JPS6329924A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a low-resistance thin-film extremely easily at a low temperature without elevating a substrate temperature by depositing an amorphous silicon layer containing a microcrystalline silicon layer and annealing the amorphous silicon layer by a laser. CONSTITUTION:The manufacture of a semiconductor device includes a process, in which a thin-film containing a microcrystalline silicon layer as a crystallite is deposited, and a process in which the thin-film is irradiated with laser beams. An amorphous silicon P layer 101 in film thickness of 700Angstrom is deposited on a glass substrate 100 through a plasma CVD method, and a microcrystalline silicon N layer 102 in film thickness of 2300Angstrom is deposited. The microcrystalline silicon N layer 102 is irradiated by using a krypton fluoride excimer laser. Accordingly, since microcrystalline silicon is annealed by the laser, the thin-film having low resistance is formed, thus acquiring the thin-film having high conductivity extremely easily at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for obtaining a low resistance thin film using a low temperature process.

[Prior art and its problems]

Amorphous silicon and its compounds are easy to form and can be formed on large-area substrates, so they can be used for thin film transistor arrays, image sensors, thin film pressure sensors, etc.
It has been used in various fields.

For example, a thin film transistor with a staggered structure usually has source and drain electrodes 2 on a substrate 201, as shown in FIG.
02, 203, ohmic contact layer 204, photoelectric conversion layer 2
05, a gate insulating film 206 and a gate electrode 207 were sequentially laminated.

Here, an n-type hydrogenated amorphous silicon layer is used as the ohmic contact layer 204, and a hydrogenated amorphous silicon layer is used as the photoelectric conversion layer 205, but the ohmic contact layer is used to separate the source and drain. Prior to forming the conversion layer, it must be patterned.

Therefore, since the ohmic contact layer and the photoelectric conversion layer can only be formed continuously, there is a problem that contact failure is likely to occur due to oxidation of the surface of the ohmic contact layer or residual etching residue. This was the cause of hindering its practical application.

Therefore, it is necessary to reduce the resistance of the ohmic contact layer as much as possible. To solve this problem, for example, the plasma excitation power is increased when forming an n-type hydrogenated amorphous silicon layer containing phosphorus (P) as an impurity. or increase the hydrogen (H2) dilution of the raw material gas silane (SiH4) to form an n-type hydrogenated microcrystalline silicon (μc-St:H) with a film thickness of 60 to 100.
I try to form layers. However, with this method, even if the amount of impurity doping is maximized, the conductivity of the thin film obtained is at most about 10 (0 cm), which is a level that can be used practically as an ohmic contact layer of a staggered thin film transistor. It wasn't.

Similar problems are also seen in thin film pressure sensors, image sensors, etc., and the demand for low resistance thin films is increasing.

The present invention has been made in view of the above-mentioned circumstances, and one of its objectives is to easily obtain a low-resistance thin film at low temperatures.

[Means for solving problems]

Therefore, in the present invention, when forming a low-resistance thin film, the process includes a step of depositing a thin film including a microcrystalline silicon layer having microcrystals with a grain size smaller than that of amorphous silicon, and a step of irradiating the thin film with a laser beam. There is.

[Effect]

The present inventors have discovered that by irradiating a microcrystalline silicon layer with a small grain size with laser light, the crystal grain size can be significantly increased.

The present invention has been made with this in mind. For example, an amorphous silicon layer including a microcrystalline silicon layer is deposited by a plasma CVD method with increased plasma power, and then an amorphous silicon layer is deposited by laser annealing. By recrystallizing silicon, it becomes possible to obtain an amorphous silicon layer with an extremely large crystal grain size. In this way, an amorphous silicon layer with low resistance can be easily obtained.

〔Example〕

Hereinafter, a method for forming a low resistance thin film according to an embodiment of the present invention will be explained.

First, as shown in FIG. 1(a), an amorphous silicon p layer 101 having a thickness of 700 nm is deposited on a glass substrate 100 by plasma CVD.

Next, as shown in FIG. 1(b), a microcrystalline recon (μ
c-5i) Deposit n-layer 102.

This layer is assumed to contain phosphorus (P) as an impurity.

