Embodiment of this invention. It is a figure which shows the structural example of the imaging system by 3rd Embodiment of this invention, and a mobile body.

[First Embodiment]
A solid-state imaging device and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating a schematic configuration of the solid-state imaging device according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing the structure of the solid-state imaging device according to the present embodiment. 3 and 4 are graphs showing the relationship between the film thickness and the reflectance of the antioxidant film made of the plasma SiN film. 5 and 6 are process cross-sectional views illustrating the method for manufacturing the solid-state imaging device according to the present embodiment. FIG. 7 is a schematic view of a film forming apparatus used for forming a silicon oxide film. FIG. 8 is a graph showing the results of measuring the behavior of copper at the interface between the copper wiring and the antioxidant film by the SIMS method.

  First, the structure of the solid-state imaging device according to the present embodiment will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the solid-state imaging device according to the present embodiment includes a pixel region 10, a vertical scanning circuit 20, a column readout circuit 30, a horizontal scanning circuit 40, a control circuit 50, and an output circuit 60. doing.

  The pixel region 10 is provided with a plurality of pixels 12 arranged in a matrix over a plurality of rows and columns. Each pixel 12 includes a photoelectric conversion unit that performs photoelectric conversion, and a readout circuit unit that reads a signal based on the charge generated by the photoelectric conversion unit. The readout circuit unit includes a transfer transistor that transfers charge, a reset transistor that resets the charge-voltage conversion unit, an amplification transistor that outputs a signal corresponding to the potential of the charge-voltage conversion unit, and a selection transistor that selects the amplification transistor. The readout circuit unit may include a charge holding unit that holds charges from the photoelectric conversion unit. In the circuit part other than the photoelectric conversion part, for example, the charge holding part, incident light is blocked by the light shielding member. In addition, the pixel region 10 is provided with a color filter for controlling spectral sensitivity characteristics and a microlens for condensing light on the photoelectric conversion units, and light shielding for preventing color mixture between the photoelectric conversion units. A member may be formed. Further, the pixel region 10 may include pixels that do not output an image, such as an optical black pixel in which the photoelectric conversion unit is shielded from light and a dummy pixel that does not have the photoelectric conversion unit, in addition to effective pixels.

  Each row of the pixel array in the pixel region 10 is provided with a control signal line 14 extending in the row direction (lateral direction in FIG. 1). The control signal line 14 is connected to each pixel 12 arranged in the row direction, and forms a common signal line for these pixels 12. Each column of the pixel array in the pixel area 10 is provided with a vertical output line 16 extending in the column direction (vertical direction in FIG. 1). The vertical output lines 16 are respectively connected to the pixels 12 arranged in the column direction, and form a signal line common to these pixels 12.

  The control signal line 14 in each row is connected to the vertical scanning circuit 20. The vertical scanning circuit 20 is a circuit unit that supplies a control signal for driving the reading circuit unit of the pixel 12 to the pixel 12 via the control signal line 14 when reading the pixel signal from the pixel 12. One end of the vertical output line 16 of each column is connected to the column readout circuit 30. The pixel signal read from the pixel 12 is input to the column readout circuit 30 via the vertical output line 16. The column readout circuit 30 is a circuit unit that performs predetermined signal processing such as amplification processing and AD conversion processing on the pixel signal read from the pixel 12. The column readout circuit 30 may include a differential amplifier circuit, a sample / hold circuit, an AD conversion circuit, and the like.

  The horizontal scanning circuit 40 is a circuit unit that supplies the column readout circuit 30 with a control signal for sequentially transferring the pixel signals processed in the column readout circuit 30 to the output circuit 60 for each column. The control circuit 50 is a circuit unit for supplying control signals for controlling the operation and timing of the vertical scanning circuit 20, the column readout circuit 30, and the horizontal scanning circuit 40. The output circuit 60 includes a buffer amplifier, a differential amplifier, and the like, and is a circuit unit for outputting the pixel signal read from the column readout circuit 30 to a signal processing unit outside the solid-state imaging device.

  FIG. 2 is a partial cross-sectional view of the pixel 12 of the solid-state imaging device according to the present embodiment. FIG. 2 shows a photodiode PD and two transistors M1 and M2 constituting a photoelectric conversion unit among elements constituting the pixel 12. The transistor M1 is a transfer transistor. The transistor M2 is another transistor constituting the readout circuit unit, that is, a reset transistor, an amplification transistor, or a selection transistor.

