JPH042159A - Resistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the thermal resistance between a resistor and the reverse side of a substrate and thus radiate heat efficiently from the resistor through the back of the substrate by forming the resistor on a substance having a high heat conductivity. CONSTITUTION:An insulating film 4, a thin-film resistor 1, an electrode, and an insulating film 3 are formed on a semiconductor substrate 5 in that order. The substrate is etched from its back to remove the substrate and the insulating film 4 in part beneath the resistor and make a recess. The recess is filled with substance 1 (6) that has a low dielectric constant and a high heat conductivity. Then, metal 7 (substance 2), having a high heat conductivity, is applied to the reverse side of the substrate so that the metal is in contact with the substance 1. The substance 2 is Au plating.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a resistor and a method for manufacturing the same.

(Prior Art) The development of semiconductor devices in recent years has been remarkable. As the performance and speed of silicon and compound semiconductor devices increase, the operating range of analog and digital circuits formed with these devices is also expanding from several GHz to several tens of GHz.
This is beginning to extend to the Hz frequency range. By the way, the resistance elements of these high-speed operation circuits include those that use a semiconductor layer (Fig. 5 (C)) activated by impurity diffusion such as ion implantation as a resistor (11), and those that use a semiconductor layer (Fig. A conductive layer with high resistance (Fig. 5 (
A device using d)) as a resistor (technique 2) is known. However, in resistors formed using a portion of these semiconductor substrates, junction capacitance is created in the peripheral region of the resistor, and parasitic capacitance is created due to the effects of traps and the like in the semiconductor substrate. In the high frequency range, the capacitance component also becomes sharper, increasing the propagation delay time of the circuit. Furthermore, in a resistor provided on a semiconductor laminated structure, carrier camping between the resistor layer and another conductive layer causes a large frequency dispersion of the resistance value in the ultra-high frequency region of GHz or higher. There is also the problem that the values deviate greatly from the original design values.

To solve this problem, a thin film resistor (1) on an insulating film (4) as shown in FIG. 5(a) is adopted. In the case of a resistor having this structure, the capacitance component can be kept small even in a high frequency range by the insulating film (4) under the resistor (1), and a stable resistance value can be obtained in a wide frequency range.

(Problems to be Solved by the Invention) However, in a thin film resistor on an insulating layer, the temperature of the resistor tends to rise due to the heat generated when electricity is applied. This is because the insulating film has poor thermal conductivity. This rise in temperature of the resistor significantly changes the resistance value unless the temperature coefficient of resistivity of the resistor material is brought to zero. Furthermore, even if the temperature coefficient of the resistive material is made zero, there are problems such as non-linearity of the resistance value depending on the current level and irreversible change at a certain temperature or higher. These problems become more noticeable as circuits become smaller and more integrated, making it impossible to ensure the reliability of circuit operation.

When the temperature of the resistor increases due to the heat generated by the resistor and the resistance value changes, the circuit operating point deviates from the originally designed operating point at an appropriate value, impairing the high speed and reliability of the circuit.

Consider the temperature rise of the resistor using the following heat conduction equation.

Q=λ(T2-Tρ1) Here, Q is the amount of heat radiated from the substance per unit area per unit time, λ is the thermal conductivity, T2 is the temperature of the resistor, T1 is the external temperature, and L is the heat conduction path. It is the distance. From this formula,
A material with a large thermal conductivity λ efficiently dissipates heat, thereby reducing the temperature rise of the element.

By the way, the semiconductor surface including the element is protected by an insulating film, but the thermal conductivity of the insulating film is generally low, and in the case of silicon dioxide, it is about 3.3 x 10 cal/cm-s.00. Therefore, the heat dissipation effect to the substrate surface is small, and it is therefore preferable to use a structure that dissipates heat from the back surface of the substrate.

For example, in the case of power transistors, the semiconductor substrate below the transistor element is removed by etching.
The area is filled with metal using a plating method, etc., and a heat sink structure is formed by applying metal to the entire back side of the board.
A method is used to efficiently dissipate the heat generated in the element part from the back surface of the substrate, suppress the temperature rise in the element part, and prevent malfunction of the transistor due to the temperature rise. Further, the heat sink metal is directly attached to the source electrode of a field effect transistor and the emitter electrode of a bipolar transistor, and also serves as a ground.

