WO2023035247A1

WO2023035247A1 - Chemical-mechanical polishing device and control method therefor

Info

Publication number: WO2023035247A1
Application number: PCT/CN2021/117815
Authority: WO
Inventors: 赵林献; 王海峰; 麻勰光
Original assignee: 华为技术有限公司
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2023-03-16
Also published as: CN117769478A

Abstract

Embodiments of the present disclosure provide a chemical-mechanical polishing device and a control method therefor. The chemical-mechanical polishing device comprises a polishing platform which is adapted to carry a polishing pad and drive the polishing pad to move; and a polishing head which is adapted to drive an object to be polished to rotate about the central axis of the polishing head between the polishing head and the polishing pad; a metal measuring member which is arranged such that the metal measuring member remains fixed relative to the axial position of the polishing head; and a sensor which is disposed on the polishing platform and is adapted to at least obtain a signal value of the metal measuring member caused by an eddy current effect on the sensor. By means of providing the metal measuring member, the thickness of the polishing pad can be determined in real time. Once the thickness of the polishing pad can be precisely determined, the thickness of a metal film can be accurately and precisely obtained, and the obtained thickness of the metal film is further used for closed-loop control, thus the planarization uniformity and precision of a silicon wafer can be significantly improved. In addition, the addition of the metal measuring member does not require a large structural adjustment to the original chemical-mechanical polishing device, so the planarization uniformity and precision of a silicon wafer can be significantly improved at low cost. Moreover, in the foregoing means, it is not necessary to calibrate sensor parameters after each time the polishing pad and polishing solution are replaced, thereby improving the ease of use of the device.

Description

Chemical mechanical polishing equipment and its control method

technical field

The present disclosure generally relates to the field of chip manufacturing, and particularly relates to a chemical mechanical polishing device for polishing a silicon wafer and a control method thereof.

Background technique

Chemical-Mechanical Polishing (CMP), also known as Chemical-Mechanical Planarization (CMP), was originally used to obtain high-quality glass surfaces, such as military telescopes. CMP technology was gradually applied to the manufacture of semiconductor devices, and is currently widely used in the polishing of substrate silicon wafers in integrated circuits (Integrated Circuit, IC) and ultra large scale integration (Ultra Large Scale Integration, ULSI) circuits, that is, for Planarization of wafers or silicon wafers or other substrate materials being processed.

Different from traditional pure mechanical or pure chemical polishing methods, CMP avoids the surface damage caused by pure mechanical polishing and the slow polishing speed, surface flatness and Disadvantages such as poor polishing consistency. It uses the principle of "soft grinding hard" in wear, that is, polishing with softer materials to achieve high-quality surface polishing. In the presence of a certain pressure and polishing fluid, the workpiece to be polished moves relative to the polishing pad, and a smooth surface is formed on the surface of the workpiece to be polished by means of the organic combination of the grinding effect of nanoparticles and the corrosion effect of the oxidant. At present, it is generally believed that when the feature size of the device is below 0.35 μm, global planarization must be carried out to ensure the accuracy and resolution of lithographic image transmission, and CMP is currently almost the only technology that can provide global planarization. Its application range is expanding.

Contents of the invention

The present disclosure relates to a technical solution of chemical mechanical polishing, and specifically provides a chemical polishing device for polishing a wafer and a control method thereof.

In a first aspect of the present disclosure, a chemical mechanical polishing apparatus is provided. The chemical mechanical polishing equipment includes a polishing platform, adapted to carry a polishing pad and drive the polishing pad to move; a polishing head, adapted to drive the object to be polished around the center of the polishing head between the polishing head and the polishing pad a shaft rotates; a metal detector arranged such that the axial position of the metal detector relative to the polishing head remains fixed; and a sensor coupled to the polishing platform and adapted to acquire at least The signal value of the sensor caused by the eddy current effect. By setting the metal detection part, when the metal detection part passes the sensor, the impedance in the detection coil of the sensor will change due to the eddy current effect, which is finally reflected in the change of the output signal value of the sensor. In this case, the thickness of the polishing pad can be determined in real time only by determining the relationship between the thickness of the polishing pad and the signal value. After the thickness of the polishing pad can be accurately determined, the thickness of the metal film can be accurately and precisely obtained, and the obtained thickness of the metal film is further used for closed-loop control, thereby significantly improving the flattening uniformity and precision of the silicon wafer. In addition, the addition of metal detection parts does not require major structural adjustments to the original chemical mechanical polishing equipment, and can significantly improve the planarization uniformity and precision of silicon wafers at low cost. In addition, the relationship between the thickness of the polishing pad and the signal value only needs to be calibrated and stored when the polishing pad is used for the first time, and sensor parameters do not need to be calibrated every time the polishing pad is replaced, thereby improving the usability of the device.

In some implementations, the chemical mechanical polishing apparatus further includes a dresser adapted to rotatably move within a predetermined range of the polishing pad to dress the polishing pad. In this way, real-time conditioning of the polishing pad can be performed, thereby improving polishing and conditioning efficiency.

