JP2007305644A - Single wafer etching system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To etch the edge of a wafer uniformly by preventing the leakage of an etching liquid to the lower surface of the wafer. <P>SOLUTION: While rotating a single thin disklike silicon wafer 11 mounted to a wafer chuck 12 horizontally, the upper surface of the wafer is etched by supplying the etching liquid 14 thereto. A groove 27a for storing the etching liquid 14 flowing downward from the upper surface of the wafer 11 along the edge 11a of the wafer 11 is formed in a chuck 12 to oppose the edge 11a of the wafer 11; and a doughnut-like adhesion form 28 is provided in the chuck 12 having an upper surface adhering to the periphery of the lower surface of the wafer 11 mounted to the wafer chuck 12, and preventing the leakage of the etching liquid 14 stored in the groove 27a to the lower surface of the wafer 11. The outside diameter B of the adhesion form 28 is smaller by 6-0.2 mm than the outside diameter A of the silicon wafer 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for etching wafers one by one while rotating the wafers.

  In general, the manufacturing process of a semiconductor wafer consists of chamfering, mechanical polishing (lapping), etching, mirror polishing (polishing) and cleaning of a wafer obtained by slicing and slicing from a single crystal ingot. It is produced as a wafer having a degree. A wafer that has undergone a machining process such as block cutting, outer diameter grinding, slicing, or lapping has a damaged layer, that is, a work-affected layer on the upper surface thereof. The work-affected layer must be completely removed because it induces crystal defects such as slip dislocations in the device manufacturing process, lowers the mechanical strength of the wafer, and adversely affects the electrical properties. Etching is performed to remove the work-affected layer. As the etching process, immersion etching or single-wafer etching is performed.

  Since the single wafer etching can control the surface roughness and texture size of a large-diameter wafer, it has been studied as an optimum etching method. Single wafer etching is a method in which an etching solution is dropped onto the upper surface of a flattened single wafer, and the etched etching solution is spread over the entire upper surface of the wafer by rotating (spinning) the wafer. The etching solution supplied to the upper surface of the wafer spreads from the supplied location to the entire upper surface of the wafer due to the centrifugal force generated by rotating the wafer, and reaches the edge of the wafer. Will be. Most of the supplied etching solution blows off from the edge portion of the wafer by centrifugal force and is collected by a cup or the like provided in the etching apparatus. However, there is a problem that part of the etching solution flows from the edge portion of the wafer to the lower surface of the wafer and also etches the edge portion of the wafer and the lower surface of the wafer.

In order to eliminate this point, the rotation drive unit is connected to the central axis of the rotation base, a positioning unit for placing the wafer at a predetermined position around the rotation base is provided, and a holding member that holds the peripheral surface of the wafer Is disclosed between positioning portions around the rotating base, and a single wafer processing mechanism is disclosed in which a processing nozzle for sending an etching solution is provided above the rotating base (see, for example, Patent Document 1). In this single wafer processing mechanism, when the protrusion height Xmm of the positioning portion and the holding member based on the contact portion with the rotating base on the lower surface of the wafer is Amm, the thickness of the peripheral edge portion of the wafer is 0 <X <(A + 0). .5). A gas supply block is provided around the central axis of the lower portion of the rotary base, and a supply port through which gas from the block is fed is provided through the rotary base.
In the single wafer processing mechanism configured as described above, the protrusion heights of the positioning portion and the holding member are set to the above ratios, so that turbulent air flow and repelling of the etching solution can be suppressed during high-speed rotation of the wafer. Further, by sending gas from the supply port provided in the block, the atmospheric pressure in the space between the rotating base and the lower surface of the wafer is increased, so that it is possible to prevent the etching solution from entering the lower surface of the wafer.
JP-A-11-289002 (Claims 1 and 2, paragraph [0010], paragraph [0018], paragraph [0019], paragraph [0021])

However, in the conventional single wafer processing mechanism disclosed in Patent Document 1, gas is sent below the wafer to prevent the etching solution from flowing to the lower surface of the wafer. The staying time becomes longer, the portion where the etching solution stays is etched more than necessary, and the shape of the peripheral surface of the wafer that has been chamfered may collapse locally, and the edge portion of the wafer may not be etched uniformly. there were.
An object of the present invention is to provide a single wafer etching apparatus capable of uniformly etching an edge portion of a wafer while preventing an etching solution from flowing into the lower surface of the wafer.

In the invention according to claim 1, as shown in FIG. 1, a single thin disk-shaped silicon wafer 11 obtained by slicing a silicon single crystal ingot is rotated while being held on a wafer chuck 12. However, this is an improvement of the single wafer etching apparatus that supplies the etching solution 14 to the upper surface of the wafer 11 to etch the upper surface of the wafer 11.
The characteristic configuration is that the groove 12a for storing the etching solution 14 flowing down from the upper surface of the wafer 11 through the edge portion 11a of the wafer 11 is formed in the chuck 12 so as to face the edge portion 11a of the wafer 11, The chuck 12 is provided with a doughnut-shaped contact form 28 that prevents the etching solution 14 that has an upper surface closely attached to the periphery of the lower surface of the wafer 11 placed on the surface 12 and collects in the concave grooves 27 a to the lower surface of the wafer 11.

In the wafer single wafer etching apparatus according to claim 1, when the wafer 11 is first placed and held on the chuck 12, the wafer 11 is rotated and the etching solution 14 is supplied to the upper surface of the wafer 11. Due to the centrifugal force generated with the rotation of the wafer 11, the etching solution 14 gradually moves from the supply location to the edge portion 11 a side of the wafer 11 while etching the upper surface of the wafer 11. The etching solution 14 then reaches the upper chamfered portion 11d constituting the edge portion 11a, and reaches the outer peripheral surface portion 11f from the upper chamfered portion 11d. The etching solution 14 that has reached the outer peripheral surface portion 11f has its surface tension overcome the centrifugal force and is transmitted to the lower chamfered portion 11e, and accumulates in the concave groove 27a formed in the chuck 12. The etching solution 14 accumulated in the concave groove 27 a overflows and scatters outward due to the centrifugal force accompanying the rotation of the wafer 11. Thus, the presence of the concave groove ensures that the etching solution 14 comes into contact with the lower surface chamfered portion 11e constituting the edge portion 11a and uniformly etches all the edge portion 11a.
On the other hand, since the chuck 23 is provided with the doughnut-shaped contact form 28, the contact form 28 comes into close contact with the periphery of the lower surface of the wafer 11 placed on the wafer chuck 12, and the etching solution 14 collected in the concave groove 27 a of the wafer 11. Prevents wraparound to the bottom surface. As a result, a situation where the lower surface of the wafer 11 is etched by the etching solution 14 that has entered the lower surface of the wafer 11 is avoided.

The invention according to claim 2 is the invention according to claim 1, wherein the outer diameter B of the doughnut-shaped contact form 28 is 6 to 0.2 mm smaller than the outer diameter A of the silicon wafer 11 placed on the wafer chuck 12. Features.
In the wafer single wafer etching apparatus according to the second aspect, the etching solution 14 accumulated in the concave groove 27a is reliably prevented from entering the lower surface of the wafer 11, and the etching solution 14 that has entered the lower surface of the wafer 11 is used. A situation in which the lower surface is etched can be effectively avoided.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the adhesive foam 28 is made of polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoro It consists of ethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (PTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or derivatives thereof. It is characterized by.
In the single wafer etching apparatus according to the third aspect, the chemical resistance of the contact form 28 and the close contact with the wafer 11 can be ensured, and the etching solution 14 accumulated in the groove 27a of the wafer 11 can be secured. While preventing the wraparound to the lower surface, the lifetime can be extended.

As described above, according to the present invention, the groove is formed in the chuck so as to face the edge portion of the wafer so that the groove for storing the etching solution flowing down from the upper surface of the wafer through the edge portion of the wafer is formed. The etching solution supplied to the wafer moves to the edge side due to the centrifugal force generated by the rotation of the wafer, reaches the upper chamfered portion that constitutes the edge portion, reaches the outer peripheral surface portion from the upper chamfered portion, and further lower chamfered. It is transmitted to the part and accumulates in the concave groove formed in the chuck. Since the etching solution collected in the concave groove is surely brought into contact with the bottom surface forming part constituting the edge part, all of the edge part can be uniformly etched.
In addition, since the chuck has a doughnut-shaped contact form that prevents the etching solution that is in close contact with the periphery of the lower surface of the wafer placed on the wafer chuck and collects in the concave groove from flowing into the lower surface of the wafer, the contact form is formed on the wafer chuck. The upper surface is closely attached to the periphery of the lower surface of the wafer placed on the substrate, and the etching solution accumulated in the concave groove is prevented from entering the lower surface of the wafer 11. As a result, it is possible to avoid a situation in which the etching solution flows from the concave groove to the lower surface of the wafer and the lower surface is etched.

  In this case, if the outer diameter of the doughnut-shaped contact foam is 6 to 0.2 mm smaller than the outer diameter of the silicon wafer placed on the wafer chuck, it is possible to surely prevent the etching solution accumulated in the concave groove from entering the lower surface of the wafer. It can be made of polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer If it is made of any one of coalescence (PTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE) or derivatives thereof, the chemical resistance of the adhesive foam and the adhesion to the wafer can be improved. Can be secured in the groove Thereby preventing the wraparound of the lower surface of the wafer circle etchant can also prolonging its life.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, a single wafer etching apparatus 10 for a silicon wafer 11 includes a wafer chuck 12 that is housed in a chamber and holds a single thin disk-shaped silicon wafer 11 and holds the wafer 11 horizontally. Rotating means 13 for rotating in a horizontal plane around a vertical center line, etching solution supplying means 16 for supplying an etching solution 14 to the upper surface of the wafer 11 held by the chuck 12, and an edge of the wafer 11 placed on the chuck 12 And a liquid suction mechanism 22 for sucking the etching liquid 14 flowing down through the portion 11 a and scattered by the centrifugal force accompanying the rotation of the wafer 11. The wafer 11 is obtained by slicing a silicon single crystal ingot. The outer peripheral edge of the wafer 11, that is, the edge portion 11a, as shown in the enlarged view of FIG. 1, is a chamfered portion 11d continuous with the upper surface 11b and the lower surface 11c of the wafer. 11e and the outer peripheral surface part 11f which connects the outer peripheral edge of the chamfered parts 11d and 11e of the upper and lower sides with a predetermined curvature radius.

  The chuck 12 is rotatable via a bearing 24 through a cylindrical base member 23 having a diameter larger than the diameter of the wafer 11 and a through hole 23a formed in the center of the base member 23 so as to extend in the vertical direction. And a disc-shaped suction plate 27 provided coaxially with the holding shaft 26 at the upper end of the holding shaft 26. A through hole 26a extending in the vertical direction is formed at the center of the holding shaft 26, and the lower end of the through hole 26a is connected to a vacuum pump (not shown). A disc-shaped suction plate 27 provided coaxially with the holding shaft 26 is attached to the upper end of the holding shaft 26 with its upper surface being flush with the upper end edge of the holding shaft 26. The wafer 11 is configured to be placed concentrically with the holding shaft 26 on the upper surface of 26. When the vacuum pump of the gas injection mechanism 17 is driven and the inside of the through hole 26a becomes negative pressure, the negative pressure in the through hole 26a attracts the lower surface of the wafer 11 to the upper edge of the holding shaft 26 and the upper surface of the suction plate 27. Thus, the wafer 11 is held horizontally.

  The rotating means 13 has a drive motor (not shown) that rotates the holding shaft 26 and also rotates the suction plate 27 together with the holding shaft 26. By rotating the holding shaft 26 by the drive motor, the wafer 11 sucked and held on the upper edge of the holding shaft 26 and the upper surface of the suction plate 27 is configured to rotate together with the holding shaft 26 and the suction plate 27. Further, the etching solution supply means 16 is provided above the wafer 11 and has a nozzle 16b provided with a discharge port 16a facing the upper surface of the wafer 11 at the tip, and an etching solution 14 connected to the base end of the nozzle 16b through the nozzle 16b. And a supply pump (not shown) for supplying the discharge port 16a and nozzle moving means (not shown) for moving the nozzle 16b in the horizontal direction.

