JP2805801B2 - Solid-state imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly, to a CCD solid-state imaging device having a two-layer polycrystalline silicon transfer gate electrode.

[Prior Art] In an interrun transfer type CCD solid-state imaging device, vertical transfer CCDs are respectively arranged between rows of light receiving elements, and the vertical transfer CCDs are connected to a horizontal readout CCD at a lower portion.

FIG. 3 (a) is a plan view of a conventional solid-state CCD of an interline transfer type, in which rows of light receiving elements 2 and charge transfer regions 10a are alternately arranged. A channel stop region 3 is formed between the charge transfer region 10a and the transfer region 4 except for a transfer region 4 for transferring signal charges from the light receiving element to the charge transfer region. A first transfer gate electrode 8 formed of polycrystalline silicon and a second transfer gate electrode 9 also formed of polycrystalline silicon are alternately arranged on the charge transfer region 10a to form a vertical transfer CDD 10. With this CCD, signal charges can be sequentially transferred from the top to the bottom of the figure. Above the channel stop region 3 separating the light receiving elements 2 from each other, a first connection wiring 6 made of polycrystalline silicon, which connects the first transfer gate electrodes 8 to each other in the lateral direction, Transfer gate electrode 9
The second connection wiring 7 made of polycrystalline silicon, which connects the two in the horizontal direction, is formed by lamination, and the signal charges of the vertical transfer CCD 10 in each column can be simultaneously transferred from the top to the bottom.

FIG. 3 (b) is a cross-sectional view taken along the line IIIb-IIIb of FIG. 3 (a). As shown in FIG. 3 (b), the light receiving element 2 has a ^p.sup. Channel stop area 2
This is an n-type region which is formed by being separated into a region. First and second connection wirings 6 and 7 are arranged on channel stop region 3 so as to be surrounded by an oxide insulating film 5 formed by oxidizing the surface of a semiconductor region or a polycrystalline silicon layer.

In such a solid-state imaging device, incident light is subjected to public-electric conversion in each light-receiving element 2, and charges generated by this photoelectric conversion are accumulated here for a certain period, and then read out to the second transfer gate electrode 9. Is applied to the electrode transfer region 10a via the transfer region 4, and then sequentially transferred to the lower horizontal readout CCD (not shown).

[Problems to be Solved by the Invention] By the way, in such a CCD solid-state imaging device, the vertical transfer C
In some cases, the vertical transfer CCD is driven at high speed in the reverse direction or in the forward direction by providing a sweeping drain above the CD, or providing a storage CCD between the vertical transfer CCD and the horizontal read CCD. However, in the solid-state imaging device as described above, a large number (for example, 510) of vertical transfer C
Since the CDs must be driven in parallel at the same time, in the case of such a high-speed drive, the resistance values of the transfer gate electrodes 8 and 9 including the connection conductors 6 and 7 and the distance between the adjacent transfer gate electrodes and between the transfer gate electrodes The capacitance between the semiconductor region (including the connection wiring) and the semiconductor region becomes a problem. As described above, since the connection conductor and the transfer gate electrode are formed of polycrystalline silicon, the connection conductor and the transfer gate electrode have a high resistance value, so that the (resistance / capacitance) product also has a large value. When a vertical transfer CCD having such an electrode is driven at a high speed, the voltage of the driving pulse drops greatly and the waveform of the pulse becomes large. As a result, the amount of charge that can be transferred decreases, the charge cannot be completely transferred, and some charge remains in the vertical transfer. This residual charge is mixed with the next signal charge to increase smear.

