JP3022637B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, and more particularly to an interline transfer type or frame interline transfer type CCD image pickup device.

[0002]

2. Description of the Related Art In recent years, the solid-state imaging device has been developed to have a larger number of pixels and a smaller chip size. Normally, a drive pulse is applied to the transfer electrode formed of a polysilicon film from an aluminum wiring layer connected to both ends or one end thereof. However, when the pattern is miniaturized as described above, the resistance of the transfer electrode increases. The drive pulse waveform deteriorates at a position away from the connection with the aluminum wiring layer. This causes problems such as a decrease in transfer efficiency and a decrease in transfer charge amount, which limits high-speed operation. In order to improve such inconveniences, there is a known method for reducing the effective resistance of the transfer electrode by providing a contact portion on the transfer channel and connecting the polysilicon transfer electrode and the aluminum wiring layer. I have.

FIG. 3A is a plan view showing the configuration of such a conventional horizontal register, and FIG. 3B is a plan view of FIG.
FIG. 3 is a sectional view taken along line XX of FIG. In this example, it is assumed that the buried channel type is a buried channel type in which an n-type buried layer 16 having a conductivity type opposite to that of the substrate is provided on the surface of a P-type silicon substrate 15 and a two-layer driven horizontal register having a barrier region 7. . The transfer electrodes (storage electrode 5 and barrier electrode 6) formed of polysilicon are connected to the intermediate layer 13 a of polysilicon or the first contact portions 8 and 9 provided on the n-type buried layer 16 of the horizontal transfer channel 2. 13b. Further, the polysilicon intermediate layers 13a and 13b are composed of two aluminum wiring layers 14a arranged in parallel to which different driving pulses are applied by a second contact portion 10 provided at a position different from the first contact portion. , 14b.
That is, the transfer electrode formed of polysilicon is connected to the aluminum wiring layer on the transfer channel via the intermediate layer of polysilicon.

[0004]

Generally, aluminum is alloyed with polysilicon by alloy processing. Therefore, in a solid-state image pickup device, a contact is provided on a transfer electrode of polysilicon of a register and on a transfer channel and directly connected to aluminum wiring. The potential of the transfer channel immediately below the unit is fluctuated, which causes a problem of adversely affecting transfer efficiency and transfer charge amount. Therefore, as described above, the transfer electrode of polysilicon and the aluminum wiring layer are connected via the intermediate layer of polysilicon. However, in this method, it is necessary to provide the first contact portion and the second contact portion at different positions, so that it is difficult to reduce the electrode pitch and increase the density. Also,
Since two aluminum wiring layers are arranged in parallel, it is impossible to shield the gap between them.

An object of the present invention is to provide a new solid-state imaging device which eliminates the above-mentioned conventional disadvantages.

[0006]

A solid-state imaging device according to the present invention comprises a plurality of transfer electrodes which are arranged on a transfer channel of a semiconductor substrate via an insulating film, each of which is formed of polysilicon, and which is driven by these transfer electrodes. In a solid-state imaging device having a wiring layer formed of aluminum provided for applying a pulse and making contact between the wiring layer and the transfer electrode on the transfer channel, the transfer electrode and the wiring layer A refractory metal layer formed on an interlayer insulating film provided therebetween, used as an intermediate layer connecting the transfer electrode and the wiring layer, and used as a light-shielding film covering the transfer channel. It is characterized by the following.

[0007]

FIG. 1A is a plan view showing the configuration of a horizontal register according to a reference example of the present invention , and FIG. 1B is a sectional view taken along line XX of FIG. 1A.

In this reference example , a plurality of storage electrodes 5 and barrier electrodes 6 (transfer electrode pairs) are arranged on a n-type buried layer 16 formed on the surface of a p-type silicon substrate 15 via a gate oxide film 15. And every other pair of transfer electrodes is connected to the same aluminum wiring layer 14a or 14b via an intermediate layer 12a or 12b made of a tungsten film.

That is, similarly to the conventional example of FIG. 3, a buried channel type in which an n-type buried layer 16 of a conductivity type opposite to that of the substrate is provided on the surface of a p-type silicon substrate 15 and has a barrier region 7. A two-phase driven horizontal register is assumed. Transfer electrode (storage electrode 5, barrier electrode 6) formed of polysilicon
Are connected to the intermediate layer 12a or 12b of a high melting point metal such as tungsten by the first contact portions 8 and 9 provided on the horizontal transfer channel 2. Further, the intermediate layer 12a or 12b of tungsten is formed of two aluminum wiring layers 14a or 2 arranged in parallel to which different driving pulses are applied by the second contact portions 10 and 11 provided at the same position as the first contact portion. 14b
And are connected respectively. Tungsten is a commonly used aluminum alloy processing temperature of 400 to 4
Since it does not alloy with polysilicon or aluminum at about 50 ° C., even if the first contact portion and the second contact portion are provided at the same position as shown in FIG. There is no. Therefore, in this case, it is possible to increase the density by reducing the electrode pitch. In this embodiment, an example is shown in which the intermediate layer of tungsten is individually arranged only around the first and second contact portions. However, the intermediate layer of tungsten may have a continuous shape similarly to the intermediate layer of polysilicon in the conventional example of FIG. it can.

