In general, a chemical mechanical polishing, or planarization, (CMP) process has been used for polishing a top face, or a device side, of a wafer during fabrication of a semiconductor device on the wafer. The wafer is “planarized” or smoothed one or more times in order for the top surface, or device side, of the wafer to be as flat as possible.
Typically, the CMP process involves holding and rotating a wafer of one or more materials against a wetted surface of a polishing pad under controlled chemical, pressure, and temperature conditions. A chemical slurry containing a polishing agent (also referred to as a “polishing slurry”), such as alumina or silica, is used as an abrasive material. Additionally, the chemical slurry contains selected chemicals which etch various surfaces of the wafer during the CMP process. Such a combination of mechanical and chemical removal of material during the CMP process allows the polished surface to be optimally planarized, e.g., removing a substantial amount of materials above the polished surface while remaining various device features formed below the polished surface substantially intact. Among the above-mentioned conditions, the temperature is typically considered as one of the most decisive factors to reach such an end.
In particular, the temperature may be referred to as the temperature on the surface of the polishing pad (hereinafter “pad temperature”). Although when the pad temperature is increased, a polishing rate can be accordingly increased, which increases throughput (i.e., reducing cost), various defects (e.g., corrosion/dishing effects) can be also formed on the polished surface. On the other hand, when the pad temperature is decreased, the polishing rate is accordingly decreased, which may require the use of additional chemical slurries. In turn, the cost may be significantly increased. Thus, it is generally desirable to perform the CMP process under an optimal temperature, and such an optimal temperature is desired to remain substantially constant.
To maintain the pad temperature substantially constant, the existing CMP apparatus (i.e., the equipment performing the CMP process) generally relies on dispensing only one chemical slurry controlled at a first temperature onto a polishing pad, and based on variation of temperature of the polishing pad (e.g., pad temperature), adjusting the first temperature of the chemical slurry. Such a technique may cause additional defects on a polished surface partially because of a delay induced while adjusting the first temperature of the only one chemical slurry. Therefore, existing CMP apparatuses are not entirely satisfactory.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that various features are not necessarily drawn to scale. In fact, the dimensions and geometries of the various features may be arbitrarily increased or reduced for clarity of illustration.
The following disclosure describes various exemplary embodiments for implementing different features of the subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
The present disclosure provides various embodiments of a CMP (chemical mechanical polishing) apparatus including at least two polishing slurries that are maintained at respective different temperatures. In some embodiments, the at least two polishing slurries, maintained at two different temperatures, are concurrently dispensed, but at respective different flow rates, onto a polishing pad of the CMP apparatus while performing a CMP process. Moreover, in some embodiments, such respective different flow rates of the at least two polishing slurries are determined based on a continuously monitored temperature of the polishing pad. As such, in some embodiments, the temperature of the polishing pad can be precisely and responsively maintained at a pre-defined constant value, which may substantially eliminate the above-mentioned issues observed in existing CMP apparatuses.
As shown in
Further, in some embodiments, when the sample 103 is held, by the sample carrier 102, against a top surface 114′ of the polishing pad 114 and the sample 103 and polishing pad 114 rotate at respective speeds (which will be discussed below), a first polishing slurry 116 containing an abrasive fluid, such as silica or alumina abrasive particles suspended in either a basic or an acidic solution, is dispensed onto the top surface 114′ of the polishing pad 114; and concurrently or subsequently, a second polishing slurry 126 containing the same abrasive fluid is also dispensed onto the top surface 114′ of the polishing pad 114.
More specifically, in some embodiments, the first polishing slurry 116 is dispended onto the polishing pad 114 through a conduit 118 and from a reservoir 120, and a flow rate of the first polishing slurry 116 is adjusted by a valve 122 coupled to the conduit 118; and the second polishing slurry 126 is dispended onto the polishing pad 114 through a conduit 128 and from a reservoir 130, and a flow rate of the second polishing slurry 126 is adjusted by a valve 128 coupled to the conduit 128. In other words, volumes (e.g., milliliters) of the first polishing slurry 116 and second polishing slurry 126 dispensed onto the polishing pad 114 over a period of time are respectively adjusted by the valves 122 and 132. In some embodiments, the conduit 118 and the corresponding valve 122 may be collectively referred to as a first dispenser; and the conduit 128 and the corresponding valve 132 may be collectively referred to as a second dispenser. Although in the illustrated embodiment of
Moreover, according to some embodiments, although the first polishing slurry 116 and second polishing slurry 126 contain the same abrasive fluid, the first polishing slurry 116 and the second polishing slurry 126 may be at respective different temperatures “T1” and “T2.” In some embodiments, the reservoir 120, containing the first polishing slurry 116, is maintained at the temperature T1; and the reservoir 130, containing the second polishing slurry 126, is maintained at the temperature T2, wherein T1 is higher than T2, for example.
In some embodiments, a temperature sensor 140 (e.g., an infrared radiation detection device, etc.) may be coupled to the polishing pad 114 at an area 141 of the top surface 114′. In some embodiments, such an area 141 may be located along a traveling path of the sample carrier 102 (and the to-be polished sample 103), which will be discussed in further detail below. Although in the illustrated embodiment of
Referring still to
Referring now to
As mentioned above, the disclosed CMP apparatus 100 is configured to dynamically (e.g., concurrently) adjust the flow rates of the first and second polishing slurries 116 and 126 so as to maintain the pad temperature at a substantially constant value.
In some embodiments, at time “t0,” the sample 103 is held by the sample carrier 102 with a to-be polished surface facing down against the top surface 114′ of the polishing pad 114. A speed of the drive motor 112, to rotate the polishing platen 114, is set at about 30 to 80 rpm, for example, and a speed of the drive motor 106, to rotate the sample carrier 102, is set at about 5 to 30 rpm, for example. Moreover, the sample carrier 102 is set to apply a pressure of about 6 to 12 psi between the sample 103 and the polishing pad 114, through the application of force 107. As such, the sample 103 and the polishing pad 114 may rotate in accordance with the sample carrier 102 and the polishing platen 110, respectively. In some embodiments, at time t0, neither the first polishing slurry 116 nor the second polishing slurry 126 is dispended onto the polishing pad 114. Thus, the pad temperature 201 may be substantially lower than the constant value Tc.
Subsequently, at time “t1,” while keeping the sample 103 and polishing pad 114 rotating at respective speeds, the first polishing slurry 116, which is maintained at the higher temperature T1, is dispensed onto the polishing pad 114 through the conduit 118 to saturate the polishing pad 114. More specifically, as shown in the illustrated embodiment of
Next, at time “t2,” as more of the first polishing slurry 116 is dispensed onto the polishing pad 114 during the CMP process, the pad temperature 201, which is continuously monitored by the temperature sensor 140, may exceed the constant value Tc. In response, the controller 150 may cause the valve 122 to reduce the flow rate of the first polishing slurry 116, and the valve 132 to increase the flow rate of the second polishing slurry 126. As such, from time “t2” to time “t3,” the flow rates of the first polishing slurry 116 and second polishing slurry 126 are kept decreasing and increasing, respectively, until the pad temperature 201 is maintained at the contact value Tc for a certain period of time, for example, t3 minus t2. More specifically, when the first polishing slurry 116 and second polishing slurry 126 are both dispensed onto the polishing pad 114, a mixture of the first polishing slurry 116 and second polishing slurry 126 are in present between the sample 103 and the polishing pad 114, which causes the pad temperature 201 to be between the temperatures T1 and T2, according to some embodiments. And when the flow rates of the first polishing slurry 116 and second polishing slurry 126 are concurrently adjusted, the pad temperature 201 can be controlled to maintain at the constant value Tc.
Although in the illustrated embodiment of
In some embodiments, the method 300 starts with operation 302 in which a first polishing slurry at a first temperature is dispensed onto a rotating polishing pad using a first flow rate. In the above example, the first polishing slurry 116, which is maintained at the higher temperature T1, is dispensed onto the polishing pad 114 through the conduit 118 in a flow rate adjusted by the valve 122 that is coupled to the conduit 118. Next, the method 300 continued to operation 304 in which a second polishing slurry at a second temperature is dispensed onto the rotating polishing pad using a second flow rate. Continuing with the above example, the second polishing slurry 126, which is maintained at the lower temperature T2, is dispensed onto the polishing pad 114 through the conduit 128 in a flow rate adjusted by the valve 128 that is coupled to the conduit 128. Next, the method 300 continues to operation 306 in which a temperature of the rotating polishing pad is monitored. Continuing with the above example, the temperature of the rotating polishing pad, which is the pad temperature 201, is monitored by the temperature sensor 140, and further reported to the controller 150. Next, the method 300 continues to operation 308 in which a polishing process is performed under a substantially constant temperature by adjusting at least one of the first and second flow rates. Since the pad temperature 201 is dynamically monitored by the controller 150, when the pad temperature 201 exceeds, or drops below, the pre-determined constant temperature Tc, the controller 150 may adjust the valve 122 to control the first flow rate of the first polishing slurry 116 and/or adjust the valve 132 to control the second flow rate of the second polishing slurry 126 so as to maintain the pad temperature 201 substantially close to pre-determined constant temperature Tc, as discussed above.
The foregoing outlines features of several embodiments so that those ordinary skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
In an embodiment, an apparatus for performing a polishing process includes: a rotatable polishing pad; a temperature sensor configured to monitor a temperature on a top surface of the rotatable polishing pad; a first dispenser configured to dispense a first slurry that is maintained at a first temperature on the rotatable polishing pad; and a second dispenser configured to dispense a second slurry that is maintained at a second temperature on the rotatable polishing pad, wherein the second temperature is different from the first temperature so as to maintain the temperature on the top surface of the rotatable polishing pad at a substantially constant value.
In another embodiment, a method includes: dispensing a first slurry at a first temperature using a first flow rate on a rotating polishing pad; dispensing a second slurry at a second temperature using a second flow rate on the rotating polishing pad, wherein the second temperature is different from the first temperature; and performing a polishing process on a sample under a substantially constant temperature by adjusting at least one of the first rate of the first slurry and the second flow rate of the second slurry.
In yet another embodiment, a method includes: dispensing a first slurry with a first temperature using a first flow rate on a polishing pad; dispensing a second slurry with a second temperature using a second flow rate on the polishing pad, wherein the second temperature is different from the first temperature; rotating the polishing pad to polish a sample by holding the sample against the polishing pad in a presence of a mixture of the first and second slurries; monitoring a temperature on a top surface of the polishing pad; and when the temperature is offset from a substantially constant temperature, adjusting at least one of the first and second flow rates so as to maintain the temperature at the substantially constant temperature.
This application is a continuation of U.S. patent application Ser. No. 17/405,933, filed Aug. 18, 2021, which is a continuation of U.S. patent application Ser. No. 15/901,796, filed Feb. 21, 2018, now U.S. Pat. No. 11,103,970, which claims priority to U.S. Provisional Patent Application No. 62/545,666, filed on Aug. 15, 2017, each of which are incorporated by reference herein in their entireties.
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Official Action issued Feb. 15, 2019, in corresponding Taiwan Patent Application No. 10820109390. |
Number | Date | Country | |
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20230286106 A1 | Sep 2023 | US |
Number | Date | Country | |
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62545666 | Aug 2017 | US |
Number | Date | Country | |
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Parent | 17405933 | Aug 2021 | US |
Child | 18198727 | US | |
Parent | 15901796 | Feb 2018 | US |
Child | 17405933 | US |