JP5454776B2 - Through hole formation method - Google Patents

Description

  The present invention relates to a through hole forming method, and more particularly to a method of forming a through hole such as a hole or a trench in a substrate by plasma etching.

Conventionally, in a process of manufacturing a semiconductor device by etching, a plasma etching method is frequently used in which etching gas plasma is generated and etching is performed by the action of the plasma. In this case, when the interlayer insulating film formed on the substrate is subjected to plasma etching using a CF ₄ / Ar etching gas with bias power applied to form a wiring groove, the bottom of the interlayer insulating film has a mountain shape, and the bottom There is a problem in that a micro-trench (micro-recess) shape with a part cut away is generated (see, for example, Patent Document 1). The formation of such micro-trench is thought to be due to the wraparound of ions due to charge-up.

  In recent years, for example, in a technical field such as NEMS, MEMS (sensors, actuators, vibrators, oscillators, transmitters, wafer level packaging), semiconductor packaging (packaging), a through hole is provided in a substrate or a substrate on which a multilayer film is formed. Is required. However, in the case of plasma etching, when a plurality of through holes are formed, if the etching rate is fast or slow depending on the position on the object to be processed, over-etching occurs at a place with a fast rate. Therefore, in order to form the through hole, it is necessary to continue etching at a place where the rate is low. As a result, there is a problem that the surface of the substrate support stage on which the substrate is placed is damaged and the substrate stage must be replaced when the damage progresses.

  An etching method is known in which trenches penetrating through a silicon semiconductor substrate are collectively formed (see, for example, Patent Document 2). In this case, wet etching is performed on a plurality of silicon semiconductor substrates using an alkaline etching solution.

  Further, an imprint mold is known in which a microtrench (a minute recess) is formed in the uneven pattern of the mold (see, for example, Patent Document 3). In this case, in Si dry etching using an IPC dry etching apparatus, the Si substrate is etched to a predetermined depth using the resist pattern as a mask, the resist pattern is stripped, and the bottom of the bottom of the recess of the Si substrate A micro trench is formed in the portion. The micro-trench is merely provided to reduce defects in the resist pattern caused by the gas taken in between the imprint mold and the resist during imprinting.

JP 2002-289577 A (paragraph 0004) JP 2008-41676 A (Claims) JP 2007-42715 A

  An object of the present invention is to solve the above-mentioned problems of the prior art, by forming a micro-trench (sub-trench) around the bottom when forming a hole or trench in a substrate by plasma etching. An object of the present invention is to provide a method for simply forming a through hole in a substrate.

In the through hole forming method of the present invention, when a mask pattern is formed on a substrate and a hole or trench is formed by plasma etching under a bias power of 500 to 1000 W, a micro trench is formed around the bottom of the hole or trench. Then, etching is performed until the bottom surface of the micro-trench reaches the same level as the bottom surface of the substrate, or etching is performed until the bottom surface of the micro-trench portion is removed by an impact that does not break the substrate. It is characterized by forming.

  If the bias voltage is less than 500 W, micro-trenching is difficult to occur, and if the bias voltage exceeds 1000 W, etching proceeds too much and damages the substrate support stage.

  Conventionally, in order to suppress the micro-trench that is formed at the bottom of the wiring trench and causes a leakage current, the etching process was increased in pressure and the bias voltage was reduced, but according to the present invention, Through holes can be formed using the microtrench.

  As the substrate, a substrate on which a laminated film is provided is used.

In the plasma etching, C ₄ F ₈ is used as an etching gas.

  Etching is performed while the substrate is placed on a tray to form a through hole in the substrate.

  By performing etching by placing the substrate on the tray, the tray itself on which the substrate having the through hole is placed can be carried out of the vacuum chamber, and the etching residue can be collected there. In addition to this, damage to the surface of the substrate stage can be avoided.

  According to the present invention, there is an effect that a through hole can be easily formed in a substrate.

