Method and arrangement for analyzing a semiconductor element and method for manufacturing a semiconductor component

Abstract

According to the improved concept, a method for analyzing a semiconductor element comprising polymer residues located on a surface of the semiconductor element is provided. The method comprises marking at least a fraction of the residues by exposing the semiconductor element to a fluorescent substance and detecting the marked residues by visualizing the marked residues on the surface of the semiconductor element using fluorescence microscopy.

Claims

1. An arrangement for analyzing a semiconductor element comprising polymer residues located on a surface, the arrangement comprising: a pressure chamber configured to receive the semiconductor element; a mixing chamber configured to generate a mixture containing liquid carbon dioxide and a fluorescent substance within the mixing chamber; a feed line connecting the mixing chamber and the pressure chamber via an intake valve to supply the mixture to the pressure chamber; a control unit configured to control a pressure and a temperature inside the pressure chamber and the intake valve to expose the semiconductor element to the mixture until the fluorescent substance is affixed to at least a fraction of the residues; and a fluorescence microscope configured to visualize the residues to which the fluorescent substance is affixed.

2. The arrangement according to claim 1, wherein the fluorescence microscope is configured to visualize the marked residues while the semiconductor element is located inside the pressure chamber.

3. An arrangement for analyzing a semiconductor element comprising polymer residues located on a surface, the arrangement comprising: a pressure chamber configured to receive the semiconductor element; a mixing chamber configured to generate a mixture containing liquid carbon dioxide and a fluorescent substance within the mixing chamber; a feed line connecting the mixing chamber and the pressure chamber via an intake valve to supply the mixture to the pressure chamber; a control unit configured to control a pressure and a temperature inside the pressure chamber and the intake valve to expose the semiconductor element to the mixture until the fluorescent substance is affixed to at least a fraction of the residues; and a fluorescence microscope configured to visualize the fraction of the residues to which the fluorescent substance is affixed, while the semiconductor element is inside the pressure chamber.

Description

(1) In the drawings,

(2) FIG. 1 shows a flow chart representing an exemplary implementation of a method for analyzing a semiconductor element according to the improved concept;

(3) FIG. 2 shows a cross section of a semiconductor element and aspects of an exemplary implementation of a method for analyzing the semiconductor element according to the improved concept;

(4) FIG. 3 shows an image of a top view of a semiconductor element analyzed employing an exemplary implementation of a method for analyzing a semiconductor element according to the improved concept;

(5) FIG. 4 shows a pressure-temperature phase diagram of carbon dioxide;

(6) FIG. 5A shows a schematic representation of an exemplary implementation of an arrangement according to the improved concept;

(7) FIG. 5B shows a schematic representation of a further exemplary implementation of an arrangement according to the improved concept;

(8) FIG. 6A shows a further exemplary implementation of an arrangement according to the improved concept; and

(9) FIG. 6B shows a further exemplary implementation of an arrangement according to the improved concept.

DETAILED DESCRIPTION

(10) FIG. 1 shows a flow chart representing an exemplary implementation of a method for analyzing a semiconductor element according to the improved concept.

(11) According to block 110, a semiconductor element SE comprising polymer residues located on a surface of the semiconductor element is placed in a pressure chamber PC. In block 120, a mixture containing a fluorescent substance is supplied to the pressure chamber PC. In addition to the fluorescent substance, in the mixture comprises for example a solvent, for example carbon dioxide, in particular liquid carbon dioxide. The fluorescent substance is for example dissolved in the solvent. The fluorescent substance is for example implemented as a fluorescent dye, in particular an organic fluorescent dye. The organic fluorescent dye comprises for example an aromatic organic compound.

(12) As an alternative to supplying the mixture to the pressure chamber PC, the fluorescent substance and the carbon dioxide may be supplied to the pressure chamber PC separately. Then, the fluorescent substance is for example supplied to the pressure chamber PC in form of an additional mixture containing the fluorescent substance dissolved in additional solvent such as dimethyl sulfoxide, isopropyl alcohol or deionized water. The carbon dioxide may for example be supplied to the pressure chamber PC as gaseous, liquid or solid carbon dioxide. Then, the mixture, in particular the solution of the fluorescent substance in the carbon dioxide may be generated within the pressure chamber for example by evaporating the solid carbon dioxide.

(13) In optional block 130, the mixture is transferred from its liquid phase to its supercritical phase or close to its supercritical phase for example by increasing the temperature in the pressure chamber PC beyond or close to the critical temperature of carbon dioxide and/or by increasing the pressure in the pressure chamber PC beyond or close to the critical pressure of carbon dioxide. For further details it is referred to FIG. 4 and the corresponding description.

