JPH06216095A - Apparatus and method for detecting wafer polishing amount - Google Patents

Abstract

PURPOSE:To provide an apparatus and a method for detecting a wafer polishing amount in which the polishing amount of a wafer can be accurately detected when the surface of the wafer is polished to be flattened. CONSTITUTION:Coated abrasives are laid on a polishing base 7 to be rotatably driven, and a wafer 13 mounted on a holder 8 to be rotatably driven is CMP- polished while supplying polishing chemicals. In this case, the rotation of the holder 8, etc., is controlled to be fed back under stable conditions by a controller 21, and a rotary torque operating at the holder 8, i.e., a polishing resistance is monitored by a torquemeter 22. Since the resistance is abruptly reduced when the wafer 13 is flattened, a time in which the flattening is finished can be accurately detected. Further, a first silicon oxide film doped with impurity, a second silicon oxide film not doped with impurity are sequentially deposited on the wafer, and the flattening time can be sensed, even if impurity concentration, a pH value, resistivity, etc., in chemicals after polishing are monitored, can be detected from the polishing amount of a thickness of a first insulating film.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, with higher integration of semiconductor devices formed on a semiconductor wafer, miniaturization and multilayering of wiring layers have been progressing in order to avoid an increase in the area of semiconductor chips.

One of the important issues in the multilayer wiring technique is the planarization of the interlayer insulating film. Although several methods have been proposed as a method for planarizing an interlayer insulating film, chemical mechanical polishing (hereinafter, referred to as CMP), which can realize almost complete planarization at low temperature, has recently been attracting attention.

A conventional CMP will now be described with reference to the drawings.
An example of a method of manufacturing a semiconductor device that employs the planarization technique according to the above will be described.

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

In FIGS. 11A to 11D, 1 is a silicon substrate on which a semiconductor element is formed, and 2 is a silicon substrate 1.
Lower-layer aluminum wiring in the multilayer wiring structure formed above, 3 is a silicon oxide film formed on the lower-layer aluminum wiring 2, 5 is upper-layer aluminum wiring, and 6 is a connection between the lower-layer aluminum wiring 2 and the upper-layer aluminum wiring 5. The through holes are formed in the silicon oxide film 3.

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

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

The operation of the flattening method by CMP configured as described above will be described below with reference to FIGS. 11 and 12.

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

Next, the wafer 1 on which the silicon oxide film 3 is formed
3 is fixed to the holder 8, the wafer 13 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 the chemical solution from the supply nozzle 10. Then, after a certain time has passed, the arm 9 is raised and the wafer 1
When the wafer 3 is taken out, the wafer 13 is in a state in which the upper silicon-based oxide film 3 is flattened, as shown in FIG.

Next, after cleaning the wafer 13, FIG.
Through holes 6 are formed in the silicon oxide film 3 as shown in FIG.

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

[0014]

However, in the above-described polishing amount detecting apparatus and polishing amount detecting method, the silicon-based oxide film 3 shown in FIGS. 11 (a) to 11 (b) is used.
However, there is a problem in that the polishing amount cannot be detected. Therefore, it has been necessary to empirically estimate the polishing amount from the polishing conditions and the polishing time, which causes a deviation from the target polishing amount. As a result, insufficient polishing causes the thickness of the silicon oxide film 3 to be excessively large immediately above the lower aluminum wiring 2, and even if the etching for forming the through hole 6 is performed under a predetermined condition, the silicon oxide film 3 is formed. Is not completely removed to cause conduction failure, or conversely, the lower aluminum wiring 2 is exposed on the surface of the silicon oxide film 3 due to excessive polishing,
There is a possibility that a short circuit with the upper layer aluminum wiring 5 may occur.

The present invention has been made in view of the above circumstances, and an object thereof is to provide means for accurately detecting the amount of wafer polishing during polishing of the wafer in order to flatten the surface of the wafer. This effectively prevents the conduction failure due to insufficient polishing and the short circuit between the upper and lower wirings due to excessive polishing.

[0016]

In order to achieve the above-mentioned object, the means of the present invention as set forth in claim 1 is configured so that a wafer mounted on a holder is supplied while supplying a polishing chemical on a polishing table which is rotationally driven. It is premised on a wafer polishing amount detection device arranged in a wafer polishing device that is designed to perform polishing.

