JPH07263401A - Wet treating method and device - Google Patents

Abstract

PURPOSE:To acquire the title wet treating technology having reproducibility and the less possibility of developing crystalline defects by a method wherein a planar workpiece may be held in the jigs in almost parallel with the turning treating solution for immersing the workpieces. CONSTITUTION:Wafers 3 held by wafer holding jigs 1, 2 in plural positions are arranged in a cylindrical container wherein a wet treating solution is contained to be turned in the arrow direction. At this time, the wafers 3 are arranged in almost parallel with the running direction of the wet treating solution stably turning so that the wet treating step may be performed on the surface of the wafers 3. In such a constitution, the wafer holding jigs 1, 2 are formed so that the sectional areas in the perpendicular direction to the running direction of the wet treating solution may be narrowed not to disturb the running wet treating solution. Through these procedures, the uneven treatment of the wafer surface can be avoided thereby enabling the reproducibility of the treating rate to be improved.

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.
The present invention relates to a technique for performing a wet process on a flat object to be processed such as a group VI compound semiconductor wafer having a relatively small diameter.

[0002]

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

FIG. 5A shows the simplest method. The bottom of the beaker 51, with the side to be wet-treated facing up II-
A wafer 53 such as a group VI compound semiconductor is arranged,
An etching solution 52 such as sodium hydroxide type or Br-methanol type is poured from above. The operator handles the beaker 51 by hand.
Hold and shake to rotate and stir the etching solution to perform etching. After the etching is completed, the etching solution is discarded and a large amount of pure water is poured in to rinse.

FIG. 5B shows a method using a jig.
The wafer 53 is placed in a basket 54 in which a liquid drainage void is sufficiently formed. After pouring the etching liquid 52 into the beaker 51, the lower portion of the basket 54 is immersed in the etching liquid 52. By manually moving the basket 54 up and down, the etching liquid is uniformly moved on the surface of the wafer 53. At the end of etching, the basket is taken out of the beaker 51 and brought into another beaker in which pure water has overflowed.

[0005]

When such a simple wet process is performed, it is difficult to form a stable process liquid flow. When etching ZnSe, which is a II-VI group compound semiconductor crystal, ZnSe has strong ionicity, so even a slight disturbance of the etching solution causes unevenness of etching, which disturbs mirror-like etching.

Since the speed of progress of the wet processing is governed by the flow of the processing liquid by manual work, it is difficult to stably perform the wet processing with reproducibility. In the case of etching, variations occur in etching rate and etching depth. When the wafer is placed on the bottom of the beaker, it is difficult to supply sufficient etching liquid because the back surface of the wafer is in contact with the bottom of the beaker. It is done only on the surface.

Further, when arranging the wafers on the bottom of the beaker, it is difficult to arrange a plurality of wafers. If a plurality of wafers overlap or collide with each other when the etching liquid is stirred, it may cause uneven etching and poor reproducibility.

When the wafer is placed on the bottom of the beaker and the etching solution is rotated, the wafer rubs against the bottom surface of the beaker and collides with the side surface. Due to such mechanical impact, there is a risk that defects will be introduced into the wafer crystal.

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

[0010]

The wet treatment method of the present invention comprises a step of rotating a treatment liquid in a cylindrical container and a method of using a jig so that a flat object to be treated is substantially parallel to the flow of the treatment liquid. Holding and immersing in a rotating treatment liquid to perform wet treatment.

[0011]

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

By immersing the flat object to be processed held in the jig in this treatment liquid in a direction substantially parallel to the flow of the treatment liquid, the flat object to be treated is maintained while maintaining a stable flow of the treatment liquid. The treatment liquid can be brought into contact with the surface of the object to be treated without giving an excessive mechanical impact.

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

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 a plurality of wafer holding jigs 1 and 2 at a plurality of locations, and is placed in a cylindrical container 5. The wet treatment liquid 4 is poured into the cylindrical container 5 and rotated in the direction of the arrow.

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

The wafer holding jigs 1 and 2 are formed with a small cross-sectional area in the 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 than that. Composed of. Furthermore, it is preferable to provide many through openings so as not to obstruct the flow of the processing liquid 4.

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

The four wafer holding jigs 1a to 1d
Although 4 sets of 2a to 2d are illustrated, these holding jigs 1a to 1d and 2a to 2d may be respectively configured by a single member. Further, the entire wafer holding jigs 1 and 2 can be made into a single structure.

Since the wet treatment liquid 4 rotates in the cylindrical container 5, the flow velocity of the wet treatment liquid 4 depends on the radial position in the cylindrical container 5. In order to uniformly perform the wet processing on all the wafers, it is preferable to arrange each wafer 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 two parts, that is, the part that flows outside the wafer and the part that flows inside the wafer. When uniform wet processing is performed on both surfaces of the wafer, it is desirable that almost the same wet processing liquid contacts the front surface and the back surface of the wafer. For this reason, it is preferable to select the radial position where the wafer 3 is arranged so that the wet processing liquid 4 is divided into two parts having substantially the same volume inside and outside.

In the following, without limitation, examples of etching ZnSe which is a II-VI group compound semiconductor will be described. ZnSe prepared by liquid phase growth
The crystal was sliced along an arbitrary plane orientation, for example, the (111) plane, and processed into a wafer. The ZnSe wafer thus produced was lapped and polished by mechanical polishing to have a mirror-finished surface. After mirror polishing, ultrasonic cleaning was performed in order to remove the polishing agent adhering to the surface of the wafer.

A plurality of wafers thus prepared are held by a jig and etched in a beaker. Figure 2
(A), (B) is a top view which shows two types of jigs which hold | maintain a wafer. 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 rhombus mesh portions 6 for holding the wafer 3 so as to drop it on the circumference of the same radius. The rhombus of each mesh portion is arranged so that one diagonal line faces in the radial direction and the other diagonal line faces in the circumferential direction. These mesh portions 6 are connected to a common central portion 7 by an arm 8. The central portion 7 is provided with a circular opening for passing the support column.

A cylindrical outer peripheral portion 9 is connected to the outside of the mesh portion 6. 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 the central portion 12. The central portion 12 is provided with a circular opening for passing the above-mentioned support. The outer end of each arm 11 is connected to a columnar outer peripheral portion 13. The outer peripheral portion 13 has a height suitable for disposing the object to be processed substantially at the center of the processing liquid depth, and the arm 11 is connected to the upper end thereof.

The jigs shown in FIGS. 2A and 2B are made of Teflon having high chemical resistance. In order to realize a smooth flow of the etching solution, both jigs are formed of thin plate members 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 are substantially the same as the inner wall of the beaker. That is, the etching solution is prevented from flowing from the outside of the basket body, and the flow is supplied only from the inside of the basket. With such a configuration, a stable flow is realized.

In FIG. 3, the basket net jig 2 is overlaid on the basket base jig 1 and held in common by the columns 13.
The state arrange | positioned in the beaker 5 is shown. For example, beaker 5
Is a 100 ml beaker, the outer diameter of the jigs 1 and 2 is about 50 mm. Before inserting the jigs 1 and 2, beaker 5
A 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 lines of the diamond-shaped opening portion of the basket net jig 2, and the lower end is inserted into the groove 10 of the basket base jig 1.

The position at which the wafer 3 is held is determined by the volume of the etching liquid flowing inside the wafer 3 and the wafer 3
The configurations of the jigs 1 and 2 are designed so that the volume of the etching liquid flowing outside is substantially equal. With such a configuration, the difference in the etching state depending on the orientation of the wafer is reduced.

An etching solution 17 is poured into the beaker 5. By rotating the etching liquid 17 with the stirrer 15, stable rotation of the etching liquid 17 can be obtained. As the etching solution 17, a potassium permanganate-sulfuric acid aqueous solution-based etching solution capable of performing mirror surface etching on all plane orientations 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 this 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 etching solution is
It flows in a direction substantially parallel to the wafer surface.

After the lapse of a predetermined etching time, the baskets 1 and 2 were taken out, washed with water, replaced with water by methanol, and ultrasonically washed in dichloromethane for about 30 minutes. The flow rate of the etching solution can be controlled by the rotation speed of the stirrer.
In the state where the above-mentioned basket jigs 1 and 2 were arranged, the flow rate of the etching solution changed almost linearly with respect to the stirrer rotation speed in the range of the stirrer rotation speed of 200 to 1000 rpm. By using such a linear region, control of etching becomes easy.

