TWI724361B - Single side polishing method for wafer - Google Patents

Abstract

Problem to be solved: A single side polishing method for a wafer is provided, and the method is capable of obtaining a wafer having the desired ESFQD precisely. Solution: In the present invention, the polishing method for a wafer includes: a first step (step S10) of calculating the protruding amount of a wafer (=central thickness of the wafer – thickness of retainer ring); a second step (step S20) of determining the concentration of water-soluble polymer contained in the polishing slurry based on the protruding amount; a third step (step S30) of causing rotation plate and polishing head to rotate relatively, and polishing the single side of the wafer while supplying the polishing slurry having the concentration of water-soluble polymer determined in the second step.

Description

Single-side polishing method of wafer

The present invention relates to a single-side polishing method for wafers.

One of the surface polishing methods for wafers requiring high flatness, such as semiconductor wafers, is a single-side polishing method that polishes only one side of the wafer. From rough polishing using a relatively hard polishing pad to fine polishing using a relatively soft polishing pad, the single-side polishing method is widely used.

In the past, a single-side polishing device 200 as shown in FIG. 4 was used for rough polishing. The single-side polishing apparatus 200 includes a rotating platform 10 to which a polishing pad 12 for polishing one side of the wafer W is attached. In addition, the single-side polishing apparatus 200 includes a back pad 22 as the other holding surface of the wafer W and a retainer ring 24 attached to the outer edge of the back pad 22 on the holding surface side, and is equipped with a rotating The platform 10 is arranged opposite to the polishing head 20. Here, the guard ring 24 is generally composed of a hard resin material or the like. In addition, the single-side polishing apparatus 200 includes a slurry supply unit 30 that supplies a polishing slurry 32 containing a water-soluble polymer onto the polishing pad 12. Here, the polishing slurry 32 contains silicon oxide particles that function as abrasive grains, a water-soluble alkaline compound that functions as an etchant for the wafer, and a water-soluble polymer that functions as a protective agent for the wafer. In addition, the polishing head 20 includes a shaft portion 26 for raising, lowering and rotating the polishing head 20, and a rotating frame portion 28 provided at the lower end of the shaft portion 26 and having a back pad 22 attached to the lower surface. In addition, the single-side polishing apparatus 200 includes a table rotating shaft 14 connected to the rotating table 10 to rotate. In addition, the shaft portion 26, the table rotating shaft 14 and the like are connected to a driving mechanism (not shown) such as a motor. In the single-side polishing apparatus 200, the rotating table 10 and the polishing head 20 rotate together, whereby the rotating table 10 and the polishing head 20 rotate relatively, while supplying the polishing slurry 32 from the polishing slurry supply part 30 to the polishing pad 12 Only one side of the wafer W is polished.

In the above-mentioned single-sided polishing apparatus 200, the shape of the polished wafer will change according to the use time of the back pad 22 and the guard ring 24, which will cause the stability of the flatness of the wafer. problem. Patent Document 1 describes a technique for improving the flatness of the wafer by using the following method in the single-side polishing apparatus 200 shown in FIG. 4. That is, in the single-side polishing apparatus 200 shown in FIG. 4, polishing conditions such as the rotation speed of the rotating table 10 and the polishing head 20, the polishing pressure, the type of the backing pad 22, and the like are adjusted. The above adjustment is performed to reduce the amount of change in the depth of the recess defined by the inner peripheral surface of the guard ring 24 and the guard ring side surface of the back pad 22 for accommodating and holding the wafer W before and after polishing. As a result, the maximum absolute value of ESFQD (Edge Site flatness Front reference leastsQuare Deviation) of the wafer is suppressed. In addition, the so-called "ESFQD" is an index indicating the flatness of the wafer, and the smaller the maximum value of its absolute value, the higher the flatness of the wafer.

[Advanced Technical Literature] [Patent Literature] Patent Document 1: Japanese Patent Application Publication No. 2017-87328

[The problem to be solved by the invention]

In Patent Document 1, in order to improve the flatness of the polished wafer, the maximum absolute value of the ESFQD of the wafer is suppressed. Indeed, in the case of using a wafer just after rough grinding as a polished wafer, it is required to reduce the maximum value of ESFQD of the wafer just after rough grinding. However, the ESFQD of the wafer just after rough polishing may not necessarily have a small maximum value. For example, in the case where a wafer just after rough grinding is provided for epitaxial growth to obtain an epitaxial wafer, the shape of the wafer just after rough grinding needs to be a roll-off shape in advance. That is, it is necessary to make the ESFQD of the rough-polished wafer a negative specific value in advance. The reason is that since the epitaxial growth rate of the outer peripheral part of the wafer is higher than that of the central part, if it is not an edge roll-off shape, a flat epitaxial wafer cannot be obtained. Therefore, in the wafer just after rough grinding, it is not only necessary to reduce the ESFQD, but to accurately approximate the desired ESFQD corresponding to the epitaxial wafer, the polished wafer, etc.

In view of the above-mentioned problems, the present invention aims to provide a single-side polishing method for wafers, which can obtain wafers with desired ESFQDs with high accuracy. [Means to Solve the Problem]

In Patent Document 1, controlling the amount of change before and after polishing of the depth of the recess is equivalent to controlling the protrusion amount of the wafer defined by the difference between the center thickness of the wafer and the thickness of the guard ring. This protrusion amount is caused by the unevenness of the center thickness of the wafer to be polished and the elapsed wear of the guard ring, and it changes every time the wafer is polished. Therefore, whenever the wafer is polished, the ESFQD of the polished wafer deviates from the desired value. However, in reality, it is difficult to perform high-precision control in units of μm so that the amount of protrusion is always kept constant. For example, although it is considered to use a single-sided polishing device that can independently raise and lower a chuck holding a guard ring, a wafer, etc., and can control the distance between the polished surface of the wafer and the lower surface of the guard ring, In this single-side polishing device, a large number of sensors, control parts, etc. are required, which makes its structure complicated.

Therefore, the present inventors studied a single-side polishing method for a wafer that can obtain a wafer with a desired ESFQD with high accuracy even without controlling the protrusion amount of the wafer. Therefore, it is found that the correlation between the protrusion amount of the wafer and the ESFQD obviously depends on the concentration of the water-soluble polymer as the protective agent of the wafer contained in the polishing slurry. Therefore, the following concept is reached: the concentration of the water-soluble polymer is appropriately determined in accordance with the protrusion amount of the wafer, so that even if the protrusion amount of the wafer is not controlled, it is possible to obtain a wafer with the desired ESFQD with high accuracy.

The present invention was completed based on the above-mentioned concept, and its gist is structured as follows. [1] A single-side polishing method for a wafer, which is a single-side polishing method of a wafer using a single-side polishing device for a wafer. The single-side polishing device for the wafer includes: A rotating platform for the polishing pad on one side; a backing pad as the holding surface of the other side of the wafer, and a guard ring mounted on the outer edge of the holding surface side of the backing pad, and arranged opposite to the rotating platform A polishing head; and a slurry supply unit that supplies a polishing slurry containing a water-soluble polymer to the polishing pad; the method is characterized by including: first calculating the protrusion amount of the wafer based on the following formula (1) Step; Based on the protrusion amount, the second step of determining the concentration of the water-soluble polymer contained in the polishing slurry; and the relative rotation of the rotating platform and the polishing head, on the polishing pad, while supplying the second step The third step of polishing the polishing slurry with the determined concentration of the water-soluble polymer on one side of the wafer. [Projection]=[Thickness of Wafer Center]-[Thickness of Guard Ring]･･･(1)

[2] In the single-sided polishing method for a wafer as described in [1] above, in the second step, the concentration of the water-soluble polymer is determined based on the following formula (2); where A, B, C, and D is a coefficient obtained by linear regression analysis of the actual value of the single-side polishing of the wafer. [The desired ESFQD]=A×([Projection amount]-B)×([Concentration of water-soluble polymer]-C)+D･･･(2)

[3] The single-sided polishing method for a wafer as described in [2] above, wherein the protrusion amount is 75 μm or more and 200 μm or less.

