JP2000012507A - Manufacture of three-dimensional silicon device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a three-dimensional shape precisely on an Si substrate without an increase in manufacturing cost. SOLUTION: In this manufacturing method, A heat oxidation film serving as an etching mask is formed for an Si substrate having <100> crystal orientation. The heat oxidation film is formed at a temperature causing almost no defect of oxygen condensation in the Si substrate, for example, at 104 deg.C or less, preferably between 840 and 1000 deg.C. Specifically, an oxidation temperature T and an oxidation time (t) are set so as to satisfy T<=0.0012 t2-0.9884t+1042.2 (below a curve of the figure). The heat oxidation film is formed in such a condition so as to suppress the growth of oxygen condensation in the Si substrate to a degree that no problem occurs in an actual processing, thereby precisely forming a three-dimensional shape by an anisotropic etching using KOH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thermal oxide film on a <100> Si substrate and performing anisotropic etching with KOH using the thermal oxide film as a mask to form a precise three-dimensional shape. Method.

[0002]

2. Description of the Related Art As a method of forming a three-dimensional shape such as a concave portion on a Si substrate, processing by a wet anisotropic etching method using a chemical solution such as KOH is known. For example, when this anisotropic etching is performed on a Si substrate having a crystal orientation of <100>, it is possible to accurately form a concave portion or a through hole having a rectangular opening.
Therefore, it is advantageous when a precise three-dimensional shape must be formed.

[0003] Such a processing method of anisotropic etching is applied to, for example, formation of a flow path of a recording liquid in a liquid jet recording apparatus. FIG. 4 is a perspective view showing an example of the liquid jet recording apparatus, and FIG. In the figure, 1
Is a liquid flow path substrate, 2 is an element substrate, 3 is a thick film layer, 4 is a liquid supply port, 5 is a common liquid chamber, 6 is a bypass flow path, 7 is a liquid flow path, 8 is a heating resistor, and 9 is a nozzle. It is. In this example,
As an example of the liquid ejection recording apparatus, a thermal liquid ejection recording apparatus using a heating resistor 8 that converts electric energy into heat energy as an energy conversion element is shown. In addition, there are several methods such as a method using a piezoelectric element as an energy conversion element.

The liquid flow path substrate 1 is provided with a plurality of grooves serving as liquid flow paths 7 and through holes serving as common liquid chambers 5.
The penetrating opening is the liquid supply port 4. Element substrate 2
Is provided with a heating resistor 8 corresponding to each liquid flow path 7, and a wiring, a driving circuit, and the like for supplying electric energy to the heating resistor 8 are formed. Further, a thick film layer 3 made of, for example, polyimide or the like is provided thereon. The thick film layer 3 includes a portion of a bypass channel 6 connecting the liquid channel 7 formed in the liquid channel substrate 1 and the common liquid chamber 5,
The portion on the heating resistor 8 has been removed. This thick film layer 3
Is necessary to form the bypass flow path 6 in this manner, and serves as a protective layer provided to prevent the wiring and the drive circuit formed on the surface of the element substrate 2 from being eroded by the liquid. Play a role. Such a liquid flow path substrate 1
And the element substrate 2 are aligned and joined to form a liquid jet recording apparatus.

As shown by arrows in FIG. 5, liquid used for recording is supplied from a liquid supply port 4. Liquid supply port 4
Is supplied to the liquid flow path 7 through a bypass flow path 6 formed by removing the thick film layer 3 from the common liquid chamber 5.

FIG. 6 is a diagram illustrating an example of a liquid ejecting process in a thermal type liquid ejecting recording apparatus. 11 is an individual electrode, 12 is a common electrode, 13 is a liquid, 14 is a bubble, 15
Is a droplet. As shown in FIG. 6A, in a state where the liquid 13 is supplied to the liquid flow path 7, the individual electrode 11 and the common electrode are applied to the heating resistor 8 to be driven based on an externally applied image signal. 12 supplies electrical energy.

