TW202040662A - Silicon wafer etching method and etching apparatus - Google Patents

Abstract

The present invention provides a silicon wafer etching method characterized by: comprising a spin-etching process in which a silicon wafer is rotated while an acidic etchant is supplied to an obverse or reverse surface of the silicon wafer by a supply nozzle in order to supply the acidic etchant over the entire surface to perform acid etching, the spin-etching process being repeated to continuously machine a plurality of silicon wafers; comprising a process of recovering and returning used acidic etchant to an etchant tank during the continuous machining to obtain acidic etchant again, and an etchant discard/supply process in which a prescribed quantity of recovered acidic etchant is discarded and a prescribed quantity of fresh acidic etchant is supplied, the acidic etchant being used in the spin-etching process after the etchant discard/supply process.

Description

Silicon wafer etching method and etching device

The invention relates to an etching method and an etching device for silicon wafers.

In the manufacturing process of silicon wafers, wafers thinly sliced from the state of single crystal ingots are generally flattened by chamfering and grinding. At this time, on the front and back of the wafer, scratches or processing distortions of different sizes caused by the above-mentioned processing are formed. Such scratches or processing distortions may become a serious quality problem if they become obvious in the subsequent process.

Therefore, etching is usually performed to remove such scratches or processing distortions. Known etching methods are: a batch method in which the front and back surfaces of a plurality of wafers are processed at the same time, or a spin etching method in which the front and back surfaces of the wafers are processed sequentially in a single piece (refer to Patent Document 1) . Also, depending on the purpose, there are two methods of treatment with acid etching solution and alkali etching solution. For example, in the case of acid etching, generally the concentration of hydrofluoric acid and nitric acid is appropriately adjusted. And so on mixed acid. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2007-53178 A

[Problem to be solved by invention]

When performing acid etching using the spin etching method, the used etching solution is usually recovered and used as the etching solution again, so the concentration of hydrofluoric acid and nitric acid contained in the etching solution will continuously change depending on the number of processed pieces . As a result, since the etching rate also continuously changes, there is a problem that a fixed amount of processing cannot be maintained. In addition, in reality, not only the etching rate but also the margin distribution in the wafer surface changes depending on the number of processed wafers, so there is a problem that the wafer shape after etching cannot be maintained constant.

In the past, most of the response to this problem was to replenish hydrofluoric acid. With this method, although the etching rate can be maintained, it cannot respond to changes in wafer shape after etching. Therefore, when the shape change becomes large, it is unavoidable that the processing must be temporarily interrupted to perform the replacement operation of the etching solution.

In view of this, the object of the present invention is to provide a silicon wafer etching method, which can perform continuous processing while maintaining a fixed etching rate and the shape of the wafer after etching processing. [Solving the problem]

In order to solve the above-mentioned problems, the present invention provides a silicon wafer etching method, which includes a spin etching step in which an acid etching solution stored in an etching solution tank is supplied to the surface of the silicon wafer through a supply nozzle. / Or on the back side, while rotating the silicon wafer, thereby expanding the supply range of the acid etching solution to the entire surface and/or back surface of the silicon wafer for acid etching; By repeating the rotary etching step, continuous processing of multiple silicon wafers is performed, In this continuous processing, the following steps are included: In the recovery step, the acid etching solution used in the spin etching step is recovered, and returned to the etching solution tank to be used as the acid etching solution again; and In the draining/liquid supply step, the recovered acid etching solution is discharged in a predetermined amount, and then a new amount of the acid etching solution is supplied; The acid etching solution after the liquid discharge/liquid supply step is used in the spin etching step.

In the case of such a silicon wafer etching method, by performing acid etching in the spin etching method while draining/supplying the liquid, it is possible to prevent the increase in the amount of Si dissolved in the acid etching solution and the resulting acid etching The dynamic viscosity of the liquid changes, so even during continuous processing, a fixed etching rate and processed wafer shape can be obtained.

At this time, in the liquid discharge/liquid supply step, it is preferable to determine the amount of the liquid discharged and the amount of the liquid supplied according to the amount of Si dissolved in the recovered acid etching solution.

Such a method can more reliably prevent the increase in the amount of Si dissolved and the change in the dynamic viscosity of the acid etching solution caused by this.

In addition, in the liquid discharge/liquid supply step, it is preferable that the amount of liquid discharged and the amount of liquid supplied be the same.

With such a method, since the amount of Si dissolved can be kept constant, the change in the dynamic viscosity of the acid etching solution can be more reliably prevented.

Moreover, in the spin etching step, it is advisable to change the rotation speed of the silicon wafer to perform acid etching according to the amount of Si dissolved in the acid etching solution in the etching solution tank.

In such a method, the rotation speed of the silicon wafer is changed by the amount of Si dissolved in the acid etching solution, thereby suppressing the change in the etching rate distribution within the wafer surface. In addition, the shape of the wafer after etching can be improved.

In addition, as the acid etching solution, a mixed solution containing hydrofluoric acid and nitric acid, or a mixed solution in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is further added thereto is preferably used.

If it is such a mixed solution, it can be applied to rotary etching of silicon wafers.

In addition, the present invention provides an etching device, which includes: The supply nozzle is used to supply the acid etching solution stored in the etching solution tank to the surface and/or back surface of the silicon wafer: The platform, by holding and rotating the silicon wafer, expands the supply range of the acid etching solution to the entire surface and/or back of the silicon wafer for acid etching; and A recovery mechanism for recovering the acid etching solution used in the acid etching and returning it to the etching solution tank; The etching device further includes: A liquid drain mechanism for draining a predetermined amount of the acid etching solution from the etching solution tank; and The liquid supply mechanism is used to supply a predetermined amount of new acid etching solution to the etching solution tank.

If it is the etching device of the present invention, because the liquid discharge mechanism and the liquid supply mechanism perform the acid etching of the spin etching method while performing the liquid discharge/liquid supply, it is possible to prevent the increase in the amount of Si dissolved in the acid etching solution and therefore The resulting change in the dynamic viscosity of the acid etching solution allows a fixed etching rate and processed wafer shape to be obtained even during continuous processing. [Invention Effect]

In the case of the silicon wafer etching method and the etching apparatus of the present invention, by performing acid etching in the spin etching method while draining/supplying the liquid, the increase in the amount of Si dissolved in the acid etching solution can be prevented, and therefore The resulting change in the dynamic viscosity of the acid etching solution enables a fixed etching rate and processed wafer shape to be obtained even during continuous processing. The rotational speed of the silicon wafer is changed by the amount of Si dissolved in the acid etching solution, thereby suppressing the variation of the etching rate distribution in the wafer surface. In addition, even if the amount of Si dissolved increases, the wafer shape after etching can be maintained well.

As mentioned above, when performing acid etching using the spin etching method, the used etching solution is usually recovered and used as the etching solution again. Therefore, the etching speed and the margin distribution in the wafer surface will be dependent on the continuous processing. The number of processed pieces varies.

After careful research, the inventor found that when the dissolved amount of Si in the acid etching solution changes, the dynamic viscosity of the acid etching solution changes. Therefore, in the acid etching of the rotary etching method, the fluid characteristics of the etching solution cannot be ignored. The etching rate distribution in the circular surface changes, and as a result, the processed shape of the wafer after etching is changed.

Therefore, in order to maintain the quality of the processed shape in the acid etching of the rotary etching method, a rotary acid etching method and etching device have been developed, which can prevent the increase of the amount of Si dissolved in the acid etching solution while maintaining Under the composition concentration of the acid etching solution, the wafer shape and etching speed after etching are maintained constant.

That is, the present invention is a silicon wafer etching method, which includes a spin etching step, the spin etching step is while the acid etching solution stored in the etching solution tank is supplied to the surface of the silicon wafer and/or through a supply nozzle On the back side, while rotating the silicon wafer, thereby expanding the supply range of the acid etching solution to the entire surface and/or back surface of the silicon wafer for acid etching; By repeating the rotary etching step, continuous processing of multiple silicon wafers is performed; In this continuous processing, the following steps are further included: A recovery step, in the continuous processing, recovering the acid etching solution used in the spin etching step, and returning it to the etching solution tank to be used as an acid etching solution again; and In the draining/liquid supply step, the recovered acid etching solution is discharged in a predetermined amount, and then a predetermined amount of new acid etching solution is supplied; The acid etching solution after the liquid discharge/liquid supply step is used in the spin etching step.

Moreover, an etching device of the present invention includes: The supply nozzle is used to supply the acid etching solution stored in the etching solution tank to the surface and/or back surface of the silicon wafer: The platform, by holding and rotating the silicon wafer, expands the supply range of the acid etching solution to the entire surface and/or back of the silicon wafer for acid etching; and A recovery mechanism for recovering the acid etching solution used in the acid etching and returning it to the etching solution tank; The etching device further includes: A liquid drain mechanism for draining a predetermined amount of the acid etching solution from the etching solution tank; and The liquid supply mechanism is used to supply a predetermined amount of new acid etching solution to the etching solution tank.

In the case of such a silicon wafer etching method and etching device, by performing acid etching in the spin etching method while draining/supplying the liquid, it is possible to prevent the increase in the amount of Si dissolved in the acid etching solution and the resulting The dynamic viscosity of the acid etching solution changes, so even during continuous processing, a fixed etching rate and processed wafer shape can be obtained.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to this description.

Fig. 1 is a schematic diagram of an embodiment of the etching apparatus of the present invention to which a liquid supply and discharge mechanism is connected. Specifically, for example, a liquid supply and discharge mechanism is connected to a rotary etching machine MSE-7000EL-MH manufactured by Sanyi Semiconductor Industry Co., Ltd. used in the rotary etching method.

The etching device of the present invention is provided with: an etching solution tank for storing acid etching solution; a supply nozzle for supplying acid etching solution to the surface and/or back of the silicon wafer; and a platform for holding and making the silicon wafer Rotation; recovery mechanism to recover the acid etching solution and return to the etching solution tank; drainage mechanism to discharge the acid etching solution from the etching solution tank; and liquid supply mechanism to supply new acid etching solution to the etching Liquid tank.

As shown in FIG. 1, the etching apparatus 100 of the present invention may be composed of an etching processing part 14 and an etching solution supply part 13.

The etching processing unit 14 may include a vacuum adsorption platform (platform) 2, a supply nozzle 3, and an etching liquid recovery cup 19. In this case, the supply nozzle 3 may be provided not only on the front side but also on the back side, so that both sides of the wafer can be etched at the same time.

The etching solution supply unit 13 may include: an etching solution tank 6; a liquid feeding pump 18 to send the acid etching solution from the etching solution tank 6 to the etching processing part; and a recovery mechanism 21 to recover the acid etching solution from the etching solution recovery cup 19 to The recovery pump 20 of the etching solution tank 6; and the drainage/liquid supply mechanism 17.