(14) According to block 140, the semiconductor element SE is exposed to the mixture and therefore to the fluorescent substance. In particular, the semiconductor element SE may be exposed to the mixture until the fluorescent substance is affixed to at least a fraction of the residues. Consequently, by exposing the semiconductor element SE to the mixture and the fluorescent substance, at least the fraction of residues, to which the fluorescent substance is affixed, is marked.

(15) By exposing the semiconductor element SE to the mixture, the mixture and consequently the fluorescent substance is for example brought into the polymer matrix of the residues. It may be particularly advantageous to use carbon dioxide in its supercritical phase, since a solubility of the fluorescent substance in the carbon dioxide may be increased and a surface tension of the mixture may be decreased in this way. Alternatively, the carbon dioxide may be used in its liquid phase, for example at a temperature and pressure close to the critical point. Also in this way, a sufficiently high solubility of the fluorescent substance and sufficiently low surface tension may be achieved. Consequently an increased amount of the fluorescent substance may be brought into the polymer matrix. In a sense, the residues are impregnated with the mixture in this way.

(16) When the semiconductor element is exposed to the mixture for affixing the fluorescent substance, a pressure inside the chamber is for example between 30 C. and 40 C., for example between 32 C. and 35 C. A pressure inside the chamber is then for example between 60 bar and 80 bar, for example between 60 bar and 70 bar.

(17) According to block 150, the mixture or the carbon dioxide is transferred to its gaseous phase for example by decreasing the temperature and/or the pressure inside the pressure chamber PC. The fluorescent substance affixed to the residues, however, remains affixed to the residues. The gaseous carbon dioxide may then be pumped down.

(18) In blocks 160 and 170, the marked residues are detected by visualizing the marked residues on the surface of the semiconductor using fluorescence microscopy. To this end, in block 160 at least a part of the semiconductor element is illuminated with electromagnetic radiation, for example with a fluorescence microscope, in particular a light source of the fluorescence microscope. In this way, the fluorescent substance affixed to at least the fraction of the residues is illuminated with the electromagnetic radiation and thus excited. The light source may for example be implemented as a laser, for example a helium-neon laser.

(19) The electromagnetic radiation used for illuminating the semiconductor element may have a wavelength matching or approximately matching an absorption wavelength of the fluorescent substance. Hence, by illuminating the fluorescent substance is transferred to an excited state. As a consequence, the fluorescent substance emits fluorescent electromagnetic radiation as a response to the illumination. In block 170, the fluorescent electromagnetic radiation is detected for example with the fluorescence microscope, in particular with a photosensitive device, for example a camera, of the fluorescence microscope.

(20) Based on the detected fluorescent radiation, for example images of the semiconductor element or of the marked residues may be generated. These images may for example be used to perform a statistical evaluation of the residues located the semiconductor element. In particular, a wafer map representing the residues may be generated based on the images.

(21) FIG. 2 shows a cross section of a semiconductor element and aspects of an exemplary implementation of a method for analyzing the semiconductor element according to the improved concept.

(22) The semiconductor element is for example a semiconductor wafer, in particular a semiconductor wafer at a certain stage of manufacturing. In FIG. 2, only a part of the semiconductor wafer may be shown. The semiconductor wafer comprises a semiconductor substrate SUB and an active layer stack AL arranged on the substrate SUB. In the shown example, the semiconductor element SE further comprises an optional handling wafer HW and an optional connecting layer CL connecting the handling wafer HW and the active layer stack AL. Using the handling wafer HW may be advantageous the substrate SUB is relatively thin at the corresponding stage of manufacturing. This may origin for example from a preceding wafer thinning step.

(23) The active layer stack AL comprises for example electronic components EC, which contains for example active circuitry such as transistor circuitry and/or CMOS circuitry. The active layer stack AL comprises for example metallization layers ML. The metallization layers ML may for example be electrically connected to at least some of the electronic components EC (connection not shown).

(24) The substrate SUB comprises through-semiconductor-vias, TSVs, in particular four TSVs S1, S2, S3, S4. The TSVs S1, S2, S3, S4 are for example connected to the metallization layers ML. The TSVs S1, S2, S3, S4 are for example intended for providing an electrical connection of the metallization layers ML to a back side metallization (not shown) on a back side BS of the substrate SUB. Therein, the back side BS of the substrate SUB corresponds to a side of the substrate SUB being opposed to the side of the substrate SUB facing the active layer stack AL. The back side BS also represents a back side of the wafer at the shown stage of manufacturing. For providing the electrical connection, a TSV-metallization layer (not shown) may be deposited on the sidewalls and/or the bottom of the TSVs S1, S2, S3, S4. In addition, a spacer layer (not shown), in particular a dielectric spacer layer, may be arranged between the TSV-metallization layer and the material of the substrate SUB. The spacer layer may for example comprise or consist of silicon dioxide.

