JP2019009291A - Processing method of wafer - Google Patents

Abstract

To form a wafer gettering layer on a wafer, by controlling the melting of alkaline fine grains contained in an abrasive pad while supplying pure water.SOLUTION: A processing method of a wafer (W) includes a polishing step of polishing the reverse face (W2) of the wafer with action of dissolved alkaline fine grains by pressing a polishing pad against a silicon substrate with a predetermined pressure, while supplying pure water to a polishing pad (47) containing solid-phase reaction fine grains (81) inducing solid-phase reaction with silicon, gettering fine grains (82) having a Mohs hardness higher than that of silicon and forming a gettering layer, and alkaline fine grains (85), and a gettering layer formation step of forming the gettering layer by pressing the polishing pad with a pressure lower than the predetermined pressure, while supplying pure water of water temperature for lowering the solubility of the alkaline fine grains, after executing the polishing step, and scratching the reverse face of the wafer by polishing with the polishing pad.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer processing method for forming a gettering layer on a wafer.

  In the semiconductor device manufacturing process, a semiconductor device is formed by dividing a semiconductor wafer on which a plurality of devices are formed along a street. In order to reduce the size and weight of a semiconductor device, the back surface of the semiconductor wafer is ground before the semiconductor wafer is divided. When the semiconductor wafer is ground in this way, a grinding strain layer of about 1 μm composed of microcracks is formed on the back surface of the semiconductor wafer. When the thickness of the semiconductor wafer is reduced to 100 μm or less, there is a problem that the bending strength of the semiconductor device is lowered by the grinding strain layer.

  In order to solve such a problem, after grinding the semiconductor wafer to a predetermined thickness, the back surface of the semiconductor wafer is subjected to polishing processing, wet etching processing, dry etching processing, etc., and grinding distortion generated on the back surface of the semiconductor wafer is generated. The layer is removed to prevent a reduction in the bending strength of the semiconductor device.

  On the other hand, in a semiconductor wafer in which a plurality of semiconductor devices having a memory function such as a DRAM and a flash memory are formed, there is a problem that the memory function is degraded when the grinding strain layer is removed. This is because the gettering effect disappears when the grinding strain layer on the backside of the semiconductor wafer is removed, and metal ions such as copper contained in the semiconductor wafer float on the surface side where the device is formed, causing current leakage. This is considered to occur.

  In order to solve such a problem, a polishing pad for forming a gettering layer made of microcracks having a thickness of 0.2 μm or less on the back surface of a semiconductor wafer has been proposed (see, for example, Patent Document 1). . The polishing pad of Patent Document 1 is a liquid in which solid-phase reaction fine particles (polishing abrasive grains) that induce a solid-phase reaction with silicon and gettering fine grains (gettering abrasive grains) having a Mohs hardness higher than that of silicon are mixed. The nonwoven fabric is impregnated with a binder.

  In the wafer processing method using this polishing pad, after grinding the semiconductor wafer to a predetermined thickness, the back surface of the semiconductor wafer is polished with the polishing pad while supplying the alkaline solution from the alkaline solution supply source. Thereby, the solid phase reaction fine particles work, and the grinding strain layer by the grinding wheel remaining on the back surface of the semiconductor wafer can be removed. Then, the back surface of the semiconductor wafer is polished with a polishing pad while supplying pure water from a pure water supply source. As a result, the gettering fine particles work to form a slight scratch on the back surface of the semiconductor wafer that does not reduce the bending strength, thereby forming a gettering layer.

JP2015-46550A

  However, in the above processing method, it is necessary to handle an alkaline solution. Further, since it is necessary to provide an alkaline solution supply source in the polishing apparatus in addition to the pure water supply source, there has been a problem that the apparatus configuration becomes complicated and the cost is high.

  The present invention has been made in view of the above points, and provides a wafer processing method capable of forming a gettering layer satisfactorily on a wafer by controlling the dissolution of alkali fine particles contained in the polishing pad while supplying pure water. One of the purposes is to do.

  The wafer processing method of one embodiment of the present invention is a wafer processing method for processing a wafer having a device formed on the surface of a silicon substrate, and a protective member is attached to the surface of the wafer, and the holding surface of the chuck table A wafer holding step for holding the protective member side, solid phase reaction fine particles that induce a solid phase reaction with silicon, gettering fine particles having higher Mohs hardness than silicon and forming a gettering layer, and alkali fine particles. A polishing step for polishing the back surface of the wafer by the action of alkali fine particles dissolved by rotating the chuck table while rotating the polishing pad while pressing the polishing pad against the silicon substrate while supplying pure water to the polishing pad After carrying out the process, while supplying pure water with a water temperature at which the solubility of the alkali fine particles decreases, the polishing pad is moved above the predetermined pressure. Including a gettering layer forming step of forming a gettering layer scratch the back side by polishing the back surface of the wafer by the polishing pad while rotating the chuck table with rotating while pressing with pressure.

  According to this configuration, the alkali fine particles are contained in the polishing pad together with the solid phase reaction fine particles and the gettering fine particles. By supplying pure water to the polishing pad, the alkali fine particles are dissolved to generate an alkaline solution. Therefore, it is not necessary to handle the alkaline solution, and the wafer can be processed safely. Further, it is not necessary to provide an alkaline solution supply source for supplying the alkaline solution in the polishing apparatus, and the wafer can be processed with a simple apparatus configuration. Further, in the polishing step, by supplying room temperature pure water to the polishing pad, the alkali fine particles are dissolved and the solid phase reaction fine particles can be used, so that the wafer can be polished well. In the gettering layer forming step, by supplying pure water to the polishing pad at a temperature at which the solubility of the alkali fine particles is lowered, the dissolution of the alkali fine particles is suppressed, and the function of the solid phase reaction fine particles is suppressed. Thereby, since the gettering fine particles can be used in the gettering layer forming step, the gettering layer can be favorably formed on the wafer.

  According to the present invention, the gettering layer can be satisfactorily formed on the wafer by controlling the dissolution of the alkali fine particles contained in the polishing pad while supplying pure water.

It is a perspective view of the polish device concerning this embodiment. It is a schematic diagram of the grinding | polishing means which concerns on this Embodiment. It is a figure which shows the solubility with respect to the pure water of the alkali particulates contained in the polishing pad which concerns on this Embodiment. It is a figure which shows the wafer holding process which concerns on this Embodiment. It is a figure which shows the grinding | polishing process which concerns on this Embodiment. It is a figure which shows the gettering layer formation process which concerns on this Embodiment.

  Hereinafter, the polishing apparatus will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a polishing apparatus according to the present embodiment. Note that the polishing apparatus according to the present embodiment is not limited to a polishing-dedicated apparatus as shown in FIG. 1, and is, for example, a fully automatic type in which a series of processes such as grinding, polishing, and cleaning are performed automatically. You may incorporate in a processing apparatus.

  As shown in FIG. 1, the polishing apparatus 1 is configured to polish a wafer W by chemical mechanical polishing (CMP) using a polishing pad 47 described later. The wafer W is made of a silicon wafer, and a plurality of streets are formed in a lattice shape on the surface W1, and devices (not shown) such as ICs and LSIs are formed in regions partitioned by the streets. When the back surface W2 of the wafer W is ground to a predetermined thickness (for example, 100 μm), a protective tape as a protective member is provided on the front surface W1 of the wafer W in order to protect the device formed on the front surface W1 of the wafer W. T is attached. The wafer W is held by a chuck table 21 described later with the back surface W2 that is the processing surface facing upward.

  A rectangular opening extending in the Y-axis direction is formed on the upper surface of the base 11 of the polishing apparatus 1, and this opening is covered with a table cover 12 movable together with the chuck table 21 and a bellows-shaped waterproof cover 13. ing. Below the waterproof cover 13, a moving unit 24 that moves the chuck table 21 in the Y-axis direction and a rotating unit 22 that continuously rotates the chuck table 21 are provided. On the surface of the chuck table 21, a holding surface 23 that holds the wafer W via a protective tape T is formed by a porous porous material. The holding surface 23 is connected to a suction source (not shown) through a flow path in the chuck table 21.

  The moving means 24 includes a pair of guide rails 51 arranged on the base 11 and parallel to the Y-axis direction, and a motor-driven Y-axis table 52 slidably installed on the pair of guide rails 51. Yes. A nut portion (not shown) is formed on the back side of the Y-axis table 52, and a ball screw 53 is screwed into the nut portion. The chuck motor 21 is moved in the Y-axis direction along the pair of guide rails 51 by rotating the drive motor 54 connected to one end of the ball screw 53. The rotating means 22 is provided on the Y-axis table 52 and supports the chuck table 21 so as to be rotatable around the Z-axis.

  A column 14 is installed on the base 11, and the column 14 is provided with a processing feed means 31 for processing and feeding the polishing means 41 in the Z-axis direction. The processing feed means 31 has a pair of guide rails 32 arranged in the column 14 and parallel to the Z-axis direction, and a motor-driven Z-axis table 33 slidably installed on the pair of guide rails 32. . A nut portion (not shown) is formed on the back side of the Z-axis table 33, and a ball screw 34 is screwed to the nut portion. The ball screw 34 is rotationally driven by a drive motor 35 connected to one end of the ball screw 34, whereby the polishing means 41 is processed and fed along the guide rail 32.

  The polishing means 41 is attached to the front surface of the Z-axis table 33 via a housing 42 and is configured by providing a polishing pad 47 below the spindle unit 43. The spindle unit 43 is provided with a flange 45, and the polishing means 41 is supported on the housing 42 via the flange 45. A mount 44 is attached to the lower part of the spindle unit 43, and a polishing tool 48 including a support base 46 and a polishing pad 47 is attached to the mount 44. The polishing means 41 is connected with pure water piping and low-temperature pure water piping.

  The polishing apparatus 1 is provided with a control unit 70 that performs overall control of each part of the apparatus. The control unit 70 controls the valves 65 and 66. The control unit 70 includes a processor that executes various processes, a memory, and the like. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. In the polishing apparatus 1 configured as described above, the polishing pad 47 approaches the wafer W held on the chuck table 21 while being rotated about the Z axis. Then, the wafer W is polished by the rotational contact of the polishing pad 47 with the back surface W2 of the wafer W.

  Here, in general, in order to remove the grinding strain layer and form a gettering layer after grinding, the back surface of the wafer is first polished by chemical mechanical polishing. In chemical mechanical polishing, since the wafer is polished by the action of the solid phase reaction fine particles while supplying the alkaline solution to the wafer, it is necessary to handle the alkaline solution. Moreover, since it is necessary to install an alkaline solution supply source for supplying an alkaline solution to the polishing apparatus, the apparatus configuration becomes complicated. Therefore, a polishing pad containing water-soluble alkali fine particles together with solid phase reaction fine particles and gettering fine particles has been studied. In this polishing pad, the alkaline fine particles contained in the polishing pad are dissolved by pure water supplied to the polishing pad to generate an alkaline solution. The frictional heat generated when the polishing pad is in rotational contact with the wafer accelerates the dissolution of the alkali fine particles, and the alkaline solution can be supplied to the wafer. Thereby, it is not necessary to install an alkaline solution supply source, and the wafer can be safely processed with a simple apparatus configuration.

  However, when the gettering layer is formed with gettering fine particles while supplying pure water to the polishing pad after removing the grinding strain layer, the alkali fine particles are dissolved. For this reason, there has been a problem that the solid phase reaction fine particles act to polish the wafer more strongly than the gettering layer is formed, and the gettering layer cannot be formed satisfactorily. Therefore, in the present embodiment, in the gettering layer forming step, the pure water is brought to a temperature at which the solubility of the alkali fine particles is lowered and the polishing pad is supplied to suppress the dissolution of the alkali fine particles, so that the gettering layer is formed. Forms well.

  First, the structure of the polishing pad and the pure water supply system will be described in detail with reference to FIG. FIG. 2 is a schematic diagram of the polishing means according to the present embodiment. FIG. 3 is a diagram showing the solubility of alkali fine particles contained in the polishing pad according to the present embodiment in pure water. In FIG. 3, the vertical axis represents the amount (solubility) of sodium carbonate dissolved in 100 [g] pure water, and the horizontal axis represents the temperature of pure water.

  As shown in FIG. 2, the polishing pad 47 is attached to an annular support base 46 to constitute a polishing tool 48. The support base 46 is made of an aluminum alloy or the like, and a hole 46a through which the polishing liquid passes is opened at the center. The polishing pad 47 is formed in an annular shape, and a hole 47 c communicating with a hole 46 a formed in the support base 46 is opened at the center of the polishing pad 47.

