JPH09213674A - Method and device for etching semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent exhaustion of liquid from the surface of a wafer in transferring from etching step to rinsing step in spray etching process. SOLUTION: Time counting is started simultaneously in opening an etching liquid control valve 4 and upon expiration of etching time, a rinse liquid control valve 7 is opened while opening the etching liquid control valve 4. Rinse being fed from a rinse supply unit under a constant pressure is introduced to a rinse supply pipe 6 and jetted through a nozzle 5. Within 1sec after starting the jetting of rinse, the etching liquid control valve 4 is closed to finish the jetting of etching liquid and then a switching of the etching liquid jetted to the wafer 1 is made to rinse within 1sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for etching a semiconductor substrate such as a silicon wafer, and a method for etching a semiconductor substrate which includes a step of spraying an etching solution onto a wafer surface and simultaneously spraying a rinse solution. Regarding the device.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor substrate, there is a step of etching the surface of the semiconductor substrate with a chemical solution for the purpose of removing the processing strained layer and impurities such as heavy metals remaining on the surface in the preprocessing.

The etching process is carried out by immersing a dedicated carrier containing a large number of wafers in an etching solution prepared by mixing hydrofluoric acid, nitric acid, acetic acid, water and the like at a predetermined mixing ratio (hereinafter referred to as batch type immersion etching). Law and description) are implemented.

In the batch type immersion etching method, the reaction rate of the etching solution is governed by the composition ratio of the etching solution, the solution temperature, the stirring method, etc. In order to stabilize the etching accuracy, the composition and temperature of the etching solution are precisely controlled. There is a need to. Furthermore, the reaction heat generated during the etching of the silicon wafer raises the temperature of the etching solution and accelerates the reaction rate, making it difficult to control the reaction rate of the etching solution.

In recent years, a wafer diameter of 8 inches has become mainstream,
It is considered that large-diameter wafers of 12 inches or more will become the mainstream in the future, and the reaction heat during etching will be proportional to the surface area of the wafer, that is, the wafer diameter. As the wafer diameter increases, the reaction rate of the etching solution It becomes difficult to control.

Therefore, as a means for solving the reaction rate fluctuation due to reaction heat, which is a problem of the batch type immersion etching method, a method of directly injecting an etching solution onto a wafer surface with a spray nozzle to perform etching (hereinafter referred to as a spray etching method). Is proposed) (Japanese Patent Laid-Open No. 4-340226)
No.).

[0007]

The etching process of the spray etching method is performed by directly injecting an etching liquid from a spray nozzle onto the wafer to etch the wafer and by directly injecting a rinse liquid from the spray nozzle onto the wafer to perform etching. It consists of a rinse step of stopping the reaction and washing away the etching solution on the wafer surface.

In the spray etching method, when a liquid surface is cut off and the wafer surface is exposed,
NOx generated by the reaction of nitric acid in the etching reaction process reacts with the surface of the wafer to form a nitride film, which causes poor appearance. Therefore, when switching from the etching process to the rinsing process, there is performed a process of spraying the rinsing liquid at the same time while spraying the etching liquid onto the wafer surface for the purpose of preventing the liquid on the wafer surface from running out (hereinafter referred to as an overlap process). .

In the overlap step, the etching liquid and the rinsing liquid are simultaneously sprayed onto the wafer surface, and the etching liquid and the rinsing liquid are irregularly mixed on the wafer surface. In other words, at the final stage of etching, the wafer surface will be etched with an etching solution that has a very unstable reaction.
The surface quality of the wafer after etching was deteriorated. In particular, in the case of a wafer having a specific resistance value of 0.1 Ω · cm or less, deterioration of the surface properties of the wafer was feared.

An object of the present invention is to provide a semiconductor substrate etching method having an optimized overlapping step in the etching processing step of the spray etching method for the purpose of providing an overlapping step capable of improving the wafer surface quality after etching. And the purpose of providing the device.

