JPH036028A - Manufacturing method of thin film transistor - Google Patents

Abstract

PURPOSE:To enhance a throughput of a hydrogen treatment process by a method wherein a heater and a plasma generator are installed at the outside of a reactor and a gas composed mainly of hydrogen is introduced into the reactor. CONSTITUTION:When a thin-film transistor(TFT) 2 using poly-Si as an active layer is treated with hydrogen inside a reactor, a heater 3 and a plasma generator 4 are installed at the outside of the reactor 1. This reactor is a quartz tube into which H2 gas can be introduced and in which an evacuation operation can be executed; a shape of the reactor 1 may be, e.g. of a bell jar type other than a tubular shape. A material of the reactor 1 may be other than quartz; however, it is necessary to pay attention to a contamination from the reactor 1. The TFT 2 is arranged inside the reactor 1; hydrogen is introduced into the TFT 2 by the operation of the heater 3 and the plasma generator 4. Thereby, a good TFT characteristic can be obtained and a throughput can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a thin film transistor, and more particularly, to a method for manufacturing a thin film transistor used in a drive circuit for a life-size photosensor, a liquid crystal display device, or the like.

[Prior Art] A typical manufacturing method for a thin film transistor (hereinafter sometimes referred to as rTFTJ) using poly-3L (polycrystalline silicon) as an active layer includes (i) First, a polycrystalline silicon (polycrystalline silicon) layer is formed on an insulating substrate to form an active layer. Crystalline silicon is deposited by CVD or the like and processed into a predetermined pattern. (ii) Next, a gate oxide film is formed by thermal oxidation, etc., and polycrystalline silicon that will become the gate electrode is deposited on it by CVD method, etc., and after processing into a predetermined pattern, the gate, source, and drain are formed. Diffuse impurities to lower resistance. (Later) Thereafter, a film such as 5L02, which will become an insulating film between the eyebrows, is deposited by CVD or the like, and contact holes are formed at the connection parts with the source/drain and gate.

(iv') Then, a metal such as AΩ, which will become the wiring, is evaporated,
Examples of methods include depositing the material by sputtering or the like and processing it into a predetermined pattern.

Since such a poly-3i TFT has a small photocurrent, there is no increase in OFF current even if no optical shield layer is provided. This means that if a poly-5i TFT is used in, for example, a liquid crystal display device, the amount of charge stored in the liquid crystal layer will leak only small, and sufficient charge can be retained even when the TPT is in the OFF state. ing.

Further, poly-3i TFTs have high mobility and have the advantage that a sufficiently large ON current can be obtained without increasing the channel width. Furthermore, poly-5i TFTs have the advantage that they can be formed on glass substrates and are suitable for large-area applications.

By the way, such poly-3i TFTs often have a high threshold voltage (vth), as shown in Figure 3 (,), and tend to change slowly from the OFF state to the ON state. This tendency is observed.

Therefore, in order to apply TFTs to various fields such as equispectral light sensors and liquid crystal display devices,

It is necessary to reduce vth, increase mobility, and obtain a large ON current.

In order to meet such demands, conventionally, ρol
A method has been adopted in which dangling bonds in the y-5i TFT are filled with hydrogen atoms (hydrogen treatment).

Hydrogen treatment methods include (1) hydrogen plasma treatment in which hydrogen is introduced into the TPT using an 8-coupled hydrogen plasma generation amount, (2) H+ ions are implanted into the TFT and activated by annealing at approximately 400°C. (3) annealing (heat treatment) in a hydrogen atmosphere in which hydrogen is introduced into the TPT using thermal diffusion of hydrogen, and the like.

[Problem to be solved by the invention]

However, the above (1) has a high RF power density (1~ha/f
f1), it is difficult to increase the area of the electrode. This leads to a limit on the number of sheets that TPT can process. It is also conceivable that hydrogen plasma may cause contamination of the electrode gold A1 and the chamber. The problem with (2) above is that the ion implantation device is expensive. Also, the above (3) is the same as the above (1).
Compared to (2), there are fewer hydrogen dose groups and the hydrogen treatment effect is less effective.

However, although these methods (1,), (2), and (3) have advantages as well as disadvantages, in terms of throughput (processing ability), method (3) is the best; (1) is considered to be the worst.

A first object of the present invention is to provide a method for manufacturing a thin film transistor, which eliminates the defects and inconveniences described above, provides good TPT characteristics, and improves throughput. A second object of the present invention is to provide a method for manufacturing a thin film transistor that can be expected to reduce device costs.

[Means to solve the problem]

The method for manufacturing a thin film transistor of the present invention includes poly-3
When hydrogen-treating a thin film slang transistor with i as an active layer in a reactor, a heater and a plasma generator are provided outside the reactor, and a gas containing hydrogen as a main component is introduced into the reactor. It is characterized by the introduction of

Incidentally, the present inventor has added a heating and plasma generation means to the means (3) above to produce a large number of TP sheets.
It has been confirmed that hydrogen treatment of T is possible and that throughput can be significantly improved. The method of the present invention was achieved in this manner. That is, to put it simply, the method of the present invention attempts to perform hydrogen treatment on TPT placed in a reactor (for example, a quartz tube) using a heating section and a plasma generation section provided outside the reactor. be.

In the following, the method of the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an example of an apparatus suitable for the method of the present invention, in which 1 is a reactor, 2 is a TPT, 3 is a heating section (heater), and 4 is a plasma generation section (plasma generator). It represents.

The reactor 1 here is a quartz tube into which H2 gas can be introduced and which can be evacuated. The shape of the reaction 4a1 may be other than a tubular shape, for example, a bell jar shape.

Further, the material of each reactor 1 may be other than quartz, but it is necessary to be careful about contamination from the reactor 1. A TFT 2 is disposed inside the reactor 1, and hydrogen (or a gas mainly composed of hydrogen and nitrogen, if necessary) is introduced into the TFT 2 by the action of a heater 3 and a plasma generator 4.

It is necessary that the temperature of the heating section 3 can be controlled within the range of 350 to 550°C, and a lamp heater may be used to increase the cooling rate at the end of heating, or as the case may be.
It is also desirable to have a cooling mechanism.

If the heating temperature is outside the range of 350-550℃,
Since the substrate temperature is too low or too high, the amount of hydrogen atoms dosed to the TPT does not reach the intended value.

Hydrogen plasma is generated in the reactor 1 by applying a high frequency of 13.56 MHz to the coil-shaped plasma generator 4, but the plasma generation conditions are adjusted by adjusting the amount of vAH2 gas introduced and the degree of vacuum in the reaction tube. Set.

Note that it is also possible to use microwaves or ECR as another plasma generation method.

When poly-5i TFTs are subjected to hydrogen treatment using such a method and apparatus, it is possible to process a large number of sheets by selecting the reactor size, as in the case of the conventional example (3) above, resulting in a significant throughput. Furthermore, by using plasma, the effect of hydrogen treatment on TFTs, which was insufficient with (3) above, can be improved by using plasma (1) and (2) above.
) Same effect as 1! ).

〔Example〕

Here, an apparatus as shown in FIG. 2, that is, a reactor 11
This is a quartz tube with an inner diameter of 250 mm whose both ends are sealed with flanges, and is provided with a gas introduction part and a vacuum exhaust part. In addition, a lamp heater 3 is used as a heating heater provided on the outer periphery of the reactor 11, and this lamp heater 13 and a high frequency coil 14 for hydrogen plasma generation are used.
and placed relative to each other. By adopting such an arrangement, uniformity in heating and discharging of the plurality of TPTs housed in one reactor 11 is ensured.

On the other hand, a quartz substrate (250mm x 50mm x 1
, 6 mm), a MOS type TPT was prepared in which the ρoly-5i film was used as a semiconductor active layer and the thermal oxide film was used as a gate insulating film.

The poly-3L film was manufactured using the LP-CVD method (temperature: 630°C, 1 reaction gas: SiH).

The gate insulating film was formed using a dry oxidation method (temperature: 1025℃).
, reaction gas 0. (3% IICU, flow rate 10103C
C-Niyotte film was formed.

A total of 20 TFTs 12, 10 on the gas upstream side and 10 on the downstream side, were set in the reactor 11 using a quartz boat. Note that dummy quartz plates were also placed at both ends of each of the 10 TFTs 12.

The hydrogen treatment conditions were a substrate temperature of 400°C and a total RF performance.
y -1.5KW, H2 flow rate 50SCCM, pressure 0.
1 torr, and the discharge time was 60 minutes. Also,
The total hydrogen treatment time from setting the TPT substrate to taking it out was 120 minutes.

The TPT characteristics before hydrogen treatment in this example are shown in Figure 3(a).
TPT after hydrogen treatment as shown in
As shown in Fig. 3(b), the characteristics are that the ON current increases and the OFF current decreases significantly, and the hydrogen treatment reduces T.
It can be seen that the PT characteristics were significantly improved.

This improvement result is almost equivalent to the conventional effects (2) and (3).

For comparison, Figure 4 shows the hydrogen treatment effect when TPT before hydrogen treatment is annealed in a hydrogen atmosphere at 400°C.
It is shown as FI' characteristic. It can be seen that the hydrogen treatment of Example 1 has a stronger effect than thermal annealing in a hydrogen atmosphere.

〔Effect of the invention〕

According to the method of the present invention, (i) Compared to the conventional methods (1) and (2), the throughput of the hydrogen treatment process can be significantly improved.

(it) Compared to the conventional example (3) above, a sufficient hydrogen treatment effect can be obtained.

<m) Compared to the conventional example (2) above, effects such as reduction in device cost are recognized.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of two sides of a preferred apparatus for carrying out the method of the present invention. FIG. 3 is a graph showing the TPT characteristics of a poly-5i TFT before and after hydrogen treatment. FIG. 4 is a graph showing TPT characteristics when annealed in a hydrogen atmosphere at 400°C.

Claims (1)

[Claims] (1) When hydrogen-treating a thin film transistor having poly-Si as an active layer in a reactor, a heater and a plasma generator are provided outside the reactor, and hydrogen is mainly contained in the reactor. 1. A method for manufacturing a thin film transistor, comprising introducing a gas.