Wafer processing method

Abstract

To provide a wafer processing method which can use one kind of slurry to perform processes for polishing and oxide film formation.SOLUTION: A processing method of a wafer 100 includes: a polishing step in which a processing device relatively presses a rotating polishing pad 42 against the wafer 100 at a first pressure to polish the wafer 100 while supplying slurry S containing an alkaline solution, abrasive grains, and a hydrogen peroxide solution to a processing point P; and an oxide film formation step in which the processing device presses the rotating polishing pad 42 against the wafer 100 at a second pressure smaller than the first pressure to form an oxide film on a polishing surface of the wafer 100 while supplying the slurry S to the processing point P.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for processing a wafer. [Background technology]

[0002] The polished surface of a wafer made of silicon (hereafter also referred to as "Si wafer") becomes hydrophobic, and the polished wafer dries before cleaning, causing problems such as adhesion of foreign matter and slurry marks. Therefore, immediately after polishing the wafer, the polishing slurry is switched to a hydrophilic slurry containing organic matter such as cellulose to attach cellulose to the wafer surface and make it hydrophilic, and then the wafer is generally cleaned with a dedicated cleaning solution to remove the cellulose and form an oxide film.

[0003] Also, a wafer processing method is known in which a polishing process is performed to polish the wafer, a hydrophilization process is performed by supplying the wafer with a hydrophilization treatment liquid containing organic matter such as cellulose, and then a cleaning process is performed to remove polishing debris generated during the polishing process using a cleaning liquid (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-004910 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional technology, there are problems in that the cost increases because two types of slurry, a polishing slurry and a hydrophilic slurry, are used in the polishing process, and additional steps are required to form an oxide film in the cleaning process. Therefore, there is a problem to be solved in wafer processing, which is to reduce the cost and the steps.

[0006] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a wafer processing method capable of realizing both polishing and oxide film formation processes by using one type of slurry. [Means for solving the problem]

[0007] The wafer processing method of the present invention includes a polishing step in which a slurry containing an alkaline solution, abrasive grains, and hydrogen peroxide solution is supplied to a processing point while a rotating polishing pad is pressed against the wafer at a first pressure to polish the wafer, and an oxide film formation step in which an oxide film is formed on the polished surface of the wafer by supplying the slurry to the processing point while pressing the rotating polishing pad against the wafer at a second pressure smaller than the first pressure.

[0008] In the wafer treating method of the present invention, the hydrogen peroxide solution may be 0.15 mass % to 0.30 mass % based on the total mass of the slurry.

[0009] Moreover, the wafer processing method of the present invention may further comprise a cleaning step of cleaning the wafer after the oxide film forming step.

[0010] In addition, the wafer processing method of the present invention may include carrying out a film forming step of forming a film on the oxide film formed in the oxide film forming step while the oxide film is left in a state where the oxide film is left.

[0011] The polishing pad in the wafer processing method of the present invention may be a nonwoven fabric or polyurethane that does not contain abrasive grains. Effect of the Invention

[0012] According to the present invention, it is possible to provide a wafer processing method capable of realizing both polishing and oxide film formation processes by utilizing one type of slurry. [Brief description of the drawings]

[0013] [Figure 1]1A to 1C are diagrams for explaining a polishing step and an oxide film forming step of the wafer processing method according to the present embodiment. [Diagram 2] 1A to 1C are diagrams for explaining a transport step and a cleaning step of the wafer processing method according to the present embodiment. [Diagram 3] 1A to 1C are diagrams for explaining a film forming step of the wafer processing method according to the present embodiment. [Figure 4] 1 is a perspective view showing an example of a processing apparatus for carrying out a wafer processing method according to an embodiment of the present invention. [Diagram 5] 1 is a table showing the composition of each component contained in a slurry. [Figure 6] 1 is a graph showing experimental results of polishing speed when the mass percentage of hydrogen peroxide contained in a slurry is changed. [Figure 7] 1 is a table showing the experimental results of each parameter of a slurry when the mass percentage of hydrogen peroxide solution contained in the slurry is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The wafer processing method according to the present embodiment will be described with reference to Figs. 1 to 7. Fig. 1 is a diagram for explaining the polishing step and the oxide film forming step of the wafer processing method according to the present embodiment. Fig. 2 is a diagram for explaining the transport step and the cleaning step of the wafer processing method according to the present embodiment. Fig. 3 is a diagram for explaining the film forming step of the wafer processing method according to the present embodiment. Fig. 4 is a perspective view showing an example of a processing apparatus for carrying out the wafer processing method according to the present embodiment. Fig. 5 is a table showing the composition of each component contained in the slurry. Fig. 6 is a graph showing the experimental results of the polishing speed (polishing rate) (μm / min) when the mass % of the hydrogen peroxide solution contained in the slurry is changed. Fig. 7 is a table showing the experimental results of each parameter of the slurry when the mass % of the hydrogen peroxide solution contained in the slurry is changed, similar to Fig. 6.

[0015] The X-axis, Y-axis, and Z-axis directions in each diagram are perpendicular to each other. The X-axis and Y-axis directions are nearly horizontal, and the Z-axis direction is up-down (vertical). In each diagram, of the two arrows indicating the X-axis direction, the -X side is the left, and the +X side is the right. Of the two arrows indicating the Y-axis direction, the -Y side is the front, and the +Y side is the rear. Of the two arrows indicating the Z-axis direction, the +Z side is the up, and the -Z side is the down.

[0016] As shown in FIG. 4, the processing apparatus 1 includes an apparatus main body 10, a first grinding unit 20, a second grinding unit 30, a polishing unit 40, a polishing feed unit 50, a load sensor 60, a slurry supply section 65, a turntable 70, for example, four holding tables 75 installed on the turntable 70, a control unit 80, cassettes 91, 92, an alignment unit 93, a carry-in unit 94, an unloading unit 95, a cleaning unit 96, and a carry-in / out unit 97.

[0017] In this embodiment, the wafer 100 to be processed by the processing apparatus 1 is a workpiece such as a disk-shaped semiconductor wafer or an optical device wafer, whose base material is silicon, sapphire, gallium arsenide, etc. The wafer 100 may or may not have dividing lines or devices formed on a surface 101.

[0018] 4, the turntable 70 is a disk-shaped table provided on the upper surface of the apparatus body 10, is provided so as to be rotatable in a horizontal plane, and is rotated at a predetermined timing. On the turntable 70, for example, four holding tables 75 are arranged at equal intervals, for example, at a phase angle of 90°. These four holding tables 75 are moved sequentially to a carry-in / carry-out position 201, a rough grinding position 202, a finish grinding position 203, a polishing position 204, and the carry-in / carry-out position 201 by the rotation of the turntable 70.

[0019] The upper surfaces of the suction portions 77 of these four holding tables 75 are holding surfaces 78 on which the wafer 100 is placed and which suction-hold the placed wafer 100. The holding surface 78 suction-holds the front surface 101 side of the placed wafer 100, for example, on which the wafer 100 is placed with its back surface 102, which is to be processed (surface to be ground or polished), facing upward.

[0020] These four holding tables 75 are provided on the turntable 70 independently of the turntable 70, and are connected to a rotary drive source (not shown) so as to be rotatable about a predetermined rotation axis passing through the center of the holding table 75 by the rotary drive source (not shown). In addition, below these four holding tables 75, a rotary axis adjustment unit (not shown) is provided for tilting the rotation axis of the holding table 75 with respect to the Z-axis direction parallel to the vertical direction. The rotary axis adjustment unit (not shown) provided on the holding table 75 is used to adjust the inclination of the holding surface 78 of the holding table 75 when rough grinding is performed by the first grinding unit 20 described later, when finish grinding is performed by the second grinding unit 30, and when polishing is performed by the polishing unit 40.

[0021] As shown in FIG. 4, the first grinding unit 20 is attached to the lower end of the spindle 21, and while rotating a grinding wheel 23 having grinding wheels 22 arranged in a ring shape, the first grinding feed unit 24 presses against the holding surface 78 of the holding table 75 positioned at the rough grinding position 202 and the back surface 102 of the wafer 100 held on the holding table 75 along the grinding feed direction (the Z-axis direction parallel to the vertical direction), thereby roughly grinding the holding surface 78 of the holding table 75 and the back surface 102 of the wafer 100 with the grinding wheel 22.

[0022] The second grinding unit 30, similar to the first grinding unit 20, is attached to the lower end of a spindle 31, and while rotating a grinding wheel 33 having grinding wheels 32 arranged in a ring shape, the second grinding feed unit 34 presses the holding surface 78 of the roughly ground holding table 75 positioned at the finish grinding position 203 and the back surface 102 of the roughly ground wafer 100 held on the holding table 75 along the grinding feed direction, thereby finish-grinding the holding surface 78 of the holding table 75 and the back surface 102 of the wafer 100 with the grinding wheel 32.

[0023] In addition, the processing method of the wafer 100 according to this embodiment does not require grinding by the first grinding unit 20 and the second grinding unit 30, and may be performed by a processing apparatus 1 that does not have the first grinding unit 20 and the second grinding unit 30.

[0024] 1 and 4, the polishing unit 40 is attached to the lower end of the spindle 41, and while rotating the wheel base 43 on which the polishing pad 42 is disposed facing downward, the polishing unit 40 presses the polishing pad 42 side of the wheel base 43 along the polishing feed direction (Z-axis direction) by a polishing feed unit 50 described later against a holding surface 78 of a holding table 75 positioned at a polishing position 204 and a back surface 102 of a finish-ground wafer 100 held on the holding table 75. The polishing unit 40 performs a polishing step of polishing the back surface 102 of the wafer 100 and an oxide film forming step of forming an oxide film on the back surface 102 of the wafer 100 by changing the pressure applied in the polishing feed direction by the polishing feed unit 50.

[0025] In this embodiment, when polishing the back surface 102 of the wafer 100, the polishing pad 42 is preferably made of, for example, a nonwoven fabric that does not contain abrasive grains or a resin having elasticity such as polyurethane. Since nonwoven fabric and polyurethane are not excessively soft like suede, they have the characteristic of being able to efficiently polish the grinding marks generated in the grinding process. Since the crystal orientation of the grinding marks is disturbed, the effect of alkali is low, and physical polishing by the abrasive grains contained in the slurry S is mainly required. From this viewpoint, in this embodiment, a nonwoven fabric or polyurethane that is not excessively soft and has a moderate softness is used as the polishing pad 42.

[0026] The slurry supplying part 65 supplies the slurry S, which contains an alkaline solution, abrasive grains, and hydrogen peroxide solution (H2O2), to the processing point P of the polishing unit 40. In this embodiment, the slurry S is used as a polishing liquid for polishing and is also used to form an oxide film. The slurry supplying part 65 supplies the slurry S to the processing point P of the polishing unit 40 through the through hole 49 of the polishing unit 40. When polishing the wafer 100 in the polishing step, the polishing unit 40 uses the polishing pad 42 to polish the back surface 102 of the wafer 100 by chemical mechanical polishing (CMP) at a first pressure. When forming an oxide film on the wafer 100 in the oxide film forming step, the polishing unit 40 uses the polishing pad 42 to rub the back surface 102 of the wafer 100 at a second pressure.

[0027] As the polishing pad 42 rotates, the slurry S supplied from the slurry supply unit 65 is spread and supplied by centrifugal force over the entire surface between the polishing pad 42 and the wafer 100. Therefore, in this embodiment, the processing point P is not limited to one point on the back surface 102 of the wafer 100, but includes the entire surface where the polishing pad 42 contacts the back surface 102 of the wafer 100.

[0028] The polishing step and the oxide film forming step of the wafer processing method according to this embodiment are performed by a polishing unit 40. The polishing unit 40 is a CMP apparatus that polishes the wafer 100 by supplying a polishing liquid from a polishing pad 42 onto the wafer 100.

[0029] The polishing unit 40 is configured to press the polishing pad 42 against the wafer 100 held by the holding table 75, and rotate the holding table 75 and the polishing pad 42 while supplying a polishing liquid, slurry S, from a slurry supply unit 65. In the chemical mechanical polishing performed by the polishing unit 40, the wafer 100 is etched by the chemical components of the polishing liquid, and the wafer 100 is mechanically polished by the abrasive grains contained in the polishing pad 42 or the slurry S. The rotation direction of the holding table 75 and the rotation direction of the polishing pad 42 may be the same or opposite.

[0030] 4, the polishing feed unit 50 supports a cover member 45 covering the outer periphery of the spindle 41 of the polishing unit 40 so as to be movable along the polishing feed direction (Z-axis direction). The polishing feed unit 50 moves the polishing unit 40 along the polishing feed direction via the cover member 45, thereby moving the polishing pad 42 facing the lower surface side of the wheel base 43 relatively closer to or farther away from the holding surface 78 of the holding table 75 positioned at the polishing position 204, as shown in FIGS.

[0031] The polishing feed unit 50 can press the polishing pad 42 relatively against the wafer 100 with a first pressure and a second pressure. The second pressure is smaller than the first pressure. Specific examples of the first pressure and the second pressure will be described later.

[0032] The horizontal feed unit 55 moves the polishing unit 40 along a direction (Y-axis direction) in a horizontal plane perpendicular to the polishing feed direction (Z-axis direction), thereby changing the distance between the rotation axis of the polishing pad 42 facing the underside of the wheel base 43 and the rotation axis of the holding surface 78 of the holding table 75.

[0033] 4, the load sensor 60 is attached to the polishing unit 40. The load sensor 60, which measures the load applied by the polishing pad 42 against the wafer 100 held on the holding surface 78 of the holding table 75, is disposed so as to be sandwiched between the polishing unit 40 and the holding table 75 from above and below. Note that, although the load sensor 60 is attached to the polishing unit 40 in this embodiment, the present invention is not limited to this, and the load sensor 60 may be attached to the holding table 75.

[0034] The load sensor 60 can detect the pressure of the pressing force generated by the polishing pad 42 relative to the wafer 100. Therefore, the polishing unit 40 can change the height of the spindle 41 based on the pressure detected by the load sensor 60 to control the pressure for pressing the polishing pad 42 relative to the wafer 100 by selectively using a first pressure or a second pressure.

[0035] The control unit 80 controls the operation of various components of the processing apparatus 1 to cause the processing apparatus 1 to perform rough grinding, finish grinding, polishing, oxide film formation, cleaning, and film formation on the back surface 102 of the wafer 100. The control unit 80 also controls the operation of various components of the processing apparatus 1 to cause the processing apparatus 1 to perform the wafer 100 processing method according to this embodiment. The control unit 80 controls the load sensor 60 to measure the polishing load continuously or at predetermined short time intervals, and acquires the measured polishing load. The control unit 80 performs feedback control based on the acquired polishing load, and controls the polishing feed amount of the polishing pad 42 by the polishing feed unit 50 while maintaining the measured polishing load at a predetermined value.

[0036] In this embodiment, the control unit 80 includes a computer system. The computer system included in the control unit 80 includes an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. The arithmetic processing device of the control unit 80 performs arithmetic processing according to a computer program stored in the storage device of the control unit 80, and outputs control signals for controlling the processing device 1 to various components of the processing device 1 via the input / output interface device of the control unit 80.

[0037] 4, the cassettes 91 and 92 are containers for accommodating a plurality of wafers 100. The alignment unit 93 is a table on which the wafer 100 removed from the cassette 91 is temporarily placed and whose center is aligned.

[0038] The carry-in unit 94 has a suction pad, and holds the pre-grinding and pre-polishing wafer 100 aligned by the alignment unit 93 by suction, and carries it onto the holding table 75 positioned at the carry-in / out position 201. The carry-out unit 95 has a transport arm 111 (see FIG. 2) and two claws 112 (see FIG. 2) provided at the lower end of the transport arm 111. Note that, although two claws 112 are provided in FIG. 3, this is not limited, and it is sufficient that at least two or more are provided at different positions in the circumferential direction of the wafer 100. Preferably, when three or more claws 112 are provided, the stability of the state in which the wafer 100 is held is improved. Also, the claws 112 may be provided in a ring shape that continues in the circumferential direction of the wafer 100. The unloading unit 95 hooks the wafer 100 after grinding, polishing and oxide film formation, which is held on the holding table 75 positioned at the loading / unloading position 201, with two claws 112, and unloads it to the cleaning unit 96 by the transport arm 111. The cleaning unit 96 cleans the wafer 100 after grinding and polishing, and removes contamination such as grinding debris and polishing debris adhering to the ground and polished processed surface.

[0039] The carry-in / out unit 97 is, for example, a robot pick equipped with a circular hand 99, and transports the wafer 100 by suction-holding the wafer 100 with the circular hand 99. Specifically, the carry-in / out unit 97 carries the wafer 100 before grinding and polishing from the cassette 91 to the alignment unit 93, and carries the wafer 100 after grinding and polishing from the cleaning unit 96 to the cassette 92.

[0040] A description will now be given of a wafer processing method of this embodiment using the processing apparatus 1 configured as above. The wafer processing method of this embodiment includes a polishing step, an oxide film forming step, a transport step, and a film forming step.

[0041] (Polishing step) The polishing step according to this embodiment will be described with reference to Fig. 1, Fig. 4, and Fig. 5. The polishing step is performed by the control unit 80 controlling the polishing unit 40. As shown in Fig. 1, in the polishing step, a slurry S is supplied to a processing point P, while a rotating polishing pad 42 is pressed relatively against the wafer 100 with a first pressure to polish the wafer. The slurry S is configured to contain an alkaline solution, abrasive grains, and hydrogen peroxide solution. The composition of the slurry S will be described later.

[0042] As shown in FIG. 1, in the polishing step, the slurry S supplied from the slurry supply unit 65 is uniformly supplied over the entire surface between the polishing pad 42 and the wafer 100 by utilizing centrifugal force as the polishing pad 42 rotates.

[0043] In the polishing step, the higher the relative pressure of the polishing pad 42 with respect to the wafer 100, the easier it is to remove the oxide film formed on the wafer 100. Therefore, when pressing the polishing pad 42 relatively to the wafer 100 in the polishing step, the polishing unit 40 presses the polishing pad 42 relatively to the wafer 100 with a first pressure by the polishing feed unit 50.

[0044] This first pressure is greater than the second pressure applied in the oxide film forming step, so that the wafer 100 can be polished while the oxide film formed on the wafer 100 by the chemical reaction of the slurry S is removed by the strong pressure.

[0045] Therefore, in the polishing step, it is necessary to apply a first pressure that is higher than the second pressure applied in the oxide film forming step. Therefore, as shown in Fig. 5, in consideration of the experimental results, the first pressure is selected to be in the range of 15 to 30 kPa, which is included in the range of "30" kPa selected as the upper limit of the pressure that can perform sufficient polishing in the polishing step and "15" kPa selected as the lower limit of the pressure that can perform the minimum necessary polishing in the polishing step. More ideally, the first pressure is more preferably 25 kPa.

[0046] (Oxide film formation step) The oxide film forming step according to this embodiment will be described with reference to FIG. 1. The oxide film forming step is performed by the control unit 80 controlling the polishing unit 40. The oxide film forming step is performed after the polishing step. The oxide film forming step can be performed by switching to the oxide film forming step when an arbitrary time has elapsed after the start of the polishing step. The arbitrary time can be set to a time at which it is determined that polishing has been performed sufficiently in the polishing step.

[0047] As shown in FIG. 1, in the oxide film formation step, a slurry S is supplied to a processing point P while a rotating polishing pad 42 is pressed against a wafer 100 with a second pressure smaller than the first pressure to form an oxide film on the polished surface of the wafer.

[0048] As shown in FIG. 1, in the oxide film formation step, similar to the polishing step, the slurry S supplied from the slurry supply section 65 is evenly supplied to the entire surface between the polishing pad 42 and the wafer 100 by utilizing centrifugal force as the polishing pad 42 rotates.

[0049] In the oxide film forming step, when the polishing pad 42 is pressed relatively to the wafer 100, the polishing unit 40 presses the polishing pad 42 relatively to the wafer 100 with a second pressure by the polishing feed unit 50. This second pressure is smaller than the first pressure. Therefore, a new oxide film can be formed on the polished surface of the wafer 100 without removing the oxide film formed by the chemical reaction of the slurry S, thereby imparting hydrophilicity.

[0050] In the oxide film forming step, an oxide film is not formed by simply supplying the slurry S onto the wafer 100. Therefore, in this embodiment, friction is generated on the wafer 100 by pressing the wafer 100 with a predetermined pressure or more, and an oxide film can be formed on the wafer 100 by the frictional heat generated as a result.

[0051] However, if the pressure applied to the wafer 100 is excessively high, the already formed oxide film will be scraped off by the polishing pad 42. Therefore, in order to impart hydrophilicity to the wafer 100, the pressure for pressing the polishing pad 42 is set to a second pressure that is equal to or higher than the minimum pressure at which an oxide film is formed and equal to or lower than the maximum pressure at which friction occurs.

[0052] Therefore, in the oxide film forming step, it is necessary to apply a second pressure that is lower than the first pressure applied in the polishing step. Therefore, as shown in Fig. 5, in consideration of the experimental results, the second pressure is selected to be in the range of 1 to 8 kPa, which is included in the range of "8" kPa selected as the upper limit of the pressure that does not remove the oxide film in the oxide film forming step and "1" kPa selected as the lower limit of the pressure that can generate frictional heat due to friction in the oxide film forming step. More ideally, the second pressure is more preferably 5 kPa.

[0053] The composition of the slurry S supplied in the polishing step and the oxide film forming step, the polishing speed when the mass % of the hydrogen peroxide solution contained in the slurry S is changed, and the experimental results of each parameter will be described below with reference to Figures 5, 6, and 7. The slurry S supplied in the polishing step and the slurry S supplied in the oxide film forming step in this embodiment are the same.

[0054] Since the wafer 100 is made of Si, when the slurry S is alkaline, the reactivity with Si increases, and the polishing speed (polishing rate) improves. On the other hand, when the slurry S is acidic, the reactivity with Si decreases, and the polishing speed decreases. Since the hydrogen peroxide solution is acidic, the polishing speed by the polishing unit 40 decreases as the mass % of the hydrogen peroxide solution contained in the slurry S increases, as shown in Figs. 6 and 7. Therefore, when the production speed of the wafer 100 is taken into consideration, the upper limit of the polishing speed (μm / min) needs to be "1.00" or more. As a result, in this embodiment, "0.30" is selected as the upper limit of the mass % of the hydrogen peroxide solution at which the polishing speed (μm / min) is "1.00" or more.

[0055] In order to efficiently polish the wafer 100 made of Si, it is effective that the slurry S is alkaline. Therefore, in this embodiment, the slurry S is adjusted to be alkaline. Specifically, an alkaline solution is added so that the pH of the slurry S becomes 9.0 to 10.5 as shown in FIG. 5. By adjusting the slurry S to be alkaline, the reactivity with Si is improved, and thus the polishing speed of the wafer 100 made of Si can be improved. As the alkaline solution to be added to the slurry S, at least one of potassium hydroxide, sodium hydroxide, potassium carbonate solution, and tetramethylammonium hydroxide (TMAH), or a combination thereof, is selected as shown in FIG. 5.

[0056] In order to remove the oxide film formed on the wafer 100 in the polishing step, it is preferable that the size of the abrasive grains contained in the slurry S is large. Therefore, as shown in Fig. 5, the size of the abrasive grains contained in the slurry S (abrasive grain size) is selected as a large range of 25 to 100 nm, which is shown as an experimental result. Furthermore, it is preferable that the size of the abrasive grains contained in the slurry S is selected as a small range of 30 to 80 nm, which is shown as an experimental result. Note that the experimental results of the abrasive grain size shown in Fig. 5 are shown in terms of average abrasive grain size.

[0057] In addition, in order to remove the oxide film in the polishing step, it is preferable that the concentration of abrasive grains contained in the slurry S is high. Therefore, as shown in Fig. 5, the concentration of abrasive grains contained in the slurry S is selected from 2 to 20 wt%, which is shown as an experimental result.

[0058] In the experimental results regarding the oxide film formation step, as shown in FIG. 6 and FIG. 7, it has been confirmed that the hydrophilicity of the wafer 100 tends to decrease when the mass % of the hydrogen peroxide solution is decreased. Specifically, based on the experimental results of FIG. 7, the hydrophilicity of the wafer 100 is evaluated by a contact angle measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.). The contact angle indicates the angle formed when pure water contacts the surface of the wafer 100, and when the contact angle is small (for example, 20 degrees or less), the wafer 100 is evaluated as having high hydrophilicity. Therefore, in this embodiment, if the contact angle is 20 degrees or less, the wafer 100 is evaluated as having high hydrophilicity, and the wafer 100 is considered to meet the hydrophilization standard. Conversely, if the contact angle exceeds 20 degrees, the hydrophilicity is evaluated as being low, and it is determined that the hydrophilization is insufficient. Based on this result, the lower limit of the mass % of the hydrogen peroxide solution to maintain the appropriate hydrophilicity of the wafer 100 is selected to be "0.15".

[0059] As shown in FIG. 6 and FIG. 7, the smaller the mass % of the hydrogen peroxide solution is, the more the number of particles (dust, polishing debris, dust, etc.) adhering to the back surface 102 of the wafer 100 increases. In the experimental results of FIG. 7, when the mass % of the hydrogen peroxide solution is reduced from "0.15" to "0.10", the number of particles increases rapidly from "1228" to "17316". Therefore, in consideration of the experimental results of the number of particles generated in the processing of the wafer 100, "0.15" is selected as the lower limit of the mass % of the hydrogen peroxide solution. Note that the particle measurement results shown in FIG. 6 are obtained by automatically measuring the number of particles of 0.3 μm or more by a measuring device (KLA-Tencor: SP-1 / DLS) using scattered laser light after performing the polishing step, oxide film forming step, and cleaning step of this embodiment on a wafer 100 having a thickness of 300 μm. In the above-mentioned embodiment, the number of particles adhering to the back surface 102 of the wafer 100 is measured.

[0060] 5, 6, and 7, taking into consideration the polishing rate of the wafer 100 in the polishing step and the experimental results of hydrophilicity in the oxide film forming step, it is preferable that the hydrogen peroxide solution contained in the slurry S in a large range of 0.15 to 0.30%, which is included in the range of "0.15" selected as the lower limit of the mass % of the hydrogen peroxide solution in consideration of the hydrophilicity of the wafer 100 and "0.30" selected as the upper limit of the mass % of the hydrogen peroxide solution at which the polishing rate (μm / min) is "1.00" or more, is selected as the mass % relative to the total mass of the slurry S. In FIGS. 6 and 7, the range surrounded by the thick dotted line is shown as the large range selected in this embodiment.

[0061] Furthermore, when the production rate of the wafer 100 in the polishing step is taken into consideration, the upper limit of the polishing rate (μm / min) should preferably be "1.20" or more. For this reason, "0.25" is selected as the upper limit of the mass% of hydrogen peroxide solution at which the polishing rate (μm / min) is "1.20" or more. Therefore, when the polishing rate of the wafer 100 in the polishing step and the experimental results of hydrophilicity in the oxide film formation step are taken into consideration, it is preferable that the hydrogen peroxide solution contained in the slurry S in the middle range of 0.15 to 0.25%, which is included in the range of "0.15" selected as the lower limit of the mass% of hydrogen peroxide solution in consideration of the hydrophilicity of the wafer 100 and "0.25" selected as the upper limit of the mass% of hydrogen peroxide solution at which the polishing rate (μm / min) is "1.20" or more, is selected as the mass% relative to the total mass of the slurry S.

[0062] Furthermore, when the production rate of the wafer 100 in the polishing step is taken into consideration, more preferably, the upper limit of the polishing rate (μm / min) needs to be "1.40" or more. For this reason, "0.20" is selected as the upper limit of the mass% of hydrogen peroxide solution at which the polishing rate (μm / min) is "1.40" or more. Therefore, when the polishing rate of the wafer 100 in the polishing step and the experimental results of hydrophilicity in the oxide film formation step are taken into consideration, it is preferable that the hydrogen peroxide solution contained in the slurry S in a small range of 0.15 to 0.20%, which is included in the range of "0.15", which is selected as the lower limit of the mass% of hydrogen peroxide solution in consideration of the hydrophilicity of the wafer 100, and "0.20", which is selected as the upper limit of the mass% of hydrogen peroxide solution at which the polishing rate (μm / min) is "1.40" or more, is selected as the mass% relative to the total mass of the slurry S.

[0063] In the conventional method, when forming an oxide film on the wafer 100, it was necessary to switch from the polishing slurry to a hydrophilic slurry immediately after polishing. This resulted in the use of two types of slurries, which increased costs. On the other hand, in this embodiment, it is possible to continue using the slurry S used in the polishing step in the oxide film formation step. Therefore, it is possible to perform both the polishing and oxide film formation processes using one type of slurry S. This allows costs to be reduced.

[0064] (Washing step) 2 and 4, the cleaning step according to this embodiment will be described. The cleaning step is performed by the control unit 80 controlling the unloading unit 95 and the cleaning unit 96. The cleaning step is performed after the oxide film forming step.

[0065] As shown in FIGS. 2 and 4, in the cleaning step, the unloading unit 95 transports the wafer 100 placed on the holding table 75 at the loading / unloading position 201 to the cleaning unit 96. The unloading unit 95 hooks the edge 103 on the front surface 101 side of the wafer 100 from below with a claw 112, and transports the wafer 100 to the cleaning unit 96 with the slurry S remaining on its upper surface (rear surface 102). The cleaning unit 96 then cleans the transported wafer 100. In the cleaning step, the cleaning unit 96 cleans the wafer 100 after grinding and polishing, and removes contamination such as grinding debris and polishing debris adhering to the ground and polished processed surface.

[0066] In the conventional technology, the polished surface of the Si wafer 100 polished in the polishing step becomes hydrophobic, and the polished wafer 100 dries before being cleaned in the cleaning step, resulting in problems such as adhesion of foreign matter and traces of the slurry S.

[0067] In contrast, in the processing method for the wafer 100 of this embodiment, the surface of the wafer 100 after the oxide film formation performed after the polishing step is made hydrophilic, so that the polished wafer 100 is maintained in a wet state by the slurry S. Therefore, cleaning in the cleaning step can be performed in a wet state without drying the surface of the wafer 100, and cleaning can be performed without adhesion of foreign matter or generation of traces of the slurry S.

[0068] (Deposition step) The film formation step according to this embodiment will be described with reference to Figures 3 and 4. The film formation step is performed by the control unit 80 controlling the film formation unit 98. The film formation unit 98 is disposed in a processing apparatus other than the processing apparatus 1 shown in Figure 4, but this is not limited thereto, and the film formation unit 98 may be disposed in the processing apparatus 1 shown in Figure 4. The film formation step is performed after the oxide film formation step.

[0069] As shown in FIG. 3, in the film forming step, the film forming unit 98 forms a film on the oxide film 121 formed on the back surface 102 of the wafer 100 in the oxide film forming step while leaving the oxide film 121.

[0070] 3, the film forming unit 98 forms a film on the wafer 100 by a CVD (Chemical Vapor Deposition) method. As a gaseous precursor used in the film formation (hereinafter referred to as a "film formation gas"), tetraethoxysilane (TEOS) is used to form an oxide film, and silicon nitride (SiN) is used to form a nitride film.

[0071] The film forming unit 98 includes a chamber 131, a support 132, and a film forming material 133. The film forming material 133 supplies a film forming gas into the chamber 131. The wafer 100 transferred into the chamber 131 of the film forming unit 98 is held by the support 132 with the back surface 102 facing upward and the front surface 101 facing downward. The inside of the chamber 131 may be depressurized to a vacuum by operating a vacuum pump (not shown). The film forming material 133 is irradiated with an electron beam to heat and evaporate it, whereby the film forming gas is converted by a chemical reaction, and a thin film such as a TEOS film can be formed on the oxide film 121 formed on the back surface 102 of the wafer 100.

[0072] Conventionally, after polishing the wafer 100, the alkaline polishing slurry is switched to a hydrophilic slurry containing organic matter such as cellulose to impart hydrophilicity to the wafer 100. The cellulose contained in the slurry is decomposed by heating and may remain as foreign matter on the wafer 100, so a process of cleaning and removing it is required before a film formation step such as CVD film formation. As a result, in the conventional method using a hydrophilic slurry after polishing, it is essential to remove the cellulose before film formation and to form an oxide film by cleaning with 60° SC-1 (Standard Cleaning 1) rinse or ozone water rinse to remove the film to be hydrophilized. For this reason, it was not possible to form a film while leaving the slurry on the wafer 100.

[0073] In this embodiment, an oxide film is formed using hydrogen peroxide water in an oxide film forming step performed after the polishing step. The oxide film made of hydrogen peroxide water does not decompose even when heated, and can maintain the bonded state of the oxide film. Even if TEOS (PTEOS) or SiN is formed on the oxide film formed in the oxide film forming step, it remains as an oxide film without being decomposed. Therefore, in order to remove cellulose, it is not necessary to switch from the polishing slurry to the hydrophilic slurry after polishing the wafer 100, and the slurry S can be left on the wafer 100 and formed in the film forming step. As a result, it is possible to perform the processing of the wafer 100 including both the polishing step and the oxide film forming step using one type of slurry S without generating additional man-hours.

[0074] The embodiments of the present invention are not limited to the above-mentioned embodiments and modifications, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological progress or a different technology derived therefrom, the present invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of ​​the present invention.

[0075] In the above embodiment, the polishing unit 40 controls the pressure for pressing the polishing pad 42 relatively to the wafer 100 by selectively using a first pressure and a second pressure by changing the height of the spindle 41 based on the pressure detected by the load sensor 60, but this is not limited to the above. For example, a pressure sensor may be provided on a holder (not shown) that holds the spindle 41. The polishing unit 40 may control the pressure for pressing the polishing pad 42 relatively to the wafer 100 by selectively using a first pressure and a second pressure by changing the height of the spindle 41 based on the pressure at which the spindle 41 is pressed against a mount (not shown) and crushed by the pressure sensor.

[0076] In the above embodiment, the oxide film forming step is switched to when an arbitrary time has elapsed after the start of the polishing step, but this is not limited to the above. For example, the polishing step may include a thickness sensor that measures the thickness of the wafer 100 while polishing. In this case, the oxide film forming step may be switched to when the thickness of the wafer 100 becomes less than an arbitrary thickness in the polishing step. The thickness sensor may employ a technology that utilizes interference or reflection of light. The thickness sensor can detect a change in the characteristics of light according to the thickness and composition of the wafer 100 and measure the thickness based on the information. The thickness sensor can measure the thickness of the wafer 100 by introducing light through a hole (not shown) opened in the holding table 75. The thickness sensor may also measure the thickness of the wafer 100 by introducing light into a gap of the through hole 49 through which the slurry S passes. [Industrial Applicability]

[0077] As described above, the wafer processing method of the present invention can realize both polishing and oxide film formation processes by using one type of slurry, and is therefore particularly useful in the field of wafer processing. [Explanation of symbols]

[0078] 1: processing device, 10: device body, 40: polishing unit, 41: spindle, 42: polishing pad, 43: wheel base, 45: cover member, 49: through hole, 50: polishing feed unit, 55: horizontal feed unit, 60: load sensor, 65: slurry supply unit, 70: turntable, 75: holding table, 77: suction unit, 78: holding surface, 80: control unit, 94: loading unit, 95: Unloading unit, 96: Cleaning unit, 97: Loading / unloading unit, 98: film forming unit, 100: Si wafer, 101: front surface, 102: back surface, 103: edge, 111: transfer arm, 112: claw, 121: oxide film, 131: chamber, 132: support, 133: film forming material, 204: polishing position, P: Processing point, S: Slurry

Claims

1. A method for processing a wafer, comprising the steps of: A slurry containing an alkaline solution, an abrasive grain, and hydrogen peroxide solution is supplied to a processing point, The rotating polishing pad is pressed against the wafer with a first pressure to polish the wafer. A polishing step; While supplying the slurry to the processing point, Pressing the rotating polishing pad against the wafer with a second pressure less than the first pressure. Forming an oxide film on the polished surface of the wafer An oxide film forming step; A wafer processing method comprising:

2. The hydrogen peroxide solution is mixed with the slurry in an amount of: 0.15% by mass to 0.30% by mass 2. The method for processing a wafer according to claim 1.

3. After the oxide film forming step, Further comprising a cleaning step of cleaning the wafer.

3. The method for processing a wafer according to claim 1 or 2.

4. In a state in which the oxide film formed in the oxide film forming step remains, A film forming step is carried out to form a film on the oxide film.

3. The method for processing a wafer according to claim 1 or 2.

5. The polishing pad is made of non-woven fabric or polyurethane that does not contain abrasive particles.

3. The method for processing a wafer according to claim 1 or 2.

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