TW200422139A - Method of determining chemical mechanical polishing endpoint - Google Patents

Abstract

This invention provides a method for determining the endpoint of chemical mechanical polishing, using the temperature slope change for a polishing pad. At least a carrier is provided which is used to position a semiconductor wafer on a rotating work table with a polishing pad installed on top of it, such that the wafer and polishing pad will rotate and rub against each other. A measuring element is used to measure at least one ambient temperature and at least one temperature at certain point on the polishing pad. Subtract the ambient temperature from the measured polishing pad temperature to obtain the temperature difference. Use numerical analysis method to obtain the temperature difference curve relative to time, and the relationship between the curve slope and time is used to determine the polishing endpoint. This method can easily determine the polishing endpoint on line rapidly and accurately without affecting the manufacturing process.

Description

200422139 V. Description of the invention (1) Technical field to which the invention belongs The present invention relates to the field of chemical mechanical polishing, and more particularly to a method for judging the measurement end point of chemical mechanical polishing by using the slope change of the temperature of the polishing pad. Prior art

With the continuous development of semiconductor technology, in order to achieve the effect of increasing the speed of components in deep sub-micron semiconductor processes, the resolution of lithography exposure has been continuously improved, and the depth of focus has also been continuously increased. To zoom out. In order to achieve the above-mentioned purpose of improving the lithographic exposure resolution and reducing the depth of field, it is necessary to produce a wafer surface that is fully planarized. Therefore, chemical mechanical polishing (CMP) has been developed. polishing). The first figure is an explanatory diagram of the conventional chemical mechanical polishing equipment. Referring to the first picture, the process of chemical mechanical polishing is to set at least one carrier 101 and use the carrier 101 to position the wafer 120 on a rotary table 131 with a polishing surface 13o on the surface. The circle 12 0 and the polishing pad 13 0 will rotate with each other; and when performing chemical mechanical polishing, the polishing liquid 1 4 0 composed of abrasive particles will be continuously sprayed into the carrier 11 0 and the polishing pad along a conveying pipe 1 41 1 3 ′ $ ′ causes the wafer located between the carrier 11 0 and the polishing pad 1300 to produce mechanical and chemical interactions, thereby removing excess metal deposits on the surface of the wafer 12

Page 5 200422139 V. Description of the invention (2) layer, to make the wafer meet the requirements of overall planarization. In the chemical mechanical polishing process, the surface of the wafer is rotated by the carrier and firmly pressed against the polishing pad by the pressing force, so it is not easy to judge the end point of the polishing by measuring the condition of the wafer surface. According to statistical data, using the previous method to determine the end point of chemical mechanical polishing, each batch of wafers manufactured must be measured for an additional two hours after the polishing is finished to understand Wafer grinding is accurate or not. For this reason, the productivity of equipment will be reduced by 50%, resulting in a significant increase in the manufacturing cost of semiconductor products. The following briefly describes the detection method of the CMP end point of the prior art. U.S. Patent No. 5, 1 96, 353, patent name " Method for controlling a semiconductor (CMP) process by measuring a surface temperature and developing a thermal image of the wafer " The thermal image of the surface is used as a reference for adjusting process parameters. However, in practical applications, because the wafer surface is closely attached to the polishing pad, taking thermal images of the wafer surface has its obstacles. U.S. Patent No. 5,597,442, patent name " Chemical / mechanical planarization (CMP) endpoint method using measurement of polishing pad temperature "

200422139 V. Description of the invention (3) Degree is the index of grinding end point 'This method judges the grinding end point by measuring the measured temperature at least 2 ° C lower than the previous measured temperature. However, in the implementation process, the temperature of the polishing liquid needs to be controlled, and the measured temperature will fluctuate up and down due to the influence of the polishing liquid. Therefore, it is difficult to judge the polishing end point by the temperature falling by 2 ° C. U.S. Patent No. 5,645,050, patent name " Chemical / mechanical polish (CMP) thickness mon i tor ", discloses that the measured polishing pad temperature is integrated over time, and the result of the integration can indicate the removed Thin film thickness. However, it requires a complicated calculation process, and the thickness of the thin film on the wafer surface is not uniform, so it is very difficult to accurately determine the polishing end point. US Patent No. 5,647, 952, patent name " Chemical / mechanical polish ( CMP) endpoint method ", and the Republic of China Patent No. 299,462, the patent name " A method for measuring the endpoint of polishing using chemical / mechanical polishing (CMP) to expose selected areas of the wafer surface on the polishing pad by measuring The temperature is determined by the point where the temperature changes. The grinding end point is reached. However, in the implementation process, the temperature of the polishing liquid needs to be controlled, and the measured temperature will fluctuate up and down due to the influence of the polishing liquid. It is difficult to judge the end point of the polishing with the measured temperature of the polishing pad. US Patent No. 5,722,875, Patent name " Method and

200422139 V. Description of the invention (4) apparatus for p〇1 ishing ", which revealed that the end point of grinding was determined by measuring the temperature on the grinding mill with an infrared sensor. However, the measured temperature will fluctuate up and down due to the influence of the polishing liquid. Therefore, it is difficult to accurately determine the end point of the polishing only by measuring the temperature of a single point on the polishing pad. U.S. Patent No. 6,007,408, patent name " Method and apparatus for endpointing mechanical and chemical-mechanical polishing of substrates ", discloses the simultaneous measurement of the temperature of the wafer back surface, polishing pad, polishing liquid and polishing waste liquid. Judge the end point of grinding. However, in the implementation process, the temperature of the grinding waste liquid does not change significantly. Moreover, the temperature of the grinding waste liquid has decreased before being measured, so it is not easy to determine the grinding end point. US Patent No. 6,077,783 The patent name " Method and apparatus for detecting a polishing endpoint based upon heat conducted through a semiconductor wafer " 'exposed heats the wafer so that the wafer surface reaches a specific temperature. When the wafer surface is removed, the surface's The temperature will change to determine the polishing end point. However, in the implementation process, the magnitude of the temperature change on the wafer surface will decrease after passing the carrier, which will increase the difficulty of determining the polishing end point. US Patent 6,150,271 No.'Patent name " Differential temperature control in chemical mechanical

200422139 V. Description of the invention (5) Polishing processes " discloses the installation of heating and cooling coils in the carrier to control the surface removal rate of the wafer, and thereby judges the polishing end point. However, in the implementation process, the temperature of the carrier is easily changed by the influence of the environment, which will cause difficulties in temperature control and determination of the polishing end point. Summary of the Invention

The present invention is a method for judging the end point of chemical mechanical polishing by detecting the change in the temperature slope of the polishing pad. The present invention is characterized by using a non-contact temperature 1 measuring device to measure the temperature distribution of the grinding mill, and to calculate the data measured by the temperature measurement device through a simple numerical method to make the relationship between the temperature slope and the time change. Illustration. With this figure, the present invention can easily and clearly change the degree of…, and can affect the process without affecting the process = find two: accurately determine the end point of grinding on the ground, avoiding that the previous technology cannot accurately determine the end point of grinding on the line in real time Defects. In addition, the present invention is further designed to measure an ambient temperature, so as to avoid the disadvantage that measurement results caused by polishing liquid or the environment are prone to change. °

The chemical mechanical polishing device of the present invention includes at least one carrier, and the carrier is used to position the wafer on a rotating work ^ with a polishing pad on the surface, and the wafer and the polishing pad will rotate with each other; while performing chemical mechanical polishing ^, The polishing liquid composed of $ abrasive particles will be continuously sprayed between the carrier and the polishing pad along a conveying pipe, so that the wafer generator ^ and chemical action between the carrier and the polishing pad will remove the crystals. Excess metal deposits on the round surface

200422139 V. Description of the invention (6) The round surface is smooth. In addition, the present invention sets at least one non-contact temperature measurement device near the polishing pad, and uses the device to measure at least one ambient temperature. The above-mentioned non-contact temperature measurement device can be a single-point temperature measuring instrument and a A thermal imager that captures thermal images. The temperature measuring device can be an infrared temperature measuring device. The above-mentioned measurement location of the ambient temperature can be located in the central area of the polishing pad and the edge area of the polishing pad of the chemical polishing machinery equipment. ; External chemical grinding machinery and equipment, and any point in the environment with a stable temperature. Next, use a temperature measuring device to measure the temperature of at least one point on the surface of the polishing pad just after being rubbed with the crystals; after that, measure the white to use at least one computing device for data processing. The present invention calculates the temperature change of the polishing pad in order to eliminate the ^ j 'of the polishing liquid to the measuring instrument. The temperature of the polishing pad measured above is subtracted from the ambient temperature, so as not to increase due to polishing. Temperature difference, and use simple values ^ sound] b to give the temperature curve and time change curve, and use this curve to make a graph of the relationship between the slope and the time, and use this curve to determine the end point of grinding (Qing T The computing device described in Method 0 can be built in the measuring device or built in external. The above numerical method can be the least square method or other linear regression.

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200422139 V. Description of the invention (7) The invention is described more clearly with the following illustrations and description of the embodiments. Embodiment The second figure is a diagram of a chemical mechanical polishing equipment of the present invention. Referring to the second figure, the present invention sets a carrier 2 10, and uses the carrier 2 10 to position the wafer 2 2 on a rotating table 231 with a polishing pad 23 0 on the surface, and the wafer 220 and the polishing pad 塾23 0 will rotate with each other and produce mechanical effects. When performing chemical mechanical polishing, a polishing liquid 24 0 composed of abrasive particles is continuously sprayed into a carrier 210 and a polishing pad 23 0 along a conveying pipe 241 so as to be located between the carrier 2 1 0 and the polishing pad. Wafers between 2 3 2 2 2 have a chemical effect. The chemical mechanical polishing process combines the above mechanical and chemical actions, which will remove the excess metal deposition layer on the surface of the wafer 220 and make the surface of the wafer 220 smooth. In addition, the present invention further installs a non-contact thermal imager 250 near the polishing pad 230, and connects the thermal imager 250 to a personal computer 260. The second figure is an explanatory diagram of the relationship between the wafer, the carrier and the rotary table of the present invention. Referring to the third figure, in the chemical mechanical polishing process, the polishing pad 230 will increase the temperature due to polishing, and the increased temperature is related to the relative speed and friction coefficient between the polishing 塾 230 and the wafer 220. . When the process is started, the polishing pad only rubs against the first film 221 of the wafer. At this time, the elevated temperature is only related to the relative speed between the polishing pad 230 and the wafer 220 and the first speed of the polishing pad 230 and the wafer. The friction coefficient between a layer of film 221 is related, so

200422139 V. Description of the invention (8) The temperature increased by the mill 230 is linearly related to time. The first thin film mentioned above may be a metal material.

Then 'when the first layer of film 221 of the wafer is removed to a certain stage, the polishing layer 23 0 will start to polish the second layer of film 222 of the wafer, and at this time, the polishing pad 23 0 will simultaneously polish the first layer of wafer 220 The film 221 and the second film 222 'cause the temperature of the polishing pad 230 to increase with the relative speed between the polishing pad 230 and the wafer 220 and the first film 221 and the second film of the polishing pad 230 and the wafer 220. The friction coefficient between the two layers of thin film 22 2 is related. Therefore, at this time, the temperature of the polishing pad 230 measured by the temperature measurement device will be the same as that of the first layer 221 and the second layer 22 2 of the wafer 220. A function of the content of the ingredients, and the temperature will vary significantly non-linearly. The second thin film may be a dielectric material. After that, when the first film 221 of the wafer 220 is completely removed, the temperature raised by the polishing pad 230 will be related to the relative speed between the polishing pad 230 and the wafer 220, and the polishing pad 230 and the wafer The friction coefficient between the two thin films 2 2 2 is related. At this time, the temperature raised by the polishing pad 230 is only related to the relative speed between the polishing pad and the wafer and the second layer of the polishing pad 2 3 0 and the wafer 2 2 0. The friction coefficient between the films 2 2 2 is related, so the temperature raised by the polishing pad 230 will be linearly related to time again, and the position corresponding to the turning point from the above non-linear change to the linearly related again is chemical mechanical polishing The end of the process. The fourth figure is an explanatory diagram of the measuring method of the present invention. Referring to the fourth figure, this

Page 12 200422139

The invention uses the thermal imager 250 to first measure an ambient temperature, and the measuring position of the ambient temperature may be at any point of the central area of the polishing pad 41, the edge area of the polishing pad, or any other area of the polishing pad that has not rubbed against the wafer. . Next, using a thermal imager 250, the wafer 塾 grinding 塾 area 420 immediately after rubbing was measured at a position below the carrier 210. After that, the measured polishing pad temperature is processed by a personal computer 26′〇, and the temperature is subtracted from the ambient temperature to obtain the relative temperature of the polishing pad which is increased by friction. The fifth graph is a graph of the relative temperature change of the polishing pad due to friction measured with the present invention over time. Referring to the fifth figure, the dots represented by _ are corresponding to the measured polishing pad area at different points in time. 4 2 1 The relative temperature rise due to friction. The straight part is using the personal computer 2 6 〇 Using the least square method (least square method), the temperature curve of the relative temperature rise of the grinding 升高 due to friction is calculated. The sixth figure is the use of the temperature curve of the fifth figure to make the temperature curve. Graph of slope vs. time. Referring to the sixth figure, the first fixed slope line segment 601 represents that the polishing pad only rubs against the first layer of the wafer; the non-fixed slope line segment 602 represents that the first layer and the second layer of the wafer are polished simultaneously Thin film; the second fixed slope line segment 603 represents that the polishing pad only rubs against the second layer of the wafer, that is, the first layer of the wafer is completely removed, so the turning point 604 represents the end point of the chemical mechanical polishing. The above-mentioned fixed values of the first fixed-value slope line segment 601 and the second fixed-value slope line segment 60 3 may be

Page 13 200422139 V. Description of the Invention (ίο) Changes within a predetermined range. The above predetermined range may be 5% above and below the fixed value. Of course, the above are only preferred embodiments of the present invention, and the scope of implementation of the present invention cannot be limited by this. That is, all equal changes and modifications made in accordance with the scope of the patent application for the present invention should still fall within the scope of the patent for the present invention.

Page 14 Γ Ρ; Λ 200422139 Brief description of the diagram The first diagram is an illustration of the conventional chemical mechanical polishing equipment. The second figure is a diagram of the chemical mechanical polishing equipment of the present invention. The third figure is an explanatory diagram of the relationship between the wafer, the carrier and the rotary table of the present invention. The fourth figure is an explanatory diagram of the measuring method of the present invention. The fifth graph is a graph of the relative temperature change of the polishing pad due to friction measured with the present invention over time. The sixth diagram is the relationship between the slope of the temperature curve and the change of time using the temperature curve of the fifth diagram. 101 Carrier 1 2 0 Wafer 1 3 0 Polishing pad 131 Rotary table 1 4 0 Polishing liquid 141 Conveyor tube 210 Carrier 2 2 0 Wafer 221 First film of wafer 222 Second film of wafer 2 2 3 Wafer substrate 230 Polishing pad 231 Rotary table

Page 15 200422139 Brief description of the drawings 240 Abrasive liquid 241 Conveying tube 250 Thermal imager 2 6 0 Personal computer 410 Central area of the polishing pad 411 Edge area of the polishing pad 420 Polishing pad area immediately after the wafer and polishing pad are rubbed Measure Polishing pad area 601 first constant value slope line segment 6 0 2 non-constant value slope line segment 603 second constant value slope line segment 6 0 4 turning point (finishing end point)

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Claims (1)

200422139 VI. Scope of patent application1. A method for measuring the end point of chemical mechanical polishing. The method mainly includes the following steps: (a) Setting at least one carrier 'and using the carrier to transfer a wafer containing a plurality of different material layers Positioned on a rotary table with a polishing pad on the surface, the wafer and polishing pad will rotate and rub against each other; (b) Use a measuring device to measure at least one ambient temperature; (c) Use a measuring device to measure at least one point of polishing Pad temperature, the measurement position is located on the surface of the polishing pad after the wafer in step (a) has just been rubbed; (d) the temperature measured in step (c) is subtracted from the ambient temperature of step (b) to obtain Temperature difference; and (e) calculating a slope of the temperature difference in time (d) versus time, the curve having at least a first constant slope, a non-definite slope, and a second constant slope The turning point between the non-constant slope and the second constant slope is the end point of grinding. 2 · The method for detecting the end point of chemical mechanical polishing as described in the first item of the patent application ', wherein the measuring device in step (a) of the method is a single-point temperature measuring instrument and a thermal imaging instrument. 3. The method for detecting the end point of chemical mechanical grinding as described in the second item of the patent application, wherein the temperature measuring instrument is an infrared temperature measuring instrument. • The method for detecting the end point of chemical mechanical polishing as described in the first item of the patent application ', wherein the position of the measured ambient temperature in step (b) of the method 2 is in the central area of the polishing pad and the polishing pad of the chemical polishing mechanical equipment Edge areas, chemical grinding machinery and equipment except rotary tables, and the environment 200422139 6. Scope of patent application Any point with stable temperature. • The method for detecting the end point of chemical mechanical polishing as described in the first item of the patent application, wherein steps (d) to (e) of the method use a computing device to detect the chemistry described in the fifth item of the patent application The method of the end point of mechanical grinding, wherein the computing device of the method is built in the measuring device of step (c) of the patent application or in an external computer. The detection of chemical mechanical polishing according to item 1 of item m ends, wherein step (e) of the method is achieved by a numerical method. 8. The detection method as described in item 7 of the patent application, wherein the numerical method is the method of grinding the end point by the least square method. Jiu Bingta's Linear Regression Loss Test Chemistry as described in Item No. 1 where the squared value of the slope t point of the temperature difference curve of the step of the method can be varied within a predetermined range. The solidity reached by the slope 1 0. The detection chemistry method described in item 9 of the patent application, wherein the predetermined range is a fixed 5% grinding end point