JPH04225231A - Method and apparatus for etching silicon wafer - Google Patents

Abstract

PURPOSE:To etch only one surface of silicon oxide film formed on a silicon wafer substrate flatly. CONSTITUTION:A wafer 1 is held so that the surface to be etched faces downward. Droplets 4 of the aqueous solution of hydrofluoric acid are attached to the wafer through a nozzle 3 from the lower side. The wafer is moved to the positions of cleaning-liquid cleaning nozzles 5 and 7. Cleaning waters 6 and 8 are sprayed on the wafer, and the wafer is cleaned.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for etching only a silicon oxide film on one side of a silicon wafer.

0002

[Prior Art] Silicon wafer substrates on which epitaxial growth is performed are usually highly doped substrates, but during epitaxial growth performed at high temperatures, high concentration dopants in the substrate are liberated and diffuse into the epitaxial layer, an autodoping phenomenon. is generally known, and has disadvantages such as not being able to obtain a predetermined resistivity of the epitaxial layer.

In order to prevent this, a method has been adopted in which a silicon oxide film is formed in advance on the back surface of a highly doped silicon substrate to prevent autodoping during epitaxial growth. However, when a silicon oxide film is normally formed on a silicon substrate, it is formed on both sides, and when it is removed during polishing, due to the difference in etching speed of the silicon and silicon oxide films in a polishing solution (usually an alkaline solution), a flat surface is formed. There was a drawback that a polished surface could not be obtained. Also, among the silicon oxide films formed on both sides,
There is a method of etching only one side, in which a resist is applied to the non-etched side and then etched, but it has the disadvantage of requiring many steps and high cost.

0004

[Problems to be Solved by the Invention] Conventionally, there is no simple method for etching only one side of the silicon oxide film formed on both sides, and polishing (usually with an alkaline solution)
There was also a drawback that a flat surface could not be obtained when removing the surface. An object of the present invention is to provide a technique for easily etching a silicon oxide film on one side.

[0005]

[Means for Solving the Problems] In the method of the present invention, when etching a silicon oxide film formed on one side of a silicon wafer, the surface to be etched is held downward, and droplets of an aqueous solution of hydrofluoric acid are applied from below. Adhere and etch,
This silicon wafer etching method is characterized in that the silicon wafer is then cleaned by spraying cleaning water. The apparatus of the present invention capable of suitably carrying out this method includes: means for holding a silicon wafer with the surface to be etched facing downward; an etching liquid supply nozzle for applying an etching liquid to the surface to be etched from below; A cleaning liquid supply nozzle for cleaning the surface to be etched, a means for relatively moving the wafer holding means from the etching liquid supply nozzle to the cleaning liquid supply nozzle, and a means for treating drainage of the etching liquid and the cleaning liquid. This is a silicon wafer etching apparatus characterized by the following.

One side of the wafer with silicon oxide films formed on both sides of the silicon wafer substrate is held horizontally by chucking, and a hydrofluoric acid aqueous solution (5 to 50 vol.
%) droplets (0.5 to 10 cc) are deposited, and only the silicon oxide film on one side of the silicon wafer is etched by erosion.

[0007]

[Function] The present inventor found that the selective etching ratio of a hydrofluoric acid aqueous solution to single crystal silicon of a silicon oxide film is very large, and that a hydrofluoric acid aqueous solution (5 to 50 vol%) is applied to a silicon oxide film surface by 0.5 to 50 vol. We discovered that one side can be completely etched by just depositing 10cc.
The present invention was completed based on this knowledge.

As shown in FIG. 1A, the wafer chucking shaft 2 holds the silicon wafer 1 so that the surface to be etched of the wafer 1 faces down. The wafer 1 is moved in the direction of the arrow 10 to bring it close to the hydrofluoric acid aqueous solution supply nozzle 3, and the hydrofluoric acid aqueous solution 4 is supplied to the nozzle 3.
Hydrofluoric acid aqueous solution 4 and silicon wafer 1 are brought into contact. The shaft 2 is rotated as indicated by the arrow 11. Immediately after the silicon oxide film on the back surface is etched with the hydrofluoric acid aqueous solution, the wafer chucking shaft 2 is moved in the direction of the arrow 12, as shown in FIG. 1(b). Pure water 6 is jetted from the pure water supply nozzle 5 onto the back surface of the wafer. At the same time, the top surface of the wafer 1 is rinsed with pure water 8 from the pure water nozzle 7 on the top surface.

The device is not limited to a mechanism for moving the chucking shaft 2 in the direction of the arrow 12;
Of course, a mechanism may be used in which the shaft 2 is fixed and the two supply nozzles 3 and 5 are moved to perform etching and cleaning.

0010

[Example] Highly doped P-type boron C with a diameter of 6 inches
A silicon oxide film was formed on a brightly etched Z substrate (resistivity: 20/1000 Ω-cm). This silicon oxide film was formed by LP-CVD growth in a horizontal furnace. As shown in FIG. 2, two wafers were bonded together and placed on a quartz boat 9 to form a silicon oxide film. For this reason, a silicon oxide film is formed mainly on the periphery of the wafer surface to be etched. This is shown in Figure 1 (a
), after contacting with 50% hydrofluoric acid aqueous solution 4 for 2 seconds, 20 seconds later, rinsing with pure water as shown in FIG. 1(b) was performed, and the silicon oxide film was etched on only one side. I was able to do that.

[0011]

According to the present invention, by using the corrosive effect of hydrofluoric acid on the silicon oxide film, one-sided etching of the silicon oxide film can be performed in less than 1/5 of the work time compared to the protection method using resist coating. It was possible to reduce manufacturing costs. Furthermore, a wafer with a flat surface could be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sketch of a stage for etching only the lower surface of a wafer with a hydrofluoric acid aqueous solution and a stage for rinsing with pure water according to the present invention.

FIG. 2 is a sketch of a state in which two wafers are bonded together and a silicon oxide film is grown in a model furnace.

[Explanation of symbols]

1 Silicon wafer 2 Wafer chucking shaft 3 Hydrofluoric acid aqueous solution supply nozzle 4 Hydrofluoric acid aqueous solution 5 Pure water supply nozzle 6 Pure water 7 Pure water supply nozzle 8 Pure water 9 Quartz boat

Claims (2)

[Claims] [Claim 1] When etching a silicon oxide film formed on one side of a silicon wafer, the surface to be etched is held downward, droplets of a hydrofluoric acid aqueous solution are applied from below for etching, and then washed. A silicon wafer etching method characterized by cleaning by spraying water. 2. means for holding a silicon wafer with the surface to be etched facing downward; and an etching liquid supply nozzle for applying an etching liquid to the surface to be etched from below;
A cleaning liquid supply nozzle for cleaning the surface to be etched, a means for relatively moving the wafer holding means from the etching liquid supply nozzle to a cleaning liquid supply nozzle, and a means for treating drainage of the etching liquid and the cleaning liquid. A silicon wafer etching device characterized by: