CN1546426A - Barium strontium titanate ferroelectric thin film material and preparation method thereof - Google Patents

Abstract

The invention discloses a strontium titanate barium ferrum conductive film material and process for preparing the material, wherein the preparation process comprises the steps of, (1) preparing strontium acetate, barium acetate and butyl titanate into sol by the mol ratio of x:1-x:1 using ethylene glycol monoethyl ether as solvent, (2) charging manganous acetate, catalyst and addition agent into the sol to obtain MBST sol, (3) coating MBST sol on substrate to needed thickness, heat treating to obtain inorganic thin film, (4) fast heat treating to obtain MBST ferrum conductive film.

Description

Barium strontium titanate ferroelectric film material and preparation method thereof

Technical field

Patent of the present invention relates to responsive first ferroelectric membranc material of non-refrigeration infrared detector focal plane arrays (FPA) (UFPA) and preparation method thereof.

Background technology

The non-refrigeration infrared detector focal plane arrays (FPA) has been represented the new way of starring array thermal imaging development, is the key part of preparation non-refrigerant thermal imaging instrument.It comprises two funtion parts: sensitive element array and signal treatment circuit.The non-refrigeration infrared detector focal plane arrays (FPA) can be finished on the integrated circuit technology line of common scale, needn't rely on extremely expensive super large-scale integration (VLSI) producing apparatus of investment.The gordian technique of preparation non-refrigeration infrared detector focal plane arrays (FPA) is that the preparation high-performance is surveyed sensitive unit and little heat insulating construction thereof, and the ferroelectric thin-flim materials of excellent property can prepare high performance responsive unit, guarantees that device has high detectivity and stability.

(Ba_1-xSr_x) TiO₃(being called for short BST) is a kind of typical perovskite structure matrix material, and it has BaTiO concurrently₃High-k, low-dielectric loss and SrTiO₃Characteristics such as materialization is stable.This film has good pyroelectricity, ferroelectric, piezoelectric property and non-linear optical effect.Therefore, utilize bst thin film to prepare various devices in recent years, as ultra-large dynamic RAM, high frequency bypass integrated capacitance, decoupling capacitance, microwave monolithic integrated circuit (MMIC), tuning microwave device and high-performance non-refrigeration infrared detector focal plane arrays (FPA).The method for preparing bst thin film has radio-frequency sputtering, organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD) and colloidal sol-gel (Sol-Gel) method etc.Compare with other method ratio, the Sol-Gel method prepares film and has unique advantages: 1) good uniformity, starting material reach the molecular level contact, can guarantee correct stoichiometric ratio, form single crystalline texture; 2) easily carry out trace doped improvement film performance; 3) thermal treatment temp is low, easily with the semiconductor integrated circuit technique compatibility, film and semiconducter device can be integrated on the same chip, with the reliability of raising device and improve integrated level; 4) can cheaply prepare large-area high purity films, be easy to industrialization.Yet the ferroelectric membranc that will obtain practicability still has a major issue to wait to solve: be used to do the bst thin film of the sensitive unit of non-refrigeration infrared detector focal plane arrays (FPA), because thinner thickness (≤2 μ m), with body material ratio, its total electrical resistance descends, the insulativity variation, and the rheology of promptly leaking electricity is big.This will consume the pyroelectricity electric current of larger proportion, introduce bigger noise, disturb infrared radiation signal, cause the unstable and even inefficacy of system performance.Therefore, prepare high performance non-refrigeration infrared detector focal plane arrays (FPA), ferroelectric thin-flim materials also must good insulation preformance except that having good pyroelectric property, and promptly resistivity wants high, and leakage current is little.

Summary of the invention

The present invention proposes a kind of barium strontium titanate ferroelectric film material and preparation method thereof, its objective is to adopt Mn to improve (Ba as modified materials_1-xSr_x) TiO₃The electrical property of (strontium-barium titanate is called for short BST) ferroelectric membranc to reduce leakage current, improves resistivity; And the barium strontium titanate ferroelectric film material (MBST) for preparing the manganese doping vario-property with improved SOL-GEL method makes thin-film material not only have good pyroelectricity, also has high resistivity, little leakage current.

