CN111549329A

CN111549329A - Preparation method of ferroelectric film, ferroelectric memory and preparation method thereof

Info

Publication number: CN111549329A
Application number: CN202010401254.XA
Authority: CN
Inventors: 廖敏; 郇延伟; 戴思维; 刘兆通; 曾斌建; 周益春
Original assignee: Xiangtan University
Current assignee: Xiangtan University
Priority date: 2020-05-13
Filing date: 2020-05-13
Publication date: 2020-08-18

Abstract

The embodiment of the application provides a preparation method of a ferroelectric film, a ferroelectric memory and a preparation method thereof. The preparation method of the ferroelectric film comprises the following steps: carrying out atomic layer deposition by taking a main element source as a reaction precursor, depositing the main element on the surface of the substrate, and adsorbing most of free bonding points on the surface of the substrate by controlling the deposition time; then using inert gas as purge gas to clean and purge the chamber; then, taking a doping element source as a reaction precursor to carry out atomic layer deposition, so that the doping element adsorbs the residual free bonding points on the surface of the substrate; purge purging using an inert gas as a purge gas; at the moment, the two precursors exist on the surface of the substrate at the same time, and then oxidation treatment is carried out by using oxidizing gas; then using inert gas as purge gas to perform scavenging purging; repeating the steps to obtain the ferroelectric film with the target thickness. The method of the embodiment of the application can realize better low-concentration uniformity doping.

Description

Preparation method of ferroelectric film, ferroelectric memory and preparation method thereof

Technical Field

The application belongs to the technical field of ferroelectric film preparation, and particularly relates to a preparation method of a ferroelectric film, a ferroelectric memory and a preparation method of the ferroelectric memory.

Background

With the development of the information technology industry and the progress of the society, the development of the memory plays an important role in enhancing the international competitiveness, maintaining the national security and the like. So far, mainstream memories such as high-density and low-cost DRAMs and NAND Flash have been increasingly difficult to meet the requirements of high-speed computation and low power consumption, and development of new memory technologies has become a necessary trend. Meanwhile, it is currently widely considered that a ferroelectric memory is one of the most promising new memories, in which a ferroelectric thin film is used as a storage medium to store information. The conventional perovskite ferroelectric thin film material cannot meet the requirement of the electronic device towards the miniaturization direction, so that the development of new storage medium materials is always a key research topic by the semiconductor force nation. Since the 2011 discovery of ferroelectricity in silicon-doped hafnium oxide thin films, more and more institutions and researchers have been involved in the research of hafnium oxide-based ferroelectric thin films. The novel hafnium oxide-based ferroelectric thin film exhibits numerous advantages including a wide band gap, good compatibility with CMOS processes, and strong radiation resistance, and among them, the most critical problem is the preparation of the thin film.

The ferroelectric film is prepared mainly by sol-gel method, magnetron sputtering method, pulsed laser deposition method, atomic layer deposition method, etc. Compared with other preparation methods, the atomic layer deposition method has the advantages of very accurate thickness control and component control of the film, capability of growing the film in a large area, no limitation on the shape of the substrate, better step coverage and the like.

In the process of preparing some ferroelectric films with low doping concentration by an atomic layer deposition method, the doping concentration of the prepared ferroelectric film is difficult to control, the doping concentration of the prepared ferroelectric film is often far higher than the target doping concentration, and the doping uniformity of the prepared ferroelectric film is not good when some thin films are prepared.

Disclosure of Invention

An object of the embodiments of the present application is to provide a method for manufacturing a ferroelectric thin film, a ferroelectric memory, and a method for manufacturing the same, which can obtain a ferroelectric thin film with good uniformity and low doping concentration.

In one aspect, an embodiment of the present application provides a method for preparing a ferroelectric thin film, including:

carrying out atomic layer deposition by taking a main element source as a reaction precursor, and depositing the main element on the surface of the substrate to adsorb most of free bonding points on the surface;

using inert gas as purge gas to perform purge purging;

carrying out atomic layer deposition by taking a doping element source as a reaction precursor, so that the doping element adsorbs the residual free bonding points on the surface of the substrate;

using inert gas as purge gas to perform purge purging;

performing oxidation treatment with an oxidizing gas;

using inert gas as purge gas to perform purge purging;

repeating the steps to obtain the ferroelectric film with the target thickness.

