JP3428615B2 - Etching apparatus and etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer etching apparatus and etching method, and more particularly to an etching technique for bubbling a semiconductor wafer being etched.

[0002]

2. Description of the Related Art As a conventional etching apparatus, for example, one disclosed in Japanese Patent Publication No. 7-85471 is known. This etching apparatus was equipped with a bubbling tube that discharges air bubbles into the etching liquid tank. By blowing clean air from the bubbling tube, the etching solution is agitated to uniformly etch the wafer surface.

[0003]

However, in this etching apparatus, the bubbling tube is fixed to the semiconductor wafer holding casing. Therefore, the air bubbles to be blown hit a certain portion with a certain strength during etching. Therefore, the flatness of the surface of the semiconductor wafer has not been good. Or
A ring mark (a ring-shaped mark) formed by the etching solution was formed on the wafer surface.

Therefore, as a result of diligent research, the inventor has found that the air bubble blown away from the semiconductor wafer can increase the flatness of the wafer surface, and the closer the blowout port can remove the ring mark. did. Further, they have found that an inert gas or the like is suitable as the bubbling gas to be sprayed together.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the flatness of a wafer surface during etching and improve its surface quality. An object of the present invention is to prevent deterioration of the etching solution.

[0006]

According to a first aspect of the present invention, there is provided an etching solution tank into which an etching solution is injected, a wafer holder for holding a semiconductor wafer in the etching solution tank, and an inside of the etching solution tank. to be disposed, etched and a gas supply means for supplying the bubbling gas toward the semiconductor wafer held by the wafer holder instrumentation
The gas supply means is located at the bottom of the etching solution tank.
A bubbling gas supply pipe is installed and configured.
The bubbling gas supply pipe of the device close to the wafer holder
It is an etching device that can be separated and moved .

According to a second aspect of the present invention, in an etching method in which a bubbling gas is sprayed onto a rotating semiconductor wafer immersed in an etching solution, the strength of the bubbling gas sprayed is high after the etching is started.
In other words, this is an etching method that weakens this after a certain period of time .

[0008]

In the etching apparatus according to the first aspect of the invention,
In that case, by separating the bubbling gas supply pipe
Bubbling gas can be applied to semiconductor wafers from afar.
It can be sprayed in two positions, the Kukarato. It changes its strength. As a result, the ring mark on the surface of the wafer can be removed and at the same time the flatness thereof can be improved. A high flatness is obtained by blowing gas from a distance, and a ring mark on the surface is removed by blowing gas from a near distance.

In the etching method according to the second aspect, by controlling the blowing intensity of the bubbling gas according to time , for example, by controlling the blowing from a distance and the blowing from near , according to the time .
The wafer surface flatness and the ring mark removal are simultaneously obtained. For example, if the etching time is 30 minutes
For example, 15 minutes after the start of etching, it ’s strong from near,
A distant spray shall be performed for the following 15 minutes.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an etching apparatus according to the present invention will be described below. FIG. 1 is a sectional view showing an etching apparatus according to an embodiment of the present invention. In this embodiment, the etching apparatus includes an etching solution tank 11 filled with an etching solution, a rack 12 for holding wafers arranged in the etching solution tank 11, and an approaching / separating operation with respect to the rack 12. And a bubbling gas supply pipe 13 provided freely.

The rack 12 is a known rotary rack, has a substantially cylindrical shape, and has a structure in which three support rods 14 are arranged between side plates 12A and 12B arranged at both ends in the axial direction. . The silicon wafer is rotatably held between the support rods 14 while the outer edge surfaces (side surfaces) thereof are in contact with each other. Reference numerals 15A and 15B denote rotation axes of the rack 12. Although not shown in the figure, the drive mechanism is configured by using a known gear mechanism.

The bubbling gas supply pipe 13 is constructed so as to be vertically and horizontally movable in the etching liquid tank 11, and a large number of holes 13A are formed on its outer surface at substantially equal intervals along the axial direction. And this bubbling gas supply pipe 1
3 is capable of supplying a predetermined gas from the gas supply source 16 to the gas flow path inside the tube. Reference numeral 17 indicates a valve provided in the supply path. As the bubbling gas, N ₂ gas or the like is used in addition to the inert gas such as argon gas. In addition, the gas pressure, the flow velocity, and the like to be sprayed can be arbitrarily controlled by the gas supply source 16.