In the etching solution tank 6, an acid etching solution 8 flows, and the recovered acid etching solution flows into an acid etching solution that has dissolved a predetermined amount of Si. The liquid discharge/liquid supply mechanism 17 may have: a liquid supply mechanism 22 consisting of a liquid supply tank 11 and a liquid supply pump 12 that sends the acid etching liquid from the liquid supply tank 11 to the etching liquid tank 6; and a liquid discharge mechanism 23, It is composed of a liquid drain treatment unit 16 and a drain pump 15 that takes out the acid etching solution from the etching liquid tank 6 of the etching solution supply unit 13 and sends it to the drain liquid treatment unit 16. In the liquid supply tank 11, what is necessary is just to load the acid etching liquid whose Si is in an undissolved state and which has the same component concentration as the acid etching liquid 8 charged in the etching liquid tank 6.

The surface or the back surface of the silicon wafer 1 is set to face upward and horizontally arranged in the center of the vacuum suction platform 2, and the silicon wafer 1 can be held on the vacuum suction platform 2 connected to the vacuum source 10 by vacuum suction.

The vacuum suction platform 2 is made up of a rotation unit composed of a θ-axis motor and a θ-spindle, which are not shown below the platform, and the center of the vacuum suction table 2 can be rotated in the θ direction in the figure as a rotation axis.

Next, taking the case of using the etching apparatus 100 of FIG. 1 as an example, the etching method of the silicon wafer of the present invention will be described. FIG. 2 illustrates the processing flow of the silicon wafer etching method of the present invention.

The etching method of the silicon wafer of the present invention includes a spin etching step in which the acid etching solution stored in the etching solution tank is supplied to the surface and/or back surface of the silicon wafer through a supply nozzle (Step 1 in FIG. 2), While rotating the silicon wafer, the supply range of the acid etching solution is expanded to the entire surface of the silicon wafer to perform acid etching (etching process, step 2 in FIG. 2). The acid etching solution can be a mixed solution containing hydrofluoric acid and nitric acid, but it can also be mixed by appropriately combining acetic acid, sulfuric acid, or phosphoric acid. Such a mixed solution is suitable for rotary etching of silicon wafers. The mixing ratio can be an acid etching solution prepared by mixing 1 to 80% of hydrofluoric acid and 10 to 80% of nitric acid by mass%, or it can be mixed with acetic acid such as 10 to 30% and sulfuric acid such as 10 to 80% by mass. 25%, phosphoric acid, for example, 10-50%, mixed in any ratio.

At this time, as shown in FIG. 1, the acid etching solution 8 is supplied from the etching solution tank 6 of the etching solution supply part 13 to the supply nozzle 3 located above the vacuum adsorption platform 2 via the liquid feeding pump 18, and the acid etching solution 8 can be supplied To hold and rotate the silicon wafer 1 on the vacuum suction platform 2. During the supply of the acid etching solution 8, as shown by the arrow 4 (moving direction of the supply nozzle) in FIG. 1, the supply nozzle 3 generally passes through the center of the silicon wafer 1 and performs linear reciprocating movement in the radial direction of the silicon wafer 1. .

Furthermore, in the silicon wafer etching method of the present invention, the continuous processing of a plurality of silicon wafers is performed by repeating the above-mentioned spin etching step. In addition, the continuous processing includes the step of recovering the acid etching solution used in the spin etching step and returning it to the etching solution tank to use it as the acid etching solution again (Step 3 in FIG. 2).

The acid etching solution 8 supplied on the silicon wafer 1 moves on the silicon wafer 1 following the rotation of the silicon wafer 1, and forms droplets 5 from the outer periphery of the silicon wafer 1 and is discharged from the wafer.

The discharged droplets 5 enter the etching solution recovery cup 19 and can be recovered to the etching solution tank 6 by the recovery pump 20. The recovered acid etching solution recovered in the etching solution tank 6 becomes the acid etching solution 8 again.

After satisfying the predetermined etching margin, after the etching process is completed, stop the supply of the acid etching solution 8 from the etching solution tank 6 (step 4 in FIG. 2), and supply water 9 from the water supply source 7 to the supply nozzle 3, and the water 9 is supplied to the silicon wafer 1 held and rotated on the vacuum suction platform 2 (cleaning, step 6 of FIG. 2).

The water 9 supplied to the silicon wafer 1 moves on the silicon wafer 1 following the rotation of the silicon wafer 1, and while replacing the acid etchant 8 remaining on the silicon wafer 1 with water 9, The outer peripheral part of the circle 1 becomes the droplet 5 and is discharged.

In addition, the method for manufacturing a silicon wafer of the present invention includes a drain/supply step of discharging a predetermined amount of the recovered acid etching solution, and then supplying a predetermined amount of a new acid etching solution (Step 5 in FIG. 2). Then, the acid etching solution after the liquid discharge/liquid supply step is used in the spin etching step in the continuous processing of multiple silicon wafers.

After the supply of the acid etching solution 8 is stopped, an appropriate amount of the recovered acid etching solution can be discharged from the etching solution tank 6 to the draining treatment part 16 via the drain pump 15 of the draining/liquid supply mechanism 17. Thereafter, an appropriate amount of new acid etching solution can be supplied to the etching solution tank 6 from the liquid supply tank 11 of the liquid discharge/liquid supply mechanism 17 via the liquid supply pump 12. Also, after the replacement of water by the acid etching solution 8 on the silicon wafer 1 is completed, the water supply 9 from the water supply source 7 is stopped, and the silicon wafer 1 is rotated at a high speed, so that all the water on the silicon wafer 1 can be scattered. , And a dried silicon wafer 1 is obtained (cleaning and drying, step 6 in Figure 2).

At this time, in the liquid discharge/liquid supply step, it is preferable to determine the amount of liquid discharged and the amount of liquid supplied based on the amount of Si dissolved in the recovered acid etching solution. The amount of dissolved Si can be calculated from a predetermined etching margin of the silicon wafer, but it can also be obtained by a mechanism for measuring the amount of dissolved Si provided in an etching bath or the like without particular limitation. If this is the case, by performing a proper amount of draining/supplying of the amount of Si dissolved by the molar calculation of the amount of Si dissolved by etching, etc., it is possible to more reliably prevent the acid etching solution The increase in the amount of Si dissolved and the resulting change in the dynamic viscosity of the acid etching solution.

In addition, in order to keep the amount of Si dissolved constant, it is preferable to discharge a fixed amount of the recovered acid etching solution in which Si has been dissolved, and then supply the same amount of a new acid etching solution that has not dissolved Si. In this way, the amount of Si dissolution can be returned to the amount of Si dissolution before the increase due to etching.

In addition, the liquid discharge/liquid supply step only needs to be performed during the continuous processing of a plurality of silicon wafers, and the timing is not particularly limited. By maintaining a fixed amount of Si dissolved in each rotary etching step of the etching process, the The shape quality remains fixed. For example, in each single-chip etching process, the amount of liquid draining/supplying in accordance with the etching margin can be performed to keep the amount of Si dissolved in the acid etching solution constant. In addition, the consumption of hydrofluoric acid and nitric acid is proportional to the amount of dissolved Si. Therefore, the amount of dissolved Si in the acid etching solution is kept constant by draining/supplying, which is equivalent to making the amount of hydrogen fluorine in the same acid etching solution The acid concentration and nitric acid concentration are kept fixed.

In addition, the amount of Si dissolved in acid etching of the spin etching method is preferably 12 g/L or less. If it is in such a range, the characteristics of the fluid will not change too much, and the processed wafer shape in the impingement jet area formed directly under the nozzle for supplying the acid etching liquid is good.

Regarding the etching margin of each silicon wafer, it is usually appropriate to remove 3-8μm of the processed deterioration layer introduced to the surface of the silicon wafer during the polishing process or surface grinding process of the previous process as a single-sided etching Margin. For example, in the cleaning after the spin etching step, each time the amount of liquid draining/supplying based on the amount of Si molar calculated from the etching margin is performed, it can be performed when the amount of dissolved Si is kept at a fixed amount The continuous etching process below makes the continuous process more reliable while maintaining the etching rate and the shape after etching.

Furthermore, in the present invention, in the spin etching step, it is preferable to change the rotation speed of the silicon wafer to perform acid etching according to the amount of Si dissolved in the acid etching solution in the etching solution tank. This step can be performed as described in other aspects described later.

(Other aspects) When performing acid etching of a silicon wafer using a spin etching method, the used etching solution is usually recovered and used as an etching solution again. Therefore, when the silicon wafer is subjected to acid etching, the amount of dissolved Si contained in the etching solution increases according to the number of processed wafers. In addition, since the increase in the amount of Si dissolved means that the etching chemical species contained in the etching solution decreases, the average etching rate decreases. Therefore, during continuous processing, the reduction of the average etching speed cannot be avoided.

In addition, the wafer etching rate in rotary etching has an in-plane distribution of the wafer according to the processing conditions and the fluid characteristics of the etching solution. This distribution changes when only one of the processing conditions and fluid characteristics changes. Therefore, when performing a rotary etching process with a change in the amount of dissolution of Si as described above, not only the average etching rate but also the change in the etching rate distribution within the wafer surface should be considered. In the past, hydrofluoric acid replenishment was generally performed during continuous processing. However, this method has a problem that although it can cope with a decrease in the average etching rate, it cannot cope with a change in the etching rate distribution in the wafer surface.

The present invention is made in view of the above situation, and another object of the present invention is to provide a silicon wafer etching method, even if the amount of Si dissolved in an acid etching solution changes, the change in the etching rate distribution in the wafer surface can be suppressed, and the etching The shape of the subsequent wafer is maintained well.

In order to solve the above-mentioned other problem, the present invention provides a silicon wafer etching method, which includes a spin etching step in which an acid etching solution is supplied to the surface and/or back surface of the silicon wafer through a supply nozzle , While rotating the silicon wafer, thereby expanding the supply range of the acid etching solution to the entire surface and/or back surface of the silicon wafer for acid etching; In the spin etching step, the rotation speed of the silicon wafer is changed according to the amount of Si dissolved in the acid etching solution in the etching solution tank to perform acid etching.

If so, the rotation speed of the silicon wafer is changed by the amount of Si dissolved in the acid etching solution, thereby suppressing the change in the etching rate distribution within the wafer surface due to the increase in the amount of Si dissolved. In addition, even if the amount of Si dissolved increases, the wafer shape after etching can be made good.

At this time, by repeating the spin etching step, continuous processing of multiple silicon wafers is performed, In the continuous processing, it is preferable to recover the acid etching solution used in the spin etching step and return it to the etching solution tank storing the acid etching solution to be used again as the acid etching solution.

According to this method, even during continuous processing with a change in the amount of dissolved Si, the change in the shape of the silicon wafer can be minimized.

In addition, as the acid etching solution, a mixed solution containing hydrofluoric acid and nitric acid, or a mixed solution in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is further added to it is suitable.

If it is such a mixed solution, it can be applied to the rotary etching of silicon wafers.

In such a silicon wafer etching method, the rotation speed of the silicon wafer is changed by the amount of Si dissolved in the acid etching solution, thereby suppressing changes in the etching rate distribution in the wafer surface. In addition, even if the amount of Si dissolved increases, the wafer shape after etching can be made good.

As described above, in the acid etching using the spin etching method, when the dissolved amount of Si in the acid etching solution changes, there is a problem that the etching rate distribution in the wafer surface changes.

When the dissolved amount of Si in the acid etching solution increases, not only does the etching reaction chemical species contained in the acid etching solution decrease, but the dynamic viscosity of the acid etching solution also decreases. Therefore, in the rotary acid etching in which the fluid characteristics of the acid etching solution cannot be ignored, the increase in the amount of Si dissolved not only reduces the average etching rate, but also changes the distribution of the etching rate in the plane.

Generally, since the silicon wafer in the rotary etching process rotates at a fixed angular velocity, the etching speed when using a diffusion-limited acid etching solution increases at the outer periphery of the wafer with a faster peripheral speed. Therefore, in general, the etching margin increases toward the outer periphery of the wafer.

Here, as the amount of dissolved Si increases, the dynamic viscosity of the acid etching solution decreases. Therefore, the average flow rate of the acid etching solution in the region where the peripheral velocity of the wafer is fast decreases compared to when the amount of dissolved Si decreases. Therefore, the etching margin of the outer periphery of the wafer is reduced compared to when the amount of dissolved Si is small.

In addition, in rotary etching, generally, the rotation center of the wafer and the position of the nozzle that supplies the acid etching solution to the wafer are the same, but in the vicinity, the etching rate is affected by the impinging jet formed directly under the nozzle. The center of the impinging jet has a stagnation point. At the stagnation point, the flow velocity of the acid etching solution in the direction parallel to the wafer surface is theoretically 0 μm/s.

Generally, the stagnation area is a negligible size, and the flow rate of the acid etching solution is immediately increased by the peripheral speed of the wafer, so the etching margin does not appear to decrease. However, if the amount of Si dissolved increases and the dynamic viscosity of the acid etching solution decreases, it is difficult to increase the average flow rate of the acid etching solution even with the peripheral speed. Therefore, the etching speed becomes slower than when the amount of Si dissolved is small. Therefore, the area The etching margin is reduced.

That is, even if an acid etching solution with the same processing conditions and the same composition is used, due to the above reasons, the etching rate distribution in the wafer surface changes due to changes in the etching rate around the periphery and center of the silicon wafer. The difference in the amount of dissolving Si in the wafer results in different wafer shapes after rotary etching.

As a means to respond to such changes in wafer shape, the wafer rotation speed is controlled depending on the amount of Si dissolved. Specifically, in an acid etching solution with a small amount of Si dissolved and a large dynamic viscosity, the wafer rotation speed is set to a low rotation speed for etching, while in an acid etching solution with a large amount of Si dissolved and a small dynamic viscosity, the crystal The circular rotation speed is set to a high rotation and the etching is performed, whereby the change in the wafer shape due to the amount of dissolution of Si can be suppressed to the minimum.

Hereinafter, this aspect is described in detail, but the present invention is not limited to this description.

FIG. 10 is a schematic diagram of a general etching device used in the spin etching method. Specifically, for example, a rotary etching machine MSE-7000EL-MH manufactured by Sanyi Semiconductor Industry Co., Ltd. can be used.

Generally speaking, the etching apparatus 200 is composed of an etching processing unit 14 and an etching solution supply unit 13.

The etching processing unit 14 may include a vacuum suction platform 2 and a supply nozzle 3. In addition, the etching solution supply unit 13 may include an etching solution tank 6 and a liquid feeding pump 18 to send the acid etching solution 8 from the etching solution tank 6 to the etching processing unit 14.

The surface or the back of the silicon wafer 1 is set to face upwards and horizontally arranged at the center of the vacuum suction platform 2, and the silicon wafer 1 can be held on the vacuum suction platform 2 connected to the vacuum source 10 by vacuum suction.

The vacuum suction platform 2 is a rotation unit composed of a θ-axis motor and a θ spindle, which are not shown in the figure, located below the platform, and the center of the vacuum suction platform 2 can be rotated in the θ direction of the figure as a rotation axis.

Next, taking the case of using the etching apparatus 200 of FIG. 10 as an example, the etching method of the silicon wafer in this aspect is described.

In the etching method of the silicon wafer of this aspect, a spin etching step is included in which the acid etching solution 8 stored in the etching solution tank 6 is supplied to the surface and/or back surface of the silicon wafer through a supply nozzle. The silicon wafer rotates to expand the supply range of the acid etching solution to the entire silicon wafer 1 for acid etching.

In the spin etching step, the acid etching solution 8 is supplied from the etching solution tank 6 of the etching solution supply part 13 to the supply nozzle 3 located above the vacuum adsorption platform via the liquid feeding pump 18, and the acid etching solution 8 can be supplied to the holding and rotating On the silicon wafer 1 on the vacuum suction platform 2.

During the supply of the acid etching solution 8, as shown by the arrow 4 (moving direction of the supply nozzle) in FIG. 10, the supply nozzle 3 generally passes through the center of the silicon wafer 1 and moves linearly back and forth in the radial direction of the silicon wafer 1 .

The acid etching solution 8 supplied to the silicon wafer 1 moves on the silicon wafer 1 following the rotation of the silicon wafer 1, and flutters and falls from the outer periphery of the silicon wafer 1 as droplets 5, and is removed from the etching processing part. discharge.

At this time, in this aspect, the rotation speed of the silicon wafer is changed according to the amount of dissolved Si contained in the acid etching solution to perform acid etching.

As mentioned above, even if the acid etching solution with the same processing conditions and the same composition is used, the etching rate distribution in the wafer surface changes due to the change in the etching rate at the periphery and near the center of the silicon wafer. Therefore, when the Si in the acid etching solution is dissolved The amount is different, resulting in different wafer shapes after rotary etching. In this aspect, the rotation speed of the silicon wafer is changed by the amount of Si dissolved in the acid etching solution, thereby suppressing the change in the etching rate distribution within the wafer surface due to the increase in the amount of Si dissolved. In addition, even if the amount of Si dissolved increases, the wafer shape after etching can be maintained well.

That is, in the case of using an acid etching solution with a small amount of dissolved Si and a high dynamic viscosity, in order to make the flow rate of the acid etching solution on the wafer moderate, the wafer rotation speed is set to a low rotation speed, and the amount of dissolved Si is used In the case of an acid etching solution with a large and low dynamic viscosity, in order to suppress a drop in the flow rate of the acid etching solution on the wafer, the wafer rotation speed can be set to a high rotation speed.

The wafer rotation speed can be changed, for example, the amount of Si dissolved is 6g/L. When the amount of Si dissolved is less than 6g/L, it can be set to a rotation speed of less than 1300rpm. When the amount of Si dissolved is 6g/L or more, it can be set to 1300rpm or more. Speed and so on. However, since the appropriate amount of Si dissolution differs depending on the processing conditions or the composition of the acid etching solution, the amount of Si dissolution for changing the wafer rotation speed is not limited to 6 g/L. In addition, the wafer rotation speed before and after the change may be appropriately determined depending on the processing conditions or the composition of the acid etching solution.

After the predetermined etching margin is satisfied, after the etching process is completed, the supply of the acid etching solution 8 from the etching solution tank 6 is stopped, and the water 9 is supplied from the water supply source 7 to the supply nozzle 3, and the water 9 can be supplied to the holding and rotating Vacuum adsorption platform 2 on silicon wafer 1.

The water 9 supplied to the silicon wafer 1 moves on the silicon wafer 1 following the rotation of the silicon wafer 1, and while replacing the acid etching solution 8 remaining on the silicon wafer 1 with water 9, The outer peripheral part of the circle 1 becomes the droplet 5 and is discharged.

After the replacement of water by the acid etching solution 8 on the silicon wafer 1 is completed, the water supply 9 from the water supply source 7 is stopped. By rotating the silicon wafer 1 at a high speed, all the water on the silicon wafer 1 can be scattered. A dried silicon wafer 1 is obtained.

Moreover, in this aspect, the continuous processing of a plurality of silicon wafers is performed by repeating the above-mentioned spin etching step. In the continuous processing, the acid etching solution used in the above-mentioned spin etching step is preferably recovered and used Return to the etching solution tank and use it as an acid etching solution again. According to this method, even during continuous processing with a change in the amount of dissolved Si, the change in the shape of the silicon wafer can be minimized.

The droplets 5 of the acid etching solution discharged from the outer periphery of the silicon wafer 1 can be recovered to the etching solution tank 6 by the etching solution recovery mechanism 24. In this way, the recovered acid etching solution can be used as the acid etching solution 8 again.

In this aspect, the amount of dissolution of Si can be calculated from the etching margin of each silicon wafer 1, for example, to calculate the cumulative amount of dissolution of Si during continuous processing. When the appropriate amount of dissolution of Si is reached, the wafer rotation speed is changed. In the rotary etching process at the time of continuous processing with a change in the amount of dissolved Si, continuous processing can be performed that minimizes the change in the shape of the wafer after processing. In addition, the method for calculating the amount of dissolution of Si is not particularly limited, and it can also be obtained by a mechanism 25 for measuring the amount of dissolution of Si provided in an etching solution tank, etc., and the amount of dissolution of Si can be changed according to the amount of dissolution of Si. Rotating speed. In addition, depending on the amount of Si dissolved, the rotation speed of the silicon wafer can be increased in proportion to this value.

In addition, the acid etching solution used in this aspect may be a mixed solution containing hydrofluoric acid and nitric acid, but it may also be mixed by appropriately combining acetic acid, sulfuric acid, or phosphoric acid. Such a mixed solution can be applied to the rotary etching of silicon wafers. The mixing ratio can be an acid etching solution prepared by mixing 1 to 80% of hydrofluoric acid and 10 to 80% of nitric acid by mass%, or acetic acid such as 10 to 30% and sulfuric acid such as 10 to 25% in mass%. , Phosphoric acid, such as 10-50%, is mixed in any ratio.

In addition, in the above, a case where the single side of a silicon wafer is subjected to rotary etching is described as an example. However, the present invention is not limited to this. The acid etching solution can be supplied not only from the top surface, but also from the bottom surface, and the front and back surfaces are simultaneously performed. Etching. [Example]

The following examples and comparative examples illustrate the present invention in more detail, but the present invention is not limited to the following examples.

[Example] Using the etching device shown in FIG. 1, in accordance with the processing flow of FIG. 2, while draining and supplying the acid etching solution in the etching solution tank, 100 silicon wafers are continuously processed. At this time, the liquid discharge/liquid supply step is performed at the end of the spin etching step for each silicon wafer. The acid etching solution used in the examples is a mixed solution of hydrofluoric acid and nitric acid, and the mixing ratio is 4% by mass% hydrofluoric acid and 47% nitric acid (the remaining part less than 100% is water). An acid etching solution with a Si dissolution amount of 10 g/L was used. As the acid etching solution for the first sheet, an acid etching solution containing no Si atoms was used as a new acid etching solution for supply. The amount of liquid to be discharged and supplied is the same amount, which is determined based on the amount of Si dissolved obtained from the etching margin.

Figures 3, 4, and 5 respectively show the changes in the etching rate, the amount of dissolved Si, and the shape of the wafer after processing by repeating the spin etching step while draining/supplying the liquid for continuous processing. Variety.

[Comparative example] Using a generally used etching device that does not have a liquid discharge mechanism or a liquid supply mechanism, 100 silicon wafers are continuously etched without liquid discharge or liquid supply. The acid etching solution used in the comparative example is a mixed solution of hydrofluoric acid and nitric acid, and the mixing ratio is 4% by mass% hydrofluoric acid and 47% nitric acid (the remaining part less than 100% is water.). An acid etching solution with a Si dissolution amount of 10 g/L was used as the acid etching solution for the first sheet, and continuous processing was started.

In FIGS. 6, 7, and 8, respectively, the change of the etching rate, the change of the amount of dissolved Si, and the processed wafer during continuous processing by repeated acid etching in a rotating manner without draining/supplying liquid are shown. Changes in shape.

As shown in Fig. 3, Fig. 4, and Fig. 5, when draining/supplying liquid has been performed, the amount of dissolution of Si remains approximately constant, and the variation of the etching rate during the continuous 100 wafer processing is within ±7%. Regarding the shape of the processed wafer, the flatness TTV (Total Thickness Variation) of the processed first, 50th, and 100th wafers is equivalent. As shown in Fig. 6, Fig. 7, and Fig. 8, when the liquid discharge/supply is not performed, as the amount of Si dissolved monotonously increases, the etching rate monotonously decreases. The etching rate in the processing of 100 pieces is approximately that of the first piece. 70%. In addition, the shape of the processed wafer changes as the number of processed wafers increases, and the processed TTV of the 100th wafer deteriorates by 2.6 times compared with the first wafer.

From the foregoing, it can be seen that if the silicon wafer etching method and the etching apparatus of the present invention are used, by performing liquid discharge/liquid supply, a fixed etching rate and processed wafer shape can be obtained even during continuous processing.

[Reference Example] The etching device shown in FIG. 10 was used to perform etching processing of the silicon wafer. At this time, using acid etching solutions with different Si dissolving amounts, the silicon wafers are processed at low rotation speeds, specifically 300 rpm and 800 rpm, and high rotation speeds, specifically 1800 rpm and 2500 rpm. Shows the change in flatness caused by the amount of dissolved Si when the rotation speed of the silicon wafer is changed. The so-called flatness here is the margin P-V (Peak-Valley; peak-valley) in the surface of the silicon wafer. At this time, the acid etching solution uses a mixed solution of hydrofluoric acid and nitric acid (4% by mass% hydrofluoric acid, 47% nitric acid, and the remaining part less than 100% is water), and the amount of the etching solution is 2.5L/m, The acid etching solution temperature is 24°C for processing.

As shown in Figure 9, if the wafer is fixed at a low rotation speed such as 300rpm or 800rpm for processing, the flatness of the wafer will deteriorate to around 1.0μm in this example when the amount of Si dissolved increases; When processing at a high rotation speed, for example, 1800 rpm or 2500 rpm, the wafer flatness is opposite to the low rotation speed. When the amount of dissolution of Si is small, it deteriorates to around 1.0 μm in this example.

Therefore, according to the example shown in FIG. 9, it can be seen that when the dissolved amount of Si in the acid etching solution is less than 6g/L, it is changed to a low speed such as 300rpm or 800rpm; when the amount of dissolved Si is greater than 6g/L, it is changed to a rotation speed, for example. Etching at a high rotation speed like 1800rpm or 2500rpm can make the wafer flatness less than 0.7μm regardless of the amount of dissolved Si.

It can be seen from the above that the method of the present invention uses the dissolved amount of Si contained in the acid etching solution to change the rotation speed of the silicon wafer, thereby suppressing the etching rate in the wafer surface caused by the increase in the amount of dissolved Si The distribution change can maintain good wafer flatness even if the amount of Si dissolved in the acid etching solution changes.

In addition, the present invention is not limited to the above-mentioned embodiment. The above-mentioned embodiment is only an example, and as long as it has substantially the same structure as the technical idea described in the scope of the patent application of the present invention, and has the same effect, it is included in the technical scope of the present invention.

1: Silicon wafer 2: Vacuum adsorption platform 3: supply nozzle 4: arrow 5: droplets 6: Etching solution tank 7: Water supply source 8: Acid etching solution 9: water 10: Vacuum source 11: Liquid supply tank 12: Liquid supply pump 13: Etching solution supply part 14: Etching Department 15: Discharge pump 16: Drainage treatment department 17: Drain/liquid supply mechanism 18: Liquid delivery pump 19: Etching liquid recovery cup 20: Recovery pump 21: Recycling agency 22: Liquid supply mechanism 23: Drainage mechanism 24: Etching solution recovery mechanism 25: Institution 100: Etching device 200: Etching device

[Fig. 1] A schematic diagram of an embodiment of the etching apparatus of the present invention to which the liquid supply and discharge mechanism is connected. [Fig. 2] A flowchart of an embodiment of the silicon wafer etching method using the present invention. [Fig. 3] A graph showing the transition of etching rate during continuous processing by repeating the spin etching step while draining and supplying liquid. [Fig. 4] A graph showing the transition of the amount of Si dissolved during continuous processing by repeating the spin etching step while draining and supplying liquid. [Fig. 5] A graph showing the change in the shape of the wafer after processing when the spin etching step is repeated while draining/supplying liquid for continuous processing. [Fig. 6] A graph showing the transition of the etching rate during continuous processing by repeated acid etching in a rotating system without draining and supplying liquid. [Fig. 7] A graph showing the transition of the amount of Si dissolved in continuous processing by repeated acid etching in a rotating system without draining/supplying. [Fig. 8] A graph showing the change in the shape of the wafer after processing when the rotary acid etching is repeated without liquid discharge/liquid supply for continuous processing. [Figure 9] A graph of the change in flatness caused by the amount of Si dissolved when the rotation speed of the silicon wafer is changed. [Fig. 10] A schematic diagram of a general etching device used in the spin etching method.

1: Silicon wafer

2: Vacuum adsorption platform

3: supply nozzle

4: arrow

5: droplets

6: Etching solution tank

7: Water supply source

8: Acid etching solution

9: water

10: Vacuum source

11: Liquid supply tank

12: Liquid supply pump

13: Etching solution supply part

14: Etching Department

15: Discharge pump

16: Drainage treatment department

17: Drain/liquid supply mechanism

18: Liquid delivery pump

19: Etching liquid recovery cup

20: Recovery pump

21: Recycling agency

22: Liquid supply mechanism

23: Drainage mechanism

100: Etching device

Claims (10)

A method for etching a silicon wafer includes a rotary etching step. The rotary etching step is to supply the acid etching solution stored in an etching solution tank to the surface and/or back surface of the silicon wafer through a supply nozzle, while making the silicon crystal Circular rotation, thereby expanding the supply range of the acid etching solution to the entire surface and/or back surface of the silicon wafer for acid etching; By repeating the rotary etching step, continuous processing of multiple silicon wafers is performed; In this continuous processing, the following steps are included: In a recovery step, the acid etching solution used in the spin etching step is recovered, and returned to the etching solution tank to be used as an acid etching solution again; and In the draining/liquid supply step, the recovered acid etching solution is discharged in a predetermined amount, and then a predetermined amount of new acid etching solution is supplied; The acid etching solution after the liquid discharge/liquid supply step is used in the spin etching step. Such as the etching method of silicon wafer of claim 1, in which, In the liquid drain/liquid supply step, the amount of the liquid drain and the amount of the liquid supplied are determined according to the amount of Si dissolved in the recovered acid etching solution. Such as the etching method of silicon wafer of claim 1 or 2, where, In the liquid discharge/liquid supply step, the amount of the liquid discharged and the amount of the liquid supplied are the same amount. Such as the etching method of silicon wafer of claim 1 or 2, in which, In the spin etching step, the rotation speed of the silicon wafer is changed according to the amount of Si dissolved in the acid etching solution in the etching solution tank to perform acid etching. Such as the etching method of silicon wafer of claim 3, wherein: In the spin etching step, the rotation speed of the silicon wafer is changed according to the amount of Si dissolved in the acid etching solution in the etching solution tank to perform acid etching. Such as the etching method of silicon wafer of claim 1 or 2, in which, A mixed liquid containing hydrofluoric acid and nitric acid, or a mixed liquid in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is added thereto is used as the acid etching liquid. Such as the etching method of silicon wafer of claim 3, wherein: A mixed liquid containing hydrofluoric acid and nitric acid, or a mixed liquid in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is added thereto is used as the acid etching liquid. Such as the etching method of silicon wafer of claim 4, wherein: A mixed liquid containing hydrofluoric acid and nitric acid, or a mixed liquid in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is added thereto is used as the acid etching liquid. Such as the etching method of silicon wafer of claim 5, wherein, A mixed liquid containing hydrofluoric acid and nitric acid, or a mixed liquid in which at least any one of acetic acid, phosphoric acid, and sulfuric acid is added thereto is used as the acid etching liquid. An etching device comprising: The supply nozzle is used to supply the acid etching solution stored in the etching solution tank to the surface and/or back surface of the silicon wafer: The platform, by holding and rotating the silicon wafer, expands the supply range of the acid etching solution to the entire surface and/or back of the silicon wafer for acid etching; and A recovery mechanism for recovering the acid etching solution used in the acid etching and returning it to the etching solution tank; The etching device further includes: A liquid drain mechanism for draining a predetermined amount of the acid etching solution from the etching solution tank; and The liquid supply mechanism is used to supply a predetermined amount of new acid etching solution to the etching solution tank.

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