The block diagram which shows one structural example of the etching apparatus used by this invention. The flowchart for demonstrating formation of the through-hole by this invention. It is a SEM photograph which shows the result of the etching by Example 1, (a) is a result of a comparative example, (b) is a result of an Example.

According to the embodiment of the through hole forming method of the present invention, a substrate on which a predetermined mask pattern is formed is placed on a tray (for example, an Al tray), and the tray is placed in an etching vacuum chamber. C ₄ F ₈ (or C _x F _y , C _x) is used as an etching gas when mounting and forming holes or trenches by plasma etching under conditions of bias power of 500 to 1000 W, preferably 500 to 850 W. H _y F _z gas, etc.), a micro trench is formed around the bottom of the hole or trench, that is, at the bottom of the bottom etching residue (for example, a chevron-shaped etching residue), and the bottom surface of the micro trench is the bottom surface of the substrate Etching until the same level as in step 1 By forming by etching until the level of quenching residual escapes, it is possible to form a through hole in the substrate.

  The tray used in the present invention is preferably made of a material that is difficult to be etched, and examples thereof include Al, SUS, Fe, a ceramic material, silicon, and carbon depending on conditions. The substrate is placed on a tray and fixed by an electrostatic chuck or a mechanical chuck, which is a normal method. Although this embodiment will be described using a tray, a synthetic resin sheet or the like may be used instead of the tray.

Also for a substrate provided with a laminated film, through holes can be formed in the laminated film and the substrate in the same manner as described above. As the substrate, for example, a substrate made of SiO ₂ , glass, resin (preferably synthetic resin), Low-K material, ferroelectric material (for example, PZT, LiNbO ₃ , LiTaO ₃ ), or silicon in some cases is used. The laminated film may be a single layer or a plurality of layers. For example, an interlayer insulating film made of SiO ₂ or the like, a multilayer film composed of a plurality of insulating film layers other than SiO ₂ , a metal and an insulating film A multilayer film composed of layers can be used.

  The mask pattern can be formed by a known photolithography method using a known mask material, and is formed in accordance with the arrangement of holes or trenches that form through holes.

  When a hole or trench is formed by plasma etching the substrate with a predetermined bias power, the bottom of the substrate, that is, the bottom of the hole or trench is, for example, a mountain shape, and a skirt is cut off. Shape occurs. In the present invention, etching is performed until the bottom surface of the micro-trench reaches the same level as the bottom surface of the substrate, or the bottom surface of the micro-trench portion is broken due to an impact that does not break the substrate, and the mountain-shaped portion at the bottom of the hole or trench is formed. For example, by etching to a thickness of about 1.0 μm until the level is easily removed, the mountain-shaped portion can be easily removed, and a through hole is formed.

  In particular, when etching is performed with the substrate placed on the tray, if the bottom of the micro trench is etched to the same level as the bottom of the substrate, the tray is removed from the vacuum chamber and removed from the tray outside the chamber. As a result, an unetched mountain-shaped portion remains on the tray, and a through hole is formed. Further, if etching is performed until the bottom surface of the micro-trench portion is broken by an impact that does not break the substrate, the mountain-shaped portion can be extracted by giving a light impact to the tray carried out of the vacuum chamber. The use of the tray is preferable in terms of maintenance of the vacuum chamber, and damage to the surface of the substrate stage caused by placing the substrate directly on the substrate stage can be avoided. When the tray with the mountain-shaped portion discarded can be reused and the etching damage of the tray becomes large, it can be replaced with a new tray.

  The dry etching apparatus for carrying out the through hole forming method according to the present invention may be any known dry etching apparatus (apparatus described in Japanese Patent Application Laid-Open No. 2002-343775), for example, discharge plasma (NLD plasma). ) Using an NLD plasma etching apparatus.

  An etching apparatus used in the present invention will be described with reference to FIG. This etching apparatus 101 uses discharge plasma (NLD plasma) generated in a region including zero magnetic field, and has a vacuum chamber 103 provided with a vacuum pumping means 102 such as a dry pump, a rotary pump, or a turbo molecular pump. .

  The vacuum chamber 103 includes an upper plasma generation chamber 105 having a cylindrical side wall 104 made of a dielectric material such as quartz and a lower substrate processing chamber 106. Three magnetic field coils 107a, 107b, and 107c are provided outside the cylindrical side wall 104 at predetermined intervals to constitute a magnetic field generating means. The three magnetic field coils 107a, 107b and 107c are attached to a yoke member (not shown) made of a high magnetic permeability material so as to surround the outside from above and below. In this case, a current in the same direction is supplied to the upper and lower magnetic field coils 107a and 107c, and a current in the opposite direction is supplied to the intermediate magnetic field coil 107b. As a result, a continuous magnetic field zero position is formed inside the cylindrical side wall 104 in the vicinity of the level of the intermediate magnetic field coil 107b, and an annular magnetic neutral line 108 is formed.

  The size of the annular magnetic neutral line can be appropriately set by changing the ratio of the current flowing through the upper and lower magnetic field coils 107a and 107c and the current flowing through the intermediate magnetic field coil 107b. The position in the vertical direction can be appropriately set according to the ratio of currents flowing through the upper and lower magnetic field coils 107a and 107c. Further, as the current flowing through the intermediate magnetic field coil 107b is increased, the diameter of the annular magnetic neutral wire 108 becomes smaller, and at the same time, the gradient of the magnetic field at the zero magnetic field position becomes gentler. An antenna coil 109 for generating a high-frequency electric field is provided between the intermediate magnetic field coil 107b and the cylindrical side wall 104, and this antenna coil 109 is connected to a first high-frequency power source 110 to constitute a magnetic field generating means. Then, an alternating magnetic field is applied along the annular magnetic neutral line 108 formed on the upper portion of the vacuum chamber 103 by the three magnetic field coils 107a, 107b and 107c, and discharge plasma (NLD plasma) is generated in the magnetic neutral line. It is configured as follows.

  In the substrate processing chamber 106, a substrate electrode 111 having a circular cross section, which is a substrate stage on which the substrate S is placed, is opposed to the surface formed by the annular magnetic neutral wire 108 via an insulator member (not shown). Is provided. The substrate electrode 111 is connected to the second high-frequency power source 113 via the capacitor 112, and is configured to be a floating electrode in terms of potential and to have a negative bias potential.

  A top plate 114 provided on the upper part of the plasma generation chamber 105 is hermetically fixed to the upper flange of the cylindrical side wall 104 via an insulating member (not shown), and functions as a counter electrode in a potential floating state. To do. A gas introducing means 115 for introducing an etching gas into the vacuum chamber 103 is provided on the inner surface of the top plate, and the gas introducing means 115 is connected to a gas source via a gas flow rate control means (not shown). ing. The top plate 114 is branched from the middle of the feeding path from the first high-frequency power source 110 to the antenna coil 109 via the variable capacitor, so that high-frequency power is applied via the capacitor, and self-bias is applied to the counter electrode. It may be configured to occur.

A focus ring (electrode pressing member) 116 surrounding the substrate S is provided on the substrate electrode 111 in order to direct the flow of process gas and plasma toward the surface of the substrate S. The focus ring 116 is usually made of quartz. However, when the etching of the present invention is performed due to oxygen generated from quartz, the resist pattern as a mask is damaged, and the mask selection ratio is not perfect. Resist wear occurs. Therefore, in practicing the above-described etching method _consists Al ₂ O 3, AlN or _Y 2 _O focus ring made from _{3 Al} 2 _O 3 or on the quartz surface,, AlN or _Y 2 _{O 3} spray A focus ring provided with a film, a CVD film or a sputtered film is used to prevent resist consumption during the etching process.

The sprayed film, the CVD film, and the sputtered film made of Al ₂ O ₃ , AlN, and Y ₂ O ₃ must be formed in close contact with the quartz surface, for example, on the entire surface of the focus ring. It can be formed by a known thermal spraying method, CVD method or sputtering method. If this film thickness is about 100 to 300 μm, film peeling does not occur during the etching of the present invention.