(25) The semiconductor element SE further comprises for example polymer residues RB located on the back side BS and/or polymer residues RS located on a sidewall and/or a bottom of the second and the fourth TSVs S2, S4. It is highlighted that in FIG. 2 the specific locations of the polymer residues RB, RS are chosen exemplarily only. In particular, the semiconductor element SE may comprise polymer residues at additional and/or different positions, in particular on sidewalls and/or bottoms of the first and the third TSVs S1, S2.

(26) The TSVs S1, S2, S3, S4 are for example generated employing a deep reactive-ion etching, DRIE, process comprising a series of alternating etch and deposition cycles. During the deposition cycles, a polymer layer is deposited as a passivation layer covering the sidewalls or parts of the sidewalls of the TSVs S1, S2, S3, S4 to prevent from lateral etching during the etch cycles. After finishing all of the etch cycles, the polymer layer may be removed for example by using a cleaning process including ashing and/or wet cleaning steps using for example amine stripping solutions.

(27) However, the removal of the polymer layer may be incomplete giving rise to the residues RS located in the TSVs and/or the residues RB located on the back side BS of the substrate SUB.

(28) In addition or alternatively, the polymer residues RS, RB may for example originate from an incomplete removal of a photoresist layer. The photoresist layer may for example be utilized for example for structuring further layer for example after generating the TSVs S1, S2, S3, S4. The further layer may for example be a metal layer, in particular the back side metallization and/or the TSV-metallization layer, or the spacer layer.

(29) In addition or alternatively, the residues may for example originate from processes used for depositing the further layer.

(30) The residues RS, RB may for example comprise fluoropolymer and/or acrylic polymer materials. The residues RS, RB may for example comprise polymer particles with a thickness in the order of a several nanometers.

(31) The residues RS, RB may be disadvantageous for a further processing of the semiconductor element SE. In particular, the residues RS, RB may reduce an adhesion of additional layers to be deposited on the semiconductor element SE. Therefore, it is desirable to analyze the semiconductor element SE with respect to the amount, density, distribution or the like of the residues RS, RB.

(32) To this end, the semiconductor element SE of FIG. 2 may be analyzed with a method for analyzing according to the improved concept, for example as described with respect to FIG. 1.

(33) Thus, the residues RB, RS are marked by affixing the fluorescent substance to the residues RB, RS as described for example with respect to FIG. 1. Then the marked residues are detected using fluorescence microscopy as described for example with respect to FIG. 1.

(34) FIG. 2 also shows incoming electromagnetic radiation LI which is for example generated by the fluorescence microscope for illuminating the semiconductor element SE. Furthermore, fluorescent electromagnetic radiation LF is shown that is being emitted by the fluorescent substance affixed to the residues RB, RS in response to the illumination as described for example with respect to FIG. 1. Images may be generated based on the detected electromagnetic radiation LF.

(35) It is noted that, instead of the semiconductor wafer, the semiconductor element SE may for example be a semiconductor chip or die.

(36) FIG. 3 shows an image of a top view of a semiconductor element analyzed employing an exemplary implementation of a method for analyzing a semiconductor element according to the improved concept.

(37) FIG. 3 shows a fraction of the back side BS of an actual semiconductor wafer comprising a TSV S5. A circular outline of the TSV S5 is indicated by a dashed white line. Several polymer residues RB are located on the back side BS and appear as white speckles on the black background. In addition, polymer residues RS are located inside the TSV S5 and appear as a white undulated line on the black background.

(38) For generating the image of FIG. 3, the residues RB, RS have been marked using a method for analyzing according to the improved concept, for example as described with respect to FIG. 1, for example using a mixture containing supercritical carbon dioxide and an ATTO 647N dye as the fluorescent substance. Then, the semiconductor element has been illuminated with red visible light with a wavelength matching or approximately matching the absorption wavelength of the fluorescent substance. The nominal absorption wavelength of the ATTO 647N dye is 644 nm.

(39) Due to the illumination, the affixed fluorescent substance was excited and consequently emitted fluorescent light with a wavelength corresponding to the emission wavelength of the fluorescent substance. The emission wavelength of the ATTO 647N dye is 669 nm. The fluorescent light is visible in form of the speckles and the undulated line at the positions of the residues RS, RB. The fluorescent light has been detected with the fluorescence microscope, in particular with a camera, which resulted in the image shown in FIG. 3.

