JPH09325331A - Formation of electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reform part of an aluminum material to a dense insulating film down to the prescribed depth from its surface and to make a leak current smaller and a breakdown voltage higher even if the film is thin by irradiating the surface of an aluminum material formed on a substrate by prescribed patterning with an excimer laser. SOLUTION: The insulative substrate 1 consisting of glass fibers is first washed and an Al film is deposited thereon. This film is exposed and developed by using an ordinary positive type resist and is etched by using an etchant, by which gate wirings 2 are formed on the substrate 1. The film is thereafter reformed to Al2 O3 down to the prescribed thickness from the surface of the Al by the excimer laser method and, further, the gate insulating films 7 consisting of SiNx are subjected to required patterning by using an ordinary stage and depositing a hydrogenated amorphous semiconductor layer 4 and a doped semiconductor layer 5 thereon. Finally, Al of main electrodes 6 is deposited and is subjected to required patterning, by which the element parts are completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly has a large area, high definition, and is compatible with moving images.
The present invention relates to a method for forming an electronic device, such as an image reading device or a liquid crystal display device, which is suitable for forming low resistance wiring on a substrate.

[0002]

2. Description of the Related Art Conventionally, in an image information processing apparatus such as a facsimile or an image reader, an optical sensor has been used as its photoelectric conversion means. Particularly, in recent years, an optical sensor using hydrogenated amorphous silicon as a photoelectric conversion layer constitutes a long line sensor in a one-dimensional array on one substrate, and a high-sensitivity image mounted with this line sensor is provided. Readers have already been proposed. Further, in recent years, a liquid crystal display compatible with a large screen, which is driven by a two-dimensional optical sensor or a thin film transistor that is two-dimensionally arranged on a large area substrate by combining a thin film transistor and an optical sensor using hydrogenated amorphous silicon. The development and manufacturing of the device are actively carried out.

FIGS. 10 and 11 show a radiation detection device for a large area, which has been proposed in the past, for one pixel in a plan view and a cross section. That is, in these figures, a thin film transistor (T11) including a gate electrode 2, a gate insulating layer 7, a hydrogenated amorphous silicon semiconductor layer 4, a doping semiconductor layer 5 and a main electrode 6 is provided on an insulating substrate 1, and a lower side thereof. Each element of the MIS type optical sensor (S11) including the electrode 2, the insulating layer 7, the hydrogenated amorphous silicon semiconductor layer 4, and the doping semiconductor layer 5, and the capacitor (C11) including the upper electrode 6 is formed. Thus, one pixel is formed.

A large number of similar pixels are arranged two-dimensionally on a substrate having a large area, and a protective layer 8 made of SiNx for protecting each pixel is further provided thereon, and incident radiation is provided. The phosphors 9 for converting the light into visible light are respectively formed to constitute a radiation detection device that can cope with a large area.

Further, FIG. 9 shows a liquid crystal display device for a large screen, which has been conventionally proposed, in a cross section of one pixel. That is, in FIG. 9, the insulating substrate 1
Above, a thin film transistor (TFT) including a gate electrode 2, a gate insulating layer 7, a hydrogenated amorphous silicon semiconductor layer 4, a doping semiconductor layer 5, and a main electrode 6, and a pixel (PX1) including a pixel electrode 10, Further, each element such as a capacitor (CS) is formed, and by arranging a large number of these elements over a large two-dimensional area, a liquid crystal display device compatible with a large screen is configured.

[0006]

However, the above-mentioned prior art has the following problems to be further improved. That is, in the configurations shown in FIGS. 9 to 11, the constituent materials of the gate electrode 2 are Cr and A.
Materials such as 1 / Cr, Mo / Ta and Ta are used. These have good adhesion to the insulating substrate 1, have excellent fine workability by photolithography, and do not generate hillocks during the next step of depositing the gate insulating layer 7 at a temperature of 300 to 350 ° C. For these reasons, these materials are eventually formed with a specific resistance of 50 μΩ · cm or more.

Therefore, a larger screen, higher definition,
Alternatively, when trying to apply to a moving image, the specific resistance of the wiring is high, the wiring length is long, and the wiring becomes finer due to the finer wiring, and as a result,
There is a problem in that the pulse replacement time becomes long, and the above-mentioned object, that is, a large screen and high definition cannot be achieved.

