KR100268782B1 - Method for manufacturing capacitor of semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming a capacitor of a semiconductor device is provided to improve the electrical characteristics of the capacitor and thus to improve the characteristics and the reliability of the semiconductor device. CONSTITUTION: A bottom structure like an isolation film and a gate oxide and a gate electrode and a bit line is formed on a semiconductor substrate(11). Then, a planarization film is formed, and a contact hole is formed using an interlayer insulation film as a contact mask. And, a contact plug is formed by etching a poly silicon film, and a charge storage electrode(13) is formed to contact with the contact plug. And, a native oxide on a surface of the charge storage electrode is removed using HF+H2O or HF+NH4F+H2O. Then, the charge storage electrode nitrifies the whole surface of a doped poly silicon. The nitrified surface of the charge storage electrode is plasma-processed to form a nitride oxide(SiOxNy). A Ta2O5 film(17) is deposited on an upper part of the oxidized charge storage electrode by an LPCVD method, and is annealed in an N2O or O2 atmosphere. And, after depositing a TiN, a plate electrode is formed by depositing a doped poly silicon. And, a capacitor is completed by patterning the plate electrode.

Description

Capacitor Formation Method of Semiconductor Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a capacitor of a semiconductor device, and in particular, when using an LPCVD Ta ₂ O ₅ film having excellent step coverage as a dielectric of a capacitor, a special treatment is performed on the surface of the charge storage electrode before forming the LPCVD Ta ₂ O ₅ film. By doing so, the present invention relates to a technology capable of improving electrical characteristics of capacitors and thereby improving characteristics and reliability of semiconductor devices.

Recently, due to the trend toward higher integration of semiconductor devices, it is difficult to form capacitors with sufficient capacitance due to a decrease in cell size.

In particular, in a DRAM device composed of one MOS transistor and a capacitor, a material having a high dielectric constant is used as the dielectric film, a thickness of the dielectric film is increased, or the surface area of the charge storage electrode is increased to increase the capacitance of the capacitor. There is a way.

Although not shown, looking at the capacitor manufacturing method of the semiconductor device according to the prior art as follows.

First, a device isolation oxide film and a gate oxide film are formed on a semiconductor substrate, and a MOS field effect transistor including a gate electrode and a source / drain electrode is formed, and then an interlayer insulating film is formed on the entire surface of the structure.

Next, a charge storage electrode contact hole is formed by removing an interlayer insulating layer on an upper portion of the source / drain electrode, which is intended to be a charge storage electrode contact, and polycrystalline a charge storage electrode contacting the source / drain electrode through the contact hole. After forming a silicon layer pattern, a dielectric film having a laminated structure of an oxide film, a nitride film, or an oxide film-nitride film-oxide film is coated on the surface of the charge storage electrode, and a plate electrode is formed on the dielectric film to surround the charge storage electrode. Complete

In the capacitor of the semiconductor device according to the prior art as described above, the dielectric film requires high dielectric constant, low leakage current density, high dielectric breakdown voltage, and stable interfacial characteristics with the upper and lower electrodes. The oxide film has a dielectric constant of about 3.8. The nitride film is relatively small at about 7.2, and the polysilicon layer used as an electrode has a relatively high resistivity of about 800 to 1000 mu OMEGA cm.

In order to solve the above problems, a high-k dielectric film such as a Ta ₂ O ₅ film is used instead of a dielectric film having a stacked structure of an oxide film-nitride film-oxide film.

The Ta ₂ O ₅ film is widely considered to be used as a dielectric film of a capacitor of a high density memory device of 256M DPAM or more.

However, in the capacitor using the Ta ₂ O ₅ film as the dielectric film, the electrical characteristics of the capacitor change greatly according to the deposition method of the Ta ₂ O ₅ film.

That is, when the Ta ₂ O ₅ film is deposited to form a flat plate capacitor by plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD) is called. The electrical properties are better than that of the Ta ₂ O ₅ film.

