JPH10214868A - Evaluation of cmp treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To priovde a method for evaluating a chemimechanical polishing(CMP) process, which can measure a surface roughness of a wafer after subjected to the CMP treatment in a non-destructive inspection to realize an inline sequence of evaluation of the CMP process. SOLUTION: A specimen S is brought into contact with a probe 1a arranged opposing thereto, the probe 1a and specimen S are relatively scanned to detect a physical quantity generated by an interaction between the probe 1a and a surface of the specimen. In this connection, a scanning probe microscope (AFM) is used for measuring the form of the specimen surface at an atomic level of resolution on the basis of the detected physical quantity. A wafer to be measured is positioned under the probe 1a, the probe 1a is linearly scanned under a condition that the probe 1a is located at a predetermined position (measurement point) of the wafer, to measure a surface form of the wafer in a non-destructive inspection and to judge whether or not the CMP process has been properly carried out on the basis of its measurement result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating a wafer subjected to a CMP process in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Various microfabrication techniques have been developed in response to the increase in the size and density of VLSI devices. One of them is CMP (Chemical Mechanical Polishing).
Chemical-mechanical polishing) technology has recently received a great deal of attention.

In the semiconductor manufacturing process for performing high-precision and high-density processing, this CMP technology is not suitable for the step depth due to the presence of steps and unevenness on the device surface.
Since sufficient resolution cannot be obtained during photolithography or wiring pattern formation, etc., this technology is used to flatten the device surface (global flattening) in order to eliminate steps and irregularities on the device surface. In the production of devices requiring a multi-layer wiring structure, its importance is attracting attention.

At present, a scanning electron microscope (hereinafter, referred to as SEM) and an optical method are employed for evaluating the CMP processing performed in such a semiconductor manufacturing process.

[0005]

By the way, the flattening of the surface unevenness by the CMP process is a process of finishing the unevenness value to the order of several hundred nm to several thousand nm. Therefore, observation using an SEM or an optical method is difficult. Because of the problem of the depth of focus, it is impossible to grasp the surface shape of the sample from directly above. Therefore, a method of destroying a part of the wafer to be evaluated to produce the sample and observing the cross section with an SEM is not adopted. Not get.

As described above, at present, there is no non-destructive (non-crackable) evaluation method, which hinders the in-line evaluation of the CMP process in the semiconductor manufacturing process.

The present invention has been made in view of such circumstances, and it is possible to non-destructively measure the surface unevenness of a wafer after a CMP process, thereby enabling inline evaluation of the CMP process to the process. CMP that can be realized
The purpose is to provide a method for evaluating processing.

[0008]

Means for Solving the Problems To achieve the above object, the present invention provides a method for evaluating a CMP process, in which a sample and a probe arranged opposite to the sample are brought close to each other, and the probe and the sample are relatively moved. By scanning, a scanning probe microscope (A) that detects a physical quantity generated by an interaction between the probe and the sample surface and measures the shape of the sample surface at an atomic level resolution.
Using an FM (Atomic Force Microscope), a wafer to be measured is arranged below the probe and searched at a predetermined position of the wafer (for example, device wiring pattern forming portions P1,..., P5; see FIG. 2). In a state where the needles are aligned, the probe is linearly scanned to measure the surface shape of the wafer, and the quality of the CMP process is determined from the measurement result.

The present invention provides the advantages of a scanning probe microscope,
In other words, focusing on the fact that the surface shape of a sample can be measured with atomic-level resolution, the use of such a scanning probe microscope allows even the wafer after CMP processing to remove steps and irregularities on the surface of the wafer. Enable non-destructive measurement without destruction. In addition, in the evaluation method of the present invention, in a scanning probe microscope of this type, a portion having surface irregularities, for example, a portion where a device wiring pattern is formed is linearly formed instead of performing a two-dimensional scan which is usually performed. Since the surface unevenness of the portion is measured by scanning, observation in a short time becomes possible. As a result, it becomes possible to incorporate the evaluation of the CMP process into the process line.

[0010]

FIG. 1 is a block diagram showing a configuration of a scanning probe microscope used for carrying out a method for evaluating a CMP process according to the present invention.

The mechanism of the scanning probe microscope shown in FIG. 1 is a cantilever 1 having a probe 1a at the tip, and a Z-axis fine movement mechanism (PZT) for driving the probe 1a in the Z-axis direction.
2. An XY fine movement mechanism (P) for scanning the probe 1a in the X and Y directions.
ZT) 3 and a XY coarse movement stage 4 which has a structure capable of loading a sample S to be measured, that is, a wafer after the CMP process, and moves and arranges an arbitrary position of the sample S under the probe 1a. It is configured.

The control system of the scanning probe microscope includes a Z-axis driver 2 a for driving the Z-axis fine movement mechanism 2, an XY fine-motion mechanism 3
XY scanning driver 3a for driving the XY coarse movement driver 4a for driving the XY coarse movement stage 4, and its X
The control unit 8 supplies a drive command signal to the Y scanning driver 3a and the XY coarse movement driver 4a.

The detection system controls a Z-axis driver 2a to keep the position of the probe 1a constant based on an output signal of the displacement detector 5 for detecting the displacement of the probe 1a. The servo mechanism 6 supplies a drive signal, and a drive control signal (current signal) of the servo mechanism 6 is provided.
Is converted into a digital signal by the A / D converter 7 and input to the control means 8.

In the scanning probe microscope having the above structure, the position of the probe 1a in the Z-axis is controlled to be constant by the drive control of the Z-axis fine movement mechanism 2 by the servo mechanism 6 described above. Measurement points P1 ... P5 (Fig. 2
) Can be measured by an operation such as linear scanning (line scanning) of the sample S. In such a scanning process, the amount by which the servo mechanism 6 drives and controls the Z-axis fine movement mechanism 2 determines the surface shape of the sample S. The surface shape data is stored in the recording device 9 for each line scan. Further, the surface shape data stored in the recording device 9 is displayed on the display device 10 in a form illustrated in FIG.

Next, an example in which the evaluation method of the present invention is performed using the above-described scanning probe microscope with the wafer shown in FIG. 2 as a sample S to be measured will be described with reference to the flowchart of FIG. I do.

First, the wafer shown in FIG. 2 has been subjected to a CMP process in a VLSI manufacturing process. In this example, five VLSI devices D,. Device D located at
Are defined as measurement points P1... P5. The wiring pattern of each device D,... D of the wafer in this example is formed in parallel with the Y direction.

Now, when the sample S is mounted on the XY coarse movement stage 4 and observation with a scanning probe microscope is started,
By the drive control of the XY coarse movement stage 4 by the control means 8, first, the position of the measurement point P1 of the sample S is positioned below the probe 1a.

Next, by controlling the driving of the XY fine movement mechanism 3,
Probe 1a is in X direction (perpendicular to device wiring pattern)
After the drive control signal from the servo mechanism 6 is digitized by the A / D converter 7 every predetermined minute time in this scanning process,
The data is stored in the recording device 9 via the control means 8 as surface shape data of the sample S. At this time, the scanning distance on the X axis and the scanning distance on the next Y axis are both about 100 μm.

Then, by driving the XY coarse movement stage 4, the position of the probe 1a with respect to the sample S is positioned at the scanning position of the measurement point P1 in the Y direction. The needle 1a is line-scanned in the Y direction (a direction parallel to the device wiring pattern), and the surface shape data collected in the scanning process is stored in the recording device 9.

Positioning of the sample S in the same manner as described above, and X,
The line scan in the Y direction is performed at the measurement points S2,.
For all measurement points S1... S5
After the line scan in the X and Y directions is completed, the surface shape data is displayed for each of the measurement points S1.
(See display example in FIG. 4).

Then, the values of the concavities and convexities on the X axis and the Y axis (see FIG. 4) displayed on the display device 10 are compared with a preset upper limit value (for example, several hundred nm) to judge the quality of the CMP process. .

In the above-described embodiment, a procedure is adopted in which after the line scan in the X and Y directions is completed for one measurement point, the line scan for the next measurement point is executed. For the measurement points S1 to S5, only a line scan in the X direction may be performed first, and then a line scan in the Y direction at each measurement point S1 to S5 may be performed.

In the above embodiment, it is known in advance from the design of the device that there is no surface unevenness due to the wiring pattern in either the X or Y axis direction (for example, FIG. 4), only the line scan in the direction in which the surface unevenness exists (for example, the X-axis direction) may be performed.

Further, in the above embodiment, an example is shown in which one line scan is executed in each direction of the X and Y axes, but a plurality of line scans are executed at a predetermined pitch for each axis. Alternatively, a method of observing each measurement point by a band-like scan may be adopted. In this case, the surface shape of the sample S can be measured in more detail, and the reliability of the evaluation can be improved. Will be possible.

Here, in the above embodiment, the sample (CM) is transferred to the XY coarse movement stage 4 of the scanning probe microscope.
If a handling device for automatically carrying, setting, and resetting a P-processed wafer) is incorporated in the line, automation of the entire process including evaluation of the CMP process can be achieved.

Further, in this case, the control means 8 has a function of determining whether or not the surface shape data obtained by the line scan of the probe 1a is within a preset upper limit value (see FIG. 4). However, if the upper limit is exceeded, that is, if the CMP processing is defective, an alarm or the like is generated to notify the user of the failure, so that the operator does not need to monitor the display device 10. In addition, further automation and labor saving can be achieved.

[0027]

As described above, according to the present invention,
The method uses a scanning probe microscope that can measure the surface shape of the sample with atomic-level resolution, such as linear scanning of the sample surface. It can be measured nondestructively and in a short time. As a result, the quality of the CMP process can be monitored and managed inline in the semiconductor device manufacturing process.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a scanning probe microscope used for carrying out a CMP processing evaluation method of the present invention.

FIG. 2 is a diagram showing an example of a sample (CMP-processed wafer) to be evaluated.

FIG. 3 is a flowchart illustrating an example of an evaluation procedure performed in the present invention.

FIG. 4 is a diagram showing a display example of surface shape data of a sample S;

[Description of Signs] 1 Cantilever 1a Probe 2 Z-axis fine movement mechanism 3 XY fine movement mechanism 4 XY coarse movement stage 5 Displacement detector 6 Servo mechanism 7 A / D converter 8 Control means 9 Recording device 10 Display device S Sample (CMP) Processing wafer)

Claims (1)

[Claims] 1. A method for evaluating a wafer which has been subjected to a CMP process in a semiconductor manufacturing process, comprising: bringing a sample and a probe arranged opposite to the sample close to each other, and relatively scanning the probe and the sample. Using a scanning probe microscope that detects the physical quantity generated by the interaction between the probe and the sample surface and measures the shape of the sample surface with atomic-level resolution, the wafer to be measured is placed below the probe. While the probe is positioned at a predetermined position on the wafer, the probe is linearly scanned to measure the surface shape of the wafer, and the quality of the CMP process is determined from the measurement result. Evaluation method of CMP processing.