Further, the wafer polishing amount detecting device is provided with a polishing resistance measuring means for measuring the polishing resistance of the wafer by monitoring the force applied from the polishing table to the holder during polishing.

According to a second aspect of the present invention, in the invention of the first aspect, the driving mechanism for forcibly rotating and driving the holder, and the rotation for controlling the driving mechanism so that the holder rotates in a stable condition. A speed control means is provided, and the polishing resistance measuring means is a torque meter for measuring the 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 rotary driven holder is polished while a polishing chemical is supplied on a rotary driven polishing table. At this time, the rotation torque acting on the holder is measured, and the time when the flattening of the wafer is completed is detected based on the change characteristic of the rotation torque.

According to a fourth aspect of the present invention, a means for detecting a polishing amount of a wafer arranged in a wafer polishing apparatus for polishing a wafer while supplying a polishing chemical 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.

Further, the wafer polishing amount detecting device includes 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. The configuration is such that a concentration measuring means is provided.

According to a fifth aspect of the invention, in the invention of the fourth aspect, the impurity concentration measuring means is a plasma generating means for vaporizing the recovered chemical solution in a vacuum atmosphere to generate plasma. And a light emission detector for detecting plasma light emission.

According to a sixth aspect of the present invention, as a method for detecting a wafer polishing amount, a first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are previously formed on the surface of a wafer. When the wafer is polished while sequentially depositing and supplying a polishing chemical, at least a part of the chemical after polishing is recovered, and the recovered chemical after polishing is introduced into a vacuum atmosphere and vaporized. After that, plasma is generated, the intensity of the plasma emission of the impurities is measured, and the polishing amount of the wafer is detected based on the change characteristic of the intensity of the plasma emission.

According to a seventh aspect of the present invention, a means for detecting a wafer polishing amount is arranged in a wafer polishing apparatus which polishes a wafer while supplying a polishing chemical 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.

Further, in the wafer polishing amount detecting device, a liquid collecting means for collecting at least a part of the chemical liquid after polishing, and a pH measuring means for measuring the pH value of the chemical liquid after polishing collected by the liquid collecting means. And is provided.

The means taken by the invention of claim 8 is, as a method for detecting a wafer polishing amount, a first insulating film having impurities introduced thereinto and a second insulating film not having impurities introduced thereinto on the surface of the wafer in advance. When the wafer is polished while sequentially supplying the polishing chemicals, at least a part of the chemicals after polishing is recovered, the pH value of the recovered chemicals is measured, and the pH of the chemicals changes. This is a method for detecting the polishing amount of the wafer based on the characteristics.

According to a ninth aspect of the present invention, there is provided a wafer polishing amount detecting device arranged in a wafer polishing device for polishing a wafer while supplying a polishing chemical on a rotary table for polishing. 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 wafer polishing amount detecting device includes a liquid collecting means for collecting at least a part of the chemical liquid after polishing, and a specific resistance measurement for measuring the specific resistance of the chemical liquid after polishing collected by the liquid collecting means. And means for providing the means.

According to a tenth aspect of the present invention, as a method for detecting a wafer polishing amount, a wafer polishing amount is previously detected on the surface of the wafer.
A first insulating film into which impurities are introduced and a second insulating film into which impurities are not introduced are sequentially deposited, and at the time of polishing a wafer while supplying a polishing chemical, at least a part of the chemical after polishing is This is a method in which the specific resistance value of the recovered 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.

According to an eleventh aspect of the present invention, in the above-mentioned first, second, fourth, fifth, seventh or ninth aspect of the present invention, the wafer is polished by using a silicon-based oxide as a polishing chemical liquid on a polishing table. The chemical mechanical polishing is intended to planarize the insulating film formed on the wafer surface through the polishing cloth laid on the substrate.

[0034]

With the above construction, in the invention of claim 1, the polishing resistance is sharply reduced when the wafer surface is flattened by polishing the wafer while the wafer is being polished.
Therefore, the polishing resistance measuring means monitors the force received by the holder from the polishing table and detects when the polishing resistance sharply decreases, so that the flattened state of the wafer can be reliably detected, and it is empirical. In addition, it is possible to avoid defects in wafer characteristics due to insufficient polishing or excessive polishing that occur when determining the end of polishing.

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

According to the invention of claim 4, the progress of polishing causes
When the second insulating film on the top surface of the wafer is polished, the first
The insulating film is exposed on the surface, impurities in the first insulating film are mixed in the polishing chemical, and the concentration of impurities in the recovered chemical after polishing sharply rises at that time. Therefore,
By monitoring the impurity concentration in the chemical liquid after polishing by the impurity concentration measuring means, the polishing amount corresponding to the thickness of the first insulating film can be accurately detected.

In the invention of claim 5 or 6, since the change in the impurity concentration in the chemical liquid after polishing is detected by utilizing the plasma emission intensity of the impurities, the measurement of the impurity concentration becomes easy, and the polishing amount of the wafer is increased. Is also easily detected.

In the invention of claim 7 or 8, 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 chemical solution after polishing is 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.

In the invention of claim 9 or 10, 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 chemical solution after polishing is 1 Rapid change 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 eleventh aspect of the present invention, even in the CMP method which aims to perform highly accurate flattening with a very small polishing amount, the polishing amount can be reliably detected by the invention of each claim, and the multilayer wiring can be obtained. The characteristics of the wafer, such as the insulation characteristics during the interval and the conductive characteristics at the contact portion, are maintained well.

[0041]

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

First, a first embodiment according to the first and second aspects of the invention will be described.

FIG. 1 shows a schematic structure of the polishing apparatus in the first embodiment. In FIG. 1, reference numeral 7 denotes a polishing table that can rotate in a horizontal plane, and a polishing cloth (not shown) for polishing the wafer 13 is laid on the upper surface thereof.
The wafer 8 is provided on the upper surface of the polishing table 7 so as to face it.
Is a holder for fixing and is rotatably supported by an arm 9 in a horizontal plane. Reference numeral 10 denotes a supply nozzle for supplying the polishing chemical to the polishing table 7, and the supply port of the supply nozzle 10 is directed to the upper surface of the polishing table 7. Reference numeral 11 denotes a polishing table motor for rotating the polishing table 7, which is attached to the rotary shaft of the polishing table 7. Further, 12 is a holder motor as a drive mechanism according to the invention of claim 2, which rotates the holder 8, and is attached to the rotating shaft of the holder 8.

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

2A to 2D are process sectional views showing changes in the sectional structure in the chemical mechanical polishing process for flattening the wafer 13. As shown in FIG.

In FIGS. 2A to 2D, reference numeral 1 is a silicon substrate on which a semiconductor element is formed, and 2 is a film thickness of 800 n in a multilayer wiring structure formed on the silicon substrate 1.
m lower layer aluminum wiring, 3 is, for example, a 2000 nm silicon-based oxide film formed on the lower layer aluminum wiring 2,
5 is, for example, an upper aluminum wiring having a film thickness of 1000 nm,
6 is a lower layer aluminum wiring 2 and an upper layer aluminum wiring 5
It is a through hole for connecting to and is formed on the lower aluminum wiring 2 penetrating the silicon oxide film 3.

Further, FIG. 3 shows a change in the torque applied to the holder 8 when the wafer 13 having the sectional structure as shown in FIG. 2 is flattened by CMP, and the polishing amount is about 6
The torque is almost constant up to 00 nm (about 10.5 N in the figure).
However, when the polishing amount exceeds 600 nm, the torque sharply decreases, and the torque reaches a substantially constant value (about 7.8 Nm) from the vicinity of the polishing amount of about 900 nm. That is, it is understood that the polishing resistance sharply decreases and the torque drops due to the flattening of the surface irregularities by CMP.

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

First, as shown in FIG. 2A, a silicon oxide film 3 is formed on the lower layer aluminum wiring 2 to a thickness of at least the lower layer aluminum wiring 2. Then, the wafer 13 on which the silicon oxide film 3 is formed is fixed to the holder 8, and the wafer 13 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. For example, the polishing table 7 and the holder 8 are rotated at a rotation speed of 15 while supplying a chemical solution containing 200 to 300 angstroms of silicon oxide particles (so-called colloidal silica) at a supply rate of 230 ml per minute, for example.
Rotate at rpm. During this period, 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 this condition, 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, as the flattening progresses, the torque applied to the holder 8 becomes smaller, and for example, the torque is completely flattened at 7.8 Nm and becomes saturated. Arm 9 when saturated
And the wafer 13 is taken out.

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 oxide film 3.