FIG. 8 shows the relationship between the wiring resistance and the displayable size or definition with the pulse delay time as a parameter. As is clear from this graph, by reducing the wiring resistance, it is possible to increase the screen size and the definition, and to support moving images. Therefore, in order to solve these problems, C having a low specific resistance is used.
Currently, development using u is actively continued, but it has not been put to practical use because of poor adhesion to the substrate, easy oxidation of the surface, poor microfabrication, etc. .

Further, aluminum having a low specific resistance is used as an anode to oxidize it, and 2000 to 30
An example has already been proposed in which the formation of alumite with a thickness of 00 angstrom achieves the prevention of hillocks in the subsequent thermal process and the reduction of the resistance of the wiring. However, the alumite formed by anodic oxidation is much more porous than Al ₂ O ₃ obtained as a bulk, and therefore the leak current is slightly higher than that of the gate insulating film that is formed next. Moreover, the dielectric breakdown voltage is slightly low. Therefore, in order to prevent these, the anodic oxide film is required to have a film thickness of 2000 to 3000 angstroms.

However, in a thin film transistor used in an image reading device or a liquid crystal display device, the gate insulating film is usually formed by S by P-CVD method.
Since iNx is used and the film thickness thereof is 2000 to 4000 angstroms, for example, anodized alumite: 2000 angstroms and a base Al: 12000.
If the SiNx to be coated is 3000 angstroms as a good quality film for the fine wiring of angstrom, the thickness of the film to be covered is the same as or thinner than the film thickness of the underlayer. However, there is a problem in that a defective coating or a change in film quality at the step portion causes an interlayer short circuit, a large leak current, or a decrease in dielectric breakdown voltage of the thin film transistor portion.

Further, in order to prevent these problems from occurring, wiring having a taper angle is formed on the substrate on its cross section and this wiring is used, but the substrate has a large area, for example, If it is 550 mm x 650 mm square,
It is very difficult to control the wiring so that the wiring is formed with a uniform taper angle over the entire substrate, and thus the area is further increased, the definition is increased, or the thin film transistor is further reduced to increase the aperture ratio. For the movement to realize the thinning of the gate insulating film in order to increase it,
It becomes difficult and many problems occur, including the yield problem.

Further, in the anodic oxidation process, the wiring formed by patterning is often manually performed such as attaching or detaching an external electrode for anodizing, and the process is complicated, Since it is different from the conventional microfabrication process, it is difficult to manage the liquid and the work, or to solve problems such as bringing impurities into the subsequent processes.

Therefore, in the present invention, the above-mentioned problem is solved by forming an insulating film on the surface of the patterned aluminum material by the modification by the excimer laser.

[0014]

Therefore, in the present invention,
After forming an aluminum material on the surface of the insulating substrate by required patterning, irradiating the surface of the aluminum material with an excimer laser to modify a part from the surface of the aluminum material to a required depth into an insulator. It is characterized by doing.

In this case, the surface of the aluminum material is irradiated with an excimer laser to be modified into an insulator, and
₂ O ₃ is preferred. Further, the total film thickness of the Al ₂ O ₃ modified as an insulator and the aluminum material left thereunder may be less than or equal to the film thickness of the material deposited in the next step. Further, as an embodiment thereof, the aluminum material left after the irradiation of the excimer laser constitutes the gate electrode and the gate wiring of the thin film transistor.

As a result, a dense insulator can be formed on the surface of the aluminum material formed by desired patterning. Further, in this case, since the modification by the excimer laser is a dry process, there is no need for manual work such as attachment and removal of the external electrode by the anodic oxidation method, and further liquid management and work management are included. Since there is no problem such as bringing impurities into the subsequent steps, an electronic device such as a semiconductor device can be formed with high throughput and high yield.

Furthermore, since the formed insulating film is dense,
Even if the film thickness of Al ₂ O ₃ etc. is thin, the leakage current is small and the dielectric breakdown voltage is high, so it can be formed thinner than the film thickness of the material deposited in the next step. At this time, even if the taper angle of the volume cross section is not strictly controlled, the coverage is good and the interlayer short circuit of the completed thin film transistor can be reduced. Therefore, a thin film transistor having a small leak current and a high dielectric breakdown voltage can be formed with a high yield.

Further, since an aluminum material can be used for the gate electrode and the gate wiring, the conventional C
Compared with materials such as r, Al / Cr, Mo / Ta, and Ta, the specific resistance is 1/20 or less, and the gate electrode and gate of a large-area image reading device or image display device with a two-dimensional pixel array. Since it can be used as a wiring and the pulse delay time can be reduced, a high-speed, high-aperture image reading device and image display device can be constructed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) The present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing a two-dimensional image reading apparatus including a gate electrode and a gate wiring 2 using aluminum, which is achieved by the present invention. It can also correspond to. Here, reference numeral 1 is an insulating substrate made of glass or the like, 2 is a gate electrode and a gate wiring made of aluminum, 7'is a gate insulating film made of Al ₂ O ₃ , and 7 is S.
A gate insulating film made of iNx and SiO ₂ , 4 is a semiconductor layer made of hydrogenated amorphous silicon, 5 is a doped semiconductor layer for ohmic contact, and 6 is a main electrode made of aluminum or the like. Here, as in the case shown in FIG. 11, the thin film transistor portion (T11),
And MIS type optical sensor section (S11) and condenser section (C
Each element of 11) constitutes one pixel.

Further, a large number of similar pixels are two-dimensionally arranged over a large area of the substrate, and a protection layer 8 made of SiNx for protecting each pixel is further provided thereon, and the incident radiation is also applied. Phosphors 9 for converting the light into visible light are formed, for example, in an effective area of 460 mm square,
That is, a radiation detection device that is configured with 8 million pixels and that also supports moving images is configured.

In this structure, the X-ray generated from the X-ray source and passing through the human body is incident on the phosphor 9 by the incident X-ray.
It is converted into visible light according to the strength of the line. The converted visible light is incident on the optical sensor unit of S11, and an optical output corresponding to its intensity is generated from the optical sensor unit S11 as an electric signal. The generated electric signal is accumulated in the capacitor unit C11 and output to the outside by the thin film transistor T11. Then, a two-dimensional image reading device can be configured thereby.

Further, in the two-dimensional image reading apparatus shown in FIG. 1, especially, the gate electrode 2 and the gate insulating film 11 are used.
A method of forming the electrodes 7 and 7 will be described below with reference to FIGS. Here, first, the insulating substrate 1 made of glass
Was cleaned, and an Al film was formed on the
Deposit to a thickness of 00 Å (see FIG. 2). As deposition conditions, substrate temperature: 100 ° C., discharge power:
When Al is deposited by the DC sputtering method under the conditions of 10 W / cm ² and Ar pressure: 1 × 10 ⁻³ Torr, a thin film having a specific resistance of 2.8 μΩcm, which is close to that of bulk, is obtained.

This is about 1/20 that of the conventional gate electrode material such as Cr. This is exposed to light and developed using a normal positive resist (see FIG. 3), and H ₃ P is added.
By etching with an etchant composed of O ₄ , HNO ₃ , CH ₃ COOH, and H ₂ O,
The gate line 2 made of Al having a minimum line width of 5 μ is formed on the substrate so that the taper angles on both sides of the cross section are about 70 to 90 ° (see FIG. 4).

After that, the excimer laser method (described later)
To a thickness of 500 angstroms from the surface of Al by modifying Al ₂ O ₃ (see FIG. 5), and then using a normal process to form the gate insulating film 7 made of SiNx.
At a thickness of 3000 Å at 350 °,
By the P-CVD method, the hydrogenated amorphous semiconductor layer 4 and the doping semiconductor layer 5 were each heated to 300 at 250 ° C.
0 Å and 500 Å thick, deposited and patterned as required, and finally:
The element portion shown in FIG. 1 is completed by depositing Al of the main electrode 6 by the sputtering method and performing the required patterning.

In FIG. 6, the surface of Al shown in FIG.
The schematic configuration of the excimer laser used to modify to ₂ O ₃ is shown. Here, a laser beam 18 extracted from the excimer laser oscillation source 14 passes through a mask 15 having a rectangular slit installed in an optical system, is folded by a mirror 16, passes through a lens system 17, and has a sample having a quartz window. The sample 11 placed in the tank 12 is irradiated. The sample tank 12 is installed on a stage 13 that is controlled and moved in the XY directions, and is provided with a reaction gas introduction port and a discharge port (both not shown), and the discharge port is a vacuum pump. Connected to.

In order to form Al ₂ O ₃ by surface-modifying Al using the system shown in FIG. 6, the formed sample 11 is placed in the sample tank 12 as shown in FIG. Then, the inside of the sample tank 12 is evacuated using a vacuum pump. Then, using a heater (not shown), the sample 11 is heated to about 150 ° C., N ₂ O which is a reaction gas is introduced through the reaction gas introduction port, and the pressure is maintained at 200 Torr.