FIG. 4 is a graph showing the relationship between the flow rate of the etching liquid 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 /
sec, and the vertical axis represents the etching rate in μm / min. As is clear from this graph, it was found that the etching rate increased linearly in proportion to the increase in the etching solution flow rate.

By measuring such basic data in advance, by controlling the stirrer rotation speed, Zn
Se etching can be controlled with high precision. Zn
As a result of investigating the relationship between the etching solution flow rate and the etching unevenness in the Se wafer etching, at the etching solution flow rate exceeding 20 cm / sec, the etching solution was disturbed in rotation and the etching unevenness was generated. However, good mirror surface etching was possible by setting the etching liquid flow rate to 20 cm / sec or less.

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 the etching liquid is stably rotated by using the rotary drive mechanism such as the stirrer, the etching proceeds stably and uniformly. It is also possible to change the stirrer rotation speed to change the etching rate with high accuracy. For example, in the case of mirror surface etching, the etching rate can be changed while maintaining the mirror surface 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 with respect to the wafer is changed, which causes the surface state after etching to be rough. When the etching rate is changed by changing only the flow rate while keeping the composition and temperature of the etching solution constant, the etching rate can be controlled in a wide range while maintaining the basic etching performance.
When the above etching solution was used, the etching rate could be arbitrarily controlled within the range of 0.3 to 0.8 μm / min.

The etching solution rotates circularly inside the beaker,
The basket type jig can arrange all the wafers in parallel and symmetrically with respect to the flow. Therefore, etching uniformity is high even when a plurality of wafers are simultaneously processed.

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.
Therefore, 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 the same characteristics, the cleaning effect on the entire wafer is enhanced. Since the wafer surface can be uniformly etched, the work-affected layer can be effectively removed by polishing or the like, and a good semiconductor device can be manufactured.

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

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

[0041]

The flow of the wet processing liquid can be controlled stably and with good reproducibility. Therefore, the unevenness of the processing on 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 accuracy by the flow speed of the wet processing liquid without changing the temperature or composition ratio of the wet processing liquid such as the etching liquid. Since the wafer is held in a state that is almost stationary,
It is possible to effectively prevent the introduction of defects due to mechanical shock.

[Brief description of drawings]

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

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

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

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

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

[Explanation of symbols]

 1, 2 Wafer holding jig 3 Wafer 4 Wet processing liquid 5 Cylindrical container 15 Stirrer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication H01L 21/68 N (72) Inventor Kazushi Tamura 1-24-10 Nagatsuda, Midori-ku, Yokohama-shi, Kanagawa Naso 203 (72) Inventor Tsuyoshi Maruyama 305 Kitamikata, Takatsu-ku, Kawasaki City, Kanagawa Prefecture

Claims (6)

[Claims] 1. A step of rotating a treatment liquid in a cylindrical container, and a flat object to be treated is held by a jig so as to be substantially parallel to the flow of the treatment liquid, and immersed in a rotating treatment liquid. Wet processing method including a step of performing wet processing. 2. The volume of the processing liquid flowing inside the plate-shaped processing object and the volume of the processing solution flowing outside the plate-shaped processing object in a state where the plate-shaped processing object is immersed in a rotating processing solution. The wet processing method according to claim 1, wherein the wet processing methods are 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 or 2, which is a group VI compound semiconductor wafer. 4. The step of rotating the processing solution comprises rotating the etching solution with a stirrer so that the flow rate on the surface of the flat object is about 20 cm / sec or less.
The wet treatment method according to any one of 3 above. 5. A cylindrical container having an open top, a rotating mechanism for rotating the processing liquid in the cylindrical container, and a flat plate-shaped object to be held substantially parallel to the rotating flow of the processing liquid. Wet processing apparatus having a jig. 6. The flat plate-shaped member at a radial position that divides the volume of the processing liquid into approximately two parts when holding the flat plate-shaped object when the jig includes thin plate-shaped members arranged at at least two different heights. The wet processing apparatus according to claim 5, which is capable of holding an object to be processed along a circumferential direction.