JPH07221067A - Method for flattening substrate - Google Patents

Abstract

PURPOSE:To eliminate pattern dependency in a polishing process and to increase utilization efficiency of slurry liquid solution in the method for flattening the substrate by chemical machine polishing. CONSTITUTION:By mixing glycerin or a high-viscosity liquid solution such as a liquid solution where glycerin is added to Arabian rubber, the viscosity of a slurry liquid solution 17 used for polishing is adjusted to perform chemical machine polishing. Also. at this time, the viscosity of the slurry liquid solution 17 is monitored immediately before a polishing pad 16 of a polishing device and the amount of supply of the high-viscosity liquid solution is controlled by a control system 24 according to the monitoring result, thus maintaining the viscosity to be an optimum value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of flattening a substrate, for example, a step of globally flattening 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 to be applied to.

[0002]

2. Description of the Related Art With the high integration of semiconductor devices, the wirings thereof are becoming finer and multilayered. On the other hand, however, the high integration of the wiring may cause a decrease in the reliability of the semiconductor device. This is because with the progress of miniaturization and multilayering of wiring, the level difference of the interlayer insulating film becomes large and steep, and the processing accuracy and reliability of the wiring formed thereon are deteriorated.

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

Up to now, various insulating film forming techniques and flattening techniques as shown in Table 1 have been developed, and these techniques are applied to the interlayer insulating film of the fine and multi-layered wiring. In this case, there are problems such as insufficient flatness when the wiring interval is large and connection failure between the wiring due to generation of voids in the interlayer insulating film in the portion between the wirings.

[Table 1]

Therefore, as a means for solving this problem, it has recently been proposed to use a method called a chemical mechanical polishing method, which is an application of the conventional mirror polishing method for a silicon wafer, for planarizing an interlayer insulating film. The method will be briefly described below.

FIG. 3 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 53 on the polishing plate 53 is polished from a slurry supply port 55 of a slurry supply system 54. Slurry solution 57 on cloth 56
Is supplied to adjust the number of rotations of the polishing plate rotating shaft 58, the number of rotations of the carrier rotating shaft 59 and the pressure of the polishing pressure adjuster 60 to polish the wafer 51. At this time, in order to etch the insulating film, KOH or the like is added to the slurry solution 57 and polishing is performed in a basic atmosphere.

[0007]

However, this method also has some problems to be solved. That is, in the future multilayer wiring, it is necessary to perform flattening processing with good productivity, but since the current polishing rate of chemical mechanical polishing has so-called pattern dependence, a good flattened shape cannot be obtained. In order to explain this, for example, as shown in FIG. 4A, a first interlayer insulating film 102 made of silicon oxide or the like and an Al wiring layer 103 are sequentially formed on a semiconductor substrate 101 made of silicon or the like, and formed thereon. A case of planarizing the second interlayer insulating film 104 will be considered.

That is, as shown in FIG. 4A, a wide Al wiring layer 103 is formed on the surface of the second interlayer insulating film 104.
A wide convex portion is formed on the upper part of the Al wiring layer, and a narrow convex portion is formed on the upper Al wiring layer 103.
When polishing the inter-layer insulating film 104, the polishing rate of the narrow convex portion becomes higher than that of the wide convex portion, so that the second inter-layer insulating film 1 after polishing is polished as shown in FIG. 4B.
The surface of 04 is not flattened. This is because the viscosity of the currently used slurry solution is low, so the narrow pattern A
One of the causes of this is that the slurry solution 57 enters into the concave portions between the convex portions of the second interlayer insulating film 104 formed on the upper part of the 1 wiring layer 103. On the contrary,
Although a method of solving this problem by forming a polishing stopper layer can be considered, it cannot be denied that the process becomes complicated.

Further, the slurry solution 57 in the current polishing apparatus is supplied by pouring it from the periphery of the wafer 51 as shown in FIG. Therefore, a large amount of the slurry solution 57 flows out to the outside, which is not efficient.

Therefore, an object of the present invention is to provide a method for planarizing a substrate which can be planarized without pattern dependence.

Another object of the present invention is to provide a method of flattening a substrate which can increase the efficiency of use of a slurry solution used for polishing.

[0012]

In order to achieve the above object, the method of flattening a substrate according to the present invention comprises at least one step of flattening a substrate having a step using a chemical mechanical polishing method. In the substrate flattening method, the chemical mechanical polishing is performed by adjusting the viscosity of a slurry solution used for the chemical mechanical polishing.

Here, the viscosity of the slurry solution is adjusted by adding a solution for adjusting the viscosity of the slurry solution to the slurry solution.

As the solution for adjusting the viscosity of the slurry solution, for example, glycerin or a solution obtained by adding glycerin to gum arabic is used.

The solution for adjusting the viscosity of the slurry solution is preferably added to the slurry solution immediately before the slurry supply port of the polishing apparatus.

In a preferred embodiment of the method for flattening a substrate according to the present invention, a solution for monitoring the viscosity of the slurry solution immediately before the polishing pad and adjusting the viscosity of the slurry solution based on the monitored viscosity. Control the supply amount of.

[0017]

According to the present invention, since the viscosity of the slurry solution used for chemical mechanical polishing can be adjusted to be high, it is possible to make it difficult for the slurry solution to enter the concave portions between the narrow convex portions. The polishing rate at that portion can be reduced. This makes it possible to flatten the substrate without pattern dependence.

Further, by increasing the viscosity of the slurry solution in this way, the slurry solution does not easily spill from the periphery of the polishing pad, and the slurry solution can be used efficiently.

[0019]

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. The polishing apparatus shown in FIG. 1 is used in the first embodiment of the present invention. As shown in FIG. 1, 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, and a polishing plate is supplied from a slurry supply port 15 of a slurry supply system 14. The slurry solution 17 is supplied onto the polishing cloth 16 called a pad on the wafer 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 adjust the wafer 11
Polishing. As the slurry of the slurry solution 17, for example, colloidal silica slurry is used.

As shown in FIG. 1, in this polishing apparatus, in addition to the above-described structure similar to that of the polishing apparatus shown in FIG.
A mixer 22 is provided immediately before the slurry supply port 15 so that the high viscosity solution of the high viscosity solution supply system 21 can be mixed with the slurry solution 17 from the slurry supply system 14 immediately before the slurry supply port 15. ing. Further, a viscosity monitor 23 is provided downstream of the mixer 22, that is, immediately before the polishing pad 16, so that the viscosity of the slurry solution 17 can be monitored immediately before the slurry supply port 15. Has become.

The viscosity monitored by the viscosity monitor 23 is sent to the control system 24. The control system 24 controls the high-viscosity solution supply system 21 according to the monitored viscosity, and controls the supply amount of the high-viscosity solution mixed with the slurry solution 17 from the slurry supply system 14. The viscosity of the slurry solution 17 used for polishing can be adjusted.

The above-mentioned structure of the polishing apparatus is merely an example, and the wafer mounting method and the like, the number and structure of platens and carriers, and the types of pads and slurries are not particularly limited.

FIG. 2 shows a first embodiment of the present invention. In the first embodiment, as shown in FIG. 2A, first, a first interlayer insulating film 32 made of silicon oxide or the like and an Al wiring layer 33 are formed on a semiconductor substrate 31 made of silicon or the like, and further thereon. A wafer on which the second interlayer insulating film 34 is formed is prepared.

Next, chemical mechanical polishing of the second interlayer insulating film 34 is performed using the polishing apparatus shown in FIG. 1 under the following conditions. At this time, the viscosity monitor 23 provided immediately before the slurry supply port 15 constantly monitors the viscosity of the slurry solution 17 immediately before the polishing pad 16, and the high viscosity solution supply system 21 is controlled by the control system 24 according to the monitor result.
The amount of the high-viscosity solution supplied from the slurry supply system is controlled to keep the viscosity of the slurry solution 17 used for polishing at a desired value higher than that of the slurry solution 17 supplied from the slurry supply system.

Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30-40 ° C. Slurry solution flow rate: 225 ml / min

This polishing condition is a general polishing condition for the insulating film. Here, a slurry prepared by suspending the slurry in KOH / water / alcohol is used for chemical mechanical polishing under a basic atmosphere.

In the first embodiment, the slurry solution 17 used for polishing is a slurry solution 17 from the slurry supply system 14 in which glycerin is mixed as a highly viscous solution in a volume ratio of 1: 2. To do.

FIG. 2B shows a state after polishing the second interlayer insulating film 34. As shown in FIG. 2B, the second interlayer insulating film 34 can be planarized without pattern dependence. This is because the viscosity of the slurry solution 17 used for polishing is increased due to the addition of the high-viscosity solution as described above, and therefore the concave portions between the narrow convex portions on the surface of the second interlayer insulating film 34 shown in FIG. 2A. This is because it becomes difficult for the slurry solution 17 to enter, and the polishing rate at that portion decreases.

As described above, according to the first embodiment,
Since the second interlayer insulating film 34 is flattened by using the high-viscosity slurry solution 17 obtained by adding the high-viscosity solution to the slurry solution 17 from the slurry supply system 14, this second pattern is not dependent on the pattern. Second interlayer insulating film 34
Can be completely flattened, and a good flattened shape can be obtained.

Further, since the slurry solution 17 supplied from the slurry supply port 15 has a high viscosity, the slurry solution 17 is less likely to spill from the periphery of the polishing pad 16. Therefore, the usage efficiency of the slurry solution 17 can be increased.

Next, a second embodiment of the present invention will be described. In the second embodiment, as in the first embodiment, as shown in FIG. 2A, the first interlayer insulating film 3 made of silicon oxide or the like is formed on the semiconductor substrate 31 made of silicon or the like.
2 and an Al wiring layer 33 are formed, and a second wiring is formed on the Al wiring layer 33.
A wafer on which the inter-layer insulating film 34 is formed is prepared.

Next, chemical mechanical polishing of the second interlayer insulating film 34 is performed using the polishing apparatus shown in FIG. 1 under the following conditions. At this time, the viscosity monitor 23 provided immediately before the slurry supply port 15 constantly monitors the viscosity of the slurry solution 17 immediately before the polishing pad 16, and the high viscosity solution supply system 21 is controlled by the control system 24 according to the monitor result.
The amount of the high-viscosity solution supplied from the slurry supply system is controlled to keep the viscosity of the slurry solution 17 used for polishing at a desired value higher than that of the slurry solution 17 supplied from the slurry supply system.

Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30-40 ° C. Slurry solution flow rate: 225 ml / min

This polishing condition is a general polishing condition for the insulating film. Here, a slurry solution suspended in KOH / water / alcohol is used for polishing in a basic atmosphere.

In this second embodiment, a mixture of glycerin 1 and gum arabic 1.5 in a weight ratio is used as a high viscosity solution, and the high viscosity solution and the slurry solution 17 from the slurry supply system 14 are used. A mixture having a volume ratio of 1: 1 is used as a slurry solution 17 used for polishing.

By carrying out the chemical mechanical polishing in this way, as in the first embodiment, as shown in FIG. 2B, the planarization process of the second interlayer insulating film 34 can be performed without pattern dependence. it can.

According to the second embodiment, the same advantages as those of the first embodiment can be obtained. The present invention is naturally not limited to the embodiments described above, and the structure, conditions and the like can be changed as appropriate without departing from the spirit of the present invention. For example, the slurry supply system 14
Then, a high-viscosity solution may be mixed with the slurry solution 17 therein, and chemical mechanical polishing may be performed using this. Further, glue or the like may be mixed in order to increase the viscosity of the slurry solution 17 used for polishing.

Furthermore, in the above-mentioned embodiment, the case where the present invention is applied to the planarization of the interlayer insulating film 34 has been described, but the present invention can also be applied to the planarization of the metal film.

[0040]

As described above, according to the present invention,
It becomes possible to perform planarization by chemical mechanical polishing without pattern dependence, which has been a bottleneck of the conventional planarization method. As a result, a semiconductor device such as a VLSI can be manufactured with a high yield in a highly reliable process.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a polishing apparatus used in a first embodiment and a second embodiment of the present invention.

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

FIG. 3 is a schematic diagram showing a configuration of a conventional polishing apparatus.

FIG. 4 is a cross-sectional view for explaining a conventional flattening method.

[Explanation of symbols]

 11 Wafer 13 Polishing Plate 14 Slurry Supply System 15 Slurry Supply Port 17 Slurry Solution 21 High Viscosity Solution Supply System 22 Mixer 23 Viscosity Monitor 24 Control System 31 Semiconductor Substrate 32, 34 Interlayer Insulating Film 33 Al Wiring Layer

Claims (5)

[Claims] 1. A method of planarizing a substrate having at least one step of planarizing a substrate having a step using a chemical mechanical polishing method, wherein the viscosity of a slurry solution used for the chemical mechanical polishing is adjusted. A method of planarizing a substrate, characterized in that chemical mechanical polishing is performed. 2. The flatness of the substrate according to claim 1, wherein the viscosity of the slurry solution is adjusted by adding a solution for adjusting the viscosity of the slurry solution to the slurry solution. Method. 3. The method for flattening a substrate according to claim 1, wherein the solution for adjusting the viscosity of the slurry solution is glycerin or a solution obtained by adding glycerin to gum arabic. 4. The method for flattening a substrate according to claim 1, wherein a solution for adjusting the viscosity of the slurry solution is added to the slurry solution immediately before the slurry supply port of the polishing apparatus. 5. The viscosity of the slurry solution is monitored immediately before the polishing pad, and the supply amount of the solution for adjusting the viscosity of the slurry solution is controlled based on the monitored viscosity. The method for planarizing a substrate according to claim 1.