JP2875722B2 - Semiconductor wafer etching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer etching apparatus for maintaining the flatness (TTV) of a wafer by subjecting a silicon wafer or the like to etching with a mixed acid (hydrofluoric acid, nitric acid, acetic acid, water) solution. About.

[0002]

2. Description of the Related Art A silicon wafer is manufactured by sequentially lapping, etching, and polishing a thin disk obtained by slicing a silicon single crystal. When this polishing step is performed by so-called mechanochemical polishing, a submicron silica sol dispersed in an alkaline aqueous solution is used as an abrasive in order to minimize processing scratches on the finishing mirror surface, and the wafer is wet and in a soft porous state. Light weight (eg, 5
0-100 g / cm ² · wafer). Therefore, if the shape accuracy of the wafer surface before the polishing step is poor, it is not possible to expect any further mirror shape accuracy. Therefore, in a highly integrated wafer, there is a strong demand for improving the surface shape accuracy in an etching process.

In such an etching step, etching is performed in a diluted mixed aqueous solution of hydrofluoric acid, nitric acid, water or acetic acid. In general, when the concentration of nitric acid is high, the diffusion is rate-determined. Surface reaction rate-determining,
Both water and acetic acid are believed to act as diluents. Also, it is estimated that the macro shape accuracy is maintained under the condition of diffusion control but is inferior to the micro shape accuracy, and conversely, the micro shape accuracy is improved but the macro shape accuracy is deteriorated under the condition of the surface reaction control. Have been.

[0004]

However, conventionally, in etching a wafer such as silicon, a carrier containing a large number of wafers is rotated in a mixed acid solution having a predetermined chemical composition filled in one etching tank. After immersion and etching, the immersion was performed by immersion in a washing tank. For this reason, the fine structure formed on the wafer surface by the treatment with one kind of mixed acid solution is uniquely determined, and the etching is performed at the expense of either the macro or micro shape accuracy of the silicon wafer surface. We had to choose the conditions. Therefore, the obtained wafer could not satisfy both macro and micro shape accuracy. In addition, in the conventional etching method, the flatness (TTV) of the wafer may be deteriorated due to the reaction heat due to the increase in the wafer diameter.

[0005] The present invention has been made in view of such problems of the prior art, and it is an object of the present invention to provide an etching apparatus capable of maintaining the flatness of a wafer.

[0006]

In order to achieve the above object, an apparatus for etching a semiconductor wafer according to the present invention comprises:
Upon sequentially immersing the semiconductor wafer in two or more etching tanks filled with an etchant and etching the semiconductor wafer, a wafer magazine containing the semiconductor wafer, and a plurality of the etchant filled and arranged in parallel with each other An etching tank, a cleaning tank slidably provided along each of the etching tanks, and a transfer mechanism for transferring the wafer magazine between each of the etching tanks and the cleaning tank. I have.

[0007] The transfer mechanism is provided on a slide table provided with the cleaning tank, and swings between the cleaning tank and each of the etching tanks by a first drive unit. A hanger rotatably supported about the tip of the wafer, and a second rotating the wafer magazine held by the hanger with respect to the hanger.
And a transmission mechanism.

[0008]

The two or more etching tanks are divided into two types, one of which is filled with an etchant having a diffusion-controlled chemical composition, and the other is filled with an etchant having a stirring-controlled chemical composition. Then, etching is first performed with an etchant having a diffusion-controlled chemical composition, and then etching is performed with an etchant having a stirring-controlled chemical composition. Accuracy, that is, the flatness created in the lapping process is maintained. After that, the surface reaction is rate-controlled by the action of the stirring rate-controlled etchant, and the microscopic shape accuracy of the semiconductor wafer is improved, and an arbitrary roughness can be selected. At the same time, the amount of heat generated by the chemical reaction can be reduced by dividing the etching, and even if the wafer diameter increases, there is no possibility that the flatness (TTV) is adversely affected.

For this reason, in the etching treatment apparatus of the present invention, while the etching tanks satisfying the two types of etchants are provided side by side, the cleaning tank is slidably provided along these etching tanks. Therefore, the semiconductor wafer to be etched is stored in a wafer magazine, and the wafer magazine is held by a hanger and immersed in a first etching tank filled with a diffusion-controlled etchant by a transfer mechanism. The wafer magazine is rotated by the second drive unit and the transmission mechanism in the etching tank to promote agitation of the semiconductor wafer and the etchant.

When the etching in the first etching tank is completed, the arm is swung by the first drive unit, and the wafer magazine held by the hanger is immersed in the cleaning tank.
As a result, a chemical reaction caused by a diffusion-controlled etchant can be suppressed. In the cleaning tank, as in the first etching tank, the wafer magazine is rotated by the second drive unit and the transmission mechanism to promote the agitation of the semiconductor wafer and the cleaning liquid.

Then, the slide base is slid to the second etching tank filled with the stirring-controlled etchant, the arm is swung by the first drive unit, and the wafer magazine held by the hanger is moved to the second etching tank. Soak in In this etching tank, the wafer magazine is rotated by the second drive unit and the transmission mechanism to promote agitation of the semiconductor wafer and the etchant, similarly to the first etching tank and the cleaning tank.

Further, when the etching in the second etching bath is completed, the arm is swung by the first drive unit, and the wafer magazine held by the hanger is immersed in the cleaning bath. As a result, it is possible to suppress the chemical reaction caused by the stirring-controlled etchant. In the cleaning tank,
As in the first and second etching tanks and the cleaning tank, the wafer magazine is rotated by the second drive unit and the transmission mechanism to promote agitation of the semiconductor wafer and the cleaning liquid.

As described above, in the etching apparatus of the present invention, a plurality of etching tanks are provided side by side, and a cleaning tank for suppressing a chemical reaction of etching is provided slidably with respect to each etching tank and shared. Therefore, the size of the processing apparatus can be reduced, and the transport time can be reduced.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an etching apparatus according to one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. FIG. 4 is a sectional view showing the transfer mechanism according to the embodiment.

First, in the etching apparatus of this embodiment, a first etching tank 1 and a second etching tank 2 are provided side by side, and a slide base 3 is movable along these two etching tanks 1 and 2. It is provided in. The first and second etching tanks 1 and 2 are respectively composed of tank bodies 1a and 2a filled with an etchant, and overflow tanks 1b and 2b for draining the etchant overflowing from the tank body. The new etchant sent from the tank 4 is introduced from the bottoms of the tank bodies 1a and 2a shown in FIG. 2, while the etchant overflowing into the overflow tanks 1b and 2b is returned to the respective etchant exchange tanks 4 via the return pipe 5. Is returned to.

A plurality of wheels 8 are mounted on the slide base 3 so as to be able to reciprocate linearly by the operation of a fluid cylinder 7 fixed to the apparatus main body 6, and the wheels 8 are provided on rails provided on the apparatus main body 6. 9 so that the slide base 3 follows the track of the rail 9
The cleaning tank 10 provided on the slide base 3 reciprocates between a position close to the first etching tank 1 and a position close to the second etching tank 2.

Semiconductor wafer W to be etched
Is processed in a state of being stored in the wafer magazine 11, specifically, as shown in FIG.
The wafer W is stored between the partition plates provided therebetween in parallel with the partition plate, and the falling off of the wafer is prevented by using both end plates 11a and fixing bars for fixing the plurality of partition plates. Further, a support rod 11b is provided so as to protrude from the end plate 11a, and the wafer magazine 11 can be gripped by the hanger 12 by locking the support rod 11b in a notch formed in a hanger 12 described later.
A gear 11c is provided outside the right end plate shown in FIG. 3 in order to rotate the wafer magazine 11 while being held by the hanger 12 and to promote agitation of the wafer W with the etchant and the cleaning liquid. I have. The rotation mechanism of the wafer magazine 11 will be described later.

A cleaning tank 10 provided on the slide base 3 and moving as the slide base reciprocates.
Is provided for the purpose of washing away the etchant adhering to the wafer W which has been etched by the first or second etching tanks 1 and 2 to immediately stop the etching reaction. In that sense, the cleaning tank 10
Shower nozzles 13 are provided at the upper edge and the lower portion (see FIG. 2) so that the cleaning liquid is evenly discharged to the wafer. Further, the etchant adhering to the wafer is mixed into the cleaning solution, but if the wafer is immersed in this etchant, the etching reaction proceeds. Is provided with a quick drain valve 14.

Next, the transfer mechanism of the wafer magazine 11 will be described. As shown in FIG. 4, the wafer magazine transfer mechanism according to the present embodiment includes a first rotating shaft 1 supported by two bearings 15 fixed to the slide base 3.
6a (16b is a driven shaft), and the first rotating shafts 16a and 16b are fixed to the arm 17. Since the first rotation shaft 16a is rotated in both directions by the first drive motor 18, when the first drive motor 18 is operated in either direction, the arm 17 rotates in the corresponding direction.

On the other hand, the hanger 12 is rotatably supported around the vicinity of the tip of the arm 17 and supports the wafer magazine 11 described above in the notch 12a formed at the tip of the hanger 12. If the bar 11b is locked,
Even if the arm 17 swings, the side plate of the hanger 12 rotates relatively to the arm 17 so as to always follow the vertical direction due to the weight of the wafer magazine 11.

By operating the first drive motor 18 by such a transfer mechanism, the wafer magazine 11 immersed in the etching tanks 1 and 2 can be transferred to the cleaning tank 10 or, conversely, can be transferred to the cleaning tank 10. The wafer magazine 11 immersed in the wafer 10 can be transferred to the etching tanks 1 and 2 (see FIG. 2).

On the other hand, a mechanism for rotating the wafer magazine 11 held by the hanger 12 is configured as follows. That is, the second rotation shaft 19 is inserted through the first rotation shaft 16a and rotatably provided, the second base motor 20 is provided on the slide base 3, and the pulley 21
And the second rotating shaft 19 is rotated via the belt 22. A gear 23 is attached to the other end of the second rotation shaft 19, and the rotation of the gear 23 is provided on the hanger 12 via a plurality of gears 24, 25, 26, 27 provided on the arm 17. It is transmitted to the other gears 28, 29, 30. Then, the gear 30 finally located is engaged with the gear 11c (see FIG. 3) provided on the wafer magazine 11, so that the rotational drive of the second drive motor 20 is finally transmitted to the wafer magazine 11, and The wafer magazine 11 rotates while being held by the hanger 12.

When a wafer is etched using this etching apparatus, the etching is performed as follows. First, an etchant having a diffusion-controlled chemical composition, for example, hydrofluoric acid: nitric acid: acetic acid:
Water = 1: 5 to 20: 2 to 12: 1 to 12 are supplied and circulated. In addition, an etchant having a stirring-controlled chemical composition, for example, hydrofluoric acid: nitric acid: acetic acid = 1: 1 to 4: 1 to 3 is supplied to the second etching tank 2 and circulated in a volume percentage.
Setting the circulation rate of these etchants to about 50 liters per minute is effective for diffusion of reaction heat.

Then, the plurality of semiconductor wafers W to be etched are housed in the wafer magazine 11, and the support bars 11 b of the wafer magazine 11 are gripped by engaging the notches 12 a of the hanger 12. From this state, the first drive motor 18 is operated to move the arm 17 to the first position.
The wafer magazine 11 held by the hanger 12 is immersed in the first etching tank 1 filled with a diffusion-controlled etchant by tilting the wafer magazine 11 toward the etching tank 1. At the same time, by operating the second drive motor 20, the wafer magazine 11 is moved, for example, at a rate of 20
The semiconductor wafer and the etchant are rotated at a rotation speed of about twice to promote agitation of the etchant.

When the etching in the first etching tank 1 is completed, the first drive motor 18 is operated to rotate the arm 17 so that the arm 17 is tilted to the cleaning tank 10 side.
2 is immersed in the cleaning tank 10. As a result, a chemical reaction caused by a diffusion-controlled etchant can be suppressed. In the cleaning tank 10, as in the first etching tank 1, the wafer magazine 1
1 is rotated by the second drive motor 20 to promote the agitation of the semiconductor wafer W and the cleaning liquid. After washing for a predetermined time, the quick drain valve 14 is opened and the washing liquid in the washing tank 10 is immediately discarded. Thereby, the progress of the etching reaction due to the etchant mixed into the cleaning liquid from the wafer W can be suppressed.

Then, the fluid cylinder 7 is operated to slide the slide base 3 to the second etching tank 2 filled with the stirring-controlled type etchant, and the arm 17 is oscillated by the first drive motor 18 so as to hang the hanger. The wafer magazine 11 gripped by 12 is immersed in the second etching tank 2. In the second etching tank 2, similarly to the first etching tank 1 and the cleaning tank 10, the second drive motor 20 is provided.
To rotate the wafer magazine 11 to promote agitation of the semiconductor wafer and the etchant.

When the etching in the second etching tank 2 is completed, the arm 17 is swung by the first drive motor 18, and the wafer magazine 11 held by the hanger 12 is immersed again in the cleaning tank 10. As a result, it is possible to suppress the chemical reaction caused by the stirring-controlled etchant. In the cleaning tank 10, similarly to the first and second etching tanks 1 and 2, the wafer magazine 11 is
Of the semiconductor wafer and the cleaning liquid. When cleaning is performed for a predetermined time, the quick drain valve 14 is opened, and the cleaning liquid in the cleaning tank 10 is immediately discarded. Thus, the progress of the etching reaction due to the etchant mixed into the cleaning liquid from the wafer can be suppressed.

The embodiments described above are described to facilitate understanding of the present invention, but not to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, in the embodiment described above, the etching tank is
And the second configuration, the diffusion-controlled etchant and the stirring-controlled etchant may be divided and accommodated in a plurality of tanks, and the etching process and the cleaning may be performed while sequentially moving the slide base. .

[0029]

As described above, according to the present invention, a plurality of etching tanks are juxtaposed, and a cleaning tank for suppressing a chemical reaction of etching is provided slidably with respect to each of the etching tanks, and is shared. Therefore, the processing apparatus can be reduced in size, and the transport time can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an etching apparatus according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a cross-sectional view showing a transfer mechanism according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st etching tank 2 ... 2nd etching tank 3 ... Slide base 7 ... Fluid cylinder 8 ... Wheel 9 ... Rail 10 ... Cleaning tank 11 ... Wafer magazine 12 ... Hanger 13 ... Shower nozzle 14 ... Rapid drain valve 16 ... 1st Rotation axis 17 Arm 18 First drive motor 19 Second rotation axis 20 Second drive motor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-328829 (JP, A) JP-A-57-2541 (JP, A) JP-A-6-45314 (JP, A) JP-A-2- 205042 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/306-21/3063 H01L 21/304 H01L 21/308

Claims (2)

(57) [Claims] When a semiconductor wafer is etched by sequentially immersing a semiconductor wafer in two or more etching tanks filled with an etchant, a wafer magazine accommodating the semiconductor wafer and a wafer magazine filled with the etchant are parallel to each other. A plurality of etching tanks provided, a cleaning tank slidably provided along each of the etching tanks, and a transfer mechanism for transferring the wafer magazine between each of the etching tanks and the cleaning tank. An etching apparatus for a semiconductor wafer, comprising: 2. The transfer mechanism according to claim 1, wherein the transfer mechanism is provided on a slide table provided with the cleaning tank, and is configured to swing between the cleaning tank and each of the etching tanks by a first driving unit. A hanger rotatably supported around a tip of the hanger, a second drive unit and a transmission mechanism for rotating the wafer magazine held by the hanger with respect to the hanger. 2. The apparatus for etching a semiconductor wafer according to claim 1.