JPS60119181A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent a solid-state image pickup device provided with a signal reading part consisting of the 2nd conductive type area and having density higher than the 2nd conductive type area between a photoelectric conversion element part and a charge transfer device from a residual image phenomenon by contacting the 2nd conductive type area having a high density in said signal reading part with the charge transfer device and separating the area from the photoelectric conversion element. CONSTITUTION:A curve 11' is potential distribution under an electrode 9 at the OFF state of a transfer gate and a curve 12'a is potential distribution under the electrode 9 at the ON state of the transfer gate. If a photodiode is set up so as to be depleted with low potential by reducing the concentration of an impurity in the n type area 1 of the photodiode, the signal charge of the photodiode is completely transferred to a vertical shift register. Since the electrode 9 is formed by polysilicon and an area under a part obtained by oxidizing the polysilicon electrode 9 is p<-> type area 6 even if the side of the polysilicon electrode 9 is oxidized, the electrode 9 is depleted at the ON state of the transfer gate and the potential distribution shown by the curve 12'b is supposed. Consequently, complete charge transfer from the photodiode to the vertical shift register takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging device, and particularly to a charge transfer type solid-state imaging device.

A charge transfer device using the conventional interline transfer method is
As shown in FIG. 1, there are multiple columns of vertical shift registers 2 driven by charge transfer ′-′ pole groups, and the −(111) of each vertical shift register is connected through U7 through a transfer gate 5. mutually electrically separated light M], conversion unit l
At one end of the vertical shift register 2 there is provided an electrical connection [~6', a load transfer horizontal shift register 3, and at one end of the horizontal soft register a signal type, load detecting device P+-4 is provided. An imaging device using such an interline transfer method is optical 1. The charges accumulated in the converter l according to the amount of incident light are transferred to the corresponding vertical shift registers 2 via the transfer gates 5. The fl charge is transferred to the vertical shift register, *a, the transfer gate is closed, and the photoelectric conversion unit 1 accumulates the signal charge for the next cycle. On the other hand, the signal charges transferred to the vertical shift register 2 are transferred in parallel in the vertical direction, and the signal charges transferred to each vertical shift register 2 are transferred in parallel in the vertical direction, and the signal charges transferred to each vertical shift register 2 are transferred in parallel in the vertical direction, The data is transferred to the horizontal shift register 3 in the fourth horizontal row.

The charges sent to the horizontal shift register are transferred horizontally as signals 1 and lr while the signals are being sent from the next vertical shift register, and are transferred from signal 1 to signal 1 to
, and is taken out to the outer circle'. FIG. 2(a) schematically shows a cross section of the I-7 set shown in the first section. i i%ll On the surface of the substrate 7, there is a low rotation P2
A contact region 6 is formed from the 11th region, and further within the P-type region 6 is an n-type region of the photodiode.
A vertical region 2 of the nft register is formed. An insulating layer 8 is provided on the surface of the substrate t.

The electrode 9 performs charge transfer in the vertical direction in the rough-surfaced shift register and also transmits light. 1
1.71! ,,<The signal from the converter 1 to the vertical shift register 2 is transferred fIli (I). A depth P-type impurity region 5 is formed between the lin-type region 1 and the n-type region 2.
I'm here.

An image device like this? ], when the signal charge is transferred from the photoelectric conversion unit J to the vertical shift register 2, the complete accumulated charge is transferred to the vertical shift register within the transfer interval 114n, causing an afterimage. The fear is shown in Figure 2(b) as follows. Figure 2 (b
) schematically shows the horizontal potential distribution of the structure shown in FIG. 2(a). Curve 11 shows the position distribution under the electrode 9 when the transfer gate is in the off state.Curve 1
2 is the city when the transfer gate is on; pole 9
is the ′potential distribution under .

When the transfer gate is closed 1, the light incident on the photodiode 1 is converted into light%1 when the transfer gate is in the off state, and the signal box.

