JPH0230836Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the improvement of an etching apparatus for semiconductor substrates. In particular, it is an experimental method for etching a plurality of semiconductor substrates in order to be able to easily etch a small amount of semiconductor substrates and to improve the flatness and accuracy. The etching process is carried out by rotating the rotating jig for fixing the etching using a first rotating mechanism, and also rotating the etching solution using a second rotating mechanism.

Generally, when manufacturing semiconductor devices, wet etching performed in a solution and dry etching using plasma are incorporated into the process in order to adjust the thickness of a semiconductor substrate and remove unnecessary portions.

Among these, the conventional wet etching apparatus is shown in FIG.

FIG. 1 is a schematic cross-sectional view of a conventional example, in which 1 is a cylindrical etching tank (hereinafter simply referred to as the etching tank), 2 is an etching solution made of, for example, a mixed acid of hydrofluoric acid, nitric acid, and acetic acid, and 3 is an etching process. A semiconductor substrate to be etched (hereinafter referred to as a silicon substrate), 4 is a stand on which the silicon substrate 3 is fixed with wax or the like, and θ is an angle at which the etching bath 1 is tilted with respect to the horizontal direction. In such an etching apparatus, a silicon substrate 3 is immersed in an etching solution 2 whose temperature is controlled (not shown). Then, the etching bath 1 is tilted by hand and the entire etching bath 1 is swung in a circular motion for a predetermined period of time so that the etching bath 1 circulates well within the etching bath 1. conduct. Here, the predetermined time for etching is determined based on data obtained by previously investigating the relationship between etching thickness and time. After a predetermined period of time has elapsed, the etching process is stopped, and then pure water is poured into the etching tank 1. Further, at this time, the silicon substrate 3 may be taken out from the etching bath 1 within a short period of time, the etching solution 2 may be drained off, and then the silicon substrate 3 may be immersed in pure water. In the etching process, the etching tank 1 is tilted at an angle θ because the etching tank 1 rotates and the etching solution 2 also rotates, and the etching solution 2 in contact with the etched surface of the silicon substrate 3 rotates. This is to keep it constantly stirred.
That is, the etching solution 2 in contact with the etching surface of the silicon substrate 3 is easily replaced by shaking the entire etching tank 1 without rotating the etching tank 1 itself.

Further, the silicon substrate 3 advances in the direction of the water flow of the etching solution 2 while rotating along the periphery of the etching bath 1 .

FIG. 2 shows a silicon substrate 3 etched in this manner.

FIG. 2 is a cross-sectional view showing the silicon substrate etched using the apparatus shown in FIG. ₁ and _B2 portions tend to have a higher etching ratio than the A portion. Furthermore, the etched surface of each part is not a smooth surface. This uneven etching, that is, the difference in etching that occurs on the finished product 3b after etching, is because most of the etching solution 2 supplied to the center A is etched from the edges B ₁ and B ₂ . Due to the etching rate relationship, the etching rate is slower than that of the new solution, and new solution is always supplied to the ends B ₁ and B ₂ , resulting in a fast etching rate. There is. This occurs because the stirring speed, etching rate, and depth of the etched surface are in a proportional relationship, and if the stirring is not uniformly applied to the etched surface of the silicon substrate 3 or the stirring speed is not constant. Uneven etching occurs. Furthermore, experimental data obtained by etching three silicon substrates (diameter 32 mm, Fz-Si, resistivity 30 Ω-cm) using the etching apparatus shown in FIG. 1 is described below.

The etched surface of the silicon substrate is 20μ on average over the entire surface.
When etching was performed with a target of m, the standard deviation of the etching depth of the silicon substrate was 2 μm.
The difference between the maximum etching depth occurring at the end _B2 and the minimum etching depth occurring at the center A was about 7 .mu.m on average. Further, when the silicon substrate 3 shown in FIG. 2 and the three silicon substrates described above are etched, the portions not to be etched are covered with a protective film such as an oxide film.

Thus, the etching apparatus described above not only causes uneven etching but also has poor reproducibility, making it difficult to manufacture a good product.

Therefore, the present invention has been devised to eliminate the above-mentioned problems, and the semiconductor etching apparatus according to the present invention will be explained below with reference to FIG.

FIG. 3 is a partially cutaway side view of an etching device according to an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view showing a silicon substrate after etching with the etching apparatus shown in the figure.

In FIG. 3, the etching apparatus uses a first rotating mechanism 5 to stir the etching solution 2' on the etching surface of the silicon substrate uniformly and to keep the stirring speed constant. The etching liquid 2' is rotated by the second rotation mechanism 6 .

In the first rotation mechanism 5 , 3' is a silicon substrate, and 5a is an 8 to which a plurality of silicon substrates 3' are fixed.
A prismatic rotating jig, 5b is a rotating shaft, 5c is a support plate,
5d is a stopper for fixing the rotating shaft 5b to the support plate 5c, 5e is a universal joint, 5f is a motor, 5g is a shaft of the motor 5f, and 5h and 5h' are mounting parts for attaching the universal joint 5e to the rotating shaft 5b and the shaft 5g. This is a screw for fixing. In these configurations, a motor 5f is provided to rotate an octagonal prism rotation jig 5a that fixes a silicon substrate 3', and the rotation of this motor 5f is transmitted to a universal joint 5e attached to a shaft 5g of the motor 5f. However, due to the rotation of this joint 5e, the rotating shaft 5b
This involves rotating an octagonal prism rotating jig 5a fixed to the.

Further, in the second rotation mechanism 6 , 6a is a cylindrical etching tank (hereinafter simply referred to as an etching tank);
6b is a circular rotating pedestal that supports the etching bath 6a, 6c is a rotating shaft fixed to the center of the rotating pedestal 6b, 6d is a box-shaped support, and 6e and 6e' rotatably support the rotating shaft 6c. metal fittings fixed to the side surface P of the support stand 6d; 6f and 6f' are pulleys;
g is a V-belt that transmits rotation from pulley 6f' to pulley 6f, 6h is a motor vertically attached to the side surface P of support base 6d, and 6i is the shaft of motor 6h. These configurations include a motor 6h for rotating the etching bath 6a, and transmit the rotation of the motor 6h to a pulley 6f' that is firmly engaged with the shaft 6i of the motor 6h to rotate the V-belt 6g. The rotary shaft 6c fixedly engaged with the pulley 6f is rotated through the rotary shaft 6c, and the rotary base 6b fixed to the rotary shaft 6c is rotated by the rotation of the rotary shaft 6c, and further fitted into the rotary base 6b. The etching tank 6a supported by the etching tank 6a is rotated. Here, reference numeral 7 denotes a box-shaped support base having a stopper 5c fixed to the left side surface of the upper part fixed on the support base 6d, and a motor 5f attached to the top.

When etching silicon substrates 3' in such an etching apparatus, first of all, nine silicon substrates 3' are fixed with wax or the like to the side and bottom surfaces of an octagonal column rotating jig 5a in the atmosphere. . Next, an etching tank 6a containing a temperature-controlled etching solution 2' is placed on a rotating base 6b, and the motor 6h is driven to rotate it in the direction of arrow A. Next, the rotating jig 5a to which the silicon substrate 3' is fixed is immersed in the rotating etching solution 2', the rotating jig 5a is fixed to the support plate 5c with the stopper 5d, and the motor 5f is driven in the direction of arrow B. Rotate. After a predetermined period of time has elapsed, the rotation of the motor 5f is stopped, the stopper 5d is removed from the support plate 5c, and the rotating jig 5a is quickly pulled out of the etching solution 2' and immersed in pure water. Then, the rotation of the motor 6h that rotates the etching bath 6a is stopped. The piece that has been etched in this way is removed from the octagonal prism rotating jig 5a. In this embodiment, the etching apparatus is designed to etch one side of the silicon substrate 3', but it is also possible to etch both sides and partially by changing the rotating jig. When performing the etching process, the rotation speed of the etching bath 6a is around 160 rpm, and the rotation speed of the octagonal prism rotating jig 5a is 350 rpm.
The vicinity was perfect.

The product etched in this manner is shown in FIG.

FIG _. 4 is _a cross-sectional view showing a silicon substrate etched using the device shown in FIG.
The part corresponding to ₂ parts of B ₁ , A, and B shown in the figure, 3
A' is a portion where the silicon substrate 3' has been removed by etching, and 3b' is a portion finished by etching. As can be seen from the figure, the etched surface 3b' obtained by etching has a uniform and flat etched surface.

Furthermore, using the etching apparatus shown in FIG.
The experimental data obtained by etching a silicon substrate are shown below. The etching solution, silicon substrate, and etching time used at this time were the same as those for the three silicon substrates that were etched using the conventional etching method described above.

The etched surface of the silicon substrate is 20μ on average over the entire surface.
When etching was performed with a target of m, the standard deviation of the etching depth of the silicon substrate was 0.3 μm.
The difference between the maximum and minimum etching depths was about 0.8 μm on average.

As described above, the etching apparatus according to the present invention was able to obtain excellent results as described above, compared to the standard deviation of 2 .mu.m and the difference between the maximum and minimum etching depths of 7 .mu.m in the conventional etching process. This is because the etching solution 2' is continuously supplied by the rotation of the etching tank 6a, instead of the rotation of the rotating jig 5a at 350 rpm.
This is because the variation in the supply of etching liquid between A' and the ends B ₁ ' and B ₂ ' can now be ignored.

In this way, the semiconductor etching apparatus according to the present invention replaces the conventional etching apparatus, in which a stand is mounted on a silicon substrate and the entire etching bath is manually swung around without rotating the etching bath itself, a rotating apparatus that fixes multiple semiconductor substrates. a jig, a first rotation mechanism that rotates the rotating jig, and a cylindrical etching tank that stores an etching solution for dipping a plurality of semiconductor substrates;
and a second rotation mechanism for rotating the etching tank, and after rotating the second rotation mechanism, the rotation jig is placed in the etching solution and the first rotation mechanism is driven to perform the etching process. This is what I did.

In this manner, by providing a simple rotation mechanism, it is possible to provide a semiconductor etching apparatus that eliminates variations in semiconductor substrates and further improves finishing accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a conventional semiconductor substrate etching apparatus, FIG. 2 is a cross-sectional view showing a silicon substrate etched by the apparatus shown in FIG. 1, and FIG. 3 is an etching diagram of an embodiment of the present invention. equipment 1
FIG. 4 is a cross-sectional view showing a silicon substrate etched by the apparatus shown in FIG. 3. 2, 2'... Etching liquid, 3, 3'... Semiconductor substrate, 5 ... First rotating mechanism, 5a... Rotating jig, 6 ... Second rotating mechanism, 6a... Cylindrical etching Tank.

Claims (1)

[Scope of utility model registration request] A rotating jig for fixing a plurality of semiconductor substrates, a first rotating mechanism for rotating the rotating jig, and a cylindrical etching device for storing an etching solution for soaking the rotating jig for fixing the plurality of semiconductor substrates. A tank and
1. An etching apparatus for semiconductor substrates, comprising: immersing said rotating jig in an etching solution to drive a first rotating mechanism, and then a second rotating mechanism that rotates said etching tank.