JP2000252255A - Method and device for wet etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve yield of a semiconductor device by suppressing minute foreign materials from sticking to a semiconductor wafer surface, in a wet etching process for a semiconductor wafer. SOLUTION: Related to a series of wet etching processes wherein a plurality of semiconductor wafers 2 are submerged in a chemical liquid bath 1 at the same time and are submerged in a washing bath for washing, a partition 3 which separates the plurality of semiconductor wafers 2 is provided at least at a gas-liquid interface part when the semiconductor wafer 2 is taken out of the chemical liquid bath 1 as well as at delivery of it to the washing bath 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet etching method and a wet etching apparatus. More particularly, in a semiconductor wafer processing process, a plurality of semiconductor wafers are simultaneously etched with an HF aqueous solution or a mixed solution thereof, and then washed with water. In a series of wet etching processes for drying, foreign substances generated from an adjacent wafer when passing through a gas-liquid interface are prevented from adhering to the wafer surface.

[0002]

2. Description of the Related Art Generally, a wet etching process for a semiconductor wafer is performed using HF and an aqueous solution thereof.
A batch type processing apparatus having a plurality of processing tanks and simultaneously processing a plurality of wafers is mainly used. Recently, a one-bath processing apparatus that performs etching, washing, and drying in one processing tank has also appeared.

FIG. 8 shows, for example, Japanese Patent Application Laid-Open No. H10-200000.
FIG. 1 is a diagram showing a cleaning unit used for cleaning a semiconductor wafer disclosed in Japanese Patent Application Laid-Open Publication No. H10-115,004. In the figure, 11 is a cleaning unit, 12 is an etching tank, 13 is a pure water flow tank, 14
Denotes a first pure water dip cleaning tank, 15 denotes a second pure water dip cleaning tank, 16 denotes a first pure water cleaning tank, and 17 denotes a second pure water cleaning tank. In the cleaning unit of the present etching processing apparatus, in order to improve the yield of semiconductor devices, in the pure water flow tank 13, the flow rate at the time of water washing after etching is increased, and foreign matter adhesion and surface generated from the backside oxide layer of the adjacent wafer are increased. What suppresses roughening is shown.

[0004]

The conventional wet etching apparatus is configured as described above. In the pure water flow tank 13, a turbulent flow occurs when the flow rate is increased, and conversely, the number of adhered foreign substances increases. Had. On the other hand, the inventors have found that in the wet etching process, foreign substances are attached during the transfer of the wafer into and out of the etching liquid or the cleaning liquid, rather than in the state where the wafer is immersed in the etching liquid or the cleaning liquid. . FIG.
FIG. 2 is a diagram illustrating such a problem in a conventional etching apparatus. In the figure, reference numeral 2 denotes a semiconductor wafer, and 4 denotes a minute foreign substance. If the oxide film 20 is formed thickly on the back surface of the semiconductor wafer 2, as shown in FIG. 9, when the wafer 2 is taken in and out of the etching solution or the cleaning solution, the back surface of the adjacent wafer is passed when the wafer 2 passes through the gas-liquid interface. Oxide layer 2
Fine particles having a particle diameter of about 0.1 μm generated from 0 adhere to the wafer surface, and it is very difficult to obtain a wafer having a clean surface.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to solve the problems described above when a wafer is immersed in a cleaning solution, when a wafer is taken out from an etching solution or a cleaning solution, and when a wafer passes through a gas-liquid interface. It is an object of the present invention to provide a wet etching method and a wet etching apparatus capable of obtaining a wafer having a clean surface without adhering foreign matter generated from the back surface.

[0006]

According to a first aspect of the present invention, there is provided a wet etching method in which a plurality of semiconductor wafers are simultaneously immersed in a chemical bath to perform wet etching, and then immersed in a cleaning bath for cleaning. In the wet etching step, when the semiconductor wafer is taken out of the chemical bath and when the semiconductor wafer is taken in and out of the cleaning bath, a baffle for partitioning the plurality of semiconductor wafers is provided at least at the gas-liquid interface. Things.

In the wet etching method according to the second method of the present invention, when a semiconductor wafer is immersed in a chemical solution bath or a cleaning bath, a partition between the semiconductor wafers by a baffle plate is removed.

A wet etching apparatus according to a first structure of the present invention is a wet etching apparatus for immersing a plurality of semiconductor wafers simultaneously in a chemical bath to perform wet etching, and then immersing the semiconductor wafers in a cleaning bath for cleaning. When taking out the semiconductor wafer from the tank, and when taking the semiconductor wafer into and out of the cleaning tank, a baffle plate is installed at least at the gas-liquid interface of the chemical liquid tank and the cleaning tank, and partitions the plurality of semiconductor wafers. It is provided.

In a wet etching apparatus according to a second configuration of the present invention, a baffle for partitioning between semiconductor wafers is detachably installed in a chemical solution tank and a cleaning tank.

A wet etching apparatus according to a third aspect of the present invention includes a transfer means for transferring a plurality of semiconductor wafers with a baffle sandwiched between the semiconductor wafers.

[0011] In a wet etching apparatus according to a fourth configuration of the present invention, the baffle for partitioning the semiconductor wafers has a flow portion through which the liquid can flow in a portion immersed in the liquid.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The following can be considered as a cause of foreign matter generated from an oxide layer on the back surface of an adjacent wafer adhering to the wafer surface.

The surface of the wafer after etching with HF or an aqueous solution thereof becomes more hydrophobic, and is in a surface state to which foreign matter is likely to adhere. On the other hand, if the oxide film is formed thick on the back surface of the wafer, foreign matter is likely to be generated. In particular, when there is an oxide film remaining on the back surface even after etching, foreign substances are easily generated. When a plurality of such wafers are simultaneously immersed in an etching solution or a cleaning solution for etching or washing, when passing through a gas-liquid interface, the Marangoni convection due to a difference in meniscus shape or a difference in surface tension of the liquid surface causes the adjacent wafer from the back surface to the front surface. A flow at the liquid level that occurs,
As a result, foreign matter adheres to the wafer surface.

In the present invention, when etching and cleaning of the etching solution, a baffle plate for partitioning the wafers at the gas-liquid interface of the chemical solution bath and the washing bath is provided, so that adjacent wafers can pass through the gas-liquid interface. This is to prevent foreign matter generated from the back surface layer from adhering and to obtain a wafer with a clean surface.

FIG. 1 is a conceptual diagram showing a wet etching processing method which is the basis of the present invention. This drawing shows the time of lifting a wafer when processing a plurality of wafers.
Here, 1 is a chemical bath filled with HF and an aqueous solution thereof or a washing bath filled with pure water, 2 is a semiconductor wafer, and a thick oxide layer 20 is formed on the back surface. 3 is a baffle,
4 is a minute foreign substance.

Next, the operation will be described. When removing the plurality of semiconductor wafers 2 from the chemical tank or the washing tank 1, the baffle plate 3 is installed between the plurality of semiconductor wafers 2, and at that time, the baffle plate 3 is connected to the gas-liquid interface between the chemical solution or pure water and the outside air. When the semiconductor wafer 2 passes through the gas-liquid interface, the foreign matter 4 generated from the oxide layer 20 on the back surface of the adjacent wafers flows along the liquid surface from the back surface of the wafer to the front surface when the semiconductor wafer 2 passes through the gas-liquid interface. In addition, since it is blocked by the baffle plate 3, adhesion of foreign matter to the hydrophobic wafer surface is suppressed, and a wafer with a clean surface can be obtained.

In FIG. 1, the case where a plurality of semiconductor wafers 2 are lifted from the chemical solution tank or the washing tank 1 has been described. It is good to install in the same position as.

FIG. 1 shows the case where the baffle plate 3 is installed when a plurality of semiconductor wafers 2 are lifted from the chemical tank or the washing tank 1. When it is immersed inside, the baffle 3 may be left at the above-mentioned position, or the baffle 3 may be removed. When the baffle plate 3 is removed, there is an effect that the flow of the liquid between the wafers is improved.

In FIG. 1, the baffle plate 3 is shown as reaching the bottom of the chemical tank or the washing tank 1. However, as shown in FIG. 2, the baffle plate 3 is formed of at least a chemical or pure water and the outside air. What is necessary is just to install so that it may come to a gas-liquid interface part.
Providing the baffle plate 3 only at the gas-liquid interface has the effect of improving the flow of liquid between the wafers. In addition, a portion of the baffle plate 3 that reaches the bottom surface and that is immersed in the liquid may be provided with a hollow to allow the liquid to flow.

FIG. 1 shows a case where the plurality of semiconductor wafers 2 and the baffle plate 3 are separately put into and taken out of the chemical solution tank or the washing tank 1, but a baffle plate for partitioning the plurality of semiconductor wafers and the wafers is described. 3 may be simultaneously carried through a series of etching steps in a state of being placed on one carrying means.

An oxide film 20 is formed on the back surface of the semiconductor wafer 2.
Although there is a case where there is, there may be one without an oxide film.

[0022]

The present invention will be specifically described below with reference to examples. Embodiment 1 FIG. FIG. 3 is a perspective view showing a wet etching apparatus for a semiconductor wafer according to the first embodiment of the present invention, which is a straight arrangement type two-lot transfer processing apparatus. 4A and 4B are explanatory diagrams illustrating details of a chemical tank or a washing tank according to the first embodiment of the present invention. FIG. 4A illustrates a state of a baffle plate at the time of opening and closing, and FIG. 4 (a)
FIG. 3 is a sectional view taken along line AA of FIG. In the figure, 21 is a loader unit, 22 is a cassette for storing semiconductor wafers, 23 is a TR robot, 24 is a dedicated tray, 25 is an R robot having a function of holding a semiconductor wafer, 26a, 26b,
26c and 26e are chemical solution tanks, 26d, 26f and 26g are rinsing tanks, 26h is a chuck claw part washing tank, and 26i is a drying tank.

Next, the operation will be described. When the cassette 22 containing the semiconductor wafer before processing is carried to the loader unit 21, the TR robot 23 transfers the semiconductor wafer before and after processing between the cassette 22 and the dedicated tray 24. The R robot 25 sequentially transports the plurality of semiconductor wafers in the dedicated tray 24 to the processing tanks 26a to 26i such as a chemical tank and a rinsing tank, and returns the semiconductor wafers to the loader unit 21 again. Chemical solution tanks 26a, 26
b, 26c, 26e, rinse tanks 26d, 26f, 26g
4, a baffle plate that can be opened and closed is attached as shown in FIG. 4 (the baffle plate is omitted in FIG. 3). When a semiconductor wafer is taken in and out of each processing tank, the baffle plate is closed and the baffle plate is placed in the processing tank. I try to soak. In this case, the baffle is configured to come to the gas-liquid interface. Further, the length of the baffle plate is not in contact with the bottom surface of the processing tank, and the liquid can flow between the immersed semiconductor wafers. After the semiconductor wafer is taken out, the baffle is kept open. With such a configuration, the semiconductor wafer is not affected by the foreign matter generated from the back surface oxide layer of the adjacent wafer, so that the foreign matter (number) adhering to the wafer surface is suppressed.

Embodiment 2 FIG. FIG. 5 is a conceptual diagram showing a wet etching method according to the second embodiment of the present invention. In Example 1, the baffle was kept installed while the semiconductor wafer was immersed in the chemical solution or pure water. In this example, the baffle of FIG. The baffle has been removed from the liquid. As a result, the flow near the liquid surface is improved, the efficiency of replacement and removal of foreign matter in the liquid is increased, and foreign matter attached to the baffle plate can be separately washed, and the number of foreign matter attached to the wafer surface can be further reduced.

Embodiment 3 FIG. FIG. 6 shows a state of a baffle plate in which a cutout (flow portion) 5 is provided in a portion of the baffle plate immersed in the liquid to partition only the gas-liquid interface. This has the effect of improving the flow of liquid between the wafers.

Embodiment 4 FIG. FIG. 7 is a view showing a case where simultaneous processing is performed with a baffle sandwiched between wafers through a series of etching steps, and shows a state in which the wafer is lifted. In the drawing, reference numeral 6 denotes a wafer transfer jig, which shows a state in which the baffle plate 3 is fixed to a lifter in a cassetteless wafer transfer mode. In the case of the cassette carrying mode, the baffle plate is fixed to the cassette. With such a configuration, in a series of etchings, since a state in which the wafers are always partitioned by the baffle plate is maintained, the wafers are not affected by foreign substances generated from the back surface oxide layer of the more adjacent wafers. Foreign matter adhering to wafer surface (number)
Is suppressed.

[0027]

As described above, according to the first method of the present invention, a plurality of semiconductor wafers are simultaneously immersed in a chemical solution bath and wet-etched, and then immersed in a cleaning bath for cleaning. In the wet etching step, when the semiconductor wafer is taken out of the chemical bath and when the semiconductor wafer is taken in and out of the cleaning bath, the baffle for partitioning the plurality of semiconductor wafers is provided at least at the gas-liquid interface. In addition, the adhesion of minute foreign matter to the wafer surface can be significantly improved as compared with the conventional method, and as a result, the yield of semiconductor devices can be improved.

According to the second method of the present invention, in the first method, when the semiconductor wafer is immersed in the chemical solution bath or the cleaning bath, the partition between the semiconductor wafers by the baffle plate is removed. This has the effect of improving the flow of liquid between them.

According to the first structure of the present invention, in a wet etching apparatus in which a plurality of semiconductor wafers are simultaneously immersed in a chemical bath to perform wet etching, and then immersed in a cleaning bath to perform cleaning, When taking out the semiconductor wafer, and when taking the semiconductor wafer into and out of the cleaning tank, a baffle plate is provided at least at the gas-liquid interface of the chemical liquid tank and the cleaning tank, and partitions the plurality of semiconductor wafers. As a result, the adhesion of minute foreign matter to the wafer surface can be greatly improved as compared with the conventional apparatus, and as a result, the yield of semiconductor devices can be improved.

According to the second configuration of the present invention, in the first configuration, the baffle for partitioning between the semiconductor wafers is detachably installed in the chemical solution tank and the cleaning tank, so that the baffle plate can be easily formed. This has the effect that it can be installed at the gas-liquid interface.

According to the third structure of the present invention, in the first structure, the semiconductor device is provided with the transfer means for transferring a plurality of semiconductor wafers with the baffle sandwiched between the semiconductor wafers. Can be suppressed, and the configuration of a one-bath processing apparatus for performing etching → water washing → drying becomes easy.

According to the fourth structure of the present invention, in the first to third structures, the baffle for partitioning between the semiconductor wafers has a flow portion through which the liquid can flow in a portion immersed in the liquid. This has the effect of improving the flow of the liquid between the semiconductor wafers.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a wet etching processing method which is a basis of the present invention.

FIG. 2 is a conceptual view showing another wet etching method which is the basis of the present invention.

FIG. 3 is a perspective view showing a semiconductor wafer wet etching apparatus according to Embodiment 1 of the present invention.

FIG. 4 is an explanatory diagram illustrating details of a chemical solution tank or a washing tank according to the first embodiment of the present invention.

FIG. 5 is a conceptual view showing a wet etching method according to a second embodiment of the present invention.

FIG. 6 is a conceptual view showing a wet etching method according to a third embodiment of the present invention.

FIG. 7 is a conceptual diagram showing a wet etching method according to a fourth embodiment of the present invention.

FIG. 8 is a view illustrating a conventional wet etching method for a semiconductor wafer.

FIG. 9 is a view showing a problem in a conventional wet etching method for a semiconductor wafer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Chemical tank or water washing tank, 2 Semiconductor wafer, 3 Baffles, 4 Fine foreign matter, 5 Distribution part, 6 Wafer transfer jig, 11 Cleaning unit, 12 Etching tank, 13
Pure water flow tank, 14 First pure water dip washing tank, 15
2nd pure water dip cleaning tank, 16 1st pure water cleaning tank, 17 2nd pure water cleaning tank, 20 oxide film, 21 loader section, 22 cassette for accommodating semiconductor wafer, 23
TR robot, 24 dedicated tray, 25 R robot, 26a, 26b, 26c, 26e chemical tank, 26d,
26f, 26g Rinse tank, 26h Chuck claw part washing tank, 26i drying tank.

Claims (6)

[Claims] In a series of wet etching steps, a plurality of semiconductor wafers are simultaneously immersed in a chemical bath to perform wet etching, and then immersed in a cleaning bath to perform cleaning.
When removing the semiconductor wafer from the chemical solution tank, and when taking the semiconductor wafer into and out of the cleaning tank, a baffle for partitioning the plurality of semiconductor wafers is provided at least at a gas-liquid interface. Etching method. 2. The wet etching method according to claim 1, wherein when the semiconductor wafer is immersed in the chemical bath or the cleaning bath, the partition between the semiconductor wafers by the baffle plate is removed. 3. A wet etching apparatus for simultaneously immersing a plurality of semiconductor wafers in a chemical bath for wet etching and thereafter immersing the semiconductor wafers in a cleaning bath for cleaning, wherein the semiconductor wafer is taken out from the chemical bath and A wet etching apparatus, comprising: a baffle plate that is installed at least in a gas-liquid interface between the chemical liquid tank and the cleaning tank when a semiconductor wafer is taken in and out of the cleaning tank, and that partitions the plurality of semiconductor wafers. 4. The wet etching apparatus according to claim 3, wherein the baffle for partitioning between the semiconductor wafers is detachably installed in the chemical tank and the cleaning tank. 5. The wet etching apparatus according to claim 3, further comprising a transfer unit configured to transfer the plurality of semiconductor wafers with a baffle sandwiched between the semiconductor wafers. 6. The wet etching apparatus according to claim 3, wherein the baffle for partitioning between the semiconductor wafers has a flow portion through which the liquid can flow at a portion immersed in the liquid.