Patent Publication Number: US-2022216118-A1

Title: Methods and apparatus for test pattern forming and film property measurement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 16/820,447, filed Mar. 16, 2020, which claims priority benefit of U.S. Provisional Application No. 62/819,518, filed Mar. 16, 2019, and which is a continuation-in-part application of U.S. application Ser. No. 16/095,930, filed Oct. 23, 2018 (now U.S. Pat. No. 10,790,203, issued on Sep. 29, 2020), which is a national stage application under 35 U.S.C. § 371 of International Application No. PCT/US2017/029424, filed internationally on Apr. 25, 2017, which claims priority benefit of U.S. Provisional Application No. 62/458,490, filed Feb. 13, 2017, and U.S. Provisional Application No. 62/458,500, filed Feb. 13, 2017, and U.S. Provisional Application No. 62/494,177, filed Jul. 30, 2016, and U.S. Provisional Application No. 62/391,426, filed Apr. 29, 2016, and U.S. Provisional Application No. 62/391,331, filed Apr. 26, 2016. The contents of all of the above patent applications are incorporated by reference herein in their entirety for all purposes. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with Government support under 1632322 awarded by the National Science Foundation. The Government has certain rights to this invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention is in the field of thin film electrical characterization methods and apparatus. More particularly, the present invention provides methods and tools for electrical parameter measurement and depth profiling for thin layers used in semiconductor device structures. 
     BACKGROUND OF THE INVENTION 
     With the advancement of the semiconductor industry, electronic devices are getting more and more complex and they employ advanced semiconductor materials. To be able to develop and optimize such advanced devices, it is essential to measure the various electrical properties, such as mobility and carrier concentration of the layers within their structures accurately and rapidly. Some of the techniques that have been used to electrically characterize semiconductor layers include Spreading Resistance Profiling (SRP), four-point probe, Scanning Spreading Resistance Microscopy (SSRM), Secondary Ion Mass Spectrometry (SIMS), and Electrochemical Capacitance-Voltage profiling (ECV). 
     A wet technique for profiling an electrical parameter of a semiconductor layer was disclosed in U.S. Pat. 7,078,919. International application No PCT/US2017/029424 (Publication Number WO/2017/189582, titled “Methods and systems for material property profiling of thin films”) describes various embodiments to controllably oxidize or thin down a test region of a semiconductor layer using a solution or an etchant gas, and to measure electrical properties as the layer at the test region is thinned down. In some of the references cited above, a sample comprising a semiconductor layer to be characterized may have the semiconductor layer in the form of a test pattern. Therefore, the test pattern may have to be formed before the sample is introduced into the electrical characterization system. Typically, the test pattern may be formed using a photolithography step followed by a plasma etching step. This approach is time consuming and requires use of different types of equipment and multiple process steps such as resist dispensing, masking, light exposure, annealing, resist developing, rinsing, drying, etching, etc. There is a need to develop a simple, low cost and fast test pattern formation process and an integrated tool with ability to accept “blanket” samples (i.e. with no test pattern) of semiconductor layers for electrical characterization. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top (left) and cross-sectional (right) view of a layer to be electrically characterized, wherein the layer has a top surface and it is disposed over a substrate. 
         FIG. 1B  shows a pattern forming head of a test pattern generation apparatus, wherein the pattern forming head is pushed against the top surface of the layer of  FIG. 1A . 
         FIG. 1C  shows a test pattern formed by the pattern forming head of  FIG. 1B , wherein the test pattern may be electrically isolated from its surroundings by a trench (see structure [i]) or an insulating plug (see structure [ii]). 
         FIG. 1D  shows a method for electrical parameter depth profiling using a depth profiling nozzle and the test pattern formed as shown in  FIG. 1C . 
       FIG. 2  shows a three-dimensional side view and a cross-sectional bottom view of an exemplary pattern forming head. 
       FIG. 3  shows multi-function module of an integrated tool with capability for pattern making as well as electrical characterization. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1A ,  FIG. 1B , and  FIG. 1C  show a process sequence to form a test pattern comprising a section of a layer to be electrically characterized.  FIG. 1D  shows how an electrical parameter of the layer may be measured and depth profiled using the test pattern. Sketches on the left are top views and those on the right are cross sectional side views taken along line X-X shown in  FIG. 1A . 
       FIG. 1A  shows a stacked structure  200 , comprising a layer  201  to be electrically characterized. The layer  201  may be a semiconductor layer, which may be disposed on a substrate  202 . The substrate  202  may be a wafer. The layer  201  may comprise a top surface  201 A. There may be an insulating interface  203 , such as a rectifying junction or a thin insulator, between the layer  201  and the substrate  202 . The insulating interface  203  may electrically insulate the layer  201  from the substrate  202 . 
     In a preferred embodiment, as shown in  FIG. 1B , a pattern forming head  204  of a test pattern generation apparatus may be pushed against the top surface  201 A of the layer  201 . The pattern forming head  204  may comprise a test-pattern-shaped inner seal  205 , an outer seal  206  and a channel  207  encircling the test-pattern-shaped inner seal  205 . A larger cross-sectional view of the channel  207  is shown as an inset in  FIG. 1B . The channel  207  may have a width “W” and a height “h”. There may also be at least one channel electrode  208  that is exposed to the channel, in other words, configured to touch any fluid that may be introduced into the channel  207 . There may be one or more external contacts  209  outside the outer seal  206 . Although the one or more external contacts  209  may be moved independently from the pattern forming head  204 , they may preferably be attached to the pattern forming head  204  and configured to touch and establish electrical contact to the top surface  201 A when the pattern forming head  204  is pushed against the top surface  201 A by a first moving mechanism (not shown). Although, in the above example the pattern forming head  204  is pushed against the top surface  201 A by the first moving mechanism, it is also possible that the top surface  201 A is pushed against the pattern forming head  204 . Therefore, the first moving mechanism may provide relative motion between the pattern forming head  204  and the layer  201 . In the example of  FIG. 1B , there are eight external contacts  209  surrounding the outer seal  206 , and one channel electrode  208  in the form of a wire extending substantially the whole length of the channel  207 . The channel electrode  208  may preferably be placed in proximity of an upper wall of the channel  207 . As can be seen in the cross-sectional view of  FIG. 1B , when the pattern forming head  204  is pushed against the top surface  201 A of the layer  201 , the test-pattern-shaped inner seal  205  and the outer seal  206  may press against the top surface  201 A, forming a cavity  210 . The cavity  210  is enclosed by the channel  207  and a sacrificial portion  201 AA of the layer  201  that is exposed to the channel  207 . The cavity  210  may be leak-free. In other words, when a gas or liquid is introduced into the cavity  210  from a fluid supply unit (not shown), the gas or liquid may contact the top surface  201 A only at the sacrificial portion  201 AA, which encircles the test-pattern-shaped inner seal  205 , and is between the test-pattern-shaped inner seal  205  and the outer seal  206 . 
     After forming the cavity  210 , a first fluid may be introduced into the cavity  210  to convert the sacrificial portion  201 AA into an insulator by either removing it and forming a trench  221 , or transforming it into a very high resistivity or insulating plug  222  (see  FIG. 1C ). Both approaches may form an electrically isolated test pattern  220  under the test-pattern-shaped inner seal  205 . 
     As shown in  FIG. 1C , the first fluid may be used to form the test pattern  220  surrounded either by the trench  221  (structure [i]) or the insulating plug  222  (structure [ii]). It should be noted that in both structure [i] and structure [ii], the test pattern  220  may be electrically isolated from an outer portion  223  of the layer  201 , such isolation being provided by the insulating interface  203  and the trench  221  (in structure [i]) or the insulating plug  222  (in structure [ii]). 
     In one embodiment, the first fluid may comprise an etchant in the form of a gas that may form the trench  221  and yield the structure [i] of  FIG. 1C . In another embodiment the first fluid may comprise a first solution and the structure [i] may be produced in three different ways. In the first approach, the first solution may comprise a liquid etchant with the ability to etch and remove the sacrificial portion  201 AA of the layer  201  when it is introduced into the cavity  210 . In the second approach, the first solution may comprise an electrochemical etching liquid that may remove the sacrificial portion  201 AA by electrochemical etching when it is introduced into the cavity  210  and a potential difference is applied between the one or more external contacts  209  and the channel electrode  208 , preferably rendering the channel electrode  208  cathodic with respect to the one or more external contacts  209 . In the third approach, the first solution may comprise an electrochemical oxidation liquid that may oxidize, but not remove the sacrificial portion  201 AA when it is introduced into the cavity  210  and the potential difference is applied between the one or more external contacts  209  and the channel electrode  208 . Following this oxidation step the electrochemical oxidation liquid may then be taken out of the cavity  210  and an etchant may be brought in to chemically etch away the oxidized material, thus creating the trench  221 . In this third approach, if the layer  201  is thick (such as thicker than  100 nm) it is also possible to use multiple oxidation/chemical etching process sets, each process set removing only a slice of the sacrificial portion  201 AA until the structure [i] shown in  FIG. 1C  may be obtained. 
     In yet another embodiment, the structure [ii] may be produced if the first solution comprises the electrochemical oxidation liquid and the potential difference is applied between the one or more external contacts  209  and the channel electrode  208  rendering the channel electrode cathodic with respect to the one or more external contacts  209 . In this case, under the applied potential difference the sacrificial portion  201 AA may be transformed into the insulating plug  222 . 
     As can be seen from  FIG. 1C , the test pattern  220  may be in the form of a cross, defined by the test-pattern-shaped inner seal  205  of  FIG. 1B . The shape of a test pattern may be changed by selecting an inner seal with a desired shape, such as a square, a rectangle, a circle, a cloverleaf, among many other shapes. In a preferred embodiment the width “W” of the channel  207  may be smaller than 5 mm, preferably smaller than 3 mm and more preferably smaller than 2 mm. The height “h” of the channel  207  may be smaller than 8 mm, preferably smaller than 5 mm and more preferably smaller than 4 mm. A maximum lateral dimension of the test pattern  220  may be smaller than 15 m, preferably smaller than 10 m and most preferably smaller than 8 mm. The channel electrode  208  may comprise an inert material such as Pt. Although the channel  207  in the above example has a cross shape with uniform width “W”, and height “h”, the width as well as the height of a channel may be varied as will be seen in the example of FIG. 2 , which shows a round outer seal defining a variable channel width. 
     FIG. 2  shows a three-dimensional side view and a cross-sectional bottom view of an exemplary pattern forming head  204 A. As depicted in this figure, the exemplary pattern forming head  204 A may comprise a round outer seal  206 A circling a cross-shaped inner seal  205 A. There may be a fluid inlet  300  and a fluid outlet  301  connected to a fluid channel  207 A between the round outer seal  206 A and the cross-shaped inner seal  205 A. A first electrode  302  placed outside the round outer seal  206 A may be electrically connected to a first terminal  302 A. A second electrode  303  may be placed in the fluid channel  207 A, preferably close to the cross-shaped inner seal  205 A, and it may be electrically connected to a second terminal  303 A. The first electrode  302  and the second electrode  303  may serve purposes similar to the external contacts  209  and the channel electrode  208  shown in  FIG. 1B . During a pattern forming process, after the exemplary pattern forming head  204 A is pushed against a layer or film surface (not shown) which may also be contacted by the first electrode  302 , a fluid such as an electrochemical etching liquid or electrochemical oxidation liquid may be flown to the fluid channel  207 A through the fluid inlet  300  using a device such as a pump, and a potential may be applied between the first terminal  302 A and the second terminal  303 A to electrochemically remove or convert into an insulating plug, a portion of the film exposed to the fluid as described before in reference to  FIG. 1B  and  FIG. 1C . Alternately, as described before an etchant gas or liquid may be delivered to the fluid channel  207 A to chemically remove the portion of the film exposed to the fluid. This process may form a cross-shaped test pattern that is electrically isolated from its surroundings. 
     Once the test pattern  220  is formed, an electrical parameter of the layer  201  may be measured using the test pattern  220  which comprises a section of the layer  201 . The electrical parameter may be one of sheet resistance, mobility, resistivity and carrier concentration. For these measurements the test pattern  220  may be contacted by at least two electrical contacts. In the example shown in  FIG. 1D , four electrical contact elements  230 A,  230 B,  230 C and  230 D are applied to or pushed onto contact regions  240  of the test pattern  220  by a measurement head (not shown). The contact elements may be spring loaded contact pins. Contact regions  240  may be at predetermined locations on the test pattern  220 . The electrical contact elements  230 A,  230 B,  230 C and  230 D may preferably be attached to the measurement head and configured to touch the test pattern  220  at contact regions  240  when the measurement head and the test pattern  220  are brought close to each other. An electrical parameter may then be measured by techniques that involve passing a first set of test currents between the contact regions  240 . Such techniques include Van der Pauw and Hall effect measurements. 
     As will be further discussed in relation with FIG. 3  it is preferable to carry out the test pattern formation and electrical characterization steps sequentially in an integrated tool comprising a test pattern generation apparatus, a measurement head, and electronics for electrical characterization steps. The test pattern generation apparatus may comprise a pattern forming head, a holder to hold a substrate comprising a layer to be processed, a supply unit providing various fluids used, a computer, an optional power supply and a first moving mechanism to provide relative motion between the holder and the pattern forming head so that the pattern forming head may be pushed against a top surface of the layer to be processed. The integrated tool may further comprise a second moving mechanism to provide relative motion between the holder and the measurement head so that the test pattern formed by the test pattern generation apparatus may be contacted by electrical contact elements of the measurement head to carry out electrical measurements. The integrated tool may also comprise a third moving mechanism to provide relative motion between the holder, the pattern forming head and the measurement head. Although the holder, the pattern forming head, and the measurement head may all be moved independently, it is preferred that either the pattern forming head and the measurement head are stationary and the holder is moved, or the holder is stationary and the pattern making head and the measurement head are moved together. In other words, the pattern making head and the measurement head may be at fixed locations with respect to each other and the only relative motion between them may be the motion provided by the first moving mechanism and the second moving mechanism. This relatively small motion is in vertical direction shown by arrows in the example given in FIG. 3 . In a preferred embodiment positions of the pattern making head and the measurement head may be calibrated with respect to each other. Such calibration may be achieved by attaching the two heads to a rigid structure and adjusting and fixing their relative positions and orientations so that when a test pattern, such as the test pattern  220  is formed and then the measurement head is brought close to the test pattern  220  for electrical characterization, electrical contact elements of the measurement head may touch the test pattern  220  exactly at the predetermined contact regions  240 . 
     Referring back to  FIG. 1D  the test pattern  220  may also be used to depth profile the electrical parameter of the layer  201  after the electrical parameter is measured using the first set of test currents. In this case an open end of a depth profiling nozzle  235  may be sealed against the test pattern  220  such that a test region  236  on the test pattern  220  may be exposed to the open end. An elastomer seal  237  of the depth profiling nozzle  235  may seal around the test region  236  such that any fluid delivered by the depth profiling nozzle  235  may touch the test region  236 . The location of the test region  236  on the test pattern  220  may be configured such that the test region  236  is outside the contact regions  240  and all of an electrical current passing between contact regions  240  may pass through the test region  236 . It is preferred that electrical contact elements  230 A,  230 B,  230 C and  230 D and the depth profiling nozzle  235  are attached to the measurement head (not shown to simplify the drawing) and configured such that contacting the test pattern  220  with the electrical contact elements  230 A,  230 B,  230 C and  230 D at contact regions  240  also seals the open end of the depth profiling nozzle  235  against the test pattern  220 . The depth profiling nozzle  235  may deliver an electrolyte  238  onto the test region  236 . There may be a cathode  239  touching the electrolyte  238 . To reduce the thickness of the layer  201  at the test region  236 , a voltage may be applied between at least one of the electrical contact elements  230 A,  230 B,  230 C and  230 D, and the cathode  239  to etch, or convert into an insulating solid, a segment  250  of the layer  201  at the test region  236  of the test pattern  220 , thus forming a residual layer  251 . The electrical parameter of the residual layer  251  may then be measured by passing a second set of test currents between the contact regions  240 . Depth profiling the electrical parameter may be continued by repeating the thickness reduction and measurement steps until no residual layer is left. 
     The steps of test pattern formation shown in  FIG. 1A ,  FIG. 1B  and  FIG. 1C  may be carried out using a test pattern generation apparatus, and the electrical characterization steps described in reference to  FIG. 1D  may be carried out in a separate electrical characterization module comprising the measurement head. However, as discussed before, it is preferred that these steps are carried out in an integrated tool comprising the test pattern generation apparatus, the measurement head, electronics for electrical characterization steps, and moving mechanisms. The measurement head may optionally have a depth profiling capability as described in  FIG. 1D  to controllably reduce the thickness of the layer to be characterized at a test region. The layer to be characterized may be stationary during the test pattern formation and electrical characterization steps, and the pattern forming head and the measurement head may be moved over the layer sequentially to carry out the various steps described above. Although the first fluid employed in pattern formation and the electrolyte employed in depth profiling the electrical parameter may comprise different chemicals, it is preferred that the first fluid and the electrolyte are the same. 
     In a preferred embodiment of the present inventions an integrated tool may have a configuration partially depicted in FIG. 3 . Supply units providing fluids, optional power supply, electronics, etc. are not shown in this figure. In the exemplary configuration of FIG. 3 , which is shown in side view, a holder  390  may hold a sample  400  comprising a layer to be electrically characterized. The sample holder  390  may be stationary. There may be a carrier arm  402  tied to a precision linear actuator  401 . Components such as a microscope  404 , a pattern making head  405  (which may be similar to the pattern forming head  204  of  FIG. 1B  or the exemplary pattern forming head  204 A of FIG. 2 ) and a measurement head  406  may be attached to the carrier arm  402  via linear guides  403  that provide vertical motion. Mechanisms attaching these various components to the linear guides  403  may be configured with x-y translation and rotation capability so that relative positions and orientations of the components may be calibrated, adjusted and fixed. The precision linear actuator  401 may be used to move the carrier arm  402  horizontally along with the components attached to it. Linear guides  403  may move down and press the pattern making head  405  or the measurement head  406  onto the sample  400  with pre-set pressure values, when the sample  400  is under the pattern making head  405  or the measurement head  406 , but otherwise retract them up to a home position. The microscope may also be moved to above the sample  400  by the linear actuator  401 . The microscope  404  may be used for alignment of the sample  400  when required, and for inspection of the sample  400 , for example after formation of a test pattern from the layer to be electrically characterized. The microscope  404  may preferably be a digital type with the display located outside the integrated tool for easy view by an operator. There may be one or more auxiliary head(s)  407  attached to the carrier arm  402  to perform optional auxiliary processes or tests on the sample  400 . An auxiliary process may be, for example, a deposition process for conductive material deposition, such as metallic ink deposition, on contact regions on the test pattern formed. An auxiliary test may be for checking test pattern isolation to make sure the test pattern is well isolated from its surroundings. This may be a measurement of resistance between a contact region of the test pattern and a portion of the layer outside the test pattern. If the resistance is low the test pattern may be sent back to the pattern making head for further processing. As briefly discussed before, a benefit of the integrated tool described above is that the exact positions and orientations of the various heads may be carefully calibrated with respect to each other so that, for example, when a cross-shaped test pattern is formed by the pattern generating head  405  and the measurement head  406  is brought over and lowered onto the formed test pattern, electrical contact elements attached to the measurement head may touch the test pattern exactly at the contact regions located at the end of the four arms of the cross, and an optional depth profiling nozzle of the measurement head seals against the test pattern at the exact predetermined location of a test region. These factors improve the speed and accuracy of the electrical measurements. 
     Therefore, according to the above, some examples of the disclosure are directed to a method for electrically characterizing a layer disposed on a substrate and electrically insulated from the substrate, the said method comprising: forming a test pattern; contacting the test pattern with electrical contact elements at contact regions; and measuring an electrical parameter of the layer by passing a first set of test currents between contact regions, wherein forming the test pattern comprises: pushing a pattern forming head against a top surface of the layer, the pattern forming head comprising a test-pattern-shaped inner seal, an outer seal, and a channel between the outer seal and the test-pattern-shaped inner seal, wherein pushing the patter forming head against the top surface forms a cavity enclosed by the channel and a sacrificial portion of the layer; introducing a first fluid into the cavity, and converting the sacrificial portion of the layer into an insulator using the first fluid and forming the test pattern under the test-pattern-shaped inner seal, wherein the test pattern is electrically isolated from an outer portion of the layer that lies outside the outer seal. Additionally or alternatively to one or more of the examples above, in some examples, converting the sacrificial portion of the layer into an insulator comprises removing the sacrificial portion of the layer by the first fluid and forming a trench. Additionally or alternatively to one or more of the examples above, in some examples, removing the sacrificial portion of the layer comprises applying a potential difference between an external contact touching the top surface outside the outer seal and a channel electrode configured to touch the first fluid. Additionally or alternatively to one or more of the examples above, in some examples, the external contact is attached to the pattern forming head and configured to touch the top surface when the pattern forming head is pushed against the top surface of the layer forming the cavity. Additionally or alternatively to one or more of the examples above, in some examples, the method further comprises depth profiling the electrical parameter, said depth profiling comprising: sealing an open end of a depth profiling nozzle against the test pattern such that a test region on the test pattern is exposed to the open end; delivering an electrolyte onto the test region through the open end after measuring the electrical parameter of the layer; reducing the thickness of the layer at the test region thus forming a residual layer by applying voltage between a cathode touching the electrolyte and at least one of the electrical contact elements, and measuring the electrical parameter of the residual layer by passing a second set of test currents between contact regions, wherein the electrical contact elements and the depth profiling nozzle are attached to a measurement head, and wherein contacting the test pattern with electrical contact elements at contact regions also seals the open end of the depth profiling nozzle against the test pattern. Additionally or alternatively to one or more of the examples above, in some examples, forming the test pattern and depth profiling the electrical parameter are carried out sequentially in an integrated tool comprising the pattern forming head, the measurement head, a holder holding the substrate, and a moving mechanism providing relative motion between the holder and the two heads. Additionally or alternatively to one or more of the examples above, in some examples, the first fluid and the electrolyte are the same. Additionally or alternatively to one or more of the examples above, in some examples, converting the sacrificial portion of the layer into an insulator comprises: applying a potential difference between an external contact touching the top surface outside the outer seal and a channel electrode configured to touch the first fluid, and transforming the sacrificial portion of the layer into an insulating plug. Additionally or alternatively to one or more of the examples above, in some examples, the external contact is attached to the pattern forming head and configured to touch the top surface when the pattern forming head is pushed against the top surface forming the cavity. Additionally or alternatively to one or more of the examples above, in some examples, the method further comprises depth profiling the electrical parameter, said depth profiling comprising: sealing an open end of a depth profiling nozzle against the test pattern such that a test region on the test pattern is exposed to the open end; delivering an electrolyte onto the test region through the open end after measuring the electrical parameter of the layer; reducing the thickness of the layer at the test region thus forming a residual layer by applying voltage between a cathode touching the electrolyte and at least one of the electrical contact elements, and measuring the electrical parameter of the residual layer by passing a second set of test currents between contact regions, wherein the electrical contact elements and the depth profiling nozzle are attached to a measurement head, and wherein contacting the test pattern with electrical contact elements at contact regions also seals the open end of the depth profiling nozzle against the test pattern. Additionally or alternatively to one or more of the examples above, in some examples, applying the voltage between the cathode and at least one of the electrical contact elements converts a segment of the layer at the test region into an insulating solid. Additionally or alternatively to one or more of the examples above, in some examples, forming the test pattern and depth profiling the electrical parameter are carried out sequentially in an integrated tool comprising the pattern forming head, the measurement head, a holder holding the substrate, and a moving mechanism providing relative motion between the holder and the two heads. Additionally or alternatively to one or more of the examples above, in some examples, the first fluid and the electrolyte are the same. 
     Some examples of the disclosure are directed to a test pattern generation apparatus for forming a test pattern from a layer disposed on a substrate comprising: a supply unit providing a fluid; a pattern forming head comprising a test-pattern-shaped inner seal, an outer seal, and a channel between them; a holder to hold the substrate; a first moving mechanism providing relative motion between the holder and the pattern forming head so that the pattern forming head may be pushed against a top surface of the layer to form a cavity enclosed by the channel and a sacrificial portion of the layer; and a fluid inlet configured to deliver the fluid from the supply unit to the channel to convert the sacrificial portion of the layer into an insulator, forming the test pattern. Additionally or alternatively to one or more of the examples above, in some examples, the test pattern generation apparatus further comprises a channel electrode; one or more external contacts; and a power supply connected between the channel electrode and one or more external contacts, wherein the channel electrode is configured to touch the fluid delivered by the fluid inlet, and wherein one or more external contacts are attached to the pattern forming head and configured to touch the top surface of the layer outside the outer seal when the pattern forming head is pushed against the top surface forming the cavity. 
     Some examples of the disclosure are directed to an integrated tool for forming a test pattern from a layer disposed on a substrate and electrically characterizing the said layer, the tool comprising: a supply unit providing a fluid; a pattern forming head comprising a test-pattern-shaped inner seal, an outer seal, and a channel between them; a holder to hold the substrate; a first moving mechanism providing relative motion between the holder and the pattern forming head so that the pattern forming head may be pushed against a top surface of the layer to form a cavity enclosed by the channel and a sacrificial portion of the layer; a fluid inlet configured to deliver the fluid from the supply unit to the channel to convert the sacrificial portion of the layer into an insulator, forming the test pattern; a measurement head comprising electrical contact elements; and a second moving mechanism configured to provide relative motion between the holder and the measurement head so that the electrical contact elements can touch the test pattern at predetermined contact regions. Additionally or alternatively to one or more of the examples above, in some examples, the integrated tool further comprises: a channel electrode; one or more external contacts; and a power supply connected between the channel electrode and one or more external contacts, wherein the channel electrode is configured to touch the fluid delivered by the fluid inlet, and wherein one or more external contacts are attached to the pattern forming head and configured to touch the top surface of the layer outside the outer seal when the pattern forming head is pushed against the top surface forming the cavity. Additionally or alternatively to one or more of the examples above, in some examples, the integrated tool further comprises a source to provide an electrolyte; a depth profiling nozzle attached to the measurement head and having capacity to deliver the electrolyte to its open end, wherein the open end is configured to seal against the test pattern at a test region when the electrical contact elements touch the test pattern at predetermined contact regions; a cathode configured to touch the electrolyte; and a power source capable of applying a voltage between the cathode and at least one of the electrical contact elements. Additionally or alternatively to one or more of the examples above, in some examples, the integrated tool further comprises an auxiliary process head for depositing a conductive material on contact regions of the test pattern. Additionally or alternatively to one or more of the examples above, in some examples, the integrated tool further comprises an auxiliary test head for checking test pattern isolation by measuring a resistance between the teat pattern and a portion of the layer outside the test pattern. 
     Although the foregoing description has shown, illustrated and described various embodiments of the present invention, it will be apparent that various substitutions, modifications and changes to the embodiments described may be made by those skilled in the art without departing from the spirit and scope of the present inventions.