JPS6184070A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enab1e to control the gradations of a liquid crystal using a nonlinear element by a method wherein the nonlinear element is constituted of the laminated material, which consists of three layers of the one conductive type non-single crystal semiconductor layer, which is provided on the light-transmitting insulating substrate, the intrinsic semiconductor layer, which is made to contain carbon by adding methyl silane and is provided on the one conductive type non-single crystal semiconductor layer, and the non-single crystal semiconductor layer, which has the same conductive type as that of the one conductive type non-single crystal semiconductor layer and is provided on the intrinsic semiconductive layer, and has the characteristics of reversely faced rectification. CONSTITUTION:A first electrode 21 constituted of a light-transmitting conductive film 17 of ITO or SnO2 and a light-shielding Cr electrode 11 is provided on a light-transmitting insulating substrate 20 consisting of non-alkali glass and a composite diode 2 consisting of an N type layer 12 of a non-single crystal semiconductor, an I-type layer 13 being made to contain carbon by adding methyl silane and an N type layer 14 having the same conductive type as that of the N type layer 12 is formed on the first electrode 21. Then, an SnO2 or ITO layer 15 and an Al layer 16 are laminated on the composite diode 2, the laminated material is formed as a second electrode 22, and the NiN type nonlinear element is constituted. The threshold values of the I type layer 13 on its front and back interfaces are controlled in such a way to make the stability to bias and a temperature treatment augment. As a result, the gradations of a liquid crystal can be suitably controlled using this nonlinear element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a solid-state display device, which aims to solidify the display part of a micro convenience store, a word processor, a television, etc. by providing a display element, preferably a liquid crystal display panel; The present invention relates to a method for manufacturing a semiconductor device having nonlinear characteristics that is applied to an image sensor or a liquid crystal printer.

``Prior Art'' For solid-state display panels, a system in which each picture element is controlled independently is effective for large-area displays. As a panel using such an active element, a non-linear element having an NrN junction structure made of only amorphous silicon and used in 1=1 connection with all pixels is known. However, even if this old N junction is used, it is unclear what the NI or IN junction interface looks like, and sufficient nonlinear characteristics have not yet been obtained.

``Problems to be solved by the invention'' However, when trying to use a nonlinear element, it is necessary to
Even if the layers are gradually laminated by plasma CVD, phosphorus, which is an N-type impurity, is mixed into the I-type semiconductor layer at this NT interface. Further, at the IN interface, a mixed N layer of an I-type semiconductor and an N-type layer is formed in the interface region. If such impurities and mixing of constituent components exist at the interface, it is completely impossible to achieve symmetry in the V-■ characteristics.

"Means for solving the problem" In order to solve the problem, the present invention uses a nonlinear element made of a non-single crystal semiconductor to which hydrogen or a halogen element is added, and carbon is added to the I-type semiconductor. Si
-3ixC+-x (0<X4) -' The main feature is that it has a Si structure.

The nonlinear element used in the present invention does not use a diode composed of a single PIN junction and electrodes that make contact above and below it, but instead uses a diode that has ohmic contact with each of the pair of electrodes but has reverse rectification characteristics. A typical example is an NIN structure in which an N-type semiconductor, a ■-type (hereinafter referred to as intrinsic or substantially intrinsic) semiconductor, and an N-type semiconductor are stacked, that is, an Nl junction. The IN junction is electrically connected in the opposite direction,
In addition to semiconductors with integrated NIN junctions, their variations such as NN-N, NP-N, and PIP
, a composite diode having a PP structure or a PN-P structure.

The threshold voltage of such a composite diode makes the diode characteristics opposite to each other, and the build-in (rise) voltage (threshold) changes the conductivity type near the N-type semiconductor and I-type semiconductor of the Nl junction or the Nr interface. It can be determined by the concentration of impurities such as trace amounts of phosphorus, and the concentration of additives such as carbon, which determines the energy band width. Therefore, by controlling the manufacturing process, it is possible to control the value of the threshold voltage of a desired element, the difficulty of current flow below the threshold value, and the ease of current flow above the threshold value. Furthermore, since it is a semiconductor-semiconductor junction method without using the physical properties of the insulating film-semiconductor interface, temperature treatment, B-T treatment (
It has the feature that there is no instability due to processing (bias - temperature).

Therefore, for a solid state display element, for example, a liquid crystal, the AC bias can be controlled by controlling the level of the other electrode lead of the liquid crystal, and gradation control is also possible.

"Function" This ■-type semiconductor is made into 5ixC+-x (0<X<1), and instead of using a hydrocarbon such as methane and a silicon compound such as silane, methylsilane (Si
By using an alkyl molecule having a C--Si bond inside the molecule, such as (CH:+)nlia-n n = 1 to 3), the output of plasma discharge can be lowered.

