JP4313144B2 - PZT film cleaning method - Google Patents

Description

  The present invention relates to a method for cleaning and removing unnecessary Pb, Zr, and Ti-based PZT films deposited in a reaction chamber, a jig, or the like in a film forming apparatus or the like in the semiconductor field.

  In an apparatus for manufacturing a thin film or a thick film, unnecessary films are deposited on the inner wall of the apparatus, jigs and the like. For this reason, the film deposited on unnecessary portions in the reaction chamber must be removed.

Currently, as a method for removing a film, there is thermal cleaning using a gas containing fluorine atoms in molecules such as ClF ₃ and F ₂ (Patent Document 1). This method utilizes the fact that the reactivity of ClF ₃ and F ₂ is high and the boiling point of the compound obtained by the reaction is lower than the film forming process temperature.

However, compounds obtained by the reaction of Zr, Pb, Ti, which are metal elements contained in the PZT film, and a gas containing fluorine atoms in the molecule have a high boiling point and are difficult to gasify and remove. is there. For this reason, the generated fluorine compound is deposited in the apparatus and piping, and is not suitable for cleaning.
Japanese Patent Laid-Open No. 03-041199

  As a result of intensive studies, the present inventors conducted a specific pretreatment, and then obtained a PZT film mainly composed of Pb, Zr, and Ti while obtaining a high cleaning rate by reacting with β-diketone. A method for cleaning was found and the present invention was achieved.

That is, the present invention, Pb, Zr, and upon Ti PZT film cleaning removed mainly comprising, on the PZT film by thermal reaction treatment at 200 to 600 ° C. using a gas containing chlorine atom in its molecule After chlorinating Pb, Zr and Ti contained, Pb, Zr and Ti contained in the PZT film are reacted with β-diketone, and the reaction product is removed by cleaning at a temperature of 0 to 500 ° C. A method for cleaning a PZT film is provided.

In the present invention, the target PZT film is a film having a composition made of PbZr _1-x Ti _x O ₃ . However, x is 0.3 <x <0.7.

  Hereinafter, the contents of the present invention will be described in detail.

In the present invention, as a cleaning order, chlorination is first performed at 200 to 600 ° C. using a gas containing chlorine atoms in the molecule. The purpose is to chlorinate Ti, Zr and Pb contained in the PZT film by chlorination. By chlorination, Ti and Zr become TiCl ₄ and ZrCl ₄ , and the product can be gasified and removed from the reactor. The remaining Pb becomes PbCl ₂ and accumulates in the pipe, but becomes more complex than the untreated state.

The gas for chlorinating the PZT film used in the present invention is not particularly limited as long as it contains chlorine atoms in the molecule and releases chlorine atoms by heating, and examples thereof include HCl and Cl ₂ . In particular, HCl having good reactivity is preferable. This is because HCl is highly reactive, and H atoms contained in HCl react with O atoms contained in the PZT film to generate H ₂ O, so that the reaction easily proceeds.

The conditions of thermal reaction treatment (chlorination process), the temperature is preferably in the range of 200 to 600 ° C.. If it is less than 0 ° C., the reactivity is weak, and if it exceeds 800 ° C., corrosion in the reactor becomes a problem, which is not preferable. Further, since the boiling points and sublimation points of TiCl ₄ and ZrCl ₄ produced by the reaction are 136 ° C. and 189 ° C., respectively, the produced TiCl ₄ and ZrCl ₄ are converted into a reactor by chlorination at 200 ° C. or higher. It can be removed simultaneously from within. The pressure is preferably 1.33 × 10 ^{2 to} 1.33 × 10 ⁴ Pa. The flow rate is not particularly limited.

  Next, when the chlorination treatment is completed, a reaction treatment (complexation treatment) of the PZT film is performed. Examples of β-diketone used in the present invention include 2,4-pentanedione, 1,1,1-trifluoro-2,4-pentanedione, 1,1,1,5,5,5-hexafluoro-2. , 4-pentanedione, 3-methyl-2,4-pentanedione, 3-isopropyl-2,4-pentanedione, 2,2-dimethyl-3,5-hexanedione, 1,1,1-trifluoro- 5-methyl-2,4-hexanedione, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,2,2,6,6,6-octa Fluoro-3,5-hexanedione, 2,2-dimethyl-3,5-heptanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 1,1,1,2,2- Pentafluoro-6-methyl-3,5- Butanedione, 1,1,1,2,2-pentafluoro-6,6-dimethyl-3,5-heptanediene, 1,1,1,2,2,3,3-heptafluoro-4,6-heptane Dione, 1,1,1,5,5,6,6,7,7,7-decafluoro-2,4-heptanedione, 1,1,1,2,2,6,6,7,7, 7-decafluoro-3,4-heptanedione, 7-methyl-2,4-octanedione, 1,1,1,2,2,3,3-heptafluoro-4,6-octanedione, 1,1 1,1,2,2,3,3-heptafluoro-7-methyl-4,6-octanedione, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4, 6-octanedione, 1,1,1,2,2,6,6,7,7,8,8,8-dodecafluoro-3,5-octane Examples include dione. In particular, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione is most desirable. 1,1,1,5,5,5-hexafluoro-2,4-pentanedione is highly reactive with Zr and Pb contained in the PZT film and has a vapor pressure at room temperature of the complex formed. This is because it is expensive and suitable for cleaning.

As conditions for the complexing treatment, the temperature is preferably in the range of 0 to 500 ° C. If the temperature is less than 0 ° C., the vapor pressure of the compound used for complexation is low, and if the temperature exceeds 500 ° C., thermal decomposition of the complex occurs. The pressure is preferably 1.33 × 10 ^{2 to} 1.03 × 10 ⁵ Pa. If it is too low, the amount of the compound supplied per unit volume is small, and a high cleaning rate cannot be obtained.

  According to the method of the present invention, in a PZT film forming apparatus or the like, it is possible to clean unnecessary substances deposited in a reaction chamber, a jig or the like while obtaining a high cleaning speed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not limited to this Example.

Example 1
FIG. 1 is a schematic system diagram of a cleaning device used in the present invention. A wafer in which a PZT film (PbZr _0.52 Ti _0.48 O ₃ ) of 300 nm was formed on Si was cut into a size of 50 mm × 25 mm and placed in the center of the quartz tube 5.

HCl (gas) 1 is flowed at a temperature of 300 ° C. and a pressure of 1.33 × 10 ⁴ Pa through the mass flow controller 2 at a flow rate of 100 sccm for 30 minutes, and the sample surface after the reaction is subjected to energy dispersive X-ray fluorescence analysis (Energy Dispersive X-ray analysis). X-ray Fluorescence Spectrometer (EDX) was used for analysis.

  Next, a sample prepared by the same operation as described above was taken out, and 10 cc of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione was dropped onto the sample. After drying, heat treatment was performed for 5 minutes on a hot plate heated to 200 ° C. The sample surface after the reaction was similarly analyzed using energy dispersive X-ray fluorescence analysis (EDX).

  The results obtained by the above operation are shown in Table 1 together with the analysis results of the untreated sample. The surface of the sample treated with HCl has a higher Cl ratio than the untreated sample, indicating that chlorination has progressed. Furthermore, the composition of the sample after being treated with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione is close to the composition of the untreated sample. This is considered that the chlorinated layer formed a complex with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, and the complex was volatilized by the heat treatment.

  From the above results, it was shown that the PZT film can be cleaned by repeating the chlorination treatment and the 1,1,1,5,5,5-hexafluoro-2,4-pentanedione treatment.

Example 2
A wafer in which a PZT film was formed to 300 nm on Si used in Example 1 and a wafer in which a 500 nm film was formed were analyzed using fluorescent X-ray analysis. From the obtained X-ray intensity, a calibration curve for each of Ti, Zr and Pb components was prepared.

HCl (gas) was treated at a temperature of 300 ° C. and 500 ° C. under conditions of a pressure of 1.33 × 10 ⁴ Pa and a flow rate of 100 sccm for 10 minutes, and the sample surface after the reaction was analyzed using fluorescent X-ray analysis. The removal rate of each composition was determined from the calibration curve. The results are shown in Table 2. It was found that the PZT film can be chlorinated with HCl and removed from the wafer. However, since PbCl ₂ produced by chlorination accumulates in the pipe, it must be subsequently complexed with β-diketone.

Example 3
PbCl ₂ and 1,1,1,5,5,5 reactivity with hexafluoro-2,4-pentanedione was investigated using TG analysis. N ₂ was bubbled into a container containing 200 mL of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione at a flow rate of 50 sccm, and 20.55 mg of PbCl ₂ was charged as the gas after bubbling. It was introduced into a thermogravimetric analyzer. The temperature of the reaction tube was raised at 10 ° C./min, and the reactivity of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and PbCl ₂ was examined.

The results are shown in FIG. PbCl ₂ is complexed and removed, reducing weight. That is, it was found that PbCl ₂ can be cleaned with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.

It is a schematic system diagram of the plasma cleaning apparatus used in the present invention. PbCl represents ₂ and 1,1,1,5,5,5 thermogravimetric analysis value by reaction with hexafluoro-2,4-pentanedione.

Explanation of symbols

1: HCl cylinder 2: Mass flow controller 3: N ₂ cylinder 4: PTFE container 5: Quartz tube 6: Electric furnace 7: Pressure regulating valve 8: Dry pump 9: Detoxifying device

Claims (1)

When cleaning and removing the PZT film mainly composed of Pb, Zr, and Ti, Pb, Zr contained in the PZT film is subjected to a thermal reaction treatment at 200 to 600 ° C. using a gas containing chlorine atoms in the molecule. , And Ti are chlorinated, then PbT, Zr, and Ti contained in the PZT film are reacted with β-diketone, and the reaction product is removed by cleaning at a temperature of 0 to 500 ° C. How to clean the membrane.