KR100384868B1 - Method for fabricating capacitor - Google Patents

Abstract

The present invention is to provide a method of manufacturing a capacitor suitable for suppressing the increase in the effective oxide film thickness of the capacitor due to the oxide or organic matter remaining on the surface of the lower electrode after the isolation between the neighboring metal lower electrode between the cells, and the degradation of the leakage current characteristics. Depositing a capacitor oxide film on a semiconductor substrate having a predetermined process, selectively etching the capacitor oxide film to form a recess to form a lower electrode, depositing a ruthenium film on the entire surface including the recess, and depositing the capacitor oxide film Etching the ruthenium film until it is exposed, leaving the ruthenium film only in the recess, cleaning to remove the by-products remaining after etching the ruthenium film, and sequentially forming a dielectric film and an upper electrode on the cleaned ruthenium film. Including the steps .

Description

Manufacturing method of a capacitor {METHOD FOR FABRICATING CAPACITOR}

The present invention relates to a method for manufacturing a capacitor of a semiconductor device, and more particularly, to a method of forming a capacitor using a tantalum oxide film having a MIM structure.

As semiconductor devices are highly integrated, the capacitor structure is formed into a complex structure such as cylinder, pin, stack, or hemispherical silicon (HSG) to secure sufficient capacitance, thereby increasing the charge storage area. In addition, studies on high dielectric materials such as Ta ₂ O ₅ , TiO ₂ , SrTiO ₃ , and (Ba, Sr) TiO, which have a higher dielectric constant than SiO ₂ or Si ₃ N ₄ , are being actively conducted.

In particular, a tantalum oxide film (Ta ₂ O ₅ ) using Low Pressure Chemical Vapor Deposition (LPCVD) has a relatively high dielectric constant and is known to have high applicability.

Recently, as the device size decreases due to the integration of devices, the effective oxide film thickness is required to be reduced, and in order to manufacture a more reliable device, electrical characteristics such as a decrease in ΔC and a leakage current according to a bias voltage are required. It is necessary to improve.

In order to improve these characteristics, MIM (Metal-Insulator-Metal) capacitors, which use metal films instead of polysilicon as upper and lower electrodes, have been studied.In the manufacture of MIM capacitors, the effective oxide film thickness (T _ox ) and reliability of leakage current characteristics are improved. The process of depositing a high quality capacitor dielectric film will be very important to fabricate the device.

In particular, when manufacturing a MIM capacitor using a tantalum oxide film as a dielectric film, the tantalum oxide film has a directionality according to the orientation of the metal electrode, and the dielectric constant increases, and the metal electrode has an electrical energy barrier (or work function) with polysilicon. Since the effective oxide film thickness (T _ox ) can be reduced because of this large, there is an advantage of reducing the leakage current at the same effective oxide film thickness.

1 is a view showing a tantalum oxide film capacitor of the MIM structure manufactured according to the prior art.

Referring to FIG. 1, an interlayer dielectric (ILD) 13 is formed on a semiconductor substrate 11 on which a transistor manufacturing process including a source / drain 12 is completed, and then an interlayer dielectric 13 is selectively selected. Etching to form a contact hole through which a predetermined portion of the source / drain 12 is exposed.

Subsequently, after the polysilicon is formed on the entire surface including the contact hole, the polysilicon plug 14 embedded in the predetermined portion of the contact hole is formed by recessing the substrate to a predetermined depth by an etch back process. On the plug 14, a laminated film of titanium silicide 15 and titanium nitride 16 is formed.

At this time, the titanium silicide 15 forms an ohmic contact between the polysilicon plug 14 and the subsequent lower electrode, and the titanium nitride 16 remains in the lower electrode during the subsequent heat treatment of the tantalum oxide film. It serves as a diffusion barrier film that prevents oxygen from diffusing into the polysilicon plug 14 or the semiconductor substrate 11.

Next, the nitride-based etch stop film 17 and the capacitor oxide film 18 are formed on the interlayer insulating film 13 including titanium nitride 16, and then the capacitor oxide film 18 and the etch stop film are formed as storage node masks. (17) is sequentially etched to form a lower electrode region (hereinafter abbreviated as 'concave portion') aligned with the polysilicon plug 14.

Subsequently, a ruthenium film is deposited along the surface of the capacitor oxide film 18 including the open recesses, and then the ruthenium lower electrode 19 is isolated from each other between neighboring cells by leaving the ruthenium film only in the recesses through etch back or chemical mechanical polishing. ).

Subsequently, after the tantalum oxide film 21 is deposited on the entire surface including the ruthenium-lower electrode 19, a heat treatment for removing oxygen deficiency and a heat treatment for removing impurities remaining in the tantalum oxide film 21 are sequentially performed. do.

Next, a titanium nitride (hereinafter abbreviated as 'CVD-TiN') or ruthenium film by CVD is deposited as the upper electrode 22 on the tantalum oxide film 21.

However, in the related art, when the ruthenium lower electrode between adjacent cells is separated by etch back or chemical mechanical polishing, ruthenium forms an oxide 20 and is etched. After the isolation process, the oxide 20 is present on the surface of the lower electrode. After the deposition and heat treatment of the dielectric film, the effective oxide film thickness (T _ox ) is increased by the oxide between the dielectric film and the lower electrode, and oxidation of the lower electrode occurs due to oxygen diffusion of the oxide even at the same heat treatment temperature. There is a problem that the characteristics are deteriorated. In addition, even when an organic material is present on the lower electrode surface, there is a problem that the electrical characteristics are deteriorated.

Therefore, prior to depositing the dielectric film, a cleaning process such as an oxide or an organic material on the lower electrode surface is necessary.

The present invention has been made to solve the above-mentioned problems of the prior art, the isolation of the metal lower electrode between the neighboring cells after the increase in the effective oxide film thickness and the leakage current characteristics of the capacitor due to the oxide or organic residue remaining on the surface of the lower electrode It is an object of the present invention to provide a method for manufacturing a capacitor suitable for suppressing the problem.

1 is a view showing a tantalum oxide capacitor of the MIM structure manufactured according to the prior art,

2A to 2D are cross-sectional views illustrating a method of manufacturing a tantalum oxide film capacitor having a MIM structure according to an embodiment of the present invention;

3 is a view comparing the leakage current characteristics of the ruthenium film with or without the SC-1 cleaning.

* Explanation of symbols for the main parts of the drawings

31 semiconductor substrate 34 polysilicon plug

35: titanium silicide 36: titanium nitride

38 capacitor oxide film 39 ruthenium-lower electrode

41 tantalum oxide film 42 upper electrode

According to another aspect of the present invention, there is provided a method of manufacturing a capacitor, the method comprising: depositing a capacitor oxide film on a semiconductor substrate on which a predetermined process is completed, and selectively etching the capacitor oxide film to form a recess to form a lower electrode; Depositing a ruthenium film on the entire surface including a recess, etching the ruthenium film until the capacitor oxide film is exposed, leaving the ruthenium film only in the recess, and cleaning to remove by-products remaining after the ruthenium film is etched, And sequentially forming a dielectric film and an upper electrode on the cleaned ruthenium film.

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

2A to 2D are cross-sectional views illustrating a method of manufacturing a tantalum oxide film capacitor having a MIM structure according to an embodiment of the present invention, wherein a tantalum oxide film is used as a dielectric film of a capacitor, a ruthenium film is used as a lower electrode, and a TiN or The case where a ruthenium film is used is shown.

As shown in FIG. 2A, an interlayer insulating film (ILD) 33 is formed on the semiconductor substrate 31 on which the transistor manufacturing process including the source / drain 32 is completed.

After forming a contact mask on the interlayer insulating layer 33 through normal exposure and development, the interlayer insulating layer 33 is etched using the contact mask to form a contact hole through which a predetermined portion of the source / drain 32 is exposed. And remove the contact mask.

Subsequently, after the polysilicon is formed on the entire surface including the contact hole, the polysilicon plug 34 embedded in the predetermined portion of the contact hole is formed by recessing it by a predetermined depth by an etch back process.

After depositing titanium (Ti) on the entire surface, rapid thermal treatment (RTP) causes a reaction between the silicon (Si) atoms of the polysilicon plug 34 and the titanium (Ti) to cause the titanium on the polysilicon plug 34. The silicide 35 is formed. At this time, the titanium silicide 35 is an ohmic contact layer for improving the contact resistance between the polysilicon plug 34 and the subsequent lower electrode.

Subsequently, after the titanium nitride (TiN) 36 is formed on the titanium silicide 35, the titanium nitride 36 is subjected to chemical mechanical polishing (CMP) or etching until the surface of the interlayer insulating film 33 is exposed. It is refilled and embedded in the contact hole.

Here, the titanium nitride 36 serves as a diffusion barrier film that prevents oxygen remaining in the lower electrode from diffusing into the polysilicon plug 34 or the semiconductor substrate 31 during the subsequent heat treatment of the tantalum oxide film.

As shown in FIG. 2B, after the nitride-based etch stop layer 37 and the capacitor oxide layer 38 are formed on the interlayer dielectric layer 33 including titanium nitride 36, the capacitor oxide layer 38 is formed as a storage node mask. ) And the etch stop layer 37 are sequentially etched to open the recesses aligned with the polysilicon plug 34.

Subsequently, a ruthenium film, such as ruthenium-lower electrode 39, is deposited using low pressure chemical vapor deposition (LPCVD) along the surface of the capacitor oxide film 38 having the recesses open.

The low pressure chemical vapor deposition method of the ruthenium-lower electrode 39 is as follows. The ruthenium-lower electrode 39 is abbreviated as a ruthenium film.

First, as a source material of the ruthenium film, dicyclopentadiene ruthenium [Ru (Cp) ₂ ], trioctane dionate (hereinafter abbreviated as 'Ru (od) ₃ '), and diethylcyclopentadiene ruthenium [hereinafter referred to as 'Ru' (EtCp) ₂ 'abbreviated as', dimethylcyclopentadieneruthenium [Ru (MeCp) ₂ ], preferably using either of the economically inexpensive Ru (od) ₃ or Ru (EtCp) ₂ and vaporizing Vaporizer is used to bring the source material into the vapor phase.

As such, argon gas is used as a carrier gas to flow the ruthenium source material into the reaction chamber, and the flow rate of argon gas is maintained at 50 sccm to 200 sccm.

Next, only the pure ruthenium film is deposited by pyrolysing the ruthenium source material by flowing oxygen gas which is a reaction gas into the reaction chamber.

At this time, the flow rate of the oxygen gas is maintained at 50sccm to 400sccm, the pressure of the reaction chamber is maintained at 0.1torr to 10torr, and the substrate on which the ruthenium film is deposited is maintained at 230 ° C to 350 ° C.

Next, argon is flowed as a diluent gas to remove oxygen gas and reaction byproducts, and the flow rate of argon gas is maintained at 400 sccm to 800 sccm.

By such low pressure chemical vapor deposition, a ruthenium film 39 having a thickness of 100 kPa to 300 kPa is deposited.

Next, the ruthenium-lower electrode 39 is left only in the recess through etch back or chemical mechanical polishing. That is, the ruthenium-lower electrode 39 is isolated from neighboring cells.

At this time, an oxide or organic material remains on the surface of the ruthenium-lower electrode 39 when the ruthenium-lower electrode 39 is isolated, and a cleaning process is performed to remove the ruthenium-lower electrode 39.

The above washing process is performed for 5 minutes to 10 minutes with a solution containing an SC-1 solution, such as NH ₄ OH: 4H ₂ O ₂ : 2OH ₂ O.

As illustrated in FIG. 2C, a tantalum oxide film 41 is deposited on the entire surface including the ruthenium-lower electrode 39 on which the surface cleaning process is performed by low pressure chemical vapor deposition.

The low pressure chemical vapor deposition method of the tantalum oxide film 41 is described as follows.

First, tantalum ethylene [Ta (OC ₂ H ₅ ) ₅ ] is flowed through nitrogen (N ₂ ), which is a carrier gas, as a raw material in the reaction chamber. At this time, the flow rate of nitrogen is maintained at 350 sccm to 450 sccm.

Then, oxygen is flowed into the reaction chamber as a reaction gas (or an oxidant) at a flow rate of 20 sccm to 50 sccm, and then a tantalum oxide film is thermally decomposed on the substrate to be thermally decomposed on the substrate heated at a temperature of 300 ° C to 450 ° C. Deposit. At this time, the reaction chamber maintains a pressure of 0.1torr to 2torr.

On the other hand, since tantalum ethylene is widely used as a source for forming a tantalum oxide film, it is liquid at room temperature and has a property of vaporizing at 145 ° C. Should be made. For example, tantalum ethylene is changed into a gaseous state in a vaporizer maintained at 170 ° C to 190 ° C, and then loaded into nitrogen gas and supplied into the reaction chamber.

As described above, after the tantalum oxide film 40 is deposited, plasma heat treatment or UV / O ₃ heat treatment is performed at low temperature to remove oxygen vacancies in the tantalum oxide film.