In one implementation, the metal detector is fixedly attached to the periphery of at least one of the polishing head or the dresser. In this way, the flexibility of arranging the metal detection parts can be effectively improved.

In some implementations, the metal detector is annular. The ring-shaped metal detection part can avoid invalid induction caused by inconsistent paths of the polishing head passing through the sensor, thereby improving the reliability of real-time determination of the thickness of the polishing pad.

In some implementations, the chemical mechanical polishing apparatus further includes a housing fixedly attached to an outer periphery of at least one of the polishing head or the dresser and adapted to hermetically accommodate the metal detector. The accommodating part can effectively prevent the metal detection part from being corroded by the polishing liquid, thereby improving the service life and reliability.

In some implementation manners, the accommodating portion includes: an opening adapted to allow the metal detection piece to enter the accommodating portion; and a cover adapted to seal the opening. In this way, the assembly and maintenance of the metal detector can be facilitated.

In some implementations, the sensor is disposed on a lower surface of the polishing platform opposite the surface carrying the polishing pad. In this way, the sensor can acquire the thickness of the polishing pad and the metal film of the object to be polished in real time without any influence on the polishing process.

According to a second aspect of the present disclosure, a method of controlling a chemical mechanical polishing apparatus is provided. The method includes acquiring a first signal value from a sensor in real time during operation of the chemical mechanical polishing apparatus, wherein the first signal value is a metal detector arranged to remain fixed relative to the axial position of the polishing head The sensor of the chemical mechanical polishing device is caused by the eddy current effect; the real-time thickness of the polishing pad is determined according to the obtained first signal value and the thickness-signal value relationship, wherein the thickness-signal value relationship represents the the relationship between the thickness of the polishing pad and the signal value; and modify the measured thickness of the metal film of the object polished by the chemical mechanical polishing device according to the determined real-time thickness to determine the corrected thickness. In this way, the precision and reliability of polishing performed by the chemical mechanical polishing equipment can be improved.

In some implementations, the method further includes adjusting a control parameter of the chemical mechanical polishing apparatus based on the determined corrected thickness until the corrected thickness is within a threshold range. In this way, the precision of the chemical mechanical polishing apparatus can be further improved by the closed control method.

In some implementations, the method further includes the step of determining the measured thickness of the metal film: acquiring a second signal value in real time during the operation of the chemical mechanical polishing apparatus, wherein the second signal value is the metal film passing through The sensor is caused by an eddy current effect; and the measured thickness of the metal film is determined based on the second signal value.

In some implementations, the method further includes the step of determining the thickness-signal value relationship: during operation of the chemical mechanical polishing apparatus using a plurality of polishing pads of different thicknesses, resulting corresponding plurality of signal values; and determining the thickness-signal value relationship based on the plurality of signal values and corresponding thicknesses of the plurality of polishing pads. In this way, it is possible to avoid having to correct the sensor every time the polishing pad, polishing solution, etc. is changed, thereby improving the ease of use and reliability of the chemical mechanical polishing apparatus.

It should be understood that what is described in the Summary of the Invention is not intended to identify key or important features of the disclosure, nor is it intended to limit the scope of the disclosure. Other features of the present disclosure will become easily understood through the following description.

Description of drawings

The above and other objects, features and advantages of embodiments of the present disclosure will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the present disclosure are shown by way of illustration and not limitation.

Fig. 1 shows the simplified three-dimensional schematic view of the chemical mechanical polishing equipment in the traditional scheme;

Fig. 2 shows the simplified schematic side view of the chemical mechanical polishing equipment in the traditional scheme;

Fig. 3 shows the relationship between the sensor signal value and metal film thickness corresponding to different polishing pad thicknesses;

Figure 4 shows a simplified schematic side view of a chemical mechanical polishing apparatus according to an embodiment of the disclosure;

5 shows a top view of a polishing head of a chemical mechanical polishing apparatus according to an embodiment of the present disclosure;

FIG. 6 shows a schematic side-view cross-sectional view of a polishing head of a chemical mechanical polishing device according to an embodiment of the present disclosure;

7 shows a schematic side view of a partial cross-sectional view of a polishing head of a chemical mechanical polishing device according to an embodiment of the present disclosure; and

FIG. 8 shows a flowchart of a method of controlling a chemical mechanical polishing device according to an embodiment of the present disclosure.

Throughout the drawings, the same or similar reference numerals are used to designate the same or similar components.

