JP5368070B2 - Solid-state imaging device, manufacturing method thereof, and electronic information device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent degradation in picture quality by suppressing the dark current, in a more proper manner. <P>SOLUTION: In a plasma nitride silicon film forming step, a plasma nitride silicon film (plasma SiN film 22) is formed on a wiring layer 19, which is a patterned metal layer located above a photodiode 12, by a plasma CVD method for setting RF power representing plasma generation energy, set on a device side, to be 700-1,500 W. As a result, higher the RF power representing plasma generation energy set to the device side is raised, from 700 W to 900 W or higher, when forming the plasma SiN film 22, the larger the amount of hydrogen leaving from the plasma SiN film 22 will be, at a low temperature processing during later sintering treatment, thereby making the sintering treatment sure. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a solid-state imaging device including a semiconductor element that photoelectrically converts image light from a subject to image, a solid-state imaging device manufactured by the manufacturing method, and imaging using the solid-state imaging device as an image input device The present invention relates to electronic information equipment such as digital video cameras and digital still cameras used in the department, image input cameras, scanner devices, facsimile devices, camera-equipped mobile phone devices, and the like.

  In this type of conventional solid-state imaging device, a SiN film is formed as a passivation film by plasma CVD on the entire surface including the photodiode (PD), transfer gate (TG), and CCD, and a sintering process is performed by heat. Thus, the dark current on the surface of the photodiode as the photoelectric conversion unit (light receiving unit) constituting each pixel can be suppressed. This is disclosed in the method for manufacturing a solid-state imaging device of Patent Document 1.

In Patent Document 1, a PSG film having a film thickness of, for example, about 5000 to 6000 angstroms as a first passivation film for surface protection is formed on the entire surface including the photodiode (PD), transfer gate (TG), and CCD, for example, under reduced pressure. It is formed at a low temperature of about 400 degrees Celsius by the CVD method. A silicon nitride film (Si ₃ N ₄ film) having a film thickness of about 3000 to 5000 angstroms by a normal plasma CVD method using SiH ₄ and ammonia (NH ₃ ) gas, for example, as a second passivation film on the PSG film, That is, a plasma Si ₃ N ₄ film is formed. In this plasma CVD method, it is possible to form a film by decomposing constituent gases with plasma at a low temperature. If metal wiring such as Cu wiring or Al wiring is in the lower layer, these metal wiring melts at a high temperature of 500 degrees Celsius or higher. Therefore, the film formation temperature of the plasma CVD method should be as low as 300 to 400 degrees Celsius. Can do.
JP-A-63-185059

However, the above conventional technique has a problem that the dark current is not sufficiently suppressed depending on the conditions for forming the passivation film of the Si ₃ N ₄ film, and the image quality is deteriorated.

  The present invention solves the above-described conventional problems, and can more reliably prevent image quality degradation by better suppressing dark current or improving and stabilizing blue sensitivity. An imaging device manufacturing method, a solid-state imaging device manufactured by the solid-state imaging device manufacturing method, and an electronic information device such as a camera-equipped mobile phone device using the solid-state imaging device as an image input device in an imaging unit are provided. For the purpose.

  According to another aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device comprising: a solid-state imaging device provided with a light-receiving element that photoelectrically converts incident light from a subject; Or a plasma silicon nitride film forming step of forming a plasma silicon nitride film on the interlayer insulating film thereon by a plasma CVD method in which RF power indicating plasma generation energy set on the apparatus side is set to 700 W to 1500 W; And a sintering process for performing a sintering process by applying heat to the plasma silicon nitride film, whereby the above object is achieved.

According to another aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device comprising: a solid-state imaging device provided with a light-receiving element that photoelectrically converts incident light from a subject; Alternatively, a plasma silicon nitride film is formed on the interlayer insulating film thereon by a plasma CVD method in which the RF power indicating the plasma generation energy set on the apparatus side is set to 850 W to 1500 W so as to increase the amount of hydrogen released during the sintering process. A plasma silicon nitride film forming step for forming the film, whereby the above object is achieved.

  Preferably, the method further includes a sintering process step of performing a sintering process by applying heat to the plasma silicon nitride film in the method for manufacturing a solid-state imaging device of the present invention.

  Further preferably, when the plasma silicon nitride film is formed in the method for manufacturing a solid-state imaging device of the present invention, the RF power indicating the plasma generation energy set on the apparatus side is set to 930 W to 1130 W.

  Preferably, when the plasma silicon nitride film is formed in the method for manufacturing a solid-state imaging device of the present invention, the RF power indicating the plasma generation energy set on the apparatus side is set to 900 W to 1500 W.

  Further preferably, when the plasma silicon nitride film is formed in the method for manufacturing a solid-state imaging device of the present invention, the RF power indicating the plasma generation energy set on the apparatus side is set to 1000 W to 1500 W.

Further preferably, the plasma silicon nitride film forming step in the method for manufacturing a solid-state imaging device of the present invention is performed using SiH ₄ gas and NH ₃ gas at a temperature of 350 to 450 degrees Celsius and a pressure of 2 to 7 Torr. A silicon nitride film having a thickness of 250 nm to 350 nm is formed.

  More preferably, the film thickness of the plasma silicon nitride film in the method for manufacturing a solid-state imaging device of the present invention is an amount sufficient to supply hydrogen from the plasma silicon nitride film to the surface of the light receiving element during the sintering process. The thickness is such that hydrogen can be detached from the plasma silicon nitride film.

  Furthermore, preferably, the RF power in the method for manufacturing a solid-state imaging device of the present invention is an ionization ability that brings a constituent gas into a plasma state.

  More preferably, the patterned metal layer in the method for manufacturing a solid-state imaging device of the present invention is a wiring pattern, and the plasma silicon nitride film forming step includes forming a second plasma silicon nitride film thereon after forming the wiring pattern. Is deposited.

  Further preferably, the patterned metal layer in the method for manufacturing a solid-state imaging device of the present invention is a transfer gate for transferring a signal charge from the light receiving device, and the plasma silicon nitride film forming step includes: After the transfer gate is formed, a first plasma silicon nitride film is formed on the entire surface of the substrate.

  Further preferably, the plasma silicon nitride film forming step in the method for manufacturing a solid-state imaging device of the present invention is performed after forming a transfer gate for transferring the signal charge from the light receiving device as the patterned metal layer. A first plasma silicon nitride film forming step for forming a first plasma silicon nitride film on the entire surface of the substrate, and a second plasma silicon nitride film is formed thereon after forming a wiring pattern as the patterned metal layer A second plasma silicon nitride film forming step, and the sintering process is performed simultaneously after the first plasma silicon nitride film forming step and the second plasma silicon nitride film forming step, or This is performed after each of the first plasma silicon nitride film forming step and the second plasma silicon nitride film forming step.

  Further preferably, the first plasma silicon nitride film in the method for manufacturing a solid-state imaging device of the present invention is also formed on the light receiving device as an antireflection film.

  Further preferably, the patterned metal layer in the method for manufacturing a solid-state imaging device of the present invention is a gate electrode for transferring a signal charge from the light receiving device and a metal light shielding film thereon, and the plasma nitriding In the silicon film forming step, after forming an interlayer insulating film for flattening a step between the metal light shielding film and the light receiving element, the plasma silicon nitride film is formed thereon.

  Further preferably, in the method for manufacturing a solid-state imaging device of the present invention, the metal wiring in the peripheral region of the imaging region provided with the light receiving device and provided with a peripheral circuit composed of a number of transistors The plasma silicon nitride film is also formed as a moisture-proof passivation film on the formed surface.

  The solid-state imaging device of the present invention is manufactured by the above-described method for manufacturing a solid-state imaging device of the present invention, and a silicon surface defect caused by plasma dry etching is repaired, thereby achieving the above object.

  The solid-state imaging device of the present invention is manufactured by the method for manufacturing a solid-state imaging device of the present invention, and has improved and stabilized blue sensitivity, thereby achieving the above object.

  Preferably, in the solid-state imaging device of the present invention, each of the plurality of pixel units is provided with the light receiving element as a photoelectric conversion unit for each pixel unit, and is adjacent to the light receiving element and from the light receiving element. A charge transfer transistor for transferring the signal charge to the charge-voltage converter, and the signal charge transferred to the charge-voltage converter by the charge transfer transistor for each light receiving element is converted into a voltage, and the conversion voltage is A CMOS solid-state imaging device having a readout circuit that is amplified and read out as an imaging signal for each pixel unit.

  Further preferably, in the solid-state imaging device of the present invention, each of the plurality of pixel units is provided with the light receiving element as a photoelectric conversion unit for each of the pixel units, and adjacent to the light receiving element, from the light receiving element. This is a CCD solid-state imaging device in which a charge transfer unit for transferring signal charges in a predetermined direction and a gate electrode for controlling charge transfer of the read signal charges are arranged thereon.

  The electronic information device of the present invention uses the solid-state imaging device of the present invention as an image input device in an imaging unit, and thereby achieves the above object.

With the above configuration, the operation of the present invention will be described below.
In the present invention, a plasma silicon nitride film is formed on the patterned metal layer above the light receiving element by a plasma CVD method in which RF power indicating plasma generation energy set on the apparatus side is set to 700 W to 1500 W. A plasma silicon nitride film forming step is included.

  As a result, the RF power indicating the plasma generation energy set on the apparatus side during the formation of the plasma SiN film as the plasma silicon nitride film is increased from 700 W to 900 W and further, the lower the temperature from the plasma SiN film during the subsequent sintering process. As a result of the increased amount of desorbed hydrogen and reliable sintering, the surface of the photodiode is more reliably repaired on the surface of the silicon layer caused by plasma dry etching of the metal layer, and the dark current is better controlled. Thus, image quality deterioration is more reliably prevented.

  In the present invention, a plasma silicon nitride film is formed on the patterned metal layer by a plasma CVD method in which RF power indicating plasma generation energy set on the apparatus side is set to 850 W to 1500 W. It has a film forming process.

  As a result, the RF power is set to 850 W to 1500 W, and the plasma silicon nitride film is formed as a passivation film by the plasma CVD method, so that the blue sensitivity is improved and stabilized, and image quality deterioration can be prevented more reliably. It becomes possible.

  As described above, according to the present invention, as the RF power indicating the plasma generation energy set on the apparatus side when the plasma SiN film as the plasma silicon nitride film is formed is increased from 700 W to 900 W and further higher, Sintering can be performed reliably by increasing the amount of hydrogen desorbed from the plasma SiN film at a low temperature, and more reliably repairing silicon surface defects generated during plasma dry etching of metal layers on the photodiode surface Thus, dark current can be suppressed more favorably, and image quality deterioration can be prevented more reliably.

  Further, since the plasma silicon nitride film is formed as a passivation film by the plasma CVD method with the RF power set to 850 W to 1500 W, blue sensitivity can be improved and stabilized, and image quality deterioration can be prevented more reliably. .

  Hereinafter, a case where the present invention is applied to a CMOS image sensor (CMOS solid-state image sensor) for dark current suppression will be described as Embodiments 1 and 2 of the solid-state image sensor of the present invention, and Embodiment 3 of the solid-state image sensor of the present invention will be described. As a fourth embodiment of the solid-state imaging device of the present invention, a CMOS image sensor and a CCD for improving blue sensitivity will be described. After applying to an image sensor, Drawing 5 about Embodiment 5 of electronic information appliances, such as a mobile telephone apparatus with a camera, which used any of these solid-state image sensor Embodiments 1-4 as an image input device for an image pick-up part. Details will be described with reference to FIG.

  Here, the features of the CMOS image sensor and the CCD image sensor will be briefly described.

