JP3177549B2 - Wafer polishing amount detection apparatus and wafer polishing amount detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting a wafer polishing amount in polishing for flattening a semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices formed on a semiconductor wafer has increased, the wiring layers have been miniaturized and multilayered in order to avoid an increase in the area of semiconductor chips.

[0003] One of the important issues of the multilayer wiring technique is flattening of an interlayer insulating film. Several methods have been proposed as a method for planarizing an interlayer insulating film. However, recently, chemical mechanical polishing (hereinafter, referred to as CMP) capable of realizing almost complete planarization at a low temperature has been attracting attention.

Hereinafter, a conventional CMP will be described with reference to the drawings.
An example of a method for manufacturing a semiconductor device employing a planarization technique according to the present invention will be described.

FIG. 11 shows a sectional structure of a semiconductor device in a process of flattening by conventional CMP.

In FIGS. 11A to 11D, reference numeral 1 denotes a silicon substrate on which a semiconductor element is formed, and 2 denotes a silicon substrate.
The lower aluminum wiring in the multilayer wiring structure formed thereon, 3 is a silicon-based oxide film formed on the lower aluminum wiring 2, 5 is the upper aluminum wiring, 6 is the connection between the lower aluminum wiring 2 and the upper aluminum wiring 5. Through holes formed in the silicon-based oxide film 3.

FIG. 12 shows a schematic configuration of a conventional polishing apparatus for flattening by CMP.

In FIG. 12, reference numeral 7 denotes a polishing table which is rotatable in a horizontal plane, and a polishing cloth (not shown) for polishing the wafer 13 is laid on an upper surface thereof. Reference numeral 8 denotes a holder provided to face the upper surface of the polishing table 7 to fix the wafer 13 and is supported by an arm 9 so as to be rotatable in a horizontal plane. 10 is a polishing table for polishing chemicals.
The supply port of the chemical solution supply nozzle 10 is directed to the upper surface of the polishing table 7.
A polishing table motor 11 for rotating the polishing table 7 is attached to a rotating shaft of the polishing table 7. Reference numeral 12 denotes a holder motor for rotating the holder 8, which is attached to a rotation shaft of the holder 8.

The operation of the above-structured planarization method by CMP will be described below with reference to FIGS.

First, as shown in FIG. 11A, a silicon-based oxide film 3 is formed on a lower aluminum interconnection 2 until at least the concave portion has a thickness equal to or larger than the polishing position.

Next, the wafer 1 on which the silicon-based oxide film 3 is formed
3 is fixed to the holder 8, the wafer 9 is brought into contact with the polishing table 7 by the arm 9, and the polishing table 7 and the holder 8 are rotated while supplying a chemical solution from the supply nozzle 10. Then, after a certain time has elapsed, the arm 9 is raised and the wafer 1
When the wafer 3 is taken out, the wafer 13 is in a state where the upper silicon-based oxide film 3 is flattened as shown in FIG.

Next, after cleaning the wafer 13, FIG.
As shown in FIG. 6, a through hole 6 is formed in the silicon-based oxide film 3.

After that, as shown in FIG. 11D, an upper aluminum wiring 5 is deposited on the silicon-based oxide film 3.

[0014]

However, in the above-described apparatus and method for detecting the amount of polishing, the silicon-based oxide film 3 shown in FIG. 11A to FIG.
There is a problem that the amount of polishing cannot be detected. For this reason, the polishing amount has to be empirically estimated from the polishing conditions and the polishing time, resulting in a deviation from the target polishing amount. For this reason, even if the etching for forming the through hole 6 is performed under a predetermined condition due to insufficient polishing, the thickness of the silicon-based oxide film 3 becomes excessively high just above the lower aluminum wiring 2 under predetermined conditions, the silicon-based oxide film 3 is not polished. And the lower aluminum wiring 2 is exposed on the surface of the silicon-based oxide film 3 due to excessive polishing.
There is a possibility that a short circuit with the upper aluminum wiring 5 may occur.

The present invention has been made in view of the above, and an object of the present invention is to provide a means capable of accurately detecting a polishing amount of a wafer while polishing the wafer to flatten the surface of the wafer. Accordingly, it is possible to effectively prevent a conduction failure due to insufficient polishing and a short circuit between upper and lower wirings due to excessive polishing.

[0016]

Means for Solving the Problems In order to achieve the above object, the means according to the first aspect of the present invention is to supply a polishing chemical solution on a rotatingly driven polishing table while removing a wafer attached to a holder. It is assumed that a device for detecting the amount of polished wafer is arranged in a polisher that is polished.

[0017] Then, the detection device of the wafer polishing amount, the force of the holder acting from the grinding stand during polishing the holder
In this configuration, a polishing resistance measuring means for monitoring the polishing resistance of the wafer by monitoring in the storage section is provided.

According to a second aspect of the present invention, in the first aspect of the present invention, the drive mechanism for forcibly rotating the holder and the drive mechanism for rotating the holder under stable conditions are provided on the holder section. And a rotational speed control means for controlling the polishing resistance, and the polishing resistance measuring means is a torque meter for measuring a rotational torque acting on the holder.

According to a third aspect of the present invention, as a method of detecting a wafer polishing amount, a wafer mounted on a rotationally driven holder is polished while a polishing chemical is supplied on a rotationally driven polishing table. when, by measuring the rotational torque acting on the holder based on the variation characteristics of the torque, the upper
This is a method for detecting when the flattening of the wafer attached to the holder is completed.

The means of the invention according to claim 4 is an apparatus for detecting a polishing amount of a wafer, which is arranged in a wafer polishing apparatus which polishes a wafer while supplying a polishing chemical on a rotationally driven polishing table. Is assumed.

Then, a first insulating film formed by introducing impurities and a second insulating film not doped with impurities are sequentially deposited on the surface of the wafer.

The apparatus for detecting the amount of polished wafer further comprises a liquid collecting means for collecting at least a part of the chemical liquid after polishing, and an impurity for measuring the concentration of impurities in the chemical liquid after polishing collected by the liquid collecting means. It provided a concentration measuring means, the impurity concentration measuring means, the recovered chemical solution is vaporized in a vacuum atmosphere, and a plasma generating means for generating a plasma, which was constituted by the emission detector for detecting a plasma emission is there.

According to a fifth aspect of the present invention, there is provided a method of detecting a polishing amount of a wafer, wherein a first insulating film doped with impurities and a second insulating film not doped with impurities are formed on the surface of the wafer in advance. When the wafer is polished in sequence while supplying the polishing chemical liquid, at least a part of the polished chemical liquid is collected, and the collected polished chemical liquid is introduced into a vacuum atmosphere and vaporized. Then, plasma is generated, the intensity of the plasma emission of the impurity is measured, and the polishing amount of the wafer is detected based on the change characteristic of the intensity of the plasma emission.

[0024] The means adopted in the invention of claim 6 is a wafer polishing amount detecting device arranged in a wafer polishing apparatus for polishing a wafer while supplying a polishing chemical solution on a polishing table which is rotationally driven. Is assumed.

Then, a first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited on the surface of the wafer.

The apparatus for detecting the amount of polished wafer further includes a liquid collecting means for collecting at least a part of the chemical liquid after polishing, and a pH measuring means for measuring a pH value of the chemical liquid after polishing collected by the liquid collecting means. Are provided.

The means taken in the invention of claim 7, as a method of detecting the wafer polishing amount on the surface of the pre-Meu E c, the second insulating without introducing the first insulating film and the impurities formed by introducing impurities When a wafer is polished while a film is sequentially deposited and a polishing chemical is supplied, at least a part of the polished chemical is collected, and the pH value of the collected chemical is measured, and the pH of the chemical is measured. In this method, the polishing amount of the wafer is detected based on the change characteristics of the wafer.

[0028] The means adopted in the invention of claim 8 is an apparatus for detecting a wafer polishing amount arranged in a wafer polishing apparatus for polishing a wafer while supplying a polishing chemical on a polishing table which is driven to rotate. Is assumed.

Then, a first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited on the surface of the wafer.

Further, the apparatus for detecting the amount of polished wafer has a liquid collecting means for collecting at least a part of the chemical liquid after polishing, and a resistivity measuring means for measuring the specific resistance of the chemical liquid after polishing collected by the liquid collecting means. And means are provided.

The means taken in the invention of claim 9, as a method of detecting the wafer polishing amount on the surface of the pre-Meu E c, the second insulating without introducing the first insulating film and the impurities formed by introducing impurities Films are sequentially deposited, and at the time of polishing a wafer while supplying a polishing chemical, at least a portion of the polished chemical is collected, and the specific resistance value of the collected polished chemical is measured. In this method, a polishing amount of a wafer is detected based on a change characteristic of a specific resistance value of a chemical solution.

In a tenth aspect of the present invention, the polishing of the wafer according to the first, second, fourth, sixth or eighth aspect is performed by laying the wafer on a polishing table using a silicon-based oxide as a polishing chemical. This is a chemical mechanical polishing for the purpose of flattening an insulating film formed on the wafer surface via the polishing cloth thus formed.

[0033]

With the above arrangement, in the first aspect of the present invention, while the wafer is being polished, the polishing resistance sharply decreases when the wafer surface is flattened by the wafer polishing.
Therefore, by monitoring the force received by the holder from the polishing table at the holder portion by the polishing resistance measuring means and detecting when the polishing resistance sharply decreases, the flattened state of the wafer is reliably detected. In addition, defects in wafer characteristics due to insufficient polishing or excessive polishing, which may occur when empirically determining the end of polishing, can be avoided.

According to the second or third aspect of the present invention, the polishing resistance is accurately measured by utilizing the rotational torque applied to the holder which is rotationally driven under stable conditions by the rotational speed control means, and the flattening of the wafer is completed. Time will be detected more accurately.

According to the fourth aspect of the present invention, as the polishing progresses,
When the second insulating film on the top surface of the wafer is polished,
The insulating film is exposed on the surface, and the impurities in the first insulating film are mixed into the polishing chemical, and the concentration of the impurities in the recovered polished chemical is rapidly increased at that time. Therefore,
By monitoring the impurity concentration in the chemical liquid after polishing by the impurity concentration measuring means during polishing, the polishing amount corresponding to the thickness of the first insulating film can be accurately detected. Only
In addition, since the change in the impurity concentration in the chemical solution after polishing is detected by using the plasma emission intensity of the impurity, the impurity concentration can be easily measured, and the polishing amount of the wafer can be easily detected.

