JPH1167702A - Method and device for cleaning semiconductor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve electric contact and physical connection by forming argon ions by plasma, activating hydrogen gas by bringing the argon gas into contact with hydrogen gas, bringing the activated hydrogen gas into contact with a semiconductor electrode on a semiconductor wafer and cleaning the surface of the electrode. SOLUTION: In a plasma generating chamber 21, argon ion Ar<+> is generated by plasma. The Ar<+> ions are accelerated with the potential of several tens of volts of an accelerating electrode 26 and massively flow into hydrogen gas H2 in a hydrogen-radical generating chamber 31. Furthermore, the hydrogen flows into the generating chamber partly becomes hydrogen ion H<+> and flows into the generating chamber 31. Then, in the generating chamber 31, the hydrogen gas is ionized to more activated radical H<+> ions and H3 <+> ions by the Ar<+> ions. Mainly, these H<+> ions and H3 <+> ions collide into a semiconductor water 32, and the surface of a semiconductor electrode (pad) is cleaned, on oxide alminum is chemically reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cleaning the surface of minute semiconductor electrodes provided on a high-density semiconductor IC.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional semiconductor IC manufacturing process. In the figure, 1 is a circuit design, 2 is a pattern layout, 3 is a mask fabrication, 4 is a wafer process, 5 is a wafer test, Reference numeral 6 denotes each step of assembly and mounting, and reference numeral 7 denotes each step of the reliability test. In this manufacturing process, the level of the process technology constituting the wafer process 4 provides a standard for circuit design and is positioned at the core of the manufacturing.
(For example, see "VSLI thin film technology" page 1: Maruzen Co., Ltd.)

FIG. 5 illustrates the wafer process 4 in detail. In the figure, reference numeral 8 denotes formation of a silicon oxide film on a wafer, 9 denotes application of a photosensitive agent (photoresist), 10 denotes
Is an exposure that prints an IC pattern using a photomask,
11 denotes development, 12 denotes etching for dissolving an oxide film, 13 denotes impurity diffusion, 14 denotes removal of a photosensitive agent (resist), and 15 denotes aluminum deposition of wiring and electrodes. 8a is the start of the wafer process, which is continued from the mask manufacturing step 3 in FIG. Reference numeral 15a denotes the end of the wafer process, which shows the connection to the wafer test 5 in FIG. Actually, an IC is manufactured by repeating the steps from generation 8 of the silicon oxide film to removal 14 of the photosensitive agent (resist) several times. (For example, see "Understanding Semiconductors" on page 64: See Nihon Jitsugyo Publishing Company.)

As described above, in the manufacture of semiconductor ICs, since the electrodes are generally formed of aluminum, the electrodes easily react with oxygen in the atmosphere and the surface thereof is changed to aluminum oxide. Its thickness is said to be tens of angstroms. Regarding this electrode, in the wafer test process 5,
Tungsten probe needle of probe card connected to test equipment (for details, see Published Utility Model, Showa 57-146)
No. 340) is contacted with this electrode to conduct an electrical test, and in an assembling step 6, a metal wire is ultrasonically thermocompression-bonded to this electrode and connected to the electrode on the lead frame. In any of these steps,
Aluminum oxide on the surface of the aluminum electrode is not preferable in sufficiently exhibiting the function of contact with the probe needle and connection with the metal wire.

Conventionally, regarding the former contact between the electrode surface made of aluminum oxide and the probe needle, a certain pressure is applied to the probe needle to slide the electrode over the electrode, thereby scraping the aluminum oxide on the surface and removing the pure aluminum underneath. It is joined to aluminum to enable electrical connection with good contact resistance. In addition, regarding the connection between the electrode and the metal wire whose surface is made of aluminum oxide, the aluminum oxide on the surface is removed with ultrasonic energy or a crack is created, and it is joined with pure aluminum under it, and good bonding strength is obtained. Physical connection is possible.

[0006]

By the way, the recent trend of rapid densification of semiconductor ICs has emerged as a demand for miniaturization of the aforementioned semiconductor electrodes. In other words, the miniaturization of the electrodes and the narrowing of the gap between the electrodes.
m to 50 μm × 50 μm. in this way,
When the contact surface of the electrode becomes small, (1) the tip diameter of the probe needle must be reduced, (2) the work of adjusting the position (length, width, height) of the probe needle becomes extremely difficult, (3) the contact Defects are likely to occur, and (4) adverse effects such as abrasion marks of the probe needle weakening the wire bonding force will occur.

As a result, in response to the trend of miniaturization of the electrodes, regarding the electrical connection, the contact resistance increases due to the aluminum oxide on the electrode surface adhering to the bottom surface of the tip of the probe needle which has become thinner. In some cases, conduction failures occur early, and maintenance costs due to processing work increase due to frequent polishing of the tip of the probe needle. Also, regarding physical connection, the proportion of probe marks on the electrode surface that do not contribute to the bonding force occupy the entire area of the electrode increases, leading to a decrease in wire bonding force and a decrease in IC reliability. ing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In a semiconductor electrode which is miniaturized in parallel with the increase in the density of a semiconductor IC, the above-mentioned electrical contact and physical An object of the present invention is to provide a method and an apparatus for cleaning a semiconductor electrode for obtaining an electrode having good connection.

[0009]

According to the method for cleaning a semiconductor electrode of the present invention, argon ions are generated by plasma.
The argon ions are exposed to hydrogen gas to activate the hydrogen gas, and the activated hydrogen gas is brought into contact with a semiconductor electrode on a semiconductor wafer to clean the surface of the semiconductor electrode. is there.

In the method for cleaning a semiconductor electrode according to the present invention, the cleaning of the semiconductor electrode is performed immediately before a wafer test is performed by applying a probe needle to the surface of the semiconductor electrode, or immediately before a metal wire is connected to the surface of the semiconductor electrode. It is characterized in that it is carried out in the following manner.

Further, the method for cleaning a semiconductor electrode according to the present invention comprises the steps of:
The present invention is characterized in that a space for contacting an activated hydrogen gas with a semiconductor electrode is separated.

Further, the semiconductor electrode cleaning apparatus of the present invention comprises a reaction tank in which a semiconductor wafer having a semiconductor electrode on the surface is disposed inside and a hydrogen gas flowing therethrough, and a plasma generating tank for flowing an argon gas to generate plasma. Means for applying argon ions generated in the plasma generation tank to hydrogen gas in the reaction tank.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a flowchart showing a wafer process in a manufacturing process of a semiconductor device according to an embodiment of the present invention. The manufacturing process before entering the wafer process
The description is omitted because it is the same as that shown in FIG. As shown in FIG. 1, the wafer process of this embodiment includes a step 8 of forming a silicon oxide film on a wafer, a step 9 of applying a photosensitive agent (photoresist), and an exposure for printing an IC pattern using a photomask. Step 10, development step 1
1, an etching step 12 for dissolving an oxide film, an impurity diffusion step 13, a photosensitive agent (resist) removing step 14, an aluminum deposition step 15 for wiring and electrodes, and a cleaning step 16. 8a indicates the start of the wafer process, and 16a indicates the end of the wafer process, that is, the connection to the next wafer test. In practice, the steps from the step 8 of forming the silicon oxide film to the step 14 of removing the photosensitive agent (resist) are repeated several times to obtain
C is produced.

In the above-described wafer process, the steps from the step 8 of forming a silicon oxide film on the wafer to the step 15 of depositing wiring and electrodes on aluminum are the same as the steps shown in FIG. The cleaning step 16 is a step added in this embodiment. That is, in this embodiment, the surface of the semiconductor electrode is brought into contact with the probe and the wafer testing process 5 is performed.
Immediately before performing or immediately before bonding a metal wire to the surface of the semiconductor electrode, a step of cleaning the electrode surface is provided. Thereby, a good contact and a good wire bonding force can be obtained.

In general, for cleaning or cleaning in a wafer process, there is a "cleaning" operation of washing away residual resist and dust with ultrapure water (not shown in FIG. 2). Aluminum oxide adhering to the surface cannot be removed by this cleaning.

In this embodiment, a method of cleaning aluminum by removing aluminum oxide from the electrode surface by reducing aluminum oxide on the electrode surface with a reducing agent having a reducing action (hereinafter referred to as reduction cleaning). )I take the. As the reducing agent, hydrogen is selected from hydrogen, argon, nitrogen, carbon, carbon monoxide, aluminum, iron and the like. Then, in order to generate hydrogen ions for the reduction cleaning, argon ions generated by argon plasma are used.

FIG. 2 is a diagram showing an example of a schematic configuration of a cleaning apparatus for performing the cleaning step of this embodiment. FIG.
, 20 is a plasma generation tank, 21 is a plasma generation chamber, 22 is a plasma generation electrode, 23 is an argon gas inlet, 24 is an argon gas outlet, and 25 is an accelerating electrode for accelerating the generated argon ions. , 26 are supply ports for argon ions. Reference numeral 30 denotes a reaction tank (hydrogen radical generation chamber), 31 denotes a reaction chamber (hydrogen radical generation chamber), 32 denotes a semiconductor wafer as a material to be cleaned, 33
Is a wafer holder on which the wafer 32 is placed, 34 is a hydrogen gas inlet, and 35 is a hydrogen gas outlet.

FIG. 3 is a diagram showing another schematic configuration example of a cleaning apparatus for performing the cleaning step of this embodiment.
In the figure, the same reference numerals as those in FIG. 2 indicate the same or corresponding parts, and thus detailed description will be omitted. In this example, a plasma generation tank 20 and a reaction tank (hydrogen radical generation tank) 30 are arranged vertically.

Next, the operation of this apparatus will be described with reference to FIG. In this embodiment, first, in the plasma generation chamber 21, argon ions are generated by plasma. The preferred plasma apparatus used in this embodiment is of the DC type, not the high frequency type, and the level of generated energy is very small. In the plasma generator in the plasma generating chamber 21 is primarily argon gas becomes plasma (workinggas) of Ar ⁺ ions, the Ar ⁺
The ions are accelerated at a potential of several tens of volts at the acceleration electrode 26 and flow into the hydrogen gas H ₂ in the hydrogen radical generation chamber 31. Further, the hydrogen that has partially entered the plasma generation chamber 21 becomes hydrogen ions H ⁺ ions, and the hydrogen radical generation chamber 31
Flows to

Next, a reaction chamber (hydrogen radical generation chamber) 21
, A semiconductor electrode (pad) of the semiconductor wafer 32
The cleaning of the surface is mainly by chemical reduction with hydrogen H. By Ar ⁺ ions are ionized more activated radical H ⁺ ions and H ₃ ⁺ ions are hydrogen gas, mainly the H ⁺ ions and H ₃ ⁺ ions (reactive
gas) collides with the object to be cleaned to clean the surface or chemically reduce aluminum oxide.

2, the argon ions generated in the plasma generation chamber 21 and emitted from the argon ion supply port 26 to the reaction chamber (hydrogen radical generation chamber) 21 do not directly irradiate the wafer 32. It is configured as follows. In addition, the hydrogen radical generation chamber 31 includes:
Conventionally, an rf electric field or the like, which is normally applied, is not applied, and the reduction cleaning is caused substantially without an electric field.

Next, a reaction chamber (hydrogen radical generation chamber) 31
The reaction formula for removing the aluminum oxide generated in the above is shown below. Al ₂ O ₃ + 9H ⁺ → 2Al + 3H ₃ O ⁺ The product on the right side is removed by evacuation. next,
The following reaction occurs on the aluminum electrode surface from which aluminum oxide has been removed. ^{Al + 3O - + 3H + →} Al (OH) 3 Al + 3OH - → Al (OH) 3 As a result, for some time, the oxidation of the aluminum surface does not proceed. During this time, a probing operation or a wire bonding operation is performed, and a wafer test and electrode attachment can be performed on a clean surface without aluminum oxide. afterwards,
The exposed aluminum electrode surface eventually becomes aluminum oxide Al ₂ O ₃
become.

The surface of the IC electrode treated under such conditions has a feature that aluminum oxide is removed and a good electrical contact or physical connection is obtained, and a highly reliable electrode having a miniaturized electrode is provided. Mass production of high density ICs.

Although the method for cleaning the electrodes before the wafer test has been described above, the cleaning before the wire bonding is performed similarly and has the same effect.

Although omitted in the above description, of the electrodes and wirings (patterns) formed of an aluminum film, the wirings are coated with polyimide or the like, so that aluminum oxide only in the electrode portions is reduced and cleaned. Will be done.

Further, although reduction cleaning of an electrode made of aluminum has been described here, foreign substances on the surface of an electrode made of another metal can be removed by a reducing action, and the same effect can be obtained. It is clear that this will happen.

In some cases, the surface of a semiconductor substrate or the like is conventionally cleaned by irradiation with argon ions or the like. However, the method of applying argon ions or the like to a semiconductor electrode (pad) is as follows. Things happen. That is, since the atomic weight of argon is 40 times as large as that of hydrogen, argon damages the surface of the pad to be cleaned,
The surface may be uneven. This is because cleaning with argon or the like is a physical etching action.
When the pad surface is roughened in this way, the aluminum of the pad base material protrudes from the very thin aluminum oxide (several tens of angstroms), and even the protruding portion becomes aluminum oxide, and the aluminum oxide layer on the pad surface becomes uneven. It will be thicker. In this embodiment, as described above, reduction cleaning is performed mainly by radical hydrogen ions, so that the pad surface is not damaged.

As described above, in this embodiment, the electrode surface is cleaned immediately before the wafer test is performed by contacting the surface of the semiconductor electrode with a probe, and immediately before bonding a metal wire to the surface of the semiconductor electrode. Into the process. Thereby, good contact connection can be obtained. Also, a good wire bonding force can be obtained. If this cleaning step is performed immediately before a wafer test or the like, a more reliable effect can be obtained. In addition, it is possible to produce highly reliable ICs by removing aluminum oxide and the like adhering to the surface of the semiconductor electrode before the wafer test or wire bonding and performing a semiconductor IC manufacturing process having a process of cleaning the electrode surface. it can.

[0029]

As described above, according to the present invention, radical hydrogen ions are generated by irradiating hydrogen gas with argon ions, thereby removing aluminum oxide and the like on the surface of the semiconductor electrode to clean the surface. Since it is performed, a wafer test and wire bonding can be performed with good performance, and good contact connection and good wire bonding force can be obtained. As a result, a highly reliable semiconductor device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a wafer process in a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an apparatus for performing a cleaning step in a wafer process according to an embodiment of the present invention.

FIG. 3 is a diagram showing another example of the configuration of an apparatus for performing a cleaning step in a wafer process according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a conventional semiconductor IC manufacturing process.

FIG. 5 is a flowchart showing a wafer process in a conventional IC manufacturing process.

[Explanation of symbols]

1 circuit design process, 2 pattern layout process, 3
Mask manufacturing process, 4 wafer process process, 5 wafer test process, 6 assembly / mounting process, 7 reliability test process, 8 silicon oxide film generation process, 9 photosensitizer application process, 10 exposure process, 11 development process, 12 etching Process, 13 impurity diffusion process, 14 photosensitizer removal process, 15 wiring and electrode aluminum deposition process, 16 cleaning process, 20 plasma generation tank, 21 plasma generation chamber, 2
2 plasma generation electrode, 23 argon gas inlet,
24 Argon gas discharge port, 25 Acceleration electrode, 26 Argon ion supply port, 30 Reaction tank (hydrogen radical generation tank), 31 Reaction chamber (hydrogen radical generation chamber), 32 Semiconductor wafer, 33 Wafer holder, 34 Hydrogen gas inlet , 35 Hydrogen gas outlet.

Claims (4)

[Claims] An argon ion is generated by plasma, and the argon ion is applied to a hydrogen gas to activate the hydrogen gas. The activated hydrogen gas is brought into contact with a semiconductor electrode on a semiconductor wafer to clean the surface of the semiconductor electrode. A method of cleaning a semiconductor electrode, wherein the method is to clean. 2. The method according to claim 1, wherein the cleaning of the semiconductor electrode is performed immediately before a wafer test is performed by applying a probe needle to the surface of the semiconductor electrode, or immediately before a metal wire is connected to the surface of the semiconductor electrode. The method for cleaning a semiconductor electrode according to claim 1. 3. The method for cleaning a semiconductor electrode according to claim 1, wherein a space for generating argon ions by plasma and a space for contacting the activated hydrogen gas with the semiconductor electrode are separated. 4. A reaction tank in which a semiconductor wafer having a semiconductor electrode on its surface is disposed and in which hydrogen gas flows, a plasma generation tank in which argon gas flows to generate plasma, and argon ions generated in the plasma generation tank. And a means for applying hydrogen gas to the hydrogen gas in the reaction tank.