JPH04124813A - Manufacture of thin-film semiconductor and apparatus therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, an apparatus therefor, and a semiconductor device using the same, and in particular, an amorphous film is annealed at a low temperature to achieve high-quality crystallinity. This invention relates to a method for manufacturing thin films with good reproducibility.

[Problem to be solved by the invention]

Laser annealing is a low-temperature local annealing method for amorphous films for forming thin film semiconductor devices.

Conventionally, there are the following three methods as this type of technology.

(1) Amorphous film (a-
A method of irradiating Si:H) with CWAr+ laser (for example,
JP-A-58-114435, JP-A-63-200
Publication No. 572).

(2) A method of irradiating the same amorphous film with pulsed excimer laser (for example, Japanese Patent Laid-Open No. 63-25913).

(3) Amorphous film deposited by sputtering method (a-5i)
CWAr+laser irradiation method (for example, Japanese Journal of Shearbride Physics No. 2)
Volume 8, No. 11, pages L1871 to L1873 (19
89) (Jpn, J, Appl, Phyo, V
ol, 28. NQll.

Novekakuber, 1989 pp, L1871-
L1873).

[Problem to be solved by the invention]

The above conventional technology does not take into account the following points.

Regarding CWAr+ laser irradiation, high energy irradiation is necessary for high quality.

Throughput is low. Furthermore, a low-cost glass substrate with a low strain point is easily broken.

Regarding pulsed excimer laser irradiation, peeling between the substrate and film and unevenness occur on the surface of the thin film.

An object of the present invention is to provide a method for producing a low-temperature, high-quality film with excellent throughput, without peeling or surface irregularities, and with good reproducibility and uniformity.

[Means to solve the problem]

In order to achieve the above objective, after the thin film semiconductor layer is formed, it is preheated by irradiation with continuous wave laser light, and then irradiated with pulsed laser, which eliminates the peeling rate of the semiconductor film and does not affect the substrate. It is characterized by not giving

Furthermore, the present invention enables local crystallization of a thin film semiconductor layer.

[Effect]

The invention works as follows.

When attempting to crystallize an amorphous semiconductor thin film deposited on a substrate by laser irradiation, irradiation with the strong laser necessary for crystallization may cause peeling of the semiconductor thin film or surface irregularities. In order to prevent the above-mentioned peeling, etc., continuous wave (CW) laser light is first irradiated. CW laser irradiation enables good crystallization by heating the thin film on the substrate at an appropriate temperature increase rate and reaching temperature. In addition, in the case of hydrogenated amorphous silicon films or fluorinated amorphous silicon films that contain hydrogen or fluorine, hydrogen or fluorine can be evaporated and scattered by continuous wave laser light irradiation, and when irradiated with high-intensity pulsed laser light, hydrogen or fluorine can be evaporated and scattered. It is also possible to prevent membrane roughening due to bumping of hydrogen and fluorine.

Furthermore, since a beam-shaped laser beam is used, local heating is also possible, and local crystallization is possible without affecting areas other than the desired area.

Next, in order to crystallize the amorphous semiconductor thin film, it is necessary to irradiate it with high energy laser light. Therefore, by using a pulsed laser, even if a high-energy beam is irradiated, the effect on the substrate and underlying film can be eliminated. This makes it applicable to the manufacture of three-dimensional devices. Additionally, pulse oscillation generally has better throughput than using a continuous wave laser.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, embodiments to which the method for producing high quality thin film polycrystals according to the present invention is applied will be described with reference to the drawings.

First, in FIG. 1(a), a deposition temperature of 300°C was deposited on a 10OIII glass substrate LO by a plasma CVD method.
``CRF power 60W, pressure 0.6 Torr.

