JP2929861B2 - High precision etching method and 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 disk-shaped semiconductor single crystal wafer (hereinafter simply referred to as "wafer") obtained by slicing a rod of a semiconductor single crystal such as silicon and polishing the main surface thereof. The present invention relates to a high-precision etching method and apparatus suitable for uniformly etching a surface.

[0002]

2. Description of the Related Art Chemical etching of a wafer is used for the purpose of removing a strained layer on the wafer surface caused by mechanical processing such as slicing or polishing, observing crystal defects, and performing fine processing by using selective etching. An object of the present invention is to provide an etching method for a wafer, which is generally adopted in the related art, in which a wafer is rotated while rotating the wafer in a flow of a chemical solution by bubbling or the like. In this case, it is difficult to control the liquid flow rate of the chemical solution, and therefore, it is difficult to reduce the variation in the etching allowance in the wafer surface, and it is difficult to obtain a chemically etched wafer having high precision flatness. .

[0003]

The wafer is subjected to an etching treatment by bringing a chemical solution for etching into contact with the surface of the wafer while moving the same. At this time, the relative position between the wafer and the chemical solution in contact with the wafer at each part is determined. Unless the average flow velocity is kept as uniform as possible ,
To reduce the variation in the etching allowance of
-The flatness of the wafer surface cannot be increased . for that reason,
With the conventional etching method, it has been difficult to produce a chemically etched wafer having high precision flatness. Further, streaks or random irregularities are formed on the surface of the wafer due to the reaction gas generated during the etching process. Therefore, it is necessary to smooth the wafer by rotating the wafer. After the chemical liquid strikes the edge of the outer edge of the wafer, it flows substantially parallel to the main surface of the wafer toward the center thereof, and the relative average flow velocity of the two locally changes at the edge. Therefore, the etching process of the edge portion tends to be particularly incomplete. FIG.
1 and FIG. 12 show this state. That is, as shown in FIG. 11, when the chemical liquid flows in the direction of the arrow in a state where the wafer 2 rotates or does not rotate,
As described above, the flow velocity changes at the edge portion, and a local shape abnormality 47 occurs at the edge portion as shown in FIG .
Due to the occurrence of the shape abnormality 47, the surrounding area is also affected,
Since a uniform etching process is not performed, a flat shape cannot be obtained. FIG. 12 shows the wafer 2 in the vertical direction.
The thickness direction is shown, and the horizontal direction shows the radial direction, and each is enlarged and displayed.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and makes the relative average flow velocity between the chemical solution and the wafer as uniform as possible to reduce the variation in the etching allowance in the wafer surface and the unevenness due to the reaction gas, thereby achieving high precision. An object of the present invention is to provide a high-precision etching method and apparatus which can form a wafer having flatness, have a relatively simple structure, and can be easily implemented.

[0005]

According to a first aspect of the present invention, there is provided a high-precision etching method for rotating a semiconductor single crystal wafer in a chemical solution for etching while rotating the wafer, and etching the surface of the wafer. And flowing the chemical solution along an arc-shaped flow path, rotating the wafer in the same rotational direction as the direction in which the chemical liquid flowing in the flow path bends, and the relative average of the chemical liquid to each part of the wafer surface. It is characterized by making the flow velocity uniform.

According to a second aspect of the present invention, in the high-precision etching apparatus, the semiconductor single crystal wafer is immersed in a chemical for etching, and the relative average speed of the chemical with respect to each part of the wafer surface is made uniform. A high-precision etching apparatus for etching the surface of a wafer,
An arc-shaped channel through which the chemical solution flows, suction means for sucking and holding the wafer, and flowing the wafer through the channel.
And providing a rotating means for rotating the same rotational direction as the direction in which the chemical solution is bent to.

[0007] High precision etching method according to claim 3 of the present invention, by immersing while chemical rotating the semiconductor single crystal wafer for etching, the surface of the wafer a etching method for etching a circle Cyclic medicine
Store the chemical solution in the liquid tank, and immerse the wafer in the chemical solution.
While revolving along the chemical tank in the
The wafer is rotated in the rotation direction opposite to the revolving direction so as to make the relative average flow rate of the chemical solution to each part of the wafer surface uniform.

In the high-precision etching apparatus according to a fourth aspect of the present invention, the semiconductor single crystal wafer is immersed in a chemical solution for etching, and the relative average flow rate of the chemical solution to each part of the wafer surface is made uniform. A high-precision etching apparatus for etching the surface of a wafer,
And chemical bath of annular shape 蓄溜standing the chemical, and suction means for attracting and holding the wafer, a revolving means for revolving along the wafer circumference of the chemical bath, said revolving direction the wafer rotating means for rotating in the opposite direction of rotation
And providing a.

According to a fifth aspect of the present invention, there is provided a high-precision etching apparatus according to the first aspect of the present invention, wherein the suction means includes an outer edge of the wafer, which is separated from the outer edge of the wafer by an appropriate gap, and is substantially the same as the surface of the wafer to be etched. A template provided on the surface is provided.

[0010]

According to the high-precision etching method of the first aspect,
The etching solution is allowed to flow along the arc-shaped flow path,
Etching is performed by rotating the wafer in the same rotational direction as the direction in which the chemical solution flowing in the flow path bends. In this method, the synthesis of the flow rate of the chemical solution and the rotation of the wafer becomes the actual relative flow rate.
In order to make this relative flow rate uniform over time, the principle of polishing is used. In polishing, the wafer (top ring) rotates and the lower platen rotates, but by adjusting the top ring rotation speed and the platen rotation speed, the relative speed in the wafer plane (wafer and polishing cloth) is made uniform. ing. Therefore, by making the flow of the chemical solution into an arc shape and rotating the wafer in the same rotation direction as the direction in which the chemical solution flowing in the flow path bends, the same conditions as in polishing can be created. That is, in the method of the present invention, the chemical for etching corresponds to a polishing cloth in polishing, the flow of the chemical or the revolution of the wafer corresponds to the rotation of a platen (polishing cloth) in polishing, and the rotation of the wafer is the top in polishing. This corresponds to the rotation of the wafer by the ring. In the case of etching, a uniform relative average flow rate (time-average relative flow rate) can be generated in-plane by combining an appropriate wafer rotation speed and an appropriate chemical solution flow rate. When the flow of the chemical solution is a completely parallel flow, it is impossible to obtain a uniform in-plane relative average flow velocity (the outer periphery of the wafer is fast) at any wafer rotation speed except zero.

In the high-accuracy etching apparatus according to the second aspect, an arc-shaped flow of the chemical solution can be created by the arc-shaped flow path, and the wafer is sucked and held by suction means for sucking and holding the wafer and rotating means for rotating the wafer. attracting and holding quality
Direction in which the chemical flowing through the arc-shaped flow path in the chemical is bent
Will be able to rotate in the same rotation direction as
The above-mentioned uniform etching becomes possible.

In the high-precision etching method according to the third aspect of the present invention, the wafer is placed on the chemical solution stored and settled in the annular chemical solution tank.
Immerse and revolve along the chemical tank in this state
Then, by rotating the wafer in the rotation direction opposite to the revolving direction and making the relative average flow rate of the chemical solution to each part of the wafer surface uniform, conditions similar to the above-mentioned polishing are created.

[0013] revolving in the high-precision etching apparatus according to claim 4, the chemical bath of annular shape 蓄溜standing chemical, along a suction means for holding the adsorption of the wafer, the wafer circumferentially of the chemical tank and revolving means for, prior to the wafer
And rotating means for rotating the serial revolution direction opposite to the rotational direction to have e Bei <br/>, chemical wafers immersed in the drug solution
Revolves along the tank and the wafer
Since it can be rotated in the rotation direction opposite to the direction, the uniform etching can be performed.

