Apparatus for electrochemical processing of semiconductor substrates and process using same

Abstract

An apparatus for electrochemical processing of semiconductor substrates is provided, comprising at least one first tank filled with an electrolyte and including at least one first electrode, at least one second tank filled with an electrolyte and including at least one second electrode, a separation unit for electrically isolating the first tank containing its electrolyte from the second tank containing its electrolyte, a power source connected to the first and second electrodes, transport means configured for transporting the substrate over the first and second tanks, and a controller for controlling the transport means in a specific manner.Furthermore, a process for electrochemically processing semiconductor substrates using the apparatus described herein is disclosed.

Description

[Technical field]

[0001] The present disclosure relates generally to an apparatus for electrochemical processing of a semiconductor substrate and a process for electrochemically processing a semiconductor substrate using the apparatus, for example a process for rendering the semiconductor substrate porous. [Background technology]

[0002] Electrochemical etching processes are commonly used to create semiconductor substrates with various layer properties. They may also be used to create porous layers with controlled porosity in the surface regions of the semiconductor substrate. Typically, porous layers are formed on semiconductor substrates, such as Si wafers, by anodic formation, which involves immersion of the substrate in an aqueous hydrogen fluoride solution and application of a specific current density to the substrate region to be treated.

[0003] Such etching processes require the application of current densities in the processing area. For this reason, typical processes have used contacts on the backside of the substrate. Some contacts are full contacts that cover the area of ​​the backside of the substrate. Sometimes ring contacts have been used at the edge of the substrate wafer. Alternatively, line contacts on the substrate surface or on the substrate holder have been fabricated, for example as an additional lithography plane within or on the backside of the semiconductor substrate. However, there have been exceptions where the full contacts or holders used to contact the backside of the semiconductor substrate interfere with automated processes or are not accurately processed at the edge of the substrate. Line contacts on the additional planes of the substrate or in the holder result in additional fabrication steps and therefore a lower throughput of the overall manufacturing process.

[0004] In the manufacture of solar panels or solar cells, rectangular wafer substrates are typically processed. The substrates are processed by an electrochemical etching process. Most conventional equipment is capable of processing rectangular substrate wafers with sufficient uniformity, but problems arise with circular substrates. Some experiments have shown that round shaped substrates result in non-uniform porosity in the processed areas when conventional processing equipment is used.

[0005] In view of the above, there is a need for improved processing conditions and improved apparatus that allow for processing of semiconductor substrates of various shapes. Further, there is a need for an apparatus that allows for the application of uniform current densities to substrates of various shapes over time. Summary of the Invention

[0006] According to one embodiment, an apparatus for electrochemical processing of semiconductor substrates comprises at least one first tank filled with an electrolyte, each tank comprising at least one first electrode, at least one second tank filled with an electrolyte, each tank comprising at least one second electrode, and a separation unit for electrically separating at least one first tank containing its own electrolyte from at least one second tank containing its own electrolyte. In the present description, the first electrode and the second electrode refer to different types of electrodes having different electrical potentials. Thus, if the first electrode is an anode, the second electrode is a cathode and vice versa. Furthermore, the apparatus may comprise a power source connected to the at least one first electrode and the at least one second electrode. The power source can be configured to supply an electric current to the electrodes, the current density being adjusted taking into account the desired electrochemical processing.

[0007] The device may further comprise a transport means configured to transport the substrate over the first and second tanks such that the surface of the substrate to be treated is in direct contact with at least one of the electrolyte filled in the at least one first tank and the electrolyte filled in the at least one second tank, thereby causing a charge transfer between the at least one first electrode and the substrate and between the substrate and the at least one second electrode, resulting in an electrochemical treatment of the substrate surface. The charge transfer process results in an electrochemical treatment of the substrate surface. Transporting the substrate over said tank means in the context of the present description that the substrate can be moved or is moved over the tank filled with electrolyte and is brought into contact with the electrolyte by a fluid bridge connection. Thus, the distance from the surface of the electrolyte solution to the substrate surface to be treated is small enough to contact the electrolyte and form a fluid bridge due to the surface tension of the electrolyte. The electrolyte can flow over the top edge of the tank to fill the gap between the wet electrode, i.e. the electrolyte, and the substrate surface. A continuous flow can be generated by pumping the electrolyte cyclically into the first or second tank, for example via an inlet at the bottom of the tank. The electrolyte flowing over the upper edge of the tank can be collected in a collection tank and pumped again into the first or second tank by electrolyte pump means. The transport means for transporting the substrate over the first or second tank can be selected according to the overall structure and can include, for example, rotating rolls between or above said tanks and a holding or robotic arm adjusted to move the substrate in a defined manner over the tank containing the wet electrolyte.

[0008] Furthermore, the device may comprise a controller for controlling the transport means such that the substrate masks at least one first electrode and / or at least one second electrode when viewed from above during the majority of the time during the electrochemical treatment of the surface of the substrate during the movement of the substrate over the first and second tanks. In this context, most of the time means that the substrate masks at least one of the electrodes at any time during the electrochemical treatment process. In particular, the electrode with anodic potential may be masked by the substrate during the electrochemical treatment process or for most of the time of the treatment process. The electrode with cathodic potential does not necessarily have to be masked by the substrate, but may be located in its own tank similarly or symmetrically to the electrode with anodic potential. At some points in the process, for example when the orientation of the substrate is changed by the controller, no electrode may be simultaneously masked by the substrate. According to the embodiments described herein, this state lasts as short as possible. Correspondingly, at least one of the first electrode and the second electrode, particularly the electrode having an anodic potential, is masked for greater than 90% of the time of the electrochemical treatment process, particularly greater than 95% and more particularly greater than 98% of the time.

[0009] An embodiment of a process for electrochemical treatment of a semiconductor substrate may use an apparatus according to any of the embodiments and / or examples described herein. The process may include a step of moving the substrate over a first tank and a second tank. The transport means are thus configured such that the surface of the substrate to be treated is in direct contact with at least one of the electrolyte filled in the first tank and the electrolyte filled in the second tank. Direct contact means that a liquid bridge between the substrate surface to be treated and a wet electrode, i.e. electrolyte, in either the first tank or the second tank is created by bringing said substrate surface close to the electrolyte surface. When such a liquid bridge occurs, charge transfer between the first electrode and the substrate and between the substrate and the second electrode can be achieved, resulting in electrochemical treatment of the substrate surface. In this process, the substrate is moved to a first tank containing a first electrode, and the substrate surface is brought into contact with the electrolyte filled in the first tank, thereby bringing the substrate surface to a positive potential. In this case, the first electrode is an anode. The substrate is then transferred to a second tank containing a second electrode. At this time, the substrate surface is brought into contact with the wet electrode of the second tank, and the desired reaction occurs, for example porosification of the substrate surface in contact with the wet electrode of the second tank, which may be a cathode. During the treatment, the substrate is simultaneously contacted with the first tank and the second tank to provide a current flow, but different parts of the substrate surface to be treated are alternately contacted with the first electrolyte and then with the second electrolyte. This allows the surface substrate to be treated to be moved alternately between the first tank and the second tank, provided that the substrate masks at least one first electrode and / or at least one second electrode from above during the majority of the time during the electrochemical treatment of the substrate surface during the transfer of the substrate over the first tank and the second tank. In particular, the electrode with the anodic potential can be masked during the electrochemical treatment process. Thus, the entire substrate surface can be treated uniformly.

[0010] The elements in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present invention. Like reference characters indicate corresponding like parts. Features of the various illustrated examples may be combined unless mutually exclusive. Examples are shown in the drawings and will be described in detail in the following specification. [Brief description of the drawings]

[0011] [Figure 1] 1 shows a top view of a processing area of ​​an apparatus according to an exemplary embodiment of the present application. [Diagram 2] 4 shows a top view of a processing area of ​​an apparatus according to another exemplary embodiment of the present application. [Diagram 3] 4 shows a top view of a processing area of ​​an apparatus according to a further exemplary embodiment of the present application; [Figure 4] 1 shows a top view of a processing area of ​​an apparatus according to an exemplary embodiment of the present application. [Diagram 5] 4 shows a top view of a processing area of ​​an apparatus according to another exemplary embodiment of the present application. [Figure 6] 6 illustrates a cross-sectional view of a half-cell portion of the exemplary embodiment shown in FIG. 5. [Figure 7A-D] 1A-1D show cross-sectional views of four different alternative half-cell portions of exemplary embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the following detailed description, an apparatus for electrochemical processing of a semiconductor substrate and a process for electrochemical processing of a semiconductor substrate using the apparatus are described. The semiconductor substrate may include or consist of at least one of a semiconductor wafer or one or more epitaxial layers. The epitaxial layer may include an epitaxial structure, for example, within or on a surface area of ​​the epitaxial layer or wafer. For example, the substrate may include only an epitaxial layer and may be devoid of a wafer. For example, the wafer used for epitaxial growth may have been removed in a previous processing step. In other examples, a wafer may be at least partially present within the substrate, for example, on the back side of a semiconductor substrate, while the front side of the semiconductor substrate is provided with one or more epitaxial layers. In this case, the semiconductor substrate to be processed may be the wafer on the back side of the semiconductor substrate. For example, a semiconductor device may be fabricated from a semiconductor substrate, such as a Si, SiC, GaN, or other III / V or II / VI semiconductor substrate, a surface region of which is treated by the electrochemical process described herein. The substrate surface to be treated preferably does not include lithographic elements within the treatment region of the surface. Of course, the apparatus may also be used with other substrates not expressly described herein that are suitable for electrochemical treatment processes.

