Patent Application
20220063050
The present invention relates a polishing apparatus.
In a manufacturing process of semiconductor devices, a flattening technology of a device surface is becoming more and more important. The most important of the flattening technology is chemical mechanical polishing (CMP). In this chemical mechanical polishing (which is referred to as CMP), using a polishing apparatus, a substrate such as a wafer is brought into sliding contact with a polishing surface while supplying a polishing liquid (slurry) containing abrasive grains such as silica (SiO2) and ceria (CeO2) onto a polishing pad, and the substrate is polished.
CMP (Chemical Mechanical Polishing) apparatus is used in a process of polishing a surface of a substrate in the manufacture of semiconductor devices. The CMP apparatus holds the substrate with a polishing head, rotates the substrate, and presses the substrate against a polishing pad on the rotating polishing table to polish the surface of the substrate. During polishing of the substrate, a polishing liquid (slurry) is supplied to the polishing pad, and the surface of the substrate is flattened by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid.
Japanese laid-open patent publication No. 2004-363229
A polishing rate of the substrate depends on a surface temperature of the substrate. Therefore, in the manufacture of semiconductor devices, it is important to control the polishing rate of the substrate based on the surface temperature of the substrate. A method of measuring the temperature of the polishing pad instead of directly measuring the surface temperature of the substrate during polishing of the substrate is known. In such a method, the surface temperature of the substrate is obtained based on the measured temperature of the polishing pad. However, in order to control the polishing rate more accurately, it is desirable to directly measure the surface temperature of the substrate.
A configuration is conceivable in which a temperature measuring device is provided on the polishing head for holding a back surface of the substrate. In such a configuration, the temperature measuring device measures a back surface temperature of the substrate from the polishing head side. However, since the substrate is thick, it is not possible to accurately obtain the surface temperature of the substrate even if the back surface temperature of the substrate is measured. Further, since an electronic device is processed on a front surface of the substrate, a type of temperature measurement sensor that comes into contact with the front surface of the substrate cannot be generally used.
Therefore, a polishing apparatus capable of accurately measuring the surface temperature of the substrate is provided.
In an embodiment, there is provided a polishing apparatus comprising: a window member configured to penetrate infrared rays; a polishing pad configured to embed the window member; a polishing head configured to hold a substrate rotatably and press the substrate against the polishing pad; and an infrared thermometer arranged below the window member, and configured to measure a surface temperature of the substrate held by the polishing head.
In an embodiment, a wavelength band, through which the window member penetrates, comprises a wavelength band in which the infrared thermometer can temperature measure.
In an embodiment, a wavelength band, through which the window member penetrates, is 1.5 micrometers or less, or 6.0 micrometers or more.
In an embodiment, the infrared thermometer has an infrared absorbing film made of an indium compound.
In an embodiment, a material of the window member is selected from an infrared permeability resin, calcium fluoride, synthetic quartz, germanium, magnesium fluoride, potassium bromide, sapphire, silicon, sodium chloride, zinc selenium, and zinc sulfide.
In an embodiment, the polishing apparatus has a function of recording or displaying a temperature distribution in a radial direction of the substrate measured by the infrared thermometer.
In an embodiment, a temperature measurement frequency of the substrate measured by the infrared thermometer is 10 Hz or higher.
According to the present invention, the surface temperature of the substrate can be accurately measured in a non-contact manner during polishing of the substrate.
Embodiments will be described with reference to the drawings. In the drawings described below, the same or corresponding components are designated by the same reference numerals, and duplicate description will be omitted.
The polishing table 2 is coupled to a table motor 6 arranged below a table shaft 5 via the table shaft 5, and the table motor 6 rotates the polishing table 2 in a direction indicated by the arrow. The polishing pad 1 is attached to an upper surface of the polishing table 2, and the upper surface of the polishing pad 1 constitutes a polishing surface 1a for polishing the substrate W. The polishing head 3 is fixed to a lower end of a head shaft 7. The polishing head 3 is configured to hold the substrate W on its lower surface by vacuum suction. More specifically, the polishing head 3 holds a front surface (device surface) of the substrate W downward. A surface opposite to the front surface is a back surface of the substrate W, and the polishing head 3 sucks and holds the back surface of the substrate W.
The head shaft 7 is coupled to a rotation mechanism (not shown) installed in a head arm 8, and the polishing head 3 is rotationally driven via the head shaft 7 by this rotation mechanism.
The polishing apparatus further includes a dressing device 24 for dressing the polishing pad 1. The dressing device 24 includes a dresser 26 which is slidably contacted with the polishing surface 1a of the polishing pad 1, a dresser arm 27 for supporting the dresser 26, and a dresser swivel shaft 28 for swiveling the dresser arm 27. The dresser 26 swings on the polished surface 1a as the dresser arm 27 turns. A lower surface of the dresser 26 constitutes a dressing surface composed of a large number of abrasive grains such as diamond particles. The dresser 26 rotates while swinging on the polishing surface 1a, and dresses the polishing surface 1a by slightly scraping off the polishing pad 1. Pure water is supplied from a pure-water supply nozzle 25 onto the polishing surface 1a of the polishing pad 1 during dressing of the polishing pad 1.
The polishing apparatus further includes an atomizer 40 for injecting a mist-like cleaning fluid onto the polishing surface 1a of the polishing pad 1 to clean the polishing surface 1a. The cleaning fluid is a fluid containing at least a cleaning liquid (usually, pure water). More specifically, the cleaning fluid is composed of a mixed fluid of the cleaning liquid and a gas (e.g., an inert gas such as nitrogen gas), or only the cleaning liquid. The atomizer 40 extends along a radial direction of the polishing pad 1 (or polishing table 2) and is supported by a support shaft 49. The support shaft 49 is located outside the polishing table 2. The atomizer 40 is located above the polishing surface 1a of the polishing pad 1. The atomizer 40 removes polishing debris and abrasive grains contained in the polishing liquid from the polishing surface 1a of the polishing pad 1 by injecting a high-pressure cleaning fluid onto the polishing surface 1a.
The polishing-liquid supply mechanism 4 includes a slurry supply nozzle 10 for supplying the polishing liquid onto the polishing pad 1, and a nozzle swirling shaft 11 to which the slurry supply nozzle 10 is fixed. The slurry supply nozzle 10 is configured to be able to swivel around the nozzle swivel shaft 11.
The substrate W is rotatably held by the polishing head 3. The polishing head 3 presses the substrate W against the polishing pad 1, and the polishing of the substrate W proceeds by sliding between the polishing pad 1 and the substrate W. When polishing the substrate W, the polishing liquid (slurry) is supplied onto the polishing pad 1 from the slurry supply nozzle 10.
The polishing apparatus has a configuration in which a surface temperature (i.e., the temperature on the device surface side) of the substrate W is directly measured without contacting the substrate W during polishing of the substrate W. Hereinafter, the configuration will be described with reference to the drawings.
An infrared thermometer 51 is arranged directly below the window member 50. The infrared thermometer 51 is a thermometer that measures the surface temperature of the substrate W based on an intensity of infrared rays emitted from the substrate W.
The polishing table 2 is formed with an embedded portion 52 communicating with the window hole 1b, and the infrared thermometer 51 is arranged in the embedded portion 52. In the embodiment shown in
A space Si having no obstacles is formed between the back surface 50b of the window member 50 arranged on the polishing pad 1 and a light receiving portion 51a of the infrared thermometer 51. In other words, the space Si is a space for reliably measuring the surface temperature of the substrate W by the infrared thermometer 51.
The substrate W is generally made of silicon. Since silicon (Si) absorbs light in the region of 1.5 to 6.0 micrometers, a radiation of infrared rays in the same region is low. In the embodiment, since the infrared thermometer for measuring the temperature of a radiator in a non-contact manner based on the amount of infrared radiation is used, it is not desirable to measure a wavelength band in which an infrared radiation is low.
Therefore, an infrared thermometer using an infrared absorbing film suitable for measuring the amount of radiated infrared rays having a wavelength of 1.5 micrometers or less, or 6.0 micrometers or more is used. A wavelength range of the measured amount of radiated infrared rays is 0.8 to 1.5 micrometers, or 6.0 to 1000 micrometers.
The infrared thermometers in which an indium compound such as InGaAs, InAs, InAsSb, InSb, etc is used as infrared absorbing films is considered desirable. However, it is not necessary to limit the material as long as the infrared absorbing film having sufficient sensitivity in the wavelength region to be measured is used.
The window member 50 installed on the polishing pad 1 needs to be made of a material that penetrates infrared rays having a wavelength to be measured. Example of the material that penetrates the wavelength include an infrared permeability resin, calcium fluoride, synthetic quartz, germanium, magnesium fluoride, optical glass (N-BK7), potassium bromide, sapphire, silicon, sodium chloride, zinc selenium, or zinc sulfide. However, if the above conditions are satisfied, it is not necessary to limit the material.
In this manner, the infrared ray radiated from the substrate W made of silicon penetrates the window member 50 without being attenuated (or with sufficiently small attenuation) by selecting the materials for the window member 50 and the infrared absorbing film. Moreover, the amount of radiated infrared rays can be measured by the infrared thermometer 51. As a result, the surface temperature of the substrate W can be measured.
The window member 50 comes into contact with the substrate W to be polished. Therefore, it is more desirable that the window member 50 is made of a material having mechanical, thermal, and chemical properties similar to those of the polishing pad 1 as much as possible.
The window member 50 and the infrared thermometer 51 are arranged on the rotating polishing pad 1 and the polishing table 2, respectively. Therefore, the window member 50 and the infrared thermometer 51 rotate together with the polishing table 2. Therefore, the surface temperature of the substrate W, which is the object to be measured, is measured only for the time when the window member 50 and the infrared thermometer 51 pass directly under the substrate W, and the time is generally as short as 1 second or less. Therefore, the temperature measurement frequency is at least 10 Hz or higher, preferably 100 Hz or higher.
As shown in
As shown in
As described above, the dresser 26 (see
In one embodiment, the window member 50 may be made of a material that penetrates infrared rays and has the same hardness as the polishing pad 1. In this case, the dresser 26 scrapes off the front surface 50a of the window member 50 together with the polishing pad 1. Therefore, even if the polishing surface 1a of the polishing pad 1 is scraped off, the front surface 50a of the window member 50 and the polishing surface 1a of the polishing pad 1 are arranged in the same plane.
In one embodiment, the polishing apparatus may have a configuration in which the window member 50 is lowered according to a wear-out of the polishing pad 1. For example, an actuator (not shown) for lowering the window member 50 is connected to the window member 50. In one embodiment, the window member 50 may be coupled to the infrared thermometer 51 and the actuator may be connected to the infrared thermometer 51. In this case, the actuator lowers the window member 50 together with the infrared thermometer 51. The actuator may include an air cylinder. The dressing device 24 includes a displacement sensor (not shown) for measuring a position of the dresser 26 in a height direction of the dresser 26. These actuator and displacement sensor are connected to the control device 100 (see
When the polishing pad 1 wears out, a distance between the dresser 26 and the displacement sensor becomes larger than a distance between the dresser 26 and the displacement sensor before the polishing pad 1 wears out. Therefore, the control device 100 calculates an amount of wear-out of the polishing pad 1 based on an amount of change in these distances. The control device 100 operates the actuator to lower the window member 50 by the calculated amount of wear-out. In this manner, the window member 50 descends as the polishing pad 1 wears out. As a result, even if the polishing pad 1 wears out, the front surface 50a of the window member 50 and the polishing surface 1a of the polishing pad 1 are arranged in the same plane.
The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.
The present invention is applicable to a polishing apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-002430 | Jan 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/041029 | 10/18/2019 | WO | 00 |
