JP3153701B2 - Wet processing method and wet processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet processing technique for a flat object to be processed such as a semiconductor wafer, and more particularly to a wet processing technique.
The present invention relates to a technique for performing wet processing on a flat object having a relatively small diameter, such as a group VI compound semiconductor wafer.

[0002]

2. Description of the Related Art II- such as ZnSe, ZnTe, ZnS, etc.
Group VI compound semiconductor wafers are still small in size. In experiments and the like, a small-area wafer may be used even for a Si wafer. When a wet process is performed on a semiconductor wafer having such a relatively small size, a simple method described below is performed.

FIG. 5A shows the simplest method. The surface to be wet-processed is placed on the bottom of the beaker 51 with II-
A wafer 53 of a group VI compound semiconductor or the like is arranged, and aqua regia,
An etching solution 52 such as a sodium hydroxide system or a Br-methanol system is poured from above. Beaker 51 by hand
The etching is performed by rotating and stirring the etchant by shaking. After the etching is completed, the etching solution is discarded, and a large amount of pure water is poured to perform rinsing.

FIG. 5B shows a method using a jig.
The wafer 53 is placed in a basket 54 in which a liquid drain gap is sufficiently formed. After pouring the etching liquid 52 into the beaker 51, the lower part of the basket 54 is immersed in the etching liquid 52. By moving the basket 54 up and down by hand, the etchant is evenly moved on the surface of the wafer 53. At the end of the etching, the basket is taken out of the beaker 51 and brought into another beaker in which pure water overflows.

[0005]

When such simple wet processing is performed, it is difficult to form a stable flow of the processing liquid. When etching ZnSe, which is a II-VI group compound semiconductor crystal, since ZnSe has strong ionicity, even a slight disturbance of the etchant causes unevenness of the etching, and the mirrored etching is disturbed.

Since the progress speed of the wet processing is governed by the flow of the processing liquid by hand, it is difficult to stably perform the reproducible wet processing. In the case of etching, variations occur in the etching rate and the etching depth. When a wafer is placed at the bottom of the beaker, it is difficult to supply a sufficient etching solution because the back surface of the wafer is in contact with the bottom of the beaker. Only done on the surface.

When arranging a wafer at the bottom of a beaker, it is difficult to arrange a plurality of wafers. Overlapping or collision of a plurality of wafers during the stirring of the etching solution causes etching unevenness and reduced reproducibility.

When the wafer is placed on the bottom of the beaker and the etching solution is rotated, the wafer rubs against the bottom of the beaker and collides with the side. Such mechanical shock risks introducing defects into the wafer crystal.

It is an object of the present invention to provide a wet processing technique which is reproducible and has a low risk of introducing defects into crystals. It is another object of the present invention to provide a wet processing technique capable of stably and efficiently performing mirror-etching of a II-VI compound semiconductor wafer.

[0010]

A wet processing method according to the present invention comprises a step of rotating a processing liquid in a cylindrical container, and a step of rotating each of a plurality of flat objects to be processed substantially in parallel with the rotation direction of the processing liquid. And along the circumferential surface of the cylindrical container at substantially the same radial position so that the treatment liquid is divided into two parts, a part flowing outside the plate-shaped object and a part flowing inside the plate-shaped object. Holding by a jig, and immersing in a rotating processing solution to perform wet processing.

[0011]

By rotating the wet processing liquid in the cylindrical container, a stable flow of the processing liquid can be formed.

A stable flow of the processing liquid is maintained by immersing the plate-like processing object held in the jig substantially parallel to the flow of the processing liquid in the processing liquid at substantially the same radial position. In addition, the processing liquid can be brought into contact with the surface of the object to be processed without giving an excessive mechanical impact to the flat object to be processed.

In this manner, stable wet processing can be performed. Even in the case of mirror-surface etching, etching can proceed uniformly on the wafer surface.

[0014]

FIG. 1 is a schematic plan view for explaining a wet process according to an embodiment of the present invention. The wafer 1 is held by the wafer holding jigs 1 and 2 at a plurality of locations, and is placed in the cylindrical container 5. The wet processing liquid 4 is injected into the cylindrical container 5 and rotated in the direction of the arrow.

