JPS6384080A - Photoelectric transducer - Google Patents

Abstract

PURPOSE:To increase photocurrents while preventing the effect of external environment by forming a region, into which at least one kind of atoms belonging to a V group is doped as an impurity, near the interface of a semiconductor layer and an insulating film. CONSTITUTION:A glass substrate 101 is washed, and Al 102 is deposited through a sputtering method and the gate electrode 102 functioning as a control electrode and a light-shielding film in combination is shaped through etching. An SiNx:H layer 103 and an N-type amorphous semiconductor hydride region 104 are formed through glow discharge. 10%SiH4(a H2 base)300sccm is flowed and an I-type a-Si:H semiconductor layer 105 is shaped and an N<+> layer 106 as an ohmic contact layer is formed through glow discharge. Cr and Al are deposited through the sputtering method, main electrodes 4, 4' are shaped through etching, a-Si and the SiNx:H layer between elements are removed, and the main electrodes 4, 4' are connected by an electric wire 108.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photoelectric conversion device, in particular, for example, a photoelectric conversion device having a -dimensional line sensor, and an original document placed close to the -dimensional line sensor. The present invention relates to a photoelectric conversion device suitable for application to a facsimile device and an image league device that read image information while relatively moving the device.

[Prior Art] Conventionally, a photo sensor is used as a photoelectric conversion device in an image information processing device such as a facsimile, a digital copying machine, or an image reader.

In particular, in recent years, amorphous silicon (hereinafter referred to as a-5t:H) has been developed by arranging photosensors in one dimension to form a long line sensor, and using this as a photosensor used in highly sensitive image reading devices. A g-film semiconductor is used.

Photosensors using this G-film semiconductor are roughly divided into two types: photodiode type and photoconductive type.

In the photodiode type, a reverse bias voltage is applied to the junction between the electrodes, so the electrons and electrons generated by light are
The hole pair reaches each electrode and a primary photocurrent flows, and no more carriers are injected from the electrode.

On the other hand, in the photoconductive type, since electrons or holes can be injected from the electrodes, the density of electrons or holes in the semiconductor becomes sufficiently high, and by applying a voltage between the electrodes, the photodiode type A much larger output current (secondary photocurrent) can be obtained.

By the way, the following techniques are known or proposed as prior art of photoelectric conversion units having conventional photoconductive sensors.

■Technology using the TFT shown in Figure 11 as an optical sensor (
Journal of the Institute of Image Electronics Engineers, Vol. 15, No. 1, 1986, hereinafter this technology will be referred to as the conventional example).

In FIG. 11, on an insulating substrate 1 made of glass or ceramics, CdS/Se, a-3i:
A semiconductor layer 2 such as H is formed, and a pair of main electrodes 4 and 4' are formed through doped semiconductor layers 3 and 3' for ohmic contact. However, if the carriers injected from the electrode into the semiconductor layer 2 are electrons, the doped semiconductor layers 3 and 3' are n-type, and if the carriers are holes, they are p-type -r! be.

In such a configuration, when light is incident from the insulating substrate 1 side (when the insulating substrate 1 is transparent) or the main electrode 4 and main electrode 4' side, the semiconductor layer z between the main electrode 4 and the main electrode 4'
Inside, the density of electrons or holes that contribute to conduction increases due to photoexcitation.

Therefore, as shown in the figure, if a voltage is applied between the main electrode 4 and the main electrode 4', a large secondary current will flow as a signal current due to the incident light, and a large output will be generated from both ends of the load resistor (not shown). can be obtained.

■Technology using TFT as an optical sensor shown in Figure 12 (
Patent Application No. 142986 of 1988 (hereinafter this technique will be referred to as Prior Example 1; this technique is not publicly known).

This technique was proposed by the applicant as a configuration in which an auxiliary electrode is provided in the sensor section in order to stabilize the photocurrent and improve the linearity of the photocurrent depending on the light illuminance.

FIG. 12 is a basic configuration diagram for explaining the outline of a photoconductive sensor and its driving element in an improved photoelectric conversion device already proposed by the applicant.

In FIG. 12, a transparent or opaque conductive layer is patterned on a transparent or opaque insulating substrate 1 to form a gate electrode 5, and further.

An insulating film 6 made of Sin, SiNx, etc. is formed by a sputtering method, a glow discharge method, or the like.

On the insulating film 6, a-
3t:H semiconductor layer 2, doped semiconductor layers 3 and 3'
, main electrode 4 and main electrode 4' (here, drain electrode 4
and a source electrode 4'. ) are formed respectively.

However, here, a case is shown in which the doped semiconductor layers 3 and 3° are formed of n-type and electrons are used as injected carriers.

In a photoconductive sensor having such a configuration, as shown in the figure, a DC power supply 7 is connected between the main electrode 4 and the main electrode 4', and a variable DC power supply 8 is connected between the source electrode 4' and the gate electrode 5. Connect each. However, it is assumed that the polarity of the variable DC power supply 8 can also be changed.

In this example, the sensor section is operated with a negative gate potential (VG). At this time, as shown in FIG. 1(A), the semiconductor E) (L layer) has a band depleted by about 1 lm in the a-3t layer 13 due to the space charge distribution according to Poisson's equation. be done. In other words, the i-type a-St layer 13 on the gate side is particularly strongly converted to p-type.

Technology used as a driving element for
No. 6, hereinafter this technique will be referred to as Prior Example 2, and this technique is also not publicly known.) [Problems to be Solved by the Invention] However, the above-mentioned prior art has the following problems.

■In the conventional example, the amount of light and the photocurrent of the sensor when light with an illuminance of F is incident on the sensor shown in Fig. 11 from the main electrode 4.4' side between the main electrodes 4 and 4'. There is a problem in that the linearity of the light amount dependence (γ: IpaCF) with respect to the photocurrent is poor (that is, γ becomes smaller than 1) in relation to the current flowing between the two sides.

■Preceding example 1 When light of illuminance F is incident on the sensor shown in FIG. Figure 2 shows the linearity (γ: I, ocF) of the light intensity dependence on the photocurrent in relation to Ip (current flowing between 4.4 degrees).

In FIG. 2, the curve indicated by (L) indicates the photocurrent I in the optical sensor shown in FIG. 12, and the curve indicated by (b) indicates γ.
shows.

As shown in FIG. 2, if the gate electrode 5 of the optical sensor is made negative, the linearity of the photocurrent as a function of the amount of light is improved, but there is a problem in that the photocurrent decreases.

Note that this is due to the carrier (
In this case, the lifetime of the electrons) becomes shorter, and the gain of the secondary photocurrent G G = τE/L JL: Electron mobility τ: Main electron lifetime E: Electric field strength L: The distance between the electrodes decreases, and therefore, It is thought that the photocurrent decreases.

In order to obtain the photocurrent necessary to configure it as a line sensor, the thickness of the semiconductor layer must be increased.
Usually, it is 0.5 g or more, and it is necessary to make it 1 to 2 JL. As a result, there are problems in that not only the film formation time becomes longer, but also the contact hole for taking out the gate electrode becomes deeper, making contact failure more likely to occur, which is inconvenient in terms of production.

Furthermore, since the band of the semiconductor layer is almost uniformly inclined, the surface of the gap between the main electrode 4 and the main electrode 4' is sensitive to the influence of ions, moisture, etc. Since the deep interface states present at the interface with the insulating film are strongly influenced by traps, etc., there is a problem in that passivation, interface formation conditions, etc. are restricted.

■Preceding example 2 In the technology using the TFT shown in FIG. 12 as an optical sensor and a driving element of the optical sensor, in the TPT described above, a large number of traps exist near the interface between the gate insulating film 12 and the semiconductor layer 13. , where carriers are gradually captured. As a result, there is a problem that the threshold voltage VT shifts and the drain current changes over time, and it is susceptible to the effects of interfaces (ions and traps).
There is a problem in that the stability and reproducibility of the semiconductor layer near the interface is poor.

The first invention according to the present application is a photoconductive type that uses a secondary photocurrent as a signal, and a gate electrode is provided in order to improve the linearity of the photocurrent with respect to the amount of light and to make it possible to control the photocurrent. An object of the present invention is to provide a photoelectric conversion device in an optical sensor that increases the photocurrent and has stable characteristics where the surface between electrodes and the interface between a gate insulating film and a semiconductor layer are not affected by the external environment. .

Another object of the present invention is to provide a photoelectric conversion device with improved photoresponsiveness, which is considered to be fatally slow in photoconductive photosensors.

A second invention according to the present application, in addition to the object of the first invention, is to provide a photoelectric conversion device in which the threshold voltage VT does not shift and the drain current does not change over time.

[Means for Solving the Problems] A first invention according to the present application includes an insulating substrate, a semiconductor layer formed on the insulating substrate, and a pair of opposing main electrodes formed on the semiconductor layer. and a gate electrode formed on the semiconductor layer via an insulating film, and a photoelectric conversion device having an optical sensor configured to allow light to enter the semiconductor layer from the outside, wherein atoms belonging to group V The region doped with at least one kind of impurity of the semiconductor layer is
The photoelectric conversion device is characterized in that it is formed near an interface between the semiconductor layer and the insulating film.

A second invention according to the present application includes an insulating substrate, a semiconductor layer formed on the insulating substrate, a pair of opposing main electrodes formed on the semiconductor layer, and an insulating film interposed between the semiconductor layer and the semiconductor layer. an optical sensor having a gate electrode formed on the semiconductor layer and configured to allow light to enter the semiconductor layer from the outside; a semiconductor layer formed on the insulating substrate; and a pair of semiconductor layers formed on the semiconductor layer. In a photoelectric conversion device having a driving element for driving the photosensor, the driving element includes main electrodes facing each other and a gate electrode formed on the semiconductor layer with an insulating film interposed therebetween, in which atoms belonging to Group V are used. A region doped with at least one kind of impurity is formed in the vicinity of the interface between the semiconductor layer and the insulating film of the optical sensor, the drive element, and each of the semiconductor layers. It is a photoelectric conversion device.

As the insulating substrate, for example, glass, ceramics, etc. may be used.Also, a transparent insulating substrate or an opaque insulating substrate may be used.If a transparent insulating substrate is used, this insulating substrate Light can be made to enter the semiconductor layer through the substrate.

