JPH08102456A - Electronic material cleaning method and cleaning equipment - Google Patents

Abstract

PURPOSE: To provide a waveguide optical control element wherein the form of a waveguide can be controlled with high precision, characteristics are stable, guided light can be intensively confined in the width direction, miniaturization and integration are possible, and large refractive index change can be obtained by a low voltage. CONSTITUTION: A high refractive index layer 2 is formed on a substrate 1 and the refractive index of the layer 2 is higher than that of the substrate 1. Trenches 4 are formed in the high refractive index layer 2 and demarcate an optical waveguide 3. Conductor is buried in the trenches 4, and electrodes are formed. The branching.combining or modulation of a guided light are performed by applying a voltage to the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic material cleaning method and cleaning apparatus for cleaning electronic materials such as silicon wafers in a single-wafer method in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, surface contaminants such as fine particles adhered to the surface of a silicon wafer cause deterioration of device characteristics, which is a major cause of defective products. Therefore, in order to improve the reliability of the semiconductor device, it is necessary to keep the surface of the silicon wafer as clean as possible in the manufacturing process. One of the methods to clean the surface of the silicon wafer,
There is a wet cleaning method. In this wet cleaning method, a silicon wafer is etched with various solutions or washed with ultrapure water. This wet cleaning method is a batch method in which a plurality of silicon wafers are collectively processed with a cleaning solution,
It is classified into a single-wafer method that processes one by one. In the present circumstances,
From the viewpoint of improving product throughput, the batch method is the mainstream, but this method has the following drawbacks. That is, the cleaning liquid is contaminated by introducing the contaminated silicon wafer, and the contamination is transferred to the adjacent silicon wafer. There is also a drawback that the cleaning device becomes large.

Therefore, in the semiconductor manufacturing process, a single wafer wet cleaning method is also used.
For example, in the photolithography process and the wet etching process, a single wafer wet cleaning method is used.

That is, in the photolithography process, a silicon wafer is coated with a photosensitive polymer film called a resist, the resist is dried, and then a gate electrode, a contact window and a metal wiring drawn on a glass mask are drawn. A circuit pattern such as is transferred onto a silicon wafer by ultraviolet rays or the like, and thereafter, the silicon wafer is washed by single-wafer wet cleaning and developed.

Further, in the wet etching process, the silicon wafer is exposed to an etching solution to selectively remove deposits or contaminants such as an oxide film and polycrystalline silicon formed on the front surface or the back surface of the silicon wafer. After that, the silicon wafer is washed by single-wafer wet cleaning using ultrapure water.

FIG. 10 is a schematic view showing a conventional single wafer type silicon wafer cleaning apparatus. The sample table 31 is arranged horizontally, and is driven by an appropriate rotating means to be rotatable around a vertical axis at an arbitrary speed. This sample stand 3
A silicon wafer 32 as a member to be cleaned is provided on
Is provided with a chuck 34 for fixing. Further, a nozzle 37 for supplying the cleaning liquid is arranged above the center of rotation of the sample table 31 with its ejection direction facing downward.

The operation of the conventional cleaning device thus constructed will be described below. First, the silicon wafer 32 to be cleaned is fixed on the sample table 31 by the chuck 34. Then, this silicon wafer 32 is rotated together with the sample table 31. Further, the cleaning liquid is discharged from the nozzle 37. The cleaning liquid ejected from the nozzle 37 is ejected onto the surface of the silicon wafer 32 to clean the deposits and contaminants on the surface of the silicon wafer 32. Then, this cleaning liquid flows down to the outside of the silicon wafer 32 by the rotation of the sample table 31, further flows down from the sample table 31, and is discharged from the lower part of the apparatus.

In such a cleaning apparatus, since the cleaning liquid is constantly supplied to the surface of the silicon wafer 32 to be cleaned, contamination of the surface of the silicon wafer 32 by the cleaning liquid can be reduced. Further, the rotation of the sample table 31 facilitates the separation of the silicon wafer 32 and the cleaning liquid.