[0013] In the context of the present application, electrochemical treatment of a semiconductor substrate may involve etching or porosifying the surface of the substrate by means of applying an electrochemical potential to the substrate, thereby modifying the structure of the treated surface area, for example increasing the porosity of the substrate surface. Such electrochemical treatment processes are generally known in the art and the present application is not limited to any particular one. More specifically, electrochemical treatment may involve modifying the porosity of the substrate surface being treated. Depending on the applied current density, it is possible to specifically adjust the thickness or pore volume of the substrate surface.

[0014] The device comprises at least two types of cells, namely one or more first cells and one or more second cells. The two or more cells of each type may be arranged alternately or in a specific pattern, at least when they are electrically separated by a separating means that electrically separates the first and second cells adjacent to each other. In the following, the embodiments and examples are described in more detail by identifying the first cell as an anodic cell, the first electrode as an anode, the second cell as a cathodic cell, and the second electrode as a cathode. Alternatively, the first cell may be a cathodic cell and the second cell may be an anodic cell, where the respective corresponding electrodes are included therein. A person skilled in the art will be able to adjust the arrangement of the respective anodes and cathodes, even though in the following description of a preferred embodiment of the device and the method of using the device, a specific embodiment is shown only for the first alternative.

[0015] According to one embodiment, the apparatus may comprise a processing area including at least one first tank and at least one second tank, the processing area being circular, elliptical or oblong in shape when viewed from above. In some examples, the processing area may be elliptical or oblong in shape, and at least one first electrode and / or at least one second electrode may be located in a circular arrangement in the processing area. For example, at least two, or at least three, or more than three first electrodes may be arranged in a first half of the circular processing area in the first tank, i.e., arranged side by side on a circular line extending in the two halves of the processing area. At least two, or at least three, or more than three second electrodes may be arranged on the same circular line in the second half of the processing area in the second tank. This arrangement allows a circular substrate to simultaneously mask all of the first and second electrodes if the diameter of the substrate is larger than the outer diameter of the electrode arrangement described above. A symmetrical arrangement of the first and second electrodes, as described in the previously illustrated embodiment including a circular arrangement of two or more (e.g. at least three) electrodes in each tank, is merely optional and may be advantageously used in a reverse pulse process as described later in this specification. If the reverse pulse method is not used, the cathode electrode may be arranged outside the area covered by the substrate. In particular, the anode electrode may be arranged so that it is masked by the substrate most of the time during the electrochemical treatment process in order to provide sufficient uniformity of the treated surface area of ​​the substrate. By rotating the substrate on the two halves of the treatment area, i.e. by masking portions of the surface of the substrate alternately by the first electrode in the first tank and the second electrode in the second tank, it is possible to electrochemically treat the substrate surface in a uniform manner. In order to increase the uniformity, in addition to the rotational movement, a movement of rotating the substrate in a linear direction along the elliptical or oval shape of the treatment area may be performed. In this case, it is preferable that the first and second electrodes are masked by the substrate most of the time of the treatment process. Thus, an electrode array including a first electrode and a second electrode may be configured such that the diameter of the circularly arranged electrode array is smaller than the diameter of the substrate.For example, the diameter of the electrode array may be within a range of about 5-90% of the diameter of the substrate, and in some instances, the diameter of the electrode array is within a range of about 30-70% of the diameter of the substrate. If more electrodes are used, the diameter of each electrode may be at least 5% of the diameter of the substrate, and more particularly, for example, within a range of about 5-20%.

[0016] According to certain embodiments, the anodic tank can be filled with an electrolyte and includes an anode for correspondingly charging the electrolyte so that it can be used as a wet electrode. Similarly, the cathodic tank can be filled with the same or different electrolyte and includes a cathode. An exemplary electrolyte for electrochemical processing of semiconductor substrates is an aqueous HF (hydrogen fluoride) solution, optionally including an organic surfactant or organic solvent component such as ethanol, oxalic acid, acetic acid, etc. The electrolyte filled in the tank functions as a wet electrode when it is brought into contact with the substrate to be processed. A power source is connected to the anode and cathode for generating a current flow when the surface of the substrate to be processed is in direct contact with at least one of the electrolyte filled in the anodic tank and the electrolyte filled in the cathodic tank, thereby causing a charge transfer from the anode to the substrate and from the substrate to the cathode, resulting in electrochemical processing of the substrate surface. The wet electrodes provided by the electrolyte in the cathodic tank and the electrolyte in the anodic tank can be brought into contact with the surface of the substrate by a liquid bridge that is generated and maintained by the surface tension of the electrolyte. The distance between the surface of the wet electrode and the surface of the substrate is therefore adjusted so that the surface tension can maintain the liquid bridge while the substrate moves over the wet electrode. The appropriate distance is known in the art and depends on the surface tension of the aqueous electrolyte solution on the substrate surface. The aqueous electrolyte solution is preferably continuously pumped from the bottom of the chamber into the anodic and cathodic chambers so that the electrolyte flows over the upper edge of the chamber walls. This system thus provides a continuous renewal of the electrolyte surface. Furthermore, the electrolyte surface thus obtained is somewhat higher than the edge of the chamber walls, facilitating the creation of a fluid bridge with the substrate surface to be treated. Furthermore, any gas bubbles that may occur during the chemical reaction on the substrate surface will be carried to the edge of the chamber and dissipated by the electrolyte flowing over the edge of the chamber walls. This allows for a further improvement of the processing results.

[0017] The first electrode disposed in the first tank or the second electrode disposed in the second tank, i.e., the anode or cathode, can be any electrode shape suitable for generating a wet electrode in each tank. The illustrated electrode is a surface electrode that can be disposed at the bottom of each tank. Alternatively, two or more electrodes can be disposed in each tank instead. In some examples, the electrodes are disposed in different parts of the tank to generate a uniform potential in each tank. In general, the electrode shape and material can be selected so that the wet electrode current density generated at the surface of the electrolyte in each tank is uniform.

[0018] In some embodiments, the device may further include a treatment area covering means. One or more treatment area covering means may reduce the active treatment area when viewed from above. Exemplarily, the treatment area covering means may be arranged in a portion of the treatment area provided by the first and second tanks where neither the first nor the second electrode is present. In the case of an elliptical or oval-shaped treatment area, for example, the electrodes may be present in a circular arrangement in the center of the treatment area. The treatment area covering means thus extends over the entire treatment area except for a central circular opening, said opening having an opening diameter at least the outer diameter of the circular arrangement of the first and second electrodes. The electrodes in this example are therefore not covered by the treatment area covering means. The function of the treatment area covering means is to reduce the active area of ​​the wet electrodes. The active area of ​​the treatment area is thus concentrated in the portion of the wet electrodes where the first electrode in the first tank and the second electrode in the second tank are located. Furthermore, the treatment area covering means reduces the surface area of ​​the electrolyte open to the environment. Since the electrolyte generally evaporates from time to time, especially when it warms up due to electrochemical reactions during processing, the processing area cover means allows for a reduction in the evaporation of the electrolyte by reducing the interface between the electrolyte and the surrounding environment.

[0019] In the case of two tanks, one first tank and one second tank, arranged in two halves of a circular or elliptical or oblong processing area, separated by a separating means, the first and second electrodes are arranged near the separating area in the center of the processing area. The substrate can then be moved over the first and second electrodes by a rotational movement and, optionally, overlapped by a small lateral movement, preferably in a direction perpendicular to the separating means. The diameter of the opening of the processing area cover means is in this case similar to the size of the substrate. Exemplary opening diameters are about 50-250 mm, in particular 60 mm-160 mm, for example 60 mm or 75 mm or 150 mm. For a substrate with a diameter of 200 mm, the diameter of the opening may be in the range of at least 170 mm and at most 230 mm, more particularly about 180 mm-220 mm.

[0020] The aforementioned treatment area cover means may be in the form of a perforated plate that is placed at the level of the electrolyte in the first and second vessels or at a position somewhat lower than the level of said electrolytes. Thus, gaseous products generated during the treatment process can be guided out of the electrolytes due to the through holes in the treatment area cover means. In some examples, the perforated plate can be made of a material with low electrical conductivity, for example a plastic or polymeric material. This allows electrical shielding at the periphery of the treatment area and improved uniformity of the porosity of the wafer surface after treatment.

[0021] According to some embodiments, the controller is arranged to turn off at least parts of the first and second electrodes from the at least one first electrode and / or the at least one second electrode. Roughly speaking, the electrodes that are not masked by the substrate during the electrochemical process are turned off as long as they are not masked by the substrate. After the substrate has moved over these electrodes during its movement, the electrodes are turned on again. The controller can calculate the substrate movement path or receive substrate measurements and timely turn off the electrode current from the electrodes that are no longer in the substrate movement path. The controller can receive feedback measurements temporarily or continuously. Alternatively, the substrate path and its timing are pre-calculated before the electrochemical process starts and the values ​​are stored in the controller for each substrate. This calculation may include the size of the substrate, the movement path, the speed and further parameters.

[0022] Turning off the current in parts of the electrodes, especially those that are not actually masked by the substrate, improves the results of the electrochemical process, for example improving the uniformity of the porosity obtained in the areas of the entire substrate surface that are in contact with the electrolyte. It is assumed that when all active electrodes are masked by the substrate, the current flowing from the electrodes to the wet electrodes and then to the substrate can be more evenly distributed on the substrate surface. It is assumed that the increase in current at the edge of the surface of the wet electrodes where there are active but unmasked electrodes is prevented by turning off the unmasked electrodes.

[0023] According to some embodiments, the device may further comprise a current baffle. This current baffle may be provided in at least a part of the treatment area including at least one first electrode and at least one second electrode. A current baffle in this context means a means for deflecting or guiding the movement of the current generated by the electrodes into the wet electrolyte in order to match the current density of the wet electrolyte in each of the cells. The current baffle may be a perforated sheet or net made, for example, of a plastic or polymeric material. In general, the electrical conductivity of the material is low. The current baffle may be provided in the first cell and in the second cell, or only in one of the cells. It is appropriate to provide the current baffle in the area where the first electrode or the second electrode is located. In some examples, the entire cell comprises a net-like current baffle. In other embodiments, the current baffle extends from the side of the electrodes to the treatment area cover means. In this case, the current baffle covers the opening of the cell that is not covered by the treatment area cover means. In some examples, the current baffle is provided in the cell at the same height as the treatment area covering means, i.e. approximately at the level of the electrolyte surface, or somewhat lower than the electrolyte surface, for example by a few mm below the electrolyte surface. In some examples, the current baffle may not be parallel to the electrolyte surface, but is arranged at an inclined angle in the cell. For example, the upper end is provided on the side of the cell near the separating means and the lower end is near the location of the area covered by the treatment area covering means. Alternatively, the upper end is near the edge of the treatment area covering means and is inclined towards the side of the cell near the separating means. In general, the current baffle is provided in a plane higher than the upper ends of the electrodes. Optionally, the current baffle may extend over the entire area of ​​the first cell and / or the second cell, i.e. also below the treatment area covering means if provided on the periphery of the cell.

[0024] To avoid direct contact between the two wet electrodes or between the electrolyte of the anodic and cathodic cells, a separation means can be provided around each anodic or cathodic cell, preventing the current from flowing directly from one wet electrode to the other. This allows the current to flow from one electrode to the substrate and then from the substrate to the other electrode when the substrate is moved from one cell to the other cell at the opposite potential. Roughly speaking, the substrate is positively charged by contacting the substrate surface with the wet electrode of the anodic cell, and then moved to the cathodic cell and contacted with the wet electrode of the cathodic cell. In this cathodic half-cell, the substrate is electrochemically treated, for example by increasing the porosity of the substrate surface. The reaction usually involves a chemical reaction that may include the evolution of gas. The type of physical or chemical reaction that occurs in the cathodic charge transfer reaction depends on the substrate to be treated, the electrolyte, the current density and the potential applied in the cell. Each of these reactions is known in the art and can be readily carried out using the equipment described herein.

[0025] Exemplary separation means may be a fixed wall or a separation tank that does not contain electrolyte. Sometimes, air or an inert gas component is filled in the tank of the separation means to avoid electrical contact between the electrolyte in the first tank and the electrolyte in the second tank. Alternatively, an air knife may be used to separate the first tank and the second tank. The air knife works with a flow of air or inert gas that usually enters the separation means at the bottom of the separation means, providing a flow of air or inert gas from the bottom to the open space between the first tank and the second tank, thus providing improved separation of the electrolyte filled in each of the first tank and the second tank. In addition, the flow of air or inert gas reaches the bottom surface of the substrate as it moves over the processing region, and allows the anode wet electrolyte and the cathode wet electrolyte that wet the substrate surface during the electrochemical treatment process to be separated at their respective positions on the anode tank or the cathode tank, respectively. The air knife thus serves to separate the anode and cathode chambers and the respective wet electrolytes, thus preventing direct current from the anode wet electrolyte to the cathode wet electrolyte.Furthermore, instead of or in addition to the air knife, a lip portion that projects into the path of the substrate and whips the bottom of the substrate may be provided as a separation means.

[0026] According to an embodiment, the first or second tank, or both the first and second tanks, have a spiral shape when viewed from above, and the first and second tanks can be configured to be at least partially intertwined with each other. The spiral shape of the first or second tank can provide a processing area that is simply circular. Due to this circular arrangement of at least one of the tanks, i.e. the first and / or second tank, the surface of the substrate to be processed can be moved over the processing area, so that a similar current density can be achieved over time on each part of the substrate surface, even if the substrate is circular. This can improve the application of the current density over time for substrates with different shapes. In particular, the porosity of the surface of a particularly round substrate, such as a semiconductor wafer, can show improved uniformity when viewed from above when processed in an apparatus including a spiral-shaped first and / or second tank.

[0027] In some examples, at least one of the first tank or the second tank extends spirally outward from the center of the device when viewed from above. When the tank has a shape that extends spirally outward from the center of the device, the tank and the separation unit surrounding the tank divide the device into two separate areas, where one of the two areas is the area of ​​the first tank. The second area can automatically be the area of ​​the second tank, which can be the area not occupied by the area of ​​the first tank. Within this area of ​​the second tank, the second tank can be arranged to fill the remaining space, or it can be arranged only in one or more portions of the remaining space between the area of ​​the first tank.

[0028] The separating means can be provided between the first and second tanks, which can be in the shape of a spiral, and the first and second tanks can be separated by said separating unit. Thus, according to some embodiments, the first or second tanks, which extend in a spiral outward from the center, can be arranged such that, as seen from above, they divide the device into two separate regions in the shape of a spiral. The area of ​​the two spiral tanks can be similar or approximately the same. In the case of the first and second tanks extending in a spiral, this can be achieved if the width of the tanks is similar or approximately the same in each part of the spiral shape that has the same distance to the center of the two first and second tanks arranged in a spiral. In this case, the two spirals can be intertwined over the entire length.

[0029] According to a further embodiment, an apparatus for electrochemical processing of semiconductor substrates comprises at least one first tank filled with an electrolyte and each tank comprises a first electrode, at least one second tank filled with an electrolyte and each tank comprises a second electrode, and a separation unit for electrically separating at least one first tank containing its own electrolyte from at least one second tank containing its own electrolyte. At least one in this context means one, two, three or more first or second tanks. In some examples, there may be more than one first tank. In some embodiments, one smaller first tank is provided within the second tank, for example at the end of the second tank. In this case, the first tank is located within one segment of the second tank. The size and shape of the first and second tanks can vary, for example according to the substrate and its shape. In the case of a round wafer, for example, the circular second vat may contain the first vat within one segment of the second vat when viewed from above. If the second vat is rectangular in shape, the first vat may be located within, for example, one quarter of the second vat. Alternatively, the first vat may have a circular shape even if the second vat is rectangular in shape.

[0030] The device may further comprise at least one first electrode and at least one second electrode, and a power supply connected to the treatment region. The device may further comprise a transport means configured to transport the substrate over the first and second tanks, such that the surface of the substrate to be treated is in direct contact with at least one of the electrolyte filled in the at least one first tank or the electrolyte filled in the at least one second tank, thereby causing a charge transfer between the first electrode and the substrate and between the substrate and the second electrode, resulting in an electrochemical treatment of the surface of the substrate. The substrate surface to be treated can be brought into contact with the wet electrodes of the first and second tanks, i.e. by the electrolyte, for example by using a liquid bridge as described for the previous embodiment.

[0031] According to some embodiments, the processing area of ​​the apparatus may have a circular shape when viewed from above. When two or more first tanks are included, the first tanks may be arranged in separate sectors of the processing area, and the second tanks may be arranged between adjacent ones of the first tanks and may be separated from the first tanks by a separation unit.

[0032] In some examples, the second tank can be separated into two or more tanks according to the shape and configuration of the three or more first tanks. This particular configuration in which several first tanks are disposed within the second tank can allow for improved uniformity of the resulting porous substrate surface even if the substrate shape is different from a rectangular shape, for example, when a wafer of approximately round shape is processed.

[0033] In some examples, the apparatus can include at least three first vessels, which can be arranged in a ring shape with n-fold rotational symmetry within the processing region, where n is the number of first vessels included within the apparatus of the example.

[0034] In a further example, the first tank in the first sector has a smaller surface area than the first tank in the second sector, and optionally the surface area of ​​the first tank in the third sector and the further sectors is larger than the surface area of ​​the first tank in the second sector. That is, the surface area of ​​the effective treatment area of ​​the wet electrode provided by the first tank may be different from the effective treatment area of ​​the second tank and the further first tank. This allows to find a method of treatment of the substrate surface over the entire treatment area, so that a similar current density can be achieved over time on each part of the substrate surface, even if the substrate has a shape different from a square. This can improve the uniformity of application of the current density over time for substrates with complex shapes, such as circular.

[0035] In yet another embodiment, the first baths in each sector of the processing area of ​​the apparatus can have a triangular or sectoral shape, with side walls extending variably from the outer edge of the processing area. In one example, the baths are aligned so that their tips are located on a spirally formed line extending from the center of the bottom plane of the apparatus. Thus, the current density effectively applied to the substrate surface can be increased in each sector containing the first bath according to the surface area provided by each first bath in that sector of the processing area. By spirally varying the surface area of ​​the first baths, and therefore the surface area of ​​each of the wet electrodes responsible for charge transfer, and by moving the substrate in a rotational configuration about its axis, and by simultaneous translational movement, the uniformity of the current density applied to each portion of the substrate can be increased. Thus, the apparatus can be used to improve the uniformity of the substrate surface being processed, for example the porosity of the substrate surface of a rounded semiconductor wafer.