However, the capacitor actually used is a device having various structures such as a cylindrical shape and a fin structure, and since these devices have a large step, the Ta ₂ O ₅ film should have excellent step coverage.

However, the Ta ₂ O ₅ film deposited by the PECVD method is very poor step coverage compared to the Ta ₂ O ₅ film deposited by the LPCVD method, there is a problem that causes high leakage current when applied to the actual device.

The present invention uses a Ta ₂ O ₅ film deposited by the LPCVD method with excellent step coverage when forming a capacitor, and charge storage before depositing the Ta ₂ O ₅ film deposited by the LPCVD method to form a capacitor It is an object of the present invention to provide a method for forming a capacitor of a semiconductor device by improving the electrical characteristics of the capacitor and thereby improving the characteristics and reliability of the capacitor by special treatment on the electrode surface.

1 is a cross-sectional view showing a method of forming a capacitor of a semiconductor device according to the present invention.

2 is a graph showing leakage current characteristics of a method for forming a capacitor of a semiconductor device according to the present invention.

<Explanation of symbols for main parts of drawing>

11: semiconductor substrate 13: doped polycrystalline silicon

15 plasma treated nitride film 17 LPCVD Ta ₂ O ₅ film

In order to achieve the above object, a method of forming a capacitor of a semiconductor device according to the present invention comprises the steps of forming a charge storage electrode of the doped polycrystalline silicon on the semiconductor substrate, the step of nitriding the entire surface of the charge storage electrode; a step of oxidizing the surface of the nitride charge storage electrode, and a step of depositing a Ta ₂ O ₅ LPCVD film method to the charge electrode electrode surface, the step of plasma processing the Ta ₂ O ₅ film and the Ta ₂ O ₅ film And a step of forming a plate electrode on the entire surface.

On the other hand, the principles of the present invention for achieving the above object, the step coverage is deposited as excellent LPCVD method, because the step coverage which when the dielectric film formed deposited PECVD method Ta ₂ O ₅ film of the capacitor to poor Ta ₂ O uses ₅ film, and oxidation after the LPCVD method as-deposited Ta ₂ O ₅ as a film by nitriding Chemistry a lower layer prior to depositing a film of Ta ₂ O ₅ deposition by the LPCVD method to have excellent electrical characteristics the plasma treatment, the The Ta ₂ O ₅ film deposited by the LPCVD method is deposited to perform plasma treatment or UV-O ₃ gas treatment, and heat treatment is performed to polycrystalline the Ta ₂ O ₅ film, thereby improving the electrical characteristics of the capacitor.

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

1 is a cross-sectional view showing a method of forming a capacitor of a semiconductor device according to the present invention.

First, lower structures such as an isolation layer (not shown), a gate oxide layer (not shown), a gate electrode (not shown), and a bit line (not shown) are formed on the semiconductor substrate 11.

Next, a planarization film (not shown) is formed over the entire surface.

Then, an interlayer insulating film (not shown) is formed of an undoped oxide film.

In addition, the interlayer insulating layer forms a contact hole (not shown) in a portion that is intended to be a contact portion using a contact mask.

Then, a polysilicon film (not shown) is formed on the entire surface of the structure by chemical vapor deposition (CVD), and then etched so that the polycrystalline silicon film remains only inside the contact hole (not shown). As a result, a contact plug (not shown) filling the contact hole (not shown) is formed.

In addition, the charge storage electrode 13 is formed to contact the contact plug (not shown). Here, the charge storage electrode 13 is formed of polycrystalline silicon doped with impurities, and the structure of the charge storage electrode may have a cylindrical shape, a fin shape, and another structure. In addition, hemispherical grained silicate glass (HSG) may be used for the structure of the charge storage electrode 13.

Next, the natural oxide film generated on the surface of the charge storage electrode 13 is removed. The natural oxide film is removed using HF + H ₂ O or HF + NH ₄ F + H ₂ O, which is an oxide film etching solution.