  A CMOS image sensor, like a CCD image sensor, transfers signal charges from each light receiving unit that photoelectrically converts incident light by a vertical transfer unit, and horizontally transfers signal charges from the vertical transfer unit by a horizontal transfer unit. The signal charge is read out from the light-receiving unit for each pixel and converted into a voltage by a selection control line composed of aluminum (Al) wiring or the like as in a memory device without using a CCD for charge transfer. The image pickup signal amplified in response to the signal is sequentially read out from the selected pixel. On the other hand, the CCD image sensor requires a plurality of positive and negative power supply voltages for driving the CCD. However, the CMOS image sensor can be driven by a single power supply and consumes less power than the CCD image sensor. And low voltage drive. Furthermore, since a CCD original manufacturing process is used for manufacturing a CCD image sensor, it is difficult to apply a manufacturing process generally used in a CMOS circuit as it is. On the other hand, since the CMOS image sensor uses a manufacturing process generally used in a CMOS circuit, a driver circuit for display control, a driver circuit for imaging control, a semiconductor memory such as a DRAM, and a logic circuit A logic circuit, an analog circuit, an analog-digital conversion circuit, and the like can be formed at the same time by a CMOS process frequently used in manufacturing. That is, the CMOS image sensor can be easily formed on the same semiconductor chip as the semiconductor memory, the driver circuit for display control, and the driver circuit for imaging control. There is an advantage that a production line can be easily shared with a driver circuit for display control and a driver circuit for imaging control.

(Embodiment 1)
FIG. 1 is a longitudinal sectional view schematically showing an example of the configuration of the main part of a CMOS solid-state imaging device according to Embodiment 1 of the present invention.

  In FIG. 1, in each pixel unit 1 of the CMOS solid-state imaging device 10 of Embodiment 1, a photodiode 12 as a photoelectric conversion unit (light receiving element) is formed for each pixel as a surface layer of the semiconductor substrate 11. Yes. Adjacent to the photodiode 12, there is provided a charge transfer portion 13 of a charge transfer transistor for transferring signal charges to a floating diffusion portion (charge voltage conversion portion) FD. On the charge transfer portion 13, a transfer gate 15 that is an extraction electrode is provided via a gate insulating film 14. Further, the signal charge transferred to the floating diffusion portion FD for each photodiode 12 is subjected to voltage conversion, amplified by an amplification transistor (not shown) in accordance with the converted voltage, and read out as an imaging signal for each pixel portion. Read circuit.

  This read circuit a reset transistor for resetting the floating diffusion portion FD to a predetermined voltage (for example, power supply voltage), and amplifies the signal according to the potential of the floating diffusion portion FD after resetting and outputs the signal to the signal line An amplifying transistor is provided in the logic transistor region 2, and the logic transistor region 2 is provided between the pixel portions 1 via the element isolation layer STI. Each of the reset transistor and the amplification transistor includes a source (S) / drain (D) and a gate (G).

  Above these transfer gate 15, floating diffusion portion FD, and logic transistor region 2, a circuit wiring portion of this readout circuit and a circuit wiring portion connected to transfer gate 15 and floating diffusion portion FD are provided. Yes. A first insulating film 16 is formed on the gate insulating film 14 and the transfer gate 15, a first wiring 17 is formed thereon, a second insulating film 18 is formed thereon, and a second wiring 19 is formed thereon. The circuit wiring portion is configured by forming.

  Also, between the wiring layer 17 and the transfer gate 15, between the wiring layer 17 and the floating diffusion portion FD, and between the wiring layer 17 and the source (S) / drain (D) and gate (G) of the logic transistor region 2, respectively. Contact plugs 20 made of a conductive material (for example, tungsten) are formed, and contact plugs 21 are formed between the wiring layers 17 and the wiring layers 19 thereon, respectively. And the transfer gate 15, the floating diffusion portion FD, and the source (S) / drain (D) and gate (G) of the logic transistor region 2 are electrically connected to each other.

  Further, on the second insulating film 18 and the wiring layer 19, dark current on the surface of the photodiode 12 constituting each pixel portion 1 (charge is generated in a state where no light is applied) is suppressed by a sintering process using heat. Therefore, the plasma SiN film 22 is formed as a passivation film by the plasma CVD method.

  On this plasma SiN film 22, a color filter (not shown) of R, G, B color arrangement (for example, Bayer arrangement) arranged for each photodiode 12 is formed, and further a planarizing film ( (Not shown) is formed, and a condensing microlens 23 to the photodiode 12 as a light receiving portion is formed thereon. In this case, the microlens 23 may be formed of a color filter material, and in this case, the color filter and the flattening film are not necessary.

Here, the passivation film forming step in the method for manufacturing the CMOS solid-state imaging device 10 of Embodiment 1 will be described in detail.
As a passivation film for protecting the surface, for example, by plasma CVD using SiH ₄ (silane gas) and ammonia (NH ₃ ) gas, the temperature is 350 to 450 degrees Celsius (here, 300 degrees Celsius), and the pressure is 2 to 7 Torr (here) Under a pressure of 2 Torr, the film thickness is 250 nm to 350 nm (here, the film thickness is 300 nm; a film thickness capable of detaching a sufficient amount of H ₂ to supply hydrogen from the SiN film to the surface of the photodiode 12 during the sintering process. ) Silicon nitride film (Si ₃ N ₄ film), that is, a plasma SiN film 22 is formed. In this plasma CVD method, the plasma SiN film 22 can be formed by decomposing the constituent gases at a low temperature with plasma. If metal wiring such as Cu wiring or Al wiring is in the lower layer of the plasma SiN film 22, these metal wiring melt at a high temperature of 500 degrees Celsius or higher, and therefore the film formation temperature of the plasma CVD method is 350 to 450 degrees Celsius. Convenient because of low temperature.

  The RF (radio frequency; radio frequency) power for forming the plasma SiN film 22 is in the range of 700 W to 1500 W. More preferably, the RF power for forming the plasma SiN film 22 is 900 W to 1500 W (or 1000 W to 1500 W). The RF power indicates the plasma generation energy set on the apparatus side, and is an ionization ability that brings the constituent gases into a plasma state. The RF power refers to a high-frequency power value that excites plasma.

  FIG. 2 is a diagram showing the dependence of dark current on RF power when forming a passivation film in the solid-state imaging device of FIG.

