JPH02228044A - Charge transfer device - Google Patents

Abstract

PURPOSE:To lower the resistance of wiring and prevent the fluctuation of potential in a transfer region by connecting the first semiconductor layer acting as a transfer electrode to the second semiconductor layer through a contact hole and connecting the second semiconductor layer to a metal wiring layer in a region other than the contact hole. CONSTITUTION:There is the first polysilicon layer 14 acting as a transfer electrode on a transfer region 12 and the first polysilicon layer 14 is connected to the second polysilicon layer 17 by a contact hole 16 located on the above layer 14. Then the second polysilicon layer 17 is connected to a metal wiring layer 19 on the second polysilicon layer except a part on the contact hole. Then the position of the contact hole 16 which is formed between the first and second polysilicon layers 14 and 17 and the position where the metal wiring layer 19 on the second polysilicon layer is connected to the second polysilicon layer 17 hold different positions in terms of a plane layout. Then the lower part of a region at which the metal wiring layer 19 is connected to the polysilicon layer 17 allows the first polysilicon layer 14 to be positioned in such a manner that the first polysilicon layer 14 does not have an effect on potential. In this way, lowering of the resistance of wiring is performed and the fluctuation of work functions is thus prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a charge transfer device in which charges are transferred by a transfer electrode formed on a transfer region, and particularly to a charge transfer device having a structure in which a metal wiring layer is connected to a semiconductor layer. The present invention relates to a charge transfer device.

[Summary of the invention]

The present invention provides a charge transfer device in which charges are transferred by a transfer electrode formed on a transfer region, in which a first semiconductor layer serving as a transfer electrode is connected to a second semiconductor layer via a contact hole, and the second semiconductor layer is connected to the second semiconductor layer through a contact hole. By connecting the semiconductor layer with the metal wiring layer in a region other than the contact hole, the resistance of the wiring can be reduced and the potential of the transfer region can be prevented from changing.

[Conventional technology]

In a charge transfer device such as a COD, it is required to reduce the sheet resistance of a transfer electrode in order to perform high-speed transfer or to miniaturize a wiring layer. As a technique for reducing the resistance of such transfer electrodes, Japanese Patent Application Laid-Open No. 56-873
As disclosed in Japanese Patent No. 79, a technique is known in which a metal thin film such as an aluminum wiring layer is provided to be connected to a part of the transfer electrode, and a transfer lock pulse is applied to the transfer electrode via the metal thin film. In order to reduce the resistance of the electrode, techniques for forming a high melting point metal layer or a silicide layer are also known. Further, in the case where an aluminum wiring layer is formed on a transfer electrode, there is a technique of forming a barrier metal layer of molybdenum, titanium, or the like under the aluminum wiring layer to prevent reaction with metal.

[Problem to be solved by the invention]

However, in charge transfer devices that have a structure in which a silicide layer or a high-melting point metal layer is formed, it is difficult to form an insulating film such as an oxide film well, so it is difficult to form a good insulating film such as an oxide film. It is difficult to form them by overlapping them.

In addition, in a charge transfer device in which a metal thin film is connected to a transfer electrode and a transfer lock pulse is supplied via the metal thin film,
When a thin metal film is formed directly on the transfer electrode, the depth of the potential well changes due to variations in the work function below the metal thin film, making it impossible to transfer charge as designed.

Further, in the case of forming a barrier metal layer, there arise problems such as an inability to maintain a selectivity with respect to the underlying insulating film (oxide film).

Therefore, in view of the above-mentioned technical problems, the present invention aims to provide a charge transfer device that achieves low resistance, solves the problem of the barrier metal layer, and further prevents fluctuations in the potential of the transfer region. shall be.

[Means to solve the problem]

In order to achieve the above object, the charge transfer device of the present invention includes a transfer region for transferring charges, a first semiconductor layer formed on the transfer region and functioning as a transfer electrode, and a first semiconductor layer formed on the transfer region and functioning as a transfer electrode. an insulating film covering a semiconductor layer, a contact hole formed in the insulating film on the first semiconductor layer, a second semiconductor layer connected to the first semiconductor layer through the contact hole, and the contact hole. It is characterized by having a metal wiring layer connected to the second semiconductor layer on the second semiconductor layer other than the top.

In the present invention, the first semiconductor layer and the second semiconductor layer are
For example, it is made of a material such as a polysilicon layer.