The heating resistor 8 converts the applied electric energy to heat energy and heats the liquid 13 in the liquid flow path 7. In the liquid flow path 7, the liquid 13 boils rapidly, and bubbles 14 are generated as shown in FIG. The generated bubbles 14 grow rapidly in the liquid flow path 7. At this time, the liquid 13 in the liquid flow path 7 is pushed to both sides by the pressure at the time of growth of the bubble 14, and one is pushed out from the nozzle 9 as shown in FIG.

Thereafter, as shown in FIG.
Is reduced, and the liquid in the liquid flow path 7 receives a force in a direction to be drawn toward the heating resistor 8. However, the liquid 13 extruded from the nozzle 9 continues to move as it is due to inertial force.
Then, a part thereof is torn off from the liquid 13 in the liquid flow path 7, and FIG.
As shown in (E), it flies as a droplet 15. The flying droplets 15 adhere to a recording medium (not shown) such as paper,
A recording pixel is formed on a recording medium.

In the above-described liquid jet recording apparatus,
The liquid flow path substrate 1 is formed of, for example, a Si substrate, a resin, a metal plate, or the like. As described above, the liquid flow path substrate 1 is formed with a large number of fine grooves serving as the liquid flow paths 7 and through holes serving as the common liquid chambers 5. At this time, the liquid flow path substrate 1
<100> Si substrate is used, for example,
No. 99409, KOH
It can be processed by wet anisotropic etching using a chemical such as

FIG. 7 is a process chart showing an example of a method for manufacturing a liquid flow path substrate in a liquid jet recording apparatus. In the figure, 2
1 is a Si substrate, 22 is a SiO ₂ film, and 23 is a SiN film. Si substrate 2 serving as liquid flow path substrate 1 shown in FIG.
Relative to 1, SiO ₂ by thermal oxidation in Fig. 7 (B)
A film 22 is formed. Here, it is formed by wet oxidation at 1100 ° C. for 180 minutes. And FIG. 7 (C)
In step (1), a portion serving as a liquid flow path 7 including a nozzle and a portion serving as a common liquid chamber 5 are patterned using photolithography and dry etching. Si substrate 2 to be used
The crystal orientation of No. 1 is a <100> plane.

Subsequently, as shown in FIG.
The SiN film 23 is formed by the method D, and the portion to be the common liquid chamber 5 is patterned by photolithography and dry etching as shown in FIG.

Subsequently, the Si substrate 21 is etched with a KOH aqueous solution using the SiN film 23 as an etching mask. This etching is performed until it penetrates the Si substrate 21 as shown in FIG. 7F, and the through hole becomes the liquid supply port 4.

Subsequently, as shown in FIG.
3 is removed with a phosphoric acid solution, and then the Si substrate 21 is etched with a KOH aqueous solution using the SiO ₂ film 22 as an etching mask to form a groove serving as the liquid flow path 7 as shown in FIG. I do. Finally, the SiO ₂ film 22
Is selectively removed by hydrofluoric acid solution, and FIG.
As shown in (I), a Si substrate 21 serving as the liquid flow path substrate 1
Complete the processing of

FIG. 8 is a plan view showing an example of a Si substrate 21 serving as a liquid flow path substrate in a conventional liquid jet recording apparatus. In the figure, 31 is an over-etched portion. Through the manufacturing process shown in FIG. 7, the Si substrate 21 is provided with grooves and common liquid chambers 5 serving as liquid flow paths 7 corresponding to a large number of liquid flow path substrates.
Further, a through hole serving as the liquid supply port 4 is formed. This Si substrate 21 is bonded to a Si substrate on which a number of element substrates 2 formed separately are formed, and then separated into individual liquid jet recording devices by dicing. At this time, in the portion where the liquid flow paths 7 are arranged, cutting is performed by dicing at a nozzle dicing position indicated by a broken line in FIG. 8, and processing is performed so that the liquid flow paths 7 are opened to the cut surface. The open end of the liquid flow path 7 becomes the nozzle 9. As described above, since the groove serving as the liquid flow path 7 is formed by wet anisotropic etching of the <100> Si substrate 21 using a KOH aqueous solution, the cross sections of the nozzle 9 and the liquid flow path 7 are also shown in FIG. It becomes triangular.