Detailed ways

Hereinafter, the principle and spirit of the present disclosure will be described with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that these specific embodiments are described only to enable those skilled in the art to better understand and realize the present disclosure, rather than to limit the scope of the present disclosure in any way. In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

As used herein, the term "comprising" and its analogs should be interpreted as an open inclusion, ie "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be read as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects, and are used only to distinguish the referred objects without implying a specific spatial order, temporal order, important sexual order, and so on. In some embodiments, values, processes, selected items, determined items, equipment, devices, means, components, components, etc. are referred to as "best", "lowest", "highest", "minimum" , "Maximum", and so on. It should be understood that such a description is intended to indicate that a selection may be made among many available functional options, and that such selection need not be better, lower, higher, smaller, lower, or better than the other selections in another or all respects. large or otherwise preferred. As used herein, the term "determining" can encompass a wide variety of actions. For example, "determining" may include computing, calculating, processing, deriving, investigating, looking up (eg, in a table, database, or another data structure), ascertaining, and the like. Also, "determining" may include receiving (eg, receiving information), accessing (eg, accessing data in a memory), and the like. Furthermore, "determining" may include resolving, selecting, selecting, establishing, and the like.

As used herein, the term "circuitry" refers to one or more of: (a) hardware circuit implementations only (such as analog and/or digital circuit implementations only); and (b) a combination of hardware circuits and software, Such as (if applicable): (i) combinations of analog and/or digital hardware circuits and software/firmware, and (ii) any part of a hardware processor and software (including etc., digital signal processors, software, and memory that perform various functions); and (c) hardware circuits and/or processors, such as microprocessors or parts of microprocessors, that require software (e.g., firmware) to operate , but can be without software when it is not required for operation. The definition of electrical circuit applies to all uses of this term in this application, including in the claims. As a further example, the term 'circuitry' as used herein also covers an implementation of merely a hardware circuit or processor (or multiple processors), or a portion thereof, or accompanying software or firmware. For example, the term "circuitry" also covers baseband integrated circuits or processor integrated circuits, network equipment, terminal equipment, or similar integrated circuits in other devices, if applicable to a particular claim element.

Multilayer metal technology is an integrated circuit manufacturing technology that has appeared as early as the 1970s. Multilayer metal technology enables the interconnection of millions of transistors and supporting elements within a single integrated circuit. Moreover, this technology effectively utilizes the vertical space of the chip, making it possible to further increase the integration density of the device. But the larger surface relief that comes with it becomes a disadvantage for submicron patterning, because more layers are added to make the surface of the silicon wafer uneven. Uneven wafer surface topography is not ideal, and it leads to several other problems, the most serious of which is the inability to pattern on the wafer surface because it is limited by the focal depth of the stepper lens used in optical lithography. In order to solve these problems, chemical mechanical polishing (Chemical Mechanical Polishing, CMP) technology was proposed. As a global flat sum method, CMP technology is the key technology to realize multi-layer integration, and currently plays an indispensable role in the field of integrated circuit manufacturing. It can be said that without CMP, it is basically impossible to produce VLSI chips.

From a macroscopic point of view, chemical mechanical polishing technology is a combined technology of mechanical grinding and chemical etching. The basic process is: pressing the rotating polished object W (such as a silicon wafer or wafer) on the polishing pad 201 rotating in the same direction, The polishing liquid flows continuously between the silicon wafer and the polishing pad 201 . The polishing head 102 and the polishing platform 101 run in reverse at high speed, the reaction products on the surface of the polished silicon wafer are continuously stripped, new polishing liquid is added, and the reaction products are taken away with the polishing liquid. The newly exposed silicon wafer plane undergoes a chemical reaction again, and the product is peeled off again and goes round and round. With the help of the organic combination between the polishing effect of nanoparticles and the corrosion effect of the oxidant, the metal film on the object W to be polished is polished to a predetermined level. thickness of. In order to obtain a high-precision polished workpiece, it is usually necessary to clean and inspect the polished object W after the polishing process to check whether the precision requirements are met, so as to guide the subsequent process.

The equipment and consumables used in CMP technology include: chemical mechanical polishing equipment 100, polishing fluid 1061, polishing pad 201, cleaning equipment, polishing endpoint detection and process control equipment, polishing fluid distribution system, waste treatment and testing equipment, etc. 1 and 2 show a schematic perspective view and a side view of a chemical mechanical polishing apparatus 100 in a pre-polishing stage. The chemical mechanical polishing equipment 100 is referred to as a polishing machine for short, and generally includes the aforementioned polishing platform 101 and the polishing head 102 , and the consumables used are the aforementioned polishing liquid 1061 and the polishing pad 201 . During polishing, an object W to be polished such as a silicon wafer is placed on the polishing head 102 and faces the polishing pad 201 placed on the polishing platform 101 . Polishing is accomplished by relative motion between the silicon wafer and the polishing pad 201 . Most chemical mechanical polishing equipment uses rotary or orbital motion.

The polishing head 102 is also called a grinding head, which is a tool for keeping the silicon wafer above the polishing pad 201 on the surface of the polishing platform 101 . When polishing a silicon wafer, an axially downward force is applied toward the polishing platform 101 , as shown in FIGS. 1 and 2 . The downward force of the polishing pad 201 and the rotational motion of the polishing platform 101 affect the uniformity of polishing. During the polishing process, the polishing head 102 often uses a vacuum to hold the silicon wafer. In some polishing processes, the vacuum may also be turned off or otherwise a positive pressure applied. In some polishing heads 102, a multi-layer liner is installed between the silicon wafer and the polishing head 102 to accommodate the backside of the silicon wafer and compensate for the unevenness caused by the backside of the silicon wafer and particles. Some liners are sponge-like with small holes for ventilation.