  The film formed by the thermal spraying method can be formed by a known method, for example, a method described in JP-A No. 2003-166043, and is not particularly limited. For example, in accordance with a plasma spraying method such as a known low-pressure plasma spraying method, a dense sprayed film having good adhesion can be formed at a predetermined temperature at a predetermined temperature.

The film formed by the CVD method is a known method, for example, in the case of an yttria film, Y (C ₁₁ H ₁₉ O ₂ ) ₃ as a precursor material, nitrogen (10 sccm) as a carrier gas, and O ₂ (500 to 1000 sccm) as a diluent gas. ), A dense yttria film with good adhesion can be formed on the entire surface of the substrate under conditions of a substrate temperature of 400 to 500 ° C. and a chamber pressure of 133 to 1330 Pa.

The film formed by the sputtering method is a known method, for example, in the case of an yttria film, after placing the substrate on the substrate holder, the substrate is evacuated to a high vacuum state by a vacuum pump, and argon gas is 6.7 × 10 6 from the gas introduction hole. ^-2 Pa is introduced, then the RF power supply is activated to generate a high frequency voltage, 1.0 kW RF sputtering power is applied to the yttria film formation target, and a parallel magnetic field is formed on the substrate surface by a magnetic circuit. While performing RF magnetron sputtering, a dense yttria film with good adhesion can be formed on the entire surface of the substrate with a predetermined thickness. During magnetron sputtering, it is preferable to use a substrate heating heater and maintain the substrate temperature at about 270 ° C.

  By using the etching apparatus 101 configured as described above, the above-described etching gas is introduced into the vacuum chamber, and a predetermined bias power is applied to etch the substrate, thereby forming a through hole.

  Next, an embodiment of a method for forming a through hole according to the present invention performed using the etching apparatus shown in FIG. 1 will be described.

An etching gas composed of C ₄ F ₈ is introduced under the conditions of 1000 to 3000 W for the plasma generating high frequency power source and 500 to 1000 W for the substrate bias high frequency power source (12.56 MHz), and 0.2 to 2. Under a pressure of 0 Pa, the substrate was discharged at a substrate set temperature of -20 to 50 ° C. for a predetermined time, and the substrate was etched to form a trench. The result will be described with reference to the etching process shown in FIGS. 2 (a), (b), and (c).

  A resist (G-ray resist) is applied on the substrate 202, and a pattern formed by photolithography (resist pattern 203) is placed on the tray 201, fixed (FIG. 2 (a)), and placed in a vacuum chamber. To do. Thereafter, when the trench is formed by etching the substrate 202 using the above-described etching gas, a trench having, for example, a mountain shape and a bottom having a micro-trench (small concave portion) A formed by cutting off the bottom portion thereof is obtained. (FIG. 2B). In FIG. 2B, reference numeral 202a denotes a substrate on which a micro trench A is formed. If the bottom surface of the micro-trench A reaches the bottom surface of the substrate 202, the tray 201 is taken out of the vacuum chamber, and the substrate 202a is removed from the tray 201, whereby the substrate 202a having a through hole is obtained (FIG. 2 (c)). Even if the bottom surface of the micro-trench A does not reach the bottom surface of the substrate and a very small thickness remains, if a slight impact is applied to the tray 201 carried out of the vacuum chamber, that is, the substrate 202, the micro-trench A can be easily obtained. A substrate 202a having a through-hole formed with a broken thickness is obtained. In the case of the method of the present invention, the consumption of the resist pattern is extremely small as compared with the conventional case, and the through hole can be easily formed. Next, if a CMP process is performed as desired, the substrate surface can be flattened. Note that the resist pattern 203 can be peeled off by a known method.

  Hereinafter, the present invention will be specifically described by way of examples.

In this example, plasma etching was performed using C ₄ F ₈ as an etching gas using the etching apparatus shown in FIG. 1, and a through hole was formed in a SiO ₂ substrate having a diameter of 15 cm and a thickness of 100 μm.

  As the conditions for this plasma etching, the etching gas is used under the condition that the power of the plasma generating high frequency power supply (13.56 MHz) is 2300 W (antenna power) and the power of the substrate bias high frequency power supply (12.56 MHz) is 650 W (bias power). Was discharged at a substrate set temperature of 0 ° C. for a predetermined time under a pressure of 0.5 Pa to etch the substrate.

  For comparison, the above etching method was repeated with an antenna power of 2300 W and a bias power of 450 W.

  About the said etching result, the SEM photograph of a board | substrate cross section is shown to Fig.3 (a) and (b). FIG. 3A shows the result of etching performed for comparison, and FIG. 3B shows the etching result of this example.

  In the case of this example, when etching was further continued, a 20-μm-high non-etched portion having a height of 20 μm was formed at the bottom of the substrate, and a micro-trench reaching the bottom of the substrate was formed at the bottom. Thus, a substrate having a through hole was obtained.

  In this example, the substrate was etched under the same conditions as in Example 1 except that the power of the substrate bias high frequency power supply (12.56 MHz) was 500 W (bias power) as the plasma etching conditions.

  Also in this example, when the etching was further continued, an unetched portion having a mountain shape with a height of 20 μm was formed at the bottom of the substrate, and a micro-trench reaching the bottom of the substrate was formed at the bottom. Thus, a substrate having a through hole was obtained.

  In this example, the substrate was etched under the same conditions as in Example 1 except that the power of the substrate bias high frequency power source (12.56 MHz) was set to 1000 W (bias power) as the plasma etching conditions.

  Also in this example, when the etching was further continued, an unetched portion having a mountain shape with a height of 20 μm was formed at the bottom of the substrate, and a micro-trench reaching the bottom of the substrate was formed at the bottom. Thus, a substrate having a through hole was obtained.

(Comparative Example 1)
In this comparative example, the substrate was etched under the same conditions as in Example 1 except that the power of the substrate bias high frequency power supply (12.56 MHz) was 1100 W (bias power) as the plasma etching conditions.

  In the above case, the etching of the micro-trench has progressed too much, causing damage to the substrate holding stage.

  According to the present invention, since a through-hole can be easily formed in a substrate, the present invention relates to NEMS, MEMS (sensor, actuator, vibrator, transmitter, wafer level packaging), semiconductor packaging (packaging) And the like can be effectively used in the field of semiconductor devices.

DESCRIPTION OF SYMBOLS 101 Etching apparatus 102 Vacuum exhaust means 103 Vacuum chamber 104 Cylindrical side wall 105 Plasma generating chamber 106 Substrate processing chamber 107a, 107b, 107c Magnetic field coil 108 Annular magnetic neutral wire 109 Antenna coil 110 First high frequency power supply 111 Substrate electrode 112 Capacitor 113 First 2 High frequency power supply 114 Top plate 115 Gas introduction means 116 Focus ring 201 Tray 202 Substrate 202a Substrate 203 with a through-hole formed therein Resist pattern S Substrate A Micro trench

Claims (4)

When a mask pattern is formed on a substrate and a hole or trench is formed by plasma etching under a bias power of 500 to 1000 W, a microtrench is formed around the bottom of the hole or trench, and the bottom surface of the microtrench is the substrate. A through hole is formed in the substrate by etching until it reaches the same level as the bottom surface of the substrate or by etching until the bottom surface of the micro-trench portion is removed by an impact that does not break the substrate. Forming method. 2. The through hole forming method according to claim 1, wherein a substrate on which a laminated film is provided is used as the substrate. 3. The through hole forming method according to claim 1, wherein C ₄ F ₈ is used as an etching gas in the plasma etching. The through-hole forming method according to any one of claims 1 to 3 , wherein the substrate is etched while being placed on a tray to form a through-hole in the substrate.