KR20000026969A - Method for fabricating capacitor of semiconductor device - Google Patents

Abstract

PURPOSE: A method for fabricating a capacitor of a semiconductor device is provided to eliminate the press strain due to volume expansion by preventing oxidation except a surface. CONSTITUTION: A method for fabricating a capacitor of a semiconductor device comprises a polycrystal silicon film(20) formation step, a first platinum film(30) formation step, a platinum silicide(40) formation step, a second platinum film(30) formation step, a ferroelectric film(60) formation step, and an upper electrode film(70) formation step. The silicon film(20) is formed on the upper part of a lower structure(10) where interlayer dielectric is deposited. The first platinum film is formed on the silicon film. The platinum silicide is formed by heat-treating the silicon film and the first platinum film under oxygen atmosphere. The second platinum film is formed on the silicide. The ferroelectric film is formed on the second platinum film.

Description

How to Form Capacitors in Semiconductor Devices

The present invention relates to a method of manufacturing a capacitor of a ferroelectric memory device, and more particularly to a method of forming a lower electrode which greatly affects the characteristics of the ferroelectric memory device.

Ferroelectric memory devices are a kind of nonvolatile memory devices that not only store the stored information even when the power supply is cut off, but also operate at the same speed as the next-generation memory devices, comparable to the existing DRAM (Dynamic Random Access Memory). SrBi ₂ Ta ₂ O ₉ (hereinafter referred to as “SBT”) and Pb (Zr _x Ti1-x) O ₃ (hereinafter referred to as “PZT”) thin films are mainly used as ferroelectrics used in the capacitor of the ferroelectric memory device. In order to obtain the ferroelectric properties of the ferroelectric as described above, it is essential to select upper and lower electrode materials and to control appropriate processes. In particular, the influence of the lower electrode on the ferroelectric properties is enormous. As the electrode material, a material such as platinum (Pt) having excellent oxidation resistance and a conductive oxide of lrO ₂ , RuO ₂ or metal lr, Ru is used. The lower electrode is deposited on the interlayer insulating film, which is generally a silicon oxide film, and a ferroelectric thin film is formed thereon.

In order to exhibit the inherent characteristics of the ferroelectric thin film, a high temperature process of more than 650 ° C. in an oxygen atmosphere is required after the ferroelectric thin film deposition. However, thin films such as platinum (Pt) and lr have poor adhesion to the underlying silicon oxide film due to their characteristics, and thus undergo high temperature thermal processes in an oxygen atmosphere, etching processes for capacitor patterning, and subsequent cleaning processes. While peeling from the lower silicon oxide film occurs. Conventionally, in order to suppress such peeling phenomenon, about 200 micrometers thick titanium film was formed as an adhesion layer between a lower electrode and a silicon oxide film, and the lower electrode comprised from the multilayer film of a platinum film and a titanium film was used. That is, the titanium film was used as an adhesive film because of its excellent adhesion between both the lower silicon oxide film and the upper platinum film.

However, not only the deposition of the ferroelectric film but also several subsequent high temperature thermal processes in the oxygen atmosphere, the titanium is oxidized and converted to titanium oxide (TiO ₂ ) at the same time as the severe interdiffusion between the platinum and the titanium film TKD. In this case, most of the titanium atoms move to the upper platinum film and the interface between the titanium and silicon oxide becomes weak, and all the titanium is changed to titanium oxide to expand the volume, thereby generating a large compressive stress on the lower electrode film. Therefore, the lower electrode, which is a multilayer film of platinum and titanium, loses adhesive force and peels again. In addition, in the process of solving the compressive stress, a large amount of hillock is generated on the surface of the lower electrode, which makes the surface roughness characteristic very weak. This increases the leakage current of the ferroelectric thin film, and in severe cases, a short circuit occurs, which has a fatal effect on the yield of the device.

Accordingly, an object of the present invention is to provide a capacitor of a semiconductor device using platinum silicide instead of titanium as an adhesive film, so that during the subsequent high temperature oxygen atmosphere thermal process, since it is not oxidized except for the surface, there is no fear of compressive stress due to volume expansion. To provide.

1A to 1G are cross-sectional views illustrating respective process steps in accordance with an embodiment of the method for forming a capacitor of the present invention.

Explanation of symbols on the main parts of the drawings

10: lower structure 20: polycrystalline silicon film

30: platinum film 40: platinum silicide

50: lower electrode 60: ferroelectric film

70: upper electrode

In order to achieve the above object, the present invention provides a method of forming a capacitor of a semiconductor device, the method comprising: forming a polycrystalline silicon film on top of a lower structure on which an interlayer insulating film is deposited; Forming a first platinum film on the polycrystalline silicon film; Performing a heat treatment in an oxygen atmosphere so that the polycrystalline silicon film and the first platinum film are formed of platinum silicide; Forming a second platinum film on the platinum silicide; Forming a ferroelectric film on the second platinum film; It provides a capacitor forming method of a semiconductor device comprising the step of forming an upper electrode film on the ferroelectric film.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1A to 1G.