While rotating the wet processing liquid 4 stably,
By arranging the wafer 3 in the wet processing liquid substantially parallel to the flow of the wet processing liquid, the wet processing proceeds uniformly on the surface of the wafer 3.

The wafer holding jigs 1 and 2 are formed with a reduced cross-sectional area in a direction perpendicular to the flow of the wet processing liquid 4 so as not to hinder the flow of the wet processing liquid 4. For example, the wafer holding jig 1 is composed of one thin plate arranged so as to be in contact with the lower surface of the wafer 3, and the wafer holding jig 2 is another thin plate jig arranged at a higher position. It consists of. Further, it is preferable to provide many through openings so as not to hinder the flow of the processing liquid 4.

It is preferable that the jigs 1 and 2 have a space capable of accommodating the rotating mechanism formed below the wafer accommodating space.
The rotation mechanism can be constituted by a magnetic stirrer, a motor drive fin, or the like.

The four wafer holding jigs 1a to 1d
Although four sets of and 2a to 2d are shown, these holding jigs 1a to 1d and 2a to 2d may be each constituted by a single member. Further, the entire wafer holding jigs 1 and 2 may be formed into a single structure.

Since the wet processing liquid 4 rotates in the cylindrical container 5, the flow rate of the wet processing liquid 4 depends on the radial position in the cylindrical container 5. In order to uniformly perform wet processing on all wafers, it is preferable that each wafer be arranged along a substantially predetermined cylindrical surface.

As described above, when a plurality of wafers are arranged at substantially the same radial position, the wet processing liquid 4 is roughly divided into a portion flowing outside the wafer and a portion flowing inside the wafer. In a case where uniform wet processing is to be performed on both surfaces of the wafer, it is desirable that substantially equal wet processing liquids come into contact with the front and back surfaces of the wafer. For this reason, it is preferable to select the radial position at which the wafer 3 is arranged so that the wet processing liquid 4 is divided into two substantially equal volumes inside and outside.

An embodiment in which ZnSe, which is a II-VI group compound semiconductor, is etched without limitation is described below. ZnSe prepared by liquid phase growth
The crystal was sliced along an arbitrary plane orientation, for example, along the (111) plane, and processed into a wafer. The ZnSe wafer thus produced was lapped and polished by mechanical polishing, and the surface was mirror-finished. After the mirror polishing, ultrasonic cleaning was performed to remove the abrasive attached to the wafer surface.

The plurality of wafers thus prepared are held by a jig and etched in a beaker. FIG.
(A), (B) is a plan view showing two types of jigs for holding a wafer. FIG. 2A shows a basket net jig arranged on the upper side, and FIG. 2B shows a basket base jig arranged on the lower side.

In FIG. 2 (A), the basket net jig 2 has eight rhombic mesh portions 6 on the circumference of the same radius for holding the wafer 3 by dropping it. The rhombus of each mesh portion is arranged such that one diagonal is oriented in the radial direction and the other diagonal is oriented in the circumferential direction. These mesh portions 6 are connected to a common central portion 7 by arms 8. The central portion 7 is provided with a circular opening through which the column is passed.

Outside the mesh portion 6, a cylindrical outer peripheral portion 9 is connected. The outer peripheral portion 9 has a height suitable for holding the wafer 3 stably, and the mesh portion 6 is connected to the upper end thereof.

In FIG. 2B, the basket base jig 1 radially has eight arms 11 having grooves 10 for holding the wafer 3 from below. Each arm 11
They are connected at a central portion 12. The central portion 12 is provided with a circular opening through which the above-mentioned column is passed. The outer end of each arm 11 is connected to a cylindrical outer peripheral portion 13. The outer peripheral portion 13 has a height suitable for disposing the object to be processed at substantially the center of the processing liquid depth, and the arm 11 is connected to the upper end thereof.

The jig shown in FIGS. 2A and 2B is made of Teflon having high chemical resistance. In order to realize a smooth flow of the etching solution, both jigs are formed of a thin plate member having a thin and smooth surface except for the outer peripheral portion. Further, it is preferable that the outer diameters of the outer peripheral portions 9 and 13 be substantially equal to the inner wall of the beaker. That is, the flow of the etchant from the outside of the basket body is prevented, and the flow is supplied only from the inside of the basket. With such a configuration, a stable flow is realized.

FIG. 3 shows that the basket net jig 2 is superimposed on the basket base jig 1 and held in common by the support columns 13.
It shows a state where it is arranged in the beaker 5. For example, beaker 5
Is a 100 ml beaker, the outer diameter of the jigs 1 and 2 is about 50 mm. Before inserting jigs 1 and 2, beaker 5
The magnetic stirrer 15 is arranged on the bottom surface.
The stirrer 15 has a diameter of about 8 mm and a length of about 30 mm.
The wafer 3 is inserted on the same circumference along the opposing line of the rhombic opening of the basket net jig 2, and the lower end is inserted into the groove 10 of the basket base jig 1.

The position for holding the wafer 3 depends on the volume of the etching solution flowing inside the wafer 3 and the position of the wafer 3.
The structures of the jigs 1 and 2 are designed so that the volumes of the etching liquid flowing outside the outer sides are substantially equal. With such a configuration, the difference in the etching state depending on the direction of the wafer is reduced.

An etching solution 17 is injected into the beaker 5. By rotating the etching solution 17 with the stirrer 15, a stable rotation of the etching solution 17 can be obtained. As the etching solution 17, a potassium permanganate sulfuric acid aqueous solution-based etching solution capable of mirror-etching in any plane orientation of the ZnSe crystal was used. The composition ratio is KMnO ₄ : H ₂ SO ₄ : H ₂ O = 120 m
g: 12 ml: 48 ml. The stirrer was rotated in a beaker containing the etching solution, and the number of rotations of the stirrer was set so as to obtain a desired etching solution flow rate. After the flow velocity is stabilized, the basket jig 1 on which the wafer 3 is placed,
2 was immersed in the etching solution 17. The etchant is
It flows in a direction substantially parallel to the wafer surface.

After a lapse of a predetermined etching time, the baskets 1 and 2 were taken out, washed with water, replaced with water with methanol, and subjected to ultrasonic cleaning in dichloromethane for about 30 minutes. The flow rate of the etching solution can be controlled by the rotation speed of the stirrer.
In a state where the basket jigs 1 and 2 are arranged, in the range of the stirrer rotation speed of 200 to 1000 rpm, the etching solution flow rate changes almost linearly with respect to the stirrer rotation speed. The use of such a linear region facilitates the control of etching.

FIG. 4 is a graph showing the relationship between the flow rate of the etching solution flowing on the wafer surface and the etching rate. The horizontal axis represents the flow rate of the etching solution on the wafer surface in cm / cm.
The vertical axis indicates the etching rate in μm / min. As is clear from this graph, it was found that the etching rate linearly increased in proportion to the increase of the etching solution flow rate.

By measuring such basic data, it is possible to control the stirrer rotational speed to obtain Zn
Se etching can be controlled with high accuracy. Zn
As a result of examining the relationship between the etching liquid flow rate and etching unevenness in Se wafer etching, when the etching liquid flow rate exceeded 20 cm / sec, the rotation of the etching liquid was disturbed, and the etching unevenness occurred. However, when the flow rate of the etching solution was set to 20 cm / sec or less, good mirror surface etching was possible.

Although the case where a jig having a specific shape is used has been described, the shape and dimensions of the jig can be variously changed. Also, the material of the jig can be changed in consideration of the relationship with the etching solution.

As described above, since the etching is performed while rotating the etching solution stably using the rotation drive mechanism such as the stirrer, the etching proceeds stably and uniformly. The etching speed can be changed with high accuracy by changing the stirrer rotation speed. For example, in the case of mirror etching, the etching rate can be changed while maintaining the mirror etching ability.

Conventionally, in order to change the etching rate, the temperature and composition ratio of the etching solution have been changed. In the case of such a method, the etching performance itself for the wafer changes, which causes a rough surface state after the etching. By changing only the flow rate while keeping the composition and temperature of the etching solution constant, the etching rate can be controlled over a wide range while maintaining the basic performance of etching.
When the above-mentioned etching solution was used, the etching rate could be arbitrarily controlled in the range of 0.3 to 0.8 μm / min.

The etchant rotates in a circle in the beaker,
The basket type jig can arrange all the wafers in parallel and symmetrically with respect to the flow. Therefore, the uniformity of etching is high even in the simultaneous processing of a plurality of wafers.