In the liquid ejecting recording apparatus, a change in ejection characteristics such as the volume and speed of the droplet ejected from the nozzle 9 affects the image quality. Since the ejection characteristics of such droplets largely depend on the shape of the nozzle 9 and the cross-sectional area of the liquid flow path 7, the accuracy of forming the liquid flow path 7 in the above-described step of FIG. Required. However, there is a problem that the over-etched portion 31 is partially generated in the liquid flow path 7 on the Si substrate 21 manufactured in the conventional process as shown in FIG. When such an over-etched portion 31 occurs, the number of unetched portions between the respective liquid flow paths 7 decreases, so that the respective liquid flow paths 7 cannot be separated, and a jetting failure of droplets occurs. Further, even if each liquid flow path 7 can be separated, the volume of the ejected droplet increases due to the increase in the flow path width, and the flying speed decreases.
For this reason, the droplets do not fly with normal applied energy, or the recording density or recording position changes, and the image quality is greatly reduced.

FIG. 9 is a graph showing a distribution of nozzle widths formed by an example of a conventional method of manufacturing a liquid jet recording apparatus. In the graph shown in FIG. 9, the horizontal axis indicates the nozzle width design value subtracted from the actually measured nozzle width. For example, assuming that the tolerance of the nozzle width error is ± 1 μm, it can be seen that there are a good product group finished almost as designed and a defective product group whose nozzle width is outside the upper limit of the specified value. The ratio was also extremely low at 18%, and excessive etching as described above was a major problem in the manufacturing process.

As described in, for example, the above-mentioned Japanese Patent Application Laid-Open No. 5-299409, such an excessive etching is carried out in a high-temperature oxidation step of forming the SiO ₂ film 22 shown in FIG. This is due to oxygen condensation defects generated inside 21. Oxygen is previously doped in the Si substrate 21 in order to maintain the mechanical strength of the Si substrate 21. The oxygen condenses upon application of heat and becomes defective. The growth rate of this defect increases as the temperature of the heat treatment increases, and increases as the temperature increases. FIG. 10 is a schematic diagram showing an example of an etched shape when an oxygen condensation defect has occurred in the Si substrate 21. In the figure, 32 is an oxygen condensation defect portion. When the oxygen condensation defect 32 is generated inside the Si substrate 21, the speed at the time of the anisotropic etching increases around the defect 32. Therefore, an over-etched portion 31 occurs around the oxygen condensation defect portion 32 inside the Si substrate 21 as shown in FIG. As in the conventional process of forming a SiO ₂ film, when an SiO ₂ film is formed by oxidation at, for example, 1100 ° C. for 180 minutes, many oxygen condensation defects have occurred.

As a method for solving this problem, for example, Japanese Unexamined Patent Publication (Kokai) No. 7-1737 discloses a method in which a silicon nitride layer formed at a low temperature is used as an etching mask instead of a SiO ₂ film formed by thermal oxidation. A method for suppressing occurrence is disclosed. According to this method, although a defect due to an oxygen condensation defect can be avoided, it is necessary to form another layer for separating the two silicon nitride layers, and there is a disadvantage that the manufacturing cost increases.

The above-mentioned Japanese Patent Application Laid-Open No. 5-299409 describes that etching is performed using ethylenediamine-pyrocatechol (EDP) water instead of KOH. Because EDP does not etch the SiO ₂ film, it is possible to reduce the SiO ₂ film used as a mask. Therefore, oxygen condensation can be reduced by forming the SiO ₂ film in a short time. However, there is a problem in that the etching rate is low and the manufacturing time is long, so that the manufacturing cost is increased.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances. Accordingly, it is possible to accurately form a three-dimensional silicon on a Si substrate without increasing manufacturing costs. It is an object of the present invention to provide a device manufacturing method.

[0021]

SUMMARY OF THE INVENTION According to the present invention, when a thermal oxide film used as a mask is formed on a Si substrate in wet anisotropic etching using KOH, oxygen condensation defects almost occur in the Si substrate. It is formed at a temperature not higher than 1040 ° C., preferably 840-1000 ° C. Further, the present invention is characterized in that a thermal oxide film is formed within a temperature and time range in which oxygen condensation defects hardly occur in the Si substrate. Thus, even when anisotropic etching is performed by KOH using the thermal oxide film as a mask, excessive etching due to oxygen condensation defects does not occur, and a three-dimensional shape can be accurately formed. Therefore, accurate processing can be performed without increasing the manufacturing cost.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a three-dimensional silicon device according to the present invention will be described. Here, as an example, a case where the Si substrate 21 of the liquid jet recording apparatus as shown in FIGS. 4 and 5 is manufactured will be described. The manufacturing process of the Si substrate of the liquid jet recording apparatus to which the present invention is applied is almost the same as the conventional manufacturing process described with reference to FIG. 7, but the process of forming the SiO ₂ film 22 in FIG. different. As described above, oxygen is doped in the Si substrate 21 in advance in order to maintain the mechanical strength of the Si substrate 21, and the oxygen condenses by heating at a high temperature for a long time to become a defect. Therefore, in the present invention, a step of forming the SiO ₂ film 22 by processing at a high temperature (FIG. 7B)
At a temperature at which oxygen condensation defects hardly occur in the Si substrate 21, for example, 1040 ° C. or less, preferably 840 to 1
An SiO ₂ film 22 is formed at 000 ° C. It is desirable that this step be completed within a time range in which oxygen condensation defects hardly occur in the Si substrate 21 at this temperature.
By forming the SiO ₂ film 22 in this manner, the growth of oxygen condensation defects in the Si substrate 21 can be suppressed to a level that does not hinder actual processing.

Thereafter, through the steps of FIGS. 7C to 7G, KOH is formed in the step of FIG. 7H using the SiO ₂ film 22 formed in the steps of FIGS. 7B and 7C as a mask. To perform wet anisotropic etching. FIG. 2 is a plan view showing an example of a Si substrate 21 serving as a liquid flow path substrate of a liquid jet recording apparatus manufactured by applying one embodiment of the method for manufacturing a three-dimensional silicon device of the present invention. FIG. 7 (B)
Since almost no oxygen condensation defects are generated in the Si substrate 21 in the step (1), the overetched portion as shown in FIG. 8 does not occur, and the groove to be the liquid flow path 7 is precisely formed as shown in FIG. Can be formed.

Next, the temperature and time for forming the SiO ₂ film 22 in the present invention will be further described. FIG. 1 is a graph showing the relationship between the temperature and time when a SiO ₂ film is formed, and the occurrence of non-defective / defective products. Here, the temperature and time for forming the SiO ₂ film 22 were changed when the liquid flow path substrate of the liquid jet recording apparatus was manufactured as described above. Then, the width of the groove that finally becomes the liquid flow path 7 formed on the Si substrate 21 was measured and compared with a specified value. At this time, the case where the width of all the formed grooves is within the allowable range from the specified value is regarded as a non-defective product, and is marked with a circle in FIG. In addition, if any one of them exceeds the allowable range, it is marked with a cross in FIG. 1 as a defective product.