However, in the above-mentioned cleaning apparatus, if contaminants such as particles are mixed in the cleaning liquid, the contaminants may adhere to the surface of the silicon wafer.
Further, contaminants from the outside of the apparatus may be mixed in the cleaning liquid and adhere to the surface of the silicon wafer. Furthermore, there is a possibility that contaminants once removed from the surface of the silicon wafer during the cleaning process may reattach to the silicon wafer while the cleaning liquid is being drained from the surface of the silicon wafer.

In order to solve such a difficulty, conventionally,
Especially in the deionized water cleaning process, by connecting a device that generates a negative DC voltage to the chuck and applying a negative voltage to the surface of the silicon wafer, particles that are negatively charged in pure water can be used by electrostatic repulsion. A method of removing by means is known (JP-A-3-49223).

[0011]

However, the above-mentioned cleaning method has the following problems. That is, the positively charged contaminants in pure water cannot be removed, and conversely tend to adhere to the silicon wafer. In addition, the cleaning liquid is not limited to pure water, and an acidic or alkaline solution may be used, and the polarity and the amount of charge of contaminants change depending on the solution. Therefore, it is difficult to effectively remove the contaminants in the cleaning liquid. Further, the product generated by the reaction between the silicon wafer and the cleaning liquid is difficult to remove because it is unknown which polarity the product is charged with.

The present invention has been made in view of the above problems, and it is possible to effectively remove the contaminants from the member to be cleaned, and the removed contaminants and the contaminants in the cleaning liquid are removed from the member. It is an object of the present invention to provide an electronic material cleaning method and a cleaning apparatus capable of suppressing redeposition on the surface of the member and further cleaning the surface of the member.

[0013]

The electronic material cleaning method according to the first invention of the present application applies a first electric potential to a member to be cleaned, and at the same time, applies the first electric potential to an electrode arranged facing the member. The member is washed with a washing liquid while applying a second potential having the same polarity as that of the above and an absolute value larger than the first potential.

An electronic material cleaning apparatus according to a second invention of the present application is a conductive supporting member for supporting a member to be cleaned, an electrode supporting member for arranging an electrode at a position facing the member, the member and the electrode. And a cleaning liquid supply unit that supplies a cleaning liquid to the member, and a voltage applying unit that applies a voltage having the same polarity and a larger absolute value to the electrode.

In the electronic material cleaning method according to the third invention of the present application, while maintaining the member to be cleaned at the ground potential, the cleaning liquid is applied while applying the first potential to the first electrode arranged facing the member. A first cleaning step of cleaning the member,
A second cleaning step of maintaining the member at ground potential and cleaning the member with a cleaning liquid while applying a second potential having a polarity opposite to the first potential to the second electrode arranged facing the member. It is characterized by having.

In the electronic material cleaning apparatus according to the fourth invention of the present application, a conductive support member for supporting the member to be cleaned, and the first electrode can be arranged at a position facing the member and a position away from the conductive support member. A first electrode supporting member, a second electrode supporting member capable of disposing a second electrode at a position facing the member and a position deviating therefrom, the first electrode and the second electrode applying a ground potential to the member And a cleaning liquid supply unit for supplying a cleaning liquid to the member, the voltage applying unit selectively applying a positive or negative voltage.

[0017]

In the first and second inventions of the present application, the voltage (second potential) is applied to the electrodes, and the voltage having the same polarity as the second potential (first potential) is applied to the member to be cleaned. The absolute value of this second potential is larger than the first potential. The contaminants in the cleaning liquid are positively or negatively charged. Among these pollutants, the pollutants charged with the opposite polarity to the electrode and the cleaning member are
It is electrostatically attracted and captured by the electrode of the second potential having a large absolute value. Further, the pollutants charged to the same polarity as the electrodes and the cleaning member migrate to the cleaning member side by the electrostatic repulsive force from the electrode having the second potential. However, since this cleaning member also has the same polarity, contaminants do not adhere to the surface of the cleaning member.

In the third and fourth inventions of the present application,
The cleaning member is grounded, and the positive or negative first electrode is applied to the first electrode.
An electric potential is applied (first cleaning step). Then, the pollutant charged with the opposite polarity to the first potential is captured and removed by the first electrode. On the other hand, contaminants charged to the same polarity as the first potential adhere to the surface of the cleaning member. Therefore, thereafter, a second potential having a polarity opposite to the first potential is applied to the second electrode (second cleaning step). Then, the pollutant charged with the opposite polarity to the second potential, that is, the same polarity as the first potential is released from the surface of the cleaning member and is captured by the second electrode together with the contaminant in the cleaning liquid. In this way, contaminants are removed. In this case, in the second cleaning step, at the same time,
By applying a voltage having the same polarity as the second potential to the first electrode, it is possible to remove contaminants attached to the first electrode in the first cleaning process.

[0019]

The present invention will be described in more detail below.
There are various possible contaminants in the cleaning liquid, and silicon-based particles such as silicon, silicon nitride, and silicon dioxide are actually representative of those that affect the performance of semiconductor devices and the product yield. The force acting between these particles can be described by the sum of the Van der Waals intermolecular attraction force and the repulsive force due to static electricity. However, it is difficult to control the van der Waals intermolecular attraction. On the other hand, the electrostatic force has a strong correlation with the zeta potential, which is approximated to the surface potential of the particles. You can control the force that acts on your.

The zeta potential is not a value peculiar to a substance, but depends on the properties of the medium of the solution, pH, electrolyte concentration and type, and not on the particle size of the particles. For example, the zeta potential of silicon particles is considered to be equivalent to that of silicon wafers. For example, when cleaning a silicon wafer, if the surface of the silicon wafer is positively (plus) charged, particles having the same polarity on the surface of the silicon wafer, that is, a positive zeta potential, are unlikely to adhere to the surface of the silicon wafer,
Particles having different polarities, that is, negative zeta potentials, tend to adhere to the silicon wafer surface.

In order to confirm the above-mentioned knowledge, the inventors of the present application, when the silicon wafer is immersed in an acidic or alkaline solution in which silicon nitride is mixed as simulated particles, the zeta potential of the silicon wafer as a cleaning member,
The product of the zeta potential of silicon nitride as a contaminant,
The relationship with the number of foreign matters having a size of 0.2 μm or more attached to the surface of the silicon wafer was investigated. The particle concentration is 5 x 1
It is set to 0 ³ cm ^-3 .

FIG. 1 is a graph showing the relationship between the zeta potential of the silicon wafer and the zeta potential of silicon nitride on the horizontal axis and the number of foreign substances on the surface of the silicon wafer on the vertical axis. . As is clear from FIG. 1, when the product of the zeta potential of the silicon wafer and the zeta potential of silicon nitride is positive, that is, when the zeta potential of the silicon wafer and the zeta potential of silicon nitride have the same polarity, the silicon The number of foreign particles on the wafer is decreasing. Therefore, it was confirmed that when the surface of the silicon wafer is charged, particles charged to the same polarity as the surface of the silicon wafer are unlikely to adhere to the silicon wafer. The present invention has been made from this point of view.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 2 is a schematic view showing an electronic material cleaning apparatus according to the first embodiment of the present invention, and FIGS. 3 and 4 are schematic views showing a cleaning method using this cleaning apparatus. In this cleaning apparatus, a silicon wafer 2 to be cleaned is placed on a sample table 1. The sample table 1 is rotatably driven at an arbitrary speed around the vertical support shaft 1a by an appropriate rotating means. A chuck 4 for fixing a silicon wafer is mounted on the sample table 1.
Is provided. The chuck 4 has conductivity and is connected to the variable potential generator 5. Electrodes 3 are provided on the silicon wafer 2 in parallel with each other so as to face the silicon wafer 2. The electrode 3 is connected to the variable potential generator 6. A cleaning liquid supply nozzle 7 as a cleaning liquid supply unit is arranged above the electrode 3. The cleaning liquid supply nozzle 7, the electrode 3, and the sample table 1 are housed in an appropriate housing, and drainage is discharged from the lower part of the housing.

It is desirable that the chuck 4 does not become a contamination source for the sample such as the silicon wafer 2. That is,
It is desirable that the chuck 4 is made of a material that does not chemically react with the cleaning liquid and that does not damage the silicon wafer 2. As such a material,
For example, there is silicon or silicon carbide. If the member to be cleaned has no problem with metal contamination, the chuck 4 may be formed using a metal such as aluminum that is easy to process.

Next, the operation of the electronic material cleaning apparatus thus constructed will be described. First, as shown in FIG. 3, the silicon wafer 2 is placed on the sample table 1, and the silicon wafer 2 is fixed by the chuck 4. Then, a positive first potential is applied to the silicon wafer 2 from the variable potential generator 5 via the chuck 4.

A second potential having the same polarity as the first potential is also applied to the electrode 3 from the variable potential generator 6. The absolute value of this second potential is larger than that of the first potential. Then, the sample table 1 is rotated and the cleaning liquid is supplied from the cleaning liquid supply nozzle 7 toward the silicon wafer 2. Then, the cleaning liquid passes through the electrode 3 and reaches the surface of the silicon wafer 2, and the surface of the silicon wafer 2 is cleaned.

The contaminants adhering to the surface of the silicon wafer 2 migrate in the cleaning liquid because they are charged to a positive or negative zeta potential in the cleaning liquid. In addition, contaminants mixed in the cleaning liquid in advance also migrate because they are positively or negatively charged.

In this case, the second voltage applied to the electrode 3
Since the potential is a higher positive potential, the negatively charged pollutant having the opposite polarity to the second potential is electrostatically attracted to the electrode 3 to be attached to the electrode 3 and captured. On the other hand, the positively charged contaminant migrates from the electrode 3 to the silicon wafer 2 side. However, since the surface of the silicon wafer 2 is also positively charged with the same polarity, the contaminant is transferred to the silicon wafer 2. Does not adhere to the surface. Since the silicon wafer 2 is rotating together with the sample table 1, the cleaning liquid on the surface of the silicon wafer 2 flows toward the outer edge side of the silicon wafer 2 and further flows down from the sample table 1 and is drained.

When the cleaning of the silicon wafer 2 is completed, the electrode 3 is cleaned by applying a negative potential having a polarity opposite to that applied during the cleaning, and the adsorbed contaminants are removed.

In this way, the negatively charged contaminant does not adhere to the electrode 3 and does not adhere to the silicon wafer 2, and the positively charged contaminant does not adhere to the silicon wafer 2 and is discharged together with the cleaning liquid. Therefore, the contaminants on the surface of the silicon wafer 2 can be effectively removed.

Also, as shown in FIG. 4, when a negative first potential is applied to the silicon wafer 2 and a second potential having a negative polarity and a large absolute value is applied to the electrode 3, the same action is obtained. , Pollutants are removed. That is, the positively charged contaminants are attached and removed to the electrode 3 having a negative polarity and a large absolute value, and the negatively charged contaminants flow down from the silicon wafer 2 without adhering to the surface of the silicon wafer 2 and the drained liquid is discharged. To be done. Therefore, the contaminants on the surface of the silicon wafer 2 can be effectively removed.

It goes without saying that the variable potential generator 5 and the variable potential generator 6 may be integrated.

5 and 6 are schematic views showing an electronic material cleaning apparatus according to the second embodiment of the present invention. A silicon wafer 12 to be cleaned is placed on the sample table 11. Further, the sample table 11 is rotatable about the support shaft 11a at an arbitrary speed, and a chuck 4 for fixing the silicon wafer 12 is provided thereon. The chuck 4 is electrically conductive and is grounded. A pair of a first electrode 13 and a second electrode 18 arranged in parallel to the silicon wafer 12 is provided at a position facing the silicon wafer 12, and the electrodes 13 and 18 are each a variable potential generator. 16,
It is connected to 15. Both of the electrodes 13 and 18 can move between a position facing the silicon wafer 12 above the silicon wafer 12 and a retracted position deviated from this position. A cleaning liquid supply nozzle 17 for supplying a cleaning liquid is arranged above the silicon wafer 12. Further, a cleaning liquid supply nozzle 19 for cleaning the electrodes 13, 18 when the electrodes 13, 18 are in the retracted position.
Is located above it.

Next, the operation of the electronic material cleaning apparatus thus constructed will be described. As shown in FIG. 5, the silicon wafer 12 is placed on the sample table 11, the silicon wafer 12 is fixed by the chuck 4, and the silicon wafer 12 is grounded via the chuck 4. Further, one electrode 13 is arranged above the silicon wafer 12, and a positive potential is applied to the electrode 13 by the variable potential generator 16.

