JP2000277483A - Surface treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment device which is capable of very accurately and uniformly treating all the surface of a wafer. SOLUTION: An etching pot 1 is filled up with heated etching liquid 23, a wafer 7 is supported on the bottom of the pot as its periphery is sealed, and the etched surface of the wafer 7 facing upward is in contact with the etching liquid 23. The periphery of the wafer 7 in the pot 1 is heated by a jig heater 19 and a heating ring 5. After etching is carried out, the jig heater 19 serving as a heat source is thermally separated from the pot 1. A heating temperature of the jig heater 19 can be changed corresponding to the etching conditions of the wafer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment apparatus for performing an etching process, a plating process, and the like on a surface of a semiconductor wafer. Things.

[0002]

2. Description of the Related Art Conventionally, several hundreds to several
Approximately 000 concave portions are formed using an etching solution such as potassium hydroxide, and semiconductor sensors such as pressure sensors and acceleration sensors are manufactured.

As shown in FIG. 5, a sensor wafer 50 is provided.
Is that one surface 50a is a circuit surface constituting a circuit and the other surface 50b is a sensor shape (that is, the concave portion 5a).
The surface to be etched for forming 1) is formed. By changing the shape of the mask on the surface to be etched 50b, a product (recess 51) suitable for the function of the sensor can be manufactured. Specifically, as shown in detail in FIG. 6, each chip 52 on the wafer 50 has a pressure sensor in which the center of the chip is concaved,
As shown in, there are various shapes such as an acceleration sensor carved around the island leaving an island-shaped bulge in the center of the chip,
These are devised with a mask 53 and dissolved with an anisotropic etching solution such as potassium hydroxide to form a shape having a space (recess) 54.

[0004] The performance of these chips as a sensor is determined by the accuracy of the thickness t1 of the cross section of each chip. Therefore, it is necessary to perform the etching with high precision so that the thickness t1 of all the chips 52 on the wafer 50 accurately reaches the target value.

In a conventional etching apparatus, as shown in FIG. 8, a circuit surface 50a of a wafer is protected from an etching solution 56 by an etching jig 55, and a surface 50b to be etched is formed.
The etching process is performed by bringing the liquid into contact with the etching liquid 56. More specifically, an etching solution 56 heated to an etching temperature by a preheating device (not shown) is introduced from a liquid supply port 57, and the etching jig 55 is used as an etching tank. Further, the etching liquid 56 in the etching jig 55 is precisely controlled by the stirring blade 58 and the heater 59 to the target etching temperature, and the wafer 5
0 is etched until the target thickness t1 is reached. When the desired thickness is reached, pure water is introduced from the liquid supply port 57 and washed with water,
The etching is terminated by stopping the etching reaction.

FIG. 9 shows a change in the etching amount by the conventional etching apparatus. When the vertical axis represents the silicon thickness (t1 value in FIGS. 6 and 7) and the horizontal axis represents the etching time, the variation in the amount of etching in the wafer surface from the original wafer thickness to the target thickness increases, Finally, FIG.
A trapezoidal distribution with a small amount of etching on the outer periphery of the wafer as shown in FIG. That is, FIG. 10 shows the result of measuring the etching amount on a line parallel to the orientation flat of the wafer as shown in FIG. In this example, the in-plane variation of the etching amount (the etching amount of the deepest concave portion−the etching amount of the shallowest concave portion)
Is 2.7% of the etching amount.

This is because the etching rate (unit: μm /
This is because the distribution of the amount of etching is sensitive to the temperature of the etchant and reflects the temperature distribution in the wafer surface.

The problem is that the conventional etching apparatus has a structure in which the temperature is maintained by heating the etchant, so that the heat is removed by the etching jig 55 shown in FIG. This occurs because the temperature of the portion (X portion in FIG. 8) decreases, and the temperature of the outer peripheral portion of the wafer also decreases during the etching due to heat radiation from the outer periphery of the etching jig 55.

