JPS5837917A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve singlecrystallization by crystallizing a non-singlecrystal Si in a well-controlled manner after being subjected to the energy beam irradiation through the use of the crystallizing temperature difference in terms of the impurity density. CONSTITUTION:A non-singlecrystal semiconductor (a polycrystalline Si for instance) 4 is formed via an insulating film (a gate oxide film here) 3 on a substrate 1, and this non-singlecrystal semiconductor 4 is single-crystallized by enlarging its crystal grains by means of the energy beam irradiation. In that case the impurity density in the non-singlecrystal semiconductor region 4 is made partially varied beforehand. For instance, ions are implanted by using an SiO2 film 5 as a mask so that the impurity density at the peripheral parts of the region 4 is made higher than that of the center parts. Because of this, crystallization after the energy beam irradiation starts from the low impurity density parts at the center and proceeds to the higher density parts, thereby enlarging crystal grains.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for enlarging crystal grains of non-single crystal silicon or for single crystallizing it.

In the development process of semiconductor devices, non-single crystal silicon, polycrystalline silicon, or amorphous silicon is irradiated with an energy beam, that is, a beam of light or an electron beam, to enlarge its crystal grains or to expand a certain region. The non-single-crystal silicon to be formed is made into single-crystal silicon.

In this case, for each non-single crystal silicon region,
In general, the temperature at the periphery is lower than that at the center, and crystallization after melting is more likely to start from the periphery. Measures are required to achieve this objective (e.g., for single crystallization by original beam irradiation, the reflectance of the light beam in the central part of the target non-single crystal region is higher than that in the surrounding parts) A method in which the temperature of the central part is lower than that of the surrounding part, the central part reaches the crystallization temperature first, and the crystallization progresses from here toward the periphery to achieve single crystallization,
Or for single crystallization by irradiation with arbitrary energy beams,
By making the thermal resistance between the central part of the target non-single crystal inclined wall and the bottom surface of the substrate lower than the thermal resistance between the other parts of the non-single crystal region and the bottom surface of the substrate. , a method of proceeding crystallization from the center toward the periphery has been proposed.

However, the above method is subject to limitations such as requiring precise control of the thickness of the thin film for which optical interference is applied, or its application may be limited depending on the structure of the target semiconductor device. ing.

An object of the present invention is to achieve the expansion of the crystal grains of non-single-crystalline silicon by energy beam irradiation, or to increase the single-crystal ratio by a method that is familiar to and widely applicable to semiconductor device manufacturing methods.

The object of the present invention is to partially change the impurity concentration within the non-single crystal silicon region, for example, by making the impurity concentration in the peripheral part of the region higher than in the central part. Since the crystallization temperature in the areas with high impurity concentration is lower than in the areas with low impurity concentration, crystallization after irradiation with energy beams is achieved by starting from the areas with low impurity concentration and progressing to the areas with high impurity concentration. .

Hereinafter, the present invention will be specifically explained using examples and drawings.

First #I, Figure 1 shows arsenic (As) as an impurity in silicon.
) is shown as a function of the impurity concentration and the crystallization temperature when implanted. As shown in Figure 1, the crystallization temperature is As 1lJW4
1410'cf4 at x 10 t'/cd
While there is V Te, A8 density is 1.5 x 10! l
/d, it changes by about 1300°C, and if the A+s concentration is further increased, it approaches the eutectic temperature of 1073°C.

By applying this difference in crystallization temperature and cooling due to impurity concentration,
MO3 type field effect transistor (hereinafter referred to as MO8FE)
An example of enlarging the crystal grains of polycrystalline silicon constituting the gate (referred to as T) will be described.

FIG. 2 is a cross-sectional view of this embodiment, in which a field insulating film 2 is selectively formed on a P-type silicon substrate 1 by thermal oxidation, and then a gate oxide film 3 is formed to a thickness of approximately 40 mm. death,(
A polycrystalline silicon film 4 is formed to a thickness of approximately 500° C. by thermal decomposition of monosilane (SiH) at 600 to 700° C.
m-ic shadow formation. Next, a silicon oxide (810 g) film 5 is formed by chemical vapor deposition using monosilane to a thickness of about 150%. After that, the silicon dioxide film 5 and the polycrystalline silicon film 4 are selectively removed to form a gate electrode. form. After that, silicon dioxide M5 on the gate electrode
As shown in FIG. 3, a portion having a width of 10 .mu.S around the entire periphery is selectively removed.

Next, As+ ions were applied to xx1016/c at 120KeV.
After performing ion implantation at a dose of 11, irradiate the substrate pre-heated to 500°C with a 15W continuous wave laser beam diameter of about 50μ and a scanning speed of about 10aa/sec. Heat treatment was carried out by this.

As a result, the size of the polycrystalline silicon crystal grains forming the gate electrode is several tens of nanometers before the heat treatment, but after the heat treatment, the size significantly increases to several tens to several meters. expanded, and the resistivity value is several too
m/jl was obtained.

In addition to the above-mentioned embodiments, for example, an SIO (8
111con On In5ulatinf, mubg
In the manufacturing process of a semiconductor device with a trate) structure, when island-like isolated regions made of non-single crystal silicon on an insulating substrate surface are made into single crystals by irradiation with energy beams,
It is possible to implement the invention in exactly the same way.

In this case, if impurities in the peripheral area of the formed single crystal silicon region are inconvenient, the problem can be solved by selectively removing the area or using an insulator such as oxide. It is.

When the width of the region to be single-crystallized is approximately equal to the diameter of the irradiating beam, grain expansion is achieved by increasing the impurity concentration along both edges of the region to saddle the energy distribution of the irradiating beam. A similar effect can be obtained by using the Saddl.) type. Generally, when the pattern of the target area is rectangular, it is desirable to scan the energy beam in the long side direction of the rectangle.
Favorable results can be obtained if the impurity concentration is varied stepwise or continuously from the periphery or both ends of the target non-single crystal region toward the center.

As explained above, the present invention expands crystal grains of non-single crystal silicon by energy irradiation, or crystallization after energy irradiation starts from a region with a low impurity concentration and moves to a region with a high impurity concentration. By making progress, the goal will definitely be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a change in crystallization temperature due to an impurity source Flχ, and FIG. 2 is a cross-sectional view showing an embodiment of the present invention.
The figure is a plan view showing an embodiment of the present invention. In the figure, 1 is a substrate, 2 is a field insulating film, 3 is a gate oxide film, 4 is a polycrystalline silicon film, and 5 is a silicon dioxide film.

Claims (1)

[Claims] A method for manufacturing a semiconductor device in which a region made of a non-single crystal semiconductor is formed on a substrate, and the non-single crystal semiconductor is melted and crystallized by irradiation with energy beams to enlarge crystal grains or to make the region a single crystal. A method of manufacturing a semiconductor device, characterized in that the irradiation with the energy beam is performed while partially changing the concentration of impurities in the non-single crystal semiconductor region.