JPH01257366A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To improve the performance of logic circuit part by a method wherein one of a plurality of gate insulating films is composed of an oxynitride film which has a high dielectric constant. CONSTITUTION:Gate oxide films 3 and 4 which have predetermined thicknesses are formed in element regions between field oxide films 2 on the surface of a semiconductor substrate 1. Gates 15 and 16 are provided on the gate oxide films 3 and 4 respectively. Thus two transistors Tr1 and Tr2 are formed. The thickness of the gate insulating film 3 is so predetermined as to be sufficient for high voltage application. On the other hand, the gate insulating film 4 is composed of a silicon oxynitride film and, although it has the thickness same as the gate insulating film 3, as the silicon oxynitride film has a dielectric constant than a silicon oxide film, a large gate capacitance is obtained. With this constitution, the gate insulating film 4 functions like the thinner silicon oxide film and the current driving force can be increased and the fine structure can be realized so that a high performance logic circuit can be formed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is applicable to semiconductor devices that require gate insulating films of different thicknesses due to circuit operation requirements, such as memory circuits and logic circuits. The present invention relates to a semiconductor device having the present invention and a method for manufacturing the same.

(Prior Art) Due to demands for higher integration and faster processing of semiconductor devices, the thickness of gate insulating films tends to become thinner.

However, the thickness of the gate insulating film and the voltage that can be applied to the gate oxide film are interrelated, and when applying a high voltage, it is necessary to increase the thickness of the gate insulating film. For example, in dynamic RAM, a word line boost method is adopted in which the voltage V applied to the word line is made higher than the power supply voltage (V DD) in order to guarantee the charge stored in the capacitor in the memory circuit. Voltage V
By thickening the gate insulating film of the transistor to which is applied,
Its reliability is being ensured. Therefore, in a semiconductor chip that constitutes a dynamic RAM, the thickness of the gate insulating film is thicker than that in a semiconductor chip that consists only of logic circuits.

(Problems to be Solved by the Invention) As described above, in conventional semiconductor chips having a memory circuit and a logic circuit, in order to set the gate oxide film thick from the viewpoint of gate insulating film reliability required for the memory circuit,
If it is attempted to use a gate insulating film of the same thickness also in the logic circuit section, it becomes difficult to miniaturize the transistors in the logic circuit section, and the driving force of the transistors decreases, which impedes the high performance of the logic circuit section. Furthermore, if the thickness of the gate insulating film is to be changed between the memory circuit section and the logic circuit section, a thin gate insulating film must be formed after etching the gate insulating film, making it difficult to control the film thickness.

The present invention has been made in consideration of the above circumstances, and in order to improve the performance of the logic circuit section, gate insulating films of different thicknesses are effectively formed on the same chip even though the actual film thickness is the same. An object of the present invention is to provide a semiconductor device formed in the same manner and a manufacturing method therefor.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides that, among a plurality of gate insulating films formed on a semiconductor substrate of a single semiconductor chip, one is made of a silicon oxide film and the other is made of a silicon oxide film. Provided is a semiconductor device characterized in that is a silicon oxynitride film.

Further, the method for manufacturing this semiconductor device includes the steps of forming a plurality of gate insulating films made of silicon oxide films on a semiconductor substrate, forming a masking layer on the silicon oxide film,
A method for manufacturing a semiconductor device comprising the steps of: removing a part of the gate insulating film to expose a part of the gate insulating film; and nitriding the exposed gate insulating film to form a silicon oxynitride film. provide.

(Function) In the semiconductor device according to the present invention, the oxynitride gate insulating film has a higher dielectric constant than the original silicon oxide gate insulating film, so even though the actual film thickness is the same, the effective film thickness is It functions similarly to a thin silicon oxide gate insulating film. Therefore, if an oxynitride gate insulating film is used in the logic circuit section, the performance of the logic circuit section will be improved.

Further, in the manufacturing method according to the present invention, an oxynitride film and a silicon oxide film can be formed on the same semiconductor chip.

(Example) Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 shows a sectional view of a semiconductor device according to an embodiment of the present invention. A gate oxide film 3.4 having a predetermined thickness is formed in the element region between the field oxide films 2 on the surface of the semiconductor substrate 1. Under each gate oxide film 3.4 is a source/drain diffusion layer 10.
is provided, and an electrode (aluminum electrode) 12 is connected to this source/drain diffusion layer 10. Gates 15 and 16 are provided on the gate oxide film 3.4.

In this way, two transistors Tr1 and Tr2 are formed. This transistor T "1° Tr2,
One transistor Tri constitutes, for example, a memory circuit, and the other transistor Tr2 constitutes, for example, a logic circuit. Then, the gate insulating film 3 of the transistor Tri
is made of a silicon oxide film, and the transistor Tr2
The gate insulating film 4 is made of a silicon oxynitride film. The gate insulating film 3 is set to have a thickness that allows application of a high voltage, and the transistor Tri having this gate insulating film 3 constitutes a highly reliable memory circuit. On the other hand, the gate insulating film 4 made of a silicon oxynitride film has the same thickness as the gate insulating film 3, but has a higher relative dielectric constant than the silicon oxide film, and thus has a larger gate capacitance. Therefore, it functions in the same way as a thin silicon oxide film, and it is possible to increase current driving power and miniaturize the structure, so that a high-performance logic circuit can be constructed.

Next, the manufacturing method of the present invention will be explained with reference to FIG.

After forming the field reversal prevention layer on the semiconductor substrate 1,
A field oxide film 2 is formed by selective oxidation. Thereafter, a gate insulating film 3.4 made of a silicon oxide film is grown in the device region between the field oxide films 2, and ions are implanted into the substrate region under this gate insulating film 3.4 to form impurity regions 13.14. Form. This impurity region 13.14
is the threshold voltage (V T
) i) Contributes to improvement of adjustment and bunch-through withstand voltage. After forming impurity regions 13 and 14, polycrystalline silicon 5 is applied to the entire surface.
is deposited to a predetermined thickness (FIG. 2(a)).

Next, a photoresist pattern is formed on the polycrystalline silicon 5, and using this as a mask, the polycrystalline silicon layer 5 on the gate insulating film 4 on one side of the transistor is removed to expose the gate insulating film 4 (FIG. 4(b)). ). As described above, the gate insulating film 4 is the gate insulating film of the transistor Tr2 constituting the logic circuit, and is then converted into oxynitride. As a method for oxynitriding, an appropriate method such as thermal nitriding or plasma nitriding can be adopted. By this oxynitride conversion, the gate insulating film 4 changes from a silicon oxide film to a silicon oxynitride film, and the dielectric constant increases.

In addition, when converting to oxynitride, the surface of the polycrystalline silicon layer 5 is also nitrided! 11k7 is formed, but the gate oxide film 3 covered with the polycrystalline silicon layer 5 is not converted into oxynitride (FIG. 3(C)).

Subsequently, polycrystalline silicon 8 is deposited on the entire surface including the exposed surface of the gate insulating film 4, and a resist 9 having the same etching rate as the polycrystalline silicon is deposited thereon to flatten the surface (see FIG. (d)). After etching back the resist 9 and polycrystalline silicon 8 and etching away the nitride layer 7, phosphorus is diffused into the remaining polycrystalline silicon 8.5.
are patterned to form gates 15 and 16 (FIG. 1(e)).

After that, as shown in Figure 1, the source is
After forming the drain diffusion layer 10 and depositing the insulating film 11, a hole is formed in the insulating film 11 and an electrode 12 is formed in the hole. Thereby, the transistor Tri having the gate insulating film 3 made of a silicon oxide film and the transistor Tr2 having the gate insulating film 4 made of a silicon oxynitride film can be formed on a single semiconductor chip.

Such a manufacturing method eliminates the need for the step of etching the gate insulating film 4 to make it thinner, resulting in better controllability of the film thickness. Further, by converting the gate insulating film 4 to oxynitride, diffusion of impurities from polycrystalline silicon into the substrate through the gate insulating film can be suppressed.

[Effects of the Invention] As described above, the present invention uses an oxynitride film with a high specific inductivity as part of the plurality of gate insulating films, so that it is possible to increase the current driving power of the transistor and to miniaturize it. On the other hand, the reliability of other gate oxide films against high voltage application can be guaranteed. Further, the manufacturing method of the present invention converts a silicon oxide film into an oxynitride film to obtain a silicon oxynitride film, and eliminates the need for a step of forming a thin film, resulting in good film thickness controllability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor device according to an embodiment of the present invention;
FIG. 2 is a sectional view showing the manufacturing process. 1... Semiconductor substrate, 3... Silicon oxide film, 4...
- Silicon oxynitride film, 5.8... Polycrystalline silicon layer, 15.16... Gate. Applicant's representative Sato-Yo Tri Tr2 Trap 1 Figure Trap 2 Figure

Claims (1)

[Claims] 1. Among the plurality of gate insulating films formed on the semiconductor substrate of a single semiconductor chip, one is made of a silicon oxide film and the other is a silicon oxynitride film. semiconductor devices. 2. A step of forming a plurality of gate insulating films made of silicon oxide on a semiconductor substrate, and a step of forming a masking layer on the silicon oxide film and removing a part of the masking layer to expose a part of the gate insulating film. and nitriding the exposed gate insulating film to form a silicon oxynitride film.