Thereafter, the entire surface of the doped polycrystalline silicon, which is the charge storage electrode 13, is nitrided. Here, the nitride of the charge storage electrode 13 is 40 ~ 100 seconds at a temperature of about 800 ~ 900 ℃ by the method of rapid thermal nitration (RTN) using NH ₃ gas. Conduct.

In addition, the surface of the nitrided charge storage electrode is treated in a plasma state using a gas containing oxygen such as N ₂ O and O ₂ to form a thin oxynitride layer (SiOxNy). At this time, the power (power) for generating the plasma is about 100 ~ 200W.

The nitrided charge storage electrode has a substrate temperature of about 150 to 450 ° C. and a pressure of about 1 mTorr to 9 Torr.

On the other hand, instead of oxidizing the surface of the charge storage electrode 15 nitrided by the plasma excitation gas, the surface of the nitrided charge storage electrode 15 is oxidized by dry or wet oxidation using O ₂ or H ₂ O steam. You can. However, such an oxidation method requires a process at a high temperature of 700 ° C. or higher, so that the oxidation resistance of the nitride film itself is destroyed and oxidized to the doped polycrystalline silicon 13 under the nitride film, thereby increasing the effective oxide film thickness of the capacitor. There is this.

In addition, the process of oxidizing the nitrided charge storage electrode 15 may deposit a portion of the Ta ₂ O ₅ film to be deposited on the surface of the nitrided charge storage electrode 15 by PECVD, and then again by LPCVD. Alternatively, the remainder of the Ta ₂ O ₅ film can be deposited and oxidized.

At this time, by using the PECVD method, the Ta ₂ O ₅ film is formed using N ₂ O or O ₂ gas and Ta (OC ₂ H ₅ ) ₅ as a raw material. ) Ta ₂ O ₅ film is deposited on the condition of power of 5 ~ 50Å.

For reference, when the temperature is higher than 900 ° C. under the conditions of the RTN process or the processing time is long, the nitrided part becomes thick on the surface of the charge storage electrode so that the nitrided part is not sufficiently oxidized in the subsequent oxidation process. If not, will occur.

Table 1 below shows the thickness of the nitride film on the semiconductor substrate at different RTN temperatures.

Even if the surface of the nitrided charge storage electrode is changed to an oxynitride film, the effect on the effective oxide film thickness of the capacitor using the Ta ₂ O ₅ film is 3 kΩ or less, but the leakage current characteristics can be improved.

That is, when the RTN treatment is performed after the charge storage electrode HF cleaning process, a SixNy film is formed on the surface of the charge storage electrode, and the surface is subjected to plasma oxidation (N ₂ O), thereby transforming SixNy into SixOyNz to reduce the leakage current of the capacitor.

Then, a Ta ₂ O ₅ film 17 is deposited to a predetermined thickness on the oxidized charge storage electrode by LPCVD. At this time, the Ta ₂ O ₅ film 17 is deposited using a N ₂ O or O ₂ gas and Ta (OC ₂ H ₅ ) ₅ as a raw material at a pressure of about 1mTorr ~ 9Torr and a temperature of about 350 ~ 450 ℃. (Figure 1)

Then, to remove oxygen and carbon deficiency in the Ta ₂ O ₅ film, is processed by the Ta ₂ O ₅ N ₂ O or O film temperature of 150 ~ 450 ℃ to the plasma gas degree by the _second gas. Here, instead of the plasma treatment by the N ₂ O or O ₂ gas may be treated with UV-O ₃ gas activated by ultraviolet light.

In order to polycrystallize the Ta ₂ O ₅ film, heat treatment is performed in an N ₂ O or O ₂ atmosphere at a temperature of about 700 to 820 ° C.

Subsequently, TiN is deposited on the entire surface in a subsequent process, and then doped polycrystalline silicon is deposited to form a plate electrode.

The plate electrode is then patterned to complete the capacitor formation process.