The curves in the figure are good (good) and defective (good).
Mark) indicates the boundary. Incidentally, this curve has a relationship of T = 0.0012 t ² −0.9884 t + 1042.2, where T is the oxidation temperature and t is the oxidation time. Area above this curve (T> 0.00)
At 12t ² -0.9884t + 1042.2), a defect has occurred. This is due to the high temperature and long-time oxidation
Oxygen condensation defects occur in the i-substrate 21, and the groove width is widened by the over-etched portion 31 as shown in FIGS. 8 and 10. In addition, the area below this curve (T ≦ 0.0
012t ² -0.9884t + 1042.2), it can be seen that no failure occurs. It is considered that this is because almost no oxygen condensation defects occurred in the Si substrate 21 due to the low-temperature and short-time oxidation as in the present invention. As can be seen from this curve, when the oxidation temperature is 1040 ° C. or lower, the SiO ₂ film can be formed without causing oxygen condensation defects in the Si substrate by adjusting the oxidation time. Particularly, at a temperature of 840 ° C. to 1000 ° C., no excessively etched portion due to oxygen condensation defects was actually observed, and a groove serving as a liquid flow path could be formed accurately.

When the oxidation temperature is lowered and the oxidation time is shortened, the thickness of the SiO ₂ film 22 is reduced. 7 In the process shown in (H), is to etch the Si substrate 21 with KOH the SiO ₂ film 22 as a mask, this time SiO ₂ film 2
2 is also etched, though in trace amounts. If the SiO ₂ film 22 formed in the step of FIG. 7B becomes too thin, the SiO ₂ film 22 may disappear during the etching of the Si substrate 21 in the step of FIG. There is. Therefore, the thickness of the SiO ₂ film 22 and
The etching conditions such as the concentration and temperature of KOH are adjusted in accordance with the etching amount of the groove and the like formed in the Si substrate 21, and the SiO ₂ ratio with respect to the etching rate of the Si substrate 21 is adjusted.
What is necessary is just to make the ratio of the etching rate of the film 22 small. Conversely, by setting such etching conditions, KO
H etching is possible, and processing can be performed by high-speed anisotropic etching. Therefore, the manufacturing cost does not increase.

FIG. 3 shows an example of the distribution of the width of the nozzles formed on the liquid flow path substrate of the liquid jet recording apparatus manufactured by applying one embodiment of the method for manufacturing a three-dimensional silicon device of the present invention. It is a graph. Here, the Si substrate 21 was oxidized to form an SiO ₂ film 22 under the conditions of an oxidation temperature of 900 ° C. and an oxidation time of 180 minutes, which is one of the conditions under which a good product was manufactured in the graph shown in FIG. The thickness of the SiO ₂ film 22 formed in this step was 300 nm.

Thereafter, a groove serving as the liquid flow path 7 was formed on the Si substrate 21 by etching, and the width of the formed groove was measured. When the frequency distribution was examined based on the difference between the measured value and the design value, the result shown in FIG. 3 was obtained. Here, the allowable range is ± 1 μm from the design value. As can be seen from FIG. 3, all the formed grooves are within the allowable range, and the non-defective rate (yield) is 100%.

Further, as can be seen from comparison with FIG. 9, it can be seen that etching has not occurred such that the actual groove width greatly exceeds the design value. That is, according to the manufacturing method of the present invention, it is possible to suppress the growth of oxygen condensation defects in the Si substrate, thereby achieving high-precision processing and improving the manufacturing yield.

Further, by applying the manufacturing method of the present invention to the manufacturing process of the liquid jet recording apparatus as described above, the liquid flow path and the nozzle can be formed accurately. As a result, the amount and speed of the ejected droplets are uniform, and the image quality can be improved. Furthermore, it is possible to arrange the liquid flow paths and the nozzles at a high density to configure a liquid jet recording apparatus capable of performing high-resolution recording.

The method of manufacturing a three-dimensional silicon device according to the present invention has been described above by taking the case of manufacturing a liquid jet recording apparatus as an example. However, the present invention is not limited to this. However, the present invention can be applied to any use for forming a three-dimensional shape by anisotropic etching.

Further, in the above-mentioned example, SiO ₂ by thermal oxidation is used.
Although an example of film formation has been described, for example, a chemical vapor deposition method (CV
Even in the case of using D), by setting the temperature or the conditions of the temperature and the time as described above and performing the processing, the oxygen condensation defects in the Si substrate are reduced as described above, and the three-dimensional shape is precisely formed. Can be formed.