In optical sensors and drive elements. As a material for a semiconductor layer formed on an insulating substrate.

a-3i:H is well implemented. Also, Cd5-3e
It is clear that similar effects can be achieved by other commonly known semiconductor materials.

The positional relationship between the pair of main electrodes formed oppositely on the semiconductor layer and the gate electrode formed through the semiconductor layer and the insulating film is of the type shown in FIG. 4CD (upper gate stagger type). ), so-called lower gate coplanar type, upper gate coplanar type, or lower gate stagger type.

As atoms belonging to Group V, atoms belonging to V(b) are mainly used. For example, N, P, As, Sb,
It is Bi.

Moreover, these atoms may be used alone or in combination of two or more types.

The impurity doped region is up to 100 OA from the interface between the semiconductor layer and the insulating film, and the impurity concentration in this region is O
, 1 to 11000PP, and.

It is preferable that the impurity concentration be higher than the impurity concentration of atoms belonging to the v(b) group that are inevitably mixed into the semiconductor layer.

The impurity may be uniformly distributed in the doped region, or
The doping concentration at the interface between the semiconductor layer and the insulating substrate, which may be distributed non-uniformly, may be O, and the doping may be done with a constant concentration gradient starting from this interface.

Conversely, if the impurity concentration near the gate insulating film is increased by increasing the impurity concentration in the film thickness direction, and the band is separated from the insulating film, the band of the n-type semiconductor near the insulating film will move more sharply toward the insulating film. Can be bent deeply.

Note that the main electrode may be made of a conductive metal such as Cr, and may be formed by a commonly used method such as a spark method.

In addition, as impurity doping means, in the case of glow discharge decomposition method from 5iHa gas, PH3, N2, N
Various conventional means can be used, such as doping by mixing H3, ASH3 gas, etc.

[Operation] First, the operation when the vicinity of the gate insulating film is made n-type by doping will be described with reference to the drawings.

FIG. 1 is a model diagram showing the band state of the semiconductor layer 13 in a sensor with a gate electrode.

FIG. 1(a) shows Prior Example 1, in which an a-3i semiconductor layer including only an i layer is used as the semiconductor layer.

By doping the semiconductor layer 13 in the vicinity of the gate insulating film 12 to make it n-type, the band of the semiconductor F313 in the vicinity of the insulating Tl212 is changed to the insulating film 1 as shown in FIG. 1(b).
It peaks at a certain thickness from 2 and decreases as it approaches the insulating film 12.

FIG. 2(C) shows the charging current characteristics in the optical sensor when the band structure as shown in FIG. 1(b) is formed by doping.

The light amount-dependent linearity (γ) of this optical sensor was almost the same as the curve without doping (FIG. 2(b)).

In the present invention, an extremely thin n region in a semiconductor layer.

Since it mainly acts as a current bus for photocurrent (secondary photocurrent), gain is increased, and the thickness of the semiconductor layer can be reduced to the extent that sufficient light absorption is achieved.

Note that the light absorption is 90% or more at 5000A. Therefore, even with the configuration of the present invention, the thickness of the semiconductor layer can be reduced to 5000 Å or less.

Furthermore, the presence of the n region near the interface between the semiconductor layer and the insulating film loosens the band profile, which is considered to be influenced by the shape of the surface interface between the sensor gap.

This may be the reason why the stability of photocurrent, γ, etc. under high temperature and high humidity, and the small fluctuations in sensor characteristics due to the etching method and conditions between the sensor gaps, which will be explained in the examples described later, are small.

As is well known, the current flowing through an optical sensor can be divided into a primary photocurrent component and a secondary photocurrent component, and the secondary photocurrent component is usually much larger than the primary photocurrent component. The behavior of the secondary photocurrent component determines the behavior of the photocurrent of the optical sensor.

However, this secondary photocurrent component is proportional to the concentration of electrons in the conduction band (= hole concentration) that are re-injected during the lifetime of electrons other than those generated by light in the semiconductor layer (= hole lifetime). Therefore, if a negative bias is applied to the gate electrode 11 and a depletion layer is expanded within the semiconductor layer 13, the electron lifetime will be shortened.
The photocurrent decreases. Electrons and holes generated by light are the first
The holes move in mutually opposite directions along the potential gradient in the semiconductor layer 13 due to the electric field from the gate electrode 11 as shown in the figure, and as time passes after light irradiation, the holes move between the gate insulating film 12 and the semiconductor layer 13. Gradually accumulates near the interface with.

Furthermore, due to the accumulation of holes, the effect of the electric field from the gate electrode 11 into the semiconductor layer 13 is gradually weakened, and accordingly, the width of the depletion layer becomes narrower, and the photocurrent increases.

The rise response of the photocurrent is determined by the process described above. This process is dominated by the movement and accumulation of charges, especially holes, generated by light, so if the amount of light incident on the sensor section of the optical sensor is small, the rise response of the photoconductive sensor will be much larger than the desired section. It becomes a far cry.

Next, the response of the element after blocking the incident light will be described. The primary photocurrent attenuates quickly as the incident light is cut off, but the secondary photocurrent is mainly due to holes captured in traps remaining in the semiconductor for a considerable period of time without being recombined. An electron current commensurate with that continues to flow in the optical sensor, and the fall characteristics of photoconductive sensors are generally poor.

