JPS62266819A - Formation of semiconductor thin film - Google Patents

Abstract

PURPOSE:To form a high mobility element in good reproducibility by giving the damage of ion implantation to a semiconductor layer to have the value of required ESR center density. CONSTITUTION:A semiconductor thin film is formed by heat treatment after 1.03X10<19>/cm<3> or more damages due to ion implantation of ESR(electron spin resonance) center density are given to a semiconductor layer. This enables realizing high mobility element characteristics without giving any bad effect to the reproducibility of an element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a semiconductor thin film for forming a semiconductor element such as a TPT (thin film transistor), and particularly to a method for forming a semiconductor thin film that achieves high mobility.

[Summary of the invention]

The present invention relates to a method of growing crystals to form a semiconductor thin film for use in semiconductor devices.
4 fX as ESR center density 1.03XIQIS pieces/c
113 or more and heat-treating it, a thin film exhibiting high mobility can be obtained.

[Conventional technology]

Generally, as a method for forming a thin film semiconductor layer for use in a semiconductor element such as a TPT (thin film transistor), polycrystalline silicon is deposited on a semiconductor substrate such as a silicon substrate or an insulating substrate by a method such as CVD, and then annealed. Heat treatments such as these are used to promote grain growth and improve mobility.

Here, if we present and explain specific numerical values, for example, L
The particle size (grain size) of a polycrystalline silicon layer deposited by a method such as the P-CVD method (low pressure CVD method) is about 50 to 200 grains in terms of pleasure. If annealing treatment of about 100'c is applied to the crystalline silicon layer, the grain size of the polycrystalline silicon layer will grow by about 800 people.

[Problem that the invention seeks to solve]

However, due to the demand for higher density devices, the channel length must be shortened or the thickness of the semiconductor thin film must be increased from 200 to 400 mm.
When a film is made to be as thin as a human being, variations in device characteristics become noticeable, and even if heat treatment such as annealing is performed simply to obtain high mobility, reproducibility becomes a problem.

Furthermore, if the intention is to further improve the performance of the device, it is necessary to grow the grain size to an even larger size to achieve high mobility, and the above-mentioned method will not necessarily meet that requirement. I can't say.

On the other hand, ion implantation is performed before heat treatment such as annealing,
A method is also known in which a semiconductor thin film is made amorphous and then subjected to heat treatment to increase the grain size.

However, it is not easy to quantify the degree of amorphization based on the dose of ion implantation, and it is difficult to quantify the degree of amorphization depending on the dose of ion implantation, and it is difficult to quantify the degree of amorphization due to the trend toward miniaturization, which requires a high degree of reproducibility. I can't say it.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention aims to provide a method for forming a semiconductor thin film that achieves high mobility device characteristics without any adverse effect on device reproducibility.

[Means for solving problems]

The present invention performs ion implantation into a semiconductor layer to eliminate damage thereto.
SR (electron spin resonance) center density is 1゜03 x 10
The above-mentioned problems are solved by a method of forming a semiconductor thin film in which heat treatment is performed after applying an IS (II/cI of 13 or more).

[Effect]

For example, by implanting ions of Si or the like into a semiconductor layer made of silicon, covalent bonds of Si-3i bonds are broken and dangling bonds increase. Such dangling bonds contribute to the capture and scattering of free electrons, affect electrical conductivity, and directly quantify the degree of amorphization of silicon, etc.

Based on these facts, the present invention reliably grasps the amount of the dangling bonds through ESR analysis, and calculates this with an ESR (electron spin resonance) center density of 1.03XIOl.
By setting the number of particles/cs to 3 or more, a semiconductor thin film that achieves high mobility can be obtained.

This makes the ESR center density 1.03X101! piece/cIm
When the value is 3 or higher, a phenomenon of critical electrical mobility improvement can be found, and ion implantation that causes damage to the value of the ESR center density described above can reliably create a high mobility element. It can be formed with good reproducibility.

Here, ESR (electron spin resonance) analysis measures the transition of electron spin from a low energy state to a high energy state, and is a phenomenon in which degenerate levels transition in a magnetic field (Zeeman effect). ) is quantified by the amount of energy (hν) absorbed in the microwave band, and in the present invention, the amount of the dangling bonds can be determined by the strength of absorption of microwaves of 9.5 GHz, for example. .

〔Example〕

Examples of the present invention will be described based on experimental examples.

The method for forming the semiconductor thin film in this experimental example is to first form a polycrystalline silicon layer as a semiconductor layer using the LP-CVD method.
0℃r S t A mixed gas of H4 gas and He gas (20%) was used, and the vacuum degree was 70 Pa.

Approximately 800 people were deposited at a deposition rate of 60 to 70 people/min.

Next, using Si (silicon) ions as ions to be introduced into such a polycrystalline silicon layer, a 40ke
A sample was prepared with an implantation energy of V and a dose amount of the following capacity.

(Hereinafter, blank spaces) Table 1 Here, for each of the samples ■ to ■, except for sample ■, ion implantation was performed at the predetermined dose described above, and as a result of this ion implantation, the polycrystalline silicon layer was damaged ( damage), the covalent bonds in the polycrystalline silicon layer are broken, and the amount of dangling bonds increases.

Note that the ions to be introduced are not particularly limited to Si ions, and may be other electrically inactive elements or other high-energy particles.

Then, the ESR center density corresponding to each of the above-mentioned doses was measured, and the results shown in Table 2 below were obtained. The measurement was performed at a microwave output of 8.0 mW, ±50 mT during magnetic field sweep, and 6.3 mT during modulation.
μT, 1ilJ It was conducted at a constant temperature of -120°C.

Table 2 These ESR center density values directly represent the amount of dangling bonds in the polycrystalline silicon layer of the sample. The film was made ultra-thin from 800 to 200, and as a result of heat treatment, it was annealed at a low temperature of about 600°C and then annealed at a high temperature of about 1000°C. As a result, the mobility and ESR center as shown in Figure 1 were reduced. A correlation of density values has been obtained. In Fig. 1, * is the sampling point, the horizontal axis shows the ESR center density (fll/cm3), and the vertical axis shows the mobility (crm2/'J・5).
ec), and in addition to the data of the above samples ① to ②, other data are also supplemented and shown.

As shown in Figure 1, the mobility is ESR center density 1.0
It shows critical behavior from 3×101 pieces (pieces/piece 3), and the ESR center density is 1.03×1015 (pieces/piece 3).
) A sample having an ESR center density value of greater than or equal to ) will certainly have the property of high mobility.

Therefore, as is clear from the above experimental example, ES
The value of R center density can directly quantify the amount of dangling bonds in a semiconductor thin film, and as shown in FIG.
By damaging the semiconductor thin film by ion implantation so that it has an ESR center density value of cts3) or more, a high mobility element can be reliably formed with good reproducibility.

By the way, during annealing at a low temperature of about 600° C., grain size already grows, and the grain size has grown to about 2,500 to 10,000 grains. At this time, it is in a dendritic state, and there are so-called twin crystals in the crystal.
It is possible to obtain polycrystalline silicon crystal grains having many crystal defects such as a lamellar structure, and it may be possible to achieve similar effects by using such a crystal mechanism.

In addition, in the above-mentioned experimental example, a polycrystalline silicon layer was used as a semiconductor layer, but the semiconductor layer is not limited to this and may be made of other materials.

〔Effect of the invention〕

As described above, the method for forming a semiconductor thin film of the present invention is based on the ES
The value of the R center density can directly quantify the amount of dangling bonds in the semiconductor thin film, and the value of the R center density can directly quantify the amount of dangling bonds in the semiconductor thin film.
t of ion implantation into the semiconductor layer to have the value of the central density
By providing i-wounds, it is possible to reliably form high-mobility elements with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the correlation between ESR center density and mobility based on an experimental example for explaining the method of forming a semiconductor thin film of the present invention. Patent applicant Sony Corporation agent Patent attorney Koike Mima Sakae Tamura

Claims (1)

[Claims] A method for forming a semiconductor thin film in which ions are implanted into a semiconductor layer to cause damage to the ESR center density of 1.03×10^1^9 ions/cm^3 or more, and then heat treatment is performed.