[0036] According to another embodiment, an apparatus for electrochemical processing of semiconductor substrates comprises a plurality of first tanks filled with an electrolyte and each of which comprises a first electrode, a second tank filled with an electrolyte and comprising a second electrode, and a separation unit for electrically separating the plurality of first tanks containing their electrolyte from the second tank containing their electrolyte. The apparatus of this embodiment further comprises a power source connected to the first and second electrodes, and a transport means. The transport means is configured for transporting the substrate over the plurality of first and second tanks such that the surface of the substrate to be processed is in direct contact with at least one of the electrolytes filled in the first tank and the electrolyte filled in the second tank, thereby causing a charge transfer between the first electrode and the substrate and between the substrate and the second electrode, resulting in an electrochemical processing of the substrate surface. The transport means are adjusted to provide a stable liquid bridge between the substrate surface to be processed and the wet electrodes in the first and second tanks, as described above for the first embodiment.

[0037] The device may further comprise a plurality of first tanks arranged in the second tank, thereby providing a treatment area for carrying out the surface treatment reaction. Each first tank may be electrically isolated from the second tank by a separation unit arranged around each first tank. The term "plurality" here means that there are at least three or more first tanks in the second tank. According to the size of the first tank, which is usually selected according to the size of the substrate to be treated, more than three first tanks, in particular more than five or six tanks, may be provided in one second tank. The more the number of first tanks, the more uniform the substrate may be, for example, of the porous layer of the substrate, as a result of electrochemical treatment of the substrate.

[0038] In some embodiments, the first reservoir may be circular in shape. Circular in this context means round or nearly round, but may be elongated in one direction. In yet another example, the first reservoir may be arranged in a dot pattern within the second reservoir. More specifically, the dot pattern may be a regular arrangement in which the distance between adjacent first reservoirs is similar or the same.

[0039] According to one embodiment, the anode cell, the cathode cell, or both of these cells have a helical shape when viewed from above. Moreover, at least one of the first cell or the second cell extends in a helical shape outward from the center of the device, thereby dividing the bottom plane of the processing area of ​​the device into two separate areas, the anode cell area and the cathode cell area, said two areas having a helical shape. Alternatively, the two cells may be helical and intertwined with each other. Moreover, they may be separated by a separation unit aligned between the two helical shaped cells or between the anode and cathode areas. The helical shape of the cells and the separation unit is according to the present description seen from above and describes the surface area of ​​the cells in a top view. Thus, in a top view, the entire processing area may be divided into alternating rings of anode processing areas and rings of cathode processing areas separated by a separation unit when viewed from one side of the entire processing area to the other. In view of this specially patterned treatment area, the substrate surface, or more specifically different parts of the substrate surface, can be moved alternately over anodic and cathodic baths containing respective wet electrodes, whereby a positive or negative potential is applied, i.e. so-called pre-charged (in the present context the term "pre-charged" means the application of a positive or negative potential to the parts of the substrate surface in contact with the wet electrolyte, e.g. a positive potential is applied when the electrolyte is in contact with the anodic bath) and treated alternately several times during the movement from one side of the treatment area to the other (in the present context the term "treated" means that the parts of the substrate surface are electrochemically altered, e.g. porosified). In some embodiments, the substrate is moved over the treatment area in a circular form following the spiral shape of the baths while at the same time rotating about its own axis.

[0040] In order to move the substrate over the above-mentioned specific processing areas of the device, transport means for transporting the substrate over the anodic and cathodic chambers may be provided so that the substrate can be freely moved from one wet electrode to the next in a predefined manner. By "moving" in this context it is meant that the transport means are configured to rotate the substrate about its axis and, optionally, to move the substrate laterally over the first and second chambers. Lateral movement in this context can be a translational movement of the substrate in a plane parallel to the plane of the first and second chambers, i.e. the upper surface of the anodic and cathodic chambers. In particular, said movement is performed so that the surface to be treated is close enough to generate a liquid bridge between the respective wet electrodes and the substrate surface. Other movements, such as a rotation of the substrate, superimposed on a translational movement, are explicitly included in this definition. Furthermore, the lateral movement can include an eccentric movement of the substrate in a plane parallel to the plane of the first and second chambers. Simultaneously with such eccentric movement, the substrate may be rotationally moved in a predetermined manner by the transport means.

[0041] In some examples of the device of this embodiment or the previous embodiment, the processing area of ​​the first tank is similar to the processing area of ​​the second tank when viewed from above, and the processing area, which may be the same as the bottom area of ​​the first tank, has a ratio of 0 to 110% compared to the processing area of ​​the second tank. When the processing areas of the first and second tanks are approximately the same, it is possible to use the first tank as an anode tank, the first electrode as an anode, the second tank as a cathode tank, and the second electrode as a cathode, or alternatively, the first tank as a cathode tank, the first electrode as a cathode, the second tank as an anode tank, and the second electrode as an anode. Thus, the cathode processing area and the anode processing area can be interchanged with each other, provided that the two areas are arranged alternately. This makes it possible in such embodiments to apply pulsed direct current with alternating polarity without changing the processing time and processing area of ​​each wet electrode.

[0042] In a further embodiment, an apparatus for electrochemically processing semiconductor substrates comprises at least one anodic cell, for example three or four, filled with an electrolyte and each containing an anode, at least one cathodic cell, filled with an electrolyte and each containing a cathode, a separation unit separating the anodic cell containing its own electrolyte from the cathodic cell containing its own electrolyte, and a power supply connected to the anode and the cathode. The apparatus further comprises transport means configured to transport the substrate over the anodic and cathodic cells such that the surface of the substrate to be processed is in direct contact with at least one of the electrolyte filled in the anodic cell or the electrolyte filled in the cathodic cell, whereby a charge transfer takes place from the anode to the substrate and from the substrate to the cathode, resulting in an electrochemical processing of the surface of the substrate as described in the previously identified examples.

[0043] According to this example, the device has a circular processing area. By circular, it is meant that the processing area, including the anode and cathode cells, is approximately circular in its planar shape when viewed from above. In some examples, it can extend in one direction, i.e. it can be elliptical rather than strictly circular. A plurality of first cells (e.g., anode cells), in particular two or more first cells, are arranged in separate sectors of the processing area, and a second cell (e.g., cathode cell) is arranged between adjacent ones of the first cells and separated from the first cell by a separation unit. The cathode cell can be configured as a single cell or as two or more separate cells arranged such that an alternating arrangement of anode and cathode cells occurs in the main processing area of ​​the device when viewed from a predetermined movement path of the substrate over the anode and cathode cells in the processing area. The cathode chamber can be separated from the anode chamber by a separation unit, which prevents the flow of charging current between the two wet electrodes in the anode and cathode chambers from directly passing from one electrode to the other, and thus current flows from the anode wet electrode to the substrate and from the substrate to the cathode wet electrode, as previously described in other embodiments.

[0044] In one example of an apparatus for electrochemical processing of semiconductor substrates, the anode cells provided in separate sectors of the processing area can be arranged in a ring shape with n-fold rotational symmetry in the processing area. In this example, n is the number of anode cells included in the apparatus of this embodiment. If three or four anode cells are provided in the processing area, the processing area is divided into three or more separate sectors, each sector being interrupted by a cathode cell between two of the adjacent anode cells. The cathode cells can be connected to each other with one cathode cell surrounding each of the anode cells. The illustrated apparatus thus allows for a highly symmetrical alternation of the anode and cathode cells, improving the processing results.

[0045] In some examples of this embodiment, the anode bath in the first sector may have a smaller surface area than the cathode bath in the second sector, and optionally the surface area of ​​the anode bath in the third sector and further sectors may be larger than the surface area of ​​the anode bath in the second sector. Thus, the surface of each anode wet electrode in each sector may have different sizes, which may result in different current densities being applied to the surface of the substrate as it moves over the anode bath during the treatment process. More specifically, the specific configuration of the anode bath and thus the anode wet electrode having a larger treatment area in the circumferential portion of the treatment area may increase the potential applied to the outer area of ​​the substrate surface of a circular substrate, while the potential applied at the center of the substrate may be reduced compared to the ongoing treatment process. This allows the process results, such as the porosity of the treated substrate surface, to be influenced by the different sectors, so that each portion of the substrate surface achieves approximately the same potential over the treatment time. This can improve the uniformity of the processing results, and therefore the apparatus is well-adjusted for processing circular substrates such as semiconductor wafers.

[0046] In some other examples, the anode bath in each sector can have a triangular or sector shape, with side walls extending variously from the outer edge of the processing area of ​​the device and aligned such that the leading edge of the bath is located on a line formed in a spiral shape extending from the center of the bottom plane of the device. Correspondingly, the surface area of ​​the anode wetted electrode arranged in this embodiment can be larger at the periphery of the circular processing area and extend from only one side to the center of the processing area. This particular arrangement therefore also allows for the potential applied to the substrate surface to be adjusted so that each portion of the substrate surface achieves approximately the same current density over the processing time, particularly during processing of circular substrates.

[0047] In yet another embodiment, the device comprises a plurality of anode chambers, filled with an electrolyte and each containing an anode, arranged in a cathode chamber filled with the electrolyte and containing a cathode. The device further comprises a separation unit for electrically separating the anode chamber containing the electrolyte from the cathode chamber containing the cathode, a power supply connected to the anode and the cathode, and a transport means. The transport means are configured for transporting the substrate over the plurality of anode and cathode chambers such that the surface of the substrate to be treated is in direct contact with at least one of the electrolyte filled in the anode chamber or the electrolyte filled in the cathode chamber, thereby causing a charge transfer from the anode to the substrate and from the substrate to the cathode, resulting in an electrochemical treatment of the substrate surface. The transport means may be adjusted to provide a stable liquid bridge between the substrate surface to be treated and the wet electrolyte in the anode chamber and the wet electrolyte in the cathode chamber, as described above for other examples.

[0048] A plurality of anode cells are arranged in the cathode cell, thereby providing a treatment area for carrying out a surface treatment reaction, such as porosification. Each anode cell is electrically isolated from the cathode cell by a separation unit arranged around each anode cell. A plurality in this context means that there are at least three or more anode cells in the cathode cell. A larger number of anode cells for precharging the substrate surface to be treated may improve the homogeneity of the obtained substrate result, for example the porous layer of the substrate.

[0049] According to a process for electrochemically treating a semiconductor substrate using a device according to one of the previously described embodiments, the substrate can be transported or moved alternately over the anodic and cathodic tanks, whereby a portion of the substrate surface is precharged in the anodic treatment area and surface treated in the cathodic treatment area. The surface of the substrate to be treated can be brought into direct contact with at least one of the electrolytes filled in the anodic tank and the electrolytes filled in the cathodic tank, whereby a liquid bridge is created between the surface of the substrate to be treated and the wet electrolyte in one of the anodic and cathodic tanks by bringing the substrate surface close to the electrolyte surface. When such a liquid bridge is created, a charge transfer between the respective electrodes and the substrate can be achieved, resulting in electrochemical treatment of the substrate surface. In this process, the substrate can be moved to an anodic tank containing an anode, whereby the substrate surface can be brought into contact with the electrolyte filled in the anodic tank, whereby the substrate surface is brought to a positive potential. The substrate is then transferred to a cathodic tank containing a cathode. At this time, the substrate surface is brought into contact with the wet electrode of the cathode, and the desired reaction occurs, for example, porosification of the substrate surface in contact with the wet electrode of the cathode bath, i.e., the cathode. During the treatment, the substrate or at least a portion of the substrate is moved alternately between the anode bath and the cathode bath, so that the entire substrate surface is uniformly treated over time. The treatment time generally depends on the reaction to be performed, the material of the substrate, the potential applied to the substrate surface, and the current density in the portion of the substrate being treated. For semiconductor substrates such as 6-8 inch (150-200 mm) wafers made of Si or SiC, the treatment time can be adjusted within a few minutes, for example about 5-60 minutes, more particularly 10-30 minutes, in particular about 15-20 minutes. For larger wafers, the time can be longer.

[0050] A regular distribution of the first bath within the second bath in the treatment plane and in the direction of movement improves the treatment result: a higher regularity in distribution may result in a higher uniformity of the electrochemical treatment reaction.

[0051] The process described herein may be used to porosify a semiconductor substrate, such as a round wafer. In some examples, the process is defined by using a power source that supplies a direct current to an electrode. For example, a direct current may be applied to the anode to precharge the semiconductor substrate within at least a portion of the surface of the semiconductor substrate to be processed, i.e., a positive potential is applied to the portion of the semiconductor surface that is in contact with the anode electrolyte. During the process, an electrochemical reaction may occur at the surface of the substrate to be processed by applying a current density. Depending on the applied current density, it is believed that gaseous components may be generated near the substrate surface. Since the substrate surface in this processing region is completely wetted by the anode wetted electrode, it is believed that gas bubbles may appear under the substrate. By moving the substrate over the anode and cathode chambers, the gas bubbles may be carried to the edge of the wetted region. At the edge of the wetted region, the gas bubbles are easily lifted from the substrate surface. As explained above, the electrolyte is continuously pumped into the chamber, which causes the electrolyte to flow over the edge of the chamber wall. In this electrolyte flow, gas bubbles are carried into the electrolyte overflow tank. If the gas bubbles are not continuously carried away from the substrate surface, they will interfere with the pre-charging (application of a positive potential) of the surface beneath them, thus reducing the process reaction in the next step. Therefore, the substrate is moved in a regular manner, by rotation and by translation of the substrate, which reduces the number and size of the gas bubbles in the process area.

[0052] Since the processing reactions in the cathodic bath region may also give rise to gaseous products, the movement of the substrate over the cathodic processing region has the same effect as described for the anodic processing region. It is therefore preferable to avoid or limit as much as possible the number of gas bubbles beneath the surface of the substrate being processed by rotating the substrate and moving it over the processing region at a desired speed. The speed is adjusted so that the number and size of the gas bubbles are small.

[0053] In an alternative embodiment, the direct current can be applied for a short period of time, in which case the polarity of the applied direct current is reversed. Thus, the process according to this embodiment can include a power supply providing pulses of direct current power with alternating different polarities in each pulse. Exemplary pulse lengths are in the range of a few seconds. In some examples, particularly where the anodic and cathodic processing areas have similar or identical areas, the pulse length can be less than 1 second, for example 200-900 ms, more particularly 300-600 ms, especially about 400 ms.

[0054] In general, the treatment area of ​​each of the anodic and cathodic cells is adjusted to be large enough to apply a sufficient current density at the substrate surface to be treated. The larger the treatment area, the higher the current that can be applied to the substrate by the wetted electrodes. Thus, the treatment time can be shorter and the electrochemical reaction that occurs can be improved. In particular, the treatment area of ​​the cathodic cell serves to improve the surface treatment according to the current density applied to the substrate surface.

[0055] Further embodiments will now be described with reference to figures showing various types of arrangements of a first and a second tank in top view.

[0056] Referring now to Figure 1, there is shown a schematic diagram of an apparatus for electrochemically processing round wafers. In particular, the processing area 100 of the apparatus is shown with the specific arrangement of the anodic and cathodic chambers 10 and 20, and the separating means 30 between the two chambers. The power supply means and the transport means are not shown. Furthermore, the anodes and cathodes disposed within the anodic and cathodic chambers, respectively, are not shown. The electrodes can be one or more electrodes disposed within the chambers, but can also be surface electrodes provided at the bottom of the chambers.

[0057] The processing area is preferably larger than the wafer to be processed. For a 200 mm wafer, the diameter of the processing area 100 may be at least 250 mm. The dimensions of the anodic cell 10 and cathodic cell 20, including the side walls but excluding the separating means 30, are about 25-50 mm, in the present example shown in FIG. 1, about 35 mm. Thus, if the diameter of the processing area is about 350 mm, the anodic cell may be wound several times around the center of the processing area, for example about 2.5 times. If a larger processing area is used, the anodic cell may be wound 3, 4 or more times around the center.

[0058] The device comprises an anodic cell 10, which extends in a spiral shape from the center of the processing area 100 as viewed from above, and a cathodic cell 20, which has a similar spiral shape as viewed from above, where the cathodic cell is located in the space between the spiral-shaped anodic cells. The processing area 100 can therefore be divided into two similar processing areas, namely an anodic processing area and a cathodic processing area. A separating means 30 is located between both cells, electrically separating the anodic and cathodic cells. To electrically connect the substrate surfaces to be processed, an electrolyte, i.e. a generally HF-based electrolyte containing at least about 15% ethanol, for example 30-60% ethanol, more particularly about 50% ethanol, can be pumped from the bottom of the anodic and cathodic cells into the respective cells. The above cells are open at the top, so that the electrolyte flows over the walls of the cell and is collected in a collection cell (not shown). The separating means 30 may be a common separating means spirally formed between the anode cell 10 and the cathode cell 20 over the entire length of the anode cell wall, for example an air knife. Alternatively, whipping means may be used instead of the air knife shown in this embodiment.

[0059] The substrate (here a round wafer) is transported over the processing area by a transport means in the form of a holding arm. Since the processing area is larger than the wafer substrate, only the part of the substrate surface that is in contact with the anode wetted electrode is pre-charged. At the same time, the part in contact with the cathode wetted electrode can be electrochemically processed, since a current is passed through the substrate part that is not in contact with the first and second electrolytes. During the translational movement over the processing area, the previously pre-charged part of the substrate surface is moved to the cathode bath and its processing area. In this position, the previously pre-charged substrate surface comes into contact with the cathode wetted electrode, which causes an electrochemical process on the substrate surface. In this case, the surface of the semiconductor wafer is made porous according to the applied current density. The next cycle on this part of the substrate surface is carried out as soon as the substrate is moved over the next part of the anode bath.

[0060] To prevent direct electrical current between the anode and the cathode, the substrate surface is struck with a lip of a separation means directed at the substrate surface between the anode and cathode chambers, or with an air flow provided by an air knife as shown in this embodiment. This cycle of pre-charging and treatment steps is carried out continuously while the substrate surface moves over the treatment region 100. The substrate can be rotated about its axis while moving laterally over the treatment region 100 in a linear translational or oscillating motion to generate a more homogenous treatment reaction, thereby achieving uniform porosification over the entire substrate surface area.

