JP2006216655A - Charge transfer element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge transfer element to which alignment residual in patterning process at the time of formation does not lead to the variation in the photodetecting area of a photoelectric converter, and to provide its manufacturing method when configuring the image pick-up part of, for example, a solid state image sensor. <P>SOLUTION: A plurality of the photoelectric converters 3 are arranged in the image pick-up part, and transfer electrodes 5-8 of a single layer structure constituting a perpendicular transfer 13 which transfers a signal charge to the ambients perpendicularly. First, insulating films 10 and 11 between the electrodes and an insulating film 12 are formed between transfer electrode-shadowing films by patterning the insulating material layer at the identical process using a common mask on a substrate 1, and the mutual position of the transfer electrode 4 and a photodetecting receiver 3 is decided. Then, after an electrode material layer is deposited on the substrate 1 in the state that the photodetecting receiver 3 is masked with a mask material, it is flattened to form the transfer electrodes 5-8. Then, the mask material is removed in the state where the transfer electrodes 5-8 are covered with an insulating film 19, etc., and the aperture of the photodetecting receiver 3 is opened while the generation of a white blemish is suppressing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charge transfer device and a method for manufacturing the same, and more particularly to a charge transfer device having a charge transfer electrode having a single layer structure suitable as a solid-state imaging device and a method for manufacturing the same.

  A solid-state imaging device such as a CCD (Charge Coupled Device) used for an area sensor or the like has a charge transfer electrode for transferring a signal charge from a photoelectric conversion unit. A plurality of charge transfer electrodes are arranged adjacent to each other on a charge transfer path formed on the semiconductor substrate, and are driven by a drive circuit.

  2. Description of the Related Art Conventionally, as a charge transfer electrode such as a CCD, an electrode having a two-layer structure in which adjacent transfer electrodes overlap each other at the end is used. The charge transfer electrode with a two-layer structure makes it easy to reduce the potential pocket that occurs in the charge transfer path, but the transfer electrode part height increases at the overlapping part, and part of the light incident on the photoelectric conversion part is blocked. Or because the upper portion of the transfer electrode is not flat, it is difficult to sufficiently cover the transfer electrode portion with a light-shielding film, and smear characteristics are not good. In addition, for the production, it is necessary to repeat the process of forming the electrode material layer, the process of patterning the electrode material layer, the process of forming the insulating film on the surface of the electrode by a thermal oxidation method, etc. twice. There is also a problem that the process becomes complicated and the manufacturing cost increases.

  On the other hand, there is also a single-layer charge transfer electrode in which adjacent transfer electrodes are opposed to each other across a narrow gap without overlapping vertically, and the transfer electrodes are insulated by an interelectrode insulating film disposed in the gap. Proposed. The charge transfer electrode with a single-layer structure has a low transfer electrode part, so that the light incident on the photoelectric conversion part is less likely to be blocked, and the transfer electrode part is flat. Since it becomes easy to coat, the smear characteristic is improved. Further, for the production, each process such as formation of an electrode material layer and formation of an electrode pattern may be performed once, and the number of manufacturing processes may be reduced. Further, since there is no overlapping portion between adjacent electrodes, the capacitance between the transfer electrodes is small and suitable for high-speed transfer.

  Although the charge transfer electrode having a single layer structure has the above-mentioned characteristics, if the gap between adjacent transfer electrodes is not sufficiently small, a potential pocket is generated in the charge transfer path in the gap, and signal charges are retained therein, A transfer failure occurs. In order to prevent the generation of potential pockets, it is necessary to process the gap between the transfer electrodes to 0.2 to 0.3 μm or less, and it has been difficult to produce such a single-layer charge transfer electrode in the past. .

  However, recent advances in microfabrication technology have made it possible to produce charge transfer electrodes having a single layer structure. For example, in Japanese Patent Laid-Open No. 5-315588, an electrode material layer is patterned by lithography and etching utilizing the reduction of the groove width by forming a sidewall, and a CVD method (chemical vapor phase) is formed in the gap between the formed transfer electrodes. A method of embedding an insulating material such as silicon oxide by a growth method has been proposed.

  On the other hand, as a material for the transfer electrode, conventionally, a silicon-based conductive material having a sheet resistance value of several tens of Ω such as polycrystalline silicon doped with phosphorus has been used. However, in recent years, the number of imaging pixels has increased in solid-state imaging devices, and accordingly, it has become necessary to transfer signal charges at high speed, that is, to drive the transfer electrodes with high-frequency pulses. Low resistance is required. As a method for reducing the resistance of the electrode, a composite film in which a metal film having a sheet resistance value of several Ω or a silicide film thereof is laminated on a silicon-based conductive material film instead of a single film of a silicon-based conductive material is used. Has been proposed.

  The charge transfer electrode with a single layer structure has a separate interelectrode insulating film formed in the gap. Therefore, unlike the charge transfer electrode with a two layer structure, the electrode needs to be thermally oxidized to form an insulating film between the electrodes. There is no. For this reason, the electrode material is not limited to the silicon-based conductive material, and it is easy to use a metal film or a metal silicide film, which is suitable for reducing the resistance of the electrode.

  However, when the charge transfer electrode having a single layer structure is formed of a composite film of a polycrystalline silicon film and a metal film such as tungsten, a gap is formed when silicon oxide is embedded in the gap between the electrodes by a high temperature low pressure CVD method or the like. It has been found that a metal electrode such as tungsten forming the side wall of the metal is oxidized, and the formation of the gap is broken due to the volume expansion of the electrode due to the oxidation.

  In order to solve this problem, in Patent Document 1 to be described later, an electrode formed by forming a trapezoid pattern below the electrode material layer in the vicinity of the region where the gap is formed and rising above the trapezoid pattern is formed. A solid-state imaging device having a charge transfer electrode in which a metal layer is not exposed in a gap by selectively removing an upper metal layer of a material layer by a planarization process has been proposed.

  Even if the problem of oxidation of the metal electrode layer can be avoided as described above, the method of patterning the electrode material layer and embedding an insulating material in the gap between the formed transfer electrodes to form an interelectrode insulating film is a transfer method. When the distance between the electrodes is reduced to, for example, 0.1 μm or less, it becomes extremely difficult to embed an insulating material without a gap in the gap. The gap (air gap) remaining in the gap causes deterioration of the withstand voltage performance of the transfer electrode.

  Further, in the conventional manufacturing method in which the electrode material layer is patterned and the gap is formed between the transfer electrodes, when the charge transfer path is formed, the ion transfer can be performed in a self-aligned manner in the charge transfer path forming region of the semiconductor substrate other than the gap portion. It is impossible to do so.

  Therefore, Patent Document 2 described later proposes a method of manufacturing a solid-state imaging device capable of forming an interelectrode insulating film of 0.1 μm or less without being embedded in a gap. In this manufacturing method, first, a dummy pattern is formed on a substrate, a side wall made of an insulating material having a thickness of 0.1 μm or less is formed on the side surface, and then the dummy pattern is removed to leave only the side wall, thereby An insulating film to be an inter-insulating film is formed on the substrate in advance. Next, an electrode material layer is formed on the entire surface of the substrate, the electrode material layer is planarized, and then patterned to form a transfer electrode.

  According to this method, when the insulating film is embedded in the electrode material layer, the basic structure of the transfer electrode in which the electrode material is partitioned by the insulating film is automatically formed, and after that, the electrode material layer is simply patterned. A transfer electrode can be formed. Further, since the interval between the transfer electrodes is automatically determined by the thickness of the side wall formed in the dummy pattern, a gap of 0.1 μm or less can be easily formed. Further, by performing ion implantation at a stage where an insulating film is formed and an electrode material layer is not yet formed, ion implantation can be performed in a charge transfer path formation region other than the gap by self-alignment.

JP 2003-60189 (Page 5-7, Fig. 3-6) JP-A-2004-119795 (page 6-8, FIG. 2)

  17-20 is explanatory drawing for showing the subject of this invention. FIGS. 17A and 17B are a plan view (1) and a cross-sectional view (2) schematically showing a pixel structure of an image pickup unit of a CCD (charge coupled device) solid-state image pickup device having a charge transfer electrode having a single layer structure. However, the cross-sectional view (2) is a cross-sectional view at the position indicated by the line BB in the plan view (1). 18 to 20 are a plan view (1) and sectional views (2) and (3) showing the manufacturing process. Cross-sectional views (2) and (3) are cross-sectional views at the positions indicated by the BB line and the CC line in FIG. 17 (1).

  In the imaging unit of the CCD solid-state imaging device, a plurality of photoelectric conversion units 103 shown in FIG. 17A are arranged in a matrix in the horizontal and vertical directions, and unit cells (units) are centered on each photoelectric conversion unit 103. Pixel). A transfer electrode 105 having a single-layer structure that forms a vertical transfer unit 107 that transfers signal charges in the vertical direction is formed on the transfer electrode unit 104 around each photoelectric conversion unit 103. An insulating film 106 is formed.

  As shown in FIG. 17 (2), in the unit pixel of the imaging unit, a gate insulating film 102 is formed on the surface of the silicon substrate 101, and the silicon substrate 101 below the gate insulating film 102 is formed at the center of FIG. 17 (2). A photoelectric conversion unit 103 formed of a pn junction (buried photodiode) is formed, and an n-type region 108 serving as a charge transfer path of the vertical transfer unit 107 is sandwiched between the readout gate unit 112 on the left side of the photoelectric conversion unit 103. Is formed.

  A transfer electrode 105 is formed on the n-type region 108 of the charge transfer path so as to be in contact with the gate insulating film 102, and transfer that insulates between the transfer electrode 105 and the light shielding film 111 on the side surface and the upper surface of the transfer electrode 105. An insulating film 109 and an insulating film (cap film) 110, which are insulating films between the electrodes and the light shielding film, are formed, and a light shielding film 111 that shields the transfer electrode portion from incident light is formed so as to cover them.

  At the time of light reception, signal charges (electrons) accumulated in the photoelectric conversion unit 103 are extracted to the charge transfer path 108 of the vertical transfer unit 107 via the read gate unit 112 by the read voltage applied to the transfer electrode 105, Thereafter, the vertical transfer unit 107 is transferred in the vertical direction, and further, a horizontal transfer unit (not shown) is transferred in the horizontal direction, and then converted into an output signal by an amplifier (not shown).

  2. Description of the Related Art In recent years, solid-state imaging devices typified by CCDs have significantly increased the number of pixels and the size of devices, and the area of the photoelectric conversion unit 103 of unit pixels has been reduced accordingly. When the thickness of the insulating film 109 is reduced, the area of the light receiving region can be increased accordingly. Therefore, in order to ensure the area of the light receiving region in the trend of miniaturization of the solid-state imaging device, it is an important issue to reduce the thickness of the insulating film 109, for example, to reduce the thickness to about 0.1 μm or less. It has been demanded. In Patent Document 2 described above, although a method for manufacturing a transfer electrode having a thickness of 0.1 μm or less is described, the method for manufacturing the insulating film 109 is not described.

  Thus, the state shown in FIG. 18A is formed on the silicon substrate 101, and the problem of processing this to form the transfer electrode 105 and the insulating film 109 having a single layer structure is considered. In the state shown in FIG. 18A, the gate insulating film 102 is formed on the surface of the silicon substrate 101, and the interelectrode insulating film 106 made of silicon nitride is formed on the vertical transfer portion 107 on the gate insulating film 102. In the photoelectric conversion portion 103, a silicon nitride film 121 that is processed into the insulating film 109 later is formed by masking the photoelectric conversion portion 103.

  In one method of performing the above processing, first, as shown in FIG. 18B, an electrode material layer is formed on the entire surface of the silicon substrate 101, and this surface is formed by a CMP method (chemical mechanical polishing method) or the like. The transfer electrode 105 is formed by planarization. At this time, the silicon nitride film 121 functions as a mask layer for masking the photoelectric conversion unit 103.

  Next, as shown in FIG. 18C, an insulating material layer 122 is formed on the entire surface of the silicon substrate 101. Thereafter, as shown in FIG. 19D, the silicon nitride film 121 and the insulating material layer 122 are patterned by lithography and etching, and the electrode-light shielding film insulating film 109 covering the side and upper portions of the transfer electrode, respectively. Then, an insulating film (cap film) 110 is formed.

  Next, as shown in FIG. 19E, the light shielding film 111 is formed by patterning.

  In the above process, in forming the insulating film 109 between the electrode and the light shielding film, one main side surface is formed when the silicon nitride film 121 of FIG. 18A is formed, and the patterning process shown in FIG. The other main side surface is formed, and the patterning process by lithography and etching is performed twice. This is not only complicated, but also causes a variation in the thickness of the insulating film 109 between the electrode and the light-shielding film due to the alignment error of the mask or the like in the two lithography processes, resulting in a variation in the area of the light-receiving region of the photoelectric conversion unit 3. Become. Further, when the error is large, the transfer electrode 105 and the light shielding film 111 are in contact with each other, and there is a concern that a short circuit defect may occur in which the transfer electrodes are short-circuited via the light shielding film 111.

  In another method for performing the above-described processing, after the transfer electrode 105 is formed in the step shown in FIG. 18B, the silicon nitride film 121 is completely removed as shown in FIG. An insulating film 109 for covering the film is formed. In this case, although the thickness of the insulating film 109 can be controlled well, the transfer electrode 105 is exposed to the photoelectric conversion unit 103 when the silicon nitride film 121 is removed and the photoelectric conversion unit 103 is opened. There is a possibility that the metal material constituting the electrode 105 is scattered on the photoelectric conversion unit 103 and causes a white spot defect.

  Further, in any of the above processing methods, the step of positioning the charge transfer path 108 and the step of positioning the insulating film 109 (the main side surface on the photoelectric conversion unit 3 side) are performed in separate steps. The misalignment causes the light receiving area of the photoelectric conversion unit 3 to vary.

  The present invention has been made in view of such a situation, and an object of the present invention is, for example, when an image pickup unit of a solid-state image pickup device is configured, and an alignment error in a patterning process at the time of fabrication is received by a photoelectric conversion unit. An object of the present invention is to provide a charge transfer device that does not lead to variations in the area of the region and a method for manufacturing the same.

That is, according to the present invention, a plurality of charge transfer electrodes are arranged on a charge transfer path of a semiconductor substrate via a gate insulating film, adjacent charge transfer electrodes are opposed to each other with a gap therebetween, and the first insulating film is formed in the gap. In the charge transfer element having the arranged charge transfer electrode portion,
A second insulating film disposed between a light-shielding film that shields the charge transfer electrode portion from incident light and a side surface of the charge transfer electrode is integrally connected to the first insulating film. A charge transfer element, and a method of manufacturing the charge transfer element,
Forming an insulating material layer on the semiconductor substrate in contact with the gate insulating film;
Patterning the insulating material layer with a common mask to form the first insulating film and the second insulating film;
Forming an electrode material layer on the entire surface of the semiconductor substrate;
Removing unnecessary portions of the electrode material layer, and forming the charge transfer electrode in the charge transfer electrode portion surrounded by the first insulating film and the second insulating film;
Forming a light shielding film material layer on the entire surface of the semiconductor substrate so as to cover the second insulating film;
And a step of patterning the light shielding film material layer to form the light shielding film.

In the charge transfer device according to the present invention, a plurality of charge transfer electrodes are arranged on a charge transfer path of a semiconductor substrate via a gate insulating film, adjacent charge transfer electrodes face each other with a gap therebetween, and a first insulation is formed in this gap. A charge transfer element having a charge transfer electrode portion on which a film is disposed,
Since the second insulating film disposed between the light-shielding film that shields the charge transfer electrode portion from incident light and the side surface of the charge transfer electrode is integrally connected to the first insulating film. The relative position between the charge transfer electrode portion on which the first insulating film is disposed and the second insulating film, and thus the light shielding film, is accurately determined regardless of the alignment error such as the mask in the patterning process at the time. Yes.

  For this reason, for example, if the light receiving area of the photoelectric conversion unit is formed in an area that is defined by the second insulating film and is not covered by the light shielding film, the light receiving area of the light receiving area is the position in the patterning process at the time of manufacturing. A solid-state imaging device that does not vary due to the effect of alignment errors can be formed. In addition, since it is not necessary to take a margin for the alignment error, the area defined by the second insulating film can be used to the maximum extent as the light receiving area, and the sensitivity and size of the solid-state imaging device can be increased. It is effective for. Further, since the relative position between the charge transfer electrode portion and the photoelectric conversion portion is fixed, the charge is placed at the correct relative position with respect to the photoelectric conversion portion by a method such as self-alignment based on the second insulating film. Since a reading portion or the like can be formed, variation in reading voltage is reduced.

