KR20000041422A - Detect method of polish ending point and chemical mechanical polishing apparatus using the method - Google Patents

Abstract

PURPOSE: A method for exactly detecting a polish ending point by using a diffused reflection of light on a wafer surface and a chemical mechanical polishing(CMP) apparatus using the detect method are provided. CONSTITUTION: To exactly detect a polish ending point, light is projected on a target of polish during a chemical mechanical polishing(CMP) process, and then a reflected light from the target is measured. A rough surface of the target before the CMP process will be turned into a flat surface as the CMP process progresses. Consequently, strength of the reflected light is gradually increased. Finally, strength of the reflected light reaches constant values so the surface of the target becomes flat. Accordingly, the ending point can be exactly detected from the time when the light is uniformly reflected. A wafer(10) having the target thereon is mounted on a polish table(32) and rotated by a supporter(33). Light generated from a light source(40) is incident on the wafer(10) and then reflected to a detector(20). The detector(20) sends a signal to an analyzer(60) via an amplifier(50), and the analyzer(60) transmits an analysis data to a monitor(70) and a motor(90) via a feedback system(80). According to the data, the motor(90) stops a rotation of the supporter(33) at the ending point.

Description

A method for detecting the end point of polishing using diffuse reflection of light on the wafer surface and a chemical mechanical polishing apparatus using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for detecting an end point at which polishing should be stopped in a chemical mechanical polishing process and a chemical mechanical polishing apparatus using the same.

In the semiconductor device manufacturing process, as the device diversifies and the degree of device integration increases, the step difference between layers increases. As part of an effort to secure the process margin by removing the step, chemical mechanical polishing (CMP) is referred to. ) Process is adopted.

In the CMP process, a method of polishing the desired portion, that is, detecting the end point, has emerged as an important technical factor. Conventional endpoint detection methods include motor current detection and optical detection.

The motor current test method detects the end point by measuring the current change of the driving motor that rotates the carrier holding the wafer, and the friction coefficient between the pad and the wafer surface is changed when the polishing layer is changed. The current change point is regarded as the end point by using the change of the current of the spindle drive motor to change and match the same spindle speed. The motor current test method can be applied only to a material having a significantly different friction coefficient, and thus, it is difficult to apply the same material when polishing the same material such as polishing for planarization of an inter poly oxide (IPO).

On the other hand, the optical detection method is to detect the end point by using the difference of interference phenomena according to the thickness of the thin film by injecting light to the backside of the wafer, this method is when a plurality of layers are stacked in a multilayer structure on the wafer The disadvantage is that it is not applicable.

As described above, when the polishing point is not accurately detected by the conventional polishing end point detection device, if polishing is not completed, the polishing process is performed again to delay the process time or when the polishing is excessive, the lower layer. There is a problem damaging it.

The present invention devised to solve the above problems is a method for detecting the end point of chemical mechanical polishing using the diffuse reflection of light on the wafer surface, which can detect the polishing end point more accurately in the chemical mechanical polishing process and chemical mechanical polishing using the same The purpose is to provide a device.

1A and 1B are schematic diagrams for explaining the principle of an endpoint detection method of chemical mechanical polishing according to the present invention;

2 is a graph showing a change in relative light intensity with polishing time;

3 is a schematic diagram of a chemical mechanical polishing apparatus according to an embodiment of the present invention;

4 is an explanatory view showing a positional relationship between a polishing table and a wafer of a chemical mechanical polishing apparatus according to an embodiment of the present invention;

* Explanation of reference numerals for the main parts of the drawings

10: wafer 11: polishing target layer

12: incident light 20: detector

31: polishing table support 32: polishing table

33: wafer support 34: slurry

40: light source 50: amplifier

60: Analyzer 70: Monitor

80: feedback system 90: motor

The present invention for achieving the above object is irradiated with light on the polishing target layer formed on the front surface of the wafer during the polishing process and by measuring the intensity of the light reflected from the polishing target layer, the intensity of the reflected light increases and then constant Provided is an endpoint detection method in a polishing step of detecting a point of degradation as an endpoint of polishing.

In addition, the present invention for achieving the above object is a polishing table; A polishing table support for supporting the polishing table; A wafer support, one end of which is connected to a rear surface of the wafer and driven by a power supply to rotate the wafer; A light source for irradiating light to the polishing target layer formed on the front surface of the wafer; Detection means for detecting light incident from the light source and reflected from the polishing target layer; Amplifying means connected to an output end of the detecting means and amplifying a signal input from the detecting means; Analysis means for analyzing an intensity of light connected to an input end of the amplification means; Display means connected to said analysis means for displaying information; And a power supply means for rotating the wafer support.

According to the present invention, as the planarization by chemical mechanical polishing progresses, the surface roughness is alleviated and the detected light intensity increases, and when polishing proceeds beyond the polishing end point, the surface roughness does not change and the light intensity is constant. It is a feature of the present invention to provide a method for detecting the polishing endpoint and a chemical mechanical polishing device using the same.

1A and 1B are schematic diagrams for explaining the principle of an endpoint detection method of chemical mechanical polishing according to the present invention. FIG. 1A illustrates that incident light 12 of a specific wavelength irradiated onto the rough surface of the polishing target layer 11 formed on the wafer 10 is diffusely reflected on the polishing target layer 11 and then detected by the detector 20 before polishing. 1B shows a state in which the intensity of the specific wavelength light is not large, and FIG. 1B shows that when the polishing is completed and the surface of the polishing target layer 11 is flat, diffuse reflection hardly occurs and the intensity of the specific wavelength light detected by the detector 20 is relatively high. Is showing great status.

As such, the reflection of light due to the diffuse reflection phenomenon is different depending on the roughness of the surface of the polishing target layer. That is, the rougher the surface of the layer to be polished, the more diffused reflection occurs, so the light intensity detected by the detector fixed at a predetermined position is smaller, and the flatter the surface of the layer to be polished, the greater the intensity of light detected under the same conditions is.

FIG. 2 is a graph showing relative changes in light intensity according to polishing time. As the polishing proceeds, the surface is flattened and the detected light intensity increases. When polishing proceeds beyond the polishing end point, there is no change in surface roughness. It shows that the intensity is constant.

Therefore, the inflection point that is increased while the light intensity is increased by detecting the light intensity during the CMP process may be recognized as the polishing endpoint.

In the chemical mechanical polishing apparatus according to the embodiment of the present invention, as shown in FIG. 3, the polishing table 32, the polishing table support 31 for supporting the polishing table 32, and one end thereof are the rear surface of the wafer 10. A wafer support 33 for rotating the wafer and driven by a motor 90, a light source 40 for irradiating light to the polishing target layer formed on the front surface of the wafer 10, and incident and polished from the light source 40. A detector 20 for detecting light reflected from the target layer, an amplifier 50 connected to an output terminal of the detector 20 to amplify a signal input from the detector 20, and the amplifier 50 The input terminal is connected to the output terminal of the analyzer, the first output terminal is connected to the feedback system 80, and the second output terminal is connected to the monitor 70, the input terminal to the analyzer 60 Is connected and the output terminal is connected to the motor 90 A feedback system 80 for stopping the polishing apparatus at the fish endpoint, a monitor 70 connected to the analyzer 60 for displaying information and a signal applied from the feedback system 80 A motor 90 is applied to rotate the wafer support 33. In FIG. 3, reference numeral 34 denotes a slurry.

FIG. 4 is an explanatory view for explaining the positional relationship between the polishing table 32 and the wafer 10 of the polishing apparatus as shown in FIG. 3, wherein reference numeral 10c denotes the center of the wafer 10. FIG. 32c represents the center of the polishing table 32. As shown in FIG. 4, while the polishing is in progress, a portion of the edge of the polishing target layer formed on the wafer 10 is exposed to the edge of the polishing table 32 while rotating, and the polishing amount remains constant even when the wafer edge portion is exposed. In order to achieve this, the polishing table 32 and the wafer 10 are rotated simultaneously. In this case, a motor (not shown) for rotating the polishing table support 31 is provided.

As the polishing proceeds, the edge of the polishing target layer rotates outside the edge of the polishing table 32 and is exposed to the polishing target layer by irradiating light of 5000 Å to 8000 Å wavelength from the light source 40 to the edge of the exposed polishing target layer. When the detector 20 detects the light, the amplifier 50 amplifies the detected signal, and the analyzer 60 analyzes the amplified signal to recognize the end point, it gives a signal to the feedback system 80 to perform polishing. Stop it. Polishing may be manually stopped without feedback system 80 when analyzer 60 recognizes the polishing endpoint.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

The present invention as described above can overcome the limitation that only a specific polishing method is applied to a specific polishing target layer, unlike the conventional endpoint detection apparatus by detecting the end point by using the diffuse reflection phenomenon of the surface of the wafer with respect to light of a specific wavelength. . Therefore, the end point detection method according to the present invention can be applied uniformly to the process of polishing the same material as well as chemical mechanical polishing between layers composed of different materials, and it is possible to control the exact process, so that over polishing or The process can be completed accurately in one polishing without under polishing.

In addition, unlike the conventional back measuring method used in the conventional optical method, by directly measuring the polishing target layer formed on the front surface of the wafer, it is possible to improve the incidence of measurement error and difficulty in detecting the end point in the multilayer structure. End-point detection can be done in-situ to reduce the loss of wafers due to inaccurate end-point detection and delays in processing time due to regrinding, as well as to measure thickness after polishing. Since the process can be omitted, productivity can be improved.

Claims (5)

In the end point detection method in the polishing step, During the polishing process, by irradiating light to the polishing target layer formed on the front surface of the wafer and measuring the intensity of light reflected from the polishing target layer, An end point detection method in a polishing step of detecting a point where the intensity of reflected light increases and becomes constant as the end point of polishing. In the chemical mechanical polishing apparatus, Polishing table; A polishing table support for supporting the polishing table; A wafer support, one end of which is connected to a rear surface of the wafer and driven by a power supply to rotate the wafer; A light source for irradiating light to the polishing target layer formed on the front surface of the wafer; Detection means for detecting light incident from the light source and reflected from the polishing target layer; Amplifying means connected to an output end of the detecting means and amplifying a signal input from the detecting means; Analysis means for analyzing an intensity of light connected to an input end of the amplification means; Display means connected to said analysis means for displaying information; And Power supply means for rotating the wafer support Chemical mechanical polishing apparatus comprising a. The method of claim 2, The chemical mechanical polishing device, And a feedback system having an input end coupled to the analysis means and an output end coupled to the power supply means for automatically stopping the polishing apparatus at an end point. The method of claim 2 or 3, The center of the wafer support, And position the wafer to expose a portion of the edge of the wafer out of the edge of the polishing table. The method of claim 4, wherein The chemical mechanical polishing device, Further comprising a power supply means for rotating the polishing table support, And the polishing table and the wafer are simultaneously rotated when polishing is performed.