KR20000046961A - Burn-in test vcp voltage controller of memory device - Google Patents

Abstract

PURPOSE: A burn-in test VCP voltage controller is provided to enhance the reliability of tests by performing burn-in tests through the selection of an appropriate value for the test environments. CONSTITUTION: A plurality of transfer transistors(12, 14, 16, 18) transfer the Vcp of plural voltage levels. A multiplexer(20) selectively operates the plural transfer transistors(12, 14, 16, 18). The multiplexer(20) receives two control signals and outputs four signals(a, b, c, d). The output value(a, b, c, d) of the multiplexer(20) becomes '0001' when the control signal is '00'. At this time, the transistor(18) is turned on so that the potential value of the Vcp<3> is outputted to the Vcp_out. The voltage applied to a cell plate becomes the voltage of the Vcp<3>.

Description

Vac voltage controller for burn-in test of memory devices

The present invention relates to a Vcp voltage controller for burn-in test of a memory device, and more particularly, to test while controlling a Vcp voltage applied to various conditions in order to confirm a failure of a cell capacitor during burn-in test of a memory device. A Vcp voltage controller for burn-in test of memory devices.

Since the memory element has a great influence on the reliability by each process element of the manufacturing step, it is adjusted to form desired shape, doping state, etc. through various experiments and inspections at each step of the manufacturing process, but very small error of the manufacturing process Since each one can greatly influence the operation of the semiconductor device, the manufactured semiconductor device is inspected whether it is manufactured as designed through an inspection step using equipment for testing (probe station, tester, etc.).

After completing the above test, the product is tested again for functional operation, and the products passed the test are put into a package and completed as a memory device.

The packaged memory device performs a burn-in test that stresses the voltage and the ambient temperature to more severe conditions than actual use conditions for the entire memory device to detect an early defect early.

1 is a circuit diagram showing a cell structure of a general DRAM.

As shown here, one cell is composed of one transistor and one capacitor as a unit memory device to store data in units of one bit.

Therefore, the cell array is configured as an aggregate in which the above unit memory elements of the memory device are gathered in a matrix form.

In such a unit cell, a word line WL, which is a signal line for selecting and activating a cell, is connected to a gate G of a cell transistor Tc, and a bit line BL, which is a line for inputting / outputting data of a cell, is a cell transistor Tc. The cell capacitor Cc, which is connected to the source S and retains and preserves data, is connected to the drain D.

The well bias voltage VBB is applied to adjust the threshold voltage Vt of the cell transistor Tc by applying a bias voltage to the well of the cell transistor Tc.

This well bias voltage (VBB) changes the bias of the semiconductor substrate from GND to negative voltage, thereby reducing the substrate bias effect of the threshold voltage (Vt), increasing the punch-through voltage, reducing the junction capacitance, and reducing the undershoot. It is used to get the advantages such as preventing data destruction by the.

The burn-in test process of the memory device as described above may be divided into a test for screening a fail of the gate oxide layer of the cell transistor and a test for screening the fail of the cell capacitor.

First, a screen for screening a gate oxide gate of a cell transistor is applied by applying a high voltage of 6.3V when Vcc is 3.3V and connecting Vcc and Vext voltage to each other.

The test for screening the failure of the cell capacitor is performed by setting the potential Vblp of the bit line, which is half Vcc, to ground and the potential Vcp of the cell plate to have a constant value in the level range of 2.94 to 3.35 V through the metal option. Proceed with giving the capacitor overstress due to high electric field.

However, due to the characteristics of the burn-in test, the initial fail rate screened by three factors, voltage, temperature, and test time, is determined, and the level of applied voltage should be determined as a correlation between temperature and test time. However, when fixed by the metal option to have a constant potential value, the applied temperature and test time variables are also limited to one type.

In addition, a long test time is required due to the characteristics of the burn-in test. However, when the test time is limited to one of the above values, there is a problem in that the reliability of the memory device to be tested cannot be increased as much as a restriction occurs in the test under various conditions.

The present invention has been made to solve the above problems, and an object of the present invention is to generate a variety of Vcp voltage applied to the cell plate of the cell capacitor during burn-in test of the memory device and to control the various generated Vcp voltage The present invention provides a Vcp voltage controller for burn-in test of a memory device having a multiplexer for selecting any one value by a signal so that burn-in test can be performed under various conditions.

1 is a circuit diagram showing a cell structure of a general DRAM.

Fig. 2 is a circuit diagram showing a Vcp voltage controller for burn-in test of a memory device according to the present invention.

-Explanation of symbols for the main parts of the drawings

12,14,16,18: first through fourth transfer transistors

20: multiplexer

Tc: Cell Transistor

Cc: Cell Capacitor

The present invention for achieving the above object is characterized by consisting of a plurality of transfer transistors each delivering a Vcp having a plurality of voltage levels, and a multiplexer for selectively operating the plurality of transfer transistors by a control signal.

Referring to the operation of the present invention made as described above are as follows.

By generating the Vcp voltage applied to the cell plate of the cell capacitor to have various voltage values and connecting the output values of the plurality of transfer transistors capable of transferring them to the Vcp input terminal of the cell capacitor, only one operation signal is output by the control signal. The multiplexer operates these multiple transfer transistors to perform burn-in tests while varying the Vcp voltage applied to the cell plate.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the present embodiment is not intended to limit the scope of the present invention, but is presented by way of example only and the same parts as in the conventional configuration using the same reference numerals and names.

Fig. 2 is a circuit diagram showing a Vcp voltage controller for burn-in test of a memory device according to the present invention.

As shown here, four transfer transistors 12, 14, 16, and 18 and four transfer transistors 12, 14, 16, and 18 for transferring Vcp &lt; 0: 3 &gt; having four potential values, respectively. ) Is a multiplexer 20 that selectively operates by a control signal cntl.

The multiplexer 20 receives two control signals cntl and outputs four signals a, b, c, and d.

The above operating conditions are shown in Table 1.

cntl 〈0〉 cntl 〈1〉 Multiplexer Output Values (a, b, c, d) Vcp_out 0 0 0,0,0,1 Vcp 0 One 0,0,1,0 Vcp One 0 0,1,0,0 Vcp 〈1〉 One One 1,0,0,0 Vcp

As shown in Table 1, when the control signal cntl is '00', the output values a, b, c, and d of the multiplexer have a value of '0001' to turn on the fourth transfer transistor 18 so that Vcp &lt; Since the potential value of 3> is outputted to Vcp_out, the voltage applied to the cell plate becomes the Vcp <3> voltage.

In this way, the voltage applied to the cell plate according to the control signal cntl can be selected to a value suitable for the burn-in test condition.

As described above, the present invention can extract a more accurate initial fail rate by adjusting the Vcp voltage applied to the cell plate to have an appropriate value in the test environment according to the control signal to screen the fail of the cell capacitor during the burn-in test. There is an advantage that can improve the reliability of.

In addition, since the test time can be adopted in various ways through the correlation with the voltage temperature during the burn-in test, the test time can be shortened, thereby reducing the development time of the memory device.

Claims (1)

A plurality of transfer transistors each delivering a Vcp having a plurality of voltage levels; A multiplexer selectively operating the plurality of transfer transistors by a control signal Vcp voltage controller for burn-in test of a memory device, characterized in that consisting of.