In the etching apparatus having the above structure, the silicon wafer is held on the rack 12 and rotated at a predetermined rotation speed in an etching solution (HF system, HF / HNO ₃ system, etc.) to remove the surface of the silicon wafer. Etching is performed. At this time, the bubbling gas supply pipe 13 is brought closer to a position separated from the rack 12 (which is rotating at a fixed position) by a predetermined distance. Then, the inert gas is blown out through the hole
It is jetted from 3A at a constant speed (the supply gas pressure is kept at a constant value). As a result, the etching liquid near the surface of the silicon wafer is largely stirred, and the surface traces such as the ring mark are erased. Or it does not occur. And
After a lapse of a predetermined time, the bubbling gas supply pipe 13 is moved away from the above position by a predetermined distance in a state where the gas ejection is continued (gas pressure is constant). As a result, the flatness of the wafer surface is improved, and the deterioration of the etching solution is prevented as a whole. This is the effect that the etching solution as a whole is sufficiently stirred. When the gas supply pipe 13 is fixed, the rack 12 may be moved toward and away from the gas supply pipe 13.

2 to 4 show another embodiment of the present invention. In this embodiment, a bubbling tube 22 is arranged at the bottom of the etching tank 21 so as to be horizontally movable along the bottom surface. The bubbling pipe 22 is located at a position horizontally separated by 160 mm from the center of the jig 23 and at a distance of 120 m.
It is configured so as to be able to reciprocate between a position separated by m (wafer radius + 20 mm). Further, 2.0 kg / cm ² of N ₂ gas is blown from the bubbling pipe 22. This bubbling time is shortened by about 3 seconds from the etching time (40 seconds). Within this time, the bubbling pipe 22 is moved from the 140 mm position to the 120 mm position, further away from the 160 mm position, and moved back to the 140 mm position. Figure 3 shows a distant position (160 mm
The degree of the ring mark when the gas is supplied only from one of the position (position) and the close position (100 mm position) is shown. The step of the ring mark is large at a distant position and small at a near position (about 1/10). Further, FIG. 4 similarly shows the relationship of the wafer surface flatness. TTV (Total Thickness Variation) becomes worse as it is closer (about 1/10). Conventionally, since the liquid was supplied from one place, the ring mark and the flatness were intermediate. Then, as a result of moving the position of the bubbling tube as described above, it is understood that the bubbling gas can be supplied from both positions, and the surface flatness and the ring mark removal can both be achieved.

The two bubbling gas supply pipes are fixed at two places in the etching solution tank, that is, the central portion and the corner portion of the bottom surface.
It can also be installed. With this configuration, the same effect as that of the above-described embodiment can be exhibited. That is, by spraying the inert gas from the tube directly below the wafer for a certain period of time and then alternately from the tube at the corner, both wafer surface flatness and ring mark removal can be achieved. Further, by changing the gas pressure blown out from one supply pipe stepwise within the etching time, the strength of the blown gas can be changed.

[0016]

According to the present invention, the surface of the wafer after etching can be maintained with high flatness, and at the same time, the ring mark can be removed from the surface. In addition, deterioration of the etching solution can be prevented.

[Brief description of drawings]

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

FIG. 2 is a schematic sectional view showing an etching apparatus according to another embodiment of the present invention.

FIG. 3 is a graph showing a ring mark generation rate in an etching apparatus according to another embodiment of the present invention.

FIG. 4 is a graph showing the surface flatness of a wafer by an etching apparatus according to another embodiment of the present invention.

[Explanation of symbols]

11 etching liquid tank, 12 rack (wafer holder), 13 bubbling gas supply pipe.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Nakajima 1-5-1 Otemachi, Chiyoda-ku, Tokyo Mitsubishi Materials Silicon Co., Ltd. (56) Reference JP-A-63-86525 (JP, A) JP HEI 4-186834 (JP, A) JP 62-132325 (JP, A) JP 7-58078 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21 / 304,21 / 306,21 / 308

Claims (2)

(57) [Claims] 1. An etching solution tank into which an etching solution is injected, a wafer holder for holding a semiconductor wafer in the etching solution tank, and a semiconductor arranged in the etching solution tank and held by the wafer holder. It is an etching apparatus equipped with gas supply means for supplying bubbling gas toward the wafer.
Te, said gas supply means Baburinguga etchant bath bottom
Bubbling
The gas supply pipe can be moved toward and away from the wafer holder
The etching equipment provided . 2. An etching method of spraying a bubbling gas onto a rotating semiconductor wafer immersed in an etching solution, wherein the strength of the bubbling gas to be sprayed is started.
It is a strong etching method and weakens it after a certain period of time .