  When a passivation film, which is a plasma SiN film 22, is formed after forming the uppermost aluminum (Al) wiring pattern and before forming a color filter, the RF power (W; watt) indicating the plasma generation energy set on the apparatus side is 700 W or more. By setting the power to 1500 W or less, dark current can be suppressed and image quality can be improved. Even if the RF power is 700 W, the dark current can be suppressed to about half of the normal RF power of 650 W. When the RF power is 700 W, as shown in FIG. 2, the dark current value changes greatly as compared with other regions. As shown in FIG. 2, the RF power for raising the rate needs to be 900 W or more and 1500 W or less (or 1000 W or more and 1500 W or less) at which the change rate of the dark current with respect to the RF power approaches a constant value. In this case, the dark current can be suppressed to 1/3 or less of the normal RF power of 650 W and not only can the image quality be improved, but even if the output value varies between devices, Thus, the dark current value can be made equal, which is advantageous for mass production. Also, in the number of steps for forming the plasma SiN film, the higher the RF power, the easier it is to attach the film. If the RF power is set to 900 W or more and 1500 W, the production efficiency is 7 to 8% compared to the normal RF power of 650 W. improves. The RF power below 1500 W is a limit value of the RF power of the apparatus.

  As described above, as the RF power is increased, the amount of hydrogen desorbed from the plasma SiN film 22 at a lower temperature during the subsequent sintering process increases and the sintering process is performed more reliably. As a result, the plasma of the metal layer is formed on the surface of the photodiode 12. Silicon surface defects generated during dry etching can be repaired, dark current can be further suppressed, and image quality can be improved more reliably.

  In this case, the RF power of the plasma CVD method according to the first embodiment is 700 to 1500 W higher than the normal 650 W, and is the ability to bring the constituent gases into a plasma state, which increases the ionization rate compared to the normal ionization rate. Thus, the hydrogen in the plasma SiN film is easily desorbed at a low temperature.

(Embodiment 2)
In the first embodiment, the plasma SiN film 22 is formed and the sintering process is performed after the uppermost aluminum (Al) wiring pattern is formed and before the color filter is formed. A case where a plasma SiN film 24 to be described later is formed also on the surface side of the diode 12 via the gate insulating film 14 of an oxide film to perform a sintering process will be described in detail.

  FIG. 3 is a longitudinal sectional view schematically showing an example of the configuration of the main part of a CMOS solid-state imaging device according to Embodiment 2 of the present invention. In addition, the same member number is attached | subjected and demonstrated to the structural member which show | plays the same effect as the structural member of the CMOS solid-state image sensor 10 of FIG.

  In FIG. 3, in each pixel portion 1 of the CMOS solid-state imaging device 10 </ b> A of the second embodiment, a photodiode 12 as a photoelectric conversion portion (light receiving element) is formed for each pixel as a surface layer of the semiconductor substrate 11. Yes. Adjacent to the photodiode 12, there is provided a charge transfer portion 13 of a charge transfer transistor for transferring signal charges to a floating diffusion portion (charge voltage conversion portion) FD. A transfer gate 15 that is an extraction electrode is provided on the charge transfer portion 13 via a gate insulating film 14.

  A plasma SiN film 24 is formed on the entire surface of the gate insulating film 14 and the transfer gate 15 by plasma CVD in order to suppress dark current on the surface of the photodiode 12 constituting each pixel unit 1 by a sintering process using heat. It is formed as a passivation film.

  Above the transfer gate 15, the floating diffusion portion FD, and the logic transistor region 2, the signal charge transferred to the floating diffusion portion FD for each photodiode 12 is voltage-converted and amplified according to the converted voltage. First wiring 17 on the first insulating film 16 as a circuit wiring part of a readout circuit for reading out as an imaging signal for each pixel part, or a circuit wiring part connected to the transfer gate 15 and the floating diffusion part FD, Second wirings 19 on the second insulating film 18 are formed above and below.

  Further, a plasma SiN film 22 is formed on the second insulating film 18 and the wiring layer 19 by plasma CVD in order to suppress dark current on the surface of the photodiode 12 constituting each pixel unit 1 by heat sintering. It is formed as a passivation film.

  On this plasma SiN film 22, a color filter (not shown) of R, G, B color arrangement (for example, Bayer arrangement) arranged for each photodiode 12 is formed, and further a planarizing film ( (Not shown) is formed, and a condensing microlens 23 to the photodiode 12 as a light receiving portion is formed thereon.

  Here, the passivation film forming step in the method for manufacturing the CMOS solid-state imaging device 10A of Embodiment 2 will be described in detail.

In the first passivation film forming step, the transfer gate 15 on the gate insulating film 14 is formed into a predetermined gate shape by plasma dry etching, and then plasma SiN is formed on the entire surface of the gate insulating film 14 and the transfer gate 15 by plasma CVD. The film 24 is formed as a passivation film. In this case, the RF power (W; watt) indicating the plasma generation energy set on the apparatus side is set to 700 W or more and 1500 W or less as described above. Preferably, the RF power is set to 900 W or more and 1500 W or less (or 1000 W or more and 1500 W or less) as described above. For example, by plasma CVD using SiH ₄ (silane gas) and ammonia (NH ₃ ) gas as constituent gases, the temperature is 350 to 450 degrees Celsius (here, 300 degrees Celsius), and the pressure is 2 to 7 Torr (here, the pressure is 2 Torr). A silicon nitride film having a film thickness of 250 nm to 350 nm (here, the film thickness is 300 nm; a film thickness capable of detaching a sufficient amount of H ₂ from the SiN film to supply hydrogen to the surface of the photodiode 12 during the sintering process). (Si ₃ N ₄ film), that is, a plasma SiN film 24 is formed.
Thereby, it is possible to function as an antireflection film for returning incident light reflected from the surface side of the gate insulating film 14 to the photodiode 12 side by the plasma SiN film 24. In addition, as a first passivation film forming step under the same conditions as in the first embodiment, a plasma SiN film 24 formed on the surface side of the photodiode 12 also as an antireflection film via the gate insulating film 14 is used. To sinter.

Next, in the second passivation film forming step, an aluminum (Al) wiring pattern is formed into a predetermined gate shape by plasma dry etching, and then a passivation film which is a plasma SiN film is formed on the wiring pattern. In this case as well, the RF power (W; watt) indicating the plasma generation energy set on the apparatus side is set to 700 W or more and 1500 W or less as described above. Preferably, the RF power is set to 900 W or more and 1500 W or less (or 1000 W or more and 1500 W or less) as described above. Further, by a plasma CVD method using, for example, SiH ₄ (silane gas) and ammonia (NH ₃ ) gas as constituent gases, the temperature is 350 to 450 degrees Celsius (here, 300 degrees Celsius), the pressure is 2 to 7 Torr (here, the pressure is 2 Torr). ) Is nitrided with a film thickness of 250 nm to 350 nm (here, the film thickness is 300 nm; a film thickness capable of detaching a sufficient amount of H ₂ from the SiN film to supply hydrogen to the surface of the photodiode 12 during the sintering process). A silicon film (Si ₃ N ₄ film), that is, a plasma SiN film 22 is formed.

  When the first passivation film forming process after the transfer gate is formed and the second passivation film forming process after the wiring pattern is formed are only the second passivation film forming process of the first embodiment. In comparison, the dark current can be further suppressed and the image quality can be improved more reliably.

(Embodiment 3)
In the first and second embodiments, the case where the plasma SiN film is formed by setting the RF power to 700 W or more and 1500 W under the CMOS solid-state image sensor has been described. However, in the third embodiment, the RF power is set in the CCD solid-state image sensor. The case where the plasma SiN film is formed with the power set at 700 W or more and 1500 W will be described.

  FIG. 4 is a vertical cross-sectional view schematically showing an exemplary configuration of a main part of a CCD solid-state imaging device according to Embodiment 3 of the present invention.

  In FIG. 4, each pixel portion of the CCD solid-state imaging device 30 of Embodiment 3 is provided with a photodiode portion 32 that photoelectrically converts incident light as a light receiving element to generate a signal charge on a semiconductor substrate 31. A charge transfer unit 33 for transferring the signal charge from the photodiode 32 adjacent to each photodiode 32 and a gate insulating film 34 on the charge transfer part 33 are controlled to charge transfer the read signal charge. A gate electrode 35 is disposed as a charge transfer electrode for this purpose. A stop layer 37 as an element isolation layer is provided between the pixel portions 36 (between horizontal directions) including the photodiode 32 and the charge transfer portion 33.

  A light shielding film 39 is formed on the gate electrode 35 through an insulating layer 38 to prevent incident light from being reflected by the gate electrode 35 and generating noise. An opening 39 a is formed in the light shielding film 39 above the photodiode 32.

  An interlayer insulating film 40 for flattening the stepped portion between the surface of the photodiode 32 and the light shielding film 39 is formed. On this interlayer insulating film 40, RF power (W; indicating plasma generation energy) set on the device side in order to suppress dark current on the surface of the photodiode 32 constituting each pixel portion 36 by a sintering process by heat. As described above, the plasma SiN film 41 is formed as a passivation film by the plasma CVD method in which the watt is set to 700 W or more and 1500 W or less. Also in this case, it is preferable to set the RF power to 900 W or more and 1500 W or less (or 1000 W or more and 1500 W or less) as described above.

  On this plasma SiN film 41, a color filter 42 of each color arrangement (for example, Bayer arrangement) of R, G, B arranged for each photodiode 32 is formed, and further, a planarizing film 43 is formed thereon, On top of that, a condensing microlens 44 to the photodiode 32 as a light receiving portion is formed.

  Here, the passivation film forming step in the method for manufacturing the CCD solid-state imaging device 30 of the third embodiment will be described in detail.

As in the case of the first and second embodiments, the temperature is 350 to 450 degrees Celsius (here, by a plasma CVD method using SiH ₄ (silane gas) and ammonia (NH ₃ ) gas as a passivation film for surface protection, for example. 300 degrees Celsius), pressure 2-7 Torr (here, pressure 2 Torr), film thickness 250 nm to 350 nm (here, film thickness 300 nm; sufficient to supply hydrogen from the SiN film to the surface of the photodiode 32 during the sintering process. A silicon nitride film (Si ₃ N ₄ film), that is, a plasma SiN film 41 having a thickness capable of releasing an amount of H ₂ is formed.

  With the above configuration, light incident on an imaging region in which the plurality of pixel portions 36 are two-dimensionally arranged is first condensed by the microlens 44 and incident on the photodiode 32. Next, the light incident on the photodiode 32 is photoelectrically converted by the photodiode 32 to become signal charges. This signal charge is read out to the charge transfer unit 33 and sequentially transferred in a predetermined direction.

  Therefore, according to the third embodiment, as the RF power is increased from 700 W to 900 W and further to 1000 W or more, the amount of hydrogen desorbed from the plasma SiN film 41 at a low temperature during the subsequent sintering process increases and the sintering process is reliably performed. As a result, silicon surface defects generated during the plasma dry etching of the metal layer on the surface of the photodiode 32 can be more reliably repaired, dark current can be further suppressed, and image quality can be improved.

(Embodiment 4)
In the first to third embodiments, in the CMOS solid-state imaging device and the CCD solid-state imaging device, the RF power is set to 700 W or more and 1500 W or less in order to more effectively suppress dark current and more reliably prevent image quality deterioration. In the fourth embodiment, the RF power is set to 850 W or more and 1500 W or less in order to improve and stabilize blue sensitivity and more reliably prevent image quality degradation. A case where a plasma SiN film is formed by plasma CVD will be described.

  FIG. 5 is a longitudinal sectional view schematically showing an example of the configuration of the main part of a CMOS solid-state imaging device according to Embodiment 4 of the present invention. In addition, the same code | symbol is attached | subjected to the structural member which show | plays the same effect as each structural member of FIG. 1, and the description is abbreviate | omitted.

  As shown in FIG. 5, in the CMOS solid-state imaging device 50 according to the fourth embodiment, the darkness of the surface of the photodiode 12 constituting each pixel unit 1 is formed on the second insulating film 18 and the wiring layer 19 by a sintering process using heat. The plasma SiN film 22A is passivated by plasma CVD in order to suppress current (charge is generated in the absence of light), improve and stabilize blue sensitivity, and more reliably prevent image quality degradation. It is formed as a film. At this time, the RF power indicating the plasma generation energy set on the apparatus side is set to 850 W or more and 1500 W or less.

  On the plasma SiN film 22A, as described above, a color filter (not shown) of R, G, B color arrangement (for example, Bayer arrangement) arranged for each photodiode 12 is formed. A planarizing film (not shown) is formed thereon, and a condensing microlens 23 for the photodiode 12 as a light receiving portion is formed thereon. In this case, the microlens 23 may be formed of a color filter material, and in this case, the color filter and the flattening film are not necessary.

  The passivation film forming step in the method for manufacturing the CMOS solid-state imaging device 50 of the fourth embodiment having the above configuration will be described in detail.

As a passivation film for protecting the surface (for moisture resistance), for example, by a plasma CVD method using SiH ₄ (silane gas) and ammonia (NH ₃ ) gas, the temperature is 350 to 450 degrees Celsius (here, 300 degrees Celsius), and the pressure is 2 7 Torr (here, pressure 2 Torr), film thickness 250 nm to 350 nm (here, film thickness 300 nm; sufficient amount of H ₂ can be removed to supply hydrogen from the SiN film to the surface of the photodiode 12 during the sintering process. A silicon nitride film (Si ₃ N ₄ film), that is, a plasma SiN film 22A. In this plasma CVD method, the plasma SiN film 22A can be formed by decomposing the constituent gases with plasma at a low temperature. When metal wiring such as Cu wiring or Al wiring is in the lower layer of the plasma SiN film 22A, these metal wiring melt at a high temperature of 500 degrees Celsius or higher, and the film formation temperature of the plasma CVD method is 350 to 450 degrees Celsius. Convenient because of low temperature.

  Film formation is performed within the range of RF power of 850 W to 1500 W when forming the plasma SiN film 22A. More preferably, in order to further stabilize the blue sensitivity, the film formation is performed at an RF power of 930 W to 1130 W when forming the plasma SiN film 22A. As described above, the RF power indicates the plasma generation energy set on the apparatus side, and is an ionization ability that brings the constituent gases into a plasma state. The RF power refers to a high-frequency power value that excites plasma.

  FIG. 6 is a diagram illustrating the RF power dependency when the passivation film is formed with a large blue sensitivity in the solid-state imaging device of FIG.

  Of the three primary colors, R (red), G (green), and B (blue), the B (blue) color light is most easily absorbed and attenuated by the plasma SiN film 22A. Is obtained in FIG. 6 as blue sensitivity to B (blue) color light (wavelength 450 nm). If the RF power changes, the film quality (particularly the refractive index) of the plasma SiN film 22A changes with respect to B (blue) color light (wavelength 450 nm). In short, if the RF power is increased, the refractive index of the plasma SiN film 22A is lowered with respect to B (blue) color light (wavelength 450 nm). In this case, the light transmittance of the plasma SiN film 22A is also improved with respect to B (blue) color light (wavelength 450 nm). In particular, if the RF power is increased, the transmittance for B (blue) color light (wavelength 450 nm) is increased and the blue sensitivity is improved, so that image quality deterioration can be more reliably prevented (a clear image can be obtained). Further, if the RF power is increased, dark current can be suppressed (noise suppression) more satisfactorily and image quality deterioration can be more reliably prevented (a clear image can be obtained). Note that there is no significant change in R (red) and G (green) color light even if the RF power changes.

  As shown in FIG. 6, the solid line indicates the average value of the blue sensitivity with respect to the RF power (W), and the dotted lines above and below the maximum and minimum values of the blue sensitivity with respect to the RF power (W). Each value is shown.

  When the standard value of blue sensitivity is set to the spec “76”, the standard value of blue sensitivity is set as long as the RF power (W) is 850 W or more with respect to the minimum value of the blue sensitivity with respect to the RF power (W). The value spec “76” or more can be satisfied. Therefore, if the maximum RF power for using the apparatus stably for a long period is 1500 (W), the RF power when forming the plasma SiN film 22A is within the range of 850 W to 1500 W. Good. More preferably, in order to further stabilize the blue sensitivity, film formation may be performed within the range of RF power for forming the plasma SiN film 22A within a range from 930 W to 1130 W.

Although not particularly described in the first to fourth embodiments, the first to fourth embodiments are applied to a solid-state imaging device, and after formation of metal wiring such as a logic circuit and a drive control circuit of a semiconductor device. It can be applied as a passivation film for surface protection (for moisture prevention). As described above, for example, SiH ₄ (silane gas) and ammonia are used as a moisture-proof passivation film on the surface after formation of metal wiring such as a logic circuit and a drive control circuit composed of a plurality of transistors of a semiconductor device other than a solid-state imaging device. The plasma SiN film 22 or 22A can be formed at a low temperature by plasma CVD using (NH ₃ ) gas. Also, on the surface after forming the metal wiring in the peripheral region of the imaging region where the light receiving element is provided, and in the peripheral region where the peripheral circuit portion (logic circuit or drive control circuit) composed of many transistors is provided Alternatively, the plasma SiN film 22 or 22A may be formed as a moisture-proof passivation film.

  In the fourth embodiment, in the CMOS solid-state imaging device 10 of the first embodiment, the RF power is 850 W or more and 1500 W or less, instead of the plasma SiN film 22 formed under the condition that the RF power is 700 W or more and 1500 W or less. In the above description, the plasma SiN film 22A is formed as a passivation film for improving and stabilizing the blue sensitivity. However, the plasma SiN film 22A is formed together with the plasma SiN film 22A or separately from the plasma SiN film 22, as shown in FIG. In place of the plasma SiN film 24 formed with RF power of 700 W or more and 1500 W or less in the CMOS solid-state image pickup device 2A, the plasma SiN film 22A is improved and stable in blue sensitivity under the condition of RF power of 850 W or more and 1500 W or less. It may be formed as a passivation film .

  Furthermore, in the fourth embodiment, in the CMOS solid-state imaging device 50, the case where the plasma SiN film 22A is formed as a passivation film for stabilizing the blue sensitivity under the condition where the RF power is 850 W or more and 1500 W or less has been described. As shown in FIG. 4, in the CCD solid-state imaging device 30 of the third embodiment, instead of the plasma SiN film 41 formed under conditions where the RF power is 700 W or more and 1500 W or less, the CCD solid-state imaging device 30A has an RF power of 850 W or more. The plasma SiN film 41A may be formed as a passivation film for stabilizing blue sensitivity under the condition of 1500 W or less. In addition to the plasma SiN film 41A or separately from the plasma SiN film 41, the plasma SiN film 24 or 24A described above may be formed on the entire surface of the gate insulating film 14 and the transfer gate 15 in FIG.

