WO2016106765A1

WO2016106765A1 - Method for preparing cerium oxide crystals and cmp polishing application thereof

Info

Publication number: WO2016106765A1
Application number: PCT/CN2015/000898
Authority: WO
Inventors: 尹先升; 房庆华; 贾长征; 周仁杰; 王雨春
Original assignee: 尹先升; 房庆华; 贾长征
Priority date: 2014-12-29
Filing date: 2015-12-14
Publication date: 2016-07-07
Also published as: CN105800665A; TWI676717B; TW201623704A

Abstract

A method for preparing cerium oxide crystals, comprising: adding an alkaline precipitant to a cerium source aqueous solution to which an organic additive has been added, so as to obtain cerium hydroxide by precipitating; adding carbon dioxide to the precipitated mixture by bubbling, so as to obtain a basic cerium carbonate by precipitating; and collecting and calcinating the basic cerium carbonate at a high temperature to obtain cerium oxide crystals. The prepared cerium oxide particles have a uniform size, and are easily dispersed into a liquid phase by means of mechanical force. A CMP polishing solution, which uses the dispersed cerium oxide as an abrasive material, shows an excellent planarization polishing efficiency in STI polishing applications.

Description

Preparation method of cerium oxide crystal and application of CMP polishing

Technical field

The invention discloses a preparation method of cerium oxide crystals, in particular to a preparation method of cerium oxide abrasive particles applied in an STI polishing slurry.

Background technique

Cerium oxide is a chemical mechanical polishing abrasive that has received much attention in recent years, mainly due to its high polishing activity to silica and high polishing performance at a lower solid content. Therefore, chemical mechanical polishing fluids using cerium oxide as an abrasive have greater application prospects and market advantages in terms of performance and cost compared to conventional silica or alumina materials.

At present, cerium oxide has been widely used as an abrasive for shallow trench isolation (STI) process polishing. For example, patent 201310495424.5 reports a chemical mechanical polishing (CMP) composition for shallow trench isolation (STI) process. The composition uses yttrium oxide as the abrasive, and the polishing requirement is high, and the silicon oxide/silicon nitride polishing selection ratio is high; Patent 200510069987.3 reports a chemical mechanical polishing slurry and a method for polishing the substrate, wherein the polishing film is a silicon oxide layer, and the requirement is The silicon oxide has a high polishing rate and low defect generation, and exhibits a low polishing rate for silicon nitride, thereby achieving a high silicon oxide/silicon nitride polishing selectivity ratio. The above reported patents all achieve polishing requirements for polishing liquids by selecting suitable chemical additives. However, when yttrium oxide is used as an abrasive, its own particle characteristics are critical to the polishing effect. For example, in STI polishing applications, it has been reported in the literature that the size and morphology of cerium oxide particles have an important influence on the generation of defects and the polishing rate selection ratio during polishing. At present, there are few reports on the control and synthesis of cerium oxide abrasive properties based on the requirements of STI polishing applications.

Summary of the invention

The object of the present invention is to provide a method for preparing cerium oxide crystals, which firstly prepares cerium carbonate by two-step precipitation, further calcined cerium carbonate obtained at a high temperature to obtain cerium oxide, and the prepared cerium oxide particles have a uniform particle size through mechanical force. It is easy to disperse cerium oxide particles in the liquid phase; the CMP polishing liquid using the dispersed cerium oxide as an abrasive exhibits excellent planarization polishing efficiency in STI polishing applications.

An aspect of the present invention provides a method for preparing a cerium oxide crystal, the method comprising:

Step 1: adding a basic precipitant to the aqueous solution of the cerium source to which the organic additive is added, and precipitating to obtain cerium hydroxide;

Step 2: adding carbon dioxide to the precipitation mixture in the first step, and precipitating to obtain basic cesium carbonate;

Step 3: Collecting the basic cesium carbonate in the second step, and calcining the basic cesium carbonate at a high temperature to obtain cerium oxide crystals.

In the foregoing step 1, the aqueous solution of the cerium source may be one or more aqueous solutions of cerium nitrate, cerium chloride or cerium acetate. The molar concentration of the aqueous solution of cerium source (calculated as cerium ions) is in the range of 0.05 M to 1.0 M.

In the foregoing step 1, the alkaline precipitating agent is not particularly limited and may be one or more of ammonia water or sodium hydroxide, and there is no special requirement for the concentration of the alkaline precipitant, and the molar concentration thereof is preferably 0.01 M-1.0. Between the M range.

In the foregoing step 1, the organic additive may be a high molecular polymer such as one or more of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) or polyvinyl alcohol (PVA), preferably polyethylene. Pyrrolidone (PVP) having an average molecular weight of from 1000 to 10,000. The concentration of the organic additive is such that the molar ratio of the cerium source to the organic additive is from 1.0:1.0 to 10.0:1.0.

In the foregoing step 1, the precipitation reaction temperature is not particularly required, and the temperature is preferably in the range of 20 ° C to 60 ° C, and the pH of the precipitation end point is 8.5-12.0. After the reaction is completed, the mixture is stirred for 30 minutes.

In the foregoing step two, the temperature ranges from 80 ° C to 100 ° C, and the reaction end point pH is 6.5-8.5. After the reaction is completed, the temperature is further stirred for 0.5-10 hours.

Preferably, the abrasive particles obtained in the second step are washed three times with pure water, and then calcined. The calcination temperature is 400-900 ° C, and the calcination time is 0.5-10 hours to obtain cerium oxide crystals.

Preferably, the synthesized cerium oxide crystal is further subjected to a dispersion treatment, and the dispersion treatment process is not particularly limited, and may be mechanical grinding such as ball milling, jet milling, etc., and an organic dispersing agent may be added during the dispersion process, and the organic dispersing agent may be Polyacrylic acid and its salts.

Another aspect of the present invention is to provide a polishing liquid comprising the cerium oxide crystal prepared by the above method, and the formulation of the polishing liquid can be a conventional formulation in the art, and is a general knowledge of those skilled in the art.

The yttrium oxide crystal synthesized by the invention can be applied to the field of STI polishing, and can achieve a higher TEOS polishing rate and a TEOS/SiN polishing selection ratio.

detailed description

The advantages of the present invention are further illustrated by the following specific examples, but the scope of the present invention is not limited only to the following examples.

The reagents and starting materials used in the present invention are commercially available.

Example 1

At room temperature, firstly, 0.05 mol of PVP (average molecular weight of 10,000) was dissolved in 1 L of deionized water, 0.05 mol of lanthanum nitrate was weighed and dissolved in the above PVP aqueous solution, and a concentration of 0.05 M ammonia was added to the above mixed solution under stirring. The precipitated turbid liquid is obtained, and the temperature of the precipitation reaction process is 20 ° C; the sedimentation end point is controlled by detecting the pH value of the turbid liquid, and when the pH of the precipitate reaches 8.5, the addition of ammonia water is stopped, stirring is continued for 30 minutes; and the above precipitate mixture is heated and heated to 100 ° C. And adding carbon dioxide gas to the precipitation mixture, while stirring the mixture, when the pH of the mixture reaches 6.5, the bubbling is stopped, the stirring is continued for 10 hours, the hydrothermal crystallization reaction, and the obtained precipitate is washed with pure water. After that, the filter cake is obtained by filtration to obtain cerium carbonate powder; the obtained cerium carbonate powder Further calcination in static air at 400 ° C for 10 hours, after cooling to obtain cerium oxide powder; by adding 0.01% polyacrylic acid as a dispersing agent, the obtained cerium oxide powder is ball-milled and dispersed, and the ball milling dispersion time is controlled to obtain STI polished cerium oxide abrasive.

Example 2

At room temperature, first 0.1 mol of PVA (average molecular weight of 1000) was dissolved in 1 L of deionized water, and 1.0 mol of cesium acetate was weighed and dissolved in the above PVA aqueous solution, and the concentration was 1.0 M to the above mixed solution under stirring. Ammonia water, the precipitation turbid liquid is obtained, the temperature of the precipitation reaction process is 60 ° C; the sedimentation end point is controlled by detecting the pH value of the turbid liquid, and when the pH of the precipitation reaches 12.0, the addition of ammonia water is stopped, stirring is continued for 30 minutes; the above precipitation mixture is heated to 80. °C, and adding carbon dioxide gas to the precipitation mixture while stirring the mixture, when the pH of the mixture reached 8.5, the bubbling was stopped, the stirring was continued for 10 hours, and the hydrothermal crystallization reaction was carried out, and the obtained precipitate was washed with pure water. After 3 times, the filter cake was dried to obtain cerium carbonate powder; the obtained cerium carbonate powder was further calcined in static air at 900 ° C for 0.5 hour, and cooled to obtain cerium oxide powder; by adding polyacrylic acid as a dispersing agent, The obtained cerium oxide powder was subjected to a ball-milling dispersion treatment, and by controlling the ball-milling dispersion time, a cerium oxide abrasive which can be applied to STI polishing was obtained.

Example 3

At room temperature, first 0.25 mol of PEG (average molecular weight of 3000) was dissolved in 1 L of deionized water, 0.5 mol of cesium acetate was weighed and dissolved in the above PEG aqueous solution, and 0.5 M of hydric hydroxide was added to the above mixed solution under stirring. Sodium, the precipitated turbid liquid is obtained, the temperature of the precipitation reaction process is 30 ° C; the sedimentation end point is controlled by detecting the pH value of the turbid liquid, and when the pH of the sediment reaches 9.5, the sodium hydroxide solution is stopped, stirring is continued for 30 minutes; the above precipitation mixture is heated. The temperature was raised to 100 ° C, and carbon dioxide gas was bubbled into the precipitation mixture while stirring the mixture. When the pH of the mixture reached 7.0, the bubbling was stopped, and the mixture was further stirred for 6.5 hours, and the resulting precipitate was subjected to hydrothermal crystallization. After washing with pure water for 3 times, the filter cake is filtered to obtain cerium carbonate powder; the obtained carbon The acid bismuth powder is further calcined in static air at 600 ° C for 4 hours, and then cooled to obtain cerium oxide powder; by adding polyacrylic acid as a dispersing agent, the obtained cerium oxide powder is ball-milled and dispersed, and the ball milling dispersion time is controlled to obtain A cerium oxide abrasive applied to STI polishing.

Example 4

At room temperature, first 0.25 mol of PVP (average molecular weight of 4000) was dissolved in 1 L of deionized water, 0.5 mol of cesium chloride was weighed and dissolved in the above PVP aqueous solution, and 0.25 M of hydrogen was added to the above mixed solution under stirring. Sodium oxide, a precipitated turbid liquid is obtained, and the temperature of the precipitation reaction process is 60 ° C; the pH of the turbid liquid is detected to control the end point of the precipitation, and when the pH of the precipitate reaches 10.5, the sodium hydroxide solution is stopped and stirring is continued for 30 minutes; The temperature was raised to 100 ° C by heating, and carbon dioxide gas was bubbled into the precipitation mixture while stirring the mixture. When the pH of the mixture reached 8.0, the bubbling was stopped, and the mixture was stirred for 0.5 hour for hydrothermal crystallization, and the resulting precipitate was obtained. After washing with pure water for 3 times, the filter cake is dried to obtain cerium carbonate powder; the obtained cerium carbonate powder is further calcined in static air at 700 ° C for 3 hours, and cooled to obtain cerium oxide powder; by adding polyacrylic acid as a powder The dispersant is subjected to a ball mill dispersion treatment on the obtained cerium oxide powder, and a cerium oxide abrasive which can be applied to STI polishing is obtained by controlling the dispersion time of the ball mill.

Example effect

The cerium oxide prepared by using 1-4 in the above examples was used as an abrasive, and by adding 0.5% of PAA (molecular weight of 4000), the slurry was prepared to have a cerium oxide content of 0.5% and a pH of 5.0. The polishing rate and polishing selection ratio of the polishing liquid corresponding to the above embodiment were tested.

The blank wafer was polished by the polishing liquid prepared in 1-4 of the above examples, and the polishing conditions were the same. The polishing parameters were as follows: Logitech polishing pad, downward pressure 3 psi, turntable rotation speed / polishing head rotation speed = 60/80 rpm, polishing time 60 s. , chemical mechanical polishing slurry flow rate of 100mL / min. The wafer slices used for polishing are all sliced from commercially available (for example, SVTC, USA) 8-inch coated wafers. The thickness of the metal film on the metal film wafer slice used for polishing is produced by NAPSON The film thickness of TEOS and SiN was measured by an RT-7O/RG-7B tester manufactured by TEOS NANO Matrics. The metal film removal rate was obtained by dividing the difference in thickness measured before and after polishing by the polishing time, and the polishing time was 1 minute.

Table 1 shows the results of the polishing test. The results show that the synthesized cerium oxide abrasive can achieve higher TEOS polishing rate and TEOS/SiN polishing selectivity. The prepared cerium oxide has good STI polishing application characteristics.

Table 1 Polishing effect of the chemical mechanical polishing liquid embodiment of the present invention

It should be understood that the wt% of the present invention refers to the mass percentage.

The specific embodiments of the present invention have been described in detail above, but are merely exemplary, and the invention is not limited to the specific embodiments described above. Any equivalent modifications and substitutions to the invention are also within the scope of the invention. Accordingly, equivalents and modifications may be made without departing from the spirit and scope of the invention.

Claims

A method for preparing cerium oxide crystals, the preparation method comprising:

Step 1: adding a basic precipitant to the aqueous solution of the cerium source to which the organic additive is added, and precipitating to obtain cerium hydroxide;

Step 2: adding carbon dioxide to the precipitation mixture in the first step, and precipitating to obtain basic cesium carbonate;

Step 3: Collecting the basic cesium carbonate in the second step, and calcining the basic cesium carbonate at a high temperature to obtain cerium oxide crystals.
The preparation method according to claim 1, wherein in the first step, the aqueous solution of the cerium source may be one or more aqueous solutions of cerium nitrate, cerium chloride or cerium acetate.
The production method according to claim 1, wherein the aqueous solution of the cerium source has a molar concentration of 0.05 M to 1.0 M in terms of cerium ions.
The production method according to claim 1, wherein the alkaline precipitating agent is one or more of ammonia water or sodium hydroxide.
The production method according to claim 1, wherein in the step 1, the organic additive is a high molecular polymer.
The production method according to claim 5, wherein the high molecular polymer is one or more of polyvinylpyrrolidone, polyethylene glycol or polyvinyl alcohol.
The production method according to claim 1, wherein in the step 1, the organic additive has an average molecular weight of from 1,000 to 10,000.
The production method according to claim 1, wherein in the step 1, the molar ratio of the cerium source to the organic additive is from 1.0:1.0 to 10.0:1.0.
The production method according to claim 1, wherein in the first step, the temperature ranges from 20 ° C to 60 ° C, and the precipitation end point pH is from 8.5 to 12.0.
The production method according to claim 1, wherein in the second step, the temperature ranges from 80 ° C to 100 ° C, and the reaction end point pH is from 6.5 to 8.5.
The process according to claim 1, wherein in the third step, the calcination temperature is from 400 to 900 ° C and the calcination time is from 0.5 to 10 hours.
A polishing liquid comprising the cerium oxide crystal prepared as claimed in any one of claims 1 to 11.