Optionally, the primary element source comprises a hafnium source; the hafnium source is selected from hafnium tetramethyamine, hafnium tetra-tert-butyl and the like; when atomic layer deposition is carried out by taking a main element source as a reaction precursor, the temperature of a cavity is 280-300 ℃, the heating temperature of the reaction precursor is 75-80 ℃, and the pressure intensity in the cavity is kept at 150-185 mtorr.

Optionally, the target thickness of the ferroelectric thin film is 3-100 nm.

Optionally, the doping element source is selected from Trimethylaluminum (TMA), tris (dimethylamino) silane (3DMAS), tris (isopropylcyclopentylalkyl) lanthanum, and the like; when the doping element source is used as a reaction precursor for atomic layer deposition, the temperature of the cavity is 280-300 ℃, the heating temperature of the reaction precursor is 75-80 ℃, and the pressure intensity in the cavity is kept at 150-185 mtorr.

Optionally, the purge gas is an inert gas, and the inert gas includes argon.

Optionally, the oxidizing gas comprises H₂O、O₂And/or O₃Ozone gas is preferred.

In a second aspect, embodiments of the present application provide a method for manufacturing a ferroelectric memory, including preparing a ferroelectric thin film, where the ferroelectric thin film is obtained by using the method of any one of the above embodiments.

In a third aspect, embodiments of the present application provide a ferroelectric memory, which is obtained by the method for manufacturing a ferroelectric memory according to the foregoing embodiments.

According to the preparation method of the ferroelectric film, the main element source is used as a reaction precursor to carry out atomic layer deposition to generate a chemical adsorption effect, main element molecules are adsorbed on the surface of the substrate to occupy most of free bonding point positions of the surface of the substrate, then inert gas is selected to remove and purge molecules in the cavity, the doping element source is directly introduced to be used as the reaction precursor to carry out atomic layer deposition after the cleaning is finished, the doping element molecules are adsorbed to the remaining free bonding points on the surface of the substrate, and the two precursor molecules can be well mixed in situ before oxidation. The method is an improved deposition method provided by utilizing self-limiting and self-saturation adsorption of the atomic layer deposition surface, and the precursors are mixed in situ in advance and are adsorbed on the surface of the substrate together, so that the uniform ferroelectric film with low doping concentration can be realized on the single-layer level, and the integral doping uniformity of the film is ensured. The method reduces the process steps and can realize better uniform doping. The ferroelectric film with uniform low doping concentration can be obtained, thereby providing possibility for memory development and application.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

The summary of various implementations or examples of the technology described in this application is not a comprehensive disclosure of the full scope or all features of the disclosed technology.

Drawings

In the drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. Like reference numerals having letter suffixes or different letter suffixes may represent different instances of similar components. The drawings illustrate various embodiments, by way of example and not by way of limitation, and together with the description and claims, serve to explain embodiments of the application. The same reference numbers will be used throughout the drawings to refer to the same or like parts, where appropriate. Such embodiments are illustrative, and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

FIG. 1 is a schematic diagram of a clean substrate according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram illustrating a hafnium source precursor reaching a surface of a deposition substrate to generate chemisorption and surface reaction according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the structure of the chamber after purging the remaining precursor molecules in the chamber with an inert gas according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a doping element precursor injected into a chamber to adsorb remaining free bonding sites on the surface of the substrate according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of the structure of the chamber after purging the remaining precursor molecules in the chamber with an inert gas according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a chamber filled with ozone gas for oxidation treatment according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of the structure of the chamber purged with the inert gas after purging residual ozone molecules in the chamber according to the embodiment of the present invention.

Reference numerals: 1-a substrate; 2-oxygen atom; 3-a main element precursor; 4-argon atom; 5-doping element precursor; 6-ozone; 7-a main element metal oxide; 8-doped elemental metal oxide.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings of the embodiments of the present application. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the application without any inventive step, are within the scope of protection of the application.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. As used in this application, the terms "first," "second," and the like do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

Detailed descriptions of known functions and known components are omitted in the present application in order to keep the following description of the embodiments of the present application clear and concise.

The embodiment of the application discloses a preparation method of a ferroelectric film. The method comprises the following steps:

carrying out atomic layer deposition by taking a main element source as a reaction precursor, and depositing a main element on the surface of the substrate; injecting a main element source precursor into a chamber with a well-set chamber temperature to perform surface reaction, and controlling the deposition time to adsorb most of free bonding points on the surface of the substrate;

using inert gas as purge gas to perform purge purging; removing redundant reactants and byproducts through purging;

using inert gas as purge gas to perform purge purging;

performing oxidation treatment with an oxidizing gas;

using inert gas as purge gas to perform purge purging;

repeating the steps to obtain the ferroelectric film with the target thickness.

According to the preparation method of the ferroelectric film, the main element source is used as a reaction precursor to carry out atomic layer deposition to generate a chemical adsorption effect, main element molecules are adsorbed to the position of the free bonding points on the surface of the substrate, and the number of the free bonding points adsorbed by the main element molecules and the number of the remaining free bonding points reach a target ratio by controlling the deposition time. And then, selecting inert gas to remove molecules in the purging chamber, directly introducing a doping element source as a reaction precursor after purging to perform atomic layer deposition, wherein the doping element molecules can only be adsorbed to the residual free bonding points on the surface of the substrate, and the two precursor molecules can be well mixed in situ before oxidation. Through in-situ mixing, the doping proportion can be controlled, and the concentration of low doping can be accurately controlled. The uniformity and ferroelectric property of the film are improved by utilizing the in-situ mixing of the precursors, the uniform stoichiometric ratio of the whole film can be kept, and the ferroelectric film with low doping concentration is obtained, so that the possibility is provided for the development and application of a memory.

In some embodiments, the primary element source comprises a hafnium source. In an exemplary embodiment, the hafnium source is organohafnium. For example, the hafnium source may be selected from hafnium tetramethyamine, hafnium tetra-tert-butoxide, and the like.

In some embodiments, when atomic layer deposition is performed using the main element source as a reaction precursor, the temperature of the chamber is 280-300 ℃, the heating temperature of the reaction precursor is 75-80 ℃, and the pressure inside the chamber is maintained at 150-185 mtorr.

In some embodiments, the ferroelectric thin film has a target thickness of 3 to 100 nm.

Different ferroelectric thin films have different doping concentrations to achieve better performance. Some exhibit optimum ferroelectric properties only at very small doping concentrations. The method of the embodiment of the application can realize the uniform doping proportion with low doping concentration. In exemplary embodiments, the source of doping elements is selected from Trimethylaluminum (TMA), tris (dimethylamino) silane (3DMAS), tris (isopropylcyclopentylalkyl) lanthanum, and the like. Of course, other organometallic materials may be used as the source of the doping element.

In some embodiments, when the atomic layer deposition is performed by using the doping element source as the reaction precursor, the temperature of the chamber is 280-300 ℃, the heating temperature of the reaction precursor is 75-80 ℃, and the pressure inside the chamber is maintained at 150-185 mtorr.

In some embodiments, the purge gas is an inert gas, preferably argon.

In some embodiments, the oxidizing gas comprises H₂O、O₂And/or O₃. For example, O may be selected₃The gas acts as an oxidizing gas.

In a second aspect, embodiments of the present application provide a method for manufacturing a ferroelectric memory, including preparing a ferroelectric thin film, where the ferroelectric thin film is obtained by using the method of any of the above embodiments.

In a third aspect, embodiments of the present application provide a ferroelectric memory, which is obtained by the method for manufacturing the ferroelectric memory of the above embodiments.

Fig. 1 to 7 are process schematic diagrams illustrating a method for manufacturing a ferroelectric thin film according to an embodiment of the present application. The present application is further illustrated by way of example in connection with fig. 1-7.

Example 1

The main element precursor 3 is hafnium source precursor, specifically selected to be tetramethylethylaminohafnium (purity is 99.9%), the doping element precursor 5 is aluminum source precursor, specifically selected to be trimethylaluminum (TMA, purity is 99.9%), O₃Is used as an oxygen source precursor, and Ar is used as a carrier gas and a purified gas. The aluminum-doped hafnium oxide-based ferroelectric film with low doping concentration is prepared by utilizing an improved atomic layer deposition process, and the target doping concentration is 2%. The method comprises the following steps:

a clean and tidy substrate 1 (see fig. 1) is prepared and placed in the chamber of the atomic layer deposition apparatus.

The temperature of the cavity is preferably set to 280 ℃ and kept constant, then argon is introduced into the reaction chamber for 30s, and the pressure value in the reaction chamber is controlled to be 180 mtorr. The heating temperature of the reaction precursor is 75-80 ℃. Under the condition, a main element precursor 3, namely tetramethylethylaminohafnium, is introduced to carry out plasma pulse for 3s, the hafnium source precursor is injected into the chamber to reach the surface of the deposition substrate 1, gas-solid phase chemical adsorption can occur, and the proportion of free bonding points adsorbed on the surface of the substrate reaches a target proportion (namely the proportion of hafnium in the target ferroelectric film) by controlling the deposition time, referring to fig. 2.

And (3) selecting an inert gas argon 4 as a purging gas, reducing the pressure value in the chamber to 90mtorr, and purging with argon for 30s to remove the residual main element (hafnium source) precursor gas molecules and some byproducts in the chamber. See fig. 3 for a schematic diagram of the structure after purging of the remaining precursor molecules in the chamber.

The adjusted pressure value is 180 mtorr. And introducing a doping element precursor 5 Trimethylaluminum (TMA) at 180mtorr for plasma pulse, wherein the duration is 0.5-1 s, and the aluminum source precursor can adsorb residual free bonding points on the surface of the substrate after being injected into the chamber. See fig. 4 for a schematic diagram of the structure after adsorbing the remaining free bonding points on the surface of the substrate.

And (3) selecting an inert gas argon 4 as a purging gas, reducing the pressure value in the chamber to 90mtorr, and purging argon for 30s to remove residual aluminum source precursor gas molecules and some byproducts in the chamber. Referring to fig. 5, a schematic diagram of the structure of the inert gas purged chamber after purging the remaining dopant precursor molecules is shown.

Introducing an oxygen source precursor ozone gas as an oxidizing gas 6 under the pressure value of 90mtorr, and oxidizing two organic metal gas-phase molecules adsorbed on the substrate together for 15s to obtain the target product, namely the ferroelectric film of main element metal oxide 7, hafnium oxide and doped element metal oxide 8, aluminum oxide. Refer to fig. 6 for a schematic structural view of the oxidation process performed by introducing ozone gas.

The inert gas argon 4 is selected as a purge gas to remove residual ozone gas molecules and some by-products in the chamber. See fig. 7 for a schematic diagram of the structure after purging the residual ozone molecules in the chamber.

In the above-described embodiment, the total number of times of the hafnium source precursor is 1 and the total number of times of the aluminum source precursor is 1, and the embodiment may be referred to as a cycle. The film growth amount of one period is about 0.1-0.5 nm, and the predetermined film thickness is 10nm, so that the ferroelectric film with the target thickness can be obtained by multiple periods. The doping amount of aluminum in the obtained ferroelectric thin film was 2.1%.

Example 2

Selecting hafnium tetra-tert-butyl (purity 99.9%) as precursor of hafnium source, tris (dimethylamino) silane (3DMAS, purity 99.9%) as precursor of silicon source, O₃Is used as an oxygen source precursor, and Ar is used as a carrier gas and a purified gas. And preparing the silicon-doped hafnium oxide-based ferroelectric film with low doping concentration by utilizing an improved atomic layer deposition process. The target doping concentration was 3%. The method comprises the following steps:

a clean and clean substrate (see fig. 1) is prepared and placed into the chamber of the atomic layer deposition apparatus.

The temperature of the cavity is preferably set to 280 ℃ and kept constant, then argon is introduced into the reaction chamber for 30s, and the pressure value in the reaction chamber is controlled to be 180 mtorr. The heating temperature of the reaction precursor is 75-80 ℃, the hafnium source precursor tetra-tert-butyl hafnium is introduced under the condition for plasma pulse, the duration time is 2.5s, the hafnium source precursor is injected into the chamber to reach the surface of the deposition substrate, gas-solid phase chemical adsorption can occur, and the hafnium source precursor is adsorbed to most of free bonding points on the surface of the substrate by controlling the deposition time, and refer to fig. 2.

And (3) selecting inert gas argon as a purging gas, reducing the pressure value in the chamber to 90mtorr, and purging the argon for 30s to remove residual hafnium source precursor gas molecules and some byproducts in the chamber. See fig. 3 for a schematic diagram of the structure after purging of the remaining precursor molecules in the chamber.

The adjusted pressure value is 180 mtorr. And introducing a precursor of doped element tris (dimethylamino) silane (3DMAS) at 180mtorr for plasma pulse, wherein the duration is 2-3 s. The silicon source precursor is injected into the chamber to adsorb the remaining free bond sites on the substrate surface. See fig. 4 for a schematic diagram of the structure after adsorbing the remaining free bonding points on the surface of the substrate.

And (3) selecting inert gas argon as purging gas, reducing the pressure value in the chamber to 90mtorr, and purging argon for 30s to remove residual silicon source precursor gas molecules and some byproducts in the chamber. Referring to fig. 5, a schematic diagram of the structure of the inert gas purged chamber after purging the remaining dopant precursor molecules is shown.

And introducing an oxygen source precursor ozone gas as an oxidizing gas under the pressure value of 90mtorr, and oxidizing two organic metal gas-phase molecules adsorbed on the substrate together for 15s to obtain the target product. Refer to fig. 6 for a schematic structural view of the oxidation process performed by introducing ozone gas.

And (3) selecting inert gas argon as a purging gas, reducing the pressure value in the chamber to 90mtorr, and purging the chamber for 30s by using the argon to remove residual ozone gas molecules and some byproducts in the chamber. See fig. 7 for a schematic diagram of the structure after purging the residual ozone molecules in the chamber.

In the above implementation process, the total number of times of the hafnium source precursor is 1, and the total number of times of the silicon source precursor is 1, the implementation process may be referred to as a cycle, the film growth amount in one cycle is about 0.1 to 0.5nm, and the predetermined film thickness is 10nm, so that the ferroelectric film with the target thickness needs to be obtained through multiple cycles. The doping amount of silicon in the obtained ferroelectric thin film was 2.8%.

Example 3

Selecting hafnium tetra-tert-butyl (purity 99.9%) as a precursor of a hafnium source, lanthanum tri (isopropylcyclopentylalkyl) (purity 99.9%) as a precursor of a lanthanum source, and O₃Is used as an oxygen source precursor, and Ar is used as a carrier gas and a purified gas. And preparing the lanthanum-doped hafnium oxide-based ferroelectric film with low doping concentration by utilizing an improved atomic layer deposition process. The target doping concentration was 5.5%. The method comprises the following steps:

The temperature of the cavity is preferably set to 280 ℃ and kept constant, then argon is introduced into the reaction chamber for 30s, and the pressure value in the reaction chamber is controlled to be 180 mtorr. The heating temperature of the reaction precursor is 75-80 ℃, the hafnium source precursor tetra-tert-butyl hafnium is introduced under the condition for plasma pulse, the duration time is 2s, the hafnium source precursor is injected into the chamber to reach the surface of the deposition substrate, gas-solid phase chemical adsorption can occur, and the deposition time is controlled to enable the hafnium source precursor to be adsorbed to most of free bonding points on the surface of the substrate, referring to fig. 2.

The adjusted pressure value is 180 mtorr. And introducing a precursor of doped element lanthanum tris (isopropylcyclopentylalkyl) at 180mtorr for plasma pulse, wherein the duration is 3-3.5 s. The lanthanum source precursor, when injected into the chamber, adsorbs the remaining free bond sites on the substrate surface. See fig. 4 for a schematic diagram of the structure after adsorbing the remaining free bonding points on the surface of the substrate.

And (3) selecting inert gas argon as a purging gas, reducing the pressure value in the chamber to 90mtorr, and purging the argon for 30s to remove residual lanthanum source precursor gas molecules and some byproducts in the chamber. Referring to fig. 5, a schematic diagram of the structure of the inert gas purged chamber after purging the remaining dopant precursor molecules is shown.

In the implementation process, the total number of times of the hafnium source precursor is 1, the total number of times of the lanthanum source precursor is 1, the implementation process can be called a period, the film growth amount in one period is about 0.1-0.5 nm, the predetermined film thickness is 10nm, and therefore, the ferroelectric film with the target thickness needs to be obtained through multiple periods. In the obtained ferroelectric thin film, the doping amount of lanthanum was 5.9%.

Comparative example

For the preparation of the ferroelectric film by the traditional atomic layer deposition process, when the pulse deposition is respectively carried out on the substrate by the metal precursor according to the preset sequence, the next pulse deposition can be carried out only after the required metal oxide is obtained by carrying out carrier gas purging and oxidation treatment once after the pulse deposition is finished, and the lanthanum-doped hafnium oxide-based ferroelectric film is taken as an example to be compared with an improved deposition process. The target doping concentration was 5.5%. The specific process steps are as follows:

a clean and clean substrate (see fig. 1) is prepared and placed into the chamber of the atomic layer deposition apparatus. The temperature of the cavity is preferably set to 280 ℃ and kept constant, then argon is introduced into the reaction chamber for 30s, and the pressure value in the reaction chamber is controlled to be 180 mtorr.

The heating temperature of the reaction precursor is 75-80 ℃, the hafnium source precursor tetra-tert-butyl hafnium is introduced under the condition for plasma pulse, the duration is 15s, the hafnium source precursor is injected into the chamber to reach the surface of the deposition substrate, gas-solid phase chemical adsorption can occur, and single-layer saturated adsorption is ensured by controlling the pulse time of the precursor. The pressure was then reduced to 90mtorr and an argon purge was performed for 30 s. Introducing oxygen source precursor oxygen under the pressure value of 90mtorr to perform plasma pulse for 15s to obtain a hafnium metal oxide; the argon purge was conducted for 30 seconds, and the cycle was repeated 14 times from the time the hafnium source precursor introduction step was performed.

The adjusted pressure value is 180 mtorr. And introducing a precursor of doped element tri (isopropyl cyclopentyl) lanthanum under 180mtorr for plasma pulse, wherein the duration is 15s, and the single-layer saturated adsorption of a lanthanum source is ensured. The pressure was then reduced to 90mtorr and an argon purge was performed for 30 s. Introducing oxygen source precursor oxygen under the pressure value of 90mtorr to perform plasma pulse for 15s to obtain lanthanum metal oxide; and introducing argon for purging for 30s, and executing for 1 time from the step of introducing the lanthanum source precursor.

It should be noted that the total number of times of the hafnium source precursor introduction is 15 times and the total number of times of the lanthanum source precursor introduction is 1 in the above implementation process, which may be referred to as a cycle. The period comprises 16 times of introducing the metal source precursor, the film growth amount of one period is about 0.5-1 nm, the preset film thickness is 10nm, and therefore the ferroelectric film with the target thickness is obtained by multiple periods. In the obtained ferroelectric thin film, the doping amount of lanthanum was 6.5%.

According to the principle, when the traditional deposition process is used for preparing the ferroelectric film with low doping concentration, the organic source is required to be deposited once for oxidation once, and the process has more cycle times and is more complicated. The traditional deposition method can also realize the doping with low doping concentration, firstly, the main element source is deposited for a plurality of times, then, the doping element source is deposited for one time, and then, the main element source is deposited for a plurality of times, so that the low-concentration doping of the doping element is realized in a multi-layer-to-one-layer cyclic mode through the cycle, but the required number of deposition cycles is more. However, in the case of a thin film having a relatively small thickness, the desired film thickness can be achieved with only a small number of deposition cycles, which leads to the problem that the doping concentration is very inhomogeneous. Moreover, when the doping concentration is low, because the deposition of the doping element is performed after the oxidation of the main element, the number of free bonding points which can be absorbed by the doping element is large, the proportion is difficult to control, and the actual doping concentration of the doping element is often higher than the target doping concentration.

In the embodiment of the application, an improved deposition method is provided by utilizing the self-limiting growth principle of atomic layer deposition, precursors are mixed well in advance and are adsorbed on the surface of a substrate together, and a target product is obtained after the precursors are oxidized together, and the target product is doped at a uniform low concentration of doping elements on the level of a single layer, so that the integral uniformity of a film can be ensured, and the integral film can keep a uniform stoichiometric ratio.

The invention aims to protect a preparation method of a ferroelectric film, which adopts an improved atomic layer deposition process to prepare the ferroelectric film, wherein the improved process is carried out under the traditional process condition, precursors are mixed in proper proportion in advance, and then a target product is obtained after the precursors are jointly oxidized, so that the uniform ferroelectric film with low doping concentration is realized on a single-layer level.

In the preparation of the ferroelectric film, metal elements such as lanthanum, silicon, aluminum and the like are doped and deposited at a certain concentration, and the deposition time and the annealing temperature of each pulse are strictly controlled to ensure the performance of the film.

The invention selects the hafnium oxide-based ferroelectric film, is completely compatible with a CMOS (complementary metal oxide semiconductor) process line, has good micro-shrinkage and is beneficial to promoting the application of the ferroelectric memory.

The above description is intended to be illustrative and not restrictive. For example, the above-described examples (or one or more versions thereof) may be used in combination with each other, and it is contemplated that the embodiments may be combined with each other in various combinations or permutations. The scope of the application should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A method for preparing a ferroelectric thin film, comprising:

carrying out atomic layer deposition by taking a main element source as a reaction precursor, and depositing the main element on the surface of the substrate to adsorb most of free bonding points;

using inert gas as purge gas to perform purge purging;

performing oxidation treatment with an oxidizing gas;

using inert gas as purge gas to perform purge purging;

repeating the steps to obtain the ferroelectric film with the target thickness.

2. The method of claim 1, wherein the primary elemental source comprises a hafnium source; the hafnium source is selected from hafnium tetramethyamine, hafnium tetra-tert-butoxide and the like.

3. The method of claim 1, wherein the chamber temperature is set to 280-300 ℃, the reaction precursor heating temperature is 75-80 ℃, and the pressure inside the chamber is maintained at 150-185 mtorr during atomic layer deposition using the main element source as the reaction precursor.

4. The method of claim 1, wherein the ferroelectric thin film has a target thickness of 3 to 100 nm.

5. The method of claim 1, wherein the source of doping element is selected from the group consisting of trimethylaluminum, tris (dimethylamino) silane, and tris (isopropylcyclopentylalkyl) lanthanum.

6. The method of claim 1, wherein the chamber temperature is set to 280-300 ℃, the reaction precursor heating temperature is 75-80 ℃, and the pressure inside the chamber is maintained at 150-185 mtorr during the atomic layer deposition using the dopant source as the reaction precursor.

7. The method of claim 1, wherein the purge gas is an inert gas comprising argon.

8. The method of claim 1, wherein the oxidizing gas comprises H₂O、O₂And/or O₃。

9. A method for manufacturing a ferroelectric memory, comprising preparing a ferroelectric thin film obtained by the method of any one of claims 1 to 8.

10. A ferroelectric memory obtained by the method for manufacturing a ferroelectric memory according to claim 9.