[0011]

As a result of various studies aimed at optimizing the overlap process in the spray etching method, the inventor found that the rinse liquid was sprayed within 1 second while spraying the etching liquid at the end of the etching process. By stopping the supply of the etching solution, that is, by setting the time at which the etching solution and the rinsing solution are simultaneously sprayed to the workpiece within 1 second, the wafer surface is etched with the etching solution and the rinsing solution mixed irregularly. By being prevented from being etched by the liquid, good surface properties can be stably obtained, and by setting the overlap time to 0.5 to 1 second, the specific resistance value is 0.1 Ω · cm. The inventors have found that good surface properties can be stably obtained even in the following semiconductor substrates, and completed the present invention.

Further, as a result of various studies on the supply system of the etching solution and the rinsing solution for the purpose of an etching apparatus in which the overlap time can be set within 1 second, the inventor found that the etching nozzle and the rinsing nozzle were separately provided in the apparatus. In the configuration arranged in, the etching liquid supply pipe and the rinse liquid supply pipe are connected by a pipe between the spray nozzle and the liquid control valve via a backflow prevention valve in which the liquid flows only from the rinse liquid pipe to the etching liquid pipe. By having the liquid supply means, when the etching liquid control valve is opened and the etching liquid is sprayed onto the wafer for the required time to perform etching, the backflow preventive valve works when only the etching liquid is supplied, and the etching liquid flows into the rinse liquid pipe. Inflow can be prevented, and the rinse liquid control valve is opened immediately before the etching setting time is completed to supply the rinse liquid. Once started, the rinse liquid, which has a higher liquid pressure than the etching liquid, flows into the etching liquid supply pipe through the check valve, and the inside of the etching liquid supply pipe is instantly switched to the rinse liquid, which is supplied to the wafer surface. It was found that the etching solution can be instantly switched to the rinse solution, and the present invention was completed.

Further, as a result of various studies on the etching apparatus in which the spray nozzles for both etching and rinsing are arranged in the apparatus, the inventor has found that a pipe for supplying the etching liquid to the main pipe for supplying the liquid to the combined nozzle. And the rinsing solution supply pipes are connected together via control valves, the control valve for the etching solution is opened and the etching solution is sprayed on the wafer for the set time to perform etching. It was found that switching the etching solution to the rinse solution can be completed within 1 second by opening the control valve and starting the supply of the rinse solution and closing the control valve of the etching solution within 1 second and stopping the supply of the etching solution. , Completed this invention.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Configuration 1 An etching method according to the present invention will be described with reference to FIGS. The etching apparatus shown in FIG. 1 has the same basic configuration as the etching apparatus proposed by the applicant (Japanese Patent Laid-Open No. 4-340226) described above, and the wafer 1 is held by a wafer rotation roller 11 in a self-supporting manner. A nozzle chamber 8 to which an etching nozzle 2 and a rinsing nozzle 5 are attached on both sides thereof is held and arranged by a swing arm 9. In the nozzle chamber 8, an etching solution supply pipe 3 equipped with an etching solution control valve 4,
A rinse liquid supply pipe 6 equipped with a rinse liquid control valve 7 is connected.

By rotating the wafer rotating roller 11 by a motor (not shown), the wafer 1 held by the roller 11 is rotated. Wafer 1
When the rotation speed of (1) reaches the set rotation speed, the rocking arm 9 holding the nozzle chamber 8 is rocked around the rocking center 10 by a driving device (not shown). After the rocking is started, the etching liquid control valve 4 is opened, and the etching liquid supplied from the etching liquid supply device (not shown) at a constant pressure is introduced into the etching liquid supply pipe 3 so that the etching nozzle 2
The etching liquid is sprayed toward the wafer 1 to perform etching.

When the etching liquid control valve 4 is opened and the time counting is started at the same time, and the counting of the time set as the etching processing time ends, the rinsing liquid control valve 7 is opened with the etching liquid control valve 4 open. A rinse liquid, which is fed under a constant pressure from a supply device (not shown), is introduced into the rinse liquid supply pipe 6, and the rinse liquid is sprayed from the rinse nozzle 5 toward the wafer 1 to start the rinse.

Next, the etching liquid control valve 4 is closed within 1 second of the start of the rinse liquid injection to complete the injection of the etching liquid, and the etching liquid sprayed on the surface of the wafer 1 is switched to the rinse liquid within 1 second. After rinsing the wafer 1 with the rinsing liquid for a set time, the rinsing liquid control valve 7 is closed to stop the rinsing liquid from the rinsing nozzle 5. After the rinsing liquid has been jetted, the oscillating arm 9 stops oscillating, the wafer 1 continues to rotate for a certain period of time, and the rinsing liquid adhering to the wafer surface is blown off by a centrifugal force to dry. After that, the rotation of the wafer rotation roller is stopped, the rotation of the wafer 1 is stopped, and the etching process is completed.

Structure 2 An etching method according to the present invention will be described with reference to FIGS. 2 and 4. The etching apparatus shown in FIG. 2 has the same basic configuration as that of the above-described etching apparatus, and the wafer 1 is self-supported by the wafer rotation roller 11.
An etching solution nozzle chamber 12 having etching nozzles 2 attached to both sides thereof is held and arranged by a swing arm 9. An etching liquid supply pipe 3 having an etching liquid control valve 4 is connected to the etching liquid nozzle chamber 12. Also, wafer 1
The rinse liquid nozzle chamber 13 to which the rinse nozzle 5 is attached is arranged above. A rinse liquid supply pipe 6 having a rinse liquid control valve 7 is connected to the rinse liquid nozzle chamber 13.

The wafer 1 self-supported by the wafer rotation roller 11 rotated by a motor (not shown) rotates, and when the rotation speed of the wafer 1 reaches a set rotation speed,
A swinging arm 9 holding the etching liquid nozzle chamber 12 is swung about a swinging center 10 by a driving device. After the rocking is started, the etching solution control valve 4 is opened to introduce the etching solution fed under a constant pressure from the etching solution supply device (not shown) into the etching solution supply pipe 3, and the etching nozzle 2 moves toward the wafer 1. Etching is performed by spraying an etching solution.

At the same time when the etching liquid control valve 4 is opened, the time counting is started, and after the time set as the etching processing time is finished, the rinsing liquid control valve 7 is opened with the etching liquid control valve 4 still open. A rinsing liquid fed under a constant pressure from a supply device (not shown) is introduced into the rinsing liquid supply pipe 6, and the rinsing nozzle 5
The rinse liquid is further jetted toward the wafer 1 to start the rinse.

Then, the etching liquid control valve 4 is closed within 1 second of the start of the rinse liquid injection to complete the injection of the etching liquid, and the etching liquid sprayed on the surface of the wafer 1 is switched to the rinse liquid within 1 second. After rinsing the wafer 1 with the rinsing liquid for a set time, the rinsing liquid control valve 7 is closed to stop the rinsing liquid from the rinsing nozzle 5. Further, the swing arm 9 is used after the rinsing liquid injection is stopped.
Of the wafer 1 is continued for a certain period of time, and the rinse liquid adhering to the wafer surface is blown off by centrifugal force to dry. After that, the rotation of the wafer rotation roller is stopped, the rotation of the wafer 1 is stopped, and the etching process is completed.

Structure 3 The etching method according to the present invention will be described with reference to FIGS. The etching apparatus of FIG. 3 has a structure in which the wafer 1 is held horizontally by a wafer chuck 14, and an etching nozzle 2 and a rinsing nozzle 5 are arranged above the wafer 1. An etching solution supply pipe 3 having an etching solution control valve 4 is connected to the etching nozzle 2, and a rinse solution supply pipe 6 having a rinse solution control valve 7 is connected to the rinsing nozzle 5.

The wafer chuck 14 is rotated by a motor (not shown) to rotate the wafer 1, and when the rotation speed reaches the set rotation speed, the etching solution control valve 4 is opened and pressure is fed from the etching solution supply device at a constant pressure. The etching liquid is introduced into the etching liquid supply pipe 3, and the etching liquid is jetted from the etching nozzle 2 toward the wafer 1 to perform etching.

At the same time when the etching liquid control valve 4 is opened, time counting is started, and after the count of the time set as the etching processing time ends, the rinsing liquid control valve 7 is opened with the etching liquid control valve 4 still open. The rinse liquid fed under pressure from the rinse liquid supply device at a constant pressure is introduced into the rinse liquid supply pipe 6, and the rinse liquid is sprayed from the rinse nozzle 5 toward the wafer 1 to start the rinse.

Then, the etching liquid control valve 4 is closed within 1 second of the start of the spraying of the rinse liquid to complete the spraying of the etching liquid, and the etching liquid sprayed on the surface of the wafer 1 is switched to the rinse liquid within 1 second. After rinsing the wafer 1 with the rinsing liquid for a set time, the rinsing liquid control valve 7 is closed to stop the rinsing liquid from the rinsing nozzle 5. The rotation of the wafer 1 is continued for a certain period of time after the spraying of the rinse liquid is stopped, and the rinse liquid adhering to the wafer surface is blown off and dried by centrifugal force. Then wafer chuck 1
The rotation of No. 4 is stopped, the rotation of the wafer 1 is stopped, and the etching process is completed.

Structure 4 Either structure of the etching apparatus shown in FIG. 1 or 2 for independently holding the wafer 1 by the wafer rotating roller 11 or the etching apparatus shown in FIG. 3 for holding the wafer 1 horizontally by the wafer chuck 14. Also in this case, the etching method of the present invention can be performed with simple control by using a configuration in which the etching solution supply pipe 3 and the rinse solution supply pipe 6 are connected via a valve on the way as shown in FIG. 5 in the liquid supply means. Easy to implement.

As shown in FIG. 5, the etching liquid supply pipe 3
And the rinse liquid supply pipe 6 connect the flow from the etching liquid supply pipe 3 to the rinse liquid supply pipe 6 between the etching nozzle 2 and the etching liquid control valve 4 and between the rinse nozzle 5 and the rinse liquid control valve 7. It is connected via a check valve 15 for preventing the backflow. The etching liquid supply pipe 3
The rinse liquid supply pipe 6 is connected to each supply source via a backflow prevention valve 16 in order to prevent each liquid from flowing back to a different liquid supply source.

In the apparatus shown in FIGS. 1 and 2, the wafer 1 is rotated about its own axis, the swing arm 9 is swung, and FIG.
The wafer 1 is rotated by the apparatus shown in FIG. Next, in FIG. 5, the etching solution control valve 4 is opened and the etching solution supplied from an etching solution supply device (not shown) at a constant pressure is supplied with the etching solution supply pipe 3
Then, the etching liquid is sprayed from the etching nozzle 2 toward the wafer 1 to perform etching. Note that the etching liquid does not flow into the connected rinse liquid supply pipe 6 by the action of the check valve 15.

When the etching liquid control valve 4 is opened and the time counting is started at the same time, and the counting of the time set as the etching processing time ends, the rinsing liquid control valve 7 is opened with the etching liquid control valve 4 left open. A rinse liquid having a pressure higher than the etching supply liquid pressure is introduced into the rinse liquid supply pipe 6 from a supply device (not shown), and the rinse liquid is sprayed from the rinse nozzle 5 toward the wafer 1 to start the rinse.

Here, the liquid pressure of the rinse liquid is set to be higher than the etching liquid pressure, the rinse liquid passes through the check valve 15 and flows into the etching liquid supply pipe 3, and the inside of the etching liquid supply pipe 3 is adjacent to the etching liquid supply pipe 3. At times, the etching liquid is replaced with the rinse liquid, and the etching liquid sprayed from the etching nozzle 2 is instantly switched to the rinse liquid. Then, when the switching to the rinse liquid is completed, the etching liquid control valve 4 is closed. After rinsing the wafer 1 with the rinsing liquid for a predetermined time, the rinsing liquid control valve 7 is closed to stop spraying the rinsing liquid from the rinsing nozzle 5.

After the injection of the rinse liquid is stopped, in the apparatus shown in FIGS. 1 and 2, the swinging of the swinging arm 9 is stopped, the rotation of the wafer 1 is continued for a certain period of time, and the rinse liquid adhering to the wafer surface is centrifugally applied. Blow off and dry. After that, the rotation of the wafer rotation roller 11 is stopped in the apparatus of FIGS. 1 and 2, the rotation of the wafer chuck 14 is stopped in the apparatus of FIG. 3 to stop the rotation of the wafer 1, and the etching process is completed.

