JPH10242089A - Polishing end point detecting method, polishing equipment and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing end point detecting method which easily and precisely detects the end point of polishing. SOLUTION: Step-difference is generated on a polysilazane film 33 and an insulating film 34 which are deposited in order and formed on a metal wiring 32, and flattening is necessary. For flattening, a wafer 3 is polished from the side of the insulating film 34, by using abrasive agent containing solvent having hydroxyl groups. When polishing is progressed, the surface of the wafer 13 is flattened, and the surface of the polysilazane film 34 is partly exposed at last. Then ammonia gas is generated by chemical reaction of the solvent and the polysilazane film 33. The generated ammonia gas is detected by a detector, and the gas generation is set as the reference for the end point of polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing end point detecting method, a polishing apparatus, and a semiconductor device, and more particularly to a method for polishing a surface of a semiconductor device by polishing a film.

[0002]

2. Description of the Related Art In the field of semiconductor devices, finer patterns and multi-layers have been developed as devices become more sophisticated. In the technique of processing wiring to be multilayered, the surface of an interlayer insulating film must be flattened in order to form a highly reliable wiring. As a technique for obtaining a planarized interlayer insulating film, for example, various CVD techniques, an SOG coating method, a combination of a CVD technique and an etching technique, a resist etch-back method, and the like are used.

In recent years, a chemical mechanical polishing method (Chemic polishing) for chemically and mechanically polishing and planarizing an interlayer insulating film has been proposed.
al Mechanical Polishing (hereinafter referred to as CMP method) has been proposed. The CMP method is
This is a method of planarizing the surface of a film by chemical dissolution caused by a solvent in an abrasive and mechanical abrasion of abrasive particles in the abrasive. The CMP method is a technique originally applied to the polishing of a substrate such as a silicon wafer, and the polishing technique has been diverted to flatten the surface of an interlayer insulating film.

For example, the surface of an interlayer insulating film formed by CVD or the like on the surface of a wafer having irregularities on the surface by metal wiring or the like has irregularities corresponding to the irregularities on the substrate surface. Polishing is performed on the surface of the interlayer insulating film having irregularities, and planarization is performed until there are no convex portions or concave portions.

[0005]

In the planarization of the surface of an interlayer insulating film using the CMP method, it is extremely difficult to determine the end point (hereinafter, referred to as the end point) of polishing when the surface has no irregularities. If polishing is completed before the end point, irregularities remain on the film surface, which adversely affects the exposure process after planarization. Further, when the polishing is excessively performed, for example, the metal wiring layer below the interlayer insulating film is exposed, and there is a possibility that a short circuit may occur with the wiring layer on the interlayer insulating film.

[0006] The conventional method for detecting the end point is to perform polishing only for a reference time required for polishing. In this method, the interlayer insulating film provided on the wafer is polished in advance on a test basis, and the time required to obtain a desired polishing amount is grasped.

However, in this detection method, the reproducibility of whether or not the surface of the interlayer insulating film is appropriate at the end point is low, and accordingly, the accuracy of the surface of the interlayer insulating film is reduced. There is a problem that it becomes low. In addition, since a test polishing is required, there is a problem that it takes time. Further, there is a problem that the time required for polishing differs for each pattern of the elements integrated on the wafer, and it is necessary to grasp the end point for each pattern.

In view of the above problems, an object of the present invention is to provide a polishing end point detection method for easily and accurately detecting a polishing end point, and a polishing apparatus and a semiconductor device used for the method.

[0009]

According to a first aspect of the present invention, there is provided a method for detecting a polishing end point, comprising first and second films in order, preparing a workpiece having the first film as a surface; The first film is polished using a gas generating substance which reacts with the second film to generate a gas, and the generation of the gas is used as the polishing end point.

A polishing end point detecting method according to a second aspect is the polishing end point detecting method according to the first aspect, wherein the workpiece is formed on a semiconductor substrate on which elements are integrated by the second and the first. Are stacked in this order, the first film is an insulating film, the second film contains polysilazane, and the gas generating substance has a hydroxyl group.

According to a third aspect of the present invention, in the polishing apparatus, the object to be polished containing the gas generating substance is polished inside, and the polishing agent is used to induce gas generation from the gas generating substance. A polishing unit for polishing the polishing body; and a detecting unit for detecting gas from the gas generating substance.

A polishing apparatus according to a fourth aspect is the polishing apparatus according to the third aspect, wherein the isolation container has a supply port and an exhaust port for a carrier gas, and the flow path of the carrier gas. The detection means is located downstream of the polishing means.

A polishing apparatus according to a fifth aspect is the polishing apparatus according to the fourth aspect, wherein the carrier gas is an inert gas.

According to a sixth aspect of the present invention, there is provided a semiconductor device, comprising: a substrate having elements integrated on a surface thereof; an insulating gas generating film formed on the surface; and an insulating film on the gas generating film. Is provided.

[0015]

FIG. 1 is a sectional view illustrating the structure of an apparatus 10 for polishing an interlayer insulating film according to the present embodiment.
The polishing apparatus 10 includes a disk-shaped surface plate 11 rotatably supported by a rotation shaft 15a. A polishing cloth 12 is stuck on the surface plate 11 with an adhesive.
A head 14, which is rotatably supported by a rotating shaft 15 b and holds the wafer 13 during polishing, is installed at a position facing the surface plate 11. Rotating shafts 15a, 15b
Is connected to well-known driving means (not shown).

FIG. 2 is a sectional view illustrating the structure of the wafer 13. Silicon substrate 31 constituting wafer 13
The surface of the metal wiring 32 which is a part of the integrated device
Are formed. A polysilazane film 33 and an insulating film 34 such as a silicon oxide film are sequentially formed on the silicon substrate 31 having the metal wiring 32 by deposition. The polysilazane film 33 and the insulating film 34 are
2 is an interlayer insulating film for insulation. What is polysilazane?

[0017]

Embedded image

Is a substance represented by Polysilazane is O
By reacting with a substance having an H group (hydroxyl group), for example,

[0019]

Embedded image

As described above, ammonia is generated.

Depending on the thickness of the metal wiring 32, the metal wiring 3
The polysilazane film 33 and the insulating film 34 formed on 2 have irregularities or steps. In order to properly perform the exposure process in the photomechanical technology, it is necessary to eliminate irregularities and steps and to flatten the surface of the wafer 13 by polishing.

When polishing, first, the wafer 13 is mounted so that the insulating film 34 side of the surface of the wafer 13 is opposite to the head 14 in FIG. I do. Next, the head 14 is set on the platen 1
The insulating film 34 is pressed against the surface of the polishing pad 12 by pushing down the insulating film 34 in the direction 1.

A nozzle 17 for supplying an abrasive 16 containing a solvent having a hydroxyl group is disposed above the surface plate 11 illustrated in FIG. The platen 11 and the head 14 are rotated by rotating shafts 15a and 15b, while the abrasive 16 is supplied from the nozzle 17 to the polishing cloth 12. The insulating film 34 illustrated in FIG. 2 is polished by friction with the polishing pad 12 containing the polishing agent 16.

As the polishing of the insulating film 34 progresses, the polysilazane film 33 is exposed as illustrated in FIG. FIG.
Is a cross-sectional view illustrating a state where a part of the surface of the polysilazane film 33 is exposed. As shown in the figure,
When the polysilazane film 33 starts to be exposed, the wafer 1 composed of the polysilazane film 33 and the insulating film 34
The surface of No. 3 has already been flattened. Polysilazane film 33
FIG. 1 shows a state in which polysilazane is partially exposed.
Reacts with the abrasive 16 in the polishing cloth 12 to generate ammonia gas 18.

The partition 1 of the chamber constituting the polishing apparatus 10
Due to 9, the ammonia gas 18 is confined inside the polishing apparatus 10. The partition wall 19 has an ammonia gas 18
An air supply port 20 and an exhaust port 21 are provided in order to improve the detection sensitivity by giving directionality to the flow of air. In the middle of the exhaust port 21 on the downstream side with respect to the wafer 13,
A detector 22 is attached.

The ammonia gas 1 generated from the wafer 13 by the carrier gas flowing from the air supply port 20
Reference numeral 8 denotes a detector 22 which does not stay in the partition 19 immediately.
To reach. As a result, the generation of the ammonia gas 18 can be promptly grasped by the detector 22, and the end point of polishing described later can be determined at an appropriate time.

When an inert gas is used as the carrier gas, there is no possibility that the ammonia gas 18 will disappear due to the reaction with the carrier gas. Further, the carrier gas prevents the outside air from entering the inside of the partition wall 19. As a result, there is no possibility that the detector 22 fails to detect the ammonia gas 18 even though the ammonia gas 18 is generated, and the possibility that the ammonia gas in the outside air is detected by the detector 22 is eliminated. Done in

The detector 22 is a densitometer that identifies ammonia gas and measures its concentration. The detector 22 inputs a detection signal 23 relating to the ammonia gas 18 to the control unit 24. The control unit 24 determines the end point of polishing based on the input of the detection signal 23. For example, this determination is made by setting the time when the concentration of the ammonia gas 18 becomes equal to or higher than a certain set value as the polishing end point, and the end point is detected. By using the ammonia concentration equal to or higher than the set value as a criterion for determination, it is possible to avoid that the polysilazane film 33 illustrated in FIG. .

The control unit 24 determines the end point of the polishing and uses a driving means (not shown) to rotate the rotary shaft 15b and the head 1
4 is lifted, and the wafer 13 is separated from the polishing pad 12. Thus, the polishing of the insulating film 34 and the polysilazane film 33 illustrated in FIG. 3 provided on the wafer 13 is completed, and the wafer 13 has a flat interlayer insulating film composed of the insulating film 34 and the insulating polysilazane film 33. Covered by the surface.

