TWI235692B - Apparatus and method for detecting film thickness in polishing machine - Google Patents

Abstract

An apparatus and a method for detecting film thickness detection in a polishing machine are disclosed for preventing moisture interference, wherein the polishing machine can be a chemical mechanical machine. The present invention is to pass hot gas flow through a gap between a pad window and a diffuser underneath the pad window, thereby enabling the temperature of the upper surface of the pad window to be the same as that of the lower surface thereof for preventing the pad window from having fogging; removing the water residing in the gap for preventing the moisture from interfering the accuracy of the film thickness detection via a laser module.

Description

1235692 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a film thickness method of a kind of polishing machine ', and more particularly to a method for chemical mechanical polishing and mechanical polishing (CMP) , To prevent the 22nd emical (Laser Module) from detecting the thick sound of the film layer on the wafer =: ^ Laser mode setting and method. Detecting the accuracy of the degree of accuracy | [Previous technology] The chemical mechanical polishing process uses a grinding machine similar to a sharpening machine (appropriate polishing liquid or grinding polymer) to smooth out the different contours of the wafer surface. A comprehensive (Gbalbal) flattening technique ^ volt == materials that can be ground in the manufacturing process include ..., cranes and τ steel and for example, oxide stone, nitride stone and other dielectric materials ί =! ㈣, as long as various The process parameters are properly controlled, and the use of chemistry can provide a flatness of more than 90%. Due to the chemical machine * Dufa provides good uniformity, surface flatness and control, U has entered the deep sub-micron generation and Damascene technology introduction;,, i ,, 'The mechanical grinding method has been widely used The ground is applied to the metal layer and low-level. =) In the manufacturing process of the dielectric layer, it has become an important planarization technology for semiconductor manufacturing today. = 仃 Chemical mechanical polishing process, the most commonly encountered-the problem is difficult ia 2 = f process is complete, that is, whether the wafer has been polished to achieve the desired level of jealousy ^ ^ ^. The factors that cause the material removal rate to change are roughly the σ aridity of the wafer, the composition of the slurry, the temperature effect, the state of the polishing pad, and polishing. Page 6 1235692 5. Description of the invention (2) The relative between the pad and the wafer The speed is required to reach the end of the grinding; These factors make the difference. Therefore, in the CMP process, it is often used to determine the Point Detect through the grinding time function to detect the research. ^ Using an end point detector (End 疚 continence Φ # ϋ A +, r grinding ,,,,; The endpoint detection system judges the age through the change in the intensity of the sinusoidal epidemic 1 slogan when the thickness of the dielectric layer or the current layer is turbid. Grinding should be stopped. Please refer to Figure 1A if the thickness of the wood layer has reached the end of the grinding process. The thickness of the coating layer is as follows: aa ^ ^, Η | ^ ^ ' / Up (not %%) M is placed on a polishing platform (piaten) 30 with a polishing pad 15. During the polishing step, the grinding polymer 25 is injected simultaneously to the upper surface of the polishing pad 15 = as a chemical aid. In the polishing platform 3 Q, a laser module 35 is installed to measure the thickness of the film layer on the wafer being polished synchronously. First, γ emits a laser through the control of the laser module 35. The light beam 45 reaches the lens 50. After the reflection from the lens 50, the laser light beam 45 sequentially passes through the light transmission above the grinding platform 30 (Diffuser) 40 and the polishing pad window 20 in the polishing pad 15 are irradiated on the surface of the wafer being polished. After the laser beam 45 is irradiated on the wafer 10, reflected light is generated. Then, the reflected light passes through the polishing pad window 20 and the light-transmitting sheet 40 in order and is received by the detector 5 5 also located in the laser module 35. Then, due to the reflected light of the laser beam 45 Intensity versus time has a periodic variation of a sinusoidal waveform, so after analyzing and processing this periodic variation of the sinusoidal waveform, the film thickness of the wafer 10 can be monitored and its polishing end point determined. Therefore, the laser beam 4 5 Whether the sine waveform of the reflected light is accurate and consistent is critical

Page 7 1235692 V. Description of the invention (3) The accuracy and reliability of detecting the film thickness of the wafer 10. In addition, since the grinding platform 30 used is usually an aluminum alloy material, a light-transmitting sheet 40 made of acrylic or other light-transmitting materials needs to be added. Similarly, 'from: the polishing pad 5 is also made of opaque material, so it is necessary to install a polishing pad window 20 similar to PU material, the polishing pad window 20 is located above the transparent sheet 4' The laser beam 45 and its reflected light pass. Please refer to FIG. 1B ', which is an enlarged schematic diagram showing the grinding and finishing of a conventional chemical mechanical grinding machine. Generally speaking, the polishing pad 15 is composed of a first polishing layer 15a with a harder material and a second polishing pad layer 5b with a softer material. Among them, the first polishing pad layer 15a is positioned above the second pad bottom layer 15b. The polishing pad window 20 is disposed in the first polishing pad layer 15a, and the second polishing pad layer 15b has a gap 22 (which is a cavity in the second polishing pad layer 15b), and the gap 22 is located corresponding to the polishing pad window 20 In the area, the laser beam 45 and its reflected light are passed. Since the light-transmitting sheet 40 is below the second polishing pad layer 15b, there is a gap 22 between the window 20 of the polishing pad and the light-transmitting sheet 40 below. During the chemical mechanical polishing process, the temperature of the wafer 10 (as shown in Fig. U) is increased due to frictional heat generation, and the temperature of the upper surface of the polishing pad window 20 in contact with the wafer Followed up. At this time, because there is a line in the gap 22 between the window 20 and the light-transmitting sheet 40, the temperature of the lower surface of the polishing pad is relatively low, which results in different temperatures above and below the polishing pad window 2 and makes the polishing pad window 2 〇 Fogging is easy to occur: On the other hand, during the chemical mechanical polishing process, the slurry 25 of the agent is continuously supplied between the wafer 10 and the polishing pad 15 and the moisture t will be along the first polishing. Water layer between 5 a and polishing pad window 2 〇

1235692 V. Description of the invention (4) The joint penetrates into the polishing pad 15 and the infiltrated water gas collects in the gap 22 between the first polishing pad layer 15a and the light transmitting sheet 40 (the bottom of the polishing pad window 20) surface). All the situations described above will cause the polishing pad window 2 to be blurred, and the laser beam 45 emitted by the laser module 35 will not be able to accurately observe the polishing situation through the polishing pad window 20, resulting in a laser. The module 35 detects an abnormality, and an abnormal laser light interference pattern is generated, so that the thickness of the film layer and the end point of grinding cannot be accurately detected. In particular, during the chemical mechanical polishing process of the oxide layer, for example, when a shallow trench isolation structure is formed, the end point of the oxide layer is not easy to observe, which leads to poor yield. In addition, 'the polishing pad saturated with water will interfere with the detection of the endpoint, so' it is necessary to replace the polishing pad with a new one from time to time to provide a good endpoint observation window. = This' It is very necessary to develop a device for detecting the thickness of the film thickness of the polishing machine. ^ ^ '' Incorrect to effectively improve the phenomenon of fogging on the polishing pad window; Remove: = between the polishing pad and light transmission Moisture between tablets; greatly reduces the 7 knives in the polishing pad to solve the problems of conventional technology. SUMMARY OF THE INVENTION Therefore, the visual inspection device and method of the present invention provide another polishing device to improve the detection of the end point of the polishing pad window starting by providing a polishing device and another purpose detection device and method. Disturbance is to provide a kind of grinding to remove the phenomenon of detecting fog of the thickness of the film layer collected on the grinding table, and to avoid improving the yield. Water between the pad thickness of the machine and the transparent sheet

1235692 V. Description of the invention (5) / ¾ ’while avoiding customers & According to the above objectives of μ, +, ρ, _ of the present invention, a method for detecting the thickness of a film layer of a polishing machine is provided, which is suitable for a chemical mechanical polishing machine that performs a chemical mechanical polishing process. ^ ^ A preferred embodiment of the month, the detection of the film thickness of this grinding machine is set to include: polishing pads, light transmission sheets, laser modules, air intake pipes, and exhaust official circuits. Grinding The pad is composed of a first polishing pad layer and a second polishing pad layer f ^ ΐ under the first polishing heat layer. The first polishing pad layer has a polishing window. The second polishing pad layer has a gap, and this The gap is located in the area corresponding to the window of the polishing pad in the first polishing pad. The transparent sheet is located below the polishing pad. The laser module is used to detect the end of the chemical mechanical polishing process. One end of the gap is used to pass gas into the gap, and one end of the exhaust pipe is connected to the other end of the gap to exhaust gas from the gap. In addition, the thickness of the film layer of the grinding machine of the present invention is Detection methods include at least Between the polishing window and the light-transmitting sheet; and using a laser module to measure the end of the chemical mechanical polishing process. Therefore, the application of the present invention can effectively improve the fogging of the window of the polishing pad. To avoid interference between the detection of the film thickness and the polishing end point; remove the water accumulated between the polishing pad and the light-transmitting sheet, and avoid the problem of difficult detection of the film thickness and the polishing end point to improve the yield; It can reduce the moisture in the polishing pad, so it can prolong the service life of the grinding pad without the need to change the polishing pad frequently, thereby reducing the production cost.

Page 10 1235692 V. Description of the invention (6) [Embodiment] According to the conventional techniques for detecting the thickness of the film layer, it can be known that the temperature of the upper and lower surfaces of the polishing pad window is different; and between the polishing pad and the transparent sheet The presence of moisture in the voids will cause the laser module to detect abnormally, and an abnormal laser light interference pattern will be generated, so that the thickness of the film layer and the end point of grinding cannot be accurately detected. Therefore, the present invention is characterized in that a hot gas is provided to flow between the window of the polishing pad and the light-transmitting sheet, thereby balancing the temperature of the upper and lower surfaces of the window of the polishing pad, and taking away the moisture existing in the gap. Please refer to FIG. 2, which illustrates a schematic structural diagram of a film thickness detection device for preventing water vapor interference according to the present invention. The polishing pad 5 is composed of a first polishing pad layer 15a and a second polishing pad layer 15b. The first polishing pad layer i5a has a polishing window 20 'and the second polishing pad layer 15b is located on the first polishing pad layer. Below 1 5 a, the second polishing pad layer 1 5 b has a gap 2 2 (void), and the gap 2 2 is located in the region corresponding to the polishing pad window 2 〇 in the second polishing pad layer 5 b. The laser beam emitted by the shooting module 35 can pass through the gap 22 and the polishing pad window 20 to the wafer (not shown). Below the second polishing pad layer 15b is a light-transmitting sheet 40, so the gap 22 is located between the light-transmitting sheet 40 and the first polishing pad 15. ≪ The present invention is characterized in that an intake pipe and an exhaust pipe are installed at both ends of the gap 22 to circulate gas into the gap 22. The air inlet pipe 100 is connected to one end of the gap 22 for passing gas into the space, and the knowledge of the exhaust pipe Π 0 is connected to the other end of the gap 2 2 from the gap 22 2 Exhaust gas. The gas circulating in the gap 22 can take away

Page 11 1235692 V. Description of the invention (7) Moisture. In addition, the present invention can further use a heated gas, the temperature of which can be approximately equal to the highest temperature of the first polishing pad 15a during the chemical mechanical polishing process. For example: when the chemical mechanical polishing process of tungsten metal layer is performed, the temperature of the polishing pad will rise to about 60 ° C. Therefore, when the airflow of about 60 ° C is passed, the temperature of the upper and lower surfaces of the polishing pad window can be balanced , While preventing the polishing pad window 20 from generating fog. Gases usable in the present invention are, for example, nitrogen, compressed dry air, inert gas, and any mixtures thereof. In addition, in the present invention, a valve 120 may be installed at the other end of the exhaust pipe 110. After the valve 120 is closed to seal the gas in the gap 22, the type change of the gas in the gap 22 (for example, whether there is a blister) can be observed to determine whether there is moisture in the gap 2 2. Furthermore, the present invention can further install a pressure measuring device (not shown) in the gap 22, and determine whether there is moisture infiltration into the gap 22 by measuring the pressure change (for example, pressure reduction) of the gas in the gap. It is worth noting that the present invention is not limited to chemical mechanical polishing machines and processes, and the present invention is also applicable to other polishing machines and processes.口 / 、 义 ΐ 上 ： ί ’ϊϊί: The method for detecting the thickness of the film layer of the grinding machine. For example, the chaos flows between the window of the polishing pad and the light-transmitting sheet. After that, a laser module is used to detect the end of the CMP process. ',,, = The above-mentioned preferred embodiment of the present invention shows that the advantages of applying the present invention can effectively improve the moisture between the fogging window of the polishing pad window and the light-transmitting sheet to avoid, ", = a and remove Focus on the interference of polishing pad measurement, and improve the yield. I ^ I 子 /, / μ, and winter point detection extend the life of the polishing pad without "C moisture" to lower production costs. ％ 而 日 守 守 Replace the grinding 塾 ’and then drop

Page 121235692___ 5. Description of the Invention (8) Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art will not depart from the spirit and scope of the present invention. Various modifications and retouching can be made, so the protection scope of the present invention shall be determined by the scope of the attached patent application.

Page 13123592 Brief description of the drawings [Simplified description of the drawings] In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings, The detailed description is as follows: FIG. 1A is a schematic diagram showing a structure of a film thickness detecting device of a conventional chemical mechanical polishing machine. Fig. 1B is an enlarged view showing a polishing pad of a conventional chemical mechanical polishing machine.

Fig. 2 is a schematic diagram showing the structure of a film thickness detecting device for preventing water vapor interference according to the present invention. [Simple description of component representative symbols] 10 · Wafer 15a: First polishing pad 2 0: Polishing pad window 2 5: Grinding slurry 3 5: Laser module 4 5: Laser beam 5 5: Detector 1 1 0: exhaust line 15: polishing pad 15b: second polishing pad 22: gap 3 0: polishing platform 40: light transmitting sheet 50: lens 1 0 0: intake line 120: valve

Page 14

Claims (1)

1235692__ VI. Application for patent scope 1. A device for detecting the film thickness of a grinding machine to prevent water vapor interference, wherein the device for detecting the film thickness of the grinding machine includes at least: a polishing pad; a polishing pad A window is located in the polishing pad; a light-transmitting sheet is located below the polishing pad, wherein a gap is formed between the light-transmitting sheet and the grinding pad; an air inlet pipe is connected to one end of the gap for A gas is introduced into the gap; and 'a = air pipe, wherein one end of the exhaust pipe is connected to the other end of the gap' for exhausting the gas from the gap. The debt measurement device for the thickness of the film layer of the polishing machine described in item 2 of the scope of the patent application, wherein the polishing pad further includes at least: a first polishing pad layer having the polishing pad window; and The polishing pad layer is located below the first polishing pad, wherein the gap is located in an area corresponding to the polishing pad window of the second polishing pad layer and in the polishing machine described in item 2 of the patent application scope. The thickness of the film layer is measured, wherein the temperature of the gas is substantially equal to the highest temperature of the first polishing pad layer in the chemical mechanical polishing process. / The detection of the thickness of the film layer of the grinding machine as described in item 1 of the scope of the patent application, wherein the gas system is a hot gas. Page 15 1235692 6. Scope of patent application 5 · The film thickness detection device of the grinding machine as described in item 1 of the scope of patent application, wherein the gas is selected from the group consisting of nitrogen, compressed dry air (CDA), and inert gas. A group of gases and any mixture thereof. 6 · The device for detecting the film thickness of a grinding machine as described in item 1 of the scope of patent application, further comprising at least: '' a valve installed at the other end of the exhaust pipe. 7 · The device for detecting the thickness of the film layer of the grinding machine as described in item 1 of the scope of the patent application, further including at least: & 'pressure measurement I, installed in the gap, so as to measure the The pressure of the gas. 8 · The device for detecting the film thickness of a grinding machine as described in item 1 of the scope of the patent application, further including at least: ， ， and flute module ’to measure the end of the chemical mechanical polishing process. 9 · The film thickness detection and measurement device of the grinder as described in item 1 of the scope of the patent application, wherein the grinder is a chemical mechanical polishing ((: 1 ^ 1111 (^) [Mechanical Polishing; CMP) Machine: 1 〇—A kind of film thickness detection device for grinding machine to prevent water vapor Page 16 1235692 6. The scope of the patent application interference, wherein the device for detecting the film thickness of the polishing machine includes at least: a polishing pad, and at least: a first polishing pad layer; and a polishing pad window located in the Among the first polishing pad layer, a second polishing pad layer is located below the first polishing pad layer, wherein the second polishing pad layer has a gap, and the gap is located in the polishing pad of the second polishing pad layer. In a region corresponding to the window; a light-transmitting sheet under the second polishing pad; a laser module to detect the end of the chemical mechanical polishing process; an air inlet pipe connected to the gap One end is used to pass a gas into the gap; and an exhaust pipe, wherein one end of the exhaust pipe is connected to the other end of the gap to discharge the gas from the gap. 11. The device for detecting the thickness of a film layer of a polishing machine as described in item 10 of the scope of patent application, wherein the temperature of the gas is substantially equal to the highest temperature of the first polishing pad in the chemical mechanical polishing process. 1 2. The device for detecting the film thickness of a grinding machine as described in item 10 of the scope of patent application, wherein the gas system is a hot gas. I · 1 3. The device for detecting the film thickness of a grinding machine as described in Item 10 of the scope of patent application, wherein the gas is selected from the group consisting of nitrogen, compressed dry air, inert gas, and any mixture thereof. Form one of the ethnic groups. Page 17 1235692 6. Application for Patent Scope 1 4 · The device for detecting the film thickness of the grinding machine as described in Item 10 of the scope of patent application, further includes at least: a valve installed on the exhaust pipe another side. 1 5 · The device for detecting the film thickness of a grinding machine as described in item 10 of the scope of patent application, further comprising at least: a pressure measuring device installed in the gap to measure the gas in the gap. pressure. 16 · The device for detecting the film thickness of a grinding machine as described in Item 10 of the scope of patent application, wherein the grinding machine is a chemical mechanical grinding machine. 1 7. —A method for detecting the thickness of a film layer of a polishing machine to prevent water vapor interference, wherein the polishing machine at least includes a polishing pad and a light-transmitting sheet located below the polishing pad. The polishing pad has A polishing pad window, and the method for detecting the film thickness of the polishing machine at least includes: providing a gas to flow between the polishing pad window and the transparent sheet of the polishing pad; and using a laser module to detect Measure the end of the grinding process. 1 8. The method for detecting a film thickness of a polishing machine according to item 17 of the scope of patent application, wherein the polishing pad further comprises at least: a first polishing pad layer having the polishing pad window; and Page 18 1235692___ VI. Patent application scope A second polishing pad layer is located below the first polishing pad, wherein a region corresponding to the polishing pad window of the second polishing pad layer has a gap, and the gas It circulates in this space. 19 · The method for detecting the film thickness of a polishing machine as described in item 17 of the scope of patent application, wherein the temperature of the gas is substantially equal to the highest temperature of the first polishing pad in the polishing process. 2 0. The method for detecting the film thickness of a grinding machine as described in item 17 of the scope of the patent application, further comprising at least: Observing the pressure change of the gas in the gap to determine whether moisture has penetrated into the gap . 2 1. The method for detecting the film thickness of a grinding machine as described in item 17 of the scope of patent application, wherein the gas system is a hot gas. 2 2. The method for detecting the film thickness of a grinding machine as described in item 17 of the scope of patent application, wherein the gas is selected from the group consisting of nitrogen, compressed dry air, inert gas and any mixture thereof . 2 3. The method for detecting the film thickness of a grinding machine as described in item 17 of the scope of patent application, wherein the grinding process is a chemical mechanical grinding process. Page 19