KR100292682B1 - Electrostatic heat junction method of semiconductor substrate - Google Patents

Abstract

PURPOSE: An electrostatic heat junction method of a semiconductor substrate is provided to adhere one silicon substrate to the other silicon substrate or one silicon substrate to a glass substrate under a low temperature and a low voltage by using an electron beam deposition device having a high depositing speed. CONSTITUTION: A power supply portion(2) is used for applying a supply voltage to an N type silicon substrate(1) and a silicon substrate(2) including a glass film. A heating portion(4) is used for heating the silicon substrate(2) including the glass film according to a control operation of a thermal control portion(5). The N type silicon substrate(1) and the silicon substrate(2) including the glass film are adhered to each other by applying the voltage and the heat the N type silicon substrate(1) and the silicon substrate(2) including the glass film.

Description

Electrostatic Thermal Bonding Method of Semiconductor Substrate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrostatic thermal bonding of semiconductor substrates, and is particularly suitable for vacuum mounting of field emission display devices by bonding silicon substrates or silicon substrates and glass substrates at low temperature and voltage using an electron beam evaporator with a fast deposition rate. It relates to a method of electrostatic thermal bonding of a semiconductor substrate.

Conventionally, a glass thin film is deposited on a silicon substrate by sputtering, and a silicon substrate on which the glass thin film is deposited is bonded to a silicon substrate by using an electrostatic thermal bonding process. Thus, field-assisted bonding is performed. Electrothermal bonding technology, also called anodic bonding, is widely used in many fields, such as micromachining and SOI, because it can be bonded without the treatment of chemicals for hydrophilization at a lower temperature than the direct bonding technology. Electrostatic thermal bonding was avoided in 1969. egg. Daniel I. Pomerantz of P. R. MALLOIY made it known for the first time by bonding a silicon substrate and a glass substrate at a temperature of 300-600 ° C and a voltage of 200-2000V. Subsequently, a method of electrothermal bonding using glass thin films deposited by Brooks and Donnavan in 1972 was developed, and silicon-silicon bonding under lower temperature and voltage than the first method using glass substrates. By doing this, we have shown greater potential for electrostatic thermal bonding. In particular, many researches and applications have been made in the field of micromachining. Currently, Corning's Corning # 7740 glass target is used to deposit a thin film on a silicon substrate by sputtering to perform electrostatic thermal bonding. According to the structure, the Corning # 7740 glass substrate is directly electrostatically thermally bonded to a silicon device. In the manufacture of semiconductor devices using electrostatic thermal bonding, bonding is required under low temperature and low pressure conditions to reduce possible damage to the devices.Since 1972, electrostatic thermal bonding has been sputtered. Silicon-silicon bonding was performed using the deposited glass thin film, and the method of electrostatic thermal bonding of a substrate using the conventional sputtering will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing the electrostatic thermal bonding mechanism between silicon substrates using a glass thin film. As shown in FIG. 1, the silicon substrate 1 and the silicon substrate 2 on which the glass thin film is deposited by sputtering are connected to each other. ), Sodium (Na) and lithium (Li) ions contained in the glass thin film move to the anode of the power supply voltage (DC), and oxygen ions remain between the silicon substrate 2 and the glass thin film. A kind of depletion layer is formed. In other words, it is the material of PYREX glass in the glass the thin film comprises elements such as sodium or lithium is ionized at room temperature is easy, in particular the sodium element in the form of a Corning (corning # 7740) glass is sodium oxide (Na ₂ O) The coefficient of thermal expansion is very similar to that of silicon, which minimizes damage to the substrate during thermal bonding. The sodium ions described above are easily ionized even at room temperature, so that the sodium ions are present in the glass thin film in an ionic state under static charge. When sodium ions receive heat above a certain temperature, mobility increases to obtain kinetic energy that can move inside the glass thin film. At this time, when an electric field is applied from the outside, sodium ions move to the anode, and oxygen ions remain on the cathode to form a depletion layer. As a result, as shown in Fig. 1A, positive charges are distributed on the silicon substrate 1 side of the bonding surface, and negative charges are distributed on the silicon substrate 2 side on which the glass thin film is deposited. This charge distribution is caused by the formation of a depletion layer on the glass thin film deposited on the silicon substrate and consequently by the electrostatic force generated by the strong electric field distribution formed on the silicon substrate 1 side as shown in Fig. 1B. ) And the glass thin film is permanently bonded.

In addition, in order to manufacture the silicon substrate 2 on which the glass thin film is deposited, conventionally, sputtering performed in an argon or oxygen atmosphere at low temperature and low pressure was used. That is, a glass target is used by depositing a glass thin film by 1 micrometer or more by sputtering on a silicon substrate using a glass target.

However, the electrostatic thermal bonding method of the semiconductor substrate using the sputtering as described above is 0.5 seconds per second using sputtering on the top of the silicon substrate Å Because it can deposit about a thin glass film, 1 μ It takes a long time to deposit a glass thin film of m or more, there is a limit to use in the actual product production, and the characteristics of the glass target, which is the source of sputtering, and the glass thin film that are actually deposited are different depending on the atmosphere of the gas during sputtering There was a problem that the reliability of the product is reduced.