First, referring to FIG. 1A, the polycrystalline silicon film 20 is deposited on the substrate on which the predetermined lower structure 10 is formed to have a thickness of about 100 kPa to about 200 kPa by chemical vapor deposition, and then sputtering on the top thereof. To deposit the platinum film 30. The platinum film 30 is deposited to a thickness of 50% larger than the thickness of the polycrystalline silicon film 20.

Next, referring to FIG. 1B, a heat treatment is performed in an oxygen atmosphere at about 500 ° C. to about 700 ° C. by using an electric furnace, and the polysilicon film 20 and the platinum film 30 are reacted with each other to form a platinum silicide film. 40 is formed. In this case, the platinum silicide layer 40 may have a PtSi structure and may contain some unreacted platinum. In addition, since the heat treatment is performed in an oxygen atmosphere, the surface of the platinum silicide film 40 is oxidized. However, the inside of the platinum silicide film 40 is not oxidized.

Next, referring to FIG. 1C, a platinum film 50 is again deposited on the platinum silicide film 40 to form a lower electrode.

Next, referring to FIG. 1D, in order to form the ferroelectric film 60 on the lower electrode 50 having the above structure, first, a ferroelectric film having a thickness of about 1000 μs is deposited by a Sol-Gel method. The heat treatment is then performed in a rapid heat treatment apparatus at an oxygen atmosphere of about 700 ° C. to about 750 ° C., preferably about 725 ° C. for about 30 seconds. Then, once again about 1000 kV ferroelectric film was deposited in the same manner, and then heat-treated under the same conditions as described above. The ferroelectric film 60 deposited as described above is heat-treated again in an electric furnace in an oxygen atmosphere, about 800 ° C. for about 1 hour, thereby completing the ferroelectric film 60.

Next, referring to FIG. 1E, a platinum film 70 for an upper electrode is deposited on the ferroelectric layer 60 to a thickness of about 1500 kV.

Next, referring to FIG. 1F, in order to form a capacitor having a predetermined shape, an upper electrode platinum film 70 other than a desired portion is removed using a conventional photomask and an etching method.

Next, referring to FIG. 1G, the ferroelectric layer 60, the platinum layer 50 for the lower electrode 50, and the platinum silicide layer 40 other than the desired portion are removed using a conventional photomask and an etching method. Then, in order to recover the deterioration of the film caused by the etching plasma, an electric furnace is used to perform a heat treatment at a temperature of about 600 ° C. to about 800 ° C. for about 1 hour in an oxygen atmosphere to finally complete the capacitor.

When the lower electrode film and the adhesive film are formed in the same manner as described above, the adhesion between the lower electrode and the oxide film is excellent. Since the generation is suppressed and the leakage current characteristic of the ferroelectric film is greatly improved, the characteristics and the reliability of the device are greatly improved.

Claims (7)

In the capacitor formation method of a semiconductor device, Forming a polycrystalline silicon film on top of the underlying structure on which the interlayer insulating film is deposited; Forming a first platinum film on the polycrystalline silicon film; Performing a heat treatment to form the polycrystalline silicon film and the first platinum film as a platinum silicide film; Forming a second platinum film on the platinum silicide film; Forming a ferroelectric film on the second platinum film; And Forming an upper electrode film on the ferroelectric film Capacitor formation method of a semiconductor device comprising a. The method of claim 1, Removing the upper electrode film other than the portion to be used as a capacitor by using a photomask and dry anisotropic etching; Removing the ferroelectric film, the lower electrode film, and the platinum silicide film other than the portion to be used as a capacitor by using a photo mask and a dry anisotropic etching method; And Heat-treating the patterned capacitor Capacitor forming method of a semiconductor device further comprising. The method of claim 2, The heat treatment of the patterned capacitor, A method of forming a capacitor in a semiconductor device, which is performed by performing an oxygen atmosphere heat treatment at a temperature of about 600 ° C. to about 800 ° C. using an electric furnace. The method of claim 1, And depositing the first platinum film using a sputtering method, the thickness being 50% greater than the thickness of the polycrystalline silicon film under the sputtering method. The method of claim 1, Forming the platinum silicide film, A method for forming a capacitor of a semiconductor device, which is performed by performing an oxygen atmosphere heat treatment at a temperature of about 500 ° C to about 700 ° C using an electric furnace. The method of claim 1, Wherein the ferroelectric film is SrBi ₂ Ta ₂ O ₉ and has a thickness of about 1000 kPa to about 3000 kPa. The method of claim 1, And the upper electrode film is platinum, and has a thickness of about 1000 mW to about 3000 mW.