JP2009200297A - Aperture opening method of pad electrode, manufacturing method of solid-state imaging element, solid-state imaging element, and electronic information equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of a bonding failure of a pad electrode by suppressing the amount of over-etching on the pad electrode by reducing the peeling of a passivation film caused by Al-hollowing on the pad electrode caused by subsequent sintering processing. <P>SOLUTION: An oxide film on the pad electrode and an insulating film 5 are removed only on the pad electrode by soft-etching. Only a Ti barrier metal layer 3 of the pad electrode is removed by dry-etching. Thus, damage to a metal layer 4 of the pad electrode caused by over-etching in dry-etching is significantly suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device composed of a semiconductor element that photoelectrically converts image light from a subject and images the same, a manufacturing method thereof, a pad electrode opening method used in the manufacturing method of the solid-state imaging device, and the solid-state imaging device. For example, digital cameras such as digital video cameras and digital still cameras used as image input devices as image input devices, image input cameras such as in-vehicle cameras and security cameras, electronic information devices such as scanners, facsimiles, and camera-equipped mobile phone devices .

  This type of conventional solid-state imaging device is provided with a plurality of light receiving units (photoelectric conversion units) that photoelectrically convert image light from a subject in an imaging region in the center of the chip, and a peripheral circuit unit around the light receiving unit. Further, the periphery thereof is a chip edge region, and a plurality of pad electrodes for external wiring are provided in the chip edge region. An insulating film is laminated so as to cover the pad electrode, and a window opening step for opening the insulating film (opening; rectangular or square in plan view) to expose the surface of the pad electrode is performed. Is going.

  FIG. 6 shows a conventional pad electrode opening method as a part of the conventional solid-state imaging device manufacturing method described above.

  FIG. 6 is a longitudinal sectional view of a main part of a pad electrode portion showing a pad electrode opening process in a conventional solid-state imaging device manufacturing method divided into a plurality of processes, and FIG. 6A is a pad opening pattern formation by a photolithography process. The main part longitudinal cross-sectional view of the pad electrode part after, (b) is a main part longitudinal cross-sectional view of the pad electrode part after dry etching, (c) is the main part of the pad electrode part after resist peeling and passivation film deposition It is a longitudinal cross-sectional view.

  First, as shown in the photolithography process of FIG. 6A, a planarizing insulating film 2 made of a silicon oxide film is formed on a predetermined edge 1 of the semiconductor substrate on a predetermined film 1 of a semiconductor substrate. The planarization insulating film 2 is formed as an upper layer of the solid-state image sensor. On this planarization insulating film 2, a pad electrode, an Al-based metal layer 4 (for example, an Al—Cu layer) as a pad electrode lower layer, and a Ti-based barrier metal layer 3 (for example, a Ti / TiN film) as an upper layer of the pad electrode. The two-layer structure is used. An insulating film 5 (oxide film) is formed on the pad electrode (Ti-based barrier metal layer 3 and Al-based metal layer 4) and the planarizing insulating film 2, and only the insulating film 5 above the pad electrode is formed thereon. A pad opening pattern is formed in the photoresist film 6 for opening.

  Next, as shown in the dry etching step of FIG. 6B, in order to open the pad electrode (Ti-based barrier metal layer 3 and Al-based metal layer 4), the insulating film 5 and the pad electrode are formed only by dry etching. The upper Ti-based barrier metal layer 3 (Ti / TiN film or the like) is removed by etching, and the Al-based metal layer 4 is over-etched halfway to expose the surface of the Al-based metal layer 4 from the opening.

  Thereafter, as shown in the passivation film forming / sintering process in FIG. 6C, the photoresist film 6 is removed by an ashing process using oxygen-based plasma, and a passivation film 7 such as a silicon nitride film is deposited. Further, in a state where the pad electrode is covered with the passivation film 7, a sintering process is performed by heat of 300 to 500 degrees Celsius (here, for example, 440 degrees Celsius).

A similar conventional pad electrode opening method is also proposed in Patent Document 1, for example.
In Patent Document 1, a passivation film, a planarizing film as an upper layer film, and an overpassivation film are formed in this order on the pad electrode. Then, a window forming process for exposing the surface of the pad electrode by forming openings at once in the plurality of insulating films of the passivation film, the planarizing film and the overpassivation film on the pad electrode by one dry etching process Has been implemented. In this case, the pad electrode is provided on the gate electrode via an insulating film.
JP-A-10-321828

  However, in the conventional technique including the above-mentioned patent document 1, in the dry etching of FIG. 6B and the above-mentioned patent document 1, for example, the case of FIG. 6B will be described. Since the etching rate ratio with the barrier metal layer 3 (Ti / TiN film or the like) is low, it is performed only by time control. This time control includes variations in the deposited film thickness of the insulating film 5, CMP variations, etching variations, and the like. It is necessary to consider all variations in the thickness of the Ti-based barrier metal layer 3.

  For example, after depositing the insulating film 5 on the Ti-based barrier metal layer 3 of the pad electrode so as to have a film thickness of about 550 nm, it is polished in the CMP process until the insulating film 5 on the pad electrode has a film thickness of 350 nm. The The amount of over-etching applied to the Al-based metal layer 4 (Al—Cu layer) of the pad electrode when the opening is opened only by dry etching on the pad electrode is due to variations in the deposited film thickness of the insulating film 5 and the CMP process. Considering all of polishing variation, etching variation, and variation in film thickness of the Ti-based barrier metal layer 3 in the upper layer of the pad electrode, the total variation is about 100 nm, and the Al-based metal layer 4 in the lower layer of the pad electrode On the other hand, the overetching was abnormal. This also means that large over-etching is performed on the pad electrode in the case of the dry etching disclosed in Patent Document 1 as well.

  Further, when excessive over-etching is applied to the pad electrode in this way, a reaction product (metal film) adheres to the inner wall of the opening of the insulating film 5. When such a reaction product (metal film) is present in the underlayer, the passivation film 7 on the base layer is peeled off. Therefore, it is necessary to remove the reaction product (metal film) from the inner wall of the opening by chemical treatment. During this chemical treatment, Cu atoms in the Al-based metal layer 4 (Al—Cu layer) are also selectively removed, so that a lot of fine cavities are formed here, and during the subsequent sinter treatment, the pads are sealed with heat. The Al in the electrode aggregates with each other to form a larger cavity immediately below the passivation film 7. When this is severe, the passivation film 7 is warped due to a cavity extending under the passivation film 7 to cause film peeling. If a subsequent on-chip process is performed with the passivation film 7 peeled off, the pad electrode surface is exposed to an organic solvent or the like, which causes problems such as inducing bonding defects in the pad electrode.

  The present invention solves the above-described conventional problems, and by suppressing the amount of overetching applied to the pad electrode, it reduces the film peeling of the passivation film due to Al cavitation on the pad electrode that occurs in the subsequent sintering process. A solid-state imaging device capable of suppressing defective bonding of the pad electrode and a manufacturing method thereof, a pad electrode opening method used in the manufacturing method of the solid-state imaging device, and a camera using the solid-state imaging device as an image input device in an imaging unit An object is to provide an electronic information device such as a mobile phone device.

  In the method for opening a pad electrode according to the present invention, the etching is stopped on the upper barrier metal layer constituting the pad electrode by wet etching to remove all the insulating film on the pad electrode, and the upper barrier metal layer is removed by dry etching. Then, a pad electrode opening forming step of forming an opening on the pad electrode is provided, whereby the above object is achieved.

  The opening method of the pad electrode of the present invention is the first dry etching, the etching is stopped by the etching stopper film provided on the upper barrier metal layer constituting the pad electrode, and all the insulating film on the etching stopper film is removed, The etching stopper film is entirely removed by second dry etching to expose the upper barrier metal layer, and the upper barrier metal layer is entirely removed by third dry etching to form an opening on the pad electrode. It has an opening formation process, and the above object is achieved thereby.

  Further, the pad electrode opening forming step in the pad electrode opening method of the present invention includes forming a photoresist film on the insulating film, and forming a pad opening pattern on the photoresist film, A wet etching step of exposing the surface of the pad electrode by selectively wet-etching the insulating film using the pad opening pattern as a mask; and a lower metal layer constituting the pad electrode using the pad opening pattern as a mask And a dry etching step of selectively etching the upper barrier metal layer of the upper barrier metal layer to expose the surface of the lower metal layer.

  Further, the pad electrode opening forming step in the pad electrode opening method of the present invention includes forming a photoresist film on the insulating film, and forming a pad opening pattern on the photoresist film, A first dry etching step of exposing the surface of the etching stopper film by dry etching the insulating film to the etching stopper film using the pad opening pattern as a mask; and the etching stopper film using the pad opening pattern as a mask, A second dry etching step of exposing the surface of the upper barrier metal layer by dry etching to the upper barrier metal layer of the lower metal layer and the upper barrier metal layer constituting the pad electrode; and the pad opening pattern Using the upper barrier metal layer as a mask And a third dry etching step for exposing the surface of said lower metal layer by dry etching.

Further, after the dry etching step in the pad electrode opening method of the present invention, a passivation film forming step of forming a passivation film on the pad electrode and the insulating film,
And a sintering process step of performing a sintering process with heat using residual hydrogen in the passivation film.

  Further, the reaction product attached to the inner wall of the opening of the insulating film by overetching the pad electrode between the dry etching process and the passivation film forming process in the pad electrode opening method of the present invention is removed. It has a chemical treatment process for performing chemical treatment.

  Furthermore, the lower metal layer constituting the pad electrode in the pad electrode opening method of the present invention is an Al-based metal layer, and the upper barrier metal layer is a Ti-based barrier metal layer.

  Further, the Al-based metal layer in the pad electrode opening method of the present invention is an Al-Cu layer, and the Ti-based barrier metal layer is a Ti / TiN film.

  Further, the Ti-based barrier metal layer in the pad electrode opening method of the present invention has a thickness of 300 nm to 600 nm.

  Further, in the pad electrode opening method of the present invention, a planarization film is formed as an upper layer of a solid-state imaging device on a predetermined film of a semiconductor wafer, a pad electrode is formed on the planarization film, the pad electrode and the planarization The insulating film is formed on the film.

  Furthermore, the wet etching step in the pad electrode opening method of the present invention uses an HF chemical solution.

  Furthermore, the HF chemical solution in the pad electrode opening method of the present invention is buffered hydrofluoric acid.

  Furthermore, the buffered hydrofluoric acid in the pad electrode opening method of the present invention is used in a ratio of 100: 0.1 to 5 with respect to the solvent.

  Furthermore, the wet etching step in the pad electrode opening method of the present invention is isotropic etching.

Further, the dry etching in the pad electrode opening method of the present invention uses a CF-based gas and an O ₂ -based gas.

Further, the dry etching in the pad electrode opening method of the present invention is performed under the dry etching conditions of CHF ₃ / O ₂ = 140/30 sccm, pressure 60 mT, and source power 800 W.

  Furthermore, in the photoresist film forming step in the pad electrode opening method of the present invention, the opening area of the pad opening pattern is formed in an opening smaller than the pad electrode area.

  Furthermore, in the photoresist film forming step in the pad electrode opening method of the present invention, the opening area on the pad electrode is set so that the etching stops at the upper edge edge position or upper surface corner position of the pad electrode when wet etching ends. .

  Furthermore, the opening area on the pad electrode in the pad electrode opening method of the present invention is an effective area where external wiring can be bonded to the pad electrode.

  The solid-state imaging device of the present invention is manufactured by including the pad electrode opening method in the manufacturing method of the solid-state imaging device of the present invention of the present invention, whereby the above object is achieved.

  Further, in the solid-state imaging device of the present invention, a plurality of light receiving units that photoelectrically convert image light from a subject is imaged in the imaging region at the center of the chip, and a peripheral circuit unit is provided around the light receiving unit. A chip edge region is provided in the periphery, and a plurality of pad electrodes for external wiring are provided in the chip edge region.

  The manufacturing method of the solid-state imaging device of the present invention is a method of laminating the insulating film in the opening method of the pad electrode of the present invention above the pad electrode on the surface of the semiconductor substrate on which the imaging device is formed. The above objective is achieved.

  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, as an opening method of the pad electrode, wet etching is used to stop etching on the upper barrier metal layer constituting the pad electrode, to remove all the insulating film on the pad electrode, and to remove the upper barrier metal layer by dry etching. Then, there is a pad electrode opening forming step for forming an opening on the pad electrode, or etching is stopped by an etching stopper film provided on the upper barrier metal layer constituting the pad electrode by the first dry etching. All the insulating film on the etching stopper film is removed, all the etching stopper film is removed by the second dry etching to expose the upper barrier metal layer, and all the upper barrier metal layer is removed by the third dry etching, and then on the pad electrode A pad electrode opening forming step for forming an opening inAs a result, by suppressing the amount of overetching applied to the pad electrode, it is possible to reduce film peeling of the passivation film due to Al cavitation on the pad electrode that occurs in the subsequent sintering process, and to suppress pad electrode bonding failures. The object of the present invention can be achieved.

  As described above, according to the present invention, by suppressing the amount of over-etching applied to the pad electrode, the film peeling of the passivation film due to the formation of Al cavities on the pad electrode that occurs in the subsequent sintering process is reduced, and the bonding of the pad electrode Defects can be suppressed.

  Embodiments 1 to 3 of the pad electrode opening method of the present invention will be described below with reference to the drawings when applied to the solid-state image sensor of the present invention and the method for manufacturing the same. The electronic information device used for the part will be described as Embodiment 4 with reference to the drawings.

(Embodiment 1)
FIG. 1 is a longitudinal cross-sectional view illustrating an exemplary configuration of a main part of a pad electrode portion in a solid-state imaging device according to Embodiment 1 of the present invention.

  In FIG. 1, the solid-state imaging device 10 according to the first embodiment is not particularly illustrated here, but a plurality of light receiving units (photographing images obtained by photoelectrically converting image light from a subject in an imaging region in the center of the semiconductor chip) Photoelectric conversion portion), a peripheral circuit portion is provided in the periphery thereof, and the periphery thereof is a chip edge region, and a plurality of pad electrodes for external wiring are provided in the chip edge region. . An insulating film is laminated so as to cover the pad electrode, and a window opening step for opening the insulating film (opening; rectangular or square in plan view) to expose the surface of the pad electrode is performed. Is going.

  A planarization insulating film 2 made of a silicon oxide film is provided as an upper layer of a solid-state imaging device on a predetermined film 1 of a semiconductor wafer on which a plurality of semiconductor chips are arranged. On this planarization insulating film 2, as a pad electrode, a metal layer 4 (for example, Al-Cu layer) below the pad electrode and a barrier metal layer 3 for wiring reliability above the pad electrode (Ti-based barrier metal such as Ti) / TiN film) are sequentially formed. A passivation film 7 for sintering treatment that does not transmit oxygen or moisture is formed on an insulating film 5 having an opening on the barrier metal layer 3. In this case, the opening of the insulating film 5 on the pad electrode is wide open with a shape opened upward.

A semiconductor device is prepared in which a region to be a solid-state imaging device provided with a plurality of light receiving portions is formed. As described above, the planarization insulating film 2 is an insulating film on the predetermined film 1 formed on the surface of the semiconductor wafer, and the pad electrode constituted by the barrier metal layer 3 and the metal layer 4 is the planarization insulation of the base layer. It is connected to the wiring through the film 2. The insulating film 5 is an insulating film that covers the entire region to be a solid-state imaging device. This insulating film 5 is characterized by comprising an insulating film made of SiO. Specifically, a SiO ₂ film, a SiOF-based film, a SiOC-based film, and the like formed by a CVD method. The window opening process is performed by forming a desired pad opening pattern on the insulating film 5 by a photolithography process.

  Here, the pad electrode opening process in the chip edge region in the manufacturing method of the solid-state imaging device of FIG. 1 will be described.

  2 (a) to 2 (d) are main part longitudinal sectional views of the pad electrode part showing the pad electrode opening process in the solid-state imaging device manufacturing method of FIG. FIG. 4B is a longitudinal sectional view of the main part of the pad electrode part after the formation of the pad opening pattern by the photolithography process, FIG. 5B is a longitudinal sectional view of the main part of the pad electrode part after the wet etching, and FIG. The principal part longitudinal cross-sectional view of a pad electrode part, (d) is a principal part longitudinal cross-sectional view of the pad electrode part after resist peeling and passivation film deposition.

  First, as shown in the photolithography process of FIG. 2A, a planarization insulating film 2 made of a silicon oxide film is provided on a predetermined film 1 of a semiconductor wafer as an upper layer of the solid-state imaging device. 2 is a stacked structure of an Al-based metal layer 4 (for example, an Al—Cu layer) below the pad electrode and a barrier metal layer 3 (for example, a Ti / TiN film; film thickness of 300 nm to 600 nm) above the pad electrode. It is formed. An insulating film 5 (oxide film) is formed on the pad electrode (barrier metal layer 3 and Al-based metal layer 4) and the planarization insulating film 2, and above the pad electrode to perform the above-described window opening process. A pad opening pattern is formed in the photoresist film 6 so as to open only.

  Next, as shown in the wet etching step of FIG. 2B, an HF-based chemical solution having an etching rate ratio between the barrier metal 3 and the insulating film 5 (for example, buffered hydrofluoric acid; BHF, 100: 0. 1 to 5 (here, 100: 1) wet etching is performed, and then the surface of the barrier metal 3 of the pad electrode is exposed. At this time, since the insulating film 5 is isotropically etched by wet etching, it is necessary to control so that the surface of the Al-based metal layer 4 (Al—Cu layer) of the pad electrode is not exposed during the etching or at the end of the etching. There is. Therefore, the opening area on the pad electrode that is opened in the photolithography process is made smaller (narrower) than the pad electrode by the amount that the opening is increased by wet etching so that the side wall of the pad electrode is not exposed at the end of wet etching. It is necessary to adjust to. This is because when the wet etching chemical solution permeates from the side wall of the pad electrode, the insulating film 5 is further etched away in the lateral direction, and the Al-based metal layer 4 may be exposed.

Subsequently, as shown in the dry etching step of FIG. 2C, the Ti-based barrier metal 3 is removed by dry etching, and the surface of the pad electrode portion formed of the Al-based metal layer 4 (Al—Cu layer). As a result, the photoresist film 6 is removed by an ashing process using oxygen-based plasma, and a post-etching process (chemical solution process) is performed, so that the reactive organism (metal film) attached to the inner wall of the opening of the insulating film 5 during etching is removed. remove. In this case, dry etching is performed under dry etching conditions such as CHF ₃ / O ₂ = 140/30 sccm, pressure 60 mT, and source power 800 W, for example.

  Further, as shown in the passivation film formation / sinter processing step of FIG. 2D, a passivation film 7 such as a silicon nitride film is deposited and formed, and the pad electrode is covered, and the temperature is 300 to 500 degrees Celsius. Sintering with the heat of In this case, since the opening is greatly opened by wet etching, the heat treatment can be performed effectively. The passivation film 7 is removed in a later on-chip process so that the surface of the Al-based metal layer 4 is exposed so that bonding with external wiring is possible.

  That is, the opening method of the pad electrode in the chip edge region is performed by wet etching to stop the etching on the upper barrier metal layer 3 constituting the pad electrode and remove all of the insulating film 5 on the pad electrode, thereby removing the upper barrier metal. There is a pad electrode opening forming step in which the layer 3 is removed by dry etching to form an opening on the pad electrode. In this pad electrode opening forming step, a photoresist material is formed on the insulating film 5, and a photoresist film forming step for forming a pad opening pattern in the photoresist film 6, and an insulating film using the photoresist film 6 as a mask. Of the lower metal layer 4 and the upper barrier metal layer 3 constituting the pad electrode using the photoresist film 6 as a mask. A dry etching step of selectively dry-etching the upper barrier metal layer 3 to expose the surface of the lower metal layer 4.

  Here, the effect will be described.

  FIG. 3 is a diagram showing the number of cavity defects due to Al agglomeration after chemical treatment / sintering with respect to the overetching time (sec), and FIG. 4 schematically shows the state of the cavity defects with respect to the overetching time (sec). FIG. In this case, the inspection apparatus that looks at the state of the cavity defect can take an image of the wafer surface with a microscope, display an image obtained by subtracting the reference screen by comparing the images, and output the image as a micrograph.

  As shown in FIG. 3 and FIG. 4A, the number of cavity defects is “0” when the overetching time (sec) is “0” sec after 25 sec, as shown in FIG. 3 and FIG. When the overetching time (sec) is 103 sec, the number of cavity defects is about 1200. As shown in FIGS. 3 and 4C, the number of cavities is about 5800 after the overetching time (sec) is 208 sec. It was. Thus, when the surface of the material after overetching time (sec) is 103 sec is viewed with a microscope, it is as shown in FIG. 4B, and when the surface of the wafer material after overetching time (sec) is 208 sec is viewed with an optical microscope. It can be seen that the number of cavity defects is significantly increased as shown in FIG. 4C compared to the surface of the wafer material after the overetching time (sec) of 103 seconds in FIG. 4B. If the pad electrode opening process of the present invention is used, the overetching time (sec) can be suppressed to about 25 sec.

As described above, according to the first embodiment, the oxide film on the pad electrode and the insulating film 5 described above are removed only on the pad electrode by wet etching, and only the Ti-based barrier metal layer 3 of the pad electrode is removed by dry etching. By doing so, damage due to overetching of dry etching given to the metal layer 4 of the pad electrode can be greatly suppressed. As a result, defects on the pad electrode that occur after sintering (cavity defects that cause film peeling) can be reduced.
(Embodiment 2)
In the first embodiment, the insulating film 5 is isotropically etched by wet etching when the surface of the barrier metal 3 of the pad electrode is exposed in the wet etching step of FIG. In the second embodiment, the etching time is controlled so that the surface and side surfaces of the Al-based metal layer 4 (Al—Cu layer) are not exposed. In the second embodiment, the opening area on the pad electrode that is opened in the photolithography process is described. The opening area on the pad electrode is set so as to stop at the surface position of the barrier metal 3 of the pad electrode at the end of the wet etching even if the opening is largely etched away by the insulating film 5 by wet etching. May be. The exposed area of the barrier metal 3 of the pad electrode only needs to secure an effective area for bonding.

