JPS6043814A - Manufacture of semiconductor crystalline film - Google Patents

Abstract

PURPOSE:To obtain a semiconductor thin film having excellent crystallizability by irradiating an insulating film with an electron beam to recrystallize a semiconductor film after making thicker the thickness of the insulating film on the region with center at an element forming portion than that in the surrounding region. CONSTITUTION:An SiO2 film 12 is formed on 001 single crystal Si substrate 11. Next, after a polycrystalline Si film 13 and an SiO2 film 14 are sequentially cladded on the SiO2 film 12, the SiO2 14 is formed so as to provide an insular convex portion 15. When the SiO2 film 14 is annealed by scanning a CW electron beam, a single crystal containing few defects is obtained under the convex portion 15 of the SiO2 film. A polycrystalline silicon gate electrode 18 is formed via a gate oxide film 17 in the region of the single crystal and impurities are doped to form a source 16 and a drain 19, thereby producing an N-channel transistor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a semiconductor crystal thin film on an insulating substrate using a beam annealing method.

[Prior Art and Its Problems] Conventionally, it has been known that semiconductor thin films on insulating substrates, for example, have advantages over bulk semiconductors, as seen in 5OS (silicon on sapphire). In other words,■
When cutting into islands or performing dielectric isolation, isolation between elements can be easily and reliably achieved. (2) By reducing the pn junction area, stray capacitance can be reduced.

SO8 is expensive because it uses single-crystal sapphire, so it is expensive to use on a fused quartz plate, amorphous SiO2 formed by oxidizing a large Si substrate, an amorphous SiOz film deposited on Si, or an amorphous 8iN film. There is a method in which a semiconductor film is further deposited. Since these 5i02 and SiN are not single crystal films, a polycrystalline film is grown thereon. The grain size of this polycrystalline film is about several hundred x, and even if a MOS transistor is formed on it, its carrier mobility is
OB) It is about one tenth of that of a transistor. In recent years, attempts have been made to increase the crystal grain size by focusing a narrow laser or electron beam and scanning the semiconductor thin film in a pattern to melt and solidify the semiconductor thin film. With this method, crystal grains of several μm, which is 100 times the conventional grain size, can be obtained.
Therefore, the characteristics of devices made on top of it also improve.

However, the device obtained by this method has the following drawbacks. In other words, when measuring the carrier mobility of a MOS transistor with a small area such as a channel length of 6 μm and a channel of 2 μm, we find that
Some are about 400d/v-see, while others are about tens of c.
There are many devices with low l/v-sec L and devices with a large amount of residual leakage current between source and drain. When these causes were analyzed, the following problems were found. In other words, since the energy distribution of laser beams and electron beams has a Gaussian distribution, when the beam is scanned, it causes melting and solidification from the edges of the beam toward the center. Therefore, crystal grains grow finely from the edge of the beam to the center. In such a case, the crystal grain size increases to a certain extent, but it does not reach the point where all the regions in which the device is to be formed are made into single crystals, and the presence of crystal grain boundaries within the region deteriorates the device characteristics as described above. This resulted in deterioration and non-uniformity.

[Purpose of the Invention] This invention was made in view of the above-mentioned circumstances, and it is possible to melt a semiconductor thin film by electron beam irradiation and suppress the growth of nuclei from the edge of the beam during solidification, thereby making it possible to form polycrystalline polycrystalline films. The purpose is to provide a method for obtaining excellent semiconductor thin films.

[Summary of the invention] In the present invention, an insulating film 0 is deposited on a semiconductor film on an insulating substrate,
Part or all of the insulating layer outside of the predetermined island-shaped area was removed, and the thickness of the insulating film on the area of the semiconductor film centered on the element formation area was increased even further than that of the area 1711 around the area. After that, the semiconductor film is recrystallized by irradiating it with an electron beam.

[Effects of the Invention] According to the present invention, when a semiconductor thin film is irradiated with an electron beam, the energy input to the island-shaped portion of the semiconductor thin film covered with a thick insulating film is greater than that of the part covered with a thin insulating film. Since there is less oxidation, the solidification process starts faster than the surrounding area in the solidification stage after melting. Therefore, crystal growth must proceed from the island-like area covered with a thick insulating film to its surroundings without creating grain boundaries, and the characteristics of the device fabricated in that area will be uniform and excellent. becomes.

[Embodiments of the Invention] The present invention will be described in detail with reference to FIGS. 1(a) to (d). First, a 1 μm thick 5 iOz film is formed on a (001') single crystal Si substrate 11 (FIG. 1(a)).

Next, a polycrystalline Si film 12 with a thickness of 0.6 ttm is placed on top of the polycrystalline Si film 12.
After the SiO2 film 13 of 0.3 μm is deposited for the first time (FIG. 1 (+))), island-shaped convex portions 15 are formed on the 5IO2 film 13 by phosphorography. At this time, the areas other than the convex portions are etched to a depth of 1 μm (
Figure 1 (C)). For the prototype made in this way,
Annealing was performed by focusing a CW electron beam to a beam diameter of 150 μm and scanning with an acceleration energy of 7 eV, a beam current of 2.5 mA, and a step width of 10 μm. When the crystallinity of the Si film 13 after annealing was evaluated using a transmission electron microscope, it was found that under the 5i02 film convex portion 15, it was a single crystal containing almost no defects. In this single crystal region, a polycrystalline silicon gate electrode 18 is formed through a 600X gate oxide film 17, and an impurity is doped to form a source 15 and a drain 19. An n channel with a channel length of 4 μnl and a channel width of 8 μm. A transistor was made (Figure 1(d)). The effective carrier mobility was measured and was 800 cffl/v-see.
It was confirmed that the results were almost the same as those using bulk St. Also, 'I?' when forming similar number of area KMO8) transistors? The uniformity of the properties was also excellent. Furthermore, even when elements are present on the 3i substrate 11,
A device with the same excellent characteristics as above is S i Jl
It was found that the method can be formed to a p4 size and is sufficient as a method for manufacturing a laminated device.

In the above example, Sl was used for the thin film, but Ge
, GaAs, etc., and it is clear that the effect is not diminished depending on the material and formation method of the underlying substrate insulating film. Of course, the shape and size are not limited to these.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) are process sectional views illustrating an embodiment of the present invention. 11...Single crystal 3i substrate, 12...8 i0z film, B...polycrystalline SIs 14...S iOz film, 1
5... Convex portion, 16... Source, 17... Gate oxide tube, 18... Gate electrode, 19 - Drain. (7317) Kasuke, close to patent attorney (and 1 other person) Figure 1

Claims (1)

[Claims] The method includes a step of depositing a semiconductor film on an insulating substrate, and a step of depositing an insulating film on the semiconductor film, and after removing part or all of the insulating film outside the desired island-shaped region, A method for producing a semiconductor crystal thin film, which comprises irradiating the substrate with an electron beam.