According to the fifth aspect of the present invention, since the change in the impurity concentration in the chemical solution after polishing is detected by using the plasma emission intensity of the impurity, the impurity concentration can be easily measured and the polishing amount of the wafer can be easily adjusted. Is detected.

According to the sixth or seventh aspect of the present invention, when the second insulating film on the uppermost surface of the wafer is polished, the first insulating film is exposed on the surface, and the pH value in the polished chemical solution becomes the first value. It changes rapidly due to impurities in the insulating film. Therefore, by monitoring the pH value in the chemical solution collected by the pH measuring means, the polishing amount of the wafer can be accurately detected.

According to the eighth or ninth aspect of the present invention, when the second insulating film on the uppermost surface of the wafer is polished, the first insulating film is exposed on the surface, and the specific resistance value in the polished chemical solution becomes the second value. 1 Rapidly changes due to impurities in the insulating film. Therefore, by monitoring the specific resistance value in the chemical solution collected by the specific resistance measuring means, the polishing amount of the wafer can be accurately detected.

According to the tenth aspect of the present invention, in particular, even in the CMP method for achieving high-precision flattening with a small amount of polishing, the amount of polishing is reliably detected and the multilayer wiring The properties of the wafer, such as the insulating properties between the gaps and the conductive properties at the contact portions, are favorably maintained.

[0040]

Embodiments of the present invention will be described below with reference to the drawings.

[0041] or not a, a description will be given of a first embodiment.

FIG. 1 shows a schematic configuration of a polishing apparatus according to the first embodiment. In FIG. 1, reference numeral 7 denotes a polishing table which is rotatable in a horizontal plane, and a polishing cloth (not shown) for polishing the wafer 13 is laid on an upper surface thereof.
Reference numeral 8 denotes a wafer 13 provided facing the upper surface of the polishing table 7.
Is held by the arm 9 so as to be rotatable in a horizontal plane. Reference numeral 10 denotes a supply nozzle for supplying a polishing chemical to the polishing table 7, and a supply port of the supply nozzle 10 is directed to the upper surface of the polishing table 7. A polishing table motor 11 for rotating the polishing table 7 is attached to a rotating shaft of the polishing table 7. Further, 12 is a holder for motor as a moving mechanism drive that rotates the holder 8 is attached to the rotation shaft of the holder 8.

Here, as a feature of the present invention, a tachometer 20 for measuring the rotation of the holder 8 with respect to the holder motor 12, and the rotation of the holder 8 is stabilized by receiving a signal from the tachometer 20. A control device 21 serving as a rotation speed control means for performing feedback control of the holder motor 12 and a torque meter 22 serving as a polishing resistance measuring means for measuring a rotation torque applied to the holder 8 are provided so as to perform the above operations.

FIGS. 2A to 2D are process cross-sectional views showing changes in the cross-sectional structure in a chemical mechanical polishing process for flattening the wafer 13.

2A to 2D, reference numeral 1 denotes a silicon substrate on which a semiconductor element is formed, and 2 denotes, for example, a film thickness of 800 nm in a multilayer wiring structure formed on the silicon substrate 1.
m, a lower aluminum wiring 3; a silicon-based oxide film of, eg, 2000 nm formed on the lower aluminum wiring 2;
5 is, for example, an upper aluminum wiring having a thickness of 1000 nm;
6 is a lower aluminum wiring 2 and an upper aluminum wiring 5
And is formed on lower aluminum interconnection 2 through silicon-based oxide film 3.

FIG. 3 shows a change in torque applied to the holder 8 when the wafer 13 having a sectional structure as shown in FIG. 2 is flattened by CMP.
The torque is substantially constant up to 00 nm (about 10.5 N in the figure).
m), when the polishing amount exceeds 600 nm, the torque sharply decreases, and the torque becomes a substantially constant value (about 7.8 Nm) from the vicinity where the polishing amount is about 900 nm. That is, it is understood that the polishing resistance is sharply reduced and the torque is reduced by the flattening of the surface irregularities by the CMP.

Next, the operation of the wafer polishing apparatus and the polishing process will be described with reference to FIGS. 1, 2 and 3.

First, as shown in FIG. 2A, a silicon-based oxide film 3 is formed on the lower aluminum interconnection 2 until the thickness of the silicon oxide film 3 becomes at least the thickness of the lower aluminum interconnection 2. Then, the wafer 13 on which the silicon-based oxide film 3 is formed is fixed to the holder 8, and the wafer 9 is brought into contact with the polishing cloth of the polishing table 7 by the arm 9 at a pressure of, for example, 7 psi. While supplying a chemical solution (so-called colloidal silica) containing silicon oxide particles of 200 to 300 angstroms at a supply rate of, for example, 230 ml per minute, the polishing table 7 and the holder 8 are rotated at, for example, 15 rpm.
Rotate at rpm. During this time, the rotation speed of the holder 8 is measured by the tachometer 20, and the rotation speed is controlled by the control device 21 so that the rotation speed becomes constant.

Under these conditions, the silicon oxide 3 is, for example, 1
It is polished by a thickness of about 000 nm and flattened as shown in FIG. The torque applied to the holder 8 at this time is measured by the torque meter 22. As shown in FIG. 3, the torque applied to the holder 8 decreases as the flattening progresses. For example, the flattening is performed at 7.8 Nm, and the holder 8 is saturated. Arm 9 when saturated
And take out the wafer 13.

Next, after cleaning the wafer 13, as shown in FIG. 2C, a through hole 6 communicating with the lower wiring 2 is formed in the silicon-based oxide film 3.

Thereafter, as shown in FIG. 2D, an upper aluminum wiring 5 is formed on the silicon-based oxide film 3.

As described above, according to this embodiment, the tachometer 20, the control device 21, and the torque meter 22 are provided on the holder 8, and the wafer 13 is kept in a state where the polishing conditions such as the number of rotations are stable.
By measuring the change in the torque applied to the holder 8 during polishing, the flattening of the wafer 13 is completed by utilizing the characteristic that when the wafer 13 is flattened, the torque decreases sharply due to the reduction in polishing resistance. It is possible to accurately detect when the connection is made, and thus it is possible to effectively prevent the occurrence of a connection failure or short circuit between the upper layer wiring and the lower layer wiring.

In the first embodiment, the holder 8 for mounting the wafer 13 is forcibly rotated. However, the present invention is not limited to this embodiment . For example, the holder can be freely rotated. Or a fixed one. Even in such a case, the polishing resistance can be measured by, for example, attaching a strain gauge to the shaft of the holder and measuring a change in the polishing resistance from the stress applied to the shaft.

[0054] In the following, a second embodiment will be described.

FIG. 4 is a process sectional view of a wafer for detecting a wafer polishing amount in the second embodiment.

4A to 4D, reference numeral 1 denotes a silicon substrate on which a semiconductor element is formed, and 2 denotes, for example, a film thickness of 800 n in a multilayer wiring structure formed on the silicon substrate 1.
m is a first silicon-based oxide film, which is a first insulating film containing , for example, 6% of phosphorus having a thickness of, for example, 1000 nm and formed on the lower aluminum wiring 2, and 4 is a first silicon-based oxide film. For example, a film thickness of 10 formed on the film 3
A second silicon-based oxide film which is the second insulating film nm, phosphorous is not doped in this second insulating film 3. Reference numeral 5 denotes an upper aluminum wiring having a thickness of, for example, 1000 nm, and reference numeral 6 denotes a through hole for connecting the lower aluminum wiring 2 and the upper aluminum wiring 5, and is formed in the first silicon-based oxide film 3.

FIG. 5 shows a schematic configuration of a polishing apparatus according to the second embodiment.

In FIG. 5, the basic configuration of the polishing apparatus is the same as that of the first embodiment, and only different portions will be described.
In the second embodiment, a container 23 for recovering a chemical solution after polishing is provided below the outer peripheral portion of the polishing table 7.
A pipe 24 for discharging the chemical solution after polishing is connected to the bottom of the container 23. A branch pipe 25 for recovering a part of the chemical solution is connected at one position in the middle of the pipe 24, and a part of the chemical solution is supplied to a vacuum chamber 27 by a motor 26. The container 23, the pipe 24, the branch pipe 25, and the motor 26
Thus, a liquid recovery means is configured.

Reference numeral 28 denotes a nozzle for vaporizing the collected chemical in the vacuum chamber 27.
7 is installed inside. Reference numeral 29 denotes an equilibrium plate electrode for generating plasma, which is provided inside the vacuum chamber 27. Reference numeral 30 denotes an oscillator for generating plasma, which is connected to the balanced plate electrode 29. 31 is an exhaust pump for keeping the vacuum chamber 27 at a vacuum, 32 is a detection window for detecting the emission of plasma, 33 is an emission detector for detecting the emission of generated plasma, and the emission detector 33 is , Vacuum chamber 27
It is installed in contact with the detection window 32 so as to detect the light emission inside. The vacuum chamber 27, the nozzle 28, the balanced plate electrode 29, Ri by the oscillator 30 and the emission detector 33, not <br/> pure concentration measurement means is constituted. Also, of which the nozzle 28, Ri by the equilibrium plate electrode 29 and the oscillator 30, up <br/> plasma generating means is constituted.

FIG. 6 shows a change in the luminescence intensity of phosphorus when the wafer having the sectional structure of FIG. 4 is planarized by CMP. That is, the polishing amount is 600 n
Up to about m, the phosphorous-free second silicon-based oxide film 4 is deposited on the phosphorus-containing first silicon-based oxide film 3 of the wafer 1, so that the emission intensity of phosphorus is extremely low. When the polishing amount increases, the first silicon-based oxide film 3 is exposed on the surface, so that the amount of phosphorous emission sharply increases, and the polishing amount becomes 9%.
When the thickness is about 00 nm, the first silicon-based oxide film 3 shows most of the surface, and the emission intensity of phosphorus has a substantially constant value.

The operation of the apparatus for detecting the amount of polishing by CMP configured as described above will be described below with reference to FIGS. 4, 5 and 6.

First, as shown in FIG. 4A, a first silicon-based oxide film 3 containing phosphorus is formed on a lower aluminum interconnection 2.
Is formed, for example, to a thickness of 1000 nm.