The first semiconductor layer may be a single layer or may have a structure consisting of multiple layers. Further, the second semiconductor layer is a semiconductor layer formed above the uppermost layer of the first semiconductor layer, and an insulating film is interposed between the second semiconductor layer and the first semiconductor layer. A part of the second semiconductor layer may function as a transfer electrode, and this second semiconductor layer does not matter whether it is a single layer or multiple layers. Furthermore, the charge transfer device may be a solid-state imaging device having light receiving sections arranged in an area or in a line. An example of the metal wiring layer is an aluminum wiring layer, but other high melting point metals, silicide layers, etc. may also be used.

[Effect]

In the charge transfer device of the present invention, the position of the contact hole formed between the first semiconductor layer and the second semiconductor layer and the metal layer &AltIN formed on the second semiconductor layer are The positions connected to the layers are different from the planar layout. Therefore, the first semiconductor layer is not located below the region where the metal wiring layer connects to the second semiconductor layer in a manner that affects the potential, resulting in lower resistance and fluctuations in the work function. This problem is solved and the barrier metal becomes unnecessary.

〔Example〕

Preferred embodiments of the present invention will be described with reference to the drawings.

First Example This example is an example in which the metal wiring layer is an aluminum wiring layer, and a buffer layer is formed over the contact hole of the first layer of polysilicon layer, which is a layer below the aluminum wiring layer. .

In its structure, as shown in FIG. 1, a transfer region 12 for transferring charges is formed on the surface of a silicon substrate 11. Required impurities are introduced into this transfer region 12 so as to form a transfer part or a storage part.

A first polysilicon layer 14 serving as a transfer electrode is formed on the transfer region 12 with an insulating film 13 interposed therebetween. Although not shown, this first polysilicon layer 14 is adjacent to another polysilicon layer via an insulating film in a direction perpendicular to the cross section. The first polysilicon layer 14 is a first or second polysilicon layer.

First polysilicon layer 14 is covered with interlayer insulating film 15 . A contact hole 16 is formed in this glabellar insulating film 15, and the first polysilicon layer 14 faces the bottom of the contact hole 16.

A second polysilicon layer 17, which is a second semiconductor layer, is connected to the first polysilicon layer 14 through its contact hole 16. That is, the second polysilicon layer 17
is connected to the first polysilicon layer 14 in the area of the contact hole 16, and is formed to extend over the glabellar insulating film 15 around that area, and the end of the second polysilicon layer N17 is connected to the glabellar insulating film 15. It is provided on the membrane 15. In addition,
The second polysilicon Jii17 is, for example, a third polysilicon layer.

A buffer N18 is then formed over the contact hole 16 region of the second polysilicon layer 17. This buffer layer 18 is a layer for preventing mutual diffusion between the next aluminum wiring layer 19 and the second polysilicon layer 17,
For example, it is formed using a silicon oxide layer or a silicon nitride layer. The region where this buffer layer 1 is formed is the region above the contact hole 16, and the second polysilicon layer 17 in the region over the contact hole 16 is covered with the buffer layer 18.

The second polysilicon layer 17 covered with the buffer layer 18 in the area of the contact hole 16 is connected to the aluminum wiring layer 19 in the area outside the buffer layer 18, that is, in the area other than the area of the contact hole 16. Aluminum wiring layer 1
By using 9 as a wiring layer, sheet resistance can be reduced compared to a polysilicon layer. Furthermore, since the buffer layer 18 exists in the region of the contact hole 16, adverse effects such as fluctuations in the potential of the transfer region 12 due to the aluminum wiring layer 19 are suppressed.

In this way, in the charge transfer device of this embodiment, the aluminum wiring layer 19 is connected to the first polysilicon layer 14 via the second polysilicon layer 17, but the first polysilicon layer 14 and the second A buffer layer 18 is formed on the contact hole 16 between the polysilicon [17], and this buffer layer 18
The aluminum wiring layer 19 and the polysilicon layer 1 are
It is possible to prevent mutual diffusion of 4. Therefore, it is possible to prevent fluctuations in the potential of the transfer region 12 under the first polysilicon layer 14, and there is no problem of barrier metal etching.Of course, the aluminum wiring layer 19 can reduce the resistance of the wiring layer. It is possible to achieve this goal.

