JPS5835475A - Measuring method for semiconductor device - Google Patents

Abstract

PURPOSE:To determine the thermal resistance of a semiconductor device from the active region thereof to the outside in the state of the working operation of the device, by finding the change in temperature of the active region from the thermal dependency of the characteristic values of the device and the difference in the characteristic values in the state of double operations thereof, and by dividing the change by the difference in a consumed power. CONSTITUTION:An information retention time period t of MOS dynamic RAM shows such thermal dependency as expressed by t=tOeE<a/>KT... (1), wherein t0 is a specific constant, K is a Boltzmann constant, T is a temperature in an active region, and Ea is an activation energy. The dependency of the information retention time period on an ambient temperature is measured by a prescribed signal pattern, and the activation energy in the formula (1) is determined. Then, the thermal resistance R is determined from the consumed power PH in a test signal pattern SH for a large consumed power and from the consumed power PL in a test pattern SL for a small consumed power, and from information retention time periods tH and tL. The thermal resistance is calculated by conducting the operation of R=DELTAt/(PH-PL), where DELTAt is the difference in temperature between the patterns SH and SL.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring method for determining the thermal resistance from the active region of a semiconductor device to the outside world in a practical operating state.

Conventionally, when performing this type of measurement, the temperature rise in the active region of a semiconductor device has been measured based on the forward current/voltage characteristics of the PN junction. In many semiconductor devices, it is not possible to pass a forward current through the PN junction during practical operation and measure its current/voltage characteristics. Therefore, after a certain amount of heat is generated, a forward voltage is applied and the was taking measurements.

Therefore, a situation different from that in actual operation occurs, and there is a drawback that the true temperature rise under actual operating conditions cannot be measured.

In order to solve these drawbacks, the present invention measures the temperature rise in the active region of a semiconductor device under practical operating conditions, and calculates the thermal resistance from the active region to the outside world (from the component part to the periphery of its envelope). A detailed explanation will be given below using examples.

[Embodiment 1] An example in which the present invention is applied to a MOS dynamic type rough random access memory will be described. MOS dynamic type rough random access memory cost and power can be changed depending on practical operating conditions such as cycle time. Further, the information retention time t generally exhibits temperature dependence as shown in the following equation.

t = tekT (1) where to is a constant specific to the semiconductor device, Boltzmann's constant T is the temperature of the active region Ea is the ambient temperature dependence of the information retention time is measured using a test signal pattern with a constant activation energy, Find the activation energy in equation (1). Next, the power consumption PH'P in the test signal pattern SII with the highest power consumption and the test signal pattern SL with the lowest power consumption.
The thermal resistance R is determined from L and the information retention times tH and 1L using the following formula.

R: ΔT/(PHPL) (2) However, Δ
T is the temperature difference in pattern SHs 8L, and is determined by the following equation.

However, TL is the active region temperature at the time of pattern SL,
When PL is sufficiently small, it approximates the ambient temperature Ta.

Table 1 shows an example of a test signal pattern 5H1SL that realizes two operating states.

Table 1 Examples of test patterns Information is written to the test memory cell A, and after a certain non-selection period, the information is read out and tested. By varying the non-selection period, find the maximum time for normal operation and use it as the information retention time. During the non-selection period, other memory cells B that do not affect the test memory cell are operated at high speed, resulting in a pattern S□ with large power consumption. If all other memory cells are also rendered inactive during the non-selection period of memory cell A, a pattern SL with low power consumption will be obtained.

Tables 2 and 3 show data obtained by measuring thermal resistance using the above method. Table 2 shows the temperature dependence of information retention time measured using pattern SL. When the activation energy Ea was determined from this data and equation (1), Ea was 0.59oV.

Table 2 Temperature dependence of information retention time Table 3 shows data on power consumption and information retention time when information retention time was measured using test signal patterns sH and SL. Note that the temperature at the time of measurement was room temperature 25°C.

Using the data in Table 3, pattern sH and pattern SL
When calculating the temperature difference ΔT from the above equation (3), ΔT =
13.2℃, and its ΔT and PH1PL in Table 3
If we calculate the thermal resistance R from the above formula (2) using
It becomes 50°C/W.

In a semiconductor device using a dynamic circuit, power consumption does not increase unless a clock signal is input during actual use. In addition, in the case of the conventional example in which forward current flows through the PN junction,
Heat is generated in a location different from that during actual use, making it impossible to obtain data that corresponds to actual usage conditions. In contrast, in the present invention, as shown in the above embodiment, the characteristic values under actual use conditions can be used, so that thermal resistance evaluation of such a semiconductor device under actual use conditions can be appropriately performed. .

[Embodiment 2] An example in which the present invention is applied to a C-MO8 IC (complementary MO8 integrated circuit) will be described. The power consumption of a C-MOS IC depends on the input signal frequency f, and the propagation delay time τ depends on the temperature. Therefore, the temperature dependence of τ at a constant input frequency is determined. Next, different input frequencies fH at the same ambient temperature,
, power consumption PH1PL and propagation delay time τ□ for fL
, τ1 is determined. The temperature dependence of τ is □, and the temperature difference ΔT between the two operating states is determined from τ1 and substituted into equation (2) to determine the thermal resistance.

In C-MO3JC, forward current cannot flow except in a very small portion of the circuit near the input/output terminals.

Since the present invention is a method that uses characteristic values under actual use conditions, it is possible to appropriately evaluate the thermal resistance of such a semiconductor device.

In addition to the above measurement items, the present invention can be applied to measurement items that exhibit temperature dependence, such as output voltage level, output current, and noise.

As explained above, the present invention is a method for determining thermal resistance by 1 ft11 in actual use using commonly used measurement items. Therefore, there is an advantage that a thermal resistance matching the heat generation distribution under actual use conditions can be obtained without requiring a special measuring device.

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Claims (1)

[Claims] In the measurement force method for semiconductor devices that have characteristic measurement items that show multiple practical operating states with different power consumption and temperature dependence, temperature changes in the active region can be determined from the temperature dependence of characteristic values and the difference between characteristic values in two operating states. 1. A method for measuring a semiconductor device, characterized in that the thermal resistance from the active region to the outside world is determined by calculating and dividing by the difference in power consumption.