KR101459269B1 - Chemical mechanical polishing method and apparatus using same - Google Patents

Abstract

The present invention relates to a chemical mechanical polishing method and a chemical mechanical polishing system using the same, and more particularly, to a chemical mechanical polishing method and polishing method for polishing a wafer by polishing a surface of the wafer while pressing the wafer against the polishing pad; An abrasive layer thickness sensing step of sensing whether an abrasive layer thickness of the wafer reaches a first predetermined value; A polishing pad height measuring step of measuring a height deviation in the radial direction of the polishing pad in a state in which the thickness of the polishing layer of the wafer has reached the first value; Modifying the polishing pad with a varying pressing force based on a height deviation of the polishing pad obtained in the polishing pad height measuring step while continuing the polishing step for a first predetermined time after the wafer thickness sensing step is performed, A finish polishing step of finishing the polishing of the wafer; So that even if there is a deviation in the polishing surface of the wafer at the beginning of the finishing step of the chemical mechanical polishing process, the final state of the wafer polishing surface after the CMP process is compensated in the finishing polishing step, The present invention also provides a chemical mechanical polishing method capable of forming a polishing layer.

Description

Technical Field [0001] The present invention relates to a chemical mechanical polishing method and a chemical mechanical polishing system using the same,

The present invention relates to a chemical mechanical polishing method and a chemical mechanical polishing system using the same. More particularly, the present invention relates to a chemical mechanical polishing method and a chemical mechanical polishing system using the chemical mechanical polishing method. And more particularly, to a chemical mechanical polishing method and a chemical mechanical polishing system using the same.

The chemical mechanical polishing (CMP) process is widely used for planarization to remove a height difference between a cell region and a peripheral circuit region due to deviation of a wafer surface generated by repeatedly performing masking, etching, and wiring processes during a semiconductor device manufacturing process, Polishing the surface of the wafer in order to improve the surface roughness of the wafer due to contact / wiring film separation and highly integrated elements.

The CMP process is performed by the chemical mechanical polishing apparatus 1 shown in Figs. 1A and 1B. The wafer W is placed on the bottom surface of the carrier head 20, and the polishing surface of the wafer W is rotated And the slurry is supplied to the central portion of the polishing pad 11 through the supply port 32 of the slurry supply unit 30. [ The wafer W is mechanically polished by the polishing pad 11 rotating with the polishing table 10 while being pressed against the carrier head 20 which rotates 20d and at the same time, (W) to perform chemical polishing with the slurry.

The slurry supplied to the central portion of the polishing pad 11 is smoothly introduced into the wafer W and the conditioning disk of the conditioner 40 is moved in a swiveling motion so that the mechanical polishing of the wafer W by the polishing pad 11 is smoothly performed. The surface of the polishing pad 11 is maintained in a constant state by rotating the polishing pad 11 while pressing the polishing pad 11 with a predetermined pressing force while rotating the polishing pad 11d.

2, the carrier head 20 includes a base 22, which is integrally rotated by external driving means, and a membrane 21 of a flexible material is coupled to the base 22 through a coupling member 222 do. A plurality of ring-shaped flips 211 are formed on the membrane 21 so that the flip 211 is coupled to the base 22 and a plurality of pressure chambers 21 are formed between the base 22 and the membrane 21. [ (C1, ..., C5) are formed. In some cases, the pressure chamber CO may be formed through the base 22 and the membrane 21 to directly control the pressure.

During the chemical mechanical polishing process, the wafer W is pressed through the membrane 21 by the pressure of the pressure chambers C0, C1, ..., C5 of the independently controlled carrier head 20, And is polished by friction with the pad 11. At this time, the polishing surface of the wafer W corresponding to the regions of the pressure chambers C0, ..., C5 is also deformed due to the centrifugal force due to the rotation of the wafer W and the fine height deviation of the polishing pad 11. [ There arises a problem that a difference in polishing thickness is caused for each of the regions A0, A1, ..., A5 as shown in Fig.

Therefore, there is a desperate need to solve the problem that the variation in polishing thickness occurs in the area of the wafer during the chemical mechanical polishing process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical background, and it is an object of the present invention to solve the difference in polishing thickness of a wafer on which a chemical mechanical polishing process is performed, thereby realizing a uniform polishing as a whole.

Particularly, the present invention aims to more reliably prevent occurrence of a difference in polishing thickness in each region when the wafer is pressed while pressing the wafer in different areas with different pressing forces.

It is another object of the present invention to accurately polish the wafer by a simple control method while allowing the wafer to be polished to a uniform degree in each region.

In order to achieve the above object, the present invention provides a polishing method comprising: a polishing step of polishing a polishing surface of a wafer while pressing the wafer against a polishing pad; An abrasive layer thickness sensing step of sensing whether an abrasive layer thickness of the wafer reaches a first predetermined value; A polishing pad height measuring step of measuring a height deviation in the radial direction of the polishing pad in a state in which the thickness of the polishing layer of the wafer has reached the first value; Modifying the polishing pad with a varying pressing force based on a height deviation of the polishing pad obtained in the polishing pad height measuring step while continuing the polishing step for a first predetermined time after the wafer thickness sensing step is performed, A finish polishing step of finishing the polishing of the wafer; The present invention also provides a chemical mechanical polishing method comprising the steps of:

This is because, when the polishing surface of the wafer pressed by the wafer carrier during the chemical mechanical polishing process is unevenly polished, the surface of the polishing pad becomes uneven due to a nonuniform polishing surface condition, The pressing force for modifying the polishing pad is adjusted based on the height deviation of the measured polishing pad on the basis of the time when the polishing surface of the wafer is polished to some extent and the finish polishing process is imminent (when the polishing layer thickness reaches the first value) To uniformly adjust the uneven polishing surface of the wafer during the polishing finish step of the wafer by the deviation of the surface height of the polishing pad.

