JPS63164274A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent problems such as restriction on high speed driving and power consumption due to a means for forming transfer electrodes in a solid-state image sensing device and a driving method, by applying a DC voltage on a first electrode layer, and applying every other pulse of two-phase pulses on a second metal electrode layer. CONSTITUTION:A second electrode layer 25 is made to be a metal electrode. A DC voltage is applied to a first electrode layer 24. Every other pulse of two-phase pulses is applied to the second metal electrode layer. For example, an insulating film 22 is formed on the surface of a P-type silicon substrate 21. Thereafter, an n-type embedded region 23 is formed. The first transfer electrode layer 24 is formed with polycrystalline silicon, in which P and the like are doped, on the insulating film 22. The insulating film other than a part beneath the transfer gate 24 is removed, and an insulating film 222 is formed. An n-type impurity region 26 is formed so as to form a step for a potential. Thereafter, the second transfer electrode layer 25 is formed with a metal such as AlMoSi. A specified DC voltage is applied to the first transfer electrode layer 24. A two-phase pulse voltage, which has the reverse phase in every other pulse, is applied to the second transfer electrode layer 25. Thus the charge is made to transfer.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to high-speed driving of semiconductor devices.

(Prior art) In the prior art, the transfer electrode of a solid-state imaging device is as shown in Fig. 3(a).
It is configured as shown in (d). First, a first layer insulating film 12-1 is formed on the silicon substrate 11, and a first layer transfer 1413 is formed thereon. Next, a second layer of insulation 11112-2 is placed on the insulation IPJ 12-1 including the transfer electrode 13.
form. Thereafter, the portion of the insulating film 12-2 where the second transfer electrode is to be formed is etched using, for example, NH, F (ammonium fluoride) solution, and the insulating film 12-3 is again formed.

Finally, the second transfer electrode 14 is formed.

In a solid-state imaging device, the transfer electrode configured as described above is driven by four-phase pulses as shown in FIG. 4, and charges are sequentially transferred. FIG. 4(a) shows a cross section, and FIG. 4(b) shows a potential diagram of the transfer section.

(Problems to be Solved by the Invention) i) Currently, two-layer transfer electrodes are formed of polycrystalline silicon doped with P (phosphorus) or the like to lower resistance. Therefore, when high-speed pulses are applied, problems such as waveform distortion and delay occur due to the resistance of the transfer electrodes, making high-speed transfer difficult.

ji) Two-phase drive has a faster transfer speed than four-phase drive, but since two-phase pulses are applied to the 1st W1 transfer electrode and the 2nd layer transfer electrode, the electrode area to which the pulses are applied becomes larger. , as the capacity increases, problems such as waveform distortion and delay occur.

High-speed transfer becomes difficult. Also, the capacity is large.

Power consumption also increases.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a semiconductor device that prevents problems such as high-speed drive restrictions and power consumption caused by a means for forming a transfer electrode of a solid-state imaging device and a drive method. With the goal.

[Structure of the invention]

(Means for solving problems) In the present invention, prior to forming the second transfer electrode.

An n-type or p-type impurity layer is formed on a part of the silicon substrate that should be under the second transfer electrode, and then a second transfer electrode is formed of metal, and a DC voltage is applied to the first transfer electrode. High-speed driving is achieved by applying two-phase pulses to every other second transfer electrode.

(Function) By using a metal ffi electrode as a transfer electrode, the resistance of the electrode is significantly lowered compared to a polycrystalline silicon electrode.

As a result, the rate at which the applied pulses become dull or delayed is significantly reduced.

In addition, each of the two-phase pulses is applied to the 1st P! Instead of applying a DC voltage to the first and second layer transfer electrodes, a DC voltage is applied to the first layer transfer electrode, and every second layer is applied to the second layer transfer electrode.
By applying phase pulses, the area to which the pulses are applied becomes smaller, making it possible to apply high-speed pulses. This also allows power consumption to be reduced.

(Example) Fig. 1 (
The explanation will be based on a) to (d).

First, the surface of the P-type silicon substrate 21 is thermally oxidized, and the insulating film 22 is
- Form 1000 people. Thereafter, an n-type buried region 23 is formed by ion implantation on the surface of the P-type silicon substrate 21 by a known method (FIG. 1a), and polycrystalline silicon doped with P (phosphorus) or the like is placed on the insulating film 22 on the substrate 21. The first layer transfer electrode 24 is patterned and formed by RIB, CDE, or Vet etching (FIG. 1b).
The insulating film other than the transfer electrode 24 in the first layer and below is removed by etching, and then the insulating film 22-2 between the first transfer electrode 24 and the second transfer electrode 25 is formed by thermal oxidation. In order to form a potential step in a part of the substrate 21 where the second layer transfer electrode 25 is to be formed,
A type impurity region 26 is formed (FIG. 1c), and then AQ
A second layer transfer electrode 25 was formed of a metal such as Mosi (FIG. 1d).

In the solid-state imaging device having the above structure, a certain DC voltage is applied to the first layer transfer electrode 24.

Two-phase pulse voltages with opposite phases were applied to every other transfer electrode 25 in the second layer to transfer charge to every other electrode. Second
Figure (a) is a cross-sectional view, (b) is a potential diagram showing charge transfer on the substrate surface, and (c) is a pulse waveform diagram. In the above embodiment, the transfer direction can be reversed by forming a p-type impurity region instead of an n-type impurity region under the second layer transfer electrode.

Further, although the case of a COD solid-state imaging device has been described here, the present invention is not limited to this and can be similarly applied to other semiconductor devices.

【Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a solid-state imaging device that can apply pulses with less rounding and delay and has improved transfer speed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the present invention in the order of steps, FIG. 2 is a view showing its operation, FIG. 3 is a view showing a conventional structure, and FIG. 4 is a view showing its operation. In the figure, 11.21...P-type silicon substrate, 12.22.
...Insulating film, 13.24...First electrode (polycrystalline silicon). 23...n-type buried region, 26...n-type impurity phase. 25... Second electrode (metal). Agent Patent Attorney Noriyuki Ken Yudo Kikuo Takehana Figure 2, tvcm-4V (C) Figure 2

Claims (1)

[Claims] In a semiconductor device having two layers of electrodes on a semiconductor substrate, the second layer electrode is a metal electrode, a DC voltage is applied to the first layer electrode, and one layer is applied to the second layer metal electrode. A semiconductor device characterized in that a two-phase pulse is applied every other time.