JPH0453671A - Thermal deformation control type double face polishing device - Google Patents

Abstract

PURPOSE:To enable a thermal deformation control of good accuracy by arranging a displacement measuring device and heating device on the opposite face of at least one part of the upper/lower surface plates of a double face polishing device for wafer, and performing the control for turning a heater ON-OFF based on the displacement value of the surface plate. CONSTITUTION:A distortion gage 31 of a displacement measuring mean and heater 30 of a heating means are arranged in more than one pair at least at the specified position on the face opposite to at least one part of the polishing faces of upper/lower surface plates l, 2 of a both face polishing device, and the ON-OFF of the heater 30 are performed based on the detection quantity with the detection of the displacement. In the case of a temperature rise with the polishing face side being heated according to the progress of polishing, therefore, the face of the opposite side thereof is heated by the external heat source of a heater 30, etc., in the form of compensating this temperature rise and the temperature distributions of the upper and lower faces of the surface plate 1 are made equal. So the temperature distribution inside the surface plate becomes about symmetrical vertically and the thermal deformat ion control for minimizing the thermal deformation of the surface plate 1 is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a thermal deformation-controlled double-sided polishing device, and in particular to an upper and lower polishing surface plate (hereinafter referred to as upper surface plate) of a double-sided polishing device for, for example, a silicon wafer during processing. This invention relates to a thermal deformation-controlled double-sided polishing device that directly controls the thermal deformation of a lower surface plate (referred to as a lower surface plate).

[Prior Art] Conventionally, in a double-sided polishing apparatus for, for example, a silicon wafer, which mainly consists of an upper surface plate, a lower surface plate, a polishing cloth, a planetary carrier, a sun gear, and an internal gear, heat is applied to the polished surface during polishing. It has been pointed out that the upper and lower surface plates are heated, resulting in non-uniform temperature distribution and deformation due to the heat generation (particularly in chemical polishing such as mechanochemical boring). In this way, when the surface plate deforms during the polishing process, the form of contact between the wafer and the polishing surface constantly changes. Depending on the degree and progress of deformation, this can have an extremely negative effect on the flatness of the wafer after processing. This results in a situation where the processing becomes meaningless.

Therefore, there is a need for a double-sided polishing device that can control the thermal deformation of the surface plate, but generally the temperature of the polishing surface of the surface plate is measured and this is used as a control target to indirectly control the deformation. Methods of controlling (perhaps it would be more appropriate to say "controlling") are being implemented as countermeasures. Here, such an apparatus will be referred to as a temperature-controlled double-sided polishing apparatus.

Fig. 4 is a schematic cross-sectional view of an example of a conventional temperature-controlled double-sided polishing device, and Fig. 5 is a schematic plan view of its main parts.
Ultra-precision polishing and mirror finishing technology - Comprehensive technical data collection - 1 Published by Management Intermediate Center Publishing Department, October 31, 1988, P.
375-383). 6 is a partially enlarged schematic diagram shown to explain the operation of the apparatus shown in FIGS. 4 and 5, and FIG. 6 (a) is a sectional view of the main part, and (b) is a plan view. It is. In each of the above figures, 1 is an upper surface plate having a water channel 3 and an abrasive cloth 5 attached to the lower surface, 2 is a lower surface plate having a water channel 3a and an abrasive cloth 5 attached to the upper surface, and both water channels 3 .38
is connected to a cooling water chiller 21 via a pipe line 4.

A flow control needle valve 22 and a solenoid valve 2 are connected in series to the pipe line 4.
3 is provided, and an adjustment function is provided to adjust the flow rate or to turn the flow rate on and off, and the cooling water circulates through the water channel 3.38. 6 is a sun gear disposed in the center of the lower leg l112, 7 is a plurality of planetary carriers that also serve as carriers for the silicon wafer 9, 8 is an internal gear that meshes with the planetary carrier 7, and the planetary carrier 7 is the sixth As seen in (b) of the figure, rotation and revolution occur between the sun gear 6 and the internal gear 8. Silicon wafer 9 is placed on upper and lower surface plates 1.2
It is set in a planetary carrier 7 sandwiched between them, and is held under a predetermined pressure between polishing cloths 5 attached to the opposing surfaces of the upper surface plate 1 and the lower surface plate 2. 10 is a temperature sensor, upper surface plate 1
and the abrasive cloth 5 attached thereto at a predetermined point on the adhesive surface thereof, the temperature-sensing part is attached to the abrasive cloth 5,
The output signal is input to a thermometer and microcomputer controller 13 via a temperature signal transmitting antenna 11 and a temperature signal receiving antenna 12. Note that 14 is a pulse motor that operates the flow rate control needle valve 22 and is operated by a thermometer and a command from the microcomputer controller 13. Further, in FIG. 6(a), the silicon wafer 9, the water channel 3.3a, and the polishing cloth 5 are not shown.

In the temperature-controlled double-sided polishing apparatus described above, the upper surface plate 1,
The lower surface plate 2, sun gear 6, internal gear 8, and planetary carrier 7 rotate independently, creating a rotational speed difference (relative speed) between the silicone wafer 9 and the surface plate (actually, the polishing cloth 5). In this way, both sides of the silicon wafer 9 are polished. In this case, as a means of temperature control, a water channel (also called an ice chamber) 3.3a is installed on the surface plate to supply and circulate water to keep the surface plate constantly below 40℃ (for example, 30℃).
It is characterized by two points: (1) temperature control by detecting the temperature of the surface plate and controlling the temperature and flow rate of the water supplied to the water channel 3.3a according to the difference from the target temperature. It is something to do.

The conventional examples shown in Figures 4 to 6 are double-sided polishing machines, but in other polishing machines (for example, single-sided polishing machines), polishing is generally performed by the above-mentioned physical polishing. It is. Further, as mentioned above, chemical polishing (such as mechanochemical boring) that utilizes chemical changes between the polishing agent and the wafer may be the main processing method. Particularly in chemical polishing, which generates a large amount of heat, the polishing surface generates a large amount of heat during the polishing process, so the surface plate is heated, resulting in uneven temperature distribution and deformation.

[Problems to be Solved by the Invention] In the conventional double-sided polishing apparatus as described above, the temperature is accurately detected by a temperature sensor, and the amount of water at a predetermined temperature to be supplied to the water channels of the upper and lower surface plates is determined based on this temperature. Although efforts have been made to minimize thermal deformation of the surface plate by controlling the temperature of the surface plate, it is still difficult to obtain wafers with highly accurate flatness. In addition, even in temperature-controlled double-sided polishing equipment designed to indirectly control the deformation of the surface plate, there is no means to directly control thermal deformation, so deformation cannot be adequately controlled. It has been impossible to manufacture wafers with excellent flatness.

This invention was made to solve the above-mentioned problems, and provides a double-sided polishing device with excellent workability by directly detecting the thermal deformation of the surface plate and controlling it based on the detected amount. The purpose is to

[Means for Solving the Problems] A thermal deformation controlled double-sided polishing apparatus according to the present invention is a wafer double-sided polishing apparatus mainly composed of upper and lower surface plates, a polishing cloth, a planetary carrier, a sun gear, and an internal gear. ,
A cooling means provided inside at least one of the upper and lower surface plates and having a water channel for supplying cooling water at a predetermined temperature and a predetermined flow rate; and a cooling means installed on the opposite surface of the polishing surface of at least one of the upper and lower surface plates. a displacement measuring means for detecting thermal deformation of at least one of the upper and lower surface plates; a heating means for increasing the temperature of at least one of the upper and lower surface plates based on a detected value of the displacement measuring means; and a displacement measuring means. and a control device for controlling thermal deformation of at least one of the upper and lower surface plates by turning on and off the operation of the heating means during polishing of the wafer based on the output of the heating means.

[Function] In this invention, at least one pair or more of a strain gauge as a displacement measuring means and a heater as a heating means are placed at predetermined positions on at least one of the upper and lower surface plates of the double-sided polishing device, on the surface opposite to the polishing surface. It has a configuration in which displacement (strain) is detected and the heater is turned on and off based on the detected amount. Therefore, if the polishing surface side generates heat and rises in temperature as the polishing process progresses, if the opposite surface is heated with an external heat source such as a heater to compensate for this temperature rise, the upper and lower surfaces of the surface plate (polishing surface and the opposite side)
Therefore, the temperature distribution inside the surface plate becomes almost vertically symmetrical, and thermal deformation control is carried out to minimize thermal deformation (distortion) of the surface plate. The above is the basic function of thermal deformation control, but the actual thermal deformation control system
The heater is turned on and off by measuring the strain (distortion), and instead of directly controlling the temperature of the surface plate, it controls the temperature distribution to suppress displacement (distortion) as described above. It has become. In addition, in the thermal deformation control means of this invention, the surface plate is heated from above and below, but by constantly flowing cooling water at a constant temperature and constant flow rate into the water channel, the temperature of the surface plate does not rise more than necessary during processing. That's what I do.

[Embodiment] FIG. 1 is a schematic diagram of the main part showing an embodiment of a surface plate of a thermal deformation controlled double-sided polishing apparatus according to the present invention.

FIG. 1(a) is a partial plan view showing one quadrant of the upper surface plate as an example, and FIG. 1(b) is a sectional view taken along the line A--A shown in FIG. 1(a). In the figure, the same or corresponding parts as in the conventional example shown in FIGS. 4 to 6 are denoted by the same reference numerals, and the explanation thereof will be omitted. In this embodiment, a ring-shaped heater 3 with different diameters is provided on the surface opposite to the polishing surface of the upper surface plate 1 (see (b) in FIG. 1).
0 are glued and arranged concentrically. Also, corresponding to each heater 30, a strain gauge 31 is provided in the vicinity thereof.
Place.

In this case, the heater 30 is formed by a heater wire embedded in an insulator (not shown) and a terminal of the heater wire connected to two linear terminal electrodes adhesively formed on the insulator of the heater 3o. It is in constant contact with a spring pressure contact type heater terminal connected to a heater control circuit (not shown) even during rotation. Each of the strain gauges 31 has a strain signal transmitting antenna (not shown) on its upper part, and the strain signal transmitted from this antenna is received by a strain signal receiving antenna provided in the heater control circuit, and the strain signal is taken into the control circuit. It looks like this. Each strain output signal is transmitted at a different frequency for each strain gauge 31, so that the output of each strain gauge can be received separately. Figure 2 shows individual heaters 30. This is an example of a control block diagram corresponding to the strain gauge 31, which constitutes a control circuit. In addition,
Although not shown, the lower surface plate 2 also has a similar strain gauge 81. A heater 3o is arranged.

In the above configuration, first, as in the conventional example shown in FIG. Cooling water is supplied at a constant temperature and constant flow rate. Then, when the polishing process is started, the polishing surface side is heated and the temperature rises. For this reason, the upper surface plate 1 (hereinafter referred to as the surface plate in the description of the embodiment) begins to deform so as to bend upward. This thermal deformation is detected by a strain gauge (or displacement meter) 31. Therefore, as shown in FIG. 2, a predetermined reference value (strain) for on/off judgment of the heater 3o is used as a reference signal, and a comparator 32 is sent together with the actual displacement (strain) measured by the strain gauge 31. The deviation value is used to control on/off of the heater (heating device) 30. FIG. 3 is a diagram showing the relationship between the on-off signal of the heater 30 and the output of the strain gauge 31. Figure 3 (a
) shows the output of the strain gauge (vertical axis is strain) and time (horizontal axis), and (b) in Fig. 3 shows the on-off of the heater 30 (vertical axis).
and time (horizontal axis). As shown in the figure, when the output of the strain gauge 31 (wavy curve) exceeds the reference value (dotted line) for determining whether the heater 3o is on or off, the heater 80 is turned on (see (b) in Figure 3), and the Heat the outside surface of the board. The distortion increases slightly immediately after the heater 30 is turned on, but decreases with the passage of time. Then, when the distortion becomes less than the reference value, the heater 30 is turned off. By repeatedly performing this operation by the control device, thermal deformation control that can suppress the displacement to near the reference value is performed. In addition,
In the above embodiment, a strain gauge is used as a displacement measuring means, but a displacement meter can also be used if the mounting method is devised.

In addition, after the polishing process starts, the deformation of the surface plate is observed using the strain gauge 31, and the heater 30 is turned on or off according to the output of the strain gauge.
In thermal deformation control that turns off the heater 30, the output value of the strain gauge 31, which is the reference for turning on and off the heater 30, is determined by taking into consideration the specifications of the surface plate, the performance (characteristics) of the heater, the processing conditions, etc. It has become.

As is clear from the embodiments described above, the thermal deformation of the surface plate can be stabilized at a constant value compared to conventional temperature-controlled double-sided polishing equipment, so the machining defect rate of the tool can be reduced. Furthermore, processing accuracy (flatness) can be increased.

In the above embodiment, the strain gauge and heater were arranged on the upper surface plate, but depending on the case, they may be similarly arranged on the lower surface plate, or they may be arranged on both the upper and lower surface plates. You can.

[Effects of the Invention] As described above, according to the present invention, a displacement measuring device (such as a strain gauge) and a heating device (such as a strain gauge) and a heating device ( heater)
Since the heater is controlled to turn on and off based on the displacement value of the surface plate, the actual displacement of the surface plate can be controlled, compared to the conventional simple temperature control method.
Accurate thermal deformation control becomes possible. As a result, the processing defect rate of wafers can be significantly reduced, and processing accuracy (flatness) can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of the surface plate portion of an embodiment of the present invention, Fig. 2 is a control block diagram showing an embodiment of control corresponding to each heater and strain gauge, and Fig. 3 is a heater Figure 4 is a schematic cross-sectional view showing an example of a conventional temperature-controlled double-sided polishing device, and Figure 5 is the conventional example of Figure 4. FIG. 6 is a partially enlarged schematic diagram for explaining the operation of the conventional device. In the figure, 1 is an upper surface plate, 2 is a lower surface plate, 3 and 3a are water channels, 5 is a polishing cloth, 6 is a sun gear, 7 is a planetary carrier, 8 is an internal gear, 9 is a silicon wafer, and 10 is a temperature sensor , 30 is a heater, 31 is a strain gauge, and 32 is a comparator.

Claims (1)

[Scope of Claims] A double-sided polishing apparatus that polishes a wafer set on the planetary carrier, the main structure being an upper and lower polishing surface plate, a polishing cloth, a planetary carrier, a sun gear, and an internal gear, a cooling means provided on at least one of the lower polishing surface plates and having a water channel for constantly supplying cooling water controlled at a predetermined temperature and a predetermined flow rate; and an opposite polishing surface of at least one of the upper and lower polishing surfaces. displacement measuring means installed on the surface to detect thermal deformation of at least one of the upper and lower polishing plates; A heating means for raising the temperature, and an operation of the heating means is turned on and off during polishing of the wafer based on the output of the displacement measuring means to prevent thermal deformation of at least one of the upper and lower polishing plates. 1. A thermal deformation controlled double-sided polishing device, comprising: a control device for controlling thermal deformation.