Polishing fluid 1061, also known as abrasive, is a mixture of fine abrasive particles and chemicals, and is used in CMP to grind away special materials on the surface of silicon wafers. It is an important consumable in CMP because it contains the chemical components and polishing particles required for planarization. The polishing liquid 1061 is sometimes ejected through the polishing liquid nozzle 106 . Precise mixing of the slurry 1061 and batch-to-batch consistency are critical to achieving wafer-to-wafer, batch-to-lot, and repeatability. During the polishing process, it is also important that the polishing liquid 1061 is evenly distributed on the surface of the silicon wafer. The quality of the polishing solution 1061 is a factor in avoiding surface scratches during polishing.

The polishing pad 201 is adhered to the upper surface of the polishing platform 101, which is an important component in determining the polishing rate and planarization ability in CMP. In order to keep the polishing liquid 1061, the polishing pad 201 is usually made of polyurethane, because the polyurethane has mechanical properties and porous water absorption properties like a sponge, and the small holes in the polishing pad 201 can help transmit abrasives and improve polishing. Uniformity. After polishing some silicon wafers, the thickness of the polishing pad 201 will gradually become thinner, and the surface will become flat and smooth, reaching a state called a smooth surface. Significantly reduces polishing rate.

The polishing pad 201 requires periodic conditioning to reduce the effects of the smooth surface. The goal of conditioning is to achieve consistent polishing performance over the life of polishing pad 201 . The polishing pad 201 is conditioned by some technique, such as mechanical rubbing or spraying with deionized water, to regenerate the rough surface after conditioning. Another method is to use a trimmer 105 as shown in FIGS. 1 and 2 . The dresser 105 is also called a diamond wheel, which rotates and contacts the surface of the polishing pad 201 . The conditioning process removes material from the surface of the polishing pad 201 and thus is a factor that has a significant impact on the life of the polishing pad 201 . The CMP apparatus shown in Fig. 1 can carry out in-situ (real-time) dressing to the polishing pad 201, that is, when the dressing wheel is done dressing at one position of the polishing pad 201, the silicon wafer is carried out at another position of the polishing pad 201. polishing. Yet another conditioning process is referred to as off-site polishing pad 201 conditioning. In off-site polishing pad 201 conditioning, conditioning is not performed during the polishing process, but only after a certain number of silicon wafers have been polished. The following will mainly take the CMP device shown in FIG. 1 as an example to describe the concept of the present disclosure. It should be understood that other types of CMP devices are similar, and will not be described in detail below.

After polishing a predetermined number of silicon wafers or when parameters such as the thickness of the polishing pad 201 indicate that the polishing pad 201 can no longer be used, the polishing pad 201 needs to be replaced. The replaced and reconditioned polishing pad 201 has a thickness difference from the original polishing pad 201 , which is an important factor affecting the quality of the polishing object W. In order to determine whether the metal film of the polishing object W has been polished to the correct thickness, general CMP equipment provides the Metal Endpoint Detection (M-EPD) function, which is used to detect the metal film on the silicon wafer during the CMP process in real time. subsequent state of change. The endpoint detection and the control of the polishing head 102 form a closed-loop control to more accurately and effectively realize the planarization of the silicon wafer.

A sensor 104 for the M-EPD function is coupled to the polishing platform 101 , for example, the sensor 104 is typically integrated on the lower surface of the polishing platform 101 as shown in FIG. 2 . The lower surface here refers to the surface of the polishing platform 101 axially opposite to the surface carrying the polishing pad 201 . Such sensors 104 are usually provided with measuring coils to detect the thickness of the metal film on the silicon wafer according to the eddy current principle. Specifically, because the alternating magnetic field generated by the measuring coil generates eddy currents on the metal film of the silicon wafer, the impedance of the measuring coil changes. By measuring the signal generated by the corresponding impedance change (such as the current signal, etc.), the thickness of the corresponding metal film on the surface of the silicon wafer can be calculated.

In practical applications, changes in the distance between the sensor 104 of the M-EPD and the silicon wafer will affect the detection results. That is to say, in the case that the thickness of the sensor 104 and the metal film to be measured are both constant, the change of the distance between the two will cause the sensor 104 to sense a difference in the magnitude of the signal. The change in the distance between the sensor 104 and the metal film under test is mainly caused by the change in the thickness of the polishing pad 201 . That is to say, the signal value sensed by the sensor 104 is not only related to the thickness of the metal film, but also related to the thickness of the polishing pad 201 . Fig. 3 shows the relationship between the metal film thickness corresponding to the thickness of various polishing pads 201 and the signal value of the sensor 104, wherein the abscissa shows the thickness of the metal film, and the ordinate shows the sensor 104 signal value. As shown in Figure 3, under the situation that polishing pad 201 thickness is different, for example, when polishing pad 201 thickness is respectively under the situation of 3.0mm, 3.3mm and 3.5mm, the relationship between metal film thickness and sensor 104 signal value is also There are differences. Therefore, when determining the thickness of the metal film through the signal value of the sensor 104, the thickness of the polishing pad 201 is a key influencing factor.

