JP3277427B2 - Flattening method and polishing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planarizing method and a polishing apparatus, for example, for globally planarizing an interlayer insulating film in the manufacture of a semiconductor integrated circuit such as a highly miniaturized and integrated semiconductor memory device. It is suitable for application to the process.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, their wirings are becoming finer and more multilayered. However, high integration of wiring may cause a reduction in reliability of a semiconductor device. This is because with the progress of miniaturization and multilayering of wiring, the step of the interlayer insulating film is large and steep, and the processing accuracy and reliability of the wiring formed thereon are reduced.

[0003] For this reason, it is necessary to improve the flatness of the interlayer insulating film, especially at the present time when it is difficult to greatly improve the step coverage of the wiring with Al. This is becoming important from the viewpoint of a decrease in the depth of focus due to a reduction in the wavelength of exposure light used in lithography.

Until now, various insulating film forming techniques and flattening techniques as shown in Table 1 have been developed. However, these techniques have been applied to an interlayer insulating film of a finer and multilayered wiring. In such a case, there are problems such as insufficient flattening when the wiring interval is large, and poor connection between the wirings due to generation of voids in the interlayer insulating film in a portion between the wirings.

[Table 1]

In order to solve this problem, it has recently been proposed to use a method called a chemical mechanical polishing method which applies a conventional mirror polishing method for a silicon wafer to planarize an interlayer insulating film. This method is briefly described as follows.

FIG. 6 shows a polishing apparatus used in this method. In this polishing apparatus, a carrier 52 on which a wafer 51 is set is set so that the wafer 51 faces a polishing plate 53 called a platen, and a polishing pad called a pad on the polishing plate 53 is supplied from a slurry supply port 55 of a slurry supply system 54. This is an apparatus for supplying a slurry 57 onto a cloth 56 and adjusting the number of rotations of the polishing plate rotation shaft 58, the number of rotations of the carrier rotation shaft 59, and the pressure of the polishing pressure regulator 60 to polish the wafer 51. At this time,
Polishing is performed in a basic atmosphere by adding KOH or the like to perform etching of the insulating film.

[0007]

However, this method has some problems to be solved. That is, in consideration of future multilayer wiring as described above, it is necessary to polish and flatten both the insulating film and the metal film. However, if this is to be performed by one polishing apparatus, the metal film is exposed to a basic atmosphere. Therefore, it is necessary to perform polishing in an acidic atmosphere because polishing is difficult.

However, it is not practical to perform polishing under an acidic atmosphere and a basic atmosphere with a single polishing apparatus because the restrictions on the apparatus are considerably increased. Also, in consideration of future multilayer wiring, a polishing planarization method with high polishing dimension accuracy is required, but actual polishing dimension control is performed only by controlling physical parameters as described above. At present, it is difficult to obtain a high polishing size.

It is therefore an object of the present invention performs a chemical mechanical polishing with high have polishing dimensional accuracy is to provide a planarization method and a polishing apparatus capable of obtaining a good planarization shape.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that in order to perform the chemical mechanical polishing of the metal film and the chemical mechanical polishing of the insulating film by the same polishing apparatus, these polishing methods are required. It is sufficient to carry out the chemical mechanical polishing in a basic atmosphere, and to perform chemical mechanical polishing with high polishing dimensional accuracy, it is necessary to control not only the physical parameters but also the chemical parameters. We have come up with the invention.

[0011]

That is, in order to achieve the above object, a flattening method according to a first aspect of the present invention includes a step of flattening a stepped substrate at least once using chemical mechanical polishing. In the method, the concentration of a chemical used for chemical mechanical polishing is monitored, and the supply amount of the chemical is controlled based on the monitoring result.

In the flattening method according to the first aspect of the present invention, preferably, the concentration of the chemical solution is constantly monitored immediately before the polishing pad for flattening.

In the flattening method according to the first aspect of the present invention, more preferably, the concentration of the chemical solution is constantly monitored immediately before the polishing pad for flattening and at the waste liquid collecting part after polishing.

In the flattening method according to the first aspect of the present invention, a difference between the concentration of the chemical solution monitored immediately before the polishing pad and the concentration of the chemical solution monitored in the waste liquid collecting section is obtained, and the chemical solution is determined based on the difference. To control the supply amount.

A polishing apparatus according to a second aspect of the present invention comprises:
It has a concentration monitor for monitoring the concentration of a chemical solution used for chemical mechanical polishing, and control means for controlling a supply amount of the chemical solution based on the concentration of the chemical solution monitored by the concentration monitor. is there.

In the polishing apparatus according to the second aspect of the present invention, the concentration monitor is preferably provided immediately before the polishing pad for flattening. In the polishing apparatus according to the second aspect of the present invention, more preferably, the concentration monitors are respectively provided immediately before the polishing pad for flattening and in the waste liquid collecting sections after the polishing.

In the polishing apparatus according to the second aspect of the present invention, preferably, the control means controls the concentration of the chemical solution monitored by a concentration monitor provided immediately before the polishing pad and the concentration monitor provided in the waste liquid collecting section. The difference from the concentration of the chemical solution monitored by is obtained, and the supply amount of the chemical solution is controlled based on the difference.

[0019]

[Action]

According to the planarization method according to the first aspect of the present invention, the concentration of the chemical used for chemical mechanical polishing, that is, the chemical parameter can be controlled, so that the polishing rate can be controlled. Therefore, a high polishing dimensional accuracy can be obtained, and a good flattened shape can be obtained.

In particular, the difference between the concentration of the chemical solution monitored immediately before the polishing pad and the concentration of the chemical solution monitored at the waste liquid collecting section is determined, and the supply rate of the chemical solution is controlled based on the difference, thereby reducing the polishing rate. More precise control,
Higher polishing dimensional accuracy can be obtained.

According to the polishing apparatus of the second aspect of the present invention, the control means can control the concentration of the chemical solution used for chemical mechanical polishing, that is, the chemical parameters, thereby controlling the polishing rate. Can be.
Therefore, a high polishing dimensional accuracy can be obtained, and a good flattened shape can be obtained.

[0023]

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

First, a first embodiment of the present invention will be described. In the first embodiment, the polishing apparatus shown in FIG. 6 is used. As shown in FIG. 6, in this polishing apparatus, a carrier 52 on which a wafer 51 is set is set so that the wafer 51 faces a polishing plate 53 called a platen. The slurry 57 is supplied onto a polishing cloth 56 called a pad on the pad 53, and the rotation speed of the polishing plate rotation shaft 58, the rotation speed of the carrier rotation shaft 59, and the pressure of the polishing pressure regulator 60 are adjusted to polish the wafer 51. I do. As the slurry 57, for example, a colloidal silica slurry is used.

The configuration of the polishing apparatus described above is merely an example, and there is no particular limitation on the method of mounting a wafer, the number and configuration of platens and carriers, and the types of pads and slurries.

FIG. 1 shows a first embodiment of the present invention. In the first embodiment, both the metal film and the insulating film between the Al wiring layers are planarized by chemical mechanical polishing.
As shown in FIG. 1A, first, a first interlayer insulating film 2 made of silicon oxide or the like is formed on a semiconductor substrate 1 made of silicon or the like.
Then, a wafer on which the first Al wiring layer 3 is sequentially formed is prepared.

Next, as shown in FIG. 1B, the Al wiring layer 3
After the second interlayer insulating film 4 is formed thereon, chemical mechanical polishing of the interlayer insulating film 4 is performed using the polishing apparatus shown in FIG. 6 under the following conditions. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

These polishing conditions are general conditions for polishing an insulating film. Here, a slurry suspended in KOH / water / alcohol is used to perform chemical mechanical polishing in a basic atmosphere.

FIG. 1C shows a state after polishing of the interlayer insulating film 4. Next, after forming a resist pattern (not shown) having a predetermined shape on the interlayer insulating film 4 by lithography, the opening 5 is formed by dry-etching the interlayer insulating film 4 using the resist pattern as a mask. All of these steps are performed under normal conditions.

Next, as shown in FIG. 1D, an Al film 6 is formed on the second interlayer insulating film 4 so as to fill the opening 5 by high-temperature sputtering under the following conditions. The thickness of the Al film 6 is, for example, 500 nm. Ar gas flow rate: 100 SCCM Pressure: 0.27 to 0.40 Pa Temperature: 500 to 550 ° C. DC output: 10 kW Since a high-temperature sputtering method is used, a self-flow shape is obtained, and an Al film is formed in the opening 5. 6 can be embedded.

Next, chemical mechanical polishing of the Al film 6 is performed by the chemical mechanical polishing apparatus shown in FIG. 6 under the following conditions. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 6 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

Here, in order to perform chemical mechanical polishing in a weakly basic atmosphere, a slurry in which KOH / water / alcohol is used is used. Also, since the Al film 6 is soft, the polishing pressure is slightly lowered, and the concentration of KOH is set to a value one tenth that of the insulating film. By performing the chemical mechanical polishing in this manner, as shown in FIG.
The surface of the film 6 is completely planarized. Next, this Al film 6
Is patterned to form a second wiring layer.

In the first embodiment, K is used as the basic substance.
OH was added, but is not limited thereto. For example, methylamine, ethylamine, isopropylamine, or the like can be used as the organic base, and the amount is determined together with the addition amount in consideration of the polishing rate and the conditions for forming the Al film.

Thereafter, a third interlayer insulating film (not shown) is formed under ordinary conditions, and thereafter, a multilayer wiring is formed by the same method. As described above, according to the first embodiment, both the chemical mechanical polishing of the interlayer insulating film 4 and the chemical mechanical polishing of the Al film 6 are performed in a basic atmosphere. Chemical mechanical polishing of the interlayer insulating film 4 and the Al film 6 can be performed. Then, the interlayer insulating film 4 and the Al film 6 can be planarized by the chemical mechanical polishing.

Next, a second embodiment of the present invention will be described. The second embodiment also takes an Al wiring as an example and is a case where both the metal film and the insulating film are flattened. However, mechanical polishing is used for the Al film.

In the second embodiment, as in the first embodiment, as shown in FIG. 1A, a first interlayer insulating film 2 made of silicon oxide or the like and an Al wiring are formed on a semiconductor substrate 1 made of silicon or the like. A wafer having the layer 3 formed thereon is prepared.

Next, as shown in FIG. 1B, the Al wiring layer 3
After the second interlayer insulating film 4 is formed thereon, chemical mechanical polishing of the interlayer insulating film 4 is performed using the polishing apparatus shown in FIG. 6 under the following conditions. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

These polishing conditions are general conditions for polishing an insulating film. Here, a slurry suspended in KOH / water / alcohol is used to perform chemical mechanical polishing in a basic atmosphere. FIG. 1C shows a state after polishing of the interlayer insulating film 4.

Next, the interlayer insulating film 4 is formed by lithography.
After a resist pattern (not shown) having a predetermined shape is formed thereon, the opening 5 is formed by dry-etching the interlayer insulating film 4 using the resist pattern as a mask. All of these steps are performed under normal conditions.

Next, as shown in FIG. 1D, an Al film 6 is formed on the second interlayer insulating film 4 so as to fill the opening 5 by high-temperature sputtering under the following conditions. The thickness of the Al film 6 is, for example, 500 nm. Ar gas flow rate: 100 SCCM Pressure: 0.27 to 0.40 Pa Temperature: 500 to 550 ° C. DC output: 10 kW Since a high-temperature sputtering method is used, a self-flow shape is obtained, and an Al film is formed in the opening 105. 106 can be embedded.

Next, the mechanical polishing of the Al film 6 is performed by the chemical mechanical polishing apparatus shown in FIG. 6 under the following conditions. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

Here, in order to perform mechanical polishing under a neutral atmosphere, a slurry in which only water / alcohol is used is used. In addition, the polishing pressure is slightly increased accordingly. In this way, the Al film 6 on the wafer can be completely flattened even by using a mechanical polishing method in a part of the process, and the second wiring layer can be formed by patterning the Al film 6. it can. Thereafter, a third interlayer insulating film (not shown) is formed under normal conditions, and thereafter, a multilayer wiring is formed by the same method. According to the second embodiment, chemical mechanical polishing of the interlayer insulating film 4 and mechanical polishing of the Al film 6 can be performed by the same polishing apparatus. Then, the interlayer insulating film 4 and the Al film 6 can be flattened.

Next, a third embodiment of the present invention will be described. The third embodiment is an example in which a so-called plug is formed in order to establish electrical connection between wirings, in which both the metal film and the insulating film are flattened. In the third embodiment, similarly to the first embodiment, as shown in FIG. 2A, a first interlayer insulating film 2 made of silicon oxide or the like and an Al wiring layer 3 are formed on a semiconductor substrate 1 made of silicon or the like. Prepare the formed wafer.

Next, as shown in FIG. 2B, the Al wiring layer 3
After the second interlayer insulating film 4 is formed thereon, the interlayer insulating film 4 is planarized by chemical mechanical polishing using the polishing apparatus shown in FIG. 6 in the same manner as in the first and second embodiments. . FIG. 2C shows a state after polishing of the interlayer insulating film 4.

Next, in the same manner as in the first and second embodiments, the opening 5 is formed in the interlayer insulating film by dry etching.
To form All of these steps are performed under normal conditions.

Next, as shown in FIG. 2D, a blanket W film 7 is formed on the second interlayer insulating film 4 so as to fill the opening 5.
Is formed under the following conditions. The thickness of the blanket W film 7 is, for example, 500 nm. Gas flow rate: WF ₆ / SiH ₄ / H ₂ = 50/35/5
00SCCM Pressure: 67 Pa Temperature: 450 ° C. Here, since the blanket W method is used, a conformal shape is obtained, and the blanket W film 7 is formed in the opening 5.
Can be embedded.

Next, mechanical polishing of the blanket W film 7 is performed by the polishing apparatus shown in FIG. 6 under the following conditions. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

Here, as in the case of the second embodiment, a slurry in which only water / alcohol is used is used for mechanical polishing in a neutral atmosphere. In addition, the polishing pressure is slightly increased accordingly. In this manner, the blanket W film 7 on the wafer can be completely flattened by using a mechanical polishing method in a part of the process. next,
By patterning the W film 7, a second wiring layer is formed.

Thereafter, a third interlayer insulating film (not shown) is formed under ordinary conditions, and thereafter, a multilayer wiring is formed by the same method. According to the third embodiment, chemical mechanical polishing of the interlayer insulating film 4 and mechanical polishing of the W film 7 can be performed by the same polishing apparatus. Then, the interlayer insulating film 4 and the W film 7 can be planarized.

FIG. 3 shows a polishing apparatus used in the fourth embodiment of the present invention. As shown in FIG. 3, in this polishing apparatus, a carrier 12 on which a wafer 11 is set is set so that the wafer 11 faces a polishing plate 13 called a platen. The slurry 17 is supplied onto a polishing cloth 16 called a pad on the polishing pad 13, and the rotation speed of the polishing plate rotation shaft 18, the rotation speed of the carrier rotation shaft 19, and the pressure of the polishing pressure regulator 20 are adjusted to polish the wafer 11. I do.

As shown in FIG. 3, this polishing apparatus has the same configuration as the polishing apparatus shown in FIG.
A chemical concentration monitor 21 is provided immediately before the slurry supply port 15, and the chemical concentration monitor 21 can monitor the concentration of the chemical solution immediately before the polishing pad. There are various methods of monitoring this concentration,
Here, the specific resistance of the chemical is simply monitored. The concentration monitored here is fed back to the slurry supply system 14 via the control system 22, and the supply amount is controlled according to the monitoring result.

Thus, the concentration of the chemical solution used for polishing can be kept constant, and the polishing rate can be kept constant. Alternatively, in some cases, by controlling the concentration of the chemical solution to change as desired, the polishing rate can be controlled to change according to the change. The method of mounting a wafer, the number and configuration of platens and carriers, and the types of pads and slurries are not limited to the above examples.

FIG. 4 shows a fourth embodiment of the present invention. In the fourth embodiment, the interlayer insulating film on the Al wiring is flattened.

In the fourth embodiment, as shown in FIG. 5A, a first interlayer insulating film 2 made of silicon oxide or the like and an Al wiring layer 3 are formed on a semiconductor substrate 1 made of silicon or the like.
A wafer on which is formed is prepared.

Next, as shown in FIG. 4B, after the second interlayer insulating film 4 is formed, chemical mechanical polishing of the interlayer insulating film 4 is performed using the polishing apparatus shown in FIG. 3 under the following conditions. . In this case, chemical mechanical polishing is performed under the following conditions while constantly monitoring the concentration of the chemical solution and controlling the supply amount of the chemical solution by the chemical concentration monitor 12 provided immediately before the slurry supply port 15. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min

These polishing conditions are general conditions for polishing an insulating film. Here, a slurry suspended in KOH / water / alcohol is used to perform chemical mechanical polishing in a basic atmosphere. FIG. 4C shows a state after polishing of the interlayer insulating film 4.

In the fourth embodiment, KOH of 10 ^{-3 is} specified.
As described above, when chemical mechanical polishing is performed as described above, by constantly monitoring the concentration and controlling the supply amount of the chemical solution, the polishing dimensional accuracy can be improved by, for example, about 20% compared to the conventional method. Can be. In the fourth embodiment, KOH was added as a basic substance, but the present invention is not limited to this. For example, organic bases such as methylamine, ethylamine, and isopropylamine can be used, and may be determined together with the addition amount in consideration of the polishing rate and the conditions for forming the interlayer insulating film 4.

FIG. 5 shows a polishing apparatus used in the fifth embodiment of the present invention. As shown in FIG. 5, in this polishing apparatus, in addition to the same configuration as the polishing apparatus shown in FIG. 3 used in the fourth embodiment, another chemical concentration monitor 24 is provided at the waste liquid recovery port 23. Have been. That is, in this polishing apparatus, the concentration of the chemical solution immediately before the polishing pad can be monitored by the chemical concentration monitor 21 provided immediately before the slurry supply port 21, and the chemical concentration monitor 24 provided in the waste liquid collecting unit. The concentration of the drug solution can be monitored. The concentrations monitored by the chemical solution concentration monitors 21 and 24 are both sent to the control system 22. Then, the difference between these concentrations is calculated by the control system 22, and the slurry supply system 14 is controlled in accordance with the difference in concentration to control the supply amount.

FIG. 5 shows a fifth embodiment of the present invention. The fifth embodiment is also a case where the interlayer insulating film on the Al wiring layer is flattened. In the fifth embodiment, similarly to the fourth embodiment, as shown in FIG. 4A, a first interlayer insulating film 2 made of silicon oxide or the like and an Al wiring layer 3 are formed on a semiconductor substrate 1 made of silicon or the like. Prepare the formed wafer.

Next, as shown in FIG. 4B, after the second interlayer insulating film 4 is formed, chemical mechanical polishing of the interlayer insulating film 4 is performed using a polishing apparatus shown in FIG. 5 under the following conditions. . In this case, the KOH concentration is constantly monitored immediately before the supply and at two places of the waste liquid by a chemical concentration monitor 12 provided immediately before the slurry supply port 15 and a chemical concentration monitor 24 provided at the waste liquid recovery port 23, and controlled. Chemical mechanical polishing is performed while controlling the supply amount of KOH by calculating the difference between the concentrations by the system 22. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min These polishing conditions are general polishing conditions for an insulating film. Here, a slurry obtained by suspending the slurry in KOH / water / alcohol is used to perform chemical mechanical polishing under a basic atmosphere. The KOH concentration used is 10 ⁻³ as in the fourth embodiment. FIG. 4C shows a state after polishing of the interlayer insulating film 4.

In the fifth embodiment, as described above, KOH
Is monitored at two points immediately before the supply and after the waste liquid is collected, and the difference is arithmetically processed by the control system 22 to control the supply amount of KOH. It can be improved by 25%.

As described above, according to the fifth embodiment,
Polishing dimensional accuracy of the interlayer insulating film 4 can be further improved. The present invention is, of course, not limited to the embodiments described above, and the structure, conditions, and the like can be appropriately changed without departing from the gist of the present invention. For example, the monitoring of the concentration of a drug solution requires p
H and the like can be monitored.
In some cases, the concentration of the drug solution can be monitored by an optical method or the like.

[0063]

As described above, according to the present invention ,
By performing chemical mechanical polishing with high polishing dimensional accuracy, a good flattened shape can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view for explaining a second embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a configuration of a polishing apparatus used in a fourth embodiment of the present invention.

FIG. 4 is a sectional view for explaining a fourth embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of a polishing apparatus used in a fifth embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a configuration of a conventional polishing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2, 4 Interlayer insulating film 3 Al wiring layer 6 Al film 7 W film 11 Wafer 13 Polishing plate 14 Slurry supply system 15 Slurry supply port 17 Slurry 21, 24 Chemical solution concentration monitor 22 Control system

Claims (8)

(57) [Claims] 1. A step is formed using a chemical mechanical polishing method.
Flatness having at least one step of flattening a substrate
In the conversion method, Monitor the concentration of the chemical used for chemical mechanical polishing,
The supply amount of the above chemical solution is controlled based on the monitoring result.
It was to so A flattening method characterized by the above-mentioned. 2. A polishing pad for flattening the concentration of the chemical solution.
The service is characterized by always monitoring immediately before
The flattening method according to claim 1. 3. A polishing pad for flattening the concentration of the chemical solution.
Always monitor immediately before and after polishing
2. The method according to claim 1, wherein 4. A monitor monitored immediately before the polishing pad.
The concentration of the chemical and the drug monitored by the waste liquid collection section
The difference from the solution concentration is determined, and based on the difference,
2. The method according to claim 1, wherein the amount of supply is controlled.
Method of flattening. 5. The concentration of a chemical solution used for chemical mechanical polishing.
A concentration monitor for monitoring the The concentration of the drug solution monitored by the concentration monitor
Control means for controlling the supply amount of the chemical solution based on With
Polishing apparatus characterized by performing. 6. The polishing apparatus according to claim 1, wherein the concentration monitor is a polishing pad for flattening.
6. The device according to claim 5, wherein the device is provided immediately before the device.
Polishing equipment. 7. The polishing apparatus according to claim 1, wherein the concentration monitor is a polishing pad for flattening.
Provided in the waste liquid collection section immediately before and after polishing, respectively.
The polishing apparatus according to claim 5, wherein 8. The polishing pad is directly controlled by the control means.
Monitored by the concentration monitor provided above
The concentration of the chemical solution and the concentration provided in the waste liquid recovery unit
The difference from the concentration of the above solution monitored by the monitor
Control the supply amount of the chemical based on the difference.
Claims characterized by the following: 8. The polishing apparatus according to 7.