  The silicon substrate 100 is provided with an element isolation region 102 that defines an active region. FIG. 2 shows an active region provided with a photodiode PD and a transistor M1 and an active region provided with a transistor M2 as active regions defined by the element isolation region 102.

  Impurity regions 104 and 106 are provided apart from each other in the silicon substrate 100 in one active region (left side in FIG. 2). The impurity region 104 has a function as a charge storage region of the photodiode PD. The impurity region 106 is a floating diffusion region. On the silicon substrate 100 between the impurity region 104 and the impurity region 106, a gate electrode 112 of the transistor M1 is provided via a gate insulating film. Impurity regions 108 and 110 are provided apart from each other in the silicon substrate 100 in the other active region (right side in the figure). On the silicon substrate 100 between the impurity region 108 and the impurity region 110, a gate electrode 114 of the transistor M2 is provided via a gate insulating film.

  An antireflection film 116 made of, for example, a silicon nitride film and an interlayer insulating film 118 made of, for example, a silicon oxide film are provided on the silicon substrate 100 provided with the photodiode PD, the transistors M1, M2, and the like. The antireflection film 116 has a function of preventing reflection of incident light at the interface between the silicon substrate 100 and the interlayer insulating film 118. A contact plug 122 electrically connected to the impurity regions 106, 108, 110 and the gate electrode 112 is disposed in the antireflection film 116 and the interlayer insulating film 118.

An interlayer insulating film 124 is provided on the interlayer insulating film 118 on which the contact plug 122 is disposed. The interlayer insulating film 124 is a silicon oxide film formed by converting and reacting a film forming gas containing at least one of an alkoxysilane compound and an alkoxysiloxane compound with an oxygen-containing gas described later. The aforementioned oxygen-containing gas is at least one gas selected from the group comprising O ₂ , N ₂ O, NO ₂ , CO, CO ₂ and H ₂ O. The result of analyzing the silicon oxide film formed under such conditions by FT-IR has a peak indicating a bond between carbon and nitrogen (hereinafter, C—N bond). The diffusion coefficient of copper in the insulating film containing a C—N bond is very small. In other words, the interlayer insulating film 124 has a function of suppressing copper diffusion. A copper wiring 128 electrically connected to the contact plug 122 is disposed in the interlayer insulating film 124.

  On the interlayer insulating film 124 on which the copper wiring 128 is disposed, an antioxidant film 130 and an interlayer insulating film 132 are provided. The antioxidant film 130 is made of, for example, a silicon nitride film having a thickness of 10 nm or less. The antioxidant film 130 functions as an antioxidant film for preventing the copper wiring 128 from being oxidized when the interlayer insulating film 132 is formed. The interlayer insulating film 132 is a silicon oxide film that is formed under the same conditions as the interlayer insulating film 124 and has a function of suppressing copper diffusion. A copper wiring 138 electrically connected to the copper wiring 128 is disposed on the antioxidant film 130 and the interlayer insulating film 132.

  On the interlayer insulating film 132 on which the copper wiring 138 is disposed, an antioxidant film 140 and an interlayer insulating film 142 are provided. Similar to the antioxidant film 130, the antioxidant film 140 is made of, for example, a silicon nitride film having a thickness of 10 nm or less. The antioxidant film 140 functions as an antioxidant film for preventing the copper wiring 138 from being oxidized when the interlayer insulating film 142 is formed. The interlayer insulating film 142 is a silicon oxide film formed under the same conditions as the interlayer insulating films 124 and 132 and having a function of suppressing copper diffusion. A copper wiring 144 electrically connected to the copper wiring 138 is disposed on the antioxidant film 140 and the interlayer insulating film 142.

  An antioxidant film 146 and an interlayer insulating film 148 are provided on the interlayer insulating film 142 on which the copper wiring 144 is disposed. Similar to the antioxidant films 130 and 140, the antioxidant film 146 is made of, for example, a silicon nitride film having a thickness of 10 nm or less. The interlayer insulating film 148 is made of, for example, a silicon oxide film. A via plug 152 electrically connected to the copper wiring 144 is disposed on the antioxidant film 146 and the interlayer insulating film 148.

  On the interlayer insulating film 148 provided with the via plug 152, an aluminum wiring 154 electrically connected to the via plug 152 and a pad electrode 156 are provided. A passivation film 158 having a pad opening 160 provided on the pad electrode 156 is provided on the interlayer insulating film 148 provided with the aluminum wiring 154 and the pad electrode 156.