As an excimer laser, Ar is used.
F: Energy wavelength: 10 using wavelength of 193 nm
The sample is irradiated with 0 mJ / cm ² , and the Al material is modified into Al ₂ O ₃ by irradiation with about 500 pulses at a thickness of about 500 Å from the surface of Al. At this time, by controlling the XY stage and irradiating each irradiation surface with about 500 pulses, Al ₂ O ₃ is converted from the surface of Al to a depth of 500 Å over the entire area of 460 mm square of the substrate. Can be quality.

When the completed element was evaluated, no hillock was generated due to the thermal history of Al, and no short circuit between the upper and lower sides was observed. In this embodiment, the gate wiring 2 made of Al is formed with a taper angle of about 70 to 90 °, but since the total film thickness of Al / Al ₂ O ₃ is sufficiently thinner than the gate insulating film 7, Even if the taper angle is not precisely controlled, the coverage with the gate insulating film 7 is good, and as a result, when a voltage is applied to the gate electrode 2 and the main electrode 6, the leakage current is 10 ⁻ at an applied voltage of 20 ^{−. It was} as good as ¹⁴ A or less, and the withstand voltage was maintained at about 300 V as in the case of using the conventional gate electrode 2 of Cr or the like. Furthermore, T
The ON / OFF ratio of the FT was obtained in about 7 digits, the wiring resistance of the gate electrode was 1/20 or less of the conventional one, and the pulse delay was small, so that a large-area two-dimensional reading device could be formed.
Further, the surface modification by the excimer laser has very good controllability, and since no liquid or the like is used, there is no fear of bringing impurities into the next step. as a result,
Thin Al ₂ O ₃ provides good yield and good performance over a large area without adequate taper angle control 2.
The dimension reading device was completed. (Second Embodiment) FIG. 7 shows a liquid crystal display device having a gate electrode and a gate wiring 2 using Al, which is achieved by the present invention, and in particular, here, a diagonal of 25 inches or more. The array is shown in cross section, which can be used for large screens. Reference numeral 1 is an insulating substrate made of glass or the like, 2 is a gate electrode and a gate wiring made of Al,
7'is a gate insulating film made of Al ₂ O ₃ , and 7 is SiN
x, a gate insulating film made of SiO ₂ , 4 a semiconductor layer made of hydrogenated amorphous silicon, 5 a doping semiconductor layer for ohmic contact, 6 a main electrode made of Al or the like, 10 a pixel electrode made of ITO or the like is there.

Similar to the case shown in FIG. 9, the thin film transistor section (TFT), the pixel section (PX1), the capacitor section (C
Each element including S) and the like constitutes one pixel, and a large number of pixels are arranged two-dimensionally to constitute the entire array portion of the liquid crystal display device. In the method of forming a liquid crystal display device for a large screen shown in FIG. 7, the insulating substrate 1 made of glass is washed, and an Al film is deposited thereon to a thickness of 2500 angstroms by sputtering. ing.

And here, the substrate temperature: 100 ° C.,
Discharge power: 10 W / cm ² , Ar pressure: 1 × 10 ⁻³ To
Al was deposited by the DC sputtering method under the condition of rr. This is a normal photolithography process, the minimum line width: 5μ
The gate wiring 2 made of Al has a taper angle of about 60 °.
Formed at ~ 80 °. After that, the substrate 1 is placed on the XY stage 13 of the excimer laser processing system shown in FIG.
Heated to 0 ° C.

Further, as an excimer laser, F ₂ :
Energy density: 80 mJ using a wavelength of 157 nm
/ Cm ² , the sample was irradiated and modified to Al ₂ O ₃ with a thickness of about 1000 Å from the surface of Al by reaction with O ₂ in air. After that, the film deposition and the photolithography process were repeated in a usual process to complete the liquid crystal display device shown in FIG.

When the completed element was evaluated, the thermal history of Al
No hillocks were seen due to the
There was no yoto. In this embodiment, the thickness of the gate insulating film 7
3,000 Angstroms, Al / Al_TwoO_Threeof
The gate wiring 2 and the gate insulating film 7'have a thickness of 2500
Since it is about ngstrom, gate wiring made of Al 2
Is formed with a taper angle of its cross section of about 60-80 °.
However, as a result, the coverage with the gate insulating film 7 is good.
So, the leakage current is 10V when the applied voltage is 20V. ^-14
It is as good as A or less, and has a withstand voltage of conventional Cr or other gate
Maintain about 300 volts as with electrode 2.
Was.