In the polishing pad 47, solid phase reaction fine particles 81 for inducing a solid phase reaction with silicon, gettering fine particles 82 having a Mohs hardness higher than that of silicon, and alkali fine particles 85 are introduced into a liquid binder, and the liquid binder is impregnated. A non-woven fabric is formed by drying. As the solid phase reaction fine particles 81, SiO ₂ , CeO ₂ , ZrO ₂ or the like is used, and the particle diameter of the solid phase reaction fine particles 81 is preferably 2 μm, for example. It is preferable that the gettering fine particles 82 have a Mohs hardness of 9 or more. Examples of the gettering fine particles 82 include SiC such as diamond, GC (Green Carbide), Al ₂ O ₃ , WC, TiN, TaC, ZrC, and AlB. , B ₄ C, etc. are used. The particle diameter of the gettering fine particles 82 is preferably, for example, 0.5 μm.

  Alkali fine particles 85 are contained in the polishing pad 47 so that the alkali solution generated when dissolved by pure water supplied from the pure water supply source 61 to be described later to the polishing pad 47 is pH 10 or more and pH 12 or less. Yes. The alkali fine particles 85 may be any substance that has a difference in solubility depending on the temperature of pure water to be dissolved, such as sodium carbonate, TMAH (tetramethylammonium hydroxide), piperazine, potassium hydroxide, and sodium hydroxide. Of these, sodium carbonate is more preferable.

  As the liquid binder, for example, a liquid obtained by dissolving urethane in a solvent is used, and as the solvent, dimethylformamide, dimethyl sulfoxide, acetone, ethyl acetate, or the like is used. The polishing pad 47 may contain two or more kinds of solid-phase reaction fine particles 81, gettering fine particles 82, and alkali fine particles 85.

  The polishing tool 48 configured in this way is attached to the lower surface of the mount 44 attached to the lower end of the spindle unit 43. At this time, the flow path 43 a formed at the center of the spindle unit 43 communicates with the holes 46 a and 47 c formed in the support base 46 and the polishing pad 47.

  A pure water supply source 61 and a low-temperature pure water supply source 62 are connected to the flow path 43a of the spindle unit 43 via valves 65 and 66, respectively. Pure water at normal temperature is supplied from the pure water supply source 61, and pure water at a temperature lower than normal temperature is supplied from the low temperature pure water supply source 62. Pure water from the pure water supply source 61 or low-temperature pure water from the low-temperature pure water supply source 62 is supplied to the polishing pad 47 through the flow path 43a and the holes 46a and 47c. The pure water at room temperature from the pure water supply source 61 may be supplied from piping in a factory where the polishing apparatus 1 is installed. The low-temperature pure water from the low-temperature pure water supply source 62 may be supplied via pure water supplied from a pipe in the factory via a cooling facility.

  When the grinding strain layer is removed from the wafer in the polishing process, the valve 65 is opened and normal temperature pure water is supplied from the pure water supply source 61 to the flow path 43a. The pure water supplied to the flow path 43a spreads on the polishing surface of the polishing pad 47, and the alkali fine particles 85 contained in the polishing pad 47 are dissolved. As a result, the alkaline solution is generated, so that the solid-phase reaction fine particles 81 contained in the polishing pad 47 can work in the polishing process, and the wafer W can be polished.

  When the gettering layer is formed on the wafer W in the gettering layer forming step, the valve 66 is opened, and pure water having a water temperature at which the solubility of the alkali fine particles 85 is reduced is supplied from the low-temperature pure water supply source 62 to the flow path 43a. Supplied.

Here, as shown in FIG. 3, the solubility of pure water of, for example, sodium carbonate (Na ₂ CO ₃ ) as the alkali fine particles 85 contained in the polishing pad 47 is such that the temperature of the pure water is about 40 ° C. or less. It becomes higher as the temperature of pure water rises. Sodium carbonate has a solubility of about 18 [g] when the temperature of pure water is around 20 ° C., whereas the solubility is about 11 [g] when the temperature of pure water is around 10 ° C. The solubility is lowered by lowering of the value. Thus, sodium carbonate has the property that the difference in solubility depending on the temperature of pure water is large when the temperature of pure water to be dissolved is in the range of about 40 ° C. or less. Therefore, the dissolution of sodium carbonate contained in the polishing pad 47 can be controlled by changing the temperature of pure water supplied to the polishing pad 47.

