JP6846284B2 - Silicon wafer processing method - Google Patents

Description

The present invention relates to a method for processing a silicon wafer that forms a gettering layer on the 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 the 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 generated 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 due to this 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, wet etching, dry etching, etc., and the grinding strain generated on the back surface of the semiconductor wafer is generated. The layer is removed to prevent a decrease 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 deteriorated when the grinding strain layer is removed. This is because the gettering effect disappears when the grinding strain layer on the back surface of the semiconductor wafer is removed, and metal ions such as copper contained inside the semiconductor wafer float on the surface side where the device is formed, resulting in current leakage. Is thought to occur.

In order to solve such a problem, a technique 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). After grinding the semiconductor wafer to a predetermined thickness, the back surface of the semiconductor wafer is polished with a polishing pad made of urethane foam or non-woven fabric while supplying an alkaline slurry containing abrasive grains such as GC (Green Carbide). .. As a result, the grinding strain layer due to the grinding wheel remaining on the back surface of the semiconductor wafer can be removed. After that, the supply of the alkaline slurry is stopped, and while the pure water is supplied, the back surface of the semiconductor wafer is polished with a polishing pad filled with abrasive grains such as GC during polishing. As a result, a slight scratch that does not reduce the bending strength can be formed on the back surface of the semiconductor wafer to form a gettering layer.

In addition, a non-woven fabric containing a liquid binder containing solid-phase reaction fine particles (abrasive grains for polishing) that induce a solid-phase reaction with a silicon wafer and gettering fine particles (abrasive grains for gettering) having a higher moth hardness than silicon. A polishing pad constructed by impregnating with silicon has been proposed (see, for example, Patent Document 2). With this polishing pad, the grinding strain layer remaining on the back surface of the semiconductor wafer can be removed, and the gettering layer can be formed on the back surface of the semiconductor wafer.

Japanese Unexamined Patent Publication No. 2013-244537 Japanese Unexamined Patent Publication No. 2015-046550

However, in the wafer processing method of Patent Document 1, since the Mohs hardness of the GC abrasive grains contained in the slurry is high, the pipe that supplies the slurry to the polishing pad may be damaged, and this processing method should be used in actual production. Was difficult. Further, the crystal defects of the wafer have a gettering effect, and the required thickness of the gettering layer differs depending on the state of the crystal defects of the wafer. Therefore, for example, in a wafer with few crystal defects, it is necessary to form a thick gettering layer. is there. Therefore, in the polishing pad of Patent Document 2, when wafers having different amounts of crystal defects are continuously processed, the amount of impregnated fine particles for gettering of the polishing pad is impregnated in order to form a gettering layer having an appropriate thickness for each wafer. It is necessary to adjust the processing conditions by adjusting the amount to an appropriate amount for each wafer. For this reason, it becomes necessary to replace the polishing pad for each wafer, which causes a problem that the operation becomes complicated.

The present invention has been made in view of this point, and is a silicon wafer capable of preventing damage to the piping for supplying the polishing liquid and forming a gettering layer under appropriate processing conditions according to the type of wafer. One of the purposes is to provide a processing method.

The method for processing a silicon waher according to one aspect of the present invention is a method for processing a silicon waher for forming a gettering layer that regulates the induction of metal ions on the back surface of the waha in which a device is formed on the surface of a silicon substrate. , A powder for forming a gettering layer on the polished surface of a polishing pad, which is obtained by mixing solid-phase reaction fine particles that induce a solid-phase reaction with silicon into a liquid binder, impregnating the non-woven fabric with it, and drying it. The step of impregnating the entire surface of the polished surface with fine particles for gettering, and the back surface of the wafer held by the chuck table are pressed by rotating the polishing pad while rotating the chuck table holding the wafer. After performing the polishing step of polishing the back surface of the wafer with the polishing pad, the polishing step and the fine particle impregnation step for gettering while supplying the alkaline polishing liquid to the back surface of the wafer and the polishing pad, the chuck table and the polishing pad are combined. While supplying pure water to the back surface of the waha and the polishing pad that presses the waha while rotating, the gettering layer forming step of forming the gettering layer on the back surface of the waha by acting the gettering fine particles impregnated in the polishing pad. , Equipped with.

