JP2002237478A - Method of polishing cmp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of polishing a CMP which controls the quantity of the components of abrasive liquid for the CMP rapidly and accurately and prevents the generation of a defect in the CMP to raise the yield of the manufacture of the CMP. SOLUTION: In a method of polishing the CMP, the concentration of each component of the abrasive liquid for the CMP is found by measuring the conductivity, ultrasonic propagation speed and temperature of the abrasive liquid containing at least two components in addition to water, and the relative ratio of the quantity or concentration of each component to the quantities or concentrations of the other components is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CMP (Chemical Chemistry) suitable for flattening an interlayer insulating film, an insulating film for isolating a shallow trench, a conductive metal film and the like in a semiconductor device manufacturing process.
ical Mechanical Polishing).

[0002]

2. Description of the Related Art In the field of ultra-large-scale integrated circuits, various microfabrication techniques have been studied and developed in order to increase the packaging density, and the design rules have already been on the order of sub-half micron. One of the techniques for satisfying such strict requirements for miniaturization is a CMP polishing technique. This technology enables miniaturization by completely flattening a layer to be exposed in a semiconductor device manufacturing process, thereby improving the yield. For example, an interlayer insulating film, an insulating film for shallow trench isolation, This technology is essential when planarizing a film, a conductive metal plug, a conductive metal wiring, and the like.

At present, insulating films of semiconductor devices include:
Silicon oxide films formed by a method such as plasma-CVD (Chemical Vapor Deposition), low-pressure-CVD, and ozone plasma-CVD are frequently used. Silica or ceria is used as abrasive particles for flattening these insulating films, and a slurry in which abrasive particles are dispersed in water is mixed with various agents for adjusting viscosity, PH or polishing rate. Type, or a two-part type consisting of an abrasive particle dispersion slurry and a drug aqueous solution,
It is used as a polishing liquid for the insulating film.

On the other hand, a method of forming an aluminum or alloy film thereof has conventionally been used as a method of forming a wiring for a semiconductor. However, recently, a groove is formed in advance and a copper or alloy film thereof is buried thereon. A method of removing an excess metal film by CMP and flattening it is being adopted. Polishing particles are not necessarily required for polishing such a metal film, and polishing can be performed by a corrosive action.
H or a solution containing at least one kind of agent for controlling the polishing rate, and a solution obtained by mixing an oxidizing agent for oxidizing the metal film with C
Used as MP polishing liquid.

In many cases, the components and concentrations of the polishing liquid are not disclosed by the polishing liquid maker in the CMP polishing liquid of either the insulating film or the conductive metal film. And there was no effective means for preventing defects caused by the polishing liquid beforehand. Further, even with the two-liquid type polishing liquid, the polishing characteristics could not be sufficiently controlled due to the fluctuation of the two-liquid mixing ratio caused by the problem of the weighing accuracy or the flow rate control accuracy.
Furthermore, since the abrasive particles are particularly likely to settle, the concentration is
There is a possibility that the conditions may be easily changed by changing the stirring conditions in the tank in which the polishing liquid is put or the conditions for sending the polishing liquid to the CMP apparatus.

[0006] In order to solve the above problem, conventionally, there has been only a method of measuring the weight of the abrasive particles by heating and removing all components other than the abrasive particles, including water, to determine the concentration of the abrasive particles. However, this method requires a long time for measurement, and it is impossible to solve a problem actually occurring on the spot due to the polishing liquid on the spot. Moreover, with this method, it is difficult to accurately determine the concentration of components other than the abrasive particles.

[0007]

SUMMARY OF THE INVENTION According to the first and second aspects of the present invention, the component concentration of a polishing slurry for CMP can be immediately known on the spot, so that the component amount can be controlled quickly and accurately. It is another object of the present invention to provide a CMP polishing method capable of preventing defects from occurring and improving the yield.

[0008]

According to the present invention, the concentration of each component is determined by measuring the conductivity, ultrasonic wave propagation speed and temperature of a polishing slurry for CMP containing at least two components other than water. The present invention relates to a CMP polishing method characterized by controlling an amount or a concentration relative ratio.

The present invention also relates to the above-mentioned CM in which the concentration of each component can be displayed from measured values of temperature, conductivity and ultrasonic wave propagation velocity by obtaining a calibration curve in advance.
It relates to a P polishing method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The CMP polishing liquid of the present invention is not particularly limited, except that the solvent or the dispersion liquid is mainly water. The polishing particles such as silica, alumina, and ceria, and the low-molecular or high-molecular dispersant are used. , An organic or inorganic acid, a salt thereof, an oxidizing agent, an anticorrosive, and the like, if necessary, in two or more components. The present invention relates to the use of C
The main point is to accurately determine the concentration of each component other than water in the CMP polishing liquid by accurately measuring the conductivity, the ultrasonic wave propagation velocity, and the temperature of the MP polishing liquid.

According to the present invention, the concentration of each component in the CMP polishing solution can be measured accurately and in-line immediately by suppressing the disturbance of the flow. It is preferable that the detector is relatively small. Also, when considering the cross section of the pipe in the pipe through which the CMP polishing liquid flows, the center area thereof (when the pipe is a circle having a radius of R mm, a concentric circle having a radius of 2 mm) Preferably, no detector is located. Further, when a coil is used as a detector of the conductivity measuring device, it is more preferable to install the detector outside the pipe, such as installing the coil outside the pipe. If the conductivity measuring device or the ultrasonic propagation velocity measuring device has a temperature measuring function including a thermocouple, a thermistor, or the like, it is not necessary to newly install a temperature measuring device.

The conductivity and ultrasonic wave propagation speed of the CMP polishing liquid vary depending on the component concentration and the temperature when the constituents of the solution are the same. In general, the higher the temperature, the higher the conductivity and the ultrasonic wave propagation speed. Tends to be faster. For this reason, in order to determine the concentration, it is necessary to also measure the temperature. It is preferable that these devices are provided with a software program function capable of converting and displaying the measured values of the conductivity, the ultrasonic wave propagation velocity and the temperature into the concentration.

In the present invention, the conductivity measuring device or the ultrasonic wave propagation speed measuring device itself is not particularly limited, and may be a commercially available device. The conductivity measuring device is, for example, a system to which electromagnetic induction by alternating current is applied. Those having low conductivity and high measurement sensitivity are preferred. Further, the ultrasonic wave propagation velocity measuring device is preferably a system including, for example, an ultrasonic element and a reflecting plate, which also has high measurement sensitivity.

The fluctuation of the component concentration in the CMP polishing liquid can be detected by the fluctuation of the conductivity and the ultrasonic wave propagation velocity value when the liquid temperature is constant, but by changing the temperature of the CMP polishing liquid and the concentration of each component variously. It is preferable to prepare different polishing liquids, measure their electric conductivity and ultrasonic wave propagation speed, and obtain a calibration curve (calibration curve) in advance so that the concentration can be quickly converted to a concentration. Even if the CMP polishing liquid is changed by installing the data for each of the different polishing liquids in a ROM or the like in advance, the ROM
Etc. need only be exchanged, which is more preferable in terms of efficiency.

The present invention will be described below with reference to FIGS. FIG. 1 is an example of an apparatus configuration in the present invention,
FIG. 2 shows another example of the device configuration in the present invention. Here, FIG. 1 shows a case where the CMP polishing liquid is one liquid or two liquids, and the two liquids are mixed in a container in advance before supplying the polishing liquid to the polishing section. FIG. 2 shows a case where the liquids are mixed.

In FIG. 1, the detector 103 for measuring the temperature and the conductivity 103 and the detector 104 for measuring the ultrasonic propagation velocity of the conductivity measuring apparatus 101 having a temperature measuring function and the ultrasonic wave propagation velocity measuring apparatus 102 are used to circulate the polishing liquid. Although it is installed in the pipe 105, it may be installed in the supply pipe 106 for supplying the polishing liquid to the polishing section. In FIG. 2, the conductivity measuring detector 201 and the conductivity measuring detector 203 and the temperature measuring and ultrasonic wave propagation velocity measuring detector 204 of the ultrasonic wave velocity measuring apparatus 202 having a temperature measuring function are connected to the flow of the polishing liquid. Although they are installed in series, they may be installed in parallel by attaching a bypass.
Further, when the concentration is to be measured, that is, when two or more main components affect the polishing characteristics in each of the two liquids, two pipes before mixing the two liquids, that is, one of the two liquids are used in FIG. It is preferable to install a conductivity measuring device with a temperature measuring function, an ultrasonic wave propagation speed measuring device, and the like in each of the liquid supply pipe 205 and the other liquid supply pipe 206 of the two liquids.

Although various polishing characteristics change when the concentration of the main component in the CMP polishing liquid changes, the polishing rate changes most simply. Therefore, when accurate concentration control of the main component cannot be performed in real time, precise polishing becomes difficult.

[0018]

Next, the present invention will be described by way of examples. In the following example, an 8-inch wafer covered with a silicon oxide film (p-TEOS film) was used for CM while measuring the component concentration in line with the apparatus shown in FIGS.
Polishing was performed using a P polishing apparatus EPO-111 (manufactured by Ebara Corporation), and film thickness was measured using Lambda Ace VLM8000 (manufactured by Dainippon Screen Mfg. Co., Ltd.) to obtain a polishing rate.

Example 1 The degree of neutralization of carboxylic acid with diethanolamine was 85.
%, A polyacrylic acid amine salt aqueous solution containing 40% by weight of a polyacrylic acid amine salt having a weight average molecular weight (measured by GPC and converted to standard polystyrene; the same applies hereinafter), which was diluted ten-fold. Is a cerium oxide slurry additive solution A (concentration: 4% by weight).

Next, 2 kg of cerium carbonate hydrate was placed in a container made of platinum and calcined at 850 ° C. for 2 hours in air to obtain cerium oxide powder. Deionized water was added so that the cerium oxide particles became 4% by weight of water, and ammonium polyacrylate having a neutralization rate of carboxylic acid with ammonia of 45% and a weight average molecular weight of 10,000 was converted to cerium oxide particles. 0.8% by weight based on the weight of the mixture, and added to the dispersion using a horizontal wet ultrafine dispersion / pulverizer.
The pulverization and dispersion treatment was performed at 0 revolutions / minute for 120 minutes. The obtained liquid is referred to as cerium oxide slurry B (concentration: 4% by weight).

FIG. 3 shows a representative example of the results of measuring the conductivity and the ultrasonic wave propagation speed while changing the mixing ratio and the temperature of the liquid A and the liquid B.
It was shown to. Based on these results, the concentration of the cerium oxide particles and the concentration (% by weight) of the polyacrylic acid amine salt in the liquid mixture of the liquid A and the liquid B can be displayed. Here, the ultrasonic propagation velocity measuring device is FUD-1 manufactured by Fuji Industry Co., Ltd.
As the conductivity meter, MC-111T manufactured by Electrochemical Meter Co., Ltd. was used.

A mixture obtained by mixing 50 kg of liquid A and 30 kg of liquid B was obtained.
Using a CMP polishing liquid having a polyacrylic acid amine salt concentration of 2.50% by weight and a cerium oxide particle concentration of 1.50% by weight,
Polishing was actually performed.

The above-mentioned mixed solution was put into a cylindrical container having a diameter of 40 cm, and a screw having a diameter of 10 cm was stirred at a position of 1 cm from the bottom of the container at 400 revolutions / minute. Circulation was performed at a flow rate of 1 liter per minute in a circulation pipe in which a detector of the velocity measuring device was installed. At the time of polishing, a three-way valve and a flow control valve as shown in FIG. 1 are used to supply a polishing liquid at a rate of 200 milliliters per minute onto a polishing pad of a CMP polishing apparatus, thereby forming a silicon oxide film (p-TEOS film). ) Was polished for 2 minutes, and the operation of stopping the supply of the polishing liquid to the polishing apparatus was repeated 10 times over 2 minutes for exchanging the wafer.

The residual liquid after the polishing was removed, and 60 kg of liquid A was removed.
Was replaced with a new CMP polishing liquid having a polyacrylic acid amine salt concentration of 2.67% by weight and a cerium oxide particle concentration of 1.33% by weight. Polishing was performed. FIG. 4 shows the concentration of cerium oxide particles, the concentration of polyacrylic acid amine salt, and the polishing rate when 20 sheets were polished.

From the results shown in FIG. 4, it is apparent that the polishing rate and the two-component concentration in the CMP polishing liquid are completely correlated, and that the polishing rate is constant when the two-component concentration is constant.

Example 2 In the same manner as in Example 1, a CMP polishing liquid having a polyacrylic acid amine salt concentration of 2.0% by weight and a cerium oxide particle concentration of 2.0% by weight obtained by mixing 50 kg of liquid A and 50 kg of liquid B was used. And polishing was performed.

However, in this embodiment, a polishing liquid stirring blade having a diameter of 10 cm for stirring the CMP polishing liquid was located at a position 5 cm from the bottom of the container, and the rotation speed was further reduced to 150 revolutions / minute. FIG. 5 shows the cerium oxide particle concentration, the polyacrylic acid amine salt concentration and the polishing rate at this time.

When the agitation of the polishing liquid was weaker than that in Example 1, the cerium oxide particles settled down a little, so that the cerium oxide particle concentration fluctuated with the lapse of time, and the polishing rate was completely proportional to the cerium oxide particle concentration. It can be seen that it fluctuates.

From the above results, it is clear that, for example, when there is a change in the cerium oxide particle concentration due to a problem in the stirring conditions, the change can be detected on the spot and in real time. Since the polishing rate can be known only after polishing, the present invention makes it possible to prevent or quickly improve the occurrence of defects due to polishing.

Example 3 50 kg of the liquid A was placed in each of two cylindrical containers having a diameter of 40 cm.
And liquid B containing cerium oxide particles were stirred at 400 rpm with a screw having a diameter of 10 cm at a position 1 cm from the bottom of the container. Detector of conductivity measuring device and ultrasonic propagation velocity measuring device with temperature measuring function,
As shown in FIG. 2, the two liquid mixtures are installed in series in a pipe for supplying to a CMP polishing machine. When polishing, the two tube pumps of FIG. 2 are operated (for 2 minutes), and when not polishing (wafer). Work to stop the supply of polishing liquid
Repeated 0 times. FIG. 6 shows the relationship between the cerium oxide particle concentration and the polishing rate when the flow rate of the liquid A is 100 ml / min and the flow rate of the liquid B is 100 ml / min. When the flow rate as set in advance actually flows stably, the concentration of cerium oxide is 2.0% by weight and the concentration of amine polyacrylate is 2.0% by weight.

From the results shown in FIG. 6, it is clear that the flow rate set in advance is actually flowing stably, and as a result, the polishing rate is also stable.

[0032]

According to the CMP polishing method of the first and second aspects, the component concentration of the polishing liquid for CMP can be quickly and accurately known on the spot, thereby controlling the component amount quickly and accurately. It is possible to prevent the occurrence of defects and improve the yield.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a device configuration in the present invention (a case where two liquids are mixed in a container in advance before a polishing liquid is supplied to a polishing section).

FIG. 2 is a schematic diagram showing another example of the apparatus configuration in the present invention (a case where two liquids are mixed immediately before supplying a polishing liquid to a polishing section).

FIG. 3 is a graph showing a representative example of the results of measuring the conductivity and the ultrasonic wave propagation speed in Example 1 by changing the mixing ratio of the liquid A and the liquid B and the temperature.

FIG. 4 shows the concentration of cerium oxide particles and the concentration of polyacrylic acid amine salt (the concentration of polycarboxylic acid) in Example 1.
And a graph showing a polishing rate.

FIG. 5 shows the concentration of cerium oxide particles and the concentration of polyacrylic acid amine salt (the concentration of polycarboxylic acid) in Example 2.
And a graph showing a polishing rate.

FIG. 6 is a graph showing a cerium oxide particle concentration and a polishing rate in Example 3.

[Explanation of symbols]

 101: Conductivity measuring device with temperature measuring function 102: Ultrasonic propagation velocity measuring device 103: Detector for temperature measurement and conductivity measurement 104: Detector for ultrasonic propagation velocity measuring 105: Circulation piping of polishing liquid 106: Polishing liquid Supply pipe to the polishing section 107: Wafer to be polished 108: Polishing pad 109: Pump for supplying polishing liquid to the polishing section 110: Pump for circulating polishing liquid 111: Motor for polishing liquid stirring 112: Polishing liquid stirring blade 201: Conductivity measuring device 202: Ultrasonic propagation velocity measuring device with temperature measuring function 203: Conductivity measuring detector 204: Temperature measuring and ultrasonic propagation velocity measuring detector 205: Supply pipe for one of two liquids 206: Supply piping for the other of the two liquids 207: Liquid supply pump 208: Liquid supply pump

Claims (2)

[Claims] 1. C containing at least two components other than water
A CMP polishing method characterized by determining the concentration of each component by measuring the conductivity, ultrasonic wave propagation speed and temperature of a polishing liquid for MP, and controlling the amount or concentration relative ratio of each component. 2. The CMP polishing method according to claim 1, wherein a concentration curve of each component can be displayed from measured values of temperature, conductivity and ultrasonic wave propagation speed by obtaining a calibration curve in advance.