In the above-described embodiment, only the transfer region 12 is formed on the surface of the silicon substrate 11, but the aluminum distribution may have a structure having a light receiving section and other regions.
Aii19 may also be used for light shielding.

Second Embodiment This embodiment is an example in which the second polysilicon layer is extended and connected to an aluminum wiring layer, and has the structure shown in FIG.

As shown in FIG. 2, in the structure, a transfer region 22 for transferring charges is formed on the surface of a silicon substrate 21. Required impurities are introduced into this transfer area 22 so as to form a transfer part or a storage part. A first polysilicon layer 24 serving as a transfer electrode is formed on the transfer region 22 with an insulating film 23 interposed therebetween, and is adjacent to another polysilicon layer with the insulating film interposed in a direction perpendicular to the cross section. The first polysilicon layer 24 is the first or second polysilicon layer, and is covered with the glabella insulating film 25. This interlayer insulating film 25 has a contact hole 2
6 is formed to expose the first polysilicon layer 24.

The second polysilicon layer 27, which is a second semiconductor layer, is connected to the first polysilicon layer 24 through the contact hole 26, and is patterned to extend further onto the glabella insulating film 25. The second polysilicon layer 27 extended in this manner is covered with a glabellar insulating film 28, and the glabellar insulating film 28 is opened to connect with the aluminum wiring layer 30. contact hole 2
9 is formed. Then, an aluminum wiring layer 30 is formed in the contact hole 29 to reduce the sheet resistance of the wiring. Here, the position of the contact hole 29 is not a position on the area of the contact hole 26 on the first polysilicon layer 24, but a position other than the area of the contact hole 26, and extends on the glabella insulating film 25. It is formed in the portion of the second polysilicon layer 27 that has been removed. Since the positions of the two contact holes 26 and 29 are shifted in this manner, fluctuations in the work function due to the aluminum wiring layer 30 can be suppressed, and fluctuations in the potential of the transfer region 22 can be suppressed.

As described above, in the charge transfer device of this embodiment, since the two contact holes 26 and 29 are located at different positions, fluctuations in the potential of the transfer region 22 are suppressed, and problems such as aluminum spikes are also prevented. .

In this embodiment, only the transfer region 12 is formed on the surface of the silicon substrate 11, but a structure having the light receiving section 1 and other regions may be used.

Third Embodiment This embodiment is an example in which the second polysilicon layer functions as a part of the transfer electrode.

In its structure, as shown in FIG. 3, a transfer region 32 for transferring charges is formed on the surface of a silicon substrate 31. A first polysilicon layer 34, which is a first semiconductor layer, is formed on the transfer region 32 with an insulating film 33 interposed therebetween, and functions as a transfer electrode.

This first polysilicon layer 34 is the first polysilicon layer. This first polysilicon layer 34 is the insulating film 3
5, and a contact hole 3 is formed in the insulating film 35.
6 is formed. A second polysilicon layer 37 made of a second polysilicon layer is connected through this contact hole 36. Second polysilicon layer 37 extends from above first polysilicon layer 34 to above insulating film 33 . Therefore, the first polysilicon layer 34 and the second polysilicon layer 37 function as transfer electrodes, and the transfer region 2
The corresponding regions of 2 function as a storage section and a transfer section depending on the impurity concentration, etc.

The second polysilicon layer 37 is covered with an insulating film 38, and the second polysilicon layer 37 is covered with the insulating film 38.
A contact hole 39 is formed for connecting the aluminum wiring layer 40 to the aluminum interconnection layer 40 .

Then, an aluminum wiring layer 40 is formed in a desired pattern on the contact hole 39, and a transfer lock signal is supplied to each polysilicon layer 37, 34 through this aluminum wiring layer 40.

Here, the contact hole 39 is located at a position other than above the contact hole 36. Therefore, fluctuations in the work function due to the aluminum wiring layer 40 can be suppressed, and fluctuations in the potential of the transfer region 32 can be suppressed. In addition, alloy spikes can be prevented without the need for variamecle.

Fourth Embodiment This embodiment has a structure having three polysilicon layers and is an example of preventing the adverse effects of an aluminum wiring layer.

In its structure, as shown in FIG. 4, an insulating film 43 is formed on a silicon substrate 41. On the surface of the silicon substrate 41 under the insulating film 43, impurities are introduced into required regions to form transfer regions and the like (not shown). A first polysilicon layer 44 functioning as a transfer electrode is formed on this insulating film 43 by patterning. 1st
The polysilicon layer 44 is the first polysilicon layer. This first polysilicon layer 44 is covered with an insulating film 45. The insulating film 45 includes a first polysilicon layer 44.
A contact hole 46 is formed above.

Next, a second polysilicon layer 47 and 48, which is a second semiconductor layer, is formed using the second polysilicon layer. The second polysilicon layer 47 has contact holes 4
6 to the first polysilicon layer 44 , and extends from the contact hole 46 along the insulating film 45 on the first polysilicon layer 44 . Further, the second polysilicon layer 48 has an insulating film 4 on the first polysilicon layer 44.
5, one end overlaps the first polysilicon layer 44, and the other end faces the silicon substrate 41 via the insulating film 43. Therefore, the second polysilicon layer 48 is used to control the potential of the surface of the silicon substrate 41. Furthermore, a third polysilicon layer 50 is formed on the second polysilicon layer 48 with an insulating film 49 interposed therebetween.

This third polysilicon layer 50 also has the same cross-sectional shape as the second polysilicon layer 4, with one end overlapping the second polysilicon layer 48 and the other end overlapping the insulating film 43. It is formed facing the silicon substrate 41 through it. This third
The second polysilicon layer 50 is also the second polysilicon layer 48
Similarly, it is used to control the potential on the surface of the silicon substrate 41.

These second polysilicon layers 47, 48 . The third polysilicon layer 50 is covered with an interlayer insulating film 51, respectively. Then, each polysilicon layer 47, 48 .
50, contact holes 52, 53, and 54 are formed by opening the glabellar insulating film 51. Here, the position of the contact hole 52 is shifted from the position of the contact hole 46 in a plane. Further, the second polysilicon layer 48° 3N at the bottom of the contact holes 53 and 54
The eye polysilicon layers 50 are overlaid on the other polysilicon layers 44 and 48, respectively, and contact holes 53 and 54 are formed at the overlapping ends thereof, respectively. Each aluminum wiring layer 55 is connected to each polysilicon layer 47, 48, 50 via these contact holes 52, 53, 54.

In a charge transfer device having such a structure, a polysilicon layer such as that which exists directly on the insulating M2S in the region below the contact holes 52, 53, and 54 is not formed. ! 55
The diffusion of aluminum prevents adverse effects such as fluctuations in the work function. Furthermore, alloy spikes and the like can be prevented without the need for a barrier metal, and the aluminum wiring layer 55 can also reduce the sheet resistance of the wiring layer.

Note that the first polysilicon layer 44 is a transfer electrode,
The second polysilicon layer 48 and the third N-th polysilicon layer 50 may each be a transfer electrode, or may be a control electrode such as a read gate or an overflow control gate in a solid-state imaging device such as a COD.

〔Effect of the invention〕

In the charge transfer device of the present invention, as described above, the second semiconductor layer is connected to the metal wiring layer in a region other than the contact hole connecting the first semiconductor layer and the second semiconductor layer. Therefore, the first semiconductor layer is no longer located under the region where the metal wiring layer connects to the second semiconductor layer in a manner that affects the potential, and the barrier metal becomes unnecessary.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of essential parts of an example of a charge transfer device of the present invention, FIG. 2 is a schematic cross-sectional view of main parts of another example of a charge transfer device of the present invention, and FIG. 3 is a schematic cross-sectional view of main parts of an example of a charge transfer device of the present invention. FIG. 4 is a schematic cross-sectional view of still another example of the charge transfer device of the present invention. 11, 21. 3 12, 22. 3 13, 23. 3 14, 24. 3 15, 25. 3 16, 26. 3 17, 27. 3 1.41...Silicon substrate 2...Transfer region 3.43...Insulating film 4.44...First polysilicon layer 5.45...Insulating film 6.46...Contact Hole 7.47...Second polysilicon layer l8...Buffer layer 19°30°55...Aluminum wiring layer

Claims (1)

[Claims] a first semiconductor layer serving as a transfer electrode on the transfer region;
The contact hole on the first semiconductor layer
The semiconductor layer is connected to a second semiconductor layer, and the second semiconductor layer is connected to a metal wiring layer on the second semiconductor layer other than over the contact hole.