As mentioned above, since the polishing pad 201 itself is a consumable, as the number of polished silicon wafers increases, the thickness of the polishing pad 201 gradually becomes thinner, for example, from 3.5mm to 3.0mm. At the same time, the thickness of the polishing pad 201 is also affected by the water content on the polishing pad 201 . Therefore, in the process of determining the thickness of the metal film in real time, if the variation of the thickness of the polishing pad 201 is not considered, the obtained thickness of the metal film is also inaccurate.

In the traditional solution, in order to solve the above-mentioned problem, the measures taken roughly estimate the polishing pad 201 after polishing the predetermined number of silicon wafers by obtaining the initial thickness of the polishing pad 201 and the relationship between the thickness and the number of polished silicon wafers. thickness of. The estimated thickness is fed back to the final detection module, and finally the detection result of the metal film is corrected by the estimated thickness. However, because the initial thickness of each polishing pad 201 has a certain error, and there may be differences in each polishing pad 201 used to polish the silicon wafer, the thickness of the estimated polishing pad 201 is not accurate, that is, between the silicon wafer and the sensor 104 There is also a deviation in the distance, which leads to inaccurate thickness of the metal film obtained in the final inspection.

In addition, due to the difference in the trimming effect of the trimmer 105, the thickness of a polishing pad 201 is not uniform, resulting in a change in the distance between the silicon wafer and the sensor 104, and ultimately affecting the accuracy of metal film thickness detection. . In addition, this method of estimating the thickness of the polishing pad 201 requires re-calibration of the sensor 104 after each change in the polishing pad 201, polishing liquid 1061, dresser 105, and ionized water flow rate, etc., which seriously affects the accuracy of detection. and ease of use of CMP equipment.

In view of the above-mentioned problems and other potential problems existing in conventional solutions, embodiments of the present disclosure provide a chemical mechanical polishing device 100 and a control method thereof. Through the chemical mechanical polishing apparatus 100 and the corresponding control method, the thickness of the polishing pad 201 can be accurately determined, and thus the thickness of the metal film can be detected more accurately.

FIG. 4 shows a schematic side view of a chemical mechanical polishing apparatus 100 according to an embodiment of the present disclosure. As shown in FIG. 4 , in general, a chemical mechanical polishing apparatus 100 according to an embodiment of the present disclosure includes a polishing platform 101 , a polishing head 102 , a sensor 104 and a metal detection element 103 . The polishing platform 101 is suitable for carrying the polishing pad 201 and driving the polishing pad 201 to move. FIG. 4 shows that the polishing platform 101 supports the polishing pad 201 to rotate around its main axis. It should be understood that this is only illustrative and not intended to limit the protection scope of the present disclosure. Any other suitable movement is also possible. For example, in some embodiments, some polishing platforms 101 can also carry the polishing pad 201 to perform linear reciprocating motion or any other suitable form of motion. Hereinafter, the concept of the present disclosure will be described mainly by taking the polishing platform 101 shown in FIG. 4 carrying the polishing pad 201 to rotate as an example. It should be understood that other motion modes are also similar, and will not be described in detail below.

The polishing head 102 is used to drive the polishing object W such as a silicon wafer to rotate around the central axis 1022 of the polishing head 102 between the polishing head 102 and the polishing pad 201 . During this process, the polishing liquid 1061 applied on the polishing pad 201 through an appropriate nozzle 106 flows continuously between the polishing object W and the polishing pad 201 . The polishing head 102 and the polishing platform 101 run in reverse at a high speed, the reaction products on the surface of the object W to be polished are continuously stripped, new polishing liquid 1061 is added, and the reaction products are taken away with the polishing liquid 1061 . The newly exposed plane of the polished object W undergoes a chemical reaction again, and the product is stripped off and the cycle is repeated. With the help of the organic combination between the grinding effect of the nanoparticles and the corrosion effect of the oxidant, the metal film of the polished object W can be polished. reach the desired thickness.

The sensor 104 may be the aforementioned eddy current sensor 104 for endpoint detection, which is usually arranged on the lower surface of the polishing platform 101 . When the metal film of the object W to be polished passes the sensor 104, the alternating magnetic field generated by the measuring coil in the sensor 104 generates an eddy current on the metal film of the silicon wafer, which will cause the impedance of the measuring coil to change. The "passing" here refers to the process in which the metal film on the object W and the sensor 104 overlap at least partially in the axial direction during the movement of the object W to be polished. By measuring the signal value (for example, the current value or the impedance value) corresponding to the corresponding impedance change, the thickness of the corresponding metal thin film of the polishing object W can be calculated. It is also shown in FIG. 4 that in some embodiments, the chemical mechanical polishing apparatus 100 according to an embodiment of the present disclosure includes a dresser 105 capable of rotating within a range of motion to perform in-line dressing of the polishing pad 201 .