Further, in the high-accuracy etching apparatus according to the fifth aspect, the suction means is disposed near the outer edge of the wafer, with an appropriate gap from the outer edge of the wafer, and substantially on the same plane as the surface of the wafer to be etched. Since the template is provided, the flow of the chemical solution is rectified by the template during etching, so that an abnormal shape is not generated at the outer edge of the wafer.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 show a first embodiment of the etching apparatus of the present invention, and FIGS. 5 to 8 show a second embodiment thereof.

Embodiment 1 As shown in FIG. 1, a chemical solution for etching enters an arc-shaped (1/4 arc in the figure) flow path 1 from C and has a substantially uniform flow rate along an arc as shown by an arrow. And flows out of D. The disk-shaped wafer 2 is provided in the flow path 1. This wafer 2 is rotated in the same direction as the arc-shaped flow direction of the chemical solution as shown by the arrow. As shown in FIG. 2, the wafer 2 is suction-held by a suction disk 8 of a suction means 3 described later, and is rotated by a rotation means 4. Further, a template 5 is arranged on the outer edge side of the wafer 2 with a gap δ interposed therebetween. In FIG. 2, arrow E indicates the flow direction of the etching chemical, and arrow F indicates the vacuum suction direction of the suction means 3.

FIG. 3 shows the specific shape of the flow path 1 through which the chemical solution 10 flows, and the structure of the supply and discharge system of the chemical solution 10. 1/4 arc-shaped arc-shaped box 9 forming the flow path 1
As shown in FIG. 4, a support for supporting a frame 9a for accommodating the wafer 2 and the suction disk 8 and an opening / closing lid 9b which is openably and closably engaged with the opening side thereof and a rotary shaft 11 connected to the suction disk 8 are provided. The portion 9c is formed. As shown in FIG. 3, distributors 14 and 15 are connected to the supply side and the discharge side of the arc-shaped box 9 via dispersion plates 12 and 13. The distributor 14 on the supply side is connected to a chemical circulation tank 20 for storing the chemical 10 via a pipe 19 in which a flow meter 16, an on-off valve 17 and a pump 18 are arranged. In addition, a pipe 21 for supplying pure water is connected to the pipe 19 via an on-off valve 22. The chemical liquid circulation tank 20 is heated to an appropriate temperature by the temperature controller 23. On the other hand, the discharge side distributor 1
A return pipe 25 is connected to 5 via a three-way opening / closing valve 24 to return the chemical solution 10 to the chemical solution circulation tank 20. In addition, chemical solution circulation tank 2
Numeral 0 is connected to the drain side via an on-off valve 26, and the three-way on-off valve 24 is also connected to the drain side via a discharge pipe 27. The chemical solution 10 heated to an appropriate temperature by the above structure is supplied from the chemical solution circulation tank 20 into the arc-shaped box 9 via the pump 18 and the like.
After flowing through the arc-shaped flow path 1, it is returned again into the chemical solution circulation tank 20 and circulates.

Next, the suction means 3 will be described. As shown in FIG. 4, the disk-shaped suction disk 8 is accommodated and arranged in the flow path 1 of the arc-shaped box 9, and the wafer 2 is mounted on the surface thereof. A rotary shaft 11 is connected to the suction disk 8, and an air hole (not shown) formed through the inside of the rotation shaft 11 is formed in the suction disk 8.
It communicates with a number of suction holes 28 formed through the inside. On the other hand, the air hole in the rotating shaft 11 is connected to a vacuum tank 30 via an on-off valve 29 by a pipe line 31.
Is connected to a vacuum pump 32 to vacuum the inside of the vacuum tank 30.
To By opening the on-off valve 29 with the above structure, the wafer 2 is held by vacuum suction on the surface of the suction disk 8.