After this, as shown in Figure 1(c), krypton fluoride (
KrF) excimer laser is used, and laser light (λ-24
The microcrystalline silicon n-layer 102 is irradiated with 9 nm and power of 124 mJ/cm2.

The number of irradiations at this time and the microcrystal silicon n
The relationship with the resistance value of the layer is shown in FIG. As is clear from this figure, the conductivity was 10 (0 cm) before laser light irradiation.
)-', but due to laser light irradiation, it became 50
(0cm)" and after irradiating 3 to 4 times it reaches 62.5 (
0 cm)-1 could be obtained.

As described above, according to the method of the present invention, a low-resistance thin film can be obtained extremely easily at low temperatures without increasing the substrate temperature.

After forming a low-resistance thin film in this way, it can be patterned into a desired shape by photolithography, and an electrode pattern can also be formed thereon to be used as a strain gauge for a pressure sensor.

In this method, the resistance of the microcrystalline silicon n-layer as a pressure-sensitive resistance layer can be reduced, so that it can be made thinner and the pattern accuracy can be reduced by one layer.

Furthermore, the H degree characteristics are also improved, making it possible to provide a highly reliable thin film pressure sensor.

Next, as another embodiment of the present invention, a method for manufacturing a staggered thin film transistor will be described.

FIGS. 3(a) to Cl0) are diagrams showing the manufacturing process of a thin film transistor for driving a display panel using liquid crystal.

First, as shown in FIG. 3(a), a black tantalum oxide film with a thickness of 2,000 yen was deposited on a transparent substrate 1 made of alkali-free glass made by HOYA, also known as NA-40, by RF sputtering. (TaOX, x<2.5) film 2' is deposited. The deposition conditions at this time were: tantalum pentoxide was used as a target, argon (Ar) pressure was 5 x 10 Torr, applied power was 500 W, and substrate temperature was 35
The duration was 0°CIO minutes. The transmittance of the tantalum oxide film as a light shielding film deposited in this way at a wavelength of 550 nm was 2%.

Next, as shown in FIG. 1(b), a light shielding film 2 is formed by a normal photolithography process using a photomask with a reverse pattern of the source/drain electrodes and the source bus.
Then, the tantalum oxide film 2' is patterned. As the etchant, a hydrofluoric acid aqueous solution of hydrofluoric acid (HF):water (H20)-1:10 was used.

Subsequently, as shown in FIG. 3(C), an indium tin oxide (ITO) layer 3 is formed as a transparent conductive film by DC sputtering.
' Deposit 2000 people. The sputtering conditions at this time were an oxygen partial pressure of 8 x 10-5 Torr, a mixed gas pressure of oxygen (02) + argon (Ar) of 5 x 10-3 Torr, and a direct current (DC) current of 0. 8A, substrate temperature 300° C., and deposition time 10 minutes.

The sheet resistance ρS of this film was 10Ω/mouth.

Next, using the plasma CVD method, a microcrystalline silicon n medium layer (n" μc-S
i) 30OA of 4' was deposited. The deposition conditions at this time are as shown in the following table. The resistivity ρ of the microcrystalline silicon n middle layer formed in this way is 0.5Ωc
It was m.

Thereafter, as shown in FIG. 3(e), a krypton fluoride excimer laser is used to irradiate the microcrystalline silicon n middle layer with a laser beam having a wavelength of 249 nm for laser annealing, thereby reducing the resistance.

After that, after applying a Tokyo Ohka type negative resist commonly known as 0MR85, the substrate is exposed from the back side to form a resist pattern in a self-aligned manner with respect to the tantalum oxide film pattern 2, and this is used as a mask for etching. By doing so, patterns of source/drain electrodes 3a, 3b and a source bus are formed, and a microcrystalline silicon n medium layer 4' as an ohmic contact layer is formed. At this time, the etching of the microcrystal silicon n middle layer is carried out using hydrofluoric acid (HF), nitric acid (HNO3), acetic acid (CH
A mixed solution of 3C00H)-1:20:30 was used. (Fig. 3(f)) After this, as shown in Fig. 3(f), amorphous silicon (a-5
i) Deposit layer 5'. (The deposition conditions are shown in the table below.) Next, as shown in FIG. 3(g), a silicon nitride (SiNx) layer 6' with a thickness of 2,500 yen was deposited using the plasma CVD method.
Deposit. (Deposition conditions are below*2.500ppm H
Further, as shown in FIG. 3(i), an aluminum layer 7' having a thickness of 3,000 wafers is deposited by the electron beam evaporation method.