[0033]

As is apparent from the above description, according to the present invention, in the step of forming a silicon oxide film used as a mask at the time of etching, the silicon oxide film is formed under conditions that hardly cause oxygen condensation defects.
There is an effect that a three-dimensional shape can be accurately formed, and a manufacturing yield can be improved. At this time, KOH conventionally used as an etching solution is used.
Since it can be used as it is and can be manufactured with the same number of steps as before, there is also an advantage that the processing speed is reduced and the manufacturing cost is not increased.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the temperature and time when a SiO ₂ film is formed, and the occurrence of non-defective / defective products.

FIG. 2 is a plan view showing an example of a Si substrate 21 serving as a liquid flow path substrate of a liquid jet recording apparatus manufactured by applying one embodiment of the method for manufacturing a three-dimensional silicon device of the present invention.

FIG. 3 is a graph showing an example of a width distribution of nozzles formed on a liquid flow path substrate of a liquid jet recording apparatus manufactured by applying one embodiment of the method for manufacturing a three-dimensional silicon device of the present invention. .

FIG. 4 is a perspective view illustrating an example of a liquid jet recording apparatus.

FIG. 5 is a cross-sectional view of an example of a liquid jet recording apparatus taken along line A.

FIG. 6 is a diagram illustrating an example of a liquid ejection process in a thermal type liquid ejection recording apparatus.

FIG. 7 is a process chart showing an example of a method for manufacturing a liquid flow path substrate in the liquid jet recording apparatus.

FIG. 8 is a plan view showing an example of a Si substrate 21 serving as a liquid flow path substrate in a conventional liquid jet recording apparatus.

FIG. 9 is a graph showing a distribution of nozzle widths formed by an example of a conventional method for manufacturing a liquid jet recording apparatus.

FIG. 10 is a schematic diagram showing an example of an etched shape when an oxygen condensation defect occurs in a Si substrate 21.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid flow path substrate, 2 ... Element substrate, 3 ... Thick film layer, 4 ... Liquid supply port, 5 ... Common liquid chamber, 6 ... Bypass flow path, 7 ... Liquid flow path, 8 ... Heating resistor, 9 ... Nozzle, 11 ... individual electrode,
12: Common electrode, 13: Liquid, 14: Bubble, 15: Droplet, 21: Si substrate, 22: SiO ₂ film, 23: SiN
Film, 31: over-etched portion, 32: oxygen condensation defect portion.

Continued on the front page (72) Inventor Akitaka Inoue 2274 Hongo, Ebina-shi, Kanagawa Prefecture F-term within Fuji Xerox Co., Ltd. 2C057 AF93 AG12 AG44 AP02 AP14 AP34 AQ02 BA05 BA14 5F043 AA02 BB02 DD30 FF10 GG06 GG10

Claims (4)

[Claims] 1. A method for manufacturing a three-dimensional silicon device in which a three-dimensional shape is formed by performing anisotropic etching with KOH using a thermal oxide film formed on a <100> Si substrate as a mask. A method for manufacturing a three-dimensional silicon device, comprising forming a silicon substrate at a temperature at which oxygen condensation defects hardly occur. 2. A method for manufacturing a three-dimensional silicon device in which a three-dimensional shape is formed by performing anisotropic etching with KOH using a thermal oxide film formed on a <100> Si substrate as a mask. A method for manufacturing a three-dimensional silicon device, wherein the method is performed within a temperature and time range in which oxygen condensation defects hardly occur in a Si substrate. 3. The method for manufacturing a three-dimensional silicon device according to claim 1, wherein said thermal oxide film is formed by wet oxidation at a temperature of 1040 ° C. or less. 4. The method for manufacturing a three-dimensional silicon device according to claim 3, wherein said thermal oxide film is formed at a temperature of 840 to 1000 ° C.