Next, the rotating means 4 will be described. Rotating shaft 11
As shown in FIG. 4, is supported by the sealing portion 33 of the support portion 9c of the arc-shaped box body 9. A pulley 36 on the drive motor 35 side is connected via a pulley belt 34 to a pulley (not shown) provided on the rotating shaft 11 side. Also,
A drain panel 37 is provided between the rotary shaft 11 and the vacuum tank 30 for collecting the chemical solution 10 leaking from around the rotary shaft 11, and communicates with the drain via a pipe 38. By operating the drive motor 35 according to the above structure, the wafer 2 sucked by the suction disk 8 rotates in the flow path 1.

Next, the template 5 will be described.
As shown in FIGS. 2, 4 and 9, a ring-shaped template 5 is fixed to the outer periphery of the suction cup 8. The wafer 2 held by suction on the inner wall side of the template 5 and on the suction disk 8
A gap δ is formed between the outer edge and the outer edge. The value of the gap δ is set experimentally and empirically. The upper surface of the template 5 and the surface (upper surface) of the wafer 2 to be etched are formed on substantially the same plane.

Next, the operation of the present embodiment will be described. As described above, the wafer 2 is disposed substantially in the middle of the flow path 1. The vacuum pump 32 is operated to hold the wafer 2 on the suction board 8 by suction. The pump 18 is operated to send the chemical 10 in the chemical circulation tank 20 to the distributor 14 on the supply side. The chemical solution 10 and the like flow into the arc-shaped box body 9 by the dispersion plate 12 and form the arc-shaped flow of the chemical solution 10 as shown in FIG. The chemical solution 10 having passed through the flow path 1 is collected via the dispersion plate 13 and the distributor 15 on the discharge side, and is returned into the chemical solution circulation tank 20. On the other hand, when the drive motor 35 is operated, the wafer 2 rotates on its own. As shown in FIG. 3, the wafer 2 rotates in the direction of arrow G (the same rotational direction as the arrow H indicating the flow direction of the chemical solution), and the chemical solution 10 flows in the flow path 1 as indicated by the arrow H, and the speeds of the two are appropriately adjusted. By controlling, it is possible to make the relative average flow velocity of the chemical solution 10 to each part on the surface of the wafer 2 substantially uniform. When the relative average flow rate becomes uniform, the variation in the etching allowance on the surface of the wafer 2 decreases, and as a result, an etched wafer having flatness is formed. On the other hand, since the template 5 having the above-described shape is arranged near the outer edge of the wafer 2, the flow of the chemical solution 10 from the arrow B is rectified by the template 5 as shown in FIG. Is reduced, and the shape change of the outer edge is reduced. FIG. 10 shows this state, and it can be seen that abnormalities in the shape at the edge portion are greatly improved as compared with the case of FIG.

Embodiment 2 In this embodiment, the wafer 2 is rotated and revolved, and the chemical 10
And an etching apparatus that keeps the relative average flow rate of the chemical solution to each part on the surface of the wafer 2 as uniform as possible.
As shown in FIG. 5, the chemical solution 10 is stored in the annular (doughnut-shaped) chemical solution tank 7 in a stationary state, and the wafer 2 is indicated by an arrow J.
It is formed so as to rotate in the direction and revolve in the direction of arrow K (the direction of arrow J and the direction of arrow K are opposite to each other). As shown in FIG. 6, the wafer 2 is suction-supported on the lower surface side of the suction plate 8a of the suction means 3a in the drawing. Also, a template 5 is provided on the outer edge side of the wafer 2 in the same manner as shown in FIG.
a is provided. FIGS. 7 and 8 show FIG. 5 in more detail. The wafer 2 is held by the suction means 3a and the rotation means 4a (described later) disposed on the tip side of the revolving means 6. As shown in FIG. 8, the suction means 3a is formed in the same way as the suction means 3 shown in FIG. In this case, the suction means 3a is arranged on the revolving means 6 side described later to revolve with the wafer 2 (detailed structure is omitted). In FIG. 6, arrow K indicates the rotation direction of the wafer 2, and arrow M indicates the vacuum suction direction.

Next, the means for revolving and rotating the wafer 2 and the supply / discharge system of the chemical 10 to the chemical tank 7 will be described with reference to FIG. The revolving means 6 includes a center shaft 39 pivotally supported on the immobile side of the apparatus at the center position of the chemical solution tank 7, a revolving drive motor 40 for rotating the center shaft 39, and a base end connected to the center shaft 39 and a distal end. It comprises an arm member 41 and the like on which the suction means 3a and the rotation means 4a are mounted. On the other hand, the rotating means 4a includes a drive motor 42 fixed to the arm member 41, and the drive motor 42 is connected to the rotating shaft 11 connected to the suction disk 8a. Chemical liquid 1 in chemical liquid circulation tank 20a
0 is supplied into the chemical tank 7 via the pipe 43 and the on-off valve 44. The chemical solution 10 in the chemical solution tank 7 is supplied to the three-way on-off valve 4.
5, the liquid is returned to the chemical liquid circulation tank 20a and the drain side. The chemical solution 10 in the chemical solution circulating tank 20a is supplied to the temperature controller 23.
Heated to an appropriate temperature by a. The chemical circulation tank 20a is connected to the drain via an on-off valve 46. With the above structure, the wafer 2 sucked and held by the suction means 3a arranged on the tip end side of the arm member 41 of the revolving means 6,
It is revolved by the rotating means 4 a and revolved via the arm member 41 by operating the revolving drive motor 40.

Next, the operation of this embodiment will be described.
The wafer 2 sucked and held by the suction means 3a is immersed in the chemical solution 10 stored and held in the chemical solution tank 7, and is arranged downward. The revolution and rotation of the wafer 2, the relative chemical flow between the wafer 2 and the drug solution 10 occurs, more by setting the rotational speed and direction of the revolution and rotation of the wafer appropriately, wafer 2 and the chemical It is possible to keep the relative average flow velocity between the ten almost uniform, and it is possible to improve the etching effect substantially the same as in the first embodiment. Of course,
With the template 5a, the shape change of the edge portion of the wafer 2 is also reduced.

In the above embodiment, the suction means 3, 3a, the rotation means 4, 4a, the revolving means 6 and the like as shown are employed, but the detailed structure is not limited to that shown. In addition, the flow path 1 of the first embodiment has a quarter-arc shape, but is not limited thereto. Further, although the single wafer 2 is engaged with the flow path 1 and the chemical solution tank 7, the present invention is not limited to this. Further, the chemical solution tank 7 is a simple donut-shaped one, but may be a concentric multilayered one.

[0026]

According to the present invention, the following remarkable effects are obtained. (1) An apparatus structure is adopted in which a chemical solution flows in an arc-shaped flow path and the wafer rotates in the flow path, and the wafer rotates and revolves in an annular chemical solution tank for storing the chemical solution. The relative average flow velocity between each part of the wafer surface and the chemical solution can be made substantially uniform. Thereby, the accuracy of the flatness of the wafer can be improved. (2) By rotating the silicon wafer at a relative average flow velocity, unevenness due to a reaction gas generated at the time of etching is reduced, a smooth etching process is performed, and a high-precision flatness is obtained. (3) By providing the template close to the outer edge of the wafer, the flow of the chemical solution around the outer edge of the wafer is rectified, the change in the shape of the edge is reduced, and a highly accurate chemically etched wafer can be formed. (4) Since the device structure is compact and simple and does not use any special equipment, it can be implemented with relatively low equipment costs.

[Brief description of the drawings]

FIG. 1 is a plan view for explaining a first embodiment of the present embodiment.

FIG. 2 is an axial sectional view showing an engagement state between the wafer suction means and a template according to the first embodiment.

FIG. 3 is a configuration diagram showing a flow path and a supply / discharge path structure of a chemical solution to the flow path according to the first embodiment.

FIG. 4 is a configuration diagram showing suction means and wafer rotation means of the first embodiment.

FIG. 5 is a plan view for explaining a second embodiment of the present invention.

FIG. 6 is an axial sectional view showing an engagement state between a wafer suction unit and a template according to a second embodiment.

FIG. 7 is a configuration diagram showing a wafer revolving means and a supply / discharge system of a chemical solution to a chemical solution tank according to a second embodiment.

FIG. 8 is a plan view showing a schematic structure of a chemical tank and an adsorbing means according to a second embodiment.

FIG. 9 is an explanatory plan view for explaining effects of the template in the first and second embodiments.

FIG. 10 is a diagram showing the effect of a template.

FIG. 11 is an explanatory plan view for explaining a problem of a conventional wafer.

FIG. 12 is a diagram showing a shape change of an edge portion of a wafer in a conventional etching apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow path 2 Semiconductor crystal wafer (wafer) 3, 3a Suction means 4, 4a Rotation means 5, 5a Template 6 Revolving means 7 Chemical solution tank 8, 8a Suction board 9 Arc box 9a Frame part 9b Opening lid 9c Support part 10 Chemical liquid 11 Rotary shaft 12, 13 Dispersion plate 14, 15 Distributor 16 Flow meter 17, 22, 26, 29, 44, 46 On-off valve 18 Pump 19, 21, 31, 38 Pipeline 20 Chemical liquid circulator 20a Chemical liquid circulation tank 23 , 23a Temperature controller 24 Three-way on-off valve 25 Return pipe 27 Discharge pipe 28 Suction hole 30 Vacuum tank 32 Vacuum pump 33 Sealing means 34 Pulley belt 35, 42 Drive motor 36 Pulley 37 Drain panel 39 Center shaft 40 Revolution drive motor 41 Arm member 43 Piping 45 Three-way on-off valve

Claims (5)

(57) [Claims] 1. An etching method for immersing a semiconductor single crystal wafer in a chemical solution for etching while rotating, and etching the surface of the wafer, wherein the chemical solution is circulated along an arc-shaped flow path. A high-accuracy etching method, characterized in that the wafer rotates in the same rotational direction as the direction in which the chemical solution flowing in the flow path bends, so that the relative average flow rate of the chemical solution to each part of the wafer surface is uniform. 2. A high-precision etching apparatus for immersing a semiconductor single-crystal wafer in a chemical solution for etching, making the relative average speed of the chemical solution to each part of the wafer surface uniform, and etching the surface of the wafer. Te, an arcuate flow path for circulating the chemical solution, a suction means for attracting and holding the wafer, the channel said wafer
Precision etching apparatus and providing a rotating means for rotating in a direction identical to the rotational direction of the drug solution is bent flowing. 3. A semiconductor single crystal wafer in the chemical for etching is immersed while rotating, the surface of the wafer a etching method for etching processing, an annular
The chemical solution is stored in the chemical solution tank of, and the wafer is immersed in the chemical solution.
While revolving along the chemical tank in the state of being immersed,
A high-precision etching method, characterized in that the wafer is rotated in the direction of rotation opposite to the revolving direction to make the relative average flow rate of the chemical solution to each part of the wafer surface uniform. 4. A high-precision etching apparatus for immersing a semiconductor single-crystal wafer in a chemical solution for etching, making the relative average flow rate of the chemical solution to each part of the wafer surface uniform, and etching the surface of the wafer. Te, a chemical bath of annular shape 蓄溜standing the chemical, and suction means for attracting and holding the wafer, a revolving means for revolving along the wafer circumference of the chemical bath, the said wafer revolution precision etching apparatus and providing a rotating means for rotating in the opposite rotational direction to the direction. 5. A template provided in the vicinity of the outer edge of the wafer of the suction means, provided at an appropriate distance from the outer edge of the wafer and substantially on the same plane as the surface of the wafer to be subjected to the etching process. The high-precision etching apparatus according to claim 2 or 4, wherein