Gas flow rate Hz: 5iHa =200: 70sccr
Under film formation conditions of n, hydrogenated amorphous silicon C or less a-
A Si:H) film 11 is deposited. After that, as shown in FIG. 1(b), the CWAr+laser L^ is output 5. OW, beam diameter 1mm, scanning speed 1.0■/s e
Irradiate at c. Through the above process, the a-Si:H film 11 is heated, and the upper layer of the thin film is modified into a microcrystalline silicon (hereinafter referred to as μC-5i) film 12. C.W.
The energy density of Ar + laser L^ is a-5i:H film 1
It does not require high energy to crystallize the entirety of 1. After that, as shown in Fig. 1(c), the XeCρ excimer laser Lx (wavelength 308 nm, pulse width 28 ns)
The μC-Si film 12 was irradiated with 240 mJ/d of
The whole melts and solidifies, forming polycrystalline silicon (hereinafter referred to as poly-S).
i) Modified into film 13. The X-ray diffraction intensities of poly-Si13 obtained by the above process are shown in FIG. 2 for film thicknesses of 800 and 2000. These results show that a-Si:H film can be made from poly-
Can be modified to 5i film. Also, the scanning microscope Jl! According to the investigation, the surface was smooth, with no protrusions or voids.

Through the above process, a thin polycrystalline film with good film quality and no surface irregularities could be produced.

FIG. 3(a) shows an example of a manufacturing apparatus for carrying out the present invention. Use CWAr+laser L^ with cylindrical ripple lens R to make the beam shape rectangular, or
Alternatively, an optical system is constructed by superimposing several CW A r + lasers so that they are lined up in a straight line. At this time, Figure 3(b)
As shown in , the radiation d of cwAr+laser LA is XeC
The beam shape of the Q excimer laser Lx is deIXdez (
When the width in the direction parallel to da is del), d,
6. Also, regarding the scanning method, it is sufficient to move the stage on which the sample is set and the laser beam relative to each other. By using the above manufacturing apparatus, it has become possible to manufacture a high-quality polycrystalline film with excellent throughput.

Further, an embodiment in which the present invention is applied to a thin film transistor (hereinafter referred to as TPT) will be described below with reference to the drawings.

First, in FIG. 4, 1200 Crl[i] is deposited as a gate electrode on a 100-μm glass substrate 10 by a sputtering method at a deposition temperature of 100''C and an Ar pressure of 1 mTorr, and patterned by a photoetching process.Then, a gate electrode is formed by a plasma CVD method. SiN as an insulating film
x film deposition temperature 325”C, RF power 175W, pressure 0.6Torr gas flow rate SiH number: NH8:Nx=
3500 layers were deposited under film formation conditions of 10:60:200 sec cm, and a-5i was deposited to form a continuous channel layer.
: Deposition temperature of H film 11: 300°C, RF power: 60W, pressure: 0.6 Torr, gas flow rate: H2: 5iHn=200
: 2000 people deposited under the film formation condition of 70 seconds.

Here, the method for manufacturing a thin film polycrystal of the present invention is applied. a-
CWAr+laser LA output 5.0 on Si:H film 11
W, beam diameter 1.0■, scanning speed 10.
After irradiation with Owm/sec, XeC (1 excimer laser Lx (wavelength 308 nm, pulse width 28 ns,
The a-Si:H film is crystallized by irradiating the a-Si:H film with a beam shape of 8.5-mm). (Figure 5) p obtained by the above process
The oly-Si film 13 is homogeneous, has excellent crystallinity, and has high electrical characteristics.

Next, by plasma CVD method, n+-Si containing phosphorus was
The film was deposited at a temperature of 230°C, an RF power of 60W, and a left side of 0.
6Torr, gas flow rate H2:SiH4:PH8=12
350 people deposited under the film forming conditions of 0:48:120 seconds, and after the photomatching step, 600 people formed a Cr electrode under the same conditions as the gate electrode, and 3700 people deposited using the AQ main electrode sputtering method. In addition, the sauce is added to the photoetching process.

The electrical characteristics of the TPT created as described above are as follows: forming the drain and completing the TPT as shown in FIG.
The effective mobility μeff''=50 aJ/V·S and the threshold voltage VTR=5V or less were good.

Further, an embodiment regarding a liquid crystal display will be described below.

Forming the drive circuit on the same substrate as the pixels in a liquid crystal display has significant advantages in terms of cost and the like. However, a-Si TFT has small mobility (0
, 3L: about i/v-9), it is difficult to assemble a drive circuit for a liquid crystal display.