Then, while rotating the sample table 11,
The cleaning liquid is supplied from the cleaning liquid supply nozzle 17 to the silicon wafer 12
Supply for. Then, the cleaning liquid reaches the surface of the silicon wafer 12 and removes contaminants adhering to the surface of the silicon wafer 12. This contaminant migrates in the washing solution because it has a positive or negative zeta potential.
In addition, contaminants mixed in the cleaning liquid in advance also migrate because they are positively or negatively charged.

In this case, the pollutants in the cleaning liquid, which are negatively charged, migrate in the cleaning liquid toward the electrode 13 by the positive potential of the first electrode 13 and adhere to the electrode 13. on the other hand,
The positively charged contaminants migrate toward the silicon wafer 12 and redeposit on the surface of the silicon wafer 12, or because the silicon wafer 12 is rotating, it flows down from the silicon wafer 12 together with the cleaning liquid.

After the first cleaning step, the first electrode 13 moves from the position facing the silicon wafer 12 to the retracted position as shown in FIG. Then, instead, the second electrode 18 is arranged at a position facing the silicon wafer 12. A negative potential is applied to the second electrode 18. As a result, the positively charged contaminants adhering to the silicon wafer 12 are removed from the silicon wafer 12 and adhere to the electrodes 18. Further, a negative potential is applied to the first electrode 13 as well, and the cleaning liquid is supplied from the cleaning nozzle 19 toward the electrode 13 to remove the negative pollutants attached to the electrode 13.

In this way, by the first cleaning step of applying a positive potential to the first electrode 13 and the second cleaning step of applying a negative potential to the second electrode 18, contamination attached to the silicon wafer 12 is contaminated. The substances that are positively charged and those that are negatively charged are sequentially removed.

In the above embodiment, the first electrode 1
3 may be movable up and down so as to approach the silicon wafer 12 at a position facing the silicon wafer 12.

Then, another silicon wafer 12 is placed on the sample stage 11, the first electrode 13 is again placed above the sample stage 11 on which this silicon wafer is placed, and a positive potential is applied to the first electrode 13. Apply the voltage and move to the next cleaning step. In this case, the second electrode 18 can be similarly cleaned by applying a positive potential below the nozzle 19.

In this manner, the negatively charged contaminants are attached to the first electrode 13 and removed from the silicon wafer 12, and then the positively charged contaminants are also attached to the second electrode 18 to be removed. Thereby, the contaminants on the surface of the silicon wafer 12 can be effectively removed.

A negative potential is applied to the first electrode 13,
Of course, a positive potential may be applied to the second electrode 18. Further, although the first and second electrodes 13 and 18 are moved in the present embodiment, the silicon wafer may be moved to a position facing the first and second electrodes 13 and 18 for cleaning.

Further, in the first and second embodiments, the size of the electrodes is preferably equal to or larger than that of the silicon wafer. 7A and 7B are plan views showing the shapes of the electrodes. As shown in FIG. 7 (a), the electrode can be formed in a donut shape having an opening at the center.
As shown in (b), a mesh shape can also be used.
With such a shape, the cleaning liquid can be supplied to the silicon wafer from above the electrodes.

Further, FIG. 8 is a schematic view showing a modification of the method for supplying the cleaning liquid onto the silicon wafer 22 from the cleaning nozzle 24. As shown in FIG. 8, after the silicon wafer 22 is fixed on the sample table 21, the sample table 21 and the sample table 2 are fixed.
The electrode 23 parallel to 1 may be inclined at an arbitrary angle while maintaining the parallel state to each other, and the cleaning liquid may be supplied from the nozzle 24 between the electrode 23 and the silicon wafer 22.

Further, as shown in FIG. 9, after fixing the silicon wafer 26 on the sample table 25 and arranging the electrode 27 in parallel with the silicon wafer 26, the cleaning nozzle 28 is lowered to lower the electrode 27 and the silicon wafer. The cleaning liquid may be supplied to the surface of the silicon wafer 26 through a gap between the surface and the surface of the silicon wafer 26.

With such a supply method, the cleaning liquid can be supplied onto the silicon wafers 23 and 26 without stagnation, and the cleaning liquid is easily separated from the silicon wafers 23 and 26.

[0047]

As described above, according to the present invention,
Contamination in the cleaning liquid is applied because an electric potential is applied to the member to be cleaned, and the member is cleaned while applying an electric potential having the same polarity as the electric potential but a larger absolute value to the electrode arranged facing the member. It is possible to effectively prevent the substance from adhering to the member to be cleaned, and to effectively remove the contaminant on the member.

Further, the member to be cleaned is grounded, and the first potential is applied to the first electrode for cleaning, and then the second electrode is also grounded and the second electrode is of the opposite polarity to the first potential. By applying two electric potentials to the member to clean it, contaminants on the member can be effectively removed.

[Brief description of drawings]

FIG. 1 is a graph showing the number of silicon nitride particles attached to a silicon wafer against the product of the zeta potential of the silicon wafer and the zeta potential of silicon nitride.

FIG. 2 is a schematic diagram showing an electronic material cleaning apparatus according to a first embodiment of the present invention.

FIG. 3 is a schematic view showing the cleaning method of the same.

FIG. 4 is a schematic view showing a cleaning method of the same.

FIG. 5 is a schematic diagram showing a first cleaning step in the operation of the electronic material cleaning apparatus according to the second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a second cleaning step in the same operation.

FIG. 7 is a plan view showing an example of an electrode structure of an electronic material cleaning apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic diagram showing a modified example of the method of supplying the cleaning liquid of the electronic material cleaning apparatus according to the embodiment of the present invention.

FIG. 9 is a schematic diagram showing another modified example of the cleaning liquid supply method.

FIG. 10 is a schematic view showing a conventional single wafer type silicon wafer cleaning apparatus.

[Explanation of symbols]

 1, 11, 12, 25, 31; sample stage 1a; support shafts 2, 12, 22, 26, 32; silicon wafers 3, 27; electrodes 4, 14, 34; chucks 5, 6, 15, 16; variable potential Generator 7, 17, 19, 24, 28, 37; Cleaning liquid supply nozzle 13; First electrode 18; Second electrode

Claims (6)

[Claims] 1. A second potential which is applied to a member to be cleaned and which has the same polarity as the first potential and is larger in absolute value than the first potential to an electrode arranged facing the member.
An electronic material cleaning method comprising cleaning the member with a cleaning liquid while applying a potential. 2. Next, a third potential having a polarity opposite to the first potential is applied to the member, and an electrode arranged facing the member has the same polarity as the third potential and an absolute value of the third potential. The electronic material cleaning method according to claim 1, wherein the member is cleaned with a cleaning liquid while applying a fourth potential higher than the third potential. 3. A conductive support member for supporting a member to be cleaned, an electrode support member for arranging an electrode at a position facing the member, and the member and the electrode having the same polarity and the electrode having the same polarity. An electronic material cleaning apparatus comprising: a voltage application unit that applies a voltage having a large absolute value; and a cleaning liquid supply unit that supplies a cleaning liquid to the member. 4. A first cleaning step of maintaining a member to be cleaned at a ground potential and cleaning the member with a cleaning liquid while applying a first potential to a first electrode arranged facing the member, A second cleaning step of maintaining the member at ground potential and cleaning the member with a cleaning liquid while applying a second potential having a polarity opposite to the first potential to the second electrode arranged facing the member. An electronic material cleaning method comprising: 5. In the second cleaning step, while simultaneously applying a voltage having a polarity opposite to the first potential to the first electrode,
The electronic material cleaning method according to claim 4, wherein the first electrode is cleaned with a cleaning liquid. 6. A conductive support member for supporting a member to be cleaned, a first electrode support member capable of disposing a first electrode at a position facing the member and a position away from the member, and a first electrode support member facing the member. A second electrode supporting member in which a second electrode can be arranged at a position where the first electrode and the second electrode are separated from each other, and a voltage of positive polarity or negative polarity selectively applied to the first electrode and the second electrode. An electronic material cleaning apparatus comprising: a voltage applying unit that applies a cleaning liquid; and a cleaning liquid supply unit that supplies a cleaning liquid to the member.