JP2004055625A - Method for etching thin film utilizing rotary processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for etching a thin film utilizing a rotary processor. <P>SOLUTION: On the rotary etching processor, a wafer is wetted at first with pure water and an etching solution in order to remove contaminants and a thin film surface layer from the wafer surface. It is then rotated at a low speed (about 0-50 rpm), and the etching solution is poured and deposited on the wafer surface such that the etching solution remains on the wafer. It is further rotated at a low speed (about 0-50 rpm), and paddle wet etching is performed while keeping the etching solution on the wafer. Upon the completion of etching, rotation is accelerated and the wafer is cleaned by injecting pure water. Finally, moisture is removed from the IPA followed by the complete removal of moisture from the wafer by high-speed rotation. <P>COPYRIGHT: (C)2004,JPO

Description

【０００９】
本実施例がステップ３及びステップ５において消費する時間は２３ｓｅｃ×６００ｃｃ　　／ｍｉｎ＝２３ｓｅｃ×１０ｃｃ／ｓｅｃ＝２３０　ｃｃである。回転湿式蝕刻は大量の蝕刻溶液（薄膜の厚さに応じて決まる）を消費するが、例えば、１０００Åの二酸化シリコン膜が必要とする時間は１０００／２８＝３６　ｍｉｎで、計３６　ｍｉｎ×６００ｃｃ／ｍｉｎ＝２１，６００ｃｃで、パドル湿式蝕刻の１０００倍である。蝕刻溶液の使用量により製造コストが高騰するほか、廃液の処理コストも増加する。即ち、本発明の実施により、環境保護を達成し、コスト削減をも成し遂げることができる。
【００１０】
【発明の効果】
上記のように、本発明のパドル湿式蝕刻法により蝕刻の均一度及び蝕刻率を向上させることができる。さらに、蝕刻溶液の使用量を減らすことができるため、コスト削減及び環境保護を達成することができる。
【図面の簡単な説明】
【図１】公知の回転蝕刻プロセッサの加熱灯ハウジングが液体注入管をウエハ上方まで伸ばす様子を示す断面図である。
【図２】公知の回転蝕刻プロセッサの液体注入管が離れた後に、加熱灯ハウジングが下降する様子を示す断面図である。
【図３】薄膜湿式蝕刻のフローチャートである。
【符号の説明】
１　ベース
２　蝕刻チャンバ
３　モータ
４　ウエハチャック
５　ウエハ
６　加熱灯ハウジング
７　加熱灯
８　石英インドウ
９　ファン
１０　液体注入管
１１　排液管
１２　排気管
１３　通気管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wet etching method for a semiconductor manufacturing process. In particular, the present invention relates to a wet etching method in which a so-called paddle is formed by retaining an etching solution on a wafer using a kind of rotating processor.
[0002]
[Prior art]
In a semiconductor manufacturing process, various thin films such as a silicon dioxide film, a nitrogen silicon film, a nitrogen dioxide silicon film, a polysilicon film, a metal film, and a metal silicon film are etched by wet etching or rotary etching using a single wafer rotary processor. Is used.
However, the former cannot be applied to a wafer having a large area. The latter is suitable for single processing of a wafer of 8 inches or more. However, since etching is performed while rotating, a large amount of etching solution is wasted. In addition, the time during which the etching solution stays in the central portion and the peripheral portion is different, so that the uniformity is insufficient.
On the other hand, dry etching has a problem that the cost of equipment and gaseous materials is too high, and cannot be applied when isotropic etching or selective etching is required.
[0003]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION In order to solve the disadvantages of the known structure, an object of the present invention is to provide a thin film etching method using a rotating processor.
It is a wet single etching method that can improve the uniformity of etching.
It can also reduce the amount of etching solution used.
Furthermore, it can improve the etching rate.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a thin film etching method using the following rotary processor.
It mainly includes the following steps.
In step 1, the wafer is set on a rotary etching processor and rotated at 800 to 1200 rpm for 1 second.
In step 2, while rotating the wafer at 800 to 1200 rpm for 5 to 10 seconds, pure water is injected to wet the wafer.
In step 3, an etching solution is injected at 600 cc / min from the front and rear cleaning tubes (BSR), and the wafer is wetted at a rotation speed of 800 to 1200 rpm for 10 to 20 seconds. In this process, the surface layer of the thin film is removed, and the thin film on the surface and the photoresist on the back surface are removed. At this time, the rotation speed must not be too slow, because the scattering of the etching solution carries away the fine particles.
In step 4, the injection of the etching solution is stopped while the rotation speed is maintained at 800 to 1200 rpm, and the etching solution on the wafer is shaken off by rotation. Time is about 1 sec.
In step 5, a paddle of the etching solution is formed by injecting the etching solution. In this embodiment, HF: H ₂ O = 1: 100 diluted HF (diluted HF, DHF) is used for etching the silicon dioxide film, the flow rate is 0.6 to 5 1 / min, and the time is about 3 sec. , Depending on the type of wafer. Larger wafers require more etching solution. At this time, the rotational speed of the wafer is maintained at 0 to 50 rpm, and the injected etching solution is allowed to remain on the wafer. If the rotation speed is too high, the etching solution is shaken off the wafer, and if not rotated, the distribution of the etching solution becomes non-uniform.
In step 6, the rotation speed is maintained at 0 to 50 rpm (15 rpm is ideal), the etching solution is not scattered, and the rotation must not be stopped. The wafer must be rotated at a low speed so that the etching solution remains even on the wafer and paddle etching occurs. The etching time may be determined according to the thickness of the thin film.
In step 7, the rotation speed is increased to 800 to 1200 rpm, pure water is injected from the liquid injection pipe and the BSR, and the wafer is cleaned. Time is about 20-25 seconds.
In step 8, the pure water and the BSR are stopped and rotated at 600 to 1000 rpm for 1 second to shake off the pure water.
In step 9, IPA is injected, the rotation speed is reduced to 40 to 100 rpm, and the rotation is performed for 1.5 seconds. Utilizing the Marangoni effect, water on the wafer is removed cleanly.
In step 10, the wafer is rotated at 1000 to 2000 rpm for 2 seconds to dry the wafer.
In step 11, the wafer is accelerated to 3000 rpm to completely dry the wafer.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view of a rotary etching processor. The invention is not limited to the processor of FIG. 1, but applies to all processors used for wet etching of wafers.
In FIG. 1, a base 1 is a fixed base that supports the entire body. The etching chamber 2 is a cylindrical or rectangular hollow chamber, and the wafer chuck 4 holds the wafer 5 by vacuum suction or electrostatic suction. The rotation of the wafer chuck 4 is interlocked with the motor 3, and the rotation speed is adjustable. The ideal speed is 0 to 3000 rpm. A liquid injection tube 10 is provided above the wafer 5 to supply pure water or an etching solution. Separately, a rear washing tube (not shown) is provided. In both cases, the flow rate can be adjusted, and the liquid can be injected or separated from the wafer 5 when the wafer 5 rotates. As a result, the heating lamp housing 6 can be lowered as shown in FIG. 2, so that the temperature can be adjusted during rotation or etching of the wafer, and evaporation of the etching solution, pure water and the like can be prevented. A heating lamp 7 is provided in the heating lamp housing 6 to quickly heat the wafer to a control temperature. The lamp irradiates the wafer through the quartz window 8 and the hot air flows out and is removed by the fan 9. Clean air or nitrogen flows through the ventilation tube 13 around the four circumferences of the heating lamp housing 6 to cool the etching chamber 2 and prevent corrosion of the walls of the chamber 2 due to evaporation of the etching solution. The gas is discharged from the exhaust pipe 12 to a waste gas treatment apparatus (not shown), and the etching solution is discharged from the drain pipe 11 to a waste liquid treatment apparatus (not shown).
[0006]
In the first embodiment of the present invention, a method of wet etching a silicon dioxide film as shown in FIG. 3 will be described.
First, the wafer 5 is set on the wafer chuck 4.
In Step 1, the wafer is rotated at 800 to 1200 rpm for 1 second to remove contaminants.
In step 2, while rotating the wafer at 800 to 1200 rpm, pure water is injected to wet the wafer. Time is about 5-10 seconds.
In step 3, while maintaining the rotation speed at 800 to 1200 rpm, an etching solution is injected from the liquid injection tube 10 and the rear cleaning solution tube, the wafer is completely covered with the etching solution, and the thin film on the surface and the photoresist on the back surface are removed. . At this time, the rotation speed must not be too slow, because the scattering of the etching solution carries away the fine particles. Time is about 10-20 sec.
In step 4, the injection of the etching solution is stopped while the rotation speed is maintained at 800 to 1200 rpm, and the etching solution on the wafer is shaken off by rotation. Time is about 1 sec.
In step 5, the rotation speed is reduced to 0 to 50 rpm to form the paddle by allowing the implantation etching solution to remain on the wafer. The time is about 3 sec and the flow rate is 0.6 to 5 1 / min.
[0007]
In step 6, the rotation speed is maintained at 0 to 50 rpm (15 rpm is ideal). The rotation speed at this time is determined according to the type of the thin film and the viscosity of the etching solution. If the speed is too high, the etching solution will be shaken off, but if it is stationary, the distribution of the etching solution will be uneven, so it must not be stationary. If the thin film is a film having excellent hydrophilicity such as silicon dioxide, the rotation speed is slightly increased, and if the thin film is poorly hydrophilic such as polysilicon, the rotation speed is reduced. The etching time is determined according to the thickness of the thin film and the etching rate.
In step 7, the rotation speed is increased to 800 to 1200 rpm, pure water is injected from the liquid injection tube 10 and the BSR, the wafer is washed, and the etching solution on the back surface is removed. Time is about 20-25 seconds.
In step 8, the supply of pure water and BSR is stopped, and the supply of pure water and BSR is rotated at 600 to 1000 rpm for 1 second to shake off the pure water.
In step 9, IPA is injected, the rotation speed is reduced to 40 to 100 rpm, and the rotation is performed for 1.5 seconds. This makes it possible to cleanly remove water on the wafer by utilizing the Marangoni effect. That is, at this time, many polka dots are formed on the wafer and removed by centrifugal force.
In step 10, the wafer is rotated at 1000 to 2000 rpm for 2 seconds to dry the wafer.
In the final step 11, the wafer is accelerated to 3000 rpm (the faster the better), the wafer is dried, and the etching process is completed.
[0008]
Table 1 shows the uniformity and the etching rate by the paddle wet etching, and Table 2 shows the uniformity and the etching rate by the known rotary etching. As Table 1 shows, the 3σ uniformity of the paddle wet etching solution is 2.3%. Excellent compared to 3.45% uniformity of rotational etching of 5.45% in Table 2. Further, the etching rate of the paddle wet etching is 33.5 ° / min, which is slightly faster than the rotational etching of 28.6 ° / min. That is, since the paddle wet etching has a sufficient time for bringing the etching solution into contact with the thin film, the etching rate is high. On the other hand, the rotational etching has a poor etching rate because the time for contacting the thin film is insufficient.
A comparison between the test wafer A (rotational rotation speed is 600 rpm) and the test wafer B (rotational etching rotation speed is 1000 rpm) in Table 2 shows that even if the rotation speed is increased, the uniformity cannot be improved. . On the contrary, some data gets worse and the etching rates are almost the same.

[0009]
The time consumed by the present embodiment in step 3 and step 5 is 23 sec × 600 cc / min = 23 sec × 10 cc / sec = 230 cc. Rotary wet etching consumes a large amount of etching solution (depending on the thickness of the thin film). For example, the time required for a silicon dioxide film of 1000 ° is 1000/28 = 36 min, for a total of 36 min × 600 cc /. min = 21,600 cc, which is 1000 times the paddle wet etching. Depending on the amount of the etching solution used, the production cost rises and the waste liquid treatment cost also increases. That is, by implementing the present invention, environmental protection can be achieved and cost reduction can be achieved.
[0010]
【The invention's effect】
As described above, the uniformity of etching and the etching rate can be improved by the paddle wet etching method of the present invention. Further, since the amount of the etching solution used can be reduced, cost reduction and environmental protection can be achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a state in which a heating lamp housing of a known rotary etching processor extends a liquid injection tube to a position above a wafer.
FIG. 2 is a cross-sectional view showing a state where a heating lamp housing is lowered after a liquid injection tube of a known rotary etching processor is separated.
FIG. 3 is a flowchart of a thin film wet etching.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base 2 Etching chamber 3 Motor 4 Wafer chuck 5 Wafer 6 Heating lamp housing 7 Heating lamp 8 Quartz window 9 Fan 10 Liquid injection pipe 11 Drainage pipe 12 Exhaust pipe 13 Vent pipe

Claims (6)

A paddle wet etching method mainly for a thin film, comprising the following steps:
In step a, the wafer is set on a rotary etching processor and rotated at 800 to 1200 rpm,
In step b, pure water is injected while rotating the wafer at 800 to 1200 rpm to wet the wafer,
In step c, the front and side surfaces of the wafer are etched at a rotation speed of 800 to 1200 rpm to remove the surface thin film,
In step d, the injection of the etching solution is stopped, and the etching solution on the wafer is shaken off by rotation while maintaining the rotation speed at 800 to 1200 rpm.
In step e, maintaining the first rotation speed, injecting the etching solution at the first flow rate,
In step f, the injection of the etching solution is stopped, and wet etching is performed at the second rotation speed.
In step g, pure water is injected from the front and back sides, and the wafer is washed at 800 to 1200 rpm.
In step h, stop the injection of pure water, shake off the pure water at 600 to 1000 rpm,
In step i, IPA is injected, and water is removed at 40 to 100 rpm.
In step j, the wafer is dried at 1000 to 2000 rpm,
In step k, the wafer is accelerated to 3000 rpm to dry the wafer.
Regarding the above steps,
After wetting the wafer in step b, proceed to step c to inject an etching solution, etch the front and side surfaces of the wafer at a rotation speed of 800 to 1200 rpm, remove a surface thin film,
After removing the etching solution in step d, proceed to step e, inject the etching solution at a first rotation speed and a first flow rate,
A thin film etching method using a rotary processor, wherein the paddle wet etching is performed at a second rotation speed after the wet etching in step e, and then proceeding to step f. 2. The method as claimed in claim 1, wherein the thickness of the surface layer of the thin film removed in the step (c) is 5 [deg.] To 200 [deg.]. 2. The method of claim 1, wherein the first rotation speed is in a range of 0 to 50 rpm, and the rotation speed of the etching solution does not remain on the wafer. 2. The method according to claim 1, wherein the first flow rate is 0.6 to 5/1 / min. 2. The thin film etching method according to claim 1, wherein the second rotation speed is 0 to 50 rpm, and the etching solution does not stay on the wafer and does not separate. 2. The thin film etching method using a rotating processor according to claim 1, wherein in step e, a guard is required above the wafer so as not to hinder the intake or air flow of the high efficiency filter (hepa).

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