In the method of detecting the end point of polishing according to the present invention, the insulating property of each polysilazane and the gas generating property of generating ammonia gas by reacting with a solvent containing a hydroxyl group are effectively utilized, and The end point is detected and the interlayer insulating film is obtained. For example, when a material having a gas generating property with a solvent but having no insulating property is used in place of the polysilazane film 34, the end point of polishing can be detected, but the interlayer for insulating the metal wiring 32 can be detected. An insulating film cannot be obtained. Therefore, it is understood that polysilazane is a very useful material for a semiconductor device that requires a planarized interlayer insulating film.

In the above description, the polysilazane film 34 is used. However, any substance other than polysilazane may react with a substance that can be mixed as a solvent for the polishing agent to generate gas, and if it has an insulating property. It is possible to use it.

In the method for detecting the end point of polishing according to the present invention, the presence or absence of gas generation is used as a criterion for detection, and the end point of polishing can be grasped easily and accurately. In addition, since the planarization can be accurately performed on each wafer, it is possible to equalize the degree of planarization of the interlayer insulating film among a plurality of wafers.
Even when the types of wafers are different from each other, since the generation of gas and the end point of polishing are linked, it is not necessary to know in advance the end point of polishing for each type.

By using the above-described polishing apparatus 10, the method of detecting the end point of polishing according to the present invention can be suitably performed in a state where gas does not flow in and out. Further, it is not necessary to carry out a test polishing as in the prior art, and the interlayer insulating film can be quickly flattened.

[0034]

According to the first aspect of the present invention, when the first film is polished and the second film is exposed, a gas is generated by the reaction between the second film and the gas generating substance. The generation of this gas is a reference for the polishing end point. The presence or absence of gas generation is bipolar information, and the first film is polished constantly between a plurality of workpieces. Thereby, the plurality of workpieces are polished uniformly.

According to the structure of the second aspect, when the first film having a step due to the integrated elements is planarized, the second film containing polysilazane is used to planarize the first film. At the same time, the interlayer insulating film of the semiconductor device is realized by the first and second films due to the insulating property of polysilazane.

According to the third aspect of the present invention, the gas from the gas generating substance is detected with time when the polishing means is operated in a state where the gas does not flow to and from the outside of the isolation container. When the polishing end point detecting method according to the first aspect is performed in the polishing apparatus according to the third aspect, it is possible to detect the polishing end point without making an erroneous determination using an external gas.

According to the configuration of the fourth aspect, it is possible to quickly know the change of the gas in the isolation container by the flow of the carrier gas. This makes it possible to quickly detect the generation of gas from the gas generating substance, grasp the polishing end point without delay from the polishing end point, and end the polishing. Therefore, excessive polishing is avoided.

According to the fifth aspect of the present invention, the gas generated from the gas generating substance does not react with the carrier gas. The generated gas is surely detected by the detecting means, and when the polishing end point detecting method according to the first aspect is performed, the polishing end point can be reliably detected.

According to the structure of the sixth aspect, the first aspect is provided.
Can be actually performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the structure of an apparatus for polishing an interlayer insulating film according to the present invention.

FIG. 2 is a cross-sectional view illustrating the structure of the wafer of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure after polishing of the structure illustrated in FIG. 2;

[Explanation of symbols]

Reference Signs List 10 polishing apparatus, 11 surface plate, 12 polishing cloth, 13 wafer, 14 head, 15a, 15b rotation axis, 16
Abrasive, 17 nozzles, 18 ammonia gas, 19
Partition wall, 20 air supply port, 21 exhaust port, 22 detector,
23 detection signal, 24 control unit, 31 silicon substrate,
32 metal wiring, 33 polysilazane film, 34 insulating film.

Claims (6)

[Claims] 1. A work piece having a first film and a second film in order and having a surface on the first film is prepared, and a gas generating substance which reacts with the second film to generate a gas is used. A polishing end point detection method, wherein the polishing of the first film is performed while the generation of the gas is used as the polishing end point. 2. The polishing end point detecting method according to claim 1, wherein the workpiece is a semiconductor device in which the second and first films are stacked in this order on a semiconductor substrate on which elements are integrated. Wherein the first film is an insulating film, the second film contains polysilazane, and the gas generating substance has a hydroxyl group. 3. An isolation container in which an object to be polished containing a gas generating substance is polished inside, and a polishing means for polishing the object to be polished by using an abrasive for inducing gas generation from the gas generating substance. A polishing apparatus comprising: a detection unit configured to detect a gas from the gas generating substance. 4. The polishing apparatus according to claim 3, wherein the isolation container has a supply port and an exhaust port for a carrier gas, and the flow path of the carrier gas is downstream of the polishing means. A polishing apparatus, wherein the detection means is located on the side of 5. The polishing apparatus according to claim 4, wherein said carrier gas is an inert gas. 6. A semiconductor device comprising: a substrate on which elements are integrated on a surface; an insulating gas generating film formed on the surface; and an insulating film on the gas generating film.