KR19990060920A - Method for forming charge storage electrode of semiconductor device - Google Patents

Abstract

1. Technical field to which the invention described in the claims belongs

The present invention relates to a method of forming a charge storage electrode of a semiconductor device, and more particularly, to a method of forming a charge storage electrode of a semiconductor device for improving capacitance by changing the structure of a cylindrical charge storage electrode.

2. Technical problem that the invention tries to solve

It is intended to increase the charge storage capacity of the charge storage electrode of the semiconductor device due to the high integration of the semiconductor device.

3. Summary of the solution of the invention

The present invention increases the capacitance by forming the lower electrode structure of the capacitor in a weave hill cylinder structure so as to increase the surface area of the charge storage electrode.

4. Important uses of the invention

Applied in semiconductor device manufacturing.

Description

Method for forming charge storage electrode of semiconductor device

The present invention relates to a method of forming a charge storage electrode of a semiconductor device, and more particularly, to a method of forming a charge storage electrode of a semiconductor device for improving capacitance by changing the structure of a cylindrical charge storage electrode.

In general, as the integration of semiconductor devices proceeds, the size of unit cells becomes smaller, and the charging capacity required for device operation tends to increase slightly. At present, the charge storage capacity required for devices larger than 64M DRAM is over 22pF per unit cell, and the charge capacity is increased through the modified capacitor structure in which the fin and cylinder types, which are conventional three-dimensional capacitor structures, are modified. To increase.

The method of increasing the charging capacity of the capacitor will be described with reference to [Equation] below.

[Equation]

Q = (ε ₀ ε ₁ × A) / d

Where Q is the charge storage capacity, ε ₀ is the dielectric constant (air), ε ₁ is the dielectric constant of dielectric material 1, A is the capacitance area, and d is the thickness of the film.

First, the use of a high dielectric constant material, in general, such a material has the disadvantages that there is a lot of leakage current and it is difficult to control the production (Ta ₂ O ₅ , PZT, etc.) of the material. In general, the dielectric material used in the semiconductor device uses an ONO structure formed of a silicon oxide film and a silicon nitride film.

Second, to reduce the thickness of the dielectric material. However, reducing the Tox (oxide conversion thickness) to about 40 kW or less in the ONO structure that is currently used makes it difficult to maintain a stable charge storage capacity because a leakage current occurs and breaks down easily.

Third, as a method of increasing the area of the capacitor, in most cases, the capacitor is formed in a three-dimensional structure to increase the surface area. Such capacitors are typical of the cylinder of FIG. 1A and the fin of FIG. 1B. However, as the integration degree of the device increases, the charge capacity per unit area increases, and thus a modified three-dimensional capacitor structure is used. Such a structure includes a meta-stable polysilicon (MPS) type of FIG. 1C and a bellows structure of FIG. 1D. The MPS structure has a problem that it is difficult to form because there are many variables (heat treatment conditions, doping level, MPS uniformity, etc.) in the formation of MPS. Alternatively, formation of non-uniform doping levels of the dope polysilicon layer occurs during the thermal process.

Accordingly, the present invention provides a method of forming a charge storage electrode of a semiconductor device which improves charge storage capacity by forming a wave hill charge storage electrode, a modified cylinder capacitor structure that forms irregularities on the surface of the charge storage electrode of the capacitor. Its purpose is to.

According to an aspect of the present invention, there is provided a method of forming a contact hole in which a substrate is exposed after forming an interlayer insulating film on a substrate on which various elements for forming a semiconductor device are formed. Forming a first polysilicon layer on the interlayer insulating film including the first polysilicon layer; forming a plurality of nitride film patterns on the first polysilicon layer by a nitride film deposition and patterning process; and thermal oxidation using the nitride film pattern as an oxide barrier layer Forming an oxide film on an exposed portion of the first polysilicon layer, removing the nitride film pattern and the oxide film so that the surface of the first polysilicon layer has a wave hill structure, and then depositing and patterning the oxide film. Forming a core oxide film, and forming a second polysilicon layer on the first polysilicon layer including the core oxide film After the etching the front system and the second and first polysilicon layer to form a charge storage electrode of the cylinder structure, characterized by comprising the step of removing the oxide core.