Unlike conventional chemical mechanical polishing equipment, the chemical mechanical polishing equipment 100 according to an embodiment of the present disclosure includes a metal detection part 103 . The metal detector 103 is arranged such that the axial position of the metal detector relative to the polishing head 102 remains fixed. Here, “the axial position remains fixed” means that for the polishing head 102 , the axial position of the metal detection element 103 is fixed. This can be achieved, for example, by fixing the metal detection element 103 on the polishing head 102 . "The axial position remains fixed" also means that the position of the metal detection member 103 relative to the polishing head 102 in other directions (such as the radial direction) can be arbitrary, for example, it can be changed or unchanged. For example, alternatively or additionally, in some embodiments, the metal detector 103 may also be disposed on the trimmer 105 . When it is fixedly arranged on the trimmer 105, in the axial direction, the relative position between the metal detection piece 103 and the polishing head 102 is basically fixed, and the relative position in the radial direction will change, but it also satisfies "Axial position remains fixed" condition. That is to say, as long as the condition of "the axial position remains fixed", the metal detecting element 103 can be arranged in any suitable position, for example, the metal detecting element 103 is fixedly attached to the polishing head 102 or The periphery of at least one of the trimmers 105 . Hereinafter, the concept according to the present disclosure will be described by taking the metal detection piece 103 fixedly attached to the polishing head 102 shown in FIG. 4 as an example. It should be understood that other suitable arrangements are also possible, which will not be described in detail below.

By setting the metal detection part 103, when the metal detection part 103 passes the sensor 104, similar to the case of the metal film, the impedance in the detection coil of the sensor 104 will change due to the eddy current effect, which will be reflected as the change of the detected signal value. Since the axial position of the metal detection piece 103 relative to the polishing head 102 is fixed, and the thickness and shape of the metal detection piece 103 will not change, the signal value corresponding to the metal detection piece 103 is basically only affected by the thickness of the polishing pad 201 . The thickness of the polishing pad 201 can be determined in real time only by obtaining the relationship between the thickness of the polishing pad and the signal value. Because it has been mentioned above that when measuring the thickness of the metal film, the signal value caused by the metal film in the sensor is not only affected by the thickness of the metal film itself, but also by the thickness of the polishing pad 201 (actually between the metal film and the detection coil of the sensor). distance), therefore, by determining the thickness of the polishing pad 201 in real time, the thickness of the metal film can be corrected through the obtained thickness of the polishing pad 201 . That is to say, after the thickness of the polishing pad 201 can be accurately determined, the thickness of the metal film can be accurately and accurately obtained. In addition, the thickness of the obtained metal film is further used for closed-loop control, so that the flattening uniformity and precision of the silicon wafer can be significantly improved.

In addition, the metal detecting element 103 can be arranged on the periphery of at least one of the polishing head 102 or the dresser 105 in any appropriate manner, and this solution does not need to add additional sensors, and the existing sensors on the chemical mechanical polishing equipment 100 can be used directly. Can achieve the above functions. In other words, the addition of the metal detection element 103 does not require major structural adjustments to the original chemical mechanical polishing equipment 100, and can significantly improve the planarization uniformity and precision of the silicon wafer at low cost.

Since the polishing head 102 is constantly rotating and the polishing platform 101 is also constantly rotating, the path and position of the metal detection piece 103 may be different each time it passes the sensor 104 . Therefore, in some embodiments, in order to ensure that when the polishing head 102 passes the sensor 104, the metal detection part 103 can produce an effective and consistent eddy current effect with the detection coil of the sensor 104, in some embodiments, the metal detection part 103 can be in the shape of a ring , as shown in Figure 5. FIG. 5 shows a schematic top view of the polishing head 102 , which shows that the metal detection element 103 is fixedly arranged on the outer periphery of the polishing head 102 . In this way, continuous real-time detection of the thickness of the polishing pad 201 can be ensured, thereby further improving the flattening uniformity and precision of the object W to be polished.

Of course, it should be understood that the embodiment in which the metal detection element 103 has the annular shape shown in FIG. The thickness of pad 201, any other suitable shape or configuration is also possible. For example, in some alternative embodiments, the metal detection element 103 may also adopt other suitable closed structures, such as polygons.

In some embodiments, in order to avoid possible corrosion of the metal detection element 103 by the polishing liquid 1061 , the chemical mechanical polishing device 100 may further include a receiving portion 1025 . The receiving portion 1024 may be fixedly attached to the outer periphery of at least one of the polishing head 102 or the dresser 105 to hermetically accommodate the metal detection piece 103 , as shown in FIG. 6 . FIG. 6 shows a schematic cross-sectional side view of a polishing head 102 according to an embodiment of the disclosure. As shown in FIG. 6 , the polishing head 102 includes a housing 1021 , a central shaft 1022 , a metal part 1023 and a non-metal part 1024 . An object W to be polished such as a silicon wafer is held in the polishing head 102 . In some embodiments, the receiver 1025 is fixedly attached to the periphery of the polishing head 102 by suitable means.

