JPH0620990A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a capacitor with the increased bottom electrode surface area by growing a silicon crystal grains by vapor growth using a crystal growing core formed on the surface of the base as the forming core. CONSTITUTION:An element separating silicon oxide film 2 is formed on a silicon substrate 1, is exposed to the mixed atmosphere of NH3 gas and HCl gas at a temperatuer of 600-650 deg.C under a pressure of 0.1-1.0Torr for the surface roughening and nitride adsorption and a crystal growing core 3 is formed. Then, a polycrystalline silicon film 4 which is to serve as a bottom electrode is formed by the low pressure vapor growth, which uses SiH4 gas, at a growing temperature of 600-650 deg.C under a growing pressure of 0.1-1.0Torr using the crystal growing core 3 as the core. The crystal grains are grown nonuniformly and the surface roughness is promoted. Thus, the surface area of a capacitor is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a lower electrode of a capacitor.

[0002]

2. Description of the Related Art A method of forming a capacitor in a semiconductor device manufacturing process will be described with reference to FIG.

First, as shown in FIG. 2A, a silicon oxide film 2 for element isolation is formed on a silicon substrate 1 by a selective oxidation method.
To form. Next, the columnar polycrystalline silicon film 14 to be the lower electrode is grown from SiH ₄ gas or the like at a growth temperature of 600 to 650.
C. and a growth pressure of 0.1 to 1.0 Torr are grown to a thickness of 400 to 600 nm by the reduced pressure vapor deposition method.

Next, as shown in FIG. 2B, when impurities such as phosphorus are doped, a polycrystalline silicon film 14 having crystal grains grown by thermal history is formed.

Next, as shown in FIG. 2C, the polycrystalline silicon film 14 is patterned to form a lower electrode 14A.

Next, as shown in FIG. 2 (d), a capacitive insulating film 5 is deposited, and a polycrystalline silicon film for forming an upper electrode 6 is further formed under reduced pressure vapor deposition under the same conditions as those for forming the lower electrode. After growing 100 to 200 nm by the method, impurities were introduced and patterning was performed by the lithography technique.

[0007]

With the miniaturization of semiconductor devices, the area occupied by capacitors is gradually being reduced. However, since the capacitance value of the capacitor is proportional to the capacitor surface area, it is necessary to increase the capacitor surface area without increasing the occupied area (projected area) of the capacitor in order to secure the capacitance value required for the circuit.

In the prior art, the thickness of the lower electrode is increased,
The surface area of the capacitor is increased by utilizing not only the upper surface but also the side surface of the electrode. This is a simple and highly effective method, but if the thickness of the lower electrode is made too thick in order to obtain a higher capacitance value, the step will become too large this time and the flatness will deteriorate, adversely affecting the post-process. There is a problem that it affects.

Therefore, a method of increasing the surface area of the capacitor by the unevenness of the crystal grains formed by the surface migration of the silicon film is disclosed in, for example, M. Sak.
ao) International Electron
Devices Meeting Technical Digest (International ElectronDe
Vices Meeting TECHNICAL D
IGEST) page 655 (1990). However, in order to cause surface migration, it is necessary to form a film under the conditions of amorphous-crystal transition,
There are restrictions such as strict control of process variables such as growth temperature, growth pressure, gas flow rate and growth film thickness.

An object of the present invention is to provide a method for forming a capacitor in which the surface area of a lower electrode is increased by forming irregularities of crystal grains on the surface of a base under relatively warm film forming conditions.

[0011]

A method of manufacturing a semiconductor device according to the present invention comprises a step of forming crystal growth nuclei on a surface of a base in a capacitor formation region, and vapor growth of syrincon crystal grains using the crystal growth nuclei as formation nuclei. And a step of growing by a method.