(Embodiment 5)
FIG. 7 is a block diagram illustrating a schematic configuration example of an electronic information device using, as an imaging unit, a solid-state imaging device including the solid-state imaging device according to any one of Embodiments 1 to 4 of the present invention as Embodiment 5 of the present invention. is there.

  In FIG. 7, the electronic information device 90 according to the fourth embodiment performs various signal processing on the imaging signals from the solid-state imaging devices 10, 10 </ b> A, 30, 30 </ b> A, 50, or 50 </ b> A according to the first to fourth embodiments, In addition to the solid-state imaging device 91 to be obtained, a memory unit 92 such as a recording medium that can record data after performing predetermined signal processing for recording the color image signal from the solid-state imaging device 91, and the solid-state imaging device 91 Display means 93 such as a liquid crystal display device that can display a color image signal on a display screen such as a liquid crystal display screen after predetermined signal processing for display, and the color image signal from the solid-state imaging device 91 for communication. A communication means 94 such as a transmission / reception means that enables communication processing after predetermined signal processing, and a color image signal from the solid-state imaging device 91 are subjected to predetermined signal processing for printing. Has at least one of the image output means 95 such as a printer which allows printing later.

  As described above, the electronic information device 90 includes, for example, a digital camera such as a digital video camera and a digital still camera, an in-vehicle camera such as a surveillance camera, a door phone camera, and an in-vehicle rear surveillance camera, and a video phone camera. An electronic device having an image input device such as an image input camera, a scanner device, a facsimile device, a camera-equipped mobile phone device, and a portable terminal device (PDA) is conceivable.

  Therefore, according to the fifth embodiment, on the basis of the color image signal from the solid-state imaging device 91, this is displayed on the display screen, or the image output means 95 prints it out on the paper. (Printing), communicating this as communication data in a wired or wireless manner, performing a predetermined data compression process in the memory unit 92 and storing it in a good manner, or performing various data processings satisfactorily Can do.

  In the first to third embodiments, as described above, above the light receiving element, on the patterned metal layer (the entire surface on the wiring layer 19 or the gate insulating film 14 and the transfer gate 15) or on the interlayer thereabove. A plasma silicon nitride film forming step is provided for forming a plasma silicon nitride film on the insulating film by a plasma CVD method in which an RF power indicating plasma generation energy set on the apparatus side is set to 700 W to 1500 W. Accordingly, it is possible to achieve the object of the present invention in which dark current can be suppressed more effectively and image quality deterioration can be more reliably prevented.

  In the fourth embodiment, as described above, above the light receiving element, on the patterned metal layer (the entire surface on the wiring layer 19 or the gate insulating film 14 and the transfer gate 15) or the interlayer insulating film thereon In addition, a plasma silicon nitride film forming step of forming a plasma silicon nitride film by a plasma CVD method in which an RF power indicating plasma generation energy set on the apparatus side is set to 850 W to 1500 W is provided. Thus, the object of the present invention can be achieved, which can improve and stabilize the blue sensitivity and more reliably prevent the deterioration of the image quality.

  As mentioned above, although this invention has been illustrated using preferable Embodiment 1-5 of this invention, this invention should not be limited and limited to this Embodiment 1-5. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments 1 to 5 of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention relates to a method for manufacturing a solid-state imaging device including a semiconductor element that photoelectrically converts image light from a subject to image, a solid-state imaging device manufactured by the manufacturing method, and imaging using the solid-state imaging device as an image input device Plasma SiN as a plasma silicon nitride film in the field of electronic information equipment such as digital video cameras and digital still cameras used in the department, image input cameras, scanner devices, facsimile devices, camera-equipped mobile phone devices, etc. As the RF power indicating the plasma generation energy set on the apparatus side during film formation is increased from 700 W to 900 W or more, the amount of hydrogen desorbed from the plasma SiN film at a low temperature during the subsequent sintering process is increased to perform the sintering process. Can be reliably performed on the surface of the photodiode. Te, by more reliably repaired silicon surface defects generated during plasma dry etching of the metal layer, performed better suppression of dark current, it is possible to more reliably prevent the image quality deterioration.

  Further, since the plasma silicon nitride film is formed as a passivation film by the plasma CVD method with the RF power set to 850 W to 1500 W, blue sensitivity can be improved and stabilized, and image quality deterioration can be prevented more reliably. .

It is a longitudinal cross-sectional view which shows typically the principal part structural example of the CMOS solid-state image sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the RF power dependence at the time of passivation film formation of the dark current in the solid-state image sensor of FIG. It is a longitudinal cross-sectional view which shows typically the principal part structural example of the CMOS solid-state image sensor which concerns on Embodiment 2 of this invention. It is a longitudinal cross-sectional view which shows typically the principal part structural example of the CCD solid-state image sensor which concerns on Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows typically the principal part structural example of the CMOS solid-state image sensor which concerns on Embodiment 4 of this invention. It is a figure which shows the RF power dependence at the time of passivation film film-forming of the magnitude | size of the blue sensitivity in the solid-state image sensor of FIG. It is a block diagram which shows the example of schematic structure of the electronic information apparatus which used the solid-state imaging device containing the solid-state image sensor in any one of Embodiment 1-4 of this invention for Embodiment 5 of this invention for an imaging part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 36 Pixel part 2 Logic transistor area 10, 10A, 50, 50A CMOS solid-state image sensor 11, 31 Semiconductor substrate 12, 32 Photo diode 13 Charge transfer part 14, 34 Gate insulating film 15 Transfer gate 16 1st insulating film 17 1st 1 wiring 18 second insulating film 19 second wiring 20, 21 contact plugs 22, 22A, 24, 24A, 41, 41A plasma SiN films 23, 44 microlens FD floating diffusion part STI element isolation layer S source (source region)
D Drain (drain region)
G gate 30, 30A CCD solid-state imaging device 33 charge transfer part 35 gate electrode 37 stop layer 38 insulating film 39 light shielding film 39a opening 40 interlayer insulating film 42 color filter 43 flattening film 90 electronic information equipment 91 solid-state imaging device 92 memory part 93 display means 94 communication means 95 image output means

Claims (20)

In a method for manufacturing a solid-state imaging device provided with a light-receiving element that photoelectrically converts incident light from a subject to image,
Above the light receiving element, on a patterned metal layer or on an interlayer insulating film thereon, a plasma silicon nitride film is formed by plasma CVD method in which an RF power indicating plasma generation energy set on the device side is set to 700 W to 1500 W A plasma silicon nitride film forming step of forming a film;
Method for manufacturing a solid-state imaging device and a sintering step of performing the sintering treatment by applying heat to the plasma silicon nitride film. In a method for manufacturing a solid-state imaging device provided with a light-receiving element that photoelectrically converts incident light from a subject to image,
Above the light receiving element, on the patterned metal layer or on the interlayer insulating film thereon, RF power indicating plasma generation energy set on the apparatus side is increased to 850 W so as to increase the amount of hydrogen released during the sintering process. A method for manufacturing a solid-state imaging device, including a plasma silicon nitride film forming step of forming a plasma silicon nitride film by a plasma CVD method set to ˜1500 W.   The method for manufacturing a solid-state imaging device according to claim 2, further comprising a sintering process step of performing a sintering process by applying heat to the plasma silicon nitride film.   3. The method of manufacturing a solid-state imaging device according to claim 2, wherein an RF power indicating plasma generation energy set on the apparatus side is set to 930 W to 1130 W during the formation of the plasma silicon nitride film.   4. The method for manufacturing a solid-state imaging device according to claim 1, wherein an RF power indicating a plasma generation energy set on the apparatus side is set to 900 W to 1500 W during the formation of the plasma silicon nitride film.   4. The method for manufacturing a solid-state imaging device according to claim 1, wherein an RF power indicating a plasma generation energy set on the apparatus side is set to 1000 W to 1500 W during the formation of the plasma silicon nitride film. The plasma silicon nitride film forming step forms a silicon nitride film having a thickness of 250 nm to 350 nm at a temperature of 350 to 450 degrees Celsius, a pressure of 2 to 7 Torr, using SiH ₄ gas and NH ₃ gas. Item 3. A method for producing a solid-state imaging device according to Item 1 or 2.   The thickness of the plasma silicon nitride film is such that a sufficient amount of hydrogen can be removed from the plasma silicon nitride film to supply hydrogen from the plasma silicon nitride film to the surface of the light receiving element during the sintering process. The method of manufacturing a solid-state imaging device according to claim 1 or 3.   The method of manufacturing a solid-state imaging device according to claim 1, wherein the RF power is an ionization ability that brings a constituent gas into a plasma state.   3. The solid-state imaging according to claim 1, wherein the patterned metal layer is a wiring pattern, and the plasma silicon nitride film forming step forms a second plasma silicon nitride film thereon after forming the wiring pattern. Device manufacturing method.   The patterned metal layer is a transfer gate for transferring signal charges from the light receiving element, and the plasma silicon nitride film forming step includes a first plasma nitridation on the entire surface of the substrate after the transfer gate is formed. The manufacturing method of the solid-state image sensor of Claim 1 or 2 which forms a silicon film. The plasma silicon nitride film forming step includes:
A first plasma silicon nitride film forming step of forming a first plasma silicon nitride film on the entire surface of the substrate after forming a transfer gate for transferring signal charges from the light receiving element as the patterned metal layer; ,
A second plasma silicon nitride film forming step of forming a second plasma silicon nitride film thereon after forming the wiring pattern as the patterned metal layer;
The sintering process is performed simultaneously after the first plasma silicon nitride film formation step and the second plasma silicon nitride film formation step, or the first plasma silicon nitride film formation step and the second plasma are performed. The manufacturing method of the solid-state image sensor of Claim 1 or 3 performed after each implementation of a silicon nitride film formation process, respectively.   The method of manufacturing a solid-state imaging element according to claim 11, wherein the first plasma silicon nitride film is formed on the light receiving element as an antireflection film.   The patterned metal layer is a gate electrode for transferring a signal charge from the light receiving element and a metal light shielding film thereon, and the plasma silicon nitride film forming step includes the metal light shielding film and the light receiving film. 3. The method of manufacturing a solid-state imaging element according to claim 1, wherein after forming an interlayer insulating film for flattening a step with the element, the plasma silicon nitride film is formed thereon.   The plasma silicon nitride film is provided on the surface of the peripheral area of the imaging area where the light receiving element is provided, and the peripheral area where a peripheral circuit composed of a number of transistors is formed, on the surface after the metal wiring is formed. The manufacturing method of the solid-state image sensor of Claim 1 or 3 formed as a passivation film.   A solid-state image pickup device manufactured by the method for manufacturing a solid-state image pickup device according to any one of claims 1, 3, 5, 6, 8, 12, 13, and 15, wherein a silicon surface defect is repaired by plasma dry etching.   A solid-state imaging device manufactured by the method for manufacturing a solid-state imaging device according to claim 2, wherein the blue sensitivity is improved and stabilized. Each of the plurality of pixel units is provided with the light receiving element as a photoelectric conversion unit for each pixel unit, and adjacent to the light receiving element, a signal charge from the light receiving element is transferred to the charge voltage conversion unit. A charge transfer transistor;
A readout circuit for voltage-converting the signal charge transferred to the charge-voltage conversion unit by the charge transfer transistor for each light receiving element, amplifying in accordance with the conversion voltage, and reading out as an imaging signal for each pixel unit; The solid-state imaging device according to claim 16, wherein the solid-state imaging device is a CMOS solid-state imaging device.   Each of the plurality of pixel units is provided with the light receiving element as a photoelectric conversion unit for each pixel unit, and adjacent to the light receiving element, charge transfer for transferring signal charges from the light receiving element in a predetermined direction The solid-state image pickup device according to claim 16 or 17, which is a CCD solid-state image pickup device on which a gate electrode for controlling charge transfer of the read signal charges is disposed. An electronic information device using the solid-state imaging device according to claim 16 as an image input device in an imaging unit.

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