  Therefore, in the gettering layer forming step, the water temperature in the pure water supplied from the low temperature pure water supply source 62 to the polishing pad 47 is, for example, the solubility of sodium carbonate as the alkali fine particles 85 at a room temperature around 20 ° C. From the viewpoint of lowering the temperature, the temperature is preferably lower than normal temperature, and more preferably 10 ° C. or lower. Thereby, even when pure water is supplied to the polishing pad 47 in the gettering layer forming step, the solubility of, for example, sodium carbonate as the alkali fine particles 85 can be reduced, so that the generation of an alkaline solution is suppressed, The function of the solid phase reaction fine particles 81 is suppressed. Therefore, in the gettering layer forming step, the gettering fine particles 82 included in the polishing pad 47 work, so that the gettering layer can be satisfactorily formed on the wafer W.

  As described above, the alkali fine particles are contained in the polishing pad 47 together with the solid-phase reaction fine particles 81 and the gettering fine particles 82, and an alkaline solution is generated from the alkali fine particles 85 by supplying pure water to the polishing pad 47. There is no need to supply an alkaline solution to the polishing pad 47. Therefore, it is not necessary to provide the polishing apparatus 1 with an alkaline solution supply source for supplying the alkaline solution, and the polishing apparatus 1 can have a simple apparatus configuration.

  Hereinafter, a method for processing the wafer W according to the present embodiment will be described with reference to FIGS. The processing method of the wafer W includes a wafer holding step for holding the wafer W on the chuck table 21, and the alkali fine particles contained in the polishing pad 47 are dissolved while supplying pure water at room temperature, and the back surface W 2 of the wafer W is removed by the polishing pad 47. And a gettering layer forming step of forming scratches on the back surface W2 of the wafer W with the polishing pad 47 while supplying pure water having a temperature lower than room temperature. . FIG. 4 shows a wafer holding process according to the present embodiment, FIG. 5 shows a polishing process according to the present embodiment, and FIG. 6 shows a gettering layer forming process according to the present embodiment.

  As shown in FIG. 4, a wafer holding step is first performed. The wafer W ground to a predetermined thickness is carried into the chuck table 21 with the front surface W1 to which the protective tape T is attached facing downward and the back surface W2 facing upward, and the wafer W is chucked via the protective tape T. It is held on the holding surface 23 of the table 21.

  As shown in FIG. 5, a polishing step is performed after the wafer holding step. The chuck table 21 is moved below the polishing means 41 by the moving means 24 (see FIG. 1) and positioned so that the rotation axis of the chuck table 21 and the rotation axis of the polishing pad 47 are shifted.

The chuck table 21 is rotated about the Z axis, and the polishing pad 47 is also rotated about the Z axis in the same direction as the chuck table 21. Then, the polishing pad 47 is processed and fed toward the back surface W2 of the wafer W by a polishing pressure of, for example, 300 g / cm ² by the processing feed means 31 (see FIG. 1), and the polishing surface of the polishing pad 47 is the entire back surface W2 of the wafer W. And the wafer W is polished. Thus, by making the polishing pressure in the polishing step larger than the polishing pressure in the gettering layer forming step, which will be described later, the frictional heat due to the rotational contact of the polishing pad 47 with the wafer W increases, For example, sodium carbonate as the alkali fine particles 85 contained is easily dissolved in pure water.

  At this time, the valve 66 is closed, the valve 65 is opened, and pure water at room temperature is supplied from the pure water supply source 61 to the flow path 43 a in the spindle unit 43. Pure water is supplied to the hole 47 c formed in the polishing pad 47 through the hole 46 a formed in the support base 46. The pure water spreads from the hole 47c of the polishing pad 47 to the polishing surface, and, for example, sodium carbonate as the alkali fine particles 85 contained in the polishing pad 47 is dissolved. The control unit 70 (see FIG. 1) controls the opening and closing of the valve 65 to adjust the supply amount of pure water supplied to the polishing pad 47 so that the alkaline solution is generated to have a pH of 10 or more and a pH of 12 or less. The Thereby, the wafer W is polished while the alkaline solution is supplied to the wafer W. The polishing rate is set to 0.72 μm / min, for example, and the polishing time is set to 2 minutes, for example.