In other words, in the region where the polishing of the wafer is relatively less, the height of the polishing pad is relatively low and the height of the polishing pad is relatively higher in the region where the polishing of the wafer is relatively more, The pressing force of the conditioner is increased for the region where the surface height of the polishing pad is relatively high and the pressing force of the conditioner is set for the region where the surface height of the polishing pad is relatively low in the state (when the polishing layer thickness reaches the first value) The final state of the wafer polishing surface after completion of the CMP process is compensated in the finish polishing process even if there is a deviation in the polishing surface of the wafer in the state where the polishing layer thickness has reached the first value, .

As described above, by uniformly adjusting the polishing surface of the wafer in the finish polishing step of the chemical mechanical polishing process uniformly by the simple control method of the open loop type, deviation of the polishing surface of the wafer is minimized and the polishing surface becomes uniform It is possible to obtain an advantageous effect that the chemical mechanical polishing process can be completed.

At this time, the first value may be set to a value in which the thickness of the abrasive layer of the wafer is thicker by 200 ANGSTROM to 2000 ANGSTROM than the target thickness. This means that polishing is carried out corresponding to 70% to 99% of the total polishing thickness of the wafer to be polished by the chemical mechanical polishing process, depending on the thickness of the layer to be deposited, do.

On the other hand, when a metal layer such as tungsten or copper is laminated on the wafer and the metal layer is polished by the CMP process, in a state in which the thickness of the metal layer is sufficiently left to be about 1000 to 2000 Angstroms from the target thickness, The output of the reflected light of the light to be irradiated on the surface changes rapidly. Therefore, when the metal layer is polished, the first value is the thickness of the polishing layer at the instant when the output of the reflected light reflected from the polishing surface of the wafer is abruptly changed, or the thickness of the polishing layer It is preferable to be determined.

On the other hand, when a light transmitting layer such as an oxide layer is laminated on the wafer and the light transmitting layer is polished by the CMP process, reflected light of a sinusoidal waveform is formed by optical interference due to a difference in optical path in the oxide layer, The first value can be defined as the thickness of the polishing layer at a moment when the period of the optical interference signal of the reflected light from the polishing surface of the wafer has elapsed a predetermined number of times.

At this time, since the thickness of the oxide layer deposited on the wafer may differ depending on the deposition process, the first value is set to 2, which includes different first wavelengths and second wavelengths of the reflected light from the polishing surface of the wafer It is more effective that the thickness is determined by the thickness of the abrasive layer of the wafer when the number of wavelengths reaches a predetermined value at the same time.

This is because optical interfering signals of two different wavelengths are output in the form of a sine wave of different periods and the optical interference signal value of the first wavelength in a state where the thickness of the oxide layer of the wafer reaches a predetermined first value, The optical interference signal values of the two wavelengths are output within a predetermined range of values so that when the optical interference signals for two or more different wavelengths simultaneously arrive at a predetermined range of values, 1 value is reached.

For example, in the present invention, when a predetermined number of cycles of an optical interference signal for any one of two or more different wavelengths have elapsed, the optical interference signal for the other wavelength has a predetermined range of values It is possible to reliably detect that the thickness of the oxide layer of the wafer has reached the desired first value.

It is preferable that the oxide layer thickness detecting step includes a step of detecting the number of cycles of the second interference wavelength signal with respect to the second wavelength of the reflected light when the first interference wavelength signal for the first wavelength of the reflected light is a peak value, , And the inclination of the oxide layer may be detected by detecting the thickness of the oxide layer. This is because the deviation of the interference wavelength signal from the oxide layer deposited on the wafer due to the foreign material constituting the oxide layer or the like may occur, so that the high or the low peak value The second interference wavelength signal of the second wavelength and, if necessary, the third interference wavelength signal of the third wavelength are rising or falling, It is possible to relatively detect that the thickness of the oxide layer of the wafer has reached the desired first value when the conditions such as the inclination of the interference wavelength signal such as three wavelengths and the relative positional deviation are all satisfied.

 At this time, the first wavelength and the second wavelength are determined so that an integer multiple of the period of the first wavelength and an integral multiple of the period of the second wavelength do not occur within 10 times of the period of the first wavelength. For this purpose, the first wavelength is preferably small relative to the second wavelength. Or 1.05 times to 1.45 times or 1.55 times to 1.95 times the second wavelength of the first wavelength, even if the first wavelength and the second wavelength are not close to each other.

In general, the first wavelength falls within the range of 350 nm to 600 nm, and the second wavelength falls within the range of 500 nm to 750 nm. However, when the first wavelength is 400 nm and the second wavelength is 600 nm, it is not preferable because the period of 3 times the first wavelength coincides with the period of twice the second wavelength. Therefore, when the first wavelength is 400 nm, the second wavelength is set to about 653 nm, and it is preferable that the integer times of the periods of the first and second wavelengths are not equal to each other within 10 times of the first wavelength.

Meanwhile, the wafer thickness sensing step may be performed in real time during the polishing step. This can be realized, for example, by providing a transparent window on the polishing pad, irradiating light through the transparent window, and receiving the reflected light with the reflected light. As described above, the step of irradiating light and detecting the thickness of the light-transmitting layer is performed in real time during the polishing step, so that the polishing end point is detected during the polishing process of the wafer, thereby improving the efficiency of the process.

The wafer can be pressed in multiple areas. On the other hand, since the polishing layer of the wafer is not uniformly polished by centrifugal force or the like due to the rotation of the wafer during the CMP process, the pressing force applied to the wafer is independently controlled in a plurality of regions. The polishing thickness of the abrasive layer of the wafer may be different for each region unless it is precisely performed according to the state of the pad. In the present invention, when a thickness difference of the polishing layer is generated for each region of the wafer, the height deviation of the polishing pad reflecting the variation of the polishing layer thickness is measured, and by the conditioner By correcting the height deviation of the polishing pad, even when the same pressing force is introduced to the wafer, the height deviation of the polishing pad can be readjusted, and the thickness of the polishing layer due to friction with the polishing pad of the wafer can be uniformly adjusted.

To this end, the wafer thickness step measures the thickness at two or more of the regions delimited by a plurality of ring-shaped boundaries from the center of the wafer, and the modification of the polishing pad causes the conditioning disk And pressing the polishing pad with different pressing forces depending on the angle.

Above all, the present invention is characterized in that, in the finish polishing step, the pressing force introduced into the conditioning disk is in an open loop manner determined from the height deviation of the polishing pad in a state in which the thickness of the polishing layer of the wafer reaches the first value . That is, the fact that the polishing layer thickness has reached the first value means that the polishing layer of the wafer forms a uniform polishing surface at the start of the finish polishing process since the CMP process leaves only the finish polishing process within about 5 seconds By a simple control method of an open-loop system in which a correction height deviation of a polishing pad is corrected, a pressing force of the conditioning disk is set to be a corrected height deviation collectively, and then the polishing pad is modified by a conditioning disk with a predetermined pressing force, Thereby uniformly aligning the non-uniform polishing surface of the polishing layer of the wafer.

According to another aspect of the present invention, there is provided a chemical mechanical polishing system in which a chemical mechanical polishing process is performed while pressing a surface of a wafer to bring the polishing surface into contact with the polishing pad, comprising: a plurality of pressure chambers independently controlled in pressure; A carrier head forming a pressure chamber, the carrier head pressing the wafer to the polishing pad through a membrane forming the bottom surface of the pressure chamber; A thickness sensing unit for sensing whether the thickness of the polishing layer of the wafer has reached a predetermined first value; A polishing pad height deviation measuring unit for measuring a height deviation in the radial direction of the polishing pad; A conditioner for pressing the conditioning disk in contact with the polishing pad in the course of performing the chemical mechanical polishing process to modify the polishing pad; Wherein when the thickness of the polishing layer of the wafer reaches the first value in the thickness sensing portion, the polishing process by the chemical mechanical polishing apparatus is continued for a predetermined first time, and the pressing force The control unit controlling the pressing of the conditioning disk based on the control signal. The present invention also provides a chemical mechanical polishing system comprising:

Here, the thickness sensing unit may include a light irradiating unit for irradiating light through a transparent window formed on the polishing pad; A light receiving portion for receiving reflected light reflected from the wafer by light emitted from the illumination light irradiating portion; Further, the control section may detect whether the thickness of the abrasive layer of the wafer from the reflected light reaches the first value.

It is preferable that the first time is set within 5 seconds.

The control unit determines a force for pressing the polishing pad for the first time based on the thickness deviation of the polishing pad when the polishing layer thickness reaches the first value. During the finishing polishing process for the first time, the height deviation of the polishing pad is controlled by controlling the conditioner with a predetermined pressing force (not limited to adjusting the height of the polishing pad as a whole to the same height) The thickness of the uneven wafer polishing layer can be uniformed as a whole.

The 'abrasive layer thickness' and similar terms used in this specification and claims are defined as the thickness of the layer to be polished by the CMP process of the wafer. That is, when a metal layer such as copper or tungsten is formed on the wafer and the metal layer is polished by the CMP process, the metal layer corresponds to the polishing layer. When a light transmitting layer such as an oxide layer is formed on the wafer and the light transmitting layer is polished by the CMP process, the light transmitting layer corresponds to the polishing layer.

The term 'finish polishing process' and similar terms used in this specification and claims are to be understood as meaning a polishing process carried out for a time not exceeding 5 seconds before the end of the CMP process, or a target process To a target thickness from a state in which the thickness is increased by as much as 200 to 2000 ANGSTROM.

According to the present invention, when the polishing surface of the wafer pressed by the wafer carrier during the chemical mechanical polishing process is unevenly polished, the surface of the polishing pad may be uneven due to the uneven polishing surface condition, , The pressing force of the conditioner for modifying the polishing pad is adjusted based on the height deviation of the measured polishing pad based on the point at which the polishing layer thickness reaches the first value and the finish polishing process of the wafer is started By adjusting the height deviation of the polishing pad and locally varying the frictional force of the polishing surface of the wafer using the height deviation of the corrected polishing pad, the thickness of the polishing layer of the wafer, which was not uniform during the finish polishing process, The difference in polishing thickness of the wafer is solved at the time of termination It is possible to obtain an advantageous effect that implements the same polishing.

That is, according to the present invention, even if there is a deviation in the polishing surface of the wafer at the beginning of the finishing step of the chemical mechanical polishing process, the final polishing state of the wafer polishing surface after the CMP process is compensated in the finishing polishing step, It is possible to obtain an advantageous effect.

Further, in order to solve the deviation in the thickness of the polishing layer of the wafer, the present invention determines the pressing force of the polishing pad determined at the start of the finish polishing process and applies the predetermined pressing force in an open loop manner, So that the control method is simple, so that it is possible to reliably apply the control method without generating an error during operation.

Particularly, the present invention can more reliably prevent occurrence of a difference in polishing thickness in each region when the wafer is pressed while pressing the wafer in different areas with different pressing forces.

Fig. 1A is a front view showing the construction of a general chemical mechanical polishing apparatus,
FIG. 1B is a plan view of FIG. 1A,
FIG. 2 is a half sectional view of the carrier head of FIG.
3 is a view showing a region to be polished on a wafer,
FIG. 4 is a flowchart showing a chemical mechanical polishing method according to an embodiment of the present invention,
5 is a view showing the construction of a chemical mechanical polishing system according to an embodiment of the present invention;
Fig. 6 is a plan view of Fig. 5,
7 is a perspective view showing a part of the configuration of Fig. 5,
FIG. 8A is an enlarged view of a portion 'A' in FIG. 5 when a metal layer is deposited on a wafer,
FIG. 8B is a graph showing the intensity of light obtained in the light receiving portion of FIG. 5 when a metal layer is deposited on the wafer,
FIG. 9A is an enlarged view of a portion 'A' in FIG. 5 when a light-transmitting layer is deposited on a wafer,
FIG. 9B is a graph showing the reflected light received by the light receiving unit of FIG. 5 in the case where the light transmitting layer is deposited on the wafer in the entire frequency region, and the distribution of the reflected light at the initial stage of the chemical mechanical polishing process,
FIG. 9C is a graph showing the reflected light received by the light receiving portion in FIG. 5 when the light transmitting layer is deposited on the wafer in the entire frequency region, and FIG. 9C is a distribution chart of the reflected light in the last stage of the chemical mechanical polishing process,
FIG. 9D is a graph showing the optical interference signal with respect to time changes for the two specific wavelengths shown in FIGS. 9B and 9C,
FIG. 9E is a graph showing an optical interference signal with respect to a time change with respect to two wavelengths to explain a principle of detecting a point in time when the thickness of the oxide layer is normal,
FIG. 9F is a graph showing an optical interference signal for a time change with respect to two wavelengths for explaining the principle of detecting a time point when the thickness of the oxide layer is abnormally thick and the polishing layer thickness is the first value;
10 is a graph showing the measurement data of the surface height of the polishing pad and the pressing force control data of the conditioning disk based thereon.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the subject matter of the present invention.

As shown in the drawings, a chemical mechanical polishing system 100 according to an embodiment of the present invention is for polishing a polishing layer f formed on the bottom surface of a wafer W, (C0, C1, ... C5) of the pressure chambers (C0, ... C5) are formed and pressurize the wafer to the polishing pad through a membrane (21) A head 20, a polishing pad 111 rotating on the polishing platen 110, a slurry supply unit (not shown) supplying slurry on the polishing pad 111, a polishing pad 111 and a polishing platen 110 A light irradiating part 120 for irradiating light Li on a polished surface of the wafer W through a transparent window 111a provided in a penetrating part passing through the polishing surface of the wafer W; The thickness of the abrasive layer f is detected from the reflected light Lo received by the optical receiver 130, A thickness detecting section 140 for detecting whether the thickness of the polishing layer f has reached a predetermined first value and a polishing section for polishing the polishing pad 111 by a pressure actuator 159, A conditioner 150 for pressing the pad 111 to modify the surface of the polishing pad 111 and a polishing pad height deviation measuring unit 120 for measuring a height deviation 79 in the radial direction 99 of the polishing pad 111 And a polishing step of continuously performing a CMP process for a first predetermined time when the thickness of the polishing layer (f) of the wafer (W) reaches the first value at the thickness sensing part (140) And a control unit 170 for controlling the pressure of the air by the conditioner on the basis of the pressing force varied according to the height deviation 79 of the air conditioner 111.

A transparent window 111a is formed on the polishing pad 111 and the polishing platen to form a light Li from the light irradiating part 120 on the polishing surface of the wafer W performing the polishing process from the lower side of the polishing platen 110. [ And the reflected light Lo reflected from the polishing surface of the wafer W can be received by the light receiving unit 130. [

6, the light irradiating unit 120 irradiates light Li to a plurality of points 120x, 120y, and 120z that are spaced apart from each other at a distance from the center of the wafer W, and the light receiving unit 130 And receives reflected light Lo reflected from the polished surface of these points 120x, 120y, and 120z, respectively. Since the light irradiating unit 120 and the light receiving unit 130 irradiate and receive light at a plurality of points 120x, 120y, and 120z, the light irradiating unit 120 and the light receiving unit 130 may be formed in plural, And may be formed as a single body having a plurality of modules capable of receiving and receiving signals. For this purpose, the transparent window 111a may be formed as shown in FIG. 6, but a plurality of small transparent windows may be provided at a plurality of points for securing the optical path.

The thickness sensing unit 140 senses the thickness of the polishing layer f of the wafer W from the reflected light Lo received by the light receiving unit 130.

The conditioner 150 includes an arm 154 that performs a turning motion 151d with respect to the rotation center 152, a conditioning disk 155 that rotates on the bottom surface of the end of the arm 154, And an actuator 159 for transmitting a pressing force in a vertical direction to the polishing pad 111. The polishing pad 111 is rotated and pivoted while the polishing pad 111 is being pressed during the CMP process to modify the surface state of the polishing pad 111. [

Here, the pressing force introduced into the conditioning disk 155 is determined by the controller 170, and the pressing force introduced into the conditioning disk 155 does not vary due to the parameters caused during the CMP process, Of the abrasive layer (f) is left in a state of leaving a time of about 200 占 to about 2000 占 from the target thickness of the abrasive layer (f) It is preferable that the pressing force is varied once based on the height deviation 79 of the flat plate 111.

The polishing pad height deviation measuring section 160 irradiates light onto the polishing pad 111 rotating in a non-contact manner as shown in FIG. 7 to measure the surface height of the polishing pad 111 in the radial direction 99 . Here, the surface height of the polishing pad 111 may be an absolute dimension, and may be a height deviation with respect to an arbitrary reference height. That is, even if the absolute height dimension of the polishing pad 111 is not measured, it is sufficient for the present invention to find the height deviation in the radial direction of the polishing pad 111. Although the figure shows a configuration for measuring the height of the polishing pad 111 in a noncontact manner, the present invention is characterized in that the probe is provided in contact with the surface of the polishing pad 111 on the principle similar to the dial gauge, And a height deviation of the polishing pad 111 is measured based on the vertical movement amount of the probe according to the height variation of the polishing pad 111. [

The controller 170 controls the polishing pad 111 so that the height deviation in the radial direction 99 of the polishing pad 111 obtained from the polishing pad height deviation measuring unit 160 when the thickness of the polishing layer of the wafer W reaches the first value (For example, reference numeral 79 in Fig. 10), calculates the pressing force of the conditioner 150 that presses the polishing pad 111 based on the height deviation data of the polishing pad 111, Is applied through the actuator 159 of the conditioner 150 during the finish polishing process.

Hereinafter, a chemical mechanical polishing method (S100) using the chemical mechanical polishing system 100 according to an embodiment of the present invention constructed as above will be described with reference to FIG. 4 attached hereto.

Step 1 : First, as shown in Figs. 1A and 1B, the wafer W is pressed against the rotating polishing pad 111 rotating with the rotating carrier head 20 to perform mechanical polishing, and the polishing pad A chemical mechanical polishing process in which chemical polishing is performed by the slurry supplied to the polishing pad 111 is performed (S110).

Step 2 : During the chemical mechanical polishing process, the polishing layer thickness of the wafer W is detected (S120), and it is monitored whether or not the polishing layer thickness of the wafer W reaches a first value of a predetermined thickness (S130). Here, the state in which the thickness of the abrasive layer becomes the first value is a state in which a time within about 5 seconds is left from the end of polishing or a state in which the abrasive layer (f) May be an exact match to a predetermined thickness, but also include those falling within a predetermined thickness range.

For example, when the polishing layer of the wafer W is a metal layer of copper, tungsten or the like, the polishing surface of the wafer W is polished by the metal layer m formed on the barrier layer ba, . According to another embodiment of the present invention, the metal layer m may be formed directly on the base layer Bo without the barrier layer ba. The metal layer m formed on the barrier layer ba is not smooth before polishing and has a relatively large thickness zo, so that the metal layer m is colored. For example, when the metal layer m is formed of copper, it has a deep yellow color. Then, as the chemical mechanical polishing process proceeds, the uneven surface of the metal layer m indicated by the reference symbol So becomes the flat surface S and the thickness z becomes gradually thinner.

On the other hand, since the metal layer m can not transmit light, part of the light irradiated according to the color of the metal layer m is absorbed by the metal layer m and part of the light is reflected from the surface of the metal layer m, The reflected light Lo reflected from the polishing surface is received by the light receiving unit 130 at a constant light intensity for a certain period of time from the beginning of the polishing since the dark yellow color of the metal layer m does not change for a certain period of time after the start of polishing.

Then, when the thickness z of the metal layer m becomes thinner and reaches about 1000 Å to 3000 Å from the target thickness, the color of the barrier layer ba begins to be projected onto the color of the metal layer m and the dark yellow color gradually becomes lighter And the intensity of the reflected light Lo is output as shown in FIG. 8B. That is, when the thickness of the metal layer m is sufficiently thick, the light intensity is output at a constant value Po. However, when the thickness of the metal layer m starts to decrease, the light intensity starts to be lowered.

6, when light is received at three points 120x, 120y and 120z, the light intensity is kept constant at Po when the thickness of the metal layer m of the wafer W is sufficiently thick (Ox, Oy, Oz) at each point as the thickness of the metal layer m passes the threshold value CR starts to decrease for approximately Tx time with time difference depending on the polishing thickness, ). The time points T1, T2, and T3 passing through the thresholds CRx, CRy, and CRz are different due to the difference in the polishing thickness of the wafer at each point.

Whether or not the thickness of the abrasive layer m has reached the first value when the abrasive layer of the wafer is the metal layer m means that the thickness of the abrasive layer m at the respective points 120x, 120y, and 120z (When it is within the time range indicated by e in Fig. 8B).

On the other hand, when the polishing layer of the wafer W is a light transmitting layer such as an oxide layer, as shown in Fig. 9A, the polishing surface of the wafer W is divided into the light transmitting layer f A part of the light Li irradiated from the light irradiating unit 120 is reflected (Lo1) on the surface of the oxide layer f and is reflected by the light irradiating unit 120, A part of the light Li irradiated from the light emitting layer L passes through the oxide layer f and is reflected (Lo2) in the opaque layer Wo so that the reflected light Lo1 and Lo2 pass through the oxide layer f The interference light X is generated which interferes with each other and is similar to the sine wave form.

Since the light Li having two or more wavelengths is irradiated to the polished surface of the wafer W at each of the points 120x, 120y and 120z, the reflected light Lo reflected by the polished surface of the wafer W, The optical interference signal X is a combination of reflected light and optical interference signals P1, P2, ... for two or more wavelengths. For example, when the oxide layer f of the wafer W is irradiated with light having uniform intensity over the range of 1 nm to 1050 nm, the optical interference signals P1 and P2 , ...) are as shown in Figs. 9B and 9C.

9B, in the reflected light Lo received by the light receiving unit 130, the intensity of the interference light X over a plurality of wavelengths is a waveform sine according to the wavelength? And is repeatedly formed at a narrow interval (Y). 9C, the intensity of the interference light X is maintained to be similar to the intensity of the interference light X according to the wavelength [lambda], as shown in Fig. 9C, Y ') gradually widen.

(Or the thickness of the image quality layer) with respect to one wavelength (for example, 469 nm as the first wavelength), the interference light X for one wavelength? Has a tendency to repeat up and down similar to sine waves. This can be confirmed from FIG. 9D showing a graph in which the intensity of light for two different wavelengths? 1 and? 2 fluctuates with time. In the figure, P1 represents the intensity of the interference light over time of the first wavelength lambda 1, and P2 represents the intensity of the interference light over time of the second wavelength lambda 2.

That is, in the course of the polishing process and the thickness of the oxide layer being thinned, the optical interference signal P1 for one wavelength generates a periodic waveform, so that the optical interference signal P1 for one wavelength It is difficult to detect the thickness z of the image quality layer f. Therefore, as in the conventional case, when the cycle variation or the number of cycles of the optical interference signal (or interference light) for one wavelength is reached (for example, when three cycles have elapsed since the start of polishing, If the polishing end point is detected, if the thickness (zo) of the oxide layer (f) deposited on the wafer prior to the start of the polishing process greatly exceeds the average level, even if the predetermined number of cycles have elapsed in the interference light The polishing thickness of the image quality layer (f) still causes a problem far from the target thickness.

Thus, if the thickness z of the oxide layer f of the wafer W reaches a predetermined first value, then the optical interference signal X at each wavelength has a constant value if the property of the oxide layer is constant When the thickness z of the oxide layer f of the wafer W reaches a first value (a state in which the thickness is left to be about 200 to 2000 占 from the target thickness), the position of the optical interference signal due to the specific wavelength The optical interference signals P1 and P2 for two or more different wavelengths lambda 1 and lambda 2 determined in a state where the thickness z of the oxide layer f has reached the first value, When the range of the optical interference signal for the two or more wavelengths? 1 and? 2 reaches a known state, the optical interference signal for one wavelength forms a periodic waveform, It can be clearly known that the thickness z of the oxide layer f has reached the target thickness.

For example, as shown in FIG. 9E, the optical interference signals P1 and P2 for the different wavelengths lambda 1 and lambda 2 are not continuously tracked, and the thickness of the oxide layer f of the wafer W (z) is about 2000 Å to about 3000 Å, it is necessary to set the peak value of the waveform in which the optical interference signal (P1) is at least three times the first wavelength (λ1, for example, 469 nm) 6, if the optical interference signal of the first wavelength? 1 reaches the peak value of the sine wave after the cycle of the first wavelength? 1 reaches three times as shown in FIG. 6, the second wavelength? it is determined whether or not the thickness z of the oxide layer f of the wafer W has reached the target thickness by taking into consideration the numerical range or upward slope of the optical interference signal P2 of? 2, for example 675 nm, It is possible to accurately grasp whether or not the thickness of the polishing layer of the wafer W has reached the first value.

As another example, referring to FIG. 9F for an abnormally thick deposited oxide layer of approximately 11000 ANGSTROM, the optical interference signal P1 for the first wavelength lambda 1 is divided into upper peak values A0, A0 ', A1, , The slope of the second wavelength lambda 2 and, as the case may be, the slope of the optical interference signal P2, .. for the third wavelength. When the optical interference signal P1 for the first wavelength lambda 1 reaches the first upper peak value A0, the corresponding point B0 of the optical interference signal P2 for the second wavelength lambda 2, Since the slope (differential value is '+'), it is detected that the oxide layer (f) is not the upper peak value just before reaching the target thickness in A0. Then, in a state in which the optical interference signal P1 for the first wavelength lambda 1 reaches the second upper peak value A0 ', the optical interference signal P2 for the second wavelength lambda 2 is applied to the corresponding point B0 'has an upward slope (differential value is' + '), it is detected that the oxide layer (f) is not an upper peak value just before reaching the target thickness in A0'. Then, in a state in which the optical interference signal P1 for the first wavelength lambda 1 reaches the third upper peak value A1, the corresponding point B1 of the optical interference signal P2 for the second wavelength lambda 2 Has a horizontal slope (S1, differential value is '0'), it is sensed that A1 is not an upper peak value just before the oxide layer (f) reaches the target thickness. Then, in a state in which the optical interference signal P1 for the first wavelength lambda 1 reaches the fourth upper peak value A2, the corresponding point B2 of the optical interference signal P2 for the second wavelength lambda 2, (S2) (the differential value is '-'), it is possible to detect that A2 is the upper peak value just before the oxide layer (f) reaches the target thickness.

9E and 9F, the region except the region indicated by So in FIG. 9F is the same as FIG. 9E. The region indicated by So is the optical interference signal (P1, P2) during the polishing of the region where the thickness of the oxide layer is thicker than 7000A. When the thick oxide layer of 11000A is polished to reach 7000A, . Therefore, as described above, even when the thickness of the initial oxide layer is abnormally thick or thin, it is difficult to precisely measure the slope of the optical interference signal of the two or more wavelengths? 1,? 2, 1 < / RTI > value can be detected.

Even when the numerical value and the slope (differential value) of the second wavelength lambda 2 are compared only with the peak value of the optical interference signal P1 with respect to the first wavelength lambda 1, the thickness of the oxide layer f reaches the target thickness It is possible to accurately detect whether or not the peak value of the optical interference signal P1 of the first wavelength lambda 1 immediately before the detection is reached, while maintaining a simple control calculation method.

Step 3 : The thickness of the polishing layer is monitored by Step 2 according to the type of the polishing layer deposited on the wafer, and when it is detected that the first value has been reached, the height deviation in the radial direction 99 of the polishing pad 111 79) is measured (S140).

The height deviation 79 in the radial direction 99 of the polishing pad 111 has a tendency to vary in the region along the radial length of the polishing pad 111 as illustrated in Fig. That is, since the polishing pad 111 contacts and rotates in contact with the wafer W in a predetermined normal force, if the thickness of the polishing layer of the wafer W varies by region, the height variation of the polishing pad 111 also occurs do.

Step 4 : The finish polishing process is then performed (S150) until the polishing layer (f, m) of the wafer W reaches the target thickness from the first value to the polishing end point (EPD). The finish grinding process is performed for a time corresponding to approximately Tx to To on the basis of FIG. 8B when the metal layer is stacked, and corresponds to a time within 5 seconds.

The polishing surface of the wafer W may be uniformly performed as a whole by the CMP process according to the step 1. However, when the polishing surface of the wafer W is made non-uniformly for each region as shown in Fig. 3, A difference in the height of the polishing pad 111 is caused by the thickness of the polishing layer. That is, in the region where the height of the polishing pad 111 is relatively low, the polishing layer of the wafer W is less polished so as to have a thicker polishing layer thickness. In a region where the height of the polishing pad 111 is relatively high, The polishing of the polishing layer of the wafer W is performed to have a thinner polishing layer thickness.

Accordingly, when the thickness of the abrasive layer appears to be all but the finish polishing process (when the abrasive layer thickness has reached the first value) through the thickness sensing unit 140 in step 2, Control data for adjusting the pressing force of the conditioner 150 for modifying the polishing pad 111 is generated on the basis of the height deviation 79 data of the polishing pad 111 received from the deviation measuring unit 160.

10, when the height of the polishing pad 111 is relatively low, a low pressing force is introduced by the conditioner 150 and when the height of the polishing pad 111 is relatively high, When the polishing thickness variation of the polishing layer of the wafer W obtained at the three points 120x, 120y, and 120z is severe, the control data having the pressing force distribution 97 in which the high pressing force is introduced is generated, There may be a region where the pressing force is not applied by the conditioner 150.

Based on the control data for applying the pressing force generated by the control unit 170, the pressing force controlled through the actuator 159 of the conditioner 150 is introduced into the polishing pad 111 while the finish polishing process is performed. Since the conditioner 150 is rotated in the radial direction of the polishing pad 111 and controlled to have a difference in pressing force depending on the angular position of the pivot motion 151d, (Not necessarily all at the same height) so that a deviation in the thickness of the polishing layer of the wafer W can be corrected during the finish polishing process.

While the height deviation of the polishing pad 111 and the thickness of the polishing layer of the wafer W may be detected during the finish polishing process and the pressing force of the conditioner 150 that presses the polishing pad 111 in a feedback manner continuously may be updated, Since the control method is complicated and there is substantially no substantial effect of updating during the finishing polishing process performed in a relatively short time, the pressing force control data calculated by the control unit 170 when the thickness of the polishing layer of the wafer reaches the first value It is more effective to compensate for the thickness variation of the polishing layer of the wafer W in an open-loop manner.

Step 5 : Then, when the first time period during which the finish polishing process is performed, the chemical mechanical polishing process is terminated.

The chemical mechanical polishing method (S100) according to one embodiment of the present invention configured as described above is designed so that even if the polishing surface of the wafer pressed by the wafer carrier 20 during the chemical mechanical polishing process is unevenly polished, The height deviation of the polishing pad is measured and the control data for adjusting the pressing force of the conditioner 150 for modifying the polishing pad on the basis of the measured height deviation 79 of the polishing pad 111 is generated, 150 to compensate for the deviation of the polishing surface of the wafer at the start of the finish polishing step in the final polishing step so that the final state of the wafer polishing surface after completion of the CMP process can uniformly form the polishing surface as a whole An advantageous effect can be obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Modified, modified, or improved.

That is, in the embodiment of the present invention, the configuration in which the thicknesses of the abrasive layers of the wafers W are detected at the three points 120x, 120y, and 120z is exemplified. However, the pressure chambers C0, , C5 of the wafer W can be detected.

W: wafer f: oxide layer
Li: illumination light Lo: reflection light
d: spacing of reflected light z: oxide layer thickness
? 1: first wavelength? 2: second wavelength
P1: optical interference signal of the first wavelength P2: optical interference signal of the second wavelength
100: Chemical mechanical polishing system 110: Polishing plate
111: Polishing pad 111a: Transparent window
120: light irradiation part 130:
140: thickness detector 150: conditioner
160: Polishing pad height deviation measuring unit 170:

Claims (16)

A polishing step of polishing the polishing surface of the wafer while pressing the wafer against the polishing pad;
A polishing layer thickness sensing step of sensing whether the thickness of the polishing layer of the wafer has reached a predetermined first value that is equal to 70% to 99% of the total polishing thickness;
A polishing pad height measuring step of measuring a height deviation in the radial direction of the polishing pad;
Wherein when the polishing pad thickness of the wafer reaches the first value by the wafer thickness sensing step, the conditioning disk is pivoting for a predetermined first time, The polishing pad is pressed and modified with a different pressing force depending on the turning angle in such a manner that the pressing force is applied to a region having a higher surface height of the polishing pad as compared with a lower region A finish polishing step of finishing the polishing of the wafer after the polishing step for the wafer is continued;
Wherein the chemical mechanical polishing method comprises the steps of:
The method according to claim 1,
Wherein the first value is that the thickness of the abrasive layer of the wafer is greater than the target thickness by 200 ANGSTROM to 2000 ANGSTROM.
The method according to claim 1,
Wherein the wafer is laminated with a light transmitting layer and the first value is the thickness of the polishing layer at a moment when the period of the optical interference signal of the reflected light from the polishing surface of the wafer has elapsed a predetermined number of times .
The method according to claim 1,
Wherein the wafer thickness sensing step is performed in real time during the polishing step.
The method according to claim 1,
Wherein the first time is less than 5 seconds.
6. The method according to any one of claims 1 to 5,
Wherein the wafer is laminated with a light transmitting layer and the first value is a value at which signals for two or more wavelengths including different first wavelengths and second wavelengths of reflected light from the polishing surface of the wafer are simultaneously set to a predetermined value And the thickness of the abrasive layer of the wafer at the time of reaching the abrasive layer.
The method according to claim 6,
Wherein the first value is at least one of a period of the first interference wavelength signal for the first wavelength of the reflected light and a period number of the second interference wavelength signal for the second wavelength of the reflected light, And the thickness of the abrasive layer of the wafer when a predetermined value is reached at the same time.
The method according to claim 6,
Wherein the first value is a ratio of the number of cycles of the second interference wavelength signal to the second wavelength of the reflected light when the first interference wavelength signal for the first wavelength of the reflected light is a peak value, And the polishing layer thickness of the wafer when at least one of them reaches a predetermined value at the same time.
The method according to claim 6,
Wherein the wafer is pressed in a plurality of areas.
A chemical mechanical polishing system in which a polishing surface is pressed against a polishing surface of a wafer to perform a chemical mechanical polishing process while contacting the polishing pad,
A carrier head formed with a plurality of pressure chambers independently controlled in pressure and pressing the wafer to the polishing pad through a membrane forming the bottom surface of the pressure chamber;
An abrasive layer thickness sensing unit for sensing whether the thickness of the abrasive layer of the wafer reaches a predetermined first value that is equal to 70% to 99% of the total abrasive thickness;
A polishing pad height deviation measuring unit for measuring a height deviation in the radial direction of the polishing pad;
A conditioner for pressing the conditioning disk in contact with the polishing pad in the course of performing the chemical mechanical polishing process to modify the polishing pad;
Wherein the polishing pad height deviation measuring unit measures the polishing pad height deviation of the polishing pad while the polishing pad thickness of the wafer reaches the first value at a predetermined time, The polishing pad is pressed and modified with different pressing forces depending on the turning angle in a manner that a pressing force is applied to a region having a higher surface height of the polishing pad as compared with a lower region, A control unit for terminating the polishing of the wafer after the chemical mechanical polishing process for the wafer is continued;
Wherein the chemical mechanical polishing system comprises a chemical mechanical polishing system.
11. The apparatus of claim 10,
A light irradiation unit for irradiating light through a transparent window formed on the polishing pad;
A light receiving portion for receiving reflected light reflected from the wafer by light emitted from the illumination light irradiating portion;
Further comprising: the control section detects whether the thickness of the polishing layer of the wafer from the reflected light reaches the first value.
The method according to claim 10 or 11,
Wherein the first time is less than 5 seconds.

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