[4] The single-side polishing method for wafers as described in any one of [1] to [3] above, wherein the single-side polishing apparatus further includes storing polishing slurries with different concentrations of water-soluble polymers. The method further includes: before the grinding in the third step, first select the grinding that stores the concentration of the water-soluble polymer determined in the second step from the plurality of slurry tanks The step of slurry tank of the slurry; in the aforementioned third step, the polishing slurry stored in the selected slurry tank is supplied. [Effects of the invention]

According to the single-side polishing method of the wafer of the present invention, the wafer with the desired ESFQD can be obtained with high precision.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

First, referring to FIG. 1, a single-side polishing apparatus 100 for wafers used in an embodiment of the present invention will be described. The single-side polishing apparatus 100 includes: a rotating platform 10 to which a polishing pad 12 for polishing one side of the wafer W is attached; a back pad 22 as the holding surface of the other side of the wafer W, and a back pad 22 attached to the back pad 22 The guard ring 24 on the outer edge of the holding surface side and the polishing head 20 arranged opposite to the rotating platform 10; and the slurry supply part 30 that supplies the polishing slurry 32 to the polishing pad 12. The polishing slurry 32 contains at least a water-soluble polymer, and may also contain abrasive grains and an etchant. The water-soluble polymer may function as a protective agent for the wafer W. In addition, the guard ring 24 may be configured to have an inner diameter equal to or greater than the diameter of the wafer W.

In addition, the polishing head 20 may include a shaft portion 26 for raising and lowering the polishing head 20 and rotating it, and a rotating frame portion 28 provided at the lower end of the shaft portion 26 and having a back pad 22 mounted thereunder. In addition, the single-side polishing apparatus 100 may include a table rotating shaft 14 that is connected to the rotating table 10 and rotates the rotating table 10. In addition, the shaft portion 26, the table rotating shaft 14 and the like may be connected to a driving mechanism (not shown) such as a motor.

Moreover, the single-side polishing device 100 may be equipped with slurry tanks 40A-40X for storing polishing slurries with different concentrations of water-soluble polymers. These slurry tanks 40A to 40X can be connected to the polishing slurry supply pipes 44A to 44X that supply the polishing slurry to the polishing slurry supply part 30 through the opening and closing valves 42A to 42X, respectively.

In addition, the single-side polishing device 100 can be controlled using the control unit 50. The control unit 50 may include a control unit (not shown) that controls the opening and closing of the on-off valves 42A to 42X, the rotation of the shaft portion 26 and the table rotation shaft 14, and a calculation unit (not shown) that calculates the polishing conditions. In addition, the control unit 50 can be realized by a central arithmetic processing unit (CPU) or the like inside a computer.

Hereinafter, referring to FIGS. 1 and 2, an example of a single-side polishing method of a wafer that can be performed using the above-mentioned single-side polishing apparatus 100 will be described. In addition, the wafer that can be used in the single-side polishing method of the wafer of the present invention is not particularly limited, and examples thereof include silicon wafers, SiC wafers, and the like.

2, in the first step, the protrusion amount of the wafer W is calculated based on the following formula (1) (step S10).

[Projection]=[Thickness of Wafer Center]-[Thickness of Guard Ring]･･･(1)

Here, referring also to FIG. 1, the first step can be performed as follows: the control unit 50 reads the center thickness of the wafer W from the memory unit (not shown) (step S11); the control unit 50 reads the center thickness of the wafer W from the memory unit (not shown); The step of reading the thickness of the guard ring (step S12); and the step of using the read center thickness of the wafer W and the thickness of the guard ring, the control unit 50 calculates the protrusion amount of the wafer W based on the above formula (1) ( Step S13). In addition, "the center thickness of the wafer W" may be that the center thickness of the wafer before rough polishing is measured in advance with a well-known spectral interference displacement device, and the center thickness is stored in the memory in advance. In addition, the "thickness of the guard ring" can be the average value of the thickness at 8 points at equal intervals in the outer circumferential direction of the guard ring, measured in advance with a known spectral interference displacement device, and the value is stored in the memory in advance. That's it. However, the first step in the present invention is not limited to this. For example, steps S11 to S13 may be replaced with: whenever the wafer W is subjected to single-sided polishing, the wafer W is measured by a known spectral interference displacement device. The center thickness of W and the thickness of the guard ring.

Next, referring to FIG. 2, in the second step, based on the protrusion amount calculated in the first step, the concentration of the water-soluble polymer contained in the polishing slurry is determined (step S20).

Here, it is preferable to determine the concentration of the water-soluble polymer contained in the polishing slurry based on the following (2) formula using the predetermined coefficients A, B, C, and D, and to perform the second step by this. In addition, the control unit 50 may be used to perform this determination.

[The desired ESFQD]=A×([Projection amount]-B)×([Concentration of water-soluble polymer]-C)+D･･･(2)

In the following, the experiments carried out by the inventors until the discovery of the present invention are explained. First, prepare various polishing slurries. Then, a plurality of combinations of the polishing head 20 and the wafer W provided with the guard ring 24 that makes the protrusion amount of the wafer a specific value within a predetermined range (for example, 75 μm or more and 200 μm or less) are prepared. In the experiment, first, for these wafers W, in addition to the protrusion amount and the polishing slurry, the polishing conditions such as the pressing force and the rotation speed were fixed to perform single-side polishing. Then, the average value of ESFQD of the polished wafer is obtained. Thereby, the average value of ESFQD corresponding to the predetermined water-soluble polymer concentration and protrusion amount is obtained. Change the concentration and protrusion amount of the water-soluble polymer within the above-mentioned predetermined range, and repeat this series of operations. Focusing on the water-soluble polymer contained in the polishing slurry as a protective agent, the average value of ESFQD relative to the protrusion amount of the wafer corresponding to each concentration of the water-soluble polymer as shown in FIG. 3 The relevance. From this result, it is clear that the correlation between the protrusion amount of the wafer and ESFQD is obviously dependent on the concentration of the water-soluble polymer as the protective agent contained in the polishing slurry. Moreover, when the amount of protrusion is used as an explanatory variable, and the average value of ESFQD is used as the target variable, when linear regression analysis is performed on the correlation shown in Fig. 3, the above equation (2) is obtained. Therefore, A, B, C, and D in the above formula (2) are coefficients obtained by linear regression analysis of the actual value of the single-side polishing of the wafer in this way. Here, A is dependent on the physical properties of the backing pad and polishing pad (hardness, compression rate, thickness), polishing conditions (polishing load, number of rotations of the polishing head and rotating table, polishing time), and the dilution rate using pure water, etc. Wait. B and C are dependent on the type of water-soluble polymer. D is dependent on the shape of the end face of the wafer, the ESFQD of the wafer before polishing (that is, the ESFQD of the material), and the like.

In addition, the "ESFQD (Edge Site flatness Front reference leastsQuare Deviation)" in this manual refers to the ESFQD specified in SEMI M67. Specifically, a flatness measuring device (manufactured by KLA-Tencor: WaferSight2) was used for the measurement of ESFQD. ESFQD is an index indicating site flatness (site flatness) on the outer periphery (edge) of the wafer. ESFQD divides the outer periphery of the wafer into many (for example, 72) fan-shaped areas (parts), and calculates the inner plane of the part using the least square method based on the data in the part. The amount of displacement, there is 1 piece of data in each part. That is, ESFQD is the SFQD value of each part (the deviation of the larger of positive or negative from the smallest square in the area). The ESFQD area is the area described below. The area 2mm in the diameter direction from the outermost circumference is the exclusion area. The line segment extending from the outer reference end of the inner circumference toward the center of the diameter direction is 30mm in length and two straight lines, and It is equivalent to a roughly rectangular area surrounded by a circular arc of 5° (±2.5°) in the peripheral direction of the wafer.

The "concentration of water-soluble polymer" in the above formula (2) is preferably 0 ppm or more and 60 ppm or less, and more preferably 20 ppm or more and 50 ppm or less. This is because if it is 20 ppm or more, it is easy to suppress roll off, and if it is 50 ppm or less, it is more possible to ensure a sufficient polishing rate.

In addition, the "concentration of water-soluble polymer" means the concentration measured by the following method. That is, the sample obtained by adjusting the pH of the stock solution of the polishing slurry to 3.0 with sodium hydroxide and sulfuric acid is passed through a gas containing no carbon dioxide (for example, N ₂ ) using a centrifugal separator (manufactured by AS ONE) : MCD-2000), centrifuged at 14000 rpm for 30 minutes to obtain a supernatant from which water-soluble polymers adsorbed on silica particles contained in the polishing slurry were removed. After that, for this supernatant, a total organic carbon analyzer (TOC meter Sievers model 810) was used to measure the concentration of water-soluble polymers that were not adsorbed on the silica particles.

The "projection amount" in the above formula (2) is preferably 75 μm or more and 200 μm or less. This is because if it is 75 μm or more, the polishing rate can be ensured, and if it is 200 μm or less, it is possible to suppress cracks and chipping of the wafer.

Using the above formula (2), the concentration of the water-soluble polymer that can accurately realize the desired ESFQD can be determined, but the present invention is not limited to this. That is, in the present invention, based on the knowledge that the correlation between the protrusion amount of the wafer W and ESFQD changes according to the concentration of the water-soluble polymer contained in the polishing slurry, the amount of protrusion of the wafer W is appropriately determined to achieve the desired value. The concentration of the water-soluble polymer of ESFQD is very important.

Next, referring to Figures 1 and 2, in the third step, the rotating platform 10 and the polishing head 20 are relatively rotated, and the polishing pad 12 is supplied with the polishing slurry 32 having the water-soluble polymer concentration determined in the second step. , While polishing one side of the wafer W (step S30). In addition, the relative rotation of the rotating table 10 and the polishing head 20 may be performed by the control unit 50 rotating the table rotating shaft 14 and the shaft portion 26 respectively. In addition, the supply of the polishing slurry 32 may be performed by the control unit 50 opening the on-off valve (not shown) of the slurry supply unit. In addition, when a specific polishing time has elapsed, the control unit 50 stops the rotation of the table rotating shaft 14 and the shaft portion 26, and closes the opening and closing valve of the slurry supply unit 30, thereby completing the single-sided polishing.

Here, it may further include: before the polishing in the third step, the control unit 50 first selects the polishing slurry that stores the concentration of the water-soluble polymer determined in the second step from the slurry tanks 40A-40X. A step of a slurry tank (in this embodiment, it is assumed to be a slurry tank 40A) (step S31). In this case, in the third step, the control unit 50 opens the on-off valve 42A of the slurry tank 40A selected in step S31, thereby enabling the polishing slurry 32 stored in the selected slurry tank 40A to be stored It is supplied to the polishing pad 12 while polishing one side of the wafer W (step S32).

Next, the polishing slurry 32 that can be used in one embodiment of the present invention will be described.

The stock solution of the polishing slurry 32 may include silicon oxide particles acting as abrasive grains, a water-soluble alkaline compound acting as an etchant for the wafer, and a water-soluble polymer acting as a protective agent for the wafer. The above-mentioned polishing slurry may be used as it is, or it may be used after being appropriately diluted with an aqueous solvent such as pure water, ultrapure water, or ion exchange water. Hereinafter, each component that can be contained in the stock solution of the polishing slurry 32 will be described.

Examples of silica particles include colloidal silica, fumed silica, and precipitated silica. The silicon oxide particles may be used alone or in combination of two or more. From the viewpoint of suppressing the occurrence of scratches on the surface of the wafer and improving the polishing performance, it is particularly preferable to use colloidal silica. The concentration of the silicon oxide particles in the stock solution of the polishing slurry is preferably 8% by mass or more and 15% by mass or less. This is because if it is 8% by mass or more, a sufficient polishing rate can be ensured so that manufacturing costs can be suppressed, and if it is 15% by mass or less, the cost of polishing slurry and the occurrence of scratches on the surface of the wafer can be suppressed. Wait. The average primary particle size of the silicon oxide particles is preferably 15 nm or more and 40 nm or less. This is because if it is 15 nm or more, a sufficient polishing rate can be ensured and the manufacturing cost can be suppressed, and if it is 40 nm or less, it is possible to suppress the cost of polishing slurry and the occurrence of scratches on the surface of the wafer.

In addition, in this specification, the so-called "average primary particle diameter" is calculated based on the BET method, which means that the adsorption area of the particle surface is known to be adsorbed by molecules at the temperature of liquid nitrogen. The specific surface area of the particles is calculated, and the specific surface area is converted to the value of the diameter of the spherical particles.

The water-soluble alkaline compound can generate hydroxide ions in water that can chemically polish polishing objects such as silicon wafers. Moreover, it also assists the dispersion of silica particles. From the viewpoint of obtaining such an effect more stably, it is preferable that the water-soluble basic compound is dissolved in the composition. Examples of water-soluble basic compounds include ammonia, ammonium carbonate, ammonium bicarbonate, organic amine compounds, tetramethylammonium hydroxide, sodium hydroxide, and potassium hydroxide. One or more of the above can be used. . Examples of organic amine compounds include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethanolamine, diisopropylethylamine, ethylenediamine, and diethylenetriamine. , Triethylenetetramine (triethylenetetramine), ginseng (2-aminoethyl)amine (tris(2-aminoethyl)amine), N,N,N',N'tetramethylethylenediamine (N,N,N ′,N′-tetramethylethylenediamine), hexamethylenediamine, 1,4,7-triazacyclononane (1,4,7-triazacyclononane), 1,4,7-trimethyl-1 ,4,7-triazacyclononane (1,4,7-trimethyl-1,4,7-triazacyclononane), 1,4-diazabicyclooctane (1,4-diazabicyclooctane), piperazine (piperazine) and piperidine (piperidine), one or more of the above can be used.

The pH of the polishing slurry is preferably adjusted to 8 or more and 12 or less. This is because if the pH is 8 or higher, the wafer can be etched, and if the pH is 12 or less, it is possible to prevent the dissolution of the silicon oxide particles as abrasive grains, thereby suppressing the mechanical polishing effect of the abrasive grains. reduce.

Examples of water-soluble polymers include polymers such as polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, polypropylene glycol, polyethylene glycol, and hydroxyethyl cellulose. Those with a molecular weight of 10,000 or more can be used alone. One of the above, or two or more of them may be used in combination. From the viewpoint of increasing the polishing rate, the molecular weight is more preferably 20,000 or more.

For the purpose of adjusting the properties of the polishing slurry, capturing metal ions, and assisting the adsorption of water-soluble polymers on the polishing target (a silicon wafer is illustrated as a specific example), the raw material of the polishing slurry is also in addition to the above-mentioned components. The following additives may be included. For example, alcohols, chelate compounds, and nonionic surfactants can be mentioned, and one or two or more of the above additives can be added. Examples of alcohols include methanol, ethanol, propanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and glycerin. One or two of the above can be added More than species. Examples of chelates include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxyethylenediaminetetraacetic acid, propylenediaminetetraacetic acid ( propanediaminetetraacetic acid), diethylenetriaminepentaacetic acid and triethylenetetramine hexaacetic acid, as well as metal salts such as ammonium, sodium and potassium salts of these, can be added to the above One kind or two or more kinds. Examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkenyl ether, and polyoxyalkylene alkyl ether. , Polyoxyalkylene alkenyl ether (polyoxyalkylene alkenyl ether), alkyl polyglycoside (alkyl polyglycoside), and polyether denatured silicone, one or more of the above can be added.

In addition, the manufacturing method of the polishing slurry 32 is not specifically limited, For example, a well-known mixing apparatus, such as a wing mixer, an ultrasonic dispersion machine, a homomixer, etc. may be used, and the said each component may be mixed suitably.

Above, the present embodiment has been taken as an example to describe the single-side polishing method of the wafer of the present invention, but the present invention is not limited to the above-mentioned embodiment, and may be appropriately modified within the scope of the patent application. [Example]

(Invention example) In order to confirm the effect of the present invention, according to the single-side polishing device shown in FIG. 1 and the flowchart shown in FIG. 2, the single-side polishing of the wafer was performed, and the unevenness of ESFQD of the polished wafer was evaluated as an example of the invention. .

In the above evaluation, the following conditions were adopted. Prepare to use pure water to dilute the water-soluble polymer (polyvinylpyrrolidone, molecular weight: 20,000) with the concentration of 27ppm, 33ppm, and 50ppm, which has been measured by the above-mentioned method. Slurry. In addition, any polishing slurry contains colloidal silica as silica particles, the concentration in the stock solution is 13% by mass, and the average primary particle diameter measured by the BET method is 35 nm. In addition, the water-soluble basic compound was tetramethylammonium hydroxide, and the pH was adjusted to 10.5.

As the polishing pad, a polishing pad manufactured by Fujibo (registered trademark: POLYPAS) was used. As the back pad and the guard ring, it uses the integrated Fujibo-made template (POLYPAS_Template). The wafer is a single crystal silicon wafer. The polishing load is 150 g/cm ² , the number of rotations of the polishing head and the rotating table is 12 rpm, and the removal amount is 500 nm to 1000 nm.

200 pieces (600 pieces in total) of which the protrusion amount calculated according to the formula (1) is the value in Table 1 were prepared respectively as the wafers for polishing and the guard ring. Table 1 shows the average value of 200 pieces. However, the thickness of the guard ring is a certain value. In addition, the coefficient of the aforementioned formula (2) is obtained in advance by making the polishing conditions constant. In the formula (2), A is 0.0053/ppm, B is 50 μm, C is 12.4 ppm, and D is -25 nm. The desired ESFQD is -15nm.

(Comparative example) In the comparative example, 200 pieces (600 pieces in total) whose protrusion amount is the value in Table 1 were prepared as wafers for polishing and guard rings. Table 1 shows the average value of 200 pieces. However, the thickness of the guard ring is a certain value. Furthermore, instead of using the formula (2), only one type of polishing slurry having a polyvinylpyrrolidone concentration of 33 ppm was used to perform single-sided polishing of the wafer. In addition, other conditions are the same as in the example of the invention.

(Explanation of evaluation methods and evaluation results) In the inventive example and the comparative example, the ESFQD of the polished wafer was measured with a spectral interference shift device. Then calculate the average value of the deviation (=[desired ESFQD]-[measured ESFQD]) from the desired ESFQD. The measurement results are shown in Table 1.

※發明例為基於式(2)所決定之值[Table 1]

※The invention example is the value determined based on formula (2)

As shown in Table 1, in the invention example, the concentration of the water-soluble polymer is determined based on formula (1) and formula (2), so when the protrusion amount of the wafer is any of 100 μm, 140 μm, and 179 μm , Both can make the ESFQD of the polished wafer close to the desired ESFQD (-15nm) with high accuracy. On the other hand, regarding the concentration of the water-soluble polymer, in the comparative example where the determination based on the formula (2) was not made, when the protrusion amount was 100 μm and 179 μm, the deviation amount was larger than that of the invention example, and the polished wafer The ESFQD is close to the desired ESFQD with high precision. [Industrial Utilization Possibility]

According to the single-side polishing method of the wafer of the present invention, the wafer with the desired ESFQD can be obtained with high precision.

100‧‧‧Single-side grinding device 10‧‧‧Rotating Platform 12‧‧‧Polishing Pad 14‧‧‧Platform rotation axis 20‧‧‧Grinding head 22‧‧‧Back Pad 24‧‧‧Guard Ring 26‧‧‧Shaft 28‧‧‧Rotating frame 30‧‧‧Grinding Slurry Supply Department 32‧‧‧Grinding slurry 40A~X‧‧‧slurry tank 42A~X‧‧‧Open and close valve 44A~X‧‧‧Slurry supply piping 50‧‧‧Control Department W‧‧‧wafer

[Fig. 1] A schematic diagram showing a single-side polishing apparatus 100 for a wafer that can be used in an embodiment of the present invention. [Fig. 2] A flowchart showing a single-side polishing method of a wafer according to an embodiment of the present invention. [Fig. 3] A graph showing the correlation between the protrusion amount of the wafer and the average value of ESFQD based on the inventor's research. [Fig. 4] A schematic diagram of a conventional single-side polishing device 200 is shown.

Claims (3)

A single-side polishing method for a wafer is a single-side polishing method for a wafer using a single-side polishing device for the wafer. The single-side polishing device for the wafer includes: A rotating platform for the polishing pad; a polishing head provided with a backing pad as the holding surface on the other side of the wafer and a guard ring mounted on the outer edge of the holding surface side of the backing pad and arranged opposite to the rotating platform; And supplying the polishing slurry containing the water-soluble polymer to the slurry supply part on the polishing pad; the method is characterized by including the first step of calculating the protrusion amount of the wafer based on the following formula (1), [ Protrusion]=[the center thickness of the wafer]-[the thickness of the guard ring]. . . (1); The second step of determining the concentration of the water-soluble polymer contained in the polishing slurry based on the protrusion amount; and relatively rotating the rotating platform and the polishing head, and supplying the second polishing pad on the polishing pad. The third step in which the polishing slurry with the concentration of the water-soluble polymer determined in the step polishes one side of the wafer; in the second step, the concentration of the water-soluble polymer is determined based on the following formula (2) Concentration; [desired ESFQD]=A×([projection amount]-B)×([concentration of water-soluble polymer]-C)+D. . . (2), where A, B, C, and D are coefficients obtained by linear regression analysis of the actual value of the single-side polishing of the wafer. The single-sided polishing method for wafers as described in the first item of the scope of patent application, wherein the protrusion amount is 75 μm or more and 200 μm or less. Such as the single-side polishing method of wafer described in item 1 or 2 of the scope of patent application, where the former The single-sided polishing device further includes a plurality of slurry tanks respectively storing polishing slurries of different concentrations of the water-soluble polymer; the method further includes: before the polishing in the third step, the plurality of slurry tanks Among the hoppers, the step of selecting the slurry tank storing the polishing slurry with the concentration of the water-soluble polymer determined in the second step; in the third step, supplying one of the slurry tanks stored in the selected slurry tank Grinding slurry.

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