FIG. 2A is a plan view showing the configuration of a horizontal register according to an embodiment of the present invention , and FIG. 2B is a plan view of FIG.
FIG. 3 is a sectional view taken along line XX of FIG. This embodiment also assumes a two-phase driven horizontal register of an embedded channel type. Further, in this embodiment, the light-shielding film 4 in the pixel region is formed by a tank stainless steel which is reported to be effective in reducing smear. Transfer electrodes 5 and 6 formed of polysilicon
Denotes a first contact portion 8 provided on the transfer channel 2
And 9 by tungsten intermediate layers 12c and 1
2d. Further, two aluminum wiring layers 14a and 14a arranged in parallel by the contact portions 10 of the tungsten intermediate layers 12c and 12d.
b. In this embodiment, since both the light-shielding film and the intermediate layer can be formed in the same step by using tungsten, an independent step of forming the intermediate layer is not required. Further, as shown in the figure, by forming the tungsten light-shielding film and the intermediate layer so as to cover the transfer channel on which the aluminum wiring layer is not arranged, the transfer channel can be completely shielded from light. In the figure, the first contact portion and the second contact portion are provided at different positions, but may be provided at the same position as in FIG.

Although the embodiment of FIG. 2 shows an example of a two-phase driven horizontal register, the present invention can be applied to other cases. It is also possible to use a high melting point metal material such as titanium, molybdenum, and chromium other than tungsten for the intermediate layer.

[0012]

As described above, according to the present invention, the first contact portion and the second contact portion are connected by connecting the polysilicon transfer electrode and the aluminum wiring layer via the intermediate layer of the refractory metal. Can be provided at the same position, thereby realizing high density with a reduced electrode pitch.

Further, by covering the gap of the aluminum wiring layer with the intermediate layer, the transfer channel can be completely shielded from light, and generation of a false signal can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view (FIG. 1A) and a cross-sectional view (FIG. 1B) showing a configuration of a horizontal register according to a reference example of the present invention .
It is.

FIG. 2 is a plan view (FIG. 2A) and a cross-sectional view (FIG. 2B) showing a configuration of a horizontal register according to an embodiment of the present invention .
It is.

3A and 3B are a plan view (FIG. 3A) and a cross-sectional view (FIG. 3B) showing a configuration of a horizontal register according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transfer channel of vertical register 2 Transfer channel of horizontal register 3 Final transfer electrode of vertical register 4 Tungsten light shielding film 5 Storage electrode of horizontal register 6 Barrier electrode of horizontal register 7 Barrier region 8,9 First contact part 10,11 2 contact portions 12a, 12b, 12c, 12d Tungsten intermediate layer 13a, 13b Polysilicon intermediate layer 14a, 14b Aluminum wiring layer 15 p-type silicon substrate 16 n-type buried layer

Claims (3)

(57) [Claims] A plurality of transfer electrodes arranged on a transfer channel of a semiconductor substrate via an insulating film, each of which is formed of polysilicon; and a plurality of transfer electrodes provided for applying a drive pulse to these transfer electrodes are formed of aluminum. A solid-state imaging device having a wiring layer and a contact between the wiring layer and the transfer electrode on the transfer channel, wherein the solid-state imaging device is formed on an interlayer insulating film provided between the transfer electrode and the wiring layer. A solid-state imaging device having a refractory metal layer used as an intermediate layer connecting the transfer electrode and the wiring layer and used as a light-shielding film covering a transfer channel. 2. A transfer channel for a vertical register formed on a surface portion of a semiconductor substrate, a transfer channel for a horizontal register connected to the transfer channel for the vertical register, and a poly channel provided above the transfer channel for the horizontal register. A plurality of transfer electrodes of a horizontal register made of a silicon film, and an aluminum wiring layer provided over the transfer channel and the plurality of transfer electrodes of the horizontal register and connected to the transfer electrode of the selected horizontal register. In the solid-state imaging device having, between the transfer electrode of the horizontal register and the aluminum wiring layer, is provided running above the transfer channel and the plurality of transfer electrodes of the horizontal register,
An intermediate layer made of a refractory metal connected to a transfer electrode and an aluminum wiring layer of the selected horizontal register by a first contact portion and a second contact portion, respectively, and the vertical register of transfer channels of the horizontal register A light-shielding film provided above the side connected to the transfer channel of the horizontal register and formed simultaneously with the intermediate layer, and the transfer channel of the horizontal register is shielded from light by any of the intermediate layer, the light-shielding film, and the aluminum wiring layer. A solid-state imaging device. 3. The interlayer insulating layer for connecting the high melting point metal layer and the wiring layer to a contact hole provided in the interlayer insulating layer for connecting the high melting point metal layer and the transfer electrode. 2. The solid-state imaging device according to claim 1, wherein the contact hole provided at the first position is substantially at the same position as viewed in plan. 3.