KR100585070B1 - Apparatus for detecting end point during chemical-mechanical polishing process - Google Patents

Abstract

An endpoint detection apparatus in the chemical-mechanical polishing process of the present invention is a cell for reducing the metal ions contained in the slurry solution by receiving a slurry solution used as a chemical abrasive in the chemical-mechanical polishing apparatus, and a voltage in the cell. Potentiostat which detects the amount of current flowing in the cell by the reduction of metal ions at the same time, and sends a control command to the potentiostat, receives the detected amount of current from the potentiostat and analyzes according to the detected amount of current It is provided with a processor to determine the endpoint.

Description

Apparatus for detecting end point during chemical-mechanical polishing process

1 shows a chemical-mechanical polishing apparatus and an endpoint detection apparatus according to the present invention.

2 is a cross-sectional view of a semiconductor device shown for explaining the operation of the endpoint detection apparatus according to the present invention.

3 is a voltage-current graph shown for explaining the operation of the endpoint detection apparatus according to the present invention.

4 is a time-current graph shown for explaining the operation of the endpoint detection apparatus according to the present invention.

The present invention relates to an end point detection apparatus and method in a chemical-mechanical polishing process.

Recently, as the degree of integration of semiconductor devices increases, the structure of the semiconductor device has become a multilayer. Accordingly, the demand for a polishing process for leveling each layer of the semiconductor wafer is rapidly increasing during the manufacturing process of the semiconductor device. The chemical mechanical polishing (CMP) process is mainly applied to the polishing process. According to this process, excellent uniformity can be obtained not only in the narrow region but also in the wide region, so that the wafer is suitable for the trend of large diameter.

The chemical mechanical polishing process is a process of polishing a surface of a wafer on which a film to be planarized, such as a conductive film or an oxide film, is formed by mechanical friction and at the same time by polishing with a chemical abrasive. Here, mechanical polishing is to polish the wafer surface by friction between the polishing pad and the wafer surface by rotating the wafer with a predetermined load while the wafer is placed on the rotating polishing pad. And chemical polishing is to polish the surface of the wafer by a chemical abrasive called slurry supplied between the polishing pad and the wafer.

It is important to accurately detect when the polishing process should be terminated, i.e., the end point, in the case where the chemical mechanical polishing processor is to be polished using such a chemical mechanical polishing processor. If the endpoint is not detected correctly, problems such as unwanted film quality may be removed.

Conventionally, a method of measuring a torque of a polishing head, an optical method, a time limiting method, and the like have been used to detect an endpoint. The method of measuring the torque of the polishing head is a method of detecting the end point by measuring the torque of the polishing head that changes according to the kind of film to be polished. The optical method is a method of detecting an end point by forming a transparent window on the surface of a polishing pad and then irradiating the beam to the window to detect the intensity or wavelength of the beam reflected from the wafer surface. In addition, the time limiting method is a method of determining an end point according to whether a time elapses after the polishing process is performed.

However, the method of measuring the torque of the polishing head has a problem that the detection of the torque is not easy because the amount of torque change is minute, and the optical method has an inaccurate value of the intensity or the wavelength of the beam detected by the foreign matter generated during the polishing process. There is a problem. In addition, the time limiting method has a problem that the expected time does not coincide with the actual polishing process.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an endpoint detection apparatus capable of accurately detecting an endpoint in a chemical-mechanical polishing process.

Another object of the present invention is to provide an endpoint detection method capable of accurately detecting an endpoint in a chemical-mechanical polishing process.

In order to achieve the above technical problem, the end point detection apparatus in the chemical-mechanical polishing process according to the present invention is supplied with a slurry solution used as a chemical abrasive in the chemical-mechanical polishing apparatus to collect the metal ions contained in the slurry solution. A cell for reducing; A potentiostat which detects an amount of current flowing in the cell by applying a voltage in the cell and simultaneously reducing the metal ions; And a processor that sends a control command to the potentiostat and receives an amount of detected current from the potentiostat and performs an analysis according to the detected amount of current to determine an endpoint.

Here, it is preferable to further include a first electrode, a second electrode and a reference electrode which is inserted into the cell and connected to the potentioste to form a voltage application and a current path in the cell.

The processor may detect the end point according to a change in the content ratio of the metal component in the slurry solution by analyzing the detected current amount.

In order to achieve the above another technical problem, an endpoint detection method in the chemical-mechanical polishing process according to the present invention, (A) receiving a slurry solution used as an abrasive in the chemical-mechanical polishing process; (B) reducing the metal ions contained in the slurry solution by applying a constant potential difference to the slurry solution; (C) detecting the amount of current flowing in the slurry solution by the reduction; And (d) detecting an end point by analyzing a change in the content ratio of metal ions contained in the slurry solution by the change in the amount of current.

The method may further include diluting the slurry solution.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a chemical-mechanical polishing apparatus and an endpoint detection apparatus according to the present invention.

Referring to FIG. 1, the chemical-mechanical polishing apparatus 100 includes a rotating plate 120 that rotates along a first axis A1 and a polishing pad 120 that rotates equally over the rotating plate 120. And a polishing head 140 that sucks the wafer 130 and rotates along the second axis A2. The wafer 130 adsorbed on the polishing head 140 is polished while being in contact with the polishing pad 120 on the surface to be polished. During the polishing process, the slurry is supplied onto the polishing pad 120 through the tube 150.

During the polishing process using the chemical-mechanical polishing apparatus 100, the slurry solution used as the chemical abrasive is supplied to the endpoint detection apparatus 200.

The endpoint detection apparatus 200 may be supplied with a slurry solution to reduce the metal ions in the slurry solution at a predetermined voltage, and apply a constant voltage into the cell 210 while simultaneously applying the cell ( A control command is sent to the potentiostat 220 and the potentiostat 220 which sense current generated by the reduction of the metal ions in 210, while the potentiostat ( And a processor 230 that receives the detection signal from the 220 and determines the endpoint. The first electrode 240, the second electrode 250, and the reference electrode 260 are formed in the cell 210 to form a voltage application and a current path. The first electrode 240, the second electrode 250, and the reference electrode 260 are connected to the potentiostat 220.

The operation principle of such an endpoint detection apparatus is as follows.

2 is a cross-sectional view illustrating an example of a semiconductor structure in which a film to be polished is formed by a chemical-mechanical polishing process.

Referring to FIG. 2, an insulating film 310 is formed on the semiconductor substrate 300, and holes having a predetermined depth are formed in the insulating film 310. On the insulating layer 310, a first metal layer 320 serving as a barrier layer is formed to have a thin thickness. The second metal film 330 is formed on the insulating film 310, and is formed to completely fill the hole.

Such semiconductor structures can be planarized using the chemical-mechanical apparatus of FIG. 1. Hereinafter, with reference to FIGS. 1 and 2 will be described in more detail. In this case, in order to facilitate the description, the case where the first metal film 320 is a platinum film and the second metal film 330 is a copper film will be described.

First, the semiconductor structure is adsorbed onto the polishing head 140 such that the second metal film 330 to be polished of the semiconductor structure of FIG. 2 faces the surface of the polishing pad 120. Subsequently, the second metal layer 330 is in contact with the surface of the polishing pad 120. The polishing pad 120 and the polishing head 140 are rotated in a predetermined direction, respectively, and the semiconductor structure is loaded in a direction perpendicular to the polishing pad 120. At the same time, the slurry is supplied from the tube 150 to the polishing pad 120 surface.

As the chemical-mechanical polishing process proceeds, the slurry solution used as the chemical abrasive and discharged out of the polishing pad 120 is supplied to the endpoint detection apparatus 200. In the slurry solution, metal components of the polished second metal film 330, that is, copper metal ions are sufficiently contained.

When the slurry solution used as the chemical abrasive is supplied to the endpoint detection apparatus 200, the slurry solution is supplied to the cell 210 in the endpoint detection apparatus 200. As described above, the first electrode 240, the second electrode 250, and the reference electrode 260 are inserted into the cell 210, and the electrodes are applied with a constant voltage by the potentiostat 220. . Here, the constant voltage is a voltage required to reduce the metal ions included in the slurry solution.

When only the second metal film 330 is polished while the chemical-mechanical polishing process is performed, the metal ions included in the slurry solution are copper metal ions. Since these copper metal ions are reduced at a potential difference of about 0.337V, a potential difference of about 0.337V is applied to the cell 210. This potential difference is the potential difference between the first electrode 240 as an anode and the second electrode 250 as a cathode based on the reference electrode 260. As such, when the pre-reduction position of the copper metal ions included in the slurry solution is applied to the cell 210, the copper metal ions are reduced, and thus a current is conducted in the cell 210. The potentiostat 220 then detects the amount of current that is conducted in the cell 210 by the reduction of the copper metal ions.