The load is accumulated in the 7 otodes. The fourth level of frost on the photodiode at this time is shown by the W line]3. When the transfer box pole is turned on, the voltage A' stored in the photodiode is transferred to the M shift register. For this reason, the value of about 11L of the photodiode increases. The bar frost accumulated on the photodiode is first immediately transferred from the 7th photodiode to the vertical shift register, but when the difference in potential between the 7th position of the transfer gate 5 and the photodiode 1 is 0, that is, in the transfer gate area. When L/-1 is smaller than the Fermi level, the transfer of the signal charge from the photodiode to the vertical shift register is due to the threshold 'i'ij, and the transfer of the signal charge becomes slow. Figure 2 (ill curve 11U) is the potential of the photodiode when the potential difference between the photodiode and the transferate is p mark, and when the 111. point of the photodiode reaches C5,
fj': The movement of the load from the photodiode to the vertical shift register becomes slow due to the six sets 4 shown in the figure, and the signal '61° of the load is delayed.
The photodiode signal IJ is turned on during the 1-f retransmission period.

All of the load cannot be transferred to the iJl and iY1 shift registers and remains in the photodiode. The charge remaining in this photodiode is used to read out the next signal charge.
J+7 is exposed.

Such shortcomings should be addressed to 1.
2 (C)
7j shown on the surface line 15,
The deepest potential of the photodiode is i61 complaint 1.
I'll show you 4.

v5 is good if it is shallower than ``about m where the 1 north difference between the photodiode and the transferate becomes ρ''. 1, # of the n-type region of the photodiode is λ.
By lowering the power, the photodiode becomes depleted at a lower potential. When the photodiode becomes completely depleted, the temperature rises to 1-t.

The potential doesn't tremble deeply. L, therefore, this completely depleted frost level becomes the deepest potential of the photodiode shown by the plane line 15. When this photodiode is completely depleted, r, the potential difference between the potential and the transfer gate becomes smaller than the Ω mark. When it turns off, the signal charge is left behind in the photodiode, which makes me sweat. Impurity status in the n-type region of the photodiode! At least once so that there is no afterimage, and at least 1 (
Enough Shingetsu? 11. Even if the structure is as shown in FIG. 2(a), a solid-state imaging device without afterimages can be realized if the settings are set appropriately so as to obtain the desired effect. However, in a structure as shown in FIG. In order to increase the amount of signal charge transferred in the vertical direction of the register 2, the transfer gate section 5
In order to suppress the dark current component generated in the photodiode, it is necessary to form a highly concentrated P-type region 5 between the n-type region 1 of the photodiode and the n-type region 2 of the vertical shift register. 2nd + 9th
In the structure of (a), for example, the electrode 9 is
is formed of polysilicon and photodiode 1 is formed by ion implantation using electrode 9 as a mask. If the surface of the n-type region of photodiode 1 is oxidized, the side surfaces of electrode Pl and 9 will be oxidized. Therefore, on the portion where the P type region of the transfer gate 5 and the N type region of the photodiode 1 are in contact, the electrode 9 is likely to be oxidized. If the impurity concentration in the n-type region 1 of the photodiode is high, short-time annealing will not cause any problems because the "type region 1 will effectively expand due to lateral diffusion."
When the impurity concentration in the n-type region 1 of the photodiode is low, even if annealing is performed, the impurity will hardly spread to the n-type region due to the presence of the high concentration p-type region 5.
According to fc, there is a candy area where there is no polysilicon electrode 9 on top of the high density #P type region 5, and the transfer of the (m number box load) from the n type region of ] to the vertical resistor region of 2 is sufficient. There will be a Jru°1 conjunction that is not performed in 7C, as shown in Figure 2 (a).
In the tiller construction, the electrode 9 is formed using polysilicon using the usual method, and using it as a mask, the n-type region 1 of the photodiode is formed. Since complete charge transfer to the vertical shift register occurs, it is difficult to realize solid-state imaging without image retention.
-2.

In view of the above-mentioned drawbacks, the present invention (c) uses one polysilicon skewer to transfer the vertical shift 1/register to the vertical shift register and the shipping transfer f1 from the photodiode to the vertical shift register. .. - Provides a solid 4A imaging system without afterimages that can be performed d).

The inventive feature is that the front F
A region of the second conductivity type having a conductivity opposite to that of the substrate is formed, and the photoelectric converter 9 (element part and each element of this photoelectric conversion element part , and the signal f\i from the -& electric variable element
, a second conductivity type region having a higher concentration than the second conductivity type region, between the charge transfer device for transferring charges, and the photoelectric conversion element and the front R1″Ff function transfer device; In the signal readout five-part setup rTfcν and one-body imaging device ba, consisting of
Said Shinkan d'1 "High concentration second specialty market of 1f equipment 2 parts, ^
The light transmission device U6- is separated from the light transmission device U6-, and the light-transfer device U6- is located in the device (1).

Next, I will clarify the meaning of the fruit of incontinence #I⼼1 by using moxibustion on one side and one side.

gffi, 3 Isl・(a) This shows an example of non-invention, (7 [Fig. 2 (a)
and (like L., the first is the electric charge shown in (, 4v included).
It is something. In Fig. 3, the same function as the second (yz) is shown by the same symbol as 4, ↑・+1 t1.
The equation (shown in EXI (a))÷fi1 is the equation between the still-concentrated P-type impurity region 5' of the transfer gate or the n-type impurity region 1 of the photoquimate and the +I''i connection. , 6 are exposed on the substrate surface.According to the embodiment of the present invention shown in FIG. Complete charge transfer occurs and the afterimage phenomenon disappears.

Similar to FIG. 2(b), FIG. 3(b) schematically shows the horizontal potential distribution of the structure shown in FIG. 3(a).

Curve 11' is the potential distribution under electrode 9 when the transfer gate is in the off state, and curve 12' (a) is the potential distribution under electrode 9 when the transfer gate is in the on state. If the impurity concentration of the n-type region 1 of the photodiode is lowered and the photodiode is set to be depleted at a low potential as in Figure 1(C), the signal charge of the photodiode is completely transferred to the vertical shift register. be transferred. Further, even if the electrode 9 is formed of polysilicon and the side surface of the polysilicon electrode 9 is oxidized, the P- type region 6 exists under the oxidized portion of the polysilicon electrode, so that the transfer gate is in the on state. When, the depletion heel curve is 1.2'
Since a potential distribution as shown in (b) is expected, a complete transfer from the photodiode to the vertical shift register 7 occurs.

As explained above, complete signal charge transfer from the photodiode to the chiro shift register occurs in the third section ``Example of Yoriaki Moto which is 17 in 1(a)''. One of the disadvantages of interline transfer type charge transfer imaging devices is that they eliminate the afterimage effect [7% -? i-
It can be served. This imaging device has one 11] intermediate shift register function (1 load transfer and 4 transfers from the photodiode to the i11 direct shift register).
< −q +1. The control of the load is high because I can afford it, and I am praying for autumn. What's more, this imaging device is made of polysilicon rattan, which is a mass-produced technology.
It can be created using the six ion implantation method using the frame as a mask.

4.1 n 1 ■ 1 of 1) 11 i 11. Attack i5 Pa Ming 1st 1
II/11 on the 1-1 line shown in No. 1 and 1. It is a diagram showing a schematic diagram, the potential distribution f1.1^- under the white of the trigram. It shows the position distribution and is 1.

In the same, 1-1, 1... photoelectric cable holder, 2
...Vertical register, 5.5'...Transfer gate section, 6...N, fcP-type region formed on the surface of the N-type substrate, 8... ...indicates a silicon oxide film, 1 ], 11. '...The city when the transfer gate is on, 1) position distribution directly below pole 9,]
2. 12' (a), 12' (b) ・---
--)Positive electrode 9r = lower part distribution when the lance is off, 13... 11th position of the photodiode 'j'' when the maximum charge is accumulated in the photodiode, ]4・・・・・・Photodiode frost 4th place, 15 when the difference between transfer gate 8 and knowledge 7th place becomes ω mark
・・・・・・Indicates the potential of the photodiode when the frost on the photodiode becomes the deepest.

cormorant Carving 1 (12) (b) (C) U2 map

Claims (1)

[Claims] Enoki box 1 opposite to the substrate provided on the substrate of the first conductivity type! (In the region of the 2nd y4-electrode type, the first wave. From the photoelectric conversion element (II. ii4, higher concentration than the type region 26j:ih', type region force... (In a solid-state imaging device provided with an S readout section, the high G degree second conductive M of the signal readout section) type 2 A solid-state imaging device r'f characterized in that the region is in front ML: ?h, in contact with the loading/unloading device, and not in direct contact with the photoelectric conversion element [7].