(40) FIG. 4 shows a pressure-temperature phase diagram of carbon dioxide. Different parameter ranges, that is ranges for the temperature and the pressure, separated by solid lines are shown that correspond to different phases of carbon dioxide. Therein, temperature is shown in C. on the axis of abscissae and pressure is shown in atm on the axis of ordinates. Shown are parameter ranges for which carbon dioxide is in its solid phase s, in its gaseous phase g, in its liquid phase 1 and in its supercritical phase sc. Is highlighted that the solid lines separating the parameter ranges are not necessarily depicted accurately but for providing an overview only. This holds particularly for the lines bordering the supercritical range sc.

(41) In addition, the critical point CP, in particular the liquid-gas critical point CP, and the triple point TP of carbon dioxide are shown. In particular, the critical point is located at a temperature of 30.980 C. and a pressure of 72.79 atm. Furthermore, a sublimation point SP at a pressure of 1 atm is shown.

(42) According to a method for analyzing a semiconductor element according to the improved concept, the mixture may be supplied to the pressure chamber for example at a pressure and temperature corresponding to the liquid range 1 of carbon dioxide. Then, the temperature in the pressure chamber is for example increased such that the carbon dioxide and the mixture are transferred beyond the critical temperature into the supercritical range sc. The semiconductor element is then exposed to the mixture in its supercritical phase. Afterwards, the pressure within the pressure chamber may be decreased to reach the gaseous range g of carbon dioxide as explained above.

(43) Alternatively, the mixture may not be transferred to the supercritical phase but for example close to the supercritical range sc. In such implementations of the method, the semiconductor element may be exposed to the mixture in its liquid or gaseous phase.

(44) FIG. 5A shows a schematic representation of an exemplary implementation of an arrangement according to the improved concept. The arrangement comprises an impregnation tool IT including the pressure chamber and a fluorescence microscope FM.

(45) Steps of the method for analyzing a semiconductor element according to the improved concept may be carried out using the impregnation tool IT, including the marking of at least the fraction of residues. For further details it is referred to FIGS. 6A and 6B. Other steps of the method for analyzing a semiconductor element according to the improved concept may be carried out with the fluorescence microscope FM, including detecting the marked residues by visualizing the marked residues. The fluorescence microscope FM may for example be implemented in an upgraded automatic optical inspection, AOI, defect tool. A conventional fluorescence microscope FM may be used.

(46) FIG. 5B shows a schematic representation of a further exemplary implementation of an arrangement according to the improved concept. In the implementation of FIG. 5B, the impregnation tool IT including the pressure chamber and the fluorescence microscope FM are both comprised by a single cluster tool CT. In particular, the fluorescence microscope FM is configured to visualize the marked residues while the semiconductor element is located inside the pressure chamber of the impregnation tool IT.

(47) FIG. 6A shows a further exemplary implementation of an arrangement according to the improved concept.

(48) The arrangement comprises an impregnation tool IT and a fluorescence microscope (not shown). The fluorescence microscope is either implemented together with the impregnation tool IT in a single cluster tool as in FIG. 5B or as a separate tool as in FIG. 5A.

(49) The impregnation tool IT comprises a pressure chamber PC, a mixing chamber MC and a pump P, in particular a high-pressure pump, for example implemented as a plunger pump or a piston pump. An input of the pump P may be connected to a carbon dioxide reservoir (not shown) via a first line L1. The carbon dioxide reservoir contains for example liquid carbon dioxide. An input of the mixing chamber MC is connected to an output of the pump P via a second line L2 and a third line L3. An output of the mixing chamber MC is connected to an input of the pressure chamber PC via a fourth line L4 and a fifth line L5. An output of the pressure chamber PC is connected to a gas exhaust (not shown) via a sixth line L6.

(50) The pressure chamber PC is for example constructed of materials comprising stainless steel and/or high-pressure glass in order to avoid a cross contamination of the semiconductor element SE.

(51) The impregnation tool further comprises a control unit comprising a temperature control unit T and a pressure control unit P. The temperature control unit T is configured to control a temperature inside the pressure chamber PC and the pressure control unit is configured to control a pressure inside the pressure chamber PC.

(52) FIG. 6A also shows an optional bypass line L7 bypassing the third line L3, the mixing chamber MC and the fourth line L4. To this end, the integration tool IT may comprise corresponding bypass valves (not shown). In case the impregnation tool IT does not comprise the bypass line L7, the second and the third line L2, L3 may be implemented as a single line and the fourth line and the fifth line L4, L5 may also be implemented as a single line.

