JP4731892B2 - Method of manufacturing semiconductor substrate supply port and through-hole for liquid discharge head - Google Patents

Description

The present invention relates to a method for manufacturing a supply port and a through port of a semiconductor substrate for a liquid discharge head.

  2. Description of the Related Art Liquid discharge heads used in printers and the like, in particular, so-called side shooter type liquid discharge heads (inkjet heads) that discharge ink from discharge ports that substantially vertically penetrate the plate surface of a substrate that forms a flow path Uses a semiconductor substrate based on a silicon substrate, uses the semiconductor configured in the substrate as a discharge energy generating element (for example, a heater) and its drive circuit, and is a processing technique that is generally popular as a semiconductor manufacturing method Is applied to precisely form the fine shape of the flow path and discharge port of the liquid discharge head.

  Specifically, for example, a large number of heaters are formed on one main surface (front surface) of a silicon substrate so as to be arranged at intervals that can achieve a desired printing density (for example, 600 dpi). Surrounding channels are each formed. Usually, in order to supply liquid (ink) to be discharged to each flow path, an ink supply port that penetrates from the other main surface (back surface) of the silicon substrate to one main surface (front surface); Through-holes are formed. As described above, anisotropic etching using, for example, TMAH (Tetra Methyl Ammonium Hydroxide), which is an organic alkaline solution, is used as a method for forming a through hole penetrating a semiconductor substrate.

  In the liquid discharge head, if ink is not replenished in the flow path immediately after ink is discharged, the recording speed is remarkably reduced. In order to make this ink replenishment speed as fast as possible, the distance from the through hole to the heater must be made short and accurate. One factor that determines the accuracy of the distance between the through hole and the heater is the processing accuracy of the opening portion of the through hole on the surface of the semiconductor substrate. In order to improve the processing accuracy of the through hole, there is a technique in which a sacrificial layer is provided on the surface of the semiconductor substrate, and a through hole is formed using a recess after the sacrificial layer is removed. A technique for forming a sacrificial layer simultaneously with a wiring layer in a wiring forming process of a semiconductor manufacturing method has been proposed (see Patent Document 1).

  According to this conventional method, when a through hole serving as an ink supply port is formed by anisotropic etching using an etching solution such as TMAH, a so-called membrane film located on the surface of the semiconductor substrate acts as an etching stopper. However, immediately after the etching with TMAH, this membrane film remains on the surface of the semiconductor substrate.

  Specifically, as shown in FIG. 7A, a heater 33 for foaming ink on a semiconductor substrate 32 based on a silicon substrate 31 by a known semiconductor manufacturing method, a driver and peripheral elements not shown. Is formed between the first wiring layer (not shown) made of aluminum or the like and the second wiring layer 35 formed thereabove, which is formed together with the sacrificial layer 34. A silicon oxide film 36 (P-SiO formed by a plasma CVD (Chemical Vapor Deposition) method) as an insulating film and a silicon nitride film 37 (P-- formed by a plasma CVD method) formed as a protective film of a semiconductor substrate. SiN) is laminated. Thereafter, a resin substrate 38 is laminated on the front surface of the semiconductor substrate 32 by a known method. 7B, when the sacrificial layer 34 is removed and the silicon substrate 31 is etched to form a through hole (supply port 39), the silicon oxide film 36 and the silicon nitride film 37 are It remains unetched by TMAH to form a membrane.

The membrane film composed of the silicon oxide film 36 and the silicon nitride film 37 is removed in a step subsequent to etching by TMAH for forming a through hole (supply port 39). Specifically, the silicon oxide film 36 is removed by wet etching using a hydrofluoric acid solution (hydrofluoric acid), and then the silicon nitride film 37 is removed by dry etching using a fluorine-based gas. Thereafter, a step of patterning the resin substrate 38 on the front side of the semiconductor substrate 32 by a known method to form an ink flow path 40 and an ejection port (nozzle) 41 and a step of mounting an ink tank (not shown). And a liquid discharge head is formed.
Japanese Patent Laid-Open No. 10-181032