In particular, in the photoconductive sensor according to the first example shown in FIG. 1(a), a large amount of holes accumulate near the interface where the density of deep trap levels is large, so that residual current continues to flow for a long time. become.

FIG. 1(b) shows a band state diagram of the optical sensor in the first invention and the second invention according to the present application. 1
1 is a gate electrode, 12 is a gate insulating film, 13 is a semiconductor layer, and 14 (15) is an n-type high-density impurity layer for obtaining ohmic contact of the optical sensor. Reference numeral 16 denotes an n region doped with a small amount of group V impurity near the interface between the semiconductor layer 13 and the gate insulating film 12.

As shown in FIG. 1(b), since the n-type region 16 acts as a barrier to holes, holes cannot approach the interface between the semiconductor layer and the gate insulating film. Even if the electrons are captured in a nearby trap, they are quickly recombined due to the high electron density in this vicinity, so the photoelectric conversion device according to the present invention significantly improves the falling characteristics.

Furthermore, in the optical sensors according to the first and second inventions of the present application shown in FIG. Unlike the case of the prior example 1 shown in FIG. 1(a), it is thought that the rise characteristics are also improved because a large amount of hole accumulation process is not required.

Due to the effects described above, in the photoelectric conversion devices according to the first invention and the second invention according to the present application, both the rise characteristics and the fall characteristics of the device with respect to optical pulses can be improved.

Next, the operation of the drive element in the second invention according to the present application will be explained.

Deep traps near the interface can be effectively inactivated by appropriately selecting the position of the Fermi level of the semiconductor layer 16.

This will be explained in detail below.

First, the effect when the vicinity of the gate insulating film is made n-type by doping will be explained using the drawings.

FIGS. 1C and 1A show the case of the prior example, that is, the case where the semiconductor layer 13 is an a-3t semiconductor layer with only an i layer.

By making the semiconductor layer 13 near the gate insulating film 12 n-type by doping, the band of the semiconductor layer 13 near the insulating film 12 has a certain thickness from the insulating film 12, as shown in FIGS. It peaks at this point and decreases as it approaches the insulating film 12.

In the second invention, the deep trap near the interface can be effectively inactivated by appropriately selecting the position of the Fermi level of the semiconductor layer 16.

This will be explained in more detail below.

In the case of non-doping (in the case of the previous example), as shown in fFS1 diagrams (C) and (A), the gate insulating film 1
The acceptor type trap 40 near the interface between the gate electrode 2 and the semiconductor layer 13 has a bias voltage applied to the gate electrode 11 of zero voltage (V
e=O), it is located at an energy level slightly above the Fermi level (EF).

In addition, as shown in FIGS. 1(d) and (B), the gate electrode 1
1 (vG > 0), the trap 40 near the interface moves below the Fermi level, so the trap 40 captures electrons relatively slowly and becomes negatively charged.

This causes the drain current of the driving element to decrease over time.

On the other hand, when a small amount of n-type dopant is mixed into the semiconductor layer 13 (in the case of the embodiment of the present invention), the bias voltage to the gate electrode 11 is Even at zero potential (Vc=O), the trap 40 is located at an energy level below the Fermi level.

Furthermore, as shown in FIGS. 1(C) and (B), the gate electrode 1
Even if a positive bias voltage is applied to 1 (V6=0), the above g! 1 relationship does not change.

Therefore, even if a positive bias is applied to the gate electrode 11, the decrease in the drain current of the TFT device over time can be suppressed to a small level.

In the figure, the diagonal line at the trap level indicates a state where electrons are trapped.

In the case of non-doping (in the case of the previous example), when the gate bias changes to positive (TFT ON state), the state changes to a state where electrons are trapped at the cell level, but in the present invention, the gate bias changes to positive. It is thought that even when the gate bias is 0 to negative, the electrons remain trapped and no change occurs.

In FIG. 3, a silicon nitride film with a thickness of 3000 Å formed by plasma CVD is used as the gate insulating film, and a hydrogenated amorphous silicon layer with a thickness of 400 Å also formed by plasma CVD is used as the semiconductor layer. This figure shows the change over time in the drain current when driving the TPT using the .

In FIG. 3, a curve 31 shows the change over time when the amount of P doped into the semiconductor layer is 5 ppm, and a curve 32 shows the change over time when the semiconductor layer is not doped.

FIG. 3 shows that the closer the position of the Fermi level of the semiconductor layer 13 is to the conduction band, the smaller the change in drain current with time becomes. From this, the photoelectric conversion device of the second invention according to the present application not only allows the driving element of the optical sensor to be formed on the same substrate as the optical sensor in the same process, but also allows the driving element to change over time during driving. This has the effect of keeping it small.

[Embodiments of the invention] Examples of the present invention will be described below.

(First Example) FIG. 4 is a sectional view showing the manufacturing process of a photoelectric conversion device according to an example of the present invention.

Double-sided polished glass substrate 101 (Corning #7
059) is washed using a neutral detergent.

Next, by sputtering, AL; LiO2 was applied to 0. Deposited to IILm thickness, positive photoresist) (OFPR-800
After forming a photoresist pattern in the desired shape using Tokyo Ohka Kogyo (Tokyo Ohka Kogyo), phosphoric acid (85% aqueous solution), nitric acid (60% aqueous solution), acetic acid and water were mixed in a volume ratio of 16:1:2:1. Etching was performed using the mixed solution (hereinafter referred to as "etching solution for pattern A") to form a gate electrode 102 that served as a control electrode and a light shielding film.

After peeling off the photoresist, the glass substrate was set in a capacitively coupled glow discharge agglomeration device, and heated to an IXl 0-6 Torr.
rc7) Maintained at 200'Q under exhaust vacuum.

Next, hydrogen diluted 10% 5iHa gas (manufactured by Komatsu Electronics) was added to the device at 101005e, 99°999% (7) N H
After 3 gases were introduced at a flow rate of 100sc1005c and the gas pressure was set to 0.4 Torr, RF (Radio Freque
ncy) Perform glow discharge for 60 minutes at a discharge power of 3000A (7) S i Nx : H layer 10
3 was formed.

Subsequently, 10% SiH4 (H2 base) 3QOsec
and 10 p pm PH3 (H2 base) 1.5 sec
m (H2 base) (gas flow rate ratio 0.5 ppm
), RF discharge power 15 under the condition of gas pressure 0°3 Torr.
After performing glow discharge at 0 W for 15 minutes to form an n-type hydrogenated amorphous semiconductor region 104 (film thickness 500^), the 10 ppm PH3 gas was stopped and 10% SiH4 (H
2 base) Flowing only 300sec, type i a-3i:
The H semiconductor layer 105 was formed to have a thickness of 4000λ.

Next, 10%5iHa (H2 base) 100sec, 100p100pp (H2 base)
Glow discharge was performed for 40 minutes at RF discharge power of 500 W under the conditions of 450 sec and gas pressure of 0.5 Torr, and the n° layer (thickness: 1000 A) of the ohmic contact layer 106
was formed.

Next, by sputtering, Cr (film thickness 500 (A)),
7 photoresist patterns are formed in the desired shape using a positive photoresist, and Cr is etched using a mixed aqueous solution of ceric ammonium nitrate and perchloric acid (etching solution for Cr).
and An were etched using an etching solution for AM to form a main electrode of 4.4° (FIG. 4(B)).

Hydrofluoric acid (59% aqueous solution) using the main electrode 4.4 as a mask
, nitric acid (70% aqueous solution), and acetic acid were mixed in a volume ratio of 2=10:88 in a solution in which iodine was supersaturated.
Layer 106 was selectively etched away and the photoresist was stripped.

Next, a photoresist pattern is formed, and unnecessary portions are etched using a reactive ion etching device (RIE).
-3i and SiNx:H layers were removed to isolate the elements (FIG. 4(C)).

Thereafter, silicone resin was applied to the outside of the electrode extraction part to form a passivation material. At this time n
The 'C degree of phosphorus in the type a-3i region was examined by SIMS and was found to be 5 ppm.

Photoelectric conversion device created based on the above process and precedent example 1
The performance of the photoelectric conversion device was compared with that of the photoelectric conversion device.

(a) Table 1 shows the initial values of photocurrent and dark current.

Table 1 ■ Dependency of photocurrent/dark current on n-area etching method ■ Dependence of photocurrent/dark current on n-area etching method The photoelectric conversion device fabricated in this example hardly increases the dark current value. Photocurrent can be increased.

In addition, the rightmost column of ■ in Table 1 shows cases where CF4 or active ion etching is used in the n-layer etching method, and the rightmost column of ■ in Table 2 shows cases in which PCVD method is used as a passivation method. Created 5iNH
In this example, n″ is an example showing the case where a membrane is used.
Even if the layer etching method is changed or the passivation method is changed, the characteristics do not change much.

Therefore, in the case of this example, it can be seen that the characteristics of the photoelectric conversion device are not easily influenced by the surface condition of the leading TL layer.

(b) Furthermore, a protective layer was further formed on the entire photoelectric conversion device produced as described above, and a durability test was conducted under high temperature and high humidity.

The results are shown in FIG.

In the photoelectric conversion device of Prior Example 1, the photocurrent gradually decreased (Fig. 5, 51), but in the case of this example, the photocurrent hardly changed (Fig. 5, 52). It was found that photoelectric conversion devices are not easily affected by humidity.

(C) Next, differences in initial photoresponsiveness were investigated.

The results are shown in Table 2.

Table 2 Photoresponsive measurement Light amount of 100L, τon = light 7rf, time until the current reaches 90% of the saturation value τoff: time until the photocurrent reaches 10% of the saturation value As shown in Table 2, in this implementation The photoelectric conversion device according to the example has improved photoresponsivity than the first example, and can simultaneously satisfy a high photocurrent value and photoresponsivity.

(d) Regarding the photocurrent value (Ip) and γ, as shown in FIG. 2 (in FIG. 2, (a) is I of this example,
, (b) shows γ of the present example, and (C) shows the process ρ of the first example.) In this example, all values were superior to those in the first example.

(Example 2) A photoelectric conversion device was created using the method for creating the n-type a-3i region and the i-type a-3i layer shown in example 1.

However, the specific conditions were as follows.

First, 10% Si Ha (H2 base) 300s
ecm and l Op pmPH: + (H2 base) 5
secm (PH3/S f H4=1.7
ppm), pressure and power under the same conditions as Example 1,
Gradually tighten the flow meter of PH3, and after 15 minutes, the flow rate becomes Osccm, and the n-type a-5i layer is
00λ was formed.

Next, the i-type a-3i layer was discharged for 2 hours under the same conditions as in Example 1 to create a photoelectric conversion device.

Example 1 of the photoelectric conversion device created as described above
When the same items ((a) to (d)) were investigated, all items were superior to the first example as well as the first example.

In addition, when the impurity concentration contained in the n-type a-3i9n region was investigated in the same manner as in Example 1, the concentration gradually decreased from about 20 ppm near the interface.

(Example 3) Using N2 as a doping gas for the n-type a-5i layer, an n-type a-3i layer was formed with N as a dopant, and an n-type a-3i region was formed in the same process as in Example 1. . To be more specific, 1001000 pp of diluted hydrogen is flowed for 60 sec to 10% SiH4300 sccm diluted with hydrogen, and the gas flow rate ratio N2 /S iHa =2000 ppm,
After discharging for 15 minutes, a 500A n-type a-3i region was formed.

The subsequent formation method of the i-layer and below is the same as in Example 1.

At this time, the amount of Nl incorporated into the film was 75 ppm.

The characteristics such as Ip at this time are those of Example 1, and the gas flow rate ratio (P
H3/5iHa = 0.5 ppm), concentration in the film (SIM
S¥ measured value) It was the same size as when it was 5 ppm.

Example 1 of the photoelectric conversion device created as described above
When the same items ((a) to (d)) were investigated, all items were superior to the first example as well as the first example.

In addition, the decomposition efficiency of N2 is lower than that of PH3, and the contribution rate to changes is low.
This has the advantage that it is easy to finely adjust the impurity concentration.

(Example 4) A photoelectric conversion device was created in which the optical sensor shown in Example 1 and a driving element for driving the optical sensor having the same configuration as this optical sensor were provided on the same substrate.

FIG. 6 is a sectional view of the photoelectric conversion device.

The sensor section 109 of the optical sensor, the driving element 119, the gate electrodes 102, 112, the insulating film 103° 113, the n-type semiconductor regions 104, 114, the i-type semiconductor fi 105, 115,
The ohmic contact layers 106 and 116, the sensor main electrode 107, and the source and drain electrodes 117 of the drive element are respectively the same.

The n◆ohmic contact layer between the source and drain of the drive element may be etched in exactly the same manner as in the photoelectric conversion device of the first embodiment.

Example 1 of the photoelectric conversion device created as described above
When the same items ((a) to (d)) were investigated, all items were superior to the first example as well as the first example.

As described above, it was found that in this example, even when the optical sensor and the driving element have the same configuration and are formed on the same substrate, they have excellent characteristics. Therefore, manufacturing can be performed easily.

In addition, there was little change over time in the drain current in the optical sensor and drive element.

In addition, the characteristics of the photoelectric conversion device were exhibited uniformly and with good reproducibility.

(Example 5) The optical sensor shown in Example 1 and a drive element for driving the optical sensor having the same configuration as this optical sensor were simultaneously created on the same substrate.

That is, a photoelectric conversion device including an optical sensor, a capacitor, and a driving element was fabricated according to the same process as in Example 1, with the structure of each layer being the same.

FIG. 7 shows a cross-sectional view of the photoelectric conversion device.

The optical sensor and drive element have the same configuration as in Example 1 and Example 4,
The effect is exactly the same.

The capacitor of the charge storage section 229 created here includes, from the substrate side, the counter electrode 222, the insulating film 201, the n-type a-S
They are an im region 205, an i-type a-3i layer 205, an n-type a-St region 206, and an upper electrode 227. It has been confirmed that this capacitor operates without any problems as a capacitor.

In this embodiment, the photocurrent flowing due to light incident between the main electrodes of the optical sensor section 209 of the optical sensor is temporarily stored in the capacitor 229 of the charge storage section in the form of charge storage, and the drive element of the charge transfer section 219 is turned on. By doing so, it is transferred as a signal to an external circuit.

FIG. 8 is an equivalent circuit of an image reading device using an integrated optical sensor, a capacitor, and a driving element.

In FIG. 8, Si, l + Si, 2 +...
.

Si, x (hereinafter referred to as Sl. Here, i is the block number, and 1 to N are the number of bits in each block.

) indicates the optical sensor section 209 of the optical sensor.

Ci, l + Ct, 2 +...+Ci, s
(hereinafter referred to as Ci) is a storage capacitor representing the charge storage section 229, which stores the photocurrent from the photosensor section S+.

STi,+,ST1,2,kai...,STi,N
(hereinafter referred to as STi) is the storage capacitor CI
The charge of the load capacitor Cx1. l,Cxi,2,
・・Transfer-like switch to transfer to fist, CXi, H, SR4g, SRI, z, ..., 5R
3N (hereinafter referred to as SRi) is a discharge switch that resets the load on the storage capacitor C1.

The optical sensor unit Si, the storage capacitor Ci, the transfer switch ST, and the discharge switch SRi are each arranged in a line in an array, and N units constitute one block, and the image reading device as a whole consists of M blocks. For example, if there are 1728 sensors, N=32. M=54.