Since the etching solution is rotated by the stirrer and the wafer holding jig can be kept stationary in the beaker, it is possible to prevent the wafer from being mechanically impacted.
For this reason, it is possible to prevent defects from being introduced into the wafer.

Since almost the entire surface of the wafer can be etched simultaneously and with similar characteristics, the cleaning effect of the entire wafer is enhanced. Since the wafer surface can be uniformly etched, the affected layer can be effectively removed by polishing or the like, and a good semiconductor device can be manufactured.

The mirror etching of ZnSe has been described above, but a wet process other than the etching may be performed. Further, the processing target is not limited to ZnSe.
In particular, II-VI compound semiconductor crystals containing Zn, such as ZnS, ZnSe, ZnTe and ZnS, ZnS
This is effective for semiconductor crystals which have conventionally been difficult to perform wet processing such as etching, such as a mixed crystal of e and ZnTe.

The wafer plane orientation is not limited to the (111) plane.
The same effect can be obtained by using a wafer having any orientation such as (110) and (100). Other various changes,
It will be obvious to those skilled in the art that improvements, combinations, and the like are possible.

[0041]

The flow of the wet processing liquid can be controlled stably and with good reproducibility. For this reason, the unevenness of the processing in the wafer surface is reduced, and the reproducibility of the processing speed is improved.

The processing speed of the wet processing can be controlled with high precision by the flow rate of the wet processing liquid without changing the temperature or the composition ratio of the wet processing liquid such as the etching liquid. Since the wafer is held in a state close to the stationary state,
The introduction of defects due to mechanical impact can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a schematic plan view illustrating a wet process according to an embodiment of the present invention.

FIG. 2 is a top view of a wafer holding jig used in the embodiment of the present invention.

FIG. 3 is a schematic sectional view showing an etching state according to an embodiment of the present invention.

FIG. 4 is a graph showing a change in an etching rate with respect to a flow rate of an etching solution.

FIG. 5 is a schematic cross-sectional view for explaining etching by a conventional technique.

[Description of Signs] 1, 2 Wafer holding jig 3 Wafer 4 Wet processing liquid 5 Cylindrical container 15 Stirrer

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuyoshi Maruyama 305 Kitamikata, Takatsu-ku, Kawasaki-shi, Kanagawa Examiner Hideo Sakai (56) References JP-A-61-166134 (JP, A) JP-A-54-98181 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/304, 21/306, 21/308 B08B 3/00-3/14

Claims (6)

(57) [Claims] A step of rotating the processing liquid in a cylindrical container; and a step of rotating each of the plurality of flat processing objects substantially parallel to a rotation direction of the processing liquid so that the processing liquid is processed by the flat processing object. At a substantially same radial position, a jig is held along a circumferential surface of the cylindrical container by a jig so as to be largely divided into a part flowing on the outside of the body and a part flowing on the inside of the body. And performing a wet treatment by dipping the substrate in a wet process. 2. A process in which the volume of the processing liquid flowing inside the plate-shaped object and the flow flowing outside the plate-shaped object are immersed in the rotating processing solution. 2. The wet processing method according to claim 1, wherein the volume of the liquid is substantially equal. 3. The processing solution is an etching solution containing potassium permanganate, sulfuric acid, and water, and the object to be processed is II.
The wet processing method according to claim 1, wherein the method is a group VI compound semiconductor wafer. 4. The method according to claim 1, wherein in the step of rotating the processing liquid, the etching liquid is rotated by a stirrer at a flow rate of about 20 cm / sec or less on the surface of the flat object to be processed. The wet treatment method according to the item. 5. A cylindrical container having an open top, a rotation mechanism for rotating a processing liquid in the cylindrical container, and each of the plurality of flat plate-like objects to be processed being substantially parallel to a rotation direction of the processing liquid. In order to roughly divide the processing liquid into a portion flowing on the outside of the plate-shaped object and a portion flowing on the inside of the plate-like object, substantially at the same radial position, along the circumferential surface of the cylindrical container. A wet processing apparatus having a holding jig. 6. The jig includes a thin plate member disposed at at least two different heights, and a flat plate is formed at a radial position where a volume of a processing liquid is substantially equally divided when a flat plate-shaped object is held. The wet processing apparatus according to claim 5, wherein the workpiece can be held along a circumferential direction.