Next, as shown in FIG.
A second silicon-based oxide film 4 is formed on the silicon-based oxide film 3 to a thickness of, for example, 1000 nm. Then, the wafer 13 on which the second silicon-based oxide film 4 is formed is fixed to the holder 8, and the wafer 9 is brought into contact with the polishing table 7 by the arm 9 at a pressure of, for example, 7 psi.
The polishing table 7 and the holder 8 are rotated at, for example, 15 rpm while supplying a chemical solution containing silicon-based oxide particles of about 300 angstroms at a rate of, for example, 230 ml per minute.

The wafer 13 is moved by this CMP to the state shown in FIG.
Flatten as shown in FIG. During this time, a part of the chemical solution collected by the container 23 is sent by the motor 26 to the nozzle 28 in the vacuum chamber. The vacuum chamber 27
The pressure is controlled, for example, to 1 Torr by the vacuum pump 31.
For example, 13.56 MHz, 300 W
To generate plasma. The chemical is vaporized and sent from the nozzle 28 into the vacuum chamber 27. When the emission is observed by the emission detector 33, the emission of phosphorus increases when the planarization ends, as shown in FIG. When the light emission of phosphorus is detected, for example, at least 10 times higher than the initial emission intensity, the arm 8 is raised and the wafer 13
Take out.

Next, as shown in FIG.
After cleaning 3, through holes 6 penetrating first silicon-based oxide film 3 and communicating with lower aluminum wiring 2 are formed.

Thereafter, as shown in FIG. 4E, an upper aluminum interconnection 5 is formed on the first silicon-based oxide film 3.

As described above, according to the second embodiment,
A first silicon-based oxide film 3 containing phosphorus is deposited on the wafer 13, and a second silicon-based oxide film 4 containing no phosphorus is deposited thereon, and CMP for flattening is performed. In the meantime, since a part of the chemical solution after polishing is collected and the concentration of phosphorus in the chemical solution is measured, it is possible to detect when the second silicon-based oxide film 4 is almost polished. At this time, the planarization of the surface of the wafer 13 has already been completed. In other words, by measuring the concentration of phosphorus, the flattened state can be reliably detected. At that time, by stopping the CMP, poor conduction between the lower aluminum wiring 2 and the upper aluminum wiring 5 and the like can be obtained. The occurrence of a short circuit can be effectively prevented.

The means for measuring impurities in the chemical solution after polishing is not limited to the above-described method utilizing plasma emission, and various other analysis methods can be used. However, when plasma emission is used as in the second embodiment, the apparatus for measuring the concentration has a relatively simple configuration, and the polishing amount can be easily determined without stopping the wafer polishing while polishing the wafer. There are potential benefits.

The impurity introduced into the first silicon-based oxide film 3 in advance is not limited to phosphorus as in the second embodiment. For example, nitrogen, boron, arsenic, etc. are introduced as impurities. Has the same effect.

The first and second insulating films 3 and 4 are not necessarily limited to a silicon-based oxide film.
The present invention is also applicable to insulating films such as Ni4 and BN.

[0071] In the following, with reference to the accompanying drawings third embodiment.

FIG. 7 shows a schematic configuration of a polishing apparatus according to the third embodiment.

In FIG. 7, the basic configuration of the polishing apparatus is substantially the same as in the first and second embodiments, and only different portions will be described. In the third embodiment, a pH monitor 34 as a pH measuring means for measuring a pH value of a chemical solution is provided on a pipe 24 for discharging a chemical solution after polishing, which is connected to a container 23 for collecting a chemical solution after polishing. It is interposed.

In this embodiment, the sectional structure of the wafer 13 is the same as the sectional structure of the wafer 13 in the second embodiment (see FIG. 4).

FIG. 8 shows a change in pH value when the wafer having the sectional structure of FIG. 4 is planarized by CMP. That is, when the polishing amount is 600 nm or less, the first silicon-based oxide film 3 still does not appear on the surface, and
Since only the silicon-based oxide film 4 is removed, the chemical solution after polishing exhibits a certain degree of alkalinity due to colloidal silica. However, when the polishing progresses and the first silicon-based oxide film 3 is exposed on the surface, the chemical solution is subjected to a neutralizing action due to the phosphorus contained therein, and the pH value is rapidly lowered. Most of the surface becomes the first silicon-based oxide film 3 1000
In the vicinity of nm, the constant value is almost neutral.

The operation of the polishing apparatus configured as described above will be described below with reference to FIGS. 4, 7 and 8.

First, as shown in FIGS. 4A and 4B,
After depositing the first silicon-based oxide film 3 containing phosphorus and the second silicon-based oxide 4 not containing phosphorus on the lower aluminum wiring 2 of the wafer 13, the wafer 13 is formed in the same manner as in the second embodiment. Polishing is performed under the conditions, and flattened as shown in FIG.

During this time, the chemical solution is collected by the container 23, and p
When the pH value is measured by the H monitor 34, as shown in FIG. 8, when the second silicon-based oxide film 4 is polished and the first silicon-based oxide film 3 is exposed (the planarization has already been completed). The pH value drops sharply. When the pH value becomes, for example, 8 or less, the arm 9 is raised, and the wafer 13 is taken out. After cleaning the wafer 13, a through hole 6 is formed (FIG. 4).
(D)). Thereafter, an upper aluminum wiring 5 is formed (see FIG. 4E).

As described above, according to the third embodiment,
By providing the apparatus 34 for measuring the pH value of the chemical solution after polishing, it is possible to detect the completion of the planarization completely by utilizing the change characteristic of the pH value according to the progress of polishing.

[0080] The Contact, impurity introduced into the first silicon-based oxide film 3 is not limited to such phosphorus of the third embodiment can introduce various impurities changing the pH value in the polishing solution Needless to say. Further, the material of the first and second insulating films is not limited to the silicon-based oxide film.

Next, the fourth aspect according to the ninth and tenth aspects of the present invention will be described.
Embodiments will be described with reference to the drawings.

FIG. 9 shows a polishing apparatus according to the fourth embodiment. In FIG. 9, the basic configuration of the polishing apparatus is the same as that of each of the above embodiments, and therefore, only different portions will be described. A pipe 24 for discharging the polished chemical is connected to the container 33, and a specific resistance monitor 35 as a specific resistance measuring means for measuring the specific resistance of the chemical is provided in the middle of the pipe 24.

In the present invention, the structure of the wafer 13 is the same as the structure of the second embodiment shown in FIG.

FIG. 10 shows a change in specific resistance when a wafer having the sectional structure of FIG. 4 is planarized by CMP. That is, until the thickness reaches 600 nm, the entire surface of the substrate is occupied by the second silicon-based oxide film 4, so that the specific resistance is relatively high at 80 kΩcm or more, but the polishing amount is
m, and when the first silicon-based oxide film 3 is exposed on the surface, the chemical solution after polishing contains phosphorus, so that the specific resistance is rapidly reduced to about 20 kΩcm.

The operation of the above-configured wafer polishing apparatus using CMP will be described below with reference to FIGS. 4, 9 and 10.

First, as shown in FIG. 4A, the first silicon oxide film 3 containing phosphorus is formed on the lower aluminum interconnection 2.
Is formed, for example, to a thickness of 1000 nm, and furthermore, FIG.
As shown in FIG. 1, a second silicon oxide film 4 is formed on the first silicon-based oxide film 3, for example, to a thickness of 1000 nm.

In this state, the wafer 13 is fixed to the holder 8, and the arm 13 is used to place the wafer 13 on the polishing table 7, for example.
The polishing table 7 and the holder 8 are rotated at a rotation speed of, for example, 15 rpm while supplying a chemical solution containing, for example, silicon oxide particles having a particle size of 200 to 300 angstroms, for example, 230 ml per minute from the supply nozzle 10. During this time, the medical solution is collected by the container 23. When the specific resistance is measured by the specific resistance monitor 35, the specific resistance decreases when the planarization ends, as shown in FIG. When the specific resistance reaches, for example, about 20 kΩcm, the arm 8 is raised and the wafer 13 is taken out.
As shown in (c), the second silicon-based oxide film 4 is polished and the first silicon-based oxide film 3 is exposed (planarization has already been completed).

Next, as shown in FIG.
After cleaning 3, a through hole 6 is formed.
As shown in (e), an upper aluminum wiring 5 is formed.

As described above, according to the fourth embodiment,
When the substrate is flattened and the first silicon-based oxide film 3 containing phosphorus is exposed on the surface, the specific resistance of the chemical solution after polishing sharply drops due to phosphorus. Then, since the specific resistance monitor 35 detects the time when the specific resistance decreases, it is possible to accurately detect the polishing amount of the substrate while performing the CMP.
Poor connection or short circuit between the lower aluminum wiring 2 and the upper aluminum wiring 5 can be effectively prevented.

In the fourth embodiment, the impurity doped into the first silicon-based oxide film 3 is phosphorus.
The impurities in the present invention are not limited to the examples, and various impurities that change the specific resistance of the polishing liquid can be introduced. Further, the material of the first and second insulating films is not limited to the silicon-based oxide film.

[0091]

As described above, according to the first aspect of the present invention, a wafer polishing apparatus for polishing a wafer mounted on a holder on a rotationally driven polishing table while supplying a polishing chemical. As a configuration of the wafer polishing amount detection device arranged in the configuration, the force acting on the holder from the polishing table during polishing is monitored at the holder, and the polishing resistance of the wafer is measured. Utilizing the characteristic that the polishing resistance sharply decreases when the surface is flattened, it is possible to reliably detect when the wafer is flattened during polishing, and therefore, the wafer characteristics due to insufficient polishing or excessive polishing are reduced. Failures can be avoided.

According to the second aspect of the present invention, in the first aspect of the present invention, the holder is forcibly driven to rotate under a stable condition, and the polishing resistance is measured by a torque meter for measuring a rotational torque acting on the holder. Since the measurement is performed, the polishing resistance can be accurately measured by using the change characteristic of the rotating torque applied to the holder, and therefore,
The end of the planarization can be detected more accurately.

According to the third aspect of the present invention, as a method of detecting a wafer polishing amount, a method is employed in which a wafer mounted on a rotationally driven holder on a rotationally driven polishing table is polished while supplying a polishing chemical. The rotation torque acting on the holder is measured, and when the flattening of the wafer is completed is detected based on the change characteristic of the rotation torque, the polishing resistance is accurately determined using the rotation torque applied to the holder. Measurement can be performed, so that the end of the planarization can be more accurately detected.

According to the fourth aspect of the present invention, there is provided a wafer polishing apparatus configured to polish a wafer while supplying a polishing chemical on a rotationally driven polishing table. A first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited in advance on the surface of the wafer, and at least a part of the polished chemical solution is collected; the concentration of impurities in the chemical solution, Pula
Since the measurement is performed using the light emission of the plasma, the use of the property that the impurity concentration in the collected chemical solution after polishing sharply increases at that time when the first insulating film is exposed on the surface as the polishing proceeds. As a result, the amount of polishing of the wafer can be accurately and easily detected, so that it is possible to avoid defects in wafer characteristics due to insufficient polishing or excessive polishing.

According to the fifth aspect of the present invention, as a method for detecting a wafer polishing amount, a first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited on the surface of a wafer in advance. When polishing a wafer while supplying a polishing chemical, at least a portion of the polished chemical is collected, vaporized in a vacuum chamber, and further turned into plasma. Since the method of detecting the polishing amount is used, it is possible to easily detect a change in the impurity concentration in the chemical solution by using the plasma emission intensity of the impurity, thereby avoiding a defect in wafer characteristics due to insufficient polishing or excessive polishing. be able to.

According to the sixth aspect of the present invention, there is provided a wafer polishing apparatus which is arranged in a wafer polishing apparatus which is configured to polish a wafer while supplying a polishing chemical solution on a rotationally driven polishing table. A first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited on the surface of the wafer, and at least a part of the polished chemical solution is collected;
Since the pH value in the collected chemical solution after polishing is measured, the pH value of the collected chemical solution after polishing sharply increases at the time when the first insulating film is exposed on the surface as the polishing progresses. Utilizing the characteristics, the amount of polishing of the wafer can be accurately detected, and therefore, defects in wafer characteristics due to insufficient polishing or excessive polishing can be avoided.

According to the seventh aspect of the present invention, as a method for detecting a wafer polishing amount, a first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited on the surface of a wafer in advance. When polishing a wafer while supplying a polishing chemical, it is a method of collecting at least a part of the chemical liquid after polishing, measuring the pH value, and detecting the polishing amount of the wafer based on the change characteristic of the pH value. The amount of polishing of the wafer can be accurately detected by utilizing the change in the pH value due to impurities, and the same effect as that of the sixth aspect can be obtained.

According to the eighth aspect of the present invention, there is provided an apparatus for detecting a polishing amount of a wafer, which is arranged in a wafer polishing apparatus configured to polish a wafer while supplying a polishing chemical on a rotatingly driven polishing table. A first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited on the surface of the wafer, and at least a part of the polished chemical solution is collected;
Since the specific resistance value in the collected chemical solution after polishing is measured, the specific resistance value of the collected chemical solution after polishing sharply increases when the first insulating film is exposed on the surface as the polishing proceeds. Utilizing the characteristic that increases, the amount of polishing of the wafer can be accurately detected, so that it is possible to avoid defects in wafer characteristics due to insufficient polishing or excessive polishing.

According to the ninth aspect of the present invention, as a method for detecting a wafer polishing amount, a first insulating film containing impurities and a second insulating film containing no impurities are sequentially deposited on the surface of the wafer in advance. When polishing a wafer while supplying a polishing chemical, a method of recovering at least a part of the chemical liquid after polishing, measuring a specific resistance value, and detecting a polishing amount of the wafer based on a change characteristic of the specific resistance value; Therefore, the amount of polishing of the wafer can be accurately detected by utilizing the change in the specific resistance value due to the impurity, and the same effect as that of the eighth aspect can be obtained.

According to the tenth aspect, the above-mentioned claim is provided.
Since the invention of 1, 2, 4, 6 or 8 was applied to a CMP method for flattening an insulating film on a wafer surface via a polishing cloth using a silicon-based oxide as a polishing chemical, In particular, even in a CMP method aiming at high-precision flattening with a small amount of polishing, the effects of the invention of each claim can be obtained, and the wafer characteristics such as insulation characteristics between multilayer wirings and conductive characteristics at contact portions can be obtained. Characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a configuration of a wafer polishing apparatus according to a first embodiment.

FIG. 2 is a cross-sectional view of a wafer for explaining a progress of polishing in the first embodiment.

FIG. 3 is a characteristic diagram showing a change in rotation torque with respect to progress of polishing in the first embodiment.

FIG. 4 is a sectional view of a wafer for explaining a progress of polishing in the second, third and fourth embodiments.

FIG. 5 is a front view schematically showing a configuration of a wafer polishing apparatus according to a second embodiment.

FIG. 6 is a characteristic diagram showing a change in a phosphorus concentration with progress of polishing in a second embodiment.

FIG. 7 is a front view schematically showing a configuration of a wafer polishing apparatus according to a third embodiment.

FIG. 8 is a characteristic diagram showing a change in pH value with progress of polishing in the third embodiment.

FIG. 9 is a front view schematically showing a configuration of a wafer polishing apparatus according to a fourth embodiment.

FIG. 10 is a characteristic diagram showing a change in a specific resistance value with progress of polishing in the fourth embodiment.

FIG. 11 is a cross-sectional view of a wafer showing a wafer flattening process in a conventional example.