  The suction plate 27 constituting the chuck 12 is formed with an endless groove 27a on the entire outer periphery thereof so as to face the edge portion 11a of the wafer 11 placed thereon. The concave groove 27a is configured to accumulate the etching solution 14 which is supplied to the upper surface of the wafer 11 placed thereon and flows down from the upper surface through the edge portion 11a of the wafer 11. Therefore, the concave groove 27a is formed to face the edge portion 11a of the wafer 11, and is formed to have a width W that is the same as or slightly larger than the width H of the chamfered portion 11e that constitutes the etched portion 11a. Further, the depth d of the concave groove 27a is preferably 0.1 to 2 mm in order to allow the accumulated etching solution 14 to flow quickly.

  On the other hand, the adsorbing plate 27 constituting the chuck 12 is provided with a doughnut-shaped close contact foam 28 inside a concave groove 27a formed on the outer periphery of the upper portion thereof. The contact form 28 is configured such that the upper surface is in close contact with the periphery of the lower surface of the wafer 11 placed on the wafer chuck 12, and closes the gap between the lower surface of the wafer 11 and the contact form 28 by contacting the upper surface. It is configured to prevent the etching solution 14 accumulated in the concave groove 27 a from passing over the contact form 28 and wrapping around the lower surface of the wafer 11. For this reason, this doughnut-shaped adhesive foam is made of polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene as a material having both chemical resistance and adhesiveness.・ Made from either hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (PTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or their derivatives. Is preferred.

Further, the doughnut-shaped contact form 28 is for closing the gap between the lower surface of the wafer 11 and the contact form 28 and preventing the etching solution 14 from flowing around the lower surface of the wafer 11. The outer diameter of the contact form 28 is preferably 6 to 0.2 mm smaller than the outer diameter of the silicon wafer 11 placed on the wafer chuck 12. This is because the outer periphery of the lower surface of the wafer is 6 to 0.2 mm smaller than the outer diameter of the silicon wafer 11 including the etched portion 11a. Therefore, if the difference between the outer diameter of the contact form 28 and the outer diameter of the silicon wafer 11 is less than 0.2, the contact form 28 protrudes to the etched portion 11a of the wafer 11 and the etching solution 14 moves to the lower surface of the wafer 11. If the difference between the outer diameter of the contact foam 28 and the outer diameter of the silicon wafer 11 exceeds 6 mm, the etching solution 14 may come into contact with the lower surface of the wafer 11 to which the contact foam 28 does not adhere. There is a possibility that the lower surface of the wafer 11 is etched. A more preferable outer diameter of the doughnut-shaped close contact foam 28 is 1 to 0.2 mm smaller than the outer diameter of the silicon wafer 11.
The contact foam 28 is attached by forming a step portion 27b corresponding to the thickness t of the contact foam 28 inside the concave groove 27a of the suction plate 27 constituting the chuck 12, and the contact foam 28 is formed on the step portion 27b. The wafer 11 is configured to be mounted in contact with a portion inside the step portion 27b of the suction plate 27 provided.

  On the other hand, the liquid suction mechanism 22 includes a liquid receiver 22a provided outside the chuck 12 and the outer peripheral surface of the wafer 11 and a liquid suction means (not shown) communicated with the liquid receiver 22a. And have. The liquid receiver 22a opens toward the outer peripheral surface of the chuck 12 and the wafer 11, and this opening surface is formed in an arc shape having a central angle of about 90 degrees in a plan view although not shown. In this embodiment, four liquid receptacles 22a are arranged outside the outer peripheral surfaces of the chuck 12 and the wafer 11, and these liquid receptacles 22a surround the substantially entire circumference of the chuck 12 and the wafer 11. Composed. The base ends of the suction pipes 22b are connected to the liquid receivers 22a. The liquid suction means is constituted by a vacuum pump or the like, and is connected to the four liquid receivers 22a through the four suction pipes 22b. By this liquid suction means, the etching liquid 14 in the liquid receiver 22a is sucked together with the gas through the suction pipe 22b. Further, the liquid receiver 22a is formed in an inner surface shape having an angle at which the etching liquid 14 does not reach the upper surface of the wafer 11 even if the etching liquid 14 rebounds on the inner surface of the liquid receiver 22a.

The operation of the wafer single-wafer etching apparatus 10 thus configured will be described.
First, in a state where the wafer 11 is placed on the chuck 12, a vacuum pump connected to the lower end of the through hole 26a of the holder 26 is operated to make the through hole 23a a negative pressure, and the negative pressure causes the wafer 11 to be horizontal. Hold. In this state, the drive motor of the rotating means is operated to rotate the suction plate 27 together with the holder 26, and the wafer 11 placed on the holder 26 and the suction plate 27 is rotated in a horizontal plane. Next, by operating the suction means of the liquid suction mechanism 22, the suction pipe 22b and the liquid receiver 22a are kept at a negative pressure. Next, by operating the supply pump and nozzle moving means of the etching liquid supply means 16, the etching liquid 14 is supplied from the discharge port 16a to the upper surface of the wafer 11 while moving the nozzle 16b in the horizontal direction.

  The etching solution 14 supplied to the upper surface of the wafer 11 is subjected to the edge of the wafer 11 from a location (for example, near the center of the upper surface of the wafer 11) where the etching solution 14 is supplied due to the centrifugal force generated as the wafer 11 rotates in the horizontal plane. After moving gradually while etching the work-affected layer on the upper surface of the wafer 11 toward the portion 11a, the edge portion 11a is etched when the edge portion 11a of the wafer 11 is reached. That is, the etching solution 14 moving on the upper surface of the wafer 11 reaches the upper chamfered portion 11d constituting the edge portion 11a, and reaches the outer peripheral surface portion 11f from the upper chamfered portion 11d. The etching solution 14 that has reached the outer peripheral surface portion 11 f has its surface tension overcome the centrifugal force and is transmitted to the lower chamfered portion 11 e, and accumulates in the groove 27 a formed in the suction plate 27 constituting the chuck 12. The etching solution 14 accumulated in the concave groove 27 a overflows from the concave groove 27 a due to the centrifugal force accompanying the rotation of the wafer 11 and scatters outside the suction plate 27. As the etching solution 14 flows in this manner, the etching solution 14 uniformly etches the upper and lower chamfered portions 11d and 11e constituting the edge portion 11a and the outer peripheral edge portion 11f existing therebetween. The etchant 14 scattered from the suction plate 27 enters the liquid receiver 22a maintained at a negative pressure, and is discharged out of the chamber through the suction pipe 22b due to the negative pressure.

  On the other hand, since the doughnut-shaped contact form 28 is provided on the suction plate 27 inside the recessed groove 27 a, the contact form 28 is closely attached to the periphery of the lower surface of the wafer 11 placed on the wafer chuck 12, and the recessed groove 27 a. The accumulated etching solution 14 is prevented from entering the lower surface of the wafer 11. As a result, it is possible to effectively avoid a situation in which the lower surface of the wafer 11 is etched by the etching solution 14 that has entered the lower surface. Since the etchant 14 scattered from around the suction plate 27 is sucked by the liquid suction mechanism 22, the etchant 14 does not splash and adhere to the upper surface of the wafer 11 again, so that the upper surface of the wafer 11 is uniformly etched. can do.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, a wafer obtained by slicing a silicon single crystal ingot was chamfered, mechanically polished (lapped), and a 300 mmφ silicon wafer 11 whose front and back surfaces were planarized was prepared. Moreover, the etching liquid 14 which the mixture ratio of hydrofluoric acid, nitric acid, phosphoric acid, and water was weight%, and consists of hydrofluoric acid: nitric acid: phosphoric acid: water = 7%: 30%: 35%: 28% was prepared.

  Next, a single wafer etching apparatus 10 shown in FIG. 1 was prepared. That is, the groove 27a is formed endlessly on the outer periphery of the upper portion of the suction plate 27 constituting the chuck 12. The inner diameter of the concave groove 27a is 299.6 mm, the width W thereof is 0.5 mm, and the depth d of the concave groove 27a is 0.3 mm. On the other hand, a donut-shaped close contact foam 28 was provided inside the concave groove 27a. This contact foam was made of polytetrafluoroethylene (PTFE), and its outer diameter B was 299.5 mm, which was 0.5 mm smaller than the outer diameter of the silicon wafer 11. In addition, the adhesive foam 28 having a thickness t of 0.2 mm was used. For the attachment of the contact foam 28, a step portion 27b corresponding to the thickness t of the contact foam 28 is formed inside the concave groove 27a of the suction plate 27 constituting the chuck 12, and the contact foam 28 is attached to the step portion 27b. Provided. The wafer 11 was placed on the chuck 12 of the single wafer etching apparatus 10 shown in FIG.

Next, the wafer 11 is rotated horizontally, the etching solution 14 is supplied from the nozzle 16b provided above the wafer to the upper surface of the wafer 11, and the etching solution 14 is transferred from the wafer surface to the wafer surface by centrifugal force generated by the horizontal rotation. The work-affected layer generated by the flattening treatment was etched by spreading to the side end.
Here, the etching solution 14 was supplied at an amount of 3 liters / minute to the center of the upper surface of the wafer 11 through the nozzle 16b. Then, the discharge port 16a at the tip of the nozzle 16b was moved from the center of the upper surface of the wafer 11 to the periphery thereof at a speed of 5 mm / second, and then moved back from the periphery to the center. Under this condition, the surface of the silicon wafer 11 was etched by 20 μm. The wafer whose surface was etched in this manner was designated as Example 1.

<Comparative Example 1>
The same silicon wafer and etching solution as in Example 1 were prepared. In addition, a normal single wafer etching apparatus was prepared. That is, an etching apparatus was prepared in which the concave groove 27a was not formed on the outer periphery of the upper portion of the suction plate 27 constituting the chuck 12, and the doughnut-shaped contact form 28 was not provided on the upper surface. Then, the wafer 11 was placed on a chuck having a flat upper surface so that the surface was the upper surface, and the wafer was rotated under the same conditions as in Example 1. Then, an etching solution was supplied to the upper surface of the wafer through the supply nozzle under the same conditions as in Example 1, and the surface of the silicon wafer was etched by a total of 20 μm. The wafer whose surface was etched in this way was designated as Comparative Example 1.

<Comparative test 1 and evaluation 1>
The edge part of the silicon wafer which performed the etching of Example 1 and Comparative Example 1 was observed with the optical microscope. The results are shown in FIGS. Specifically, a photograph of the edge portion of the wafer of Example 1 observed from the outer peripheral side is shown in FIG. 2, and a photograph of the edge portion of the wafer of Comparative Example 1 observed from the outer peripheral side is shown in FIG. Moreover, the photograph figure which observed the chamfering part which followed the lower surface side of the edge part of the wafer of Example 1 is shown in FIG. 4, and the photograph figure which observed the chamfering part which continued to the lower surface side of the edge part of the wafer of the comparative example 1 Is shown in FIG. Furthermore, the photograph figure which observed the lower surface periphery of the edge part of the wafer of Example 1 is shown in FIG. 6, and the photograph figure which observed the lower surface periphery of the edge part of the wafer of Comparative Example 1 is shown in FIG.

Although FIG. 2 and FIG. 3 cannot judge the superiority or inferiority of the etching state in each of the wafers of Example 1 and Comparative Example 1, the wafer of Example 1 is compared with the wafer of Comparative Example 1 from FIGS. It can be seen that the etched portion is uniformly etched. That is, as apparent from FIGS. 4 and 6, it can be seen that the etched portion in the wafer of Example 1 is smoothly etched and not etched down to the lower surface of the wafer. On the other hand, as is apparent from FIGS. 5 and 7, it can be seen that the surface of the etched portion of the wafer of Comparative Example 1 is locally cloudy. This can be said to show that the edge portion is not uniformly etched. In the first embodiment, a concave groove is formed in the chuck on which the wafer is placed, and the contact form 28 is provided on the inner side thereof, so that the upper surface is in close contact with the periphery of the lower surface of the wafer 11 placed on the wafer chuck 12. This is considered to be due to the fact that the etching solution 14 accumulated in 27a is prevented from wrapping around the lower surface of the wafer 11.

<Comparative test 2 and evaluation 2>
Next, the cross section at the edge part of the silicon wafer of Example 1 and Comparative Example 1 was observed with an edge cross section profiler. A cross section at the edge portion of the wafer in Example 1 is shown in FIG. 8, and a cross section at the edge portion of the wafer in Comparative Example 1 is shown in FIG. Moreover, the wafer same as the wafer used for the Example and the comparative example was prepared separately, and the cross section in the edge part of the wafer before the etching prepared separately was observed with the edge cross-section profiler. The result is shown in FIG.

  As is clear from FIGS. 8 to 10, in FIG. 9 showing the edge portion of Comparative Example 1 in which the groove on which the wafer is placed is not formed and the contact form 28 is not provided, chamfering is performed in the flattening step. Compared to FIG. 10 showing the cross section of the wafer before etching, the chamfered portion at the wafer front side and the edge tip is etched more, and the etching amount of the portion continuous from the front and back surfaces to the chamfered portion is small, It can be seen that the continuous part appears as a convex shape. From this result, it can be seen that when the etching solution is not prevented from flowing around as in Comparative Example 1, the wafer edge is not uniformly etched, and the chamfered wafer edge is totally deformed.

  On the other hand, in FIG. 8 which shows the edge part of Example 1 using the etching apparatus of this invention which formed the ditch | groove in the chuck | zipper which mounts a wafer, and provided the contact | adherence form 28 inside, the wafer before an etching is shown in FIG. It can be seen that the cross-sectional structure is the same as in FIG. This is because the edge portion is uniformly etched from the concave groove 2 formed on the chuck on which the wafer is placed, and the contact form 28 provided on the inner side of the groove is formed in the concave groove 27a of the etching solution 14 to the lower surface of the wafer 11. This is thought to be due to the prevention of wraparound.

It is a principal part longitudinal cross-section block diagram of the single wafer type etching apparatus of the wafer of this invention embodiment. FIG. 3 is a photographic view of an edge portion of a wafer of Example 1 viewed from the outer periphery. It is the photograph figure which looked at the edge part of the wafer of comparative example 1 from the outer periphery. FIG. 3 is a photographic view of a chamfered portion at an edge portion of a wafer in Example 1. 6 is a photographic view of a chamfered portion in an edge portion of a wafer of Comparative Example 1. FIG. FIG. 3 is a photographic view of the periphery of the lower surface of the wafer of Example 1; 6 is a photograph showing the periphery of the lower surface of the wafer of Comparative Example 1. FIG. 1 is a sectional view of an end shape of a wafer of Example 1. FIG. 6 is a sectional view of an end shape of a wafer of Comparative Example 1. FIG. It is edge part sectional drawing of the wafer before an etching.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Single wafer type etching apparatus 11 Silicon wafer 11a Edge part 12 Wafer chuck 14 Etching liquid 27a Concave groove 28 Adhesive form A Outer diameter of silicon wafer B Outer diameter of adhering foam

Claims (3)

Etching on the upper surface of the wafer (11) while rotating while holding a single thin disk-shaped silicon wafer (11) obtained by slicing a silicon single crystal ingot on the wafer chuck (12) In the single wafer etching apparatus for supplying the liquid (14) and etching the upper surface of the wafer (11),
A concave groove (27a) for storing an etching solution (14) flowing down from the upper surface of the wafer (11) along the edge portion (11a) of the wafer (11) is opposed to the edge portion (11a) of the wafer (11). Formed on the chuck (12) to
A donut that prevents the etchant (14) that adheres to the periphery of the lower surface of the wafer (11) placed on the wafer chuck (12) and collects in the concave groove (27a) from entering the lower surface of the wafer (11). A wafer single-wafer etching apparatus, characterized in that a close contact form (28) is provided on the chuck (12).   The wafer single wafer type according to claim 1, wherein the outer diameter (B) of the doughnut-shaped contact foam (28) is 6 to 0.2 mm smaller than the outer diameter (A) of the silicon wafer (11) placed on the wafer chuck (12). Etching equipment. Adhesive foam (28) is polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer. 3. The wafer single-wafer etching apparatus according to claim 1, comprising a polymer (PTFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), or a derivative thereof.