1A to 1D are cross-sectional views of a device for describing a charge storage electrode of a conventional semiconductor device.

2A to 2F are cross-sectional views of devices for explaining a method of forming a charge storage electrode of a semiconductor device according to the present invention.

Explanation of symbols for main parts of the drawings

1 substrate 2 interlayer insulating film

3: contact hole 4: first polysilicon layer

5: nitride film pattern 6: oxide film

7: core oxide film 8: second polysilicon layer

10: charge storage electrode

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2A to 2F are cross-sectional views of devices for describing a method of forming a charge storage electrode of a semiconductor device according to the present invention.

Referring to FIG. 2A, an interlayer insulating film 2 is formed on a substrate 1 having a structure in which various elements for forming semiconductor devices such as a field oxide film, a gate oxide, a word line and a bit line are formed. Selected portions of the interlayer insulating film 2 are etched to form contact holes 3 through which the substrate 1 is exposed.

In the above, the interlayer insulating film 2 is applied to the BPSG film for planarization of the surface, the BPSG film is subjected to the reflow process at a high temperature of 800 to 900 ℃ to achieve the surface planarization. At this time, the gas used is an inert gas such as He, Ne, Ar, N ₂ or a non-reactive gas.

Referring to FIG. 2B, the BOE cleaning operation is performed after the contact hole 3 is formed, and the first polysilicon layer 4 is formed on the interlayer insulating film 2 including the contact hole 3. A plurality of nitride film patterns 5 are formed on the first polysilicon layer 4.

In the above, the first polysilicon layer 4 includes a method of depositing undoped normal polysilicon followed by POCl ₃ doping and a method of depositing a doped polysilicon layer in-situ. . The source gas for depositing the in-situ dope polysilicon layer uses PH ₃ / SiH ₄ or PH ₃ / Si ₂ H ₆ . The plurality of nitride film patterns 5 are formed by depositing a nitride film with a thickness of 500 to 1000 kPa using NH ₃ and SiH ₂ Cl ₂ mixed gas at a temperature of 500 to 950 ° C. and a pressure of 0.05 to 10 Torr. It is formed using an F-type etching gas such as CF ₄ as an etching process, and serves as an oxidation barrier layer in the local oxidation process to form irregularities on the surface of the charge storage electrode to be formed later. The nitride film pattern 5 may be simply made in the form of a line and a space, or may be made in an irregular shape.

On the other hand, the refractive index of the nitride film is 1.465 to 2.100, the nitride layer is an NH ₃ gas to the oxide film formed by a chemical vapor deposition method in forming or thermal CVD- process as formed by the nitriding process, and a thermal oxidation process using NH ₃ gas to the oxide film It can also be formed by nitriding by the thermal process used.

Referring to FIG. 2C, an oxide film 6 is formed by locally oxidizing an exposed portion of the first polysilicon layer 4 by an oxidation process using a plurality of nitride film patterns 5 as an oxide barrier layer.

In the above, the oxide film 6 is formed to a thickness of 100 to 6000 Pa by any one of wet, dry and wet / dry mixed oxidation methods at a temperature of 650 to 1200 ° C. and a pressure of 0.2 Torr to 5 atm. In addition, a dilute oxidation method may be used to lower the oxidation growth ratio. In the oxidation process, any one of O ₂ , O ₂ / O ₃ , O ₂ / H ₂ and O ₂ / O ₃ / H ₂ mixed gases is used as the reaction gas, and inert gas and non-reactive gas are used to reduce the oxidation ratio. Use by mixing. He, Ne, Ar, Kr, Xe, Rn gas is used as the inert gas, and N ₂ gas is used as the non-reactive gas. The mixing ratio of the mixed gas of the inert gas and the non-reactive gas and the reactive gas is 1: 0.012 to 100. In addition, the oxide film 6 preferably has a refractive index of about 1.44 to about 1.47 in order to efficiently remove the oxide film 6 during the etching process of the oxide film 6 that is performed later.

Referring to FIG. 2D, the nitride film pattern 5 and the oxide film 6 are removed, so that the surface of the first polysilicon layer 4 is in the shape of a wave hill.

