JPH0131301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device with small fluctuations in substrate bias voltage.

In a semiconductor device that uses a semiconductor substrate and includes a semiconductor chip that forms a semiconductor integrated circuit that operates by applying a bias voltage to the semiconductor substrate, the substrate current varies depending on the circuit operation, so the substrate bias There is a problem in that the voltage fluctuates, and if this fluctuation becomes large, the circuit will malfunction. Figure 1 shows 16K bits as an example.
This figure shows the results of measuring the substrate current of MOS RAM during operation. In the figure, 1 is a clock voltage waveform input from the outside to operate the RAM, and has an amplitude of 5V and a period of 1 μs. 2 is
This is the board current when clock 1 is input to the RAM, and the peak value flows around ±5mA. Due to this variation in substrate current, the substrate bias voltage varies greatly after the circuit operation starts (clock 1 is at a low level) and after the circuit operation ends (clock 1 is at a high level). This variation in substrate bias voltage may cause the circuit to malfunction, so it is necessary to reduce this variation, but since there is a variation in substrate current of ±5 mA, the variation in substrate bias voltage can be suppressed by using a capacitive element. If smoothing and suppression is attempted, a very large capacitance is required, and it is difficult to mount such a capacitive element on a chip because it occupies a large area. Therefore, in the past, a large smoothing capacitive element had to be provided outside the chip in order to suppress fluctuations in the substrate bias voltage.

Further, FIG. 2 shows a configuration in which a capacitor is provided on a semiconductor integrated circuit chip and the substrate bias voltage is suppressed by charging and discharging the capacitor in accordance with the circuit operation. In the figure, 10 is a semiconductor integrated circuit chip, and 11 is a portion on which a circuit is constructed. The semiconductor integrated circuit 11 is connected to a terminal 12 from the outside.
The circuit operates by inputting a clock through the circuit, but since the substrate current fluctuates due to this circuit operation, the substrate bias voltage fluctuates greatly at the start of the circuit operation and after the circuit operation ends (at the start of the precharge operation).
By the way, it can be seen from FIG. 1 that the polarity of the fluctuation in the substrate current is opposite after the circuit operation starts and after the circuit operation ends, but the amount of fluctuation is almost the same. That is, the substrate bias voltage decreases at the start of the circuit operation and increases at the end (at the start of the precharge operation). Therefore, a new capacitive element is provided on the chip, and this is charged and discharged according to the operation of the circuit to offset the fluctuations in the substrate bias voltage.

In FIG. 2, numeral 13 is a capacitive element newly installed on the chip 10 to absorb fluctuations in substrate bias voltage, and one end of this capacitive element 13 is connected to the connection point of transistors TR-1 and TR-2. is,
The other end is connected to the substrate bias supply line of the semiconductor integrated circuit 11. 14 is a circuit block that causes charging and discharging current to flow through the capacitive element 13, and includes an inverter I, delay circuits DL-1, DL-2, transistors TR-1,
It consists of TR-2. When the clock at terminal 12 is at a low level, semiconductor integrated circuit 11 is in an operating state and the substrate bias voltage tends to decrease. At this time, transistor TR-1 is on and transistor TR-2 is off, so the power supply
The capacitive element 13 is charged by V _DD to ensure that the substrate bias voltage does not decrease. On the other hand, when the clock at terminal 12 is at a high level, semiconductor integrated circuit 1
1 is in a state where the operation is completed, that is, in a precharge operation state, and the substrate bias voltage tends to increase. At this time, the transistor TR-2 is on and the transistor TR-1 is off, so the capacitive element 13
The charge is discharged through TR-2 to ensure the increase in the substrate bias voltage. In this way, by charging and discharging the capacitive element 13 according to the operation of the semiconductor integrated circuit 11, fluctuations in the substrate current are offset, and the substrate bias voltage can be kept constant. However, the capacitance element 13 must have a capacitance equal to the sum of the capacitances of the parts in the circuit 11 that perform pre-charge and discharge operations, and for this reason, it is necessary to mount a large-area capacitor on the chip. Ta.

In order to solve these drawbacks, the present invention divides the circuit on a semiconductor integrated circuit chip into a plurality of circuit blocks with different operation timings, and makes each circuit block function in the same way as the capacitive element described above. The drawings will be described in detail below.

FIG. 3 shows an embodiment of the present invention, in which a portion of a semiconductor integrated circuit is formed on a chip 10.
The circuit is divided into two circuit blocks 1-A and 11-B, and when the clock applied to the terminal 12 is at a low level, the circuit block 11-A is set as the operating period and the circuit block 11-B is set as the precharge period. Conversely, when the clock at terminal 12 is at a high level, circuit block 11-B is activated during the operation period, and circuit block 11-B is
A is the precharge period. That is,
The fluctuation of the substrate current at the start of the operation of the circuit block 11-A is suppressed by the substrate current in the opposite direction at the start of the precharge of the circuit block 11-B, and the fluctuation of the substrate current at the start of the operation of the circuit block 11-B is suppressed. The fluctuations are suppressed by the substrate current in the opposite direction of circuit block 11-A. As a result, the semiconductor integrated circuit chip 10 can suppress the substrate current during circuit operation and precharge without mounting the capacitive element 13 as shown in FIG. 2, and can reduce fluctuations in the substrate bias voltage.

Note that the present invention may be implemented by combining FIG. 2 and FIG. 3, and in that case, the capacitive element 13 in FIG.
Since it is sufficient to suppress the substrate current due to the operation of one circuit block, there is an advantage that a capacitance that is 1/n (n is the number of circuit blocks) of the capacitance required in the case of FIG. 2 is sufficient.

As explained above, according to the present invention, since fluctuations in substrate current are suppressed in accordance with circuit operation, semiconductor integrated circuits with small fluctuations in substrate bias voltage can be realized without providing a large capacitive element outside the chip. It has the advantage of being configurable.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining changes in substrate current during operation of a semiconductor integrated circuit, FIG. 2 is a diagram showing a conventional configuration,
FIG. 3 is a diagram showing an embodiment of the present invention. 10... Semiconductor integrated circuit chip, 11... Circuit component, 12... Clock input terminal, 13... Capacitive element, 14... Charge/discharge circuit.

Claims (1)

[Claims] 1. In a semiconductor device in which a semiconductor chip is arranged to form a semiconductor integrated circuit that operates by applying a bias voltage to a semiconductor substrate, the semiconductor integrated circuit is divided into an even number of circuit blocks on the substrate. What is claimed is: 1. A semiconductor device equipped with a semiconductor device, further divided into two groups so as to have the same number of circuit blocks, and having an operation period and a standby period in opposite phases between the two groups.