JP6662130B2 - Wet etching equipment - Google Patents

Description

  The present invention relates to a wet etching apparatus.

  2. Description of the Related Art Conventionally, there has been known a wet etching apparatus that immerses a processing target in a processing bath filled with an etching solution to perform etching (see Patent Document 1).

  In such a wet etching apparatus, a large number of etching solution discharge holes are provided on one of the opposed side walls of the processing tank and a large number of etching solution discharge holes are provided on the other side wall in order to allow the etching solution to flow in the processing tank in the horizontal direction. By providing a rectifying plate provided with a large number of rectifying holes in front of one and the other side walls, and a grid-like louver in front of the rectifying plate, the etching liquid stagnation portion is provided on the surface of the processing object. Is eliminated to make the flow of the etchant uniform on the surface of the processing object.

  By the way, in such a wet etching apparatus, a number of etchant discharge holes and etchant discharge holes are provided to circulate the etchant, and these are arranged so as to face each other. In the method of circulating the etchant, the etchant has a static flow at a constant flow rate along the surface of the processing object.

  However, in our experiments, it has been found that only the static flow does not sufficiently replace the etchant on the surface of the object to be processed, resulting in a distribution of the etching rate along the flow. For example, in the case of stirring the etching solution by a rotational movement using a magnet stirrer, etching unevenness close to a circle was confirmed. From this result, we can not achieve the desired distribution of the etching rate by static circulation, and that the stirring method of the etchant having a certain "turbulent component" is a method to solve the problem Was found. The present invention has been made based on such findings.

  It is an object of the present invention to provide a wet etching apparatus capable of uniformly etching the entire surface of an object to be etched.

The present invention is a wet etching apparatus having a circulating mechanism for immersing an object to be etched in an etching solution to perform etching and circulating the etching solution, wherein the circulating mechanism is provided from above a liquid level in a processing tank. Jetting means for jetting an etching solution toward the liquid surface, and by jetting the etching solution from the jetting means, a turbulent flow is generated on the surface of the object to be etched immersed in the etching solution ; The discharge means, the object to be etched, and the discharge port provided at the bottom of the processing tank are arranged so as to be aligned on the same straight line .

  According to the present invention, the entire surface of the object to be etched can be uniformly etched.

1 is a schematic configuration diagram showing a configuration of an embodiment of a wet etching apparatus according to the present invention. FIG. 2 is a plan view showing a support of the wet etching apparatus shown in FIG. 1. FIG. 3 is a cross-sectional view illustrating a configuration of a support table illustrated in FIG. 2. FIG. 7 is an explanatory diagram showing a state in which turbulence occurs in an etching solution when a raindrop-shaped etching droplet 11b is radially ejected from a spray nozzle toward a liquid surface of an etching solution in a processing tank. FIG. 3 is an explanatory diagram showing an overall flow of an etching solution in a processing tank. FIG. 4 is an explanatory diagram showing a state where generated turbulence does not contact the surface of the etching target when the depth of immersion of the etching target is large. It is explanatory drawing which showed the case where the immersion depth of the to-be-etched object was set by the amount of etching liquid. It is an explanatory view showing a state where the depth of the immersion of the object to be etched is set to a predetermined depth by adjusting the height of the legs of the support base. FIG. 3 is an explanatory diagram showing a configuration of a wet etching apparatus provided with a liquid temperature control unit for controlling the temperature of an etching liquid in a circulation pipe of a circulation mechanism. FIG. 4 is an explanatory diagram showing a configuration of a wet etching apparatus in which a filter unit for filtering an etching solution is added to a circulation pipe of a circulation mechanism.

  Hereinafter, an embodiment which is an embodiment of a wet etching apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a wet etching apparatus 10. The wet etching apparatus 10 mounts a processing tank 12 storing an etchant 11 for etching the workpiece W, a circulation mechanism 20 for circulating the etchant 11, and a state in which the workpiece W is immersed in the etchant 11. And a mounting table 31 for mounting.

  The circulation mechanism 20 discharges the etching liquid 11 in the processing tank 12 to the outside and returns the discharged etching liquid 11 to the processing tank 12.

The processing bath 12 is a cylindrical container having a circular shape in a plan view, and a discharge port 12b for discharging the etching liquid 11 is provided at the center of the bottom 12A of the processing bath 12.
[Circulation mechanism]
The circulation mechanism 20 is provided in the middle of the circulation nozzle 22, a circulation pipe 22 communicating the discharge port 12 b of the bottom 12 A of the processing tank 12 and the spray nozzle 21, and the circulation pipe 22. And a diaphragm pump 23. The spray nozzle 21 is disposed above the upper surface of the etching solution 11 in the processing bath 12 and is fixed to a position at a predetermined height H1 from a liquid surface 11A of the etching solution 11 by a support member (not shown). I have.

  The diaphragm pump 23 forcibly discharges the etching liquid 11 in the processing tank 12 from the discharge port 12b, and supplies the etching liquid 11 to the spray nozzle 21. The spray nozzle 21 jets the supplied etching liquid 11 radially toward the liquid surface 11A of the etching liquid 11 in the processing tank 12.

In this embodiment, the diaphragm pump 23 is used. However, a normal pump may be used, but a diaphragm pump 23 or a roller pump for discharging the etching liquid 11 in a pulsating flow is preferable.
[Mounting table]
The mounting table 31 has a leg (depth adjusting mechanism) 32 for adjusting the height of the mounting table 31 as shown in FIGS. 2 and 3. The mounting table 31 is a transparent PVC mushroom having a number of holes 33 formed therein, and the flow of the etching solution 11 is improved by the number of holes 33. The mounting table 31 has four female threads 31B.

  As shown in FIG. 3, the leg 32 has columns 34 and 35 having different lengths. Male threads 34 </ b> A and 35 </ b> A are formed above the columns 34 and 35, and lower portions of the columns 34 and 35 are formed below the columns 34 and 35. Female threads 34B and 35B are formed. Then, the male screw portion 34A of the support portion 34 is screwed into the female screw portion 31B of the mounting table 31, and the female screw portion 35B of the support portion 34 is screwed with the male screw portion 35A of the support portion 35, thereby forming the support portion 34 and the support portion 35. And are connected.

  The height of the mounting table 31 can be adjusted stepwise by the number of the columns 34 and 35 to be connected. That is, the columns 34 and 35 have a function as a depth adjusting mechanism for adjusting the depth of the immersion of the workpiece W by adjusting the height thereof.

  In this embodiment, the height of the mounting table 31 is adjusted step by step. However, the length of the female thread portion 34B of the support portion 34 and the male screw portion 35A of the support portion 35 are increased, so that the The height may be adjustable.

  The depth adjusting mechanism may be an adjusting mechanism for adjusting the amount of the etching liquid 11.

In addition, the spray nozzle 21, the workpiece W of the mounting table 31, and the discharge port 12 b of the processing tank 12 are aligned on the same straight line. That is, the center position of the spray nozzle 21, the center position of the mounting table 31, and the center position of the discharge port 12b are arranged on the same vertical line.
[motion]
Next, the operation of the wet etching apparatus 10 configured as described above will be described.

  First, as shown in FIG. 1, the mounting table 31 is set in the processing tank 12. This set matches the center position of the spray nozzle 21 with the center position of the mounting table 31 on the center line (not shown) of the processing tank 12. Next, the workpiece W is placed on the mounting table 31 such that the center of the workpiece W coincides with the center of the workpiece W. Then, the processing bath 12 is filled with a predetermined amount of the etching liquid 11, and the depth from the liquid surface 11A of the etching liquid 11 to the surface Wa of the workpiece W is set to a predetermined depth H2. The setting of the depth H2 is performed by adjusting the height of the leg 32 of the mounting table 31, adjusting the amount of the etching liquid 11, and the like.

  Next, the etching solution 11 in the processing tank 12 is circulated by the circulation mechanism 20. That is, the diaphragm pump 23 is driven to discharge the etching liquid 11 in the processing tank 12 from the discharge port 12 b, and the discharged etching liquid is supplied to the spray nozzle 21.

  When the etching liquid is supplied from the diaphragm pump 23, the spray nozzle 21 radially changes the raindrop-shaped etching droplet 11b toward the liquid surface 11A of the etching liquid 11 in the processing tank 12, as shown in FIG. It gushes. The range in which the etching droplet 11b enters the liquid surface 11A of the etching liquid 11 is set to substantially the same range as the surface Wa of the workpiece W. That is, it is set in a range on the liquid surface 11A immediately above the surface Wa of the workpiece W.

  When the etching liquid droplet 11b enters the liquid surface 11A of the etching liquid 11, the etching liquid 11 flows on the surface Wa of the workpiece W, and turbulence occurs in the etching liquid 11 on the surface Wa. I do. In addition, since the etching droplet 11b enters the area on the liquid surface 11A directly above the surface Wa of the workpiece W, turbulence flows over the entire surface Wa of the workpiece W. appear.

  Therefore, it is possible to prevent the etching liquid 11 on the surface Wa of the workpiece W from partially staying. That is, due to the stirring effect by the turbulent flow, the etching liquid 11 is prevented from partially staying on the surface Wa of the workpiece W, and the entire surface Wa can be uniformly etched.

  What is important here is that the etching droplet 11b discharged from the spray nozzle 21 does not directly collide with the etching object W because the etching object W is immersed in the etching solution 11. That is. In other words, the etching solution 11 existing on the etching target W serves as a buffer layer, which reduces the force of the radially ejected etching droplets 11b, and generates a turbulent flow.

On the other hand, when the etching liquid 11 in the processing tank 12 is discharged from the discharge port 12b by the diaphragm pump 23, the processing tank 12 is circular,
Good etching rate distribution is obtained. In addition, since the discharge port 12b is located at the center of the bottom of the processing tank 12, when the object to be etched W is circular, as shown by arrows P1 and P2 in FIG. The liquid 11 flows without bias toward the outer peripheral direction of the workpiece W. In other words, with the center of the center of the surface Wa of the etching object W as a center, the water flows radially on the surface Wa with a central symmetry without being biased toward the outer peripheral direction of the etching object W. Therefore, a better distribution of the etching rate can be obtained.

  Since the turbulent flow is generated in the radial flow, a stirring effect by the turbulent flow is obtained, and the entire surface Wa of the workpiece W can be uniformly etched, and the etching speed can be increased. Can be improved. Further, since the etching solution discharged from the diaphragm pump 23 is discharged as a pulsating flow, the etching droplets 11b are ejected from the spray nozzle 21 radially and in a pulsating flow. Therefore, a turbulent flow can be efficiently generated in the etching solution 11 in the processing tank 12, and the stirring effect can be obtained more efficiently. A similar effect can be obtained by using a roller pump instead of the diaphragm pump 23.

  Further, as described above, since the mounting table 31 is provided with a large number of holes 33, the etching solution 11 also flows in the direction indicated by the arrow P3. The flow of the liquid 11 is improved. For this reason, the entire surface Wa of the etching product W can be more uniformly etched, and the uniformity of the etching rate can be further improved.

  By the way, as shown in FIG. 6, when the etching object W is immersed in a deep position in the etching solution 11, the turbulence generated by the etching droplet 11b ejected from the spray nozzle 21 causes the turbulent flow of the etching object W. It occurs at a position away from the surface Wa. For this reason, the stirring effect of the turbulent flow on the workpiece W is small, and hardly contributes to the replacement of the etching solution 11 in the vicinity of the surface Wa of the workpiece W, and the effect of the turbulent flow cannot be obtained. That is, in order to obtain the stirring effect by the turbulent flow, it is necessary to set the depth of the immersion of the workpiece W to an optimum depth.

  In FIG. 7, the depth of immersion of the workpiece W is set by the amount of the etching liquid 11, and the immersion depth is set to H3 (H3> H1). Further, the height of the spray nozzle 21 from the liquid surface 11A is set to H4 (> H1), whereby the pressure at which the etching droplet 11b enters the liquid surface 11A of the etching liquid 11 is increased, and A turbulent flow is generated on the surface Wa of the object W.

  FIG. 8 shows a case in which the height of the legs 32 of the mounting table 31 is adjusted to set the immersion depth of the etching object W to a predetermined depth H3. 8, the amount of the etching solution 11 is the same as that shown in FIG. 4, and the height of the leg 32 shown in FIG. 8 is made lower than the height of the leg 3 of the mounting table 31 shown in FIG. , And the immersion depth was set to H3. That is, the immersion depth H3 of the workpiece W is increased without increasing the amount of the etching solution 11.

Thus, the immersion depth of the workpiece W can be freely set without increasing the amount of the etching solution 11.
[Experiment]
[Experimental example 1]
An experimental result of the wet etching apparatus 10 shown in FIG. 1 using the processing tank 12 having an inner diameter of φ220 mm and a depth of 200 mm will be described below.
・ Object to be etched: 3 inch Bare-Si substrate with resist mask (1 point at center and 8 points at periphery)
・ Mounting table height: 30 mm, immersion depth of workpiece W: about 10 mm
・ Etching solution composition: hydrofluoric acid (100 mL) + nitric acid (750 mL) + acetic acid (250 mL), volume mixing ratio = 2: 15: 5
・ Etching liquid temperature: no control (laboratory room temperature: 24 ° C)
・ Pump used: Diaphragm pump (made by AS ONE, model number: NF300TT18S)
・ Etching liquid discharge rate: about 1 L / min
・ Etching time: 16 minutes ・ Height position of spray nozzle 21 from liquid level: 10 cm
Results After 16 minutes of etching, the photoresist was removed with acetone after rinsing with pure water, the etching depth was determined with a stylus-type step measuring device, and the etching rate was determined from the etching time.

As a result, a good value of 4.4 μm / min was obtained at nine points and the variation in the wafer surface was ± 6.3%.
[Experimental Example 2 as Comparative Example]
In Experimental Example 2, the immersion depth of the object to be etched W was set to 30 mm for comparison with Experimental Example 1.

  The conditions are as follows.

Object to be etched: Bare-Si substrate With 9 in-plane photoresist resist mask (1 center and 8 peripherals)
・ Mounting table height: 10 mm, immersion depth of the object to be etched: approx. 30 mm
・ Etching solution composition: hydrofluoric acid (100 mL) + nitric acid (750 mL) + acetic acid (250 mL), volume mixing ratio = 2: 15: 5
・ Etching liquid temperature: no control (laboratory room temperature: 24 ° C)
・ Pump used: Diaphragm pump (made by AS ONE, model number: NF300TT18S)
・ Etching liquid discharge rate: about 1 L / min
-The height position of the spray nozzle 21 from the liquid level: 10 cm
-Etching time: 16 minutes Result After etching for 16 minutes, the photoresist was removed with acetone following pure water rinsing, the etching depth was determined with a stylus-type step measuring device, and the etching rate was determined from the etchin time.

  As a result, the etching rate obtained by averaging 9 points was 2.1 μm / min, and the variation in the wafer surface was ± 35.8%, which was lower than the etching rate in Experiment Example 1 by less than half, and the rate distribution was significantly deteriorated. did.

The reason for this is that, because the immersion depth of the object to be etched is set at a deep position of about 30 mm, the action of the etching droplet 11b discharged from the spray nozzle 21 is close to the surface Wa of the object W to be etched. Was not reached. That is, no turbulent flow is generated on the surface Wa, and the etching liquid on the surface Wa of the workpiece W is not efficiently replaced.
[Experimental example 3]
FIG. 9 shows a wet etching apparatus 110 provided with a liquid temperature control unit (temperature control means) 50 for controlling the temperature of the etching liquid 11 on the downstream side of the diaphragm pump 23 in the circulation line 22 of the circulation mechanism 20. . An experiment was performed using this wet etching apparatus 110 under the same conditions as in Experimental Example 1.

  As the liquid temperature control unit 50, a Peltier-type chemical liquid temperature controller was used. This Peltier-type chemical liquid temperature controller can be used without any problem with the etching liquid used this time because the heat exchange part is made of fluororesin.

  The temperature of the etching solution was set to 20.0 ° C. using this Peltier-type chemical solution temperature controller. The actual temperature of the etching solution in the etching bath was measured using a thermometer and found to be 20.3 ° C.

The results were as follows. The etching rate obtained by averaging nine points was 3.7 μm / min, which was slightly lower than that in Experimental Example 1. This was because the temperature of the etching solution was lower than that in Experimental Example 1. is there. The variation in the wafer surface was ± 6.1%, which was almost the same level as in Experimental Example 1.
[Experimental example 4]
FIG. 10 shows a wet etching apparatus 210 in which a filter unit (filtration apparatus) 60 for filtering the etching liquid 11 is added on the upstream side of the diaphragm pump 23 in the circulation line 22 of the circulation mechanism 20. An experiment was performed using this wet etching apparatus 210 under the same conditions as in Experimental Example 1. The filter unit 60 uses a filter unit in which a hydrophilic PTFE membrane filter is incorporated for chemical resistance. The hole diameter of the filter element is 0.05 μm.

  According to this wet etching apparatus 210, the foreign matter in the etching solution 11 is removed by the filter unit 60, so that a stable etching environment can be maintained. For this reason, the failure of the diaphragm pump 23 and the spray nozzle 21 can be prevented, and the wet etching has been performed 100 times or more, but the clogging of the spray nozzle 21 and the failure of the diaphragm pump 23 have not occurred. .

Further, in Experimental Example 4, a result of the same etching rate as that of Experimental Example 1 was obtained.
[Experimental example 5]
Experimental example 5 differs from the previous experimental examples in that the object to be etched is aluminum.

  The conditions are as follows.

・ Etching object: A 2 μm-thick aluminum film is formed on a Si wafer by sputtering. A resist mask with 9 in-plane photoresists (1 point at the center and 8 points at the periphery)
・ Mounting table height: 10mm, immersion depth of workpiece to be etched: about 10mm
・ Etching solution composition: phosphoric acid (800 mL) + nitric acid (50 mL) + acetic acid (50 mL) + pure water (100 mL), volume mixing ratio = 16: 1: 1: 2
・ Etch solution temperature: control (laboratory room temperature: 40 ℃)
・ Pump used: Diaphragm pump (made by AS ONE, model number: NF300TT18S)
・ Etching liquid discharge rate: about 1 L / min
-The height position of the spray nozzle 21 from the liquid level: 10 cm
・ Etching time: 1 minute 30 seconds Result After etching for 1 minute 30 seconds, the photoresist is removed with acetone after rinsing with pure water, the etching depth is determined with a stylus type step measuring device, and the etching rate is calculated from the etching time. I asked.

  As a result, a good value of 4.4 μm / min was obtained at nine points and the variation in the wafer surface was ± 6.3%.

  In wet etching of aluminum, there is a problem in that hydrogen is generated by the reaction of aluminum, and if the hydrogen bubbles remain on the surface of the object to be etched, the hydrogen acts as a mask to hinder etching. By using the present invention for such a problem, the bubbles can be efficiently removed, so that the factors inhibiting the etching can be removed, and high-quality etching can be performed.

  In the above embodiment, the depth of the workpiece W immersed in the etching solution 11 is set to an optimum depth by adjusting the amount of the etching solution 11 and the height of the legs 32 of the mounting table 31. However, the height may be set to an optimum height from the liquid level of the spray nozzle 21 corresponding to the depth of the workpiece W. That is, a separation distance adjusting mechanism (not shown) for adjusting the separation distance between the spray nozzle 21 and the liquid surface 11A of the etching liquid 11 is provided, and the separation distance from the liquid surface 11A of the etching liquid 11 to the spray nozzle 21 is set. adjust. Thus, turbulent flow can be reliably generated on the surface of the etching target W regardless of the depth of the etching target W immersed.

  The optimum depth of the workpiece W and the optimum height of the spray nozzle 21 are determined in advance by experiments.

  The present invention is not limited to the above embodiment, and changes and additions of the design are allowed without departing from the gist of the invention set forth in the claims.

DESCRIPTION OF SYMBOLS 10 Wet etching apparatus 11 Etching liquid 11A Liquid level 12 Processing tank 12A Bottom part 12b Discharge port 20 Circulation mechanism 21 Spray nozzle (spray means)
23 Diaphragm pump (pump)
31 mounting table 32 legs (depth adjustment mechanism)
50 Liquid temperature controller (temperature adjusting means)
60 Filter unit (filtration device)
W Object to be etched Wa Surface P Diaphragm pump

Japanese Patent No. 4050841

Claims (10)

An object to be etched is immersed in an etching solution to perform etching, and a wet etching apparatus having a circulation mechanism for circulating the etching solution,
The circulation mechanism has a jetting unit for jetting an etching solution from above the liquid level in the processing tank toward the liquid level,
By jetting the etching solution from the jetting means, a turbulent flow is generated on the surface of the etching target immersed in the etching solution ,
A wet etching apparatus, wherein the jetting means, the object to be etched, and a discharge port provided at the bottom of the processing tank are arranged on the same straight line .   The wet etching apparatus according to claim 1, further comprising a mounting table for mounting the object to be etched in an etching solution.   3. The wet etching apparatus according to claim 1, wherein the ejection unit is a spray nozzle that ejects radially over the entire surface of the etching target. 4. The wet etching apparatus according to any one of claims 1 to 3 , wherein the circulation mechanism includes a diaphragm pump or a roller pump. The wet etching apparatus according to any one of claims 1 to 3, further comprising a depth adjusting mechanism for adjusting a depth of immersion of the object to be etched.   The wet etching apparatus according to claim 5, wherein the depth adjusting mechanism has a leg supporting the mounting table, and the height of the leg is adjustable. The processing bath has a cylindrical shape, of claims 4 to 6, characterized in that said ejection means and said object to be etched and the outlet is arranged in the center line and the same straight line of the processing bath The wet etching apparatus according to claim 1. The wet etching apparatus according to any one of claims 1 to 7 , wherein the circulating mechanism includes a temperature adjusting unit that adjusts a temperature of the circulating etchant to a predetermined temperature. The wet etching apparatus according to any one of claims 4 to 8 , wherein the circulation mechanism includes a filtration device that filters the etching solution discharged from the discharge port. The wet etching apparatus according to any one of claims 1 to 9 , further comprising a separation distance adjusting mechanism for adjusting a separation distance between the ejection unit and the liquid surface of the etching liquid.