In this case, there is no situation where the wet etching chemical solution permeates from the side wall of the pad electrode, the insulating film 5 is further enlarged in the lateral direction and etched away, and the Al-based metal layer 4 is exposed.
(Embodiment 3)
In the first embodiment, the wet etching process of FIG. 2B is performed to form an opening (for example, a bowl shape) that opens the insulating film 5 so as to spread upward, and the surface of the barrier metal 3 of the pad electrode In the third embodiment, an etching stopper film (thickness of about 50 nm) having a high etching rate by dry etching is provided on the barrier metal 3, and the insulating film 5 is formed up to the etching stopper film in the photolithography process. Etching may be performed so as to open. Further, in the next separate process, the etching stopper film is removed by dry etching, and further, the barrier metal 3 is removed by dry etching so that the surface of the Al-based metal layer 4 is exposed through the opening. It may be.

  That is, the opening method of the pad electrode is the first dry etching, and the etching is stopped by an etching stopper film (not shown) provided on the upper barrier metal layer 3 constituting the pad electrode, thereby insulating the etching stopper film. All the film 5 is removed, all the etching stopper film is removed by the second dry etching to expose the upper barrier metal layer 3, and all the upper barrier metal layer 3 is removed by the third dry etching to be opened on the pad electrode. A pad electrode opening forming step for forming the portion. In this pad electrode opening forming step, a photoresist film 6 is formed on the insulating film 5 and a pad opening pattern is formed on the photoresist film 6, and an insulating film is formed using this pad opening pattern as a mask. 5 is dry-etched to the etching stopper film to expose the surface of the etching stopper film, and using the pad opening pattern as a mask, the etching stopper film is used as the lower metal layer 4 constituting the pad electrode and A second dry etching step of exposing the surface of the upper barrier metal layer 3 by dry etching up to the upper barrier metal layer 3 of the upper barrier metal layer 3, and the upper barrier metal using the pad opening pattern as a mask Layer 3 is dry etched to lower metal layer And a third dry etching step of exposing the surface of the.

  In this case, although the process of providing an etching stopper film increases, overetching to the Al-based metal layer 4 can be significantly suppressed as in the case of the first and second embodiments. As a result, by suppressing the amount of overetching applied to the pad electrode, it is possible to reduce the film peeling of the passivation film due to the formation of Al cavities on the pad electrode that occurs in the subsequent sintering process, and to suppress the bonding failure of the pad electrode. . Since the opening process can be performed only by dry etching, it is only necessary to replace the etching gas, and the mass productivity is good.

  Therefore, in the first to third embodiments, it is no longer necessary to consider the deposited film thickness variation and CMP variation of the insulating film 5 which has been considered conventionally, and only the thickness variation and etching variation of the Ti-based barrier metal 3 are considered. Therefore, the overetching amount in the above can be reduced to about 50 nm, which is about half of the overetching amount (about 100 nm) when only dry etching is performed. The film peeling can be reduced, and the bonding failure of the pad electrode can be suppressed.

Although not specifically described in the first to third embodiments, the solid-state imaging device and the manufacturing method thereof are not limited to the CMOS solid-state imaging device and can be similarly applied to a CCD solid-state imaging device. Further, the pad electrode opening method of the present invention is not limited to the method of manufacturing the solid-state imaging device of the present invention.
(Embodiment 4)
FIG. 5 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 10 according to Embodiments 1 to 3 of the present invention as Embodiment 4.

  In FIG. 5, the electronic information device 90 of the fourth embodiment includes a solid-state imaging device 91 that obtains a color image signal by performing various signal processing on the imaging signals from the solid-state imaging device 10 of the first to third embodiments, and the solid-state imaging. A memory unit 92 such as a recording medium that enables data recording after the color image signal from the device 91 is subjected to predetermined signal processing for recording, and the color image signal from the solid-state imaging device 91 is subjected to predetermined signal processing for display A display means 93 such as a liquid crystal display device that can be displayed on a display screen such as a liquid crystal display screen later, and a color image signal from the solid-state image pickup device 91 are subjected to predetermined signal processing for communication, and then communication processing is enabled. And communication means 94 such as a transmission / reception device. The electronic information device 90 is not limited to this, and in addition to the solid-state imaging device 91, at least one of a memory unit 92, a display unit 93, a communication unit 94, and an image output device 95 such as a printer. You may have.

  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, a facsimile, a camera-equipped mobile phone device and a personal digital assistant (PDA) is conceivable.