Referring to FIG. 2E, a core oxide film 7 is formed on the contact hole 3 through the oxide film deposition and patterning process on the first polysilicon layer 4 having a wave hill shape. The second polysilicon layer 8 is formed on the first polysilicon layer 4 including the core oxide film 7.

The core oxide film 7 is formed of a BPSG, PSG, TEOS oxide film or the like to a thickness of 2000 to 6500 kPa. The second polysilicon layer 8 is a method of performing POCl ₃ doping after depositing undoped normal polysilicon, and an in-situ dope using a PH ₃ / SiH ₄ or PH ₃ / Si ₂ H ₆ mixed gas as a raw material gas. It is formed to a thickness of 1000 to 2500Å by a method of depositing polysilicon.

Referring to FIG. 2F, after etching the second and first polysilicon layers 8 and 4 by a blanket etch process, the core oxide layer 7 is removed to form a charge storage electrode 10 having a cylindrical structure. Is formed. The first polysilicon layer 4 is patterned to form a lower layer of the charge storage electrode 10 by a front surface etching process, and the second polysilicon layer 8 is formed as a spacer to form the charge storage electrode 10. It becomes a cylinder bar.

Subsequently, a capacitor is completed by forming a dielectric film and a plate electrode on the entire upper surface.

As described above, the present invention increases the effective surface area by making the surface of the charge storage electrode a wave hill structure, thereby sufficiently securing the capacitance of the capacitor, thereby improving the device's electrical characteristics and reliability while improving the integration of the device. It can be realized.

Claims (10)

Forming an interlayer insulating film on a substrate on which various elements for forming a semiconductor device are formed, and then forming a contact hole through which the substrate is exposed; Forming a first polysilicon layer on the interlayer insulating film including the contact hole, and then forming a plurality of nitride film patterns on the first polysilicon layer by a nitride film deposition and patterning process; Forming an oxide film on an exposed portion of the first polysilicon layer by a thermal oxidation process using the nitride film pattern as an oxide barrier layer; Removing the nitride layer pattern and the oxide layer to form a wave hill structure on the surface of the first polysilicon layer, and forming a core oxide layer through an oxide layer deposition and patterning process; Forming a second polysilicon layer on the first polysilicon layer including a core oxide film; And etching the entire second and first polysilicon layers to form a charge storage electrode having a cylindrical structure, and then removing the core oxide layer. The method of claim 1, The nitride film is deposited to a thickness of 500 to 1000 kW using a mixture of NH ₃ and SiH ₂ Cl ₂ at a temperature of 500 to 950 ° C. and a pressure of 0.05 to 10 Torr. The method of claim 1, The refractive index of the nitride film is a method of forming a charge storage electrode of a semiconductor device, characterized in that 1.465 to 20100. The method of claim 1, The nitride layer is formed by nitriding a thermal process using NH ₃ gas in an oxide film formed by a chemical vapor deposition method. The method of claim 1, The nitride film is a method of forming a charge storage electrode of a semiconductor device, characterized in that formed on the oxide film formed by the thermal oxidation process by the nitriding process using a NH ₃ gas. The method of claim 1, The oxide film is a charge storage electrode forming method of a semiconductor device, characterized in that formed in a thickness of 100 to 6000Å at a temperature of 650 to 1200 ℃ and a pressure of 0.2 Torr to 5 atm. The method of claim 1, The refractive index of the oxide film is a method of forming a charge storage electrode of a semiconductor device, characterized in that 1.44 to 1.47. The method of claim 1, Method for forming a charge storage electrode of a semiconductor device, characterized in that any one of O ₂ , O ₂ / O ₃ , O ₂ / H ₂ and O ₂ / O ₃ / H ₂ mixed gas is used as the reaction gas when forming the oxide film . The method of claim 1, The method of forming a charge storage electrode of a semiconductor device, characterized in that for mixing the inert gas and non-reactive gas to reduce the oxidation ratio when forming the oxide film. The method of claim 1, The method of forming a charge storage electrode of a semiconductor device, characterized in that the mixing ratio of the inert gas and the non-reactive gas mixed gas and the reaction gas when forming the oxide film is 1: 0.012 to 100.