JPS6410985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charge coupled device (CCD) type solid-state imaging device.

In recent years, this type of solid-state imaging device for use in television cameras has been actively developed, and the applicant has already proposed a cross-gate type solid-state imaging device in Japanese Patent Application No. 84267-1983. are doing.

FIG. 1a shows a plan view of a conventional cross-gate solid-state imaging device, and FIG. 1b shows a cross-sectional view taken along line A--A in FIG. 1a. As shown in these figures, the conventional element directly supports a plurality of upper layer electrodes 3 and a plurality of lower layer electrodes 4 in an insulated state on a P-type semiconductor substrate 1 via a transparent insulating film 2. A gap surrounded by these upper and lower layer electrodes 3..., 4... is configured as a light incidence window, and a light receiving portion 11... consisting of an N-type region is formed on the semiconductor substrate 1 exposed through this incidence window.
It is composed of In this case, P-type channel stoppers 12 are formed on the semiconductor substrate 1 along the upper layer electrodes 3, and each stopper 12 is arranged at every other location in contact with the light receiving section 11. Its width is expanded, thereby forming unevenness complementary to the adjacent channel stoppers 12. Furthermore, channels 13 made of N-type regions are provided between the channel stoppers 12, and each of these channels 13 meander in contact with the plurality of light receiving sections 11, respectively.

In a solid-state image sensor having such a configuration, when the lower electrodes 4' in odd-numbered rows are turned on, the charge corresponding to the amount of incident light generated in the light receiving section 11 is generated as shown by the solid line arrow in FIG. The light is introduced from the light receiving portions 11', 11', .
Thereafter, by sequentially switching on the upper layer electrodes 3'' of the even-numbered columns and the lower layer electrodes 4'' of the even-numbered columns, then the upper layer electrodes 3' of the odd-numbered columns and the lower layer electrodes 4' of the odd-numbered columns, The above charges are transferred in a meandering manner from channel 13 position ○A to ○I, ○U, ○E, ○O, etc., and are outputted to the outside as an image signal from the output terminal (not shown) of such an element. .

The conventional solid-state image sensor as described above has a light receiving section 11.
Since there are no electrodes, it has the advantage of being able to directly receive incident light without attenuating it, but the potential of this light receiving section 11 cannot be controlled, and the surrounding electrodes 3
..., 4..., the light receiving section 11
The drawback was that the potential was extremely unstable. That is, for example, when the charge being transferred to the channel 13 position ○U is about to be transferred to the next position ○E, ○O, the unstable potential formed in the light receiving part 11 of the same conductivity type as the channel 13 As a result, the light receiving section 11 would become a channel, and there was a risk that the transferred charge would bypass the light receiving section 11 and flow back to position ○A, as shown by the broken line arrow in FIG.

In order to prevent such channeling of the light receiving section 11, it is possible to configure the entire light receiving section 11 with a conductivity type different from that of the channel 13, but in this case, the substrate 1 and the light receiving section 11 may be Since the conductivity types are the same, there is an inconvenience that a PN junction is not formed in the light receiving section 11. That is, if there is no PN junction in the light receiving section 11, there is a high probability that the charges excited in the light receiving section 11 by the incident light will be recombined before being introduced into the channel 13, and eventually the light will not be absorbed. It has the disadvantage of decreasing sensitivity. Also, among the charges generated in the light receiving section 11, the amount of charges generated due to long wavelength light (red light) excited deep inside the substrate 1 connected to the light receiving section 11 is excited near the surface of the light receiving section 11. Since the amount of charge generated is larger than that caused by short wavelength light (blue light), there is a drawback that the sensitivity of blue light appears to be lower than that of red light.

The present invention has been made in view of these points, and provides a cross-gate type solid-state imaging device in which a PN junction is formed while preventing the light-receiving portion from becoming a channel.

FIG. 2a shows a plan view of the solid-state imaging device of the present invention, and FIG. 2b shows a sectional view taken along the line A'-A'.

In these figures, 1, 2, 3, and 4 are a P-type semiconductor substrate, an insulating film, an upper layer electrode,
The lower layer electrode is shown, and this semiconductor substrate 1 has a P-type channel stopper 12 similar to the conventional device.
. . , N-type channels 13 . . . are formed.
The difference between the device of the present invention and the conventional device is that the light receiving section 14
The first light-receiving region 1 has a conductivity type opposite to that of the channel 13.
5 and a second light-receiving region 16 of the same conductivity type as the channel 13 are provided, and both regions 15 and 16 constitute a PN junction. For more information,
In the case of this embodiment, the P-type first light-receiving regions 15, 15 of the light-receiving section 14 are in contact with and parallel to the N-type channel 13 below the lower layer electrodes 4, 4, and the N-type second light-receiving region 16 extends between the first light-receiving regions 15, 15, and one end thereof is continuous with the N-type channel 13 under the upper layer electrode 3.