  Therefore, according to the fourth embodiment, on the basis of the color image signal from the solid-state imaging device 91, it is displayed on the display screen, or is printed out on the paper by the image output device 95. (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.

  Although not particularly described in the first to third embodiments, as in the first and second embodiments, as a pad electrode opening method, etching is performed on the upper barrier metal layer constituting the pad electrode by wet etching. Or removing all the insulating film on the pad electrode, and removing the upper barrier metal layer by dry etching to form an opening on the pad electrode, or in the third embodiment As described above, by the first dry etching, the etching is stopped by the etching stopper film provided on the upper barrier metal layer constituting the pad electrode, and all the insulating film on the etching stopper film is removed, and the etching stopper film is removed by the second dry etching. To completely remove the upper barrier metal layer, and the upper barrier metal layer is third dry etched. If there is a pad electrode opening forming step for forming an opening on the pad electrode by removing all of the pad electrode, the pad electrode generated in the subsequent sintering process can be suppressed by suppressing the over-etching amount applied to the pad electrode. It is possible to achieve the object of the present invention that can reduce the film peeling of the passivation film due to the Al cavitation and suppress the bonding failure of the pad electrode.

  As mentioned above, although this invention has been illustrated using preferable Embodiment 1-4 of this invention, this invention should not be limited and limited to this Embodiment 1-4. 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 from the description of specific preferred embodiments 1 to 4 of the present invention based on the description of the present invention and the common general technical knowledge. 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 solid-state imaging device configured by a semiconductor element that photoelectrically converts image light from a subject and images the same, and a manufacturing method thereof, for example, a digital video camera and a digital device using the solid-state imaging device as an image input device in an imaging unit. By suppressing the amount of overetching applied to pad electrodes in the fields of digital information cameras such as still cameras, image input cameras such as in-vehicle cameras and security cameras, scanners, facsimiles, and camera-equipped mobile phone devices. Further, it is possible to reduce the film peeling of the passivation film due to the formation of the Al cavities on the pad electrode, which occurs in the subsequent sintering process, and to suppress the bonding failure of the pad electrode.

It is a longitudinal cross-sectional view which shows the principal part structural example of the pad electrode part in the solid-state image sensor which concerns on Embodiment 1 of this invention. FIG. 2 is a longitudinal sectional view of a main part of a pad electrode portion showing a pad electrode opening step in the method for manufacturing the solid-state imaging device of FIG. 1 divided into a plurality of steps, where (a) is a pad after a pad opening pattern is formed by a photolithography step. The main part longitudinal cross-sectional view of an electrode part, (b) is the principal part longitudinal cross-sectional view of the pad electrode part after wet etching, (c) is the principal part longitudinal cross-sectional view of the pad electrode part after dry etching, (d) These are the principal part longitudinal cross-sectional views of the pad electrode part after resist peeling and passivation film deposition. It is a figure which shows the number of the cavity defects by Al aggregation after a chemical | medical solution process and a sintering process with respect to over etching time (sec). It is a data top view which shows typically the mode of the cavity defect with respect to over etching time (sec). As Embodiment 2 of this invention, it is a block diagram which shows the schematic structural example of the electronic information device which used the solid-state imaging device containing the solid-state image sensor of Embodiment 1 of this invention for the imaging part. It is a principal part longitudinal cross-sectional view of the pad electrode part which shows the pad electrode opening process in the manufacturing method of the conventional solid-state image sensor, Comprising: (a) is a principal part longitudinal section of the pad electrode part after the pad opening pattern formation by a photolithography process FIG. 4B is a longitudinal sectional view of the main part of the pad electrode part after dry etching, and FIG. 5C is a longitudinal sectional view of the main part of the pad electrode part after resist peeling and passivation film deposition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Predetermined layer 2 Insulating film 3 Ti-type barrier metal layer 4 of pad electrode 4 Al-type metal layer of pad electrode 5 Insulating film 6 on pad electrode Photoresist film 7 having pad opening pattern Passivation film 10 Fixed imaging device

Claims (23)