Structure 5 Either structure of the etching apparatus shown in FIG. 1 or 2 in which the wafer 1 is self-supported by the wafer rotation roller 11 or the etching apparatus shown in FIG. 3 in which the wafer 1 is horizontally held by the wafer chuck 14. Also, in the liquid supply means, the etching liquid supply pipe 3 and the rinse liquid supply pipe 6 as shown in FIG.
The etching method of the present invention can be easily carried out with simple control by using the configuration connected to.

That is, in the apparatus shown in FIG. 1, FIG. 2 or FIG. 3, as shown in FIG. 6, the chemical solution supply means is such that the etching solution supply pipe 3 and the rinse solution supply pipe 6 are jointly connected to the etching / rinsing nozzle 20. The configuration has been changed. The etching liquid supply pipe 3 and the rinse liquid supply pipe 6 are connected to respective supply sources via a backflow prevention valve 16 in order to prevent the respective liquids from flowing back to different liquid supply sources. As described above, the wafer 1 is rotated by the respective means shown in the apparatus shown in FIGS. 1, 2 and 3, and the swing arm 9 is swung in the apparatus shown in FIGS.

The etching liquid control valve 4 is opened, and the etching liquid fed from an etching liquid supply device (not shown) at a constant pressure is introduced into the etching liquid supply pipe 3, and the etching liquid is fed from the dual-purpose nozzle 20 toward the wafer 1. Spray and etch. When the etching liquid control valve 4 is opened, time counting is started at the same time, and when the counting of the time set as the etching processing time ends, the rinsing liquid control valve 7 is kept open with the etching liquid control valve 4 open.
Then, a rinse liquid having a pressure higher than the etching supply liquid pressure is introduced into the rinse liquid supply pipe 6 from a rinse liquid supply device (not shown), and the rinse liquid is sprayed from the dual-purpose nozzle 20 toward the wafer 1 to start the rinse.

Here, the liquid pressure of the rinse liquid is set higher than the etching liquid pressure, the supply of the etching liquid is suppressed by the liquid pressure of the rinse liquid, and the etching liquid sprayed from the dual-purpose nozzle 20 is instantaneously rinsed. Switched to liquid. Then, when the switching to the rinse liquid is completed, the etching liquid control valve 4 is closed. After rinsing the wafer 1 with the rinse liquid for a predetermined time, the rinse liquid control valve 7 is closed,
The injection of the rinse liquid from the rinse nozzle 5 is stopped.

After the rinsing liquid is stopped from being sprayed, the oscillating arm 9 is stopped to oscillate in the apparatus shown in FIGS. Blow off and dry. After that, in the apparatus shown in FIGS. 1 and 2, the rotation of the wafer rotation roller is stopped, and
In this apparatus, the rotation of the wafer chuck 14 is stopped, the rotation of the wafer 1 is stopped, and the etching process is completed.

In each control program of the present invention described above, the computer is programmed with the steps in advance,
Each motor, drive device, liquid supply device and valves 4, 7
Can be easily realized by a configuration whose operation is controlled by a computer.

[0038]

EXAMPLE The opening and closing of the etching liquid control valve 4 and the rinsing liquid control valve 7 were controlled by using the etching apparatus shown in FIG. 1 to set the overlap time to 0.
Etching was performed while changing the interval in 5 second intervals, and the appearance quality rate after etching was measured, which is shown in the graph of FIG. 7. As is clear from FIG. 7, when the overlap time exceeds 1 second,
The non-defective rate is remarkably reduced because the surface of the wafer is etched by the solution in which the etching solution and the rinse solution are mixed irregularly, while the overlap time is within 1 second, especially 0.5 to 1 second. It can be seen that, in the present invention set to, the appearance quality rate after etching is remarkably improved.

Further, the etching liquid control valve 4 and the rinsing liquid control valve 7 have some time loss until the valves are opened / closed in response to the opening / closing command signal input. The liquid may not be instantaneously jetted onto the surface of the wafer 1 due to the influence of time loss, and the surface of the wafer 1 is exposed due to liquid shortage and the surface reacts with NOx generated by the etching reaction to form a nitride film and reduce the yield rate. There is danger.