  In the above-described method, during wet etching with hydrofluoric acid, which is the first step in the process of removing the membrane film composed of the silicon oxide film 36 and the silicon nitride film 37, as shown in FIG. There is a risk that hydrofluoric acid will ooze out from the upper layer from a part and the resin substrate 38 may be etched by hydrofluoric acid. FIG. 7C shows the damaged portion 42. As a result, as shown in FIG. 8, the shape of the flow path 40 is disturbed, which may cause deterioration in recording characteristics. This defect is assumed when the completed film thickness of the silicon oxide film 36 or the silicon nitride film 37 constituting the membrane film becomes thinner than the assumed film thickness, or the etching rate of hydrofluoric acid is assumed. It is likely to occur when it is faster than it was.

  The membrane film is formed directly on the silicon substrate 31 on the sacrificial layer 34 (see FIG. 7A), the step generated by the LOCOS (local oxidation of silicon) process for forming the field oxide film 43, and the sacrificial layer 34. Therefore, it is formed on a step portion 45 such as a contact step generated by opening the interlayer insulating film 44. Usually, due to the step coverage shape of the membrane film in the step portion 45, the etching rate of the step portion 45 is faster than the etching rate of the flat portion on the sacrificial layer 34. Therefore, if the step coverage shape of the stepped portion 45 is worse than expected, the above-described defect is more likely to be caused.

  The wet etching with hydrofluoric acid is designed to etch the silicon oxide film 36, which is the lower layer of the membrane film. For the reasons described above, the etching rate of the silicon oxide film 36 in the stepped portion 45 is the etching of the flat portion. Since the rate is 1.5 to 2 times the rate, if the wet etching time is set so that the silicon oxide film 36 in the flat portion is completely etched, the etching of the silicon oxide film 36 in the stepped portion 45 takes a short time. The time for the silicon nitride film 37 existing thereon to be exposed to hydrofluoric acid is longer than that of the flat portion. When the time during which the silicon nitride film 37 is exposed to hydrofluoric acid in the stepped portion 45 becomes long, the silicon nitride film 37 is finally etched by wet etching using hydrofluoric acid, and is constituted by the silicon oxide film 36 and the silicon nitride film 37. Hydrofluoric acid oozes out from the membrane membrane into the upper layer. If the membrane film is partially etched by wet etching with hydrofluoric acid, the resin substrate 38 is etched with hydrofluoric acid (see FIG. 7C). Since the erosion of the resin substrate 38 is severe (damaged portion 42), the ink flow path 40 and the ejection port 41 are destroyed (see FIG. 8).

  Conventionally, for such defects, the final remaining film thickness tolerance of the silicon oxide film 36 constituting the membrane film is set within ± 9% of the predetermined film thickness, and the wet etching time This is dealt with by setting the processing conditions so that the over-etching amount of the flat portion is 10% or less even in the worst case in the calculation. Nevertheless, the above-described defects are a problem as one of the factors that lower the manufacturing yield of the liquid discharge head.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a supply port and a through-hole of a semiconductor substrate for a liquid discharge head that can accurately form a flow path and a discharge port without the need to set processing conditions particularly precisely. There is to do.

The present invention relates to a semiconductor substrate, a heater disposed on one main surface of the semiconductor substrate, and a liquid supply supply formed through the semiconductor substrate from the other main surface of the semiconductor substrate to the one main surface. in the mouth and through-hole and a manufacturing method of the supply port and the through hole of the semiconductor substrate for a liquid discharge head having the steps of forming a silicon oxide film on one principal surface of the semiconductor substrate, on the silicon oxide film, a silicon oxide A step of forming an etching stopper layer for stopping etching for removing the film, a step of forming a silicon nitride film on the etching stopper layer, a step of removing the silicon oxide film by etching, and the removal of the silicon oxide film after contact of by removing the etching stopper layer and the silicon nitride film by etching, a flow path and the supply port that the heater is located inside Seen containing a step of forming a through hole to be a part, and the etching stopper layer, and forming a heater in the same step.

  According to the present invention, it is possible to obtain a liquid ejection head having a highly accurate flow path without adding a process and making the processing conditions not so severe as compared with the conventional one.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the liquid discharge head according to the present embodiment shown in FIG. 1, a resin substrate 2 is laminated on a semiconductor substrate 1, a plurality of heaters 3 are formed in the semiconductor substrate 1, and flow between the semiconductor substrate 1 and the resin substrate 2. A path 4 is formed. Each heater 3 is located inside each flow path 4. Furthermore, a supply port 5 penetrating the semiconductor substrate 1 and communicating with each flow path 4 and a plurality of discharge ports 6 penetrating the resin substrate 2 provided corresponding to each flow path 4 are provided. ing.

  Although not described in detail, the semiconductor substrate 1 is formed with a diffusion layer and a gate electrode on one main surface (front surface) side of a silicon substrate (silicon wafer) 7 to form a MOS transistor. . A field oxide film 10 and a first interlayer insulating film 12 made of phosphorous glass are formed. A first metal wiring layer (not shown) for electrical connection to the MOS transistor, a heating resistor (heater material) 14 and a second metal wiring layer 15 are formed of a second interlayer made of a silicon oxide film 13. They are stacked via an insulating film. Further, a silicon nitride film 16 serving as a protective film and a tantalum film 17 for cavitation resistance are formed. On the other hand, the resin substrate 2 is made of a nozzle material 19, and a flow path 4 is formed between the resin substrate 2 and the semiconductor substrate 1, and a discharge port 6 is provided.

  In this liquid discharge head, the heating resistor 14 is not only a portion that functions as the heater 4 for generating discharge energy, but also a step generated by the LOCOS process, a contact step generated by opening the interlayer insulating film 13, and the like. It is also formed in the step portion. The heating resistor 14 functions as an etching stopper layer during wet etching with hydrofluoric acid. In the liquid discharge head in a completed state, the heating resistor 14 is formed on the inner wall surface of the through-hole 5a that is the connection portion of the supply port 5 to the flow path 4. The end face is exposed in a state sandwiched between the interlayer insulating film (silicon oxide film) 13 and the silicon nitride film 16.

  Next, the manufacturing method of the liquid discharge head of this embodiment will be described in detail.

  First, as shown in FIG. 2A, a P-type silicon substrate 7, specifically, a silicon wafer having a crystal orientation of <1, 0, 0> and a thickness of 625 μm is prepared, and its surface is oxidized. Then, a silicon oxide film 8 having a thickness of 10 to 50 nm is formed. Next, as shown in FIG. 2B, a silicon nitride film 9 having a thickness of 100 to 300 nm is deposited on the silicon oxide film 8 by low pressure CVD. Then, as shown in FIG. 2C, the silicon nitride film 9 is patterned into a desired shape, and if the silicon nitride film 9 is also deposited on the back side of the silicon substrate 7, it is removed by etching. . Next, as shown in FIG. 2D, the silicon oxide film 8 is partially thickened by silicon thermal oxidation to form a field oxide film (silicon oxide film) 10 having a thickness of 6000 to 12000 mm. This is a so-called LOCOS process, and the silicon oxide film 8 located under the patterned silicon nitride film 9 (active region) does not grow and does not thicken, and silicon at a position (field region) where the silicon nitride film 9 does not exist. Only the oxide film 8 grows and becomes a field oxide film 10. Then, the silicon nitride film 9 is removed by etching.

  Thereafter, although not described in detail, a diffusion layer and a gate electrode are formed in the active region by using a conventionally known semiconductor manufacturing method, and a MOS transistor constituting the driving circuit of the liquid discharge head is formed.

  Subsequently, as shown in FIG. 3A, a first wiring layer (not shown) made of aluminum or the like and a first interlayer insulating film 12 made of phosphorous glass for ensuring electrical connection of the MOS transistor. Form. A part of the first wiring layer may function as the sacrificial layer 11 as in the method described in Patent Document 1. The sacrificial layer 11 is used to accurately form a through hole serving as the supply port 5 in the silicon substrate 7.