However, in the case of a resistor, if this heat sink metal is used, a capacitive component is created between the resistor (1) and the heat sink metal (8) as shown in Figure 5 (b), and this capacitive component impairs the high-speed operation of the circuit. . Also, the electrode (2) of the resistor (1)
) are also given various potentials in the circuit, so the heat sink metal (8) cannot be directly attached to the resistor electrode (2). Therefore, the heat sink metal (8) cannot be brought close to the resistor, and an effective heat dissipation effect cannot be obtained. In addition, in the case of a thin film resistor on an insulating film, the resistor is sandwiched between upper and lower insulating films as shown in Figure 5(a), so the heat dissipation effect is even smaller, and the temperature rise The reduction in reliability of resistance values due to

The purpose of the present invention is to prevent the specific resistance from changing from its design value due to temperature rise due to heat generated when the resistor is energized, and nonlinearity and irreversible changes in resistance value due to the current level during operation. It is an object of the present invention to provide a resistor that prevents the occurrence of frequency dispersion of resistance value and capacitance component by creating a heat dissipation structure, and does not hinder ultra-high-speed operation of a circuit.

(Means for Solving the Problems) The resistor of the present invention includes a resistor formed on a semiconductor substrate or an insulating film on the semiconductor substrate, and a resistor with high thermal conductivity and low dielectric constant provided under the resistor. The semiconductor device is characterized in that it consists of a material 1 having a property of 1 and a material 2 having a property of high thermal conductivity, which is provided below the material 1 and penetrating to the back surface of the semiconductor substrate.

Note that such resistors include thin film resistors formed by forming an insulating film on a semiconductor substrate, and thin film resistors formed on this insulating film, and resistors formed by reducing the resistance of a part of a high-resistance semiconductor substrate. There are resistors formed by forming a conductive layer on a semiconductor substrate and increasing the resistance around the conductive layer.

Further, the method for manufacturing the resistor includes a step of forming the resistor on a semiconductor substrate or an insulating film on the semiconductor substrate;
A step of removing the semiconductor substrate at the bottom of the resistor from the back side, a step of filling the removed portion with a fluid substance 1 having high thermal conductivity and low dielectric constant characteristics, and subsequently solidifying the substance 1. The structure includes a step and a step of attaching a material 2 having high thermal conductivity so as to be in contact with the material 1 from the back surface of the substrate.

(Function) In the present invention, since the resistor is formed on a material with high thermal conductivity, the thermal resistance between the resistor and the back surface of the substrate is reduced, and heat generated from the resistor is efficiently transferred from the back surface of the substrate. It can dissipate heat. This makes it possible to suppress the rise in temperature of the resistor and improve the reliability of the resistor. In addition, when operating a circuit using this resistor as a load resistor in an ultra-high frequency range, this resistor is formed on a material with a low dielectric constant, so the frequency of the capacitance and resistance value between it and the substrate and the back surface of the substrate increases. Dispersion can be suppressed and high-speed operation of the circuit is not impaired. Further, the resistor according to the present invention is suitable for miniaturization because temperature rise due to heat generation is suppressed, and is therefore suitable for integrated circuits operating at ultra-high speed.

(Example) The present invention will be described in detail below. Figure 1(a)-(C
) is an insulating film (4) and a thin film resistor (
This is a resistor in which a thin film resistor (1), an electrode (2), and an insulating film (3) are sequentially formed. FIG. 6), Fig. 1(b) shows the semiconductor substrate (5) below the resistor.
) and the insulating film (4) are all removed, and part of them is replaced with substance 1 (6). Figure 1(c) shows the result in which the entire semiconductor substrate under the resistor and part of the insulating film are removed. substance 1
This is an example in which Substance 2 (7) is attached so as to be in contact with Substance 1 (6), respectively.

Further, FIG. 4 shows an embodiment of the method for manufacturing the resistor shown in FIG. 1(a). First, an insulating film (4), a thin film resistor (1), an electrode (2), and an insulating film (3) are sequentially formed on a semiconductor substrate (5) (FIG. 4(a)). Subsequently, the semiconductor substrate (5) and the insulating film (4) below the resistor are etched from the back surface of the substrate to completely remove them (FIG. 4(b)). Next, the removed portion is filled with a substance 1 (6) having a low dielectric constant and high thermal conductivity (FIG. 4(C)). Furthermore, as shown in Figure 4(d), a metal with good thermal conductivity (substance 2 (7)) is applied from the back side of the substrate to substance 1 (6).
) (for example, material 2 is Au formed by gold plating).

By the way, regarding the process of filling the substrate area under the resistor and the part from which the insulating film has been removed, even in IC level circuits, the size of the resistor is about several tens of micrometers, and the thickness of the substrate is 300 to 500 pm. Because of this, its aspect ratio is large, making it difficult to fill it with substances in terms of process. However, if fluid silicone resin or epoxy resin is used, it is possible to fill it relatively easily.