Further, in order to prevent the occurrence of defects due to running out of liquid, the configuration 4 having the liquid supply means shown in FIG. 5 and the configuration 5 having the liquid supply means shown in FIG. 6 for switching the etching liquid to the rinse liquid in the pipe. It was confirmed that the etching apparatus of 1 was particularly effective.

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, an etching solution is sprayed at the end of etching processing in the overlap step of the spray etching method which can stably obtain good surface properties of a semiconductor substrate as compared with the conventional batch type immersion etching method. However, the rinsing liquid is sprayed and the supply of the etching liquid is stopped within 1 second, that is, the overlap time at which the etching liquid and the rinsing liquid are simultaneously sprayed onto the workpiece is set within 1 second, so that the wafer surface is The etching liquid and the rinsing liquid are prevented from being irregularly mixed and etched, and more excellent surface properties can be stably obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an etching apparatus according to the present invention.

FIG. 2 is a perspective view showing another configuration of the etching apparatus according to the present invention.

FIG. 3 is a perspective explanatory view showing another configuration of the etching apparatus according to the present invention.

FIG. 4 is an explanatory diagram showing a chemical liquid supply system of the etching apparatus according to the present invention.

FIG. 5 is an explanatory view showing another chemical liquid supply system of the etching apparatus according to the present invention.

FIG. 6 is an explanatory view showing another chemical liquid supply system of the etching apparatus according to the present invention.

FIG. 7 is a graph showing the relationship between overlap time and non-defective rate.

[Explanation of symbols]

 1 Wafer 2 Etching Nozzle 3 Etching Solution Supply Pipe 4 Etching Solution Control Valve 5 Rinsing Nozzle 6 Rinsing Solution Supply Pipe 7 Rinsing Solution Control Valve 8 Nozzle Chamber 9 Swing Arm 10 Swing Center 11 Wafer Rotating Roller 12 For Etching Solution Nozzle chamber 13 Nozzle chamber for rinse liquid 14 Wafer chuck 15 Backflow prevention valve 16 Backflow prevention valve 20 Dual-purpose nozzle

Claims (4)

[Claims] 1. A method of etching a semiconductor substrate in which an etching solution is sprayed onto a surface of a semiconductor substrate to perform etching for a predetermined time, and then a rinse solution is sprayed onto the surface of the substrate to clean the surface of the semiconductor substrate. The method of etching a semiconductor substrate is characterized in that the step of switching to rinsing liquid only is simultaneously performed while performing the simultaneous blasting, and the overlap time is within 1 second. 2. The semiconductor substrate according to claim 1, wherein the semiconductor substrate has a specific resistance value of 0.1 Ω · cm or less and an overlap time of 0.
A method for etching a semiconductor substrate, which is 5 to 1 second. 3. A holding and rotating means for rotatably supporting a semiconductor substrate, an etching solution supplying means for spraying an etching solution onto a substrate surface from a spray nozzle, and a rinse solution supplying means for spraying a rinse solution onto a substrate surface from a spray nozzle. In the etching apparatus for semiconductor substrates having, the etching liquid supply pipe and the rinse liquid supply pipe whose liquid pressure is higher than the etching liquid pressure are respectively provided between the spray nozzle and the liquid control valve in the direction from the rinse liquid pipe to the etching liquid pipe. 2. The semiconductor substrate etching apparatus according to claim 1, wherein the semiconductor substrate etching apparatus is connected by a pipe through a check valve for flowing a liquid. 4. A holding and rotating means for rotatably supporting a semiconductor substrate, an etching liquid supplying means for spraying an etching liquid onto a substrate surface from a spray nozzle, and a rinse liquid supplying means for spraying a rinse liquid onto a substrate surface from a spray nozzle. In a semiconductor substrate etching apparatus having a pipe for supplying a liquid to a spray nozzle, a pipe for supplying an etching liquid and a pipe for supplying a rinse liquid are jointly connected via a control valve, and the rinse liquid pressure is higher than the etching liquid pressure. The semiconductor substrate etching apparatus according to claim 1, which is set to a high pressure.