FIG. 12 is a plan view and a front view schematically showing a configuration of a conventional wafer polishing apparatus.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 lower aluminum wiring 3 (first) silicon-based oxide film (first insulating film) 4 second silicon-based oxide film (second insulating film) 5 upper-layer aluminum wiring 6 through hole 7 polishing table 8 holder 9 arm 10 Nozzle 11 Motor for polishing table 12 Motor for holder 13 Wafer 14 Polishing table 20 Tachometer 21 Controller (rotation speed control means) 22 Torque meter (polishing resistance measurement means) 23 Container 24 Pipe 25 Branch pipe 26 Motor 27 Vacuum chamber 28 Nozzle 29 Parallel plate electrode 30 Oscillator 31 Exhaust pump 32 Emission detection window 33 Emission detector 34 pH monitor (pH measurement means) 35 Specific resistance monitor (specific resistance measurement means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-210261 (JP, A) JP-A-4-33336 (JP, A) JP-A-1-289656 (JP, A) JP-A-4-210 63427 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/304 622 B24B 37/04

Claims (10)

(57) [Claims] 1. A wafer polishing amount detection device arranged in a wafer polishing device configured to polish a wafer attached to a holder while supplying a polishing chemical solution on a rotatingly driven polishing table, the e the force acting from the grinding stand during polishing the holder
An apparatus for detecting a polishing amount of a wafer, comprising: a polishing resistance measuring means for monitoring a polishing resistance of a wafer by monitoring in a rudder section . In the detection apparatus according to claim 2] wafer polishing amount according to claim 1, a drive mechanism for driving forcibly rotating the holder, the drive mechanism so that the holder is rotated in a stable condition above
Rotation speed control means for controlling the holder portion, wherein the polishing resistance measuring means is a torque meter for measuring a rotation torque acting on the holder. 3. The method according to claim 1, further comprising: measuring a rotation torque acting on the holder when polishing the wafer attached to the rotation driven holder while supplying a polishing chemical on a rotation driven polishing table; based on the change characteristics, taken up in the holder
A method for detecting a polishing amount of a wafer, comprising detecting when the flattening of the attached wafer is completed. 4. A wafer polishing amount detection device arranged in a wafer polishing apparatus configured to polish a wafer while supplying a polishing chemical solution on a rotatingly driven polishing table, comprising: A first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited, and a liquid collecting means for collecting at least a part of the chemical solution after polishing; Impurity concentration measuring means for measuring the concentration of impurities in the collected chemical liquid after polishing, wherein the impurity concentration measuring means generates plasma after vaporizing the collected chemical liquid in a vacuum atmosphere Means for detecting the amount of polished wafers, comprising: 5. A first insulating film having impurities introduced therein and a second insulating film not having impurities introduced therein are sequentially deposited in advance on the surface of the wafer, and the wafer is polished while supplying a polishing chemical. At this time, at least a part of the chemical solution after polishing is collected, the collected chemical solution after polishing is introduced into a vacuum chamber and vaporized, plasma is generated, and the intensity of plasma emission of impurities is measured. Detecting a polishing amount of the wafer based on a change characteristic of the intensity of plasma emission. 6. A wafer polishing amount detecting device arranged in a wafer polishing apparatus configured to polish a wafer while supplying a polishing chemical solution on a rotatingly driven polishing table, comprising: A first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited, and a liquid collecting means for collecting at least a part of the chemical solution after polishing; A wafer polishing amount detecting device, comprising: a pH measuring means for measuring a pH value of the collected chemical solution after polishing. 7. A surface of the pre-Meu E c does not introduce a first insulating film and the impurities formed by introducing impurities leave second sequentially deposited an insulating film, while supplying a polishing liquid chemical wafer When polishing, at least a part of the chemical solution after polishing is collected, a pH value of the collected chemical solution is measured, and a polishing amount of the wafer is detected based on a change characteristic of the pH of the chemical solution. A method for detecting the amount of wafer polishing. 8. A wafer polishing amount detecting device arranged in a wafer polishing apparatus adapted to polish a wafer while supplying a polishing chemical on a rotatingly driven polishing table, comprising: A first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited, and a liquid collecting means for collecting at least a part of the chemical solution after polishing; A device for detecting a polishing amount of a wafer, comprising: a specific resistance measuring means for measuring a specific resistance of the collected chemical solution after polishing. 9. A surface of the pre-Meu E c does not introduce a first insulating film and the impurities formed by introducing impurities leave second sequentially deposited an insulating film, while supplying a polishing liquid chemical wafer When polishing a wafer, at least a part of the chemical liquid after polishing is collected, the specific resistance value of the collected chemical liquid after polishing is measured, and the polishing amount of the wafer is detected based on the change characteristic of the specific resistance value of the chemical liquid. A method for detecting a polishing amount in wafer polishing. 10. The apparatus for detecting the amount of polishing of a wafer according to claim 1, 2, 4, 6, or 8 , wherein the polishing of the wafer is performed by using a silicon-based oxide as a polishing chemical and laying a polishing cloth laid on a polishing table. A polishing apparatus for detecting a polishing amount of a wafer, wherein the apparatus is a chemical mechanical polishing for flattening an insulating film formed on a surface of the wafer via the substrate.