Method for coating cavities of semiconductor substrates

Abstract

A method for temporary coating of cavities, which at least partially run through a semiconductor substrate and are provided for a permanent coating and/or equipping, with a temporarily applied coating material before processing steps for processing at least one surface of the semiconductor substrate. In addition, a method for removing a temporary coating of cavities of a semiconductor substrate, whereby the coating is applied according to a previously-mentioned method and whereby, in particular immediately afterwards, a permanent coating and/or equipping of the cavities is carried out.

Claims

1. A method for temporarily coating a semiconductor substrate having at least one substrate surface and one or more cavity surfaces that define cavities formed in the semiconductor substrate, said method comprising: applying a temporary coating material to the semiconductor substrate before performing processing steps for processing the at least one substrate surface, wherein the temporary coating material applied to the semiconductor substrate includes (i) a high-adhesive part, which removably adheres to the one or more cavity surfaces, and (ii) a low-adhesive part, which faces interior regions of the cavities and thus comes into contact with contaminants.

2. The method according to claim 1, wherein the step of applying the temporary coating material to the semiconductor substrate includes applying the temporary coating material at least to an inner periphery surface and a base surface of the cavity surfaces, said temporary coating material applied with a coating thickness (d) that is smaller than half a mean diameter (D) of each of the cavities.

3. The method according to claim 1, wherein the step of applying the temporary coating material to the semiconductor substrate includes applying the temporary coating material to intermediate surfaces of the substrate surfaces, said intermediate surfaces extending between the cavities.

4. The method according to claim 3, wherein the method further comprises: removing the temporary coating material from the intermediate surfaces after applying the temporary coating material to the semiconductor substrate, without removing the temporary coating material applied to the one or more cavity surfaces.

5. The method according to claim 4, wherein the temporary coating material is removed from the intermediate surfaces by centrifuging.

6. The method according to claim 1, further comprising: cleaning the semiconductor substrate after performing the processing steps for processing the at least one substrate surface.

7. The method according to claim 1, furthered comprising: removing the temporary coating material from the cavities after performing the processing steps for process the at least one substrate surface; and immediately after the removing of the coating materials, permanently coating the one or more cavity surfaces and/or equipping the cavities.

8. The method according to claim 6, wherein the method further comprises removing the temporary coating material after cleaning the semiconductor substrate.

9. The method according to claim 7, wherein the temporary coating material is removed by introducing the coated semiconductor substrate into a solvent bath filled with a solvent for dissolving the temporary coating material.

10. The method according to claim 9, wherein the semiconductor substrate is exposed to ultrasound in the solvent bath.

11. The method according to claim 4, wherein the temporary coating material is completely removed from the intermediate surfaces.

12. The method according to claim 5, wherein the temporary coating material is removed from the intermediate surfaces by centrifuging in connection with applying a solvent for at least partially dissolving the temporary coating material.

13. The method according to claim 7, wherein the temporary coating material is removed after cleaning of the semiconductor substrate.

14. The method according to claim 13, wherein the temporary coating material is removed by introducing the coated semiconductor substrate into a solvent bath filled with a solvent for dissolving the temporary coating material.

15. The method according to claim 14, wherein the semiconductor substrate is exposed to ultrasound in the solvent bath.

16. The method according to claim 1, wherein the cavities are recesses.

17. The method according to claim 1, wherein the cavities are vias.

18. The method according to claim 17, wherein each via is one of the following: a bore hole, a clearance hole, or a contact hole.

19. The method according to claim 13, wherein the temporary coating material is removed by plasma.

20. The method according to claim 1, wherein an energy per unit of surface area of the high-adhesive part that is needed to separate the high-adhesive part from the one or more cavity surfaces is greater than 0.00001 J/m.sup.2, and wherein an energy per unit of surface area of the low-adhesive part at which the low-adhesive part adheres to the contaminants is less than 2.5 J/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 a cross-sectional view of a semiconductor substrate with cavities according to the invention,

(2) FIG. 2 an enlarged cutaway of the cavities of FIG. 1 after a coating with a coating material according to the invention,

(3) FIG. 3 a step according to the invention of an embodiment of this invention,

(4) FIG. 4a a first step of a first embodiment of the method according to the invention,

(5) FIG. 4b a second step of a first embodiment of the method according to the invention,

(6) FIG. 4c a third step of a first embodiment of the method according to the invention,

(7) FIG. 4d a fourth step of a first embodiment of the method according to the invention, and

(8) FIG. 4e a fifth step of a first embodiment of the method according to the invention.

(9) In the figures, the same components or components that have the same effect are identified with the same reference numbers. The drawings show only diagrammatically the embodiments according to the invention and are not to scale. Thus, primarily the relative thicknesses of the coating material 3 and the substrates 1 are disproportionate to one another, just as is the ratio of the above-mentioned thicknesses to the diameters of the substrates 1.

DETAILED DESCRIPTION OF THE INVENTION

(10) In a first embodiment according to the invention in accordance with FIG. 2, a coating material 3, provided as a protective layer from contaminants, is applied in particular in a centrifugal enameling device, completely on a surface 1o of a semiconductor substrate 1. The coating material 3 penetrates into cavities 2 during the coating process. The coating material 3 covers not only a surface 2o of the cavities 2 but rather also outer intermediate surfaces 1z of the substrate surface 1o. Thus, the coating according to the invention of the surface 2o of the cavities 2 is finished. This embodiment according to the invention is in particular suitable if the substrate surface 1o outside of the cavities 2 is further processed so that the coating material 3 at the intermediate surfaces 1z is not disturbed. Such a simple embodiment would be conceivable primarily in the case of back-grinding processes, back-thinning processes, and etching processes.

(11) In a second embodiment according to the invention in accordance with FIG. 3, the coating material 3 is applied, in particular in a centrifugal enameling device. After the coating material 3 has penetrated into the cavities 2, in particular immediately afterwards, a centrifuging process, in particular at high speed, and/or a cleaning exclusively of the intermediate surfaces 1z of the surface 1o of the semiconductor substrate 1 is/are performed with a solvent for the coating material. The speed is in particular higher than 1 rpm (i.e., rotations per minute”), in particular higher than 10 rpm, preferably higher than 100 rpm, and more preferably higher than 1,000 rpm.

(12) The speed of the centrifugal enameling device is selected so that the solvent for the coating material 3 does not penetrate into the cavities 2, so that the coating material 3 according to the invention remains at least predominantly, preferably virtually completely, in the cavities 2. Thus, only the cavities 2 are coated with the coating material 3 according to the invention.

(13) A subsequent removal of the coating material 3 at the intermediate surfaces 1z, performed after the coating of the coating material 3, by any physical and/or chemical process is also conceivable.

(14) The substrate surface 1o above the cavities 2 is cleared, in particular completely, of the coating material 3 and can therefore be further treated or processed at will.

(15) During the further processing of the substrate surface 1o, contaminants can penetrate into the cavities 2, in particular a temporary adhesive during a temporary bonding. An adhesion to an inner periphery 2i or a base 2b of the cavities 2 is prevented or at least hampered by the low-adhesive coating material 3, so that the contaminants can be removed easily or more easily.

(16) After the processing of the semiconductor substrate 1, cleaning according to the invention of the cavities 2 is carried out. Based on the use according to the invention of the coating material 3, the contaminants can be removed easily, quickly, inexpensively and in an energy-efficient manner from the cavities 2.

(17) After the cleaning of the cavities 2, the complete removal of the coating material 3 from the cavities 2 is carried out. Preferably, the coating material 3 is removed at least partially during the cleaning process of the cavities, but in particular after the complete removal of all contaminants.

(18) In this case, the cleaning of the cavities 2 preferably takes place in a solution bath; especially preferably, multiple semiconductor substrates 1 are stored in a solvent bath in a batch process. The temperature of a solvent, present in the solvent bath, far dissolving the coating material 3 is set in particular greater than 30° C., preferably greater than 50° C., more preferably greater than 75° C., and most preferably greater than 100° C.

(19) In a special embodiment, the semiconductor substrates 1 with the cavities 2 to be cleaned are exposed to ultrasound. The ultrasound emitters in this case can produce ultrasound waves, whose propagation direction lies normal or crosswise to the substrate surface. Also, an acoustic irradiation of the semiconductor substrates 1 by ultrasound waves, whose propagation direction lies between the normal and a parallel to the substrate surface, would be conceivable.

(20) The chemicals for the solvent that are preferably to be used primarily depend on the type of contamination. Primarily in the case of the contamination of cavities 2 by a temporary adhesive, corresponding solvents are preferred for the temporary adhesive. These are solvents that contain primarily, but not exclusively, limonenes.

(21) Additional solvents that are conceivable according to the invention would be:

(22) Organic solvents Acetone Isopropanol PGMEA Mesitylene Limonin Isododecane

(23) Inorganic solvents Water

(24) Any semiconductor substrate 1 with its substrate surface 1o has at least one cavity 2. In a special case, the cavity 2 is a via (FIG. 4a). A via is primarily distinguished by the large diameter-to-depth ratio D:t. Vias are cavities with a diameter-to-depth ratio of 1:1, preferably more than 1:2, more preferably more than 1:10, most preferably more than 1:50, and with utmost preference more than 1:100. In general, cavities that are then no longer referred to as vias can also have a diameter-to-depth ratio of 1:1, preferably more than 2:1, more preferably more than 10:1, most preferably more than 50:1, and with utmost preference more than 100:1.

(25) In a first process step, the substrate surface 1o is coated with a coating material 3 (FIG. 4b). The coating is done with an above-mentioned coating method, in particular by spin-coating.

(26) A surface 3o of the coating material 3 has a low adhesion to other materials.

(27) In another process step, the semiconductor substrate 1 is processed with a material, here by exposure to an adhesive 4, in particular an adhesive for the temporary bonding. The processing results in particular in that the adhesive 4 penetrates into the cavities 2 (see FIG. 4c).

(28) After the processing of the semiconductor substrate 1 is carried out, the adhesive 4 is removed from the cavities 2 by cleaning means 5. As cleaning means 5, in particular chemical solvents and/or gases and/or plasma and/or ultrasound waves and/or light are used.

(29) By the application of the low-adhesive coating material 3 according to the invention, the removal of contaminants such as adhesive 4 is possible in a very short time with very low expenditure of energy.

(30) After the removal of the adhesive 4 is performed, the removal of the protective layer 3 (FIG. 4e) is carried out. Especially preferably, the coating material 3 is removed as early as during the cleaning process (FIG. 4d), in particular after the removal of the adhesive 4.

(31) The preferred method for removing the coating material 3 according to the invention is the application of plasma, in particular oxygen plasma.

LIST OF REFERENCE SYMBOLS

(32) 1 Semiconductor substrate 1o Surface of the semiconductor substrate 1z Intermediate surfaces 2 Cavities 2b Base 2i Inner periphery 2o Surface of the cavities 3 Coating material 3o Surface of the coating material 4 Adhesive 5 Cleaning means d Coating thickness D Mean diameter