  As described above, in the solid-state imaging device according to the present embodiment, the interlayer insulating films 124, 132, and 142 in which the copper wirings 128, 138, and 144 are disposed are configured by silicon oxide films having a function of suppressing copper diffusion. ing. Further, on the interlayer insulating films 124, 132, 142 on which the copper wirings 128, 138, 144 are disposed, the antioxidant films 130, 140, 146 made of a silicon nitride film having a thickness of 10 nm or less are provided. ing. These insulating films extend on the photodiode PD.

  In the solid-state imaging device according to the present embodiment, since the interlayer insulating films 124, 132, 142 have a function of suppressing copper diffusion, it is not necessary to provide a diffusion prevention film separately from the interlayer insulating films 124, 132, 142. . Further, the antioxidant films 130, 140, and 146 do not necessarily have a function of suppressing copper diffusion. Therefore, the antioxidant films 130, 140, and 146 only need to have a minimum film thickness that can suppress at least the oxidation of the copper wirings 128, 138, and 144. For example, the film thickness is appropriately adjusted from an optical viewpoint. It is possible.

  Here, the antioxidant films 130, 140, and 146 formed on the copper wirings 128, 138, and 144 will be described in detail with reference to FIGS.

  In the solid-state imaging device according to the present embodiment, incident light passes through the passivation film 158, the interlayer insulating films 148, 142, 132, 124, 118, the antioxidant films 146, 140, 130, and the anti-reflection film 116, then It is detected by the diode PD. For this reason, when light interference occurs at the interface between these insulating films and incident light is reflected, the amount of light reaching the photodiode PD is reduced, which affects the sensitivity of the solid-state imaging device.

  3 and 4 show simulation results of reflectance due to light interference when the anti-oxidation films 130, 140, and 146 are formed of a silicon nitride film deposited by plasma CVD (hereinafter referred to as "plasma SiN film"). It is a graph which shows the calculated | required result.

  FIG. 3 shows the average reflectance of incident light in the wavelength range of 400 nm to 750 nm when the film thicknesses of the antioxidant films 130, 140, and 146 are changed from 90 nm to 0 nm. As shown in FIG. 3, the reflectance is reduced by reducing the thickness of the antioxidant films 130, 140, and 146. When the thickness of the antioxidant films 130, 140, and 146 is 10 nm or less, the reflectance is 0. It can be reduced to 3 or less.

Table 1 shows the plasma SiN based on the reflectance when the anti-oxidation films 130, 140, and 146 are not provided (when the thickness of the plasma SiN film is 0 nm) based on the calculation result shown in FIG. The change rate of the reflectance in each thickness of a film | membrane is put together. That is, the change rate of the reflectance in Table 1, R ₀ the reflectance when the thickness of the plasma SiN film is 0 _[nm], the film thickness of the plasma SiN film is the reflectance when the x [nm] R _x is represented by (R ₀ −R _x ) / R ₀ .

  As shown in Table 1, when the thickness of the anti-oxidation films 130, 140, and 146 made of a plasma SiN film is 20 nm or more, the reflectance change rate increases rapidly, and when the film thickness is 70 nm, 34.8%. Even the reflectivity has increased. Considering that the lower the reflectance of incident light in a solid-state imaging device, the better, the thickness of the antioxidant films 130, 140, 146 made of a plasma SiN film is preferably 10 nm or less.

  FIG. 4 shows the average reflectance of incident light in the wavelength range of 400 nm to 750 nm when the thickness of the antioxidant films 130, 140, and 146 is changed from 11 nm to 0 nm. As shown in FIG. 4, the reflectance value is the minimum value when the thickness of the antioxidant films 130, 140, and 146 is 3 nm, and gradually increases as the thickness becomes thicker than 3 nm or thinner than 3 nm. . In other words, when the thickness of the antioxidant films 130, 140, and 146 made of a plasma SiN film is 3 nm, the utilization efficiency of incident light becomes the highest, and the sensitivity of the solid-state imaging device becomes the highest.

  Table 2 summarizes the results of calculating the reflectance fluctuation rate when the thickness of the plasma SiN film is 10 nm and 3 nm based on the calculation result shown in FIG. 4. In Table 2, the fluctuation range of the reflectance is the amount of change in the reflectance when the thickness of the SiN film changes within a range of ± 1 nm. The reflectance variation rate is a reflectance variation rate when the thickness of the SiN film changes within a range of ± 1 nm.

  As shown in Table 2, when the thickness of the antioxidant films 130, 140, and 146 made of a plasma SiN film varies within a range of ± 1 nm with respect to 10 nm, the reflectance variation rate becomes ± 1.23%. . On the other hand, when the film thickness of the anti-oxidation films 130, 140, and 146 made of the plasma SiN film varies within a range of ± 1 nm with respect to 3 nm, the variation rate of the reflectance decreases to ± 0.0598%. This is because the variation of the optical characteristics with respect to the variation in the thickness of the antioxidant films 130, 140, and 146 due to the process variation is 3 nm than when the thickness of the antioxidant films 130, 140, and 146 is 10 nm. It means that the time of is lower. That is, the influence on the sensitivity as an optical sensor becomes the smallest when the thickness of the antioxidant films 130, 140, and 146 made of a plasma SiN film is 3 nm.

  The anti-oxidation films 130, 140, and 146 may be composed of a SiC film or a SiCN film deposited by a plasma CVD method in addition to the above-described plasma SiN film. Even when a plasma SiC film or a plasma SiCN film is used, by setting the film thickness of the anti-oxidation films 130, 140, and 146 to 10 nm or less, the same reflectance suppressing effect as that when using the plasma SiN film is obtained. be able to. The anti-oxidation films 130, 140, and 146 are preferably uniform and dense films from the viewpoint of oxidation resistance. As a film forming method capable of forming such a film, an ALD method or the like can be used in addition to the plasma CVD method. Good. The optimum film thickness for the antioxidant films 130, 140, and 146 is preferably set as appropriate according to the constituent materials of the antioxidant films 130, 140, and 146, the layer structure of the solid-state imaging device, and the like.

  Next, the method for manufacturing the solid-state imaging device according to the present embodiment will be described with reference to FIGS.

  First, an element isolation region 102 that defines an active region is formed on the surface portion of the silicon substrate 100 by using, for example, an STI (Shallow Trench Isolation) method. Next, semiconductor elements such as the photodiode PD and the transistors M1 and M2 are formed in the active region defined by the element isolation region 102 in the same manner as in a known method for manufacturing a solid-state imaging device (FIG. 5A). The photodiode PD includes an impurity region 104 as a charge storage region. The transistor M1 includes an impurity region 106 and a gate electrode 112 that form a floating diffusion region. The transistor M2 includes impurity regions 108 and 110 constituting a source / drain region and a gate electrode 114.

  Next, a silicon nitride film of, eg, a 50 nm-thickness is deposited on the silicon substrate 100 provided with the photodiode PD, transistors M1, M2, etc., for example, by LP-CVD, plasma CVD, ALD, or the like. Thereby, an antireflection film 116 made of a silicon nitride film is formed on the photodiode PD.

  Next, after depositing a silicon oxide film on the antireflection film 116 by, for example, a CVD method, the surface thereof is flattened by a CMP method, and an interlayer insulating film 118 made of a silicon oxide film is formed.

  Next, contact holes 120 reaching the impurity regions 106, 108, 110, the gate electrode 112, and the like are formed in the interlayer insulating film 118 and the antireflection film 116 using photolithography and dry etching.

  Next, a barrier metal such as TiN is sequentially deposited on the entire surface, for example, by sputtering, for example, tungsten is deposited by, for example, CVD, and then tungsten and barrier metal on the interlayer insulating film 118 are removed by CMP. Thereby, a contact plug 122 embedded in the contact hole 120 is formed (FIG. 5B).

  Next, an interlayer insulating film 124 made of a silicon oxide film is formed on the interlayer insulating film 118 provided with the contact plug 122 by plasma CVD.

  FIG. 7 is a schematic view showing an example of a plasma CVD apparatus used for forming a silicon oxide film constituting the interlayer insulating film 124.