In view of the above problems, the present invention is not affected by the atmosphere of the gas, and an object thereof is to provide a method of electrostatic thermal bonding of a semiconductor substrate having an increased deposition rate.

1 is an explanatory diagram showing the electrostatic thermal bonding mechanism between silicon substrates using a glass thin film.

Figure 1 (a) is a graph showing the charge distribution at the junction of the glass thin film and the silicon substrate.

Figure 1 (b) is a graph showing the electric field distribution at the junction of the glass thin film and the silicon substrate.

Figure 1 (c) is a graph showing the potential difference at the junction between the glass thin film and the silicon substrate.

2 is a structural diagram of an electrostatic thermal bonding apparatus for joining by applying voltage and heat between silicon substrates according to the present invention.

3 is a cross-sectional scanning electron micrograph of the silicon substrate bonded by FIG.

4 is an infrared transmission photograph of the silicon substrate bonded by FIG.

FIG. 5 is a cross-sectional scanning electron micrograph of the bonded pair shown in FIG. 2, mounted on a silicon substrate on which a glass thin film is deposited after forming a cavity; FIG.

6 is a structural diagram of an electrostatic thermal bonding apparatus for bonding heat and voltage to a silicon substrate and a glass semiconductor substrate according to the present invention.

Fig. 7 is a cross-sectional scanning electron micrograph of a silicon substrate and a glass substrate bonded by Fig. 6;

Explanation of symbols on the main parts of the drawings

1: Silicon substrate 2: Silicon substrate with glass thin film deposited

3: power supply and recording device 4: heating device

5: Temperature controller 6: ITO coated glass substrate with glass thin film deposited

7: Aluminum

The above object is achieved by improving the properties of low melting point glass and depositing a glass thin film using an electron beam deposition method using the improved glass as a source, and thus the electrostatic thermal bonding of a semiconductor substrate according to the present invention. The method will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram showing a method of electrostatic thermal bonding between silicon substrates according to the present invention. As shown therein, an N-type silicon substrate 1 in a direction of (100) and a silicon substrate 2 having a glass thin film deposited thereon are supplied with power. A power supply and power supply unit 3 for applying a voltage and measuring a value thereof; It is composed of a heating device 4 for applying heat to the silicon substrate 2 on which the glass thin film is deposited under the control of the temperature control device 5 to deposit the N-type silicon substrate 1 and the glass thin film in the (100) direction. Heat and voltage are applied to the silicon substrate 2 to bond the silicon substrate 1 and the silicon substrate 2 on which the glass thin film is deposited.

Hereinafter, a method for manufacturing the silicon substrate 2 on which the glass thin film is deposited will be described.

Generally, because glass has a low melting point, it is impossible to deposit on a silicon substrate using an electron beam evaporator. In order to compensate for this, in the present invention, corning glass and oxide (SiO ₂ ) are mixed at a ratio of 2: 1 and used as a source material of an electron beam evaporator, and the deposition atmosphere is 230 ° C. and a substrate temperature of 2 × 10 ⁻⁵ torr. Use a vacuum. Since the deposition of the glass thin film by the electron beam evaporator does not require any gas atmosphere, the components of the source material in which the Corning glass and the oxide are mixed 2: 1 and the glass thin film deposited on the actual silicon substrate are the same. The experimental results are shown in Table 1 below.

Si (%) O (%) B (%) Glass sauce 23.70 68.56 7.74 Glass thin film 25.90 69.69 4.41

As shown in Table 1, it can be seen that there is almost no difference in the component ratio between the glass source and the glass thin film.

In addition, when the level of the surface of the glass thin film to be deposited is severe, since the glass thin film and the silicon substrate are only partially bonded during the electrostatic thermal bonding, the smoothness of the surface of the glass thin film is important. When the glass thin film is deposited using the electron beam evaporator, the smoothness of the glass thin film deposited and the smoothness of other substrates are described in Table 2 below.

Maximum value of step Effective value of roughness Average value of roughness Median of height Silicon substrate 13 Å 1.3 Å 1.0 Å 5.8 Å Glass thin film deposited on silicon substrate 126 Å 5.4 Å 3.5 Å 25 Å ITO-coated glass substrate 150 Å 15 Å 12 Å 82 Å Glass Thin Films Deposited on ITO 199 Å 17 Å 13 Å 80 Å

As shown in Table 2 above, the maximum value of the glass thin film step is 200 Å In the following, there is no inferiority with respect to the glass film deposited by sputtering. Although the glass thin film deposited on the ITO (INDIUM TIN OXIDE) coated glass substrate has a large roughness, the step of the ITO coated glass substrate is 150 Å Top 13 of silicon substrates Å It was investigated because it is much larger.

In addition, in the case of depositing a glass thin film using an electron beam evaporator having a source material mixed with corning glass and oxide 2: 1, the glass thin film is 50 in 1 second. Å Will grow.

After manufacturing the polycrystalline silicon (2) on which the glass thin film was deposited in this manner, by using the apparatus as shown in Figure 1, by applying a temperature of 135 ~ 160 ℃ and a voltage of 35 ~ 55V for 10 minutes To make it.

3 is a view showing a cross-sectional scanning electron micrograph between the bonded silicon substrates. As shown therein, polycrystalline silicon, glass thin film, and polycrystalline silicon manufactured by the above method are sequentially provided and used for polishing. The alumina powder was marked with white dots.

4 is a diagram showing infrared transmission images of the bonded silicon substrates. As shown in FIG. 4, it can be seen that a fringe FRINGE is formed on the bonding interface, and the fringe at the top indicates that the bonding is not performed. The black dots at the bottom are formed by dust particles adhering to the silicon substrate during the experiment.

FIG. 5 is a cross-sectional scanning electron micrograph of a bonded pair mounted on a silicon substrate on which a glass thin film is deposited after forming a cavity. As shown in FIG. 5, the silicon substrate is etched isotropically using wet etching. 15mm × 15mm × 8 μ After preparing the cavity of m, the specimen mounted on the silicon substrate on which the glass thin film was deposited was cut in half, polished, and observed by an electron microscope to confirm the bonding thereof.

6 is a diagram illustrating a method of electrostatic thermal bonding of a silicon substrate and a glass semiconductor substrate according to the present invention, and as shown in FIG. 6, is the same as the equipment for electrostatic thermal bonding of the silicon substrate on which the silicon substrate and the glass thin film are deposited. The equipment is thermally bonded by applying heat and voltage to the silicon substrate 1 and the ITO coated glass substrate 6. At this time, the atmosphere in which the electrostatic thermal bonding occurs is maintained for 10 minutes in an atmosphere of a substrate temperature of 135 ~ 160 ℃ and a voltage of 35 ~ 55V, to minimize the voltage drop by the ITO coated on the ITO coated glass substrate (6) In order to use the aluminum electrode 7 is deposited on top of the ITO layer.

In order to confirm the bonding between the glass substrate 6 and the silicon substrate 1 as described above, the bonded specimen was cut in half using a diamond knife as shown in the photograph of the cross-sectional scanning electron microscope of the silicon substrate and the glass substrate shown in FIG. After cutting, the bonding is confirmed using an electron microscope.

As described above, the electrostatic thermal bonding method of the semiconductor substrate according to the present invention increases the deposition rate of the glass thin film by using an electron beam evaporator, thereby increasing the production efficiency of the actual product and by not using a specific gas atmosphere to deposit it. Since the source and the characteristics of the glass thin film deposited is the same, there is an effect of improving the reliability of the product.

Claims (7)

Mixing the glass and oxide film to produce a source of deposition; Depositing a glass thin film on a silicon substrate using an electron beam evaporator using the source of deposition; Electrostatic heat of the semiconductor substrate, characterized in that the step of bonding the silicon substrate and the silicon substrate on which the glass thin film is deposited by applying a predetermined voltage and substrate temperature to the silicon substrate and the silicon substrate on which the glass thin film is deposited. Joining method. 2. The method of claim 1, wherein the step of preparing the source of deposition by mixing the glass and the oxide film comprises a mixing ratio of the glass and the oxide film to 2: 1. The method of claim 1, wherein the bonding of the silicon substrate and the glass substrate by applying a predetermined voltage and heat for a predetermined time period comprises applying a substrate temperature of 135 to 160 ° C and a voltage of 35 to 55V for 10 minutes. Electrostatic thermal bonding method of a semiconductor substrate. Mixing the glass and oxide film to produce a source of deposition; Depositing a glass thin film on an ITO (INDIUM TIN OXIDE) coated glass substrate using an electron beam evaporator using the deposition source; A semiconductor substrate comprising the step of bonding a silicon substrate and a glass thin film deposited ITO coated glass substrate by applying a predetermined voltage and temperature to the ITO coated glass substrate and silicon substrate on which the glass thin film is deposited. Electrostatic thermal bonding method. 5. The method of claim 4, wherein the step of preparing the source of deposition by mixing the glass and the oxide film comprises a mixing ratio of the glass and the oxide film to 2: 1. The method of claim 4, wherein the bonding of the silicon substrate and the ITO coated glass substrate on which the glass thin film is deposited by applying a predetermined substrate temperature and voltage for a predetermined time is performed at a substrate temperature of 135 to 160 ° C. and a voltage of 35 to 55 V. The electrostatic thermal bonding method of a semiconductor substrate characterized by holding for a minute. The method of claim 4, wherein the bonding of the silicon substrate and the ITO coated glass substrate on which the glass thin film is deposited by applying a predetermined substrate temperature and voltage for a predetermined time comprises depositing an aluminum electrode at an edge of the ITO layer of the ITO coated glass substrate. An electrostatic thermal bonding method for a semiconductor substrate.

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