In some embodiments, the receiving portion 1025 is made of a non-metallic material such as plastic. The metal detection piece 103 can be integrally molded in the accommodating portion 1025 during the formation of the accommodating portion 1025 , so as to effectively prevent the metal detecting piece 103 from being corroded by the polishing solution 1061 . In some embodiments, the receiving portion 1025 may also adopt a split structure to facilitate the assembly and replacement of the metal detection element 103 . Specifically, the receiving part 1025 may include an opening and a cover 1026, as shown in FIG. 7 . The metal detector 103 can be put into the receiving part 1025 through the opening, and the cover 1026 is used to seal the opening. In this way, the metal detection element 103 can be protected from the corrosion of the polishing liquid 1061 and can be easily assembled and replaced.

The receiving portion 1025 may be disposed on the periphery of at least one of the polishing head 102 or the dresser 105 by any suitable means. As shown in FIG. 7 , in some embodiments, the accommodating portion 1025 may be arranged on the outer periphery of the polishing head 102 by snap-fit connection. For example, in some embodiments, a predetermined number of engaging portions 1027 are arranged at intervals on the outer circumference of the housing 1021 of the polishing head 102 . Correspondingly, the inner surface of the receiving portion 1025 is provided with a locking groove capable of being coupled to the locking portion 1027 . By accommodating the engaging portion 1027 in the engaging groove, the accommodating portion 1025 can be easily fixed to the housing 1021 of the polishing head 102 . Of course, it should be understood that this is only illustrative and not intended to limit the protection scope of the present disclosure. Any other suitable approach or structure is also possible. For example, in some alternative embodiments, the accommodating portion 1025 may also be fixedly arranged on the outer periphery of at least one of the polishing head 102 or the dresser 105 by means of adhesion, interference fit and the like.

Of course, it should be understood that the embodiment in which the metal detection element 103 is arranged on at least one of the polishing head 102 or the dresser 105 through the receiving portion is only illustrative, and is not intended to limit the protection scope of the present disclosure. Suitable arrangements are also possible. For example, in some alternative embodiments, the metal detection element 103 may also be integrally integrated in the housing 1021 of the polishing head 102 or in any other suitable position in an appropriate manner. In this way, precise control of the metal film thickness of the object W to be polished can be realized without changing the appearance of the original chemical mechanical polishing apparatus 100 .

In some embodiments, the chemical mechanical polishing apparatus 100 may further include a processing unit (not shown). The processing unit can determine the thickness of the polishing pad 201 according to the signal value obtained by the sensor 104 , and then correct the thickness of the metal film according to the thickness to make the obtained thickness of the metal film more accurate. The processing unit may be a general control unit of the chemical mechanical polishing device 100 for controlling various parameters of the chemical mechanical polishing device 100 and the like. In some alternative embodiments, the processing unit may also be other processing units independent of the chemical mechanical polishing apparatus 100 . The independent processing unit can communicate with the control unit of the chemical mechanical polishing device 100 to exchange data, thereby further improving the real-time performance of determining the thickness of the polishing pad 201 and reducing the burden on the control unit, so as to improve the stability of the chemical mechanical polishing device 100 sex.

According to another aspect of the embodiments of the present disclosure, a method for controlling the aforementioned chemical mechanical polishing device 100 is also provided. Fig. 8 shows a flowchart of the method. The method can be executed by the aforementioned processing unit to control the chemical mechanical polishing apparatus 100 accordingly. As shown in FIG. 8 , at 610 , the processing unit acquires a first signal value from the sensor 104 in real time during operation of the chemical mechanical polishing apparatus 100 . The first signal value is caused by the eddy current effect when the metal detection element 103 passes the sensor 104 of the chemical mechanical polishing device 100 , and can be acquired by the sensor 104 . The first signal value may be a current value or an impedance value or the like. After the first signal value is obtained, at 620, the real-time thickness of the polishing pad 201 is determined according to the obtained first signal value and the thickness-signal value relationship representing the relationship between the thickness of the polishing pad 201 and the signal value.

The thickness-signal value relationship is a functional relationship between the signal value and the thickness of the polishing pad 201, which in some embodiments can be determined by the following procedure. Specifically, the corresponding multiple signal values caused by the eddy current effect when the metal detector 103 passes the sensor 104 of the chemical mechanical polishing equipment 100 during the operation of the chemical mechanical polishing equipment 100 using multiple polishing pads 201 of different thicknesses. The thickness-signal value relationship is determined by performing a primary or quadratic fit to the thickness and signal values of a plurality of polishing pads 201 . This process generally only needs to be performed when the chemical mechanical polishing device 100 is initially set up, and the determined thickness-signal value relationship can be stored in a memory for subsequent use in determining the real-time thickness of the polishing pad 201 . That is to say, according to the chemical mechanical polishing equipment 100 of the embodiment of the present disclosure, the sensor 104 does not need to be recalibrated when the polishing pad 201, the polishing liquid 1061, etc. change, but only needs to be set once at the beginning. This improves the usability of the chemical mechanical polishing apparatus 100 .