In this way, it is possible to minimize the amount of plasma sputtering during film formation, [or to substantially eliminate the mixed layer at the IN interface].

Furthermore, methylsilane was subjected to photo-CVD, which was irradiated with ultraviolet light.
By using this method, sputtering at this interface can be completely removed, so the mixed layer can be completely removed. the result,
Lot-to-lot reproducibility of threshold voltage can be improved.

The present invention will be explained below according to examples.

"Example 1" This FIG. 1 will be abbreviated below.

FIG. 1(A) shows a longitudinal cross-sectional view of an actual device structure.

In FIG. 1(A), non-alkali glass (20) was used as the light-transmitting insulating substrate. Suba on this top surface.

ITO, which is a conductive film, is formed by a method or an electron beam evaporation method.
Alternatively, apply a tin oxide film to a thickness of 0.1 to 0.5 μm, and then apply a light-shielding chromium (11) to a thickness of 300 to 2500 μm on the top surface.
Laminated layers were similarly formed to the thickness of a person. After this, the first electrode (
Step 21) was performed using the first mask (2) to remove unnecessary portions and form electrodes.

Thereafter, a plasma vapor phase method is applied to these entire surfaces using a plasma vapor phase reactor as shown in Figure 2 to form a composite diode made of a non-single crystal semiconductor doped with hydrogen or halogen elements having an NIN structure. did. That is, in the drawing, it has a loading/unloading system (4), a first reaction system for forming an N-type semiconductor (5), and a second reaction system for forming an I-type semiconductor (6). Each is a doping system (50
), a reactor (30), and an exhaust system (40).

The substrate (20) opens the gate valve (17) from the preliminary chamber to the first reaction chamber (1) by the holder (IS), and both sides are connected to 1O-b.
Vacuum it sufficiently to below torr and relocate it. Here, silane to which phosphin is added (0.5χ) is introduced from (56), and by performing high-frequency glow discharge at 13.56 MHz, it is formed on the surface to be formed on the substrate maintained at 200 to 350°C. Create a non-single crystal semiconductor with an amorphous structure. Its electrical conductivity is 10-5~10-' (0
cm) -"c, with a thickness of 50 to 500 people.

Furthermore, the first and second reactors (1) and (3) are
After sufficiently evacuation to 6 to 10 torr, open the gate valve (18) and move the substrate (20) and holder to the second
was moved to the reaction chamber. Next, silane (S+mHzm+z
For example, 5iH4) with m=I from (58), and methylsilane (Silln(CHz)a-n n ~1-3)
was introduced from (59) and mixed. That is, for n ~2, HzSi (CH3) z/5il14=175~1
/200, for example, 1150 (flow rate cc). This mixed reactive gas is introduced into the plasma reactor (3), the substrate is heated by a halogen heater (63L (64)), and high frequency electric energy is applied to the pair of electrodes (68) and (68') to cause a plasma reaction. and a non-single crystal semiconductor represented by 5ixC,-x (0< to <1) to which type hydrogen or halogen elements are added ((13) in Figure 1 (A)).
N to a thickness of 0.1 to 1μ, for example 0.4μ
It was formed by laminating it on a type semiconductor. Furthermore, after this, the second
The first reactors (3) and (1) were sufficiently evacuated to 10-6 to 10-'torr using a turbo pump in the exhaust system (40). Again, the substrate (20) and the holder (IS
) into the first reaction chamber by opening the gate valve (18), then closing this gate valve again, and transferring the same N-type semiconductor (18) to the first reaction chamber.
4) as an amorphous structure on an I-type semiconductor.
They were laminated to a thickness of 0.00 mm to form an NIN bond.

By forming the N-type semiconductor and the I-type semiconductor in separate reaction chambers, it was possible to sufficiently eliminate impurities and the semiconductors from mixing with each other at the bonding interface.

As shown in Fig. 1 (A), on this upper surface, SnO□ or ITO as CTF is coated to a thickness of 500 to 1500 mm, and chromium or aluminum (500 to 1500 mm thick) is further coated as leads and electrodes. Lamination was performed by electron beam evaporation method or spunter method. Furthermore, a second electrode (
22) Except for the region to be provided as the composite diode (2), the curved portion was removed by photoetching using a second photomask (2) to form a second electrode.

That is, in FIG. 1 (8), a transparent conductive film (17) on a glass base Fi (20), a first electrode (21) consisting of a chromium electrode (11), N(12)I(13)N (1
4) Old N-junction type composite diode (
2) A second electrode (22) made of CTF (15), chromium or aluminum (16). The symbol of this NIN structure is shown in FIG. 2(B).