The gate electrodes of the transfer switches ST+ and discharge switches SR provided in an array are connected to the gate wiring section. The gate electrodes of the transfer switches STi are commonly connected within the i-th block, and the gate electrodes of the discharge switches are connected in a circular manner to the gate electrodes of the transfer switches of the next block.

Common lines in the matrix wiring section (gate drive lines Gl, G2
, . . , GM) are driven by a gate drive circuit 801.

On the other hand, signal outputs are connected to the signal processing unit 805 (in blocks) via lead lines (signal output lines DI, D2, . . . , D32) in a matrix configuration.

In addition, the optical sensor S1. I, Sl, 2,...Fist.

Sl, N + S2.1 + S2.2 + ”
..., SN, H gate electrodes 202 are connected to a drive source 803 and a negative bias is applied thereto.

In such a configuration, the gate drive line Gl.

G2. @Φ-, G54 has the gate drive unit 801 sequentially selected paths (VG 1 , VG2., VG3
, *Fist・,VGM) are supplied.

First, when the gate drive line Gl is selected, the transfer switch STI is turned on, and the charges accumulated in the storage capacitor C1 are transferred to the load capacitors Cx1 to Cx32.

Next, when the gate drive line G2 is selected, the transfer switch ST2 is turned on, and the charge accumulated in the storage capacitor C2 is transferred to the load capacitors Cx1 to CX32, and at the same time, the discharge switch SRI is activated to transfer the charge stored in the storage capacitor C2 to the load capacitor Cx1 to CX32.
1 charge is reset.

Similarly, G3. G4. ..., GM is also selected and read operation is performed.

These operations are performed for each block, and the signal outputs VX1 . VX2. ....

VX32 is the input Di, D2° of the signal processing unit 805...
The signal is sent to the DN, converted into a serial signal, and output.

Example 1 of the photoelectric conversion device created as described above
When the same items ((a) to (d)) were investigated, all items were superior to the first example as well as the first example.

As described above, it was found that this example has excellent characteristics even when the optical sensor and the driving element have the same configuration and are simultaneously formed on the same substrate. Therefore, manufacturing can be performed easily.

In addition, there was little change over time in the drain current in the optical sensor and drive element.

In addition, the characteristics of the photoelectric conversion device 2 were exhibited, such as uniformity and reproducibility.

When an image signal was read using the photoelectric conversion device according to this example, it was possible to read the image signal very clearly.

(Example 6) Fig. 9 shows a so-called lensless photoelectric conversion system in which an optical sensor, a capacitor, and a driving element are integrated on the same substrate, and light is incident from the opposite side of the substrate and reflected light from the original is detected. FIG. 3 is a partial plan view of the device.

FIG. 10 is a sectional view of a lensless photoelectric conversion device unit.

Incident light from the light source 361 passes through the entrance window 350,
The reflected light from the original 363 that illuminates the surface of the original 363 passes through the protective layer 364 and enters the sensor unit 309 .

The driving principle of this embodiment is exactly the same as that of the fifth embodiment. 3
09 is a sensor unit implemented according to the present invention, 302 is a sensor gate line, 319 is a transfer TPT, 310 is a reset TPT, 350 is an entrance window through which light from a light source passes, 35
1 is the gate wiring part of TPT, 352 is the sensor bias line, 329 is the capacitor that accumulates the photocurrent of the sensor, 35
3 is a signal wiring that sends a signal to the reading section, 365 is a box that fixes the sensor board 301, 361 is a light source, and 363 is a
362 is a platen roller that holds down the original, and 364 is a protective layer that protects the sensor section.

Example 1 of the photoelectric conversion device created as described above
When the same items ((a) to (d)) were investigated, all items were superior to the first example as well as the first example.

As described above, it was found that this example has excellent characteristics even when the optical sensor and the driving element have the same configuration and are simultaneously formed on the same substrate. Therefore, manufacturing can be performed easily.

In addition, there was little change over time in the drain current in the optical sensor and drive element.

In addition, the characteristics of the photoelectric conversion device were exhibited uniformly and with good reproducibility.

When image signals were read by the photoelectric conversion device according to this example, the reading was extremely clear, and the present invention can exhibit excellent characteristics even when applied to a lensless photoelectric conversion device. I understand.

[Effects of the Invention] According to the first invention of the present application, the following various effects can be obtained.

■Good linearity of photocurrent dependence on light amount.

■The photocurrent can be increased without increasing the dark current value.

■Various characteristics are not easily affected by environmental influences such as temperature and humidity.

■Able to simultaneously satisfy high photocurrent value and photoresponsiveness.

■The influence of passivation material conditions and surface process conditions on properties is reduced.

■Since it satisfies a high photocurrent, there is no need to increase the thickness of the semiconductor layer and it can be made into a thin film. As a result, the film formation time is shortened, the contact hole for taking out the gate electrode becomes shallow, contact defects are less likely to occur, and productivity is also good.

According to the second invention of the present application, in addition to the effects obtained by the first invention, the following effects can be obtained.

■Drain current does not change over time.

(2) The n-doped region facilitates Fermi level control, enables control of VLh, and improves the uniformity and reproducibility of the characteristics of the photoelectric conversion device.

[Brief explanation of the drawing]

FIG. 1 is a model diagram showing the band state of a semiconductor layer in a photoelectric conversion device. FIG. 2 is a graph showing the relationship between photocurrent and γ value with respect to gate voltage in photoelectric conversion devices according to the present invention and a prior example. FIG. 3 is a graph showing the change over time in the drain current of the TPT used in the present invention. FIG. 4 is a sectional view showing the manufacturing process of the photoelectric conversion device according to the first embodiment. FIG. 5 is a graph showing the durability test results of the photoelectric conversion device according to the first example. FIG. 6 is a sectional view showing a photoelectric conversion device according to a fourth embodiment. FIG. 7 is a sectional view showing a photoelectric conversion device according to a fifth embodiment. FIG. 8 is an equivalent circuit diagram of the photoelectric conversion device shown in FIG. 7. FIG. 9 is a plan view showing a photoelectric conversion device according to a sixth embodiment. FIG. 10 is a side sectional view of FIG. 9. FIG. 11 is a sectional view showing an optical sensor of a conventional photoelectric conversion device. FIG. 12 is a sectional view showing an optical sensor of a photoelectric conversion device according to Prior Example 2. l...Insulating substrate, 2...Semiconductor layer, 3.3'...Doped semiconductor layer, 4.4°...Main electrode. 5. Fist gate electrode, 6. Insulating film, 7. DC power supply, 8
...Variable DC power supply, 11.. Gate electrode, 12.. Gate insulating film, 13. Φ semiconductor layer, 14.15.. N-type high-density impurity layer, 16.. N region, 101.-Glass substrate,
102...Gate electrode (A sentence), 103...Insulating film, 1
04-・n-type semiconductor region, 105-・i-type semiconductor layer, 1
06... Ohmitsukukotact layer, 107... Main electrode, 1
12・Φ gate electrode, 113・Metal insulating film, 114...n
type semiconductor region, 115...i-type semiconductor layer, 116...ohmic contact layer, 117...electrode, 201 fist insulating film, 202-gate electrode, 205ssn type a-Si
region, 206a ai type a-Si layer, 209--sensor section, 219/bottle charge transfer section, 222/unit counter electrode, 2
27...Top electrode, 229...Charge storage unit (capacitor), 301...Box, 302Φ・Sensor gate line, 30
9・Φ sensor part, 310@- TFT for reset, 319
...Transfer TFT, 329...Capacitor, 350...
Entrance window, 351... Gate wiring section, 352... Sensor bias line, 353... Signal wiring, 361... Light source, 362
...Platen roller, 363. Document, 364.. Protective layer, 365.. Sensor board, 801.. Gate drive circuit, 803.. Drive source, 805.. Signal processing section. Figure 1 (a) Figure 1 (b) :: Figure 1 (C) Figure 1 (d) Figure 3 Time (minutes) Standing time (hr) Figure 6 Figure 9 Figure 10

Claims (1)

[Claims] 1. An insulating substrate, a semiconductor layer formed on the insulating substrate, a pair of opposing main electrodes formed on the semiconductor layer, and an insulating film formed on the semiconductor layer via an insulating film. In a photoelectric conversion device having a photosensor configured to allow light to enter the semiconductor layer from the outside, the region is doped with at least one type of atom belonging to Group V as an impurity. is formed in the semiconductor layer near an interface between the semiconductor layer and the insulating film. 2. An insulating substrate, a semiconductor layer formed on the insulating substrate, a pair of opposing main electrodes formed on the semiconductor layer, and a gate electrode formed on the semiconductor layer through an insulating film. an optical sensor configured to allow light to enter the semiconductor layer from the outside; a semiconductor layer formed on the insulating substrate; a pair of opposing main electrodes formed on the semiconductor layer; In an electric conversion device having a driving element for driving the photosensor, which comprises a gate electrode formed on the semiconductor layer via an insulating film, at least one type of atom belonging to Group V is doped as an impurity. 1. A photoelectric conversion device characterized in that a region formed in the semiconductor layer of the optical sensor, the driving element, and the respective semiconductor layers is formed near an interface between the semiconductor layer and the insulating film. 3. The photoelectric conversion device according to claim 1, wherein the distribution of the group V impurity concentration has an inclination in the film thickness direction. 4. The photoelectric conversion device according to claim 2, wherein the distribution of the Group V impurity concentration has an inclination in the film thickness direction. 5. The photoelectric conversion device according to claim 2 or 4, wherein the optical sensor, the driving element, and the thin film capacitor for accumulating the charge of the optical sensor are formed on the same substrate. 6. According to claim 1 or 3, the insulating substrate is transparent, and light for document illumination is incident on the substrate from the side opposite to the surface on which the optical sensor is formed, and an illumination window is formed on the substrate. The photoelectric conversion device described. 7. Claims 2, 4, or 7, wherein the insulating substrate is transparent, and light for illuminating the original enters from the side opposite to the surface on which the optical sensor is formed, and an illumination window is formed on the substrate. The photoelectric conversion device according to any one of the fifth items. 8. The photoelectric conversion device according to claim 1, 3, or 6, wherein the semiconductor layer is hydrogenated amorphous silicon. 9. The photoelectric conversion device according to claim 2, 4, 5, or 7, wherein the semiconductor layer is hydrogenated amorphous silicon.