JPH07245290A - Wafer etching method - Google Patents

Abstract

PURPOSE:To provide a wafer etching method whereby a more functional structure than conventional ones can be formed while a uniform etching performance is maintained. CONSTITUTION:In a shower etching method, a wafer is held fluctuation-wise while its surface is turned upward, and by a shower nozzle 1 in an etching processing vessel 5, an etching liquid is poured in a shower state on the wafer from above it. By the executing of the etching through this shower etching method, the etching liquid is fed uniformly over the whole surface of the wafer, and etching-reaction-generated bubbles are removed quickly from the surface of the wafer. Therefore, the variation of the thicknesses of the etching liquid accumulated on the surface of the wafer can be reduced, and in addition, the rear surface of the wafer can be so kept as to be in a non-etched protection state. Also, as the protective method of the one side of the wafer, the protection using a resin is performed, and the height of the resin cover is made not larger than 0.5mm. Thereby, after the etching liquid is poured on the wafer, it flows quickly from the surface of the wafer, and as a result, the new etching liquid is poured uniformly on the whole surface of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method in a process of manufacturing a semiconductor device, and more particularly to a method for etching a wafer.

[0002]

2. Description of the Related Art Conventionally, in manufacturing a semiconductor device, a wafer of a semiconductor material is processed by etching or the like to make it up. However, the wafer is often etched by immersing the wafer in an etching solution. As a batch process, many wafers can be processed at one time, which is convenient. However, on the other hand, the etching process results on the surface of the wafer vary depending on the stirring method of the etching solution and the position of the wafer. Further, the temperature of the etching solution and the concentration unevenness, and the directionality of how the etching solution hits the wafer. The thickness of the wafer becomes non-uniform due to the influence of differences such as the above, and a problem remains in the quality control of etching. As an attempt to homogenize the etching, a method of rocking the wafer has been considered. This etching is originally intended to flatten the mechanical damage of the wafer such as lapping that occurred in the previous step by etching by a chemical reaction, and in order to solve that point, in Japanese Patent Laid-Open No. 63-156324,
Etching for the purpose of removing the mechanically damaged portion of the wafer surface that occurred in the previous process.In order to make the etching uniform, the unevenness of the etching due to the supporting portion of the wafer should be eliminated. A method is adopted in which a wafer is floated to float and the wafer is etched. This method is intended to perform more uniform etching by spraying an etching solution. This is because the etching liquid is in the form of liquid droplets, so that the reaction gas generated in the etching is removed more quickly than in the immersion method and new etching liquid is replenished one after another, so that more uniform etching can be obtained.

[0003]

With the above method, the wafer can be uniformly etched. However, when a structure such as a diaphragm or a cantilever is formed on a wafer by etching, it is necessary to protect one side of the wafer and etch only from the other side, which cannot be formed by the above method. Moreover, since the wafer cannot be rocked, the attempt to homogenize the wafer is not effective.

Therefore, it is an object of the present invention to provide an etching method capable of forming a functional structure on a wafer while maintaining a uniform etching performance.

[0005]

In order to solve the above-mentioned problems, the structure of the present invention is a wafer etching method for etching a semiconductor wafer by spraying an etching solution in a shower shape in the step of manufacturing a semiconductor device. One side of the wafer is held in close contact with the wafer holding means, the other side of the wafer is installed facing upward, and only the other side of the wafer is used as the etching surface, and the etching liquid is sprayed from the upper side for etching. The structure of the related invention is characterized in that the wafer holding means is swung during etching, or a shower nozzle for spraying an etching solution is swung. The structure of the present invention is also characterized in that, in the wafer holding means, the height of the cover on the etching-processed surface side of the wafer is 0.5 mm or less from the etching surface, or the cover is made of an elastic body. It is characterized by being.

[0006]

According to the present invention, the etching liquid is uniformly supplied to the entire surface of the wafer by holding the wafer upward, rocking the wafer, and performing etching by the shower etching method in which the etching liquid is showered from above the wafer. In addition, since the etching reaction-generated bubbles are quickly removed, it is possible to reduce the variation in the thickness of the wafer surface and to keep the lower surface of the wafer protected without being etched. Also, as a one-sided wafer protection method, resin protection is used and the cover height is 0.5 m.
By setting the value to be m or less, the etching solution after hitting the wafer can be swiftly discharged so that the new etching solution is uniformly applied to the entire wafer surface.

[0007]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 shows an embodiment of a shower etching apparatus for carrying out the wafer etching method according to the present invention. In the figure, the shower nozzle 1 in the etching treatment tank 5 brings the etching solution into a shower state, and the shower nozzle hole 2 controls the shower state. Is. The etching solution is pumped up from the etching solution heating storage tank 9 by the etching solution supply pump 7 at a pressure equal to or higher than the pressure that fills the inside of the shower nozzle with the etching solution, passes through the pipe 6, and is uniformly showered from all the shower nozzle holes. And jets from the upper part of the wafer 4. The etching-treated surface of the wafer 4 is directed upward, and the non-treated surface is covered with a wafer protection material and a jig 3 so that the etching solution does not come into contact with the wafer 4. Since the etching solution hitting the wafer 4 is in a shower state,
The bubbles generated by the etching reaction are quickly removed.
The wafer 4 whose back surface is protected by the wafer protection material and the jig 3 is
The holding plate 10 with a wafer swing mechanism is swung so that the etching solution hitting the surface wets more uniformly. The etching liquid which has been in a shower state on the wafer 4 is dropped from the wafer 4 and then collected in the lower portion of the processing tank 5 to return to the etching liquid heating storage tank 8.

As a method of swinging the holding plate 10 with a wafer swing mechanism to which the wafer protection material and the jig 3 are attached, a case of circular swing for swinging the wafer 4 to rotate (a in FIG. 1),
It is considered that this is the case of vertical / horizontal rocking that rocks to the left / right (or front / rear) (b in FIG. 1).

FIG. 2 shows an apparatus having the above structure, which is 38 wt.
The figure shows the thickness variation within the wafer surface after etching the wafer by about 300 μm using a% KOH aqueous solution.
When the wafer is not rocked, the etching solution locally hits the wafer, so that the thickness variation in the wafer surface is larger than that when the wafer is rocked. In the case of wobbling, there is no difference in the thickness variation in the wafer surface due to the circular movement of 10 times / min and the vertical / horizontal movement of 5 times / min, and the same effect can be obtained. Therefore, the thickness variation within the wafer surface is about 2.5 μm or less, which is overwhelming compared to the case where there is no oscillation.

FIG. 3 shows a comparison with the conventional immersion type etching. Even in the immersion type etching, there is considerable variation without stirring, but the uniformity is improved by immersing and stirring. However, it can be seen that the present invention is more uniform and more effective.

(Second Embodiment) By the way, a wafer protective material,
The jig 3 is installed on the holding plate 10 with the wafer swinging mechanism described above, but the portion that hangs on the wafer 4 is made of a resin that is an elastic body so that the wafer can be easily mounted and the wafer is not damaged. There is. In order to prevent the back surface of the wafer 4 from penetrating the etching solution, the wafer 4 is
A protective material is applied to the outside and the periphery of the front side of the to keep it sealed. The amount indicated by h in FIGS. 4 and 6 is called the cover height. The cover height h must be provided in order to protect one side of the wafer that is not etched and the outer circumference. The presence of this cover height causes the etching solution to stay on the wafer, which affects the uniformity of etching.

FIG. 5 is a graph showing the effect of the above cover height. In the apparatus shown in FIG. 1, the wafer surface relative to the cover height when etching about 300 μm using a 38 wt% KOH aqueous solution at 82 ° C. Shows the thickness variation. The smaller the cover height, the smaller the thickness variation within the wafer surface.
It is possible to obtain a thickness variation within the wafer surface of m or less. Here, in the wafer protection jig shown in FIG. 6, there is a limit to reducing the cover height in terms of strength maintenance and sealing performance of the jig. Therefore, if the wafer is protected by using a protective resin as an elastic body as shown in FIG. 4, the cover height is sufficiently 0.5 m.
It can be less than or equal to m. For example, if the elastic body is made of a silicone resin, it has good chemical resistance and sealing properties and is suitable as a wafer protection resin.

When the held wafer is installed upward, the upward angle of the wafer should be slightly tilted from the horizontal so that the etching solution applied to the wafer surface does not stop and does not stop on the wafer. It is also effective when it is characterized by having. By doing so, when the wafer is swung, the etching solution is quickly dropped.

The degree of rocking shown in this embodiment is not particularly effective, and any rocking can be used as long as it can rock the etching solution. Even if there is, the effect is the same.

[0015]

According to the wafer etching method of the present invention, as shown in FIGS. 3 and 5, compared with the conventional immersion method, there is an effect of reducing the thickness variation in the wafer surface.

[Brief description of drawings]

FIG. 1 is a schematic view of a shower etching apparatus to which an etching method of the present invention is applied.

FIG. 2 is a comparative explanatory diagram of a conventional method and a method of the present invention.

FIG. 3 is a comparative explanatory diagram (part 2) of the conventional method and the method of the present invention.

FIG. 4 is a sectional explanatory view showing an example of a wafer holding material and a jig.

FIG. 5 is an explanatory diagram showing dependency of cover height.

FIG. 6 is a cross-sectional explanatory view showing another wafer holding material and a jig.

[Explanation of symbols]

 100 Wafer Etching Device 1 Shower Nozzle 3 Wafer Protective Material, Jig 4 Wafer 10 Wafer Swing Mechanism Holding Plate 42 Wafer Protective Resin (Elastic Body)

Front Page Continuation (72) Inventor Motoki Ito 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (4)

[Claims] 1. A wafer etching method in which a semiconductor wafer is etched by spraying an etching liquid in a shower shape in a step of manufacturing a semiconductor device, wherein one side of the wafer is closely held by a wafer holding means, and the other side of the wafer is held. Is set upward, and only the other surface of the wafer is used as an etching surface, and an etching solution is sprayed from the upper side to perform etching. 2. The wafer etching method according to claim 1, wherein the wafer holding means is swung during etching, or a shower nozzle for spraying an etching solution is swung. 3. The wafer etching method according to claim 1, wherein, in the wafer holding means, the height of the cover on the surface of the wafer to be etched is 0.5 mm or less from the etching surface. . 4. The wafer etching method according to claim 3, wherein the cover is made of an elastic material.