(53) Furthermore, an optional flowmeter F and an optional expansion valve D are shown. The expansion valve D is connected to the second line L2 via an eighth line L8 and to a further input of the pressure chamber PC via a ninth line L9. The flowmeter F is arranged to measure a flow through the ninth line L9.

(54) The semiconductor element is for example placed inside the pressure chamber PC.

(55) The liquid carbon dioxide is supplied from the carbon dioxide reservoir to the impregnation tool IT. To this end, the pump P pumps the liquid carbon dioxide to the second line L2. The liquid carbon dioxide is then pumped to the mixing chamber MC. The mixing chamber MC may contain the fluorescent substance for example dissolved in an additional solvent such as dimethyl sulfoxide, isopropyl alcohol or water. Then, the liquid carbon dioxide and the fluorescent substance are mixed in the mixing chamber MC to generate the mixture. The mixture containing the liquid carbon dioxide and the fluorescent substance is then supplied to the pressure chamber PC via the fifth line L5. To this end, an intake valve (not shown) comprised by the arrangement may be controlled by the control unit to supply the mixture to the pressure chamber PC.

(56) Then, the semiconductor element placed inside the pressure chamber PC is exposed to the mixture until the fluorescent substance is affixed to at least the fraction of the residues as described for example with respect to FIGS. 1 to 4. To this end, the temperature and/or the pressure inside the chamber may be increased by using the temperature control unit T and/or the pressure control unit P. In this way, the mixture inside the pressure chamber PC may for example be transferred to its supercritical phase or close to its supercritical phase for the exposure of the semiconductor element to the mixture.

(57) After the residues have been marked by a fixing the fluorescent substance to the residues, a pressure and/or a temperature within the chamber may be decreased by employing the pressure and temperature control units P, T such that the carbon dioxide of the mixture within the pressure chamber PC is transferred to its gaseous phase. The gaseous carbon dioxide may then be pumped down via the exhaust and the sixth line L6.

(58) Then, the marked residues may be detected with the fluorescence microscope as described above.

(59) Via the optional eighth and ninth lines L8, L9 and the expansion valve D, the pressure chamber PC may be flushed with gaseous carbon dioxide prior to and/or after exposing the semiconductor element to the mixture and/or prior to placing the semiconductor element in the pressure chamber PC. To this end, the liquid carbon dioxide that is supplied by the pump P to the eighth line L8 is expanded employing the expansion valve D and consequently supplied as gaseous carbon dioxide to the ninth line L9 and the pressure chamber PC.

(60) It is highlighted that for the sake of clearness, valves comprised by the impregnation tool IT that may be necessary for directing a carbon dioxide flow through the various lines are not shown in FIG. 6A. However, their arrangement becomes an immediately clear to the skilled reader from the purpose and function of the impregnation tool IT and the arrangement of the lines L1 to L9.

(61) FIG. 6B shows a further exemplary implementation of an arrangement according to the improved concept based on the implementation of FIG. 6A.

(62) In contrast to the implementation of FIG. 6A, the arrangement of FIG. 6B does not comprise the expansion valve D and does not comprise the eighth line L8. Instead, the ninth line L9 connects the pressure chamber PC to the carbon dioxide reservoir. The carbon dioxide reservoir is in the implementation of FIG. 6A adapted to supply liquid carbon dioxide to the first line and to supply gaseous carbon dioxide to the eighth line.

(63) Apart from these differences, the operation of the arrangement of FIG. 6B corresponds to the operation of the arrangement of FIG. 6A.

(64) By employing the improved concept, a semiconductor element may be analyzed with respect to polymer residues non-destructively and with improved efficiency. The improved concept allows for analyzing not only local structural elements such as TSVs, trenches and cavities, but also the whole wafer surface non-destructively. Therefore, mapping of residue distribution as well as statistical analysis of the results for cleaning optimization a process monitoring is possible.

(65) The improved concept may for example be applied if the semiconductor element, in particular the semiconductor substrate, does not show an intrinsic fluorescence in a same wavelength range as the used fluorescent substance.

(66) In particular, semiconductor elements with surface structures such as TSVs with large aspect ratios may be analyzed with a method according to the improved concept. This is particularly advantageous since for large aspect ratios also polymer removal becomes more difficult increasing the importance of an efficient and non-destructive analysis.

(67) However, also semiconductor elements with only a relatively small amount of polymer residues and a random distribution thereof may be efficiently analyzed according to the improved concept, which may be particularly advantageous if improved methods for polymer removal are available.