JP4264289B2 - Wafer polishing apparatus, polishing head thereof, and wafer polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer polishing technique, and more particularly to a wafer polishing apparatus, a polishing head, and a polishing method that can perform polishing in an optimal state even when the same polishing head is used for different polishing conditions.
[0002]
[Related technologies]
In the step of mirror polishing a semiconductor wafer or the like, for example, a wafer polishing apparatus as shown in FIG. 10 is used as a single-side polishing type polishing apparatus. FIG. 10 is a schematic cross-sectional view of the main part showing an example of a conventional wafer polishing apparatus. In FIG. 10, reference numeral 10 denotes a wafer polishing apparatus, which includes a polishing head 18 having a polishing head body 16 that detachably holds a wafer W, which is an object to be polished, with the surface to be polished facing downward; A rotatable polishing surface plate 14 to which a polishing cloth 12 disposed so as to face the held wafer W and having a diameter considerably larger than the diameter of the wafer W is attached, and a retainer ring for holding the outer peripheral edge of the wafer W In the polishing, the polishing agent 24 is supplied from the polishing agent supply pipe 22 onto the polishing cloth 12, and one surface of the wafer W may be held by a backing pad 26 or the like (synthetic resin, ceramics, elastic body, or the like). ) Is held on the holding surface 16a of the polishing head main body 16, and the polishing head 18 is pressurized and the other surface of the wafer is pressed against the polishing cloth 12 for polishing. It is intended. The polishing surface plate 14 is supported by a base via a drive shaft 28 and is driven to rotate by a surface plate driving mechanism. On the other hand, the polishing head 18 is rotationally driven by a polishing head drive mechanism 25 via a drive shaft 29. Further, a wafer polishing apparatus having a configuration that does not include the retainer ring 20 has also been used.
[0003]
Various types of polishing apparatuses have been developed for manufacturing such mirror-polished wafers, but many are improvements to the polishing holding method (polishing head and further wafer holding), and soft materials such as backing pads are used. Improvements have been made to hold wafers on the holding surface, vacuum suction, and templates (also called guide rings and retainer rings).
[0004]
For example, in Patent Document 1, the wafer is sucked and supported by a flexible thin wafer suction holding plate disposed in the lower opening of the wafer holding member, and the wafer holding member is attached to the housing with a stretchable cylindrical member. A polishing head is disclosed in which a highly flexible support member is supported in a suspended manner, compressed air having a predetermined pressure is introduced into a sealed chamber, the influence of the weight of the wafer holding member is eliminated, and the wafer is polished only by uniform air pressure. Yes.
[0005]
Moreover, in patent document 2, in the workpiece holding | maintenance board | substrate for grinding | polishing which comprised the workpiece holding board main body which has many through-holes which hold | maintain a workpiece | work by vacuum suction, the holding surface of the holding | maintenance board main body is the thermosetting by which the holding surface was apply | coated. A technique relating to a polishing head (wafer holding method) in which a resin is coated with a heat-cured film and the surface of the film is polished is disclosed.
[0006]
Further, in Patent Document 3, in a substrate holding device that holds a semiconductor wafer that is a polishing object and presses it against a polishing surface on a polishing table, the top ring body that holds the semiconductor wafer and the top ring body are fixed to the top ring body. Or a retainer ring that is integrally provided to hold the outer peripheral edge of the semiconductor wafer, and a fluid chamber that is provided in the top ring body and that is covered with an elastic film and supplied with fluid, and supplies pressurized fluid into the fluid chamber. Thus, a polishing head is disclosed in which a semiconductor wafer is pressed against a polishing surface through an elastic film and a retainer ring is pressed against a polishing surface (polishing cloth) by applying a pressing force to a top ring body.
[0007]
In addition, in Patent Document 4, a polishing head that holds the outer peripheral portion of the wafer in a state that can be elastically deformed in the wafer thickness direction, and in Patent Document 5, the first space portion that presses the carrier and the retainer ring are pressed. A technique that has two spaces, supplies pressure air to the first and second spaces, elastically deforms the central portion and the outer periphery of the elastic sheet, and presses the carrier and the retainer ring against the polishing surface plate is disclosed. ing.
[0008]
Among such various types of polishing apparatuses, for example, a hollow head main body in the polishing head, and an elastic body (sometimes referred to as a soft layer, a diaphragm, etc.) stretched horizontally in the head main body, and elasticity Has a ceramic wafer holder (sometimes called a carrier) fixed to the lower surface of the body and supplies pressurized air from a pressurized air source through a shaft to an air chamber defined by an elastic body Thus, the floating head structure that can press the wafer holding plate downward has the advantage that the contact pressure of the wafer against the polishing cloth can be made uniform, and the polishing allowance (polishing amount) within the wafer surface is reduced. Mainly used when polishing uniformly. At this time, a retainer ring (also referred to as a guide ring) is concentrically arranged on the outer periphery of the wafer holding plate, and the lower end of the retainer ring protrudes downward from the wafer holding plate, thereby adhering to the lower surface of the wafer holding plate. By holding the outer periphery of the wafer, it is possible to prevent the wafer being polished from coming off the wafer holder, and the wafer is surrounded by a retainer ring, and the lower end of the retainer ring is polished at the same height as the lower surface of the wafer. Thus, it is said that the phenomenon that the polishing amount at the outer peripheral portion of the wafer is larger than that at the central portion of the wafer can be prevented.
[0009]
Conventionally, as described above, it was thought that overpolishing of the outer peripheral portion of the wafer could be prevented if the lower end surface of the retainer ring was arranged almost on the same plane as the polishing surface of the wafer. In the apparatus, the retainer ring is pressed at a pressure higher than the pressing pressure of the wafer holding plate against the polishing cloth. For example, it was set to be twice or more. This is because the holding of the outer periphery of the wafer becomes more reliable when the contact pressure of the retainer ring is increased.
[0010]
However, depending on the material of the polishing cloth, etc., the polishing cloth locally swells along the inner peripheral edge of the portion that is in contact with the retainer ring, and the peripheral part of the wafer is excessively polished by this bulging part, and the polishing uniformity of the wafer The problem of being disturbed occurred.
[0011]
As disclosed in Patent Document 6 for this problem, by setting the abutment force of the retainer ring to the polishing cloth to an appropriate value that is weaker than before, the wavy deformation of the polishing cloth is prevented, and the wafer outer peripheral portion is excessively deformed. There are also things that suppress polishing. Specifically, by adjusting the ratio between the pressure-receiving width of the elastic body that applies pressure to the retainer ring and the contact area of the retainer ring with the polishing cloth, the retainer ring with respect to the polishing cloth during wafer polishing is adjusted. The ratio between the contact pressure and the pressing force of the wafer holding disc against the polishing cloth is adjusted. In other words, the polishing cloth is pressed by retainer ring to indirectly control the outer peripheral shape of the wafer.
[0012]
Another type of polishing apparatus has been developed. For example, as disclosed in Patent Document 7, pressure is applied to the outermost peripheral portion of the wafer support portion on the back surface of the wafer, and further, as disclosed in Patent Document 8, the wafer holding surface is divided into several regions. Some have a mechanism for pressurizing separately. In this method, the wafer is pressed directly from the back surface of the wafer to control the shape of the wafer.
[0013]
Further, depending on the polishing apparatus, there are a plurality of polishing stages, and polishing may be performed under the same or different polishing conditions in each stage. In such a system, there is a case where polishing is continuously performed by providing a mechanism for transferring a wafer on the way or by sequentially moving the wafer to each stage while holding the wafer on the polishing head. For example, in a polishing apparatus in which there are three surface plates to which a polishing cloth is attached, polishing is performed under a combination of polishing conditions such as corrected polishing, corrected polishing + uniform polishing, and uniform polishing. The correction polishing is polishing in which the polishing margin is not uniform within the wafer surface, and a thick portion is actively polished to obtain a wafer with high flatness, mainly rough polishing, primary polishing, etc. It is said. In rough polishing, polishing is generally performed with a large polishing allowance.
[0014]
Uniform polishing is a surface polishing of a wafer that has become high flatness by modified polishing, and is performed uniformly in-plane while maintaining the original shape, and is mainly called finish polishing. In this process, the polishing allowance is very small. Further, secondary polishing may be performed as an intermediate between them. The secondary polishing is a process in which corrected polishing and uniform polishing are mixed, and can be changed to either polishing form depending on the conditions. In particular, the polishing allowance is smaller than that in the primary polishing step, and more than the final polishing is usually set. In the secondary polishing, whether to increase the correction polishing action or to increase the uniform polishing action is set depending on the wafer shape after the primary polishing. However, in practice, it is difficult to completely distinguish between corrected polishing and uniform polishing.
[0015]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-171757
[Patent Document 2]
JP 2000-198069 A
[Patent Document 3]
JP 2002-113653 A
[Patent Document 4]
Japanese Patent Laid-Open No. 08-257893
[Patent Document 5]
JP 11-42550 A
[Patent Document 6]
JP-A-8-229804
[Patent Document 7]
Japanese Patent Application Laid-Open No. 08-339979
[Patent Document 8]
Japanese Patent Laid-Open No. 9-225821
[0016]
[Problems to be solved by the invention]
Among the polishing performed in multiple stages on the wafer, the correction polishing process is mainly performed in the primary polishing and processed to a high flatness. In the secondary polishing process and the final polishing process, the polishing amount (polishing cost, polishing allowance) It is preferable to perform uniform polishing for uniform polishing in a plane. However, it is difficult to perform stable and uniform polishing, and for example, the shape tends to collapse at the outer periphery of the wafer. In order to prevent the shape of the outer peripheral portion of the wafer from collapsing, a polishing head using the retainer ring configured as described above and a polishing head having a pressure mechanism on the back surface of the wafer are used. However, there are the following problems when controlling the outer peripheral shape of the wafer by pressing the polishing cloth with the conventional retainer ring or controlling the shape of the wafer by directly pressing the back surface of the wafer. It was.
[0017]
For example, in the wafer polishing apparatus 30 that uses a retainer ring 32 as schematically shown in FIG. 12 and adjusts the pressing force to the polishing cloth 34, the shape of the wafer W, particularly the shape of the outer periphery of the wafer can be controlled. As shown in the drawing, the influence on the polishing cloth 34 such as the polishing cloth 34 being crushed by the pressurization by the retainer ring 32 is great, and finer adjustment to the polishing cloth 34 is necessary. Therefore, it is necessary to use the polishing pad 34 with a certain degree of limitation. Further, in this wafer polishing apparatus 30, the wafer shape is likely to change sensitively due to slight pressure changes and adjustment deviations such as variations in the pressing force of the retainer ring 32 and the polishing pressure (pressure to press the wafer). However, there was a problem that the effect was small with a hard polishing cloth.
[0018]
In FIG. 12, reference numeral 36 denotes a polishing head, which has a polishing head main body 35. The lower surface of the polishing head main body 35 is a wafer holding surface 35a. Reference numeral 38 denotes a first pressure adjusting mechanism which is provided in the polishing head main body 35 and adjusts the polishing pressure. A second pressure adjusting mechanism 40 is provided on the retainer ring 32 and adjusts the pressing force of the retainer ring 32 to the polishing pad 34, and is formed by an air bag or the like.
[0019]
Further, in the case of the wafer polishing apparatus 50 that controls the shape by directly applying pressure to the outer peripheral portion of the wafer W from the back surface of the wafer W through the soft holding member 62 as shown in FIG. If there is a shape defect in the pressurized part, it may be transferred to the shape of the wafer W. Further, the polishing amount (polishing allowance) changes due to pressure fluctuations, which is not preferable for polishing to make the polishing amount (polishing allowance) uniform. In particular, since the pressure exerted on the back surface of the wafer W is sensitively affected, uniform polishing is liable to be disrupted, and a polishing apparatus having a plurality of polishing heads has a problem that variations between the polishing heads increase.
[0020]
In FIG. 13, reference numeral 52 denotes a polishing head, which has a polishing head main body 54. 56 is a guide ring (retainer ring), 58 is a polishing cloth, 60 is a fluid chamber formed between the polishing head main body 54 and the soft holding member 62, and 64 is a first adjusting the polishing pressure via the fluid chamber 60. The pressure adjusting mechanism 66 is a second pressure adjusting mechanism which is provided on the outer peripheral portion of the soft holding member 62 and presses the outer peripheral portion of the back surface of the wafer W, and is formed by an air bag or the like.
[0021]
A first object of the present invention is to provide a wafer polishing apparatus, a polishing head, and a wafer polishing method in which the shape of the outer peripheral portion of the wafer does not deteriorate due to such variations in the pressure adjusting mechanism.
[0022]
Further, when a hard wafer holding disk (carrier) such as ceramics is used, it is difficult to perform uniform polishing with a uniform polishing margin in the surface, and it is preferable to hold the wafer with a soft member. However, with such a holding configuration, the polishing pressure on the outer peripheral portion of the wafer tends to escape, and the outer periphery tends to be a honey shape.
[0023]
The present invention provides a wafer polishing apparatus, a polishing head thereof, and a wafer polishing method for manufacturing a wafer with high flatness in a polishing apparatus in which a hard wafer holding disk such as ceramics is not used but is held by a soft layer (elastic body). The second object is to provide the above.
[0024]
It is a third object of the present invention to provide a wafer polishing apparatus, a polishing head thereof, and a wafer polishing method capable of uniformly polishing a wafer surface, particularly a wafer outer peripheral portion, without breaking the shape of a wafer having a particularly high flatness. And
[0025]
However, when a polishing head specialized for uniform polishing is set as described above, it may be difficult to perform correction polishing. In the secondary polishing, there is a case where polishing with a correcting action is performed, for example, when the primary polishing is not processed to a sufficiently high flatness. For example, when a wafer is held on one polishing head and polishing is performed on a plurality of stages (surface plates) under different polishing conditions, the polishing is mainly performed on the first stage under conditions where the shape correction (corrected polishing) action is large. In the latter stage, it is carried out under the condition that the surface is uniformly polished (uniform polishing). A fourth object of the present invention is to provide a wafer polishing apparatus, a polishing head, and a wafer polishing method capable of polishing using the same polishing head for such different purposes of polishing.
[0026]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first aspect of a wafer polishing apparatus according to the present invention includes a surface plate having a polishing cloth affixed to a surface, and a surface of the wafer to be polished while holding the wafer on the polishing cloth. The other surface is abutted 1 or Comprises two or more polishing heads and a polishing head driving mechanism for polishing the other surface of the wafer with the polishing cloth by driving these polishing heads. A disc-shaped top plate portion and a cylindrical peripheral wall portion fixed to the outer periphery of the top plate portion; A polishing head main body provided with a wafer holding portion for holding the wafer, and provided in the polishing head main body so as to be orthogonal to the polishing head axis to hold the wafer. And larger than the wafer holding area. With elastic body A guide ring provided at a lower portion of the peripheral wall portion for holding the wafer so that the wafer does not jump out during polishing; A wafer polishing apparatus having a first pressure adjusting mechanism for adjusting a polishing pressure via a fluid chamber formed between the elastic body and the polishing head main body, outside the wafer holding region. A second pressure adjusting mechanism that adjusts the pressure of the elastic body portion that is positioned; and a displacement that is displaceable in the polishing head axial direction by a third pressure adjusting mechanism outside the second pressure adjusting mechanism. A pressing ring is provided. The guide ring is located between the wafer holding portion and the pressing ring and outside the wafer holding region, and is located below the elastic body portion whose pressure is adjusted by the second pressure adjusting mechanism. Provided in It is characterized by that.
[0027]
According to a second aspect of the wafer polishing apparatus of the present invention, there is provided a surface plate having a polishing cloth affixed on the surface thereof, and holding one surface of the wafer to be polished and bringing the other surface of the wafer into contact with the polishing cloth 1 Or two or more polishing heads, and a polishing head driving mechanism for polishing the other surface of the wafer with the polishing cloth by driving these polishing heads. A disc-shaped top plate portion and a cylindrical peripheral wall portion fixed to the outer periphery of the top plate portion; A polishing head body provided with a wafer holding portion for holding the wafer, and an elastic body provided in the polishing head body to hold the wafer so as to be orthogonal to the polishing head axis and to be larger than the wafer holding area. And a backup flange provided on the upper surface side of the elastic body, A guide ring provided on the peripheral wall to hold the wafer so that the wafer does not jump out during polishing; A wafer polishing apparatus having a first pressure adjusting mechanism that adjusts a polishing pressure by a first fluid chamber formed between the elastic body and the backup flange, the backup flange and the polishing A convex portion formed on the outer periphery of the lower surface of the backup flange via a second fluid chamber formed between the head main body and the pressure of the elastic body portion positioned outside the wafer holding region is adjusted. And a pressure ring that is displaceable with respect to the axial direction of the polishing head by a third pressure adjusting mechanism outside the second pressure adjusting mechanism. The guide ring is located between the wafer holding portion and the pressing ring and outside the wafer holding region, and is located below the elastic body portion whose pressure is adjusted by the second pressure adjusting mechanism. Provided in It is characterized by that.
[0028]
As described above, in the wafer polishing apparatus of the present invention, the polishing member that holds the wafer by the elastic body (soft member), the soft member portion outside the region where the wafer actually exists is independent of the wafer back surface. By applying pressure, stable uniform polishing can be performed.
[0029]
In the wafer polishing apparatus of the present invention, a mechanism that presses the soft member portion outside the region where the wafer actually exists, independently of the wafer back surface, with a polishing head that holds the wafer by such an elastic body, that is, By controlling the pressure at a position outside the wafer, even if the pressure varies, the wafer outer shape and the like can be uniformly polished in the correction polishing and uniform polishing without excessively affecting the wafer shape. . There is an advantage that shape control is easy to be performed because it is not easily affected by the installation accuracy of components (second pressure control mechanism) and the like.
[0030]
Further, in the wafer polishing apparatus of the present invention, by installing a pressing ring that can be displaced with respect to the axial direction of the head, the ratio between the correction polishing and the uniform polishing can be adjusted, and the wafer can be processed into a preferable wafer shape. In particular, the apparatus is suitable for a case where a wafer is held by one polishing head and polishing is performed with a plurality of stages (surface plates) under different polishing conditions. In the present invention, the pressure ring is not adjusted for uniform polishing, but rather the shape change due to the pressure of the pressure ring is actively used to correct the shape. The influence of the pressing ring, which is difficult to control by uniform polishing, is weakened or eliminated, and the pressure on the wafer back side (exactly, the portion outside the wafer support area) is adjusted. The pressure ring of the present invention has the same mechanism as the conventional retainer ring as shown in FIG. 12, but the conventional retainer ring also serves to hold the wafer and is located very close to the outer periphery of the wafer. Is arranged. The pressure ring of the present invention is arranged further outside than the second pressure adjusting mechanism located outside the wafer support region and is located slightly away from the wafer, and the pressure ring itself does not hold the wafer. is there. Shape control can be performed more easily than in the prior art by adopting a configuration having an appropriate interval between the wafer and the pressing ring.
[0031]
Therefore, in the wafer polishing apparatus of the present invention, it is preferable to set a guide ring for holding the wafer so that the wafer does not jump out during polishing between the wafer holding portion and the pressing ring. The guide ring may be directly attached to an elastic body or the like, but is not particularly limited as long as the outer periphery of the wafer can be held. Moreover, it is good to set thinner than the wafer to be polished. The guide ring is fixed to prevent the wafer from being detached from the wafer holding portion in order to make the wafer holding position accurate.
[0032]
The wafer polishing apparatus of the present invention is configured to hold the wafer on the surface of the elastic body. However, a backing pad may be further attached to the surface of the elastic body and the wafer may be held in that state. Although only an elastic body may be used, it is preferable to hold the wafer with a member made of a material used as a polishing cloth in consideration of prevention of scratches on the back surface of the wafer.
[0033]
As described above, the wafer polishing apparatus of the present invention polishes the wafer by adjusting the pressure in the region outside the wafer holding region.
[0034]
The polishing head of the wafer polishing apparatus of the present invention is: A disc-shaped top plate portion and a cylindrical peripheral wall portion fixed to the outer periphery of the top plate portion; A polishing head main body provided with a wafer holding portion for holding a wafer, and an elastic body provided in the polishing head main body so as to be orthogonal to the polishing head axis and configured to be larger than the wafer holding region in order to hold the wafer; A backup flange provided on the upper surface side of the elastic body; A guide ring provided on the peripheral wall to hold the wafer so that the wafer does not jump out during polishing; A polishing head of a wafer polishing apparatus having a first pressure adjusting mechanism for adjusting a polishing pressure by a first fluid chamber formed between the elastic body and the backup flange, the backup flange And a convex portion formed on the outer periphery of the lower surface of the backup flange via a second fluid chamber formed between the polishing head main body and the pressure of the elastic body portion located outside the wafer holding region. A pressure ring that has a second pressure adjustment mechanism to be adjusted, and a pressure ring that is displaceable in the axial direction of the polishing head by a third pressure adjustment mechanism outside the second pressure adjustment mechanism; The guide ring is located between the wafer holding portion and the pressing ring and outside the wafer holding region, and is located below the elastic body portion whose pressure is adjusted by the second pressure adjusting mechanism. Provided in It is characterized by that. Further, a backing pad can be provided on the surface of the elastic body that holds the wafer.
[0035]
Such polishing pressure (pressure controlled by the first pressure adjusting mechanism), pressure of the outer portion of the wafer (back surface) support region (pressure controlled by the second pressure adjusting mechanism), and pressing force of the pressing ring By using a polishing head capable of independently controlling (pressure controlled by the third pressure adjusting mechanism), the pressure of the elastic body portion outside the wafer holding region can be easily adjusted and polished. A wafer having an arbitrary wafer shape can be polished by adjusting the ratio of uniform polishing and correction polishing by the action of the pressing ring.
[0036]
The wafer polishing method of the present invention is a wafer polishing method in which correction polishing and uniform polishing are performed using the same polishing head, the wafer being held by an elastic body formed larger than the wafer holding region, and from the wafer holding region. The pressure of the outer elastic body portion is adjusted, and further, the position of the pressing ring disposed on the outer side is adjusted and polished.
[0037]
In the above correction polishing, polishing is performed in a state where the pressing ring disposed on the outside is pressed against the polishing cloth with a constant pressing force, and in uniform polishing, the pressing ring is weaker than the pressing force or the position where the pressing ring is not in contact with the polishing cloth. It is preferable to polish in a state of being retracted. The method of the present invention can be effectively carried out by using the apparatus of the present invention.
[0038]
As described above, by adjusting the height position (pressure) of the pressing ring and adjusting the pressure of the elastic body portion outside the wafer holding region, the wafer having an arbitrary wafer shape can be obtained even with one polishing head. Can be polished. It is not necessary to prepare a plurality of polishing heads that meet the polishing conditions, and polishing can be performed without providing a mechanism for transferring a wafer from the polishing head to the polishing head.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the illustrated examples are illustrative only, and various modifications can be made without departing from the technical idea of the present invention. .
[0040]
FIG. 1 is a cross-sectional schematic explanatory view of a main part showing a first embodiment of a wafer polishing apparatus of the present invention. FIG. 2 is a schematic cross-sectional explanatory view of the main part showing a second embodiment of the wafer polishing apparatus of the present invention.
[0041]
The entire structure of the wafer polishing apparatus 100 according to the present invention shown in FIG. 1 is substantially the same as the structure of the wafer polishing apparatus 10 shown in the conventional example of FIG. 10, and a detailed description thereof will be omitted. In brief, a disk-shaped surface plate (reference numeral 14 in FIG. 10, omitted in FIG. 1) is installed horizontally, and this surface plate is rotated around the axis by a surface plate drive mechanism. A polishing cloth (reference numeral 12 in FIG. 10 and reference numeral 119 in FIG. 1) is affixed over the entire upper surface.
[0042]
A head driving mechanism (reference numeral 25 in FIG. 10, omitted in FIG. 1) is fixed above the surface plate via a plurality of support columns. The head driving mechanism has a plurality of polishing heads ( 10 and 18 in FIG. 10 are provided (only one polishing head is shown in FIGS. 10 and 1). The wafer polishing apparatus 100 of the present invention is clearly different from the conventional wafer polishing apparatus 10 shown in FIG. 10 in that a new polishing head 101 different from the conventional polishing head 18 is used.
[0043]
Next, the polishing head of the wafer polishing apparatus of the present invention will be described with reference to FIGS. These FIGS. 1 and 2 exaggerately describe the main components of each polishing head, and the dimensions are different from the actual ones.
[0044]
As shown in FIG. 1, the polishing head 101 in the wafer polishing apparatus 100 of the present invention is disposed so as to be orthogonal to the polishing head axis D of the drive shaft 103 of the polishing head 101 and has a hollow polishing head main body 102 having an open lower end. And an elastic body (soft holding layer) 106 provided so as to be orthogonal to the polishing head axis D in the polishing head body 102. The polishing head main body 102 includes a disk-shaped top plate portion 104 and a cylindrical peripheral wall portion 105 fixed to the outer periphery of the top plate portion 104. The top plate portion 104 is driven by a head drive mechanism (not shown). The shaft 103 is fixed coaxially. The elastic body 106 has an area larger than the diameter of the wafer W, and a backup flange 108 is provided on the upper surface of the elastic body 106.
[0045]
The outer peripheral part of the disk-shaped elastic body 106 is fixed by the peripheral wall part 105 or the like. The elastic body 106 is made of an elastic material such as various types of rubber, and urethane rubber is mainly suitable. The thickness of the elastic body 106 is not particularly limited, but if the thickness is about 0.5 mm to 3 mm, it is easy to control the pressure and the like. The wafer W is held by the wafer holding portion of the elastic body (soft holding layer) 106 and polished.
[0046]
When polishing is performed, a configuration in which the wafer W is attached to the lower surface of the elastic body 106 via a backing pad (not shown) may be employed. The backing pad is formed of a water-absorbing material such as a non-woven fabric and can absorb the wafer with surface tension when it absorbs moisture. Examples of the material of the backing pad include various types of suede, and the backing pad may be formed with a thin glass epoxy plate and an adhesive layer for adhesion to the elastic body. A preferable thickness of this backing pad is about 0.4 to 0.6 mm.
[0047]
Further, a guide ring 118 for holding the wafer W is installed so that the wafer W does not jump out during polishing. The guide ring 118 is a ring-shaped member made of a glass epoxy plate or a PEEK material and having a width of about 10 mm to 20 mm and an inner diameter of 0.5 mm to 1 mm larger than the diameter of the wafer W. The thickness is not particularly limited, but may be set slightly thinner than the polished surface of the wafer W.
[0048]
A first flow path 107 is formed in the drive shaft 103 of the polishing head main body 102 having the above-described structure, and the first fluid chamber 110 defined between the backup flange 108 and the elastic body 106 includes a first fluid chamber 110. One flow path 107 is connected to the first pressure adjustment mechanism 112. Then, by adjusting the fluid pressure 112 a in the first fluid chamber 110 by the first pressure adjusting mechanism 112, the elastic body 106 is displaced up and down to press the wafer W against the polishing pad 119 (polishing pressure). Adjust. In general, it is sufficient to use air as the fluid.
[0049]
A second fluid chamber 114 is formed on the upper surface of the backup flange 108 and is connected to the second pressure adjusting mechanism 116 through the second flow path 115. Then, by adjusting the fluid pressure 116a in the fluid chamber 114 with the second pressure adjusting mechanism 116, the convex portion 108a formed on the outer peripheral portion of the lower surface of the backup flange 108 is pressed, and the portion outside the wafer holding region 106a. The pressure of 106b can be adjusted. Reference numeral 118 denotes a guide ring that holds the side of the wafer W so that it does not jump out during polishing.
[0050]
In the present invention, as described above, the pressure of the portion 106b outside the diameter of the wafer W is adjusted by the second pressure adjusting mechanism 116 to control the wafer shape. In other words, the first elastic chamber 106 has a wafer holding elastic body 106 having an area larger than the diameter of the wafer, and the first fluid chamber 110 formed between the elastic body 106 and the backup flange 108 adjusts the polishing pressure. In addition to the pressure adjustment mechanism 112, a second fluid chamber 114 formed on the upper surface of the backup flange 108, and a convex portion 108a formed on the outer periphery of the lower surface of the backup flange 108, a portion 106b outside the wafer holding region 106a. The second pressure adjusting mechanism 116 that can adjust the pressure is provided.
[0051]
Reference numeral 120 denotes an annular concave groove provided on the outer peripheral wall portion 105 on the outer side of the guide ring 118. The annular pressing ring 122 is always upwardly moved to the concave groove 120 by a biasing means (not shown) such as a spring. The pressure ring 122 is slidably accommodated in a biased state, and the upper space of the pressure ring 122 is a third fluid chamber 124. The fluid chamber 124 is connected to the third pressure adjusting mechanism 128 through the third flow path 126. Then, by adjusting the fluid pressure 128 a in the third fluid chamber 124 with the third pressure adjusting mechanism 128, the pressing ring 122 can be pressed downward. Therefore, when the pressing ring 122 is not pressed downward, the pressing ring 122 is retracted upward by an urging force such as a spring. On the other hand, when a downward pressing force is applied to the pressing ring 122, the surface of the polishing pad is pressed downward.
[0052]
Another example of the first to third pressure adjusting mechanisms described above will be described with reference to FIG. 2, the same or similar members as those in FIG. 1 are described using the same reference numerals. 2, the polishing head 101 of the wafer polishing apparatus 100 of the present invention has a polishing head body 102 and a wafer holding elastic body 106 having an area larger than the diameter of the wafer W, as in the example of FIG. The polishing pressure is adjusted by adjusting the fluid pressure 112 a in the first fluid chamber 110 formed between the elastic body 106 and the backup flange 108 via the first pressure adjusting mechanism 112.
[0053]
A second fluid chamber 114 is formed on the upper surface of the backup flange 108 as in FIG. 1, and the fluid pressure 116 a in the second fluid chamber 114 is adjusted via the second pressure adjusting mechanism 116. Thus, the pressure of the portion 106b outside the wafer holding region 106a can be adjusted by the action of the convex portion 108a formed on the outer peripheral portion of the lower surface of the backup flange 108. The wafer W is held by a backing pad 138 having a diameter approximately equal to the wafer diameter, and the backing pad 138 is affixed to an elastic body 106 having an area larger than the wafer diameter.
[0054]
In the example of FIG. 2, the elastic body 106 is fitted and fixed to a recess 108 b formed on the outer periphery of the backup flange 108. A convex portion 108 a is formed at the lower outer periphery of the backup flange 108, and a first fluid chamber 110 is formed between the backup flange 108 and the elastic body 106.
[0055]
A second fluid chamber 114 formed by the top plate portion 102 a of the polishing head main body 102 and the like is provided on the upper portion of the backup flange 108. As described above, by adjusting the fluid pressure 116a of the second fluid chamber 114, the pressure of the portion 106b outside the wafer holding region 106a of the elastic body 106 can be adjusted through the convex portion 108a of the backup flange 108. It has become. Similarly, the polishing pressure is adjusted by adjusting the fluid pressure 112 a of the first fluid chamber 110.
[0056]
Outside the wafer holding structure, a donut-shaped guide ring 118 for holding the wafer W is installed as a part of the structure of the polishing head main body 102. A holding piece 118 a that protrudes inward in an L shape is provided at the lower portion of the guide ring 118, so that the wafer W can be held.
[0057]
Of course, the shapes of the guide ring 118 and the backing pad 138 described above are not limited to the example shown in FIG.
[0058]
Also in the example of FIG. 2, similarly to FIG. 1, the annular pressing ring 122 adjusts the fluid pressure 128 a of the third fluid chamber 124 via the third pressure adjustment mechanism 128 to move inside the annular groove 120. It can be displaced in the vertical direction, and presses the polishing pad as necessary.
[0059]
As a conventional wafer polishing apparatus, for example, as shown in the schematic diagram of FIG. 13, in addition to the first pressure adjusting mechanism 64 that adjusts the polishing pressure, the second pressure adjustment that directly presses the outer peripheral position of the wafer back surface. Some devices use the mechanism 66 to control the wafer shape. Although this conventional polishing apparatus 50 is similar in form to the polishing apparatus of the present invention in the form of the polishing head 52, the wafer pressing position is different, and its configuration and operational effects are greatly different from those of the polishing apparatus of the present invention.
[0060]
Further, the polishing head of the present invention further includes a pressing ring that is displaceable in the axial direction of the head by the third pressure adjusting mechanism outside the second pressure adjusting mechanism. The third pressure adjustment mechanism is not particularly limited. For example, the pressure ring is retracted into the polishing head by the force of a spring and the pressure is adjusted by flowing a fluid over the pressure ring during polishing. You may do it.
[0061]
In another conventional wafer polishing apparatus, for example, as shown in the schematic diagram of FIG. 12, a ring 32 generally called a retainer ring is provided on the outer periphery of the wafer W, and the pressure of the retainer ring 32 is adjusted. The polishing head 36 having the second pressure adjusting mechanism 40 for this purpose was used.
[0062]
As shown in FIG. 12, there is an apparatus that can change the retainer ring, but it is difficult to perform accurate uniform polishing with such a polishing head. By using a polishing head having three pressure adjusting mechanisms (particularly the second pressure adjusting mechanism) as in the present invention, polishing can be performed with high accuracy.
[0063]
Various usage modes of the above-described wafer polishing apparatus of the present invention can be considered, and an example thereof will be described with reference to FIG. FIG. 9 is a schematic top view showing an example of how the wafer polishing apparatus of the present invention is used. 9, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals.
[0064]
In FIG. 9, the wafer polishing apparatus 100 of the present invention has a plurality of (three in the illustrated example) polishing stages (first polishing stage, second polishing stage, and third polishing stage) on its base 200, in other words, A plurality of surface plates 202A, 202B and 202C to which a polishing cloth is attached are provided. Each of the polishing stages 202A, 202B, and 202C can perform polishing under different polishing conditions. On the base 200, a load / unload stage 204 and a cassette stage 206 are further provided. In the loading / unloading stage 204, wafers are attached to and detached from the polishing heads 101a, 101b and 101c, 101d, and a cassette containing a large number of wafers is placed on the cassette stage 206, not shown. The wafer is transferred to and from the load / unload stage 204 by a robot hand or the like.
[0065]
The arrangement of the polishing stages 202A, 202B, 202C and the loading / unloading stage 204 on the base 200 is not particularly limited, but in the illustrated example, the first polishing stage 202A and the third polishing stage 202C are opposed to each other. In this case, the second polishing stage 202B and the load / unload stage 204 are arranged so as to face each other.
[0066]
In FIG. 9, reference numeral 208 denotes a head drive mechanism, which is positioned above the polishing stages 202A, 202B, 202C and is rotatably provided. One or more (four in the illustrated example) polishing heads 101a, 101b, 101c, and 101d are attached to the head driving mechanism 208.
[0067]
There is no particular limitation on the manner in which the polishing heads 101a, 101b, 101c, and 101d are attached to the head drive mechanism 208, but in the illustrated example, the two polishing heads 101a and 101b are the remaining two polishing heads 101c. , 101d. That is, as shown in FIG. 9, two polishing heads 101a and 101b are positioned on the first polishing stage 202A, and two polishing heads 101c and 101d are positioned on the third polishing stage 202C. It is mounted in various ways.
[0068]
The polishing mode according to the configuration of the wafer polishing apparatus 100 of FIG. 9 is as follows. The wafer to be polished is moved from the cassette stage 206 to the load / unload stage 204, the polishing heads 101a, 101b or 101c, 101d are moved to the upper part thereof, and the wafer is held on the wafer holding surface. The movement of the polishing heads 101a to 101d is performed by rotating the head driving mechanism 208. In the example of FIG. 9, the polishing heads 101a, 101b and 101c, 101d are moved to the next stage as the head driving mechanism 208 rotates 90 ° clockwise. That is, the polishing heads 101a to 101d holding the wafer on the wafer holding surface in the load / unload stage 204 are moved to the first polishing stage 202A by the 90 ° rotation of the head driving mechanism 208 in the clockwise direction. After the wafer is polished by the first polishing stage 202A, the second polishing stage 202B, the third polishing stage 203C and the polishing heads 101a to 101d are moved to repeat the polishing, and finally the wafer is transferred to the load / unload stage 204. Detached and then returned to the cassette stage 206.
[0069]
The polishing heads 101a to 101d are movable to the polishing stages 202A, 202B, 202C and the load / unload stage 204 while holding the wafer. At this time, the polishing stages (surface plates) 202A to 202C and the load / unload stage 204 side may move, or the polishing heads 101a to 101d may move. In the example of FIG. 9, the head driving mechanism 208 to which the polishing heads 101a to 101d are attached is a rotating mechanism.
[0070]
Next, the wafer polishing method of the present invention will be described. In order to perform wafer polishing by the wafer polishing apparatus 100 of the present invention shown in FIGS. 1, 2, and 9, first, a wafer is placed on the polishing cloth 119 and each of the polishing heads 101 (101a to 101d), and the polishing cloth is used. The surface plate is brought into contact with 119 and the surface plate is rotated, and polishing is performed by rotating the polishing head 101 (101a to 101d) with respect to the surface plate. This is performed on each of the surface plates 202A to 202C.
[0071]
The polishing conditions for carrying out the method for polishing a wafer of the present invention need to be set as appropriate by modified polishing and uniform polishing, but the contact pressure of the wafer against the polishing cloth (wafer holding plate pressing pressure: first pressure) The pressure controlled by the control mechanism is set to 10 kPa to 40 kPa, more preferably 20 kPa to 30 kPa.
[0072]
Further, the pressing force control (pressure controlled by the second pressure control mechanism) on the outer periphery of the wafer is equivalent to the contact pressure (polishing pressure) to about (contact pressure + 6 kPa), more preferably (contact pressure + 2 kPa). It is good to set to (contact pressure + 4 kPa).
[0073]
The method of controlling the pressing ring 122 that is displaceable with respect to the axial direction of the polishing head 101 by the third pressure adjusting mechanism 128 arranged outside the second pressure adjusting mechanism 116 is adjusted by the correction of the wafer shape. To do. That is, in the polishing step (primary polishing or secondary polishing) in which correction polishing is actively performed, the pressing ring 122 is actively pressed against the polishing pad 119 for polishing, and in the step in which uniform polishing (secondary polishing or finish polishing) is performed. Polishing is performed by retreating to a position where the pressing by the pressing ring 122 is weak or does not completely come into contact with the polishing pad 119.
[0074]
The polishing cloth is not particularly limited, and may be a single-layer polishing cloth or a multilayer polishing cloth. For example, foamed polyurethane or nonwoven fabric is preferably used. In the correction polishing, a polyurethane-based or rubber-based hard polishing cloth is used. For uniform polishing, a multilayer nonwoven fabric and a suede-like polishing cloth are mainly used.
[0075]
【Example】
Hereinafter, the present invention will be described more specifically with reference to comparative examples and examples. However, these examples are presented as examples and should not be construed as limiting.
[0076]
(Comparative Example 1)
Similar to the mechanism shown in FIG. 9, a wafer polishing apparatus in which three surface plates were arranged was used. As a polishing head of this polishing apparatus, an example using a polishing head as shown in FIG. 11 is shown. The polishing head of the polishing apparatus of FIG. 11 is a polishing head provided with both conventional first and second pressure adjusting mechanisms as shown in FIGS. That is, it has a pressure adjustment mechanism (first pressure adjustment mechanism) that adjusts the polishing pressure and a mechanism (second pressure adjustment mechanism) that can directly adjust the pressure to the back surface of the wafer. Further, a donut-shaped retainer ring for holding the wafer is arranged on the outer side of the wafer having such a configuration and moves independently of the polishing head main body. The retainer ring can hold the wafer and press the polishing cloth. (Third pressure adjusting mechanism). This retainer ring is disposed in the vicinity of the outer periphery of the wafer and serves to hold the wafer and press the polishing cloth.
[0077]
In particular, the second pressure adjusting mechanism for adjusting the pressure at the outer peripheral portion of the wafer (back surface) is made to coincide with the configuration of the polishing head of the present invention so that the difference in effect from the present invention becomes clear. To be different. That is, in the polishing head 222 of the wafer polishing apparatus 150 shown in FIG. 11, the wafer W is held by the backing pad 238 having a diameter approximately equal to the wafer diameter, and the backing pad 238 has an area approximately equal to the wafer diameter. 226 is attached.
[0078]
The shape of the elastic body 226 is greatly different from that of the device of the present invention. In the example of FIG. 11, the elastic body 226 is fitted and fixed to a recess 228 b formed on the outer periphery of the backup flange 228. A convex portion 228 a is formed at the lower outer periphery of the backup flange 228, and a first fluid chamber 230 is formed between the backup flange 228 and the elastic body 226.
[0079]
A second fluid chamber 234 formed by, for example, a top plate portion 224 a of the polishing head main body 224 is provided on the upper portion of the backup flange 228. By adjusting the fluid pressure 236a of the second fluid chamber 234, the pressure of the outer peripheral portion 226c in the region where the wafer W of the elastic body 226 exists can be adjusted through the convex portion 228a of the backup flange 228. The polishing pressure is adjusted by adjusting the fluid pressure 232a of the first fluid chamber 230.
[0080]
In this polishing head, a backing pad having a thickness of 0.6 mm is attached to a wafer holding portion with a urethane rubber having a thickness of 1.5 mm, but the diameters of the elastic body and the backup flange are smaller than those in Example 1 described later. The area pressurized by the first pressure adjusting mechanism has a diameter of 298 mm. A second pressure adjusting mechanism is installed with a width of 2 mm on the outer peripheral portion, and is configured such that the pressure on the outer periphery 2 mm of a wafer (back surface) having a diameter of 300 mm can be directly controlled separately from the polishing pressure.
[0081]
Further, a donut-shaped retainer ring 239 for holding the wafer is disposed outside the wafer holding structure. The retainer ring 239 is configured such that a pressing means 240 such as an air bag is installed on the upper surface thereof and is configured to move independently of the polishing head main body, and can hold the wafer W and press the polishing cloth 242. It has become.
[0082]
As the raw material wafer, a double-sided polished wafer having a diameter of 300 mm was used, and then secondary polishing with a strong correction polishing action, secondary polishing with a strong uniform polishing action, and final polishing with uniform polishing were performed. FIG. 7 is a bird's-eye view showing a typical wafer shape after double-sided polishing, which is a raw material wafer. Although the wafer outer periphery has a slightly sagging shape, the wafer has a high flatness of about SFQRmax = 0.12 μm to 0.19 μm.
[0083]
(Polishing at the first polishing stage)
In the first polishing stage, polishing was performed under conditions in which the actions of corrective polishing and uniform polishing were mixed. Basically, since the wafer outer peripheral shape of the raw material wafer (the above double-sided polishing wafer) is somewhat sagging, polishing was performed so that the polishing allowance of this portion was reduced. Specifically, in the first polishing stage of the apparatus shown in FIG. 9, as the polishing conditions, Rodel Nitta Co. (Suba600) was used as the polishing cloth, and the polishing agent used was an alkaline solution containing colloidal silica. The polishing head and the polishing platen were each rotated at 30 rpm. The wafer polishing pressure (first pressure adjusting mechanism) is 30 kPa. Pressurization of the wafer back surface (second pressure adjusting mechanism) was 34 kPa, and the retainer ring was pressurized at 35 kPa against the polishing cloth.
[0084]
As a result of polishing at the first polishing stage described above, a wafer having a shape as shown in the bird's-eye view of FIG. 5 was obtained. As a result of measuring the flatness of the obtained silicon wafer, the flatness of the wafer was deteriorated as SFQRmax was 0.44 μm (the SFQRmax of the double-side polishing of the wafer evaluated this time was 0.12 μm). The distribution of the polishing amount (removal allowance) at this time was confirmed in the wafer plane.
[0085]
FIG. 6 shows the difference between the thickness of the raw wafer (wafer after double-side polishing) and the thickness of the wafer after polishing on the first polishing stage. As shown in FIG. 8, the values evaluated in the circumferential direction at an interval of 4 ° (notch portion at 0 °) at the outer peripheral portion of the wafer (position of 3 mm on the outer periphery) (FIG. 6A) and values measured at intervals of 3 mm in the radial direction ( FIG. 6B).
[0086]
In FIG. 8, N indicates a notch portion of the wafer W, A indicates a scanning direction for measuring the circumferential direction (measurement of the position of the outer periphery of 3 mm), and B indicates a scanning direction for evaluating the radial direction.
[0087]
As can be seen from FIGS. 6 (a) and 6 (b), in the radial direction of the wafer, the polishing allowance of the wafer outer peripheral portion has been corrected a lot, and the polishing allowance in the circumferential direction of the wafer varies greatly depending on the location. It turns out that it is not grind | polished uniformly in the outer peripheral direction. In the wafer, a wave of 1.6 μm was generated at a position of 3 mm from the outer periphery with a period of about 180 °. As a result, the flatness such as SFQR deteriorates.
[0088]
(Polishing at the second polishing stage)
The wafer polished on the first polishing stage was then moved to the second polishing stage and polished using the same polishing head.
Here, the shape correcting action is reduced, and polishing is performed with emphasis on uniform polishing. Specifically, as polishing conditions, Suba400 manufactured by Rodel Nitta Co. was used as the polishing cloth, and an alkaline solution containing colloidal silica was used as the polishing agent. The polishing head and the polishing platen were each rotated at 30 rpm. The wafer polishing pressure (first pressure adjusting mechanism) is 30 kPa. The pressure of the second pressure adjusting mechanism was 32 kPa, and the retainer ring was polished by applying pressure to the polishing cloth at 30 kPa.
[0089]
As a result, SFQRmax was further deteriorated as a result of measuring the flatness of the obtained silicon wafer. In particular, with the polishing head having such a configuration, the outer peripheral portion of the wafer cannot often be uniformly polished. This is because the wafer shape tends to change sensitively due to slight pressure changes and adjustment deviations, such as variations in retainer ring pressing force and polishing pressure (pressure that presses the wafer). It is considered that when the shape is controlled by directly applying pressure, it is likely to be affected by the accuracy failure of the pressurized component.
[0090]
In the polishing head used in this comparative example, it is difficult to control the partial polishing allowance of the outer peripheral portion, and it is also difficult to polish the surface uniformly. Therefore, it is necessary to take measures such as using a polishing head having a different form for each stage. Usually, after this, finish polishing (uniform polishing) for the purpose of improving haze is performed at the third polishing stage, but this was not performed in this comparative example because the outer peripheral shape deteriorated.
[0091]
(Example 1)
Next, an example of polishing using the polishing apparatus having the surface plate arrangement shown in FIG. 9 and using the polishing head of the present invention as shown in FIG. A silicon wafer having a diameter of 300 mm was polished using the polishing apparatus (polishing head) of the present invention. Specifically, the polishing head main body was made of SUS, and the elastic body of the wafer holding part was a urethane rubber having a thickness of 1.5 mm and a backing pad having a thickness of 0.6 mm adhered thereto. Its diameter is 306 mm. The wafer to be polished is held in the center by a water sticking method. A second pressure adjusting mechanism is installed with a width of 2 mm on the outer peripheral portion of the urethane rubber (the convex portion of the outer peripheral portion of the backup flange is formed with a width of 2 mm so that the pressure can be controlled in the outer peripheral area from the wafer. ) That is, there is no pressurizing mechanism in the portion on the back surface of the wafer, and the pressure adjusting mechanism is arranged on the outer peripheral portion thereof. Further, the wafer is supported by a guide ring, and a pressing ring which can be moved up and down is arranged on the outside thereof.
[0092]
As in Comparative Example 1, the raw material wafer was a double-sided polished wafer having a diameter of 300 mm, and then subjected to secondary polishing having a strong correction polishing action, secondary polishing having a strong uniform polishing action, and finish polishing that was uniform polishing.
[0093]
(Polishing at the first polishing stage)
In the first polishing stage, polishing was performed under conditions in which the actions of corrective polishing and uniform polishing were mixed. Basically, since the wafer outer peripheral shape of the raw material wafer (the above double-sided polishing wafer) is somewhat sagging, polishing was performed so that the polishing allowance of this portion was reduced. Specifically, in the first polishing stage of the apparatus shown in FIG. 9, as the polishing conditions, Rodel Nitta Co. (Suba600) was used as the polishing cloth, and the polishing agent was an alkaline solution containing colloidal silica. The polishing head and the polishing platen were each rotated at 30 rpm. The wafer polishing pressure (first pressure adjusting means) is 30 kPa. The pressure on the back surface of the wafer (second pressure adjusting means) was 34 kPa, and the pressing ring was pressed against the polishing cloth at 35 kPa.
[0094]
As a result of polishing at the first polishing stage described above, a wafer having a shape as shown in the bird's-eye view of FIG. 3 was obtained. The distribution of the polishing amount (removal allowance) at this time was confirmed in the circumferential direction (FIG. 4A) and the radial direction (FIG. 4B) in the same manner as in Comparative Example 1. In the radial direction, it can be seen that the outer peripheral portion of the wafer is polished with a little polishing allowance. It can also be seen that the circumferential direction is evenly polished. As a result of measuring the flatness of the obtained silicon wafer, SFQRmax was 0.14 μm (SFQRmax of the double-side polished wafer evaluated this time was 0.19 μm), and the flatness was improved. Further, unlike the comparative example, there was almost no waviness on the outer periphery of the wafer.
[0095]
(Polishing at the second polishing stage)
This was then moved to the second polishing stage and polished while using the same head.
Here, the shape correcting action is reduced, and polishing is performed with emphasis on uniform polishing. Specifically, as polishing conditions, Suba400 manufactured by Rodel Nitta was used as the polishing cloth, and an alkaline solution containing colloidal silica was used as the polishing agent. The polishing head and the polishing platen were each rotated at 30 rpm. The wafer polishing pressure (first pressure adjusting means) is 30 kPa. The pressure of the second pressure adjusting mechanism was 32 kPa, and the pressing ring was polished by applying pressure to the polishing cloth at 30 kPa.
[0096]
Even in this polishing, there was almost no change in shape, and polishing was possible with a uniform polishing margin, and the surface quality (particularly the quality of ripples) was improved.
[0097]
(Polishing at the third polishing stage)
Finally, the wafer was finished and polished. In finish polishing, uniform polishing was performed to improve the haze level of the wafer. Even in this polishing, while being held by the same polishing head, a suede-like polishing cloth (Cirgal 7355 fm manufactured by Toray Cortex Co., Ltd.) is used as the polishing cloth, and the polishing agent is more dispersible than the polishing agent used in the first polishing stage and the second polishing stage. An alkaline solution containing good colloidal silica was used. The polishing head and the polishing platen were each rotated at 20 rpm. The wafer polishing pressure (first pressure adjusting means) is 10 kPa. The pressure of the second pressure adjusting mechanism was 11 kPa, and the pressure ring was polished with the pressure ring completely retracted from the polishing cloth. As a result, the flatness was not deteriorated and the haze level was improved.
[0098]
Thus, in the polishing apparatus of the present invention, corrective polishing and uniform polishing could be effectively performed while using the same polishing head.
[0099]
In conventional polishing heads that press the polishing cloth by retainer ring to control the outer peripheral shape of the wafer, those that directly press the back surface of the wafer to control the shape of the wafer, and combinations of polishing heads, variation in pressure control means As a result, the polishing allowance tends to vary. In particular, the polishing of the outer periphery of the wafer is likely to vary, and the flatness may be deteriorated even in the correction polishing and the uniform polishing. In the polishing apparatus of the present invention, the pressure is controlled particularly in the form of the second pressure adjusting mechanism, and the pressure of the pressing ring is also controlled with a slight gap from the outer periphery of the wafer (at least by the width of the guide ring). Therefore, since there is little influence due to variations between polishing heads or pressure adjusting means, a wafer with high flatness can be manufactured stably.
[0100]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has the same configuration as the technical idea described in the scope of claims of the present invention, and any device that exhibits the same function and effect is the present invention. Are included in the technical scope.
[0101]
For example, the method for installing the guide ring for holding the wafer, the pressing method for the second pressure adjusting mechanism, and the driving method for the pressing ring are not particularly limited.
[0102]
【The invention's effect】
As described above, the wafer polishing apparatus according to the present invention can perform polishing using the same polishing head for polishing with a purpose different from correction polishing and uniform polishing.
[0103]
In the polishing apparatus and the polishing head of the present invention, a wafer having a high flatness can be manufactured by adopting a configuration in which a hard wafer holding disk such as ceramics is not used but held by a soft layer (elastic body). .
[0104]
According to the wafer polishing method of the present invention, good polishing can be performed without causing waviness in the outer peripheral portion of the wafer.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional explanatory view of a main part showing a first embodiment of a wafer polishing apparatus of the present invention.
FIG. 2 is a schematic cross-sectional explanatory view of a main part showing a second embodiment of the wafer polishing apparatus of the present invention.
FIG. 3 is a bird's-eye view showing the shape of a polished wafer on a first polishing stage in Example 1.
FIG. 4 is a graph showing the difference between the thickness of the raw material wafer in Example 1 and the thickness of the wafer after being polished on the first polishing stage, where (a) shows the circumferential direction of the wafer, and (b) Indicates the radial direction of the wafer.
5 is a bird's-eye view showing the shape of a wafer after polishing at a first polishing stage in Comparative Example 1. FIG.
6 is a graph showing the difference between the thickness of the raw wafer and the thickness of the wafer after being polished at the first polishing stage in Comparative Example 1, wherein (a) shows the circumferential direction of the wafer, and (b) Indicates the radial direction of the wafer.
7 is a bird's-eye view showing the shape of a double-sided polished wafer used as a raw material wafer in Example 1 and Comparative Example 1. FIG.
FIG. 8 is a top view illustrating an example of a method for evaluating the shape of a wafer.
FIG. 9 is a schematic top view showing an example of a usage mode of the wafer polishing apparatus of the present invention.
FIG. 10 is a schematic cross-sectional view of a main part showing an example of a conventional wafer polishing apparatus.
FIG. 11 is a schematic cross-sectional view of a main part showing another example of a conventional wafer polishing apparatus.
FIG. 12 is a schematic cross-sectional explanatory view of a main part showing another example of a conventional wafer polishing apparatus.
FIG. 13 is a schematic cross-sectional explanatory view of a main part showing still another example of a conventional wafer polishing apparatus.
[Explanation of symbols]
10, 30, 150: Conventional wafer polishing apparatus, 12: Polishing cloth, 14: Polishing surface plate, 16: Polishing head body, 16a: Holding surface, 18: Polishing head, 20: Retainer ring, 22: Abrasive supply pipe 24: polishing agent, 25: polishing head drive mechanism, 26: backing pad, 28, 29: drive shaft, 32: retainer ring, 34: polishing cloth, 35: polishing head body, 35a: wafer holding surface, 36: polishing Head: 38: First pressure adjusting mechanism, 40: Second pressure adjusting mechanism, 50: Conventional wafer polishing apparatus, 52: Polishing head, 54: Polishing head body, 60: Fluid chamber, 62: Soft holding member, 64: First pressure adjusting mechanism, 66: Second pressure adjusting mechanism, 100: Wafer polishing apparatus of the present invention, 101, 101a to 101d: Polishing head, 102: Polishing head main body, 10 a: top plate portion, 103: drive shaft, 104: top plate portion, 105: peripheral wall portion, 106: elastic body, 106a: wafer holding region, 106b: part outside the wafer holding region, 107: first flow path , 108: backup flange, 108a: convex portion, 108b: concave portion, 110: first fluid chamber, 112: first pressure adjusting mechanism, 114: fluid chamber, 115: second flow path, 116: second Pressure adjustment mechanism, 118: guide ring, 118a: holding piece, 119: polishing cloth, 120: annular groove, 122: pressing ring, 124: third fluid chamber, 126: third flow path, 128: third 200: base, 202A: first polishing stage, 202B: second polishing stage, 202C: third polishing stage, 204: load / unload stage, 206: cassette stage, 08: head drive mechanism, 222: polishing head, 224a: top plate portion, 226: elastic body, 226c: outer peripheral portion, 228: backup flange, 228a: convex portion, 228b: concave portion, 230: fluid chamber, 234: fluid chamber 238: backing pad, 239: retainer ring, 240: pressing means, 242: polishing cloth, D: polishing head axis, W: wafer.

Claims (8)

A surface plate with a polishing cloth affixed to the surface, one or more polishing heads that hold one surface of the wafer to be polished and abut the other surface of the wafer against the polishing cloth, and drive these polishing heads A polishing head driving mechanism for polishing the other surface of the wafer with the polishing cloth, and the polishing head includes a disk-shaped top plate portion and a cylindrical peripheral wall fixed to the outer periphery of the top plate portion. And a polishing head body provided with a wafer holding part for holding the wafer, and provided in the polishing head body so as to be orthogonal to the polishing head axis to hold the wafer and larger than the wafer holding region. the abrasive and an elastic body formed has a guide ring provided at the lower portion of the peripheral wall portion to the wafer to hold the wafer so as not fly out during polishing, and the elastic member A wafer polishing apparatus having a first pressure adjusting mechanism that adjusts a polishing pressure through a fluid chamber formed between the head body and the pressure body, wherein the pressure of the elastic body portion located outside the wafer holding region is adjusted. a second pressure adjusting mechanism for adjusting, provided further pressing ring that can be displaced relative to the polishing head axis direction by a third pressure adjustment mechanism on the outer side of the pressure adjusting mechanism of the second, the guide ring Located between the wafer holding portion and the pressing ring and outside the wafer holding region, and provided below the elastic body portion where the pressure is adjusted by the second pressure adjusting mechanism. A wafer polishing apparatus. A surface plate having a polishing cloth affixed to the surface, one or more polishing heads that hold one surface of the wafer to be polished and abut the other surface of the wafer against the polishing cloth, and drive these polishing heads A polishing head driving mechanism for polishing the other surface of the wafer with the polishing cloth, and the polishing head includes a disk-shaped top plate portion and a cylindrical peripheral wall fixed to the outer periphery of the top plate portion. And a polishing head body provided with a wafer holding part for holding the wafer, and provided in the polishing head body so as to be orthogonal to the polishing head axis to hold the wafer and larger than the wafer holding region. an elastic body formed, et al provided in the peripheral wall to hold the backup flange provided on the upper surface of the elastic body, the wafer is the wafer so as not fly out during polishing Having a guide ring, and a wafer polishing apparatus having a first pressure adjusting mechanism for adjusting the grinding pressure by a first fluid chamber formed between the elastic body and the backup flange, said By means of a convex portion formed on the outer periphery of the lower surface of the backup flange via a second fluid chamber formed between the backup flange and the polishing head body, the elastic body portion positioned outside the wafer holding region is a second pressure adjusting mechanism for adjusting the pressure, provided further pressing ring that can be displaced relative to the polishing head axis direction by a third pressure adjustment mechanism on the outer side of the pressure adjusting mechanism of the second, the guide The elastic member whose ring is positioned between the wafer holding portion and the pressing ring and outside the wafer holding region and whose pressure is adjusted by the second pressure adjusting mechanism. Wafer polishing apparatus is characterized in that provided so as to be positioned below the body part. 3. A wafer polishing apparatus according to claim 1, wherein a backing pad is provided on the surface of the elastic body on the side holding the wafer. Wafer polishing apparatus according to any one of claims 1-3, characterized in that said plate is provided one or two or more. A polishing head main body comprising a disk-shaped top plate portion and a cylindrical peripheral wall portion fixed to the outer periphery of the top plate portion and provided with a wafer holding portion for holding a wafer, and for holding the wafer, An elastic body provided on the polishing head body so as to be orthogonal to the polishing head axis and formed larger than the wafer holding region, a backup flange provided on the upper surface side of the elastic body , and the wafer popped out during polishing. A guide ring provided on the peripheral wall for holding the wafer so that the polishing pressure is adjusted by a first fluid chamber formed between the elastic body and the backup flange. A polishing head of a wafer polishing apparatus having a first pressure adjusting mechanism, wherein the bag is interposed via a second fluid chamber formed between the backup flange and the polishing head body. It has a second pressure adjusting mechanism for adjusting the pressure of the elastic body portion located outside the wafer holding region by a convex portion formed on the outer peripheral portion of the upper flange lower surface, and further from the second pressure adjusting mechanism A pressure ring that is displaceable in the axial direction of the polishing head by a third pressure adjusting mechanism is provided outside, and the guide ring is located between the wafer holding portion and the pressure ring and outside the wafer holding area. In addition , the polishing head is provided so as to be positioned below the elastic body portion whose pressure is adjusted by the second pressure adjusting mechanism . 6. The polishing head according to claim 5 , wherein a backing pad is provided on the surface of the elastic body on the side holding the wafer. 5. A wafer polishing method using the wafer polishing apparatus according to claim 1 and performing correction polishing and uniform polishing using the same polishing head, wherein an elastic body formed larger than the wafer holding region is used. A wafer polishing method characterized by holding a wafer, adjusting the pressure of the elastic body portion positioned outside the wafer holding region, and adjusting and polishing the position of a pressing ring disposed further outside. In the correction polishing, polishing is performed in a state where the pressing ring disposed on the outer side is pressed against the polishing cloth with a constant pressing force, and in the uniform polishing, the pressing ring is weakened than the pressing force or the pressing ring is not in contact with the polishing cloth. 8. The wafer polishing method according to claim 7 , wherein the polishing is performed in a state of being retracted to a position.

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