  By carrying out the polishing step in this manner, the alkali fine particles 85 are dissolved to produce an alkali solution. As a result, the solid phase reaction fine particles 81 contained in the polishing pad 47 work strongly, and the back surface W2 of the wafer W is polished by a predetermined amount and etched with an alkaline solution. The ground grinding strain layer is removed.

As shown in FIG. 6, a gettering layer forming step is performed after the polishing step. As shown in FIG. 6A, the chuck table 21 is rotated about the Z axis, and the polishing pad 47 is also rotated about the Z axis in the same direction as the chuck table 21. Then, the polishing pad 47 is processed and fed toward the back surface W2 of the wafer W by a polishing pressure of, for example, 50 g / cm ² by the processing feed means 31 (see FIG. 1), and the polishing surface of the polishing pad 47 rotates and contacts the wafer W. Then, the wafer W is polished.

  Thus, by making the polishing pressure in the gettering layer forming step smaller than the polishing pressure in the polishing step, the polishing pad 47 is pressed more weakly by the wafer W than shown in FIG. Then, the wafer W can be polished with the gettering fine particles 82 protruding. Thereby, the gettering fine particles 82 are effectively brought into contact with the wafer W, and a gettering layer is easily formed on the wafer W as shown in FIG. 6B described later. In addition, since the frictional heat generated when the polishing pad 47 is in rotational contact with the wafer W can be reduced, the dissolution of the alkali fine particles 85 contained in the polishing pad 47 into pure water can be suppressed.

  At this time, the valve 65 is closed, the supply of normal pure water to the flow path 43a is stopped, and the valve 66 is opened to switch to the supply of low-temperature pure water from the low-temperature pure water supply source 62. Thereby, low temperature pure water is supplied to the hole 47c formed in the polishing pad 47 through the hole 46a formed in the support base 46 at a rate of 1.0 liter per minute, for example. It spreads from 47c to the polished surface.

  The temperature of pure water supplied from the low-temperature pure water supply source 62 to the polishing pad 47 is preferably a temperature lower than normal temperature from the viewpoint of decreasing the solubility of, for example, sodium carbonate as the alkali fine particles 85. The following is more preferable. Thereby, even when pure water is supplied to the polishing pad 47 in the gettering layer forming step, dissolution of the alkali fine particles 85 contained in the polishing pad 47 is suppressed, and the function of the solid-phase reaction fine particles 81 is suppressed. . Therefore, in the gettering layer forming step, the gettering fine particles 82 included in the polishing pad 47 work, and a gettering layer can be formed on the wafer W as shown in FIG.

  Further, by supplying low temperature pure water to the polishing pad 47 in this way, the polishing pad 47 is cooled, and the elastic modulus of the polishing pad 47 is increased. Thereby, when the polishing pad 47 is pressed against the wafer W, the sinking of the gettering fine particles 82 protruding from the surface of the polishing pad 47 is suppressed. The gettering fine particles 82 on the surface of the polishing pad 47 effectively come into contact with the wafer W, and a gettering layer can be efficiently formed on the wafer W.

  As shown in FIG. 6B, the chuck table 47 is moved in the direction of arrow N by the moving means 24 (see FIG. 1) in a state where the polishing pad 47 is in rotational contact with the wafer W while low-temperature pure water is supplied to the polishing pad 47. 21 is moved. That is, while the back surface W2 of the wafer W is slid, the rotation axis of the chuck table 21 and the rotation axis of the polishing pad 47 are moved away from each other in the Y-axis direction. The chuck table 21 is moved in the direction indicated by the arrow N, for example, at a moving speed of 0.67 mm / sec for 1 minute, and the chuck table 21 is moved about 40 mm. As a result, the rear surface W2 of the wafer W is slightly scratched.

  By performing the gettering layer forming step in this manner, generation of an alkaline solution from, for example, sodium carbonate as the alkali fine particles 85 can be suppressed. As a result, the gettering fine particles 82 contained in the polishing pad 47 work strongly, and a gettering layer can be formed on the back surface W2 of the wafer W. While supplying pure water to the polishing pad 47, the dissolution of the alkali fine particles 85 contained in the polishing pad 47 can be controlled, so that the gettering layer can be safely formed on the wafer W.

  As described above, in the processing method of the wafer W according to the present embodiment, the alkali fine particles 85 are included in the polishing pad 47 together with the solid phase reaction fine particles 81 and the gettering fine particles 82, and pure water is supplied to the polishing pad 47. As a result, the alkali fine particles 85 are dissolved to produce an alkali solution. Therefore, it is not necessary to handle the alkaline solution, and the wafer W can be processed safely. Moreover, it is not necessary to provide the polishing apparatus 1 with an alkaline solution supply source for supplying an alkaline solution, and the wafer can be processed with a simple apparatus configuration. Further, in the polishing step, by supplying pure water at room temperature to the polishing pad 47, the alkali fine particles 85 are dissolved and the solid-phase reaction fine particles 81 can work, so that the wafer W can be polished well. In the gettering layer forming step, pure water is supplied to the polishing pad 47 at a temperature at which the solubility of the alkali fine particles 85 is lowered, so that the dissolution of the alkali fine particles 85 is suppressed and the function of the solid phase reaction fine particles 81 is suppressed. The Thereby, since the gettering fine particles 82 can be used in the gettering layer forming step, the gettering layer can be satisfactorily formed on the wafer W.

  In the above embodiment, the gettering layer is formed on the back surface W2 of the wafer W by moving the chuck table 21 in the Y-axis direction by the moving means 24 in the gettering layer forming step (see FIGS. 1 and 6B). Although it is set as the structure formed, it is not limited to this. The polishing pad 47 may be moved with respect to the chuck table 21 as long as the rotation axis of the chuck table 21 and the rotation axis of the polishing pad 47 are moved while the back surface W2 of the wafer W is slid. .

  In the above embodiment, the semiconductor device wafer is used as the wafer W. However, for example, a semiconductor substrate or an oxide wafer may be used.

  Moreover, in the said embodiment, although the protective tape T was affixed on the surface W1 of the wafer W, it is good also as a structure by which a substrate is adhere | attached on the surface W1 of the wafer W.

  In the present embodiment, a polishing apparatus that polishes a wafer is exemplified as the processing apparatus. However, the present invention is not limited to this configuration. The present invention is applicable to other processing apparatuses that process the wafer W while dissolving particles contained in a processing tool that processes the processing target. For example, the present invention may be applied to a polishing apparatus and a cluster apparatus combining the same.

  Moreover, although each embodiment of the present invention has been described, as another embodiment of the present invention, the above embodiments may be combined in whole or in part.

  The embodiments of the present invention are not limited to the above-described embodiments, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by technological advancement or another derived technique, the method may be used. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea of the present invention.

  In the present embodiment, the configuration in which the present invention is applied to a polishing apparatus that polishes a wafer has been described. However, the present invention can also be applied to a processing apparatus that processes a wafer W while dissolving particles contained in a processing tool. .

  As described above, the present invention has an effect that a gettering layer can be satisfactorily formed on a wafer by controlling the dissolution of alkali fine particles contained in the polishing pad while supplying pure water. In particular, the wafer is polished. It is useful for a polishing apparatus for processing.

DESCRIPTION OF SYMBOLS 1 Polishing apparatus 21 Chuck table 23 Holding surface 46 Support base 47 Polishing pad 48 Polishing tool 61 Pure water supply source 62 Low temperature pure water supply source 65, 66 Valve 81 Solid phase reaction fine particle 82 Gettering fine particle 85 Alkali fine particle T Protective tape (Protective member)
W Wafer W1 (Wafer) Front W2 (Wafer) Back

Claims (1)

A wafer processing method for processing a wafer having a device formed on a surface of a silicon substrate,
A wafer holding step of attaching a protective member to the surface of the wafer and holding the protective member side on the holding surface of the chuck table;
While supplying pure water to a polishing pad containing solid phase reaction fine particles for inducing a solid phase reaction with silicon, gettering fine particles having a Mohs hardness higher than silicon and forming a gettering layer, and alkali fine particles, A polishing step of rotating the polishing pad while pressing it against the silicon substrate at a predetermined pressure and polishing the back surface of the wafer by the action of the alkali fine particles dissolved by rotating the chuck table;
After performing the polishing step, while supplying pure water having a water temperature at which the solubility of the alkali fine particles decreases, the polishing pad is rotated while being pressed at a pressure lower than the predetermined pressure, and the chuck table is rotated while the chuck table is rotated. And a gettering layer forming step of forming a gettering layer by scratching the backside of the wafer by polishing the backside of the wafer with a polishing pad.

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