  The above example is an example in which the charge transfer element is applied as a vertical CCD of a solid-state imaging device in combination with a photoelectric conversion element, but even in a device combined with a charge output type functional element other than the photoelectric conversion element. Similarly, the high relative positional accuracy between these functional elements and the charge transfer electrode portion is effective in reducing the size and accuracy of the device, and thus in reducing the cost by improving the manufacturing yield. Further, even if it is applied as a simple transfer register such as a horizontal CCD of a solid-state image pickup device, it is effective for downsizing the device.

According to the method for manufacturing a charge transfer device of the present invention,
Forming an insulating material layer on the semiconductor substrate in contact with the gate insulating film;
Patterning the insulating material layer with a common mask to form the first insulating film and the second insulating film, so that the relative position between the first insulating film and the second insulating film is The charge transfer element can be manufactured that is determined within the mask manufacturing accuracy. Also,
Forming an electrode material layer on the entire surface of the semiconductor substrate;
Removing the unnecessary portion of the electrode material layer, and forming the charge transfer electrode in the charge transfer electrode portion surrounded by the first insulating film and the second insulating film. At the stage of embedding a film in the electrode material layer, the basic structure of the charge transfer electrode in which the electrode material is partitioned by the first insulating film is automatically formed. The charge transfer electrode is completed simply by removing the. In addition, since the interval between the charge transfer electrodes can be automatically determined by the width (thickness) of the first insulating film, a charge transfer electrode having a so-called single layer structure can be easily manufactured.

  In the charge transfer device and the method for manufacturing the same according to the present invention, the first insulating film and the second insulating film are respectively formed at the gap position and the boundary position between the charge transfer electrode portion and the photoelectric conversion portion. The charge transfer electrode is formed of an electrode material disposed on the charge transfer electrode portion surrounded by the first insulating film and the second insulating film. A part of the solid-state imaging device may be configured.

  The first insulating film and the second insulating film are preferably formed of the same material. The first insulating film and the second insulating film may be made of silicon oxide and / or silicon nitride.

  The upper surface of the charge transfer electrode may be insulated from the light shielding film.

  The charge transfer electrode may be made of a metal layer. By configuring the charge transfer electrode with a low-resistance metal layer, the charge transfer electrode can be driven with a high-frequency pulse, and charge transfer can be performed at high speed.

  In the method for manufacturing a charge transfer device of the present invention, it is preferable that the upper portions of the first insulating film and the second insulating film are positioned and formed in the same patterning step.

  At this time, the first insulating film and the second insulating film are formed by etching the insulating material layer using the respective upper portions as a mask, and then the mask layer is in contact with the second insulating film and covers the photoelectric conversion portion. It is preferable to form the charge transfer electrode by forming the electrode material layer in a state of providing and flattening the electrode material layer to the position of the first insulating film.

  Alternatively, after the first insulating film is formed by etching using the upper portion of the first insulating film as a mask, the second insulating film is formed on the insulating material layer that is in contact with the second insulating film and covers the photoelectric conversion portion. The charge transfer is performed by forming the electrode material layer in a state in which a mask layer that covers the photoelectric conversion portion is provided in contact with the electrode layer and planarizing the electrode material layer to the position of the first insulating film. An electrode is formed, and the second insulating film is preferably formed by etching using the upper portion of the second insulating film as a mask.

  Further, it is preferable that the entire surface of the gate insulating film is covered with an insulating layer made of the same material as the insulating layer under each upper portion of the first insulating film and the second insulating film.

  The mask layer may be removed to form a structure that allows light to enter the photoelectric conversion portion.

  Next, a preferred embodiment of the present invention will be described specifically and in detail with reference to the drawings.

Embodiment 1
In Embodiment 1, a CCD solid-state imaging device including a single-layer structure charge transfer electrode as an example of the charge transfer device of the present invention and a manufacturing method thereof will be described with reference to FIGS. The manufacturing method described here mainly corresponds to the manufacturing method described in claims 7 to 9.

  1 and 2 are explanatory views showing the structure of the imaging unit of the CCD solid-state imaging device based on the first embodiment. FIG. 2 is a top view showing the main part of the imaging unit. FIG. 1 is a plan view (a) showing an enlarged unit pixel and a broken line A-X-A in the plan view (a). It is sectional drawing (b) in a position. In FIG. 2 and FIG. 1A, illustration of the members above the upper surfaces of the transfer electrodes 5 to 8, such as the light shielding film 20, is omitted for the sake of clarity.

  As shown in FIG. 2, in the imaging unit, a plurality of photoelectric conversion units 3 are arranged in a matrix in the horizontal and vertical directions, and a unit cell (unit pixel) is configured around each photoelectric conversion unit 3. . Transfer electrodes 5 to 8 having a single layer structure forming a vertical transfer unit 13 that transfers signal charges in the vertical direction are formed on the transfer electrode unit 4 around each photoelectric conversion unit 3.

  FIG. 2 shows an example in which the transfer electrodes 5 to 8 are integrated with the wiring between the electrodes and have a shape extended between a plurality of unit pixels arranged in the horizontal direction. The clock signal applied to the transfer electrode includes a two-phase clock signal, a four-phase clock signal, and the like. In FIG. 2, the transfer electrode is a set of four electrodes of the transfer electrode 5 to the transfer electrode 8. An example is shown in which these are configured and driven by a four-phase clock signal.

  As shown in FIGS. 1A and 2, between the transfer electrode 5 and the transfer electrode 6 and between them and the photoelectric conversion unit 3, an interelectrode insulating film 11 which is the first insulating film, The integrated insulating film 9, which is a feature of the present invention, is formed by integrally forming the electrode-light shielding film insulating film 12 as the second insulating film. Similarly, an integrated insulating film 9 is also formed between the transfer electrode 7 and the transfer electrode 8 and between these and the photoelectric conversion unit 3. On the other hand, a normal interelectrode insulating film 10 is formed between the transfer electrode 6 and the transfer electrode 7 and between the transfer electrode 8 and the transfer electrode 5.

As shown in FIG. 1B, in the unit pixel of the CCD solid-state imaging device, the gate insulating film 2 is formed on the upper surface of the silicon substrate 1, and the lower silicon substrate 1 includes the gate insulating film 2 shown in FIG. A photoelectric conversion unit 3 composed of a pn junction (buried photodiode) shown in the center is formed. On the left side of the photoelectric conversion unit 3, an n ⁺ -type region 14 that is a charge transfer path of the vertical transfer unit 13 is formed with the readout gate unit 21 interposed therebetween. Further, on the right side of the photoelectric conversion unit 3, an n ⁺ -type region 14 that is a charge transfer path of the photoelectric conversion unit in the right adjacent column is formed, and a channel stopper is provided between the photoelectric conversion unit 3 and the charge transfer path 14. 22 is insulated and separated.

  In the imaging unit shown in FIGS. 1 and 2, signal charges (electrons) accumulated in the photoelectric conversion unit 3 at the time of receiving light are passed through the readout gate unit 21 by the readout voltage applied to the transfer electrode 5 or the transfer electrode 7. Then, it is drawn out to the charge transfer path 14 of the vertical transfer unit 13 and then transferred to the vertical transfer unit 13 in the vertical direction by a four-phase clock signal applied to the transfer electrode 5 to the transfer electrode 8, and further, horizontal transfer not shown in the figure. After the part is transferred in the horizontal direction, it is converted into an output signal by an amplifier (not shown).

  On the upper part of the n-type region 14 of the charge transfer path, the transfer electrodes 5 to 8 (however, the transfer electrode 8 is not shown in FIG. 1B) are in contact with the gate insulating film 2 and are electrode layers. 15 and 16. The electrode layers 15 and 16 are preferably formed by laminating a metal silicide film such as tungsten and a metal film in order to achieve higher electrical conductivity.

