Semiconductor device having temperature detecting function,...

Details Semiconductor device having temperature detecting function,... Semiconductor device having temperature detecting function,...

2002-02-25

2003-12-23

Lam, David (Department: 2818)

Static information storage and retrieval

Read/write circuit

Differential sensing

C365S222000, C365S189090, C365S189110

Reexamination Certificate

active

06667925

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having a temperature detecting function to optimize the acting state in accordance with a detected temperature detected with little dispersion, so as to achieve a sufficient acting performance over the entire working temperature range including a lower temperature region and a higher temperature region and, more particularly, to an improvement in the acting performance in a semiconductor storage device.
2. Description of Related Art
Generally, a semiconductor device element constructing a semiconductor device has temperature characteristics, and a semiconductor device constructed by integrating the semiconductor device elements has temperature characteristics from its acting characteristics. Moreover, the semiconductor device is generally employed in a predetermined temperature range and is demanded to have predetermined temperature characteristics for the entire working temperature range.
FIG. 27
illustrates a consumed current IDD and various action speeds tACCESS, i.e., representative acting characteristics against the temperature for a semiconductor device constructed of CMOS device elements. Generally in the semiconductor device constructed of CMOS device elements, as illustrated in
FIG. 27
, the action speed tACCESS becomes the lower at the higher temperature, and the consumed current IDD becomes the higher at the lower temperature. The individual acting characteristics are warranted under the worst conditions so that the various acting speeds tACCESS are warranted (at (A) in
FIG. 27
) with the maximum tmax in the working temperature range, and the consumed current IDD is warranted (at (B) in
FIG. 27
) with the minimum tmin in the working temperature range. As a result, the specifications on the acting characteristics in the entire working temperature range (from tmin to tmax) are warranted.
For a semiconductor memory representing the semiconductor device constructed of CMOS device elements, the internal construction (
FIG. 28
) and the temperature characteristics (
FIG. 29
) of the construction are shown in
FIGS. 28 and 29
. Here are illustrated the temperature characteristics on the refresh control of a semiconductor memory
100
requiring the refresh action, such as a dynamic random access memory (as will be abbreviated into “DRAM”) of the semiconductor memory.
In the prior art, as shown in
FIG. 28
, the semiconductor memory
100
is controlled on a refresh period tREF of a memory cell
102
by a refresh control circuit
101
. In the memory cell
102
, as illustrated in
FIG. 29
, the leakage current increases with the rise in the temperature so that the data holding characteristics are deteriorated by the electric charge to exhibit the negative temperature characteristics in which a data holding time tST is shortened.
On the other hand, the refresh period tREF to be set by the refresh control circuit
101
is set by an oscillation circuit such as a ring oscillator. According to the temperature characteristics of the various action speeds tACCESS of CMOS device elements, however, the action speeds tACCESS are raised the higher at the lower temperature. As a result, there is a tendency in which the positive temperature characteristics appear for the working temperature (at (II) in FIG.
29
). With the setting (at (I) in
FIG. 29
) of the refresh period tREF to cross the data holding time tST in the working temperature range, there exists a temperature region (at (C) in
FIG. 29
) in which the refresh period tREF is longer than the data holding time tST, so that the data in the memory cell
102
undesirably disappear.
It is, therefore, customary to set the refresh period tREF (at (II) in
FIG. 29
) to cross the data holding time tST at a temperature exceeding the maximum tmax in the working temperature range. As a result, the refresh action is done for the refresh period tREF shorter than the data holding time tST in the entire working temperature range (from tmin to tmax), so that the data stored in the memory cell
102
do not disappear.
In the semiconductor device exemplified by CMOS device elements, however, the action warranty of the consumed current IDD and the various action speeds tACCESS are regulated by the minimum tmin and the maximum tmax in the working temperature range other than the ordinary one, so that the system employing the semiconductor device is designed/manufactured on the basis of the warranting values. Therefore, a fear and a problem arise in that the system sufficiently utilizing the acting performance of the semiconductor device in the ordinary working temperature region cannot be constructed.
In the semiconductor memory
100
, moreover, the refresh period tREF to be set in the lower temperature region of the working temperature range is set excessively short (at (D) in
FIG. 29
) due to not only the negative temperature characteristics of the data holding time tST but also the positive temperature characteristic tendency of the refresh period tREF. Therefore, the refresh control circuit
101
performs the refresh actions for a sufficiently shorter time than the data holding time tST of the memory cell
102
and in an excessive frequency more than necessary. The current consumption accompanying the excessive refresh action is so surplus that the consumed current IDD in the lower temperature region cannot be sufficiently reduced to raise a problem that the action characteristics of the consumed current IDD warranted with the minimum tmin in the working temperature range cannot be improved.
Especially in a mobile device in which the semiconductor memory
100
is ordinarily employed at a temperature lower than the room temperature, the continuous employing time by the battery drive is restricted to raise a problem by the consumed current IDD accompanying the excessive refresh action in a temperature region lower than the room temperature.
SUMMARY OF THE INVENTION
The present invention has been conceived to solve the above-specified problems of the prior art and has an object to provide a semiconductor device having a temperature detecting function to detect a predetermined temperature with little dispersion and to optimize the acting state in accordance with the predetermined temperature detected, a testing method, and a refresh control method of a semiconductor memory device having the temperature detecting function.
In order to achieve the object, according to one aspect of the present invention, there is provided a semiconductor device having a temperature detecting function, comprising: a temperature detecting unit for detecting a predetermined temperature; and a voltage biasing unit for outputting a predetermined voltage having a slight temperature dependency or a predetermined voltage having a predetermined temperature dependency, to bias the temperature detecting unit.
In the semiconductor device having the aforementioned temperature detecting function, the temperature detecting unit for detecting the predetermined temperature is biased with either the predetermined voltage having the slight temperature dependency or the predetermined voltage having the predetermined temperature dependency, as outputted from the voltage bias unit.
With the temperature dependency of the predetermined voltage for biasing the temperature detecting unit being slight, therefore, the generally constant predetermined voltage is biased as the DC characteristics to the temperature detecting unit so that the detecting precision of the temperature detecting unit can be improved. The predetermined temperature to be detected is not fluctuated by the fluctuations of the bias voltage so that the temperature can be stably detected. If the predetermined voltage for biasing the temperature detecting unit has the predetermined temperature dependency, moreover, the fluctuations of the temperature to be detected can be in the temperature direction margin for the predetermined temperature so that the temperature can be stably detected.
According to another aspect

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