WO2008099316A1

WO2008099316A1 - Defect treatment apparatus

Info

Publication number: WO2008099316A1
Application number: PCT/IB2008/050462
Authority: WO
Inventors: Georg Greuel
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N.V.
Priority date: 2007-02-13
Filing date: 2008-02-08
Publication date: 2008-08-21

Abstract

The invention relates to a method and an apparatus (100) for the treatment of defects (4) in e.g. a thin film layer (2) of an electronic component (1). The apparatus (100) comprises a conductive carrier (10) and a probe electrode (20) between which the component (1) to be treated and an insulation (30) are placed. In a preferred embodiment, the insulation (30) is a coating of the probe electrode (20). A voltage supply (40) coupled to the conductive carrier (10) and the probe electrode (20) can induce discharges at the defects (4). Moreover, the probe electrode (20) can preferably make a scanning movement along the surface of the electronic component (1).

Description

Defect treatment apparatus

FIELD OF THE INVENTION

The invention relates to an apparatus and a method for the treatment of defects in an electronic component, for example in a thin film layer of an OLED (organic light emitting diode) device.

BACKGROUND OF THE INVENTION

Many electronic components, particularly semiconductor devices and thin film devices, suffer from defects in their material that are formed during their production (e.g. due to dust or contaminants) and that may later result in a device failure. The US 5 418 680 discloses in this respect an apparatus and a method for repairing a defective semiconductor device that is electrically short-circuited at a pinhole. The method comprises the application of a high AC voltage between the substrate of the defective semiconductor device and an electrode located at a distance from the device. Electrical discharges that occur between the semiconductor device and the electrode can then remove the defects.

SUMMARY OF THE INVENTION

Based on this situation it was an object of the present invention to provide alternative means for the treatment of defects in an electronic component, wherein it is desirable that the effect of the treatment can be well controlled and localized at the defects. This object is achieved by an apparatus according to claim 1 and a method according to claim 8. Preferred embodiments are disclosed in the dependent claims. The apparatus according to the present invention serves for the treatment of defects in a layer of an electronic component, wherein the term "treatment" is to be understood in a broad sense, comprising for example the removal, the healing, the isolation and/or the mere detection of the defect. The treated "electronic component" may be any device or product that comprises (or even completely consists of) a layer which may have local defects. The adjective "electronic" shall indicate in this context that the component is usually (but not necessarily) a part of an electronic device or circuit. The potentially defective layer is in many cases a thin film layer, i.e. a layer with a thickness that is much smaller than the typical lateral dimensions of the electronic component, for example smaller than 100 μm.

One example is the OLED layer in an OLED light source or display. The apparatus comprises the following components: a) An electrically "conductive carrier", for example realized by a metallic table on which the electronic component can be placed in the operating state of the apparatus. b) A "probe electrode" which is arranged with respect to the conductive carrier in such a way that there is a working space between it and the conductive carrier in which the electronic component can be placed during the operating state of the apparatus. The probe electrode typically comprises or completely consists of a metal. c) At least one electrical insulation that shields the probe electrode and/or the conductive carrier from each other and, in the operating state, from the electronic component. In other words, the insulation is disposed in such a way that it is intersected by (at least a part of) the electrical field which is generated if a voltage is applied between the conductive carrier and the probe electrode. The insulation typically comprises a usual insulator material like ceramic or glass. d) A voltage supply that is connected with its two output terminals to the conductive carrier and the probe electrode, respectively. Thus a voltage can be applied between the conductive carrier and the probe electrode in the operating state of the apparatus. The described apparatus has the advantage that an electrical field can selectively be generated in an electronic component to be treated, wherein the reaction of the electronic component to this field at the location of a defect will be different from the reaction elsewhere. These differences can be used to detect the defects and/or to actively change them, for example via an electrical discharge or other physical processes. Due to the insulation that is present between conductive carrier and probe electrode, the electrical fields and possible discharges caused by these fields can be controlled and limited. Thus the insulation usually prevents a flow of a direct electrical current (i.e. charge carriers) between conductive carrier and probe electrode. Instead, the current flow is limited to displacement currents.

The voltage that is needed for a desired treatment depends on parameters of the electronic component and of the apparatus, e.g. their geometry and material composition. In a preferred embodiment, the voltage supply is a AC high voltage supply that is capable to provide voltages between for example 1 kV and 10 kV with a frequency ranging for example between 1 kHz and 1 MHz. The voltage supply is preferably tunable with respect to voltage amplitude and/or frequency such that it can be adjusted to different types of electronic components to be treated or even to individual components. The insulation may particularly comprise an insulating layer around the probe electrode, e.g. realized as a coating immediately on the probe electrode or as an insulating tube surrounding the probe electrode. Covering for example a metal core of a probe electrode with an insulating material is a simple and save way to guarantee that the insulation is always located between probe electrode and electronic component/conductive carrier. Moreover, the insulating layer can prevent a direct contact between the electrically conductive core of the probe electrode and an electronic component even if the probe electrode touches the electronic component with its outer surface. The insulation around the probe electrode is thus also a simple means for providing a definite distance between probe electrode and electronic component. The probe electrode preferably has some "front region" with a point-like, line-like or area- like shape, wherein said front region is the region of the whole electrode that can be located closest to an electronic component in the operating state of the apparatus. The electrical field lines that are caused by a voltage between the conductive carrier and the probe electrode will concentrate with a high density at the front region. The treatment processes will therefore be concentrated at the front region, too. The optimal shape of the front region (e.g. point, line, or area) typically depends on the geometry of the electronic component to be treated. Usually, every point of the front region should have the same distance from the surface of the electronic device. A point- like front region is therefore suited for the treatment of electronic components with general three-dimensional surface shapes, while a line- or area-like front region is optimally suited for the treatment of electronic components with a surface that is flat in one or two directions. The front region will usually be chosen with an extension as large as possible to allow the parallel treatment of maximal areas.

In a further development of the invention, the apparatus comprises a scanning mechanism for moving the probe electrode relative to an electronic component that is processed during the operating state. The scanning mechanism may for example move the probe electrode along the electronic component which is stationary with respect to the conductive carrier. Alternatively, the probe electrode and the conductive carrier may both be stationary, while the electronic component is moved with respect to them. Of course mixtures of these approaches as well as other designs are possible, too, to achieve the desired relative movement between probe electrode and electronic component. With the help of the scanning mechanism, the probe electrode can sequentially investigate different regions of the electronic component.

According to another embodiment of the invention, the conductive carrier comprises channels or holes through which a vacuum can be applied to an electronic component lying on the conductive carrier. The vacuum, which may for example be generated by some vacuum pump, pulls the electronic component towards the conductive carrier, thus guaranteeing a tight and definite contact between them.

In another variant of the invention, the apparatus comprises an climate- controller for providing a predetermined atmosphere and/or predetermined temperatures at the electronic component, the probe electrode and/or the conductive carrier during the operating state of the apparatus. A predetermined atmosphere may for example be an oxygen-rich, oxygen-free, or inert atmosphere depending on the desired physical and chemical effects that shall take place at defects in the electronic component. The climate- controller may comprise a casing that shields the apparatus from the surrounding atmosphere, or it may comprise some fan that forcibly introduces a flow of the atmosphere into regions where it is needed. For a temperature control, the climate- controller may comprise a heating device and/or a cooling device operated in a feedforward or feedback control loop. Adjusting a predetermined temperature of the carrier, the electronic component to be treated, or the probe electrode may help to treat localized defects on the electronic component in the desired way. The invention further relates to a method for the treatment of defects in a layer of an electronic component. The method comprises the application of an electrical field sequentially via the layer with the defects and via an insulation, wherein said electrical field induces electrical discharges in the layer only at the locations of a defect. The term "discharge" shall mean in this context in a broad sense any movement of electrical charge carriers (electrons, holes, ions etc.) through the layer having the defect. The method comprises in general form the steps that can be executed with an apparatus of the kind described above. Therefore, reference is made to the preceding description for more information on the details, advantages and improvements of that method. The electrical field that is applied in the method is preferably an alternating (AC) field with a frequency in the range of about 1 kHz to 1 MHz. The strength of the electrical field typically ranges between about 1 kV/cm to 10 kV/cm.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. These embodiments will be described by way of example with the help of the accompanying drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic side view of an apparatus according to the present invention during its operating state; Figure 2 shows a top view of the apparatus of Figure 1.

