JP6717706B2 - Wafer surface treatment equipment - Google Patents

Description

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

Thin semiconductor devices made of silicon are manufactured by forming circuits 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, which are impurities in the silicon wafer. When the heavy metal diffuses into the device region formed on the surface side of the silicon wafer, the device characteristics are significantly adversely affected. Therefore, in order to prevent the heavy metal mixed in the silicon wafer from diffusing into the device region, the gettering method is generally adopted. Gettering is intended to prevent 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 conventional technique. 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 protection 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, a bulk defect layer, that is, an intrinsic gettering layer 55 (commonly called “IG layer 55”) is formed between the defect-free layer 52 and the EG layer 54.

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).

JP 2010-287855 A.

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

Therefore, in the recent thinning process, without forming the IG layer 55, only the EG layer 54 is formed by using a high mesh grindstone such as gettering dry polish in which scratch abrasive grains are included in the dry polish. In some cases, However, when the EG layer 54 is formed by dry polishing, it is difficult to form the mirror-like EG layer at the same time as the back surface of the wafer W is ground and polished, and it is often done separately. Therefore, there is a problem that productivity is not good and cost is increased.

Therefore, there arises a technical problem to be solved in order to obtain a wafer surface treatment apparatus structure capable of improving productivity without lowering the gettering ability, and the present invention solves this problem. The purpose is to do.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 provides a substrate holding mechanism for holding and rotating a wafer, and one surface of the wafer held by the substrate holding mechanism. a dresser for polishing finished in a mirror-like, the surface treatment apparatus of the wafer with the dresser, a wet state, have a surface treatment pad to finish the mirror surface by a gettering layer provided on one surface of the wafer, the The surface treatment pad has an EG pad which is arranged so as to face the substrate holding mechanism and is formed by impregnating a pad base material with a resin material mixed with abrasive grains. A polishing aid hydrolyzes the resin material. At least a part of the abrasive grains is released from the surface treatment pad, and the substrate holding mechanism and the EG pad are rotated while the fixed abrasive grains contained in the EG pad are pressed against the wafer to rotate the EG pad. Provided is a surface treatment apparatus for a wafer, in which loose abrasive grains released from the roll roll on the wafer to polish the wafer and to form the gettering layer on the wafer.

According to this structure, the gettering layer can be formed on the back surface of the wafer at the same time as removing the grinding damage on the one surface of the wafer to finish it into a mirror surface. Moreover, since the processing is performed in a wet state, lubricity between the surface treatment pad and the wafer can be obtained, and the entire back surface of the wafer can be processed uniformly. Furthermore, the abrasive grains (fixed abrasive grains) contained in the EG pad are pressed against one surface of the wafer, and the abrasive grains (loose abrasive grains) loosened from the EG pad randomly roll on the EG pad, so that the getter is Since scratches in various directions are randomly formed in the ring layer, the gettering layer that can capture the heavy metal with high accuracy is formed by suppressing the local sparse scratches in the gettering layer. be able to.

According to a second aspect of the present invention, in the configuration according to the first aspect, the surface treatment pad is composed of a resin material mixed with at least SiC abrasive grains and a non-woven fabric impregnated with the resin material. A wafer surface treatment apparatus is provided.

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

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

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

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

According to this configuration, it is possible to form the gettering layer that provides the lubricity by supplying the alkaline liquid between the wafer and the pad at the time of the mirror finishing by the dresser.

According to a fifth aspect of the present invention, in the configuration according to the first, second, third, or fourth aspect, a dressing step of polishing the polishing surface of the surface treatment pad, and one surface of the wafer with a polishing aid are mirror-finished, There is provided a wafer surface treatment apparatus which sequentially performs a material polishing step of forming the gettering layer on the one surface.

According to this configuration, the dressing step and the dough polishing step are sequentially performed, whereby the mirror-like finishing and the gettering layer formation on the one surface side of the wafer can be continuously performed, so that improvement in productivity can be expected.

According to a sixth aspect of the present invention, in the configuration of the fifth aspect, the material polishing step includes a first material polishing step of roughly polishing one surface of the wafer, and a second material polishing step of precisely polishing one surface of the wafer. Provided is a surface treatment apparatus for a wafer, which comprises the steps of:

According to this configuration, the gettering layer can be formed by performing rough polishing and mirror-finishing in the first material polishing step and then successively performing fine polishing in the second material polishing step to form the gettering layer. Can be expected.

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

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

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

According to this configuration, the surface treatment pad removes the grinding damage on one surface of the wafer to finish it into a mirror surface and also to generate the gettering layer on the wafer. Therefore, the heavy metal is removed from the wafer during the polishing step and the EG layer generating step. It is possible to suppress contamination with the above. 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 conventional case where these are performed independently.

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

According to this configuration, the polishing aid remaining on the wafer after the surface treatment step is washed away, so that the wafer can be prevented from being corroded by the polishing aid.

According to a tenth aspect of the present invention, in the configuration of the ninth aspect, there is provided a wafer surface treatment apparatus in which the wafer and the surface treatment pad rotate in a non-contact state in the rinsing step.

According to this configuration, the wafer and the surface treatment pad rotate to form 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 smoothed. Since it is washed away, it is possible to prevent the wafer from being corroded by the polishing aid.

According to an eleventh aspect of the present invention, in the configuration of the tenth aspect, there is provided a wafer surface treatment apparatus which relatively reversely rotates the substrate holding mechanism and the surface treatment pad in the rinsing step.

According to this configuration, the wafer and the surface treatment pad rotate relatively in opposite directions to form a complicated water flow in the pure water interposed between the wafer and the surface treatment pad. Since the polishing aid remaining on the substrate is washed away smoothly, it is possible to further suppress the wafer from being corroded by the polishing aid.

According to a twelfth aspect of the present invention, in the structure according to any one of the ninth to eleventh aspects, a pad dresser is pressed against a processed surface of the surface treatment pad during the surface treatment step and the rinse step. Provided is a wafer surface treatment apparatus which carries out a dressing step of wiping a processed surface.

According to this structure, since the polishing aid remaining on the surface treatment pad is removed by the pad dresser before the rinse step, the polishing aid is transferred from the surface treatment pad to the wafer in the rinse step, and Can be suppressed from being corroded by the polishing aid.

According to a thirteenth aspect of the present invention, in the configuration of the first aspect , there is provided a wafer surface treatment apparatus, wherein the resin material is a polyurethane resin.

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

According to a fourteenth aspect of the present invention, in the configuration of the thirteenth aspect , the substrate holding mechanism and the surface treatment pad provide a wafer surface treatment apparatus in which the substrate rotation is relatively reversed.

According to this structure, the wafer and the EG pad rotate relatively in opposite directions to form a complicated water flow in the polishing aid interposed between the wafer and the EG pad. Since loose abrasive grains tend to roll randomly between the EG pad and the wafer and scratches in various directions are randomly formed in the gettering layer, the scratches become locally sparse in the gettering layer. This can be suppressed, and a gettering layer that can capture heavy metals with high accuracy can be formed.

The invention of claim 15, wherein, in the structure of any one of claims 1 to 14, wherein the surface treatment pad provides a surface treatment apparatus of the wafer disposed above the substrate holding mechanism.

According to this configuration, the polishing aid containing the loose abrasive grains remains on the wafer, and the free abrasive grains roll between the surface treatment pad and the wafer for a long period of time, thereby scratching the gettering layer. Is efficiently formed, so that the gettering layer composed of high-density scratches can be formed.

Invention of claim 16, wherein, in the structure of any one of claims 1 to 15, wherein the surface treatment pad includes a pad support for supporting the EG pad, and the EG pad and the pad support A surface treatment apparatus for a wafer, which is provided with a sub pad interposed between and softer than the EG pad.

According to this configuration, the sub-pad is deformed according to the waviness and warpage of the wafer, and the EG pad follows the surface shape of the wafer to generate a gettering layer on the wafer. It is possible to form a gettering layer capable of capturing a heavy metal with high accuracy.

According to the present invention, a gettering layer can be formed on the back surface of the wafer W at the same time as grinding damage on one surface of the wafer is removed and the wafer surface is mirror-finished. Productivity can be improved. Further, since the processing is performed in a wet state, lubricity between the surface treatment pad and the wafer can be obtained, processing on 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, where (a) is a diagram illustrating an EG pad unit and (b) is a diagram illustrating a pad dress unit. An example of the wafer processed in the same wafer processing shown in FIG. 1 is shown, (a) is the whole figure, (b) is the partial expanded sectional view, (c) is the partial expanded perspective view. Same as above, which is a schematic diagram illustrating a processing procedure in a texturing unit of a wafer surface processing apparatus, (a) is an explanatory view of a first dressing step, (b) is an explanatory view of a first dough polishing step, and (c) is It is explanatory drawing of a 2nd cloth|polishing process, (d) is explanatory drawing of a rinse process, (e) is explanatory drawing of a 2nd dressing process, (f) is explanatory drawing of a water polishing process. It is a flowchart explaining the procedure of the texturing process of the surface processing apparatus of a wafer same as the above. It is a schematic structure top view of the surface treatment apparatus of the wafer to which the modification of the present invention is applied. FIG. 7 is a partial side view of a polishing/texturing unit in the wafer surface treatment apparatus shown in FIG. 6, (a) illustrating an EG pad unit, and (b) illustrating a pad dress unit. 6A and 6B are schematic diagrams illustrating a procedure of processing a wafer using the wafer surface treatment apparatus shown in FIG. 6, where FIG. 6A is an explanatory diagram of a grinding process, FIG. 6B is an explanatory diagram of a polishing and texturing process, and FIG. 8A is an explanatory diagram of a cleaning step, and FIG. 8D is an explanatory diagram of a rinse step. 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 orbit of the grindstone contained in a surface treatment pad. 6 is an image showing the orientation of scratches formed on the periphery of the wafer. 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 a wafer ground by a conventional wafer surface treatment apparatus is shown, (a) is a partial sectional view thereof, and (b) is a partially enlarged perspective view thereof.

The present invention has a substrate holding mechanism for holding and rotating a wafer in order to achieve an object of a wafer surface treatment apparatus structure capable of improving productivity without lowering gettering ability. In a wafer surface treatment apparatus comprising a dresser for finishing and polishing one surface of the wafer held by the substrate holding mechanism into a mirror surface, the dresser is in a wet state, and a gettering layer is provided on one surface side of the wafer. It is realized by having a structure having the surface treatment pad for finishing the mirror surface.

Hereinafter, preferred embodiments of a wafer surface treatment 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 configuration plane showing an embodiment of a wafer surface treatment apparatus to which the present invention is applied. The 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 four chuck portions 12a to 12d as a substrate holding mechanism, and performs index rotation. It includes a turntable 13 for cleaning, 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 circumference of the turntable 13. ing. The rough grinding unit 16 roughly 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, which is a dresser for finishing and polishing one surface of the wafer W into a mirror surface. The texturing unit 19 includes an EG pad unit 19a shown in FIG. 2A and a pad dress unit 19b shown in FIG. 2B.

In the EG pad unit 19a shown in FIG. 2A, a motor 22 is suspended at the tip of an arm 21. A disc-shaped pad support 32 is attached to an output shaft 22a of the motor 22 so as to be horizontally rotatable. Further, a disk-shaped subpad 33, which is also disk-shaped, is adhered and fixed to the lower surface of the pad support 32 with a resin adhesive 34. Further, a disk-shaped surface-treated pad EG, which is also disk-shaped, is mounted on the lower surface of the subpad 33. The pad 23 is adhesively fixed via a resin material 34, and the pad support 32, the sub pad 33, and the EG pad 23 are integrated. Therefore, the pad support 32, the sub pad 33, and the EG pad 23 can be lowered together with the arm 21 in the thickness direction of the wafer W, and can be horizontally rotated.

The EG pad 23 has a disc-shaped non-woven fabric having a thickness of about 4.8 mm, and fine SiC (silicon silicon) of about 0.6 μm, and abrasive grains such as tungsten and alumina mixed in the resin material. Then, the resin is impregnated into a disc-shaped nonwoven fabric having a thickness of about 4.8 mm. The abrasive grains impregnated in the non-woven fabric together with the resin material give extremely fine damage to the back surface 20b of the wafer W and contribute to the formation of the gettering layer (EG layer 30). Instead of the non-woven fabric, a polyurethane resin or a melamine material may be used, and abrasive materials such as SiC, tungsten, or 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, is made of a material having a hardness lower than that of the EG pad 23, and is provided so as to contribute to the surface following during processing.

In the pad dress unit 19b shown in FIG. 2B, a pad dresser 27 is horizontally rotatably attached to an output shaft 26 of a motor (not shown). In the pad dresser 27, 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 in this example is impregnated with diamond abrasive grains in a resin material. It is a ground surface diamond dossa provided with a polishing layer 29.

Then, in the wafer surface processing apparatus 10, in the texturing unit 19, while one surface of the wafer W, that is, the back surface 20b side of the wafer W is extremely finely damaged, the EG layer 30 having a gettering ability is provided, It is designed to be able to perform mirror finishing. Although not shown, the texturing unit 19 can supply an alkaline liquid and water (pure water) between the wafer W and the EG pad 23. The alkaline solution here is used by diluting, for example, a solution (5 to 10%) containing an amine system (piperazine or the like).

The operation of the wafer surface treatment apparatus 10 of the present invention will be described below. First, the transfer robot 15 takes out one wafer W from the cassette 11a and transfers it to the chuck portion 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 20b thereof facing upward. It is assumed that the chuck portion 12a has been previously cleaned by the cleaning unit 14. After that, the turntable 13 is index-rotated, and the chuck portion 12a is moved to the rough grinding unit 16. At this time, another wafer W is transferred to another chuck section 12d by the transfer robot, and the same process is performed. However, this is well known, and the description thereof is 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). Then, the turntable 13 is index-rotated, and the chuck portion 12a 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 using a finish grinding wheel (not shown).

Further, after the finish grinding, the turntable 13 is index-rotated again, and the chuck portion 12a 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, texturing processing 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 seen from the back side, and FIG. FIG. 3C is a partially enlarged sectional view, and FIG. The wafer W shown in FIG. 3 has a defect-free layer 31 formed on the front 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 surface grinding. On the other hand, on the back surface 20b side, an extrinsic gettering (Entrinsic Gettering) layer (commonly called "EG layer") 30 is formed. The EG layer 30 has a scratch-like shape and is formed with a surface roughness (Ra) of 1.0 nm to Ra1.7 nm. In this example, the structure in which the IG layer is not provided between the defect-free layer 31 and the EG layer 30 is disclosed, but the structure in which the IG layer is provided may be used.

FIG. 4 is a schematic diagram illustrating the procedure of the texturing process, and FIG. 5 is a flowchart illustrating the process procedure. Therefore, next, the texturing processing in the wafer surface processing apparatus 10 is performed according to the flowchart (steps S1 to S6) of FIG. 5, and if necessary, the processing schematic diagram of FIG. 4 and the texturing unit shown in FIG. It demonstrates using the partial side view of 19. FIG.

(1) First, prior to the processing of the wafer W, the 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. Thereafter, while the EG pad 23 is being rotated 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 the EG pad 23 is also rotated on the pad dresser 27 by a motor (not shown). That is, as shown in FIG. 4A, the EG pad 23 is lightly pressed onto the polishing layer 29 for about 3 seconds to perform dressing on the polishing surface of the EG pad 23, and to sharpen the polishing surface of the EG pad 23. The shape is adjusted (step S1: first dressing process).

(2) Next, as shown in FIG. 2A, the EG pad 23 after dressing is horizontally rotated together with the arm 21 and moved above the chuck portion 12a. Then, while rotating the EG pad 23, the EG pad 23 is lowered in the thickness direction of the wafer W. Then, as shown in FIG. 4B, the lower surface of the EG pad 23 is lightly contacted with the back surface 20b of the wafer W on the chuck portion 12a which is also rotating for about 10 seconds at a pressing force of 0 V, and during that time. Is supplied with an alkaline solution as a polishing aid, and the alkaline solution imparts lubricity between the wafer W and the EG pad 23 while polishing the material (polishing), that is, roughly polishing the back surface 20b (ground surface) of the wafer W. Then, while the entire back surface 20b of the wafer W is mirror-finished, the back surface 20b side of the wafer W is extremely finely damaged, and the back surface 20b has a scratch surface (fine layer) having a gettering ability, that is, an EG layer. 30 is formed (step S2: first dough polishing step).

(3) Next, in the same position as 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 back surface 20b of the wafer W on the rotating chuck portion 12a is lightly contacted with the lower surface of the EG pad 23 by applying a pressing force of about 30V. Further, as in the first material polishing step, an alkaline solution is also supplied as a polishing aid during that time to provide lubricity between the wafer W and the EG pad 23, and 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 the back surface 20b of the wafer W is scratched, that is, the EG layer. 30 is further formed (step S3: second fabric 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 are removed. While supplying water (pure water) to the lower surface, lightly contact the surface with a pressing force of about 0 V for about 30 seconds, rinse the surface with the supplied water, and wash away the alkali content on the back surface 20b of the wafer W to remove it. (Step S4: Rinse step).

(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. After that, while the EG pad 23 is rotated by driving the motor 22, the EG pad 23 is lowered in the thickness direction of the wafer W integrally with the arm 21. Then, the lower surface of the EG pad 23 is lightly pressed for about 3 seconds on the pad dresser 27 which is also rotated by a motor (not shown), that is, on the polishing layer 29 as shown in FIG. Dressing is performed on the lower surface of the (1) and dressing is performed (step S5: second dressing step).

(6) Further, the EG pad 23 after dressing is horizontally rotated together with the arm 21, and the EG pad 23 is moved above the chuck portion 12a. Then, while rotating the EG pad 23, the EG pad 23 is lowered in the thickness direction of the wafer W. Then, as shown in FIG. 4(f), the lower surface of the EG pad 23 is lightly contacted with the back surface 20b of the wafer W on the chuck portion 12a which is also rotating for about 30 seconds at a pressing force of 0 V to perform water polishing. (Polishing), and a scratch surface having a gettering function, that is, an EG layer 30 having a surface roughness (Ra) of 1.0 nm to Ra1.7 nm is finally formed on the back surface 20b of the wafer W (step S6: water). Polishing process).

As described above, according to the wafer surface treatment apparatus 10 of the present invention, the EG layer 30, that is, the gettering layer (EG layer 30) is removed at the same time as the grinding damage on the back surface of the wafer W is removed and mirror finishing is performed. ) Can be formed, the productivity in the semiconductor process can be improved without lowering the gettering ability. Further, since the processing is performed in a wet state, lubricity between the surface treatment pad and the wafer can be obtained, and the entire back surface of the wafer can be processed uniformly, thus improving processing accuracy.

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 configuration plan view of the wafer surface treatment apparatus 40. FIG. 7 is a partial side view of the polishing/texturing unit 41 in the wafer surface treatment apparatus 40.

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

In the polishing/texturing unit 41, the EG pad 23 is provided at the lower end of the motor 22 suspended on the tip of the arm 21 via the pad support 32. The EG pad 23 is made of a polyurethane resin pad base material formed in a disk shape having a thickness of about 4.8 mm, and fine SiC particles of about 0.6 μm or abrasive grains of tungsten, alumina or the like are contained in the resin material. The resin is mixed and the pad base material is impregnated with the resin. The sub pad 24 is formed in a disk shape having a thickness of about 0.9 mm and has a hardness lower than that of the EG pad 23. Needless to say, the resin material for mixing the abrasive grains is not limited to polyurethane. Reference numeral 35 in FIG. 7A is a supply line for supplying an alkaline polishing aid or pure water to the processed surface 23 a of the EG pad 23. The supply line 35 is connected to a supply source of a polishing aid and pure water (not shown).

Next, the operation of the wafer surface treatment apparatus 40 will be described. First, the transfer robot 15 takes out one wafer W from the cassette 11a and transfers it to the chuck portion 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 thereof facing upward. The chuck portion 12a is previously cleaned by the cleaning unit 14. After that, the turntable 13 is index-rotated, and the chuck portion 12a is moved to the rough grinding unit 16. At this time, another wafer W is transferred to another chuck unit 12d by the transfer robot, and the same process 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 index-rotated, and the chuck portion 12a 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 12a is moved from the finish grinding unit 17 to the polishing/texturing unit 18.

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

Specifically, the abrasive grains (hereinafter, "fixed abrasive grains") A1 included in the EG pad 23 and the abrasive grains (hereinafter, "loose abrasive grains") A2 separated from the EG pad 23 cooperate with each other to perform polishing. Perform processing and texturing. The EG pad 2 and the wafer W rotate while the fixed abrasive A1 is pressed against the back surface Wa of the wafer W, and the loose abrasive A2 rolls on the EG pad 23. As for the free abrasive grains A2, a part of the fixed abrasive grains A1 contained in the EG pad 23 is released from the EG pad 23 as shown in FIG. 9 when the resinous adhesive 27 is swollen and hydrolyzed by the polishing aid. It is a thing.

In addition, the surface layer side of the back surface Wa of the wafer W comes into contact with a polishing aid and the oxide film (SiO2) is modified to SiOH to be softened, so that the back surface Wa of the wafer W is easily polished. Further, by rolling the free abrasive grains A2 on the wafer W, it is not necessary to perform polishing by forcing the free abrasive grains A2 into the wafer W by an external force such as cutting into the wafer W, and a very fine scratch is applied to the wafer W by a natural force. The EG layer 30 is formed in the wafer W by forming the EG layer 30.

After the polishing/texturing process, as shown in FIG. 8C, a cleaning process 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. Thereafter, while the EG pad 23 is being rotated 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 the EG pad 23 is also rotated on the pad dresser 27 by a motor (not shown). The EG pad 23 is lightly pressed and a predetermined range in the thickness direction is wiped from the processed surface 23a of the EG pad 23 to remove the polishing aid remaining on the processed surface 23a of the EG pad 23. As a result, it is possible to prevent the polishing aid remaining on the processed surface 23a from being transferred to the wafer W in the rinse step described later.

After the cleaning step, as shown in FIG. 8D, a rinse step is performed on the back surface Wa of the wafer W. In this step, the EG pad 23 horizontally rotates together with the arm 21 and moves above the chuck portion 12a. After that, 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 in proximity to the wafer W in a non-contact state, and in this state, the water flow is formed on the back surface Wa of the wafer W by rotating the wafer W and the EG pad 23 in opposite directions. be able to. In this way, the rinse treatment is performed with the supplied water, and the polishing aid remaining on the back surface Wa of the wafer W is washed off and removed.

Next, the scratches forming the EG layer 30 will be described with reference to the drawings. FIG. 10 is a schematic plan view showing the offset amount between the EG pad 23 and the wafer W. FIG. 11 is a diagram showing a rotation trajectory of a grindstone included in the EG pad 23. FIG. 12 is an image showing the orientation of scratches 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 orbit of the fixed abrasive grains A1 included in the EG pad 23, that is, the density and directionality of scratches are different depending on the offset amount, the gettering ability of the EG layer 30 desired to be imparted to the wafer W is reduced. Accordingly, the offset amount is adjusted arbitrarily. That is, the rotational trajectory of the fixed abrasive grain A1 with zero offset amount shown in FIG. 11A goes from the center o of the wafer W, which coincides with the rotation axis a2 of the chuck portion 12a, to the outer periphery while slightly curving in the circumferential direction. On the other hand, as shown in FIGS. 11B and 11C, as the offset amount increases, the rotation trajectory of the fixed abrasive grain A1 is greatly curved in the circumferential direction of the EG pad 23. The scratches formed on the wafer W become sparser toward the outside of the wafer W. Further, as shown in FIG. 12, at the periphery of the wafer W, the scratches tend to be regularly formed so that the directions of the scratches are aligned.

In addition to the scratches imparted by the fixed abrasive grains A1, the free abrasive grains A2 rolling on the EG pad 23 form scratches in the EG pad 23. The loose abrasive grains A2 do not move regularly like the fixed abrasive grains A1 described above, 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 with each other to impart scratches to the wafer W, thereby suppressing the local sparse scratches in the EG layer 30. it can.

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

The tilt mechanism 42 includes one fixed support portion 43 arranged on the tip end side of the EG pad 23 and two movable support portions 44 arranged on the base 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 is capable of inclining 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 for fastening the tilt table 45 to the fixing 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 or the like that separates the tilt table 45 and the fixed member by screwing a ball screw.

The two movable support portions 44, 44 independently move the tilt table 45 to and from the fixed member, whereby the tilt table 45 tilts at an arbitrary angle with the fixed support portion 43 as a fulcrum. As a result, the back surface Wa of the wafer W is unevenly and locally pressed against the EG pad 23, so that the density of scratches in the EG layer 30 can be partially changed.

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

Further, the fixed abrasive grains A1 contained in the EG pad 26 are pressed against the back surface Wa of the wafer W, and the loose 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 sparse scratches from being locally sparse in the EG layer 30 and form the EG layer 30 capable of capturing heavy metals with high accuracy. it can.

The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified one.

As described above, in addition to processing the back surface 20b of the wafer, it can be applied to an apparatus for processing various plate-shaped surfaces.

10, 40 Wafer surface treatment apparatus 11a, 11b Cassettes 12a to 12d Chuck portion (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 front 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 Nonwoven 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 44 Movable Support 45 Tilt Table

Claims (16)

A substrate holding mechanism for holding and rotating a wafer, a dresser for finishing and polishing one surface of the wafer held by the substrate holding mechanism into a mirror surface, and a wafer surface treatment apparatus comprising:
The dresser is in a wet state, it has a surface treatment pad to finish the mirror surface by a gettering layer provided on one surface of the wafer,
The surface treatment pad is arranged facing the substrate holding mechanism, and has an EG pad formed by impregnating a pad base material with a resin material mixed with abrasive grains,
A polishing aid hydrolyzes the resin material to release at least a part of the abrasive grains from the surface treatment pad, and the fixed abrasive grains contained in the EG pad are held on the substrate while being pressed against the wafer. The mechanism and the EG pad are rotated to cause free abrasive grains released from the EG pad to roll on the wafer, whereby the wafer is polished and the gettering layer is formed on the wafer. Wafer surface treatment equipment. The wafer surface treatment apparatus according to claim 1, wherein the surface treatment pad is composed of a resin material mixed with at least SiC abrasive grains and a non-woven fabric impregnated with the resin material. The wafer according to claim 1, wherein the surface treatment pad is composed of a resin material mixed with at least SiC abrasive grains and a polyurethane resin or melamine material mixed with the resin material. Surface treatment equipment. The surface treatment of the wafer according to claim 1, further comprising: a means for supplying an alkaline solution between the wafer and the surface treatment pad during the mirror finishing by the surface treatment pad. 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-polishing one surface of the wafer together with a polishing aid, The wafer surface treatment apparatus according to claim 1, 2, 3, or 4. The wafer according to claim 5, wherein the material polishing step includes a first material polishing step of roughly polishing one surface of the wafer and a second material polishing step of precisely polishing one surface of the wafer. Surface treatment equipment. 7. The surface treatment apparatus for a wafer according to claim 5, further comprising a pad dresser for adjusting 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 surface treatment apparatus for a wafer according to claim 1, wherein the surface treatment step is performed to polish the wafer into a mirror surface and to form the gettering layer. After the surface treatment step, while supplying pure water between the wafer and the surface treatment pad, the substrate holding mechanism and the surface treatment pad are rotated to remove the polishing aid remaining on one surface of the wafer. 9. The wafer surface treatment apparatus according to claim 8, wherein a rinsing step of flushing is performed. 10. The wafer surface treatment apparatus according to claim 9, wherein in the rinsing step, the wafer and the surface treatment pad rotate in a non-contact state. 11. The wafer surface treatment apparatus according to claim 10, wherein the substrate holding mechanism and the surface treatment pad are relatively rotated in the reverse direction in the rinsing step. 12. A dressing step of pressing a pad dresser against a processed surface of the surface treatment pad to wipe the processed surface between the surface treatment step and the rinsing step is performed. The wafer surface treatment apparatus according to item 1. The resin material is a surface treatment apparatus of the wafer according to claim 1, characterized in that the polyurethane resin. 14. The surface processing apparatus for a wafer according to claim 13, wherein the substrate holding mechanism and the surface processing pad relatively rotate in opposite directions. The surface treatment pad, surface treatment apparatus of a wafer according to any one of claims 1 to 14, characterized in that it is disposed above the substrate holding mechanism. The surface treatment pad,
A pad support that supports the EG pad,
A sub pad interposed between the EG pad and the pad support and softer than the EG pad,
Surface treatment apparatus of a wafer according to any one of claims 1 to 15, characterized in that it comprises a.