JPH04180617A - Manufacture of large crystal grain-sized polycrystal silicon and thin film semiconductor using same - Google Patents

Abstract

PURPOSE:To solid-phase crystallize amorphous Si and manufacture large grain size polycrystal Si by using said amorphous Si whose oxygen concentration does not exceed a specific amount. CONSTITUTION:In a method which manufactures large crystal grain-sized polycrystal Si by solid-phase crystallizing the amorphous Si, amorphous alpha-Si is adopted where oxygen concentration does not exceed 1X10<18>atoms/cm<3>. More specifically, alpha-Si is deposited on an insulation board or an insulation film. In that case as the deposition speed is increased, the oxygen contained in the alpha-Si is decreased. If it is necessary to reduce the concentration of oxygen to 10<18>atoms/cm<3> and lower, at least 50Angstrom /min must be called for. The alpha-Si, thus obtained is solid-phase crystallized. This construction makes it possible to obtain a large grain sized-polycrystal Si by keeping the temperature at 550 to 600 deg.C and crystallizing it.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a method for producing Poly-Si having a large crystal grain size, and a method for producing Poly-Si having a large crystal grain size obtained by the method.
A thin film semiconductor (hereinafter referred to as
(abbreviated as TPT).

[Prior art]

TPTs using Poly-Si as a semiconductor active layer are being actively researched as drive elements or circuits for various devices. In order to improve the mobility of this Poly-Si TFT, it is essential to increase the crystal grain size of Poly-Si.

Lt, a-S as a manufacturing method of large particle size Poly-Si
A solid-phase crystallization method for i has been proposed (G, Negeba
ued.

H, F. Kappert, J. Electroche.
m,Soc:5OLID-5TATESCIENCE
AND TECHNOLOGY, March, 19
84. P675).

It has also been reported that in order to increase the grain size of Poly-Si through this a-Si solid phase crystallization, it is preferable to lower the deposition temperature of a-Si.
89 Society of Physical Science and Metal Physics Classification No. 27. P-c-4).

However, the effect of a-Si on Poly-5L particle size.

This cannot be explained simply by the deposition rate.

Not everything is clear. Actually, Si,
)f as a reaction gas and when SiH4 is used as a reaction gas, as seen in FIG. 3, there is a considerable difference in the average crystal grain size.

As described above, when examining the grain size of Poly-Si crystallized in the same phase, there are aspects that cannot be explained only by the a-5L deposition temperature.

〔the purpose〕

An object of the present invention is to provide a novel method for producing Poly-Si having a large crystal grain size.6 Another object of the present invention is to provide TPT with high mobility.

〔composition〕

As a result of repeated research on a method of solid-phase crystallizing a-Si to obtain Poly-Si with a large crystal grain size, the present inventor has found that
It was discovered that oxygen present in a-Si was the cause of inhibiting crystal growth, and the present invention was completed.

That is, the first aspect of the present invention is a method for manufacturing polycrystalline silicon (hereinafter abbreviated as Poly-Si) with a large crystal grain size by solid-phase crystallizing amorphous silicon (hereinafter abbreviated as a-Si). The present invention relates to a method for producing Poly-Si having a large crystal grain size, characterized in that the a-Si has an oxygen concentration of I x 10'' atoms/am3 or less.

The second aspect of the present invention is that the oxygen concentration I
5acs" a-Si under R is 50λ/
■Claim 1, which is formed at a deposition rate of at least 1.5 in.
The present invention relates to a method for producing Poly-Si having a large crystal grain size as described above.

A third aspect of the present invention is as set forth in claim 1 or 2, wherein the a-Si having an oxygen concentration of lXl0'', preferably 5 x 101017ato/Cm'' or less, is formed by an LP-CVD method at a temperature of 500°C or less. Poly-
The present invention relates to a method of manufacturing Si.

A fourth aspect of the present invention relates to a thin film semiconductor characterized in that the poly-Si having a large crystal grain size obtained according to claim 1 is used as a semiconductor active layer.

The present invention will be explained in detail below.

A-Si is deposited on an insulating substrate or an insulating film. In order to obtain a-5L with a low oxygen concentration, it is best to use an evaporation method in an ultra-high vacuum.However, in order to increase the throughput, methods such as LP-CVD, sputtering, and p-cvo are recommended. It is also possible to use In this case, one of the very important conditions is the deposition rate, although sufficient attention must be paid to gas purity, leakage and contamination from the chamber, etc. The higher the deposition rate, the less oxygen in a-Si, but in order to achieve an oxygen concentration of 10"ato s/Cm' or less, it must be at least 50 people/win.0For example, LP-Si To achieve this deposition rate with the CVD method, it is necessary to use a reactive gas such as disilane or trisilane.
At the same time, the deposition temperature is preferably below 500°C.

The a-Si obtained by the above method is solid-phase crystallized. Crystallization takes place at a temperature of 600°C or higher.

If the temperature is too high (ex 700°C, 800°C), many crystal nuclei will be generated, making it impossible to increase the grain size.

For this reason, it is preferable to maintain the temperature at 550 to 600°C for crystallization.

The particle size of the thus obtained Poly-Si was examined by TEM observation, and it was confirmed that it was largely crystallized. Furthermore, a FT using this Poly-Si was fabricated and its mobility was evaluated, and it was confirmed that the mobility was high.

This will be explained below using examples.

[Example 1] 1000 a-Si layers were deposited on a quartz substrate by LP-CVD at a substrate temperature of 500°C. SiH4 was used as the reactive gas.
Alternatively, Si and HG were used, and the pressure during deposition was changed to vary the deposition rate in the range of 7 people/win to 70 people/win. Then, these a-Si were heated to 600"C,5
By thermal annealing for 0 hours, the Poly
-Si was obtained. Then, the crystal grain size was observed by TEH. At the same time, in order to examine the oxygen concentration in a-Si, 4,000 to 6,000 a-Si deposited at different deposition rates were deposited on single-crystal Si, and SIMS analysis was performed. In SIMS analysis, a single-crystal Si substrate is used to prevent charge-up during analysis, and the reason why the film is thick is to eliminate the adverse effect on analysis caused by adsorbed substances on the film surface. The analyzer is CAKECA IN5-
It is on the 4th floor.

Figure 1 shows the degree of a-Si deposition and solid phase crystallization of Poly-S.
The relationship between i and the average grain size is shown. The average grain size is T
The results were calculated by determining the number of grain boundaries present per unit length in the EM transmission image.

As is clear from FIG. 1, the higher the deposition rate, the larger the average crystal grain size. Further, Table 1 shows the relationship between the deposition rate and the oxygen concentration in a-Si.

It is clear from Table 1 that the higher the deposition rate, the lower the oxygen concentration. From the above results, it is clear that the lower the oxygen concentration in a-Si, the larger the particle size of Poly-Si can be obtained.

Now, in order to clarify the relationship between oxygen in a-Si and crystal growth, the crystal growth rate was determined from the relationship between the annealing time and the average crystal grain size, and the relationship with the oxygen concentration was investigated.

The results are shown in Figure 2. When the oxygen concentration in 6a-Si was 10”a
It was found that the crystal growth rate increased rapidly below toms/Cm3. [Example 2] A MOS-TFT was manufactured using Poly-3i manufactured in Example 1 as a semiconductor active layer. The TPT fabrication process is similar to the conventional C-MOS process [the gate oxide film is formed using the dry oxidation method (1020°C, film thickness 700°C), and the source and
The drain is a self-line process using ion implantation. ], and finally hydrogen plasma treatment was performed.

Table 2 shows the mobility of Nch-TPT. It can be seen that the mobility of TPT using solid phase crystallized Poly-Si is significantly improved by setting the oxygen concentration in a-Si to 10"atoms/cm" or less.

Table 2 [Effects] According to the method of the present invention, the crystal growth rate in in-phase crystallization is significantly increased, so that Poly-Si with a large crystal grain size can be obtained.

In addition, 1 Poly-Si obtained by the method of the present invention was
When used in the active layer of FT, because the crystal grain size is large, TP
T mobility was significantly improved.

[Brief explanation of the drawing]

Figure 1 shows the degree of a-Si deposition and solid phase crystallization of Poly-S.
Figure 2 shows the relationship between the average crystal grain size of i, and Figure 2 shows the relationship between the crystal growth rate and the oxygen concentration in a-5L. The relationship with the diameter is SiH
4 and Si2Hs have different relationships.

Claims (1)

[Claims] 1. In a method for producing polycrystalline silicon (hereinafter abbreviated as Poly-Si) with a large crystal grain size by solid-phase crystallizing amorphous silicon (hereinafter abbreviated as a-Si) , the oxygen concentration as the a-Si is 1×10^1^5a
A method for producing Poly-Si with a large crystal grain size, characterized by using Poly-Si with a crystal grain size of toms/cm^3 or less. 2. The oxygen concentration is 1 x 10^1^5 atoms/cm^
2. The method for producing Poly-Si with a large crystal grain size according to claim 1, wherein the a-Si under 3 is formed at a deposition rate of 50 Å/min or more using a reaction gas containing silicon hydride. 3. The oxygen concentration 1×10^1^5atoms/cm^
3. The method for producing Poly-Si with a large crystal grain size according to claim 1 or 2, wherein the a-Si having a diameter of 3 or less is formed by an LP-CVD method at a temperature of 500° C. or less. 4. Poly-S with large crystal grain size obtained according to claim 1
A thin film semiconductor characterized in that i is a semiconductor active layer.