JP2017045990A - Wafer surface treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer surface treatment device structure capable of improving productivity without reducing gettering ability.SOLUTION: The wafer surface treatment device structure includes: a substrate holding mechanism for holding and rotating a wafer W; and a dresser for performing finish polishing of one surface of the wafer to make the surface specular by being pressed to the one surface side of the wafer W. A dresser 19 has an EG pad 23 for providing the one surface side of the wafer W with an EG layer 30 and finishing it specular.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer surface treatment apparatus, and more particularly to a wafer surface treatment apparatus for polishing the surface of a semiconductor wafer (hereinafter simply referred to as “wafer”) with gettering capability.

  A thin semiconductor device made of silicon is manufactured by forming a circuit on a wafer sliced from a silicon single crystal, that is, a silicon wafer.

  One of the problems in the semiconductor process is the inclusion of heavy metals as impurities in the silicon wafer. When heavy metals diffuse into the device region formed on the surface side of the silicon wafer, the device characteristics are significantly adversely affected. Therefore, a gettering method is generally adopted in order to prevent heavy metals mixed in the silicon wafer from diffusing into the device region. Gettering is aimed at preventing heavy metal contamination in a device pre-process for forming a device on the surface of a silicon substrate.

  FIG. 13 is a partial cross-sectional view of a silicon wafer before grinding in the prior art. As shown in FIG. 13, a defect-free layer 52 is formed on the surface 51 side of a general wafer W, and a plurality of semiconductor elements 56 are provided on the surface of the defect-free layer 52. Further, in order to protect these semiconductor elements 56, a surface protective film 57 is attached to the front surface 51 of the wafer W during back surface grinding. On the other hand, on the back surface 53 side of the wafer W, an extrinsic gettering layer (commonly called “EG layer”) 54 is formed. Further, between the defect-free layer 52 and the EG layer 54, a bulk defect layer, that is, an intrinsic getterring layer 55 (commonly referred to as “IG layer 55”) is formed.

  The gettering effect of the EG layer 54 and the IG layer 55 prevents heavy metal contamination in the device pre-process (see, for example, Patent Document 1).

JP2010-287855A.

  However, in the thin wafer W in recent years, it is difficult to accurately generate the IG layer 55 in the depth direction (thickness direction) in the wafer W.

  Therefore, in the recent thinning process, only the EG layer 54 is formed by using a high mesh grindstone such as a gettering dry polish in which the dry abrasive includes scratch abrasive grains without forming the IG layer 55. There may be. However, when the EG layer 54 is formed by dry polishing, it is difficult to form a mirror-like EG layer simultaneously with the grinding and polishing of the back surface of the wafer W, and it is often performed separately. For this reason, there was a problem that productivity was not good and the cost was increased.

  Therefore, there is a technical problem to be solved in order to obtain a wafer surface processing apparatus structure that can improve productivity without reducing the gettering capability, and the present invention solves this problem. The purpose is to do.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 includes a substrate holding mechanism for holding and rotating a wafer, and one surface of the wafer held by the substrate holding mechanism. In a wafer surface treatment apparatus comprising a dresser that is finished and polished into a mirror surface, the dresser includes a surface treatment pad that provides a gettering layer on one surface side of the wafer and finishes into the mirror surface in a wet state. A surface treatment apparatus is provided.

  According to this configuration, the gettering layer can be formed on the back surface of the wafer at the same time that the grinding damage on one surface of the wafer is removed and the mirror surface is finished. In addition, since the processing is performed in the wet state, lubricity between the surface treatment pad and the wafer can be obtained, and the processing on the entire back surface of the wafer can be made uniform.

According to a second aspect of the present invention, in the configuration according to the first aspect, the surface treatment pad includes at least a resin material mixed with SiC abrasive grains and a nonwoven fabric impregnated with the resin material. Provided is a wafer surface treatment apparatus.

  According to this configuration, the surface treatment pad formed by impregnating the nonwoven fabric with a resin material mixed with SiC abrasive grains is used to remove grinding damage on one surface of the wafer and finish the one surface into a mirror surface. A gettering layer can be formed on the one surface.

  According to a third aspect of the present invention, in the configuration according to the first aspect, the surface treatment pad includes at least a resin material mixed with SiC abrasive grains, and a polyurethane resin or a melamine material mixed with the resin material. Provided is a wafer surface treatment apparatus.

  According to this configuration, a surface treatment pad formed by impregnating a polyurethane or melamine material with a resin material mixed with SiC abrasive grains is used to remove grinding damage on one surface of the wafer and make the one surface mirror-like. At the same time as finishing, a gettering layer can be formed on one surface.

  According to a fourth aspect of the present invention, in the configuration according to the first, second, or third aspect, a means for supplying an alkaline solution between the wafer and the surface treatment pad at the time of the mirror finishing by the surface treatment pad is provided. A wafer surface treatment apparatus can be provided.

  According to this configuration, a gettering layer that provides lubricity by supplying an alkaline solution between the wafer and the pad can be formed during the mirror finish processing by the dresser.

  The invention according to claim 5 is the structure according to claim 1, 2, 3 or 4, while polishing one surface of the wafer together with a dressing step for polishing the polishing surface of the surface treatment pad, and a polishing aid, Provided is a wafer surface treatment apparatus for sequentially performing a dough polishing step for forming the gettering layer on the one surface.

  According to this configuration, the mirror finish and the formation of the gettering layer on the one surface side of the wafer can be successively performed through the dressing step and the fabric polishing step in order, so that an improvement in productivity can be expected.

  According to a sixth aspect of the present invention, in the configuration according to the fifth aspect, the dough polishing step includes a first dough polishing step for roughly polishing one surface of the wafer and a second dough polishing for precisely polishing one surface of the wafer. There is provided a wafer surface treatment apparatus comprising the steps.

  According to this configuration, after the rough polishing is performed in the first fabric polishing process and the mirror finish is performed, the gettering layer can be formed continuously in the second fabric polishing process to improve the productivity. Can be expected.

  According to a seventh aspect of the present invention, there is provided a wafer surface treatment apparatus comprising the pad dresser for adjusting the polishing surface of the surface treatment pad in the configuration according to the fifth or sixth aspect.

  According to this configuration, the polishing surface of the surface treatment pad can be polished and prepared in the pad dressing process before polishing one surface of the wafer, and then the gettering layer can be formed in the polishing process. Stabilize.

  The invention according to claim 8 is the structure according to claim 1, wherein the substrate is pressed against the wafer while supplying an alkaline polishing aid between the wafer and the surface treatment pad. Provided is a wafer surface treatment apparatus for rotating a holding mechanism and the surface treatment pad to polish one surface of the wafer into a mirror surface and performing a surface treatment step for generating the gettering layer.

  According to this configuration, the surface treatment pad removes grinding damage on one surface of the wafer and finishes it in a mirror shape, and generates a gettering layer on the wafer, so that heavy metal is formed in the wafer between the polishing step and the EG layer generation step. It can suppress mixing in. Furthermore, since the polishing of the wafer and the generation of the gettering layer are performed in parallel, the surface treatment process can be performed more efficiently than in the case where these are performed independently as in the prior art.

  According to a ninth aspect of the present invention, in the configuration according to the eighth aspect, after the surface treatment step, the substrate holding mechanism and the surface treatment pad are supplied while supplying pure water between the wafer and the surface treatment pad. And a wafer surface treatment apparatus for performing a rinsing process for washing away the polishing aid remaining on one surface of the wafer.

  According to this configuration, the wafer can be prevented from corroding with the polishing aid by washing away the polishing aid remaining on the wafer after the surface treatment step.

  A tenth aspect of the present invention provides the wafer surface processing apparatus according to the ninth aspect, wherein, in the rinsing step, the wafer and the surface processing pad rotate in a non-contact state.

  According to this configuration, the rotation of the wafer and the surface treatment pad forms a water flow in the pure water interposed between the wafer and the surface treatment pad, so that the polishing aid remaining on the wafer is smooth. Therefore, the wafer can be prevented from corroding with the polishing aid.

  According to an eleventh aspect of the present invention, there is provided the wafer surface processing apparatus according to the tenth aspect, wherein the rinsing step relatively reversely rotates the substrate holding mechanism and the surface processing pad.

  According to this configuration, a complicated water flow is formed in the pure water interposed between the wafer and the surface treatment pad by rotating the wafer and the surface treatment pad relatively in opposite directions, thereby Since the polishing aid remaining on the substrate is washed away smoothly, the wafer can be further prevented from corroding with the polishing aid.

  According to a twelfth aspect of the present invention, in the configuration according to any one of the ninth to eleventh aspects, a pad dresser is pressed against a processing surface of the surface treatment pad between the surface treatment step and the rinse step. Provided is a wafer surface treatment apparatus for performing a dressing process for wiping a processed surface.

  According to this configuration, since the polishing aid remaining on the surface treatment pad is removed by the pad dresser before the rinsing step, the polishing aid is transferred from the surface treatment pad to the wafer in the rinsing step. Can be prevented from corroding with a polishing aid.

  According to a thirteenth aspect of the present invention, in the configuration according to the first aspect, the surface treatment pad is disposed opposite to the substrate holding mechanism, and the pad base material is impregnated with a resin material mixed with abrasive grains. A polishing pad that hydrolyzes the resin material to release at least a part of the abrasive grains from the surface treatment pad, and presses the wafer with the EG pad, and the substrate holding mechanism and Provided is a wafer surface processing apparatus for generating the gettering layer on the wafer by rotating the EG pad.

  According to this configuration, the abrasive grains (fixed abrasive grains) contained in the EG pad are pressed against one surface of the wafer, and the abrasive grains (free abrasive grains) released from the EG pad randomly roll on the EG pad. As a result, scratches in various directions are randomly formed in the gettering layer, so that gettering that can capture heavy metals with high accuracy is suppressed by suppressing local sparseness in the gettering layer. A layer can be formed.

  A fourteenth aspect of the invention provides the wafer surface treatment apparatus according to the thirteenth aspect, wherein the resin material is a polyurethane resin.

  According to this configuration, when the polishing aid hydrolyzes the resin material made of the polyurethane resin, a part of the abrasive grains contained in the EG pad is released as free abrasive grains, and the gettering layer has various orientations. Since scratches are formed randomly, it is possible to form a gettering layer capable of capturing heavy metals with high accuracy by suppressing local sparseness in the gettering layer.

  According to a fifteenth aspect of the present invention, there is provided the wafer surface processing apparatus according to the fourteenth aspect, wherein the substrate holding mechanism and the surface processing pad relatively reversely rotate.

  According to this configuration, a complicated water flow is formed in the polishing aid interposed between the wafer and the EG pad due to the rotation of the wafer and the EG pad in the opposite directions. The loose abrasive grains easily roll between the EG pad and the wafer, and scratches in various directions are randomly formed in the gettering layer, so that the scratches are locally sparse in the gettering layer. This can be suppressed, and a gettering layer capable of capturing heavy metals with high accuracy can be formed.

  According to a sixteenth aspect of the invention, there is provided the wafer surface processing apparatus according to any one of the thirteenth to fifteenth aspects, wherein the surface processing pad is disposed above the substrate holding mechanism.

  According to this configuration, a polishing aid containing loose abrasive grains remains on the wafer, and the loose abrasive grains roll over a long period between the surface treatment pad and the wafer, thereby scratching in the gettering layer. Therefore, a gettering layer made of a high-density scratch can be formed.

  According to a seventeenth aspect of the present invention, in the configuration according to any one of the thirteenth to sixteenth aspects, the surface treatment pad includes a pad support that supports the EG pad, and the EG pad and the pad support. Provided is a wafer surface processing apparatus including a subpad interposed therebetween and softer than the EG pad.

  According to this configuration, the sub-pad is deformed according to the waviness and warpage of the wafer, so that the EG pad follows the surface shape of the wafer and generates a gettering layer on the wafer. A gettering layer capable of capturing heavy metal with high accuracy can be formed.

  According to the present invention, the grinding damage on the one surface of the wafer is removed to finish the mirror surface, and at the same time, a gettering layer can be formed on the back surface of the wafer W. Productivity can be improved. In addition, since the processing is performed in the wet state, lubricity between the surface treatment pad and the wafer can be obtained, the processing of the entire back surface of the wafer can be made uniform, and processing accuracy is improved.

1 is a schematic configuration plan view of a wafer surface treatment apparatus to which an embodiment of the present invention is applied. FIG. 2 is a partial side view of a texturing unit in the wafer surface treatment apparatus shown in FIG. 1, (a) is a diagram for explaining an EG pad unit, and (b) is a diagram for explaining a pad dress unit. An example of the wafer processed in the same wafer processing shown in FIG. 1 is shown, (a) is an overall view thereof, (b) is a partially enlarged sectional view thereof, and (c) is a partially enlarged perspective view thereof. It is a schematic diagram explaining the processing procedure in the texturing unit of the wafer surface treatment apparatus same as the above, (a) is an explanatory diagram of the first dressing process, (b) is an explanatory diagram of the first fabric polishing process, (c) is FIG. 4 is an explanatory diagram of a second fabric polishing process, FIG. 4D is an explanatory diagram of a rinsing process, FIG. 5E is an explanatory diagram of a second dressing process, and FIG. It is a flowchart explaining the procedure of the texturing process of the surface treatment apparatus of a wafer same as the above. It is a schematic plan view of a wafer surface treatment apparatus to which a modification of the present invention is applied. FIGS. 7A and 7B are partial side views of a polishing / texturing unit in the wafer surface treatment apparatus shown in FIG. 6, in which FIG. 7A is a diagram illustrating an EG pad unit, and FIG. 7B is a diagram illustrating a pad dress unit; FIGS. 7A and 7B are schematic diagrams illustrating a procedure for processing a wafer using the wafer surface processing apparatus illustrated in FIG. 6, where FIG. 7A is an explanatory diagram of a grinding process, FIG. ) Is an explanatory diagram of a cleaning process, and (d) is an explanatory diagram of a rinsing process. It is a figure which shows typically a mode that an EG layer is produced | generated on a wafer. It is a plane schematic diagram which shows the offset amount of a surface treatment pad and a wafer. It is a figure which shows the rotation track | orbit of the grindstone contained in a surface treatment pad. It is an image which shows the direction of the scratch formed in the wafer periphery. It is a schematic diagram which shows the surface treatment pad provided with the tilt mechanism, (a) is the top view, (b) is the side view. An example of the wafer ground by the surface processing apparatus of the prior art wafer is shown, (a) is the fragmentary sectional view, (b) is the fragmentary enlarged perspective view.

  The present invention provides a substrate holding mechanism for holding and rotating a wafer in order to achieve the object of providing a wafer surface treatment apparatus structure capable of improving productivity without reducing gettering ability; A dresser for polishing and polishing one surface of the wafer held by the substrate holding mechanism into a mirror-like surface, and the wafer surface treatment apparatus, wherein the dresser is in a wet state, and a gettering layer is provided on the one surface side of the wafer. This is realized by having a surface treatment pad that is finished to the mirror surface.

  Hereinafter, preferred embodiments of a wafer surface processing apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5.

  FIG. 1 is a schematic plan view showing an embodiment of a wafer surface treatment apparatus to which the present invention is applied. A wafer surface treatment apparatus 10 shown in FIG. 1 includes cassettes 11a and 11b for storing a plurality of wafers W (for example, silicon wafers), and chuck portions 12a to 12d as four substrate holding mechanisms, and performs index rotation. A turntable 13, a cleaning unit 14 for cleaning the four chuck portions 12a to 12d, and a transfer robot 15 for transferring the wafer W.

  Further, as shown in FIG. 1, in the wafer surface treatment apparatus 10, a rough grinding unit 16, a finish grinding unit 17, a polishing unit 18, and a texturing unit 19 are arranged in order along the outer periphery of the turntable 13. ing. The rough grinding unit 16 rough-grinds the back surface 20b of the wafer W with a rough grinding wheel (not shown), and the finish grinding unit 17 finish-grinds the back surface 20b with a finish grinding wheel (not shown). Further, the polishing unit 18 polishes the back surface of the wafer W while using a polishing cloth described later.

  FIG. 2 is a partial side view of the texturing unit 19 that is a dresser that finish-polishes one surface of the wafer W into a mirror surface. The texturing unit 19 includes an EG pad unit 19a shown in FIG. 2 (a) and a pad dress unit 19b shown in FIG. 2 (b).

  In the EG pad unit 19 a shown in FIG. 2A, a motor 22 is suspended at the tip of an arm 21. A disk-like pad support 32 is attached to the output shaft 22a of the motor 22 so as to be horizontally rotatable. Also, a disk-shaped subpad 33 is bonded and fixed to the lower surface of the pad support 32 via a resinous adhesive 34. Further, the disk-shaped surface treatment pad EG is also fixed to the lower surface of the subpad 33. The pad 23 is bonded and fixed via a resin material 34, and the pad support 32, the sub pad 33, and the EG pad 23 are integrated. Accordingly, the pad support 32, the sub pad 33, and the EG pad 23 can be lowered in the thickness direction of the wafer W integrally with the arm 21, and can be rotated in the horizontal direction.

  The EG pad 23 is a non-woven fabric formed in a disk shape with a thickness of about 4.8 mm, and fine SiC (silicon silicon) of about 0.6 μm, tungsten, alumina and other abrasive grains are mixed in the resin material. The resin is impregnated into a non-woven fabric formed in a disk shape having a thickness of about 4.8 mm. The abrasive grains impregnated with the resin material on the nonwoven fabric cause extremely fine damage to the back surface 20b of the wafer W and contribute to forming a gettering layer (EG layer 30). In addition, instead of the nonwoven fabric, polyurethane resin or melamine material may be used, and abrasives such as SiC, tungsten, and alumina may be mixed in the material. On the other hand, the sub pad 33 is formed in a disk shape having a thickness of about 0.9 mm, and has a lower hardness than the EG pad 23 and is provided so as to contribute to surface following during processing.

  In a pad dress unit 19b shown in FIG. 2B, a pad dresser 27 is attached to an output shaft 26 of a motor (not shown) so as to be horizontally rotatable. In this example, the pad dresser 27 impregnates the resin material with diamond abrasive grains on the upper surface (pad surface) of the non-woven fabric 28 formed in a disk shape facing the lower surface (pad surface) of the EG pad 23. A ground surface diamond dossa provided with a polishing layer 29.

  In the wafer surface treatment apparatus 10, in the texturing unit 19, while providing an EG layer 30 having a gettering ability while giving extremely small damage to one surface of the wafer W, that is, the back surface 20 b side of the wafer W, It is possible to perform a mirror finish. In the texturing unit 19, although not shown, an alkaline liquid and water (pure water) can be supplied between the wafer W and the EG pad 23. In addition, the alkaline solution here dilutes and uses the solution (5-10%) containing amine type | system | group (piperazine etc.), for example.

  The operation of the wafer surface treatment apparatus 10 of the present invention will be described below. First, one wafer W is taken out from the cassette 11a by the transfer robot 15, and transferred to the chuck unit 12a as a substrate holding mechanism for holding and rotating the wafer W.

  The wafer W is sucked and held by the chuck portion 12a with its back surface 20b facing upward. It is assumed that the chuck portion 12a is previously cleaned by the cleaning unit 14. Thereafter, the turntable 13 is index-rotated, and the chuck portion 12 a is moved to the rough grinding unit 16. At this time, another wafer W is transferred to another chuck portion 12d by the transfer robot, and the same processing is performed. However, since this is well-known, description is abbreviate | omitted.

  In the rough grinding unit 16, the back surface 20b of the wafer W is roughly ground by a known method with a rough grinding wheel (not shown). Next, the turntable 13 is rotated by an index, and the chuck portion 12 a is moved from the rough grinding unit 16 to the finish grinding unit 17. In the finish grinding unit 17, the back surface 20b of the wafer W is finish-ground by a known method with a finish grinding wheel (not shown).

  Further, after the finish grinding, the turntable 13 is index-rotated again, and the chuck portion 12 a is moved from the finish grinding unit 17 to the polishing unit 18 and the texturing unit 19. In the polishing unit 18, the back surface 20b (ground surface) of the wafer W is wet-polished by a polishing head (not shown) shown in FIG.

  After polishing, a texturing process is performed. FIG. 3 shows an example of the wafer W after the texturing process. FIG. 3A is an overall perspective view of the wafer W viewed from the back side, and FIG. A partially enlarged cross-sectional view and FIG. The wafer W shown in FIG. 3 has a defect-free layer 31 formed on the surface 20a side, and a plurality of semiconductor elements 20c are provided on the surface of the defect-free layer 31. Further, in order to protect these semiconductor elements 20c, a protective film 20d is attached to the front surface 20a of the wafer W during back grinding. On the other hand, an extrinsic gettering layer (commonly called “EG layer”) 30 is formed on the back surface 20b side. The EG layer 30 has a scratch shape and is formed with a surface roughness (Ra) of 1.0 nm to Ra 1.7 nm. In this example, a structure in which no IG layer is provided between the defect-free layer 31 and the EG layer 30 is disclosed, but a structure in which an IG layer is provided may be used.

  FIG. 4 is a schematic diagram for explaining the texturing process procedure, and FIG. 5 is a flowchart for explaining the text processing process. Therefore, the texturing process in the wafer surface processing apparatus 10 is performed in accordance with the flowchart (steps S1 to S6) in FIG. 5 and, if necessary, the processing schematic diagram in FIG. 4 and the texturing unit shown in FIG. This will be described with reference to FIG.

  (1) First, prior to performing processing on the wafer W, dressing processing is performed on the EG pad 23. In this process, as shown in FIG. 2B, the EG pad 23 is horizontally rotated together with the arm 21, and the EG pad 23 is moved above the pad dresser 27. Then, while rotating the EG pad 23 by driving the motor 22, the EG pad 23 is lowered in the thickness direction of the wafer W integrally with the arm 21, and on the pad dresser 27 rotated by a motor (not shown). That is, as shown in FIG. 4A, the EG pad 23 is lightly pressed on the polishing layer 29 for about 3 seconds, the polishing surface of the EG pad 23 is dressed, and the polishing surface of the EG pad 23 is sharpened. The shape is adjusted (step S1: first dressing process).

  (2) Next, as shown in FIG. 2A, the dressed EG pad 23 is horizontally rotated together with the arm 21 and moved above the chuck portion 12a. Thereafter, the EG pad 23 is lowered in the thickness direction of the wafer W while rotating the EG pad 23. Then, as shown in FIG. 4B, the lower surface of the EG pad 23 is lightly brought into contact with the back surface 20b of the wafer W on the rotating chuck portion 12a for about 10 seconds with a pressing force of 0 V, An alkaline liquid is supplied as a polishing aid to the wafer W and the EG pad 23 is lubricated with the alkaline liquid while polishing the material (polishing), that is, the back surface 20b (ground surface) of the wafer W is roughly polished. Then, while the entire back surface 20b of the wafer W is mirrored, the back surface 20b side of the wafer W is subjected to extremely fine damage, and the back surface 20b has a gettering ability (scratch surface (fine layer), that is, an EG layer). 30 is formed (step S2: first fabric polishing step).

  (3) Next, at the position shown in FIG. 2A, the EG pad 23 is further lowered in the thickness direction of the wafer W integrally with the arm 21, and as shown in FIG. The lower surface of the EG pad 23 is lightly brought into contact with the back surface 20b of the wafer W on the rotating chuck portion 12a by applying a pressing force of about 30V. Further, as in the first dough polishing step, an alkaline liquid is also supplied as a polishing aid during that time, and lubrication is imparted between the wafer W and the EG pad 23 with the EG pad 23 for about 100 seconds. The back surface 20b of the wafer W is ground (polished), that is, the back surface 20b of the wafer W is finely polished, and the entire back surface 20b of the wafer W is mirror-finished, while a scratch surface, that is, an EG layer is formed on the back surface 20b side of the wafer W. 30 is further formed (step S3: second cloth polishing step).

  (4) Next, at the same position shown in FIG. 2A, as shown in FIG. 4D, the back surface 20b of the wafer W on the rotating chuck portion 12a and the EG pad 23 While supplying water (pure water) between the lower surface and lightly contact at a pressing force of about 0 V for about 30 seconds, rinse with the supplied water, and wash away and remove alkali content on the back surface 20b of the wafer W. (Step S4: Rinsing process).

  (5) Next, the dressing process for the EG pad 23 is performed again. In this process, as shown in FIG. 2B, the EG pad 23 is horizontally rotated together with the arm 21, and the EG pad 23 is moved above the pad dresser 27. Thereafter, the EG pad 23 is lowered in the thickness direction of the wafer W together with the arm 21 while rotating the EG pad 23 by driving the motor 22. Then, the lower surface of the EG pad 23 is lightly pressed for about 3 seconds onto the pad dresser 27 rotated by a motor (not shown), that is, as shown in FIG. Is dressed and dressed (step S5: second dressing step).

  (6) Next, the EG pad 23 that has been dressed is horizontally rotated together with the arm 21, and the EG pad 23 is moved above the chuck portion 12a. Thereafter, the EG pad 23 is lowered in the thickness direction of the wafer W while rotating the EG pad 23. Then, as shown in FIG. 4 (f), the lower surface of the EG pad 23 is lightly brought into contact with the back surface 20b of the wafer W on the rotating chuck portion 12a for about 30 seconds with a pressing force of 0 V to perform water polishing. (Polishing) to form a scratch surface having a gettering function on the back surface 20b of the wafer W, that is, finally an EG layer 30 having a surface roughness (Ra) of 1.0 nm to Ra 1.7 nm (step S6: water Polishing process).

  As described above, according to the wafer surface treatment apparatus 10 according to the present invention, the grinding damage on the back surface of the wafer W is removed and mirror finishing is performed simultaneously with the EG layer 30, that is, the gettering layer (EG layer 30). ) Can be formed, so that productivity in the semiconductor process can be improved without reducing the gettering ability. Further, since the processing is performed in the wet state, lubricity between the surface treatment pad and the wafer can be obtained, the processing of the entire back surface of the wafer can be made uniform, and the processing accuracy is improved.

  Next, a wafer surface treatment apparatus 40 to which a modification of the present invention is applied will be described with reference to the drawings. FIG. 6 is a schematic plan view of the wafer surface processing apparatus 40. FIG. 7 is a partial side view of the polishing / texturing unit 41 in the wafer surface processing apparatus 40.

  The wafer surface treatment apparatus 40 is different from the wafer surface treatment apparatus 10 described above in that the polishing unit 18 and the texturing unit 19 are integrated to form a polishing / texturing unit 41. The rest of the configuration is common. Therefore, the same reference numerals are given to the components common to the above-described wafer surface treatment apparatus 10, and redundant description is omitted.

  In the polishing / texturing unit 41, an EG pad 23 is provided via a pad support 32 at the lower end of the motor 22 suspended from the tip of the arm 21. The EG pad 23 is a polyurethane resin pad base material formed in a disk shape with a thickness of about 4.8 mm, and fine abrasive grains of about 0.6 μm, tungsten, alumina, etc. are contained in the resin material. The pad base material is impregnated with the resin after mixing. The sub pad 24 is formed in a disk shape having a thickness of about 0.9 mm and has a lower hardness than the EG pad 23. Needless to say, the resin material for mixing the abrasive grains is not limited to polyurethane. Moreover, the code | symbol 35 in Fig.7 (a) is a supply line which supplies an alkaline polishing aid or a pure water to the process surface 23a of the EG pad 23. FIG. The supply line 35 is connected to a supply source of polishing aid and pure water (not shown).

  Next, the operation of the wafer surface treatment apparatus 40 will be described. First, one wafer W is taken out from the cassette 11a by the transfer robot 15, and transferred to the chuck unit 12a as a substrate holding mechanism for holding and rotating the wafer W.

  The wafer W is sucked and held by the chuck portion 12a with the back surface Wa facing upward. The chuck portion 12a is previously cleaned by the cleaning unit 14. Thereafter, the turntable 13 is rotated by an index, and the chuck portion 12a is moved to the rough grinding unit 16. At this time, another wafer W is transferred to another chuck portion 12d by the transfer robot, and the same processing is performed.

  In the rough grinding unit 16, the back surface Wa of the wafer W is roughly ground by a known method with a rough grinding wheel (not shown). Next, the turntable 13 is rotated by an index, and the chuck portion 12 a is moved from the rough grinding unit 16 to the finish grinding unit 17. In the finish grinding unit 17, the back surface Wa of the wafer W is finish ground by a finish grinding wheel (not shown).

  The turntable 13 is index-rotated again, and the chuck portion 12 a is moved from the finish grinding unit 17 to the polishing / texturing unit 18.

  Grinding marks as shown in FIG. 8A are present on the back surface Wa of the wafer W after the grinding process. Therefore, in the polishing / texturing unit 18, as shown in FIG. 8B, the EG pad 23 rotates horizontally together with the arm 21 and moves above the chuck portion 12a. Thereafter, while rotating the EG pad 23 and the wafer W, the EG pad 23 is lowered and the EG pad 23 is pressed against the wafer W. In addition, an alkaline polishing aid is supplied between the EG pad 23 and the wafer W via a supply line (not shown). In this way, the polishing and texturing are performed in parallel with the wet polishing for removing the grinding traces on the back surface Wa of the wafer W to polish the back surface Wa into a mirror surface and the texturing process for generating the EG layer 30 on the wafer W. A process (surface treatment process) is performed.

  Specifically, abrasive grains (hereinafter referred to as “fixed abrasive grains”) A1 included in the EG pad 23 and abrasive grains released from the EG pad 23 (hereinafter referred to as “free abrasive grains”) A2 cooperate to perform polishing. Perform processing and texturing. The EG pad 2 and the wafer W rotate while the fixed abrasive grains A1 are pressed against the back surface Wa of the wafer W, and the free abrasive grains A2 roll on the EG pad 23. In the free abrasive grain A2, as the resinous adhesive 27 swells and hydrolyzes with the polishing aid, a part of the fixed abrasive grain A1 contained in the EG pad 23 is released from the EG pad 23 as shown in FIG. Is.

  Further, the surface layer side of the back surface Wa of the wafer W comes into contact with the polishing aid and the oxide film (SiO2) is softened by modifying it to SiOH, so that the back surface Wa of the wafer W is easily polished. Further, when the loose abrasive grains A2 roll on the wafer W, the fine abrasive scratches on the wafer W are generated by natural force, not by the forced polishing by an external force such as the free abrasive grains A2 biting into the wafer W. By forming, the EG layer 30 is generated in the wafer W.

  After the polishing / texturing step, as shown in FIG. 8C, a cleaning step is performed on the processed surface 23a of the EG pad 23. In this step, the EG pad 23 is horizontally rotated together with the arm 21, and the EG pad 23 is moved above the pad dresser 27. Then, while rotating the EG pad 23 by driving the motor 22, the EG pad 23 is lowered in the thickness direction of the wafer W integrally with the arm 21, and on the pad dresser 27 rotated by a motor (not shown). The EG pad 23 is lightly pressed to wipe a predetermined range in the thickness direction from the processed surface 23a of the EG pad 23, and the polishing aid remaining on the processed surface 23a of the EG pad 23 is removed. Thereby, it is possible to avoid the polishing aid remaining on the processing surface 23a from being transferred to the wafer W in the rinsing process described later.

  After the cleaning process, a rinsing process is performed on the back surface Wa of the wafer W as shown in FIG. In this step, the EG pad 23 rotates horizontally together with the arm 21 and moves above the chuck portion 12a. Thereafter, the EG pad 23 is lowered to approach the wafer W. Then, while supplying pure water between the back surface Wa of the wafer W on the rotating chuck portion 12a and the processed surface of the EG pad 23, the wafer W and the EG pad 23 are rotated in opposite directions. The EG pad 23 is arranged close to the wafer W in a non-contact state. In this state, the wafer W and the EG pad 23 are rotated in opposite directions to form a water flow on the back surface Wa of the wafer W. be able to. In this way, the rinsing process is performed with the supplied water, and the polishing aid remaining on the back surface Wa of the wafer W is washed away and removed.

  Next, the scratch which comprises the EG layer 30 is demonstrated based on drawing. FIG. 10 is a schematic plan view showing an offset amount between the EG pad 23 and the wafer W. As shown in FIG. FIG. 11 is a diagram illustrating the rotation trajectory of the grindstone included in the EG pad 23. FIG. 12 is an image showing the direction of the scratch formed on the periphery of the wafer W.

  As shown in FIG. 10, the rotation axis a1 of the EG pad 23 and the rotation axis a2 of the chuck portion 12a are separated by an arbitrary distance (hereinafter referred to as “offset amount”). As shown in FIG. 10, since the rotational trajectory of the fixed abrasive grains A1 included in the EG pad 23, that is, the density and directionality of the scratch, varies depending on the offset amount, the gettering ability of the EG layer 30 to be applied to the wafer W is improved. Accordingly, the offset amount is arbitrarily adjusted. That is, the rotation trajectory of the fixed abrasive grain A1 with zero offset shown in FIG. 11A goes from the center o of the wafer W coincident with the rotation axis a2 of the chuck portion 12a toward the outer periphery while slightly curving in the circumferential direction. On the other hand, as shown in FIGS. 11B and 11C, the rotation trajectory of the fixed abrasive grains A1 is greatly curved in the circumferential direction of the EG pad 23 as the offset amount increases. Further, the scratch formed on the wafer W becomes sparser toward the outside of the wafer W. Furthermore, as shown in FIG. 12, the periphery of the wafer W tends to be regularly formed so that the directions of the scratches are aligned.

  In addition to the scratch imparted by the fixed abrasive grains A1, the free abrasive grains A2 that roll on the EG pad 23 form a scratch. The loose abrasive grains A2 do not move regularly like the above-described fixed abrasive grains A1, but move randomly between the EG pad 23 and the wafer W. Therefore, the fixed abrasive grains A1 that move regularly and the loose abrasive grains A2 that move randomly cooperate to impart scratches to the wafer W, thereby preventing the scratches in the EG layer 30 from becoming locally sparse. it can.

  In order to reduce the variation in the density of scratches in the EG layer 30, the EG pad 23 may include a tilt mechanism 42 as shown in FIG.

  The tilt mechanism 42 includes one fixed support portion 43 disposed on the distal end side of the EG pad 23 and two movable support portions 44 disposed on the proximal end side of the EG pad 23. The fixed support portion 43 and the movable support portion 44 are attached to a tilt table 45 that can be inclined relative to a fixed member such as a spindle that houses a motor (not shown).

  The fixed support portion 43 is a bolt or the like that fastens the tilt table 45 to the fixed member.

  The movable support portion 44 is interposed between the tilt table 45 and the fixed member, and is, for example, a known ball screw mechanism that separates the tilt table 45 and the fixed member by screwing the ball screw.

  When the two movable support portions 44 and 44 independently move the tilt table 45 relative to the fixed member, the tilt table 45 tilts at an arbitrary angle with the fixed support portion 43 as a fulcrum. As a result, the density of the scratches in the EG layer 30 can be partially changed by the EG pad 23 being pressed not uniformly against the back surface Wa of the wafer W but locally.

  As described above, according to the wafer surface processing apparatus 40 according to the present invention, the EG pad 26 removes grinding damage on the back surface Wa of the wafer W to finish it into a mirror surface and generates the EG layer 30 on the wafer W. Thus, it is possible to suppress the heavy metal from being mixed into the wafer W between the polishing step and the EG layer generation step.

  Further, the fixed abrasive grains A1 included in the EG pad 26 are pressed against the back surface Wa of the wafer W, and the free abrasive grains released from the EG pad 26 roll on the EG pad 26 at random, whereby the EG layer 30 Since scratches in various directions are randomly formed in the EG layer 30, it is possible to suppress the local sparseness of the scratches in the EG layer 30 and form the EG layer 30 capable of capturing heavy metals with high accuracy. it can.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

  As described above, in addition to processing the back surface 20b of the wafer, the present invention can be applied to apparatuses for processing various plate-like surfaces.

10, 40 Wafer surface treatment apparatus 11a, 11b Cassettes 12a-12d Chuck part (substrate holding mechanism)
13 Turntable 14 Cleaning unit 15 Transfer robot 16 Rough grinding unit 17 Finish grinding unit 18 Polishing unit 19 Texturing unit 19a EG pad unit (dresser)
19b Pad dress unit 20a Wafer surface 20b Wafer back surface 20c Semiconductor element 20d Protective film 21 Arm 22 Motor 22a Output shaft 23 EG pad (surface treatment pad)
26 Output shaft 27 Pad dresser 28 Non-woven fabric 29 Polishing layer 30 EG layer (gettering layer)
31 Defect-free layer 32 Pad support 33 Subpad 34 Resin adhesive
41 Polishing / Texturing Unit 42 Tilt Mechanism 43 Fixed Support Unit 44 Movable Support Unit 45 Tilt Table

Claims (17)

In a wafer surface treatment apparatus comprising: a substrate holding mechanism that holds and rotates a wafer; and a dresser that finish-polishes one surface of the wafer held by the substrate holding mechanism in a mirror shape.
The wafer surface treatment apparatus characterized in that the dresser has a surface treatment pad which is provided in a wet state with a gettering layer on one surface side of the wafer to finish the mirror surface.   2. The wafer surface treatment apparatus according to claim 1, wherein the surface treatment pad comprises at least a resin material mixed with SiC abrasive grains and a nonwoven fabric impregnated with the resin material.   2. The wafer according to claim 1, wherein the surface treatment pad includes at least a resin material mixed with SiC abrasive grains and a polyurethane resin or a melamine material mixed with the resin material. Surface treatment equipment.   4. The wafer surface treatment according to claim 1, further comprising means for supplying an alkaline solution between the wafer and the surface treatment pad at the time of the mirror finishing by the surface treatment pad. 5. apparatus.   A dressing step of polishing the polishing surface of the surface treatment pad, and a dough polishing step of forming the gettering layer on the one surface while mirror-finishing one surface of the wafer together with a polishing aid are sequentially performed. The wafer surface treatment apparatus according to claim 1, 2, 3, or 4.   6. The wafer according to claim 5, wherein the fabric polishing step includes a first fabric polishing step for roughly polishing one surface of the wafer and a second fabric polishing step for precisely polishing one surface of the wafer. Surface treatment equipment.   The wafer surface treatment apparatus according to claim 5, further comprising a pad dresser that adjusts a polishing surface of the surface treatment pad.   While supplying an alkaline polishing aid between the wafer and the surface treatment pad, the surface treatment pad is pressed against the wafer, the substrate holding mechanism and the surface treatment pad are rotated, and one surface of the wafer 2. The wafer surface processing apparatus according to claim 1, wherein a surface processing step of polishing the substrate into a mirror surface and generating the gettering layer is performed.   After the surface treatment process, while supplying pure water between the wafer and the surface treatment pad, the substrate holding mechanism and the surface treatment pad are rotated to leave a polishing aid remaining on one surface of the wafer. 9. The wafer surface treatment apparatus according to claim 8, wherein a rinse step for washing is performed.   10. The wafer surface processing apparatus according to claim 9, wherein, in the rinsing step, the wafer and the surface processing pad rotate in a non-contact state.   11. The wafer surface processing apparatus according to claim 10, wherein, in the rinsing step, the substrate holding mechanism and the surface processing pad are rotated in the reverse direction relatively.   The dressing process of pressing a pad dresser on the processed surface of the surface treatment pad and wiping the processed surface between the surface treatment step and the rinsing step is performed. The wafer surface treatment apparatus according to claim 1. The surface treatment pad is disposed opposite to the substrate holding mechanism, and has an EG pad formed by impregnating a pad base material with a resin material mixed with abrasive grains,
The polishing aid hydrolyzes the resin material to release at least a part of the abrasive grains from the surface treatment pad, presses the wafer with the EG pad, and rotates the substrate holding mechanism and the EG pad. The wafer surface treatment apparatus according to claim 1, wherein the gettering layer is generated on the wafer.   The wafer surface treatment apparatus according to claim 13, wherein the resin material is a polyurethane resin.   15. The wafer surface processing apparatus according to claim 14, wherein the substrate holding mechanism and the surface processing pad rotate in a reverse direction relatively.   16. The wafer surface processing apparatus according to claim 13, wherein the surface processing pad is disposed above the substrate holding mechanism. The surface treatment pad is
A pad support for supporting the EG pad;
A subpad interposed between the EG pad and the pad support and softer than the EG pad;
17. The wafer surface treatment apparatus according to claim 13, further comprising: