JPH09330968A - Insulation film reliability evaluation method - Google Patents

Abstract

(57) Abstract: A method for quantifying an insulating film damage amount in a semiconductor device manufacturing process is provided. At least a MIS on a semiconductor substrate 100.
In the semiconductor device in which the gate insulating film 101 of the type transistor and the gate electrode 102 are formed, by injecting current into the gate insulating film 100 at a constant current density,
The total amount Qbd1 of dielectric breakdown injection charges of the insulating film 100 is measured. For a semiconductor device that has been subjected to a certain manufacturing process, the total amount Qbd2 of dielectric breakdown injection is measured by performing the same measurement, and u = 1−Qbd2 / Q
An insulating film reliability evaluation method, characterized in that the amount of damage to an insulating film due to a manufacturing process is quantified by the u value given by bd1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating reliability of an insulating film in a semiconductor device.

[0002]

2. Description of the Related Art In recent years, highly integrated semiconductor integrated circuits have made great progress, and even in MIS type semiconductor devices,
With the miniaturization of transistor elements, the thickness of a gate insulating film has been reduced. As a result, a thin gate insulating film of 6 to 8 nm is used in the 0.25 μm rule. When manufacturing a semiconductor device having such a thin gate insulating film, damage to the gate insulating film generated during the manufacturing process is expected to become a problem.

In particular, in the dry etching process, the charges injected into the wiring pattern flow through the gate insulating film, resulting in destruction and deterioration of the gate insulating film and deterioration of transistor characteristics (threshold voltage fluctuation, saturation). (Reduction of current value) becomes a big problem with miniaturization.

Therefore, in the development of a semiconductor device manufacturing process, it is necessary to optimize the process conditions so as to minimize the damage to the gate insulating film that occurs during the manufacturing process. It is required to quantify the film damage amount.

As a conventional method of quantifying the insulation film damage, the first method is quantification by evaluation of the insulation film yield, and the second method is the constant current TDDB (Time D).
independent Dielectric Break
Quantification by down evaluation has been performed.

In the evaluation of the insulating film yield of the first method, the current value I ₀ flowing when a certain voltage V ₀ is applied to the insulating film of the MOS capacitor is measured as shown in FIG. Compare with the specified value I ₁ . The same measurement is performed using a plurality of MOS capacitors manufactured by the same process, and the ratio at which the gate current value is equal to or less than the specified value I ₁ is measured, which is taken as the yield Y. This yield Y
The value of makes a comparison of process merits and demerits. That is,
The larger the value of Y, the smaller the damage to the insulating film. Here, the value of the yield Y of the obtained insulating film is a parameter which is excellent in intuition because the correlation with the yield of the entire semiconductor integrated circuit is easily obtained.

In the constant current TDDB evaluation of the second method described above, a constant current J ₀ is applied to the MOS capacitor as shown in FIG. 5 until the gate insulating film is destroyed.
The total charge amount Qbd injected into the gate insulating film is measured. A comparison of process merits and demerits is made according to the value of the Qbd value. That is, the larger the Qbd value, the smaller the damage to the insulating film. For example, in the wiring dry etching process, as shown in FIG. 6, the Qbd value monotonically decreases as the antenna ratio, which is one of the parameters expressing the plasma damage amount, increases.
It can be seen that the value has excellent characteristics as a process damage quantification method.

[0008]

However, the above-described conventional method for quantifying process damage has the following problems.

First, in the above first conventional method,
There is a problem in the accuracy of the process damage amount quantified by Y. That is, when the value of the process damage is small, the Y value may not change even though the insulating film characteristics are deteriorated. For example, FIG. 7 shows a relationship between an antenna ratio representing a plasma damage amount in a dry etching process of wiring and a gate insulating film yield Y. In the region where the antenna ratio is 1000 or less, the yield Y shows an almost constant value, though the plasma damage increases with the increase of the antenna ratio, so the damage amount by Y is quantified on the low damage side. Becomes impossible.

Further, in the above second conventional method, the Qbd value representing the amount of damage largely depends on the stress condition (current density, substrate temperature) when conducting the constant current TDDB test. As an example, FIG. 8 shows the result of evaluating an insulating film formed by the same process under each measurement condition as shown in the table below.

[0011]

[Table 1]

It can be seen that the obtained Qbd varies greatly, even though the insulating films having the same characteristics are evaluated. Therefore, the conventional method for quantifying process damage by the second method has a problem in terms of quantitativeness,
For example, a problem may occur when comparing process damage amounts between completely different manufacturing apparatuses. Further, when performing the process development considering the reliability of the insulating film, using the Qbd value has a problem that it is difficult to grasp the image of the life of the insulating film.

Therefore, in view of the above problems, it is an object of the present invention to provide a method of quantifying the amount of deterioration of an insulating film due to process damage, which is excellent in quantitativeness and allows the damage amount to be intuitively understood. It is a thing.

[0014]

In order to achieve the above object, a method for quantifying the amount of damage to a gate insulating film is provided by introducing a numerical parameter that does not depend on the evaluation conditions.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to embodiments. FIG. 1 shows the configuration of an insulating film reliability evaluation apparatus according to an embodiment of the present invention.

In FIG. 1, each reference numeral indicates the following member. 100 is a semiconductor substrate, 101 is a gate oxide film formed on the semiconductor substrate 100, and 102 is a gate oxide film 10.
1 shows a gate electrode formed on the semiconductor substrate 10
0-gate oxide film 101-MO by the gate electrode 102
An S capacitor is formed. Here, the film thickness of the gate oxide film 101 is, eg, 10 nm. Also, 103
Is a wafer stage, 104 is a temperature adjusting mechanism for adjusting the temperature of the wafer stage 103, 105 is a current source, 106 is a voltage monitor, 107 is a probe for supplying a current to the gate electrode 102, and 108 is the semiconductor substrate 100 grounded. A reference numeral 109 denotes a control system for determining when the gate oxide film 101 is broken and stopping current injection. The semiconductor substrate 100 may be grounded from the wafer stage 103 side.

Next, an insulating film reliability evaluation method using the insulating film reliability evaluation apparatus configured as described above will be described.

First, a constant current is applied from the current source 105 to the gate electrode 102 on the semiconductor substrate 100 on which the MOS capacitor is formed. The applied current density J is, for example,
It is 100 mA / cm ² . At this time, the gate voltage applied to the gate oxide film of the MOS capacitor is monitored by using a voltmeter 106, and the time Tbd at which the gate oxide film is destroyed and the gate voltage sharply drops is measured.
The Qbd value is obtained from Qbd = J × Tbd.

When a damage amount of a certain manufacturing process is evaluated, the first insulating film before the manufacturing process treatment and the second insulating film after the predetermined manufacturing process treatment are performed. By performing the same measurement using a plurality of MOS capacitors, respectively, the cumulative failure probability distribution characteristic as shown in FIG. 2 is obtained. From this result, for example, the total injected charge amount Qb such that the cumulative failure probability becomes 50%
d1 and Qbd2 are obtained. Using these, the u value which is a parameter representing the amount of gate insulating film damage due to the process is derived from the calculation of u = 1−Qbd2 / Qbd1.

The value u used in the present embodiment does not depend on the stress current density J and the substrate temperature T, which are measurement conditions when performing the constant current TDDB test. As an example, under each measurement condition as shown in (Table 1) above, the above J
Qbd2 (J, T) value, which is a value that depends on
The result of deriving the u value given by 1-Qbd2 (J, T) / Qbd1 (J, T) is shown in FIG.

Q, which has been used to quantify damage conventionally
While the bd2 value greatly depends on the evaluation condition,
It can be seen that the u value is a constant value under any measurement condition. That is, it can be seen that the u value is a parameter that uniquely represents the amount of gate insulating film damage caused by the process. Therefore, it can be said that the use of this u value facilitates comparison of damage amounts between different manufacturing processes.

[0022]

As described above, the present invention realizes a method for quantifying the amount of insulating film damage in the manufacturing process by introducing a numerical parameter u that corresponds one-to-one with the amount of insulating film damage that does not depend on the evaluation conditions. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an insulating film reliability evaluation apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing cumulative failure probability distribution characteristics.

FIG. 3 is a diagram showing the dependence of u values on measurement conditions.

FIG. 4 is a schematic diagram showing a configuration of an insulating film yield evaluation device.

FIG. 5 is a schematic diagram showing the configuration of an insulating film constant current TDDB evaluation device.

FIG. 6 is a diagram showing a relationship between an antenna ratio and a Qbd value.

FIG. 7 is a diagram showing a relationship between an antenna ratio and a yield Y.

FIG. 8 is a diagram showing the dependence of Qbd values on measurement conditions.

[Explanation of symbols]

100 semiconductor substrate 101 gate oxide film 102 gate electrode 103 wafer stage 104 temperature adjusting mechanism 105 current source 106 voltage monitor 107 probe for supplying current to gate electrode 108 probe for grounding semiconductor substrate 109 oxide film destruction determination , Control system to stop current injection.

Claims (2)

[Claims] 1. At least a MIS (Met) on a semiconductor substrate.
al Insulator Semiconductor
A method for evaluating reliability of the insulating film of a semiconductor device, wherein an insulating film to be a gate insulating film of an r) type transistor and a film to be a gate electrode are formed, the method comprising: Obtaining the total amount Q2 of dielectric breakdown injection charges of the insulating film after performing a predetermined process on the semiconductor device, and quantifying the amount of damage given to the insulating film in the predetermined process by 1-Q2 / Q1. A method for evaluating the reliability of an insulating film. 2. A constant current is applied to a plurality of insulating films, and the total amount of charges injected into a gate electrode until 50% of the plurality of insulating films is destroyed is injected into the insulating film by a dielectric breakdown. The reliability evaluation method for an insulating film according to claim 1, wherein the total charge amount is used.