As a countermeasure, conventionally, as shown in FIG. 12, a process for heating the etching jig 55 in a constant temperature bath 60 until the etching temperature reaches the etching temperature is provided, and heat radiation of the etching jig 55 is reduced. Therefore, measures such as increasing the thickness are being taken. However, the heating by the constant temperature bath 60 has a problem that the heating time is as long as one hour or more, and it is necessary to handle the etching jig 55 at a high temperature (for example, 110 ° C. or more), and the productivity is significantly reduced. Also,
The measure to increase the thickness of the etching jig 55 hinders the cooling effect at the time of stopping the etching, and also causes the thickness variation within the wafer surface at the time of stopping the etching. in this way,
Even if these measures are taken comprehensively, it has been difficult to reduce the variation in the amount of etching in the wafer surface to 2.0% or less of the amount of etching.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface treatment apparatus capable of performing highly accurate surface treatment while suppressing variations in surface treatment in a wafer surface.

[0011]

The invention according to claim 1 is characterized in that a heating means for heating the outer peripheral portion of the semiconductor wafer in the surface treatment jig is provided. By adopting this configuration, when the semiconductor wafer is supported on the bottom surface of the surface treatment jig and the surface to be treated of the upward semiconductor wafer is subjected to the surface treatment with the heated surface treatment liquid, the heating means is used. Accordingly, the temperature of the outer peripheral portion of the semiconductor wafer in the surface treatment jig can be controlled, and desired surface treatment within the wafer surface is performed. For example, by supplying an amount of heat commensurate with heat radiation to the outer peripheral portion of the semiconductor wafer, a uniform surface treatment can be performed on the wafer surface.

In this way, it is possible to perform highly accurate surface treatment while suppressing variations in surface treatment within the wafer surface. Here, when the surface treatment jig is heated to a predetermined temperature higher than the temperature of the surface treatment liquid by using a heating means before the start of the surface treatment, as described in claim 2, The initial state (for example, in the case of an etching apparatus, the distribution of the amount of etching in the wafer surface at the beginning of etching) can be made highly accurate.

Further, if the heat source of the heating means is thermally separated from the surface treatment jig after the surface treatment, the surface treatment can be stopped (for example, washed with water) promptly. it can.

Further, when the heating temperature of the heating means is changed according to the surface treatment conditions of the semiconductor wafer, the surface treatment for each wafer can be made uniform (for example, in the case of an etching apparatus, (Thickness distribution of each chip for each wafer) can be achieved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment uses a silicon wafer as a semiconductor wafer and is applied to an etching apparatus for forming a concave portion in each chip of the silicon wafer, and uses potassium hydroxide heated to about 110 ° C. as an etchant. By forming a recess in each chip, the pressure sensor of FIG. 6 and the acceleration sensor of FIG. 7 can be manufactured.

FIG. 1 shows the overall configuration of an etching apparatus for thin-wall processing as a surface treatment apparatus. The present etching apparatus has an etching pot 1 as a surface treatment jig. FIG. 2 shows an enlarged view of the etching pot 1.

The etching apparatus shown in FIG. 1 is a single wafer capable of mechanically holding the surface to be etched of the silicon wafer 7 so as to be in contact with the etching solution 23 and capable of supplying, draining, heating and stirring. In the etching apparatus, the outer peripheral portion of the silicon wafer 7 is sealed from the circuit side, which is the non-etched surface, and a heater (heat source) 19 as a heating means and a heating means are provided for the sealed portion before the start of etching and during the etching. Heating is performed by a ring (heat transfer member) 5. As a result, the distribution of the etching amount in the wafer surface is made highly accurate. When the desired etching amount is reached, pure water is injected into the pot 1 to terminate the etching.

The details will be described below. As shown in FIG. 2, the etching pot 1 includes a plate-shaped wafer base 2 and a cylindrical wafer ring 3. The wafer base 2 and the wafer ring 3 are made of a material having a high heat insulating effect, such as Teflon or polypropylene. A through hole 4 is formed in the center of the wafer base 2, and a heating ring 5 is provided in an opening above the through hole 4. The heating ring 5 has a plate shape, and a through hole 6 is formed at the center. The heating ring 5 is made of a metal such as stainless steel or nickel having excellent thermal conductivity.

The silicon wafer 7 can be placed on the heating ring 5 on the upper surface of the wafer base 2.
When the silicon wafer 7 is placed on the heating ring 5, only the outer peripheral portion on the lower surface of the wafer 7 contacts the heating ring 5.
In addition, the wafer ring 3 is arranged on the wafer 7 with one opening facing down. That is, the silicon wafer 7
Are arranged so as to cover the lower surface opening of the cylindrical wafer ring 3. A concave portion 8 is formed in an annular shape on the outer peripheral side of the wafer mounting portion (location where the heating ring 5 is disposed) in the wafer base 2, and the protrusion 9 of the wafer ring 3 is fitted into the concave portion 8. As described above, the concave portion 8 has a positioning function.
Further, a flat sealing surface S1 is formed in an annular shape on the outer peripheral side of the concave portion 8 in the wafer base 2 (around the wafer mounting portion), and a concave portion 10 is formed in the sealing surface S1 in an annular shape, and functions as a pocket for vacuum. I do.

A wafer-shaped seal packing 11 is fixed to the inner peripheral portion of the lower surface of the wafer ring 3, and the packing 11 is cut into a wafer shape to seal the upper surface of the edge of the silicon wafer 7. The wafer-type seal packing 11 can seal against an etching solution filled in the wafer ring 3. That is, the seal packing 11 is for sealing the lower surface of the wafer ring 3 and the outer peripheral portion of the wafer 7 in a liquid-tight state with the silicon wafer 7 placed on the wafer base 2. A flat sealing surface S2 is provided on the outer peripheral portion of the lower surface of the wafer ring 3.
Is formed in a ring shape, and a concave portion 12 is formed in the seal surface S2 in a ring shape to function as a vacuum pocket.

An annular X-shaped packing 13 is disposed between the sealing surface S1 of the wafer base 2 and the sealing surface S2 of the wafer ring 3. The air in the recesses (vacuum pockets) 10 and 12 is exhausted by a vacuum pump or the like, so that the X-shaped packing 13 contracts and the wafer base 2 and the wafer ring 3 are attracted. 7 is fixed with its outer peripheral portion sealed.

The etching pot 1 thus configured is mounted on a pot mounting table 14 as shown in FIG.
FIG. 3 shows the pot mounting table 14. In FIG. 3, a cylinder storage chamber 16 is formed inside the base block 15, and an elevating cylinder 17 is arranged in the storage chamber 16. For example, an air cylinder or the like is used as the elevating cylinder 17. The lifting cylinder 17 has a movable rod 18, and the rod 18 expands and contracts in the vertical direction. A jig heater 19 is attached to the rod 18. The jig heater 19 has a hole 20 formed in the base block 15.
The inside can be raised and lowered with the O-ring 21 kept airtight.

As shown in FIG. 1, when the jig heater 19 is moved upward by the lifting cylinder 17 with the etching pot 1 mounted on the pot mounting table 14, the upper surface of the heater 19 is heated. Contact 5
In this state, the heat generated by the heater 19 is supplied to the outer peripheral portion of the non-etched surface of the wafer 7 through the heating ring 5, and the outer peripheral portion of the wafer in the pot 1 can be heated. In addition, a heat insulating plate 22 is provided at the center of the upper surface of the jig heater 19, and the heat insulating plate 22 protects portions other than the contact surface with the heating ring 5 from being heated. The jig heater 19 is controlled to a target temperature by the controller 35.

In FIG. 1, the etching liquid 23 in the etching pot 1 is sealed by the wafer-type seal packing 11 and the outer peripheral portion of the silicon wafer 7 is masked (protected). Thus, etching pot 1
Is filled with a heated etching solution 23, and the silicon wafer 7 is supported in a state where the bottom surface of the pot 1 is sealed at the outer periphery. The surface to be etched of the silicon wafer 7 facing upward contacts the etching solution 23. .

The opening on the upper surface of the etching pot 1 in FIG. A stirring blade 25 is suspended from the cap 24 in a state sealed by an O-ring 26, and the stirring blade 25 rotates by the driving of a motor 27 to stir the etching solution 23. Further, a heater 28 is hung on the cap 24 while being sealed by an O-ring 29, and the etching solution 23 is heated by the heater 28. Further, a temperature sensor 30 is hung on the cap 24 in a state sealed by an O-ring 31, and the temperature sensor 3
At 0, the temperature of the etching solution 23 is detected. And
During the etching, the etching liquid 23 is sufficiently stirred by the stirring blade 25, and the heater 28 is energized so that the liquid temperature by the temperature sensor 30 becomes a predetermined temperature by the temperature controller 32.

A liquid supply port 33 and a liquid discharge port 34 are formed in the cap 24, and the liquid supply port 33 and the liquid discharge port 34 are connected to a utility (not shown). The etching liquid is supplied into the pot 1 through the liquid supply port 33, and a washing liquid (pure water) at the time of stopping the etching can be introduced. Also,
The liquid overflowing in the pot 1 can be discharged through the drain port 34.

The temperature controller 32, the motor 27, the jig heater 19, the elevating cylinder 17 and the like are controlled by a controller 35 as a device for controlling the etching apparatus. That is, the controller 35 is constituted by a computer or the like that stores the processing conditions (etching temperature, preheating time, required thickness, etc.) of the wafer, functions as a production management device, and performs heating including the heater 19 according to the wafer etching condition. Change the temperature. The present etching apparatus further includes equipment such as a measuring instrument.

Next, the operation of the etching apparatus configured as described above will be described. Controller 35 (production management device)
Is the product / processing conditions (etching temperature,
(Required thickness, etc.) and prepare for processing such as determining the etching conditions of the wafer. Then, the wafer base 2 shown in FIG.
From the state in which the silicon wafer 7 is disassembled and the wafer ring 3, the heating ring 5 is placed on the wafer base 2 by a loader (not shown) so that the surface to be etched faces upward.
On top of. Then, the wafer ring 3 is covered, and the recesses (vacuum pockets) 10 and 12 are evacuated by a vacuum pump or the like (not shown). As a result, the X-type packing 13 contracts, draws the wafer base 2 and the wafer ring 3, and seals (masks) the wafer 7 with the seal packing 11 provided on the wafer ring 3 for sealing the wafer edge. .

Further, this etching pot 1 is moved by a loading device (not shown) as shown in FIG.
It is mounted on the pot mounting table 14. And cap 2
4 is lowered into the etching pot 1 by an elevating device (not shown), and the jig heater 19 is moved upward by the driving of the cylinder 17 and pressed against the heating ring 5. In this state, the jig heater 19 is operated to transfer the heat generated by the jig heater 19 through the heating ring 5 to the wafer 7 in the pot 1.
Is heated to the liquid temperature at the start of etching. The heating temperature at this time depends on the etching conditions of the wafer.

As described above, the jig heater 19
Through the heating ring 5, the wafer outer periphery in the pot 1 and its vicinity are preheated so as to be equal to the initial temperature of the etching solution 23.

After the inside of the etching pot 1 is heated in this way, an etching solution whose temperature and concentration have been adjusted by an etching solution supply device (not shown) is supplied from a liquid supply port 33. Then, the stirring blade 25 is driven by the motor 27,
By controlling the temperature of the heater 28 by the temperature controller 32, the etching temperature condition in the etching pot 1 is adjusted. Then, the surface to be etched of the wafer 7 is etched. Even during this etching, the outer peripheral portion of the wafer 7 in the pot 1 and its vicinity are kept warm by the jig heater 19 via the heating ring 5. The heating temperature at this time depends on the etching conditions of the wafer.

As described above, the outer periphery of the wafer in the pot 1 and the vicinity thereof are kept warm by the jig heater 19 via the heating ring 5 so that the outer periphery of the wafer remains in the etching pot 1 even during the etching with the etching solution 23. Cooling by heat radiation is prevented.

When a predetermined amount of etching is performed and the thickness (t1 value in FIGS. 6 and 7) at the bottom of the concave portion (corresponding to reference numeral 54 in FIGS. 6 and 7) in the silicon wafer 7 becomes a desired value, The jig heater 19 is moved by the lifting cylinder 17 shown in FIG.
And the heat supply to the heating ring 5 is stopped. That is, at the time of cleaning after etching, the jig heater 19 is lowered by the elevating syringe 17 and stored in the base block 15 in order to enhance the cooling effect of the etching pot 1. By this operation, the jig heater 19 can be maintained in a heated state in preparation for the next cycle of etching without being cooled.

In order to stop the etching, a cleaning liquid (pure water) is introduced into the etching pot 1 from a cleaning liquid supply source (not shown) through the liquid supply port 33 in FIG. 1 to dilute and cool the etching liquid (water washing). (Cooling) to stop the etching promptly. The supplied mixed liquid of the cleaning liquid and the etching liquid is continuously discharged from the drain port 34.

After sufficient cleaning, the supply of the cleaning liquid is stopped and the motor 27 is stopped. After that, the cleaning liquid in the etching pot 1 is forcibly drained using a drainage device (not shown) such as a vacuum drainage device such as an ejector. To complete the process.

That is, the evacuation of the concave portions (vacuum pockets) 10 and 12 by the vacuum pump or the like is stopped, and the concave portions 10 and 12 are stopped.
12 is set to atmospheric pressure. Then, the cap 24 and the wafer ring 3 (seal packing 11) are removed, and the etched silicon wafer 7 is sent to the next step.

FIG. 4 shows the results of measuring the thickness distribution of the processed wafer. That is, the measurement result of the etching amount in the wafer surface when etching is performed by the above-described etching apparatus is shown. As a result, the in-plane variation of the etching amount (the etching amount at the deepest concave portion−the etching amount at the shallowest concave portion) is 0.8% of the etching amount, which is smaller than the thickness distribution accuracy of the chip manufactured by the conventional etching apparatus. The thickness variation in the wafer surface could be reduced to 1/3 or less.

Further, conventionally, in order to cope with many kinds of products, it is necessary to change the etching work for each product such as preheating temperature and time management of the etching pot 1, which requires complicated processes. Although the management was necessary, this apparatus can cope with all kinds of products by automatically setting the temperature of the jig heater 19 in one process (one kind of apparatus). Full automation can be achieved simply by instructing the controller (production management device) 35.

As described above, this embodiment has the following features. (A) When the surface to be etched of the upwardly directed wafer 7 is etched by the heated etchant 23 while the wafer 7 is supported on the bottom surface of the etching pot 1, the jig heater 19 and the heating ring 5 are used. , Pot 1
By supplying an amount of heat commensurate with the heat radiation to the outer peripheral portion of the wafer 7, the temperature distribution in the wafer surface at the start of etching and during the etching is uniformly stabilized, and higher-precision etching than before can be achieved. . Further, as shown in FIG. 12, the etching jig 55 can be etched with high accuracy without heating the etching jig 55 in the constant temperature bath 60 before starting the etching or increasing the thickness of the etching jig 55 to reduce the heat radiation. be able to. In addition, a large-scale transport device is not used. Further, since it is not necessary to increase the wall thickness in order to reduce the heat radiation of the etching jig 55, the pot 1 can be made lighter and smaller than before. In addition, since the through hole 4 (see FIG. 2) is formed in the center of the wafer base 2, the weight can be reduced by that amount.

As described above, it is possible to perform highly accurate etching while suppressing variation in the amount of etching in the wafer surface. (B) Since the jig heater (heat source) 19 is thermally separated from the etching pot 1 after the etching, the speed of the water washing, which is the etching stop processing, can be increased and the processing can be performed promptly. (C) Since the heating temperature of the jig heater 19 and the heating ring 5 is changed according to the etching condition of the wafer 7, the distribution of the thickness of each chip for each wafer can be made uniform.

In addition to those described above, the present invention may be implemented as follows. Before the start of the etching, the pot 1 is set using the jig heater 19 and the heating ring 5.
The heating may be performed by a predetermined temperature higher than the temperature of the etching solution. For example, when the liquid temperature at the start of etching is 1
If it is 10 ° C, it is increased by 20 ° C to 130 ° C. Then, the distribution of the etching amount in the wafer surface at the initial stage of the etching can be improved in accuracy.

Further, by utilizing the fact that the temperature of the outer peripheral portion of the wafer can be controlled separately from that of the central portion, if the in-plane distribution of the original thickness of the wafer is concave, the etching rate of the outer peripheral portion can be increased. Alternatively, if the in-plane distribution of the original thickness of the wafer is a convex shape, the distribution of the etching amount is controlled in accordance with the original thickness distribution of the wafer by delaying the etching of the outer periphery. In this way, high reliability and productivity that cannot be obtained conventionally can be obtained, for example, higher thickness distribution accuracy can be secured.

In the above description, the etching apparatus does not apply a potential. Needless to say, however, higher precision can be achieved by adding an electrochemical stop etching (anodizing stop) function.

The silicon wafer 7 in the pot 1
A thickness sensor may be arranged on the lower surface side of the substrate, and the etching amount of the wafer may be monitored by the thickness sensor to detect the etching end point. This makes it possible to further improve the accuracy including the repeat accuracy between wafers. That is, the shape of the jig heater 19 may be a donut shape so as to heat only the outer periphery of the wafer, and the thickness sensor may be disposed at the center of the heater 19. Alternatively, the thickness sensor may be moved in the horizontal direction to detect the etching amount of each chip (recess) in the wafer surface.

Further, in this embodiment, the rotary stirring blade 2
5 (see FIG. 1), the pot 1
The etching liquid may be stirred by swinging itself.

Further, the etching apparatus has been described. However, the present invention can be applied to a surface treatment apparatus for obtaining high quality by heating the liquid and making the temperature distribution of the wafer surface uniform, and a surface having a high temperature control such as gold plating. Similar effects can be obtained in the processing.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an etching apparatus according to an embodiment.

FIG. 2 is a sectional view of an etching pot.

FIG. 3 is a cross-sectional view of the pot mounting table.

FIG. 4 is a view showing a measurement result of an etching amount in a plane of a wafer.

FIG. 5 is a view showing a wafer.

FIG. 6 is a diagram showing a chip.

FIG. 7 is a view showing a chip.

FIG. 8 is a sectional view of a conventional etching apparatus.

FIG. 9 is a diagram showing a change in diaphragm thickness in an etching step.

FIG. 10 is a diagram showing a measurement result of an etching amount in a plane of a wafer.

FIG. 11 is a plan view of a wafer for explaining a thickness measurement location.

FIG. 12 is a sectional view of a conventional etching apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Etching pot, 5 ... Heat ring, 7 ... Silicon wafer, 17 ... Elevating cylinder, 19 ... Jig heater
23 ... etchant, 35 ... controller.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K057 WA11 WB06 WE22 WG02 WM01 WM11 WM13 WM17 WM18 WN01 4M112 AA01 AA02 DA04 EA02 5F043 AA02 BB02 DD07 DD30 EE03 EE04 EE12 EE15 EE16 EE27 EE32 FF10

Claims (4)

[Claims] 1. A semiconductor wafer is filled with a heated surface treatment liquid, and a semiconductor wafer is supported on a bottom surface of the semiconductor wafer with an outer peripheral part sealed, and a surface of the semiconductor wafer facing upward contacts the surface treatment liquid. A surface treatment apparatus comprising: a surface treatment jig; and heating means for heating an outer peripheral portion of the semiconductor wafer in the surface treatment jig. 2. The surface treatment apparatus according to claim 1, wherein before the surface treatment is started, the surface treatment jig is heated by a predetermined temperature higher than the temperature of the surface treatment liquid by using the heating means. . 3. The method according to claim 1, wherein the heat source of the heating means is thermally separated from the surface treatment jig after the surface treatment.
The surface treatment apparatus according to item 1. 4. The heating temperature of the heating means is changed according to the surface treatment conditions of the semiconductor wafer.
The surface treatment apparatus according to any one of claims 1 to 7.