KR20050001178A - Method for detecting end point in progressing CMP process - Google Patents

Abstract

PURPOSE: A method for detecting an end point in a CMP(chemical mechanical polishing) process is provided to detect an end point regardless of a pattern density by insulating metal patterns on a wafer from each other. CONSTITUTION: A semiconductor wafer with a metal layer comes in contact with the lower part of a polishing head(33). While the metal layer is in contact with a polishing pad(31), a probe(37) is driven into the outer part of the polishing pad in contact with the polishing head. While slurry is supplied through a slurry supply line, proper current flows to measure resistance. While a polishing process is performed, the polishing pad rotates to make the polishing head come to the periphery of the probe and current flows in the metal layer of the wafer. A polishing process is continuously performed in a manner that the metal layer on the wafer becomes gradually thinner and the whole resistance gets high.

Description

Method for detecting end point in progressing CMP process

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endpoint detection method in a CMP process applied to semiconductor device manufacturing, and more particularly, to a method for detecting an endpoint using a resistance value of a metal film.

In general, since the metal CMP differs from the oxide film CMP by polishing the metal, the difference in the polishing ratio from the oxide film is large, and thus it is difficult to control the polishing amount by the oxide film thickness measurement method of the EM box.

Therefore, most of the polishing amount is controlled by end point detection (EPD).

The EPD method currently used in CMP is divided into two types as follows.

The first conventional method, as shown in Figure 1, is to use the difference in the frictional force of the thin film, due to the difference in the friction between the metal thin film and the insulating film when polishing all the metal pattern is polished when the wafer reaches the end point of polishing Since the frictional force between (5) and the pad 3 is changed, the current value of the motor 7 which rotates the pad 3 is changed, and thus the endpoint is detected using this difference. Here, reference numeral 1 denotes a table.

Another conventional method, as shown in Fig. 2, uses an optical method to find an end point due to a difference in reflectance between the metal film and the insulating film. Here, the operation of the apparatus used in the existing method will be omitted. Here, reference numeral 11 denotes a belt, 13 a polishing pad, 15 a wafer, 17 a lens assembly, 19 a light path, a light source plate, and 25 a sensor.

However, in the case of the plug CMP, the density of the metal pattern is easy to apply the EPD, but in the case of damascene, the metal pattern density is very large, so it is not easy to apply the EPD. In other words, the two methods mentioned above have a high metal density, so that both friction and reflectance are less likely to detect endpoints.

Accordingly, an object of the present invention is to provide an endpoint detection method in a CMP process capable of detecting an endpoint regardless of the density of a metal pattern.

1 is a schematic view illustrating a method for measuring an endpoint according to a change in the amount of current of a motor in an endpoint detection method according to an embodiment of the prior art;

2 is a flowchart illustrating a method for measuring an endpoint according to a difference in reflectivity in an endpoint detection method according to another embodiment of the prior art;

3 is a plan view for explaining a method for measuring an endpoint according to the present invention;

4a to 4c is a cross-sectional view for explaining a method for measuring an endpoint according to the present invention,

5 is a view showing a resistance graph with time in the method for measuring an endpoint according to the present invention;

[Description of Drawing Reference]

31: polishing pad 33: polishing head

37: probe 39: metal film

41: semiconductor wafer 43: resistance gauge

In the CMP process according to the present invention for achieving the above object, an endpoint detection method includes a semiconductor wafer in which a metal film is formed under a polishing head, and the polishing head is in contact with the metal film portion on a polishing pad. Embedding the probe outward;

Measuring resistance by flowing a proper current while supplying a slurry through a slurry supply line;

Allowing the current to flow in the metal film of the wafer when the polishing pad is turned and the polishing head is near the probe as the polishing process proceeds; And

It characterized in that it comprises a step of continuing the polishing process so that the metal film on the wafer becomes thinner and the overall resistance is higher.

(Example)

Hereinafter, an endpoint detection method in a CMP process according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a plan view for explaining a method for measuring the endpoint according to the invention, Figures 4a to 4c is a cross-sectional view for explaining a method for measuring the endpoint according to the present invention, Figure 5 is a present invention In the method of measuring the end point according to the present invention, it is a diagram showing a resistance graph with time.

In the endpoint detection method in the CMP process according to the present invention, as shown in Figs. 3 and 4a, the probe is driven outward to the polishing head.

Here, when a proper current flows, since a slurry is an electrolyte, a current flows and high resistance is measured.

Then, as shown in FIG. 4B, when polishing starts and the pad is turned and the head is near the probe, a current flows through the metal film of the wafer so that the resistance measured by the probe is lowered. Will be higher. In this case, the resistance measurement is made through the resistance gate 43.

Subsequently, as polishing progresses, the metal film on the wafer becomes thinner and the overall resistance becomes higher and higher. At this time, as this state is repeated, the processes of FIGS. 4A and 4B are repeated. When the change of the resistance is represented as a graph with time, it is shown as in FIG. 5.

Then, when polishing is almost finished, as shown in Fig. 4C, the metal film disappears and no current flows on the wafer so that the resistance no longer falls and this area becomes an endpoint.

As described above, according to the endpoint detection method in the CMP process according to the present invention, since the metal patterns on the wafer are insulated from each other, such an end point can be detected regardless of the density of the pattern. It can be overcome.

On the other hand, the present invention is not limited to the above-described specific preferred embodiments, and various changes can be made by those skilled in the art without departing from the gist of the invention claimed in the claims. will be.

Claims (2)

Contacting a semiconductor wafer having a metal film formed under the polishing head, and placing the probe out of the polishing head while the metal film portion is in contact with the polishing pad; Measuring resistance by flowing a proper current while supplying a slurry through a slurry supply line; Allowing the current to flow in the metal film of the wafer when the polishing pad is turned and the polishing head is near the probe as the polishing process proceeds; And And continuing the polishing process such that the metal film on the wafer becomes thinner and the overall resistance becomes higher. The method of claim 1, wherein when the polishing pad is turned and the polishing head is near the probe, the current flows through the metal film of the wafer to lower the resistance measured by the probe. Endpoint detection method in the CMP process, characterized in that.