[0061] In the processing area 100 shown in FIG. 1, the anodic chamber 10 and the cathodic chamber 20 have approximately the same surface area. It is therefore possible to carry out a process in which the anodic and cathodic processing areas are changed by using a direct current with alternately reversed polarity pulses. In this case, an anodic chamber containing an anode becomes a cathodic chamber containing a cathode in the next pulse. The use of this alternating direct current can reduce problems caused by gas products that are generated during the electrochemical process. Gas bubbles can cause problems also known as diffusion problems in the gas-solid interphase. If the reaction is temporarily alternated, the generation of gas bubbles in the pores and on the substrate surface can be reduced. In this way, the use of a pulsed direct current can achieve more advanced electrochemical processes.

[0062] If the surface area of ​​one of the cells is significantly larger, the use of pulsed DC may not improve the treatment results since the pre-charging and treatment processes are related to the surface area of ​​each treatment area. If the anodic and cathodic treatment areas are too different from each other, the positive effect on reducing bubbles may be reduced, and the effective treatment yield may be reduced at the same time. Therefore, it is preferable to use anodic and cathodic cells 10 and 20 with similar surface areas, such as the embodiment shown in FIG. 1.

[0063] Referring now to the embodiment shown in Fig. 2, a processing area 100 of an apparatus for electrochemically processing semiconductor substrates comprises four anodic cells (11; 12; 13; 14) filled with electrolyte and each containing an anode (not shown). A cathodic cell 20 is arranged around each of the four anodic cells and is separated from the anodic cell by a separating means 30. The separating means 30 are arranged next to the wall of the anodic cell, thus allowing a complete separation of the anodic cell 10 and the cathodic cell 20. The power supply as well as the anodes and cathodes are not explicitly shown in Fig. 2.

[0064] The processing area 100 of the apparatus in this embodiment has a diameter of at least 250 mm when used for a 200 mm wafer substrate. The separating means 30 has a width between the wall of the anode cell and the wall of the adjacent cathode cell of about 15 mm or more. The area of ​​the anode cells can be increased by increasing the number of anode cells arranged in each sector or by increasing the number of anode cells arranged in the cathode cell. In the example shown in FIG. 2, the anode cell 11 has a smaller surface area than the anode cell 12, which has a smaller surface area than the anode cell 13, which is even smaller than the surface area of ​​the anode cell 14. Furthermore, the anode cell 14 extends at least to the center of the processing area, while the other three cells do not extend to the center. The tips of the four anode cells, when combined, follow a spiral line in the processing area when viewed from above. Thus, the current density applied to the substrate surface at the center can be similar compared to areas at the periphery of the round substrate. Thus, by using this particular arrangement of the anode cell, the usual increase in treatment process at the center of a round wafer, as measured in common processes, can be avoided or at least reduced.

[0065] When two anodic cells extend from two sides into the center of the treatment area, it is possible to combine separation means and place two or more cathodic cells between each adjacent anodic cell. The surface area of ​​the cathodic cells can be increased to allow shorter treatment times.

[0066] As in the previous embodiment, the wafer is moved over the processing region in an eccentric motion in this embodiment and rotated about its own axis, so that each portion of the wafer surface being processed receives a similar or the same current density and is processed for the same amount of time, resulting in the same results. Thus, the porosity of the substrate surface is uniform, even though a round wafer substrate is being processed.

[0067] Now referring to FIG. 3, this embodiment of the device described herein has a processing area 100 substantially identical to the cathode cell 20. The cathode cell in this example is a rectangular cell filled with electrolyte, including side walls. During processing, electrolyte is pumped from the bottom into the cathode cell 20 and flows over the side walls. The device thus includes an electrolyte collection cell located below the cathode cell 20 and the anode cell 10. Within the cathode cell, a number of anode cell 10 are arranged in a regular dot pattern. Each anode cell 10 is separated from the cathode cell by a common separation means for electrically separating the cathode cell and the anode cell, for example by a whipping tool as described in other embodiments herein. The anode cell can also be filled with electrolyte, which flows continuously over the ends of the side walls of the anode cell 10 and is collected in a separate electrolyte collection cell. From this cell, the electrolyte can be pumped back into the anodic cell 10, thus ensuring continuous renewal of the anodized surface, i.e. the wet electrode. In this example, the cathodic cell contains a surface electrode as the cathode. The anode is the common electrode. Any other electrode configuration can be used as the cathode and anode in this embodiment.

[0068] The substrate is moved over the elongated rectangular processing area 100 by a lateral movement superimposed by a rotation of the substrate about its own axis. This can be done by using a handling arm of the transport means, which holds the substrate, for example by vacuum suction. Since the anodes and electrodes are in the anodic and cathodic chambers, no electrical connection of the substrate to the transport means is necessary, and the holding arm can move freely, allowing the substrate to be rotated freely. An exemplary direction of movement is shown on the left side of the device in FIG. 3.

[0069] While the wafer moves linearly over the processing region 100, the portion of the substrate surface in contact with the anodic electrolyte can be pre-charged according to the size and arrangement of the anodic chambers 10, and at the same time, the porosification reaction occurs at the portion of the substrate surface in contact with the cathodic electrolyte. While the substrate moves over the anodic and cathodic chambers, all the portions of the substrate surface can be uniformly processed for a given processing time. The number and pattern and size of the anodic chambers can be adjusted for the required processing process. Similar current densities can be applied in this embodiment as in the other embodiments.

[0070] Referring now to FIG. 4, a schematic diagram of another embodiment of an apparatus 1 for electrochemically processing substrates, for example round wafers, is shown. In particular, the apparatus 1 is shown with a particular arrangement of an anodic chamber 10, a cathodic chamber 20, a separating means 30, a collecting chamber 40, electrodes 15, 25, and a processing area 100. Viewed from above, the surface area of ​​each of the anodic chamber 10 and the cathodic chamber 20 can be shaped like a crescent. In this example, two crescent-shaped chambers 10, 20 are arranged side by side on one side, resulting in an overall elliptical or oblong surface area. The total surface area of ​​the two chambers 10, 20 is the processing area 100. The anodic chamber 10 and the cathodic chamber 20 are arranged side by side on their straight sides and are separated by a separating means 30 arranged between the two chambers 10, 20. In this example, the separating means is an air knife, where an air stream flows continuously from the bottom to the top side of the separating means, thus preventing the two wet electrolytes from contacting each other.

[0071] A recovery tank 40 is provided around the anode tank 10, the cathode tank 20, and the separation means 30 to receive and recover the wet electrolyte that flows over the tank walls of the anode tank 10 and the cathode tank 20. The recovered wet electrolyte is continuously pumped back to the anode tank 10 and the cathode tank 20 to keep it in a constant surface state for electrochemical processing. A pump for pumping the electrolyte, a power supply means, and a transport means for transporting a substrate above the processing region 100 and contacting its surface with the wet electrolyte are not shown.

[0072] Additionally, disposed within the anodic and cathodic chambers 10 and 20 are an anode 15 and a cathode 25, respectively. These electrodes 15, 25 may be juxtaposed adjacent a separating means 30 within the chambers 10, 20, respectively, as shown in this example, but in other embodiments may be surface electrodes provided at the bottom of the chambers.

[0073] The processing region 100 is, in this example, larger than the wafer being processed. For a 200 mm wafer, the length of the processing region 100 can be at least 250 mm. In some examples, the length of the processing region can be 250-500 mm, for example, about 350 mm, at its shortest length.

[0074] The device with the anodic and cathodic chambers 10 and 20 has a total processing area 100 divided into two similar processing zones, the anodic and cathodic processing zones. A separating means 30 is located between the two chambers, electrically separating the anodic and cathodic chambers. To electrically connect the substrate surfaces to be processed, an electrolyte, i.e. a generally HF-based electrolyte containing at least about 15% ethanol, for example 30-60% ethanol, more particularly about 50% ethanol, can be pumped into the respective chambers from the bottom of the anodic and cathodic chambers. The upper ends of the above chambers are open, and as the electrolyte is continuously pumped into the chambers, it flows over the walls of the chamber and is collected in a collection chamber 40.

[0075] A substrate, for example a round wafer, is transported over the processing area by a transport means in the form of a holding arm (not shown). Since the processing area 100 is larger than the wafer substrate, only a portion of the substrate surface is precharged, i.e. a positive potential is applied, when it comes into contact with the anode wet electrode. The portion of the substrate surface that comes into contact with the cathode wet electrode will be processed due to the current. At said portion of the substrate surface, an electrochemical process will be induced at the substrate surface. During the translational movement over the processing area, the portion of the substrate surface previously precharged is moved into the cathode bath and its processing area. At this position, said portion of the substrate surface that is now in contact with the cathode wet electrode is in position to induce an electrochemical process at the substrate surface. In this case, the surface of the semiconductor wafer is made porous according to the applied current density. The next cycle on this portion of the substrate surface is carried out as soon as the substrate is moved over the next portion of the anode bath 10. To prevent a direct electrical current between the anode 15 and the cathode 25, the substrate surface is struck, for example, by a lip (not shown) of the separating means 30 directed at the substrate surface between the anode and cathode chambers, or by an air flow directed upwards from the bottom of the separating means 30 to the substrate surface. In some embodiments, only a lip or an air knife system is used as the separating means. This cycle of precharging and treatment steps is carried out continuously during the lateral and / or rotational movement of the substrate surface above the processing region 100. In order to generate a more homogeneous processing reaction, it is possible to move the substrate in a linear translational motion or in a swinging motion simultaneously with the rotational movement of the substrate above the processing region 100.