[Means for Solving the Problems] The solid-state imaging device according to the present invention includes a light receiving element arranged in a plurality of rows, a charge transfer area arranged for each light receiving element row, and a light receiving element and a charge transfer area. A channel stop region arranged between the light receiving elements adjacent to the portion excluding the transfer region between them, and a channel stop region arranged on the charge transfer region of each column and connected by a two-layer connection wiring on the channel stop region between the light receiving elements A transfer gate electrode formed only of polycrystalline silicon, wherein the lower one of the two layers of connection wiring is a refractory metal silicide layer and a polycrystalline silicon layer completely covering the same. It is composed of

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1A is a plan view of an interline transfer type CCD solid-state imaging device showing an embodiment of the present invention,
FIG. 1 (b) is a cross-sectional view taken along the line Ib-Ib of FIG. 1 (a). The same parts as those in the conventional example shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. The difference of this embodiment from the conventional example is that the first connection wiring 6 arranged on the p ⁺ -type channel stop region 3 separating each light receiving element 2 is formed of a refractory metal silicide layer.
6A and a polycrystalline silicon layer 6b completely covering the same. By the refractory metal silicide layer 6a, the resistance value of the connection wiring 6 narrowed on the p ⁺ type channel stop region 3 can be significantly reduced. Further, similarly to the technical example, the oxide insulating film 5 is formed by oxidizing the polycrystalline silicon layer 6b and the surface,
The first and second connection wirings 6 and 7 can be insulated and separated.

Next, another embodiment of the present invention will be described with reference to FIG. This is a view showing the same cross section as FIG. 1 (b), and the difference between this embodiment and the previous embodiment is that:
The second connection wiring 7 has a so-called polycide structure of a two-layer film of a polycrystalline silicon layer 7b and a refractory metal silicide layer 7a. By doing so, the resistance of the second connection wiring can also be reduced.

In the above embodiments, the CCD solid-state imaging device of the interline transfer type has been described.
The present invention is not limited to this, and can be applied to other types of imaging devices such as a frame interline transfer type.

[Effects of the Invention] As described above, the present invention relates to a solid-state imaging device including a plurality of light receiving element columns and a vertical transfer CCD provided for each column. Of the two layers of connection wiring arranged in the above, the lower connection wiring is composed of a refractory metal silicide layer and a polycrystalline silicon layer which completely covers the same.
According to the present invention, the resistance value of the transfer gate electrode and the resistance value
Capacity) product can be greatly reduced. Therefore, according to the present invention, even when the vertical transfer CCD is driven at a high speed, the electric charge can be completely transferred without lowering the voltage of the driving pulse or causing waveform droop. Since the upper part of the first connection wiring is made of polycrystalline silicon,
As in the conventional example, the interlayer insulating film can be easily formed by oxidizing the surface.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of the present invention, and FIG.
FIG. 2B is a cross-sectional view taken along the line Ib-Ib of FIG. 1A, FIG. 2 is a cross-sectional view showing another embodiment of the present invention, and FIG.
Is a plan view showing a conventional example, and FIG. 3 (b) is a cross-sectional view taken along the line IIIb-IIIb in FIG. 3 (a). DESCRIPTION OF SYMBOLS 1 ... Semiconductor area, 2 ... Light receiving element, 3 ... Channel stop area, 4 ... Transfer area, 5 ... Oxide insulating film, 6 ... First connection wiring, 6a ... High melting point metal silicide layer, 6b ... polycrystalline silicon layer, 7 ... second connection wiring, 7a ... refractory metal silicide layer, 7b ... polycrystalline silicon layer, 8 ... first transfer gate electrode, 9 ... second Transfer gate electrode, 10: Vertical transfer CCD, 10a: Charge transfer area.

Claims (1)

(57) [Claims] 1. A light-receiving element arranged in a plurality of rows, a charge transfer region arranged for each light-receiving element row, a portion excluding a transfer region between the light-receiving element and the charge transfer area, and an adjacent light-receiving element. A transfer gate electrode formed only of polycrystalline silicon, which is disposed between the channel stop region disposed between the charge transfer regions of each column and the channel stop region between the light receiving elements and connected by two-layer connection wiring. A solid-state image pickup device comprising: a solid-state imaging device comprising: a solid-state imaging device, wherein a lower-layer connection line among the two-layer connection lines is composed of a refractory metal silicide layer and a polycrystalline silicon layer that completely covers the same. Imaging device.