In addition, these resin materials are used in LSI encapsulation materials, and have characteristics such as good fluidity, no mobile ions that affect semiconductors, high thermal conductivity, and low dielectric constant, making them reliable in semiconductor processes. You can get sex. Further, the filled resin can be relatively easily solidified by heating at about 100 to 150°C.

Table 1 shows silicone resin, epoxy resin, GaAs, Table 1
Thermal conductivity and relative dielectric constant In the conventional thin film resistor shown in Figure 5(a), the thermal conductivity of silicon dioxide is extremely low compared to semiconductor materials such as GaAs and Si, and the upper and lower parts of the thin film resistor are made of silicon dioxide. In this structure insulated by a film, the heat generated in the resistor is difficult to transfer to the front surface of the sample and the back surface of the substrate, and as a result, the temperature of the resistor portion tends to rise. On the other hand, in the resistor with the structure shown in Figure 1(a), the substrate and insulating film at the bottom of the resistor are all removed, and that part is filled with resin, which has a thermal conductivity nearly two orders of magnitude better than silicon dioxide. , heat is effectively dissipated from the back surface of the substrate, and the temperature rise of the resistor is improved.

Furthermore, since the dielectric constant of such resin is equivalent to that of silicon dioxide, no unnecessary capacitance component is created in the resistor, and a stable resistance value can therefore be obtained. Furthermore, since a metal layer (for example, an Au layer) is provided on the back surface of the substrate so as to be in contact with the resin, the heat generated in the resistor can be efficiently radiated from the back surface of the substrate via the resin. In this structure, when the heat sink metal layer (7) is brought close to the resistor (1) to the extent that the capacitance component does not increase (FIG. 1(b)), the heat dissipation effect can be further increased.

Further, FIG. 2 shows a resistor (11) formed by reducing the resistance of a part of a high-resistance semiconductor substrate, and FIG. In the resistor (12) formed by increasing the resistance of the resistor, the entire semiconductor substrate under the resistor is replaced with substance 1,
Furthermore, this is an example in which a substance 2 is attached so as to be in contact with each substance 1. In this case, the thermal conductivity of the resin is lower than that of semiconductor materials such as GaAs and Si, so it is inferior in terms of heat conduction, but the dielectric constant is less than 1/3, so the thickness of the resin layer is optimized, and the substrate By bringing the metal heat sink close to the resistor from the back surface, it is possible to form a resistor with reduced capacitance while maintaining heat conduction.

(Effects of the Invention) As explained above, according to the present invention, the heat generated in the resistor can be effectively radiated from the back surface of the substrate by the heat sink provided at the bottom of the resistor. Changes in value and irreversible changes in the resistor can be suppressed, and reliability of the resistor can be improved.

In addition, since the capacitance component between the resistor and the substrate due to the heat sink structure can be suppressed, even when an integrated circuit including this resistor is operated in a high frequency range, there is no frequency dispersion of the resistance value, resulting in stable resistance values. can be obtained. In addition, the method for manufacturing a resistor with this structure uses a fluid material with high thermal conductivity and low dielectric constant, and fills the lower part of the resistor from which the semiconductor substrate and insulating film have been removed. It can be solidified by heating, and normal semiconductor processes can be applied.

[Brief explanation of the drawing]

FIG. 1(a) to FIG. 1(c) are structural diagrams showing one embodiment of the resistor of the present invention. FIGS. 2 and 3 are structural diagrams showing other embodiments of the resistor of the present invention. FIG. 4 is a process diagram for forming the resistor shown in FIG. 1(a). Fifth
FIGS. 5(a) to 5(d) are structural diagrams of conventional resistors. DESCRIPTION OF SYMBOLS 1... Thin film resistor, 11... Resistor, 12... Resistor, 2... Electrode, 3... Resistor protection insulating film, 40
0. Resistor base insulation, 5... Substrate, 51... Substrate region made highly resistive by implantation, 6... Substance 1.7...
・Substance 2. 8...Heat sink metal

Claims (2)

[Claims] (1) A resistor formed on a semiconductor substrate or an insulating film on the semiconductor substrate, a substance 1 having high thermal conductivity and low dielectric constant properties provided below the resistor, and a substance 1 below the substance 1. and a material 2 having high thermal conductivity that penetrates to the back surface of the semiconductor substrate. (2) A process of forming a resistor on a semiconductor substrate or an insulating film on a semiconductor substrate, a process of removing the semiconductor substrate under this resistor from the back side, and a process of forming a resistor with high thermal conductivity and low dielectricity in the removed part. a step of filling a fluid material 1 having a property of high thermal conductivity, a step of solidifying the material 1, and a step of attaching a material 2 having a property of high thermal conductivity so as to be in contact with the material 1 from the back side of the substrate. A method for manufacturing a resistor, comprising: