Wafer grinding methods and grinding equipment

Abstract

This invention discloses a wafer polishing method in which a polishing composition containing water is continuously supplied while a wafer is pressed against an polishing cloth for corrective polishing to correct the shape of the polished wafer. The method is characterized by comprising the following steps: measuring the shape of the polished wafer before the corrective polishing; determining the type and concentration of a surfactant contained in the polishing composition based on the measured shape of the polished wafer; and performing the corrective polishing while supplying the polishing composition adjusted based on the determined type and concentration of the surfactant. Thus, a wafer polishing method and apparatus are provided that can reduce wafer shape deviations generated in the preceding polishing process in subsequent polishing processes.

Description

Technical Field

[0001] This invention relates to a method and apparatus for grinding wafers. Background Technology

[0002] In recent years, with the miniaturization of semiconductor devices using silicon wafers, higher flatness has become a requirement. Flatness metrics are represented by SFQR (Site Front Least Squares Range), which is defined as the range of positive and negative deviations from a reference plane when a unit of arbitrary size (e.g., 26mm × 8mm) is defined on the surface of a semiconductor wafer, using the surface obtained by the least squares method on that unit as a reference plane. If SFQR deteriorates, the likelihood of misalignment during exposure during semiconductor device fabrication increases, leading to pattern defects.

[0003] Furthermore, from a cost-reduction perspective, the wafer is used for device fabrication up to approximately 1 mm from the outer perimeter. This necessitates flatness not only at the center but also at the edges. The flatness of the edges is represented by ESFQR (Edge Site Frontleast Squares Range).

[0004] Typically, silicon wafers are processed by grinding and polishing wafers that have been sliced ​​from ingots.

[0005] Grinding is generally carried out in multiple stages using abrasive cloths of different hardness (see, for example, Patent Document 1). Grinding damage is removed in coarse grinding, damage generated in coarse grinding is removed in secondary grinding, and roughness is created in fine grinding.

[0006] It is known that the above-mentioned SFQR and ESFQR are usually determined by the grinding process, and careful attempts have been made to improve the shape by changing the grinding conditions, etc.

[0007] On the other hand, from the perspective of surface quality, the polishing process of silicon wafers is usually performed by a multi-stage polishing process with at least two stages, as described above. In the first stage, a harder pad is used and polishing is performed at a higher rate to remove slicing or grinding damage. On the other hand, in the second stage, a softer pad is used and polishing is performed at a lower rate to avoid causing damage.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2008-205147 Summary of the Invention

[0011] (a) Technical problems to be solved

[0012] However, from the perspective of flatness, multi-stage grinding is not ideal. This is because each stage of the grinding process has a deviation from the wafer shape, and the more stages there are, the greater the deviation becomes.

[0013] Therefore, in the subsequent grinding process, corrective grinding is required to reduce the shape deviation of the grinding wafer caused by the previous grinding process.

[0014] Therefore, the present invention was made in view of such problems, and the object of the present invention is to provide a wafer grinding method and grinding apparatus that can reduce the shape deviation of the wafer generated in the previous grinding process in the later grinding process.

[0015] (II) Technical Solution

[0016] To address the aforementioned issues, this invention provides a wafer polishing method in which a polishing composition containing water is continuously supplied while a wafer is pressed against an polishing cloth for corrective polishing to correct the shape of the polished wafer. The method is characterized by comprising the following steps: measuring the shape of the polished wafer before the corrective polishing; determining the type and concentration of a surfactant contained in the polishing composition based on the measured shape of the polished wafer; and performing the corrective polishing while supplying the polishing composition adjusted based on the determined type and concentration of the surfactant.

[0017] If this is the wafer grinding method, then the shape deviation of the wafer generated in the previous grinding process can be reduced by the subsequent grinding process, namely the aforementioned corrective grinding.

[0018] Furthermore, preferably, when determining the type and concentration of the surfactant, as a preliminary test, a pre-polishing polishing is performed on a pre-polished wafer by supplying a polishing composition with altered surfactant type and concentration. The degree of shape correction is determined based on the shape change of the pre-polished wafer before and after the pre-polishing polishing, thereby pre-determining the correlation between the surfactant type, concentration, and degree of shape correction. Based on the measured shape of the polished wafer, the necessary degree of shape correction is determined. Based on the correlation, the type and concentration of the surfactant in the pre-polishing polishing are determined in a manner that yields the determined degree of shape correction.

[0019] Thus, by pre-determining the relationship between the type and concentration of surfactant and the degree of shape correction through preliminary experiments, it is possible to easily determine the type and concentration of surfactant during the correction grinding process, and to more reliably perform the desired shape correction of the grinding wafer.

[0020] Alternatively, when supplying the grinding composition for the corrective grinding, the following methods may be used: a first tank storing a first grinding composition that does not contain the surfactant; a second tank storing a surfactant solution composed of the surfactant and water; and a third tank storing a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank, and using the second grinding composition from the third tank as the grinding composition for the corrective grinding.

[0021] Thus, by storing the grinding composition without surfactant separately from the surfactant solution and mixing them in the third tank, the concentration of the surfactant used for corrective grinding can be easily adjusted.

[0022] Alternatively, the third tank may be a tank with a capacity equal to the total supply of the second grinding composition in one batch of the modified grinding.

[0023] If a tank of this capacity is used, the second grinding composition used in the correction grinding can be used up in one batch, thus reducing the loss of the grinding composition.

[0024] Alternatively, a composition containing abrasive particles can be used as the grinding composition for the modified grinding process.

[0025] By including abrasive particles, the grinding rate can be further increased.

[0026] Alternatively, a composition containing a water-soluble polymer can be used as the grinding composition for the modified grinding process.

[0027] By incorporating water-soluble polymers, the surface roughness of the wafer can be further improved.

[0028] Alternatively, a surfactant with a contact angle of less than 50 degrees with bare silicon whose surface natural oxide film has been stripped by HF impregnation can be used as the surfactant.

[0029] By using such a surfactant, it is easier to reduce the machining allowance at the outermost periphery of the wafer, and the flatness of the thinner outermost polished wafer can be further improved.

[0030] Alternatively, the grinding wafer can be a silicon wafer.

[0031] The wafer grinding method of the present invention is particularly suitable for silicon wafers requiring high flatness.

[0032] To address the aforementioned issues, this invention provides a wafer polishing apparatus comprising an polishing cloth for correcting the shape of a polished wafer, a polishing cloth, and a supply mechanism for supplying a polishing composition containing water. The wafer is pressed against the polishing cloth for correction polishing while the polishing composition is continuously supplied from the supply mechanism. The apparatus is characterized in that the supply mechanism is capable of supplying a composition containing a surfactant, the type and concentration of which are adjusted based on measurements of the shape of the polished wafer before correction polishing.

[0033] If it is such a wafer grinding apparatus, then it becomes a grinding apparatus that can reduce the shape deviation of the ground wafer generated in the previous grinding process through the subsequent grinding process, namely the aforementioned corrective grinding.

[0034] Alternatively, the supply mechanism may include: a first tank storing a first grinding composition that does not contain the surfactant; a second tank storing a surfactant solution consisting of the surfactant and water; and a third tank storing a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank, wherein the second grinding composition in the third tank can be supplied as the grinding composition for the corrective grinding.

[0035] Thus, if the supply mechanism is capable of storing the grinding composition without surfactant and the surfactant solution separately and mixing them in the third tank, the concentration of the surfactant for correcting grinding can be easily adjusted.

[0036] Alternatively, the third tank may be a tank with a capacity equal to the total supply of the second grinding composition in one batch of the modified grinding.

[0037] If the tank has this capacity, the second grinding composition used in the correction grinding can be used up in one batch, thus reducing the loss of the grinding composition.

[0038] Additionally, the supply mechanism may have a controller capable of controlling the flow rate of the surfactant solution supplied from the second tank to the third tank.

[0039] If it is such a supply organization, the concentration of the surfactant can be easily changed because the amount of surfactant mixed in the grinding composition can be easily adjusted.

[0040] In addition, the grinding composition used in the corrective grinding process may be a composition containing abrasive grains.

[0041] By including abrasive particles, the grinding rate can be further increased.

[0042] In addition, the grinding composition used in the modified grinding process may be a composition containing a water-soluble polymer.

[0043] By incorporating water-soluble polymers, the surface roughness of the wafer can be further improved.

[0044] In addition, the contact angle between the surfactant and the bare silicon whose surface natural oxide film has been stripped away by HF impregnation is less than 50 degrees.

[0045] By using such a surfactant, it is easier to reduce the machining allowance at the outermost periphery of the wafer, and the flatness of the thinner outermost polished wafer can be further improved.

[0046] Alternatively, the polished wafer may be a silicon wafer.

[0047] The wafer grinding apparatus of the present invention is particularly suitable for grinding silicon wafers that require high flatness.

[0048] (III) Beneficial Effects

[0049] As described above, with respect to the wafer grinding method and apparatus of the present invention, by performing corrective grinding corresponding to the shape of the wafer being ground, the shape deviation of the wafer generated in the preceding grinding process can be reduced. In particular, wafers with higher flatness can be obtained without deviation. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the wafer grinding method of the present invention.

[0051] Figure 2 This is a schematic diagram illustrating an example of the wafer polishing apparatus of the present invention.

[0052] Figure 3 This is a graph showing the relationship between the types, concentrations, and degrees of modification of surfactants that can be used in the wafer polishing method of the present invention.

[0053] Figure 4 This is a diagram showing the wafer shape before and after the modified grinding in Example 1.

[0054] Figure 5 This is a graph showing the wafer shape before and after the modified grinding in Example 2.

[0055] Figure 6 This is a graph showing the wafer shape before and after the modified grinding in Comparative Example 1.

[0056] Figure 7This is a graph showing the wafer shape before and after the modified grinding in Comparative Example 2. Detailed Implementation

[0057] The inventors have discovered that when a surfactant is added to an existing grinding composition for grinding, the outermost processing allowance decreases compared to the case where no surfactant is added, resulting in a so-called "warping".

[0058] Furthermore, it was found that "lifting" varies in stages depending on the type and concentration of surfactant added.

[0059] Based on these insights, it was discovered that by changing the type and concentration of surfactant added to the polishing composition according to the wafer shape during each wafer polishing, corrective polishing that can suppress wafer shape deviations generated in the preceding polishing process can be performed, thus completing the present invention.

[0060] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as an example of an embodiment, but the present invention is not limited thereto.

[0061] Figure 2 This is an example of a wafer polishing apparatus of the present invention that can be used in the above-described correction polishing process. Here, the case of a single-sided polishing apparatus will be described, but the present invention is not limited thereto; a double-sided polishing apparatus can also be applied. However, from a controllability point of view, single-sided polishing is preferred. The components, their structure, and function will be described. Figure 2 As shown, the single-sided polishing device 1 consists of a platform 2 with polishing cloth 5 attached, a polishing head 3, and a supply mechanism 4. The platform 2 can rotate by rotating the rotating shaft 6, and the polishing head 3 can also rotate. There are no particular limitations on the polishing cloth 5; it can be a foamed polyurethane pad, a pad made by impregnating polyurethane with non-woven fabric, a polyurethane suede pad, etc.

[0062] Additionally, the polishing composition 7 is supplied from the supply mechanism 4, and the polishing wafer W (referring to a separately polished wafer, also called a polishing wafer or simply a wafer) held in the polishing head 3 is slidably brought into contact with the polishing cloth 5 while the platform 2 and polishing pad 3 are rotated to polish the polishing wafer W. The present invention is particularly suitable for silicon wafers requiring high flatness.

[0063] However, it is not limited to silicon wafers.

[0064] Here, the polishing composition 7 includes a surfactant. Furthermore, the supply mechanism 4 is capable of supplying a surfactant whose type and concentration in the polishing composition 7 are adjusted according to measurements of the shape of the polishing wafer W. The measurements of the shape of the polishing wafer will be described in the description of the method of the present invention.

[0065] Preferably, the supply mechanism 4 includes: a first tank for storing a first grinding composition that does not contain a surfactant; a second tank for storing a surfactant solution consisting of a surfactant and water; and a third tank for storing a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank, and the second grinding composition that can be supplied to the third tank is used as a grinding composition for corrective grinding.

[0066] Thus, if the supply mechanism is capable of storing the grinding composition without surfactant separately from the surfactant solution and mixing them in the third tank, the concentration of the surfactant for correcting grinding can be easily adjusted.

[0067] Furthermore, preferably, the third groove is a groove with a capacity equal to the total supply of the second abrasive composition in one batch of corrective abrasive grinding. Additionally, one batch refers to a cycle in which abrasive grinding is performed simultaneously on one abrasive cloth.

[0068] If the tank has this capacity, the waste of the grinding composition 7, which contains the surfactant, can be reduced because it is used up in one batch.

[0069] In addition, the supply mechanism preferably has a controller 8, which is capable of controlling the flow rate of the surfactant solution supplied from the second tank to the third tank.

[0070] If it is such a supply organization, the concentration of the surfactant can be easily changed because the amount of surfactant mixed in the grinding composition can be easily adjusted.

[0071] From the viewpoint of increasing the grinding rate, the first grinding composition may contain abrasive particles. SiO2 is more preferably present in the abrasive particles.

[0072] Furthermore, it is preferable to include an alkaline compound. Among the alkaline compounds, tetramethylammonium hydroxide, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and ammonia are more preferred.

[0073] From the viewpoint of improving surface roughness, the first grinding composition may contain a water-soluble polymer. More preferably, the water-soluble polymer is hydroxyethyl cellulose, polyvinyl alcohol, or polyvinylpyrrolidone.

[0074] The surfactant concentration of the grinding composition 7 is basically determined by the shape before grinding, and from the viewpoint of correcting the hydrophilicity after grinding, it is preferably 1000 ppm or less, more preferably 100 ppm or less.

[0075] There is no particular limitation on the type of surfactant; any of the following can be used: nonionic surfactants, cationic surfactants, and anionic surfactants. From the viewpoint of adsorption, nonionic surfactants are preferred. Among nonionic surfactants, preferred examples include polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, EO adducts of ethylene glycol, and EO adducts of acetylene glycol.

[0076] Furthermore, the surfactant is preferably a liquid prepared by dissolving the surfactant in, for example, 10% by mass water, and dropwise applied to bare silicon that has had its native oxide film stripped using hydrogen fluoride (HF), resulting in a contact angle of 50 degrees or less. Examples of surfactants include ethylene oxide-propylene oxide block copolymers, ethylene oxide-propylene oxide random copolymers, polyoxyethylene ethers, EO-added acetylene glycol, and EO-added ethylene glycol.

[0077] By using such a surfactant, the shape of the outermost machining allowance of the wafer can be changed more efficiently. In particular, reducing the machining allowance at the outermost periphery of the wafer allows for easier improvement of the flatness of the thinner outermost polished wafer.

[0078] In addition, for example, if the outermost edge of the wafer has a large collapse shape before correction grinding, and the goal is to eliminate the collapse shape through correction grinding (to make it lift up and flatten), the smaller the contact angle mentioned above, the more efficiently the machining allowance of the outermost edge of the wafer can be reduced through correction grinding. Therefore, the lower limit of the contact angle cannot be determined and is greater than zero.

[0079] Furthermore, when measuring the contact angle of the surfactant, from the viewpoint of oxide film peeling rate, the HF concentration is preferably 0.1% by mass or more, more preferably 0.3% by mass or more. Additionally, peeling is preferably performed with the wafer immersed in HF, and from the viewpoint of peeling amount, it is preferably 10 seconds or more, more preferably 30 seconds or more, and even more preferably 60 seconds or more. After immersion in HF, to prevent the reformation of the natural oxide film, it is preferable to measure the contact angle within one week.

[0080] Furthermore, from the viewpoint of ease of comparison, the surfactant concentration for measuring the contact angle is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 10% by mass or more. However, since the contact angle cannot be accurately measured when the viscosity is too high, it is preferably 30% by mass or less, more preferably 10% by mass or less.

[0081] Furthermore, the contact angle is preferably measured by dropping a liquid droplet from the upper surface of the bare silicon. To determine the adsorption state on the wafer, it is preferable to measure at least 1 second after the droplet is dropped, more preferably at least 3 seconds later, and even more preferably at least 10 seconds later. The contact angle is obtained by imaging the dropped droplet laterally, thus measuring the angle of the contact area between the wafer and the droplet.

[0082] The following explains the use of Figure 2 The single-sided grinding apparatus 1 and the wafer grinding method of the present invention. Figure 1 This is a flowchart illustrating the wafer grinding method of the present invention.

[0083] exist Figure 1 In the example shown, it is roughly divided into a preliminary experiment and a main experiment. Furthermore, the preliminary experiment can be conducted as needed, and can be omitted if the relationship between the three components described later is known.

[0084] The following sections will elaborate on these points.

[0085] (Preliminary test)

[0086] First, prepare a pre-grinding wafer that has already undergone preliminary grinding. Here, prepare a grinding wafer (e.g., a silicon wafer, etc.) that is the same as the grinding wafer that will undergo correction grinding in the main experiment.

[0087] Measure the shape of the wafer to be ground. The method for measuring the shape is not particularly limited, and a flatness measuring instrument such as the WaferSight1 manufactured by KLA-Tencor can be used.

[0088] Next, a polishing composition with altered surfactant type and concentration is supplied to the wafer to be polished for pre-correction polishing.

[0089] Next, the shape of the wafer after the grinding process is measured.

[0090] Next, based on the shape changes before and after the grinding process, the degree of shape correction is determined. For example, the degree of correction for the outer perimeter collapse can be determined.

[0091] Determine the correlation between the degree of shape correction, the type of surfactant, and its concentration.

[0092] Thus, by determining the aforementioned correlations in advance through preliminary experiments, the type and concentration of surfactant in the corrective grinding process described later can be easily determined. Furthermore, corrective grinding can be performed more reliably to achieve the desired shape.

[0093] Furthermore, if the aforementioned relationships are already known, and all the necessary information is available to determine the conditions of the surfactant in the main experiment's modified grinding, this preliminary experiment can be omitted.

[0094] (Main Experiment)

[0095] First, such as Figure 1 As in step 1, the shape of the wafer to be corrected and polished, i.e., the polished wafer after the previous polishing process, is measured.

[0096] Furthermore, when there are multiple wafers to be corrected for polishing, in order to accurately determine the surfactant concentration for correct polishing, it is preferable to measure the shape of all wafers to be polished beforehand.

[0097] Next, as Figure 1 As in step 2, the type and concentration of surfactant contained in the polishing composition 7 are determined based on the measured shape of the polishing wafer. For example, when peripheral collapse exists, the necessary degree of shape correction is determined in order to correct the peripheral collapse and planarize the wafer. Then, based on the correlation obtained in preliminary tests, the type and concentration of surfactant that can achieve the determined degree of shape correction are determined.

[0098] Next, as Figure 1 As in step 3, a corrective grinding process is performed while a grinding composition 7, adjusted based on the determined type and concentration of surfactant, is supplied.

[0099] To perform this modified grinding, a special supply mechanism 4 is preferably used to change the surfactant concentration of the grinding composition 7 in each batch of grinding.

[0100] First, a first grinding composition is prepared in a first tank, and a surfactant solution is prepared in a second tank. The flow rate from the second tank to the third tank (and from the first tank to the third tank) is controlled using a controller 8. The desired grinding composition 7, with the type and concentration of surfactant determined in step 2, is adjusted in the third tank to become the second grinding composition.

[0101] Next, the grinding wafer is placed in the grinding apparatus 1, and the grinding composition 7 is supplied while the grinding wafer is being corrected and ground.

[0102] Each polishing wafer undergoes a series of steps in the main test. Furthermore, when there are multiple polishing wafers, steps 1 and 2 can be performed on all wafers before proceeding to step 3, depending on factors such as efficiency.

[0103] In addition, shape measurements can be performed after corrective grinding to confirm whether improvements have been made, if necessary.

[0104] Furthermore, regarding the second grinding composition, from the viewpoint of surface quality, it is preferable to supply it at a flow rate of 0.1 l / min or more, and more preferably at 0.3 l / min or more. On the other hand, from the viewpoint of cost, it is preferable to supply it at a flow rate of 5.0 l / min or less, and more preferably at 3.0 l / min or less.

[0105] Correction grinding is preferably performed after the double-sided grinding process, and even more preferably before the final fine grinding.

[0106] In addition, from the viewpoint of reducing wafer shape deviation, it is preferable to process 5 or fewer wafers per batch, and more preferably 3 or fewer.

[0107] From the viewpoint of wafer shape control, the finishing process is preferably performed for 3 seconds or more, and more preferably for 5 seconds or more. On the other hand, from a productivity viewpoint, it is preferably performed for 300 seconds or less, and more preferably for 180 seconds or less.

[0108] Regarding corrective grinding, there may also be other grinding processes that supply different grinding compositions with the same abrasive cloth before and after the grinding process.

[0109] The wafer grinding apparatus and grinding method of the present invention described above can reduce the shape deviation of the wafer generated in the previous grinding process.

[0110] Example

[0111] The present invention will be described in more detail below with reference to embodiments and comparative examples, but the present invention is not limited to the embodiments.

[0112] (Examples 1-2)

[0113] Various water-soluble polymers and surfactants were prepared as 10% (w / w) solutions and dropped onto bare silicone that had been impregnated with 1% (w / w) HF for 1 min. The contact angles were measured. The results are shown in Table 1. It was confirmed that a high contact angle was maintained in the presence of only water and in the presence of water-soluble polymers such as hydroxyethyl cellulose and polyvinyl alcohol. In contrast, the contact angles decreased significantly in the presence of surfactants such as ethylene oxide-propylene oxide block copolymer (EO-PO) and EO-addition acetylene glycol.

[0114] [Table 1]

[0115]

[0116] Examples 1 and 2 underwent the following preliminary and main experiments. First, the following experiments were conducted... Figure 1The preliminary experiment shown determined the correlation between the type, concentration, and degree of shape modification of surfactants with a contact angle of less than 50 degrees, as mentioned above.

[0117] First, prepare a pre-grinding wafer (here, a silicon wafer) identical to the one used in the main experiment described later, and measure the ZDD (radial double derivative of Z[height]) value on the wafer surface side. For this wafer, use a grinding composition that varies the concentration of EO-PO and EO-addition acetylene glycol, to... Figure 2 The polishing apparatus shown underwent pre-correction polishing. Afterwards, the ZDD value on the wafer surface was measured again according to the concentration of each surfactant, and the correlation between type, concentration, and degree of shape correction (i.e., ΔF-ZDD before and after correction polishing) was obtained. The results are presented below. Figure 3 .

[0118] Here, ZDD is an index representing the change in slope (curvature) near the edge, obtained by taking the second derivative of the profile of the wafer surface from the center to the outermost periphery. A positive ZDD value indicates that the surface has shifted in the direction of warping due to corrective grinding, while a negative ZDD value indicates that the surface has shifted in the direction of edge collapse.

[0119] Next, the main test is conducted. The polished wafer obtained from the previous process (first polishing process) undergoes corrective polishing. Details are as follows.

[0120] Multiple wafers were prepared after a single grinding process, and their cross-sectional shapes were obtained using a KLA-Tencor WaferSight1 flatness measuring instrument. The prepared wafers all exhibited a "collapsed edge" shape, with a thinner outer periphery. Additionally, there were shape deviations between the ground wafers.

[0121] In order to improve the collapse edge shape of each wafer based on the measured shape of the polished wafer, and based on Figure 3 The relationships shown determine the type and concentration of surfactants included in the polishing composition. Here, as two examples, the ethylene oxide-propylene oxide block copolymer (EO-PO) was determined to be 10 ppm (Example 1), and the EO-added acetylene glycol was determined to be 10 ppm (Example 2). When the polishing wafers of Examples 1 and 2 are in their desired shapes, by using a polishing composition with the aforementioned type and concentration of surfactants for corrective polishing, the polishing wafer is displaced in the upturned direction to eliminate the amount of collapsed edge shape, resulting in a flat polishing wafer after corrective polishing.

[0122] Next, use as follows Figure 2The polishing apparatus shown performs corrective polishing on a wafer whose shape has been measured. Corrective polishing is performed using an polishing cloth impregnated with polyurethane resin in a non-woven fabric.

[0123] As a grinding composition, a grinding composition is used that uses potassium hydroxide as an alkaline compound and contains colloidal silica as abrasive particles.

[0124] After correction and grinding, a final fine grinding and cleaning were performed, and the cross-sectional shape was obtained again using WaferSight1.

[0125] (Comparative Examples 1-2)

[0126] In addition, unlike Examples 1 and 2, tests were also conducted on a substance that does not contain water-soluble polymers or surfactants (Comparative Example 1) and a substance containing 10 ppm of the water-soluble polymer, polyvinyl alcohol (PVA) (Comparative Example 2). Furthermore, only the same polishing composition as in the prior art was used, and no preliminary tests as in Examples 1 and 2 or any consideration was given to modifying the wafer shape before polishing.

[0127] The shapes of the wafers before and after the modified polishing in Examples 1-2 and Comparative Examples 1-2 are shown respectively. Figures 4-7 In each figure, the top side shows the shape before correction and grinding, and the bottom side shows the shape after correction and grinding.

[0128] like Figure 4 As shown, in Example 1, where 10 ppm of the surfactant EO-PO was added and the milling was corrected, the result was a significant improvement in flatness, particularly near the edges.

[0129] In addition, such as Figure 5 As shown, in Example 2, where 10 ppm of surfactant, namely EO-added ethynyl glycol, was added and corrected by grinding, the flatness near the edges was also significantly improved.

[0130] The results of these Examples 1 and 2 meet the original purpose (to flatten and raise the wafer). In addition, the same method can correct edge collapse and reduce the shape deviation between wafers for other polished wafers.

[0131] On the other hand, such as Figure 6 As shown, in Comparative Example 1, where no water-soluble polymer or surfactant was added, but only potassium hydroxide and colloidal silica were used for correction and grinding, it was almost impossible to correct the shape.

[0132] In addition, such as Figure 7 As shown, in Comparative Example 2, which was modified by adding 10 ppm of PVA as a water-soluble polymer and then grinding, almost no modification was made, just like in Comparative Example 1.

[0133] In these comparative examples 1 and 2, where the present invention was not implemented, as described above, not only was it impossible to correct the collapsed edges, but it was also impossible to reduce the shape deviation between wafers.

[0134] As described above, by determining the type and concentration of surfactant in the polishing composition according to the shape of the polishing wafer, as in Examples 1-2 of the present invention, the shape of the polishing wafer produced in the preceding polishing process can be corrected, and as a result, the shape deviation between wafers can be improved.

[0135] Furthermore, the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any solution having a structure that is substantially the same as the technical concept described in the claims of the present invention and achieving the same effect is included within the technical scope of the present invention.

Claims

1. A method for polishing a wafer, wherein a polishing composition containing water is continuously supplied while the wafer is pressed against an polishing cloth for corrective polishing, so as to correct the shape of a polishing wafer that has undergone excessive coarse polishing before fine polishing, characterized in that, It includes the following processes: Measure the shape of the polishing wafer before performing the corrective polishing; Based on the measured shape of the polishing wafer, the type and concentration of the surfactant contained in the polishing composition are determined; and While supplying the polishing composition adjusted based on the determined type and concentration of surfactant, the polishing wafer after shape measurement is subjected to the corrective polishing. The corrective grinding process eliminates the displacement of the outermost periphery of the ground wafer in the upturned direction due to the collapse shape after shape measurement.

2. The wafer grinding method according to claim 1, characterized in that, When determining the type and concentration of the surfactant, As a preliminary test, a pre-polishing polishing process was performed on a pre-polished wafer by supplying a polishing composition with altered surfactant types and concentrations. The degree of shape correction was determined based on the shape changes of the pre-polished wafer before and after the pre-polishing polishing, thereby pre-determining the correlation between the surfactant type, concentration, and degree of shape correction. Based on the measured shape of the polished wafer, determine the necessary degree of shape correction. Based on the aforementioned correlation, the type and concentration of the surfactant in the corrective grinding are determined in a manner that corresponds to the degree of shape correction obtained.

3. The wafer grinding method according to claim 1, characterized in that, When supplying the grinding composition during the modified grinding process... use: The first tank stores a first grinding composition that does not contain the surfactant; The second tank stores a surfactant solution composed of the surfactant and water; and The third tank stores a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank. The second grinding composition in the third groove is used as the grinding composition during the corrective grinding.

4. The wafer grinding method according to claim 2, characterized in that, When supplying the grinding composition during the modified grinding process... use: The first tank stores a first grinding composition that does not contain the surfactant; The second tank stores a surfactant solution composed of the surfactant and water; and The third tank stores a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank. The second grinding composition in the third groove is used as the grinding composition during the corrective grinding.

5. The wafer grinding method according to claim 3, characterized in that, The third tank is a tank with a capacity equal to the total supply of the second grinding composition in the first batch of the modified grinding.

6. The wafer grinding method according to claim 4, characterized in that, The third tank is a tank with a capacity equal to the total supply of the second grinding composition in the first batch of the modified grinding.

7. The wafer grinding method according to claim 1, characterized in that, The grinding composition used in the modified grinding process is a composition containing abrasive particles.

8. The wafer grinding method according to claim 1, characterized in that, A composition containing a water-soluble polymer is used as the grinding composition during the modified grinding process.

9. The wafer grinding method according to claim 1, characterized in that, The surfactant used is a surfactant with a contact angle of less than 50 degrees with bare silicon whose surface natural oxide film has been stripped by HF impregnation.

10. The wafer grinding method according to any one of claims 1 to 9, characterized in that, The grinding wafer is set as a silicon wafer.

11. A wafer polishing apparatus for correcting the shape of a wafer that has undergone coarse polishing before fine polishing, comprising an polishing cloth and a supply mechanism for supplying a polishing composition containing water, wherein the wafer is pressed against the polishing cloth for correction polishing while the polishing composition is continuously supplied from the supply mechanism, characterized in that... The supply mechanism is capable of supplying a composition containing a surfactant, wherein the type and concentration of the surfactant in the polishing composition are adjusted according to the measured shape of the polishing wafer before the corrective polishing, for use in the corrective polishing of the polishing wafer after shape measurement. The corrective grinding is a grinding process in which the outermost periphery of the grinding wafer is displaced in the upturned direction by a certain amount to eliminate the collapsed edge shape after the shape measurement.

12. The wafer grinding apparatus according to claim 11, characterized in that, The supply organization has: The first tank stores a first grinding composition that does not contain the surfactant; The second tank stores a surfactant solution composed of the surfactant and water; and The third tank stores a second grinding composition prepared by mixing the first grinding composition from the first tank with the surfactant solution from the second tank. The second grinding composition that can be supplied to the third tank is used as the grinding composition during the corrective grinding.

13. The wafer grinding apparatus according to claim 12, characterized in that, The third tank is a tank with a capacity equal to the total supply of the second grinding composition in one batch of the modified grinding.

14. The wafer grinding apparatus according to claim 12, characterized in that, The supply mechanism has a controller that controls the flow rate of the surfactant solution supplied from the second tank to the third tank.

15. The wafer grinding apparatus according to claim 13, characterized in that, The supply mechanism has a controller that controls the flow rate of the surfactant solution supplied from the second tank to the third tank.

16. The wafer grinding apparatus according to claim 11, characterized in that, The grinding composition used in the modified grinding process is a composition containing abrasive particles.

17. The wafer grinding apparatus according to claim 11, characterized in that, The grinding composition used in the modified grinding process is a composition containing a water-soluble polymer.

18. The wafer grinding apparatus according to claim 11, characterized in that, The contact angle between the surfactant and the bare silicon whose surface natural oxide film has been stripped away by HF impregnation is less than 50 degrees.

19. The wafer grinding apparatus according to any one of claims 11 to 18, characterized in that, The polished wafer is a silicon wafer.

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