Thereafter, as shown in FIG. 3(j), a resist pattern is formed by a photolithography process, and the unnecessary portion of the aluminum layer 7' is etched using this resist pattern to form the gate electrode 7.

Finally, using this gate electrode 7 as a mask, the underlying silicon nitride layer 6', amorphous silicon layer 5', and microcrystalline silicon layer 4' are dried using tetrafluoromethane (CFa) containing 5% oxygen. The gate insulating film 6, photoelectric conversion layer 5, and ohmic contact layer 4 were selectively removed by etching to obtain patterns, as shown in FIG.
) and (Ω), a staggered thin film transistor is completed. FIG. 3(k) is a sectional view taken along line AA in FIG. 3(Ω).

In this way, when forming the ohmic contact layer, the microcrystalline silicon layer is annealed with laser light to reduce the resistance, thereby making it possible to obtain a staggered thin film transistor with extremely good characteristics.

In other words, in conventional thin film transistors with a staggered structure, it is not possible to continuously form an ohmink contact layer and a photoelectric conversion layer, so contact failures are likely to occur due to oxidation of the surface or retention of etched residual lithium, and this has not been put into practical use. In contrast, in the present invention, this problem is solved by starting with a microcrystalline silicon n layer with low surface resistance, which is annealed to further reduce the resistance, and then used as an ohmic contact layer. This made it possible to put it into practical use.

Further, in this method, only two masks are used, one for patterning the light shielding film and the other for patterning the gate electrode. The source/drain electrodes are formed in a self-aligned manner with respect to the pattern of the light shielding film by exposure from the radix side, and the gate insulating film 6, photoelectric conversion layer 5, and ohmic contact layer 4 are formed with the pattern of the gate electrode. Patterned with the same mask.

In this way, not only is the process simplified by reducing the number of masks, but also the thin film transistor array formed by the method of the present invention has high precision and high reliability.

Note that in the embodiments, a thin film pressure sensor and a thin film transistor have been described, but it goes without saying that the present invention is also applicable to other semiconductor devices.

In addition to the krypton fluoride excimer laser, the lasers used include argon fluoride (ArF) excimer laser, xenon chloride (XeCΩ) excimer laser, and Y
Other lasers such as an AG laser or a CW-Ar laser may also be used.

〔effect〕

As explained above, according to the method of the present invention,
Since a thin film with low resistance is formed by subjecting the crystal silicon to laser annealing, a thin film with high conductivity can be obtained extremely easily at low temperatures.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are diagrams showing the process of forming a low-resistance thin film according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the conductivity of the thin film and the number of laser beam irradiations in the same formation process. , FIGS. 3(a) to 3(1) are diagrams showing other embodiments of the present invention, and FIG. 4 is a diagram showing a conventional staggered structure thin film transistor. 1.100,201--Substrate, 2...Light-shielding film, 3a
. 202... Source electrode, 3b, 203... Drain electrode, 4,204... Ohmic contact layer, 5,205
... Charge conversion layer, 6,206 ... Gate insulating film, 7
゜207... Gate electrode, 101... 22 layers of amorphous silicon, 102... Microcrystalline silicon n layer. Conductivity (7 (0cm)-'Figure 3 (f)

Claims (2)

[Claims] (1) Microcrystal silicon (μc-S) on the substrate
i) a deposition step of depositing an amorphous silicon layer including the layer; and an annealing step of recrystallizing the amorphous silicon layer by irradiating the amorphous silicon layer with laser light. (2) The semiconductor according to claim 1, wherein the deposition step is a plasma CVD step in which plasma excitation power is increased to promote the formation of a microcrystalline silicon layer. Method of manufacturing the device.