[0012]

Operation: By intentionally forming crystal growth nuclei, non-uniform nucleation occurs, and silicon crystal grains cause non-uniform abnormal growth. By utilizing this, unevenness on the surface of the lower electrode is promoted and the surface area of the capacitor is increased.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

First, as shown in FIG. 1A, a silicon oxide film 2 for element isolation is formed on a silicon substrate 1 by a selective oxidation method.
To form. Next, the temperature is 600-650 ° C, the pressure is 0.1-
The crystal growth nuclei 3 are formed by exposing to a mixed atmosphere of NH ₃ gas and HC1 gas under the condition of 1.0 Torr to roughen the surface and adsorb nitride.

Next, as shown in FIG. 1B, a growth temperature of 600 to 650 ° C. and a growth pressure of 0.1 to 5 are obtained by a reduced pressure vapor phase growth method using SiH ₄ gas with the crystal growth nucleus 3 as a nucleus.
Under the condition of 1.0 Torr, the polycrystalline silicon film 4 to be the lower electrode is grown. At this time, the crystal grains grow nonuniformly (height 400 to 600 nm), and surface irregularities become severe. This makes it possible to increase the capacitor surface area.

Next, as shown in FIG. 1C, impurities such as phosphorus are introduced into the polycrystalline silicon film 4 by diffusion, and then, as shown in FIG. 1D, patterning is performed by a lithography technique. The lower electrode 4 is formed.

According to the method of the first embodiment, the unevenness of the surface of the lower electrode 4A can be increased, so that the surface area of the electrode of the capacitor is increased by 2.0 to 3.0 times as compared with the conventional method. It has become possible. Furthermore, since crystal growth nuclei can be formed and grown on the deposited polycrystalline silicon, it is possible to repeat the method of this embodiment a plurality of times to 3.
It is possible to increase the surface area of the electrode by a factor of 5 to 4.0.

In the first embodiment, NH ₃ gas and H
Although the crystal growth nuclei 3 are formed with Cl gas, the crystal growth nuclei may be formed by performing surface treatment with hydrogen plasma. That is, as a second embodiment, in FIG. 1A, a dangling bond of silicon is formed on the surface of the oxide film by hydrogen plasma treatment, and using this as a crystal growth nucleus, crystal grains of silicon are abnormally grown.

As a result, an electrode surface having more severe irregularities than that of the first embodiment is formed, and the electrode surface area can be increased by about 1.3 times that of the first embodiment. The same effect can be obtained by forming a crystal growth nucleus by ion-implanting silicon into the base.

In the above-described embodiment, the case where the lower electrode is formed by patterning after the abnormal growth of the silicon crystal grain is described. However, after the lower electrode of the polycrystalline silicon film is formed in advance, the silicon crystal grain is abnormally formed. It is also possible to increase the surface area of the side wall of the lower electrode by growing it and forming the lower electrode by etching back. Further, in the above embodiment, the case of forming the lower electrode connected to the silicon substrate has been described, but the present invention can be applied to the case of forming the lower electrode of the capacitor on the bit line via the interlayer insulating film.

[0021]

As described above, according to the present invention, the surface area of the electrode of the capacitor can be increased more than before without increasing the occupied area of the capacitor. Further, by repeating the formation and growth of crystal growth nuclei a plurality of times, it is possible to increase the surface area of the electrode to about 5 times that of the conventional case.

Further, unlike the method of using the unevenness of the crystal grains formed by the surface migration of the silicon film, the unevenness of the crystal grains can be easily formed with good reproducibility under relatively mild conditions on the underlying surface of the capacitor formation region. can do.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor chip for explaining a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 Crystal Growth Nuclei 4,14 Polycrystalline Silicon Film 4A, 14A Lower Electrode 5 Capacitance Insulating Film 6 Upper Electrode

Claims (1)

[Claims] 1. A method comprising: a step of forming crystal growth nuclei on a base surface in a capacitor formation region on a semiconductor substrate; and a step of growing silicon crystal grains by using the crystal growth nuclei as nuclei by a vapor phase epitaxy method. And a method for manufacturing a semiconductor device.