  Etching is stopped on the upper barrier metal layer constituting the pad electrode by wet etching to remove all of the insulating film on the pad electrode, and the upper barrier metal layer is removed by dry etching to form an opening on the pad electrode. A pad electrode opening method comprising a pad electrode opening forming step to be formed.   By the first dry etching, the etching is stopped by the etching stopper film provided on the upper barrier metal layer constituting the pad electrode, and all the insulating film on the etching stopper film is removed, and the etching stopper film is removed by the second dry etching. A pad electrode opening having a pad electrode opening forming step of removing all of the upper barrier metal layer to expose the upper barrier metal layer and removing the upper barrier metal layer by a third dry etching to form an opening on the pad electrode. Method. The pad electrode opening forming step includes
A photoresist film forming step of forming a photoresist film on the insulating film and forming a pad opening pattern in the photoresist film;
A wet etching step of exposing the surface of the pad electrode by selectively wet etching the insulating film using the pad opening pattern as a mask;
Using the pad opening pattern as a mask, a dry etching that selectively dry-etches the upper barrier metal layer of the lower metal layer and the upper barrier metal layer constituting the pad electrode to expose the surface of the lower metal layer. The pad electrode opening method according to claim 1, further comprising an etching step. The pad electrode opening forming step includes
A photoresist film forming step of forming a photoresist film on the insulating film and forming a pad opening pattern in the photoresist film;
A first dry etching step of exposing the surface of the etching stopper film by dry etching the insulating film to the etching stopper film using the pad opening pattern as a mask;
Using the pad opening pattern as a mask, the etching stopper film is dry-etched up to the upper barrier metal layer of the lower metal layer and the upper barrier metal layer constituting the pad electrode to thereby surface the upper barrier metal layer. Exposing a second dry etching step;
3. The pad electrode opening method according to claim 2, further comprising a third dry etching step in which the upper barrier metal layer is dry-etched using the pad opening pattern as a mask to expose the surface of the lower metal layer. A passivation film forming step of forming a passivation film on the pad electrode and the insulating film after the dry etching step;
5. The pad electrode opening method according to claim 1, further comprising: a sintering process for performing a sintering process by heat using residual hydrogen in the passivation film.   A chemical treatment process for performing a chemical treatment for removing a reaction product attached to the inner wall of the opening of the insulating film by overetching the pad electrode between the dry etching process and the passivation film forming process. Item 6. The pad electrode opening method according to Item 5.   The method for opening a pad electrode according to claim 1, wherein the lower metal layer constituting the pad electrode is an Al-based metal layer, and the upper barrier metal layer is a Ti-based barrier metal layer.   The pad electrode opening method according to claim 7, wherein the Al-based metal layer is an Al—Cu layer, and the Ti-based barrier metal layer is a Ti / TiN film.   9. The pad electrode opening method according to claim 7, wherein the Ti-based barrier metal layer has a thickness of 300 nm to 600 nm.   A planarization film is formed as an upper layer of a solid-state imaging device on a predetermined film of a semiconductor wafer, a pad electrode is formed on the planarization film, and the insulating film is formed on the pad electrode and the planarization film. The pad electrode opening method according to claim 1.   4. The pad electrode opening method according to claim 1, wherein the wet etching step uses an HF chemical solution.   The pad electrode opening method according to claim 11, wherein the HF chemical solution is buffered hydrofluoric acid.   The pad electrode opening method according to claim 12, wherein the buffered hydrofluoric acid is used in a ratio of 100: 0.1 to 5 with respect to the solvent.   The pad electrode opening method according to claim 1, wherein the wet etching step is isotropic etching. The pad electrode opening method according to claim 1, wherein the dry etching uses a CF-based gas and an O ₂ -based gas. The pad electrode opening method according to claim 15, wherein the dry etching is performed under dry etching conditions of CHF ₃ / O ₂ = 140/30 sccm, a pressure of 60 mT, and a source power of 800 W.   The pad electrode opening method according to claim 3, wherein in the photoresist film forming step, an opening area of the pad opening pattern is formed in an opening smaller than a pad electrode area.   18. The opening of the pad electrode according to claim 17, wherein in the photoresist film forming step, the opening area on the pad electrode is set so that the etching stops at the upper surface edge position or the upper surface corner position of the pad electrode at the end of wet etching. Method.   The method of opening a pad electrode according to claim 18, wherein the opening area on the pad electrode is an effective area where external wiring can be bonded to the pad electrode.   The manufacturing method of the solid-state image sensor which laminates | stacks the insulating film in the opening method of the pad electrode in any one of Claims 1-19 on the upper layer rather than the pad electrode of the semiconductor substrate surface in which the image sensor was formed.   The solid-state image sensor manufactured by the manufacturing method of the solid-state image sensor of Claim 20.   A plurality of light-receiving units that photoelectrically convert image light from a subject to be imaged are provided in an imaging region in the center of the chip, a peripheral circuit unit is provided in the periphery thereof, and a chip edge region is provided in the periphery thereof The solid-state imaging device according to claim 21, wherein a plurality of pad electrodes for external wiring are provided in the chip edge region.   An electronic information device using the solid-state imaging device according to claim 21 or 22 as an image input device in an imaging unit.

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