At 630, the measured thickness of the metal film of the object W to be polished is corrected according to the determined real-time thickness mentioned above to obtain a corrected thickness. The value of the measured thickness mentioned above is affected by the thickness of the metal film itself and the thickness of the polishing pad 201 (ie, the distance between the metal film and the detection coil of the sensor). Through the obtained accurate real-time thickness of the polishing pad 201 , the measured thickness can be effectively corrected, so as to obtain an accurate and precise corrected thickness. This corrected thickness can then be used for closed loop control. For example, in some embodiments, the processing unit may further adjust various control parameters of the chemical mechanical polishing device 100 according to the corrected thickness until the obtained corrected thickness is within a predetermined threshold range, which means that the object W to be polished has been accurately polished. ground flattening.

In some embodiments, the measured thickness of the metal film may be obtained in the following manner, that is, the processing unit acquires the second signal value in real time during the operation of the chemical mechanical polishing apparatus 100 . The second signal value is caused by the eddy current effect when the metal film passes the sensor 104 . Similar to the first signal value, the second signal value may also be a current value or an impedance value or the like. Next, the processing unit determines the measured thickness of the metal film according to the second signal value. The determined measured thickness can be corrected by the determined real-time thickness of the polishing pad 201 , so as to polish the object W to be polished more accurately.

In addition, while the above steps are depicted in a particular order, this should not be understood as requiring that the steps be performed in the particular order shown, or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking or parallel processing can be beneficial. Likewise, while the above discussion contains certain specific implementation details, these should not be construed as limitations on the scope of any invention or claims, but rather as a description of particular embodiments that may be directed to particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A chemical mechanical polishing device, comprising:

The polishing platform is suitable for carrying the polishing pad and driving the polishing pad to move;

a polishing head, adapted to drive the object to be polished to rotate around the central axis of the polishing head between the polishing head and the polishing pad;

a metal detector arranged such that the axial position of the metal detector relative to the polishing head remains fixed; and

A sensor is coupled to the polishing platform and is adapted to acquire at least a signal value of the metal detecting element caused by an eddy current effect on the sensor.
The chemical mechanical polishing device according to claim 1, further comprising:

A dresser adapted to rotatably move within a predetermined range of the polishing pad to dress the polishing pad.
The chemical mechanical polishing apparatus according to claim 2, wherein the metal detection member is fixedly attached to an outer periphery of at least one of the polishing head or the dresser.
The chemical mechanical polishing device according to any one of claims 1-3, wherein the metal detection element is in the shape of a ring.
The chemical mechanical polishing device according to claim 2 or 3, further comprising:

A receiving portion is fixedly attached to an outer periphery of at least one of the polishing head or the dresser and is adapted to hermetically accommodate the metal detector.
The chemical mechanical polishing apparatus according to claim 5, wherein the receiving portion comprises:

an opening adapted to allow the metal detection piece to enter the receiving portion; and

A cover adapted to seal the opening.
The chemical mechanical polishing apparatus according to any one of claims 1-6, further comprising:

A processing unit configured to determine the thickness of the polishing pad based at least on the signal value.
The chemical mechanical polishing apparatus according to any one of claims 1-7, wherein the sensor is arranged on a lower surface of the polishing platform opposite to a surface carrying the polishing pad.
A method of controlling chemical mechanical polishing equipment, comprising:

A first signal value is obtained from a sensor in real time during operation of the chemical mechanical polishing apparatus, wherein the first signal value is a metal detection element arranged to remain fixed relative to the axial position of the polishing head in the chemical The sensor of mechanical polishing equipment is caused by the eddy current effect;

determining the real-time thickness of the polishing pad according to the obtained first signal value and a thickness-signal value relationship, wherein the thickness-signal value relationship represents the relationship between the thickness of the polishing pad and the signal value; and

The measured thickness of the metal film of the object polished by the chemical mechanical polishing device is modified according to the determined real-time thickness to determine a corrected thickness.
The method of claim 9, further comprising:

Adjusting a control parameter of the chemical mechanical polishing device according to the determined corrected thickness until the corrected thickness is within a threshold range.
A method according to claim 9 or 10, further comprising the step of determining said measured thickness of said metal film:

acquiring a second signal value in real time during operation of the chemical mechanical polishing apparatus, wherein the second signal value is caused by an eddy current effect when the metal film passes the sensor; and

The measured thickness of the metal film is determined based on the second signal value.
A method according to any one of claims 9-11, further comprising the step of determining said thickness-signal value relationship:

acquiring a corresponding plurality of signal values caused by eddy current effects as a metal detector passes over the sensor during operation of the chemical mechanical polishing apparatus using a plurality of polishing pads of different thicknesses; and

The thickness-signal value relationship is determined based on the plurality of signal values and corresponding thicknesses of the plurality of polishing pads.