JPS63198373A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate the high resistance due to a grain boundary and to eliminate the obstruction to miniaturization due to grain growth by making use of a single crystal for a gate electrode. CONSTITUTION:An insulating film 2 is formed on a silicon substrate 1; a single- crystal film 3 is formed on the insulating film by the selective transverse- direction growth of a single crystal, e.g. single-crystal silicon, as a seed from an opening at this insulating film 2; this single-crystal film 3 is used for a gate electrode. After the single-crystal film 3 to be used as the gate and the silicon substrate 1 have been grown, they are separated by etching. As a single-crystal substrate, a III-V compound semiconductor substrate such as a germanium substrate or a GaAs substrate can be enumerated in addition to the silicon substrate. By this setup, because no crystal boundary exists inside, the resistance is lowered; the operating speed of a device is increased; at the same time, because the surface is flat and uneven parts are hardly formed thanks to the single crystal, a fine patterning process is executed easily; both the high speed and the high integration can be realized.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a semiconductor device and a method for manufacturing the same.

[Conventional technology] Conventionally, silicon MOS (Metal-Oxide-
3emi-constructor) The gate electrode of the transistor is made of polycrystalline silicon 2 as shown in FIG.
9 is used. In the figure, 30 is a silicon substrate, and 31 is a gate oxide film. This structure is formed by depositing polycrystalline silicon, patterning it, and implanting impurity ions.

[Problems to be solved by the invention] Because polycrystalline silicon has internal grain boundaries, its resistance is higher than that of single-crystal silicon, and when polycrystalline silicon is used as the gate electrode of a MOS transistor, the device This was causing a decrease in operating speed. In addition, since grain growth of crystal grains becomes more apparent as the film thickness increases, unevenness becomes noticeable, making it difficult to pattern fine elements, which is a cause of hindering the miniaturization of elements. SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device and a method for manufacturing the same that solve the above-mentioned problems.

[Means for Solving the Problems] That is, the present invention provides a semiconductor device characterized in that a single crystal is used as a gate electrode, and a semiconductor device characterized in that a single crystal is used as a gate electrode, and a single crystal substrate is formed by providing an opening in an insulating film formed on the single crystal substrate. A method for manufacturing a semiconductor device, characterized in that the single crystal substrate is exposed, and selective epitaxial growth is performed on the exposed single crystal substrate to laterally grow a single crystal also on the insulating film to form a single crystal gate film. be.

The structure of a semiconductor device according to the present invention is as shown in FIG. 1 when a silicon substrate is used as a single crystal substrate. In the figure, 1 is a silicon substrate, 2 is an insulating film, and 3 is a single crystal film. In this invention, an insulating film 2 is formed on a silicon substrate 1, and a single crystal film 3 is formed on the insulating film by selective lateral growth using a single crystal, for example, single crystal silicon, as a seed from an opening in the insulating film 2.
is formed, and this single crystal film 3 is used as a gate electrode.

After growth, the single crystal film 3 used as a gate and the silicon substrate are separated by etching.

As the single crystal substrate in the present invention, in addition to a silicon substrate, a germanium substrate or a V compound semiconductor substrate such as a Ga--As substrate can be used.

Furthermore, when a silicon substrate is used, the single crystal film may be silicon that becomes a homo-epitaxial film with respect to the silicon substrate, or may be a metal silicide or metal that becomes a hetero-epitaxial film with respect to the silicon substrate. Although a silicon substrate will be explained below as an example, the same thing can be done with other semiconductor substrates as well.

[Function] When single-crystal silicon, single-crystal metal silicide, or single-crystal metal is used, unlike polycrystalline silicon, there are no internal grain boundaries, so the resistance decreases and the operating speed of the device increases. In addition, since it is a single crystal, the surface is flat and there are not many irregularities, so it is easy to perform fine patterning, and it can be expected to achieve high speed and high integration. Furthermore, by appropriately selecting the direction of the pattern, anisotropic etching can be effectively utilized during patterning. Since anisotropic etching uses single crystal, it has the characteristic that size and shape can be minutely controlled during patterning.

When selectively growing single-crystal metal silicide or single-crystal metal, more defects may occur than in single-crystal silicon, but this is not a problem compared to grain boundaries in polycrystalline silicon.

In the case of single-crystal silicon, it is possible to create a low-resistance silicon layer by putting impurities into the substrate opening at a high concentration and taking advantage of the impurities being incorporated into the growing silicon layer, or by doping during growth. It can also be formed.

[Example] Next, the present invention will be explained by examples.

Example 1 FIG. 2 is a process diagram for explaining an example of the present invention. FIG. 2(a) shows a state in which a thin silicon oxide film 5 is formed on a single crystal silicon substrate 4, and then an opening 6 is formed in the silicon oxide film using hydrofluoric acid. In the figure, 5
A is a silicon oxide film that will become a gate oxide film in the future. FIG. 2(b) shows, for example, 5il-hcj2 as the raw material gas.
This shows a state in which a thick single crystal silicon film 8 is formed on a substrate by selective growth using HCU and HCU. At the initial stage of growth, the single crystal silicon film 8 grows selectively only on the opening 6, but when the thickness of the single crystal silicon exceeds the thickness of the silicon oxide film 5, it grows laterally onto the silicon oxide film 5. start. When the single crystal silicon film 8 is grown thickly, the single crystal silicon film 8
comes to completely cover the silicon oxide film 5. After that, the single-crystal silicon film 8 is patterned, and then impurity atoms are ion-implanted using a normal process, and a source or drain is formed in the region 10 using a self-aligning process, as shown in FIG. 2(C). A basic structure of a MOS transistor with a gate 9 made of single crystal silicon was formed.

Embodiment 2 A second embodiment of the present invention includes a method in which impurity atoms are ion-implanted shallowly and at a high concentration into the opening 6 in the state shown in FIG. 2(a). If silicon is selectively grown in such a state as shown in FIG. 2(b), impurity atoms are taken into the single crystal silicon film 8, and the gate can be doped with impurities to some extent. There are at least two advantages to using this method.

First, the implantation depth can be made shallow during the subsequent ion implantation of impurity atoms, the implantation time can be shortened, and damage to the crystal can be reduced. Secondly,
It is possible to perform ion implantation annealing at a low temperature and in a short time. Doping the impurity into the gate using this method is advantageous when forming an 0MO8 (complementary MOS) because the impurity in the seed region is doped.

Embodiment 3 As a third embodiment of the present invention, doping may be performed in the growth state shown in FIG. 2(b).

The advantages are the same as in Example 2, but compared to Example 2, it is advantageous in that high concentration doping is possible, and 0MO3
This is disadvantageous in that growth must be performed twice in the case of formation, etc.

Embodiment 4 FIG. 3 shows a fourth embodiment of the present invention in which a pattern in a specific direction is used. As a board (ioo)
A pattern is cut in the <110> direction using the silicon substrate 11, and after selective growth of the single crystal silicon film 12, the silicon oxide film 13 formed on the surface of the single crystal silicon film 12 is patterned, and a selective etching solution such as hydrazine is applied. When etching is carried out using the silicon oxide film 13, the (111) plane 14 tends to appear, so it was possible to create a shape with good controllability without much over-etching from the edge of the silicon oxide film 13, as shown in FIG. .

Example 5 FIG. 4 is a process diagram of a fifth embodiment of the present invention.

The substrate structure before growth is shown in FIG. 4(a). A thick silicon oxide film 16, a thin silicon oxide film 17, and an opening 18 are formed on the silicon substrate 15.

FIG. 4(b) shows a state in which a single crystal silicon film 19 is selectively grown to a thickness of about the same thickness as the thick silicon oxide film 16.

A structure is created in which the region without the thick silicon oxide film 16 is flattened and buried with the single crystal silicon film 19. Then the fourth
A groove 20 is formed by etching as shown in Figure (C),
Separating the gate 21, source 22, and drain 23,
A MOS transistor was formed by filling the trench 20 using oxidation or the like. In the case of such a structure, it is desirable to employ the doping method shown in Example 2 or Example 3.

Example 6 FIG. 5 shows a sixth embodiment of the invention.

FIG. 5 is a diagram corresponding to FIG. 2(b), in which a thin silicon oxide film 25 and its opening 26 are formed on a single crystal silicon substrate 24, and the silicon substrate in the opening 26 is An impurity doped portion 27 is formed by doping impurity atoms by ion implantation. A tungsten film 28 was selectively grown using WF6 as a raw material gas in the same manner as in FIG. 2, and gate metal and contact (tungsten) regions were formed by patterning.

Further, by using MOF6 as the source gas, the gate metal and the contact region can also be formed of molybdenum.

[Effects of the Invention] As described above, according to the present invention, problems such as high resistance due to grain boundaries and inhibition of miniaturization due to grain growth, which are problems when polycrystalline silicon is conventionally used as a gate, can be avoided. A semiconductor device and a method for manufacturing the same can be provided.

In addition, in the process of forming such a device, selective etching can be performed using single crystallinity, and doping methods can be selected according to the purpose and doping can be performed efficiently. Further, by changing the thickness of the oxide film on the substrate, it has the advantage that it can be combined with a fine element isolation structure, allowing various applications depending on the structure and configuration of the semiconductor device.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial cross-sectional view of a semiconductor device of the present invention, and FIG.
5 are schematic partial sectional views of a semiconductor device showing an embodiment of the present invention, and FIG. 6 is a schematic partial sectional view of a conventional semiconductor device. 1, 15.30...Silicon substrate 2...Insulating film 3...Single crystal film 4, 2
4... Single crystal silicon substrate 5, 17.25... Thin silicon oxide film 5, 18.2
6... Openings 8, 12.19... Single crystal silicon film 9.21...
Gate 10...source or drain region 11...(1
00) Silicon substrate 13... silicon oxide film 14.
...(111) plane 16...Thick silicon oxide film 20...Groove 22...
・Source 23...Drain 27...
Impurity doping part 28... tungsten film 29...
...Polycrystalline silicon 31...Gate oxide film agent Chieko Tateno 3! ! f-Rangchang gland 2 do I pull back 1 silico) base 4 anti Figure 1 Figure 3 Figure 2 Figure 4

Claims (2)

[Claims] (1) A semiconductor device characterized by using a single crystal as a gate electrode. (2) An opening is formed in the insulating film formed on the single crystal substrate to expose the single crystal substrate, and selective epitaxial growth is performed on the exposed single crystal substrate to form a single crystal on the insulating film. 1. A method for manufacturing a semiconductor device, which comprises growing a single crystal gate film laterally to form a single crystal gate film.