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

As described above, according to this embodiment, the holder 8 is provided with the tachometer 20, the controller 21, and the torque meter 22, and the wafer 13 is kept in a state where the polishing conditions such as the number of revolutions are stable.
The flattening of the wafer is completed by measuring the change in the torque applied to the holder 8 during the polishing of the wafer and utilizing the characteristic that the torque sharply decreases due to the reduction of the polishing resistance when the wafer 13 is flattened. It is possible to accurately detect the time of occurrence, and thus it is possible to effectively prevent the occurrence of a connection failure or a 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, but the present invention is not limited to such an embodiment, and for example, the holder is configured to be freely rotatable. It may be fixed or fixed. Even in such a case, it is possible to measure the polishing resistance by a method such as attaching a strain gauge to the shaft of the holder and measuring the change in the polishing resistance from the stress applied to the shaft.

Next, a second embodiment according to the inventions of claims 4 to 6 will be described.

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

In FIGS. 4A to 4D, 1 is a silicon substrate on which a semiconductor element is formed, 2 is a film thickness of 800 n in a multilayer wiring structure formed on the silicon substrate 1.
m lower layer aluminum wiring, 3 is a first silicon oxide film which is the first insulating film according to the invention of claim 4, and which contains, for example, 6% of phosphorus having a film thickness of 1000 nm formed on the lower layer aluminum wiring 2. Is a second silicon oxide film which is a second insulating film according to the invention of claim 4 and which is formed on the first silicon oxide film 3 and has a film thickness of, for example, 1000 nm.
The insulating film 3 is not doped with phosphorus. Also,
5 is, for example, an upper aluminum wiring having a film thickness of 1000 nm,
Reference numeral 6 is a through hole for connecting the lower aluminum wiring 2 and the upper aluminum wiring 5, which is formed in the first silicon oxide film 3.

FIG. 5 shows a schematic structure of the polishing apparatus in the second embodiment.

In FIG. 5, the basic structure of the polishing apparatus is the same as that of the first embodiment, and only different parts will be described.
In the second embodiment, a container 23 for collecting the chemical liquid after polishing is installed under the outer peripheral portion of the polishing table 7, and further,
A pipe 24 for discharging the chemical liquid after polishing is connected to the bottom of the container 23. A branch pipe 25 for collecting a part of the chemical liquid is connected at a part of the pipe 24, and a part of the chemical liquid is sent to a vacuum chamber 27 by a motor 26. The container 23, the pipe 24, the branch pipe 25, and the motor 26 constitute a liquid recovery means according to the invention of claims 4, 7 and 9.

Further, 28 is a nozzle for vaporizing the recovered chemical liquid in the vacuum chamber 27, and the vacuum chamber 2
It is installed inside 7. 29 is a balanced plate electrode for generating plasma, which is installed inside the vacuum chamber 27. Reference numeral 30 is 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 in 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 that the light emission therein can be detected. The vacuum chamber 27, the nozzle 28, the balanced plate electrode 29, the oscillator 30, and the light emission detector 33 constitute the impurity concentration measuring means according to the invention of claim 4. Further, the nozzle 28, the balanced plate electrode 29, and the oscillator 30 constitute the plasma generating means according to the invention of claim 4.

Here, FIG. 6 shows changes in the emission intensity of phosphorus when the wafer having the sectional structure of FIG. 4 is flattened by CMP. That is, the polishing amount is 600 n
Up to about m, since the second silicon oxide film 4 containing no phosphorus is deposited on the first silicon oxide film 3 containing phosphorus of the wafer 1, the light emission intensity of phosphorus is extremely small. When the polishing amount increases, the first silicon-based oxide film 3 is exposed on the surface, so that the phosphor emission amount rapidly increases and the polishing amount is 9%.
When the thickness is about 00 nm, the first silicon oxide film 3 shows most of the surface, and the emission intensity of phosphorus has a substantially constant value.

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

First, as shown in FIG. 4A, the first silicon oxide film 3 containing phosphorus is formed on the lower aluminum wiring 2.
To have a film thickness of 1000 nm, for example.

Next, as shown in FIG. 4B, the first
A second silicon oxide film 4 is formed on the silicon oxide film 3 to have a film thickness of 1000 nm, for example. Then, the wafer 13 having the second silicon oxide film 4 formed thereon is fixed to the holder 8, and the wafer 13 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, a rotation speed of 15 rpm while supplying, for example, 230 ml per minute of a chemical solution containing silicon oxide particles of 300 angstroms.

By this CMP, the wafer 13 is removed as shown in FIG.
It is flattened as shown in (c). During this time, a part of the chemical solution collected in the container 23 is sent to the nozzle 28 in the vacuum chamber by the motor 26. The vacuum chamber 27 is
The vacuum pump 31 controls the pressure to 1 Torr, for example.
For the balanced flat plate electrode 29, for example, 13.56 MHz, 300 W
To generate plasma by applying high frequency electric power. The chemical liquid is vaporized and sent into the vacuum chamber 27 from the nozzle 28. When luminescence is observed by the luminescence detector 33, the luminescence of phosphorus increases when the planarization is finished as shown in FIG. When the light emission of phosphorus is detected, for example, 10 times or more than the initial emission intensity, the arm 8 is raised and the wafer 13
Take out.

Next, as shown in FIG. 4D, the wafer 1
After cleaning 3, the through holes 6 penetrating the first silicon oxide film 3 and communicating with the lower aluminum wiring 2 are formed.

After that, as shown in FIG. 4E, the upper layer aluminum wiring 5 is formed on the first silicon 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 not containing phosphorus is further deposited thereon, and CMP for planarization is performed. During this period, a part of the chemical liquid after polishing is collected and the concentration of phosphorus in the chemical liquid is measured, so that it is possible to detect when the second silicon oxide film 4 is almost polished. At this time, the flattening of the surface of the wafer 13 has already been completed. That is, by measuring the phosphorus concentration, it is possible to reliably detect the flattened state, and by ending CMP at that time, conduction failure between the lower layer aluminum wiring 2 and the upper layer aluminum wiring 5 can be prevented. It is possible to effectively prevent the occurrence of a short circuit.

The means for measuring the impurities in the chemical liquid after polishing is not limited to the one utilizing the plasma emission described above, and various other analysis methods can be used. However, when plasma emission is used as in the second embodiment, the concentration measuring device has a relatively simple structure, and the polishing amount can be easily determined without stopping the wafer polishing while polishing the wafer. There are possible advantages.

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

Further, the first and second insulating films 3 and 4 are not necessarily limited to the silicon oxide film, and for example, Si ₃
It can also be applied to an insulating film such as Ni ₄ or BN.

Next, a third embodiment according to the seventh and eighth aspects of the invention will be described with reference to the drawings.

FIG. 7 shows a schematic structure of the polishing apparatus in the third embodiment.

In FIG. 7, the basic structure of the polishing apparatus is substantially the same as that of the first and second embodiments, and only different parts will be described. In Example 3 of the present subject, a pH monitor 34 as a pH measuring means for measuring the pH value of the chemical liquid is provided in a pipe 24 for discharging the chemical liquid after polishing, which is connected to a container 23 for collecting the chemical liquid after polishing. It is installed.

Further, 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 flattened by CMP. That is, when the polishing amount is 600 nm or less, the first silicon oxide film 3 does not yet appear on the surface, and the second silicon oxide film 3 is mainly used for the second
Since only the silicon oxide film 4 is removed, the chemical solution after polishing shows a certain degree of alkalinity due to the colloidal silica. However, when the polishing progresses and the first silicon oxide film 3 is exposed on the surface, the chemical solution is neutralized by the phosphorus contained therein, and the pH value sharply decreases, Most of the surface becomes the first silicon oxide film 3 1000
In the vicinity of nm, it has a constant value that is almost neutral.

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

First, as shown in FIGS. 4 (a) and 4 (b),
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 flattening is performed as shown in FIG.

During this period, the chemical solution is collected in 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 oxide film 4 is polished and the first silicon oxide film 3 is exposed (planarization is already 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, the through holes 6 are formed (FIG. 4).
(See (d)). After that, the upper aluminum wiring 5 is formed (see FIG. 4E).

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

The impurities introduced into the first silicon oxide film 3 according to the invention of each claim are not limited to phosphorus as in the third embodiment, but various kinds of substances that change the pH value in the polishing liquid. It goes without saying that impurities can be introduced.
The material of the first and second insulating films is not limited to the silicon oxide film.

Next, the fourth aspect of the present invention according to claims 9 and 10
Examples will be described with reference to the drawings.

FIG. 9 shows a polishing apparatus in the fourth embodiment. In FIG. 9, the basic structure of the polishing apparatus is the same as that of each of the above-described embodiments, so only different parts will be described. A pipe 24 for discharging the chemical liquid after polishing is connected to a container 33, and a resistivity monitor 35 as a resistivity measuring means for measuring the resistivity of the chemical liquid is provided in the middle of the pipe 24.

Also in the present invention, the structure of the wafer 13 is similar to the structure shown in FIG. 4 in the second embodiment.

FIG. 10 shows changes in specific resistance when a wafer having the sectional structure of FIG. 4 is flattened by CMP. That is, until reaching 600 nm, the entire surface of the substrate is occupied by the second silicon oxide film 4, so that the specific resistance is relatively high at 80 kΩcm or more, but the polishing amount is 600 n.
When the thickness becomes m or more and the first silicon oxide film 3 is exposed on the surface, phosphorus is contained in the chemical liquid after polishing, so that the specific resistance is rapidly reduced to about 20 kΩcm.

The operation of the CMP wafer polishing apparatus configured as described above 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 wiring 2.
Is formed to a film thickness of 1000 nm, for example, and further, in FIG.
As shown in, the second silicon oxide film 4 is formed on the first silicon oxide film 3 to a thickness of 1000 nm, for example.

In this state, the wafer 13 is fixed to the holder 8 and the arm 9 holds the wafer 13 on the polishing table 7, for example, 7.
The polishing table 7 and the holder 8 are rotated at a rotation speed of 15 rpm, for example, while supplying 230 ml per minute of a chemical solution containing silicon oxide particles having a particle diameter of 200 to 300 angstroms from the supply nozzle 10 while bringing them into contact with each other. During this time, the container 23 collects the drug solution. When the specific resistance is measured by the specific resistance monitor 35, the specific resistance decreases when the flattening is completed as shown in FIG. When the arm 8 is raised and the wafer 13 is taken out when the specific resistance becomes about 20 kΩcm, the wafer 13 is
As shown in (c), the second silicon oxide film 4 is polished and the first silicon oxide film 3 is exposed (planarization is already completed).

Next, as shown in FIG. 4D, the wafer 1
3 is washed, the through hole 6 is formed, and then, as shown in FIG.
As shown in (e), the upper layer 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 decreases due to phosphorus. Since the specific resistance monitor 35 detects the decrease in the specific resistance, it is possible to accurately detect the polishing amount of the substrate while performing CMP.
It is possible to effectively prevent a connection failure or a short circuit between the lower aluminum wiring 2 and the upper aluminum wiring 5.

In the fourth embodiment, the impurity doped in the first silicon oxide film 3 is phosphorus.
The impurities in the inventions of the respective claims are not limited to the embodiments, and various impurities that change the specific resistance of the polishing liquid can be introduced. The material of the first and second insulating films is not limited to the silicon oxide film.

[0092]

As described above, according to the first aspect of the present invention, the wafer polishing apparatus is configured to polish the wafer mounted on the holder on the rotary table for polishing while supplying the polishing chemical. As the configuration of the wafer polishing amount detection device that is arranged in the above position, the force applied from the polishing table to the holder during polishing is monitored to measure the polishing resistance of the wafer. It is possible to reliably detect when the wafer is flattened during polishing by utilizing the characteristic that the polishing resistance sharply decreases when the wafer is flattened. It can be avoided.

According to a second aspect of the present invention, in the first aspect of the invention, the holder is forcibly driven to rotate under stable conditions, and the polishing resistance is measured by a torque meter that measures the rotational torque acting on the holder. Since it is configured to measure, it is possible to accurately measure the polishing resistance by utilizing the change characteristic of the rotation torque applied to the holder.
The end of the flattening can be detected more accurately.

According to the third aspect of the present invention, as a method for detecting the amount of wafer polishing, when a wafer mounted on a holder which is rotationally driven 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 detected based on the change characteristic of the rotation torque, the rotation resistance applied to the holder is used to accurately measure the polishing resistance. It can be measured and thus the end of the planarization can be detected more accurately.

According to the fourth aspect of the present invention, there is provided a wafer polishing amount detecting device arranged in a wafer polishing device configured to polish a wafer while supplying a polishing chemical on a rotary drive polishing table. Firstly, a first insulating film containing impurities and a second insulating film not containing impurities are sequentially deposited on the surface of the wafer in advance, and at least a part of the chemical liquid after polishing is collected, and the collected chemical liquid after polishing is collected. Since the configuration is such that the concentration of impurities in the chemical liquid is measured, the characteristic that the impurity concentration in the recovered chemical liquid after polishing is rapidly increased when the first insulating film is exposed on the surface due to the progress of polishing is used. Therefore, the polishing amount of the wafer can be accurately detected, and therefore, the defect of the wafer characteristics due to insufficient polishing or excessive polishing can be avoided.

According to the invention of claim 5, in the invention of claim 4, as a means for measuring impurities, the chemical solution collected in the vacuum chamber is vaporized to generate plasma, and the emission of plasma is detected. Since the configuration is adopted, it is possible to easily detect the change in the impurity concentration in the chemical liquid by utilizing the plasma emission intensity of the impurities.

According to the invention of claim 6, as a method for detecting the amount of wafer polishing, 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, When a wafer is polished while supplying a polishing chemical, at least a part of the chemical after polishing is recovered and vaporized in a vacuum chamber, and further converted into plasma. Based on the change characteristic of the intensity of plasma emission, Since the method of detecting the polishing amount is used, it is possible to easily detect the change in the impurity concentration in the chemical liquid by utilizing the plasma emission intensity of the impurities, thus avoiding the defect of the wafer characteristics due to insufficient polishing or excessive polishing. be able to.

According to the invention of claim 7, the wafer polishing amount detecting device is arranged in the wafer polishing device which polishes the wafer on the polishing table driven to rotate while supplying the polishing chemical. , 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 chemical liquid after polishing is recovered,
Since the pH value in the recovered chemical liquid after polishing is measured, when the first insulating film is exposed on the surface due to the progress of polishing, the pH value of the recovered chemical liquid after polishing sharply increases at that time. It is possible to accurately detect the polishing amount of the wafer by utilizing the characteristics described above, and thus it is possible to avoid a defect in the wafer characteristics due to insufficient polishing or excessive polishing.

According to the invention of claim 8, as a method for detecting the amount of wafer polishing, 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, When a wafer is polished while supplying a polishing chemical, at least a part of the chemical after polishing is collected to measure the pH value, and the polishing amount of the wafer is detected based on the change characteristic of the pH value. The polishing amount of the wafer can be accurately detected by utilizing the change in pH value due to impurities, and the same effect as that of the invention of claim 7 can be obtained.

According to the ninth aspect of the present invention, there is provided a wafer polishing amount detecting device arranged in a wafer polishing device configured to polish a wafer on a polishing table which is rotationally driven while supplying a polishing chemical. , 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 chemical liquid after polishing is recovered,
Since the specific resistance value in the recovered chemical liquid after polishing is measured, when the first insulating film is exposed on the surface due to the progress of polishing, the specific resistance value of the recovered chemical liquid after polishing sharply increases at that time. It is possible to accurately detect the polishing amount of the wafer by utilizing the characteristic that rises to 0. Therefore, it is possible to avoid the defect of the wafer characteristic due to insufficient polishing or excessive polishing.

According to the tenth aspect of the invention, as a method for detecting the amount of wafer polishing, 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, When polishing a wafer while supplying a polishing chemical, at least a portion of the chemical after polishing is collected to measure the specific resistance value, and a method for detecting the polishing amount of the wafer based on the change characteristic of the specific resistance value is used. Therefore, the polishing amount of the wafer can be accurately detected by utilizing the change in the specific resistance value due to the impurities, and the same effect as that of the invention of claim 9 can be obtained.

According to the invention of claim 11, the invention of claim 1, 2, 4, 5, 7 or 9 is characterized in that a silicon-based oxide is used as a polishing chemical, and insulation on the wafer surface is performed through a polishing cloth. Since it was applied to the CMP method for flattening the film,
In particular, the effects of the invention of each claim can be obtained even in the CMP method for the purpose of performing highly accurate flattening with a small polishing amount, and the wafer such as the insulating characteristic between the multi-layered wiring and the conductive characteristic in the contact portion The characteristics of can be improved.

[Brief description of drawings]

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

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

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

FIG. 4 is a cross-sectional view of a wafer for explaining the 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 in a second embodiment.

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

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

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

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

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

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

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

[Explanation of symbols]

 1 Silicon Substrate 2 Lower Aluminum Wiring 3 (First) Silicon Oxide Film (First Insulating Film) 4 Second Silicon Oxide Film (Second Insulating Film) 5 Upper 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 Control device (rotation speed control means) 22 Torque meter (polishing resistance measuring 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 measuring means) 35 Specific resistance monitor (specific resistance measuring means)

Claims (11)

[Claims] 1. A wafer polishing amount detecting device arranged in a wafer polishing device configured to polish a wafer mounted on a holder while supplying a polishing chemical on a rotary driven polishing table, comprising: A device for detecting a wafer polishing amount, comprising a polishing resistance measuring means for measuring a polishing resistance of a wafer by monitoring a force applied to a holder from the polishing table during polishing. 2. The wafer polishing amount detection device according to claim 1, further comprising a drive mechanism for forcibly rotating and driving the holder, and a rotation speed control means for controlling the drive mechanism so that the holder rotates under a stable condition. The wafer polishing amount detecting device is characterized in that the polishing resistance measuring means is a torque meter for measuring a rotational torque acting on the holder. 3. The rotational torque acting on the holder when polishing a wafer mounted on a rotationally driven holder while supplying a polishing chemical on a rotationally driven polishing table is measured. A method for detecting the amount of wafer polishing, which detects when the flattening of the wafer is completed based on the change characteristics. 4. A wafer polishing amount detecting device arranged in a wafer polishing device for polishing a wafer while supplying a polishing chemical on a rotary driven polishing table, the device 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 recovery means for recovering at least a part of the chemical liquid after polishing, and the liquid recovery means. An apparatus for detecting a polishing amount of a wafer, comprising: an impurity concentration measuring means for measuring a concentration of impurities in the recovered chemical liquid after polishing. 5. The wafer polishing amount detecting device according to claim 4, wherein the impurity concentration measuring means includes a plasma generating means for generating plasma after vaporizing the recovered chemical liquid in a vacuum atmosphere, and a plasma emission means. An apparatus for detecting a wafer polishing amount, comprising a light emission detector for detecting. 6. 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, and the wafer is polished while supplying a polishing chemical. In this case, at least a part of the chemical liquid after polishing is collected, the collected chemical liquid after polishing is introduced into the vacuum chamber and vaporized, plasma is generated, and the plasma emission intensity of impurities is measured. Then, the method for detecting the amount of wafer polishing is characterized in that the amount of wafer polishing is detected based on the change characteristics of the intensity of plasma emission. 7. A wafer polishing amount detecting device arranged in a wafer polishing device configured to polish a wafer while supplying a polishing chemical on a polishing table which is rotationally driven. 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 recovery means for recovering at least a part of the chemical liquid after polishing, and the liquid recovery means. A wafer polishing amount detecting device, comprising: a pH measuring unit that measures a pH value of a recovered chemical liquid after polishing. 8. A wafer is polished while a polishing chemical is supplied while a first insulation film containing impurities and a second insulation film containing no impurities are sequentially deposited on the surface of the wafer in advance. When polishing, at least part of the chemical liquid after polishing is collected, the pH value of the collected chemical liquid is measured, and the polishing amount of the wafer is detected based on the pH change characteristics of the chemical liquid. How to detect quantity. 9. A wafer polishing amount detecting device arranged in a wafer polishing device configured to polish a wafer while supplying a polishing chemical on a rotary drive polishing table. 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 recovery means for recovering at least a part of the chemical liquid after polishing, and the liquid recovery means. A device for detecting the amount of wafer polishing, comprising: a specific resistance measuring means for measuring the specific resistance of the recovered chemical liquid after polishing. 10. A wafer is polished while a polishing chemical is supplied while a first insulation film containing impurities and a second insulation film not containing impurities are sequentially deposited on the surface of the wafer in advance. At this time, 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, comprising: 11. The wafer polishing amount detection apparatus according to claim 1, 2, 4, 5, 7 or 9, wherein the wafer is polished by using a silicon-based oxide as a polishing chemical and is laid on a polishing table. A wafer polishing amount detecting device characterized by chemical mechanical polishing for flattening an insulating film formed on a wafer surface through a polishing cloth.