However, by laser annealing only the portion in which the drive circuit is built and forming a poly-Si TFT, it becomes possible to incorporate the circuit.

FIG. 7 is a plan view of the liquid crystal display. 102 in the diagram
By applying the crystallization method of the present invention only to the region, high mobility poly-
5i TFT can be formed, and a driving circuit can be built into the periphery of the substrate.

In the embodiment of the present invention, an Ar+ laser is used as a continuous wave laser, and an XeCρ excimer laser is used as a high-intensity pulsed laser, but other lasers with wavelengths that match the absorption coefficient of the Si film are used, such as Nd-YAG laser for continuous wave laser,
Nd-glass laser.

As high-intensity pulsed lasers, ruby lasers, copper vapor lasers, etc. can also be used.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

By sequentially irradiating an amorphous semiconductor film deposited on a substrate with a CW laser and a pulsed laser, a high-quality polycrystalline film can be manufactured in a low-temperature process.

Furthermore, since laser light is used, local crystallization is also possible. This can be applied to the manufacture of active matrix substrates for Si thin film transistors incorporating peripheral drive circuits for liquid crystal displays.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a polycrystalline silicon film manufacturing process according to an embodiment of the present invention, FIG. 2 is a relationship diagram between pulsed laser energy and X-ray diffraction intensity, and FIG. 3 is a schematic diagram of a manufacturing apparatus of the present invention. 4, 5, and 6 are cross-sectional views of a TPT manufacturing process to which the present invention is applied, and FIG. 7 is a plan view of a liquid crystal display substrate incorporating a peripheral drive circuit prototyped according to the present invention. 10...Glass substrate, 11...Hydrogenated amorphous silicon film, 12...Microcrystalline silicon film, 13...Polycrystalline silicon film, L^...Continuous wave Ar+ laser, Lx...・Pulse oscillation XeCQ excimer laser, R...Cylindrical ripple lens, 101...
-Display pixel section, 102...display circuit section.

Claims (1)

[Claims] 1. A method for producing a thin film semiconductor, which comprises irradiating an amorphous semiconductor thin film deposited on a substrate with continuous wave laser light and then irradiating it with pulsed laser light. 2. In claim 1, the amorphous semiconductor thin film is a-S.
i-film or a-Si:H (hydrogenated amorphous silicon)
Film or a-Si:F (fluorinated amorphous silicon)
A method for manufacturing a thin film semiconductor, characterized in that it is a film. 3. In claim 1, continuous wave laser light is
^+ A method for manufacturing a thin film semiconductor, characterized in that an ion laser, a CO_2 laser, or a Nd-YAG laser is used, and the pulsed laser light is an excimer laser, a ruby laser, a Nd-YAG laser, or a metal vapor laser. 4. Claim 1 is characterized in that the amorphous semiconductor thin film is grown in a solid phase by continuous wave laser light irradiation, and is modified into a crystalline semiconductor thin film by liquid phase growth by pulsed laser light irradiation. A thin film semiconductor manufacturing method. 5. The method of manufacturing a thin film semiconductor according to claim 1, characterized in that the amorphous semiconductor thin film is locally irradiated with a laser. 6. A thin film semiconductor manufacturing apparatus comprising a stage, a CW laser, a pulsed laser, a condensing lens, a beam uniformization lens, and a scanning mechanism, characterized in that the beam width of the CW laser is made larger than the beam width of the pulsed laser. thin film semiconductor manufacturing equipment. 7. A method for manufacturing a thin film transistor, which comprises irradiating an amorphous semiconductor layer formed as an active layer of the thin film transistor with continuous wave laser light, and then irradiating it with pulsed laser light. 8. In an active matrix type liquid crystal display using thin film transistors, a method for manufacturing a thin film semiconductor characterized by locally irradiating only the peripheral circuitry with continuous wave laser light and then irradiating pulsed laser light. . 9. A method for manufacturing a thin film semiconductor, which comprises locally irradiating a drive circuit section of a line sensor with a continuous wave laser beam, and then irradiating it with a pulsed laser beam.