Like reference numbers in the Figures refer to identical or similar components.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention will in the following be described with respect to the treatment of thin film devices, though it is not limited to this application but useful for the treatment of defects in many other components. "Thin film" means that the active layer(s) are applied on - usually flat - substrates by techniques from the classes sputtering, evaporation, vapor deposition, spin coating, dipping, spraying, and others. "Thin films" are classified by the fact that the active layer thickness is by orders of magnitude smaller than one or two of the other geometrical variables of the device, e.g. a thin dielectric barrier coating of a wire, or a thin insulating coating on a two-dimensional substrate. A common problem of all thin film devices is the presence of defects which may result into device failure. Typical defects are particles, e.g. dust from the production environment, residues from all kinds of process steps, and contaminants of the raw materials or production equipment. It is impossible to reduce the probability of defects to zero. Possible approaches to heal or inactivate defects comprise:

- "burn-in" of the functional/finished device (i.e. the application of a stress level that exceeds the stress under rated (specified) conditions);

- defect isolation by local evaporation of one or two of the electrodes in film capacitors; - healing of defects by reformation of insulating oxide defects (wet aluminum electrolytic capacitors); - combination of healing and electrode transformation (from conductive to insulating) can be performed in dry Aluminum or Tantalum electrolytic capacitors;

- functional testing during the production process or during end control.

All of these processes only work with thin-film devices which have reliable and efficient self-healing capabilities. This is not true -just as an example - for OLED devices: The electrodes cannot be transformed into insulating material, and healing of the defect is also impossible. Even if a reliable healing mechanism by e.g. evaporation of the top electrode would exist, the OLED device would suffer from visible defects like black spots.

Moreover, preventive actions can be taken, for example: Minimization of atmospheric dust (clean room conditions), regular service of equipment, ultra-pure raw materials etc. Nevertheless, a certain level of defects will always be present. Of particular relevance are defects in insulating or semi-conducting thin films. Such defects may result into increased leakage current or even short-circuit failure, because they give rise to a localized current flow in the region of the defect.

Figure 1 shows a setup of an apparatus that is proposed here to address the above problems. The apparatus 100 is shown in its operating state during the treatment of an electronic component 1. The electronic component 1 may for example be a flat device with a substrate 3, e.g. a glass plate, on which a thin film layer 2, e.g. an OLED layer, is disposed. The film layer 2 comprises some defects 4 that shall be detected and ideally be removed with the apparatus 100. To this end, the apparatus 100 comprises the following components:

- A conductive carrier, realized by a metallic support table 11. The support table 11 is shown partially broken to reveal channels 12 which serve as nozzles for the application of an underpressure to the bottom side of the substrate 3, thus pulling it tight onto the table 11. - A probe electrode, realized in this case by a metallic cylinder 20 that is located above the electronic component 1. - An electrical insulation 30 that shields the probe electrode 20. The insulation 30 may for example be a ceramic dielectric coating on the cylindrical probe electrode 20 with a typical thickness between 1 μm and 1 mm.

- A high AC voltage supply 40 that is connected with its terminals to the probe electrode 20 and the conductive carrier 10.

Furthermore, the apparatus 100 may comprise additional components like a scanning mechanism for moving the probe electrode 20 in x-direction (cf. arrow) along the surface of the electronic component 1 or a vacuum pump for generating an underpressure in the channels 12. A top view of the apparatus 100 is shown in Figure 2. In its operating state, the following procedure can be executed with the apparatus 100:

- An electronic component 1 is placed on the metallic support 11 (fixed e.g. by the vacuum nozzles 12 in the support).

- The metallic probe electrode 20, coated or covered with an insulating material 30, is outlined in parallel to the substrate.

- A high AC voltage in the voltage range of 1 to 10 kV and frequency range 1 kHz to 1 MHz (depending on geometry and atmosphere) is connected to the metallic support 11 and the insulated probe electrode 20.

By the applied AC voltage, an electric field E is established in the gap between probe electrode 20 and substrate 3. Under normal conditions, this field will not result into electrical discharge inside the gap or any of the functional layers on the substrate 3.

However, at all weak spots 4 located in the thin layer 2 on the substrate 3, which represent potential sources of device failure, the local field is enhanced (geometric effect or effect related to change in permittivity). Conductive defects will - in addition - have a lower working function for electron emission. Thus, any potential failure on the substrate will generate a localized discharge. This results into a defined energy release at the defect location, sufficient to eliminate the defect by thermal means, without destroying the surrounding of the defect by excess energy. Other beneficial effects are also active: The discharge generates a local plasma (small spark). This plasma generates UV photons which can transform the defect (and eventually the nearby surrounding) in an insulating phase. Furthermore, radicals can be generated in the atmosphere, e.g. ozone. They can add to the destruction of the defect site either by direct oxidation (e.g. ozone) or by other chemical transformation, depending on the atmosphere used during the treatment. In contrast to the orientation suggested by Figure 1 , the apparatus may optionally be oriented face down during defect treatment, to avoid residues of the defect removal like small particles to rest on the electronic component under the influence of gravity. Furthermore, a flow of process gas can be used to drive the residues of the treatment away from the electronic component. An essential aspect of the proposed procedure is the use of an insulated metal part, the probe electrode 20, to establish the electrical field E over the electronic component 1. This limits the energy release during the treatment. Therefore, the discharge can be limited, to act only localized at the defect spot and eventually the near surroundings. The maximum energy release is given by the effective capacitance between the insulated probe electrode 20 and the substrate 3, in combination with the applied voltage. The size and shape of the insulated probe electrode 20 can be chosen according to the energy requirements: Point-like, line-like, or two-dimensional (e.g. a plate).

Particular advantages of the proposed apparatus 100 and method are a.o.:

- it is applicable to any kind of substrate (either insulating or conductive); - the energy released during the discharge can be determined by the applied voltage, the shape of the insulated probe electrode 20, and the distance between substrate and insulated probe electrode 20;

- the method is fast, since many defects can be healed simultaneously;

- the method can be applied during any stage of the production line: As part of substrate pre-treatment (cleaning), as well as after any steps in the production sequence;

- the method can be integrated in standard thin-film process equipment, e.g. attached next to a CVD reactor;

- the method is cheap, because it is fast and can make use of standardized technologies; - the method is reliable: exactly those defects are addressed which are also potential sources of device failure, especially if the device is based on insulating and/or semiconducting layers;

- no electrical contacts are required to the treated electronic component 1 ; - no (corona) charging effects of the treated electronic component 1;

- enhancement of thermal defect treatment by proper choice of the surrounding atmosphere and/or temperature;

- applicable to any type of thin- film device as long as the topology is smooth (small elevations w.r.t. the distance between insulated probe electrode 20 and component 1), and the device is manufactured on a substrate.

Finally it is pointed out that in the present application the term

"comprising" does not exclude other elements or steps, that "a" or "an" does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope.

Claims

CLAIMS:

1. An apparatus (100) for the treatment of defects (4) in a layer (2) of an electronic component (1), comprising a) a conductive carrier (10); b) a probe electrode (20), wherein the electronic component (1) can be placed between the conductive carrier (10) and the probe electrode (20) in the operating state of the apparatus (100); c) at least one insulation (30) that shields the probe electrode (20) and/or the conductive carrier (10); d) a power supply (40) that is connected to the conductive carrier (10) and the probe electrode (20).

2. The apparatus (100) according to claim 1, characterized in that the voltage supply is an AC high- voltage supply (40).

3. The apparatus (100) according to claim 1, characterized in that the insulation comprises an insulating layer (30) around the probe electrode (20).

4. The apparatus (100) according to claim 1, characterized in that the probe electrode (20) has a front region with the shape like a point, a line, or an area that can be located closest to the electronic component (1) in the operating state.

5. The apparatus (100) according to claim 1, characterized in that it comprises a scanning mechanism for moving the probe electrode (20) relative to the electronic component (1) in the operating state.

6. The apparatus (100) according to claim 1, characterized in that the conductive carrier (10) comprises channels (12) for applying a vacuum to an electronic component (1) lying on the carrier.

7. The apparatus (100) according to claim 1, characterized in that it comprises an climate-controller for providing a predetermined atmosphere and/or temperature at the electronic component (1), probe electrode (20) and/or conductive carrier (10).

8. A method for the treatment of defects (4) in a layer of an electronic component (1), comprising the application of an electrical field (E) that sequentially passes said layer and an insulation (30), wherein said field induces a discharge only at a defect.

9. The method according to claim 8, characterized in that the electrical field (E) is an AC field with a frequency in the range of about 1 kHz to about 1 MHz.

10. The method according to claim 8, characterized in that the electrical field (E) has a strength in the range of about 1 kV/cm to about 10 kV/cm.