JP4275125B2 - Polishing apparatus and polishing method - Google Patents

Description

  The present invention relates to a polishing apparatus and a polishing method, and more particularly to a polishing apparatus and a polishing method for polishing a material to be polished such as a semiconductor wafer in a flat and mirror-like shape.

  In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. Along with this, the depth of focus becomes shallow when circuit formation is performed by optical lithography or the like, so that a higher flatness of the imaging surface of the stepper is required.

  As means for flattening the surface of a semiconductor wafer, a polishing tool (for example, a polishing table having a polishing cloth) and a gripping member that grips a material to be polished against the polishing table and presses the polishing surface are provided. A polishing apparatus that performs polishing by relatively sliding a tool and a polishing surface while supplying a polishing liquid between these contact surfaces is known. Such an apparatus not only performs mechanical polishing using a polishing liquid as a polishing liquid, but also performs polishing with a chemical action using an alkaline or acidic polishing liquid in some cases.

  In such a polishing apparatus, the factors that govern the removal rate (polishing rate) of the surface layer of the material to be polished include pressure on the wafer polishing tool (polishing cloth), sliding speed, etc., as well as the temperature of the polishing surface. It has been pointed out that (polishing temperature) also has an effect. Controlling such a polishing rate to be constant is important not only for improving the flatness but also for detecting the end point for confirming the end point of polishing.

  Therefore, in order to improve the flatness of a single wafer, reduce the variation in flatness between wafers, and accurately detect the end point of polishing, the temperature of the polishing surface must be set. It is necessary to control to the intended temperature. Reducing the variation in flatness between wafers is particularly meaningful because it can improve reproducibility when polishing a plurality of wafers sequentially.

  Furthermore, this polishing temperature is used when, for example, a film made of different materials, such as an oxide film and a nitride film, or a metal film such as a tungsten film, a titanium film, titanium nitride and an oxide film, and a barrier metal film are polished simultaneously. It becomes a factor which prescribes | regulates the selection ratio.

  The polishing temperature is determined by a balance of frictional heat generated during polishing, heat generated or removed by the slurry supplied to the polishing surface, and heat removed through the wafer holder and the polishing tool. Is expected. Therefore, the supply slurry temperature is controlled to be constant, or a cooling channel for maintaining the polishing table at a constant temperature is provided.

  However, even if the supply slurry temperature and the polishing table temperature are controlled as described above, it has been difficult to maintain the temperature of the polishing surface itself at the target temperature only by these means. As a result, variations in thickness between the plurality of materials to be polished or in-plane non-uniformity in one material to be polished occurred. Such variation makes it difficult to control the end point at which the polishing is finished at the planned thickness.

  The present invention has been made in view of the above-described problems, and is a polishing apparatus capable of improving thickness non-uniformity between materials to be polished or in one material to be polished and facilitating polishing end point control. And to provide a method.

  The invention according to claim 1 is a polishing apparatus having a polishing chamber and a control device for polishing an object to be polished, and the polishing chamber includes a temperature sensor for measuring the temperature of the atmosphere in the polishing chamber; A polishing table having a polishing surface; a nozzle for supplying a polishing liquid to the polishing surface; and a value of a polishing target temperature with respect to a temperature of a contact surface between the object to be polished and the polishing surface input to the control device; In the polishing apparatus, the temperature of the polishing liquid is controlled based on a value measured by the temperature sensor.

  As a result, the temperature of the polishing liquid can be controlled in accordance with, for example, the target polishing temperature, and accurate polishing temperature control can be performed, and polishing with good quality without variation in the polishing thickness can be performed. As used herein, the “space for housing the polishing apparatus” refers to a space that is small enough to partition the polishing apparatus with a wall or the like from a clean room where a semiconductor manufacturing process is performed or a space where a clean material to be polished is stored, or It refers to any space that accommodates a polishing device that is not so partitioned. Usually, an air supply means and an exhaust means are provided in the space, and a temperature control means is provided in the air supply means to control the temperature of the space.

A second aspect of the present invention is the polishing apparatus according to the first aspect, wherein a temperature within an allowable range that allows a temperature range above and below the target polishing temperature is input to the control device.

  A third aspect of the present invention is the polishing apparatus according to the second aspect, wherein the polishing table has a heat retaining medium space in which a heat retaining medium is circulated.

  According to a fourth aspect of the present invention, the control device calculates a target value of the polishing liquid temperature and the temperature of the heat retaining medium based on the target polishing temperature and the temperature of the atmosphere in the polishing chamber. The polishing apparatus described.

  According to a fifth aspect of the present invention, the control device compares the polishing liquid temperature with a target value of the polishing liquid temperature and the heat retaining medium temperature with a target value of the heat retaining medium temperature, and is within the allowable range. 5. The polishing apparatus according to claim 4, wherein the start of polishing is determined based on whether or not.

  The invention according to claim 6 is the polishing apparatus according to any one of claims 1 to 4, wherein the polishing apparatus includes an infrared sensor that measures a temperature of the polishing surface.

  The polishing apparatus usually includes a holding means for a material to be polished, a polishing tool having a polishing tool surface pressed against the polishing surface of the material to be polished, and a polishing liquid supply means for supplying a polishing liquid between these contact surfaces. Have. The space for housing the polishing apparatus is usually partitioned by a wall and provided with an opening (door) for taking in and out the material to be polished.

  The polishing temperature control device controls the polishing temperature on the contact surface by controlling the temperature of the polishing tool and the temperature of the polishing liquid, for example, based on the measured temperature of the space temperature sensor. Here, the temperature of the space itself may be further controlled, or a temperature measuring means on the contact surface may be provided to control the polishing temperature based on this measured temperature. As the temperature measuring means for the contact surface, the surface temperature of the polishing tool surface may be measured, or the surface temperature of the material to be polished may be directly measured.

The invention according to claim 7 is a polishing method for polishing an object to be polished in a polishing chamber provided in the polishing apparatus, wherein the control apparatus provided in the polishing apparatus contacts the object to be polished and the polishing surface. enter the target polishing temperature is a target value of the temperature of the surface, a polishing method and controlling the polishing liquid temperature based on the temperature of the polishing chamber and the polishing target temperature.

The invention according to claim 8 is a polishing method for polishing an object to be polished in a polishing chamber provided in the polishing apparatus, wherein the control apparatus provided in the polishing apparatus contacts the object to be polished and the polishing surface. A polishing target temperature that is a target value of the surface temperature and an allowable temperature that allows a temperature range above and below the polishing target temperature are input, and a polishing liquid temperature target value and a polishing surface are provided based on the polishing target temperature. A target value of the temperature of the heat retaining medium provided inside the polishing table is calculated, and the difference between the polishing liquid temperature and the target value of the polishing liquid temperature and the difference between the heat retaining medium temperature and the target value of the heat retaining medium temperature are It is a polishing method characterized by detecting that the temperature is within an allowable range and starting polishing.

  According to the polishing apparatus and the polishing method of the present invention, the polishing temperature is controlled more accurately, the variation in the polishing thickness between the materials to be polished due to the variation in the polishing temperature, or the in-plane thickness of the same material to be polished , And the product yield can be improved and high-quality polishing can be performed.

  Hereinafter, an embodiment of a polishing apparatus according to the present invention will be described with reference to FIG. This polishing apparatus supplies a polishing table 12 with a cloth (polishing cloth) 10 on the upper surface, a top ring 14 that presses against the cloth 10 while holding the semiconductor wafer W on the lower surface, and supplies a polishing abrasive liquid Q to the polishing cloth 10. And an abrasive nozzle 16.

  Although not shown, the polishing table 12 and the top ring 14 are each provided with a driving device that rotates them independently, and a pressing means (for example, an air cylinder) that presses the top ring 14 against the polishing table 12 is provided. It has been. Further, a polishing liquid supply system for supplying the polishing liquid Q to the polishing liquid nozzle 16 via the pipe 18 is provided, and a temperature sensor 20 for detecting the temperature of the supplied polishing liquid is heated at a predetermined position of the polishing liquid supply system. Alternatively, polishing liquid temperature adjusting means 22 for cooling is provided.

  Further, the polishing table 12 is formed with a heat retaining medium space 24 through which a cooling medium (heat retaining medium) C is circulated, and this is connected to an external heat retaining medium supply pipe 28 via a rotating shaft 26 that supports the polishing table 12. Has been. This heat retaining medium supply system is also provided with a temperature sensor 30 for detecting the temperature of the supplied heat retaining medium C and a heat retaining medium temperature adjusting means 32 for heating or cooling the polishing liquid Q. Outputs of these temperature sensors 20 and 30 are input to the control device 34, and control signals from the control device 34 are output to the temperature adjusting means 22 and 32.

  The polishing apparatus is accommodated in a polishing chamber (polishing space) 38 that is partitioned from a surrounding space by a partition wall 36, and air is taken into the space from the outside, dust is removed by a filter, and temperature is further increased. An air conditioner 42 is provided that adjusts the humidity and supplies it uniformly distributed from the upper part of the polishing chamber 38 through a plurality of outlets 40. Further, an exhaust pump 46 for exhausting air containing mist and abrasive particles from the lower exhaust port 44 is provided.

  With such a configuration, a uniform downward flow of clean air is formed in the polishing chamber 38, and particles generated by the polishing liquid and polishing flow along the downward flow, so that they are wound up to contaminate the material to be polished. It is prevented. Here, the exhaust from the lower part is discharged to the external system, but some or all of the exhaust is circulated and used, or heat exchange between the supply air and the exhaust is performed in some cases to make efficient use of heat. You may plan.

  In this example, the pressure in the polishing chamber 38 is changed to a unit adjacent to the polishing apparatus, for example, a cleaning unit that cleans the polished material W or a storage unit that stores unpolished or polished material. The pressure is set smaller than the pressure in the disposed polishing chamber 38. This is because, among these rooms, the polishing chamber 38 including this polishing apparatus is the space with the lowest cleanliness. With the above configuration, particles or the like from the polishing apparatus are placed in these spaces adjacent to the polishing apparatus. Contained air does not flow out.

  A temperature sensor 48 for detecting the room temperature is attached to the polishing chamber 38 at a predetermined location, and its output is also input to the control device 34. The control device 34 sends a control signal to the air conditioner 42 based on the detected temperature and the preset polishing temperature To value inputted in advance, and controls the temperature of the air supplied to the air conditioner 42. The temperature sensor 48 is preferably one that measures a representative value of the atmospheric temperature in the polishing chamber 38, and a plurality of the temperature sensors 48 may be arranged as necessary to adopt an average value.

  In this example, one control device 34 controls the temperature adjustment devices 22 and 32 and the air conditioner 42. However, a control device and a sensor are provided in each temperature adjustment device and air conditioner, and they are integrated. The control function may be provided to another or a part of these control devices.

  A method for controlling the polishing temperature in this polishing apparatus will be specifically described below. In the present invention, the polishing temperature is adjusted in consideration of the temperature of the polishing space 38 in addition to the respective temperatures of the polishing liquid Q and the temperature maintaining medium C for adjusting the polishing tool temperature. Here, the “polishing temperature” is the temperature of the contact surface where the surface of the wafer being polished (surface to be polished) and the surface of the table on the polishing side or the surface of the polishing cloth provided on the table are in contact with each other. That's it. As a control method, various methods can be considered by selecting a parameter to be measured and an object to be controlled and combining them. Here are some typical examples.

  FIG. 2 shows a first method of controlling the polishing temperature according to the present invention. Here, it is confirmed that the temperatures of the polishing chamber 38, the polishing liquid Q, and the polishing tool heat retaining medium C have almost reached the target temperatures. Then, control is performed to start polishing. First, in step 1, the target polishing temperature To is input to the computer (control device) 34. This polishing target temperature To is determined in advance according to conditions such as the object to be polished, polishing tool, polishing liquid, polishing rate, etc., and an optimum value To is obtained.

  Preheating may be performed in advance so that the temperatures of the polishing liquid Q and the heat retaining medium C are close to the target values, respectively. Next, in step 2, the temperature sensors 48, 30, and 20 measure the room temperature Tr, the polishing liquid temperature Tq, and the table heat retaining medium temperature Tc. In step 3, the computer 34 determines whether each measured temperature is within an allowable range with respect to the target value.

  If at least one measured temperature is outside the allowable range with respect to the target value, the corresponding temperature adjusting device 22, 32 or air conditioner 42 is operated in step 4 to adjust the temperature, and the process returns to step 2. Perform measurement again. If all of these temperatures are within the allowable range, or if they have become, polishing is started in step 5. After starting polishing, return to step 2 and measure again, and control so that each temperature is within the allowable range in the loop of step 2, 3, 4 → 2 or step 2, 3, 5 → 2. Do.

  In this method, if the polishing target temperature To is set to 16 ° C. and the allowable range t is set to 2 ° C., the temperature of the supplied polishing liquid Q, the temperature of the heat retaining medium C of the polishing table 12, and the temperature in the polishing chamber 38 itself. Are all maintained at 16 ± 2 ° C. As a result, the temperature of the polishing liquid Q and the polishing table 12 is basically the same temperature, so that heat does not move from there to the space, so the temperature is accurately controlled. A uniform polishing rate and proper in-plane uniformity can be obtained.

  Below, the result of the polishing temperature measurement performed in order to show the effect of this invention is shown. Here, the polishing temperature, that is, the polishing cloth 10 when the temperature of the polishing liquid Q, the temperature of the polishing table heat retaining medium C, and the temperature of the polishing chamber 38 are all controlled (the present invention) and when only the former two are controlled (conventional). The surface temperature of

Present invention (1) Present invention (2) Conventional polishing liquid temperature 15 40 15
Table insulation medium temperature 15 40 15
Polishing chamber temperature 16 39 23
Polishing temperature 17 39 23
Polishing target temperature 16 40 16

  Thus, it has been found that the polishing temperature is accurately controlled by controlling not only the temperature of the polishing liquid Q and the polishing table 12 but also the temperature of the polishing chamber 38. The temperature of the polishing chamber 38 itself may be controlled by controlling the temperature of the air supplied thereto, which can be performed by a normal air conditioner 42 as shown in FIG.

  In this first method, the temperature of the polishing liquid Q, the polishing table heat retaining medium C, and the polishing chamber 38 may be set and controlled individually, so that the control method is simple and highly practical. In the above example, when any one of the temperatures is excessively lowered, no measures such as polishing stop or alarm generation are prepared, but such a process may be incorporated.

  Next, the second method of controlling the polishing temperature according to the present invention will be described. This does not control the temperature of the polishing space itself, but uses this as a measurement parameter to control the temperature of the polishing liquid Q and the temperature of the polishing table 12 as other parameters. That is, when the temperature of the polishing chamber 38 is higher than the target polishing temperature To, the polishing temperature becomes higher than the polishing liquid Q and the polishing table heat retaining medium temperature. Therefore, in this case, the temperature of the polishing liquid Q and the polishing table heat-retaining medium C is set low in anticipation of the temperature rising due to the polishing space temperature.

  In this system, the polishing apparatus is not a small polishing space partitioned by a partition wall as shown in FIG. 1, but is arranged in a normal clean room or other larger room, and the temperature of the space is changed only by the convenience of the polishing apparatus. This is employed in cases where this is not preferable, or when the airtightness of the polishing space is low and it is difficult to control the temperature of the polishing space.

FIG. 3 shows the control of the second method. First, in step 1, the polishing target temperature To is input to the computer (control device) 34. In step 2, the temperature sensors 48, 30, and 20 are The room temperature Tr, the polishing liquid temperature Tq, and the table heat retention medium temperature Tc are measured. In step 3, the computer 34 uses the measured values as the target values for the polishing liquid temperature Tq and the table heat retention medium temperature Tc, Tqo, Tco. For example,
Tqo = To−k ₁ ΔT, Tco = To−k ₂ ΔT
Based on the formula of However, ΔT = Tr−To, and k ₁ and k ₂ are experimentally obtained constants.

  In step 4, the measured polishing liquid temperature Tq and table heat retention medium temperature Tc are compared with their target values Tqo and Tco. If they are not within the allowable range, in step 5, the corresponding temperature adjusting devices 22 and 32 are set. Operate to adjust temperature, return to step 2 and measure again. If all of these temperatures are within the allowable range, or if they have become, polishing is started in step 6. After starting polishing, return to step 2 and measure again, so that each temperature is within the allowable range in the loop of step 2, 3, 4, 5 → 2 or step 2,3,4,6 → 2. Take control.

  In this method, if the polishing target temperature To is set to, for example, 16 ° C. and the allowable range t is set to 2 ° C., the temperature of the supplied polishing liquid Q and the temperature of the heat retaining medium C of the polishing table 12 are the same as the polishing space and the target temperature To. It is maintained at a value that compensates for the difference. As a result, the polishing temperature becomes the target temperature To, and the temperature is accurately controlled. Therefore, a uniform polishing rate and proper in-plane uniformity suitable for each object to be polished can be obtained. Below, the result of the polishing temperature measurement performed in order to show the effect of the invention in the case of this 2nd system is shown.

Present invention (3) Present invention (4) Conventional polishing liquid temperature 10 48 15
Table heat retention medium temperature 10 47 15
Polishing chamber temperature 23 23 23
Polishing temperature 17 39 23
Polishing target temperature 16 40 16

  In this embodiment, the temperature of the polishing chamber 38 is used as only one measurement parameter and is not controlled. However, it is a matter of course that the polishing space temperature may be adjusted within the range allowed by other conditions. It is.

  Further, the polishing temperature, that is, the temperature of the polishing cloth 10 or the workpiece W to be polished may be measured by an appropriate method, and the control parameters including the temperature of the polishing space may be controlled based on this. As such a sensor, a sensor embedded in a thermometer in the turntable 12 or the top ring 14, or a sensor using a radiation thermometer type that measures the temperature of the surface of the polishing cloth from the outside in a non-contact manner, such as an infrared sensor, etc. is there.

It is sectional drawing which shows typically the whole structure of the grinding | polishing apparatus of this invention. It is a flowchart which shows the control method in the grinding | polishing apparatus of this invention. It is a flowchart which shows the other control method in the grinding | polishing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing cloth 12 Polishing table 14 Top ring 16 Polishing liquid nozzle 18 Thermal insulation medium piping 20, 30, 48 Temperature sensor 22, 32 Temperature adjustment apparatus 34 Control apparatus 38 Polishing space 42 Air conditioning apparatus C Thermal insulation medium Q Polishing liquid W Polishing material

Claims (8)

A polishing apparatus having a polishing chamber and a control device for polishing an object to be polished,
In the polishing chamber,
A temperature sensor for measuring the temperature of the atmosphere in the polishing chamber;
A polishing table having a polishing surface;
A nozzle for supplying a polishing liquid to the polishing surface is provided,
The temperature of the polishing liquid is controlled based on the value of the polishing target temperature with respect to the temperature of the contact surface between the object to be polished and the polishing surface input to the control device, and the value measured by the temperature sensor. Polishing equipment. The polishing apparatus according to claim 1, wherein a temperature within an allowable range that allows a temperature range above and below the target polishing temperature is input to the control device.   The polishing apparatus according to claim 2, wherein the polishing table has a heat retaining medium space for circulating a heat retaining medium therein.   4. The polishing apparatus according to claim 3, wherein the control device calculates target values for the polishing liquid temperature and the heat retaining medium temperature based on the polishing target temperature and the temperature of the atmosphere in the polishing chamber.   The control device compares the polishing liquid temperature with a target value of the polishing liquid temperature and the heat retaining medium temperature with a target value of the heat retaining medium temperature, and starts polishing based on whether or not the temperature is within the allowable range. The polishing apparatus according to claim 4, wherein:   The polishing apparatus according to claim 1, wherein the polishing apparatus includes an infrared sensor that measures a temperature of the polishing surface. A polishing method for polishing an object to be polished in a polishing chamber provided in a polishing apparatus,
The type of target polishing temperature is a target value of the temperature of the contact surface between the polishing surface and the object to be polished to a control device provided in the polishing apparatus,
A polishing method, wherein the polishing liquid temperature is controlled based on the polishing target temperature and the temperature in the polishing chamber. A polishing method for polishing an object to be polished in a polishing chamber provided in a polishing apparatus,
A polishing target temperature, which is a target value of the temperature of the contact surface between the object to be polished and the polishing surface, and an allowable temperature that allows a temperature range above and below the polishing target temperature are input to a control device provided in the polishing apparatus. ,
Based on the polishing target temperature, the target value of the polishing liquid temperature and the target value of the temperature of the heat retaining medium provided inside the polishing table having the polishing surface are calculated,
Polishing is started by detecting that the difference between the polishing liquid temperature and the target value of the polishing liquid temperature and that the difference between the heat retaining medium temperature and the target value of the heat retaining medium temperature is within the allowable temperature range. A polishing method comprising:

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