KR20010005124A - Method for forming feram capable of preventing hydrogen diffusion - Google Patents

Abstract

PURPOSE: A method for fabricating a ferroelectric memory device having a barrier to hydrogen diffusion is provided to prevent degradation in polarization characteristics of a ferroelectric capacitor. CONSTITUTION: A transistor having a gate electrode(14) and a source/drain(15), a capacitor having lower and upper electrodes(20,22) and a ferroelectric layer(21), the first and the second metallization layers(26,28), and the like are formed on a semiconductor substrate(11). Then, an insulating layer(29) is formed on the entire resultant structure, and a barrier to hydrogen diffusion is formed thereon. Particularly, the hydrogen diffusion barrier is composed of a titanium layer(30) and a titanium oxide layer(31). Thereafter, a passivation layer(32) is formed on the hydrogen diffusion barrier(30,31). The hydrogen diffusion barrier can trap hydrogen produced during the formation of the passivation layer(32) to the interface between the titanium layer(30) and the titanium oxide layer(31).

Description

Method for manufacturing ferroelectric memory device that can prevent hydrogen diffusion {METHOD FOR FORMING FERAM CAPABLE OF PREVENTING HYDROGEN DIFFUSION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor memory device, and more particularly, to a method of manufacturing a ferroelectric memory device capable of preventing a decrease in ferroelectric properties due to hydrogen diffusion.

By using a ferroelectric material in a capacitor in a semiconductor memory device, development of a device capable of using a large-capacity memory while overcoming the limitation of refresh required in a conventional dynamic random access memory (DRAM) device has been in progress. A ferroelectric random access memory (FeRAM) device is a nonvolatile memory device that not only stores stored information even when a power supply is cut off, but also has an operation speed comparable to that of a conventional DRAM.

As the storage material of the FeRAM device, SrBi ₂ Ta ₂ O ₉ (hereinafter referred to as SBT) and Pb (Zr, Ti) O ₃ (hereinafter referred to as PZT) thin films are mainly used. Ferroelectrics have dielectric constants ranging from hundreds to thousands at room temperature, and have two stable remnant polarization states, making them thinner and enabling their application to nonvolatile memory devices. Nonvolatile memory devices using a ferroelectric thin film use the principle of inputting a signal by adjusting the direction of polarization in the direction of an applied electric field and storing digital signals 1 and 0 by the direction of residual polarization remaining when the electric field is removed. .

As the ferroelectric material of the capacitor in the FeRAM element _{PZT, SBT, Sr x Bi y} (Ta i Nb j) 2 O 9 in the conventional case of using a ferroelectric having a perovskite (perovskite) structure, such as (the SBTN) Pt, Ir The upper electrode is formed of a metal such as Ru, Pt alloy, or the like.

As described above, the FeRAM device is a memory device that uses polarization characteristics of a ferroelectric film such as SBT. Due to the characteristics of FeRAM, many polarization processes have to be repeated until the lifetime of the device can be used as a reliable device. Therefore, improvement in polarization characteristics and prevention of deterioration are basic requirements for FeRAM devices. However, deterioration in polarization characteristics occurs during the FeRAM device manufacturing process, which is a critical disadvantage in securing the reliability of the FeRAM device.

In order to protect the device after the metallization process, a double layer of SiO ₂ / Si ₃ N ₄ is deposited as a passivation layer, and the decrease in polarization characteristics is known to be caused by hydrogen generated during the formation of the device protection layer. In order to prevent the diffusion of hydrogen generated in the process of forming a device protection layer, a hydrogen diffusion preventing layer (Ti) -based single layer is formed, but the polarization characteristic is not effectively suppressed.

The present invention devised to solve the above problems is a method of forming a hydrogen diffusion barrier of a ferroelectric memory device, which can prevent the degradation of polarization characteristics of the ferroelectric capacitor due to hydrogen generated in the oxide film and nitride film forming process for device protection The purpose is to provide.

1 is a cross-sectional view of a ferroelectric memory device manufacturing process according to an embodiment of the present invention;

2 is a process sectional view showing a state where the pad is exposed.

* Description of reference numerals for the main parts of the drawings *

20: lower electrode 21: ferroelectric film

22: upper electrode 26: first metal wiring

28: first metal wiring and pad 29: insulating film

30: Ti film 31: TiO ₂ film

32: element protection film

The present invention for achieving the above object is a first step of forming an insulating film on the entire structure of the transistor, the ferroelectric capacitor and the metal wiring is completed; A second step of forming a hydrogen diffusion prevention film formed of a titanium film and a titanium oxide film sequentially deposited on the insulating film; And a third step of forming a device protection film on the hydrogen diffusion prevention film.

The present invention forms an insulating film using a source containing no hydrogen on a substrate on which metal wiring and pad formation are completed, in order to prevent degradation of ferroelectric properties due to hydrogen generated during the formation of an oxide film and a nitride film for protecting the device. It is characterized by forming a hydrogen diffusion barrier film having a two-layer structure consisting of a Ti film and a TiO ₂ film, subjecting the TiO ₂ film to oxygen plasma treatment, and then depositing a SiO ₂ film and a Si ₃ N ₄ film for device protection.

Subsequently, the Si ₃ N ₄ film, the SiO ₂ film, the TiO ₂ film, and the Ti film are selectively etched using a pad (PAD) mask to form a contact hole exposing the pad, and then the Ti film exposed on the contact hole sidewall is oxygenated. Treatment with plasma prevents shorting of the wire and the Ti film.

Hereinafter, a method of manufacturing a ferroelectric memory device according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, the first interlayer is formed on the semiconductor substrate 11 on which the transistor formation, which consists of the device isolation film 12, the gate insulating film 13, the gate electrode 12, and the source and drain 13, is completed. An insulating film 16 is formed, and a bit line 17 connected to the source and drain 15 of the transistor is formed through a contact hole formed in the first interlayer insulating film 16.

Subsequently, a second interlayer insulating film 18 is formed on the entire structure where the bit line 17 is formed, an adhesive layer 19 is formed on the second interlayer insulating film 18, and the lower electrode 20 and the ferroelectric film are formed. The capacitor which consists of 21 and the upper electrode 22 is formed.

Next, a third interlayer insulating film 23 is formed on the entire structure of the capacitor formation, the third interlayer insulating film 23 is selectively etched to form a contact hole for exposing the upper electrode 22, and the interlayer insulating film (23), the second interlayer insulating film 18 and the first interlayer insulating film 16 are selectively etched to form contact holes for exposing the source and drain 14 formed in the semiconductor substrate 10.

Next, in order to prevent deterioration of the characteristics of the capacitor during the subsequent metal wiring and diffusion barrier formation process, a first diffusion barrier layer 24 is formed to contact the upper electrode layer.

Subsequently, the second diffusion barrier 25, the first metal wiring 26, and the intermetallic insulating film 27 are formed, and the intermetallic insulating film is selectively etched to form the first metal wiring 26 and the second metal wiring. Contact holes (not shown) for connection of the second and second metal wires and pads 28 for input / output and power supply are formed.

As described above, the insulating film 29 having a thickness of 1000 to 5000 kW is used to form 0 ₃ -TEOS (tetraethyl orthosilicate) by using a source that does not use hydrogen on the entire structure where the second metal wiring and the pad 28 are completed. The Ti film 20 having a thickness of 100 kPa to 1000 kPa and the TiO ₂ film 31 having a thickness of 100 kPa to 1500 kPa are formed on the insulating film 29 by sputtering. Subsequently, oxygen plasma treatment is performed to make the TiO ₂ film metastable in TiO _x (not shown), and then an element protective film 32 made of SiO ₂ , Si ₃ N _4, or the like is formed.

As described above, by forming a double film of the Ti film 30 / TiO ₂ film 31 as the hydrogen diffusion prevention film, hydrogen generated in the process of forming the device protection film 32 can be trapped at the interface of Ti / TiO ₂ . have. In addition, the oxygen plasma treatment forms the surface of the TiO ₂ film as metastable TiO _{x so} that a broken bond of TiO _x captures hydrogen, thereby more effectively preventing hydrogen diffusion. Thus, the first trapped hydrogen prevents the penetration of hydrogen that is additionally generated during the double passivation layer deposition process, thereby suppressing a decrease in polarization characteristics of the device.

Meanwhile, as shown in FIG. 2, the device protection film 32, the TiO ₂ film 31, the Ti film 30, and the insulating film 29 are selectively etched for wiring after the device protection film 32 is formed. As a result, a contact hole exposing the pad 28 is formed. At this time, oxygen plasma treatment is performed to insulate the Ti film 30 exposed on the sidewalls of the contact hole. As such, the portion of the Ti film 30 exposed by the oxygen plasma treatment is changed to TiO _x to prevent shorts that may occur during wiring formation.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

According to the present invention made as described above, a hydrogen diffusion prevention film having a double film structure consisting of a Ti film and a TiO ₂ film is formed on the entire structure of the metal wire formation in the ferroelectric memory device manufacturing process, such as SiO ₂ and Si ₃ N ₄ . Hydrogen generated during the device protection film formation process may be trapped at the interface between the Ti film and the TiO ₂ film, thereby effectively preventing hydrogen from diffusing into the ferroelectric capacitor. In addition, TiO ₂ film by forming a TiO _x on the quasi-stable to oxygen plasma treatment can be trapped in the non-hydrogen bonding hands of TiO _x can be more effectively prevented the hydrogen diffusion.

Claims (6)

In the ferroelectric memory device manufacturing method, A first step of forming an insulating film on the entire structure of the transistor, the ferroelectric capacitor, and the metal wirings are completed; A second step of forming a hydrogen diffusion prevention film formed of a titanium film and a titanium oxide film sequentially deposited on the insulating film; And A third step of forming an element protection film on the hydrogen diffusion prevention film Ferroelectric memory device manufacturing method comprising a. The method of claim 1, The second step, Forming a Ti film on the insulating film; And A fifth step of forming a TiO ₂ film on the Ti film A ferroelectric memory device manufacturing method comprising a. The method of claim 2, After the fifth step, And a sixth step of subjecting the TiO ₂ film to oxygen plasma treatment. The method according to any one of claims 1 to 3, After the third step, A seventh step of selectively etching the device protection film, the hydrogen diffusion prevention film, and the insulating film to form a contact hole exposing a pad connected to the metal wiring; And And an eighth step of subjecting the titanium film exposed to the sidewalls of the contact hole to oxygen plasma treatment. The method of claim 4, wherein A method for manufacturing a ferroelectric memory device, characterized in that the insulating film is formed from a source containing no hydrogen. The method of claim 5, The device protective film A method of manufacturing a ferroelectric memory device, characterized in that it is formed of a SiO ₂ film and a Si ₃ N ₄ film.