However, in this case, when the film is formed by CVD (chemical vapor deposition) using tungsten hexafluoride WF ₆ as a tungsten raw material, the gate insulating film 2 is attacked by fluorine atoms generated during the film forming process. There is a risk. Therefore, when priority is given to preventing deterioration of the gate insulating film 2, a polycrystalline silicon film is first formed as a protective film, a metal film such as tungsten is then laminated, and then the polycrystalline silicon film and the metal are annealed. It is preferable to form a composite film in which a silicide film and a metal film are stacked. However, the structure of the charge transfer device of the present invention is not affected at all by forming a mixture of silicon and metal directly on polycrystalline silicon instead of forming a laminated film by annealing.

  The electrode material layer is not particularly limited to the above, and for example, a film made of titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is used instead of the polycrystalline silicon film. Can do. Moreover, it is not always necessary to embed both the polycrystalline silicon film and the metal film, and even if only one of them is embedded, the effect of the present invention is not affected at all. The metal material is preferably tungsten or aluminum, but is not limited thereto, and the use of other metal materials does not affect the effects of the present invention.

The interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 are formed of the same material. For example, both are an insulating film 17 made of silicon nitride and an insulating film 18 made of silicon oxide. It is good to be formed by. The formation of the same material is an essential requirement for making the interelectrode insulating film 11 and the electrode-light shielding film insulating film 12 into an integrated insulating film 9.
The reason why silicon nitride and silicon oxide are stacked is used to form a stacked film made of materials having different etching characteristics. Further, when the silicon nitride film 17 is formed alone, there is an advantage that the capacitance between the electrodes becomes too large by using the silicon oxide film 18 together.

  As described above, when the inter-electrode insulating films 10 and 11 and the electrode-light-shielding film insulating film 12 are formed as a stacked film of a plurality of layers made of materials having different etching characteristics, the lower layer is etched as an etching stopper when the upper layer is etched. The upper layer can be used as a mask when the lower layer is etched.

  The upper surfaces of the transfer electrodes 5 to 8 are covered with an insulating film (cap film) 19, and when the electrode layer 16 is a metal layer, the insulating film (cap film) 19 also serves as a diffusion prevention film. The material of the insulating film (cap film) 19 is preferably silicon nitride or silicon carbide. This is because silicon nitride and silicon carbide have high performance for preventing metal diffusion and relatively high adhesion to metal.

  On the side surfaces and top surfaces of the transfer electrodes 5 to 8, the transfer electrode portion is opened while the region above the photoelectric conversion portion 3 is opened with the electrode-light shielding film insulating film 12 or the insulating film (cap film) 19 interposed therebetween. A light shielding film 20 that shields 4 from incident light is formed. The material of the light shielding film 20 is preferably a material that reflects light, and more preferably, it can be thinned, does not transmit light, has a high melting point, does not diffuse even at high temperatures, and is a workable metal, specifically tungsten. Aluminum, tantalum, titanium, iridium, ruthenium, and molybdenum are preferable.

  A pixel color filter 24, a pixel microlens 25, and the like corresponding to each unit pixel are provided on the gate insulating film 2 and the light shielding film 20 above the photoelectric conversion unit 3 via a planarizing film 23. .

  3 to 6 have an integrated insulating film 9 (interelectrode insulating film 11 and electrode-light shielding film insulating film 12) and interelectrode insulating film 10 in the manufacturing process of the CCD solid-state imaging device based on the first embodiment. It is sectional drawing which shows the flow of the process of producing the transfer electrode part 4, and the top view shown supplementarily as needed. The cross-sectional view is a cross-sectional view at the position indicated by the broken line AX-A, as in the cross-sectional view of FIG. The internal structure of the silicon substrate 1 is not shown (the same applies hereinafter).

  First, by using the steps shown in FIGS. 3A to 3C, the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 formed of the insulating film 17 and the insulating film 18 are used using a common mask. It is formed in the same process including the lithography process. The insulating film 18 is used as a hard mask for processing the insulating film 17. For the reasons described above, it is preferable to use silicon nitride and silicon oxide as materials for the insulating film 17 and the insulating film 18, respectively.

  First, as shown in FIG. 3A, a gate insulating film 2 made of silicon oxide is formed on the surface of a silicon substrate 1 by a thermal oxidation method. Next, the silicon nitride film 51 and the silicon oxide film 52 processed into the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 in a later step are gate-insulated by CVD (chemical vapor deposition). It is formed by laminating on the film 2.

  Next, as shown in FIG. 3B, the silicon oxide film 52 is patterned by photolithography and etching to form the insulating film 18 that forms part of the insulating films 10-12.

  Next, as shown in FIG. 3C, the silicon nitride film 51 is patterned by etching using the insulating film 18 as a hard mask to form an insulating film 17 that forms part of the insulating films 10 to 12.

  As described above, if the relatively thin insulating film 18 is accurately positioned and formed, the thick insulating film 17 can be formed at an accurate position according to the insulating film 18, so that the photoresist is removed. Rather than patterning the insulating film 17 directly as a mask, patterning can be performed without pattern loss.

  Subsequently, as shown in FIG. 4D, a mask layer 53 is formed on the entire upper surface of the silicon substrate 1. The mask layer 53 temporarily covers the upper surface of the silicon substrate 1 on which the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 are formed, and prevents damage and contamination of the photoelectric conversion unit 3 and the like. belongs to. As a material for forming the mask layer 53, a material different from the material constituting the gate insulating film 2 and the insulating film 18 is used. In particular, it is preferable to use a material having etching characteristics different from those of these materials.

  More specifically, when the gate insulating film 2 and the insulating film 18 are made of silicon oxide, the material for forming the mask layer 53 is different from that of silicon oxide by selecting components or adding additives. SOG (Spin-0n Glass) having etching characteristics or a coating material made of a material having etching characteristics different from that of silicon oxide may be used. According to the application, the insulating films 10 to 12 formed on the surface of the silicon substrate 1 can be embedded to easily flatten the surface. However, the method for forming the mask layer 53 is not particularly limited, and there is no problem even if it is formed by, for example, a CVD method or a sputtering method.

  Note that, after the formation of the mask layer 53, if it is necessary to flatten the surface to reduce the level difference, a flattening process is performed by a CMP method, an etch back method, or the like. By flattening, patterning by lithography in a later process becomes easy and patterning accuracy is improved.

  Thereafter, transfer electrodes 5 to 8 are formed in the transfer electrode portion 4 by the steps shown in FIGS. 4 (e) to 5 (i).

  First, as shown in FIG. 4E, a photoresist 54 that covers the photoelectric conversion unit 3 is formed by photolithography. Then, dry etching is performed using the photoresist 54 as a mask, and the mask layer 53 of the transfer electrode portion 4 is selectively removed to expose the gate insulating film 2 of the transfer electrode portion 4. At this time, the side surface of the photoresist 54 does not need to be exactly coincident with the side surface of the insulating film 18, and does not have to protrude from the side surface of the insulating film 18.

  Next, as shown in FIG. 4F, the photoresist 54 is removed by ashing.

  Next, as shown in FIGS. 5G and 5H, electrode material layers 55 and 56 made of a conductive material are formed on the entire upper surface of the silicon substrate 1 and embedded in the transfer electrode portion 4. At this time, each layer is preferably formed by sputtering or CVD.

As the electrode material layers 55 and 56, in order to realize higher electrical conductivity, it is desirable to laminate a metal silicide film 55 such as tungsten and the metal film 56, for example. However, in this case, since the film is formed by the CVD method using tungsten hexafluoride WF ₆ as a tungsten raw material, the gate insulating film 2 is attacked by fluorine-based reactive species such as fluorine atoms generated during the film forming process. There is a fear.

  Accordingly, when priority is given to preventing deterioration of the gate insulating film 2, a polycrystalline silicon film 55 is first formed as a protective film, a metal film 56 such as tungsten is then laminated, and then the polycrystalline silicon film is annealed. It is preferable to form a composite film in which a metal silicide film and a metal film are laminated.

  However, the electrode material layer is not particularly limited. For example, instead of the polycrystalline silicon film 55, a film made of titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like can be used. Moreover, it is not always necessary to embed both the polycrystalline silicon film and the metal film, and even if only one of them is embedded, the effect of the present invention is not affected at all. The metal material is preferably tungsten or aluminum, but is not limited thereto, and the use of other conductive materials does not affect the effects of the present invention.

  Note that electrode material layers 55 and 56 are also formed on the mask layer 53 of the photoelectric conversion unit 3, but these electrode material layers 55 and 56 are removed by a planarization process such as the following CMP method. These conductive materials are diffused on the silicon substrate 1 by a subsequent thermal process, and white spot defects are not generated.

  Next, as shown in FIG. 5I, unnecessary portions of the electrode material layers 55 and 56 are removed by CMP to obtain transfer electrodes 5 to 8 having a single layer structure.

  According to the above process, at the stage where the interelectrode insulating films 10 and 11 are embedded in the electrode material layers 55 and 56, the basic structure of the transfer electrode in which the electrode material is partitioned by the insulating film is automatically formed. The transfer electrodes 5 to 8 are completed only by removing unnecessary portions by CMP or the like. In addition, the interval between the transfer electrodes can be automatically determined by the width (thickness) of the interelectrode insulating films 10 and 11. Further, by performing ion implantation at a stage where the insulating films 10 to 12 are formed and the electrode material layer 55 is not yet formed, a region for forming the charge transfer path 14 other than the lower portions of the interelectrode insulating films 10 and 11. In addition, ion implantation can be performed by self-alignment. At this time, if necessary, temporary sidewalls may be formed in the interelectrode insulating films 10 and 11 or the electrode-light shielding film insulating film 12 to limit the ion implantation region.

  5J to FIG. 6O, an insulating film (cap film) 19 is formed on the transfer electrodes 5 to 8, and the mask layer 53 is removed to form the photoelectric conversion unit 3. Returning to the structure in which the light is incident, the light shielding film 20 is formed on the transfer electrode portion 4.

  First, as shown in FIG. 5J, an insulating material layer 57 made of silicon oxide or the like is formed.

  Next, as shown in FIG. 5K, a photoresist 58 that covers the transfer electrode 4 is formed by photolithography. At this time, the side surface of the photoresist 58 does not need to be exactly coincident with the side surface of the insulating film 18, but is not protruded from the side surface of the insulating film 18 to the photoelectric conversion unit 3 side. Then, as shown in FIG. 6L, etching is performed using the photoresist 58 as a mask, the insulating material layer 57 is selectively removed, and an insulating film (cap film) 19 is formed on the transfer electrodes 5-8. Form. The insulating film (cap film) 19 is an electrode-light shielding film insulating film on the upper surfaces of the transfer electrodes 5 to 8 and functions as a metal diffusion preventing film when the electrode layers 15 and 16 include a metal layer.

  Next, as shown in FIG. 6M, the mask layer 53 of the photoelectric conversion portion 3 is removed, preferably by dry etching, using the photoresist 58 or the insulating film 18 as a mask. At this time, by using the previously formed insulating film 18 as a hard mask, the width (thickness) of the insulating film 12 between the electrode and the light-shielding film can be kept the same as the original.

  At this time, since the electrode material constituting the transfer electrodes 5 to 8 is not exposed at all, it is possible to avoid the electrode material from being scattered in the photoelectric conversion unit 3 when the photoelectric conversion unit 3 is opened. It is possible to avoid the occurrence of white spot defects due to the scattering of.

  Next, as shown in FIG. 6 (n), the photoresist 58 is removed by ashing. Thereafter, a photoresist is formed by patterning by photolithography to form a portion that does not require ion implantation, and ion implantation is performed using the photoresist as a mask to form an impurity diffusion layer that constitutes the photoelectric conversion unit 3.

  Next, as shown in FIG. 6 (o), a light shielding film material layer for preventing incident light from entering the transfer electrode portion 4 is formed on the entire surface of the silicon substrate 1 with tungsten or the like and patterned. Thus, the light shielding film 20 is formed. At this time, a light shielding film 20 may be formed by forming a protective layer for protecting the gate insulating film 2 of the photoelectric conversion unit 3. As the material of the light shielding film 20, aluminum, tantalum, titanium, iridium, ruthenium, molybdenum, and the like are preferable in addition to tungsten for the reasons described above.

  Thereafter, the planarization film 23, the pixel color filter 24, the pixel microlens 25, and the like are formed by a known method, and the fabrication of the CCD solid-state imaging device is completed.

  FIG. 7 is a cross-sectional view showing a part of a manufacturing process flow of a CCD solid-state imaging device based on a modification of the first embodiment. In addition, sectional drawing is sectional drawing in the position of the same AXA line as sectional drawing of FIG.1 (b).

In the above process, when there is no sufficient etching selection ratio between the mask layer 53 made of, for example, SOG and the gate insulating film 2 (SiO ₂ ), the process is shown in FIGS. 4E and 6M. In the process, the gate insulating film 2 may be partially etched during the etching of the mask layer 53, and the gate insulating film 2 may be damaged. This modification is intended to prevent such damage to the gate insulating film 2.

  In this modification, in the etching process of the silicon nitride film 51 shown in FIG. 3C, the silicon nitride film 51 is not completely etched as shown in FIG. The insulating film 59 is left with a thickness sufficient to work as

  Next, as shown in FIGS. 7 (q) and 7 (r), formation and selective removal of the mask layer 53 similar to those shown in FIGS. 4 (d) and 4 (e) are performed. In the state shown in FIG. 4E, in the final stage of etching the mask layer 53, the gate insulating film 2 is exposed and etched to be damaged. On the other hand, in the state shown in FIG. 7R, since the gate insulating film 2 is covered with the insulating film 59, the gate insulating film 2 is not damaged.

  Thereafter, as shown in FIG. 7R, the insulating film 59 is selectively removed, and the processes after FIG. 4F are performed in the same manner as described above. According to this modification, although the number of steps increases by one, damage to the gate insulating film 2 can be prevented. Although the processing of the transfer electrode portion has been described here, the processing of the photoelectric conversion portion is similarly performed.

  As described above, according to the solid-state imaging device based on the present embodiment, the charge transfer electrode in which the interelectrode insulating films 10 and 11 are arranged regardless of the alignment error of the mask or the like in the patterning process at the time of manufacture. The relative position and shape of the portion 4 and the photoelectric conversion portion 3 surrounded by the electrode-light shielding film insulating film 12 are accurately formed. Therefore, it is possible to form a solid-state imaging device in which the area of the light receiving region does not vary due to the influence of the alignment error. In addition, since it is not necessary to take a margin for the alignment error, the region surrounded by the electrode-light shielding film insulating film 12 can be used to the maximum extent as the light receiving region, and the solid-state imaging device is highly sensitive and downsized. And effective for cost reduction. In addition, since the relative position between the charge transfer electrode unit 4 and the photoelectric conversion unit 3 is determined, for example, the vertical transfer unit 7 and the photoelectric conversion unit are based on the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12. Ion implantation can be performed on the conversion unit 3 by self-alignment.

  According to the method for manufacturing a solid-state imaging device based on the present embodiment, first, the insulating film 18 that is the upper part of the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 is formed by patterning using a common mask. Since the insulating film 18 is used as a hard mask in the subsequent processing, the interelectrode insulating films 10 and 11 and the electrode-light-shielding film insulating film 12 are placed in an accurate relative position within the range of the production accuracy of the common mask. Can be formed.

  In addition, when the interelectrode insulating films 10 and 11 are embedded in the electrode material layers 55 and 56, the basic structure of the transfer electrode in which the electrode materials are partitioned by the insulating film is automatically formed. Transfer electrodes 5 to 8 are completed simply by removing unnecessary portions. In addition, since the interval between the transfer electrodes can be automatically determined by the width (thickness) of the interelectrode insulating films 10 and 11, a transfer electrode having a so-called single layer structure can be easily manufactured.

  When the mask layer 53 is removed and the photoelectric conversion unit 3 is opened, the transfer electrodes 5 to 8 are covered with the electrode-light shielding film insulating film 12 and the like, and the electrode material constituting the transfer electrodes 5 to 8 is not exposed at all. Therefore, when the photoelectric conversion unit 3 is opened, the electrode material can be prevented from scattering to the photoelectric conversion unit 3, and the occurrence of white spot defects due to the scattering of the conductive material can be avoided.

Embodiment 2
In the second embodiment, an example in which a CCD solid-state imaging device having the same structure as described in the first embodiment is manufactured mainly by a manufacturing method corresponding to the manufacturing method described in claims 7, 8 and 10. Will be described. The main difference between the present embodiment and the first embodiment is that the integrated insulating film 9 and the interelectrode insulating film 10 are not first formed, but the interelectrode insulating films 10 and 11 and the electrode-shielding film. The point is that the inter-insulating film 12 is completed separately. Even in such a case, first, a hard mask is formed in the same process using a common mask, and in the subsequent process, these insulating films 10 to 12 are formed based on the hard mask. There is no room for mask alignment errors or the like. There are no other essential differences, so avoid duplication and focus on the differences.

  First, as shown in FIG. 8A, the gate insulating film 2 made of silicon oxide is formed on the surface of the silicon substrate 1 by thermal oxidation. Next, the silicon nitride film 61, the silicon oxide film 62, and the silicon nitride film 63, which are processed into the interelectrode insulating films 10 and 11 and the electrode-shielding insulating film 12 in a later step, are formed by the CVD method into the gate insulating film. 2 are stacked on top of each other.

  The silicon nitride film 63 is for forming a hard mask when the silicon oxide film 62 is processed. The silicon nitride film 61 is used as a protective film for the gate insulating film 2 when the silicon oxide film 62 is etched. The silicon nitride film 61 is preferably formed as thin as possible so as to function as a protective film. Even when the silicon nitride film 61 is removed by etching, a hard mask formed from the silicon nitride film 63 is used as a mask, so that the thickness of the silicon nitride film 63 is sufficiently larger than the thickness of the silicon nitride film 61.

  Next, as shown in FIG. 8B, the silicon nitride film 63 is patterned by the same photolithography process and etching process using a common mask, and the interelectrode insulating films 10 and 11 and the electrode-shielding film insulating film are patterned. 12 is formed.

  Subsequently, as shown in FIG. 8C, after a silicon oxide film 64 is formed on the entire upper surface of the silicon substrate 1 by the CVD method and the insulating film 33 is embedded, as shown in FIG. The upper surface of the insulating film 33 is exposed by a planarization process using a method. This step corresponds to the step shown in FIG. 4D in the first embodiment, and the silicon oxide films 62 and 64 correspond to the mask layer 53 in the first embodiment.

  Thereafter, transfer electrodes 5 to 8 are formed by the steps shown in FIGS. 9E to 11K.

  First, as shown in FIG. 9E, a photoresist 65 that covers the photoelectric conversion unit 3 is formed by photolithography. At this time, the side surface of the photoresist 65 does not need to be exactly coincident with the side surface of the insulating film 33, and may not protrude from the side surface of the insulating film 33. Then, dry etching is performed using the photoresist 65 as a mask, and the silicon oxide films 62 and 64 of the transfer electrode portion 4 are selectively removed to form an insulating film 32 that becomes a part of the interelectrode insulating films 10 and 11. To do. Thereafter, the photoresist 65 is removed by ashing.

  Further, as shown in FIG. 10F, dry etching is performed using the insulating film 33 as a mask, the silicon nitride film 61 is selectively removed, and the insulating film which becomes a part of the interelectrode insulating films 10 and 11 31 is formed to complete the interelectrode insulating films 10 and 11, and the gate insulating film 2 of the transfer electrode portion 4 is exposed. At this time, if the upper surface of the insulating film 33 is exposed, the insulating film 33 is also slightly etched, but there is no problem because the thickness of the insulating film 33 is sufficiently larger than the thickness of the silicon nitride film 61.

  Next, as shown in FIGS. 10 (g) and 10 (h), electrode material layers 55 and 56 made of a conductive material are formed on the entire upper surface of the silicon substrate 1 and embedded in the transfer electrode portion 4.

  As described above, the electrode material layers 55 and 56 are formed by laminating a metal silicide film 55 such as tungsten and a metal film 56 in order to achieve higher electrical conductivity. When priority is given to preventing deterioration of the gate insulating film 2, a composite film in which a polycrystalline silicon film, a metal silicide film, and a metal film are laminated is formed.

  Next, as shown in FIG. 11 (i), unnecessary portions of the electrode material layers 55 and 56 are removed by CMP to obtain transfer electrodes 5 to 8 having a single layer structure consisting of the electrode layers 15 and 16.

  According to the above process, at the stage where the interelectrode insulating films 10 and 11 are embedded in the electrode material layers 55 and 56, the basic structure of the transfer electrode in which the electrode material is partitioned by the insulating film is automatically formed. The transfer electrodes 5 to 8 are completed only by removing unnecessary portions by CMP or the like. In addition, the interval between the transfer electrodes can be automatically determined by the width (thickness) of the interelectrode insulating films 10 and 11. Further, by performing ion implantation at a stage where the interelectrode insulating films 10 and 11 are formed and the electrode material layer 55 is not yet formed, the charge transfer path 14 other than the lower part of the interelectrode insulating films 10 and 11 is formed. Ion implantation can be performed in a region to be self-aligned. At this time, if necessary, temporary sidewalls can be formed in the interelectrode insulating films 10 and 11 to limit the ion implantation region.

  Subsequently, after an insulating film (cap film) 19 is formed on the transfer electrodes 5 to 8 by the steps shown in FIGS. 11J to 12O, the interelectrode-shield insulating film 12 is completed. Returning to the structure in which light enters the photoelectric conversion unit 3, the light shielding film 20 is formed on the transfer electrode unit 4.

  First, as shown in FIG. 11J, an insulating material layer 57 made of silicon oxide or the like is formed.

  Next, as shown in FIG. 11K, a photoresist 66 that covers the transfer electrode 4 is formed by photolithography. At this time, the side surface of the photoresist 66 does not need to be exactly coincident with the side surface of the insulating film 33, but is not protruded from the side surface of the insulating film 33 to the photoelectric conversion unit 3 side.

  Next, as shown in FIG. 12L, etching is performed using the photoresist 66 as a mask, the insulating material layer 57 is selectively removed, and an insulating film (cap film) is formed on the transfer electrodes 5-8. 19 is formed. The insulating film (cap film) 19 is an electrode-light shielding film insulating film on the upper surfaces of the transfer electrodes 5 to 8 and functions as a metal diffusion preventing film when the electrode layers 15 and 16 include a metal layer. Further, preferably, etching by the dry etching method is continued to remove the silicon oxide film 64, and then selectively remove the silicon oxide film 62 to form a part of the insulating film 12 between the electrode and the light shielding film. 32 is formed.

  Next, as shown in FIG. 12 (m), dry etching using the photoresist 66 or the insulating film 33 as a mask is performed to selectively remove the silicon nitride film 61 of the photoelectric conversion unit 3, and thereby the electrode-light-shielding film An insulating film 31 to be a part of the interlayer insulating film 12 is formed to complete the electrode-light shielding film insulating film 12, and the gate insulating film 2 of the photoelectric conversion unit 3 is exposed. At this time, by using the previously formed insulating film 33 as a hard mask, the insulating film 12 between the electrode and the light-shielding film can be formed with a predetermined width (thickness) at an initially set position. At this time, the insulating film 33 is also slightly etched, but there is no problem because the thickness of the insulating film 33 is sufficiently larger than the thickness of the silicon nitride film 61.

  Moreover, since the electrode material which comprises the transfer electrodes 5-8 is not exposed at this time, when opening the photoelectric conversion part 3, it can avoid that an electrode material scatters to the photoelectric conversion part 3, and conductive material Generation of white spot defects due to scattering can be avoided.

  Next, as shown in FIG. 12 (n), the photoresist 66 is removed by ashing. Thereafter, a photoresist is formed by patterning by photolithography to form a portion that does not require ion implantation, and ion implantation is performed using the photoresist as a mask to form an impurity diffusion layer that constitutes the photoelectric conversion unit 3.

  Next, as shown in FIG. 12 (o), a light shielding film material layer for preventing incident light from entering the transfer electrode portion 4 is formed on the entire surface of the silicon substrate 1, and this is patterned to form a light shielding film. 20 is formed. At this time, a light shielding film 20 may be formed by forming a protective layer for protecting the gate insulating film 2 of the photoelectric conversion unit 3. As the material of the light shielding film 20, tungsten, aluminum, tantalum, titanium, iridium, ruthenium, molybdenum, and the like are preferable for the reasons described above.

  Thereafter, the planarization film 23, the pixel color filter 24, the pixel microlens 25, and the like are formed by a known method, and the fabrication of the CCD solid-state imaging device is completed.

  FIG. 13 is a cross-sectional view showing one step of a manufacturing process of a CCD solid-state imaging device based on a modification of the second embodiment. In this step, unnecessary portions of the electrode material layers 55 and 56 are removed by etching back instead of flattening by the CMP method shown in FIG. 11 (i), and transfer of a single layer structure composed of the electrode layers 15 and 16 is performed. Electrodes 5-8 are obtained.

  In this method, in order to completely remove the electrode material layers 55 and 56 other than the transfer electrode portion 4, it is necessary to etch back until the transfer electrode portion 4 has a recess as shown in FIG. For this reason, when the insulating material layer 57 made of silicon oxide or the like is formed as in FIG. 11J, a recess is formed in the insulating material layer 57 on the transfer electrode portion 4. If this concave portion is left as it is, there is a possibility that the patterning cannot be performed accurately because the focus is not achieved when patterning the photoresist 66 in a later process. In order to avoid this, the surface of the insulating material layer 57 is planarized by CMP. Thereafter, the processes after FIG. 11K are performed in the same manner as described above.

  As described above, the present embodiment is not essentially different from the first embodiment, and needless to say, the operational effects described in the first embodiment exist.

  That is, according to the solid-state imaging device according to the present embodiment, the charge transfer electrode portion 4 in which the interelectrode insulating films 10 and 11 are disposed, and the electrode, regardless of the alignment error such as the mask in the patterning process at the time of manufacture, -The relative position and shape with respect to the photoelectric conversion part 3 surrounded by the insulating film 12 between light shielding films are formed correctly. For this reason, it is possible to form a solid-state imaging device in which the light receiving area of the light receiving region does not vary due to the influence of the alignment error. In addition, since it is not necessary to take a margin for the alignment error, the region surrounded by the electrode-light shielding film insulating film 12 can be used to the maximum extent as the light receiving region, and the solid-state imaging device is highly sensitive and downsized. And effective for cost reduction. In addition, since the relative position between the charge transfer electrode unit 4 and the photoelectric conversion unit 3 is fixed, for example, by a method such as self-alignment based on the electrode-light shielding film insulating film 12, the relative position with respect to the photoelectric conversion unit 3 is correct. Since the charge readout portion 21 and the like can be formed at the position, variations in readout voltage are reduced.

  According to the method for manufacturing a solid-state imaging device based on the present embodiment, first, the insulating film 18 that is the upper part of the interelectrode insulating films 10 and 11 and the electrode-light shielding film insulating film 12 is formed by patterning using a common mask. Since the insulating film 18 is used as a hard mask in the subsequent processing, the interelectrode insulating films 10 and 11 and the electrode-light-shielding film insulating film 12 are placed in an accurate relative position within the range of the production accuracy of the common mask. Can be formed.

  In addition, when the interelectrode insulating films 10 and 11 are embedded in the electrode material layers 55 and 56, the basic structure of the transfer electrode in which the electrode materials are partitioned by the insulating film is automatically formed. Transfer electrodes 5 to 8 are completed simply by removing unnecessary portions. In addition, since the interval between the transfer electrodes can be automatically determined by the width (thickness) of the interelectrode insulating films 10 and 11, a transfer electrode having a so-called single layer structure can be easily manufactured.

  When the mask layer 53 is removed and the photoelectric conversion unit 3 is opened, the transfer electrodes 5 to 8 are covered with the electrode-light shielding film insulating film 12 and the like, and the electrode material constituting the transfer electrodes 5 to 8 is not exposed at all. Therefore, when the photoelectric conversion unit 3 is opened, the electrode material can be prevented from scattering to the photoelectric conversion unit 3, and the occurrence of white spot defects due to the scattering of the conductive material can be avoided.

Embodiment 3
In the third embodiment, a CCD solid-state imaging device having the same structure as described in the first embodiment is manufactured by the same manufacturing method as described in the second embodiment, but the insulating film is oxidized with the silicon nitride film. An example in which the structure and process are simplified by using a two-layer structure of a silicon film will be described. Since there is no essential difference from the second embodiment, only the main points will be described.

  First, as shown in FIG. 14A, a gate insulating film 2 made of silicon oxide is formed on the surface of a silicon substrate 1 by a thermal oxidation method. Next, the silicon nitride film 71 and the silicon oxide film 72 processed into the interelectrode insulating films 10 and 11 and the electrode-shielding insulating film 12 in a later step are formed on the gate insulating film 2 by CVD. It is formed by laminating. The silicon oxide film 72 is for forming a hard mask when the silicon nitride film 71 is processed.

  Next, as shown in FIG. 14B, the silicon oxide film 72 is patterned by the same photolithography process and etching process using a common mask, so that the interelectrode insulating films 10 and 11 and the electrode-shielding film insulation are formed. An insulating film 42 to be a part of the film 12 is formed.

  Subsequently, as shown in FIG. 14C, after a silicon nitride film 73 is formed on the entire upper surface of the silicon substrate 1 by the CVD method and the insulating film 42 is buried, the insulating film 42 is planarized by the CMP method. Expose the top surface.

  Thereafter, transfer electrodes 5 to 8 are formed by the steps shown in FIGS. 14 (d) to 15 (h).

  First, as shown in FIG. 14D, a photoresist 74 covering the photoelectric conversion unit 3 is formed by photolithography. At this time, the side surface of the photoresist 74 does not need to be exactly coincident with the side surface of the insulating film 42, and may not protrude from the side surface of the insulating film 42. Then, dry etching is performed using the photoresist 74 as a mask, the silicon nitride film 73 of the transfer electrode portion 4 is removed, the silicon nitride film 71 is selectively removed, and a part of the interelectrode insulating films 10 and 11 is formed. The insulating film 41 is formed to complete the inter-electrode insulating films 10 and 11, and the gate insulating film 2 of the transfer electrode portion 4 is exposed. Thereafter, as shown in FIG. 14E, the photoresist 74 is removed by ashing.

  Further, as shown in FIGS. 15 (f) and 15 (g), electrode material layers 55 and 56 made of a conductive material are formed on the entire upper surface of the silicon substrate 1 and embedded in the transfer electrode portion 4.

  As described above, the electrode material layers 55 and 56 are formed by laminating a metal silicide film 55 such as tungsten and a metal film 56 in order to achieve higher electrical conductivity. When priority is given to preventing deterioration of the gate insulating film 2, a composite film in which a polycrystalline silicon film, a metal silicide film, and a metal film are laminated is formed.

  Next, as shown in FIG. 15 (h), unnecessary portions of the electrode material layers 55 and 56 are removed by CMP to obtain transfer electrodes 5 to 8 having a single layer structure composed of the electrode layers 15 and 16.

  Subsequently, after an insulating film (cap film) 19 is formed on the transfer electrodes 5 to 8 by the steps shown in FIGS. 15I to 16M, the interelectrode-shield insulating film 12 is completed. Returning to the structure in which light enters the photoelectric conversion unit 3, the light shielding film 20 is formed on the transfer electrode unit 4.

  First, as shown in FIG. 15I, an insulating material layer 75 made of silicon nitride or the like is formed.

  Next, as shown in FIG. 16J, a photoresist 76 covering the transfer electrode 4 is formed by photolithography. At this time, the side surface of the photoresist 76 does not need to be exactly coincident with the side surface of the insulating film 42, but is not protruded from the side surface of the insulating film 42 to the photoelectric conversion unit 3 side.

  Next, as shown in FIG. 16 (k), etching is performed using the photoresist 76 as a mask, the insulating material layer 75 is selectively removed, and an insulating film (cap film) is formed on the transfer electrodes 5-8. 43 is formed. The insulating film (cap film) 43 is an electrode-light shielding film insulating film on the upper surfaces of the transfer electrodes 5 to 8 and functions as a metal diffusion preventing film when the electrode layers 15 and 16 include a metal layer. Further, preferably, etching by dry etching is continued to remove the silicon nitride film 73, and then selectively remove the silicon oxide film 71 to form an insulating film that becomes a part of the insulating film 12 between the electrode and the light shielding film. 41 is formed to complete the electrode-light shielding film insulating film 12, and the gate insulating film 2 of the photoelectric conversion unit 3 is exposed.

  Next, as shown in FIG. 16L, the photoresist 76 is removed by ashing. Thereafter, a photoresist is formed by patterning by photolithography to form a portion that does not require ion implantation, and ion implantation is performed using the photoresist as a mask to form an impurity diffusion layer that constitutes the photoelectric conversion unit 3.

  Next, as shown in FIG. 16 (m), a light shielding film material layer for preventing incident light from entering the transfer electrode portion 4 is formed on the entire surface of the silicon substrate 1, and this is patterned to form a light shielding film. 20 is formed. At this time, a light shielding film 20 may be formed by forming a protective layer for protecting the gate insulating film 2 of the photoelectric conversion unit 3. As described above, tungsten, aluminum, thallium, titanium, iridium, ruthenium, molybdenum, or the like is preferable as the material of the light shielding film 20.

  Thereafter, the planarization film 23, the pixel color filter 24, the pixel microlens 25, and the like are formed by a known method, and the fabrication of the CCD solid-state imaging device is completed.

  As described above, the present embodiment is not essentially different from the second embodiment, and needless to say, the effects described in the second embodiment exist.

  As mentioned above, although this invention was demonstrated based on embodiment, it cannot be overemphasized that this invention is not limited to these examples at all, and can be suitably changed in the range which does not deviate from the main point of invention.

  The charge transfer device and the manufacturing method thereof according to the present invention are applied to a CCD solid-state imaging device such as an area sensor, and contribute to an increase in the number of pixels, miniaturization, high accuracy, and low cost.

2A and 2B are a plan view and a cross-sectional view, respectively, of a CCD solid-state imaging device based on Embodiment 1 of the present invention. It is sectional drawing of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of the CCD solid-state image sensor based on a modification similarly. It is sectional drawing which shows a part of manufacturing process flow of the CCD solid-state image sensor based on Embodiment 2 of this invention. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows 1 process of the manufacturing process of the CCD solid-state image sensor based on a modification. It is sectional drawing which shows a part of manufacturing process flow of the CCD solid-state image sensor based on Embodiment 3 of this invention. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. It is sectional drawing which shows a part of manufacturing process flow of a CCD solid-state image sensor similarly. In order to show the subject of this invention, it is the top view (1) and sectional drawing (2) which show the pixel structure of the imaging part of the CCD solid-state image sensor which has the charge transfer electrode of a single layer structure as a model. FIG. 2 is a plan view (1) showing the manufacturing process of the CCD solid-state imaging device and sectional views (2) and (3). FIG. 2 is a plan view (1) showing the manufacturing process of the CCD solid-state imaging device and sectional views (2) and (3). The top view (1) which shows the other example of the manufacturing process of the said CCD solid-state image sensor, and sectional drawing (2) and (3) are the same.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Gate insulating film, 3 ... Photoelectric conversion part, 4 ... Transfer electrode part,
5-8 transfer electrodes, 9 ... integral insulating film, 10, 11 ... interelectrode insulating film,
12 ... Insulating film between electrode and light shielding film, 13 ... Vertical transfer part,
14: Charge transfer path (n ⁺ -type region) of vertical transfer unit, 15, 16 ... Electrode layer,
17, 18 ... insulating film, 19 ... insulating film (cap film), 20 ... light shielding film,
21 ... Read gate part, 22 ... Channel stopper, 23 ... Planarization film,
24 ... Pixel color filter, 25 ... Pixel microlens, 31-33 ... Insulating film,
41, 42 ... insulating film, 43 ... insulating film (cap film), 51 ... silicon nitride film,
52 ... Silicon oxide film, 53 ... Mask layer, 54, 58 ... Photoresist,
55, 56 ... electrode material layer, 57 ... insulating material layer, 59, 60 ... insulating film,
61 ... Silicon nitride film, 62 ... Silicon oxide film, 63 ... Silicon nitride film,
64 ... Silicon oxide film, 65, 66 ... Photoresist, 71 ... Silicon nitride film,
72 ... Silicon oxide film, 73 ... Silicon nitride film, 74, 76 ... Photoresist,
75 ... Insulating material layer, 101 ... Silicon substrate, 102 ... Gate insulating film,
DESCRIPTION OF SYMBOLS 103 ... Photoelectric conversion part, 104 ... Transfer electrode part, 105 ... Transfer electrode, 106 ... Interelectrode insulating film,
107: vertical transfer unit, 108: charge transfer path (n-type region) of the vertical transfer unit,
109 ... Insulating film between electrode and light shielding film, 110 ... Insulating film (cap film), 111 ... Light shielding film,
112: Read gate portion, 113: Channel stopper, 114 ... Planarization film,
115 ... Pixel color filter, 116 ... Pixel microlens, 121 ... Silicon nitride film,
122. Insulating material layer

Claims (14)

A charge transfer electrode in which a plurality of charge transfer electrodes are arranged on a charge transfer path of a semiconductor substrate via a gate insulating film, adjacent charge transfer electrodes face each other across a gap, and a first insulating film is arranged in the gap In the charge transfer device having a portion,
A second insulating film disposed between a light-shielding film that shields the charge transfer electrode portion from incident light and a side surface of the charge transfer electrode is integrally connected to the first insulating film. A charge transfer element.   The first insulating film and the second insulating film stand up from the semiconductor substrate in contact with the gate insulating film at the position of the gap and the position of the boundary between the charge transfer electrode portion and the photoelectric conversion portion, respectively. The charge transfer electrode is formed of an electrode material disposed on the charge transfer electrode portion surrounded by the first insulating film and the second insulating film, and constitutes a part of a solid-state imaging device. The charge transfer device according to claim 1.   The charge transfer element according to claim 1, wherein the first insulating film and the second insulating film are formed of the same material.   The charge transfer element according to claim 1, wherein the first insulating film and the second insulating film are made of silicon oxide and / or silicon nitride.   The charge transfer element according to claim 1, wherein an upper surface of the charge transfer electrode is also insulated from the light shielding film.   The charge transfer device according to claim 1, wherein the charge transfer electrode is made of a metal layer. A method of manufacturing a charge transfer device according to claim 1,
Forming an insulating material layer on the semiconductor substrate in contact with the gate insulating film;
Patterning the insulating material layer with a common mask to form the first insulating film and the second insulating film;
Forming an electrode material layer on the entire surface of the semiconductor substrate;
Removing unnecessary portions of the electrode material layer, and forming the charge transfer electrode in the charge transfer electrode portion surrounded by the first insulating film and the second insulating film;
Forming a light shielding film material layer on the entire surface of the semiconductor substrate so as to cover the second insulating film;
Forming the light-shielding film by patterning the light-shielding film material layer.   8. The method of manufacturing a charge transfer element according to claim 7, wherein the upper portions of the first insulating film and the second insulating film are formed by positioning in the same patterning step.   The first insulating film and the second insulating film are formed by etching the insulating material layer using the upper portions as masks, and then a mask layer is provided to cover the photoelectric conversion portion in contact with the second insulating film. 9. The method of manufacturing a charge transfer element according to claim 8, wherein the charge transfer electrode is formed by forming the electrode material layer in a state and flattening the electrode material layer to the position of the first insulating film. .   After the first insulating film is formed by etching using the upper part of the first insulating film as a mask, the insulating material layer that is in contact with the second insulating film and covers the photoelectric conversion unit is in contact with the second insulating film. The electrode material layer is formed in a state where the mask layer covering the photoelectric conversion portion is provided, and the charge transfer electrode is formed by planarizing the electrode material layer to the position of the first insulating film. 9. The method of manufacturing a charge transfer element according to claim 8, further comprising forming the second insulating film by etching using the upper portion of the second insulating film as a mask.   11. The charge transfer device according to claim 9, wherein an entire surface of the gate insulating film is covered with an insulating layer made of the same material as the insulating layer under each upper portion of the first insulating film and the second insulating film. Method.   The method for manufacturing a charge transfer element according to claim 9 or 10, wherein the mask layer is removed to form a structure in which light is incident on the photoelectric conversion unit.   The method for manufacturing a charge transfer element according to claim 7, wherein the insulating film is formed using silicon oxide and / or silicon nitride.   The method for manufacturing a charge transfer element according to claim 7, wherein the charge transfer electrode is formed of a metal layer.

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