FIGS. 3(A) to 3(D) outline the operating principle of a conventionally known NIN junction type nonlinear element.

FIG. 3(8) shows a semiconductor (2) having an N(12), I(13), and N(14) structure. In this case, Ill, I
, N are all non-single crystal semiconductors of silicon containing hydrogen.

Its thickness is N (12) 700 people, I (13) 40
00 people, N(14) 700 people. The voltage is at the terminal (21
) and (22) are shown in FIG. 3(B). On the other hand, if there is a positive voltage (Va) at (22) compared to the board side terminal (21),
When , the energy hand structure shown in FIG. 3(C) is obtained. Then, the electrons (43) flow as a forward current as the barrier (41) lowers its height to (41°).

In addition, at the Nl interface (31), some of the impurity phosphorus constituting the N-type semi-field layer (21) is mixed into the I-type semiconductor (23) during film formation by plasma CvD. One layer in the vicinity is metamorphosed into an N-head note. For this reason, Nl
The barrier caused by the application of +Va at the interface became sufficiently low, and as a result, current characteristics were obtained in which only a low threshold voltage of 1 to 2 cm was obtained as shown in FIG. 5 (51).

At this time, other barriers (42), (32) (Fig. 2 (
B)) does not constitute a barrier and does not constitute a barrier to the flow of current.

Conversely, when a negative voltage (-Va) is applied to the terminal (22) (Fig. 3 (C)), the barrier (42) becomes (42'),
The electrons (43”) of the N-type semiconductor layer (14) are (42°
) flows to (13). When forming the conventional plasma CVD method using only silicon to which hydrogen is added, one layer (13) of silicon is mixed into the N layer (14), and the vicinity of the interface of this N layer (14) is In order to tend to -, the intermediate region (32) becomes wide, and even if -Va changes, the barrier height 42') cannot be made sufficiently low. As a result, a VI characteristic like the reverse current characteristic of the diode shown in FIG. 5 (51') is obtained.

As a result, asymmetrical characteristics, such as those of a PIN junction diode formed with an NIN structure, as shown by curves (51) and (51°) in FIG. 5, tend to be obtained.

It is an object of the present invention to eliminate such asymmetric diode characteristics and provide symmetry with respect to the origin. In addition 1
Another purpose is to control the threshold value by adding carbon into the layer.

FIGS. 4(A) to 4(D) outline the operating principle of the present invention.

Figure 4 (A) shows N made of amorphous silicon to which hydrogen is added.
type semiconductor (thickness 500 Å or less, preferably 100-200 Å
first semiconductor N(12), hydrogen-doped 5i
A second semiconductor I (13) made of an intrinsic or substantially intrinsic amorphous semiconductor represented by xC+−x (0<X<1)
.

A third semiconductor N (14
) structure. Its thickness is N(1
2) is 100-200 people, I (13) is 20
00-4000 people, N(14) is 100-200 people. An energy band diagram in this case when the voltage is not applied to (22) with respect to the substrate side terminal (21) is shown in FIG. 4 (8). In this drawing, Nl
The conductivities in the energy bands near the interface (31) and the IN interface have approximately the same curvilinearity (31) and (32).

In this case, the addition of DMS (dimethylsilane) to one layer was constant within one layer. That is, as shown in Figure 1 (C) (
When forming one layer, DMS/5i)I4 was set to 1150.

In FIG. 4(C), when a positive voltage (+Va) is applied to the axis 2) compared to the substrate (21), the energy hand structure of FIG. 4(C) is obtained. Then, the electron (43) passes through the barrier (
41) flows as a forward current as the height is lowered to (41'). Then, a curve (52) in FIG. 5 is obtained.

Conversely, when a negative voltage (-Va) is applied to the terminal (22), the barrier (42) becomes as low as (42'), as shown in FIG. 1(D), and the N-type semiconductor layer (14
) electron (43') flows from (14) to (13),
A curve (52') in FIG. 5 is obtained.

As a result, a nonlinear characteristic (52) as shown in FIG. 5 is obtained.

(52') can be provided corresponding to FIGS. 4(C) and (D).

Also, since carbon was added to one layer, at +Va,
The threshold value can be higher than 1-2V, for example 10 or more, which is effective for liquid crystal displays and the like.

In addition, since carbon in this one layer sufficiently bonds with 5ixC+-X and silicon, it prevents silicon from mixing into the N layer at the IN interface (32), and the opposite side (-Va side) also (52') allows the threshold to be low and (52) to have symmetry with respect to the origin.

That is, in this NIN junction, the rise voltage (threshold voltage) (100), (100') is the barrier height 41), (42) and the width (31), (32) in FIG. ) is determined by

Example 2 In the present invention, in order to make the Nl interface and IN interface on the first layer side in Example 1 more steep, the amount of carbon added was increased near the interface as shown in FIG. 1 CD). That is,
In the initial step of forming the second semiconductor, the ratio of methylsilane/silane is increased (5 to 30% by plasma vapor phase method).
A barrier (34) was formed in the extremely thin thickness of a person.

Then, this threshold value (too), (100°) becomes even steeper, and the curves (53), (53
') was able to be obtained.

In addition, if barriers are created for both the Nl interface and the IN interface, and the configuration shown in Figure 2 (E) is created, the V-1 characteristic and the 5th
Figure curves (54) and (54°) could be obtained.

The V-[characteristics in FIG. 5 are shown on a log scale with respect to the vertical axis, corresponding to FIG. 6. Then, Figure 2 (D),
If carbon is concentrated at a high concentration at the interface as shown in (E) and a barrier is formed to prevent mixing of impurities and constituents in each layer, the threshold value will have more symmetrical characteristics at +Va and -Va. Therefore, the generation regions (61) and (61°), which are low current regions, in Fig. 6 become flatter, and the diffusion current regions (62) and (62'), which are high current regions, become more steep. To stand up, rONJ.

Threshold value (100) indicating the boundary of rOFF j, (
100°) may be made clearer.

"Effects" As described above, in the present invention, carbon is added at or near the interface between the first layer and the N layer in order to construct a composite diode having symmetrical VI characteristics. Furthermore, this nonlinear element can achieve a threshold value suitable for the liquid crystal and S/N ratio used in display elements, which is its application, by controlling the amount of carbon added to one layer and the thickness of one layer. Ta. In addition, by adding a larger amount of carbon to the NI/IN junction interface than inside, it has the property of flattening the current at voltages below a threshold value and making the current steeper at voltages above this threshold value. process control.

In the present invention, carbon was added within one layer. However, instead of carbon, oxygen or nitrogen may be used.

However, since these materials are easily converted into insulators, the amount of addition thereof must be controlled more delicately, and it is more difficult to manufacture them than carbon using methylsilane.

In the examples of the present invention, a plasma gas phase reaction was shown.

However, by using the reaction between methylsilane and disilane (SizH+), it is possible to carry out a photogas phase reaction.

In such a case, heat the substrate to 250-300"C,
N-type semiconductor or 5ixC+-x (0<X<1) by irradiating light with a wavelength of 254 nm or 184 nm
An intrinsic or substantially intrinsic semiconductor may be formed.

In this case as well, considering mass productivity, the independent reactor system shown in FIG. 2 is effective.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view (A) of the composite diode of the present invention.
, (B) and concentration distribution of carbon addition to one layer (C). (D) and (E) are shown. FIG. 2 shows an outline of a plasma gas phase reactor using the present invention. FIG. 3 shows the operating characteristics of a conventionally known NIN junction using only amorphous silicon. FIG. 4 shows the operating principle of the nonlinear element of the present invention, which is an N-junction composite diode in which carbon is added in one layer. Figure 5 1. Figure 6 shows the conventional characteristics (51) and (51'
) and the characteristics of the present invention (52), (52°), (
53) , (53°) , (54) , (54°
) is shown.

Claims (1)

[Scope of Claims] 1. A nonlinear element comprising a pair of semiconductors having reverse rectification characteristics and exhibiting ohmic contact with a first electrode and a second electrode, wherein the semiconductor has a first conductivity type. a non-single-crystalline semiconductor on the semiconductor, a second non-single-crystalline semiconductor mainly composed of intrinsic or substantially intrinsic silicon, and a second non-single-crystalline semiconductor on the semiconductor having the same conductivity type as the first non-single-crystalline semiconductor on the semiconductor; 3rd having
In a method for manufacturing a semiconductor device in which a second semiconductor is formed by stacking a second semiconductor, a second semiconductor is formed by adding a silicide gas and methylsilane to the gas by a plasma gas phase reaction, a photovapor phase reaction, or a photoplasma gas phase reaction. A method for manufacturing a semiconductor device, comprising forming a second non-single crystal semiconductor whose main component is silicon to which carbon is added. 2. A method for manufacturing a semiconductor device according to claim 1, characterized in that methylsilane/silane is added in a range of approximately 1/200 to 1/5. 3. A method for manufacturing a semiconductor device according to claim 1, characterized in that in the initial step or final step of forming the second non-single crystal semiconductor, only methylsilane or methylsilane/silane>1 is formed.