JP2002184698A - Method of manufacturing electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing electronic components, whereby electrodes having a superior adhesion to a wafer and a high forming accuracy can be obtained easily for forming patterned electrodes, using the lift off method. SOLUTION: The manufacturing method comprises processing a wafer 1, having a photoresist pattern with oxygen plasma, forming a metal film on the wafer and the photoresist and removing partly the metal film based on the lift off method to form electrodes. The plasma is generated by electric discharge from a plasma-discharging antenna 7 to ion-clean the wafer 1 in vacuum, and then the metal film is successively formed by the vacuum evaporation method on the wafer 1 held at a lower temperature, than the heating temperature for forming the photoresist pattern, without exposing the atmospheric air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method of manufacturing an electronic component such as a surface acoustic wave device, and more particularly to a method of manufacturing an electronic component including a step of forming electrodes on a wafer by a lift-off method. .

[0002]

2. Description of the Related Art When manufacturing electronic components such as a surface acoustic wave device, in order to enhance mass productivity, after an electrode pattern of a plurality of electronic components is formed on a mother wafer, the wafer is divided into individual electronic components. Have been. In order to pattern an electrode, a method using a photoresist is widely used.

Japanese Patent Application Laid-Open No. Hei 9-185174 discloses an example of a method for patterning a metal film on a wafer of this type. Here, a photoresist is formed on the entire surface of the wafer, and then exposure and development are performed to pattern the photoresist. Here, the patterned photoresist is configured to have an inverted trapezoidal shape in which the width increases as going upward in the cross section.

Next, an oxygen plasma treatment is performed to remove a resist residue before forming the metal film. Further, after the oxygen plasma treatment, a metal film such as Al is formed by vapor deposition or sputtering. Thereafter, the photoresist and the metal film on the photoresist are removed by a lift-off method using a solvent such as acetone to form an electrode.

In general, when a metal film is patterned by the lift-off method, when the metal film adheres to the side surface of the photoresist, when the photoresist is removed by the lift-off method, the metal film portion adhering to the side surface of the photoresist becomes smooth. Instead, the side surface of the electrode film is jagged. Therefore, the electrical characteristics of the electronic components such as the surface acoustic wave device vary greatly, and the yield decreases.

In the prior art described in Japanese Patent Application Laid-Open No. 9-185174, in order to solve such a problem, the photoresist is patterned so that a photoresist having an inverted trapezoidal cross section is formed. Also, Japanese Patent Application Laid-Open
Further, JP-A-120443 discloses a method in which a photoresist having a trapezoidal cross section is formed and then, at the time of film formation, vapor deposition particles are incident on a wafer surface at an incident angle of approximately 90 degrees.

[0007]

However, in general, in the vapor deposition method, the kinetic energy of incident particles is smaller by one digit or more than in the sputtering method, so that the adhesion between the substrate and the finally formed metal film is not sufficient. Was not.

In addition, as described in Japanese Patent Application Laid-Open No. 9-185174, even if the wafer is cleaned by oxygen plasma prior to film formation, the wafer is temporarily exposed to the atmosphere when the wafer is moved to the film formation chamber. It is. Therefore, when exposed to the air, not only the substrate is contaminated by the contaminants generated from the resist, but also the moisture and other contaminants in the air adhere to the wafer, and the metal film and the wafer that are formed are not contaminated. Had deteriorated adhesion.

The water can be removed by heating the wafer during film formation. However, when the film is formed by the lift-off method, if the temperature of the wafer is higher than the temperature in the resist forming step, gas is released from the wafer, and the wafer is contaminated. Therefore,
Again, the adhesion between the metal film and the wafer decreases. Further, the patterned photoresist itself may be deformed by heat.

In addition, a material in which the wafer has flammability,
For example, when the wafer is made of LiTaO ₃ or LiNbO ₃ , the wafer is charged due to a temperature change when the wafer is heated or cooled. Therefore, for example, when the wafer is supported by a metal holder,
There is a problem that the wafer and the metal holder adhere to each other and the wafer is frequently cracked. Therefore, when the film is formed by the lift-off method, it is not effective to heat the wafer to a high temperature in the step of forming the metal film.

An object of the present invention is to provide a metal film forming process using a lift-off method in which contamination of a wafer can be suppressed and adhesion of the metal film to the wafer can be increased in view of the above-mentioned state of the art. An object of the present invention is to provide a method for manufacturing an electronic component.

[0012]

According to a first aspect of the present invention, there is provided a process for forming a patterned photoresist on a wafer, a process for performing an oxygen plasma treatment for removing a resist residue, and a process for forming the photoresist on the wafer. Forming a metal film on a resist; and forming a metal film in a method of manufacturing an electronic component, comprising: forming a electrode by removing the photoresist and the metal film on the photoresist by a lift-off method. However, after performing ion cleaning on the wafer in a vacuum state, continuously and without exposing it to the atmosphere, the metal is deposited by vacuum evaporation while holding the wafer at a temperature lower than the heating temperature in the patterned photoresist forming step. It is characterized by being performed by forming a film.

According to a second aspect of the present invention, there is provided a step of forming a patterned photoresist on a wafer, a step of forming a metal film on the wafer and the photoresist, and a step of forming a photoresist and a metal film on the photoresist by a lift-off method. Forming an electrode by removing the metal film, wherein the step of forming the metal film includes the step of subjecting the wafer to oxygen plasma treatment in a vacuum state and then continuously and exposing the wafer to the atmosphere. Instead, a metal film is formed by a vacuum deposition method while holding the wafer at a temperature lower than the heating temperature at the time of forming the patterned photoresist.

That is, in forming the metal film patterned by the lift-off method, the first and second inventions wash the wafer in a vacuum state, and then continuously and without exposing the metal to the atmosphere by a vacuum evaporation method. It is common that a film is formed. Therefore, the metal film is formed by the vacuum deposition method without contaminants in the air being attached to the wafer cleaned by the ion cleaning in the first invention and the wafer cleaned by the oxygen plasma treatment in the second invention. The adhesion between the film and the wafer is improved.

In the first invention, the resist residue is removed by the first oxygen plasma treatment, and then, before the formation of the metal film, ion cleaning is performed to clean the wafer. At the time of ion cleaning, a plasma formed by at least one gas selected from the group consisting of argon, oxygen and nitrogen is used, although not particularly limited.

In this case, argon, oxygen and nitrogen may be appropriately selected according to the purpose. That is, when argon is used, the photoresist is less deformed. Therefore, it is preferable to use argon when using a photoresist material that is easily deformed. When oxygen is used, oxygen acts to remove contaminants by a chemical reaction, so that damage to a wafer can be reduced. Further, nitrogen has an intermediate property between argon and oxygen, and has a lower physical impact force of ions than argon, so that it is less likely to damage the wafer.

In the second invention, the removal of the resist residue and the cleaning of the wafer are simultaneously performed by the oxygen plasma treatment. In the first invention, the above-described ion cleaning is performed in the preliminary film formation chamber using an apparatus provided with a vacuum preliminary film formation chamber continuously to the film formation chamber for forming the metal film. Is also good. Further, in the second invention, an apparatus in which a film formation preparatory chamber in a vacuum state is provided continuously to a film formation chamber for forming a metal film is used, and the oxygen plasma treatment is performed in the film formation preparatory chamber. May be applied. In these cases, by moving the wafer from the film formation preparatory chamber to the film formation chamber without exposing the wafer to the atmosphere, it is possible to reliably suppress contamination from atmospheric contaminants after ion cleaning or oxygen plasma processing. Can be.

Of course, ion cleaning or oxygen plasma treatment may be performed in the film forming chamber, and a metal film may be formed continuously in the same film forming chamber. In that case, the wafer is not exposed to the air after the ion cleaning or the oxygen plasma treatment, so that the contamination of the wafer from the contaminants in the air can be suppressed.

In the present invention, a photoresist for forming a patterned photoresist may be either a negative type or a positive type. In a specific aspect of the present invention, the wafer is made of a piezoelectric material, the electrode is at least an interdigital transducer of an interdigital transducer and a reflector of a surface acoustic wave device, and a plurality of electrodes of the surface acoustic wave device are provided on the wafer. The structure is configured.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

(First Embodiment) In this embodiment, FIG.
An electrode 3A shown in (d) is formed.
Constitutes an interdigital transducer (IDT) of the surface acoustic wave device. In this embodiment, a plurality of surface acoustic wave device IDTs are formed on the wafer 1. Therefore, a plurality of surface acoustic wave devices can be formed by finally dividing the wafer 1.

As shown in FIG. 3A, a negative photoresist layer 2 made of TLOR-N series (manufactured by Tokyo Ohka) was formed on the entire surface of a wafer 1 made of lithium tantalate. Next, a mask was placed on the photoresist layer 2 and exposed to light. After a heat treatment at 110 ° C. for 90 seconds, the photoresist layer 2 was developed. Thus, FIG.
As shown in (b), a patterned photoresist 2A was formed.

Thereafter, an oxygen plasma treatment was performed under the conditions of a gas flow rate of 100 SCCM, a gas pressure of 10 Pa, and a power of 30 W to remove resist residues. Next, the wafer 1 subjected to the oxygen plasma was set in the film forming chamber 4 shown in FIG. In the film forming chamber 4, the wafers 1 and 1 were set on a substrate holder 5 made of stainless steel.

An evaporation source 6 made of an Al alloy is arranged so as to face the wafers 1 and 1 set on the substrate holder 5. Further, in the film forming chamber 4, plasma discharge antennas 7, 7 are arranged at positions between the wafers 1, 1 and the vapor deposition source 6. The plasma discharge antennas 7, 7 are provided to form plasma during ion cleaning processing described later.

The film forming chamber 4 has a gas inlet 4a and a gas outlet 4b. The gas outlet 4b is connected to a pump P schematically shown. After the inside of the film forming chamber 4 was evacuated, argon gas was introduced from the gas inlet 4a, and the plasma was discharged from the plasma discharge antennas 7, 7 to form argon plasma. Thus, the wafers 1 and 1 were ion-cleaned. At the time of ion cleaning, the flow rate of argon gas was 100 SCCM, the pressure was 10 Pa,
The power was 100 W and the processing time was 5 minutes.

After the ion cleaning, the pressure is reduced to 1 ×
While maintaining the pressure at 10 ⁻² Pa, an Al alloy was deposited at a temperature of 70 ° C. to form a metal film made of the Al alloy on the wafer 1 and the photoresist. As shown in FIG. 3C, the metal film 3 is formed on the wafer 1 and the patterned photoresist 2A.

Next, the wafer 1 is taken out of the film forming chamber 4 and
Using acetone as a solvent, the photoresist 2A and the metal film 3 adhering thereon were removed to form a patterned electrode 3A as shown in FIG. 3 (d).

In this embodiment, before the wafer 1 is inserted into the film forming chamber 4, the photoresist residue on the wafer 1 is removed by the oxygen plasma treatment. However, the wafer 1 is transported in the atmosphere after the oxygen plasma processing and set in the film forming chamber 4. Therefore, components and contaminants in the air may be attached to the wafer 1 set in the film forming chamber 4. However, contaminants are almost completely removed before vapor deposition by the ion cleaning using the argon plasma.

Therefore, the adhesion between the finally formed electrode film 3A and the wafer 1 can be effectively improved.
In addition, when the metal film 3 is formed, the deposition is performed at a temperature of 70 ° C., that is, the deposition is performed at a temperature lower than the heating temperature 110 ° C. when the photoresist 2A is formed. Deformation of the photoresist 2A during the formation of the film 3 is unlikely to occur, and defects due to gas discharged from the photoresist 2A and the chargeability of the wafer 1 are unlikely to occur.

(Second Embodiment) In the second embodiment, the first
The patterning of the metal film is performed by the lift-off method in the same manner as in the embodiment. Therefore, each step will be described with reference to FIG. 3 as in the first embodiment.

As shown in FIG. 2, in the second embodiment, a preliminary chamber 11 is provided in a stage preceding the film forming chamber 4. Spare room 1
1 is provided for performing ion cleaning. The inside of the preliminary chamber 11 can be set in a high vacuum state similarly to the film forming chamber 4.

The spare chamber 11 has a gas inlet 11a and a gas outlet 11b, and the gas outlet 1b is connected to the pump P. A substrate holder 12 is disposed in the preliminary chamber 11, and plasma discharge antennas 13 and 13 are disposed in front of the substrate holder 12.

An airtight valve 14 for switching between a state in which the preliminary chamber 11 and the film forming chamber 4 are communicated with each other and a state in which the preliminary chamber 11 and the film forming chamber 4 are shut off is disposed between the preliminary chamber 11 and the film forming chamber 4. Further, as a transfer mechanism for moving the wafer 1 supported by the substrate holder 12 disposed in the preliminary chamber 11 together with the substrate holder 12 into the film formation chamber 4 as shown by an arrow A in FIG. 15 are provided.

An evaporation source 6 is disposed in the film forming chamber 4 so as to face the substrate holder 12 transported. Second
In the second embodiment, first, a photoresist layer 2 is formed on the entire surface of the wafer 1 as in the first embodiment.
(A)). In the second embodiment, the wafer 1 is made of lithium tantalate, and the photoresist layer 2 is TLOR-N series (manufactured by Tokyo Ohka).
Is used.

Next, as in the first embodiment, the wafer 1
Above, after exposing a mask on the photoresist layer 2, heat treatment is performed at 110 ° C. and 90 seconds, and then the resist is developed. Thus, FIG.
As shown in (b), a patterned photoresist 2A is formed.

Next, the wafer 1 having the patterned photoresist 2 A is set on the front surface of the substrate holder 12 in the preliminary chamber 11. Then, after the preliminary chamber 11 and the film forming chamber are brought into a high vacuum state, the valve 14 is closed and oxygen plasma processing is performed. This oxygen plasma treatment is performed by introducing oxygen into the preparatory chamber 11 and performing a discharge treatment from the plasma discharge antennas 13 to generate oxygen plasma. Conditions for generating oxygen plasma are as follows: oxygen gas flow rate = 100 SCCM, pressure = 20
Pa, power 50 W, processing time 5 minutes.

By the oxygen plasma treatment, the wafer 1
Above, resist residues, moisture and atmospheric contaminants can be almost completely removed. The resist residue, water and contaminants are discharged together with oxygen from the gas outlet 11b.

After performing the oxygen plasma treatment in the film forming chamber 11, the valve 14 is opened, and the wafer 1 supported by the substrate holder 12 is moved into the film forming chamber 4 by the robot arm 15. As described above, the inside of the film forming chamber 4 is previously set to a high vacuum state.

Therefore, the wafers 1 and 1 are set in the film forming chamber 4 without being exposed to the atmosphere. Next, the valve 14 is closed, and an Al alloy is vapor-deposited in the film forming chamber 4 in the same manner as in the first embodiment to form the metal film 3 (FIG. 3C).

Thereafter, the wafer 1 is taken out from the film forming chamber 4, and the photoresist 2A and the metal film adhering thereon are removed by the lift-off method as in the first embodiment, so that the metal film 3 is removed. Patterning is performed and FIG.
The electrode 3A shown in (d) is formed.

Also in the second embodiment, the removal of the photoresist residue and the removal of moisture and contaminants in the air before the vapor deposition are almost completely achieved by the oxygen plasma treatment. Therefore, the adhesion of the electrode 3A to the wafer 1 is improved.

Further, also in this embodiment, the vapor deposition is performed in the first
In the same manner as in the embodiment, the heating is performed at a low temperature of 70 ° C., and the heating is performed at a lower temperature than the heating step until the patterned photoresist 2A is formed. Therefore, the deformation of the photoresist 2A hardly occurs. Can be suppressed. Further, even when the wafer has pyroelectricity, defects due to charging of the wafer hardly occur.

In the second embodiment, a preparatory chamber 11 is connected to a stage preceding the film forming chamber 4, and oxygen plasma processing is performed in the preparatory chamber. Therefore, contamination in the film forming chamber 4 due to a resist residue generated during the oxygen plasma processing can be prevented.

Further, compared with the first embodiment, ion cleaning is not required, and only one oxygen plasma treatment is required, so that the cost can be reduced. in addition,
By setting the film forming chamber 4 in a high vacuum state in advance, the inside of the film forming chamber 4 is not exposed to the atmosphere until the wafer 1 is set in the film forming chamber 4, so that the film forming chamber 4 after the oxygen plasma processing is performed. No time is required to evacuate 4. Therefore, the number of steps can be further reduced.

In the first and second embodiments, the method of manufacturing the surface acoustic wave device has been described. However, the present invention generally applies various methods of manufacturing electronic parts having electrodes patterned by a lift-off method. can do. Further, in the above embodiment, a negative photoresist is used, but a positive photoresist may be used.

Further, the material constituting the wafer is not particularly limited, and an appropriate material such as lithium niobate or quartz can be used, and a wafer material having no pyroelectricity can also be used. .

Further, the metal material forming the electrode is not limited to the Al alloy, but Al or another metal or alloy can be used as appropriate.

[0048]

According to the manufacturing method of the first invention, prior to the formation of the metal film, the resist residue is removed by the oxygen plasma treatment. Then, after the resist residue is removed, the wafer having the patterned photoresist is subjected to ion cleaning in a vacuum state, so that moisture and contaminants in the air are almost completely removed. Therefore, after the ion cleaning, a metal film having excellent adhesion to a wafer can be obtained by forming a metal film by a vacuum deposition method continuously and without exposing it to the atmosphere. Therefore, by patterning the metal film by the lift-off method to form electrodes and dividing the wafer,
It is possible to provide an electronic component having excellent electrode adhesion to a substrate formed by dividing a wafer.

Further, since the formation of the metal film is performed at a temperature lower than the heating temperature in the photoresist pattern forming step, the deformation of the photoresist hardly occurs when the metal film is formed. Can be formed with high precision.

In the second aspect of the present invention as well, in forming the metal film, oxygen plasma treatment is performed in a vacuum state, so that the photoresist residue and the moisture and contaminants in the air are almost completely removed. Then, after the oxygen plasma treatment, since the metal film is formed by the vacuum evaporation method continuously and without being exposed to the atmosphere, the adhesion of the metal film to the wafer is effectively improved. In addition, since the deposition is performed at a temperature lower than the heating temperature in the photoresist pattern forming step, the patterned photoresist is less likely to be deformed, so that the precision of forming the metal film can be improved. Therefore, when an electrode is formed by patterning the metal film by a lift-off method after forming the metal film, an electrode having excellent adhesion to a wafer and high precision can be formed.

Therefore, similarly to the first aspect, it is possible to obtain an electronic component having electrodes with excellent adhesion to the substrate formed by dividing the wafer and having high precision.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a film forming chamber used in a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram for explaining a film forming chamber and a preliminary chamber used in a second embodiment.

FIGS. 3A to 3D are partially cutaway sectional views for explaining a step of forming a patterned electrode on a wafer in the first and second embodiments.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Wafer 2 ... Photoresist layer 2A ... Patterned photoresist 3 ... Metal film 3A ... Electrode 4 ... Film formation chamber 4a ... Gas introduction port 4b ... Gas exhaust port 5 ... Substrate holder 6 ... Evaporation source 7 ... Plasma discharge Antenna 11 ... Preparatory chamber 11a ... Gas inlet 11b ... Gas outlet 12 ... Substrate holder 13 ... Plasma discharge antenna 14 ... Valve 15 ... Robot arm P ... Pump

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H03H 3/08 H01L 41/22 Z F term (Reference) 5F004 AA09 BD01 BD07 DA23 DA25 DA26 5F043 AA37 CC16 DD22 5F046 MA12 5F103 AA01 BB41 DD28 HH10 NN01 PP01 PP18 5J097 AA31 AA32 HA07

Claims (8)

[Claims] A step of forming a patterned photoresist on a wafer; a step of performing an oxygen plasma treatment to remove a resist residue; a step of forming a metal film on the wafer and the photoresist; Forming an electrode by removing a photoresist and a metal film on the photoresist by a method, wherein the step of forming the metal film includes performing ion cleaning on the wafer in a vacuum state. Then, continuously and without exposing to the atmosphere, the metal film is formed by vacuum evaporation while holding the wafer at a temperature lower than the heating temperature in the patterned photoresist forming step. Manufacturing method of electronic parts. A step of forming a patterned photoresist on the wafer; a step of forming a metal film on the wafer and the photoresist; and removing the photoresist and the metal film on the photoresist by a lift-off method. Forming a metal film, the step of forming the metal film, after subjecting the wafer to an oxygen plasma treatment in a vacuum state, continuously and without being exposed to the atmosphere, is patterned A method for manufacturing an electronic component, comprising: forming a metal film by a vacuum deposition method while holding a wafer at a temperature lower than a heating temperature at the time of forming a photoresist. 3. The method according to claim 1, wherein the ion cleaning is performed using argon,
The method for producing an electronic component according to claim 1, wherein the method is performed using at least one gas selected from the group consisting of oxygen and nitrogen. 4. In the step of forming a metal film, a wafer on which a patterned photoresist is formed is subjected to ion cleaning in a vacuum deposition preparatory chamber, and thereafter the wafer is formed without exposing the wafer to the atmosphere. The method for manufacturing an electronic component according to claim 1, wherein the method moves to a film chamber and forms a metal film. 5. In the step of forming a metal film, a wafer on which a patterned photoresist is formed is subjected to an oxygen plasma treatment in a vacuum preparation chamber, and thereafter, without exposing the wafer to the atmosphere. The method for manufacturing an electronic component according to claim 2, wherein the method moves to a film forming chamber and forms a metal film. 6. The method of manufacturing an electronic component according to claim 1, wherein the patterned photoresist is formed using a negative photoresist. 7. The photoresist according to claim 1, wherein the patterned photoresist is formed using a positive photoresist.
5. The method for manufacturing an electronic component according to any one of items 5. 8. The wafer is made of a piezoelectric material, the electrode is at least an interdigital transducer of an interdigital transducer and a reflector of a surface acoustic wave device, and the electrode structure of a plurality of surface acoustic wave devices is formed on the wafer. The method for manufacturing an electronic component according to claim 1, wherein