  Thereafter, as shown in FIG. 3B, a second interlayer insulating film made of the silicon oxide film 13 is formed and patterned, and as shown in FIG. 3C, a heating resistor (heater material) is formed. 14 and the second wiring layer 15 are formed. Then, as shown in FIG. 3D, the second wiring layer 15 is patterned and partially removed. This point will be described in detail. The heating resistor 14 and the second electrode 14 are disposed not only in the heater region for generating discharge energy and the transistor wiring region, but also in the region immediately above the sacrificial layer 11, opposite to the discharge port 6 described later. Two wiring layers 15 are formed. Then, in the heater region, the heater 3 is formed by appropriately patterning the second wiring layer 15. In the region immediately above the sacrificial layer 11, the second wiring layer 15 is removed, leaving only the heating resistor 14.

  Next, as shown in FIG. 3E, a silicon nitride film 16 having a thickness of about 250 to 800 nm, which serves as a semiconductor protective film, is formed by plasma CVD, and shown in FIG. 3F. As described above, a tantalum film 17 having a thickness of about 50 to 600 nm, which becomes an anti-cavitation film, is formed by sputtering and processed into a desired pattern. Thereafter, although not shown, the silicon nitride film 16 is patterned and the electrodes are taken out.

As shown in FIG. 4 is a plan view, outside of the sacrificial layer 11, the first opening of the interlayer insulating film 12 is provided in order to stack more directly the sacrificial layer 11 on the silicon down board 7 It is desirable that the heating resistor 14 is formed to the outside of the portion 12a. FIG. 4 shows the active area A.

  After forming the semiconductor substrate 1 in this way, as shown in FIG. 5A, the resin substrate 2 composed of the nozzle mold material 18 and the nozzle material 19 for forming the discharge ports 6 and the flow paths 4 is replaced with the semiconductor substrate. Laminate on 1. Then, an aqueous solution of TMAH is used as the etching solution, the etching temperature is 80 to 90 ° C., the etching time is 15 to 20 hours (when the thickness of the silicon substrate 7 is about 625 μm), and the back surface side of the silicon substrate 7 (the other main) An anisotropic etching is performed from the (surface side) to form the supply port 5 penetrating the silicon substrate 7 as shown in FIG. At this time, the sacrificial layer 11 is also etched. In this etching process, the resin materials 20a and 20b disposed on the back side of the silicon substrate 7 serve as a mask, and the sacrificial layer 11 serves as a reference for forming the supply port 5 to provide a highly accurate supply port. 5 can be formed. The resin material 20b is removed thereafter.

  Next, as shown in FIG. 5C, a silicon oxide film (second interlayer insulating film) 13 that is in contact with the sacrificial layer 11 in the so-called membrane film existing in the supply port 5, and the supply port 5. The excess field oxide film 10 protruding inside is simultaneously removed by wet etching using buffered hydrofluoric acid. This process is referred to as a first membrane film etching process for removing the membrane film for convenience. In this step, the supply port 5 functions as a substantial etching mask. When the silicon oxide film (second interlayer insulating film) 13 having a thickness of about 1000 nm is present and the extra field oxide film 10 having a thickness of about 700 nm is present, the etching time using buffered hydrofluoric acid is conventionally reduced. The street is about 10 minutes. As described above, since the heating resistor 14 functions as an etching stopper layer, the wet etching time can be set longer. Therefore, it is possible to set the etching time so that the silicon oxide film (second interlayer insulating film) 13 is completely etched so as not to remain. Specifically, the etching time of the wet etching can be set to, for example, 13 minutes instead of the conventional 10 minutes.

  When such wet etching is performed, the etching rate of the stepped portion B shown in FIG. 5C is about 1.5 times the etching rate of the other flat portion by the buffered hydrofluoric acid. Therefore, in the stepped portion B, the silicon oxide film (second interlayer insulating film) 13 is removed earlier than other flat portions, and the heating resistor 14 (heater material, for example, TaSiN) in the upper layer is removed. You will be exposed to buffered hydrofluoric acid. In the case of the etching conditions described above, the heating resistor 14 is exposed to buffered hydrofluoric acid for 3 minutes or more. However, since the etching rate of the heating resistor 14 (TaSiN) with respect to buffered hydrofluoric acid is 1/100 or less compared with the etching rate of the silicon oxide film, the heating resistor 14 is slightly stronger than buffered hydrofluoric acid over 3 minutes. Even if exposed, it is hardly etched. Since the heating resistor 14 acts as an etching stopper layer in this way, the silicon nitride film in the stepped portion B can be obtained even if wet etching is performed so that the silicon oxide film (second interlayer insulating film) 13 in the flat portion can be sufficiently removed. No damage up to 16. That is, the defect accompanying the breakage of the membrane film, which has been a problem in the prior art, does not occur.

Thereafter, as shown in FIG. 6, the heating resistor 14 and the silicon nitride film 16 which are the remaining part of the membrane film are removed by dry etching using a fluorine-based or oxygen-based gas. This process is referred to as a second membrane film etching process for removing the membrane film for convenience. Also in this step, the supply port 5 functions as a substantial etching mask. In this way, the through-hole 5a which is a connection part with the flow path 4 of the supply port 5 is formed with sufficient precision.

  Thereafter, the nozzle mold material 18 made of an organic resin is removed from the resin substrate 2 using a solvent to form the ink flow path 4 in the nozzle material 19, and the nozzle material 19 communicates with each flow path 4. A discharge port 6 is formed. In this way, a liquid discharge head (inkjet head) using the semiconductor substrate 1 is completed.

  In the liquid discharge head manufactured by the method of the present embodiment described above, the flow path 4 from the supply port 5 to the discharge port 6 is accurately formed. Conventionally, a silicon oxide film (second interlayer insulating film) 13 located under a so-called membrane film is wet-etched in order to form a through-hole 5a that is a connection portion of the supply port 5 with the flow path 4. At this time, due to the difference in etching rate between the flat portion and the step portion, the etching is continued even after the silicon oxide film 13 is removed at the step portion, and the silicon nitride film 16 located above the membrane film. As a result, there was a problem that the membrane film was damaged, and as a result, the nozzle mold material 18 which is a flow path forming member was eroded. However, in the present embodiment, a heating resistor 14 made of, for example, TaSiN is provided between the silicon oxide film (second interlayer insulating film) 13 located in the lower layer of the membrane film and the silicon nitride film 16 located in the upper layer. Since the heating resistor 14 functions as an etching stopper layer, when the silicon oxide film (second interlayer insulating film) 13 is wet-etched, the silicon nitride film 16 is eroded at the stepped portion B to be membrane film. Is not damaged, and as a result, the nozzle mold material 18 which becomes the flow path forming member is not eroded. Therefore, a predetermined flow path is formed in a subsequent process, and the flow path 4 can be formed with high accuracy. Although a heater material is used as the etching stop film, a material capable of taking an etching selection ratio with respect to the interlayer insulating film can be provided exclusively for it. However, it is preferable to use the heater material as it is because an extra process does not increase.

  On the sacrificial layer 11, only the heating resistor 14 is interposed between the silicon oxide film (second interlayer insulating film) 13 and the silicon nitride film 16, and the second wiring layer 15 made of aluminum is removed in advance. This is because the process becomes complicated when the number of films to be etched to remove the membrane film increases. As long as only the heating resistor 14 effective as an etching stopper layer is present in the membrane film, the purpose of forming the flow path 4 with high accuracy can be achieved as described above.

  As described above, according to the present invention, in the liquid ejection head having the semiconductor substrate 1, the membrane film is removed during the etching to remove the membrane film by changing the configuration of the membrane film with almost no additional steps as compared with the prior art. It is possible to avoid the risk of tearing and causing a defective shape of the nozzle material. That is, the heating resistor 14 serving as an etching stopper layer in the etching of the silicon oxide film 13 with hydrofluoric acid is disposed between the silicon oxide film 13 and the silicon nitride film 16 of the membrane film. The heating resistor 14 may be a Ta-Si-N-based material or a Ta-N-based material.

  As a result, the hydrofluoric acid etching time when removing the membrane film is lengthened (for example, 600 seconds to 780 seconds), and the film thickness tolerance of the silicon oxide film 13 is relaxed (for example, ± 9% to ± 15% or more). Therefore, the yield of the liquid discharge head having the semiconductor substrate 1 can be improved, and the manufacturing cost can be reduced. In addition, as described above, it is possible to prevent the discharge failure and the decrease in the discharge speed due to the defective shape of the flow path 4 and improve the performance of the liquid discharge head such as the recording quality and the recording speed.

3 is an enlarged cross-sectional view of a main part of a liquid discharge head having a semiconductor substrate according to the present invention. FIG. FIG. 4 is an enlarged cross-sectional view illustrating a manufacturing process of the first half of the liquid ejection head illustrated in FIG. 1. FIG. 3 is an enlarged cross-sectional view showing a manufacturing process subsequent to FIG. 2 of the liquid ejection head shown in FIG. 1. FIG. 2 is a plan view of a semiconductor substrate of the liquid discharge head shown in FIG. FIG. 4 is an enlarged sectional view showing a manufacturing process subsequent to FIG. 3 of the liquid ejection head shown in FIG. 1. FIG. 6 is an enlarged cross-sectional view showing a manufacturing process subsequent to FIG. 5 of the liquid ejection head shown in FIG. 1. It is an expanded sectional view which shows the manufacturing process of the liquid discharge head which has the conventional semiconductor substrate. It is a principal part expanded sectional view of the liquid discharge head which has the conventional semiconductor substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Resin substrate 3 Heater 4 Flow path 5 Supply port 5a Through port 6 Discharge port 7 Silicon substrate (silicon wafer)
10 Field oxide film 11 Sacrificial layer 12 First interlayer insulating film 12a Opening 13 Silicon oxide film (second interlayer insulating film)
14 Heating resistor (heater material)
15 Second metal wiring layer 16 Silicon nitride film 17 Tantalum film 18 Nozzle mold material 19 Nozzle material 20a, 20b Resin material A Active region B Stepped portion

Claims (2)

A semiconductor substrate, a heater disposed on one main surface of the semiconductor substrate, and a supply for liquid supply formed through the semiconductor substrate from the other main surface of the semiconductor substrate to the one main surface in the mouth, and a manufacturing method of the supply port and the through hole of the semiconductor substrate for a liquid discharge head having a through-hole,
Forming a silicon oxide film on the one main surface of the semiconductor substrate;
Forming an etching stopper layer on the silicon oxide film for stopping the etching for removing the silicon oxide film;
Forming a silicon nitride film on the etching stopper layer;
Removing the silicon oxide film by etching;
After removing the silicon oxide film, the etching stopper layer and the silicon nitride film are removed by etching, thereby forming a through-hole serving as a connection portion between the flow path in which the heater is located and the supply port. Process,
Only including,
The method for manufacturing a supply port and a through-hole of a semiconductor substrate for a liquid discharge head , wherein the etching stopper layer is formed in the same process as the heater . Before the step of forming the silicon oxide film, a sacrificial layer is formed in the same process as the wiring layer on the one main surface of the region corresponding to the portion where the through hole is formed of the semiconductor substrate. Process,
Before removing the etching stopper layer and the silicon nitride film, removing the region of the semiconductor substrate and the sacrificial layer to form a part of the supply port;
Further including
The method for manufacturing a supply port and a through port of a semiconductor substrate for a liquid discharge head according to claim 1, wherein the etching stopper layer is formed so as to cover the sacrificial layer.

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