3 is a graph showing the relationship between the voltage applied to the cell 210 by the potentiostat 220 and the amount of current conducted in the cell 210. FIG. 4 shows the potency over time. A graph showing the amount of current detected by the auster 220 is shown. 4 shows a case where a reduction potential difference of copper metal ions is applied to the cell 210, and a graph indicated by "B" shows a case where the reduction potential difference of platinum metal ions is applied to the cell 210. Indicates.

First, as shown in FIG. 3, when 0.337 V, which is a reduction voltage (V _Cu ) of copper metal ions, is applied to the cell 210, a first current peak value 410 is generated by reduction of copper metal ions. This current peak 410 remains constant as long as copper metal ions are contained in the slurry solution. That is, as shown in FIG. 4, a constant amount of current value is detected by the potentiostat until the time point T1. However, when the time point T1 is reached and the first metal film 320 made of platinum is polished after the second metal film 330, that is, when the end point is reached, the concentration of copper metal ions in the slurry solution decreases, Instead, the concentration of platinum metal ions increases. Therefore, the amount of current due to the reduction of the copper metal ions in the cell 210 detected by the potentiostat 220 is reduced. When the time point T2 is reached, the amount of current due to the reduction of the copper metal ions is reduced and hardly appears. Since this fact is the fact that the metal layer being polished is first metal layer 320 made of platinum, the end point is determined between time point T1 and time point T2.

Although the case where the reduction potential difference of the copper metal ions which is the component of the second metal film 330 is applied to the cell 210 has been described above, the component of the first metal film 330 in the cell 210 has been described. In the case where the reduction potential difference of platinum metal ions is applied, the end point can be determined by the same method. This is described as follows.

First, as shown in FIG. 3, when -0.6 V, which is a reduction voltage (V _Pt ) of platinum metal ions, is applied in the cell 210, when metal metal ions are mainly present in the slurry solution, the reduction is performed in the cell 210. The phenomenon does not occur. Therefore, the amount of current detected by the potentiostat 220 is hardly present. Since the second metal film 330 of the semiconductor structure of FIG. 2 is mainly polished until the time point T1, copper metal ions are mainly present in the slurry solution. However, when the time point T2 is reached at the time point T2, the first metal film 320 begins to be polished and the content of platinum metal ions in the slurry solution is increased. As the content of the platinum metal ions increases, the platinum metal ions in the cell 210 start to be reduced, and current starts to be conducted in the cell 210, and a peak value 420 of the current is generated. In addition, as shown in FIG. 4, the amount of current detected by the potentiostete 220 hardly exists until the time point T1, but gradually increases to the time point T2, whereby the first metal film 320 starts to be mainly polished. After time T2, a fixed value is shown. Thus, the end point is determined between the time point T1 and the time point T2.

As described above, the end point detection apparatus and method in the chemical-mechanical polishing process according to the present invention uses an electrochemical apparatus and method that has been found to be able to analyze very precisely and thus end more precisely and accurately. There is an advantage that the point can be detected.

Claims (5)

A cell for supplying a slurry solution used as a chemical abrasive in a chemical-mechanical polishing apparatus to reduce metal ions contained in the slurry solution; A potentiostat which detects an amount of current flowing in the cell by applying a voltage in the cell and simultaneously reducing the metal ions; And And a processor for sending a control command to the potentioste, receiving a detected amount of current from the potentioste, and performing an analysis according to the detected amount of current to determine an end point. Endpoint detection device in the process. The method of claim 1, In the chemical-mechanical polishing process further comprises a first electrode, a second electrode and a reference electrode inserted into the cell and connected to the potentiostat to form a voltage application and current path in the cell. Endpoint detection device. The method of claim 1, And the processor detects the endpoint according to the change in the content ratio of the metal component in the slurry solution by analyzing the detected amount of current. (A) receiving a slurry solution used as an abrasive in the chemical-mechanical polishing process; (B) reducing the metal ions contained in the slurry solution by applying a constant potential difference to the slurry solution; (C) detecting the amount of current flowing in the slurry solution by the reduction; And (D) detecting the end point by analyzing the change in the content ratio of the metal ions contained in the slurry solution by the change in the amount of current, characterized in that the endpoint detection method in the chemical-mechanical polishing process. The method of claim 4, wherein Diluting the slurry solution further comprises the step of detecting the endpoint in a chemical-mechanical polishing process.

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