JP4839294B2 - Semiconductor wafer holding device - Google Patents

Description

  The present invention relates to a semiconductor wafer holding apparatus that holds a semiconductor wafer in a processing chamber that performs a predetermined process on the semiconductor wafer. More specifically, only the device structure portion is thinned so that ribs are formed on the outer peripheral edge thereof. The present invention relates to a semiconductor wafer holding device for semiconductor wafers.

  In a vacuum processing apparatus that performs a predetermined process such as CVD or plasma etching, a so-called electrostatic chuck of an electrostatic adsorption system is used to hold a semiconductor wafer (hereinafter referred to as “wafer”) in a processing chamber in a vacuum atmosphere. An incorporated substrate stage (substrate holding device) is arranged. When the predetermined vacuum processing is performed by holding the wafer by the electrostatic chuck as described above, not only the wafer is held so as not to be displaced but also the substrate is held with good adhesion to heat and cool the wafer. In this case, performance such as maintaining a constant in-plane temperature is required.

  By the way, recently, in order to improve productivity, there is a tendency to make a wafer large in diameter and thin (thickness of 150 μm or less). When a plurality of processing steps such as thin film formation and etching processing are performed on such a wafer to form a desired device structure, the wafer is warped in various directions. In this case, when a wafer having a large warp is placed on the substrate stage and the wafer is held by the electrostatic chuck mechanism, a problem arises in that the warped portion of the wafer cannot be held on the substrate stage.

Therefore, conventionally, a clamping means comprising a plurality of up and down drive shafts erected around the substrate stage, and a clamp ring connected to the upper end of the drive shaft and capable of applying a pressing force to the outer peripheral edge of the wafer. It is disclosed in Patent Document 1 to provide the above. In this device, with the clamp ring positioned above the substrate stage, the wafer is placed on the substrate stage, the clamp ring is lowered, and a pressing force is applied to the outer peripheral edge of the wafer to place the wafer on the substrate. In close contact with the upper surface of the stage, the electrostatic chuck mechanism is operated to attract and hold the wafer on the substrate stage. Thus, the wafer is adhered and fixed to the substrate stage by the clamping means, and the wafer is attracted and held by the electrostatic chuck in this state, so that even a warped wafer can be held with good adhesion.
JP 2001-53030 A

  Here, if the wafer has a large diameter and a thin wall, the pressure resistance is reduced, and the possibility that the wafer is damaged during each processing step of manufacturing the device structure and during transfer increases. For this reason, in recent years, it has been proposed to use a so-called ribbed wafer in which ribs are formed on the outer peripheral edge by thinning only the device structure. However, even if such a wafer with ribs is warped in various directions when each processing step is performed as in the case of a conventional wafer having no ribs, the opposite side to the rib forming surface. In order to perform predetermined processing on the surface (surface on which the device structure is formed), the ribbed wafer needs to be held on the substrate stage with good adhesion without being damaged.

  In view of the above points, an object of the present invention is to provide a semiconductor wafer holding device in which a wafer with ribs can be held (set) on a substrate mounting portion without being damaged.

  In order to solve the above-described problems, the present invention provides a semiconductor wafer placed in a processing chamber in which a predetermined process is performed on a semiconductor wafer having a rib formed on its outer peripheral edge by thinning only the device structure. A semiconductor wafer holding device comprising: a substrate mounting portion; a clamping means capable of applying a pressing force to an outer peripheral edge portion of the semiconductor wafer having the rib; and an electrostatic chuck assembled to the substrate mounting portion. The substrate mounting portion has a stepped shape with its central region protruding in a convex shape, and the upper surface of the convex protruding portion is formed smaller than the area of the chip effective portion inside the rib, and the rib is formed on the substrate mounting portion. When the semiconductor wafer is placed on the projecting portion from the opposite direction and a pressing force is applied by the clamping means, the lower end surface of the rib comes into contact with the flat surface lowered by one step, and the electrostatic chuck mechanism is When activated, Vice structure is in surface contact with the protrusion upper surface, characterized by being configured so as to be sucked and held.

  When holding the wafer with ribs by the semiconductor wafer holding apparatus of the present invention, the wafer is placed on the upper surface of the protruding portion that is smaller than the area inside the rib from the direction in which the rib faces the substrate placement portion. At this time, the wafer that has undergone a plurality of processing steps for forming the device structure is warped in various directions. When a pressing force is applied to the outer peripheral edge portion of the wafer where the rib exists by the clamp ring, the lower end surface of the rib comes into contact with the flat surface lowered by one step on the substrate mounting portion. In this case, the warpage of the wafer is corrected and held between the upper surface of the protrusions through a minute gap. Further, even when a pressing force is applied by the clamp ring, the lower end surface of the rib comes into contact with the flat surface, so that a problem such as the wafer being damaged by the pressing force does not occur. When the electrostatic chuck is actuated, the wafer is attracted and held with the inner surface of the rib being in surface contact with the upper surface of the protrusion.

  As described above, according to the present invention, even when a wafer to be processed is provided with a rib, the wafer is held with good adhesion. For example, even when the wafer is heated or cooled, the in-plane temperature is kept constant. Such performance can be exhibited.

  In the present invention, the clamp means includes a drive shaft that is vertically movable around the substrate mounting portion, and an annular clamp ring that is connected to the tip of the drive shaft, and operates the drive shaft. A configuration in which a pressing force acts on the entire outer peripheral edge of the semiconductor wafer when the clamp ring is lowered may be employed.

  By the way, after performing predetermined processing on the processing surface of the wafer with ribs, further predetermined processing such as back grinding may be performed on the surface on which the rib is formed. For this reason, it is preferable that the pressing force acting on the semiconductor wafer can be changed according to the setting direction of the wafer on the substrate mounting portion so that the wafer is not damaged.

  Referring to FIG. 1, 1 is provided in a processing chamber for performing a predetermined process such as etching on a wafer W with ribs having a rib WR formed on the outer peripheral edge by thinning only the device structure. The wafer W is held with the surface (surface on which the device structure is formed) opposite to the surface on which the rib is formed facing upward. The substrate stage 1 includes a base 2 and an electrostatic chuck 3 provided at the center of the upper surface of the base 2. The metal base 2 has a stepped shape with its central region protruding in a convex shape, and the upper surface of the convex protruding portion 2a is formed smaller than the area of the chip effective portion inside the rib.

  The electrostatic chuck 3 is configured by arranging electrodes (not shown) in a predetermined pattern in an insulator such as silicon rubber provided on the upper surface of the protruding portion 2a, and is covered by applying a voltage to the electrodes of the electrostatic chuck 3. The processing substrate S is sucked and held on the substrate stage 1. In this case, the height from the flat surface 2b of the projecting portion 2a including the electrostatic chuck 3 is such that the lower end surface of the rib WR is lowered by one step on the base 2 when a pressing force is applied by a clamping means described later. The back surface of the wafer W (the surface inside the rib) is set so as to be substantially parallel to the upper surface of the protruding portion 2a via a minute gap.

  A clamp unit 4 is provided around the base 2, and the clamp unit 4 and the substrate stage 1 having the electrostatic chuck 3 constitute the wafer holding apparatus of the present embodiment. The clamp means 4 includes a clamp ring 41 that applies a pressing force to the outer peripheral edge portion where the rib WR of the wafer W exists. A plurality of drive shafts 42 are suspended from the lower surface of the clamp ring 41, and each drive shaft 42 penetrates up and down on a flat surface 2 b lowered by one step on the substrate stage 1 to drive means 43 such as an air cylinder. It is connected. Accordingly, the clamp ring 41 is moved up and down with respect to the substrate stage 1 by the operation of the driving unit 43.

  Next, the holding operation of the wafer W with ribs on the wafer holding apparatus of the present invention will be described. First, in a state where the clamp ring 41 is in the raised position, the rib WR straddles the upper surface of the protruding portion 2a from the direction in which the rib WR faces the substrate stage 1 by a transfer robot having a known structure provided with finger portions ( The wafer W is placed with a minute gap between the side surface of the rib and the protrusion 2a. At this time, the wafer that has undergone a plurality of processing steps for forming the device structure is warped in various directions (see FIGS. 2A and 3B).

  Next, when the drive means 43 is operated to lower the drive shaft 42, the clamp ring 41 applies a pressing force to the outer peripheral edge of the wafer W where the rib WR exists, and the lower end surface of the rib WR is placed on the substrate. It comes into contact with the flat surface 2b that is lowered by one step (see FIGS. 2B and 3B). At this time, the warpage of the wafer W is corrected, and the wafer W is held substantially horizontally with a slight gap between the upper surface of the protrusion 2b. When the electrostatic chuck 3 is operated, the wafer W is held in close contact with the inner surface of the rib being in surface contact with the upper surface of the protruding portion 2a.

  Thereby, in the wafer holding means of the present embodiment, even if the wafer W to be processed has a rib WR, the wafer W can be held on the substrate stage 1 with good adhesion. Even in the case of heating and cooling, performance such as maintaining a constant in-plane temperature can be exhibited.

  In the present embodiment, since the device structure portion is formed on the surface opposite to the surface on which the rib WR is formed, the rib WR protrudes from the direction in which the rib WR faces the substrate stage 1. The case where the wafer W is placed so as to straddle the wafer has been described. However, when further predetermined processing such as back grinding is performed on the surface on which the rib is formed, the wafer W is set so that the wafer W is not damaged. It is preferable that the pressing force acting via the clamp ring 41 can be changed according to the direction to be changed. In this case, if the driving means 43 is an air cylinder, the pressing force acting via the clamp ring 41 can be changed by changing the supply pressure to the air cylinder via a regulator.

1 is a cut side view showing a semiconductor wafer holding device according to an embodiment of the present invention while holding a wafer. (A) And (b) is a figure explaining the close_contact | adherence holding | maintenance of the semiconductor wafer to the semiconductor wafer holding apparatus shown in FIG. (A) And (b) is a figure explaining the close_contact | adherence holding | maintenance of the semiconductor wafer to the semiconductor wafer holding apparatus shown in FIG.

Explanation of symbols

1 Substrate stage (substrate placement part)
2 Base 3 Electrostatic chuck 41 Drive shaft (clamping means)
42 Clamp ring (clamping means)
W Semiconductor wafer WR Rib

Claims (3)

A substrate mounting portion on which a semiconductor wafer is placed in a processing chamber for performing a predetermined process on a semiconductor wafer having a rib formed on the outer peripheral edge by thinning only the device structure portion, and a semiconductor having the rib A semiconductor wafer holding device comprising: clamping means capable of applying a pressing force to the outer peripheral edge of a wafer; and an electrostatic chuck assembled to a substrate mounting portion,
The substrate mounting portion has a stepped shape in which the central region protrudes in a convex shape, and the upper surface of the convex protrusion is formed smaller than the area of the chip effective portion inside the rib,
When the semiconductor wafer is placed on the projecting portion from the direction in which the rib faces the substrate placing portion and a pressing force is applied by the clamping means, the lower end surface of the rib becomes a flat surface lowered by one step on the substrate placing portion. A device for holding a semiconductor wafer, wherein the device structure portion is brought into surface contact with the upper surface of the protruding portion and held by suction when the electrostatic chuck mechanism is actuated.   The clamp means includes a drive shaft that can be raised and lowered standing around the substrate mounting portion, and an annular clamp ring that is connected to the tip of the drive shaft, and operates the drive shaft to lower the clamp ring. 2. A semiconductor wafer holding apparatus according to claim 1, wherein a pressing force acts on the entire outer peripheral edge of the semiconductor wafer.   3. The semiconductor wafer holding apparatus according to claim 1, wherein a pressing force acting on the semiconductor wafer is freely changeable.

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