A kind of barium strontium titanate ferroelectric film material of the present invention contains (Ba_1-xSr_x) TiO₃, wherein x is 0.05-0.04, it is characterized in that it also contains Mn, 1mol (Ba_1-xSr_x) TiO₃The addition 0.0003-0.02mol of Mn.

Described barium strontium titanate ferroelectric film preparation methods, its steps in sequence is: (1) by mol than x: 1-x: 1 gets strontium acetate Sr (CH₃COO)₂, barium acetate Ba (CH₃COO)₂With tetrabutyl titanate Ti (OC₄H₉)₄, ethylene glycol monoethyl ether HOCH₂CH₂OC₂H₅For solvent heats while stirring, become the colloidal sol that is evenly distributed, wherein x is 0.05-0.40; (2) the manganese acetate Mn (CH of adding 0.0003-0.02mol in the described colloidal sol of 1mol₃COO)₂4H₂O adds catalyzer and additive simultaneously, continues to stir, and becomes MBST colloidal sol; (3) at Pt/Ti/SiO₂Apply described MBST colloidal sol on the/Si substrate, form wet film, became the MBST inorganic thin film at 300-500 ℃ of thermal treatment 5-10 minute, if film thickness does not reach requirement as yet, can on the MBST inorganic thin film, apply described MBST colloidal sol once more, repeat this step until reaching required thickness; (4) to reaching the MBST inorganic thin film of required thickness,, make the MBST ferroelectric membranc at 600-800 ℃ of rapid thermal process 5-20 minute.

Described barium strontium titanate ferroelectric film preparation methods, it is further characterized in that the MBST colloidal sol of 1mol adds the single ether HOCH of the described solvent ethylene glycol of 700-750ml₂CH₂OC₂H₅Described catalyzer is Glacial acetic acid CH₃The MBST colloidal sol add-on of COOH, 1mol is 750-800ml; Described additive is methane amide HCONH₂With ethylene glycol C₂H₆O₂, 1mol MBST colloidal sol in respectively get 250-300ml.

Use material of the present invention and method can obtain the resistivity height, leakage current is little, and heat is released the MBST ferroelectric membranc of excellent property, and its resistivity is than high about two orders of magnitude of pure BST ferroelectric membranc; Utilize this film can prepare the responsive unit of the non-refrigeration ferroelectric membranc of high-performance infrared detector focal plane array.

Description of drawings

Fig. 1 is a process flow sheet of the present invention;

Fig. 2 shows that the MBST20 ferroelectric membranc leakage current density that adopts method of the present invention to prepare concerns with the external electric field Strength Changes;

Fig. 3 is for adopting the three-dimensional and surface topography photo of the prepared MBST20 ferroelectric membranc atomic force microscope AFM of method of the present invention.

Embodiment

1. preparation 1mol MBST20 is an example, adopts 0.80mol Ba (CH₃COO)₂(barium acetate), 0.20molSr (CH₃COO)₂1/2H₂O (strontium acetate), 1molTi (OC₄H₉)₄(tetrabutyl titanate), 0.005molMn (CH₃COO)₂4H₂O (manganese acetate) is starting material, 720ml ethylene glycol monoethyl ether (HOCH₂CH₂OC₂H₅) be solvent, 750ml Glacial acetic acid (CH₃COOH) be catalyzer, methane amide (HCONH₂) and ethylene glycol (C₂H₆O₂) respectively to get 250ml be additive, by wet 400 ℃ of thermal treatments of film of flow process shown in Figure 18 minutes, 700 ℃ of rapid thermal process of MBST inorganic thin film 12 minutes, prepare the MBST20 ferroelectric membranc, three-dimensional and the surface topography photo of its atomic force microscope (AFM) as shown in Figure 3, electrical property is: electricalresistivity=5 * 10¹¹Ω cm, pyroelectric coefficient γ=1.03 * 10^-7Ccm^-2K^-1, dielectric coefficient ε_r=300, dielectric loss tg δ=0.01.