At this time, the plasma heat treatment proceeds at a power of 200W to 500W for 30 seconds to 120 seconds at a temperature of 300 ° C to 500 ° C in a mixed gas atmosphere of oxygen (O ₂ ), N ₂ O or N ₂ + O ₂ .

And, UV / O ₃ thermal treatment is conducted while maintaining the strength of the lamp during 2-10 minutes at a temperature of 300 ℃ ~500 ℃ to ^{15㎽ / cm 2 ~30㎽ / cm 2} .

As described above, when the tantalum oxide film 40 is subjected to plasma heat treatment or UV / O ₃ heat treatment at low temperature (300 ° C. to 500 ° C.), oxygen deficiency in the tantalum oxide film can be sufficiently removed.

Next, after the oxygen deficiency in the tantalum oxide film 40 is removed, rapid thermal treatment (RTP) or furnace anneal is performed at high temperature to obtain dielectric characteristics.

At this time, rapid heat treatment is performed for 30 seconds to 60 seconds at a temperature of 500 ° C to 650 ° C in a mixed gas atmosphere of nitrogen (N ₂ ), argon (Ar) or helium (He) in an inert gas and oxygen gas. do.

The heat treatment is performed for 10 minutes to 30 minutes at a temperature of 500 ° C to 600 ° C in a mixed atmosphere of inert gas and oxygen gas of nitrogen (N ₂ ), argon (Ar) or helium (He).

In the rapid heat treatment and furnace treatment processes, the mixing ratio of oxygen and inert gas is maintained at 1:10 to 10:10.

In this manner, after the oxygen deficiency in the tantalum oxide film 41 is removed, heat treatment is performed at a high temperature (500 ° C to 700 ° C), whereby impurities such as carbon and hydrogen remaining in the tantalum oxide film 41 can be removed.

As shown in FIG. 2D, a titanium nitride or ruthenium film is deposited as the upper electrode 42 on the tantalum oxide film 41.

When the above-described process is completed, a capacitor having a concave structure is formed, and the capacitor oxide film may be diped out to form a cylindrical capacitor.

3 is a view comparing the leakage current characteristics of tantalum capacitors with and without SC-1 cleaning of ruthenium films, and the effective oxide film thickness (T _ox ) of the capacitors is different depending on the presence or absence of SC-1 cleaning. The leakage current characteristics are shown in terms of (Electric field, mV / cm).

Referring to FIG. 3, the effective oxide film thickness was 16.51 경우 when the ruthenium film was not cleaned and increased to 18.67 후 after cleaning, but the leakage current at 0.9 V was 4.28 × 10 ^-9 A at 7.98 × 10 ^-9 A / cm ² . It can be seen that it is reduced to / cm ² .

As a result, when compared with the same effective oxide film thickness, the leakage current is expected to be smaller when the cleaning process is performed.

3 is a view illustrating a case where only the cleaning process is performed before the etchback process of the ruthenium film, the electrical characteristics of the capacitor may be further improved when the post-etchback cleaning process is performed when the post-etchback cleaning process is performed. will be.

The present invention is applicable to a capacitor using a tantalum oxide film as a dielectric film and a metal using an upper and lower electrode, and all DRAM and PZT using a high-k dielectric such as BST [(Ba _x Sr _1-x ) TiO ₃ ] as a dielectric film. It is applicable to all ferroelectric memories (FeRAM) using ferroelectrics as dielectric films.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention as described above can reduce the effective oxide thickness (T _ox ) and improve the leakage current characteristics of the capacitor by cleaning the oxide or organic matter remaining on the surface of the ruthenium film after the etch back of the ruthenium film used as the lower electrode. It works.

Claims (2)

In the manufacturing method of a capacitor, Depositing a capacitor oxide film on a semiconductor substrate on which a predetermined process is completed; Selectively etching the capacitor oxide layer to form a recess in which a lower electrode is to be formed; Depositing a ruthenium film on the entire surface including the concave portion; Etching the ruthenium film until the capacitor oxide film is exposed and leaving the ruthenium film only in the recess; Washing to remove by-products remaining after etching the ruthenium film; And Sequentially forming a dielectric film and an upper electrode on the cleaned ruthenium film Method for producing a capacitor, characterized in that comprises a. The method of claim 1, The cleaning step, Method for producing a capacitor, characterized in that for 5 minutes to 10 minutes using a solution mixed with NH ₄ OH: 4H ₂ O ₂ : 2OH ₂ O.