JPH0391927A - Etching process for semiconductor wafer - Google Patents

Abstract

PURPOSE:To enable the bubbles produced during etching reaction process to be made fugacious outside the reaction system by a method wherein III-V compound semiconductor wafer is vibrated at a high frequency during the etching process. CONSTITUTION:III-V compound semiconductor wafer is high-frequency oscillated during etching process. That is, a semiconductor wafer 1 is immersed in a megasonic cleaner filled up with an etchant or a vessel containing the etchant and the semiconductor wafer 1 is immersed in the water filling up the megasonic cleaner so that the etchant may be agitated with the oscillation by the megasonic cleaner to cause an etching reaction. Through these procedures, the hydrogen bubbles produced in a V-shaped groove 3 and sticked to the surface are discharged out of the groove 3 so that the feeding of reactive material and the discharging of produced material may be performed immediately thereby enabling the diffusion determining rate to be restored to the reaction determining rate.

Description

Detailed Description of the Invention <Field of Industrial Application> This invention relates to semiconductor lasers and edge-emitting light emitting devices used as light sources for optical communication and measurement in the long wavelength band (1.3 to 1.55 μm). The present invention relates to an etching process during the manufacturing process of a diode, and more particularly to a method for preventing bubbles generated during a reaction from adhering to a substrate.

<Conventional technology and problems to be solved> Conventionally, for example, when etching a TnP semiconductor wafer,
Cover and protect the non-etched areas in advance with an acid-resistant film such as Sin2, and then apply an etching solution such as 35NHC.
I: H2 0=4:1. It was immersed in O'C for a predetermined time and etched to form a V-groove. The etching reaction in this case is carried out according to the following reaction formula.

InP + 8) IcI → TnCls + PCI5
+flz↑The hydrogen bubbles generated here could adhere to the surface of the InP semiconductor wafer and inhibit ethoching in that area, so it was necessary to promptly remove the bubbles generated in the grooves from the system. .

This reaction is also called the reaction law, and the supply of reactants and the transport and release of reactants at the reaction site (wafer surface) are sufficiently faster than the chemical reaction rate. However, although this can be applied to flat wafers, when etching is performed with grooves provided, the shape makes it difficult to quickly supply reactants and carry out produced substances.

Therefore, the in-plane uniformity of the V-groove shape is extremely poor, which increases leakage current, increases the fluctuation in the position of the active layer in the waveguide direction, reduces oscillation efficiency due to increased scattering loss, and deteriorates temperature characteristics. , which led to deterioration of far-field image characteristics.

Furthermore, generally speaking, an ultrasonic cleaner with a launch frequency of 20 to 40 kHz is used to dissolve the solute in a solvent and randomly stir it, but at this frequency, the air dissolved in the solution is Not only do they form as bubbles (cavitation effect) and impede uniform etching, but the total power is quite large, although the frequency is lower than that of Mega Sonic, so the reactants are forced into the V-groove. Because of the collision, it is difficult to control the etching depth over time, and there is a problem in that (1) variations occur in the in-plane shape of the groove.

The present invention aims to solve such problems.

Means for Solving the Problems of Imposition> The present invention has been developed as a result of various studies under such circumstances, for example, I
nP, GaAs+GaP. In the etching process of I[[-V group compound semiconductor wafers such as InAs and GaSb, high-frequency vibrations are applied to volatilize bubbles generated during the etching reaction to the outside of the system.

<Operation> According to the present invention, the oscillation frequency is 500 kHz to 5
MHz is appropriate, preferably 0.9MHz to 1.5MFI
Either an etching solution is placed in a so-called megasonic cleaning machine with an oscillation frequency of The etching reaction is caused by stirring the etching solution using high-frequency vibrations from a megasonic cleaner.

By doing this, ■ hydrogen bubbles generated in the groove and attached to the surface are discharged to the outside of the groove, and the reactant is supplied.
By quickly carrying out the export of a certain substance, it is possible to return the rate-limiting rate from diffusion to the rate-limiting reaction.

Example An embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a resist 2 is masked on the wafer 1 and wet etching is performed to form a layer Vi3. At this time, the etching solution is, for example, 35% Hcj2: H2 0=
4: Use 1, put it into an ultrasonic cleaner, then put the wafer mentioned above, and set the vibrator to 0.9~1. Vibrate at MHz.

By doing so, etching can be performed without bubbles adhering to the V-groove 3. After that, it is washed with water and dried to complete the etching.

It was confirmed that when etching was performed using the method of the present invention, no air bubbles remained in the V-groove and a good result was achieved, but when etching was performed using the conventional method, air bubbles remained constantly within the V-groove. For this reason, it was found that uniform etching was difficult to carry out, and that this tendency was more pronounced as the etching solution became contaminated.

Incidentally, sample type n (A-F in the table) when etching using the megasonic of the present invention and conventional etching without using megasonic (both were etched for 7 minutes using 35% HCI:H2 0 = 4:1) ) The average etching depth is shown in FIG. 2, and it can be seen that the etching depth by the method of the present invention is more or less constant than that by the conventional method.

Effects of the Invention> As explained above, the method of the present invention uses an oscillation frequency of 500 kHz to 5 MHz in the process of etching a semiconductor.
Because it is done using Z's so-called megasonic cleaning machine, ■
By discharging hydrogen bubbles generated in the groove and attached to the surface to the outside of the groove, and quickly supplying the reactant and carrying out the vital substance, it is possible to change the rate of diffusion from diffusion to the rate of reaction. VL etching with uniform surface distribution can be realized.

This makes it possible to improve the uniformity of the etched surface in the depth direction and the symmetry of the cross-sectional etched shape.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the present invention, and FIG. 2 is a graph showing the average etching depth when etching is performed by the method of the present invention and the conventional method. Explanation of main symbols l: wafer, 2: resist, 3: V groove

Claims (1)

[Claims] A method for etching a semiconductor wafer, which comprises applying high-frequency vibration to a III-V group compound semiconductor wafer during an etching process to volatilize bubbles generated during an etching reaction to the outside of the system.