An example of such a solid-state image sensor will be described with specific numerical values. First, P-type silicon with a resistivity of 20 Ωcm was used as the semiconductor substrate 1, and the P-type channel stopper 12 was made by implanting boron ions into the substrate 1 at 80 KeV to a concentration of 2×10 ¹⁶ /cm ³ . be.
After that, the surface of the substrate 1 is thermally oxidized to form a transparent insulating film 2 made of silicon dioxide with a thickness of 1400 Å,
Furthermore, phosphorus is ion-implanted at 120KeV from above,
By setting the concentration to 2×10 ¹⁶ /cm ^{3 ,} the surface of the substrate 1 including the channels 13 other than the channel stopper 12 is made into an N-type. Subsequently, lower layer electrodes 4, 4, . . . and insulated upper layer electrodes 3, 3, . . . are formed on the insulating film 2 using polysilicon. Furthermore, 16 locations of the second light-receiving region at the center of the light-receiving section 11 are coated with resist, and boron is ion-implanted at 100 KeV to a concentration of 2×10 ¹⁶ /cm ³ . A light-receiving region 15 is formed, and a PN junction consisting of the first and second light-receiving regions 15 and 16 is configured.

In the solid-state imaging device of the present invention having the above-described configuration, when light is incident on the first and second light receiving regions 15 and 16 made of P type and N type during the photoelectric conversion period,
Charges, that is, electrons are excited according to the amount of incident light, and the excitation of the electrons at this time is caused by the PN junction position and the second light receiving area 16 depending on the first and second light receiving areas 15 and 16 near the surface of the light receiving part 14. Depends on board 1
Since this occurs concentratedly at the PN junction position, the amount of electrons generated due to the long wavelength light excited deep inside the substrate 1 is suppressed, and the amount of electrons generated due to the short wavelength light excited near the surface of the light receiving section 14 is suppressed. The amount of electrons generated is increased. Moreover, the excited electrons are transferred to the N-type second light-receiving region 16
The holes generated together with these electrons will be absorbed by the P-type first light-receiving regions 15, 15, so there is a risk that the excited electrons and holes will recombine during the photoelectric conversion period. There isn't. During this photoelectric conversion period, a positive voltage is applied to the lower electrodes 4' in the odd numbered rows and they are in the ON state, so each light receiving section 1
4, 14..., for example, the electrons in the light receiving parts 14', 14'' in FIG. Both are accumulated in the channel 13 position ○A under the lower electrode 4' of the odd row.During the next charge transfer period, as in the conventional device shown in FIG. By sequentially switching to the ON state depending on the voltage, the electrons at channel 13 position ○A are meanderingly transferred to positions ○I, ○U, ○E, ○O, etc., and output to the outside. At this time, the channel 13 positions ○A and ○U are in contact with the first light receiving areas 15, 15 of the light receiving part 14...
Since 5 and 15 are P-type regions having a conductivity type opposite to that of the N-type channel 13, the occurrence of unstable potential due to the influence of the positive voltage of the lower electrode 4 is suppressed, and the transferred electrons are transferred to this light-receiving section. There is no risk of bypassing 14.

As is clear from the above description, the solid-state image sensing device of the present invention is a cross-gate type device, and relies on partially providing a region of a conductivity type opposite to that of the exposed portion of the semiconductor substrate of the light receiving portion. In addition, since the PN junction is extended to this exposed part, the excited charges caused by short wavelength light, that is, blue light, are concentrated by the PN junction formed near the surface of the light receiving part. This makes it possible to flatten the wavelength sensitivity characteristics of such an element. Furthermore, since electrons and holes are separated by this PN junction, recombination of excited charges is prevented, and the photosensitivity of this light receiving section can be improved. Furthermore, since it has a region of conductivity type opposite to that of the channel formed in contact with the light-receiving part, this prevents the charge being transferred through the channel from bypassing the light-receiving part, which would otherwise occur in conventional elements. Accidents such as reverse flow of electric charge can be prevented.

Therefore, according to the device of the present invention, a faithful reproduced image signal with a high S/N ratio can be obtained.

[Brief explanation of the drawing]

1A and 1B are a plan view and a sectional view of a conventional solid-state image sensor, and FIGS. 2A and 2B are a plan view and a sectional view of a solid-state image sensor of the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Insulating film, 3... Upper layer electrode, 4... Lower layer electrode, 11, 14... Light receiving part,
12... Channel stopper, 13... Channel, 15... First light receiving area, 16... Second light receiving area.

Claims (1)

[Claims] 1 A semiconductor substrate of one conductivity type, an insulating film formed on the semiconductor substrate, a plurality of lower layer electrodes arranged in parallel on the insulating film, and the lower layer provided insulated on the lower layer electrode. Both the electrodes include a plurality of upper layer electrodes arranged in a direction crossing the electrode arrangement direction, and a channel stopper formed on the surface portion of the semiconductor substrate corresponding to either the lower layer electrode or the upper layer electrode. In a solid-state image sensor in which a light receiving section is constructed using a gap surrounded by A solid-state imaging device characterized in that a PN junction extends in the exposed portion in a direction intersecting the channel stopper.