The plasma CVD apparatus 200 includes a chamber 202 that can be depressurized, an exhaust device 206 connected to the chamber 202 via an exhaust pipe 204, and an open / close valve 208 provided in the middle of the exhaust pipe 204. In the chamber 202, an upper electrode 210 and a lower electrode 216 that are arranged to face each other are provided. The upper electrode 210 has a shower head structure, and a film forming gas supplied from a gas supply pipe 222 can be introduced into the chamber 202 through the upper electrode 210. The gas supply pipe 222 includes an alkoxysilane compound or an alkoxysiloxane compound supply source, an oxygen-containing gas supply source, a hydrogen (H ₂ ) supply source, a nitrogen (N ₂ ) supply source (none of which is shown) Is connected. A representative example of the alkoxysilane compound is trimethoxysilane (TMS: SiH (OCH ₃ ) ₃ ). As a typical example of the alkoxysiloxane compound, tetramethyldisiloxane (TMDSO: (CH ₃ ) ₂ HSi—O—SiH (CH ₃ ) ₂ ) can be given. Examples of the oxygen-containing gas include oxygen (O ₂ ), nitric oxide (N ₂ O), nitrogen dioxide (NO ₂ ), carbon monoxide (CO), carbon dioxide (CO ₂ ), and water (H ₂ O). It is done. The upper electrode 210 may include a heater (not shown). The lower electrode 216 includes a heater 224 so that the substrate to be processed 226 placed on the lower electrode 216 can be heated to a predetermined temperature.

  The upper electrode 210 is connected to a power supply power source 214 that supplies high-frequency power with a frequency of 13.56 MHz via a matching box 212 for impedance matching of high-frequency power. The lower electrode 216 is connected to a power supply power supply 220 that supplies high-frequency power with a frequency of 400 kHz via a matching box 218 for impedance matching of high-frequency power. By supplying power from the power supply power sources 214 and 220 to the upper electrode 210 and the lower electrode 216, respectively, the film forming gas introduced into the chamber 202 can be turned into plasma.

The interlayer insulating film 124 is formed using such a plasma CVD apparatus 200. For example, TMS and N ₂ O (nitrous oxide) are supplied as source gases into the chamber 202, high frequency power of 13.56 MHz is applied to the upper electrode 210, and high frequency power of 400 kHz is applied to the lower electrode 216. Then, a capacitively coupled plasma is generated. The inside of the chamber 202 is controlled to a pressure of about 3 Torr by adjusting the exhaust amount by the exhaust device 206 by the open / close valve 208. In this manner, a silicon oxide film is deposited on the substrate 226 to be processed placed on the lower electrode 216.

  A silicon oxide film formed by a plasma CVD method using a source gas containing an alkoxysilane compound or an alkoxysiloxane compound and the oxygen-containing gas described above has a low dielectric constant, a low moisture content, and a high density. Excellent water resistance. It also has a high ability to prevent copper diffusion. Therefore, the silicon oxide film formed in this way is suitable as a constituent material of the interlayer insulating film on which the copper wiring is arranged. Note that a silicon oxide film formed by a plasma CVD method using a source gas containing an alkoxysilane compound or an alkoxysiloxane compound and an oxygen-containing gas is described in detail in Patent Document 3 by the same applicant.

  Next, a wiring trench 126 in which the copper wiring 128 is embedded is formed in the interlayer insulating film 124 formed in this manner by using photolithography and dry etching.

  Next, after depositing a barrier metal such as TaN by sputtering, for example, a copper film is grown by electrolytic plating using the barrier metal as a seed, and the wiring trench 126 is filled with the barrier metal and copper. Thereafter, the copper and the barrier metal on the interlayer insulating film 124 are removed by CMP to form a copper wiring 128 embedded in the wiring trench 126 (FIG. 5C).

  Next, an antioxidant film 130 is deposited on the interlayer insulating film 124 on which the copper wiring 128 is disposed. The antioxidant film 130 serves to prevent the copper wiring 128 from being oxidized in the process of depositing the interlayer insulating film 132 to be formed later.

  For example, a silicon nitride (SiN) film having a thickness of 3 nm, for example, is deposited by plasma CVD, and the antioxidant film 130 made of the plasma SiN film is formed. In addition to the plasma SiN film, an SiC film or SiCN film deposited by a plasma CVD method can also be applied to the antioxidant film 130. Further, as a film forming method, not only a plasma CVD method but also another film forming method capable of depositing a uniform ultrathin film, for example, an ALD method may be applied.

  The antioxidant film 130 only needs to have a film thickness sufficient to prevent the copper wiring 128 from being oxidized, and may not have a function of preventing copper diffusion.

  FIG. 8 is a graph showing the results of measuring the interface state between the copper film and the plasma SiN film by the SIMS method when the plasma SiN film (SiN) is deposited on the copper (Cu) film. As shown in FIG. 8, after depositing the plasma SiN film on the copper film, it can be seen that Cu atoms in the copper film diffuse about 20 nm to 30 nm from the interface between the copper film and the plasma SiN film. From the viewpoint of preventing copper diffusion, a plasma SiN film having a film thickness of 30 nm or more is required. As described above, the antioxidant film 130 of the imaging apparatus according to the present embodiment has a film thickness of 10 nm or less, for example, a film. A plasma SiN film having a thickness of about 3 nm is suitable.

  Next, an interlayer insulating film 132 is deposited on the antioxidant film 130 using the same film forming conditions as the interlayer insulating film 124 (FIG. 5D). At this time, the surface of the substrate is exposed to plasma containing oxygen. However, since the surface of the copper wiring 128 is covered with the antioxidant film 130, the copper wiring 128 is not oxidized.

  Next, a via hole 134 reaching the copper wiring 128 and a wiring groove 136 communicating with the via hole 134 are formed in the interlayer insulating film 132 by a dual damascene method using photolithography and dry etching.

  Next, after depositing a barrier metal such as TaN by sputtering, for example, a copper film is grown by electrolytic plating using the barrier metal as a seed, and the via hole 134 and the wiring trench 136 are filled with the barrier metal and copper. Thereafter, the copper and the barrier metal on the interlayer insulating film 132 are removed by CMP to form a copper wiring 138 embedded in the via hole 134 and the wiring trench 136 (FIG. 6A).

  Next, an antioxidant film 140 for preventing the copper wiring 138 from being oxidized is deposited on the interlayer insulating film 132 provided with the copper wiring 138 using the same film formation conditions as the antioxidant film 130. To do.

  Next, the same processes from the deposition process of the interlayer insulating film 132 to the deposition process of the antioxidant film 140 are repeated according to the required number of wiring layers of copper wiring. Here, assuming a case where a three-layer copper wiring is formed, an interlayer insulating film 142 provided with a copper wiring 144 and an antioxidant film 146 are formed on the interlayer insulating film 132 (see FIG. 6 (b)).

  Next, a silicon oxide film is deposited on the antioxidant film 146 by, for example, a CVD method, and an interlayer insulating film 148 made of a silicon oxide film is deposited.

  Next, a via hole 150 reaching the copper wiring 144 is formed in the interlayer insulating film 148 and the antioxidant film 146 using photolithography and dry etching.

  Next, a barrier metal such as TiN is sequentially deposited on the entire surface by, for example, sputtering, for example, tungsten by, for example, CVD, and then tungsten and barrier metal on the interlayer insulating film 148 are removed by CMP. Thereby, the via plug 152 embedded in the via hole 150 is formed.

  Next, after depositing a conductive film mainly composed of aluminum on the interlayer insulating film 148 provided with the via plug 152, the conductive film is patterned to form an aluminum wiring 154 and a pad electrode 156.

  Next, for example, a silicon nitride film is deposited by plasma CVD, for example, and a passivation film 158 made of a silicon nitride film is deposited.

  Next, a pad opening 160 exposing the pad electrode 156 is formed in the passivation film 158 by using photolithography and dry etching (FIG. 6C).

  Thereafter, as necessary, color filters and microlenses are formed on the passivation film 158 to complete the solid-state imaging device according to the present embodiment.

  As described above, according to the present embodiment, the influence of optical interference can be suppressed without complicating the manufacturing process in the solid-state imaging device including the wiring made of a conductive material mainly composed of copper. Thereby, the utilization efficiency of incident light can be improved and the sensitivity of a solid-state imaging device can be improved.

[Second Embodiment]
An imaging system according to a second embodiment of the present invention will be described with reference to FIG. The same components as those in the solid-state imaging device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. FIG. 9 is a block diagram illustrating a schematic configuration of the imaging system according to the present embodiment.

  The solid-state imaging device described in the first embodiment can be applied to various imaging systems. Examples of applicable imaging systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, in-vehicle cameras, observation satellites, and the like. A camera module including an optical system such as a lens and an imaging device is also included in the imaging system. FIG. 9 illustrates a block diagram of a digital still camera as an example of these.

  The imaging system 300 illustrated in FIG. 9 includes an imaging device 301, a lens 302 that forms an optical image of a subject on the imaging device 301, a diaphragm 304 for changing the amount of light passing through the lens 302, and protection of the lens 302. The barrier 306 is provided. The lens 302 and the diaphragm 304 are an optical system that focuses light on the imaging device 301. The imaging device 301 is the solid-state imaging device described in the first embodiment, and converts an optical image formed by the lens 302 into image data.

  The imaging system 300 also includes a signal processing unit 308 that processes an output signal output from the imaging device 301. The signal processing unit 308 performs AD conversion that converts an analog signal output from the imaging device 301 into a digital signal. In addition, the signal processing unit 308 performs an operation of outputting image data after performing various corrections and compressions as necessary. The AD conversion unit which is a part of the signal processing unit 308 may be formed on a semiconductor substrate provided with the imaging device 301 or may be formed on a semiconductor substrate different from the imaging device 301. Further, the imaging device 301 and the signal processing unit 308 may be formed on the same semiconductor substrate.

  The imaging system 300 further includes a memory unit 310 for temporarily storing image data and an external interface unit (external I / F unit) 312 for communicating with an external computer or the like. Further, the imaging system 300 includes a recording medium 314 such as a semiconductor memory for recording or reading imaging data, and a recording medium control interface unit (recording medium control I / F unit) 316 for recording or reading to the recording medium 314. Have Note that the recording medium 314 may be built in the imaging system 300 or detachable.

  The imaging system 300 further includes an overall control / arithmetic unit 318 that controls various arithmetic operations and the entire digital still camera, and a timing generation unit 320 that outputs various timing signals to the imaging device 301 and the signal processing unit 308. Here, the timing signal or the like may be input from the outside, and the imaging system 300 may include at least the imaging device 301 and the signal processing unit 308 that processes the output signal output from the imaging device 301.

  The imaging device 301 outputs an imaging signal to the signal processing unit 308. The signal processing unit 308 performs predetermined signal processing on the imaging signal output from the imaging device 301 and outputs image data. The signal processing unit 308 generates an image using the imaging signal.

  By applying the solid-state imaging device according to the first embodiment, the utilization efficiency of incident light can be improved, and a highly sensitive imaging system can be realized.

[Third Embodiment]
An imaging system and a moving body according to a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a diagram illustrating a configuration of the imaging system and the moving body according to the present embodiment.

  FIG. 10A shows an example of an imaging system related to a vehicle camera. The imaging system 400 includes an imaging device 410. The imaging device 410 is the solid-state imaging device described in the first embodiment. The imaging system 400 includes an image processing unit 412 that performs image processing on a plurality of image data acquired by the imaging device 410, and parallax (phase difference of parallax images) from the plurality of image data acquired by the imaging system 400. A parallax calculation unit 414 that performs calculation is included. The imaging system 400 also calculates a distance measurement unit 416 that calculates the distance to the object based on the calculated parallax, and a collision determination unit 418 that determines whether there is a collision possibility based on the calculated distance. And having. Here, the parallax calculation unit 414 and the distance measurement unit 416 are an example of a distance information acquisition unit that acquires distance information to the object. That is, the distance information is information related to the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 418 may determine the possibility of collision using any of these distance information. The distance information acquisition unit may be realized by hardware designed exclusively, or may be realized by a software module. Further, it may be realized by a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a combination thereof.

  The imaging system 400 is connected to a vehicle information acquisition device 420, and can acquire vehicle information such as a vehicle speed, a yaw rate, and a steering angle. In addition, the imaging system 400 is connected to a control ECU 430 that is a control device that outputs a control signal for generating a braking force for the vehicle based on a determination result in the collision determination unit 418. The imaging system 400 is also connected to an alarm device 440 that issues an alarm to the driver based on the determination result in the collision determination unit 418. For example, when the possibility of a collision is high as a determination result of the collision determination unit 418, the control ECU 430 performs vehicle control for avoiding a collision and reducing damage by applying a brake, returning an accelerator, and suppressing an engine output. The alarm device 440 warns the user by sounding an alarm such as a sound, displaying alarm information on a screen of a car navigation system, or applying vibration to the seat belt or the steering.

  In this embodiment, the imaging system 400 images the periphery of the vehicle, for example, the front or rear. FIG. 10B shows an imaging system when imaging the front of the vehicle (imaging range 450). The vehicle information acquisition device 420 sends an instruction to the imaging system 400 or the imaging device 410. With such a configuration, the accuracy of distance measurement can be further improved.

  In the above, an example of controlling so as not to collide with another vehicle has been described, but it can also be applied to control for automatically driving following other vehicles, control for automatically driving so as not to protrude from the lane, and the like. . Furthermore, the imaging system is not limited to a vehicle such as the own vehicle, but can be applied to a moving body (moving device) such as a ship, an aircraft, or an industrial robot. In addition, the present invention can be applied not only to mobile objects but also to devices that widely use object recognition, such as intelligent road traffic systems (ITS).

[Modified Embodiment]
The present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above embodiment, the solid-state imaging device including three layers of copper wiring is illustrated, but the total number of copper wiring is not particularly limited. The present invention is applicable to a solid-state imaging device provided with at least one layer of copper wiring.

  In addition, the schematic configuration and the pixel configuration of the solid-state imaging device illustrated in FIG. 1 are not limited to the above-described embodiment, and can be appropriately changed.

  The imaging system shown in the second embodiment is an example of an imaging system to which the imaging apparatus of the present invention can be applied. The imaging system to which the imaging apparatus of the present invention can be applied has the configuration shown in FIG. It is not limited to.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

PD ... Photoelectric converter (photodiode)
M1, M2 ... Transistor 12 in readout circuit unit ... Pixel 100 ... Silicon substrate 116 ... Antireflection film 124, 132, 142 ... Interlayer insulating film 128, 138, 144 ... Copper wiring 130, 140, 146 ... Antioxidation film

Claims (14)

A semiconductor substrate provided with a plurality of pixels including a photoelectric conversion unit, and a readout circuit unit that reads a signal based on the charge generated by the photoelectric conversion unit;
A first insulating film provided on the semiconductor substrate;
A wiring made of a conductive material mainly composed of copper, disposed in the first insulating film;
A second insulating film which is provided on the first insulating film and the wiring and prevents the wiring from being oxidized;
A solid-state imaging device comprising: a third insulating film provided on the second insulating film and including a bond of carbon and nitrogen. The solid-state imaging device according to claim 1, wherein the thickness of the second insulating film is 10 nm or less. The solid according to claim 1, further comprising a fourth insulating film provided between the semiconductor substrate and the first insulating film and preventing copper from diffusing into the semiconductor substrate. Imaging device. The solid-state imaging device according to claim 3, wherein the fourth insulating film has a function as an antireflection film for preventing reflection at an interface between the semiconductor substrate and the first insulating film. The first insulating film is at least one selected from the group comprising at least one of an alkoxysilane compound and an alkoxysiloxane compound, and O ₂ , N ₂ O, NO ₂ , CO, CO _2, and H ₂ O. 5. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is a silicon oxide formed by converting a film-forming gas containing an oxygen-containing gas into plasma and reacting it. The third insulating film is at least one selected from the group including at least one of an alkoxysilane compound and an alkoxysiloxane compound, and O ₂ , N ₂ O, NO ₂ , CO, CO _2, and H ₂ O. 6. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is a silicon oxide formed by converting a film-forming gas containing an oxygen-containing gas into plasma and reacting it. The said 1st insulating film, the said 2nd insulating film, and the said 3rd insulating film are extended on the said photoelectric conversion part. Any one of Claim 1 thru | or 6 characterized by the above-mentioned. The solid-state imaging device described. The solid-state imaging device according to any one of claims 1 to 7, wherein the second insulating film is a SiN film, a SiC film, or a SiCN film. The solid-state imaging device according to claim 1, further comprising: a second wiring made of a conductive material mainly composed of copper, which is disposed in the third insulating film. Forming a first insulating film on the semiconductor substrate;
Forming a wiring made of a conductive material mainly composed of copper in the first insulating film;
Forming a second insulating film on the first insulating film and the wiring to prevent the wiring from being oxidized;
Forming a third insulating film containing a bond of carbon and nitrogen on the second insulating film. A method of manufacturing a solid-state imaging device, comprising: The method for manufacturing a solid-state imaging device according to claim 10, wherein the film thickness of the second insulating film is 10 nm or less. The step of forming the third insulating film is selected from the group comprising at least one of an alkoxysilane compound and an alkoxysiloxane, and O ₂ , N ₂ O, NO ₂ , CO, CO ₂ and H ₂ O. The method for manufacturing a solid-state imaging device according to claim 10 or 11, wherein the third insulating film is formed by converting a film-forming gas containing at least one oxygen-containing gas into plasma and reacting it. A solid-state imaging device according to any one of claims 1 to 9,
A signal processing unit that processes a signal output from the pixel of the solid-state imaging device. A moving object,
A solid-state imaging device according to any one of claims 1 to 9,
Distance information acquisition means for acquiring distance information to an object from a parallax image based on a signal from the solid-state imaging device;
And a control means for controlling the mobile body based on the distance information.

Images