According to this configuration, the gettering fine particles having a high Mohs hardness for forming the gettering layer are sprayed onto the polishing pad as free fine particles to be impregnated. As a result, it is not necessary to include the gettering fine particles in the polishing liquid, so that it is possible to prevent the piping for supplying the polishing liquid from being damaged by the fine particles having a high Mohs hardness. Further, since the polishing pad can be impregnated with gettering fine particles having an amount suitable for the state of the wafer and an average particle size, a gettering layer can be formed under appropriate processing conditions according to the type of the wafer, and the thickness is appropriate for the wafer. Gettering layer can be formed.

The method for processing a silicon waher according to one aspect of the present invention is a method for processing a silicon waher for forming a gettering layer that regulates the induction of metal ions on the back surface of the waha in which a device is formed on the surface of a silicon substrate. , A step of impregnating the entire surface of the polished surface with powdered gettering fine particles for forming a gettering layer, which has a higher moth hardness than silicon and is impregnated on the polished surface of the polishing pad made of non-woven fabric. While rotating the chuck table holding the waha, rotate the polishing pad to press it against the back surface of the waha held on the chuck table, and at the same time, apply an alkaline polishing solution containing solid-phase reaction fine particles that induce a solid-phase reaction with silicon. After performing the polishing step of polishing the back surface of the wafer with the polishing pad, the polishing step and the fine particle impregnation step for gettering while supplying the back surface of the wafer and the polishing pad, the chuck table and the polishing pad are rotated and the back surface of the wafer is rotated. A gettering layer forming step is provided in which pure water is supplied to the polishing pad that presses the waha, and the gettering fine particles impregnated in the polishing pad are allowed to act to form a gettering layer on the back surface of the waha.

According to this configuration, free solid-phase reaction fine particles are contained in an alkaline polishing liquid and used for polishing the wafer. Further, in order to form the gettering layer, free gettering fine particles are sprayed onto the polishing pad. As a result, the polishing liquid contains solid-phase reaction fine particles having a low Mohs hardness, and it is not necessary to contain the gettering fine particles having a high Mohs hardness, so that the piping for supplying the polishing liquid is damaged by the gettering fine particles. Can be prevented. Further, since the polishing pad can be impregnated with gettering fine particles having an amount suitable for the state of the wafer and an average particle size, a gettering layer can be formed under appropriate processing conditions according to the type of the wafer, and the thickness is appropriate for the wafer. Gettering layer can be formed. Further, since the free solid-phase reaction fine particles are used, the solid-phase reaction fine particles can be removed from the polishing pad after the solid-phase reaction fine particles are supplied to the polishing pad in the polishing step. As a result, a large amount of gettering fine particles can be attached to the polishing pad in the gettering fine particle impregnation step.

In the method for processing a silicon wafer according to one aspect of the present invention, the step of impregnating fine particles for gettering is performed immediately after the conditioning step of removing silicon debris adhering after polishing the polished surface of the polishing pad to condition the polished surface. ..

According to the present invention, it is possible to prevent the piping for supplying the polishing liquid from being damaged, and it is possible to form a gettering layer under appropriate processing conditions according to the type of wafer.

It is a perspective view of the polishing apparatus which concerns on this embodiment. It is a figure which shows the structure of the polishing pad which concerns on this embodiment. It is a figure which shows the polishing step which concerns on this embodiment. It is a figure which shows the conditioning step which concerns on this embodiment. It is a figure which shows the fine particle impregnation step for gettering which concerns on this embodiment. It is a figure which shows the gettering layer formation step which concerns on this embodiment.

Hereinafter, the polishing apparatus will be described with reference to the attached drawings. FIG. 1 is a perspective view of the polishing apparatus according to the present embodiment. The polishing apparatus according to the present embodiment is not limited to the dedicated polishing apparatus as shown in FIG. 1, and is, for example, a fully automatic type in which a series of processing such as grinding, polishing, and cleaning is performed fully automatically. It may be incorporated in a processing device.

As shown in FIG. 1, the polishing apparatus 1 is configured to polish the 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 grid pattern on the surface W1, and devices such as ICs and LSIs (not shown) are formed in a region 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 T is attached to the surface W1 of the wafer W in order to protect the device formed on the surface W1 of the wafer W. Has been done. The wafer W is held on a chuck table 21 described later with the back surface W2, which is the surface to be processed, 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 and a bellows-shaped waterproof cover 13 that can move together with the chuck table 21. ing. Below the waterproof cover 13, a moving means 24 for moving the chuck table 21 in the Y-axis direction and a rotating means 22 for continuously rotating the chuck table 21 are provided. A holding surface 23 for holding the wafer W is formed on the surface of the chuck table 21 via a protective tape T 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. Further, on the table cover 12, a dressing means 87 and a gettering fine particle supply nozzle 82 are arranged in the vicinity of the chuck table 21, and the gettering fine particle supply nozzle 82 is provided with a gettering fine particle supply means 81 (FIG. 4 and FIG. 5) are connected.

The moving means 24 has 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. There is. A nut portion (not shown) is formed on the back surface side of the Y-axis table 52, and a ball screw 53 is screwed into the nut portion. Then, the drive motor 54 connected to one end of the ball screw 53 is rotationally driven to move the chuck table 21 along the pair of guide rails 51 in the Y-axis direction. 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 machining feed means 31 has a pair of guide rails 32 arranged in the column 14 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 surface side of the Z-axis table 33, and a ball screw 34 is screwed into the nut portion. The ball screw 34 is rotationally driven by the drive motor 35 connected to one end of the ball screw 34, so that the polishing means 41 is machined and fed along the guide rail 32.

The polishing means 41 is attached to the front surface of the Z-axis table 33 via the housing 42, and is configured by providing a polishing pad 47 at the lower part of the spindle 43. A flange 45 is provided on the spindle 43, 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 43, and a polishing tool 48 composed of a support base 46 and a polishing pad 47 is attached to the mount 44. An alkaline solution supply source 61 for polishing and a pure water supply source 62 are connected to the polishing means 41 via valves 65 and 66. The alkaline solution supply source 61 for polishing contains an alkaline solution (alkaline polishing solution), and the pure water supply source 62 contains pure water. When the valve 65 is opened, an alkaline solution is supplied to the polishing means 41 as a polishing liquid, and when the valve 66 is opened, pure water is supplied to the polishing means 41.

The polishing device 1 is provided with a control unit (not shown) that controls each unit of the device in an integrated manner. The control unit controls the valves 65 and 66. Further, as will be described later, the gettering fine particle supply nozzle 82 (see FIG. 5) is controlled to adjust the supply amount of the gettering fine particles to be sprayed on the polishing pad 47. The control unit is composed of a processor, a memory, and the like that execute various processes. The memory is composed of one or a plurality of storage media such as ROM (Read Only Memory) and RAM (Random Access Memory) depending on the intended use. In the polishing apparatus 1 configured in this way, the polishing pad 47 is brought close to the wafer W held by the chuck table 21 while being rotated around the Z axis. Then, the polishing pad 47 is brought into rotational contact with the back surface W2 of the wafer W to polish the wafer W.

Here, a gettering layer is formed on the wafer in order to prevent the gettering effect of the wafer from being lost by removing the cutting strain layer on the wafer. The gettering layer is formed by forming a slight scratch on the wafer with a polishing pad using fine particles for gettering such as GC abrasive grains having a high Mohs hardness. When the gettering fine particles were contained in the polishing liquid and supplied to the polishing pad, the piping for supplying the polishing liquid may be damaged by the gettering fine particles. Therefore, a method of forming a gettering layer on a wafer by using a polishing pad on which gettering fine particles are fixed has been proposed. However, since the required thickness of the gettering layer differs depending on the amount of crystal defects and the thickness of the wafer in the wafer, the processing conditions are constant for the polishing pad to which a predetermined amount of gettering fine particles are fixed, and the processing conditions are constant depending on the state of the wafer. It was difficult to form a gettering layer of appropriate thickness.

Therefore, in the present embodiment, the gettering fine particles are sprayed onto the polishing pad for use. As a result, it is not necessary to include the gettering fine particles in the polishing liquid, so that it is possible to prevent the piping for supplying the polishing liquid from being damaged by the gettering fine particles. Further, since the supply amount and the average particle size of the gettering fine particles to the polishing pad can be adjusted according to the crystal defects and the thickness of the wafer, the gettering layer can be formed under appropriate processing conditions for each wafer.

First, the configuration of the polishing pad 47 will be described in detail with reference to FIG. FIG. 2 is a diagram showing a configuration of a polishing pad according to the present embodiment. FIG. 2A is a perspective view of a polishing tool provided with a polishing pad. FIG. 2B is a partial cross-sectional view in which the polishing tool is mounted on the mount.

As shown in FIG. 2A, the polishing pad 47 is attached to the annular support base 46 to form the 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 in the central portion. Further, female screw holes 46b are formed in the support base 46 at intervals in the circumferential direction. The lower surface of the support base 46 forms a support surface for the polishing pad 47, and the polishing pad 47 is attached to the support surface by double-sided adhesive tape. The polishing pad 47 is formed in an annular shape and contains solid-phase reaction fine particles that induce a solid-phase reaction with silicon. Further, in the central portion of the polishing pad 47, a hole 47c communicating with the hole 46a formed in the support base 46 is opened (see FIG. 2B).

The polishing pad 47 is formed by charging solid-phase reaction fine particles that induce a solid-phase reaction with a silicon wafer into a liquid binder and drying a non-woven fabric impregnated with the liquid binder. As the solid-phase reaction fine particles, SiO ₂ , CeO ₂ , ZrO _{2, and the} like are used, and the particle size of the solid-phase reaction fine particles is preferably, for example, 2 μm. Further, as the solid-phase reaction fine particles contained in the polishing pad 47, two or more types of solid-phase reaction fine particles can be used. Further, as the liquid binder, for example, a liquid in which urethane is dissolved in a solvent is used, and as the solvent, dimethylformamide, dimethyl sulfoxide, acetone, ethyl acetate and the like are used. By fixing the solid-phase reaction fine particles to the polishing pad 47, the polishing liquid contains only the alkaline solution, so that the piping for supplying the polishing liquid is prevented from being clogged with the solid-phase reaction fine particles and the like, and the piping Maintenance is easier.

As shown in FIG. 2B, the polishing tool 48 configured in this way is mounted on the lower surface of the mount 44 attached to the lower end of the spindle 43. The mount 44 is formed with a bolt insertion hole (not shown) penetrating from the upper surface to the lower surface, and the bolt 71 inserted into the bolt insertion hole is screwed into the female screw hole 46b formed in the support base 46. As a result, the polishing tool 48 is attached to the mount 44. At this time, the flow path 43a formed at the center of the spindle 43 communicates with the holes 46a and 47c formed in the support base 46 and the polishing pad 47.

Further, the flow path 43a is connected to the polishing alkaline solution supply source 61 and the pure water supply source 62, respectively, via valves 65 and 66, respectively. When the flow path 43a communicates with the holes 46a and 47c, the alkaline solution of the alkaline solution supply source 61 for polishing or the pure water of the pure water supply source 62 passes through the flow path 43a and the holes 46a and 47c and the polishing pad 47. Is supplied to. The pipe connecting the flow path 43a and the alkaline solution supply source for polishing 61 is made of, for example, a flexible material.

Hereinafter, the method of processing the wafer according to the present embodiment will be described with reference to FIGS. 3 to 6. The processing method of the wafer W is to supply a gettering fine particle impregnation step of spraying powdery gettering fine particles having a higher moth hardness than silicon onto the polished surface of the polishing pad 47 on which solid phase reaction fine particles are fixed, and an alkaline solution. At the same time, the polishing step of polishing the back surface W2 of the wafer W with the solid phase reaction fine particles contained in the polishing pad 47 to remove the cutting strain layer, and the gettering fine particles sprayed on the polishing pad 47 while supplying pure water act. It includes a gettering layer forming step of forming a scratch on the back surface W2 of the wafer W. FIG. 3 is a diagram showing a polishing step according to the present embodiment. FIG. 4 is a diagram showing a conditioning step according to the present embodiment. FIG. 5 is a diagram showing a gettering fine particle impregnation step according to the present embodiment. FIG. 6 is a diagram showing a gettering layer forming step according to the present embodiment.

As shown in FIG. 3, a polishing 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 on the lower side and the back surface W2 on the upper side, and the wafer W is chucked through the protective tape T. It is held on the holding surface 23 of the table 21. Further, the chuck table 21 is moved below the polishing means 41 by the moving means 24 (see FIG. 1), and is positioned so that the rotation axis of the chuck table 21 and the rotation axis of the polishing pad 47 deviate from each other.

The chuck table 21 is rotated around the Z axis, and the polishing pad 47 is also rotated around 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 the processing feed means 31 (see FIG. 1) at ^{a polishing pressure of, for example, 300 g / cm 2} , and the polished surface of the polishing pad 47 is the entire back surface W2 of the wafer W. The wafer W is polished by rotational contact.

At this time, the valve 66 is closed, the valve 65 is opened, and the alkaline solution is supplied from the polishing alkaline solution supply source 61 to the flow path 43a in the spindle 43. As a result, the alkaline solution is supplied to the hole 47c formed in the polishing pad 47 through the hole 46a formed in the support base 46, for example, at a rate of 0.5 liter per minute. The alkaline solution spreads from the hole 47c of the polishing pad 47 to the polishing surface, and the wafer W is polished while the alkaline solution is supplied to the polishing pad 47. The polishing rate is set to, for example, 0.72 μm / min, and the polishing time is set to, for example, 2 minutes.

The alkaline solution contained in the polishing alkaline solution source 61 preferably has a pH of 10 or more and a pH of 12 or less. As the alkaline solution having a pH of 10 or more and a pH of 12 or less, TMAH (tetramethylammonium hydroxide), piperazine, potassium hydroxide, sodium hydroxide and the like are used.

By carrying out the polishing step in this way, the solid-phase reaction fine particles fixed to the polishing pad 47 work strongly, and the back surface W2 of the wafer W is polished by a predetermined amount and etched by the alkaline solution. The grinding strain layer generated on the back surface W2 of the wafer W by the processing is removed.

As shown in FIG. 4, a conditioning step is performed after the polishing step. A support base 86 is provided on the table cover 12 in the vicinity of the chuck table 21, and a dressing means 87 is arranged on the upper surface of the support base 86. Further, on the table cover 12, a gettering fine particle supply nozzle 82 for spraying gettering fine particles onto the polished surface after dressing is erected next to the dressing means 87 in the Y-axis direction. The gettering fine particle supply nozzle 82 is connected to the gettering fine particle supply means 81 by a dedicated pipe having high hardness. The gettering fine particles supply means 81 contains powdery gettering fine particles. The gettering fine particle supply means 81 is moved integrally with the table cover 12 by the moving means 24 (see FIG. 1). Therefore, the pipe connecting the gettering fine particle supply nozzle 82 and the gettering fine particle supply means 81 can be formed of a rigid body, and the inside of the pipe is not damaged by the gettering fine particles.

The rotation of the chuck table 21 is stopped, the table cover 12 is moved by the moving means 24, and the dressing means 87 is positioned on the outer peripheral edge of the polishing pad 47. In this state, the dressing means 87 is moved in the Y-axis direction by the moving means 24, and the dressing surface of the dressing means 87 is moved to the center of the polishing surface of the polishing pad 47, so that the entire surface of the polishing surface of the polishing pad 47 is dressed. Will be done. At this time, the valve 66 and the valve 65 are closed. As a result, the silicon dust of the wafer W adhering to the polished surface of the polishing pad 47 is removed after polishing, and the condition of the polished surface of the polishing pad 47 is adjusted.

As shown in FIG. 5, a gettering fine particle impregnation step is performed immediately after the conditioning step. The spout of the gettering fine particle supply nozzle 82 is positioned directly below the outer peripheral edge of the polishing pad 47. The powdered gettering fine particles of the gettering fine particle supply means 81 are ejected from the gettering fine particle supply nozzle 82 and sprayed onto the polished surface of the dressed polishing pad 47. The chuck table 21 is rotated around the Z axis, and the gettering fine particle supply nozzle 82 is moved in the Y-axis direction by the moving means 24, so that the entire polished surface of the polishing pad 47 is impregnated with the gettering fine particles. To. The amount of gettering fine particles sprayed on the polished surface of the polishing pad 47 can be controlled by adjusting the amount of gettering fine particles ejected from the gettering fine particle supply nozzle 82.

The conditioning step and the gettering fine particle impregnation step may be performed at the same time. In this case, the gettering fine particle impregnation step is performed after the conditioning step. Further, the gettering fine particle impregnation step may be performed at any timing as long as it is performed before the gettering layer forming step described later. Since the gettering fine particles are sprayed on the polishing pad 47 in a wet state by the alkaline solution supplied in the polishing step or the pure water supplied in the gettering layer forming step described later, the gettering fine particles are sprayed on the polishing pad 47. Is easy to adhere. Further, since the conditioning step is performed before the gettering fine particle impregnation step, the silicon dust of the wafer W adhering to the polishing pad 47 is removed from the polishing pad 47, so that the gettering fine particles are removed from the polishing pad 47. Easy to impregnate.

The average particle size of the powdery gettering fine particles contained in the gettering fine particle supply means 81 is preferably 0.1 μm or more and 5 μm or less, for example. The gettering fine particles are fine particles having a Mohs hardness higher than that of silicon, and have a hardness of damaging pipes, for example, a Mohs hardness of 9 or more. As the gettering fine particles, SiC such as diamond and GC, Al ₂ O ₃ , WC, TiN, TaC, ZrC, _{Al B, B 4} C and the like are used.

As shown in FIG. 6, a gettering layer forming step is carried out after the gettering fine particle impregnation step. As shown in FIG. 6A, the chuck table 21 is rotated around the Z axis, and the polishing pad 47 is also rotated around 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 the processing feed means 31 (see FIG. 1) at ^{a polishing pressure of, for example, 50 g / cm 2} , and the polished surface of the polishing pad 47 is rotationally contacted with the wafer W. The wafer W is polished.

At this time, the valve 65 is closed, the valve 66 is opened, and pure water is supplied from the pure water supply source 62. As a result, 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, and the pure water is supplied from the hole 47c. Spreads on the polished surface.

As shown in FIG. 6B, the chuck table 21 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 pure water is being supplied to the polishing pad 47. Will be 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 so as to be separated from each other in the Y-axis direction. The movement of the chuck table 21 in the direction indicated by the arrow N is carried out, for example, at a moving speed of 0.67 mm / sec for 1 minute, and the chuck table 21 is moved by about 40 mm. As a result, the back surface W2 of the wafer W is slightly scratched. By carrying out the gettering layer forming step in this way, the free gettering fine particles sprayed on the polishing pad 47 in the gettering fine particle impregnation step work strongly, and the gettering layer is formed on the back surface W2 of the wafer W. Can be formed.

As described above, the gettering fine particles having a high Mohs hardness are impregnated by spraying on the polishing pad 47 in the gettering fine particle impregnation step. As a result, it is not necessary to include the gettering fine particles in the polishing liquid, so that it is possible to prevent the piping connecting the polishing alkaline solution supply source 61 and the flow path 43a from being damaged by the gettering fine particles.

The supply amount of the gettering fine particles to be sprayed on the polished surface of the polishing pad 47 can be controlled by controlling the gettering fine particle supply nozzle 82 and adjusting the ejection amount of the gettering fine particles. Further, the average particle size of the gettering fine particles contained in the gettering fine particle supply means 81 can be changed according to the type of wafer W. In this way, the amount and average particle size of the gettering fine particles sprayed on the polished surface of the polishing pad 47 can be adjusted, so that the getter can be obtained under appropriate processing conditions according to the amount of crystal defects in the wafer W and the thickness of the wafer W. A ring layer can be formed.

As described above, in the processing method of the wafer W according to the present embodiment, the gettering fine particles having a high Mohs hardness for forming the gettering layer are sprayed onto the polishing pad 47 as free fine particles to be impregnated. As a result, it is not necessary to include the gettering fine particles in the polishing liquid, so that it is possible to prevent the piping for supplying the polishing liquid from being damaged by the fine particles having a high Mohs hardness. Further, since the polishing pad can be impregnated with fine particles for gettering having an amount suitable for the state of the wafer W and an average particle size, a gettering layer can be formed under appropriate processing conditions according to the type of the wafer W, and the wafer W can be formed. A gettering layer of appropriate thickness can be formed.

In the above embodiment, the solid-phase reaction fine particles used in the polishing step are fixed to the polishing pad 47, but the present invention is not limited to this. If the wafer W is supplied to the polishing pad 47 when it is polished, free solid-phase reaction fine particles may be used. In this case, the solid phase reaction fine particles are contained in the alkaline solution contained in the polishing alkaline solution supply source 61, and are supplied to the polishing pad 47 together with the alkaline solution in the polishing step. Since the solid-phase reaction fine particles have a lower Mohs hardness than the gettering fine particles, it is possible to prevent the piping for supplying the alkaline solution to the polishing pad from being damaged by the solid-phase reaction fine particles. Further, since the free solid-phase reaction fine particles are used, the solid-phase reaction fine particles can be removed from the polishing pad 47 in the conditioning step after the solid-phase reaction fine particles are supplied to the polishing pad 47 in the polishing step. As a result, a large amount of gettering fine particles can be attached to the polishing pad 47 in the gettering fine particle impregnation step.

Further, in the above embodiment, in the gettering layer forming step, the chuck table 21 is moved in the Y-axis direction by the moving means 24 (see FIGS. 1 and 6B), so that the back surface W2 of the wafer W is gettered. The structure is such that layers are formed, but the present invention is not limited to this. If the rotation axis of the chuck table 21 and the rotation axis of the polishing pad 47 are moved so as to be separated from each other while the back surface W2 of the wafer W is slid, the polishing pad 47 may be moved with respect to the chuck table 21. ..

Further, in the above embodiment, in the conditioning step and the gettering fine particle impregnation step, the dressing means 87 and the gettering fine particle supply nozzle 82 are moved in the Y-axis direction by the moving means 24 (FIG. 1). , 4 and 5), but not limited to this. If the polishing pad 47 is conditioned by the dressing means 87 and the gettering fine particles are sprayed onto the polishing pad 47 from the gettering fine particle supply nozzle 82, the polishing pad 47 may be moved with respect to the chuck table 21.

Further, in the present embodiment, a polishing device for polishing a wafer has been illustrated and described as a processing device, but the present invention is not limited to this configuration. The present invention is applicable to other processing devices for polishing a wafer W while supplying particles. For example, it may be applied to a polishing device and a cluster device in which the polishing device is combined.

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

Moreover, the embodiment of the present invention is not limited to each of the above-described embodiments, and may be variously modified, replaced, or modified 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 the advancement of technology or another technology derived from it, it may be carried out by using that method. Therefore, the scope of claims covers all embodiments that may 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 for polishing a wafer has been described, but it is also possible to apply the present invention to a processing apparatus for processing a wafer W by supplying highly hard particles to a processing means. is there.

As described above, the present invention has the effect of preventing the piping for supplying the polishing liquid from being damaged and forming a gettering layer under appropriate processing conditions according to the type of wafer, and particularly. It is useful for polishing equipment that polishes wafers.

1 Polishing device 21 Chuck table 23 Holding surface 46 Support base 47 Polishing pad 48 Polishing tool 61 Polishing alkaline solution source 62 Pure water supply source 65, 66 Valve 81 Gettering fine particle supply means 82 Gettering fine particle supply nozzle 87 Dressing means W Wafer W1 (Wafer) front side W2 (Wafer) back side

Claims (3)

A silicon wafer processing method for forming a gettering layer that regulates the induction of metal ions on the back surface of a wafer in which a device is formed on the front surface of a silicon substrate.
A powder form for forming a gettering layer on the polished surface of a polishing pad, which is obtained by mixing solid-state reaction fine particles that induce a solid-phase reaction with silicon into a liquid binder, impregnating the non-woven fabric with it, and drying it. The gettering fine particle impregnation step of spraying the gettering fine particles to impregnate the entire surface of the polished surface, and
While rotating the chuck table holding the wafer, the polishing pad is rotated and pressed against the back surface of the wafer held by the chuck table, and the polishing solution is supplied to the back surface of the wafer and the polishing pad. A polishing step of polishing the back surface of the wafer with a pad,
After performing the polishing step and the fine particle impregnation step for gettering, the chuck table and the polishing pad are rotated, and pure water is supplied to the back surface of the wafer and the polishing pad that presses the wafer. A method for processing a silicon wafer, comprising a gettering layer forming step of forming a gettering layer on the back surface of the wafer by allowing the gettering fine particles impregnated in the polishing pad to act on the polishing pad. A silicon wafer processing method for forming a gettering layer that regulates the induction of metal ions on the back surface of a wafer in which a device is formed on the front surface of a silicon substrate.
A gettering fine particle impregnation step in which powdery gettering fine particles for forming a gettering layer having a Mohs hardness higher than that of silicon are sprayed onto the polished surface of a polishing pad made of non-woven fabric to impregnate the entire polished surface.
While rotating the chuck table holding the wafer, the polishing pad is rotated to press against the back surface of the wafer held by the chuck table, and an alkaline polishing liquid containing solid-phase reaction fine particles that induce a solid-phase reaction with silicon. A polishing step of polishing the back surface of the wafer with the polishing pad while supplying the back surface of the wafer and the polishing pad.
After performing the polishing step and the fine particle impregnation step for gettering, the chuck table and the polishing pad are rotated, and pure water is supplied to the back surface of the wafer and the polishing pad that presses the wafer. A method for processing a silicon wafer, comprising a gettering layer forming step of forming a gettering layer on the back surface of the wafer by allowing the gettering fine particles impregnated in the polishing pad to act on the polishing pad. The gettering fine particle impregnation step is performed immediately after the conditioning step of removing silicon debris adhering after polishing the polished surface of the polishing pad and adjusting the condition of the polished surface, according to claim 1 or The method for processing a silicon wafer according to claim 2.

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