2. still prepare 1molMBST20, other are with example 1, but manganese acetate Mn (CH₃COO)₂4H₂The O addition is 0.0005mol, ethylene glycol monoethyl ether HOCH₂CH₂OC₂H₅Solvent is 700ml, catalyzer Glacial acetic acid CH₃COOH is 780ml, methane amide HCONH₂With ethylene glycol C₂H₆O₂Respectively get 300ml, by wet 300 ℃ of thermal treatments of film of flow process shown in Figure 1 10 minutes, 800 ℃ of rapid thermal process of MBST inorganic thin film 5 minutes were prepared the MBST20 ferroelectric membranc.

3. manganese acetate Mn (CH₃COO)₂4H₂The O addition is 0.001mol, ethylene glycol monoethyl ether HOCH₂CH₂OC₂H₅Be 720ml, Glacial acetic acid CH₃COOH800ml, methane amide HCONH₂With ethylene glycol C₂H₆O₂Respectively get 280ml, wet 500 ℃ of thermal treatments of film 5 minutes, 600 ℃ of rapid thermal process of MBST inorganic thin film 20 minutes, other are with example 1.

4. manganese acetate Mn (CH₃COO)₂4H₂The O addition is 0.01mol, wet 350 ℃ of thermal treatments of film 9 minutes, and 750 ℃ of rapid thermal process of MBST inorganic thin film 8 minutes, other are with example 3.

See Fig. 2 by the MBST20 ferroelectric membranc leakage current density that above-mentioned four embodiment are prepared with external electric field Strength Changes relation curve.

Claims (3)

1. a barium strontium titanate ferroelectric film material contains (Ba_1-xSr_x) TiO₃, wherein x is 0.05-0.04, it is characterized in that it also contains Mn, 1mol (Ba_1-xSr_x) TiO₃The addition 0.0003-0.02mol of Mn.

2. the described barium strontium titanate ferroelectric film preparation methods of claim 1, its steps in sequence is:

(1) by mol than x: 1-x: 1 gets strontium acetate Sr (CH₃COO)₂, barium acetate Ba (CH₃COO)₂With tetrabutyl titanate Ti (OC₄H₉)₄, ethylene glycol monoethyl ether HOCH₂CH₂OC₂H₅For solvent heats while stirring, become the colloidal sol that is evenly distributed, wherein x is 0.05-0.40;

(2) the manganese acetate Mn (CH of adding 0.0003-0.02mol in the described colloidal sol of 1mol₃COO)₂4H₂O adds catalyzer and additive simultaneously, continues to stir, and becomes MBST colloidal sol;

(3) at Pt/Ti/SiO₂Apply described MBST colloidal sol on the/Si substrate, form wet film, became the MBST inorganic thin film at 300-500 ℃ of thermal treatment 5-10 minute,

If film thickness does not reach requirement as yet, can on the MBST inorganic thin film, apply described MBST colloidal sol once more, repeat this step until reaching required thickness;

(4) to reaching the MBST inorganic thin film of required thickness,, make the MBST ferroelectric membranc at 600-800 ℃ of rapid thermal process 5-20 minute.

3. the described barium strontium titanate ferroelectric film preparation methods of claim 2 is characterized in that the MBST colloidal sol of 1mol adds the single ether HOCH of the described solvent ethylene glycol of 700-750ml₂CH₂OC₂H₅Described catalyzer is Glacial acetic acid CH₃The MBST colloidal sol add-on of COOH, 1mol is 750-800ml; Described additive is methane amide HCONH₂With ethylene glycol C₂H₆O₂, 1mol MBST colloidal sol in respectively get 250-300ml.

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