JPH04273440A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To form a gate oxide film which has uniform thickness by preventing white ribbon when forming the gate oxide film at the process of separating elements of a silicon substrate. CONSTITUTION:A thermal oxide film 2 is formed on a silicon substrate 1 and a silicon nitride film 3 is accumulated on the thermal oxide film 2 by CVD method. The silicon nitride film 3 is left in an activating area removing other parts by photoetching, then, dry oxygen or ozone is used as oxide pieces when forming a field oxide film 4 at the process of thermal oxidation. Thus, at the process of forming a gate oxide film, uniform film thickness is maintained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device.

0002

2. Description of the Related Art Generally, the process of forming element isolation regions of semiconductor integrated circuits is performed in stages as shown in FIG. That is, in FIG. 2(a), a thermal oxide film 2 is formed on a silicon substrate 1, and then as shown in FIG. 2(b).
A silicon nitride film (Si3N4 film) 3 is deposited on the thermal oxide film 2 by the CVD method, and then as shown in FIG. 2(c).
In step 1, the silicon nitride film 3 is left in the activated region and other parts are removed by photo-etching, and finally, in FIG. After oxidation treatment, the thickness is 1 μm.
A field oxide film (SiO2) 4 of about 100 mL is formed.

[0003] Si+2H2O →SiO2+2H2
…
......(Number 1)

0004

[Problem to be Solved by the Invention] However, water vapor reacts with the nitride film at high temperatures as shown in equation (2), and the 4NH3 generated thereby reacts with the silicon substrate 1 as shown in equation (3). It has been reported that nitrides 5 as shown in FIG. 3 are generated (for example, E. Kooi, '
Formation of Silicon Nitr
ide at a Si-SiO2 Interface
e during Local Oxidation
ofSicon and during Heat-T
Reament of Oxidized Sico
n in NH3 Gas', J. Electroch
em. Soc. (1976) Vol. 123, No. 7
, p. 1117-1120).

[0005] Si3N4 +6H2O →3SiO2+4N
H3...
...(Math. 2) 4NH3 +3Si →Si3
N4 +6H2
......(Equation 3) In this way, the so-called white ribbon of Si3N4 is generated, which prevents the uniform growth of the gate oxide film to be formed in a later process, resulting in a problem of lowering the dielectric breakdown voltage. there were. Note that wet oxygen (O2+H2) is used instead of water vapor as the oxidizing species.
Examples using O) are also known, but they have the disadvantage that the water (H2O) contained therein causes the reactions (Equation 2) and (Equation 3) described above to occur, resulting in the production of Si3N4. An object of the present invention is to provide a method for manufacturing a semiconductor device that solves the above-mentioned problems.

[0006]

[Means for Solving the Problems] The present invention uses dry oxygen or ozone as an oxidizing species during an element isolation formation process that selectively oxidizes a silicon substrate using an oxidation-resistant mask made of a silicon nitride film. This is a method of manufacturing a semiconductor device characterized by using the present invention.

[0007]

[Function] As a result of intensive research and experiments regarding the above-mentioned problem, the present inventor found that dry oxygen or ozone can be used as the oxidizing species, and has completed the present invention. Figure 1 shows 1 atm. This study investigated the relationship between oxidation time (min) and film thickness (μm) when the temperature during thermal oxidation treatment was changed using dry oxygen. As is clear from these, the film thickness can be clearly expressed as a function of thermal oxidation temperature and oxidation time, for example, 10
When oxidized at a temperature of 50°C, the oxidation time is approximately 1100 m.
It can be seen that a film thickness of 400 nm can be obtained with in. Note that ozone has a similar effect, and since it has more oxygen atoms than dry oxygen and is energetically unstable, its reaction rate tends to be faster.

As described above, according to the present invention, dry oxygen or ozone is used as an oxidizing species when selectively oxidizing a silicon substrate, so nitrides are not generated during selective oxidation, and therefore the film thickness is uniform. This makes it possible to form a gate oxide film.

[0009]

[Examples] Examples of the present invention will be described below. 95 on the silicon substrate 1 in the process shown in FIG. 2(a) mentioned above.
After forming a thermal oxide film 2 with a thickness of about 350 Å by wet oxidation at 0°C, low pressure CVD at 760°C and 0.4 Torr is performed on the thermal oxide film 2 in the step shown in FIG. 2(b).
A silicon nitride film (Si3N4 film) 3 was deposited by a method, and then, as shown in FIG. 2C, the silicon nitride film 3 was left in the active region and other parts were removed by photoetching. Thereafter, in FIG. 2(d), thermal oxidation was performed at 1050° C. using dry oxygen as the oxidizing species. As a result, it was possible to prevent the formation of white ribbons during the subsequent formation of the gate oxide film.

0010

As explained above, according to the present invention, dry oxygen or ozone is used as the oxidizing species during field oxidation, so that the thickness of the subsequent gate oxide film can be made uniform. This makes it possible to improve the quality and yield of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between oxidation time and film thickness in the method of the present invention.

FIG. 2 is a process diagram showing the formation of an element isolation region of a conventional semiconductor integrated circuit.

FIG. 3 is an explanatory diagram of the presence of nitrides.

[Explanation of symbols]

1 Silicon substrate 2 Thermal oxide film 3 Silicon nitride film 4 Field oxide film 5 Nitride

Claims (1)

[Claims] 1. A semiconductor device characterized in that dry oxygen or ozone is used as an oxidizing species during an element isolation formation process in which a silicon substrate is selectively oxidized using an oxidation-resistant mask of a silicon nitride film. manufacturing method.