JPH07161820A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form oxide films of different film thicknesses in one oxidation process by varying the introduction concentration of impurities. CONSTITUTION:The surface of a standard-withstand voltage transistor formation region 3A is covered with a resist 10. In succession, boron is introduced, by making use of the resist 10 as a mask, only into a high-withstand voltage- transistor formation region 3B in which a silicon face has been exposed. After that, the resist 10 is removed, and a wafer is wet-oxidized. Then, a thin gate oxide film 11A is formed in the boron-undoped standard-withstand voltage- transistor formation region 3A, and a gate oxide film 11B whose film thickness is thick is formed in the boron-doped high-withstand voltage-transistor formation region 3B. Since the gate oxide films 11A, 11B with different thicknesses can be formed simultaneously in one oxidation process, the number of processes can be reduced as compared with conventional cases.

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 is suitable for application to, for example, a method for manufacturing a semiconductor device containing two types of transistors having different breakdown voltages.

[0002]

2. Description of the Related Art Today, metal oxide semiconductor (MOS: meta)
In large-scale integrated circuits,
A high breakdown voltage type transistor having a thick gate oxide film is widely used to secure a breakdown voltage against a high voltage or the like.
By the way, an integrated circuit has a circuit portion that requires a high breakdown voltage and a circuit portion that has a sufficient breakdown voltage. Normally, a high breakdown voltage transistor and a standard breakdown voltage transistor are mixed.

In order to form transistors having different breakdown voltages in an integrated circuit, a manufacturing method as shown in FIG. 4 is used. First, an element isolation oxide film (LOCOS: local ox) is formed in the field region of the silicon substrate 1 by pretreatment.
Idation of silicon) 2 is formed. After that, the oxide film covering the element formation region is removed by wet etching to expose the silicon surface of the element formation region. A cross-sectional structure at this stage is FIG.

After this, the first oxidation process is performed. For this oxidation treatment, a pyrogenetic device that burns hydrogen gas and oxygen gas outside the reaction furnace is used. By this oxidation treatment, a gate oxide film having a film thickness of about 24 [nm] is formed in each of the standard breakdown voltage transistor formation region 3A and the high breakdown voltage transistor formation region 3B. The sectional structure at this stage is shown in FIG.
(B). Subsequently, as shown in FIG. 4C, the surface of the gate oxide film formed in the high breakdown voltage transistor formation region 3B is covered with a resist 4, and in this state, the gate oxide film in the standard breakdown voltage transistor formation region 3A is covered. Wet etching.

FIG. 4D shows a state in which the gate oxide film in the standard breakdown voltage transistor forming region 3A is removed by this etching process. When this step is completed, the resist 4 is removed by asking, and the second oxidation process is performed. A pyrogenetic device is also used for this oxidation treatment. As a result, the standard breakdown voltage transistor forming region 3A is formed.
Is formed with a gate oxide film formed by the second oxidation process, and the gate oxide film formed by the first and second oxidation processes is formed over the high breakdown voltage transistor formation region 3B. Will be.

That is, as shown in FIG. 4E, a gate oxide film 5A having a film thickness of 20.5 [nm] is formed in the standard breakdown voltage transistor formation region 3A, while a high breakdown voltage transistor formation region 3B is formed. 40 [nm] thick gate oxide film 5
B is formed.

[0007]

As described above, in the conventional case, two oxidation steps and a resist patterning step are required to form the gate oxide films 5A and 5B having different film thicknesses. However, if these gate oxide films can be formed in fewer steps than these steps, it is considered that the production efficiency will be further improved.

The present invention has been made in view of the above points, and an object thereof is to propose a method of manufacturing a semiconductor device which is more excellent in production efficiency than ever before.

[0009]

In order to solve such a problem, according to the present invention, the first oxide film forming region 3B in which the oxide film 11B having the first film thickness is formed and the first oxide film forming region 3B And a second oxide film forming region 3A in which an oxide film 11A having a second thin film thickness is formed. In the method for manufacturing a semiconductor device, the first and second oxide films having the silicon surface 1 exposed together are formed. Of the formation regions 3A and 3B, a step of covering the silicon surface 1 of the second oxide film formation region 3A with a resist pattern 10, and a step of introducing impurities only into the silicon surface 1 of the first oxide film formation region 3B. After removing the resist pattern 10, the first and second oxide film forming regions 3A and 3 are formed.
And a step of simultaneously oxidizing B.

[0010]

The oxide film is formed on the silicon surface having impurities introduced faster than the silicon surface having no impurities introduced. Therefore, a thick oxide film 11B can be formed in the first oxide film forming region 3B in which impurities are introduced, and a film can be formed in the second oxide film forming region 3A by one oxidation process. A thin oxide film 11A can be formed. In this way, the oxide films 11A and 11B having different film thicknesses can be formed by a single oxidation process, so that the manufacturing efficiency can be improved as compared with the conventional case.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

A manufacturing method for forming gate oxide films having different thicknesses by a single oxidation step will be described with reference to FIG. 1 in which parts corresponding to those in FIG. First, as in the conventional case, the element isolation oxide film 2 is formed in the field region by the previous process. After this, buffered hydrofluoric acid (hydrofluoric acid (H
The oxide film covering the element forming regions 3A and 3B is removed with a mixed solution of F) and ammonium fluoride (NH4F) to obtain the structure of FIG.

In the conventional manufacturing process, the first oxidation process is performed at this stage, but in this embodiment, as shown in FIG.
As shown in (B), the standard breakdown voltage transistor formation region 3
The surface of A is covered with a resist 10. Continuing with Figure 1
As shown in (C), boron (B: boron) is introduced only into the high breakdown voltage transistor formation region 3B where the silicon surface is exposed using the resist 10 as a mask.

This is to utilize the property of silicon that causes a difference in the film thickness of the oxide film grown during wet oxidation between the case where boron is introduced and the case where boron is not introduced.

For example, as shown in FIG. 2, boron is 1.0 ×
Silicon introduced about 10 ¹⁶ [atom / cm ³ ]
About 2.5 × 10 ²⁰ [atom / cm ³ ] is introduced, and there is a difference in the film thickness of the oxide film formed by wet oxidation for 40 [min] under the temperature condition of 1000 [℃]. become. That is, the film thickness of the high-concentration silicon becomes thicker than the low-concentration silicon by about several tens of nm. In the case of boron, the lower the oxidation temperature is, the more difference the oxidation rate is.

Accordingly, after the step of introducing boron, the resist 10 is removed and the wafer is wet-oxidized.
As shown in (D), the thin gate oxide film 11A is formed in the standard breakdown voltage transistor formation region 3A in which boron is not introduced, whereas the high breakdown voltage transistor formation region 3B in which boron is introduced is formed. The gate oxide film 11B having a large film thickness is formed on the substrate.

According to the above steps, the gate oxide films 11A and 11B having different film thicknesses can be formed simultaneously by one oxidation step, and the number of steps can be further reduced as compared with the conventional method. . Further, since the film thickness of the gate oxide film 11B can be controlled by the dose amount of boron to be introduced, the film thickness control of the gate oxide film can be further simplified as compared with the conventional case.

In the above embodiment, 1.0 × 10
Silicon containing about ¹⁶ [atom / cm ³ ] of boron and silicon containing about 2.5 × 10 ²⁰ [atom / cm ³ ] of boron at a temperature of 1000 [° C.] 40
The effect of introducing boron was described using wet oxidation for [minutes] as an example. However, since the thickness of the oxide film varies depending on the process conditions (oxidation time and oxidation temperature), the dose amount of boron and the process conditions are The optimum film may be used depending on the required film thickness and film thickness difference. Incidentally, if the calibration curve of the oxide film with respect to the dose amount and the oxidation temperature is obtained in advance, the dose amount can be easily determined.

Further, in the above-mentioned embodiment, the case where boron is introduced into the high breakdown voltage transistor forming region 3B has been described, but the present invention is not limited to this, and can be applied to the case where phosphorus is introduced. In this case, the characteristic curve shown in FIG. 3 is obtained. In addition to boron and phosphorus, other impurities may be introduced.

Furthermore, in the above-mentioned embodiments, the case where the gate oxide film is formed by wet oxidation has been described, but the present invention is not limited to this, and in the case where oxidation is performed by dry oxidation, hydrogen combustion oxidation or the like. Can also be applied.

Further, in the above-mentioned embodiment, the case where the oxide films having different film thicknesses are respectively formed on the silicon substrate by introducing the impurities into the silicon substrate 1 has been described. Or diffusion processing may be used.

Furthermore, in the above-mentioned embodiments, the case where the impurities are introduced only into the silicon surface of which the film thickness is desired to be increased has been described, but the present invention is not limited to this, and the film required for any silicon surface. Impurities having different concentrations may be introduced depending on the thickness.

Further, in the above-mentioned embodiments, the method of forming the standard breakdown voltage transistor and the high breakdown voltage transistor on the silicon substrate has been described, but the present invention is not limited to this, and oxide films having different thicknesses are formed on the silicon substrate. It can be widely applied to a method of manufacturing a semiconductor manufacturing device including a step of forming.

[0024]

As described above, according to the present invention, the film thickness is improved by using the property that the oxide film is formed faster on the silicon surface in which impurities are introduced than in the silicon surface in which impurities are not introduced. Different oxide films can be formed by a single oxidation step, and a semiconductor device manufacturing method with a smaller number of steps than the conventional method can be realized.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a characteristic curve diagram showing the relationship between the concentration of impurities and the growth rate of an oxide film.

FIG. 3 is a characteristic curve diagram showing the relationship between the concentration of impurities and the growth rate of an oxide film.

FIG. 4 is a process chart showing a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

1 ... Silicon substrate, 2 ... Element isolation oxide film, 3A ...
... Standard breakdown voltage transistor formation region, 3B ... High breakdown voltage transistor formation region, 4,10 ... resist, 5A, 5
B, 11A, 11B ... Gate oxide film.

[Procedure amendment]

[Submission date] December 10, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (3)

[Claims] 1. A first oxide film forming region in which an oxide film having a first film thickness is formed, and a second oxide film in which a second film thickness is formed thinner than the first film thickness. In the method of manufacturing a semiconductor device having a second oxide film forming region, a silicon pattern of the second oxide film forming region of the first and second oxide film forming regions exposed in the silicon surface is used as a resist pattern. Covering step, a step of introducing impurities into the silicon surface of the first oxide film forming region, and the first and second steps after removing the resist pattern.
And a step of simultaneously oxidizing the oxide film forming region of the above. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the impurities are introduced by a diffusion process. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second oxide film forming regions are each oxidized by a wet oxidation method.