For reference, FIG. 2 is a Ta ₂ O ₅ capacitor having an effective oxide film thickness of 30 μs on a cylinder-shaped charge storage electrode. When Ta ₂ O ₅ deposition is performed only by PECVD, after the PECVD process is sequentially deposited by LPCVD, Leakage current characteristics for each case of Ta ₂ O ₅ film formation by successive deposition by LPCVD after LPCVD.

As mentioned above, the leakage current value is highest when Ta ₂ O ₅ is deposited only by PECVD method, and the leakage current value is lowest when Ta ₂ O ₅ thin film is formed by using PE / LPCVD method. Here, when Ta ₂ O ₅ is deposited only by the PECVD method, the leakage current value is the highest because the step coverage of the PECVD Ta ₂ O ₅ is poor.

As described above, the method for forming a capacitor of a semiconductor device according to the present invention improves poor step coverage of a Ta ₂ O ₅ film deposited by PECVD in a capacitor using a Ta ₂ O ₅ film having a high dielectric constant as a dielectric film. To this end, a Ta ₂ O ₅ film is deposited by an LPCVD method having excellent step coverage, and the electrical characteristics of the capacitor are improved by specially treating the surface of the lower charge storage electrode before depositing the Ta ₂ O ₅ film deposited by the LPCVD method. There is an advantage of preventing leakage current from occurring and thereby improving characteristics and reliability of the semiconductor device.

Claims (12)

Forming a charge storage electrode with doped polycrystalline silicon on a semiconductor substrate, nitriding the entire surface of the charge storage electrode, oxidizing a surface of the nitrided charge storage electrode, and a surface of the charge storage electrode the Ta ₂ O ₅ film and the step of depositing the LPCVD method, the Ta ₂ O ₅ film is plasma treatment comprises a step of forming a step of heat-treating the Ta ₂ O ₅ film and a plate electrode on the entire surface of the upper A method for forming a capacitor of a semiconductor device. The method of claim 1, wherein the charge storage electrode is nitrided using an RTN method. The method of claim 1, wherein the RTN method is performed at a temperature of about 800 ° C. to 900 ° C. for 40 to 100 seconds. The method of claim 1, wherein the surface of the nitrided charge storage electrode is oxidized using an excited plasma gas of O ₂ or N ₂ O gas. The method of claim 1, wherein the oxidation of the surface of the nitrided charge storage electrode is performed at a temperature of about 150 ° C. to about 450 ° C. 6. The method of claim 1, wherein the oxidation of the surface of the nitrided charge storage electrode is performed by dry or wet oxidation using O ₂ or H ₂ O vapor. The method of claim 1, wherein the oxidation of the surface of the nitrided charge storage electrode is performed by depositing a portion of the Ta ₂ O ₅ film by PECVD and then depositing the remaining portion of the Ta ₂ O ₅ film by LPCVD. A method of forming a capacitor of a semiconductor device. The method of claim 7, wherein the Ta ₂ O ₅ film deposited by the PECVD method has a thickness of about 5 to about 50 GPa. The method of claim 7 or 8, wherein the PECVD method using a N ₂ O or O ₂ gas and Ta (OC ₂ H ₅ ) ₅ as a raw material to deposit at a pressure of about 1mTorr ~ 9Torr and a temperature of 350 ~ 450 ℃ A method of forming a capacitor of a semiconductor device, characterized in that. The method of claim 1, wherein the Ta ₂ O ₅ film is plasma treated at a temperature of about 150 ° C. to 450 ° C. with N ₂ O or O ₂ gas. The method of claim 1 or 10, wherein the plasma treatment of the Ta ₂ O ₅ film is performed using UV-O ₃ gas activated by ultraviolet rays. The method of claim 1 or 10, wherein the Ta ₂ O ₅ film is heat-treated in the O ₂ or N ₂ O atmosphere at a temperature of about 700 ~ 820 ℃ to form a capacitor of the semiconductor device, characterized in that the Ta ₂ O ₅ film polycrystalline Way.

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