[0076] In the processing area 100 shown in FIG. 1, the anodic chamber 10 and the cathodic chamber 20 have approximately the same surface area. It is therefore possible to carry out a process in which the anodic and cathodic processing areas are changed by using a direct current with alternate polarity pulses. In this case, the anodic chamber 10 contains the anode 15, and in the next pulse, the cathodic chamber 20 contains the cathode 25. The use of this alternating direct current can reduce problems caused by gaseous products that are generated during the electrochemical process. Gas bubbles can cause problems also known as gas-solid intermediate diffusion problems. If the reaction is temporarily alternated, the generation of gas bubbles in the pores and on the substrate surface can be reduced. In this way, the use of a pulsed direct current can achieve more advanced electrochemical processes.

[0077] If the surface area of ​​one of the cells is significantly larger, the use of pulsed DC may not improve the treatment results since the pre-charging and treatment processes are related to the surface area of ​​each treatment area. If the anodic and cathodic treatment areas are too different from each other, the positive effect on reducing bubbles may be reduced, and the effective treatment yield may be reduced at the same time. Therefore, it is preferable to use anodic and cathodic cells with similar treatment surface areas, such as the embodiment shown in FIG. 4.

[0078] 5, there is shown a schematic diagram of a further embodiment of an apparatus 1 for electrochemically processing substrates, such as round wafers. In particular, the apparatus 1 is shown with a particular arrangement of an anodic reservoir 10, a cathodic reservoir 20, a separating means 30, a collecting reservoir 40, electrodes 15, 25 and a processing region 100. All of these devices are similar or identical to those described in the embodiment shown in FIG.

[0079] However, in this embodiment, each of the anodic and cathodic chambers 10 and 20 contains more than one electrode 15, 25. In some different embodiments, only one of the anodic and cathodic chambers 10 and 20 contains more than one electrode 15, 25, while the other of the anodic and cathodic chambers 10 and 20 contains exactly one electrode 15, 25. In the embodiment depicted in FIG. 5, four electrodes, in particular two anodes 15 and two cathodes 25, are arranged inside the anodic and cathodic chambers 10 and 20, respectively. In this example, two anodes 15 and two cathodes 25 are provided in each chamber in the center of the processing area 100. In other embodiments, three anodes 15 and three cathodes 25 or more than three anodes 15 and cathodes 25 may be provided, in particular according to a circular arrangement in the center of the processing area 100. That is, the anodes 15 and the cathodes 25 may together describe a circle.

[0080] The electrodes 15, 25 may be arranged in an array within the cell as shown in this example, but in other embodiments may be arranged asymmetrically or as surface electrodes provided at the bottom of the cell. The symmetric arrangement of the anode 15 and cathode 25, particularly near the separator means, allows the use of reverse pulse application, since in this case the respective electrodes are advantageously masked most of the time during the electrochemical treatment of the substrate surface.

[0081] A substrate, for example a round wafer, is transported over the processing area by a transport means in the form of a holding arm (not shown) and an electrochemical process is carried out as described for the embodiment shown in FIG.

[0082] In this embodiment, a part of the anodic processing area of ​​the anodic cell 10 and a part of the cathodic processing area of ​​the cathodic cell 20 are covered on their surfaces by the processing area cover means 50. The processing area cover means can be provided on the outer periphery of the crescent-shaped anodic cell 10 and the crescent-shaped cathodic cell 20. In the center of the processing area 100, a circular hole exists in the two processing area cover means provided on the anodic cell 10 and the cathodic cell 20, respectively. Thus, the anode 15 and the cathode 25 are not covered by the processing area cover means 50. The processing area cover means generally reduces the evaporation of the wet electrolyte during the processing action. Furthermore, the processing area cover means can improve the guidance of the gas bubbles generated during the electrochemical processing process on the substrate surface to the outer periphery of the anodic cell 10 or the cathodic cell 20. At the same time, the processing area cover means can shield the active processing area 100, and thus improve the uniformity of the current flow from the wet electrolyte to the substrate.

[0083] In the processing area 100 shown in FIG. 1, the anodic chamber 10 and the cathodic chamber 20 have approximately the same surface area. It is therefore possible to carry out a process in which the anodic and cathodic processing areas are changed by using a direct current with alternate polarity pulses. In this case, the anodic chamber 10 contains the anode 15, and in the next pulse, the cathodic chamber 20 contains the cathode 25. The use of this alternating direct current can reduce problems caused by gaseous products that are generated during the electrochemical process. Gas bubbles can cause problems also known as gas-solid intermediate diffusion problems. If the reaction is temporarily alternated, the generation of gas bubbles in the pores and on the substrate surface can be reduced. In this way, the use of a pulsed direct current can achieve more advanced electrochemical processes.

[0084] If the surface area of ​​one of the cells is significantly larger, the use of pulsed DC may not improve the treatment results since the pre-charging and treatment processes are related to the surface area of ​​each treatment area. If the anodic and cathodic treatment areas are too different from each other, the positive effect on reducing bubbles may be reduced, and the effective treatment yield may be reduced at the same time. Therefore, it is preferable to use anodic and cathodic cells with similar treatment surface areas, such as the embodiment shown in Figure 5.

[0085] Referring now to Figure 6, a cross-sectional view of a half-cell of the exemplary embodiment shown in Figure 5 is shown in more detail. The cross-sectional view is taken perpendicular to the separating means 30, at the centre of the device 1. In Figure 6, the cathode cell 20 is shown, including a cathode 25 (in this embodiment only one of the electrodes is shown in cross-section) and a processing area cover means 50.

[0086] Referring now to Figure 7, cross-sectional views of four different alternatives of the half-cell portion of an exemplary embodiment of the present application are shown. All four alternatives show the same common configuration of electrodes 25 and processing area covering means 50 as the embodiment shown in Figure 6. Additionally, the cathode cell in the embodiment shown in Figure 7A includes a horizontal current baffle 60, which covers the open processing area not covered by the processing area covering means 50. The current baffle 60 is made of a net of polymeric material with low electrical conductivity.

[0087] In the example shown in Figure 7B, the cathode chamber 20 includes a current baffle 60 that extends from the end of the treatment area cover means 50 to the wall of the cathode chamber 20 close to the side of the separation means (not shown). The current baffle 60 in this example is in an inclined position in the treatment area, with one end attached to the wall of the cathode chamber at a height of up to 50% of the height of the cathode chamber 20 below the surface area of ​​the wet electrolyte. The angle of inclination can be adapted according to the need to deflect or guide the movement of the current generated by the electrodes into the wet electrolyte in order to match the current density of the wet electrolyte in each chamber.

[0088] In the examples shown in Figures 7C and 7D, the current baffle 60 is inclined in another direction compared to the example shown in Figure 7B and is attached to the wall of the cathode chamber 20 closer to the surface of the wet electrolyte. In this case, the current baffle will go deeper below the electrolyte surface and protrude into the cathode chamber 20. The end may be located below the edge of the treatment area cover means 50 when viewed from above. In the example shown in Figure 7D, the current baffle extends over the entire cathode chamber 20. The current baffle may for example be attached to a mounting means extending from the bottom of the cathode chamber and screwed to said mounting means.

[0089] Of course, current baffles can be provided in the first cell and in the second cell, and therefore the embodiments shown in Figures 7A-7D for the cathodic cell can be simultaneously implemented in the anodic cell in the same or similar manner.

[0090] As used herein, the terms "having," "containing," "including," "comprising," and the like are open ended terms indicating the presence of stated elements or features, but do not exclude additional elements or features. The articles "a," "an," and "the" are intended to include the plural and the singular unless the context clearly indicates otherwise.

[0091] It should be understood that features of the various embodiments described herein may be combined with one another unless otherwise specified. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that various alternative and / or equivalent embodiments may be substituted for the specific embodiments and examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or modifications of the specific embodiments described herein. Accordingly, it is intended that the present disclosure be limited only by the claims and the equivalents thereof, examples of which are set forth below.

[0092] Example 1: 1. An apparatus for electrochemical processing of a semiconductor substrate, comprising: a first vessel filled with an electrolyte and including a first electrode; a second vessel filled with an electrolyte and including a second electrode; a separation unit for electrically isolating a first reservoir containing its own electrolyte from a second reservoir containing its own electrolyte; a power source connected to the first electrode and the second electrode; A transport means, comprising: a transport means configured to transport the substrate over the first and second tanks such that the surface of the substrate to be treated is in direct contact with the electrolyte filled in the first tank or with the electrolyte filled in the second tank, thereby causing a charge transfer between the first electrode and the substrate, and between the substrate and the second electrode, resulting in an electrochemical treatment of the surface of the substrate; Equipped with An apparatus for electrochemical processing of semiconductor substrates, wherein the first tank or the second tank, or the first tank and the second tank, have a spiral shape when viewed from above, and the first tank and the second tank are configured so as to be at least partially intertwined with each other.

[0093] Example 2: 2. An apparatus for electrochemical processing of semiconductor substrates as described in example 1, wherein, when viewed from above, at least one of the first reservoir or the second reservoir extends spirally outward from a center of the apparatus.

[0094] Example 3: 3. An apparatus for electrochemical processing of semiconductor substrates as described in example 2, wherein the first reservoir or the second reservoir spirals outward from the center, dividing the apparatus into two separate regions in a spiral shape when viewed from above.

[0095] Example 4: 1. An apparatus for electrochemical processing of a semiconductor substrate, comprising: at least one first reservoir filled with an electrolyte, each reservoir including a first electrode; at least one second reservoir filled with an electrolyte and each reservoir including a second electrode; a separation unit for electrically isolating at least one first reservoir containing its own electrolyte from at least one second reservoir containing its own electrolyte; a power source connected to the at least one first electrode and the at least one second electrode; a processing area having a circular shape in a top view, the processing area including at least one first tank and at least one second tank; A transport means, comprising: transport means arranged to transport the substrate over the first and second tanks in such a way that the surface of the substrate to be treated is in direct contact with at least one of the electrolytes filled in the at least one first tank or the electrolytes filled in the at least one second tank, thereby allowing charge transfer between the first electrode and the substrate and between the substrate and the second electrode, resulting in electrochemical treatment of the surface of the substrate; 1. An apparatus for electrochemical processing of a semiconductor substrate comprising:

[0096] Example 5: two or more first tanks, the first tanks being disposed within separate sectors of the treatment area; 5. An apparatus for electrochemical processing of semiconductor substrates as described in example 4, wherein the second tank is disposed between adjacent ones of the first tanks and separated from the first tanks by a separation unit.

[0097] Example 6: 6. An apparatus for electrochemical processing of semiconductor substrates as described in embodiment 4 or 5, wherein the first tanks in separate sectors of the processing area are arranged in a ring shape with n-fold rotational symmetry within the processing area.

[0098] Example 7: An apparatus according to any one of Examples 4 to 6, wherein the first tank in the first sector has a smaller surface area than the first tank in the second sector, and optionally the surface area of ​​the first tank in the third sector and further sectors is larger than the surface area of ​​the first tank in the second sector.

[0099] Example 8: The apparatus of Example 7, wherein the first tank in each sector has a triangular or sector shape, the side walls of which extend variously from the outer edge of the processing area of ​​the apparatus, and are aligned such that the tip of the tank is positioned on a spirally formed line extending from the center of the bottom plane of the apparatus.

[0100] Example 9: 1. An apparatus for electrochemical processing of a semiconductor substrate, comprising: a plurality of first reservoirs filled with an electrolyte, each reservoir including a first electrode; a second vessel filled with an electrolyte and including a second electrode; a separation unit for electrically isolating a plurality of first reservoirs containing their own electrolyte from a second reservoir containing their own electrolyte; a power source connected to the plurality of first electrodes and the second electrode; A transport means, comprising: a transport means configured to transport a substrate over the plurality of first and second tanks such that the surface of the substrate to be treated is in direct contact with the electrolyte filled in the first tank or with the electrolyte filled in the second tank, thereby causing charge transfer between the first electrode and the substrate and between the substrate and the second electrode, resulting in electrochemical treatment of the surface of the substrate; Equipped with An apparatus for electrochemical processing of a semiconductor substrate, comprising a plurality of first chambers disposed within a second chamber.

[0101] Example 10: 9. An apparatus for electrochemical processing of a semiconductor substrate as described in example 8, wherein the first chamber has a circular shape.

[0102] Example 11: 10. An apparatus for electrochemical processing of a semiconductor substrate according to any one of embodiments 8 or 9, wherein the first reservoirs are arranged in a dot pattern within the second reservoir.

[0103] Example 12: 12. An apparatus for electrochemical processing of a semiconductor substrate according to any one of Examples 9 to 11, wherein the first electrode or the second electrode is a surface electrode.

[0104] Example 13: the first cell is an anodic cell, the first electrode is an anode, the second cell is a cathodic cell, and the second electrode is a cathode; or An apparatus for electrochemical processing of semiconductor substrates as described in any one of Examples 9 to 12, wherein the first chamber is a cathodic chamber, the first electrode is a cathode, the second chamber is an anodic chamber, and the second electrode is an anode.

[0105] Example 14: 14. An apparatus for electrochemical processing of semiconductor substrates according to any one of Examples 9 to 13, wherein, viewed from above, the processing area of ​​the first tank is similar to the processing area of ​​the second tank.

[0106] Example 15: An apparatus for electrochemical processing of a semiconductor substrate as described in any one of Examples 9 to 14, wherein the transport means is configured to rotate the substrate about its axis and move the substrate laterally over the first tank and the second tank.

[0107] Example 16: 16. An apparatus for electrochemical processing of a semiconductor substrate as described in embodiment 15, wherein the lateral movement is a translational movement of the substrate in a plane parallel to the planes of the first and second reservoirs.

[0108] Example 17: 17. An apparatus for electrochemical processing of a semiconductor substrate according to embodiment 15 or 16, wherein the lateral movement comprises an eccentric movement of the substrate in a plane parallel to the planes of the first and second vessels.

[0109] Example 18: A process for electrochemically treating a semiconductor substrate using an apparatus according to any one of the preceding embodiments, comprising a step of transporting the substrate over a first tank and a second tank, the transport means being configured such that a surface of the substrate to be treated is in direct contact with at least one of an electrolyte filled in the first tank and an electrolyte filled in the second tank, thereby causing charge transfer between the first electrode and the substrate, and between the substrate and the second electrode, resulting in electrochemical treatment of the surface of the substrate.

[0110] Example 19: The process described in Example 18 for rendering a semiconductor substrate porous.

[0111] Example 20: 20. The process of example 18 or 19, wherein the power supply provides pulses of direct current power having alternating polarities with each pulse.

Claims

1. Apparatus for electrochemical processing of semiconductor substrates, A first tank filled with an electric field material, each containing at least one first electrode, The system comprises at least one second tank, each filled with an electric field material and containing at least one second electrode, A separation unit electrically separates the at least one first tank containing its own electrolyte from the at least one second tank containing its own electrolyte, A power supply connected to the at least one first electrode and the at least one second electrode, A transfer means configured for transferring the substrate over the first and second tanks such that the surface of the substrate to be processed comes into direct contact with at least one of the electric field material filled in the at least one first tank and the electric field material filled in the at least one second tank, thereby causing charge transfer between the at least one first electrode and the substrate, and between the substrate and the at least one second electrode, resulting in electrochemical treatment of the surface of the substrate. A controller for controlling the transfer means such that, for most of the time during the electrochemical treatment of the surface of the substrate while the substrate is being transferred over the first and second tanks, the substrate is masked from above by at least one first electrode and / or at least one second electrode. An apparatus for electrochemical processing of semiconductor substrates, equipped with [a specific feature / equipment].

2. The apparatus according to claim 1, further comprising a processing area including the at least one first tank and the at least one second tank, wherein the processing area has a circular, elliptical, or oblong shape when viewed from above.

3. The apparatus according to claim 2, wherein the processing area, which includes the at least one first tank and the at least one second tank, has an elliptical or oblong shape when viewed from above, and the at least one first electrode and / or the at least one second electrode are positioned in a circular arrangement within the processing area.

4. The apparatus according to claim 2 or 3, further comprising, when viewed from above, a processing area covering means for reducing the active processing area.

5. The apparatus according to any one of claims 1 to 3, wherein the controller is adjusted to turn off at least a portion of the first electrode and / or the second electrode selected from the at least one first electrode and the at least one second electrode.

6. The apparatus according to any one of claims 1 to 3, further comprising a current baffle in at least a portion of the processing area including the at least one first electrode and the at least one second electrode.

7. The apparatus according to claim 6, wherein the current baffle is a perforated sheet.

8. The system comprises two or more first tanks, the first tanks being arranged within separate fan-shaped areas of the processing region. The apparatus according to any one of claims 1 to 3, wherein a second tank is positioned between adjacent first tanks and is separated from the first tanks by the separation unit.

9. The apparatus according to claim 8, wherein the first tanks in the separate fan-shaped regions of the processing area are arranged in a ring shape within the processing area with n-fold rotational symmetry.

10. The apparatus according to any one of claims 1 to 3, wherein the first electrode or the second electrode is a surface electrode.

11. The first tank is an anode tank, the first electrode is an anode, the second tank is a cathode tank, the second electrode is a cathode, or The apparatus according to any one of claims 1 to 3, wherein the first tank is a cathode tank, the first electrode is a cathode, the second tank is an anode tank, and the second electrode is an anode.

12. The apparatus according to any one of claims 1 to 3, wherein, when viewed from above, the processing area of ​​the first tank is the same as the processing area of ​​the second tank.

13. The apparatus according to any one of claims 1 to 3, wherein the transfer means is configured to rotate the substrate around its own axis and move the substrate laterally over the first and second tanks.

14. The apparatus according to claim 13, wherein the lateral movement is the translational motion of the substrate in a plane parallel to the planes of the first and second tanks.

15. The apparatus according to claim 13, wherein the lateral movement includes eccentric motion of the substrate in a plane parallel to the planes of the first and second tanks.

16. A process for electrochemically treating a semiconductor substrate using the apparatus according to any one of claims 1 to 3, comprising the step of transferring the substrate over a first tank and a second tank, wherein the transfer means is configured such that the surface of the substrate to be treated is in direct contact with at least one of the electrolytes filled in the first tank and the electrolytes filled in the second tank, thereby causing charge transfer between the first electrode and the substrate and between the substrate and the second electrode, resulting in electrochemical treatment of the surface of the substrate.

17. The process according to claim 16 for making a semiconductor substrate porous.

18. The process according to claim 16, wherein the power supply provides pulses of DC power having alternating different polarities in each pulse.

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