Further, the ON / OFF ratio of the TFT is about 7
A digit is obtained, the wiring resistance of the gate electrode is 1/20 or less as compared with the conventional one, and the pulse delay is small, so that a large-area liquid crystal display device can be constructed. Further, the surface modification by the excimer laser has very good controllability, and since no liquid or the like is used, it can be formed without the worry of bringing impurities into the next step.

Al ₂ O ₃ formed by the excimer laser is Al ₂ O ₃ formed by the conventional anodic oxidation method.
_Since it is denser and better than ₂ O ₃ , it can prevent hillocks in a state where it is thinner than the film thickness required in the case of the anodizing method. Since the same characteristics as those obtained by using the gate electrode 2 can be maintained, even if the film deposited in the subsequent steps is thin, the coating is good and the yield due to the short circuit between the top and bottom can be improved. Also, as an excimer laser, F ₂ : 157 nm
When the wavelength of ₂ is used, O ₂ in the air can be used for oxidation, so that the sample tank 12 and the vacuum pump are not required, and Al ₂ O ₃ having high throughput can be formed at low cost.

[0035]

As described above, according to the present invention,
By irradiating the surface of the aluminum material formed on the substrate with the required patterning with an excimer laser, a part of the aluminum material can be reformed into a dense insulating film from the surface to the required depth. Compared with the oxidation method, the leakage current is small and the dielectric breakdown voltage can be increased even if it is thinner. Therefore, even if the film thickness to be deposited in the next step is thin, the covering property is sufficient, and the coating becomes good even if the taper angle of the cross section is not sufficiently controlled at the time of patterning the aluminum material. The short circuit between the thin film transistors can be reduced, the leakage current is small,
A thin film transistor with a high dielectric breakdown voltage has a high yield,
Can be formed.

Further, since the modification by the excimer laser is a dry process, there is no need for manual work such as attachment and removal of the external electrode by the anodic oxidation method, and further, the subsequent process including liquid management and work management. There is no problem of bringing impurities into the device and it can be formed with high throughput and high yield. In addition, conventional Cr, Al / Cr, Mo /
Compared with the specific resistance of Ta, Ta, etc., 1/20 or less of that aluminum material can be used as the gate electrode and the gate wiring of the thin film transistor, so that the pulse delay is small
This can be adopted when constructing a two-dimensional, large-area image reading device or image display device, and an electronic device with high speed and high aperture ratio can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an image reading device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the forming method of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the forming method of the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the forming method of the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the forming method of the first embodiment of the present invention.

FIG. 6 is a schematic view of an excimer laser according to the forming method of the present invention.

FIG. 7 is a sectional view of an image display device according to a second embodiment of the present invention.

FIG. 8 is a graph illustrating the relationship between the wiring resistance and the displayable screen size using the pulse delay time as a parameter.

FIG. 9 is a cross-sectional view of a conventional liquid crystal display device.

FIG. 10 is a plan view of a conventional image reading device.

FIG. 11 is a sectional view of a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Gate electrode, gate wiring 4 Semiconductor layer 5 Doping semiconductor layer 6 Main electrode 7 Gate insulating film 7'Insulating film 8 Protective layer 9 Phosphor 10 Picture element electrode 11 Sample 12 Sample tank 13 XY stage 14 Oscillation Source 15 Mask 16 Mirror 17 Lens system 18 Laser light 20 Resist

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 27/146 H01L 27/14 C 29/786 29/78 613Z

Claims (4)

[Claims] 1. An aluminum material is formed on a surface of an insulating substrate by required patterning, and then the surface of the aluminum material is irradiated with an excimer laser so that a part of the surface of the aluminum material up to a required depth is exposed.
A method for forming an electronic device, which comprises reforming into an insulator. 2. A portion of the surface of the aluminum material, which has been modified into an insulator by irradiating the surface of the aluminum material with an excimer laser, is Al ₂ O.
_{3. The} method for forming an electronic device according to claim 1, wherein the number is 3. 3. The Al modified as an insulator
_3. The electronic device according to claim 2, wherein the total film thickness of ₂ O ₃ and the aluminum material left below is less than or equal to the film thickness of the material deposited in the next step. Forming method. 4. The aluminum material left after the excimer laser irradiation constitutes a gate electrode and a gate wiring of a thin film transistor.
4. The method for forming an electronic device according to any one of 3 to 3.